Evaluation of SIP Signalling and QoS for VoIP over OLSR MANET Routing Protocol

Abstract: This paper evaluates the SIP based VoIP applications over the Optimized Link State Routing protocol (OLSR) as a proactive routing protocol for Mobile Ad Hoc Networks (MANET) using Static, Uniform, and Random mobility models. The evaluation considered PCM, LQS, IPTelephony, and GSM voice codecs to study the SIP signaling performance and the voice Quality of Service (QoS) for VoIP calls over OLSR MANET. The simulation efforts performed in OPNET Modeler 17.1. The results show that VoIP over OLSR MANET has good performance over Static and Uniform mobility models while it has variable performance with Random models. SIP signaling has large delays compared with the voice signaling which reduce the VoIP performance and increases the call's duration. In addition, GSM and LQS based VoIP calls have an acceptable level of QoS while PCM and IP-Telephony based VoIP calls have a low level of QoS over different types of mobility models. Furthermore, the location and the mobility of SIP server affect the number of hops and the SIP signaling performance between the different parties of the VoIP call

Awareness of droplet and airborne isolation precautions among dental health professionals during the outbreak of corona virus infection in Riyadh city, Saudi Arabia

Background: This study aimed to determine knowledge, attitude and practice of airborne and droplet isolation precautions among Dental Health Professionals (DHPs) (dental students, interns, practitioners and auxiliaries) during the outbreak of MERS (Middle East Respiratory Syndrome), corona virus infection in Riyadh city, Saudi Arabia. Material and Methods: A cross-sectional survey was conducted among 406 dental health professionals (DHPs) working in selected dental facilities in Riyadh city, Saudi Arabia during the outbreak of MERS (April-June 2013). A structured, close-ended, self-administered questionnaire explored the knowledge, attitude, and practice towards droplet and isolation precautions. Collected data was subjected to descriptive statistics to express demographic information, mean knowledge score, mean attitude score and practice score of DHPs. Inferential statistics (MannWhitney U test and Kruskal Wallis tests, p < 0.05) were used to examine differences between study variables. Spearmanâ s rho correlation was used to identify the association between the knowledge-attitude, knowledge-practice, and attitude-practice. Results: A response rate of rate of 90.22% (406 out of 452) was obtained. The mean scores of knowledge, attitude and practice were 10.61 ± 1.19, 50.54 ± 7.53 and 8.50 ± 2.14 respectively. Spearmanâ s correlation test revealed a significant linear positive correlation between knowledge and attitude (r-0.501, P- 0.01), knowledge and practice (r-0.185, P-0.01) and attitude and practice (r-0.351, P- 0.01) of DHPs about airborne isolation precautions. Conclusions: Dental health professionals considered in the present study showed good knowledge, positive attitude and good practice towards droplet and airborne isolation precautions during outbreak of MERS

A Comprehensive Analysis of Aromatic-Proton Mediated Hydrogen Bonds

Hydrogen bonds play critical role in folding, structure and recognition of biological macromolecules (e.g., proteins, RNA, DNA). In addition to classical hydrogen bonds (e.g., ─OH---O=, ─OH---O─, ─NH---O─ etc.), structural analysis of protein and nucleic acids, almost a decade ago, showed that hydrogen bonds (e.g., CH---O) with hydrogen atoms on aliphatic carbon atoms (hereafter, aliphatic-protons) also play very important role in the structure and function of biomolecules. Even though, protons of aromatic ring systems (hereafter, aromatic-protons) are more polar than the aliphatic-protons, systematic analysis of hydrogen bonds of aromatic-protons have not been carried out. Therefore, I carried out a systematic analysis of hydrogen bonds that are made with aromatic-protons of tryptophan, tyrosine and phenylalanine amino acids in high-resolution structures of proteins and their complexes using a computer program that I created in R- and Perl languages. The analysis showed that aromatic CH---O are very common in proteins and tryptophan-CD1 is the most frequent participant in aromatic CH---O hydrogen bonds. The normalized frequency of occurrences of aromatic CH---O hydrogen bonds are greater than that of the aliphatic CH---O hydrogen bonds. Therefore, like aliphatic CH---O hydrogen bonds we anticipate that aromatic CH---O hydrogen bonds are likely to play equally, if not more, important role in macromolecular folding, stability and recognition. The numerous examples of aromatic CH---O hydrogen bonds observed here provides a good source of information that can be probed further by experiments to validate their important contribution

Secondary School Students' Perceptions and Challenges Toward Online Learning During the Covid-19 Pandemic in Saudi Arabia

The main objective of this research is to examine secondary school students' perceptions and challenges toward online learning during the Covid-19 pandemic in Saudi Arabia. Through the analysis of suggestions by students, the study sought to extract solutions for improving the learning and teaching experience in the event that the pandemic continues. This process allows for the researcher to identify weaknesses of online learning and thus forge credible solutions. SPSS will be used to examine the data and analyze the findings. Given that the quantitative research method was favored as part of the design, the data was collected using a questionnaire which provided all the information needed to carry out descriptive statistical analysis. The aforementioned tool was distributed to a study sample of (763) male and female secondary school students in Riyadh, Saudi Arabia. The findings highlight students’ perceptions amid the pandemic, and these include a myriad of privileges which are unique to online learning such as flexibility and convenience, the acquirement and mastery of technological skills, as well as greater participation from all types of students, including those who shy away from face-to-face interactions. By contrast, the results also exposed some prominent challenges including feelings of isolation, stress, and ubiquitous forms of distractions. The study recommends that future studies explore the topic of gender and how it affects the outcomes of online learnin

The experience of transition from high school to university : a qualitative exploration of perceptions of first year female students at King Saud University

Student retention has been one of the critical areas affecting university staff and students. Efforts to understand and remedy this problem have drawn research attention to the issue of transition. This study explored the problems faced by first year female students during transition to King Saud University in Saudi Arabia. Qualitative research was conducted, using an interpretive case study framework, over a longitudinal time-scale. The viewpoints of 21 participants from three faculties were captured through three phases of semi-structured interviews: one within the third week of the first semester, one at the end of the first semester, and one in the middle of the second semester. The purpose of doing so was to obtain insight into how students’ perceptions of the academic, social, and institutional (for example, support) aspects of the university changed over time as they acquired new experiences in the university setting.The findings indicate that first-year students often did not sufficiently understand the differences between high school and university in term of their responsibilities as independent learners. They were therefore unprepared for the academic and social changes they faced. Students often struggled to cope with the university’s academic demands, as they lacked a prior realistic comprehension of the learning and teaching mode in university. Socially, students were somewhat isolated at university, as a result of not participating in extra-curriculum activities and having limited relationships with lecturers. Their university participation was mainly confined to academic work. Over time, many of the students recognized the limitations of the academic skills and strategies they brought to university. First semester examinations prompted a crisis, which encouraged students in the second semester, to devote more time to their studies, to enhance their skills and competence, and to seek help from inside and outside sources. The findings challenge some aspects of existing theory. For example, students did not show a clear linear progression through the transition stages, with a marked separation from their former life. They also adopted support strategies that potentially expand the notion of communities of practice