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1 – 10 of 94
Article
Publication date: 1 January 1991

Jose A.D. PINTO, Paulo B. COIMBRA and Carlos F.L. ANTUNES

Empirical rules and experimental evidence are not capable of dealing with both geometric complexity and nonlinearities to design a sufficient accurate, reliable and…

Abstract

Empirical rules and experimental evidence are not capable of dealing with both geometric complexity and nonlinearities to design a sufficient accurate, reliable and affordable electrical device. To minimize this gap and to achieve an high performance level in the industry design of an electromagnetic device two CAD packages (electromagnetic CAD package and thermal CAD package) working in parallel processing should be used. In this paper these two packages have been used separately. The finite element technique is used to solve the heat conduction problem in complex devices of arbitrary shape with imposed boundary conditions. As an application example, the steady‐state temperature distribution will be produced for an high voltage cross‐linked polyethylene insulated power cable. The results are discussed and the importance of such a study as an aid to improve the life expectancy of high voltage power cables is pointed out. Finally, several conclusions are suggested to increase the power cable current transmission capacity.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 10 no. 1
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 6 July 2015

Tony R. Almeida and Carlos L. Antunes

In this paper a numerical simulation analysis of a modified stent-based electrode is introduced to be used as a bipolar electrode for radio frequency ablation of tumours…

Abstract

Purpose

In this paper a numerical simulation analysis of a modified stent-based electrode is introduced to be used as a bipolar electrode for radio frequency ablation of tumours located in hollow organs. The purpose of this paper is to study the possibility of achieving a more regular volume of induced lesion with the presented electrode without imperilling the ductal organ where the tumour is located.

Design/methodology/approach

Three types of bipolar electrode configurations were considered, formed by two, three and five tubular segments. Numerical simulations were performed considering a tumour located in the bile duct, where two important blood vessels – the portal vein and the hepatic artery – have a significant impact due to the convective heat transfer caused by the blood flow (heat sink effect) which significantly affects the shape of lesion that is intended to induce in order to destroy the tumour.

Findings

The results obtained show that the five-segment electrode arrangement allows a regular volume for the induced lesion, independently of the different values of applied voltage considered.

Originality/value

The presented work introduces a numerical simulation analysis on a modified based-stent electrode previously studied. In this case, the electrode is configured so it can be used as a bipolar electrode, i.e., active and ground electrode are placed in the same device. Besides the results evinced by the obtained results, this kind of electrode avoids eventual skin burns that might occur due to the need of the return electrodes when monopolar electrodes are used.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 April 1995

JoséAmérico Dias Pinto, António Paulo Breda Coimbra and Carlos F.R. Lemos Antunes

In this paper it is proposed a thermal Finite element formulation that accommodates the current density dependency on the resistivity variation with temperature. As an…

Abstract

In this paper it is proposed a thermal Finite element formulation that accommodates the current density dependency on the resistivity variation with temperature. As an application example, the steady‐state temperature distribution will be produced for a large 3‐phase induction motor as well as the hot spot temperature for different load conditions. The results produced by the proposed Finite element approach will be compared with the solution obtained considering the current density independent of the temperature as well as with experimental data.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 14 no. 4
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 6 July 2012

Carlos L. Antunes, Tony Richard O. Almeida and Nélia Raposeiro

Cholangiocarcinoma is an adenocarcinoma of the bile ducts which drain bile from the liver into the small intestine. Unfortunately, most patients are diagnosed at an…

Abstract

Purpose

Cholangiocarcinoma is an adenocarcinoma of the bile ducts which drain bile from the liver into the small intestine. Unfortunately, most patients are diagnosed at an advanced stage of the disease with almost no chances for surgery, the only potentially curative treatment. As nitinol stents can be used to reduce stricture problems of the bile duct, these can be also considered as potential electrodes for hyperthermia treatments. Previous works show that, in fact, these metallic stents might be used as part of a feasible solution for delivering radiofrequency (RF) energy into a tumor located in a hollow organ to destroy the tumor tissue. However, the tissue lesion induced is not completely uniform due to convective heat transfer associated to the blood flow in the nearby vessels. The purpose of this paper is to study the use of saline solution for modifying the electrical conductivity of the tissue in order to obtain a more uniform lesion.

Design/methodology/approach

A numerical analysis using finite element method on a simplified model of the porta hepatis is performed. The tumor tissue is divided in three sections and simulations were performed considering a higher electrical conductivity in the middle section of the tumor, imitating the presence of a saline solution in this part of the tissue.

Findings

Results show that it is possible to obtain a more regular volume, by the way the tumor tissue is preferentially heated, although there are still some risks on exceeding the dimension of the bile duct.

Originality/value

This study presents the numerical analysis of a saline‐enhanced RF tissue thermoablation of a cholangiocarcinoma considering a stent‐based electrode. Results point to the possibility of obtaining a more regular volume of damaged tissue in order to heat and preferentially destroy the tumor tissue.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 14 September 2010

Cassiano Antunes Cezario and Hilton Penha Silva

The purpose of this paper is to propose a simplified thermal circuit to estimate the temperature rise in the winding of a totally enclosed fan cooled electric motor for…

467

Abstract

Purpose

The purpose of this paper is to propose a simplified thermal circuit to estimate the temperature rise in the winding of a totally enclosed fan cooled electric motor for different loads and/or cooling conditions since the motor has already been tested for a known condition.

Design/methodology/approach

The determination of the convection resistance is based on classical Nusselt correlations and the value of conduction resistance is provided from a known load condition and the corresponding temperature rise in the winding.

Findings

Predicted temperature values showed good agreement with the experimental results, demonstrating that the hypothesis of simplification to a punctual source of thermal energy is acceptable.

Research limitations/implications

It is necessary that the motor has already been tested for a known condition (losses, temperature, and ventilation). Although the basic idea of this methodology is based on the use of a reference test condition of the same motor, as a suggestion, with small modifications the same methodology can be used to estimate the thermal behavior of different sized motors, provided a similar motor has already been tested.

Practical implications

This approach results in a fast methodology to estimate the thermal behavior of an electric motor in different loads and/or cooling conditions.

Originality/value

The differential of this circuit is the use of only two thermal resistances, one for the whole conduction and the other for the convection. This approach is a way to overcome the difficulties related to the determination of the thermal contact resistance and the equivalent conduction resistance between the winding and the different isolation systems inside the slots.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Book part
Publication date: 5 October 2018

Nicolás Marín Ruiz, María Martínez-Rojas, Carlos Molina Fernández, José Manuel Soto-Hidalgo, Juan Carlos Rubio-Romero and María Amparo Vila Miranda

The construction sector has significantly evolved in recent decades, in parallel with a huge increase in the amount of data generated and exchanged in any construction…

Abstract

The construction sector has significantly evolved in recent decades, in parallel with a huge increase in the amount of data generated and exchanged in any construction project. These data need to be managed in order to complete a successful project in terms of quality, cost and schedule in the the context of a safe project environment while appropriately organising many construction documents.

However, the origin of these data is very diverse, mainly due to the sector’s characteristics. Moreover, these data are affected by uncertainty, complexity and diversity due to the imprecise nature of the many factors involved in construction projects. As a result, construction project data are associated with large, irregular and scattered datasets.

The objective of this chapter is to introduce an approach based on a fuzzy multi-dimensional model and on line analytical processing (OLAP) operations in order to manage construction data and support the decision-making process based on previous experiences. On one hand, the proposal allows for the integration of data in a common repository which is accessible to users along the whole project’s life cycle. On the other hand, it allows for the establishment of more flexible structures for representing the data of the main tasks in the construction project management domain. The incorporation of this fuzzy framework allows for the management of imprecision in construction data and provides easy and intuitive access to users so that they can make more reliable decisions.

Details

Fuzzy Hybrid Computing in Construction Engineering and Management
Type: Book
ISBN: 978-1-78743-868-2

Keywords

Article
Publication date: 14 September 2010

Olli Mäkelä, Anna‐Kaisa Repo and Antero Arkkio

The purpose of this paper is to propose the numerical pulse test for the parameter estimation of the synchronous machine models.

Abstract

Purpose

The purpose of this paper is to propose the numerical pulse test for the parameter estimation of the synchronous machine models.

Design/methodology/approach

In order to generate data for the parameter estimation, the numerical pulse test was utilized. This test was implemented within the two‐dimensional finite element analysis (FEA). From the test data, the parameters of the equivalent circuit model were estimated. The differential evolution algorithm was used to minimize the cost function.

Findings

The equivalent circuit model with the estimated values of the parameters matches well with the data generated by the FEA. Thus, the equivalent circuit model with the parameters estimated represents the behavior of the machine accurately.

Originality/value

Previously, the numerical pulse test for synchronous machines has not been introduced. The numerical pulse test takes the real operation point of the machine into account. In the test, phenomena like the changing permeability distribution and the eddy‐currents in the damper bars (windings) are considered unlike in the standardized standstill frequency response test.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 6 July 2012

Carlos L. Antunes, Tony Richard O. Almeida, Nélia Raposeiro, Belarmino Gonçalves and Paulo Almeida

Due to its good mechanical and biocompatibility characteristics, nitinol SEMS is a popular endoprothesis used for relieving stricture problems in hollow organs due to…

Abstract

Purpose

Due to its good mechanical and biocompatibility characteristics, nitinol SEMS is a popular endoprothesis used for relieving stricture problems in hollow organs due to carcinomas. Besides its mechanical application, SEMS can be regarded as well as potential electrode for performing RF ablation therapy on the tumor. The purpose of this work is to perform numerical and experimental analyses in order to characterize the lesion volume induced in biological tissue using this kind of tubular electrode.

Design/methodology/approach

Data concerning electrical conductivity and dimension of the damaged tissue after RF ablation procedure were obtained from ex vivo samples. Next, numerical models using 3D finite element method were obtained reassembling the conditions considered at experimentation setup and results were compared.

Findings

Numerical and experimental results show that a regular volume of damaged tissue can be obtained considering this type of electrode. Also, results obtained from numerical simulation are close to those obtained by experimentation.

Originality/value

SEMSs, commonly used as devices to minimize obstruction problems due to the growth of tumors, may still be considered as an active electrode for RF ablation procedures. A method considering this observation is presented in this paper. Also, numerical simulation can be regarded in this case as a tool for determining the lesion volume.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 14 September 2010

Benedikt Schmülling, Marc Leßmann, Björn Riemer and Kay Hameyer

A fundamental disadvantage of three‐dimensional finite element (FE) simulations is high computational cost when compared to two‐dimensional models. The purpose of this…

Abstract

Purpose

A fundamental disadvantage of three‐dimensional finite element (FE) simulations is high computational cost when compared to two‐dimensional models. The purpose of this paper is to present an approach to minimize the computation time by achieving the same simulation accuracy.

Design/methodology/approach

The applied approach for avoiding high computational cost is the multi‐slice method. This paper presents the adoption of this method to a tubular linear motor.

Findings

It is demonstrated that the multi‐slice method is applicable for tubular linear motors. Furthermore, the number of slices and thereby computation time is minimized at the same accuracy of the simulation results.

Practical implications

The results of this paper offer a faster computation of skewed linear motors. At this juncture, the results are independent from the deployed FE solver.

Originality/value

The methods developed and proved permit a faster and more accurate design of tubular linear motors.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 14 September 2010

Jens Benecke, André Linde and Stefan Dickmann

The purpose of this paper is to create a model to calculate the high frequency (HF) complex impedance of common low‐voltage DC motors from construction parameters to…

Abstract

Purpose

The purpose of this paper is to create a model to calculate the high frequency (HF) complex impedance of common low‐voltage DC motors from construction parameters to predict their electromagnetic compatibility (EMC) emission behaviour and perform sensitivity analyses, and an optimization routine is developed to find combinations of construction parameters which best match a desired impedance curve.

Design/methodology/approach

The motor is divided into components. For each component, its electrical behaviour including parasitics is derived from material and geometry, and the electromagnetic interactions between components are defined. These results are then reproduced using inductances, capacitances, and resistors where applicable. Mathematical expressions are given to calculate their value from the material and geometrical parameters.

Findings

The complex impedance of DC motors can be accurately constructed from geometry and material parameters within a small range. The optimization routine successfully finds parameters to match a desired curve within specified parameter ranges. This can help finding a motor with lower conducted electromagnetic interference.

Originality/value

This analytically parameterized model constitutes a new way to describe electrical motors from an EMC perspective and define critical parameters.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

1 – 10 of 94