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The objective of this paper is to investigate the effect of using nano-additives on some geotechnical properties of expansive soils. The investigated soils were quarried from three different sites in the south of Syria. The nano-additives were nano-natural pozzolana (NVS) and nano-lime (NL). NVS was added at three percentages, i.e., 0%, 1% and 2%, whereas NL was added at 0.6%. The examined geotechnical properties were Atterberg limits, swelling and shrinkage properties, unconfined compressive strength (UCS), California bearing ratio (CBR) and shear strength. From the test results, the positive effect of adding NVS to the original soil has been clearly seen. Plasticity index (PI) was reduced by more than 50% when 2% NVS was added. Further, all investigated properties have significantly been improved when NVS and NL were added together, i.e., UCS, CBR and shear strength characteristics increased to more than twice, 20-fold and about 50%, respectively, when compared with those of the original soil. Some relationships among the soil characteristics were also developed. Thus, one can predict, for instance, the CBR value from the knowledge of UCS’ result, which is easy to be obtained. Advanced technics such as SEM and EDX were employed in the current study as well. The microstructural analysis revealed that cementitious compounds could be easily traced in all treated soil mixtures, particularly those containing both NVS and NL.

The synthesized glass system with a composition of (80-x) TeO2-10P2O5-10Nb2O5-xKCl mol% (where x = 5, 10, 15, 20, and 25) was successfully fabricated. The density (ρ) and molar volume (Vm) have been calculated. The investigated glasses were characterized using different analysis methods (differential thermal analysis (DTA) and UV-VIS-NIR spectroscopy). The radiation shielding effectiveness of the synthesized glass system was evaluated using different shielding parameters, such as mass and linear attenuation coefficients (MAC, LAC), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), and effective electron number (Neff). The results showed that with the increasing potassium chloride (KCl) concentration and decreasing tellurium oxide (TeO2) concentration, the density, refractive index, Urbach energy (Eu), and glass transition temperature (Tg) decreased, while the optical energy gap (Eopt) and thermal stability increased. As the KCl concentration increases, the values of MAC, LAC, and Zeff increase in the following order: TPNK5 % > TPNK10 % > TPNK15 % > TPNK20 % > TPNK25 %. Additionally, the shielding effectiveness of TPNK glass system showed good performance compared with some standard materials. The synthesized glass with a minimum KCl content has both good shielding effectiveness and good optical properties, in addition to reasonable thermal stability, which makes it suitable for shielding and optical applications.

The present study was carried out to evaluate the prevalence of mycotoxins (Deoxynivalenol (DON), Zearalenone (ZEA), Aflatoxin B

Load balancing is a very important and complex problem in computational grids. In load balancing, jobs should be effectively distributed among resources in order to minimize the average completion time and maximize the utilization of all resources even those with low reliabilities and capacities. However, using the less reliable and slow resources implies worse completion time, whereas always selecting the powerful and reliable resources undermines the utilization of other resources. So, it is essential to develop an efficient load balancing method which makes a good tradeoff between these criteria in a way that satisfies the quality of service of jobs and fairly distributes jobs between resources based on their reliabilities and capacities. This paper proposes an efficient multicriteria load balancing method using technique for order preference by similarity to ideal solution which treats load balancing as a multi criteria decision making problem. Also, an effective weighting mechanism is proposed, which adaptively adjusts the weights of the considered criteria according to the system’s current state and jobs’ characteristics. This mechanism can make an efficient tradeoff between the considered criteria and accurately reflect the importance of each one. By simulation, the proposed method was evaluated and compared with other approaches from the literature. In the range of examined parameters’ values, the simulation results show that proposed method minimizes the average completion time by 8.7–15.7%, increases the throughput ratio up to 15.8–19.4%, and maximizes the load balancing level by 7.68–20.1%.

This study investigates the relation between dividends payout and earnings predictability of firms listed on the Egyptian Stock Exchange as an emerging African market. We depend on a sample of firms listed on the Egyptian stock exchange (EGX100) during 2014-2018. To test the hypotheses, we use two independent sample t-test and OLS regression. The principal analysis revealed that dividends payout improves the ability of current earnings to forecast firms’ future earnings. Results also indicated that dividends payout could enhance the ability of current earnings to forecast one year-ahead cash flow. To the best of our knowledge, this is the first study that examines the implications of dividends payout on earnings predictability in the Egyptian market. The findings present new insights to investors, researchers, and regulators concerned with agency conflicts of interest within the firm. It also presents evidence on the potential alternative mechanisms for decreasing agency costs in African emerging markets. Received: 8 April 2022 / Accepted: 4 August 2022 / Published: 2 September 2022

CaCO3 nanoparticles were synthesized from CaCl2 and Na2CO3 using a new, fast and straightforward technique. Factors affecting on the particle size such as the concentration of Ca2+ and CO32-, PEG weight dissolved in Ca2+ solution, flow rate, temperature, media type, PEG weight dissolved in the used medium, the concentration of CO32-, stirring speed, medium volume and additive dissolved within Ca2+ solution were investigated. The obtained particles were characterized by SEM, XRD, EDS, IR and TGA. The characterization clarified that the particles prepared were spherical with a size range of 19-30 nm, ultra-pure, and calcite. Moreover, the preparation system was redesigned to be a continuous preparation system. The histogram showed that the CaCO3 nanoparticles obtained were homogenous in size (30 nm). Finally, the obtained nanoparticles were utilized in the preparation of nanoporous PVC film with pores size range 80-120nm

Premature loss of posterior primary teeth necessitates space maintaining to prevent space loss and compromising the dentition. Conventional stainless steel band-and-loop space maintainer (BL-SM) is a non-invasive device commonly used to maintain space after the early loss of a single deciduous tooth until the permanent tooth erupts. However, these devices require laboratory work, consume time, and are relatively expensive. Clinically, they tend to fracture, bend or debond under occlusal forces, and they are not considered esthetic. Thus, alternatives to the BL-SM have been investigated. The fiber-reinforced composite space maintainer (FRC-SM) has various advantages and has been suggested as an alternative to the BL-SM. The aim of this review is to explore the survival rate of FRC-SM reported in the literature. We have found a wide variation in the reported results, with promising results shown for FRC-SM, especially over short periods. Therefore, longer follow-up periods, placement techniques and clinical effectiveness with respect to this type of space maintainer need to be further evaluated.

The objective of this research was to investigate the effect of adding thermally treated clay on some engineering properties of the untreated expansive clayey soil. Three expansive clayey soil samples obtained from three different sites in the south of Syria have been investigated. They were thermally treated up to three different levels (450°C, 650°C and 850°C) for 3 hours. Three replacement levels of thermally treated clay were used, i.e. 0%, 10% and 20%. The X-ray diffractometer (XRD) technique has been used to detect the crystalline and glassy phase in the clayey samples before and after the thermal treatment. Pozzolanic activity of the thermally treated clayey soil has been studied using the modified Chapelle test and the mechanical strength test at each of the temperature levels. Atterberg limits, compaction, free swell, swelling pressure and linear shrinkage have particularly been investigated. Test results revealed the positive effect of thermally treated clay when added to the natural soil. Plasticity index (PI) was reduced by about 60% when 20% thermally treated clay was added to the natural soil. In addition, 6% lime was added to further investigate the combined effect of lime and calcined clay on the properties of the clayey expansive soil. All investigated properties were significantly improved when 20% thermally treated soil and 6% lime were added together. For instance, swelling pressure and linear shrinkage values were reduced to less than 15% or even much less when compared with those of the natural soil. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis were employed as well.

Although the hierarchical model appears to be an effective solution to organize the resource managements in grid systems which have more stringent demand for both scalability and efficiency, it has some limitations which need to be addressed. For example, the master/manager resources in different levels represent single points of failure and they may be sources of bottleneck and communication overhead especially if they are not efficiently selected. Moreover, the dynamic and fault-prone nature of grids cannot be treated by static structures while the manual construction and repairing are also prohibitive due to the highly caused overhead which often represents a significant obstruction to an efficient resource utilization (especially for those with intermittent availabilities). The main objective of this paper is to first introduce a self-repairing n-try dynamic hierarchical grid model for scheduling and load balancing in which each master resource will be replicated on one of its children resources. Second, an efficient methodology to elect masters–replicas resources is proposed. In this methodology, the masters–replicas are selected based on both resource reliability (in terms of MTBF) and resource proximity from the other nodes in specified groups (in terms of communication latency). Validation of the proposed methodology based on the proposed model is done via simulation. Experimental results show that the proposed model has a great impact on the overall performance. Compared to other approaches, the simulations show that our approach decrements the average completion time ( A C T ) by 18.9%–25%, increases the tree stability ratio ( T S R ) up to 26.2%–27.1%, and minimizes the total communication overhead ( T C O ) by 4.4%–18.7% in the range of system parameter values examined.

Natural pozzolan is being widely used as cement replacement. Despite the economic, ecological, and technical benefits of its adding, it is often associated with shortcomings such as the need of moist-curing for longer time and a lower early strength. This study is an attempt to investigate the effect of adding limestone filler on the compressive strength and durability of mortars/concrete containing scoria. Sixteen types of binders with different replacement levels of scoria (0, 10, 20, and 30%) and limestone (0, 5, 10, and 15%) were prepared. The development of the compressive strength of mortar/concrete specimens was investigated after 2, 7, 28, and 90 days’ curing. In addition, the acid resistance of the 28 days’ cured mortars was evaluated after 90 days’ exposure to 5% H2SO4. Concrete permeability was also evaluated after 2, 7, 28, and 90 days’ curing. Test results revealed that there was an increase in the early-age compressive strength and a decrease in water penetration depths with adding limestone filler. Contrary to expectation, the best acid resistance to 5% H2SO4 solution was noted in the mortars containing 15% limestone. Based on the results obtained, an empirical equation was derived to predict the compressive strength of mortars.

The objective of this study is to investigate the efficiency of volcanic scoria when added to the concrete binder at a nano-scale. Nano volcanic scoria (nano-VS) was obtained by grinding a local volcanic scoria for 6 h. Twenty-four concrete mixes with four w/b ratios (0.4, 0.5, 0.6 and 0.7) and six-replacement levels of nano-VS (0%, 1%, 2%, 3%, 4%, and 5%) have been produced. The investigated concrete properties were the compressive strength, the water penetration depth, the concrete porosity and the chloride ion permeability. Workability of fresh concrete mixes has been also determined. The efficiency factor (k) of nano-VS in terms of compressive strength was calculated using the Bolomey equation. Durability indicators have been used to globally evaluate the behavior of nano-VS-based binder concrete versus control concrete. The results revealed that the efficiency factor (k) decreased to some extent when the nano-VS content was bigger than 4%. The calculated durability indicators showed that the nano-VS contents of 3% and 4% had approximately the highest indicators values. These indicators would be helpful for concrete mix designers. Some correlations between the investigated properties were derived from the analyzed data. The modification of the microstructure of nano-VS-based cement paste has been observed, as well.

Clayey soils in Syria cover a total area of more than 20,000 km 2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastructures. Extensive studies have been carried out on the stabilization of clayey soils using lime. Syria is rich in both lime and natural pozzolana. However, few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils. The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils. Natural pozzolana and lime are added to soil within the range of 0%–20% and 0%–8%, respectively. Consistency, compaction, California bearing ratio (CBR) and linear shrinkage properties are particularly investigated. The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent. Analysis results of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) show significant changes in the microstructure of the treated clayey soil. A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.

This corrigendum corrects the following error. There was a missing reference in the reference list. This has been included as reference 18. [18] Al-Swaidani A M, Hammoud I., al-Ghuraibi I and Mezyab A 2019 Nanocalcined clay and nanolime as stabilizing agents for expansive clayey soil: Some geotechnical properties Advances in Civil Engineering Materials 8(3) 327-345 [19] Gueddouda M K, Goual I, Lamara M and Mekarta B 2011 Chemical stabilization of expansive clays from Algeria Global J. of Researches in Engineering: J. General Engineering 11(5) 1-8 Reference 18 should have been referred to at the following points. [20] Kariuki PC, Shephered K D and Van Der Meer F D 2006 Spectroscopy as a tool for studying swelling soils. In: alRawas AA, Goosen, MFA editors Expansive soils-recent advances in characterization and treatment 15-24 (London, UK: Taylor and Francis Group) Table 1. The reference [18] should have been indicated in the caption Figure 2(a), Figure 2(b) and Figure 2(c). The reference [18] should have been indicated. Figure 7 the reference [18] should have been indicated. The reference (Gueddouda et al.) numbered as 18 in the older copy was corrected to 19. See the selection of the reference list above. Figure 8 should include a reference to [18]. Figure 9. The reference [18] should be indicated. The reference (Kariuki et al.) numbered 19 in the older copy was corrected in this version to 20. See attached reference list above. Table 4. The reference [18] should have been indicated References list Reference [18] was added in this version. See above list.