Analysis of AC link topologies in non-isolated DC/DC triple active bridge converter for current stress minimization

This paper presents analysis of the non-isolated DC/DC triple active bridge (TAB) converter under various purely inductor-based AC link topologies. The objective of the analysis is to find the topology that incorporates the least value of the AC link inductors which leads to reduced converter footprint in addition to minimum internal current stresses. Modelling of the TAB under each of the different topologies is presented in per unit expressions of power transfer and reactive power assuming fundamental harmonic analysis. The power expressions are used to calculate the inductor values necessary to achieve same rated power transfer of Dual Active Bridge (DAB) converter for the sake of standardizing comparison. On this basis, the topology requiring the least value of interface inductors, hence lowest footprint, is identified. Furthermore, based on phase shift control, particle swarm optimization (PSO) is used to calculate optimal phase shift ratios in each of the proposed topologies to minimize reactive power loss (hence current stress). The topology with minimum stresses is therefore identified and the results are substantiated using a Matlab-Simulink model to verify the theoretical analysis

Generalized small-signal modelling of dual active bridge DC/DC converter

this paper presents a novel generalised approach of the small-signal modelling of dual active bridge (DAB) DC/DC converter. The adopted analysis is based on a per-unit fundamental frequency representation of the DAB. The outcome of the proposed modelling approach is a small signal, linearised, state-space DAB model; which is considered as a main building block for future control applications. The developed small signal DAB model includes all possible degrees of freedom affecting the performance of the DAB; this includes the voltage conversion ratio to allow the study of all DAB operation modes (i.e.: unity-gain and buck/boost modes.). Furthermore, since triple phase shift control (TPS) is used in this development work, the proposed model incorporates phase shift in addition to duty ratios. This feature allows for bridge voltage regulation, which is essential for efficient DAB operation in the case of buck/boost operation. Another key achievement is that the proposed small signal modelling methodology can be applied to any bidirectional DC-DC converter regardless of ratings, parameter values and number of ports. Extensive simulation is carried out to verify the proposed analysis

Essays on carbon disclosure and financial consequences

PhD ThesisIn boardrooms around the world, climate change has recently emerged as a major issue, matching the level of public concern. This thesis is motivated by the growing interest in assessing the financial consequences of corporate involvement in climate change beyond regulatory compliance, as evidenced by firms’ voluntary participation in the Carbon Disclosure Project (CDP). This thesis contributes to the ongoing literature by extending insights into three financial consequences of voluntary carbon disclosure, namely, financial performance, firm risk, and market reaction. We empirically investigate these financial consequences by conducting three essays using a unique dataset containing firms listed on the London Stock Exchange’s FTSE350 index for the period 2007 to 2015. In the first essay, we empirically conceptualise and investigate the impact of adopting proactive carbon strategies on financial performance, building on the resource-based view (RBV) of the firm as a theoretical framework. For this, we employ a panel data approach. The finding provides strong evidence that voluntary carbon disclosure and firm financial performance are positively associated. In the second essay, we build on the RBV theory and consider the potentially positive association between information asymmetry and firm risk, and subsequently the relationship between corporate carbon disclosure and firm risk, by appointing the panel data approach. We find that the adoption of carbon strategies significantly reduces the firm’s total, systematic, and idiosyncratic risks. In the third essay, we examine the market reaction to carbon disclosure announcements by adopting an event study method. This is done by considering investors’ perspective on the costs and benefits of carbon disclosure. The results show that the market reacts significantly negatively to carbon disclosure announcements via the CDP. Furthermore, additional tests are applied, including investigating the influence of the global financial crisis and industry status on the examined relationships. Our research findings offer fresh insights and updated policy implications for investors, management, regulators, and sustainability institutions.The Public Authority for Applied Education and Training in the State of Kuwai

Domestic thermoelectric cogeneration system optimization analysis, energy consumption and CO 2 emissions reduction

In this paper, a domestic thermoelectric cogeneration system (DCS) is suggested. This system permits to use the lost heat of exhaust gases to simultaneously heat water and produce electricity via thermoelectric generators (TEG). To proceed, the concept of the system is drawn and the corresponding thermal modeling is developed. An optimization analysis, based on the position of the thermoelectric generators within the system, is carried out using the thermal modeling. The TEGs are places on the inner or outer walls of the tank or the pipe (cases 2–5), or on all of them (case 6). Results show that water can be heated to up to 97 °C, when TEGs are located on the inner wall of the tank. More the TEGs are nearer to the exhaust gases, higher is the total power produced by the TEGs and lower is the water temperature. The power produced by one TEG in direct contact with the exhaust gases is 0.35 W and the water temperature is 76 °C. Also, a DCS with TEG located at all layers can generate up to 52 W and 81 °C hot water, however this configuration has high initial cost. An economic and environmental concerns are considered. Results show that DCS with TEGs located on the inner wall of the pipe has a payback period of 1 year and 8 months when water is heated 60 times per month. In addition to that, it was shown that the location of TEGs do not affect the amount of CO2 gas reduced which is about 6 tons yearly. Finally, this study shows that the configuration where TEGs are placed at the inner wall of the pipe is the most cost-effective energy recovery configuration

New Hybrid heat recovery concept applied to exhaust gas

International audienc

Teaching competencies that the faculty member should have to ensure the quality of the educational process of learning

Teaching is considered as one of the most important jobs performed by the faculty member, and it is one of the most important functions of the university, therefore ensuring the quality of education is related to teaching quality which includes the skills, methods, and strategies that are followed by the faculty member to achieve the desired goals. As the teaching skills and the faculty member interest in teaching and taking care of his students are the most important characteristics of his professionalism from the perspective of university students, perhaps this is why educators and politicians considered “teacher’s professionalism “ is “good teaching”, and that the “professional teacher” is characterized by the expansion of his knowledge, and his understanding of pedagogy, in addition to commitment, enthusiasm, and creativity in teaching. Therefore, this study aimed to answer the following question:  What are the Teaching competencies that the faculty member should have to ensure the quality of the educational process of learning? The researchers used the descriptive approach through a survey of previous experiences at the level of local and international organizations, as well as the studies and the scientific researches that had the same subject of this study. The study concluded a set of the Teaching competencies that the faculty member should have to ensure the quality of the educational process of learning. Key words: Teaching competencies, The faculty member, Ensuring the quality of the educational process of learning

The diagnostic and monitoring value of serum anti-mutated citrullinated vimentin antibodies (anti-MCV) in juvenile rheumatoid arthritis

Background: JRA is currently diagnosed using the American College of Rheumatology (ACR) 1987 revised criteria that are primarily based on clinical parameters. The criteria may be insufficient for the diagnosis of early RA as they are based upon measurements of disease classification predominately featuring manifestations typical of later-stage disease. Measurement of serum anti-mutated citrullinated vimentin antibodies (MCV) has been shown to be a better marker for early adult RA, and it correlates well with the disease activity score (DAS). Objectives: The aim of this work is to evaluate the role of antimutated citrullinated vimentin antibodies (anti-MCV) in the diagnosis, and in monitoring disease activity in juvenile rheumatoid arthritis. Methods: The study included 40 children with JRA fulfilling the American College of Rheumatology criteria for diagnosis of JRA: 4 children with oligoarticular JRA, 12 with polyarticular JRA and 24 children with systemic onset JRA. Fifty healthy children, matching the patients in age and sex served as a control group. The studied children with JRA were subjected to laboratory tests including CBC, ESR, CRP, ANA and rheumatoid factor (RF). Serum samples from both patients and controls were assayed for anti-MCV levels using an ELISA technique. Results: The study showed high mean serum anti-MCV antibodies level in JRA patients when compared to controls (P= 0.00). In addition, there were no significant correlations between anti-MCV antibody levels and parameters of disease activity, namely, number of swollen joints, number of tender joints, ESR and CRP. The receiver operating characteristic (ROC) curve was drawn and it showed that the area under the curve (AUC) was (0.896). At a cutoff level > 17 u/mL, anti-MCV antibodies had diagnostic specificity of 88%, diagnostic sensitivity of 87.5%, negative and positive predictive values of 89.8% and 85.4%, respectively and diagnostic efficacy of 87.8%. We also reported 3/40 of JRA patients to be positive for RF and 2/40 of JRA patients to be positive for ANA. Conclusion: Measurement of serum anti MCV antibody level holds promise as a diagnostic tool in JRA. However, they failed to show a significant efficacy in determining disease activity.Keywords: Juvenile rheumatoid arthritis, MCVEgypt J Pediatr Allergy Immunol 2012;10(2):75-8

Experimental study on heat recovery using multi tube tank: effect of changing the head shape

This work presents a heat recovery system utilized to heat water from exhaust gases of a chimney. A waste heat recovery system is suggested named as “multi tube tank”. The suggested design is illustrated and described. The system is constructed and tested. In order to enhance the system effect of changing the head shape is studied. Two head were constructed: cylindrical and conical. Results shows that conical head reflected better performance compared to cylindrical head. For a cylindrical head water temperature increase to maximum 60 °C in 275 min. while for conical 16 head water temperature increased to 70 °C in 275 min and the system was able to increase the water temperature more up to 80 °C in 400 min

Numerical simulation of multi-tubes tank heat exchanger: toward an optimized configuration

Heat recovery is the reutilization of thermal energy lost by any industrial and resident ial application. Heat exchangers play a very effective role in recovering process. This paper deals with an optimization analysis of a suggested heat recovery heat exchanger. The suggested heat recovery heat exchanger is a multi-concentric tubes tank. This heat exchanger is designed to utilize thermal energy carried out by exhaust gases of a chimney to heat water for residential usage. The analysis is carried out numerically using a computational fluid dynamics “Comsol”software. Three configurations are considered, in which one tube, three tubes and six tubes systems are studied. The results show that in order to increase water temperature from 20°C to 70°C it requires 14 hours, 8 hours and 4 hours when using one tube, three tubes and six tubes system respectively. This makes six-tubed heat exchanger the best choice to heat the water quickly. However, one-tubed heat exchanger experiences the lowest corrosion phenomenon compared to other systems that makes one-tubed system to provide the longest lifetime