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Article
Publication date: 3 January 2017

Daoyu Hu, Zhuyong Li, Zhiyong Hong and Zhijian Jin

The purpose of this paper is to analyze the influence of different types of winding configurations on the distribution of leakage field and branch currents for a 330-kVA…

Abstract

Purpose

The purpose of this paper is to analyze the influence of different types of winding configurations on the distribution of leakage field and branch currents for a 330-kVA high-temperature superconducting (HTS) transformer winding.

Design/methodology/approach

A three-dimensional electromagnetic model coupled with a circuit model validated by an experiment is developed to calculate the leakage field and current uniformity under four different types of secondary winding configurations. The four types of gaps between secondary windings are uniform gap, arithmetic progression (AP) gap, six sections with three different gaps and eight sections with four different gaps. A coefficient named as uneven degree is used to define the current nonuniformity.

Findings

The simulation results show that the currents and leakage field of double pancakes (DPs) on both sides are larger than those of the other DPs, and the currents of several middle DPs are smaller than the average rated current with an ISOB gap and larger than the average rated current with an IBOS gap. For any one of the four types of winding configurations, the type with the ISOB gap can prohibit the current nonuniformity more effectively, whereas the IBOS gap can decrease the leakage field more. The AP with the ISOB gap is a wise choice for decreasing the uneven degree and leakage field.

Practical implications

There is an optimal winding configuration for decreasing the leakage field and uneven degree of branch currents. The results and numerical model are very useful for the design of a HTS transformer.

Originality/value

The leakage field distribution and branch currents nonuniformity for 25 parallel DPs are investigated and optimized.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 3 July 2017

Ping Yang, Yawei Wang, T. Chang, H. Ma, Zhuyong Li, Zhijian Jin and Zhiyong Hong

The purpose of this paper is to propose a hybrid driving system that couples a motor and flywheel energy storage (FES) for a megawatt-scale superconducting direct current…

Abstract

Purpose

The purpose of this paper is to propose a hybrid driving system that couples a motor and flywheel energy storage (FES) for a megawatt-scale superconducting direct current (DC) induction heater. Previous studies have proven that a superconducting DC induction heater has great advantages in relation to its energy efficiency and heating quality. In this heater, a motor rotates an aluminium billet in a DC magnetic field and the induced eddy current causes it to be heated. When the aluminium billet begins to rotate, a high peak load torque appears at a low rotation speed. Therefore, driving the billet economically has been a great challenge when designing the driving system, which is the focus of this paper.

Design/methodology/approach

A hybrid driving system based on FES is designed to provide extra torque when the peak load torque occurs at a low rotation speed, which allows the successful start-up of the aluminium billet and the operation of the motor at its rated capacity. The mechanical structure of this hybrid driving system is introduced. A simulation model was constructed using Matlab/Simulink and the dynamic start-up process is analysed. The influence of the flywheel’s inertia and required minimum engagement speed are investigated.

Findings

The results of this paper show that the hybrid driving system that couples FES and a motor can successfully be used to start the aluminium billet rotating. The flywheel’s inertia and engagement speed are the most important parameters. The inertia of the flywheel decreases with an increase in its engagement speed.

Practical implications

The cost of the driving system is significantly reduced, which is very important in relation to the commercial potential of this apparatus.

Originality/value

A novel start-up strategy for driving the aluminium billet of a superconducting DC induction heater at low speed is proposed based on FES.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 5 January 2015

Yawei Wang, Hao Gao, Zhuyong Li, Yang Ping, Zhijian Jin and Zhiyong Hong

– The purpose of this paper is to analyse and improve the temperature uniformity of aluminium billets heated by superconducting DC induction heaters.

Abstract

Purpose

The purpose of this paper is to analyse and improve the temperature uniformity of aluminium billets heated by superconducting DC induction heaters.

Design/methodology/approach

A 3D electromagnetic model coupled with a heat transfer model is developed to calculate the heating process of the billets which are rotated in uniform transverse DC magnetic field. A laboratory-scale DC induction heater prototype has been built to validate the model. The results from simulation and measurement have a good agreement. The model is used to investigate the factors affecting the temperature uniformity of aluminium billets.

Findings

The results from simulation show that lower rotation speeds always mean better temperature uniformity along the radial direction, due to the increase in power penetration. However, the situation is very different for the temperature distribution along the axial direction. When the rotation speed is low, the temperature at the ends is lower than other parts. The situation reverses as the rotation speeds increase. This phenomenon is referred to as the “ending effect” in this paper.

Research limitations/implications

Because of the ending effect, a lower rotation speed does not always result in better overall temperature uniformity, especially for billets of smaller sizes.

Practical implications

There is an optimal rotation speed that yields the best overall temperature uniformity. Lower rotation speeds are not always preferred. The results and numerical model developed are very useful in the design of a superconducting DC induction heater.

Originality/value

The temperature uniformity of aluminium billets heated by DC induction heaters is investigated and optimized.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 7 April 2020

Ching-Min Chen and Baithesda Baithesda

The purpose of this study is to examine different types of primary healthcare utilization and its influencing factors among the elderly in Indonesia.

Abstract

Purpose

The purpose of this study is to examine different types of primary healthcare utilization and its influencing factors among the elderly in Indonesia.

Design/methodology/approach

Data were obtained from the 5th Indonesian Family Life Survey, a longitudinal database of demography and health information using multistage stratified sampling of households. Older adults aged at least 60 years were sampled; proxy respondents and incomplete data were excluded from the study.

Findings

Most of the elderly preferred to visit nurse/midwives practitioner (NP), followed by the community health centers (CHC). Those who lived outside of the Java region were more likely to visit NP; moreover, those without formal education and lived in the rural area were more likely to use CHC. Education level, region and chronic conditions were significant predicting factors for almost all types of primary healthcare use.

Social implications

Indonesia is moving towards an aged society in the coming decades. However, there are significant barriers to access almost all types of primary health care by the elderly in Indonesia. This shows the possibility of health care inequality for the elderly population. This study provides evidence of the various types of primary healthcare use by the elderly and its influencing factors. It hopes policymakers can use the data to develop an effective strategy to enhance the quality of primary healthcare services provides to the elderly population.

Originality/value

Indonesian nurses fulfill vital functions in the health system and are often the only human resource for health not only in remote and poor rural areas but also in urban areas. Nurses, as a part of primary care providers, require an adequately trained to contribute to the better primary care system.

Details

Working with Older People, vol. 24 no. 2
Type: Research Article
ISSN: 1366-3666

Keywords

Content available
Article
Publication date: 21 November 2014

Abstract

Details

The Journal of Risk Finance, vol. 15 no. 5
Type: Research Article
ISSN: 1526-5943

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Article
Publication date: 25 September 2019

Jiang Zhao, Ksenia Gerasimova, Yala Peng and Jiping Sheng

The purpose of this paper is to discuss characteristics of organic food value chain governance and policy tools that can increase the supply of good quality of agri-products.

Abstract

Purpose

The purpose of this paper is to discuss characteristics of organic food value chain governance and policy tools that can increase the supply of good quality of agri-products.

Design/methodology/approach

This paper discusses a national organic food supply system in China, identifying the link between an organization form with a social confidence crisis and information asymmetry as the main challenges. It develops an analytical model of the market structure of organic certification based on the contract theory, which considers the certification incentive driven by both farmers and processors. Two cases of raw milk producers and processors provide empirical data.

Findings

The argument which is brought forward is that product information asymmetry together with strict requirement for ensuring organic food integrity brings the organic milk value chain into a highly integrated organization pattern. A tight value chain is effective in the governance of organic food supply chain under third party certification (TPC), while a loose value chain discourages producing organic products because of transaction costs. TPC is found to be a positively correlation with a tight value chain, but it brings high organizational cost and it raises cost for consumers.

Originality/value

This is the first paper discussing the governance of organic food value chain in Chinese milk industry.

Details

China Agricultural Economic Review, vol. 12 no. 1
Type: Research Article
ISSN: 1756-137X

Keywords

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Article
Publication date: 2 November 2015

Suresh Chandra Babu, Jikun Huang, P. Venkatesh and Yumei Zhang

There is growing interest from the global development community in the role of agricultural research and extension (AR & E) systems to achieve development targets…

Abstract

Purpose

There is growing interest from the global development community in the role of agricultural research and extension (AR & E) systems to achieve development targets. Despite this interest, many smallholders in developing countries continue to lack access to updated agricultural information and reliable services. In an effort to increase the effectiveness, impact, and reach of AR & E programs, many governments have attempted to reform their national systems. The paper aims to discuss these issues.

Design/methodology/approach

This paper systematically compares the systems and reforms of AR & E in China and India in order to draw out lessons applicable to developing countries. This paper first reviews the existing literature on AR & E systems and their role in agricultural and economic development. The authors then provide a detailed review and comparative analysis of the reforms and approaches implemented in the AR & E systems of China and India. The authors apply this comparative analysis to draw out lessons that can be applied to inform the reformation of AR & E systems in developing countries.

Findings

The authors find that although both countries face similar agricultural development challenges, each took a different approach in the reformation of AR & E to address these challenges. Each country’s approaches had different impacts on the effectiveness of the system. Lessons from the reformation of the AR & E systems in China and India can be used to inform and improve the impact of AR & E in developing countries.

Originality/value

The paper examines two systems together using a set of common indicators and factors. The paper’s value comes from its usefulness in informing future AR & E reforms in other developing countries in order to increase the impact of these reforms on development outcomes.

Details

China Agricultural Economic Review, vol. 7 no. 4
Type: Research Article
ISSN: 1756-137X

Keywords

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