Reliability of a k-out-of-n: G System Subjected to Marshall-Olkin Type Shocks Concerning Magnitude

In this paper the reliability of a k-out-of-n: G system under the effect of shocks having the Marshall-Olkin type shock models, is studied. The magnitudes of the shocks are considered. The system contains n components and only functions when at least k of these components function. The system is subjected to (n + 1) shocks coming from (n + 1) different sources. The shock coming from the it h source may destroy the it h component, i = 1, . . . , n, while the shock coming from the (n + 1)t h source may destroy all components simultaneously. A shock is fatal, destroys a component (components), whenever its magnitude exceeds an upper threshold. The system reliability is obtained by considering the arrival time and the magnitude of a shock as a bivariate random variable. It is assumed that the bivariate random variables representing the arrival times and the magnitudes of the shocks are independent with non-identical bivariate distributions. Since the computation of the reliability formula obtained is not easy to handle, an algorithm is introduced for calculating the reliability formula. The reliability of a k-out-of-n: G system subjected to independent and identical shocks is obtained as a special case, as well as the reliabilities of the series and the parallel systems. As an application, the bivariate exponential Gumbel distribution is considered. Also, numerical illustrations are performed to highlight the results obtained

Addendum: Abubakar, U.; Mekhilef, S.; Mokhlis, H.; Seyedmahmoudian, M.; Horan, B.; Stojcevski, A.; Bassi, H.; Rawa, M.J.H. Transient Faults in Wind Energy Conversion Systems: Analysis, Modelling Methodologies and Remedies. Energies 2018, 11, 2249

The authors would like to make the following addition to their paper [...

Progress on protection strategies to mitigate the impact of renewable distributed generation on distribution systems

The benefits of distributed generation (DG) based on renewable energy sources leads to its high integration in the distribution network (DN). Despite its well-known benefits, mainly in improving the distribution system reliability and security, there are challenges encountered from a protection system perspective. Traditionally, the design and operation of the protection system are based on a unidirectional power flow in the distribution network. However, the integration of distributed generation causes multidirectional power flows in the system. Therefore, the existing protection systems require some improvement or modification to address this new feature. Various protection strategies for distribution system have been proposed so that the benefits of distributed generation can be fully utilized. This paper reviews the current progress in protection strategies to mitigate the impact of distributed generation in the distribution network. In general, the reviewed strategies in this paper are divided into: (1) conventional protection systems and (2) modifications of the protection systems. A comparative study is presented in terms of the respective benefits, shortcomings and implementation cost. Future directions for research in this area are also presented

Comprehensive review of radial distribution test systems for power system distribution education and research

A comprehensive review of existing radial distribution test systems available for power system distribution research is presented. The review can be used to establish a record of cases suitable for distribution operation and planning studies. The importance of the distribution system, the structure of the system in the grid, and various configurations of the distribution network are discussed. The primary requirement of a distribution network is highlighted to underline the important system parameters that should be considered in the design and planning stages. Various research related to the distribution network can be conducted, such as load flow algorithms, optimal incorporation of distributed generation, network reconfiguration, and optimal capacitor allocation, such as important details pertaining to each test system are given. Additional information, such as active and reactive loads and losses, minimum voltage values, and bus location with the weakest voltage values, is provided. Application of the reviewed works based on the test system is tabulated and presented. The information presented in this paper will be beneficial for future research in distribution system design and planning

Stability evaluation of a grid-tied hybrid wind/PV farm joined with a hybrid energy-storage system

This paper presents the stability-evaluation outcomes of a multimachine power system (MMPS) connected with a large-scale hybrid wind farm (WF) and photovoltaic (PV) farm or hybrid wind/PV farm (HWPF) and a hybrid energy-storage system (HESS) consisting of a vanadium redox flow battery (VRFB) and a supercapacitor (SC). A probability scheme is used to determine the rated power of the proposed HESS, where the capacities of the VRFB-ESS and the SC-ESS are designed to effectively utilize their operating features. The control strategy of the HESS is proposed to reduce the pressure of the VRFB-ESS and smooth the output power fluctuations of the HWPF. The steady-state stability, small-signal stability, dynamic performances, and transient simulations of the studied grid-tied HWPF fed to the MMPS with and without the HESS are achieved. The simulation outcomes show that the proposed HESS can enhance the stability and power-smoothing performance of the HWPF fed to the MMPS

Інновацій в управлінні персоналом: контент-аналіз

У статті зазначено, що одним із завдань управління людськими ресурсами (УЛР) є підвищення рівня задоволеності умовами праці як менеджерів, так і працівників. Головною метою дослідження є аналіз сучасних викликів, які постають перед менеджерами промислових підприємств при впровадженні практик УЛР у країнах, що розвиваються, на прикладі Марокко. Методологія практико-орієнтованого дослідження базується на якісному методі, в основі якого лежить використання контентаналізу. Детерміновану вибірку даних сформовано на основі відповідей 30 менеджерів, які взяли участь у неформальному інтерв’ю. У статті проаналізовано рівень задоволеності менеджерів функціями УЛР, описано практики, які використовуються для мотивації працівників, виявлено слабкі місця та бар’єри, що знижують ефективність УЛР на промислових підприємствах Марокко. Отримані емпіричні результати дослідження свідчать, що найбільший негативний вплив на ефективність УЛР здійснюють такі фактори як: відсутність належної структурованості відділу кадрів; не розвиненість системи документообігу; некомпетентність працівників; відсутність ефективних методів управління. При цьому авторами зазначено, що для підвищення ефективності УЛР доцільним є впровадження системи підвищення кваліфікації кадрів, розроблення системи охорони праці та системи контролю відповідності поставлених завдань, формування системи соціальної підтримки працівників пенсійного віку. У ході дослідження встановлено, що відсутність активного спілкування, чітких цілей, а також обмін недоцільною внутрішньою інформацією являються факторами-дестимуляторами ефективності УЛР. Для вирішення визначених проблем авторами запропоновано впровадити інформаційне забезпечення УЛР та відповідні ІТ інструменти. У статті доведено, що інформаційні системи стимулюють активну комунікацію між працівниками, структуроване зберігання інформації та формування баз даних, що сприяє підвищенню якості прийнятих рішень. Авторами зазначено, що результати дослідження можуть бути корисними для спеціалістів відділу кадрів та керівників підприємств.One of the objectives of human resource management (HRM) is to promote the satisfaction of both managers and employees regarding HRM practices. Since promoting satisfaction begins by assessing its current level, this study aims to analyse the challenges faced by industrial companies' managers within developing countries – such as Morocco- in terms of implementing human resource (HR) function practices. This paper presents then a practice-oriented study conducted using a qualitative method based on the content analysis approach. Thus, data collection was based mainly on semi-structured interviews to which 30 managers had participated. Indeed, this study aims to measure managers' satisfaction regarding the HR function while highlighting, at the same time, the practices used in motivation, documentation process, etc., and in terms of locating weaknesses and obstacles to better HRM. The validity of inquiry was tested and proven by two validation strategies: member checking and external audits strategies. The results found, revealed genuinely remarkable weaknesses. Indeed, it turned out to be a lack consistent in terms of the proper structuring of the HR function. In addition to the poor mastery and application of basic HRM practices, namely the primitivity of documentation processes, and the job-person inadequacy, especially in the scarcity of adoption of developed management methods such as the implementation of provisional management of jobs and skills, the establishment of an occupational health system, and maturity in terms of carrying out the tasks of the control system, or even as regards the weaknesses linked to the lack of active communication, to the clarity of the objectives targeted for all the members, and to the sharing of private information, in addition to those arising from the irrelevance of the training received by the staff. As for proposing solutions, the integration of IT tools could improve the performance of HR management processes. Indeed, information systems promote active communication, different storage data that develop the quality of the decision. They also facilitate managing administrative issues, communicating and applying procedures, programming relevant training and motivating employees. The study has important implications for HR professionals and strategic leaders that are especially interested in developing countries

Exact reliability formula for a linear consecutive k-out-of-n: F system and relayed consecutive systems with a change point for any k?n, with stress-strength application.

This paper presents exact formulas for the reliability of linear consecutive k-out-of-n: F, and relayed consecutive k-out-of-n: F systems, having a change point at position c, 1 ? c ? n, for any k?n. A change point at position c, means that the components after this point have reliabilities that are different from those before or at position c. The components are assumed to be independent. Practically, the change in the components reliabilities may be due to change in the stress applied. Assuming a change in stress, exact formulas of the stress-strength reliability of the systems are derived, considering two cases. The first case assumed strength and stress having the same form of distributions, while the second case assumed strength and stress having different forms of distributions. Estimation of the stress-strength reliability for both cases is discussed. Application to both cases are considered with numerical illustration

A comparative study of multi-objective optimal power flow based on particle swarm, evolutionary programming, and genetic algorithm

This paper compares the performance of three population-based algorithms including particle swarm optimization (PSO), evolutionary programming (EP), and genetic algorithm (GA) to solve the multi-objective optimal power flow (OPF) problem. The unattractive characteristics of the cost-based OPF including loss, voltage profile, and emission justifies the necessity of multi-objective OPF study. This study presents the programming results of the nine essential single-objective and multi-objective functions of OPF problem. The considered objective functions include cost, active power loss, voltage stability index, and emission. The multi-objective optimizations include cost and active power loss, cost and voltage stability index, active power loss and voltage stability index, cost and emission, and finally cost, active power loss, and voltage stability index. To solve the multi-objective OPF problem, Pareto optimal method is used to form the Pareto optimal set. A fuzzy decision-based mechanism is applied to select the best comprised solution. In this work, to decrease the running time of load flow calculation, a new approach including combined Newton-Raphson and Fast-Decouple is conducted. The proposed methods are tested on IEEE 30-bus test system and the best method for each objective is determined based on the total cost and the convergence values of the considered objectives. The programming results indicate that based on the inter-related nature of the objective functions, a control system cannot be recommended based on individual optimizations and the secondary criteria should also be considered

Stress Strength Reliability of Regular and Relayed Linear Consecutive k Out of n : F Systems with m Change Points

This paper presents a stress strength reliability model of regular and relayed linear consecutive k out of n : F systems with m change points. The components are assumed to be identical and independent. Explicit expressions of the reliabilities are obtained, and hence the stress strength reliability is obtained generally for any distributions of stresses and strengths. As an application, the distribution of the strength is taken to be generalized Lindely, while the stresses are exponential. The reliability estimators are obtained by applying EM algorithm. Finally, a numerical illustration is performed to highlight the theoretical results obtained