Search results

A quantitative method for the estimation of the discrete transition matrix is developed for the periodic time‐varying system of state differential equations governing electrical synchronous machine behaviour. The approach allows the eigensystem of this transition matrix to be calculated to an arbitrary accuracy without significant added computational burden by using modal structural properties of the state‐space equations.

The superiority of the fast‐decoupled loadflow [FDLF] method is attributable to the underlying decoupling assumptions which, however, may not be valid for all modes of system operation. For example, during a restoration period following an emergency or in circumstances of unusual plant outages the assumptions of near nominal voltages and small phase angle differences may not be valid. Also for equivalencing methods, if large values of shunt admittance are contributed by the equivalent external networks, or if tap‐changing transformers are included, the FDLF method has shortcomings.

This paper aims to present an inverter with a current-source input for 400 Hz avionic systems to have a system which removes DC-link capacitors and presents a high efficiency.

A battery-powered DC link inductor generates a constant-current source. A single high-frequency switch is used to provide a sinusoidally modulated current before the inverter. The output of the switch is “unfolded” by a thyristor-based H-bridge inverter to generate an AC output current. The system uses a CL low-pass filter to obtain a 400 Hz pure sine wave by removing pulse width modulation components.

Simulations and Typhoon HIL real-time experiments were performed with closed-loop control to validate the proposed inverter concept while meeting the critical standards of MIL-STD-704F.

This current source inverter topology is suitable for avionic systems that require 400 Hz output frequency. The topology uses small DC-link inductor and eliminates bulky capacitor which determines the inverter lifetime.

The study aims to optimize truck routes by minimizing social and economic costs. It introduces a strategy involving diverse drones and their potential for reusing at DNs based on flight range. In HTDRP-DC, trucks can select and transport various drones to LDs to reduce deprivation time. This study estimates the nonlinear deprivation cost function using a linear two-piece-wise function, leading to MILP formulations. A heuristic-based Benders Decomposition approach is implemented to address medium and large instances. Valid inequalities and a heuristic method enhance convergence boundaries, ensuring an efficient solution methodology.

Research has yet to address critical factors in disaster logistics: minimizing the social and economic costs simultaneously and using drones in relief distribution; deprivation as a social cost measures the human suffering from a shortage of relief supplies. The proposed hybrid truck-drone routing problem minimizing deprivation cost (HTDRP-DC) involves distributing relief supplies to dispersed demand nodes with undamaged (LDs) or damaged (DNs) access roads, utilizing multiple trucks and diverse drones. A Benders Decomposition approach is enhanced by accelerating techniques.

Incorporating deprivation and economic costs results in selecting optimal routes, effectively reducing the time required to assist affected areas. Additionally, employing various drone types and their reuse in damaged nodes reduces deprivation time and associated deprivation costs. The study employs valid inequalities and the heuristic method to solve the master problem, substantially reducing computational time and iterations compared to GAMS and classical Benders Decomposition Algorithm. The proposed heuristic-based Benders Decomposition approach is applied to a disaster in Tehran, demonstrating efficient solutions for the HTDRP-DC regarding computational time and convergence rate.

Current research introduces an HTDRP-DC problem that addresses minimizing deprivation costs considering the vehicle’s arrival time as the deprivation time, offering a unique solution to optimize route selection in relief distribution. Furthermore, integrating heuristic methods and valid inequalities into the Benders Decomposition approach enhances its effectiveness in solving complex routing challenges in disaster scenarios.

The implementation of hierarchic agglomerative methods of cluster anlaysis for large datasets is very demanding of computational resources when implemented on conventional computers. The ICL Distributed Array Processor (DAP) allows many of the scanning and matching operations required in clustering to be carried out in parallel. Experiments are described using the single linkage and Ward's hierarchical agglomerative clustering methods on both real and simulated datasets. Clustering runs on the DAP are compared with the most efficient algorithms currently available implemented on an IBM 3083 BX. The DAP is found to be 2.9–7.9 times as fast as the IBM, the exact degree of speed‐up depending on the size of the dataset, the clustering method, and the serial clustering algorithm that is used. An analysis of the cycle times of the two machines is presented which suggests that further, very substantial speed‐ups could be obtained from array processors of this type if they were to be based on more powerful processing elements.

THE earliest catalogue of Cambridge University documents was compiled by Mr. William Rysley, in 1420. Most of the documents enumerated in this list are still extant. An interesting List of the Documents in the University Registry, from the year 1266 to the year 1544, was communicated to the Cambridge Antiquarian Society by the Rev. H. R. Luard, B.D., then University Registrar, on March 6th, 1876. From this, it appears that “The earliest document which the University possesses is so late as the year 1266. The earliest in the Record office is dated 16th July, 13 Hen. III., i.e. 1229. This is a permission to scholars of the University of Paris to come to England, and remain for purposes of study.”

Multiobjective planning models for electric power distribution system planning can include multiple aspects such as community amenity values, geographical conditions of the study area, reliability evaluations (mainly in terms of service continuity), or the optimal voltage profile in the network, as well as the basic planning aspects: power demand requirements, power capacity limits and the minimization of the total system expansion costs. On the other hand, classical single objective planning models have usually considered only the basic aspects. This paper describes a multiobjective model to find the optimal voltage profile and to look for the least cost system expansion simultaneously. Furthermore, two multiobjective techniques for the application of the model to distribution system expansion problems are outlined. The computer results have shown that multiobjective models are able to find solutions which include multiple planning objectives simultaneously, and that these solutions are advantageous compared with the ones from classical single objective models.

The purpose of this survey is to find a significant sample of reference resources for electrical engineering as they are presented in subject-specific LibGuides.

The survey is based on a detailed observation and collection of sources designated as Reference Resources in LibGuides, titles found were compiled and organized.

The results are substantial; they offered a body of specialized resources, which includes e-book collections, dictionaries, handbooks, encyclopedias and other resources that are important to electrical engineering students and researchers.

A considerable amount of resources were found; nevertheless, they represent the resources found in a randomly selected sample of LibGuides; therefore, the result is limited to the group of libraries selected.

The results of this survey are valuable to subject librarians interested in comparing resources with a pool of libraries and to discover titles that can be of interest to their collections.

The work is original, as this is the first paper publishing the results of a survey of electrical engineering guides.

The purpose of this paper is to explore Portuguese academics' perceptions on higher education quality assessment objectives and purposes, in general, and on the recently implemented system for higher education quality assessment and accreditation, in particular. It aims to discuss the differences of those perceptions dependent on some academics' characteristics, such as: gender, disciplinary affiliation, type of higher education institution and experience in quality assurance activities.

An online questionnaire with Likert‐type answer scales was distributed to the Portuguese academic population (n=36,215). In total, 962 answers were collected from academics belonging to the public higher education system. Data were treated resorting to descriptive statistics, hypothesis tests and analysis of variance.

Portuguese academics tend to support the majority of goals and purposes quality assessment may have, as well as the main features of the newly designed quality assessment and accreditation system. Nevertheless they tend to support more quality assessment mechanisms privileging improvement over control. This support is slightly more evident among female academics, academics from public polytechnic institutions, from medical and health sciences and with former experience in quality assurance activities.

The study adds to the discussion on academics' perceptions on quality assurance, highlighting the influence played at this level by some of their characteristics. It is especially relevant for those working either in higher education institutions or governmental agencies, since it may contribute to the design of quality assurance systems academics are more likely to support.