Analysis of Scramjet Flight Trajectories with Oxygen Enrichment

Scramjets are proposed as a second stage for a multi-stage access-to-space system. At present the upper limit of scramjet operation is expected to be Mach 12-14. Use of oxygen enrichment is a possible method for increasing the speed and altitude of scramjet operation. This paper involves mission analysis of scramjets using oxygen enrichment. It follows on from Smart & Tetlow [5], in which trajectory studies of a threestage rocket-scramjet-rocket access-to-space system were conducted. These calculations indicated that the net thrust (scramjet thrust - vehicle drag) of a hypersonic vehicle with three scramjet engine modules was reduced to very low levels above Mach 12. The current work examines the use of oxygen enrichment in the scramjet to increase net thrust above Mach 10. Results of the study indicate that an important effect of oxygen enrichment is to allow scramjet powered vehicle operation at higher altitude

Dynamic Relationship Between Energy and Economic Growth: Evidence from D8 Countries.

Energy sector has a vital influence on an economy, on both demand and supply sides. Therefore, energy production and consumption bear great importance for the developing world. The oil embargo of 1970‘s and its impact on major macroeconomic variables throughout the world attracted many economists to examine the relationship between energy and economic prosperity. The researchers have been unable to establish a definitive direction of causality between the two variables. The purpose of this study is to empirically investigate the dynamic relationship between energy use and economic growth in the D8 countries. The evidence gathered through application of VAR Granger Causality, Johansen Cointegration and VECM proves existence of short-run and long-run correlation between energy use and economic development in all countries. The results supported either uni-directional or bi-directional causality in the D8 countries except for Indonesia in short-run where non-causality was established between the two variables. JEL classifications: C22; Q43. Keywords: Energy Use, Economic Growth, D8, VAR Granger Causality, Cointegration, VEC

Penggunaan Media Audio Visual Dalam Pembelajaran Daring Mata Pelajaran Bahasa Arab Di Sekolah Dasar Islam Terpadu Al-Halimiyah Jakarta Timur

The Covid-19 pandemic has led to online learning in almost all schools in Indonesia, one of them being SDIT Al-Halimiyah, East Jakarta. This condition requires that every subject, such as Arabic, has innovation in the usage of learning media. Learning media are tools that function to clarify learning materials and help achieve better learning. One of the media that can support online learning is audio-visual media. The focus of the research discusses the online learning process, the use of audio-visual media for online learning, and the inhibiting and supporting factors for the usage of audio-visual media in online learning for Arabic language subjects. This study uses a qualitative approach with a descriptive method. The collection technique uses interviews and observations of Arabic teachers at SDIT Al-Halimiyah. Based on the results of this study, the researcher suggested that the online learning process used video materials made by the teachers, PowerPoint, voice notes, and online meetings. Learning videos are one of the audio-visual media most often used by teachers, and for difficult materials, students can ask the teacher through WhatsApp Groups, and Google Classroom. Audio-visual media is the optimal media in the online learning process. The supporting factors are subject matter that is easily accessible and repeatedly, makes it easier for teachers to convey material to many students, and learning materials are interestingly delivered. While, the inhibiting factors are unstable internet connections, the presence of students who did not have adequate electronic devices, and the lack of socialization of the use of audio-visual media from schools to teachers and students.Keywords - Covid-19, pembelajaran online, media audio-visual, mata pelajaran Bahasa Ara

A triple-band antenna array for next-generation wireless and satellite-based applications

In this paper, a triple-band 1 × 2 and 1 × 4 microstrip patch antenna array for next-generation wireless and satellite-based applications are presented. The targeted frequency bands are 3.6, 5.2 and 6.7 GHz, respectively. Simple design procedures and optimization techniques are discussed to achieve better antenna performance. The antenna is designed and simulated using Agilent ADS Momentum using FR4 substrate (r = 4.2 and h = 1.66 mm). The main patch of the antenna is designed for 3.6 GHz operation. A hybrid feed technique is used for antenna arrays with quarter-wave transformer-based network to match the impedance from the feed-point to the antenna to 50. The antenna is optimized to resonate at triple-bands by using two symmetrical slits. The single-element triple-band antenna is fabricated and characterized, and a comparison between the simulated and measured antenna is presented. The achieved simulated impedance bandwidths/gains for the 1 × 2 array are 1.67%/7.75, 1.06%/7.7, and 1.65%/9.4 dBi and for 1 × 4 array are 1.67%/10.2, 1.45%/8.2, and 1.05%/10 dBi for 3.6, 5.2, and 6.7 GHz bands, respectively, which are very practical. These antenna arrays can also be used for advanced antenna beam-steering systems. Copyright © Cambridge University Press and the European Microwave Association 2014

A triple-band antenna array for next-generation wireless and satellite-based applications

In this paper, a triple-band 1 × 2 and 1 × 4 microstrip patch antenna array for next-generation wireless and satellite-based applications are presented. The targeted frequency bands are 3.6, 5.2 and 6.7 GHz, respectively. Simple design procedures and optimization techniques are discussed to achieve better antenna performance. The antenna is designed and simulated using Agilent ADS Momentum using FR4 substrate (r = 4.2 and h = 1.66 mm). The main patch of the antenna is designed for 3.6 GHz operation. A hybrid feed technique is used for antenna arrays with quarter-wave transformer-based network to match the impedance from the feed-point to the antenna to 50. The antenna is optimized to resonate at triple-bands by using two symmetrical slits. The single-element triple-band antenna is fabricated and characterized, and a comparison between the simulated and measured antenna is presented. The achieved simulated impedance bandwidths/gains for the 1 × 2 array are 1.67%/7.75, 1.06%/7.7, and 1.65%/9.4 dBi and for 1 × 4 array are 1.67%/10.2, 1.45%/8.2, and 1.05%/10 dBi for 3.6, 5.2, and 6.7 GHz bands, respectively, which are very practical. These antenna arrays can also be used for advanced antenna beam-steering systems. Copyright © Cambridge University Press and the European Microwave Association 2014

Factors determining e-government security

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonE-Government security is a major area of concern that has the potential to affect the success of e-Government services across the world. Much of the literature has addressed this phenomenon by applying principles of computer science or engineering which tend to be objective. User concern of e-Government service security has not been addressed applying social science principles or management that tend to be subjective and have not been addressed in the literature. Objective research outcomes are unfortunately not suitable to address subjective factors. Further, user centric approach has not been adopted in most of the empirical studies that have dealt with e-Government security leading to lack of an understanding of how users perceive or feel or comprehend about e-Government services, particularly e-Government service security. Most of the research efforts addressing e-Government security have focused on either technological issues or engineering issues neglecting user perceptions and behavioural aspects. This disadvantage has led to possible reduction in the up-take of e-Government services. There was a need to have an in-depth understanding of user centric e-Government security and user centric factors that affect it as its antecedents addressing which it is possible to enhance user confidence in e-Government and hence its success. This research has addressed this partially. While addressing the concerns raised above, this research has defined and identified certain user centric factors that are required to examine the user centric nature of e-Government service security from the management and social sciences perspective. E-Government literature was critically reviewed to determine the user centric factors and their relationship to user centric e-Government security with the help of theories, models, concepts and frameworks that have not been applied so far. Contextual factors have been identified as important user centric ones that affect user centric e-Government security with e-Government technology chosen as the main contextual determinant of user centric e-Government security. User trust and user felt risk in using e-Government services were brought in as mediators of this relationship due to the prime importance these two user centric factors carry with regard to affecting the relationship between technology and user centric e-Government security. In addition demographic factors and culture (nationality) as a factor were applied to test their influence on the relationship between user trust and user centric e-Government security mediated by user felt risk to find whether they have any impact. Moderators (Human Computer Interaction (HCI), user privacy and web design quality) of this relationship were added to the investigation as literature showed that e-Government technology could not operate in isolation. Finally empirical outcomes of testing the above relationships were practically tested by examining the influence of perceived ease of use and usefulness on the relationship between user trust and user centric e-Government security mediated by user felt risk to find whether technology impacted users in reality. Theoretical framework was drawn from the literature review leading to a conceptual model that was used to answer the research question. 12 hypotheses were tested in all. The research was conducted in the Kingdom of Bahrain which ranks high in the implementation of e-Government (e.g. 14th ranked in the world in implementing e-participation in 2014 ranked by UN). The country offered a fertile ground for conducting research as the e-Government service provided were updated technologically constantly with the latest technological advancement cloud computing introduced in e-Government service provision. Most government services were offered now through e-Government services. The population was cosmopolitan and education levels of the users of e-Government were reasonably high providing a strong basis for conducting this research. Quantitative research method and survey questionnaire strategy were used. Users of e-Government services were the target population. Sampling procedure yielded 309 valid responses. Rigourous statistical analysis provided the findings. Except for 2 hypotheses the remaining were verified and established. Technology was found to determine user centric e-Government security with the mediation by trust being stronger than risk. HCI and web design quality moderated the relationship between technology and user centric e-Government security significantly. User education and experience were found to influence user trust and user centric e-Government security. User privacy and nationality were not found to be statistically significant. Perceived ease of use and usefulness of the technology were found to influence e-Government security mediated by trust and risk. This research was perhaps one of the first to have been conducted in a context where e-Government technology used cloud computing. The research contributed to the growing body of knowledge in the field of e-Government security that has viewed this phenomenon from the lens of social sciences and management. Theoretical contribution showed how the operationalization and relationship amongst the factors could be explained by expanding the application of theories including socio-technical, behavioural, managerial, technology adoption, organiational and HCI. Practical implications showed the usefulness of this research to users, service providers and policy makers involved with e-Government services. Methodologically this research has introduced a verification stage by which it has verified the theoretical results using practical outcomes

The Role of the Urban Poor in Tabriz in Constitutional Revolution

The urban poor in Tabriz including daily-paid laborers, street vendors, porters, the unemployed, beggars and slum residents rose up in support for the Constitutional Revolution. Although they did not have enough information about the Constitutional Revolution, people encouraged the leaders and joined the queue of Constitutionalists hoping to get free from the unfair behaviors and access the welfare in life. A group of fighters was formed and the poor joined them. Some of them participated in the war and also some helped the Constitutionalists in building the forts, breaking the walls and guarding. Despite living in difficult situation, they never left the Constitutionalists alone. In this paper, we try to assess how the poor people of Tabriz joined the constitutionalists and supported them and what was their role in the revolution. We also attempt to answer this hypothesis according to which when the poor people are led by the elite in the society, a strong force can be formed that is able to resist to any military power. The poor people of  Tabriz too endured the poverty and the difficult situations and resist to Muhammad Ali Shah force

Analyzing the role of “smart” start points in coarse search-greedy search

An inherent assumption in many search techniques is that information from existing solution(s) can help guide the search process to find better solutions. For example, memetic algorithms can use information from existing local optima to effectively explore a globally convex search space, and genetic algorithms assemble new solution candidates from existing solution components. At the extreme, the quality of a random solution may even be used to identify promising areas of the search space to explore. The best of several random solutions can be viewed as a "smart" start point for a greedy search technique, and the benefits of "smart" start points are demonstrated on several benchmark and real-world optimization problems. Although limitations exist, "smart" start points are most likely to be useful on continuous domain problems that have expensive solution evaluations. © Springer-Verlag Berlin Heidelberg 2007

Towards the automated design of phased array ultrasonic transducers: Using particle swarms to find "smart" start points

Continuum Probe Designer™ by Acoustic Ideas Inc. is a tool that can help design the "best" phased array ultrasonic transducer for a given inspection task. Given a specific surface geometry for the ultrasonic transducer, one component of Continuum Probe Designer™ can determine the number of elements, and the required size and shape of each element to meet a list of ultrasonic inspection goals. Using the number of elements as a cost function, an optimization problem to find the best surface geometry for the transducer is created. Previous work has demonstrated that a (1+λ)-evolution strategy (ES) can be a very effective search technique for this problem. The performance of this ES was improved by starting it from "smart" (i.e. better than random) start points. Particle swarm optimization (PSO) can be used to improve the "smart" start points, and the overall PSO-ES hybrid is capable of finding feasible transducer designs from all of the start points in a benchmark test suite. This level of performance is an important step towards the use of Continuum Probe Designer™ as a fully automated tool for the design of phased array ultrasonic transducers