DC grid discriminating protection

High-voltage direct current (HVDC) has been proven an affordable and technically capable solution to bring vast amounts of power over long distances, though overhead lines, underground or undersea cables. As a result, a large number of point-to-point HVDC links appeared in several locations over the last decades. The technological step currently going on is the connection of point-to-point links to form a multi-terminal dc (MTDC) grid, a configuration that would bring several advantages. The construction of MTDC grids faces a few technical challenges, where the most notorious one might be dc grid protection. This thesis presents protection strategies for MTDC grids equipped with different dc fault clearance and isolation devices. These include ac circuit breakers (ACCBs), converters with fault blocking (FB) capability, dc circuit breakers (DCCBs) and fast dc disconnectors (only for isolation purposes). Each of these strategies in presented in a chapter, where the steps of the protection strategy are described and overvoltage suppression methods are proposed. The protection strategies include dc fault detection and dc fault discrimination algorithms. In literature, extensive research is available regarding dc fault discrimination, potentially the "hottest" topic in dc protection. In this thesis, discrimination algorithms are proposed being those based on analysis of local currents and voltages. Thus, link communication channels are not required, which reduces the overall decision-making time. The performance of the developed protection strategies is tested in PSCAD/EMTDC environment. DC faults are applied on two MTDC grids, including a 4-terminal meshed grid and the CIGRE 11-terminal dc grid. The main outcomes of this thesis include the discriminative fault criteria and the tailored protection strategies for dc grids equipped with either ACCBs, FB converters or DCCBs as main fault current clearance devices

Melhoria do processo de expedição de produto acabado para clientes FCA: um caso de estudo em uma empresa da indústria automóvel

Dissertação de mestrado integrado em Engenharia e Gestão IndustrialA crescente competitividade dos mercados e o aumento das necessidades e da rapidez de consumo da sociedade atual exigem muito mais de uma empresa, principalmente no setor da indústria automóvel, altamente tecnológico e em constante mudança e desenvolvimento. Para se manterem ativas e estabilizadas, as empresas têm de se conseguir adaptar a esta situação, focando-se principalmente na satisfação do cliente, no controlo dos custos e na constante melhoria e inovação. Nesta perspetiva, os conceitos de logística e cadeia de abastecimento, particularmente integrados na área da expedição, representam um papel importante, principalmente ao nível dos fluxos de materiais e informação. A presente dissertação, realizada em colaboração com a Bosch Car Multimedia Portugal, S.A., apresenta como principal abordagem a melhoria dos processos de expedição e a eliminação de picos de trabalho, tendo como maior objetivo a apresentação das propostas de melhoria definidas, a sua implementação e os principais resultados obtidos. Os vários processos e fluxos foram analisados, mapeando-se as atividades principais e aquelas nas quais o foco do trabalho incidiu. Deste modo, foi possível detetar determinadas oportunidades de melhoria, nomeadamente: falta de nivelamento do processo de cargas e existência de picos de trabalho; desatualização das instruções de trabalho, layouts e folhas de trabalho normalizado dos processos de expedição de produto acabado; falta de identificação dos storage bins e inexistência da documentação de apoio (instruções de trabalho, folhas de standard work e layouts) dos processos relativos ao material retornável; e necessidade de implementação de um novo software para o processo de validação de etiquetas que permita melhorar o fluxo de informação. Várias propostas de melhoria foram definidas, delineando-se objetivos e as ações corretivas a implementar. Na introdução do sistema para validação de etiquetas, vários problemas foram surgindo, tendo sido dados, apesar de tudo, passos importantes para a resolução do problema. A alteração das janelas de carga de determinados clientes permitiu nivelar o número de paletes expedidas ao longo da semana, tendo-se praticamente eliminado os picos de trabalho. A criação e atualização das instruções de trabalho e a normalização das tarefas permitiram eliminar os problemas associados aos processos de expedição e do material retornável.The increasing competitiveness of the markets, the needs of society and its fast consumption of goods demand a lot more from a company, especially in the automotive sector, which is highly technological and is in constant change and development. In order to stay in action and to be steady companies have to adjust themselves to this situation, focusing on customer satisfaction, costs control and constant improvement and innovation. This way, the concepts of logistics and supply chain, particularly incorporated on the shipping area of a firm, represent an important role in terms of material and information flows. This particular thesis, developed in association with Bosch Car Multimedia Portugal, S.A., presents as its main focus the improvement of the shipping processes and the elimination of peaks of workload. This document has as its main purpose the presentation of improvement proposals, their implementation and their main outcomes. Processes were analysed and flows were described, mapping the essential activities and those on which this work were based. This practice lead to the detection of some improvement opportunities, such: the shipping process was not levelled along the week and there were peaks of workload; work instructions, layout and standard work sheets for finished goods shipping process were outdated; the storage bins of the returnable packaging warehouse were unidentified and the related processes did not have the required documentation (work instructions, layouts and standard work sheets); the need of introducing a new software for label validation in order to improve the information flow. Improvement proposals were defined, goals were outlined and corrective actions were presented. In what concerned to the implementation of the label validation new software, great steps were made trying to solve the problem, despite various problems kept appearing. The changing of the loading time window for some clients allowed the levelling of the number of pallets shipped along the week, eliminating the peaks of workload. And the elaboration and updating of work instructions and the standardisation of the activities allowed the elimination of problems associated with the shipping and returnable packaging processes

Progressive fault isolation and grid restoration strategy for MTDC networks

A multi-terminal dc (MTDC) grid has a number of advantages over traditional ac transmission. However, dc protection is still one of the main technical issues holding back the expansion of point-to-point dc links to MTDC networks. Most dc protection strategies are based on dc circuit breakers (DCCBs); however, DCCBs are still under development and their arrival to the market will come at an unclear time and cost. Conversely, ac circuit breakers (ACCBs) are readily available and represent a more economic alternative to protect dc networks. Following this line, a protection strategy for MTDC grids is proposed in this paper. This uses ACCBs for dc fault current clearing and fast dc disconnectors for fault isolation. The faulty link is correctly discriminated and isolated while communication links are not required. This strategy contributes to a reduced network outage period as the non-faulty links are out of operation for a relatively short period of time and are restored in a progressive manner. The effectiveness of the proposed strategy is tested in PSCAD/EMTDC for pole-to-ground and pole-to-pole faults

Performance Evaluation of the Chinese Healthcare System

Artigo publicado em revista científica internacionalThis study aims to evaluate the performance of the Chinese healthcare system. It uses sustainable development goal (SDG) 3, set by the United Nations to ensure healthy lives and promote well-being for all at all ages as a benchmark. It uses data of 17 variables ranging from the year 2000 to 2017 and uses a multistage methodology to evaluate the performance. In the first stage, it uses difference in mean test to know whether or not the indicators show an improvement in the second decade of the 21st century compared to the first decade. In the second phase, simple linear regression has been used to know the rate of change of performance of every indicator over the sample period. The third step compares the performance of the healthcare sector with the sustainable goals set by the UN and the fourth phase attempts to forecast performance for the next five years i.e., 2018 to 2022. As per the results, the Chinese healthcare sector has performed very well on many fronts except alcohol consumption in males, road accidents and the incidence of non-communicable diseases. Alcohol consumption by males is touching dangerous levels. Therefore, the policies should focus on educating males to lower their alcohol consumption to stay fit and healthy.info:eu-repo/semantics/publishedVersio

Systemic acquired critique of credit card deception exposure through machine learning

Artigo publicado em revista científica internacionalA wide range of recent studies are focusing on current issues of financial fraud, especially concerning cybercrimes. The reason behind this is even with improved security, a great amount of money loss occurs every year due to credit card fraud. In recent days, ATM fraud has decreased, while credit card fraud has increased. This study examines articles from five foremost databases. The literature review is designed using extraction by database, keywords, year, articles, authors, and performance measures based on data used in previous research, future research directions and purpose of the article. This study identifies the crucial gaps which ultimately allow research opportunities in this fraud detection process by utilizing knowledge from the machine learning domain. Our findings prove that this research area has become most dominant in the last ten years. We accessed both supervised and unsupervised machine learning techniques to detect cybercrime and management techniques which provide evidence for the effectiveness of machine learning techniques to control cybercrime in the credit card industry. Results indicated that there is room for further research to obtain better results than existing ones on the basis of both quantitative and qualitative research analysis.info:eu-repo/semantics/publishedVersio

Exploring the Asymmetric Effect of Internal and External Economic Factors on Poverty: A Fresh Insight from Nonlinear Autoregressive Distributive Lag Model

Objective: This study examines the asymmetric impact of both internal (military, education, and health expenditures) and external (trade opening and foreign direct investment) factors that contribute to poverty reduction. Methodology: To find an asymmetric relationship between the proposed variables, we used a non-linear ARDL co-integration approach for the period ranging from 1981-2019. Findings: The findings of the study confirm the asymmetric impact of internal (education, military, health expenditures, quality of governance) and external (foreign direct investment, openness) factors on poverty. The finding confirms that ignoring nonlinear or asymmetric properties of macroeconomic variables may mislead inferences. This study has policy implications for government officials to reduce poverty. Novelty: theeconomic theory of poverty is studied from different perspectives by using internal and external factors that have direct and indirect effects on poverty. Furthermore, for in-depth analysis, a nonlinear approach is used to determine which factor has a strong contribution to eliminating poverty. Doi: 10.28991/ESJ-2023-07-03-07 Full Text: PD

A Study on Balanced Scorecard and Its Impact on Sustainable Development of Renewable Energy Organizations; A Mediating Role of Political and Regulatory Institutions

Artigo publicado em revista científica internacionalOrganizational strategic programs are continuously evolving and gaining the attention of policy makers in order to construct organizations’ ecological and socioeconomic systems. The purpose of this study is to examine the relationship between the balanced scorecard (BSC) and sustainable development involving the mediated effect of political and regulatory influence. To achieve the core objectives of the research, the quantitative (positivism) research method is applied. The goal of the current research is made possible through the quantitative method because of its objective nature of reality. A total of 320 questionnaires were distributed among the different levels of managers; 280 respondents returned the questionnaire. The data are analyzed through a modern statistical tool called Smart-PLS, Partial Least Squares (PLS) is high graphical user interference software that is used to calculate Structural Equation Modeling (SEM) through PLS path modeling. Factor analysis is conducted to eliminate the variables that have no contribution and to reduce the variables to obtain better results in regression. The implications are for energy organizations that are struggling to deal with sustainable development and these tools can help them to achieve their sustainability goals. The study concludes that the adoption of BSC is essential to ensure sustainable development regardless of its challenges. Moreover, consideration of meta-constitutional rules as political influence is important to understand and address in order to mitigate financial loss. In nutshell, the use of BSC is highly recommended to eliminate the routine problems and to ensure environmental sustainability.info:eu-repo/semantics/publishedVersio

ANALYTICAL METHOD BY HPLC-DAD ALLOWS QUANTIFICATION OF QUERCETIN MARKER IN STANDARDIZED EXTRACT OF ANADENANTHERA COLUBRINA VAR. CEBIL

Objective: The Anadenanthera colubrina (Vell.) Brennan var. cebil is a medicinal plant that has been used for the treatment of many diseases in the northeastern region of Brazil. This plant contains secondary metabolites such as quercetin, a flavonoid that is known by its antioxidant and anti-inflammatory effects. The aim of this work is to propose the validation of an analytical method using high-performance liquid chromatography with diode array detector (HPLC-DAD) for the quantification of quercetin and standardization of the hydroalcoholic extract (HAE) of A. colubrina.Methods: The A. colubrina extracts were prepared by the maceration process with powdered leaves at 20% weight: volume (w/v) and a hydroalcoholic solution at 50% volume: volume (v/v) for 120 h at room temperature. After pretreatment of the hydroalcoholic extract, the quercetin marker was used for quantification and proceeded to the evaluation of validation parameters for the method using HPLC-DAD.Results: The analytical method proved to be specific. Linear over the range 1.4–26.6 µg/ml, regression analysis showed a good correlation coefficient (R2= 0.999); the limit of detection (LOD) and the limit of quantification (LOQ) were 0.27 and 0.81 μg/ml respectively. The relative standard deviation (RSD) did not exceed 2.5% for precision. The proposed method was validated with an average recovery of 92.5–97.5%.Conclusion: The method was validated using HPLC-DAD, allowing the quantification of quercetin in the standardisation process of extracts and quality control of the herbal drug containing A. colubrina Phyto complex

An Analysis of Pakistani Corporate Sector

Khan, K. I., Qadeer, F., Mata, M. N., Dantas, R. M., Xavier Rita, J., & Martins, J. N. (2021). Debt Market Trends and Predictors of Specialization: An Analysis of Pakistani Corporate Sector. JOURNAL OF RISK AND FINANCIAL MANAGEMENT, 14(5), 1-16. [224]. https://doi.org/10.3390/jrfm14050224Recently, debt structure research has started focusing on the strategic perspective of financing choices, particularly to understand the reasons for debt specialization (DS). This paper examines trends of specialization over time and industry by using a comprehensive dataset on types of debt employed by the public limited companies during 2009-2018. The objective of the current study is to analyze the effect of debt market conditions by identifying significant predictors of DS. Time-series and cross-sectional results confirm the existence of DS, which is further validated by the findings of the cluster analysis. The empirical results indicate that overall, 61% of the companies solely rely on a single type of debt, mostly on short-term obligations accompanied by long-term secured and other debts. Moreover, small, mature, rated, group-affiliated, and low-leverage companies incline more towards this strategy. Credit rating, debt maturity, financial and interest coverage ratios serve as the primary determinants of the debt market that are significantly associated with the measures of DS. The results contribute to the capital structure literature by specifying that financing choice has an important implication in deciding the debt structure composition of the organizations.publishersversionpublishe