This paper presents a new elasticity and finite element formulation for different Young's modulus when tension and compression loadings in anisotropy media. The case studies, such as anisotropy and isotropy, were ...This paper presents a new elasticity and finite element formulation for different Young's modulus when tension and compression loadings in anisotropy media. The case studies, such as anisotropy and isotropy, were investigated. A numerical example was shown to find out the changes of neutral axis at the pure bending beams.展开更多
The time reversal is an unique self-adaptive focusing technique important to ultrasonic imaging. In this paper, the principle and the analytic expression of the ultrasound field in the realization of time reversal du...The time reversal is an unique self-adaptive focusing technique important to ultrasonic imaging. In this paper, the principle and the analytic expression of the ultrasound field in the realization of time reversal during the presence of an interface between two media are presented. Experimental results of time reversal are given and found to agree with theoretical ones.展开更多
Cryogenic energy storage(CES)has garnered attention as a large-scale electric energy storage technology for the storage and regulation of intermittent renewable electric energy in power networks.Nitrogen and argon can...Cryogenic energy storage(CES)has garnered attention as a large-scale electric energy storage technology for the storage and regulation of intermittent renewable electric energy in power networks.Nitrogen and argon can be found in the air,whereas methane is the primary component of natural gas,an important clean energy resource.Most research on CES focuses on liquid air energy storage(LAES),with its typical round-trip efficiency(RTE)being approximately 50%(theoretical).This study aims to explore the feasibility of using different gases as working media in CES systems,and consequently,to achieve a high system efficiency by constructing four steady-state process models for the CES systems with air,nitrogen,argon,and methane as working media using Aspen HYSYS.A combined single-parameter analysis and multi-parameter global optimization method was used for system optimization.Further,a group of key independent variables were analysed carefully to determine their reasonable ranges to achieve the ideal system performance,that is,RTE and liquefaction ratio through a single-parameter analysis.Consequently,a multi-parameter genetic algorithm was adopted to globally optimize the CES systems with different working media,and the energy and exergy analyses were conducted for the CES systems under their optimal conditions.The results indicated the high cycle efficiency of methane and a low irreversible loss in the liquefaction cycle.Moreover,the Joule-Thomson valve inlet temperature and charging and discharging pressures considerably affected the system performance.However,exergy loss in the CES system occurred primarily in the compressor,turbine,and liquefaction processes.The maximum optimal RTE of 55.84%was achieved in the liquid methane energy storage(LMES)system.Therefore,the LMES system is expected to exhibit potential for application in the CES technology to realize the integration of natural gas pipelines with renewable power grids on a large scale.Moreover,the results of study have important theoretical significance for 展开更多
Online learning is a very important means of study, and has been adopted in many countries worldwide. However, only recently are researchers able to collect and analyze massive online learning datasets due to the COVI...Online learning is a very important means of study, and has been adopted in many countries worldwide. However, only recently are researchers able to collect and analyze massive online learning datasets due to the COVID-19 epidemic. In this article, we analyze the difference between online learner groups by using an unsupervised machine learning technique, i.e., k-prototypes clustering. Specifically, we use questionnaires designed by domain experts to collect various online learning data, and investigate students’ online learning behavior and learning outcomes through analyzing the collected questionnaire data. Our analysis results suggest that students with better learning media generally have better online learning behavior and learning result than those with poor online learning media. In addition, both in economically developed or undeveloped regions, the number of students with better learning media is less than the number of students with poor learning media. Finally, the results presented here show that whether in an economically developed or an economically undeveloped region, the number of students who are enriched with learning media available is an important factor that affects online learning behavior and learning outcomes.展开更多
文摘This paper presents a new elasticity and finite element formulation for different Young's modulus when tension and compression loadings in anisotropy media. The case studies, such as anisotropy and isotropy, were investigated. A numerical example was shown to find out the changes of neutral axis at the pure bending beams.
基金This project supported by National Natural Science Foundation of China and the President Foundationof Institute of Acoustics
文摘The time reversal is an unique self-adaptive focusing technique important to ultrasonic imaging. In this paper, the principle and the analytic expression of the ultrasound field in the realization of time reversal during the presence of an interface between two media are presented. Experimental results of time reversal are given and found to agree with theoretical ones.
基金the National Natural Science Foundation of China(Grant No:52076159).
文摘Cryogenic energy storage(CES)has garnered attention as a large-scale electric energy storage technology for the storage and regulation of intermittent renewable electric energy in power networks.Nitrogen and argon can be found in the air,whereas methane is the primary component of natural gas,an important clean energy resource.Most research on CES focuses on liquid air energy storage(LAES),with its typical round-trip efficiency(RTE)being approximately 50%(theoretical).This study aims to explore the feasibility of using different gases as working media in CES systems,and consequently,to achieve a high system efficiency by constructing four steady-state process models for the CES systems with air,nitrogen,argon,and methane as working media using Aspen HYSYS.A combined single-parameter analysis and multi-parameter global optimization method was used for system optimization.Further,a group of key independent variables were analysed carefully to determine their reasonable ranges to achieve the ideal system performance,that is,RTE and liquefaction ratio through a single-parameter analysis.Consequently,a multi-parameter genetic algorithm was adopted to globally optimize the CES systems with different working media,and the energy and exergy analyses were conducted for the CES systems under their optimal conditions.The results indicated the high cycle efficiency of methane and a low irreversible loss in the liquefaction cycle.Moreover,the Joule-Thomson valve inlet temperature and charging and discharging pressures considerably affected the system performance.However,exergy loss in the CES system occurred primarily in the compressor,turbine,and liquefaction processes.The maximum optimal RTE of 55.84%was achieved in the liquid methane energy storage(LMES)system.Therefore,the LMES system is expected to exhibit potential for application in the CES technology to realize the integration of natural gas pipelines with renewable power grids on a large scale.Moreover,the results of study have important theoretical significance for
文摘Online learning is a very important means of study, and has been adopted in many countries worldwide. However, only recently are researchers able to collect and analyze massive online learning datasets due to the COVID-19 epidemic. In this article, we analyze the difference between online learner groups by using an unsupervised machine learning technique, i.e., k-prototypes clustering. Specifically, we use questionnaires designed by domain experts to collect various online learning data, and investigate students’ online learning behavior and learning outcomes through analyzing the collected questionnaire data. Our analysis results suggest that students with better learning media generally have better online learning behavior and learning result than those with poor online learning media. In addition, both in economically developed or undeveloped regions, the number of students with better learning media is less than the number of students with poor learning media. Finally, the results presented here show that whether in an economically developed or an economically undeveloped region, the number of students who are enriched with learning media available is an important factor that affects online learning behavior and learning outcomes.
