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Article
Publication date: 29 July 2014

Chongli Di, Xiaohua Yang, Xuejun Zhang, Jun He and Ying Mei

The purpose of this paper is to simulate and analyze accurately the multi-scale characteristics, variation periods and trends of the annual streamflow series in the Haihe…

Abstract

Purpose

The purpose of this paper is to simulate and analyze accurately the multi-scale characteristics, variation periods and trends of the annual streamflow series in the Haihe River Basin (HRB) using the Hilbert-Huang Transform (HHT).

Design/methodology/approach

The Empirical Mode Decomposition (EMD) approach is adopted to decompose the original signal into intrinsic mode functions (IMFs) in multi-scales. The Hilbert spectrum is applied to each IMF component and the localized time-frequency-energy distribution. The monotonic residues obtained by EMD can be treated as the trend of the original sequence.

Findings

The authors apply HHT to 14 hydrological stations in the HRB. The annual streamflow series are decomposed into four IMFs and a residual component, which exhibits the multi-scale characteristics. After the Hilbert transform, the instantaneous frequency, center frequency and mean period of the IMFs are obtained. Common multi-scale periods of the 14 series exist, e.g. 3.3a, 4∼7a, 8∼10a, 11-14a, 24∼25a and 43∼45a. The residues indicate that the annual streamflow series has exhibited a decreasing trend over the past 50 years.

Research limitations/implications

The HHT method is still in its early stages of application in hydrology and needs to be further tested.

Practical implications

It is helpful for the study of the complex features of streamflow.

Social implications

This paper will contribute to the sustainable utilization of water resources.

Originality/value

This study represents the first use of the HHT method to analyze the multi-scale characteristics of the streamflow series in the HRB. This paper provides an important theoretical support for water resources management.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Book part
Publication date: 22 December 2006

Dennis J. Gayle and Jonathan N. Goodrich

As both concept and process, privatization possesses ambiguous connotations and multiple meanings. Webster's Dictionary (1981) defines one related noun, privatism, as “an…

Abstract

As both concept and process, privatization possesses ambiguous connotations and multiple meanings. Webster's Dictionary (1981) defines one related noun, privatism, as “an attitude of uncommitment or uninvolvement in anything beyond one's immediate interests,” while another associated noun, privacy, denotes a state of “withdrawal from society or the public interest” (Oxford English Dictionary, 1972). If government is a means of providing a wide range of collective goods, which do not necessarily lend themselves to market exchange, the public sector is naturally a highly visible target.4 At the same time, unrestrained public-sector expansion inevitably leads to public policy failure, as problems of communication, coordination, effective cost–benefit control, and revenue satiation accumulate.5 Privatization represents a logical reaction.

Details

Comparative Public Administration
Type: Book
ISBN: 978-1-84950-453-9

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Article
Publication date: 18 February 2019

Yang Liu, Hao Zhang, Lingen Wang, Xuejun Fan, Guoqi Zhang and F. Sun

Crack and stress distribution on dies are key issues for the pressure-assisted sintering bonding of power modules. The purpose of this research is to build a relationship…

Abstract

Purpose

Crack and stress distribution on dies are key issues for the pressure-assisted sintering bonding of power modules. The purpose of this research is to build a relationship among stress distributions, sintering sequences and sintering pressures during the sintering processes.

Design/methodology/approach

Three sintering sequences, S(a), S(b) and S(c), have been designed for the double-side assembly of power module in this paper. Experiments and finite element method (FEM) analysis are conducted to investigate the crack and stress distribution.

Findings

The sintering sequence had significant effects on the crack generation in the chips during the sintering process under 30-MPa pressure. The simulation results revealed that the module sintered by S(a) showed lower chip stress than those by the other two sintering sequences under 30 MPa. In contrast, the chip stress is the highest when the sintering sequence follows S(b). The simulation results explained the crack generation and prolongation in the experiments. S(a) was recommended as the best sintering sequence because of the lowest chip stress and highest yield rate.

Originality/value

This study investigated the stress distributions of the double-side sintered power modules under different sintering pressures. Based on the results of experiments and FEM analysis, the best sintering sequence design is provided under various sintering pressures.

Details

Soldering & Surface Mount Technology, vol. 31 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 2 October 2018

Xie Xuejun, Yuanlin Zhang, Rui Wang, Yu Zhang and Mianzhao Ruan

The hollow copper wires of the generator are seriously corroded in cooling water. This paper aims to explore the mechanism of copper corrosion by thermodynamic calculation…

Abstract

Purpose

The hollow copper wires of the generator are seriously corroded in cooling water. This paper aims to explore the mechanism of copper corrosion by thermodynamic calculation and kinetic experiments and to find out the precise pH range for preventing corrosion of copper in stator internal water and dual internal water cooled generators.

Design/methodology/approach

Thermodynamic and kinetic studies were carried out for the purpose of preventing the corrosion of hollow conducting copper wires in the internal cooling water. Thermodynamic calculation results demonstrate hollow copper wires electrochemically corroded by oxygen rather than acids (H+) and find out a precise anti-corrosion pH range. Kinetic experiments research on the effect of the pH value and oxygen concentration on corrosion and protection methods of copper in desalted water.

Findings

Research results demonstrate that, in the internal cooling water, hollow copper wires are electrochemically corroded by oxygen, rather than acids (H+). The method of preventing copper from corrosion in the desalted water is to control the pH value of the stator cooling water and the dual water inner cooling water between 7.86-8.86 and 7.86-9.26, respectively.

Originality/value

The thermodynamic calculation and potentiometric-pH diagram are used to obtain the accurate pH range of the inner cooling water and inner cooling water in the inner cooling water system. The kinetic experiments provide data support for the effect of temperature, pH value and oxygen concentration.

Details

Anti-Corrosion Methods and Materials, vol. 65 no. 6
Type: Research Article
ISSN: 0003-5599

Keywords

Open Access
Article
Publication date: 8 February 2021

Xuejun Zhao, Yong Qin, Hailing Fu, Limin Jia and Xinning Zhang

Fault diagnosis methods based on blind source separation (BSS) for rolling element bearings are necessary tools to prevent any unexpected accidents. In the field…

Abstract

Purpose

Fault diagnosis methods based on blind source separation (BSS) for rolling element bearings are necessary tools to prevent any unexpected accidents. In the field application, the actual signal acquisition is usually hindered by certain restrictions, such as the limited number of signal channels. The purpose of this study is to fulfill the weakness of the existed BSS method.

Design/methodology/approach

To deal with this problem, this paper proposes a blind source extraction (BSE) method for bearing fault diagnosis based on empirical mode decomposition (EMD) and temporal correlation. First, a single-channel undetermined BSS problem is transformed into a determined BSS problem using the EMD algorithm. Then, the desired fault signal is extracted from selected intrinsic mode functions with a multi-shift correlation method.

Findings

Experimental results prove the extracted fault signal can be easily identified through the envelope spectrum. The application of the proposed method is validated using simulated signals and rolling element bearing signals of the train axle.

Originality/value

This paper proposes an underdetermined BSE method based on the EMD and the temporal correlation method for rolling element bearings. A simulated signal and two bearing fault signal from the train rolling element bearings show that the proposed method can well extract the bearing fault signal. Note that the proposed method can extract the periodic fault signal for bearing fault diagnosis. Thus, it should be helpful in the diagnosis of other rotating machinery, such as gears or blades.

Details

Smart and Resilient Transport, vol. 3 no. 1
Type: Research Article
ISSN: 2632-0487

Keywords

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Article
Publication date: 8 February 2018

Liming Fan, Xiyuan Kang, Quan Zheng, Xiaojun Zhang, Xuejun Liu, Zhoushan Geng and Chong Kang

This paper aims to focus on the tracking of a moving magnetic target by using total field magnetometers and to present a tracking method based on the gradient of a…

Abstract

Purpose

This paper aims to focus on the tracking of a moving magnetic target by using total field magnetometers and to present a tracking method based on the gradient of a magnetic anomaly. In the tracking, it is assumed that the motion of the target is equivalent to a first-order Markov process. And the unit direction vector of the magnetic moment from the gradient of the magnetic anomaly can be obtained. According to the unit direction vector, the inverse problem is turned into an optimization problem to estimate the parameters of the target. The particle swarm optimization algorithm is used to solve this optimization problem. The proposed method is validated by the numerical simulation and real data. The parameters of the target can be calculated rapidly using the proposed method. And the results show that the estimated parameters of the mobile target using the proposed method are very close to the true values.

Design/methodology/approach

The authors focus on the tracking of a moving magnetic target by using total field magnetometers and present a tracking method based on the gradient of a magnetic anomaly.

Findings

The paper provides an effective method for tracking the magnetic target based on an array with total field sensors.

Originality/value

Comparing with a vector magnetic sensor, the measurement of the scalar magnetic sensor is almost not influenced by its orientation. In this paper, a moving magnetic target was tracked by using total field magnetometers and a tracking method presented based on the gradient of a magnetic anomaly.

Details

Sensor Review, vol. 38 no. 4
Type: Research Article
ISSN: 0260-2288

Keywords

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Article
Publication date: 15 May 2019

Xuejun Shen, Minghui Yue, Pengfei Duan, Guihai Wu and Xuerui Tan

Based on the prediction of the consumption of medical materials, the purpose of this paper is to study the applicability of the grey model method to the field and its…

Abstract

Purpose

Based on the prediction of the consumption of medical materials, the purpose of this paper is to study the applicability of the grey model method to the field and its predicted accuracy.

Design/methodology/approach

The ABC classification method is used to classify medical consumables and select the analysis objects. The GM (1,1) model predicts the annual consumption of medical materials. The GM (1,1) modeling of the consumption of the selected medical materials in 2006~2017 was carried out by using the metabolite sequence and the sequence topology subsequence, respectively. The average rolling error and the average rolling accuracy are calculated to evaluate the prediction accuracy of the model.

Findings

The ABC classification results show that Class A projects, which account for only 9.79 percent of the total inventory items, occupy most of the inventory funds. Eight varieties with varying purchases and usages and complete historical data were selected for further analysis. The subsequence GM(1,1) model group constructed by two different methods predicts and scans the annual consumption of eight kinds of medical materials, and the rolling precision can reach more than 90 percent.

Originality/value

The metabolic GM (1,1) model is an ideal predictive model that can meet the requirements for a short-term prediction of medical material consumption (Zhang et al., 2014). The GM (1,1) model is more suitable for a short-term prediction of medical material consumption with less data modeling.

Details

Grey Systems: Theory and Application, vol. 9 no. 2
Type: Research Article
ISSN: 2043-9377

Keywords

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Book part
Publication date: 12 November 2016

Qihao He

Due to climate change and an increasing concentration of the world’s population in vulnerable areas, how to manage catastrophe risk efficiently and cover disaster losses…

Abstract

Purpose

Due to climate change and an increasing concentration of the world’s population in vulnerable areas, how to manage catastrophe risk efficiently and cover disaster losses fairly is still a universal dilemma.

Methodology

This paper applies a law and economic approach.

Findings

China’s mechanism for managing catastrophic disaster risk is in many ways unique. It emphasizes government responsibilities and works well in many respects, especially in disaster emergency relief. Nonetheless, China’s mechanism which has the vestige of a centrally planned economy needs reform.

Practical Implications

I propose a catastrophe insurance market-enhancing framework which marries the merits of both the market and government to manage catastrophe risks. There are three pillars of the framework: (i) sustaining a strong and capable government; (ii) government enhancement of the market, neither supplanting nor retarding it; (iii) legalizing the relationship between government and market to prevent government from undermining well-functioning market operations. A catastrophe insurance market-enhancing framework may provide insights for developing catastrophe insurance in China and other transitional nations.

Originality

First, this paper analyzes China’s mechanism for managing catastrophic disaster risks and China’s approach which emphasizes government responsibilities will shed light on solving how to manage catastrophe risk efficiently and cover disaster losses fairly. Second, this paper starts a broader discussion about government stimulation of developing catastrophe insurance and this framework can stimulate attention to solve the universal dilemma.

Details

The Political Economy of Chinese Finance
Type: Book
ISBN: 978-1-78560-957-2

Keywords

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Article
Publication date: 12 August 2020

Xuejun Wang, Dinghui Huai and Ze Lu

The purpose of this paper is to identify the impacts of financing constraints on the quality upgrading of China's agri-food sector.

Abstract

Purpose

The purpose of this paper is to identify the impacts of financing constraints on the quality upgrading of China's agri-food sector.

Design/methodology/approach

Our empirical study is performed using the “distance to the frontier” framework. We employ a merged sample of Chinese agri-food trading firms based on Chinese firm-level data from the National Bureau of Statistics of China and Chinese customs data. To verify robustness, we test whether the results hold when using different definitions of quality upgrading and alternative proxy variables for product quality and financing constraints. To examine the heterogeneous effects, we generate subsamples by firm location, export destination and the product sophistication of exports.

Findings

The results suggest that financing constraints have a significant negative impact on the product quality upgrading of Chinese agri-food export firms. In addition, the negative impacts of financing constraints are more severe for firms close to the quality frontier than for those far from the frontier. These results are robust to various checks. Moreover, the heterogeneous effects of financing constraints on quality upgrading are identified when the sample is split according to firm location, export destination and the sophistication of export products.

Originality/value

This paper reviews and applies some recent studies in the literature to investigate the relationship between financing constraints and the product quality upgrading of agri-food export firms in China. Overall, the results of this paper could be considered of importance for promoting the quality upgrading of export products in the China's agri-food sector.

Details

British Food Journal, vol. 123 no. 1
Type: Research Article
ISSN: 0007-070X

Keywords

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Article
Publication date: 8 May 2018

Kuanfang He, Wei Lu, Xiangnan Liu, Siwen Xiao and Xuejun Li

This paper aims to study acoustic emission (AE) propagation characteristics by a crack under a moving heat source, which mainly provides theoretical basis and method for…

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Abstract

Purpose

This paper aims to study acoustic emission (AE) propagation characteristics by a crack under a moving heat source, which mainly provides theoretical basis and method for the actual crack detection during welding process.

Design/methodology/approach

The paper studied the AE characteristics in welding using thermoelastic theory, which investigates the dynamical displacement field caused by a crack and the welding heating effect. In the calculation model, the crack initiation and extension are represented by moment tensor as the AE source, and the welding heat source is the Gauss heat flux distribution. The extended finite element method (XFEM) is implemented to calculate and solve the AE response of a thermoelastic plate with a crack during the welding heating effect. The wavelet transform is applied to the time–frequency analysis of the AE signals.

Findings

The paper provides insights about the changing rule of the acoustic radiation patterns influenced by the heating effect of the moving heat source and the AE signal characteristics in thermoelastic plate by different crack lengths and depths. It reveals that the time–frequency characteristics of the AE signals from the simulation are in good agreement with the theoretical ones. The energy ratio of the antisymmetric mode A0 to symmetric mode S0 is a valuable quantitative inductor to estimate the crack depth with a certain regularity.

Research limitations/implications

This paper mainly discusses the application of XFEM to calculate and analyze thermoelastic problems, and has presented few cases based on a specified configuration. Further work will focus on the calculation and analysis under different plate configurations and conditions, which is to obtain more interesting and general conclusions for guiding practice.

Originality/value

The paper is a successful application of XFEM to solve the problem of AE response of a crack in the dynamic welding inhomogeneous heating effect. The paper provides an effective way to obtain the AE signal characteristics in monitoring the welding crack.

Details

Engineering Computations, vol. 35 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

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