INTRODUCTION

Pollution is a major problem that modern societies suffer from. The presence of pollutants in water resources, especially fresh water, makes it a serious and defining problem for growth and life ^[1].Pollution issues are constantly exacerbated in Coastal areas because of the increasing of population density and human activities that pollute the environment and natural resources, including water sources and groundwater which represents the reserve stock of water used in various fields ^[2] Environmental pollution affects all elements of the living environment such as plants, animals and humans, as well as the composition of non-living nature elements such as air, water and land. This problem has exacerbated in recent decades and become a grave danger threatening all living organisms because of industrial development, technological progress, and the development of the human standard of living accompanying with the  increasing in consumption and the growing dumping of waste in the environment ^{[3, 4]} Solid waste is considered one of the major environmental problems in urban areas, due to its direct impact on the quality of human life, the appearance of civilization, and the consequent serious negative impact on  sustainable development ^[5]. Solid waste resulting from various human activities (production and consumption) has become a major threat to the environment and people because of the increasing quantities generated daily which exceed the ability of the environment to decompose and convert them into useful or harmless materials ^[4]. The increasing production of raw materials and their consumption contributed to the depletion of natural resources and caused continuous damage to the environment ^[3]. Every year, the production of raw materials destroys millions of hectares of land and trees and produces billions of tons of solid waste. It pollutes water and air ^[6], in addition to the pollution resulting from the production and use of energy needed to extract and manufacture materials ^[7]. Surface water bodies have been used for a long time, and are still used today, as places for discharging various human waste, which exacerbated the problem of fresh water pollution in rivers, lakes and water reservoirs due to a change in its physical, chemical or biological properties. In addition to the pollution caused by these wastes to groundwater when the leachate reaches it ^[8]. The presence of indiscriminate dumping near water resources (ground or surface) contributes to their pollution and the pollution of the environment in all its aspects, especially groundwater, which represents the reserve stock of water used in various fields affecting growth and life, ^{[9 ,10]}.  In wet weather, the movement of chemical and biological pollutants of solid waste materials is active, their concentration increases at the bottom of the landfill ^[11]. Most of leachate coming out of the landfills increases during periods of precipitation. solid waste forms severe pollution sources due to the abundance and diversity of chemical elements emerging from them^[12]. Problems with health and environment increase with the appearance of some heavy metals in the groundwater, as specialized references confirm that their presence (no matter how small) is linked to solid waste, as it is one of the most dangerous and toxic chemical pollutants for living organisms ^{[13, 10, 14]}, and is characterized by its long-term persistence in the aqueous medium, which ranges from several months to several years ^{[14, 15]}. The development which Syria witnessed in recent decades has been accompanied by the emergence and exacerbation of environmental pollution problems, as the surface and groundwater in the country suffer from the accelerating rate of bacterial and chemical contamination with industrial, domestic, and fertilizer waste ^[5]. It has been shown that the pollution, and the amount of waste in general, has increased with the increasing in the population in the countryside and cities, because of the weakness of the treatment plants. ^[16].  One study also showed an increasing in bacterial population in the water of wells used to irrigate some vegetables near the waste dumping site in the Al-Bassa area in Lattakia during winter ^[17]. In the same context, the study of the environmental impact of the Al-Bassa landfill   ^[18] concluded that some indicators of contamination of groundwater wells in the Al-Bassa area increased, and it was noted that the rates of BOD and NO3 increased above the permissible levels for drinking water. Another study showed bacterial and physiochemical contamination of the waters of the Al-Kabir Al-Shamali River in the Al-Jindiriya area ^[19]. The importance of this research lies in evaluating the quality of water in the wells located in the vicinity of Wadi Al-Hada Center, in addition to the clear environmental effects of waste leaching on some groundwater wells located in the vicinity of it, especially after the appearance of turbidity in two wells located in  Beit Ismael and Minya Yahmour villages. The research aims to monitoring and evaluating the quality of groundwater within ten wells located in five villages adjacent to the center of Wadi Al-Hada by determining some physical and chemical characteristics of groundwater in two wells from each village for a period of four months (until the results of the analysis became identical to the Syrian standard specifications) and determining measures to reduce the impact of major water pollutants.

MATERIALS AND METHODS

Study site and sampling sites:

This research was conducted in the area surrounding the Wadi Al-Hada Center for Solid Waste Treatment, located in the village of Al-Fatasiyah, 13 km southeast of Tartous, and at an altitude of about 180 meters above sea level. The area of the center’s land is 100 dunums. several sites next to the center are used for dumping waste resulting from the center. The center is surrounded by a group of small villages and residential communities working in agriculture (these are the villages of Yahmour, Al Zarqat, Minyat Yammour, Karm Bayram, Beit Ismail, and others…) The irrigation of crops in these villages depends on groundwater. The idea of this research came from the appearance of detectable pollution in two wells located in Minyet Yahmour and Beit Ismail, due to exposure to waste leaching. The research was divided into two stages In the first stage, a survey was conducted by distributing questionnaires to local population. This questionnaire covered 50 families, and included questions to explore their opinions about the center, their health conditions, diseases suffered by family members, and the repercussions of water pollution on them due to the old dump and treatment center in Wadi al-Hada, and the availability of a sewage network in the area. In the second stage, the impact of Wadi Al-Hada center on some wells in five villages adjacent to it was studied as shown in Figure 1. Groundwater samples were taken from 10 artesian wells (Table 1) distributed in the region, so that they represent the various conditions of the site in terms of human activity and land use, and analyzes were conducted.

Several field visits were made to the study site, and water samples were taken from these wells six times, at an interval of ten to twenty days. The sampling was stopped when the results became in conformity with the Syrian standard specifications starting from 7/27/2021 until 10/12/2021. Sample collection and analysis: Samples were collected in 1-liter polyethylene containers to determine the COD index and measure some electrolytes. The containers were washed well with distilled water and study site water three times before being filled; other samples were collected in 500 ml glass containers to determine the number of faecal bacillus FC. The containers were sterilized in an oven at a temperature of 250ºC for two hours Water analyses were conducted in the laboratories of the Directorate of Water Resources in Tartous Governorate, as follow:

Working methods:

Physical, chemical and bacteriological analysis were carried out in the laboratories of the Directorate of Water Resources in Tartous, according to the following: Some physical indicators (pH, turbidity, and electrical conductivity) were measured at the study site using newly calibrated field devices as follows:

1. The degree of pH was measured using a field pH device from HACH, model Sension 1. As for turbidity (Turb), a turbidity device from HACH, model 2100P, was used, and a conductivity device from WTW, model Cond 720, was used to measure electrical conductivity (Cond).
2. The electrolytes (chlorine – sulfate – nitrite – nitrate – phosphate – ammonia) were measured using an IC device
3. COD – (Chemical Oxygen Demand): The COD was determined using the open tube method, where the samples were digested at 150 degrees Celsius for two hours in a COD sample digester from VELP Scientifica, model ECO, in the presence of mercury sulfate, silver sulfate, sulfuric acid, and potassium dichromate. Then, the samples were calibrated using ferrous ammonium sulphate.

FC – (fecal coliform count): FC was determined using the filtration method on 0.45-micron bacterial membranes and incubated with MFC agar culture medium at 37.5°C for 24 hours using the following equipment: Bacterial isolation chamber from Lab Tech, buchner funnel for filtering bacterial samples, a bacterial incubator from Memmert, a sterilization oven from Memmert, and an autoclave from SELECTA, model AUTESTER ST

RESULTS

At the beginning of the research, the wells in Minyat Yahmour and Beit Ismael were polluted, due to the exposure of the aquifer to pollution by the waste leaching collected next to the center, but when the leachate was collected, the results returned to the permissible limits according to the Syrian standard specifications shown in “Table2”.

The pH values were moderate values tending to alkalinity, and were within the permissible limits according to the Syrian standard specifications and so was the electrical conductivity (Cond) which did not exceed 813 μM/cm in the wells. Whereas turbidity values were high in most of the wells in the first samples during July and August, especially in (well 2) Minyat Yahmour, where it reached (39ntu, 32ntu), and in (well 1) Yahmour (8ntu.2ntu) “Fig 2”. We also noted that the percentage of ammonia was above the permissible limits according to the Syrian standard specifications. “Fig 3”. COD values in all measurement locations exceeded the permissible limits according to the Syrian standard specifications (which is 2 mg/L) in the first samples, ( in July and August), “Fig 4”, and also the results of the bacteriological analysis showed high general count and a high number of coliform bacilli in the two wells located in Beit Ismail and well 2 located in Minyet Yahmour, “Fig 5” Finally, positive and negative electrolytes, It was noted that the values of the ions NO2-، NO3- ، PO43-، Cl-، SO42-did not exceed the permissible limits according to the Syrian standard specifications in the ten wells. Population survey results:  The results of the questionnaire showed the occurrence of disease cases as a result of the use of contaminated well water.

DISCUSSION

We will graphically review only the indicators that do not conform to the Syrian standard specifications and analyze their changes spatially and temporally. The pH values were within the permissible limits according to the Syrian standard specifications. There was no significant change in them according to the change in the sampling date or the location of the well. As for turbidity, we noticed high turbidity values in most of the wells in the first samples, and we can attribute this to the leaching of pollutants from the landfill into the effluent that heads from Wadi al-Hada center towards Minyat Yahmour and Beit Ismail.  Then, the values of turbidity decreased until it became within the permissible limits according to the Syrian standard specifications in November. This is because the problem was solved in the area and the leachate was collected in the rainwater collection basin and  This is consistent with studies confirming the impact of landfill leachate on groundwater ^{[20, 21]} The measurements also indicated that the electrical conductivity values of well water and surface water were within the permissible limits according to the Syrian standard specifications (1500 µm/cm), but the ammonium ions in the water influenced by human activity as the nitrogen was presented in polluted water (urine and uric acid). The production of ammonium ion during the ammonification process indicates the recent existence of contamination with organic matter and the progress of the self-purification process that carried out by microorganisms in aquatic media. ^[22].COD values: It is noted from “Fig 4” that the COD index has increased, as the highest value was recorded in well 2 located in Minyet Yahmour and the two wells located in Beit Ismail, but these values began to decline until they became within the permissible limits in the month of November, and this indicated that the aquifer was contaminated with highly concentrated organic matter that may be due to the leachate from Wadi Al-Hada. The discrepancy in the results between the wells can be explained by the difference in the slope and permeability of the soil and rocks at this location compared to the locations of other wells ^[4] “Fig 5” shows the bacteriological analysis that it exceeded the permissible limit (which is zero) in all wells except for the (two wells) in Dahr Beit Al-Ayat and (well 1) in Minyet Yahmour,the value (zero) was recorded which was good . The largest value was in the two wells (well l) in Beit Ismail and ( well 2) in Minyet Yahmour, during the first three months (July, August and September).  This may be due to the fact that there is sewage near them. As for the rest of the wells, the number of coliform bacilli was greater than zero, but it was relatively less than these wells and this is consistent with studies confirming the impact of waste leaching on the groundwater ^{[23, 24]} Positive and negative electrolytes: It was noted that the values of the ions NO2-, NO3-, PO43-, Cl-, SO42- did not exceed the permissible limits according to the Syrian standard specifications in the ten wells during the four months. This can be explained by the fact that they were not subjected to excessive fertilization, and this was indicated by many studies ^[25,26,27]; However, the results showed an increase in the concentration of ammonia ions in the two wells located in Beit Ismail and Minyat Yahmur. It was also found that there is no clear relationship between the depth of the well and the values of the pollution indicators in it. This can be attributed to the fact that the studied wells were not fed by the same aquifer ^[28]. It is important here to point out a study on Modeling the movement and transport of pollutants in the groundwater using GMS program (a quantitative model using MODFLOW, and a qualitative model using MT3D),  which was conducted at   (Al-Bassa Dump) ^[29], and the results of the quantitative modeling of the water resources system in the Al-Bassa Dump area resulted in obtaining a map of Head Contours and flow Budgets, and the ability to display cross-sections at any point of the studied area. We also were able, through qualitative modeling, to simulate the transport of pollutants, and the leakage of leachate from Al-Bassa Dump, and predict its expected changes during different periods. Therefore, it is necessary to emphasize the importance of using modeling programs to predict the movement of pollutants in the Wadi Al-Hada center area. Population survey results:   The results of the questionnaire showed the occurrence of disease cases as a result of the use of contaminated well water, the most important of which were acute intestinal diarrhea and gastrointestinal infections. 30% of the surveyed people indicated that they were exposed to diseases because of the landfill or as a result of their use of groundwater wells, and most of them stopped using this water for drinking and only used it to irrigate crops. The results also showed that 80% of the population are farmers and have lived in the area for more than 50 years, and 25% of them depend on technical drilling.

CONCLUSIONS AND RECOMMENDATIONS

We can conclude from this study the following main points:

1. The water wells in the villages of Minyat Yahmour and Beit Ismael were exposed to significant microbial contamination. High COD values were also recorded. This is an evidence of exposure to contamination by landfill leachate and sewage leakage
2. The groundwater at the site was subjected to temporary pollution that made it unfit for drinking, but after four months it became fit for drinking and within the limits of the Syrian standard specifications
3. The use of contaminated well water has led to disease cases, the most important of which are acute intestinal diarrhea and gastrointestinal infection

RECOMMENDATIONS

To avoid the health and environmental harms of the waste and sewage water, we recommend the following:

1. Emphasis on the need to construct rain drains and trenches throughout the center, and as for the landfill, emphasis must be placed on covering up and isolating both base and sides to ensure that there is no leakage into the nearby groundwater.
2. Studying the characteristics of the leachate resulting from the landfill in the future, and evaluating its impact on the surrounding environment.
3. -monitoring groundwater in the surrounding area and checking the change in the concentration of pollutants in them
4. Modeling the movement and transport of pollutants in the groundwater using Modflow and MT3D

Use a modeling program to predict pollutants by constructing a mathematical model using GMS program (a quantitative model using MODFLOW, and a qualitative model using MT3D).

INTRODUCTION

Substitutes to cement are a sustainable way to decrease the overuse of cementitious materials, and it is gradually becoming important to include them in the building sector ^[1]. Energy consumption is the major environmental concern associated with cement manufacture, including the direct use of fuel to extract and transport the raw materials as well as the high energy required for calcination, which is provided by burning of coal, coke, natural gas, diesel and fuel. Cement manufacture consumes about 1758 kWh per ton of cement. Mortar is one of the decorative building elements in addition to its role as a binder for the block and is widely used in the construction field. The mortar mixture consists of Portland cement, fine aggregate, and water. Many adjustments have been made to the mortar concerning its components ^[2]. The various construction processes are one of the main sources of high carbon emissions, as the cement industry is a significant component in increasing carbon emissions. Using other cementitious materials to produce cement-based materials is an important technique to decrease carbon emissions, where the cement industry generates nearly 8% of global CO₂ ^[1]. Fly ash and Silica fume (pozzolanic materials) are widely used as cement alternatives to produce cement-based materials ^[1]. The consumption of local raw resources is one of the obstacles to cement manufacture ^{[3] [4]}. In addition, issues related to climate change have attracted significant attention. However, more recently, issues related to local health aspects have been mentioned. Therefore, designers of building material mixtures seek to introduce sustainable technologies to reduce environmental impact ^{[5] [6]}. Current technological advances aim to improve the construction process in terms of speed, performance and financial productivity. The use of gypsum mixes that do not require high levels of heat during the production process is common ^[7]. Gypsum is a construction material known for its good performance against variations in humidity and its rapid ability to change shape and harden. However, gypsum materials have some disadvantages for use in construction, such as: not being hard or brittle, poor waterproofing and decomposing quickly. For this reason, many researchers have conducted numerous tests to determine and improve the performance of these materials. Archaeologists dated the earliest uses of gypsum about 7000 BC ^[8]. Many researchers aimed to replace raw building materials with wastes and biomass (low energy consumption binders) to increase the environmental efficiency of construction. Gypsum is considered one of these low-cost materials, that seems to be a suitable option for new constructions, in addition to being widely used in many restoration and rehabilitation operations for old buildings. The advantage in which gypsum is distinguished from cement and lime is its production at about 120-180 °C, with a much lower burning temperature and energy, while cement needs about 1500°C and lime needs about 900°C. Thus, the associated low energy makes gypsum a sustainable solution ^[9]. Concerning energy saving in buildings in European countries, around 75% of buildings need incomplete or complete repair because they are not energy efficient. Enhancing the performance of wall cladding (interior and exterior) is an important energy-saving technology as part of the rehabilitation and maintenance of damaged and older buildings [10]. As for Syria, this percentage increases very significantly as a result of the war that the country was exposed to, according to the observations of the authors themselves, to more than 90%. By the way, statistical reports issued by the International Energy Agency indicate that worldwide energy depletion in the building sector will reach 30% in 2060 if the existing ratio of increasing growth remains as it is now ^[11]. Accomplishing high energy efficiency in structures is the most demanding concern of governments internationally, which would cause a decrease in energy depletion and environmental problems related to CO₂ emissions ^[11]. Various research projects and investigations began years ago to find suitable alternatives to reduce the concentration of carbon dioxide in the atmosphere, in addition to reducing the cost of building materials ^[12][13][14]. Unpredicted environmental hazards of carbon emissions resulting from cement manufacturing required  for all structures in addition to depletion of raw resources are the most persistent tasks of future engineering. However, achieving sustainability by introducing natural materials that are affordable for various construction process is one of the preferable solutions. Due to the lack of searches done on JB, and its wide spread in the Deir ezzor region, it was necessary to draw attention to that product and define its specification. The key objective of this investigation is to determine the engineering properties of JB-based mortar. JB is used as a partial replacement of cement with varying ratios of 0%, 10%, 25%, 50% and 75% of the total cement weight. Then, comparative results between the cement mortars and JB-based mortar will be presented.

MATERIALS AND METHODS

JB: The southern region of Deir ezzor is generally famous as the extraction deposits of the raw material for the production of JB.  A large number of limestone mountains, the most important of which are the southern mountains near the Qabr al-Wali area, the Hawooz area, the Tharda Mountains, and the ancient al-Jura area. A single limestone mountain mass is called a Maqtaa, it is a huge rocky mass that has a vertical cliff surface called a Gall. The chemical composition of JB was measured to determine its components (CaO, SO₃, and H₂O). Table 1 represents these compositions.

The different compositions of compounds are due to the heating process, which leads to the release of water and thus the restructuring of other molecules. After the trailer carries the load of stones to Namura, which is the main factory of the white JB, the workers collect the stones brought from the nearby mountain. Then the second phase begins when the workers, who are spaced about 2 meters apart, break these stones into sizes smaller than egg size, and then carry them manually to the dome of Al-Namoura, where they are distributed over its surface after being sieved so that the stones smaller than 2 cm in diameter are eliminated. After paving the dome with small stones, the third phase begins including the burning process, which lasts for two days. The purpose of the burning process is to separate the desert dust and impurities from the stones in addition to modifying the structure of the stones so that they become fragile and completely free of moisture. After one cooling day, the burned stones are taken to a stone grinder to be smashed into powder. The JB is manufactured from CaSO₄⋅2H₂O (gypsum), which is obtained from the mineral rock. Upon heating at a temperature of around 160°C, the gypsum converts to CaSO₄.0.5H₂O (JB) ^[16].

Experimental program

This section compares the performance of the cement mortar (0% of JB) with the cement-JB mixture mortar with different ratios of JB. Different specimens of mortar were prepared using the materials indicated in Table 2. The weight, volume and bulk density of cement, sand and JB are determined.

The proportions of the mortar components were as follows:

• The ratio of C/S (cement/sand) was 1:3, ISO 679: 2009 recommendation. These values must be expressed in terms of weight.
• A designed ratio of W/C (water/cement) was 0.5, Recommended according to ISO679:2009.
• The number of cubic specimens, 45, was used to measure the compressive strength of the specimens with dimensions of 5 x 5 x 5 cm, according to ASTM C109/C109M-20.
• And forty-five prismatic specimens were used to measure flexural strength. The specimens had dimensions of 4 x 4 x 16 cm, according to ASTM C109.
• Bulk density was determined using fifteen cubic samples, each measuring 5 x 5 x 5 cm.
• A total of 15 cubic samples with dimensions of 5 x 5 x 5 cm were used to measure the rate of water absorption.

Cement, water and JB were mixed in a mixer for one minute before sand was added. The total mixing time is about 3 minutes to get good adhesion between the cement, Al Juss, sand and water. The cement used is local ordinary Portland cement (grade: 32.5, specific gravity: 3.15, finesse: 3360 cm²/gr, chemical composition: shown in Table 3), and the water used is safe to drink. As for sand the Table, 4 represents some specifications of the crushed limestone sand used. To accomplish the comparison, five mortar mixtures were prepared that differ from each other in the percentage of cement and Al Juss, while the control sample was produced using pure cement as a binder and four samples that include JB with different proportions 10%, 25%, 50%, and 75% of total cement weight.

RESULTS

The properties of the modified cement mortar were evaluated using JB binder. The compressive and other properties revealed lower values compared to the cement mortar. The following is a presentation of the results conducted during the study.

The finesse of Cement (Blaine value) vs. JB replacement

The relationship between the fineness of cement and the JB mixture with the used JB replacement ratios is shown in Figure 1.

The fineness of the mixture decreases as the JB replacement ratios increase as shown in (Figure 1). The mixture’s fineness affects the workability, durability, strength, and hydration rate. This decrease is due to the increase in JB related to cement because it is finer than JB which was produced manually.

properties of fresh paste and mortar:

Study of Initial and Final Setting Times of Cement-JB vs. JB Replacement:

Figure 2 illustrates the relationship between the initial setting time and final setting time (measured according to ASTM C-191) of the mixture of cement-JB pastes with the JB replacement ratios.

In the analysis of Figure 2, it can be noted how the initial and final setting times of the cement-JB mixture pastes decreased by increasing JB replacement ratios. At the 50% and 75% JB of the mixture, the initial and final setting times are close to each other. The decrease in both initial and final setting times of mixtures is due to the increase in JB, which causes them to lose their elasticity and become sufficiently rigid.

Study of Expansion of Cement-JB vs. JB Replacement according to Le Chatelier:

The expansion value of the cement and JB pastes versus JB replacement according to Le Chatelier is shown in Figure 3. The expansion value of the cement-JB mixture mortars increased by the increasing of JB ratios as shown in Figure 3. All of JB ratios do not show any significant expansion values. This increase is due to the fact that JB has a larger percentage of pore voids and is less homogeneous than cement, which was produced manually, and therefore has greater expansion values.

Study of Water Absorption value:

Figure 4 characterizes the water absorption value of cement-JB mixture mortars versus JB replacement, as the increase in the percentage of JB increases the water absorption value. JB is hydrophobic, as the increase in the percentage of JB increases water absorption value (In this case, I think that JB should be hydrophilic rather than hydrophobic). It can be clearly distinguished that all these values are less than 70%. Water absorption is the movement of liquid within unsaturated JB-cement samples’ pores under no external stress. JB, which possesses higher porosity, is known to have a more water absorption capacity, causing an increase in the absorption rate as JB content increases.

Properties of hardened mortar:

Compressive and Flexural Cement-JB Mortar Strength:  Compressive and Flexural strength of the cement-JB mortar mixtures were determined at 2, 7, and 28 days of standard curing conditions (20 ± 2°C, and relative humidity >95 or immersed in water) as it is shown in Figures 5 and 6.

The values of compressive strength cement-JB mixture mortars are shown in Figure 5. The highest compressive strength can be clearly observed in the control samples (38 MPa), followed directly by mixtures containing 10% of JB (26.5 MPa), and then by 25% of JB (10.5 MPa). On the other hand, the lowest compressive strength of cement-JB mixture mortars was obtained at 75% of JB, reaching 1.9 MPa. Adding JB to cement causes an increase in the volume of the mortar, which leads to cracking of the bonds that connect the aggregates, thus reducing the compressive strength. The outcomes derived from the flexural strength tests are shown in Figure 6. This figure displays how the cement mixtures containing 10% of JB have higher flexural strength values than the other three JB ratios investigated (0.86 MPa). When JBs are added to cement, mortar volume expands, breaking bonds and reducing flexural strength.

Study the change of dry density according to the JB replacement ratios: The dry density of the cement-JB mixture mortars with the JB replacement ratios at 28 of curing days are shown in Figure 7.

It can be simply detected that increasing the JB ratio decreases the dry density. Reducing density is attributed to certain physical properties, specifically the difference in specific gravity between JB and cement. Additionally, JB exhibits a higher porosity compared to cement, leading to increased volume and reduced overall density.

Investigation of the thermal conductivity (K-value) of the replacement of JB:To illustrate the relationship between thethermal conductivity of cement-JB mixture mortars versus JB replacement ratios, the K-value were determined. JB is categorized by low thermal conductivity against the cement mortar as shown in Figure 8, where the thermal conductivity decreases as the JB ratio increases. In general, as the JB content increased, the k-value decreased, because of its heat-insulating properties, as explained previously. The low K-value indicates that JB can be used as a suitable mortar for high-temperature applications. 

DISCUSSION

Compared with the ASTM C1329 specification, the mortar cement-JB of 10% of JB can be used instead of type M mortar cement (20 MPa) ^[17]. While the mortar cement-JB of 25% of JB can be used instead of type S mortar (14.5 MPa), which is used in building parts for exterior, at or below grade, and that of 50% of JB may be used instead of type N mortar (6.2 MPa), which is used in building parts for interior non-load-bearing^[17]. According to the ASTM specification, the cement-JB mortar of 10% of JB can only be used as type M mortar (0.8 MPa) ^[17]. While cement-JB mortars with other ratios of JB cannot be used. The initial setting time at 10% of JB is 90 min, which is in accordance with types S and M (not less than 90 min) According to the ASTM C403 specification. As for the final setting time, not more than 1440 min, all of the final setting times are smaller than this value. These setting times are important factors that affect the strength, durability, and workability of cement. For this reason, 10% of JB can be considered a suitable additive for cement within the standard limit to accomplish the best outcomes in building projects. The maximum expansion ratio at 75% reached 24 mm compared to 0% of JB, which was 16 mm. As for mortar with 10% of JB was 18 mm (only 2 mm increasing related to 0%). Thisconfirms that the JB does not display any considerable consequent expansion. If the expansion value is more than 10 mm, the JB-cement mortar is unreliable as described in ASTM specifications ^[17]. Consequently, the addition of JB had a positive outcome in the avoidance of the shrinkage property of cement that may lead to the formation of plaster cracks or deficiencies. A higher cement fineness provides very good quality, where smaller particles react faster than bigger particles. A cement particle that has a size of 10µm needs around 30 days to achieve the entire reaction, whereas a particle with a size of 1µm does not need more than 24 hours to achieve the entire reaction ^[18]. All of the water absorption ratios are less than 70%, which satisfies the conditions of ASTM specifications ^[17]. Cement mortar needs more amount of water (before and after applying, which causes the site to get very dirty) than the JB containing mortars, which means more time during the curing period in contrast with JB mortars that dry quickly and do not require any more treatment water. Mixing JB with cement at different proportions of 10%, 25%, 50%, and 75% of the cement weight does not considerably modify the dry density of the control cement mortar, which was about 18.9 KN/m³ and for the cement-JB mortar of 10%, 25% of JB was 16.5 and 15.1 KN/m³ respectively, and the reduction ratio relative to the control cement mortar was 14.5 %, 20% respectively. The two preceding types of cement-JB mortars are considered to be heavy-weight (greater than 15 KN/m³) ^[19]. Consequently, the addition of JB had a positive outcome in the avoidance of substantial volume changes, which lead to cracks in the plaster, or adherence deficiency to the wall support. The quantity of energy needed to cool and heat a building is reliant on the k-value ^[20]. The materials with a lower value of thermal conductivity have greater capability to restrain heat transmission. There are many factors affecting k-value such as mixture kind, percentage of fine aggregate, total volume of aggregate percentage, ratio of (W/C), humidity and temperature conditions, and additive types (fly ash silica fume, blast furnace slag) [20]. The results show that the thermal conductivity of cement-JB mortars increases as the ratio of JB of it gets larger. Thus such mortars are suitable for high-temperature applications and that is why the ancient residents of Deir EZZOR, whose weather is considered to be very hot, have been using the mortar of pure JB to cover their homes.

CONCLUSIONS

This paper presents the potential of combining JB and cement in the process of production of cement-JB mortars that may be used in the construction sector. Although the obtained compressive and flexural strength values were lower than those of control cement mortar, there is an encouraging outcome of the usage of JB in cement-JB mixture mortars, as the compressive strength at 10% of JB, meets the standard specification for type M cement mortar. Whereas the cement-JB mortar at 25% of JB may be used instead of type S mortar. The addition of JB to the cement mortars decreases the thermal conductivity, which gives good thermal properties and ensures energy saving. Cement mortar is prone to cracking, most cracks are caused by shrinkage, which is very common, while JB-added mortar has high elasticity and is less prone to cracking, All of the JB ratios do not show any significant expansion values, where the maximum ratio of 8 mm compared to 0% of JB.  In addition, the JB is hydrophobic which results in the moisture not remaining on the interior walls for a long time which will cause no formation of mould and mildew on these walls and prevent them of being slippery.  JB-cement mortar dries quickly, which has a 90 min initial setting time at 10% of JB, so it does not require any additional treatment water as the cement mortar which needs a great amount of it (before and after applying). The study also stated that increasing the JB ratio decreases the dry density; the reduction ratio was 14.5 %, 20% at 10%, 25% of JB, respectively. More particularly, it has been probable to confirm that the cement-JB mixture mortars with 10% or 25% of JB accomplish worthy properties, although these mortars do not meet the standards achieved by control cement mortars. On the other hand, the cement-JB mixture mortars may be used in rehabilitation works and rural buildings as a sustainable solution. Also, they can be used, as they were locally used, as interior coverage of walls and roofs in high-temperature cities like Deir EZZOR to reduce their thermal conductivity and make houses more thermally comfortable.

INTRODUCTION

Although coins and banknotes are in issues for decades, there is no agreement amongst economists on what is the theoretically optimal denomination structure of a currency [1]. Two components are usually used to identify any denomination structure, those being the structure boundary and the series within the boundary. The structure boundary includes determining the lowest coin value, the highest banknote value and the transition between coins and banknotes. The series inside the boundary includes the number of coins, banknotes, and total number of denominations [2]. Determining the optimal denomination structure of a currency is a daunting task. It involves ensuring the efficiency of the structure, its cost effectiveness and its balance in terms of having a proper mix of the various denominations [3] [4]. To ensure this task is well handled, central banks need to closely monitor the evolving changes (technology, security issues, high inflation..etc) and timely respond to them [5]. Empirically, [6] proposed the D-Metric model to determine the denomination structure of the currency. The model utilizes the relationship between the average daily wage level (D) and the denominations of the currency to identify the coins on the lower scale that need to be withdrawn from circulation, the boundary point between coins and banknotes, and the appropriate timing for the introduction of higher banknotes [7]. This study uses the D-Metric model to analyze changes in the denomination structure of the Syrian Pound between 1997 and 2022. The choice of the period is to capture the last three changes in terms of introducing a higher banknote in Syria. The study was motivated by the scarcity of previous research on the optimal denomination structure in general and in Syria, in particular. The study was further motivated by the public attention that accompanied the introduction of the SP5000 and the rumors regarding the potential issuance of the SP10000. The aim of this study is twofold. First, to analyze the denomination structure of the Syrian Pound and to verify whether the introduction of the last three high denomination banknotes was justified from the D-Metric model point of view. Second, to analyze whether a higher banknote should be introduced. The study contributes to the literature on the optimal denomination structure as it is the first that analyzes the denomination structure of the Syrian currency using the D-Metric model. The findings of the study have empirical implications for the Central Bank and the public in Syria. They will enable recommending the denomination of the higher banknote that should be issued and the timing of this issuance. The remainder of the study is organized as follows: Section one sheds light on the currency structure in Syria. Section two explains the D-Metric model. Section three analyzes the denomination structure in Syria using the D-Metric model. Section four concludes the paper.

The Currency Structure in Syria

The monetary authorities and denomination structure in Syria passed through several historical landmarks. Below is a brief highlight of this main historical changes. In the era of the French Mandate, the Bank of Syria supervised the process of issuing the currency. The name of the bank changed later on during that period to become the Bank of Syria and Lebanon. After gaining independence, the Bank of Syria and Lebanon continued on issuing the currency in both Syria and Lebanon. However, it was replaced later on by the Syrian Institute for Issuing Money. In 1953 the Legislative Decree No. /87/ was issued [8]. The Decree defined the basic monetary system in Syria and established a Council for Money and Credit to take on the tasks of the Central bank. The Central Bank of Syria did not officially start working until 1/8/1956. Below is a review of the development of the currency structure since the Central Bank of Syria became responsible for supervising the issuance of the Syrian Pound, the official currency in the Syrian Arab Republic. Figures (1) and (2) below show the development of the currency structure after the Central Bank of Syria became responsible for issuing the Pound. As per the structure of coins, after its establishment, the Central Bank of Syria continued to issue coins in the denominations of 2, 5, 25 and 50 Piasters and one Pound that previously existed. In 1960, a new coin in the denomination of 10 Piasters was issued for the first time. As shown in Figure (1), the structure of the coins remained unchanged until 1995, when new coins in the denomination of 25 Pounds were issued. In 1996, new coins in the denominations of 2, 5 and 10 Pounds were issued for the first time. In the same year, coins in the denominations of 2, 5 and 10 Piasters were withdrawn from circulation. In 2004, coins in the denominations of 25 and 50 Piasters were withdrawn from circulation. At the end of 2018, the highest denomination of coins, 50 Pounds, was issued [9]. With regard to the structure of banknotes, the Central Bank of Syria continued to issue banknotes in the denominations of 1, 5, 10, 25, 50 and 100 Pounds which previously existed. In 1958 a new banknote in the denomination of SP500 was issued for the first time. As Figure (2) reveals, the structure of banknotes remained unchanged until year 1997, when banknotes in the denominations of SP200 and SP1000 were issued for the first time. More than ten years in the Syrian crisis, which started in 2011, caused a massive economic destruction to the Syrian economy. The Syrian Pound which had a pre-crisis exchange rate on the average of USD1= SP45 gradually depreciated to exceed USD1= SP3800 in the black market. The depreciation of the Syrian Pound and the high inflation that Syria was facing triggered many questions regarding the necessity of issuing higher banknotes. In 2015, with the annual inflation rate reaching an average of 38.46%, the SP2000 note was printed for the first time. It was put into circulation in July 2017 when the annual inflation rate was 14.48% [10]. Recently, in 2021, a new note in the denomination of SP5000 was put into circulation. The 5000 note was printed in 2019 when the annual inflation rate was, on average, 13.42%] [10]. According to the official releases of the Central Bank of Syria, the SP5000 note was printed to meet the trading needs of the public in a manner that ensures facilitation of monetary transactions and reduces the cost and intensity of dealing in banknotes. The Central Bank reported that the current economic changes, and the significant rise in prices that started in the last quarter of 2019 and continued during 2020,  made the timing appropriate for putting the SP5000 into circulation [10]. Following the issuance of the SP5000, there was a public debate on whether the SP10000 needs to be issued and put into circulation or whether it is premature to do so.

 

                                                                    Figure (1): Timeline of the development of the coin structure in Syria

The following section introduces the D-Metric model that will be used to analyze the changes in the currency structure in Syria since the introduction of the three highest banknotes (SP1000, SP2000, and SP5000). 

MATERIALS AND METHODS

 The D-Metric model

Determining the optimal denomination structure includes identifying the structure boundary and the series within the boundary. That is to say, identifying the lowest coin value, the highest banknote value and the transition between coins and banknotes along with the number of coins, banknotes, and total number of denominations inside the boundary. The spacing of the denominations in most countries is based on either a binary-decimal triplets system (1-2-5) or a fractional-decimal triplets system (1-2.5-5) [2]. Syria is amongst countries that adopted a mix of the two systems. It has six denominations of coins (1, 2, 5, 10, 25, and 50) and seven denominations of banknotes (50, 100, 200, 500, 1000, 2000, 5000). The denomination of (5, 10, and 25) banknotes are legal tender although they are not issued any more by the Central Bank. As can be seen, the denominations (10, 25 and 50) follow the (1-2.5-5) system while the rest of the denominations follow the (1-2-5) system. Trying to figure out the optimal denomination structure, [6] used data from sixty currency-issuing authorities around the world. They documented a consistent relationship between the average daily pay (D) in a country and its currency structure. They reported that in most of the examined countries, the boundary denomination between coins and banknotes is located between D/50 and D/20. The top and lowest denominations are around five folds of the average daily pay (5D) and 5000 parts of the average daily pay (D/5000), respectively [12]. As shown in Figure (3), the model assumes that there are six denominations of coins and six denominations of banknotes along with one denomination at the boundary between coins and banknotes. The model can be used to advise when a modification on the denomination structure is needed. This includes the modification of the lowest-highest denominations and the transition between coins and banknotes [2]. The D-Metric model, however, is subject to several limitations. First, it is a practical method that lacks a theoretical base. Second, it ignores other factors that should be taken into consideration when determining the denomination structure of a currency. This includes, the costs associated with economic agents and users’ preferences, including payment habits [13] [14] [15]. The model also ignores the fact that payment habits, culture and wealth holding might differ across countries and could vary, within the same country, over time. In addition, the model fails to take into account the durability of monetary items and their costs when determining the boundary point between coins and notes [2]. Despite being subject to several limitations, the simplicity of the D-Metric model makes it used as a guideline to the re-denomination of currencies and it has been successfully applied in a wide range of countries around the globe [12] [16] [17]. The following section will utilize the D-Metric model to analyze the denomination structure in Syria between 1997-2022.

RESULTS

As Figure (2) indicated, bigger banknotes were issued in 1958, 1997, 2015 and 2019. Our analysis of the denomination structure in Syria is limited to years 1997, 2015 and 2019. Year 1997 was chosen as it experienced the last issuance of a higher banknote, the SP1000, prior to the eruption of the Syrian crisis.[1] Years 2015 and 2019 were chosen as they are the years in which the two higher banknotes, the SP2000 and SP5000, were issued. Years between 1997 and 2015 were not examined as there are no issuance of higher banknotes in these years. As highlighted earlier, the D-Metric model relates the average daily wage level to the denomination structure of the currency. Due to data availability issues, the nominal GDP per capita per day was used as a proxy for the average daily pay (D in the D-Metric diagram). The daily GDP per capita was adopted by many authors on their application of the D-Metric model [2] [12]. Table (1) reveals the value of D and the denomination structure in each of the examined years.

DISCUSSION

Starting with year 1997, the D-Metric model suggests that the lowest useful coin should be between SP0.02 (D/5000) and SP0.067 (D/2000). The note-coin boundary should be between SP2.7 (D/50) and SP6.7 (D/20), suggesting that the higher coin should be SP5, which can be either a coin or a banknote. The largest banknote suggested by the model is the SP500 banknote which falls between SP271 (2D) and SP677 (5D). Table (1), however, reveals mismatches between the theoretical denomination structure suggested by the D-Metric model and the actual structure in year 1997. To be more specific, the lowest coin, 25 Piasters (SP0.25), lies between D/1000 and D/500 instead of D/5000 and D/2000, as suggested by the model, and the highest coin is SP25 instead of SP5.[2] In addition, the SP10 and SP25 exist in coins and banknotes whereas the model predicts that the note-coin boundary should be SP5. Another mismatch with the D-Metric model is the existence of the SP1000 banknote whereas, according to the model, the highest banknote should be SP500 (between 271 and 677.9). Accordingly, based on the D-Metric analysis of the currency structure in year 1997, one can conclude that the structure is not the optimal one and that the introduction of the SP1000 was premature and should have been postponed until year 2005 when 5D was equal to SP1124.219. The structure recommended by the D-Metric model changes in 2015 in comparison to that in 1997. As shown in Table (1), the SP25 got pushed into the note-coin boundary whereas the SP5 and the SP10 fell into the coin category. Furthermore, the SP2000 banknote became the largest useful banknote. Unlike the mismatch in year 1997, it seems that the currency structure in 2015 complies with the theoretical denomination structure suggested by the D-Metric model in this year. The highest coin in circulation in 2015, SP25, falls into the note-coin boundary (D/20=619.989/20=30.999) and (D/50=619.989/50=12.399) and the highest banknote, SP2000, falls between (2D=2*619.989=1239.978) and (5D=5*619.989=3099.945). Therefore, it was appropriate, then, to issue the SP2000 banknote in this year. In fact, it was even appropriate to issue it in 2014, when D was SP471.6 (2D=943 and 5D=2358) [11]. Since the SP2000 was printed in 2015 but not put into circulation until 2017, the analysis requires examining whether it was put into circulation on the right timing. Knowing that in year 2017, D was equal to SP1053.99, the SP2000 falls outside what is suggested by the model (2D=2107.98 and 5D=5269.95). Accordingly, the delay in introducing the SP2000 into the market was inconsistent with the denomination structure suggested by the D-Metric model. In fact, the D-Metric analysis suggests that the SP5000 banknote could have been put into circulation in 2017 and not just the SP2000. As can be seen from Table (1) the structure recommended by the D-Metric model changes in 2019 in comparison to that in 2015. The SP50 got pushed into the note-coin boundary whereby the SP25 fell into the coin category. Furthermore, the SP5000 banknote became the largest useful banknote (lying between 2D=1437.641*2=2875.28 and 5D=1437.641*5=7188.2). The Table also reveals that the lowest useful coins for this year, SP1 and SP2, fall within D/2000-D/1000 and D/1000-D/500, respectively. The lowest useful banknote, SP50, falls into the note-coin boundary (between (D/50=1437.641/50=28.75) and (D/20=1437.641/20=71.88)). This means that the decision to issue the SP50 coin was appropriate. Adhering to the 1-2-5 system of spacing, the next useful banknotes would be 100, 200, 500, 1000, 2000, 5000 according to the model. Indeed, those are the currencies that are actually in circulation in that year. Although it is justified to put the SP5000 banknote in circulation since 2017 as indicated above, the note was not put in circulation until 2021.

Should a higher banknote be put into circulation?

Recently, there are discussions among the public and economists regarding the necessity of issuing a higher banknote (the SP10000 banknote). Issuing higher banknotes has its own advantages and disadvantages. One of the main advantages is the easy handling of transactions as people do not have to carry large quantities of money to do their daily transactions [20]. This is especially important bearing in mind the high reliance on cash and the very low reliance on E payment in Syria. Another advantage is the lower carrying and management expenses, as according to the Central Bank of Korea, issuing the higher denomination allowed a saving of 60 billion won (approximately USD 50,000,000) every year due to reductions in management expenses especially those related to logistic costs [21]. In addition, the higher notes have lower production costs as they are less frequently used and used with more caution than is the case for smaller notes [13]. The higher notes could also help reduce spending as people are less encouraged to buy something if they have to pay one big note than is the case if they are paying with several smaller notes [13]. Issuing higher notes might also protect the national identity of the country by reducing the chances of substituting the domestic currency for other currencies (dollarization) [22]. The major disadvantage of issuing higher banknotes, lies on the inflationary impact of issuing higher notes, which could be a very serious one. As expectations of inflation drive up inflation, the higher note might be followed by higher inflation. The fear is that if the cycle starts, it is not easy to stop it. More precisely, if inflation increases after the issuance of the higher banknote, this might lead to the issuance of a higher note and the cycle goes on. Other disadvantages of issuing a higher note revolves around production costs, susceptibility to forgery and facilitation of drag dealing and illegal activities [23] [24]. To determine whether a higher note, the SP10000, should be issued, we applied the D-Metric model on the daily GDP per capita for the year 2020 where D is equal to SP2101.06 [11]. As highlighted earlier, according to the model the highest note should be between 2D and 5D. This means that the highest note should be between SP 4202.12 and SP10505.3. Accordingly, the D-Metric model suggests that the SP10000 could have been issued and put into circulation since 2020. The high inflation that Syria is still facing makes us in doubts of whether a higher banknote should be issued as the SP10000 might not be enough to meet the needs of the daily transactions. Table (2) reveals the results of applying the D-Metric model on the daily GDP per capita for the year 2021 where D is equal to SP3099.93 [11]. As the table reveals the 2D and 5D are 6199.86 and 15499.65 respectively. This indicates that the 10000 note is enough and no higher note needed to be issued in that year. Unfortunately, no data of the daily GDP per capita for the year 2022 is available to conduct the analysis. To circumvent this issue, we tried to extrapolate the expected growth rate based on the historical growth rate, under two scenarios. In the first scenario, we used the daily GDP per capita in years 2015 and 2021 to calculate the average growth rate for the period.[1] This was then used to project the future daily GDP per capita on the following years. In the second scenario, we assumed that the growth rate on the daily GDP per capita between years 2020 and 2021 would remain unchanged, and we used this growth rate to project the future daily GDP per capita on the following years. Table (2) reveals the results of applying the D-Metric model based on both of the simulated scenarios. As Table (2) reveals, applying the average growth rate for the period 2015-2021 shows that the issuance of the SP20000 could be done in 2023 and should not be pushed beyond 2024. However, applying the aggressive growth rate, the one that is based on the growth rate of years 2020-2021, reveals that the issuance of the SP20000 could be done in 2022 and should not be pushed beyond 2023.  The fact that the SP10000 could have been issued and put into circulation since year 2020 and that the SP20000 should not be pushed beyond 2023-2024, indicates that the monetary authorities might have to issue both of the banknotes, 10000 and 20000, at one time or within a short time span. This, however, might have adverse outcomes on the inflation levels that are already high!

CONCLUSION AND RECOMMENDATIONS:

The aim of this study was to analyze the denomination structure of the Syrian Pound between 1997 and 2022 and to examine whether the decisions of issuing the higher banknotes (SP1000, SP2000 and SP5000) were justified based on the D-Metric model predictions. The study also aimed to examine whether higher banknotes (SP10000 and SP 20000) need to be issued and put in circulation and what is the appropriate timing for this. The study was mainly motivated by the recent issuance of higher banknotes in Syria along with expectations of further issuance of higher banknotes. When comparing the denomination structure in the examined period with that suggested by the D-Metric model, the findings revealed that the introduction of the higher note, SP1000, in 1997 was premature and should have been postponed to 2005, however the issuance of the SP2000 was on the right timing. The delay however in putting the SP2000 in circulation was not consistent with the outcomes of the D-Metric model. The SP2000 was put into circulation in 2017 when it was appropriate to issue the SP5000. The findings also reveal that the issuance of the SP5000 in 2019 was consistent with the predictions of the D-Metric model. When examining whether a higher banknote, SP10000, should be issued, the D-Metric model suggests that the SP10000 could have been issued and put into circulation since 2020. The high inflation that Syria is facing now tempted us to examine whether the SP20000 should be issued. To overcome the lack of data on daily GDP per capita after 2021, we used two growth scenarios to simulate the daily GDP per capita for the coming years. The findings indicate that the SP20,000 should not be pushed beyond 2023-2024 the latest. The fact that the issuance of the SP20000 should not be pushed beyond 2023-2024 and that the SP10000 could have been issued and put into circulation since 2020 means that the monetary authorities should not delay the issuance of the SP10000 anymore. Otherwise, the monetary authorities might have to issue the two notes SP10000 and SP20000 at the same timing or within a very short time span. This, however, might have detrimental impact on the public confidence in the currency and might trigger higher and higher levels of inflation. Although the analysis was based on the simple and easy to apply D-Metric model, the popularity of the model among central banks and the cross-country empirical evidence that supported its predictions, allow us to utilize it. The findings obtained when applying the model have important implications to the monetary authorities in Syria. They, the findings, indicate that delaying the issuance of a higher note creates further problems in terms of having to issue a further higher banknote soon, which increases the uncertainty in the market and could create higher inflationary expectations. The findings are also of high importance to the public as finding the optimal currency structure enhances the efficiency of cash payment’s settlement. Despite the important findings of the current study, they should be interpreted with caution due to several reasons. First, as highlighted earlier, the D-metric model relates the average daily pay in an economy and the currency denomination structure, however, it does not take into account other factors that affect the denomination structure. This includes amongst other things, the cost structure and economies of scale associated with the printing and minting of a currency, the presence of extra demand on specific denominations, laws and regulations, public’s perception of inflation, etc. The currency denomination structure of a country is also a function of its past economic and political events which is not taken into account by the D-Metric model [12]. Two areas for future research emerge from this study. First, a multidimensional study that takes into account other factors that could affect the denomination structure is needed to get a better understanding of the suitability of the current and future denomination structures. Second, as issuing higher notes could be a response to the higher levels of inflation, the bidirectional relationship between issuing higher notes and inflation would be very informative to the monetary authorities and the public as very little evidence exists on this area.

INTRODUCTION

social networks play a crucial role in the dissemination of information. Social media has changed the way people interact with the news. In the past, people only received news and events, while, on the contrary, social networks transformed people into engaged parties by allowing them to create, alter, and spread the news. Currently, many models have been developed to study information dissemination over social networks. The importance of social media in affecting societies has also been considered. The absence of censorship ^[1] existing in traditional media (magazines and newspapers), makes them promising environment for viral marketing ^[2], rumor breeding ^[3], and crowd control by changing their attitudes, brains, and practices. The contribution of this study is the comparison of four new inspired-based models in terms of their similarity with real data diffusion. We focus on this similarity factor because of its importance in social networks. As networks simultaneously reach billions of connected users, the model must comply with good real-data diffusion criteria to be applicable in real-life cases. This paper is organized as follows: In the next section, we discuss elementary diffusion models and some important definitions, and then introduce the four inspired-based models in more detail to show their capabilities. Next, we present and compare the experimental dataset used to test these models. Finally, we discuss the findings and suggest future work. Our research tries to answer the following question: in terms of performance of the four information diffusion models, which one is the most suited for real data diffusion? This aim reflects the goals of the study in comparing different information diffusion models and assessing their performance against real data, which can be valuable for both academic research and practical applications.

MATERIALS AND METHODS

Elementary Models and Definitions

In this section, we discuss the basic models of diffusion and the basic terms used in the remainder of this study. Social networks ^[4] are intended to disseminate innovations. Kempe et al. ^[5] are the first who model Influence Maximization (IM) through social networks. In this study, Kempe presented an analysis framework that is meant to be the first approximation guarantee for an efficient algorithm to select the most influential node-set. This framework uses the nature of greedy algorithm strategies to obtain a solution that is 63% suitable for the most basic models. Influence maximization ^[4] could be defined by selecting a seed set of nodes where the network reaches the maximum influence according to this set. The target of any influence model is to maximize influence and predict how information dissemination paths can be obtained.

Models Representations

A diffusion model represents the social network as a graph G = (V, E), where G is the graph or network, V represents the vertices that model the users in the networks, and E contains the edges that represent the relation or interaction between users in the corresponding social networks. Many diffusion models have been proposed to mimic information dissemination. Li et al. ^[6] categorized the models into two categories: progressive diffusion models and non-progressive models. In Progressive diffusion models, nodes that are activated or infected by other nodes cannot be recovered or deactivated from the dissemination propagation. Linear Threshold (LT) and Independent Cascade (IC) are examples of these models. Linear Threshold (LT) and Independent Cascade (IC) models are the primary models. LT ^[7] is defined by Granovetter as a node that can be in one of two states (active/inactive) and can be turned from active to inactive based on the activation function, which is the sum of the weights of the neighbor nodes. If the sum exceeds the threshold, then the node turns on active and starts the diffusion process. If the node is not activated on the first attempt, it will remain inactive on the next attempt. The IC model ^[8] is more likely to be LT, but the activation function is based on statistical probability to determine whether the node will be active when propagation starts or whether it will remain inactive. In non-progressive diffusion models, the node might be deactivated after some time of activation and stop propagating the diffusion. Examples of non-progressive diffusion models are typical epidemic disease models like the Voter model ^[6] and the Susceptible-Infected (SI) model ^[9] and their ancestor’s models Susceptible-Infected-Susceptible (SIS) ^[9] and Susceptible-Infected-Recovered (SIR). Kermack at al. proposed the Susceptible-Infected-Recovery (SIR) model ^[10], which is an epidemical model that considers the population as constant, while the nodes could fall into one of three modes: Susceptible where the node can get infected by the disease, Infected where the node is infected by the disease and Recovered where the node has recovered from the disease and will not get infected again. The basic models mentioned above were used in all proposed models.

Related Works

Experiments conducted with actual real-world data have played a crucial role in evaluating the effectiveness and practicality of diffusion models. These investigations highlight the importance of testing models under lifelike conditions, offering valuable insights into the intricate nature of information spread across different situations. Several noteworthy contributions that have enhanced our comprehension in this regard encompass: Ugander et al. ^[11] in their influential study, examined the diffusion of information within the Facebook network. By analyzing the spread of content such as news articles and videos, they compared the observed diffusion patterns with predictions from various models. This work revealed the nuances of information flow within an online social network, shedding light on the models’ capabilities and limitations in capturing real-world dynamics. Myers et al. ^[12] explored the retweeting behavior on Twitter, focusing on how information spreads through the network. By investigating the viral diffusion of tweets and memes, they provided insights into the role of influential users and the temporal dynamics of retweets. This study highlighted the need for temporal considerations in diffusion models and emphasized the significance of early adopters. González-Bailón et al. ^[13] Investigating the diffusion of content across the blogosphere, he examined the interplay between the content’s virality and the network structure. They found that diverse and well-connected blogs are more likely to spread information widely. This study showcased how the characteristics of the dissemination platform interact with the content itself to influence diffusion patterns. Bakshy et al. ^[14] studied the diffusion of news articles on Facebook, revealing the role of social influence and algorithmic curation in shaping the visibility and spread of content. They found that exposure to friends’ interactions with news stories significantly influenced users’ engagement. This work highlighted the interplay between social connections and platform algorithms in information diffusion. Weng et al. ^[15] conducted a comprehensive comparison of different information diffusion models using Twitter data. By analyzing the spread of hashtags, they evaluated the performance of models like Independent Cascade and Linear Threshold in predicting real-world diffusion. This study contributed to the understanding of how different models approximate observed diffusion patterns. Building upon the traditional models, Liu et al. ^[16] introduced a dynamic variation, the Time-Critical Diffusion Model, which incorporated temporal factors for predicting information spread. Their work highlighted the temporal aspect as a crucial component of diffusion modeling, especially in scenarios where the urgency and timing of information propagation play a critical role. Smith et al. ^[17] conducted an empirical study comparing several diffusion models on real-world social network data. Their findings revealed that the performance of models varied significantly depending on the characteristics of the network and the nature of the information being propagated. Additionally, Kumar et al. ^[18] introduced a new model called the modified forest fire model (MFF). Their work is based on the enhancement of an existing model and the introduction of the term ‘burnt’ to represent nodes that stop propagating information. They used real Twitter datasets to compare their model with the SIR and IC basic models to demonstrate the feasibility of their work.

Theory/Calculation

Many studies have focused on models inspired ^{[1, 19-21]} by physics, sociology, mathematics, and so on. In addition, optimizations can be obtained from these inspiration-based models to solve complex computational issues using swarm-based intelligence or to mimic natural phenomena to solve optimization problems.

Diffusion Models

In this study, we focus on four different inspired-based models to demonstrate their ability and the limitations that need to be addressed in future research. These models were selected based on their popularity and the publication dates of their research. Similarity to the diffusion of real data appears to be the most important comparison feature when dealing with social networks. Predicting the diffusion paths of any post or tweet can help in predicting its consequences and effects, the data provenance of rumors after rumor diffusion, or sources of fake news. Table 1 provides a short description of each of the four models.

Immune System-Inspired Information Diffusion Model

The Immune System-Inspired information diffusion model proposed by Liu et al. ^[21], mimics the immune system of the human body. The human immune system attempts to handle and eliminate non-self-material by recognizing microbes and studying their information to decide the best way to deal with them. However, immunity deals with antigens in different ways, using memory to prepare for action, either leaving or trying to eliminate them. This biological structure of immunity resembles the information diffusion process, where antigens represent the information received by users, and antibodies represent the users who receive the information. User responses to information vary from one user to another according to their immune system, which is represented by the fitness function. The fitness function could be formulated according to Liu ^[21] as

Where  and  represents the neighbors of node I and j in time t, when the information is disseminated, respectively. The equation represents the common friends of the node  and  at time .  represents the degree of an entire network while the  is the degree of node .  and  are weighted variables determined by the network structure. The calculation of the fitness function determines whether the value exceeds the activation threshold to start diffusion or is below the threshold to keep the information on the immune list, where it will be ignored. The immune list retains this information as a long-lasting memory to keep discarding it when the body receives it again. Diffusion between persons is not constant, as in other non-inspired models, but it is a dynamic diffusion that varies from one person to another. One of the greatest limitations of this model is that it considers time. Time progress increases the immunity of the nodes and decreases the diffusion process. In addition, this model assumes that all the nodes are simultaneously active, which is not the case in reality. Moreover, this model does not consider the content of the information, which is a critical aspect of diffusion. Different information expressions lead to different diffusion paths. However, this was not considered in the model. This model must find the most influential node with a high degree of connection to accelerate diffusion. The saturation of diffusion of a single node leads this node to lower its immunity and propagate the information forward.

Genetics-Based Diffusion Model

The Genetics-Based diffusion model was proposed by Li et al. ^[20]. The idea behind this model is to use a genetic algorithm (GA) to mimic the diffusion process in social networks. The chromosomes represent the nodes, and the gene represents the message. This model was built on top of the epidemic-spread susceptible-infection model. The main objective of this model is to spread multiple objects with different relationships across various social media platforms despite the other spreading models. The process of this model starts with crossover when the genetic algorithm begins, and the new gene contains the information that will spread across the network. The cross-over may lead to a split of the information which is called information loss. However, this problem is solved by comparing the content of the old genes with that of the new ones to ensure that the information is preserved. The breakpoint is the term meaning that the spread starts slowly until it reaches this point; then, the spread starts increasing rapidly. The computational cost ^[12] of this algorithm is low, because it’s depending on the directed graph where information is passed from the sender to recipients. This imposes to take action if the diffusion must be stopped before reaching this point. A weakness of the proposed model appears when only one message that spreads the information behaves exactly like the way in the Susceptible-infected (SI) model; the model failure appears ^[12] when attempting to spread two contradictory pieces of information as the experiment done by Li, which ends with slowing propagation and making its result unpredictable. The experiment yielded different results when conducted using two independent messages. Therefore, the behavior of this model did not proceed as expected. The best performance appears with dependent information.

Particle-Model of Diffusion

The particle model is inspired by the elastic and inelastic collisions of particles. It is presented by Xia et al. ^[1]. It is based on the particle collision system, where the influence of diffusion is represented by the kinetic energy obtained from the particle collisions, while the user influence is represented by the particle mass. Xia represents this model on a smooth surface to represent the particle collisions on the damping orbit. He ^[1] formulated a model as follows: the user should be considered a mass particle. After a collision in orbit, the user can be in one of three states:

 

Where:   represents the energy particle k obtained from  after the collision.         represents the energy particle k needs to pass the damping track. When the particle has the energy to pass through the damping orbit, it hits other particles and spreads information. The particle stops at the damping track when it has no energy to continue colliding with other particles, so the particle will be in a contracting state. Otherwise, the particle will never collide with the other particles, which represents the user in the inactive mode. The primary feature of this model is to highlight the user’s perspective in information diffusion, where the user’s influence plays a crucial role in the process. This model is based on the Susceptible-infected (SI) model. This model can work with a big network according to the proposed article where he could deal with millions of spreaders and larger networks ^[1]. The weakness of this model is that it varies depending on the initial set that determines its ability to diffuse. Diffusion starts slowly and then grows rapidly with time, and collision continues.

Potential-Driven Diffusion Model

The last model is the Potential-Driven Model, it is proposed by Felfli et al. ^[19]. This model takes advantage of a physically inspired approach. The nodes were represented as particles. The relationship between nodes is represented by the forces between particles. Each particle creates a potential at its location, which determines the influence of forces between nodes in the graph. The proposed architecture can yield good results compared with greedy algorithms, which are used to calculate the seed set to achieve influence maximization (IM) in the network; however, the computational cost of calculating this set is high, to determine the potentials for individual nodes, the net potential algorithm exhibits ^[19] a computational complexity of O(n²), where n represents the network’s size, specifically the number of nodes it comprises. The most resource-intensive step within this process is the calculation of pairwise distances (RSP), as it necessitates the inversion of an n x n square matrix, giving rise to a computational complexity of O(n³), which limits this approach to small networks and makes it infeasible for large networks. The researcher limits the samples of their networks during the experiments to be varying from 250 to 100,000 nodes, because of its highly computational cost. In addition, the features of timestamp, location, topic, and feel add complexity to the selection of seed nodes. This model ^[19] attempts to use the simulation-based approach or the sketch-based approach. The simulation-based approach variation is based on a greedy algorithm and Monte Carlo simulation. The sketch-based approach avoids using the extensive Monte Carlo calculation by using grounded sketches under the dissemination model. The most important feature of the potential-driven model is its ability to mimic the influence between nodes, such as forces between nodes. It uses an approximation to calculate the influence score of the entire network by considering this network as a closed static system of particles. This model is considered an extension of the linear threshold model. Static networks are considered one of the biggest limitations of this model. Tables (2 and 3) presents consecutively the pros and cons of the models mentioned above.

Experiment:

Selecting the diffusion model to be used in any case depends on several factors. These factors vary depending on the model’s capabilities for adapting to large networks, dynamic networks, and similarity to real data diffusion paths. The resemblance between the selected model and real diffusion offers a great opportunity for responsible parties to predict the results and consequences of the diffusion of any posted information on society.

In fake news spreading, the model provides the ability to trace the information after starting the diffusion to locate the false news spreader and take appropriate action to stop the dissemination. We applied the previously listed models to determine which one best fit the real data. We selected a hot topic that has recently arisen, “death of people after boat sinks off”. This information first appeared on Thursday September 22, 2022. We collected 2.1 million blogs from 22^nd September to 30^th September, then we counted the users who discussed this topic. The data collected using the twitter API development by selecting the trends and collected the users and data. The data collected by help from https://www.kaggle.com where the researchers could ask them to collect a data-set. Furthermore, we utilized a data-set sourced from the Twitter social network ^[22], specifically related to the hashtag #Bitcoin. Bitcoin, a decentralized digital currency commonly known as a cryptocurrency, was introduced in 2009 by an individual or group using the pseudonym Satoshi Nakamoto. The dataset encompasses tweets extracted from the period of January 21, 2021, to May 31, 2022, comprising approximately 4,569,721 tweets. In the experiment, we used the set of users who first posted the information on the first day as a seed set (initial value for node activation), and we implemented the four previous models on this data to find the best model for both data-set. The x-axis represents time, and the y-axis represents the number of engaged users in the dissemination of information over time. The similarity of the previous model with real data is shown in Fig.1. and Fig.2.

RESULTS

The findings of our research paper shed light on the performance and effectiveness of four different diffusion models: the Genetic-based Model, Potential-driven Model, Particle Model, and the Immune-based Model. Each model was subjected to rigorous experimentation and evaluation against real-world diffusion data to understand their strengths and limitations in accurately representing information dissemination dynamics in networks.

EXPERIMENT METHODOLOGY

1. Selection of Diffusion Models: We selected four different diffusion models, each presumably designed to represent the spread of information in networks in a unique way. These models are the Genetic-based Model, Potential-driven Model, Particle Model, and the Immune-based Model.
2. Collection and Analysis of Real-world Diffusion Data: we collected real-world diffusion data, which likely includes data on how information (death of people) or trends (Bitcoin) spread through networks. This data serves as the basis for evaluating the performance of the diffusion models.
3. Data Preparation: The real-world diffusion data was likely cleaned and prepared for analysis to ensure its accuracy and relevance.
4. Model Implementation: Each of the four diffusion models was implemented or simulated based on their respective algorithms and methodologies.
5. Comparison and Evaluation: The performance of each model was evaluated by comparing its predictions or simulations with the actual diffusion data.
6. Strengths and Limitations Assessment: As part of the evaluation, our aim was to understand the strengths and limitations of each diffusion model. This would involve identifying where each model excelled and where it fell short in accurately representing the dynamics of information dissemination.

DISCUSSIONS

Genetic-based Model: The Genetic-based Model exhibits a slow diffusion process initially, characterized by a gradual increase in the spread of information. However, it undergoes a turning point where the diffusion rate rapidly accelerates, leading to a swift dissemination of information throughout the network. While this high rhythm in the later stages might seem promising, it fails to align well with the actual diffusion data. The model’s behavior deviates significantly from the observed real-world diffusion patterns, making it less suitable for capturing the intricacies of information propagation in networks. This model suffers from the overfitting, when the model is trained, it learns to fit the training data as closely as possible, aiming to minimize errors and discrepancies between the model’s predictions and the actual data points. However, overfitting occurs when the model becomes too specialized in capturing the noise and intricacies present in the training data, rather than learning the underlying patterns or relationships.

Potential-driven Model: In contrast to the Genetic-based Model, the Potential-driven Model does not fit well with the real diffusion process at the outset. In the early stages of diffusion, the model exhibits discrepancies with the actual data, indicating its limited accuracy in capturing the initial spread of information. However, as the diffusion progresses towards its final stages, the Potential-driven Model starts to converge and better matches the real data. This suggests that the model’s performance improves in the later stages of diffusion, but it may not be the most reliable choice for predicting the early stages of information dissemination. This model is designed to work over Static networks where they refer to networks that do not account for the dynamic nature of relationships and interactions in real-world social networks. In reality, social networks are often highly dynamic, with relationships forming, evolving, and dissolving over time. This static representation can oversimplify the complex, evolving nature of real social networks.

Particle Model: The Particle Model demonstrates some resemblance to real diffusion, showcasing numerous conversions observed in the experiment across various diffusion paths. This indicates that the model is capable of capturing some essential aspects of information propagation in networks. However, it falls short in accurately representing the complete diffusion process, as there are still notable disparities between the model’s behavior and the observed real-world diffusion dynamics. The identified problem of this particular model lies in its sensitivity to the initial set, a factor that significantly impacts its diffusion characteristics. When the model is initiated with different sets of conditions or parameters, it exhibits varying behavior, thereby influencing its effectiveness in spreading information or influence throughout the network.

Immune-based Model: Among all the models tested, the Immune-based Model stands out as the best fit for the real diffusion process. It showcases remarkable accuracy in mimicking the spread of information across networks, consistently aligning with the observed real-world diffusion patterns. The Immune-based Model’s success is attributed to its adaptive learning mechanism, inspired by the human immune system, which enables it to identify and target influential nodes in the network effectively. This adaptive behavior allows the model to make precise predictions and accurately capture the complex dynamics of information dissemination in various network structures. In conclusion, the Immune-based Model emerges as the most promising candidate among the tested models for modeling information dissemination dynamics in networks accurately. Its ability to adaptively learn and replicate real-world diffusion processes positions it as a valuable tool for various applications, such as social media analysis, viral marketing campaigns, and epidemic spread prediction. These findings contribute to the advancement of research in network information propagation and provide essential insights for developing effective strategies to influence and control information flow in interconnected societies. However, further investigations and refinements of the other models may offer valuable insights into their potential applications in specific scenarios and provide a comprehensive understanding of their strengths and limitations.

CONCLUSIONS

The primary aim of this study was to conduct a comparative analysis of various inspired-based diffusion models. Four distinct models, namely immune-inspired, genetic-based, potential-driven, and particle collision, were evaluated based on their similarity to the diffusion patterns observed in real social networks. Through meticulous experimentation and analysis, the study conclusively determined that the immune-based diffusion model exhibited the closest fit to the actual information dissemination in social media applications.

RECOMMENDATIONS

As we move forward, future research endeavors should seek to capitalize on the strengths of each of the aforementioned models. By integrating the best aspects of these models, researchers can strive to develop a more comprehensive and refined diffusion model that is exceptionally well-suited for real-life scenarios. Moreover, addressing the performance bottleneck becomes crucial, with time emerging as a pivotal factor when dealing with the rapid spread of rumors across social media platforms. In summary, the ultimate goal is to design an enhanced diffusion model that not only accurately captures the intricacies of information propagation in social networks but also efficiently addresses the time-sensitive nature of handling misinformation and rumors on these platforms. By achieving this, we can significantly contribute to the advancement of strategies to combat misinformation and uphold the integrity of information shared through social media channels.