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1 – 5 of 5Desheng Zhang, Weidong Shi, Dazhi Pan and Guangjian Zhang
– The purpose of this paper is to predict the unstable cavitation shedding flow around a 2D Clark-y hydrofoil.
Abstract
Purpose
The purpose of this paper is to predict the unstable cavitation shedding flow around a 2D Clark-y hydrofoil.
Design/methodology/approach
The paper studies Partially Averaged Navier-Stokes (PANS) model which was employed in the two-phase flow with a homogeneous cavitation model.
Findings
Maximum density ratio affects the mass transfer rate between the liquid and the vapor significantly. The cavitating flow predicted by PANS model can resolve more turbulent scales by decreasing the parameter fk.
Originality/value
The accuracy of numerical prediction is improved by increasing the maximum density ratio and decreasing fk.
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Keywords
Xixian Lin, Yuming Zhang, Yimeng Zhang and Guangjian Rong
The purpose of this study is to design a more flexible and larger range of the dimming circuit that achieves the independence of multiple LED strings drive and can time-multiplex…
Abstract
Purpose
The purpose of this study is to design a more flexible and larger range of the dimming circuit that achieves the independence of multiple LED strings drive and can time-multiplex the power circuit.
Design/methodology/approach
The state-space method is used to model the BUCK circuit working in Pseudo continuous conduction mode, analyze the frequency characteristics of the system transfer function and design the compensation network. Build a simulation platform on the Orcad PSPICE platform and verify the function of the designed circuit through the simulation results. Use Altium Designer 16 to draw the printed circuit board, complete the welding of various components and use the oscilloscope, direct current (DC) power supply and a signal generator to verify the circuit function.
Findings
A prototype of the proposed LED driver is fabricated and tested. The measurement results show that the switching frequency can be increased to 1 MHz, Power inductance is 2.2 µH, which is smaller than current research. The dimming ratio can be set from 10% to 100%. The proposed LED driver can output more than 48 W and achieve a peak conversion efficiency of 91%.
Originality/value
The proposed LED driver adopts pulse width modulation (PWM) dimming at a lower dimming ratio and adopts DC dimming at a larger dimming ratio to realize switching PWM dimming to analog dimming. The control strategy can be more precise and have a wide range of dimming.
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Yu Zhou, Huaiqian Zhu, Li Zhu, Guangjian Liu and Yufeng Zou
Drawing from social capital theory and resource dependence theory, this paper aims to test the relationship between top management team (TMT) government social capital and firm’s…
Abstract
Purpose
Drawing from social capital theory and resource dependence theory, this paper aims to test the relationship between top management team (TMT) government social capital and firm’s innovation performance via firm’s network prestige, and the moderating effect of TMT academic social capital.
Design/methodology/approach
The authors collected data from the China Stock Market and Accounting Research Database as well as A-share listed firms’ annual reports, and finally generated a sample of 922 firms and 2,464 firm-years from 2008 to 2014. UCINET 6.0 was used to analyze the data.
Findings
The authors find that the government social capital of TMT is positively related to firms’ innovation performance and firms’ network prestige plays a mediating role in this relationship. In addition, TMT academic social capital can strengthen the links between TMT government social capital and innovation performance through firms’ network prestige.
Originality/value
This paper not only contributes to literatures on the mechanism in the relationship between government social capital and firms’ innovation, but also to literatures on the effectiveness of the heterogeneity of firm’s social capital.
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Guangjian Xu and Yan Wu
The purpose of this paper is to examine the financing and provision of basic public services in China. The main issue addressed is how to reform the public finance system to…
Abstract
Purpose
The purpose of this paper is to examine the financing and provision of basic public services in China. The main issue addressed is how to reform the public finance system to achieve quality and fairness in the provision of basic public services.
Design/methodology/approach
Based on an historical analysis of the functional transformation of the public finance system in China and on an empirical analysis of the current public finance system and the public service provision system, a comprehensive understanding was gained about the relationship between the financing and provision of basic public services.
Findings
The paper argues that there is a close relationship between the provision of basic public services and the functional changes made to the public finance system. Based on a systematic retrospective study of the Chinese Government’s efforts to improve basic public services over the last three decades, this paper offers policy suggestions on further public finance restructuring that would support better service provision.
Originality/value
By analyzing issues in the public service provision system, this paper contributes to the debate about the efficiency improvement made to governmental functions in China.
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Jinsong Zhang, Xinlong Wang, Chen Yang, Mingkang Sun and Zhenwei Huang
This study aims to investigate the noise-inducing characteristics during the start-up process of a mixed-flow pump and the impact of different start-up schemes on pump noise.
Abstract
Purpose
This study aims to investigate the noise-inducing characteristics during the start-up process of a mixed-flow pump and the impact of different start-up schemes on pump noise.
Design/methodology/approach
This study conducted numerical simulations on the mixed-flow pump under different start-up schemes and investigated the flow characteristics and noise distribution under these schemes.
Findings
The results reveal that the dipole noise is mainly caused by pressure fluctuations, while the quadrupole noise is mainly generated by the generation, development and breakdown of vortices. Additionally, the noise evolution characteristics during the start-up process of the mixed-flow pump can be divided into the initial stage, stable growth stage, impulse stage and stable operation stage.
Originality/value
The findings of this study can provide a theoretical basis for the selection of start-up schemes for mixed-flow pumps, reducing flow noise and improving the operational stability of mixed-flow pumps.
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