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Article
Publication date: 16 September 2021

JiaRong Wang, Bo He and XiaoQiang Chen

This paper aims to obtain a symmetrical step-down topology with lower equivalent capacity and wider step-down range under the condition of the same output. Two new…

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Abstract

Purpose

This paper aims to obtain a symmetrical step-down topology with lower equivalent capacity and wider step-down range under the condition of the same output. Two new symmetrical step-down topologies of star-connected autotransformers are proposed in this paper. Taking the equivalent capacity as the main parameter, the obtained topologies are modeled and analyzed in detail.

Design/methodology/approach

This paper adopts the research methods of design, modeling, analysis and simulation verification. First, the star-connected autotransformer is redesigned according to the design objective of symmetrical step-down topology. In addition, the mathematical model of two topologies is established and a detailed theoretical analysis is carried out. Finally, the theoretical results are verified by simulation.

Findings

Two symmetrical star-connected autotransformer step-down topologies are designed, the winding configurations of the corresponding topology are presented, the step-down ranges of these three topologies are calculated and the influence of step-down ratio on the equivalent capacity of autotransformer are analyzed. Through analysis, the target step-down topologies are obtained when the step-down ratio is [1.1, 5.4] and [1.1, 1.9] respectively.

Research limitations/implications

Because the selected research object is only a star-connected autotransformer, the research results may lack generality. Therefore, researchers are encouraged to further study the topologies of other autotransformers.

Practical implications

This paper includes the implications of the step-down ratio on the equivalent capacity of autotransformers and the configuration of transformer windings.

Originality/value

The topologies designed in this paper enable star-connected autotransformer in the 12-pulse rectifier to be applied in step-down circumstances rather than situations of harmonic reduction only. At the same time, this paper provides a way that can be used to redesign the autotransformer in other multi-pulse rectifier systems, so that those transformers can be used in voltage regulation.

Article
Publication date: 2 September 2019

JiaRong Wang and XiaoQiang Chen

This paper aims to obtain a symmetrical step-down topology with lower equivalent capacity and wider step-down range under the condition of the same output. Three new…

Abstract

Purpose

This paper aims to obtain a symmetrical step-down topology with lower equivalent capacity and wider step-down range under the condition of the same output. Three new symmetrical step-down topologies of zigzag autotransformer are proposed in this paper. Taking the equivalent capacity as the main parameter, the obtained topologies are modeled and analyzed in detail.

Design/methodology/approach

This paper adopts the research methods of design, modeling, analysis and simulation verification. First, the zigzag autotransformer is redesigned according to the design objective of symmetrical step-down topology. Second, the mathematical model of the designed topology is established, and the detailed theoretical analysis is carried out. Finally, the theoretical results are verified by simulation.

Findings

Three symmetrical zigzag autotransformer step-down topologies are designed, the winding configurations of the corresponding topology are presented, the step-down ranges of these three topologies are calculated and the influence of step-down ratio on equivalent capacity of autotransformer is analyzed. Through analysis, the target step-down topologies are obtained when the step-down ratio is [0.969, 1.414] and [1.414, 8].

Research limitations/implications

Because the selected research object is only zigzag autotransformer, the research results may lack generality. Therefore, researchers are encouraged to further study topologies of other autotransformers.

Practical implications

This paper includes the implications of step-down ratio on the equivalent capacity of autotransformer and the configuration of transformer windings.

Originality/value

The topologies designed in this paper enable zigzag autotransformer to be applied in step-down circumstances.

Article
Publication date: 1 August 2006

Eufrosina Otlacan and Romulus‐Petru Otlacan

To explain the objectivity of the globalisation process by using the mathematical theory of topological structures.

2207

Abstract

Purpose

To explain the objectivity of the globalisation process by using the mathematical theory of topological structures.

Design/methodology/approach

After a brief presentation of the history and features of the globalisation phenomena, there are presented the basic notions of the mathematical concept of topology. Besides geometrical distance and geometrical topology, the authors define informational distance and informational topology. An informational neighbourhood of a person P is the informational medium that he/she masters, a set of persons with whom P communicates in a well‐determined interval of time. There is presented a hierarchy of informational topologies which structured human life on Earth. Nowadays, the world benefits from the finest topology, the topology of communication by the internet (TCI).

Findings

The possibility to conceive the globalisation process as a multidimensional vector function defined on the set of the world population. The projections of this vector function on the subsystems of human life refer to the political, economic, military, cultural or religious life. The continuity of this function in the TCI sense expresses the possibility for the globalisation phenomenon to be controlled.

Practical implications

The very understanding of the objectivity of the globalisation process and an important conclusion: the control of the situation only on a compact geographic area cannot ensure the stability of this area; it must have control over a neighbourhood of the informational topology. This means possessing informational instruments so as to be able to manage the economic, political and social activity and to avoid catastrophe.

Originality/value

Concept of mathematical topological structure applied to a complex social phenomenon.

Details

Kybernetes, vol. 35 no. 7/8
Type: Research Article
ISSN: 0368-492X

Keywords

Article
Publication date: 7 December 2021

Sébastien Lalléchére, Jamel Nebhen, Yang Liu, George Chan, Glauco Fontgalland, Wenceslas Rahajandraibe, Fayu Wan and Blaise Ravelo

The purpose of this paper is to study, a bridged-T topology with inductorless passive network used as a bandpass (BP) negative group delay (NGD) function.

Abstract

Purpose

The purpose of this paper is to study, a bridged-T topology with inductorless passive network used as a bandpass (BP) negative group delay (NGD) function.

Design/methodology/approach

The BP NGD topology under study is composed of an inductorless passive resistive capacitive network. The circuit analysis is elaborated from the equivalent impedance matrix. Then, the analytical model of the C-shunt bridged-T topology voltage transfer function is established. The BP NGD analysis of the considered topology is developed in function of the bridged-T parameters. The NGD properties and characterizations of the proposed topology are analytically expressed. Moreover, the relevance of the BP NGD theory is verified with the design and fabrication of surface mounted device components-based proof-of-concept (PoC).

Findings

From measurement results, the BP NGD network with −151 ns at the center frequency of 1 MHz over −6.6 dB attenuation is in very good agreement with the C-shunt bridged-T PoC.

Originality/value

This paper develops a mathematical modeling theory and measurement of a C-shunt bridged-T network circuit.

Details

Circuit World, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 1 March 1973

D.W. KATZNER

There are many important issues arising in the non‐physical sciences which require the investigation of phenomena not, at present, capable of measurement. This paper…

Abstract

There are many important issues arising in the non‐physical sciences which require the investigation of phenomena not, at present, capable of measurement. This paper develops analytical techniques for handling them. Static, dynamic and choice models are considered.

Details

Kybernetes, vol. 2 no. 3
Type: Research Article
ISSN: 0368-492X

Article
Publication date: 1 August 2006

Andreas Hanemann, Athanassios Liakopoulos, Maurizio Molina and D. Martin Swany

Research backbone networks like GÉANT2 and the national research and education networks are used by a variety of scientists and research projects. These users and the…

1176

Abstract

Purpose

Research backbone networks like GÉANT2 and the national research and education networks are used by a variety of scientists and research projects. These users and the network engineers operating the networks would like to get access to network performance metrics to optimise their use of the network and to troubleshoot performance degradations when they happen. A variety of tools for performing network measurements already exist, and the perfSONAR architecture developed in the Joint Research Activity 1 (JRA1) of GÉANT2 aims at integrating them into a coherent framework. However, a harmonised definition of the most interesting metrics and how measurements must be carried out is still lacking.

Design/methodology/approach

This paper suggests some of the elementary metrics which are relevant for assessing network performance, along with an indication about how to post‐process (or “transform”, or “compose”) them in order to obtain derived summary values that can quickly and intuitively give an indication of network performance. Methods to perform the composition are presented, together with constraints which have to be taken into account to get accurate results. In particular, delay measurements are the most delicate ones to compose.

Findings

The authors carried out a series of experiments for proofing the validity of the composition of delay metrics, and briefly present some preliminary results, that confirm the applicability of the proposed methodology.

Research limitations/implications

Future work needs to confirm the paper's findings on other data sets, possibly collected in different network locations.

Practical implications

The practical implication of the findings is that it is possible for a network operator to accurately predict high percentiles of delays on an end‐to‐end path starting from independent delay measurements on subsequent path sections.

Originality/value

The main original contribution of this paper is the application to a real data set of a post‐processing procedure that is derived from simple statistics theory.

Details

Campus-Wide Information Systems, vol. 23 no. 4
Type: Research Article
ISSN: 1065-0741

Keywords

Article
Publication date: 1 November 1997

Masudul Alam Choudhury

Undertakes a historico‐theoretical study to outline the constitutional and developmental predicament of the Native Indian people in Canada against the hegemonic models…

1234

Abstract

Undertakes a historico‐theoretical study to outline the constitutional and developmental predicament of the Native Indian people in Canada against the hegemonic models instituted by the Federal Department of Indian Affairs and Northern Development. Analyses a factual survey done by Statistics Canada to highlight the various kinds of socio‐economic problems being faced by Native Indians and to point out the prospects before them. Recommends an ecological alternative in the light of the new land rights being signed between the Federal Government and the Native Indians in Canada. Introduces a concept of social wellbeing and formalizes this as a criterion for evaluating the economic, social and political factors in an interactive and consensual way to generate better futures with conflict resolution.

Details

International Journal of Social Economics, vol. 24 no. 11
Type: Research Article
ISSN: 0306-8293

Keywords

Article
Publication date: 17 August 2021

Saeed Alizadeh, Mohammad Farhadi-Kangarlu and Behrouz Tousi

Multilevel inverters (MLIs) have been studied widely over the past two decades because of their inherent advantages and interesting features. However, most of the newly…

Abstract

Purpose

Multilevel inverters (MLIs) have been studied widely over the past two decades because of their inherent advantages and interesting features. However, most of the newly introduced structures suffer from the increased standing voltage of the switches, which is defined as the maximum off-state voltage on the switches, losing modularity and increased number of direct current (DC) voltage sources. The purpose of this study is to propose a new hybrid MLI topology to alleviate the mentioned problems.

Design/methodology/approach

The proposed approach in this study includes using the advantage of two different topologies and combine them in a way that the advantages of both of the topologies are achieved. Therefore, the approach is to design a hybrid topology from two existing topologies so that a new topology has resulted.

Findings

This paper proposes a new hybrid MLI with lower power electronic switches and lowers DC voltage sources in comparison with the classic structures. The proposed MLIs maintain a balance between the number of switches, the standing voltage on the switches and the number of DC sources. The topology description, modulation method and comparative study have been presented. Also, another more reduced structure is presented for higher power factor operation. The MATLAB simulation and experimental results of a nine-level inverter have been presented to verify its operation.

Originality/value

The hybrid topology has a new structure that has not been presented before. It is important to emphasize that the topology combination and achieving the hybrid topology is wisely accomplished to improve some features of the MLI.

Details

Circuit World, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 5 February 2018

Ajay Vadakkepatt, Sanjay R. Mathur and Jayathi Y. Murthy

Topology optimization is a method used for developing optimized geometric designs by distributing material pixels in a given design space that maximizes a chosen quantity…

Abstract

Purpose

Topology optimization is a method used for developing optimized geometric designs by distributing material pixels in a given design space that maximizes a chosen quantity of interest (QoI) subject to constraints. The purpose of this study is to develop a problem-agnostic automatic differentiation (AD) framework to compute sensitivities of the QoI required for density distribution-based topology optimization in an unstructured co-located cell-centered finite volume framework. Using this AD framework, the authors develop and demonstrate the topology optimization procedure for multi-dimensional steady-state heat conduction problems.

Design/methodology/approach

Topology optimization is performed using the well-established solid isotropic material with penalization approach. The method of moving asymptotes, a gradient-based optimization algorithm, is used to perform the optimization. The sensitivities of the QoI with respect to design variables, required for optimization algorithm, are computed using a discrete adjoint method with a novel AD library named residual automatic partial differentiator (Rapid).

Findings

Topologies that maximize or minimize relevant quantities of interest in heat conduction applications are presented. The efficacy of the technique is demonstrated using a variety of realistic heat transfer applications in both two and three dimensions, in conjugate heat transfer problems with finite conductivity ratios and in non-rectangular/non-cuboidal domains.

Originality/value

In contrast to most published work which has either used finite element methods or Cartesian finite volume methods for transport applications, the topology optimization procedure is developed in a general unstructured finite volume framework. This permits topology optimization for flow and heat transfer applications in complex design domains such as those encountered in industry. In addition, the Rapid library is designed to provide a problem-agnostic pathway to automatically compute all required derivatives to machine accuracy. This obviates the necessity to write new code for finding sensitivities when new physics are added or new cost functions are considered and permits general-purpose implementations of topology optimization for complex industrial applications.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 7 May 2020

Jéderson da Silva, Jucélio Tomás Pereira and Diego Amadeu F. Torres

The purpose of this paper is to propose a new scheme for obtaining acceptable solutions for problems of continuum topology optimization of structures, regarding the…

Abstract

Purpose

The purpose of this paper is to propose a new scheme for obtaining acceptable solutions for problems of continuum topology optimization of structures, regarding the distribution and limitation of discretization errors by considering h-adaptivity.

Design/methodology/approach

The new scheme encompasses, simultaneously, the solution of the optimization problem considering a solid isotropic microstructure with penalization (SIMP) and the application of the h-adaptive finite element method. An analysis of discretization errors is carried out using an a posteriori error estimator based on both the recovery and the abrupt variation of material properties. The estimate of new element sizes is computed by a new h-adaptive technique named “Isotropic Error Density Recovery”, which is based on the construction of the strain energy error density function together with the analytical solution of an optimization problem at the element level.

Findings

Two-dimensional numerical examples, regarding minimization of the structure compliance and constraint over the material volume, demonstrate the capacity of the methodology in controlling and equidistributing discretization errors, as well as obtaining a great definition of the void–material interface, thanks to the h-adaptivity, when compared with results obtained by other methods based on microstructure.

Originality/value

This paper presents a new technique to design a mesh made with isotropic triangular finite elements. Furthermore, this technique is applied to continuum topology optimization problems using a new iterative scheme to obtain solutions with controlled discretization errors, measured in terms of the energy norm, and a great resolution of the material boundary. Regarding the computational cost in terms of degrees of freedom, the present scheme provides approximations with considerable less error if compared to the optimization process on fixed meshes.

1 – 10 of over 4000