Modeling and Analyzing of Inverters for Controlling Voltage and Frequency in an Islanded Microgrid

Recently, the growth of inverter-based generations (IBGs) like solar photovoltaic (PV) and wind turbine generators in the form of microgrids (MGs) has been increasing. However, control of voltage and frequency becomes a challenging task for MGs especially when they operate in an islanded mode, due to the inherent low-inertia feature of IBGs compared to a grid-tied mode where there is a grid support. This thesis deals with modeling and analyzing of inverters capable of controlling voltage and frequency through external conventional droop control for the islanded operation of MG. In this thesis, a state space model is developed for a voltage source inverter with droop control. Moreover, non-linear models for the inverters in single and parallel cases with droop control are developed and the results are verified in different load scenarios. The results show a good performance of the projected control, both in the isolated operation of an inverter supplying a load, and in the parallel operation of isolated inverters, where there is power sharing to properly feed the load. MATLAB/Simulink environment is used for the work

Earnings Per Share Versus Cash Flow Per Share as Predictor of Dividend; Evidence from Non Financial Sector of Pakistan

This research study has compared the relative predictive power of earnings and cash flow in order to find out the best predictor of dividend. This study has used panel data techniques and the data has been collected from the balance sheet analysis of 104 KSE-100 index non-financial companies. This study has employed a linear mixed effect model approach to investigate the main problem. The two models (earnings based model and cash flow based model) have been compared by using log likelihood estimator and Akaiki information criteria (AIC). The results have shown that cash flow per share is a better predictor of dividend than earnings per share in term of log likelihood estimator and Akaiki information criteria (AIC). The results have also concluded that both earnings per share and cash flow per share have a significant relationship with dividend. The study also finds out that all the control variables including firm’s size (SIZE), leverage ratio (LR), market to book value (MBV) and liquidity ratio (LIQ) have a significant relationship with dividend. Keywords: Earning per share (EPS), Cash flow per share (CFPS), Dividend, Linear mixed effect model, Log likelihood estimator, Akaiki information Criteria (AIC) and KSE-100 inde

Corporate Social Responsibility: Understanding the Legal Framework and Philanthropic Indian Companies

Business and conglomerates have never been an isolated entity as the entrepreneurs or the businessmen have always maintained a consistency in the internal and external management and also properly follow-up the movement that use to take place in the external business environment such as consumers, communities, stakeholders, shareholders, and by-laws. Gradually, with the passage of time in last three decades the changes that took place in the Indian cultural norms of corporations had brought forward the concept of corporate social responsibility (CSR) referring to bring about overall positive impact of corporations on the communities, societies, and environments in which they operate. The term CSR became popular in the 1960s and narrowly construed. It had remained a term used indiscriminately by many to cover legal and moral responsibility but in the present scenario, it has been used in a broader way. CSR promotes a vision of business accountability to a wide range of stakeholders, besides shareholders and investors. Key areas of concern are environmental protection and the wellbeing of employees, the community, civil society in general, customers, employees, investors, suppliers, and activist organizations both now and in the future. This article is exclusively based on secondary data and presents an in-depth conceptual framework of the CSR, major provisions and guidelines encrypted by the Ministry of Corporate Affairs, Government of India. Further, the fundamental principle, core elements and its role in nation development are discussed briefl y for the better understanding of the reader

A Study of Pakistan-China Defense Relations (2000-2012)

Pakistan and China have cordial bilateral relations right from the very beginning. Pakistan being the most significant Muslim country located at a geo-strategically important geological juncture and equipped with nuclear deterrent while China being the most emergent economic and technological giant have remained the focus of attention for regional and international political actors. Owing to the strategically complex regional location and the obvious involvement of major political actors of international community herein, both countries have to strengthen the mutual defense ties. Both countries are currently working jointly in all fields related to defense including nuclear cooperation and development of conventional and non-conventional weaponries.Gawadar Port is a geo-strategically important project which is being developed jointly by both countries. The said port and the respective region are constantly under attack by the countries which do not want Pak-China collaboration to flourish. In the context of War Against Terrorism, it is quite significant to examine the quantum of defense collaboration between both countries to conclude that whether Pakistan-China defense relations have been affected by the said war positively or negatively. The present study finds that in spite of various hurdles being present between both countries to improve their geostrategic relationship; both are still managing to strengthen their bilateral defense collaboration. Keywords: Pakistan, China, defense, geostrategic, relationship, War Against Terrorism

Current trends of consanguineous marriages and its association with socio-demographic variables in Pakistan

Background: A high proportion of marriages in South and Middle East Asia are contracted between close biological relatives due to cultural preference as it is a deeply rooted social fashion among these societies. The aim of this study was to determine the frequency of consanguineous marriages and ascertain their relationship to relevant sociodemographic variables.  Methods: This was a cross sectional descriptive study conducted in tertiary care hospital of Islamabad. Data were collected on a specially designed questionnaire form. Age of participants, their education, socioeconomic status, castes and number of anomalous children born to these participants, degree of consanguinity and reasons of preferences were inquired.  Results: Out of 300 women chosen by convenience sampling technique, 62% had consanguineous marriages, and 38% had a non-consanguineous union. The mean age of women presenting to maternal and child health centre was 27 years. The average age of a woman having consanguineous marriage was 21 years in contrast to 24 years for non-consanguineous nuptial. About 18% of women in consanguineous marriages were illiterate as compared to 5.4% (p = 0.001) of women in non-consanguineous unions. First cousin marriages were more common among certain castes like Rajput and Awan. None in the consanguineous group had any anomalous baby in contrast to non-consanguineous who had two anomalous children (p = 0.0001). There was no significant association between type of marriage and the number of miscarriages (p=0.69).Conclusions: Majority women still prefer cousin unions for their progeny due to traditions and family security reasons irrespective of their education and social status. Therefore, it is important to incorporate prenatal genetic counseling sessions in community programs to raise awareness about repercussions of consanguinity on future generations

Bacteriocin-mediated inhibition of some common pathogens by wild and mutant Lactobacillus species and in vitro amplification of bacteriocin encoding genes

Lactobacilli are the most common probiotics used in food and other industries because of their capability of producing bacteriocins. Bacteriocins are compounds that are used to kill pathogenic microorganisms. As most bacteria have become resistant to synthetic antibacterial tools, the importance of using probiotics as antibacterial agents has increased. This work was done to check the bacteriocin effect on some common pathogens and the influence of mutation on the bacteriocin activity of Lactobacilli was also investigated. Four strains were isolated, identified from meat and pickles samples via culturing methods, staining, biochemical tests, and ribotyping. Preliminary tests, including Gram staining and catalase test, were done for the confirmation of Lactobacillus species. All strains were gram-positive and catalase-negative. Antibacterial activity was checked against Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus thuringiensis, Escherichia coli, and Salmonella enteritis via agar well diffusion method. The mutations were done using ethidium bromide and the influence of wild and mutants were also checked. Interestingly, mutants developed more virulence than wild ones. It was also observed that they all were sensitive to pepsin. Protein estimation was done via Bradford method. Ribotyping of GCU-W-PS1 revealed 99 % homology with Lactobacillus plantarum and GCU-W-MS1 to Lactobacillus curvatus (99 % homology). Curvacin A, sakacin P, and plantaricin A genes were also amplified using specific primers. Gene sequence showed the presence of curvacin A gene in GCU-W-MS1. It was concluded that lactic acid bacteria could be used as antibacterial tools against common pathogens

A knowledge based decision support system for tool changeover in CNCs

This paper describes an application of an adaptive planning system for automatic tool changers in flexible manufacturing systems. The conventional models of predictive control usually cannot adapt to a real time dynamic environment. The proposed adaptive control model is capable of self adjusting to changing environments. The algorithm is based on a decision logic, which is constructed by breaking up knowledge and converting them into mathematical form in order to cover all possible conditions that can exist during the implementation phase. Expert thoughts and knowledge from decision logic are stored in the decision tree, which consists of circular nodes, arcs and decision nodes. The suggested system is capable of accepting further rules, new nodes and branches to the tree when additional attributes are needed. This whole knowledge is encoded in the form of production rules and each rule represents a small chunk of knowledge relating to the given domain of tool replacement. A number of related rules collectively respond to highly useful conclusions.The system uses VP Expert development shell, contains an inference engine and, a user interface. The originality of the proposed strategy lies in that a knowledge-based expert system is developed to identify and analyze the current conditions and then readjust the output that reflects the real-time environment. Compared with the various classical models, the approach can synthesize and analyze as many variables as possible to adequately and reliably identify the real-time conditions. Simulation results demonstrate the effectiveness and practicality of this tool-change planning and control strategy

Adaptive ResNet Architecture for Distributed Inference in Resource-Constrained IoT Systems

As deep neural networks continue to expand and become more complex, most edge devices are unable to handle their extensive processing requirements. Therefore, the concept of distributed inference is essential to distribute the neural network among a cluster of nodes. However, distribution may lead to additional energy consumption and dependency among devices that suffer from unstable transmission rates. Unstable transmission rates harm real-time performance of IoT devices causing low latency, high energy usage, and potential failures. Hence, for dynamic systems, it is necessary to have a resilient DNN with an adaptive architecture that can downsize as per the available resources. This paper presents an empirical study that identifies the connections in ResNet that can be dropped without significantly impacting the model's performance to enable distribution in case of resource shortage. Based on the results, a multi-objective optimization problem is formulated to minimize latency and maximize accuracy as per available resources. Our experiments demonstrate that an adaptive ResNet architecture can reduce shared data, energy consumption, and latency throughout the distribution while maintaining high accuracy.Comment: Accepted in the International Wireless Communications & Mobile Computing Conference (IWCMC 2023