Fan Yang, Wei He, Wendong Deng and Tao Chen
The purpose of this paper is to propose an improved charge simulation method (CSM) based on the real‐coded genetic algorithm (GA), in which the tedious testing and adjusting work…
Abstract
Purpose
The purpose of this paper is to propose an improved charge simulation method (CSM) based on the real‐coded genetic algorithm (GA), in which the tedious testing and adjusting work in the traditional CSM is avoided. In addition, less simulation charges are used in the simulation model for the same object compared with the traditional CSM.
Design/methodology/approach
In the improved CSM, the information of testing points are combined with the matching points, hence the size and locations of simulation charges can be only computed by the information of matching points, and the testing calculation in the traditional CSM is avoided. According to the Maxwell equations, an overdetermined equation is reformulated, and an improved GA is used to solve it. The process to create the initial population is improved, boundary condition information of part matching points and human experience are added into the initial population, which enhanced the convergence rate of the search calculation.
Findings
Combining the information of testing points into that of the matching points in the improved CSM, the tedious testing calculation can be avoided, and the GA is effective to solve the overdetermined equation for the improved CSM. By importing the information of part matching points and human experience, the search process can be accelerated and the convergence of the method is ensured. Comparison between the efficiency of traditional CSM and the improved CSM is presented, less simulation charges are used compared with the traditional CSM for the same object.
Research limitations/implications
The improved CSM cannot adjust the count of simulation charges in the equivalent model automatically.
Practical implications
Calculations of a sphere‐plane electrode model and a 64 kV insulator string are carried out to verify the validity of the improved CSM. In addition, it can also be used to compute the power frequency electric field of HV transmission apparatuses.
Originality/value
By improving the process of the traditional CSM and importing the GA, an improved CSM for the calculation of power frequency electric fields produced by high‐voltage apparatuses is presented in the paper, which can avoid the tedious testing and adjusting work in the traditional CSM.
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Hua Deng and Wendong Liu
This study aims to inform prospective listing firms, investors and regulators of the unique drivers of Chinese initial public offering (IPO) pricing on the Hong Kong Exchange.
Abstract
Purpose
This study aims to inform prospective listing firms, investors and regulators of the unique drivers of Chinese initial public offering (IPO) pricing on the Hong Kong Exchange.
Design/methodology/approach
Using a hand-collected IPO dataset, we investigate whether information uncertainty or investor exuberance drives underpricing and Chinese IPOs’ performance from 2002 to 2015, including 114 state-owned enterprises (SOEs).
Findings
Contrasting with the “listing bubble” in the China domestic stock market, generated by the overoptimism of retail investors, we highlight a “placing bubble” among Chinese firms listed in Hong Kong. This is driven by institutional investors’ buoyant demand for Chinese IPO shares, particularly those of SOEs. Chinese listing firms employ discreet earnings management strategies with their working capital accounts to smooth pre-IPO earnings, which becomes apparent to the market only in the long term.
Originality/value
This study is the first to examine the pricing of sought-after Chinese IPOs among international investors, who face various restrictions when investing in the Chinese domestic stock market. Additionally, it is the first study to measure earnings management using hand-collected pre-IPO data in IPO underpricing studies.
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Tian Zhang, Wendong Zhang, XingLing Shao and Yang Wu
Because of the small size and high integration of capacitive micromachined ultrasonic transducer (CMUT) component, it can be made into large-scale array, but this lead to high…
Abstract
Purpose
Because of the small size and high integration of capacitive micromachined ultrasonic transducer (CMUT) component, it can be made into large-scale array, but this lead to high hardware complexity, so the purpose of this paper is to use less elements to achieve better imaging results. In this research, an optimized sparse array is studied, which can suppress the side lobe and reduce the imaging artifacts compared with the equispaced sparse array with the same number of elements.
Design/methodology/approach
Genetic algorithm is used to sparse the CMUT linear array, and Kaiser window apodization is added to reduce imaging artifacts, the beam pattern and peak-to-side lobe ratio are calculated, point targets imaging comparisons are performed. Furthermore, a 256-elements CMUT linear array is used to carry out the imaging experiment of embedded mass and forearm blood vessel, and the imaging results are compared quantitatively.
Findings
Through the imaging comparison of embedded mass and forearm blood vessel, the feasibility of optimized sparse array of CMUT is verified, and the purpose of reducing the hardware complexity is achieved.
Originality/value
This research provides a basis for the large-scale CMUT array to reduce the hardware complexity and the amount of calculation. At present, the CMUT array has been used in medical ultrasound imaging and has huge market potential.
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Liu Linxian, Zhang Wendong, Zhang Guojun, Guan Linggang, Xue Chenyang, Zhang Hui and Xue Nan
The purpose of this paper is to develop a novel MEMS vector hydrophone with the key features of smaller size, better consistency, higher sensitivity and directional reception, and…
Abstract
Purpose
The purpose of this paper is to develop a novel MEMS vector hydrophone with the key features of smaller size, better consistency, higher sensitivity and directional reception, and to develop a highly effective and economical obstacle avoidance sonar system. Currently, the typical vector hydrophones are resonant vector hydrophones based on the accelerometer, which greatly increases the volume and constrains the detection sensitivity. Also, because the system is composed of a number of devices, its size is difficult to be reduced.
Design/methodology/approach
A novel double T-shape MEMS vector hydrophone is proposed with a fish’s lateral line organs as prototypes. The structure size and layout location of the piezoresistors were determined by simulation analysis, and the double T-shape microstructure was fabricated integrally by MEMS manufacturing technology, after which, the acoustic package of the microstructure was completed and the prototype was produced. Finally, the packaged hydrophone was calibrated in a standing wave field in the first-class national-defense underwater acoustic calibration station of China. Also, the design and test of an obstacle avoidance sonar system based on the vector hydrophone were completed.
Findings
The calibration data show that the double T-shape vector hydrophone has a flat frequency response curve, exhibits a sensitivity of −180 dB (1 kHz, 0 dB reference 1 V/uPa) and shows a good directivity pattern in the form of an “8” shape. The test results of the obstacle avoidance sonar system further verify the feasibility of detecting underwater acoustic signals.
Research limitations/implications
The next work is to increase the sensitivity by optimizing the microstructure and to realize orientation by organizing array.
Practical implications
The hydrophone has the advantages of smaller size, lower cost and directional reception. It can be used to develop highly effective and economical obstacle avoidance sonar system, thus solving the problems of water transport efficiency and traffic safety. The hydrophone has broad application prospects and a huge market potential in the civilian fields.
Originality/value
The MEMS technology and innovative bionic microstructure enable the miniaturization and low cost of the hydrophone. The hydrophone is easy to form array and can narrow the array aperture greatly. So, the hydrophone can be widely used in civil sonar systems.
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Xiuyun Yang and Qi Han
The purpose of this study is to investigate whether the corporate environmental, social and governance (ESG) performance of enterprise is influenced by the enterprise digital…
Abstract
Purpose
The purpose of this study is to investigate whether the corporate environmental, social and governance (ESG) performance of enterprise is influenced by the enterprise digital transformation. In addition, this study explains how enterprise digital transformation affects ESG performance.
Design/methodology/approach
The sample covers 4,646 nonfinancial companies listed on China’s A-share market from 2009 to 2021. The study adopts the fixed-effects multiple linear regression to perform the data analysis.
Findings
The study finds that enterprise digital transformation has a significant inverted U-shaped impact on ESG performance. Moderate digital transformation can improve enterprise ESG performance, whereas excessive digital transformation will bring new organizational conflicts and increase enterprise costs, which is detrimental to ESG performance. This inverted U-shaped effect is more pronounced in industrial cities, manufacturing industries and enterprises with less financing constraints and executives with financial backgrounds. Enterprise digital transformation mainly affects ESG performance by affecting the level of internal information communication and disclosure, the level of internal control and the principal-agent cost.
Practical implications
The government should take multiple measures to encourage enterprises to choose appropriate digital transformation based on their own production behaviors and development strategies, encourage them to innovate and upgrade their organizational management and development models in conjunction with digital transformation and guide them to use digital technology to improve ESG performance.
Social implications
This study shows that irrational digital transformation cannot effectively improve the ESG performance of enterprises and promote the sustainable development of the country. Enterprises should carry out reasonable digital transformation according to their own development needs and finally improve the green and sustainable development ability of enterprises and promote the sustainable development of society.
Originality/value
This study examines the relationship between enterprise digital transformation and ESG performance. Different from the linear relationship between the two in previous major studies, this study proves the inverse U-shaped relationship between enterprise digital transformation and ESG performance through mathematical theoretical model derivation and empirical test. This study also explores in detail how corporate digital transformation affects ESG performance, as well as discusses heterogeneity at the city, industry and firm levels. It is proposed that enterprises should take into account their own characteristics and carry out reasonable digital transformation according to their development needs.