Dongqing Yang, Jun Xiong and Rong Li
This paper aims to fabricate inclined thin-walled components using positional wire and arc additive manufacturing (WAAM) and investigate the heat transfer characteristics of…
Abstract
Purpose
This paper aims to fabricate inclined thin-walled components using positional wire and arc additive manufacturing (WAAM) and investigate the heat transfer characteristics of inclined thin-walled parts via finite element analysis method.
Design/methodology/approach
An inclined thin-walled part is fabricated in gas metal arc (GMA)-based additive manufacturing using a positional deposition approach in which the torch is set to be inclined with respect to the substrate surface. A three-dimensional finite element model is established to simulate the thermal process of the inclined component based on a general Goldak double ellipsoidal heat source and a combined heat dissipation model. Verification tests are performed based on thermal cycles of locations on the substrate and the molten pool size.
Findings
The simulated results are in agreement with experimental tests. It is shown that the dwell time between two adjacent layers greatly influences the number of the re-melting layers. The temperature distribution on both sides of the substrate is asymmetric, and the temperature peaks and temperature gradients of points in the same distance from the first deposition layer are different. Along the deposition path, the temperature distribution of the previous layer has a significant influence on the heat dissipation condition of the next layer.
Originality/value
The established finite element model is helpful to simulate and understand the heat transfer process of geometrical thin-walled components in WAAM.
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The Library System of China and the Information System of China are the two systems of information organisations in China. This paper discusses the types of information agencies…
Abstract
The Library System of China and the Information System of China are the two systems of information organisations in China. This paper discusses the types of information agencies in each, focusing on structural characteristics, and governing regulations and especially on programmes and activities. Included in the discussion are such topics as publications, cooperative undertakings, new services and evaluation procedures.
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Sha Zhong, Mingzhi Yang, Bosen Qian, Lei Zhang, Dongqing He, Tongtong Lin and Fue-Sang Lien
This study aims to provide new insights into aerodynamic drag reduction for increasingly faster blunt-nosed trains, such as urban and freight trains. Specifically, this work…
Abstract
Purpose
This study aims to provide new insights into aerodynamic drag reduction for increasingly faster blunt-nosed trains, such as urban and freight trains. Specifically, this work investigates two distinctly different wake structures and associated aerodynamic drag of blunt-nosed trains.
Design/methodology/approach
Three typical cases of blunt-nosed trains with 1-, 2- and 3-m nose lengths are selected. The time-averaged and unsteady flow structures around the trains are analyzed using the improved delayed detached eddy simulation model and proper orthogonal decomposition method.
Findings
The simulation results indicate that for 2- and 3-m nose lengths, the flow separates at first and then reattaches to the slanted surface of the tail, with a pair of longitudinal vortices dominating the wake. In contrast, for the 1-m nose length case, the wake structure is characterized by complete separation, attributed to the larger curvature of the slanted tail surface. Consequently, the total time-averaged drag coefficient is reduced by 27.2% and 19.2% for the 1-m nose length case compared to the 2- and 3-m cases, respectively. Moreover, the predominant unsteady structures with Strouhal numbers St = 0.30 and St = 0.28 are detected in the near-wake of the 2- and 3-m nose length cases, respectively. These structures result from periodic vortex shedding at the lower slanted tail surface. In contrast, for the 1-m nose length case, the predominant unsteady structure with St = 0.19 is induced by the nearly periodic expansion and contraction of the upper bubbles.
Originality/value
Two distinctly different wake structures in blunt-nosed trains are identified. Unlike high-speed trains with longer, streamlined noses, for blunt-nosed trains, shorter nose lengths result in lower aerodynamic drag. Insights for reducing energy consumption in blunt-nosed trains are provided.
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Ruyue Han, Xingmei Li, Zhong Shen and Dongqing Jia
The consideration of the substitution phenomenon in the project portfolio selection problem can improve the robustness of project portfolio selection and help enterprises better…
Abstract
Purpose
The consideration of the substitution phenomenon in the project portfolio selection problem can improve the robustness of project portfolio selection and help enterprises better achieve their strategic objectives. However, the existence of inter-project risk propagation will have a negative impact on project substitution. This paper proposes a new framework for project portfolio selection and constructs a risk propagation model based on strategic objectives to study the impact of risk propagation on substitution in the project portfolio.
Design/methodology/approach
The authors first construct a risk propagation model based on strategic objectives to describe the risk propagation between projects. Then the project substitution phenomenon based on risk propagation is put forward, and the calculation method of substitution loss is given. Finally, a robust project portfolio selection framework based on strategic objectives considering risk propagation is constructed.
Findings
The analysis of a case study demonstrates that (1) With the increase of risk intensity, the strategic loss of the same project portfolio increases linearly, and under the same risk intensity, the more projects in the portfolio, the stronger the robustness. (2) Considering risk propagation, the effect of project substitution is significantly weakened, and the strategic loss rate of the project portfolio is significantly increased compared with that of a direct attack.
Originality/value
This study is the first to take the project substitution into account in the project portfolio selection process. Moreover, the authors describe inter-project risk propagation and analyze the impact of risk propagation on the project substitution phenomenon. Finally, the authors extend the evaluation index of robustness. This paper puts forward a new way to solve the problem of project portfolio selection.
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Xingxing Zu, Huaming Zhou, Xiaowei Zhu and Dongqing Yao
The purpose of this study is to investigate the underlying characteristics that influence quality management implementation at manufacturing companies operating in China.
Abstract
Purpose
The purpose of this study is to investigate the underlying characteristics that influence quality management implementation at manufacturing companies operating in China.
Design/methodology/approach
The data of this study were based on 199 manufacturing companies collected from a cross‐sectional survey in China. The cultural profiles of these companies were identified through cluster analysis. Multivariate analysis of variance was conducted to identify the effects of operating characteristics and cultural profile on the implementation level of quality management practices.
Findings
The results show that in general, there is no significant difference in implementing quality management practices among companies of different operating characteristics in terms of company size, industry, ownership, and production process. This study reveals that cultural profile is a distinguishing factor to explain the difference in quality management implementation among the companies.
Originality/value
As China is becoming an important supplier of products to the global market, it is necessary to understand how product quality is controlled and managed in China. This study examines the effects of operating and cultural characteristics of companies in China on their implementation of quality management practices. The results contribute to a deeper understanding of how to build an effective quality system at companies in China.
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Dongxiao Niu, Ling Ji, Yongli Wang and Da Liu
The purpose of this paper is to improve the accuracy of short time load forecasting to ensure the economical and safe operation of power systems. The traditional neural network…
Abstract
Purpose
The purpose of this paper is to improve the accuracy of short time load forecasting to ensure the economical and safe operation of power systems. The traditional neural network applied in time series like load forecasting, easily plunges into local optimum and has a complicated learning process, leading to relatively slow calculating speed. On the basis of existing literature, the authors carried out studies in an effort to optimize a new recurrent neural network by wavelet analysis to solve the previous problems.
Design/methodology/approach
The main technique the authors applied is referred to as echo state network (ESN). Detailed information has been acquired by the authors using wavelet analysis. After obtaining more information from original time series, different reservoirs can be built for each subsequence. The proposed method is tested by using hourly electricity load data from a southern city in China. In addition, some traditional methods are also applied for the same task, as contrast.
Findings
The experiment has led the authors to believe that the optimized model is encouraging and performs better. Compared with standard ESN, BP network and SVM, the experimental results indicate that WS‐ESN improves the prediction accuracy and has less computing consumption.
Originality/value
The paper develops a new method for short time load forecasting. Wavelet decomposition is employed to pre‐process the original load data. The approximate part associated with low frequencies and several detailed parts associated with high frequencies components give expression to different information from original data. According to this, suitable ESN is chosen for each sub‐sequence, respectively. Therefore, the model combining the advantages of both ESN and wavelet analysis improves the result for short time load forecasting, and can be applied to other time series problem.
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Tang Ying and Li Wan‐Qing
The purpose of this paper is to introduce trench termination for high power buried‐gate static induction transistor (SIT) comprising three parts, which can inhibit the reverse…
Abstract
Purpose
The purpose of this paper is to introduce trench termination for high power buried‐gate static induction transistor (SIT) comprising three parts, which can inhibit the reverse leakage current substantially and paradisaical current. The simplified step‐etching process will also be discussed in detail.
Design/methodology/approach
For power buried‐gate SIT, the trench termination comprises three grooves, gate electrode etching, mesa‐groove etching and the separated groove, respectively. The simplified step‐etching process is proposed to optimize the traditional technical processing.
Findings
The tripartite trench termination of power SIT can inhibit the reverse leakage current, improve the gate‐source breakdown and increase the blocking voltage. The step‐etching process which is proposed for the first time, realizes the tripartite trench termination simultaneously which simplifies the traditional processes and is beneficial by protecting the surface of the die. The optimum etched depth of termination is also presented with experimentations.
Originality/value
The tripartite trench termination of power SIT is novel and the step‐etching process is also proposed for the first time.
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Honglin Yang, Erbao Cao, Kevin Jiang Lu and Guoqing Zhang
The aim of this paper is to investigate the effect of information asymmetry on revenue sharing contracts and performance in a dual-channel supply chain. First, the authors model…
Abstract
Purpose
The aim of this paper is to investigate the effect of information asymmetry on revenue sharing contracts and performance in a dual-channel supply chain. First, the authors model the optimum revenue sharing contract in a dual-channel supply chain under both the full information case and the asymmetric information case. Second, they contrast the optimal decisions of a dual-channel supply chain between the full information case and the asymmetric information case. Third, they explore the impact of asymmetric cost information on the performance of a dual-channel supply chain and investigate the information value.
Design/methodology/approach
The authors present two main issues associated with revenue sharing contracts to alleviate manufacturer–retailer conflicts in a dual-channel supply chain. In the first issue, a revenue sharing contract is designed in a dual-channel supply chain under asymmetric cost information conditions, based on the principal-agent model. In the second issue, an optimal revenue sharing contract under full information conditions, based on the Stackelberg game is discussed. They explore the impact of asymmetric cost information on the performance of a dual-channel supply chain and investigate the information value based on comparative static analysis.
Findings
First, the direct sale price is unchanged and independent of the retailer’s cost construct, but the wholesale price increases and the retail sale price does not decrease under asymmetric cost information. The information asymmetry leads to higher direct sale demand and lower retail sale demand. Second, information asymmetry is beneficial for the retailer, but imposes inefficiency on the manufacturer and the whole supply chain. Third, the performance of the dual-channel supply chain is improved if the retailer’s cost information is shared and the dual-channel supply chain reaches coordination. The retailer is willing to share its cost information if the lump sum side payment that the manufacturer offers can make up the retailer’s reduced profit due to sharing this information.
Originality/value
The authors proposed a contract menus design model in a dual-channel supply chain. They examine how information asymmetry affects optimal policies and performance. They compared the optimal policies under symmetric information and asymmetric information. Conditions under which the partners prefer sharing information are identified. They quantified the information value from the points of partners and the whole system.
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S.H. Chung, Ying Kei Tse and T.M. Choi
The purpose of this paper is to carry out a comprehensive review for state-of-the-art works in disruption risk management of express logistics mainly supported by…
Abstract
Purpose
The purpose of this paper is to carry out a comprehensive review for state-of-the-art works in disruption risk management of express logistics mainly supported by air-transportation. The authors aim to suggest some new research directions and insights for express logistics practitioners to develop more robust planning in air-transportation.
Design/methodology/approach
The authors mainly confined the research to papers published over the last two decades. The search process was conducted in two dimensions: horizontal and vertical. In the horizontal dimension, attention was paid to the evolution of disruption management across the timeline. In the vertical dimension, different foci and strategies of disruption management are employed to distinguish each article. Three keywords were used in the full text query: “Disruption management”, “Air transportation”, and “Airline Operations” in all database searches listed above. Duplications due to database overlap, articles other than those from academic journals, and papers in languages other than English were discarded.
Findings
A total of 98 articles were studied. The authors categorized the papers into two broad categories: Reactive Recovery, and Proactive Planning. In addition, based on the problem characteristics and their application scenarios, a total of 11 sub-categories in reactive recovery and nine sub-categories in proactive planning were further identified. From the analysis, the authors identified some new categories in the air-transportation recovery. In addition, by analyzing the papers in robust planning, according to the problem characteristics and the state-of-the-art research in recovery problems, the authors proposed four new research directions to enhance the reliability and robustness of air-transportation express logistics.
Research limitations/implications
This study provided a comprehensive and feasible taxonomy of disruption risk management. The classification scheme was based on the problem characteristics and the application scenarios, rather than the algorithms. One advantage of this scheme is that it enables an in-depth classification of the problem, that is, sub-categories of each class can be revealed, which provides a much wider and clearer horizon to the scientific progress in this area. This helps researchers to reveal the problem’s nature and to identify the future directions more systematically. The suggestions for future research directions also point out some critical research gaps and opportunities.
Practical implications
This study summarized various reasons which account for the disruption in air-transportation. In addition, the authors suggested various considerations for express logistics practitioners to enhance logistics network reliability and efficiency.
Originality/value
There are various classification schemes in the literature to categorize disruption management. Using different algorithms (e.g. exact algorithm, heuristics, meta-heuristics) and distinct characteristics of the problem elements (e.g. aircraft, crew, passengers, etc.) are the most common schemes in previous efforts to produce a disruption management classification scheme. However, the authors herein attempted to focus on the problem nature and the application perspective of disruption management. The classification scheme is hence novel and significant.
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Fakhrodin Lalegani, Mohammad Reza Saffarian, Ahmadreza Moradi and Ebrahim Tavousi
According to very small dimensions of the microchannels, producing a microchannel with smooth surfaces is approximately impossible. The surface roughness can have a specific…
Abstract
Purpose
According to very small dimensions of the microchannels, producing a microchannel with smooth surfaces is approximately impossible. The surface roughness can have a specific effect on microchannel performances. This paper aims to investigate the changes in friction and pressure drop in the microchannels by considering the different roughness elements on microchannel wall and changes in elementary geometry and flow conditions. Results show a significant effect of roughness on the pressure drop and friction.
Design/methodology/approach
Two-dimensional fluid flow in the rough microchannels is analyzed using FLUENT. Microchannels have a height of 50 µm. Water at room temperature (25°C) has been used as working fluid. The Reynolds numbers are considered in laminar flow range and from 50 to 300.
Findings
The results show that the value of friction factor reduces nonlinearly with an increase in Reynolds number. But, the pressure drops and the Poiseuille number in the microchannels increase with an increase in Reynolds number. The values of the pressure drop and the friction factor increase by increasing the height and size of the roughness elements, but these values reduce with an increase in the distance of roughness elements.
Originality/value
The roughness elements types in this research are rectangular, trapezoidal, elliptical, triangular and complex (composed of multiple types of roughness elements). The effects of the Reynolds number, roughness height, roughness distance and roughness size on the pressure drop and friction in the rough microchannels are investigated and discussed. Furthermore, differences between the effects of five types of roughness elements are identified.