Evaluating the Impact of Transmission Range on the Performance of VANET

Recently, interest in the field of Vehicular Ad-hoc Networks (VANETs) has grown among research community to improve traffic safety and efficiency on the roads. Despite the many advantages, the transmission range in vehicular network remains one of the major challenges due to the unique characteristics of VANETs such as various communication environments, highly dynamic topology, high node mobility and traffic density. The network would suffer from a broadcast-storm in high vehicular density when a fixed transmission range in VANET is used, while in sparse vehicular density the network could be disconnected frequently. In this paper, we evaluated the impact of different transmission ranges and number of flows formed between vehicles in a highway scenario using AODV as routing protocol. In order to validate the simulation of VANET, traffic and network simulators (SUMO & NS-2) have been used. The performance was evaluated in terms of packet delivery ratio and end-to-end delay. The simulation results have shown that better performance was achieved in term of higher PDR and lower end-to-end delay for less than 500 meters transmission range. On the contrary, the PDR started to decrease and end-to-end delay increased when the transmission range exceeded 500 meters. The performance degraded as the number of flows increased

The effect of the petrography, mineralogy, and physical properties of limestone on Mode I fracture toughness under dry and saturated conditions

Determining the fracture toughness of rock materials is a challenging, costly, and time-consuming task, as fabricating a sharp crack in rock specimens will lead to failure of the specimen, and preparing specimens for determining the rock fracture toughness requires special equipment. In this paper, the relationship between mode I fracture toughness (KIC) with the rock index properties, mineralogy, and petrography of limestone is investigated using simple nonlinear and simple/multiple linear regression analyses to provide alternative methods for estimating the fracture toughness of limestones. The cracked chevron notched Brazilian disk (CCNBD) method was applied to 30 limestones with different petrographic and mineralogical characteristics under both dry and saturated conditions. Moreover, the index properties of the same rocks, including the density, porosity, electrical resistivity, P and S wave velocities, Schmidt rebound hardness, and point load index, were determined. According to the statistical analyses, a classification based on the petrography of the studied rocks was required for predicting the fracture toughness from index properties. By classifying the limestones based on petrography, reliable relationships with high correlations can be introduced for estimating the fracture toughness of different limestones using simple tests. © 2022 by the authors

A Comprehensive Performance Analysis of IEEE 802.11p based MAC for Vehicular Communications Under Non-saturated Conditions

Reliable and efficient data broadcasting is essential in vehicular networks to provide safety-critical and commercial service messages on the road. There is still no comprehensive analysis of IEEE 802.11p based MAC that portrays the presence of buffer memory in vehicular networks. Besides, most of the analytical works do not fulfill some of the IEEE 802.11p specifications, such as short retry limit and back-off timer freezing. This paper proposes a 1-D and 2-D Markov model to analyze mathematically IEEE 802.11p based MAC for safety and non-safety messages respectively. The work presented in this paper takes into account the traffic arrival along with the first-order buffer memory and freezing of the back-off timer as well, to utilize the channel efficiently and provide higher accuracy in estimation of channel access, yielding more precise results of the system throughput for non-safety messages and lower delay for safety messages. Furthermore, back-off stages with a short retry limit were applied for non-safety messages in order to meet the IEEE 802.11p specifications, guaranteeing that no packet is served indefinitely, avoiding the overestimation of system throughput. A simulation was carried out to validate the analytical results of our model

YEMENI WAR AND SHIFT OF POWER: A REFLECTION ON THE HISTORY OF SOUTHERN ISSUE AND POSSIBLE SCENARIOS IN SOUTH

This paper sheds some light on the Southern Issue with reference to 2015 war in Yemen and shift of power. It has briefly surveyed the history of Southern Issue and the conflict relating to this issue, passing by 2015 war and shift of power. It has presented the history of this period impartially and neutrally and then reflected on the possible political scenarios in South Yemen in the light of the present war. It concluded with some recommendations that may help the concerned politicians involved in the Yemeni crisis to bring peace and stability to Southern Yemen particularly and Yemen generally.  Article visualizations

Modeling and analysis of IEEE 1609.4 MAC in the presence of error-prone channels

Vehicular Ad Hoc Networks (VANETs) have been developed to improve the safety, comfort and efficiency of driving on the road. The IEEE 1609.4 is a standard intended to support multi-channel in VANETs. These channels include one control channel for safety applications and six service channels for service applications. However, there is still no comprehensive analysis for the average delay and system throughput of IEEE 1609.4 MAC in VANETs considering error-prone channel under non-saturated conditions. In this paper, we propose an analytical models based on 1-D and 2-D Markov chain to evaluate the performance analysis of IEEE 1609.4 MAC in the presence of error-prone channels. Besides, freezing of the back-off timer is taken into consideration to provide an accurate estimation of access to the channel. The simulation results have been carried out to validate the analytical results of our model. The results show that the performance of our model outperforms the existing model in terms of packet delivery ratio and average delay of safety packets over CCH, and system throughput of service packets over SCHs

العوامل المؤثرة في تقبل الفصول الافتراضية لدى طلبة كلية التربية الأساسية بالكويت في ضوء نموذج قبول التقنية TAM - Factors influencing the acceptance of virtual classes among students of the Faculty of Basic Education in Kuwait in light of the TAM technology acceptance model

من أهم معايير نجاح استخدام التكنولوجيا في التعليم هو رضى المستفيدين منها وتقبلهم لها. لذا هدف هذا البحث إلى الكشف عن العوامل المؤثرة على تقبل الفصول الافتراضية لدى طلبة كلية التربية الأساسية في دولة الكويت في ضوء نموذج قبول التقنية TAM . ولتحقيق أهداف البحث واختبار فرضياته، تم استخدام المنهج المسحي، واختيار عينة قصدية بلغت ) 400 ( من طلبة كلية التربية الأساسية في الكويت خلال الفصل الأول من العام الجامعي 2018 - 2019م، وتمثلت أدوات البحث في إعداد وتصميم استبانة تكونت من ثلاثة أجزاء رئيسية، وبعد جمع بيانات البحث وتحليلها احصائياً أثبتت النتائج وجود علاقة إيجابية بين النية لاستخدام الفصول الافتراضية وعوامل الفائدة المحققة وسهولة استخدام تقنية التعليم المتاحة في الفصول الافتراضية لدى طلبة كلية التربية الأساسية في الكويت، وكذلك علاقة إيجابية بين العوامل المستقلة) الدعم الفني، التفاعل في التعليم، والكفاءة الذاتية (والفائدة المحققة، وسهولة استخدام تقنية التعليم المتاحة في الفصول الاف تراضية لديهم، وعلاقة إيجابية أيضاً بين العوامل المستقلة الدعم الفني، التفاعل في التعليم والكفاءة الذاتية( ونية الطلبة حول استخدام الفصول الافتراضية من خلال الفائدة المحققة وسهولة الاستخدام كعوامل وسيطة لدى الطلبة، إلا أنه لا يوجد تأثير لنوع جنس الطلبة في قبولهم لاستخدام التقنيات المتاحة في الفصول الافتراضية، ويوجد تأثير للخبرة في ذلك، وتم الانتهاء بذكر عدد من التوصيات التطبيقية لنتائج البحث. ***************************************************************************** The successful use of technology in education relies primarily on the satisfaction and acceptance of its beneficiaries. This research aims to reveal the factors influencing the understanding of students of Faculty of Education in Kuwait for the virtual classrooms in the light of their acceptance for the TAM Technique. Survey methodology and selection of 400 students from Faculty of Education in Kuwait as a sample during the first semester in the academic year 2018-2019 are two methods used to achieve the goals of the research and test its hypotheses. The research develops a questionnaires consists of three major parts. After collecting and analysing the data statistically ,the results proves that there is a positive relationship between the intent of using virtual classrooms, usefulness factors and the ease of using technical education in virtual classrooms for the students in Faculty of Education in Kuwait. The research also shows that there is a positive relationship betweet the independent factors such as (technical support, interactions in teaching and self-efficacy) and the usefulness and the ease of using technical education in virtual classrooms for the students. Another positive relationship is discussed by this research connects the independent factors (technical support , interactions in teaching and self-efficacy) , the students' intention of using the virtual classrooms through the usefulness and the ease of use as a feedstock for them. Besides , it is indicated that the gender of the students has no effection in their acceptance for using the information technology in virtual classrooms however the experience palys a vital role in that. The research concludes with a mention of some applied recommendations for the results of this research

Characterization and frequency of a newly identified HIV-1 BF1 intersubtype circulating recombinant form in São Paulo, Brazil

Background: HIV circulating recombinant forms (CRFs) play an important role in the global and regional HIV epidemics, particularly in regions where multiple subtypes are circulating. To date, several (>40) CRFs are recognized worldwide with five currently circulating in Brazil. Here, we report the characterization of near full-length genome sequences (NFLG) of six phylogenetically related HIV-1 BF1 intersubtype recombinants (five from this study and one from other published sequences) representing CRF46_BF1.Methods: Initially, we selected 36 samples from 888 adult patients residing in São Paulo who had previously been diagnosed as being infected with subclade F1 based on pol subgenomic fragment sequencing. Proviral DNA integrated in peripheral blood mononuclear cells (PBMC) was amplified from the purified genomic DNA of all 36-blood samples by five overlapping PCR fragments followed by direct sequencing. Sequence data were obtained from the five fragments that showed identical genomic structure and phylogenetic trees were constructed and compared with previously published sequences. Genuine subclade F1 sequences and any other sequences that exhibited unique mosaic structures were omitted from further analysisResults: of the 36 samples analyzed, only six sequences, inferred from the pol region as subclade F1, displayed BF1 identical mosaic genomes with a single intersubtype breakpoint identified at the nef-U3 overlap (HXB2 position 9347-9365; LTR region). Five of these isolates formed a rigid cluster in phylogentic trees from different subclade F1 fragment regions, which we can now designate as CRF46_BF1. According to our estimate, the new CRF accounts for 0.56% of the HIV-1 circulating strains in São Paulo. Comparison with previously published sequences revealed an additional five isolates that share an identical mosaic structure with those reported in our study. Despite sharing a similar recombinant structure, only one sequence appeared to originate from the same CRF46_BF1 ancestor.Conclusion: We identified a new circulating recombinant form with a single intersubtype breakpoint identified at the nef-LTR U3 overlap and designated CRF46_BF1. Given the biological importance of the LTR U3 region, intersubtype recombination in this region could play an important role in HIV evolution with critical consequences for the development of efficient genetic vaccines.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Hemoctr, Fundacao Prosangue, São Paulo, BrazilUniversidade Federal de São Paulo, Retrovirol Lab, São Paulo, BrazilUniversidade Federal de São Paulo, Retrovirol Lab, São Paulo, BrazilFAPESP: 06/50096-0FAPESP: 2004/15856-9FAPESP: 2007/04890-0Web of Scienc

Prevalência, fatores de risco e caracterização genética dos vírus linfotrópico de células T humana tipo 1 e 2 em pacientes infectados pelo vírus da imunodeficiência humana tipo 1 nas Cidades de Ribeirão Preto e São Paulo

The aim of this study was to define the prevalence of human T cell lymphotropic virus types 1 and 2 in patients who were positive for human immunodeficiency virus type 1 in the State of Sao Paulo, Brazil. We evaluated 319 individuals infected with HIV type 1 who were attended at specialized clinics in two cities (Ribeirao Preto and Sao Paulo). The patients were interviewed and tested for antibodies against HTLV types 1 and 2 (Ortho HTLV-1/HTLV-2 Ab-Capture enzyme immunoassay). Direct DNA sequencing of polymerase chain reaction products from the tax region of HTLV type 2 and the long terminal repeat region of HTLV types 1 and 2 were performed to differentiate and determine the subtypes. The overall prevalence of anti-HTLV type 1 and 2 antibodies was 7.5% (24/319; 95% CI: 5.2-11.5). HTLV type 1 and 2 infection was associated with a history of injected drug use and with antibodies for hepatitis C virus (p 0.05). HTLV DNA was detected in 13 out of 24 samples, of which 12 were characterized as HTLV subtype 2c and one as HTLV subtype 1a. Among the 12 HTLV type 2 samples, seven were from injected drug users, thus indicating that this route is an important risk factor for HTLV type 2 transmission among our population infected with HIV type 1.Fundacao Pr6 Sangue, Hemoctr Sao Paulo, BR-05403000 Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Lab Retrovirol, Dept Doencas Infecciosas & Parasitarias, Sao Paulo, BrazilSecretaria Estado Saude Sao Paulo, Ctr Referencia & Treinamento DST Aids, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Lab Retrovirol, Dept Doencas Infecciosas & Parasitarias, Sao Paulo, BrazilWeb of Scienc

Norovirus Genotypic Variability in Brazil

Norovirus (NoV) has been recognized as the most common etiological agent of acute gastroenteritis (AGE) in various epidemiological settings worldwide. The virus displays a high genetic diversity that can be classified into genogroups, genotypes, and recombinant strains. Only genogroups I, II, and IV have been found to infect humans. Variants of genogroup II genotype 4 are the most widely circulating strains and have been responsible for all NoV outbreaks globally since the mid-1990s. Several studies from different Brazilian regions have been conducted to detect and genetically characterize NoV from sporadic AGE cases and outbreaks. In this chapter, we have summarized the data that focused on the genetic variabilities of NoVs and thus highlight the value of a surveillance system in assessing not only the true burden of the disease, but also the detection and characterization of emerging novel variants