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Article
Publication date: 8 May 2018

Miao He, Miao Hao, George Chen, Wenpeng Li, Chong Zhang, Xin Chen, Haitian Wang, Mingyu Zhou and Xianzhang Lei

For the dramatically developed high voltage direct current (HVDC) power transmission, HVDC cables play a vital role in the power transmission across seas and connections with…

144

Abstract

Purpose

For the dramatically developed high voltage direct current (HVDC) power transmission, HVDC cables play a vital role in the power transmission across seas and connections with renewable power sources. However, the condition monitoring of HVDC cables is still a challenging research topic. This paper aims to understand the influence of external factors, namely, current, cavity location and material properties, on partial discharge (PD) characteristics in HVDC cable in a numerical way referring to the refined Niemeyer’s model.

Design/methodology/approach

The influences of the three external factors are studied by a proposed numerical model for DC PDs based on the modification of a conventional PD model for AC voltage via a finite element analysis method.

Findings

The external factors can influence the discharge magnitude and discharge repetition rate via affecting the electrical conductivity of the material: DC PD is more frequent and with higher discharge magnitude when the cavity is closer to the conductor or the current through the conductor is higher. Both DC PD repetition rate and average discharge magnitude in long-term aged material are lower than virgin material. The effect of discharge on insulation degradation becomes decreasingly significant.

Research limitations/implications

The current work is based on the numerical modelling of DC PDs. Further experimental validations and comparisons are essential for improving the model.

Practical implications

The studies of the influence factors for PDs under HVDC voltage can benefit the research and practical power transmission on DC PDs, contributing the design and test of DC PDs in HVDC cables, exploring the understandings of the DC PDs’ mechanism.

Originality/value

This paper, to the best of author’s knowledge, first studies the influence factors on DC PDs based on the numerical modelling work.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 March 2018

Miao He, Miao Hao, George Chen, Xin Chen, Wenpeng Li, Chong Zhang, Haitian Wang, Mingyu Zhou and Xianzhang Lei

High voltage direct current (HVDC) cable is an important part in the electric power transmission and distribution systems. However, very little research has been carried out on…

349

Abstract

Purpose

High voltage direct current (HVDC) cable is an important part in the electric power transmission and distribution systems. However, very little research has been carried out on partial discharge under direct current (DC) conditions. Niemeyer’s model has been widely used under alternating current (AC) conditions. This paper aims to intend to modify the Niemeyer’s model considering both electric field and charge dynamics under DC conditions, and therefore proposes a numerical model describing partial discharge characteristics in HVDC cable.

Design/methodology/approach

This paper intends to understand partial discharge characteristics under DC conditions through numerical modelling. Niemeyer’s model that has been widely used under AC conditions has been modified, taking both electric field and charge dynamics under DC conditions into consideration. The effects of loading level or current through the conductor, cavity location and material properties on partial discharges have also been studied.

Findings

Electrical conductivity is important in determining the characteristics of partial discharge under DC conditions and discharges tend to happen in short when the cavity field exceeds the inception level under the parameter values studied in the paper.

Research limitations/implications

Building the numerical model is the purpose of the paper, and there is lack in experiment and the comparison between the simulation results and experiment.

Practical implications

The proposed model provides the numerical model describing partial discharge in HVDC cable and helps understand the partial discharge mechanism under DC voltage.

Originality/value

To the best of the author’s knowledge, this paper is a very early research on the numerical modelling work on partial discharge under DC voltage.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 17 March 2016

Zhengyi Han, George Chen, Junzheng Cao, Zhiyuan He, Haitian Wang, Wenpeng Li and Chao Tang

The pulsed electro-acoustic (PEA) method is widely applied for space charge measurement in solid dielectrics. The signals, however, can be seriously distorted during transmission…

244

Abstract

Purpose

The pulsed electro-acoustic (PEA) method is widely applied for space charge measurement in solid dielectrics. The signals, however, can be seriously distorted during transmission, especially in non-planar specimens. The aim of this work is to find an efficient algorithm to correctly recover the space charge profile for different types of specimens.

Design/methodology/approach

The distortion can be associated with both geometry and material (attenuation and dispersion). Hence the recovery algorithm consists of two parts respectively. The influences of geometries, causing the divergences of electric force and acoustic waveform, can be corrected by sets of factors. The attenuation and dispersion of the material can be suppressed based on the transfer function matrix in frequency domain, which could be obtained from calibration.

Findings

A general algorithm applicable to three kinds of specimens (single-layer, multi-layer and coaxial-geometry dielectrics) has been proposed. Compared with the other two algorithms in literature, the present one offers the most accurate solution while taking relatively shorter time. In addition, this algorithm is applied on signals measured from a planar LDPE sample and the results show that the new algorithm is fairly effective with excellent stability in a real system.

Originality/value

As one of the most accurate algorithms, the present one is theoretically one third quicker than the others. This algorithm would be helpful in applications calling for large calculations, i.e. 3-D imaging of space charge distribution in XLPE cable.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 35 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 18 November 2013

Haitian Zou, Baolin Wang, Fumin Song and Lianyu Fu

The purpose of this paper is to verify the feasibility and reliability of mineral casting applied in high-precision printed circuit board (PCB) drilling machine. The mechanical…

277

Abstract

Purpose

The purpose of this paper is to verify the feasibility and reliability of mineral casting applied in high-precision printed circuit board (PCB) drilling machine. The mechanical properties of machine frame are quantified to provide a solution for machine tool industry to seek a perfect substance competing with classic materials such as cast iron and granite.

Design/methodology/approach

The optimal design of machine frame is performed via the CAD system combined with finite element analysis (FEA). The mechanical properties of the frame elements are evaluated by a series of mechanical experiments: static performance is quantified by flatness tests, dynamic behavior is estimated by experimental and numerical models, respectively. Meanwhile, the performance of the frame element with traditional materials is examined experimentally.

Findings

Mineral casting parts can be successfully applied to PCB drilling machine to meet high accuracy requirements. The characteristic of mineral casing gives the most possibilities in structural design. The frame parts show good static/dynamic behaviors by structural optimization processes. Especially, the machine frame with mineral casting gains a great weight reduction compared with traditional materials.

Originality/value

The application of mineral casting in PCB drilling machine offers greater design flexibility and innovative system solutions. The combination of FEA is convincing to achieve optimal structure and ideal weight to maximize the economic and technical benefits. Moreover, lightweight design of machine structural components achieves not only higher kinematic/dynamic precision but also considerable cost reduction.

Details

Circuit World, vol. 39 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

Available. Content available
Article
Publication date: 18 November 2013

Martin Goosey

211

Abstract

Details

Circuit World, vol. 39 no. 4
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 29 November 2018

Meryem Uluskan and A. Blanton Godfrey

The purpose of this paper is to develop a supply chain management framework covering different business environment levels, that is, macro, micro and supply chain levels, and also…

1547

Abstract

Purpose

The purpose of this paper is to develop a supply chain management framework covering different business environment levels, that is, macro, micro and supply chain levels, and also to evaluate Haiti vs China as apparel-sourcing partners by assessing macro-level, supply-chain-level and micro-level environments from the US apparel buyers’ perspective.

Design/methodology/approach

In order to achieve this, first, a framework covering these business environment levels was developed and tested through path analysis. Prior to path analysis exploratory factor analysis was conducted to verify proposed factor structures. Data were collected using face-to-face interviews with a sample of 41 apparel companies that operate in the USA and source from China and Haiti.

Findings

This study found that both supply-chain-level and micro-level environments positively impact global supply chain performance. Supply-chain-level also has a direct effect on micro-level environment and macro-level environment has only a direct effect on supply-chain-level environment. Interviews and discussions based on this framework indicate that Haiti’s proximity to the USA, price, low-wage rates, small-order sourcing opportunities and good basic sewing skills are among Haiti’s strengths.

Originality/value

This study is unique in developing a multi-level environment framework for supply chain management and in comparing Haiti and China in terms of their supply chains to evaluate the potential competitiveness of Haitian apparel supply chain.

Details

Benchmarking: An International Journal, vol. 25 no. 8
Type: Research Article
ISSN: 1463-5771

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Book part
Publication date: 26 August 2019

W. James Jacob, Huiyuan Ye, Shuo Wang, Xueshuang Wang, Xiufang Ma, Abdullah Bagci, Quan Gu and Julio Luis Méndez Vergara

In this chapter, the authors provide a historical overview of the development of comparative and international education in North America from 1920s to the beginning of the…

Abstract

In this chapter, the authors provide a historical overview of the development of comparative and international education in North America from 1920s to the beginning of the twenty-first century. The authors document the significant role some of the most influential leaders played to help lay the foundation for comparative education societies in Canada, Cuba, Haiti, Mexico, and the United States. Using historical comparative research technique, the authors examine the many interconnections of current and past leaders. The authors conclude with recommendations on how knowing the history can help strengthen comparative and international education development well into the future.

Details

Comparative and International Education: Survey of an Infinite Field
Type: Book
ISBN: 978-1-78743-392-2

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Article
Publication date: 16 January 2025

Song Tian, Haitian Long, Yumei Li, Yuhua Sun, Ping Wang and Mingyuan Gao

This study aims to develop a novel self-powered monitoring system that uses radio frequency (RF) energy harvesting and ultra-low-power management technologies for real-time…

13

Abstract

Purpose

This study aims to develop a novel self-powered monitoring system that uses radio frequency (RF) energy harvesting and ultra-low-power management technologies for real-time condition monitoring of switch rails.

Design/methodology/approach

The system is designed for integration within the jump wire holes of switch rails, ensuring structural integrity and aesthetic appeal. It features a highly efficient energy harvesting mechanism combined with optimized power management for wireless sensor nodes. An on-board antenna captures ambient RF energy, managed by high-efficiency circuits to ensure stable wireless sensor operation. An ultra-low-power system-on-chip is used to acquire and transmit multimodal data on vibration and temperature from the switch rails. The data collection is enhanced through a two-threshold approach, adapting to harvested energy levels for self-energy balancing.

Findings

Testing revealed that the energy harvesting subsystem operated stably at distances up to 2.9 m from the RF source, charging a 200 µF capacitor to 4.2 V in just 220 s. The monitoring subsystem’s average power consumption is in the low microwatt range. Continuous operation over 30 days in real conditions resulted in only a 5 mV reduction in battery voltage, indicating successful self-powered operation and validating long-term reliability in unattended scenarios.

Originality/value

This research presents an innovative solution, integrating RF energy harvesting with ultra-low-power technology, which addresses the power and stability challenges faced by traditional monitoring systems.

Details

Sensor Review, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 21 February 2022

Wismick Jean-Charles, Jocelyn Shealy McGee, Marie Judith Jean-Baptiste, Vanessa Irlande Joseph and Doris Gracita Rouzier

The purpose of this paper is to describe the development and implementation of the first telepsychology initiative in Haiti. Haiti is the world’s first black-led republic. It is…

59

Abstract

Purpose

The purpose of this paper is to describe the development and implementation of the first telepsychology initiative in Haiti. Haiti is the world’s first black-led republic. It is also the only nation established by slave revolt and the first independent Caribbean state. In this case study, the development and pilot implementation of the first telepsychology initiative in the country of Haiti is described. The initiative was designed to provide psychoeducational and emotional support to community members and frontline health workers in the wake of the COVID-19 pandemic in this under-resourced country.

Design/methodology/approach

A multi-stakeholder approach was used and brought together local, national and international partners from governmental and non-governmental organizations as well as the academic community. Program data was collected from May 2020 through November 2021. The initiative was implemented across four regions of Haiti: Nord, Artibonite, Reste-Quest and Sud.

Findings

A total of 701 individuals received telepsychology services. More community members participated (n = 508 sessions) than frontline health workers (n = 193 sessions). Service utilization ranged from one to four counseling sessions. Initial data suggest that telepsychology is a potentially acceptable and feasible option to increase access to mental health services in Haiti. Significant logistical and cultural concerns must be taken into consideration to refine services.

Originality/value

To the best of the authors’ knowledge, the telepsychology initiative is the first of its kind and may serve as an exemplar for other similar countries with limited mental health resources. The authors provide information on successes, barriers and lessons learned as well as recommendations for enhancing services.

Details

The Journal of Mental Health Training, Education and Practice, vol. 17 no. 2
Type: Research Article
ISSN: 1755-6228

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Article
Publication date: 10 March 2021

Claudel Mombeuil, Anestis K. Fotiadis and Withz Aimable

While diaspora entrepreneurs remain important sources of capital and innovation, many developing countries are facing serious challenges to tap into these sources because of their…

219

Abstract

Purpose

While diaspora entrepreneurs remain important sources of capital and innovation, many developing countries are facing serious challenges to tap into these sources because of their weak institutional settings and the endemic and systemic corruption. To this end, this study explores how institutional reforms and control of corruption can influence diaspora entrepreneurship. This study also seeks to provide perspectives on how diaspora entrepreneurs can influence institutional reforms and market policies.

Design/methodology/approach

To meet these objectives, qualitative and interpretive research approaches were employed.

Findings

Using responses collected from Haitian diaspora entrepreneurs living in the USA, this paper highlights different attributes of institutional reforms and control of corruption that can influence diaspora entrepreneurship.

Practical implications

Based on these insights, this paper argues that Haitian diaspora entrepreneurs need to play a proactive role as policy entrepreneurs by supporting competent and well-intention political leaders to gain office and by joining forces with local actors to advocate for institutional reforms, market reforms and control of corruption in order to be able to exploit market opportunities. In this respect, further perspectives for diaspora entrepreneurship, limitations and consideration for future research are highlighted.

Originality/value

By collecting insights on institutional reform and diaspora entrepreneurship from diaspora entrepreneurs, this paper makes important contribution to the entrepreneurship literature.

Details

Journal of Entrepreneurship and Public Policy, vol. 10 no. 4
Type: Research Article
ISSN: 2045-2101

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