Reducing saturation and congestion in VANET networks: Alliance‐based approach and comparisons

A vehicular ad hoc network (VANET) is composed mainly of fixed roadside entities (RSUs) and mobile entities (vehicles). In order to exchange information and data relating to the safety and comfort of road users, these different entities must establish communications between them. In these communications, one of the main problems is related to congestion and saturation of RSUs. In this paper, we first study the main protocols that involve RSUs in their strategy of routing by classifying them according to four levels. Furthermore, to deal with the problem of saturation of RSUs, we present a new approach of cooperation between the RSUs of a VANET in order to reduce its congestion and avoid as much as possible the saturation of these entities. This approach, called “D2A2RS” (defensive alliance–based approach for reducing RSUs saturation), is based on the concept of defensive alliances in graphs that ensures effective collaboration between RSUs. To evaluate the performance of the proposed approach, we conduct a comparative analysis by using both analytical models and simulations. The obtained comparison results have shown the efficiency and the performance of our approach compared with other concurrent approaches in the literature in terms of packet loss/success rate, end‐to‐end transmission delay, and network scalability.     

Variation of the specific surface area and porosity of anhydrous zinc oxalate with water vapour pressure

Specific surface areas and pore structure studies were carried out on two sets of samples of anhydrous zinc oxalate prepared from the dihydrate by heating at 130 and 180°C in various atmospheres of differing water vapour pressure. The two sets of samples were freshly prepared and aged samples. The variation of specific surface areas with water vapour pressure was found to behave in accordance with the Smith-Topley effect, with a minimum S_BET value located at 3.0 mmHg of water vapour. Analysis of the nitrogen adsorption isotherms by the t-method revealed the existence of both micropores and mesopores in the freshly prepared samples heated both at 130 and 180°C in 8.0 mmHg water vapour, and also in the aged samples prepared at 130°C in vacuo, and at 180°C in 8.0 mmHg water vapour. The rest of the samples possess only wide pores. Complete pore structure analysis for both micro- and mesopores was carried out for all samples investigated, and an attempt was made to correlate the factors affecting the development of surface area and pore structure, both in the presence and absence of water vapour, with those affecting the dehydration rate, and which occasionally lead to the Smith-Topley effect.     

The impact of cooling water types on the cement clinker properties

This paper studied the influence of the different water types on clinker properties. It concern with cement plants which are using the water for cooling the clinker (El-Minia white cement plant). The water types are Nile, ground and deionized water. The cooling was mad suddenly for clinker by three water types at the same time. The paper discusses the physical and chemical analysis and algal detection of all water types. It also discusses the chemical and physical analysis for kiln feed, clinker. The analysis of water showed that the concentration of dissolved salts in groundwater is higher than Nile water. The concentration of algae gave opposite direction; the algae concentration in Nile water is higher than groundwater. While the deionized is completely free from dissolved salts and algae. The cement tests for clinker which treated by the different water types showed that the cement strength was reducing when used the Nile water with high algae count. From another side, the high concentration of dissolved salts in groundwater does not affect on strength. The water contained the algae prevent the complete crystallization of calcium silicate for clinker. The results also showed that the best type of water, which improved cement compressive strength ranged according to algae count by the sequence deionized water > groundwater > Nile water.     

Investigation of the candesartan cilexetil antihypertensive drug microencapsulation by PLA-PVP K30 biodegradable polymers: Experimental optimization and release kinetics modelling

Candesartan is an angiotensin receptor blocker (ARB) used to treat hypertension. However, its poor aqueous solubility and oral bioavailability have limited its therapeutic applications. In order to increase bioavailability and control the release of candesartan condensation, microspheres containing biodegradable polymers (polyvinylpyrrolidone [PVP K30] and polylactic acid [PLA]) in different ratios were prepared by the o/o solvent evaporation method using Span 80 as a surfactant. In addition, the impact of encapsulation parameters (i.e., PVP K30 and PLA concentrations) on the encapsulation ratio and release percentage was investigated by the mixed factorial design method. The release kinetics of the microspheres was simulated by combining two methods, the Dragonfly algorithm and a support vector machine (DA-SVM). The experimental data were in good agreement with the predicted data, with a coefficient of determination close to unity and a mean square error close to zero. Fourier-transfer infrared spectrometry (FTIR) analysis revealed the presence of condensation in all formulations without reporting distortion in the spectra. Scanning electron microscopy (SEM) confirmed the successful synthesis of microspheres, whose sizes were between 12 and 26 μm. Formulations with a PLA-drug ratio of 6:1 (N15, N17, and N18) showed the highest encapsulation efficiency (68%, 71%, and 70%, respectively), while formulations that do contain PVP K30, such as N5, N4, and N3, showed a higher release (83%, 84%, and 89%, respectively), indicating that the agent (PVP K30) enhanced the bioavailability and release of candesartan. Overall, N3 showed a higher drug release rate at 12 h and important encapsulation efficiency, making it the optimal formulation obtained in this study.     

Activated nitriles in heterocyclic synthesis: Novel Synthesis of Pyrimidine and of Pyridine Derivatives

α-Cyanochalcone reacted with thiourea and guanidine to yield the corresponding pyrimidine derivatives 2 and 4 . On the other hand, urea reacted with the same reagent under the same experimental conditions to yield the known urea derivatives 3 . A new synthesis of polyfunction pyridine via reaction of 1a with malononitrile in presence of aniline could be developed. Similar to the behaviour of 1a , Compounds 1b , c reacted with malononitrile in presence of aniline to yield compounds 8 and 9 . In contrast to the behaviour of compounds 1a – c , 1d reacted with malononitrile to yield the malononitrile derivatives 10 or 11 based on the reaction conditions. Mechanisms to account for formation of the reaction products were suggested.