Search results

The paper aims to use aluminium alloy to substitute steel as the main material of ultra-precision hydro-static bearing system for an ultra-precision plastic electronics production system to lower the manufacturing cost. The total cost of diamond turning and nickel-based electroless coating of an aluminium alloy bearing is expected to be less than the cost of manufacturing a stainless steel bearing.

The paper used a large amount of theoretical calculation to obtain optimal specifications of the bearing system. ANSYS modelling was selected to simulate the deflection of the bearing shaft under high oil pressure. Hundreds of measurements were conducted after the bearing had been manufactured.

The paper provides industrial application insights on using aluminium alloy with a high-quality nickle-based electroless coating as a successful substitution of stainless steel. This created a more economic hydro-static bearing system.

Because of the time limit, different rotational speed tests shall be conducted in the future.

The paper provides implications for the application of nickel-based electroless coating to improve the surface property and bending strength of aluminium alloy, as well as classifying ultra-precision diamond turning as an economic finishing process.

This paper has identified the importance of aluminium alloy with a nickel-based electroless coating as the substitution of stainless steel in a precision hydro-static bearing system.

The serious friction and wear problem occurs on the mechanical seal’s faces during the start-up stage of the high-speed turbopump for a liquid rocket engine. This paper aims to propose a kind of thick metal alloy coatings on the surface of the seal’s rotor so as reduce the friction and wear.

With the pin-disk (the graphite pin and the disk with the metal coating) tribology-tester, the tribological behaviors of four metal coatings are investigated. The special friction coefficients under the dry friction, boundary friction and different temperatures of water-lubricated conditions were obtained.

The test results show that the thick metal coating has a good performance of the wear resistance and friction reduction; and the friction coefficients of a Sn-Sb-Cu coating under the dry friction and water-lubricated conditions are 0.377 and 0.043, respectively, and the corresponding mass wear volumes are only 2.74 and 0.81 mg, respectively.

The thick metal coating scheme for the mechanical seal’s faces might lend itself to the harsh working conditions of the low-viscosity liquid rocket engine.

The political influence on the determinants of capital structure has been under-researched for a long time. Taking the turnover of secretary of municipal committee as a political factor in China, this paper studies the effect of local government officials' turnover on firm's capital structure.

Starting with all A-shares listed firms in the Shanghai and Shenzhen Stock Exchanges from 2001 to 2018, this paper implements the OLS estimation, staggered difference-in-difference approach to investigate the effects of political turnover on the choice of capital structure.

The results show that, driven by government officials' turnover, firms will significantly reduce their leverage. When comparing between formal finance (bank loans) and informal finance (payables), the reduction of capital structure is mainly driven by banks, not by suppliers. Furthermore, two possible channels have been investigated. First, the reduction effects are mainly driven by the SOEs when classifying the types of corporate ownership into SOEs and non-SOEs. Second, the reduction effects exist in areas with the more intense government intervention when considering the heterogeneity of the development of institutional environment in provinces.

This paper first contributes to the literature on the determinants of corporate choice on capital structure. Second, this paper enriches the studies on the economic consequences of local government officials' turnover.

The findings suggest that reducing information processing costs as a result of better transportation is an important ingredient in promoting the pricing of firm-specific information. This study aims to discuss the aforementioned issue.

The authors adopt a difference-in-difference (DID) research design to examine the impact of information processing costs on stock price synchronicity with a sample of firms listed in the Chinese A-share market during 2007 and 2017.

This paper shows that the launch of the high-speed railway (hereafter HSR) in China is associated with lower stock price synchronicity, consistent with the theory that the HSR reduces investors’ information processing costs (cost of monitoring, acquiring and analyzing firm disclosures). This effect is more pronounced for companies located in remote areas than for those located in large cities. Further tests show that the negative association between the launch of HSR and stock price synchronicity is stronger for companies with higher information asymmetries, proxied by higher equity concentration, higher complexity and lower internal control quality.

This study contributes to the literature in the following three ways. First, prior literature relates the effects of geographic distance to information transmission and information asymmetry between insiders and outside investors (e.g. Coval and Moskowitz, 2001; Kang and Kim, 2008; Malloy, 2005). The authors supplement the literature by providing new empirical evidence from an exogenous shock (natural experiment), that is, the launch of HSR, that facilitates transportation and reduces information transmission costs. Second, prior studies have shown that new airline routes that facilitate transportation improve investment and productivity (e.g. Bernstein et al., 2016; Giroud, 2013). The authors extend this stream of studies by showing that the development of HSR networks reduces information processing costs, and promotes the incorporation of firm-specific information in the asset pricing. More importantly, in this study, the authors explicitly incorporate disclosure processing costs theory into our framework thus enhancing our understanding of how and why improvements in transport relate to better market outcomes.

The purpose of this paper is to examine the effects of top management support (TMS) and inter-organizational relationships (IORs) on external involvement (EI), and their differences across different ownerships.

To test the research hypotheses, structural equation modeling was conducted using data from 176 Chinese manufacturing firms.

TMS enhances relationship with customers and relationship with suppliers. Relationship with customers increases the degree of customer involvement, while relationship with suppliers increases the degree of supplier involvement. In addition, TMS improves customer involvement while does not improve supplier involvement directly. A further analysis reveals that the relationship between TMS and supplier involvement is partially mediated by relationship with suppliers in Chinese-controlled firms, whereas it is completely mediated by relationship with suppliers in foreign-controlled firms. Moreover, the effect of relationship with suppliers on supplier involvement is stronger in foreign-controlled firms than in Chinese-controlled firms.

This study employed perceptual data from a single respondent in each firm. In addition, the data used in this study were collected from one side of the dyad: the manufacturers.

Both Chinese-controlled and foreign-controlled firms should get support from top management and develop close relationship with customers and suppliers to improve EI.

This study extends our knowledge in the field by examining how TMS and prior history of IORs can improve the degree of EI.

To retrieve the geometric information contained in CT images, a surface reconstruction method, which is based on the similarity between the corresponding contours of adjacent sections, is presented in this paper. The correspondence of the contours of adjacent sections is determined by incorporating the topological rules and overlaps of the convex hulls of the contours. Then, the similar vertices of the corresponding contours are matched using a two‐phase strategy, consisting of overall matching followed by local matching. Dissimilar portions are extracted to construct the triangulable spatial dissimilar polygons. Finally, triangular meshes interpolating the contours are obtained by triangulating the dissimilar polygons and similar portions separately. The reconstructed surface models can be used in rapid prototyping as well as visualization. Experimental results demonstrate the validity of the method in reconstructing the surface from severe dissimilar contours.

A new type of hydrostatic and hydrodynamic non-contacting face seals has been designed to meet the requirements of lower leakage, longer life and more repeatedly start and stop on shaft seals raised by liquid rocket engine turbopumps. And an experimental study on the performance of the face seal in the actual liquid oxygen turbopump was completed where low-viscosity water was selected as the seal fluid for the sake of safety. The paper aims to discuss these issues.

Different performances of face seals under preset conditions were obtained by repeatedly running tests, and the main performance parameters encompass leakage, fluid film pressure between the faces, operating power, face temperature, and so on.

The results indicate that the designed face seal has a smaller amount of leakage, with a minimum value of 3 ml/s. Furthermore, the designed face seal has been proved to demand lower operating power. Since its operating power changes slightly with different sealed fluid pressures, the new seal can be deployed in the harsh working condition with high pressure or with high speed (greater than 20,000 rpm). However, one proviso is that when liquid is employed as the seal fluid, the groove depth should be relatively deeper (greater than 10 μm).

In response to future engineering requirements, study on the controllable spiral-groove face seals to improve the current design is being conducted.

The advancement of such non-contacting face seals proffers important insights to the design of turbo-pump shaft seal in a new generation of liquid rocket engine with regard to the requirement of frequent start and stop as well as long life on it.

The aims of this study are to conduct a systematic review of public–private partnership (PPP) studies published from 2009 to 2019, to compare the results with Ke et al. (2009) who reviewed the PPP literature published from 1998 to 2008, and to trace the evolution of the PPP knowledge in the past two decades. This study also presents the possible directions that the PPP research may go towards in the future, arguably.

This study carried out a top journal-based search to identify the quality PPP articles published from 2009 to 2019. A total of 12 top-tier construction journals were systematically searched in the database of web of science (WOS), from which 279 PPP articles were identified for review.

The number of the identified articles, the titles of the journals, institutions, the most cited papers, and prevalent research methods were analyzed and compared. The existing PPP studies in construction journals were classified into seven streams. Through analysis of the PPP research status and gaps, five future research directions were revealed.

This study contributes to the current body of knowledge by revealing the research trend of PPP from 2009 to 2019. It presents the change of PPP development trend in the past decade through comparison with Ke et al. (2009). It also reveals the major research streams and points out the directions that the PPP research may go towards in the future. Moreover, this study is helpful to the practice as well. It can enhance the practitioners' understanding of the PPP development in the past decade. In addition, it identified the research institutions contributing the most in the area of PPP, which may serve as valuable reference for practitioners to locate the best institutions for consultancy or collaboration.

Due to the increasing population and prosperity, the generation rate of municipal solid waste (MSW) has increased significantly, resulting in serious problems on public health and the environment. Every single person in the world is affected by the municipal solid waste management (MSWM) issue. MSWM is reaching a critical level in almost all areas of the world and seeking the development of MSW strategies for a sustainable environment. This paper aims to present the existing global status of MSW generation, composition, management and related problems.

A total of 59 developed and developing countries have been grouped based on their gross national income to compare the status of various MSWM technologies among them. A total of 19 selection criteria have been discussed to select appropriate MSWM technology(s) for a city/town, which affects their applicability, operational suitability and performance. All risks and challenges arising during the life cycle of the waste to energy (WtE) project have also been discussed. This paper also gives a comparative overview of different globally accepted MSWM technologies and the present market growth of all WtE technologies.

It was found that most developed countries have effectively implemented the solid waste management (SWM) hierarchy and are now focusing heavily on reducing, reusing and recycling of MSW. On the other hand, SWM has become very serious in low-income and low-middle-income countries because most of the MSW openly dumps and most countries are dependent on inadequate waste infrastructure and the informal sector. There are also some other major challenges related to effective waste policies, availability of funds, appropriate technology selection and adequacy of trained people. This study clears the picture of MSW generation, composition, management strategies and policies at the worldwide context. This manuscript could be valuable for all nations around the world where effective MSWM has not yet been implemented.

This study clears the picture of solid waste generation, composition, management strategies and policies at the worldwide context. This manuscript could be valuable for all nations around the world where effective MSWM has not yet been implemented. In this study, no data was generated. All supporting data were obtained from previously published papers in journals, the outcomes of the international conferences and published reports by government organizations.

Specialized police gang units are a rapidly emerging form of concentrated social control. Prior research, however, into the creation of specialized gang units suffers from a number of theoretical and methodological shortcomings. These shortcomings make it difficult to understand which of several potential explanations can best account for the establishment of specialized police gang units. Three perspectives are examined that have been hypothesized by policymakers and academics to explain the creation of gang units: contingency theory, social threat theory, and resource dependency theory. Using data obtained from police departments and communities around the country, the explanatory power of measures derived from these three theories is explored, while controlling for several environmental and organizational influences.