Improving the detection accuracy of rail internal defects and the generalization ability of detection models are not only the main problems in the field of defect detection but also the key to ensuring the safe operat...Improving the detection accuracy of rail internal defects and the generalization ability of detection models are not only the main problems in the field of defect detection but also the key to ensuring the safe operation of high-speed trains.For this reason,a rail internal defect detection method based on an enhanced network structure and module design using ultrasonic images is proposed in this paper.First,a data augmentation method was used to extend the existing image dataset to obtain appropriate image samples.Second,an enhanced network structure was designed to make full use of the high-level and low-level feature information in the image,which improved the accuracy of defect detection.Subsequently,to optimize the detection performance of the proposed model,the Mish activation function was used to design the block module of the feature extraction network.Finally,the pro-posed rail defect detection model was trained.The experimental results showed that the precision rate and F1score of the proposed method were as high as 98%,while the model’s recall rate reached 99%.Specifically,good detec-tion results were achieved for different types of defects,which provides a reference for the engineering application of internal defect detection.Experimental results verified the effectiveness of the proposed method.展开更多
An approach to design small scale CMOS static random access memory (SRAM) is proposed. The design of address decoder, memory cell, and the layout are included. This approach adopts flip-flop array structure. The flip-...An approach to design small scale CMOS static random access memory (SRAM) is proposed. The design of address decoder, memory cell, and the layout are included. This approach adopts flip-flop array structure. The flip-flops are used as the storage cells and they are stacked to form the whole SRAM module. The word select bit is generated from the address decoder. And one word at a time is selected for reading or writing. The design of the memory core's layout is also discussed since it should be optimized to save area and also should be convenient for realization. It's a full-custom layout. The address decoder is composed of combinational logic circuit and its layout is also designed as a full-custom layout. With all these modules, the integral structure of the SRAM is carried out.展开更多
The key techniques of modular design of heavy duty NC mathine tools are described. Amodule definition modelfor modular design and manufacturing of heavy duty NC machine tools isbulit and the essential composition of t...The key techniques of modular design of heavy duty NC mathine tools are described. Amodule definition modelfor modular design and manufacturing of heavy duty NC machine tools isbulit and the essential composition of the module definition model (MDM) is discussed in detail. Itis composed of two models: the part definition model (PDM) and the module assembly model(MAM). The PDM and MAM are built and their structures are given. Using object-oriented know-ledge representation and based on these models, an intelligent support system of modular design forheavy duty NC machine tools is developed and implemented This system has been applied to thepractical use of Wuhan Heavy Duty Machine Tool Works展开更多
The demand for quality software expands as the business environment grows internationally. Common to all software development methodologies is a design phase that focuses on the physical software model. Design criteri...The demand for quality software expands as the business environment grows internationally. Common to all software development methodologies is a design phase that focuses on the physical software model. Design criteria used to evaluate these models are important for refinement and improvement. The purpose of this research is to apply transformations of McCabe’s cyclomatic complexity as a means for improving software design and assessing risks within a design. In this research, two metrics, the management (<em>C<sub>MGT</sub></em>) and maintenance (<em>C<sub>MN</sub></em>) coefficients are introduced, and they are used to address the architectural, size, and quality dimensions of a software design.展开更多
To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against t...To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against the background of an international commercial communication satellite (INTELSAT-Ⅲ) module. Three improvements are developed, including multi-population search based on pyramid model, adaptive collision avoidance among particles, and mutation of degraded particles. In the numerical examples of the layout design of this simplified satellite module, the performance of PPSO is compared to global version PSO and local version PSO (ring and Neumann PSO). The results show that PPSO has higher computational accuracy, efficiency and success ratio.展开更多
Over the past decade, open-source software use has grown. Today, many companies including Google, Microsoft, Meta, RedHat, MongoDB, and Apache are major participants of open-source contributions. With the increased us...Over the past decade, open-source software use has grown. Today, many companies including Google, Microsoft, Meta, RedHat, MongoDB, and Apache are major participants of open-source contributions. With the increased use of open-source software or integration of open-source software into custom-developed software, the quality of this software component increases in importance. This study examined a sample of open-source applications from GitHub. Static software analytics were conducted, and each application was classified for its risk level. In the analyzed applications, it was found that 90% of the applications were classified as low risk or moderate low risk indicating a high level of quality for open-source applications.展开更多
Thin-film lithium niobate electro-optical modulator will become the key device in the future optical communication,which has the advantages of high modulation rate,low half-wave voltage,large bandwidth,and easy integr...Thin-film lithium niobate electro-optical modulator will become the key device in the future optical communication,which has the advantages of high modulation rate,low half-wave voltage,large bandwidth,and easy integration compared with conventional bulk lithium niobate modulator.However,because the electrode gap of the lithium niobate film modulator is very narrow,when the microwave frequency gets higher,it leads to higher microwave loss,and the electro-optical performance of the modulator will be greatly reduced.Here,we propose a thin film lithium niobate electro-optic modulator with a bimetallic layer electrode structure to achieve microwave loss less than 8 dB/cm in the range of 200 GHz,exhibiting a voltage-length product of 1.1 V·cm and a 3 dB electro-optic bandwidth greater than 160 GHz.High-speed data transmission test has been performed,showing good performance.展开更多
This paper applies software analytics to open source code. Open-source software gives both individuals and businesses the flexibility to work with different parts of available code to modify it or incorporate it into ...This paper applies software analytics to open source code. Open-source software gives both individuals and businesses the flexibility to work with different parts of available code to modify it or incorporate it into their own project. The open source software market is growing. Major companies such as AWS, Facebook, Google, IBM, Microsoft, Netflix, SAP, Cisco, Intel, and Tesla have joined the open source software community. In this study, a sample of 40 open source applications was selected. Traditional McCabe software metrics including cyclomatic and essential complexities were examined. An analytical comparison of this set of metrics and derived metrics for high risk software was utilized as a basis for addressing risk management in the adoption and integration decisions of open source software. From this comparison, refinements were added, and contemporary concepts of design and data metrics derived from cyclomatic complexity were integrated into a classification scheme for software quality. It was found that 84% of the sample open source applications were classified as moderate low risk or low risk indicating that open source software exhibits low risk characteristics. The 40 open source applications were the base data for the model resulting in a technique which is applicable to any open source code regardless of functionality, language, or size.展开更多
The clear differences between the atmosphere of Mars and the Earth coupled with the lack of a domestic research basis were significant challenges for the aerodynamic prediction and verification of Tianwen-1.In additio...The clear differences between the atmosphere of Mars and the Earth coupled with the lack of a domestic research basis were significant challenges for the aerodynamic prediction and verification of Tianwen-1.In addition,the Mars entry,descent,and landing(EDL)mission led to specific requirements for the accuracy of the aerodynamic deceleration performance,stability,aerothermal heating,and various complex aerodynamic coupling problems of the entry module.This study analyzes the key and difficult aerodynamic and aerothermodynamic problems related to the Mars EDL process.Then,the study process and results of the design and optimization of the entry module configuration are presented along with the calculations and experiments used to obtain the aerodynamic and aerothermodynamic characteristics in the Martian atmosphere.In addition,the simulation and verification of the low-frequency free oscillation characteristics under a large separation flow are described,and some special aerodynamic coupling problems such as the aeroelastic buffeting response of the trim tab are discussed.Finally,the atmospheric parameters and aerodynamic characteristics obtained from the flight data of the Tianwen-1 entry module are compared with the design data.The data obtained from the aerodynamic design,analysis,and verification of the Tianwen-1 entry module all meet the engineering requirements.In particular,the flight data results for the atmospheric parameters,trim angles of attack,and trim axial forces are within the envelopes of the prediction deviation zones.展开更多
A new module design concept that integrates materials engineering with thermoelectric module optimization is proposed.This concept transforms the gaps between thermoelements and couples into internal space/pores withi...A new module design concept that integrates materials engineering with thermoelectric module optimization is proposed.This concept transforms the gaps between thermoelements and couples into internal space/pores within the elements to eliminate heat loss and thus to enhance module performance.The effect of the internal pore structure on module performance was studied using two effective medium models.The modeling results demonstrated that the power generation of the proposed module design increased by~8%and the efficiency increased>20%compared to those of the traditional module design.The effect of the inclusion of the second solid phase in the composite on module performance was also studied using nine different high-efficiency thermoelectric materials as the inclusions.The modeling results showed that further increase in module performance up to~50%that of the traditional module design can be achieved.展开更多
Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few rea...Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.61573233)Guangdong Provincial Natural Science Foundation of China(Grant No.2021A1515010661)Guangdong Provincial Special Projects in Key Fields of Colleges and Universities of China(Grant No.2020ZDZX2005).
文摘Improving the detection accuracy of rail internal defects and the generalization ability of detection models are not only the main problems in the field of defect detection but also the key to ensuring the safe operation of high-speed trains.For this reason,a rail internal defect detection method based on an enhanced network structure and module design using ultrasonic images is proposed in this paper.First,a data augmentation method was used to extend the existing image dataset to obtain appropriate image samples.Second,an enhanced network structure was designed to make full use of the high-level and low-level feature information in the image,which improved the accuracy of defect detection.Subsequently,to optimize the detection performance of the proposed model,the Mish activation function was used to design the block module of the feature extraction network.Finally,the pro-posed rail defect detection model was trained.The experimental results showed that the precision rate and F1score of the proposed method were as high as 98%,while the model’s recall rate reached 99%.Specifically,good detec-tion results were achieved for different types of defects,which provides a reference for the engineering application of internal defect detection.Experimental results verified the effectiveness of the proposed method.
文摘An approach to design small scale CMOS static random access memory (SRAM) is proposed. The design of address decoder, memory cell, and the layout are included. This approach adopts flip-flop array structure. The flip-flops are used as the storage cells and they are stacked to form the whole SRAM module. The word select bit is generated from the address decoder. And one word at a time is selected for reading or writing. The design of the memory core's layout is also discussed since it should be optimized to save area and also should be convenient for realization. It's a full-custom layout. The address decoder is composed of combinational logic circuit and its layout is also designed as a full-custom layout. With all these modules, the integral structure of the SRAM is carried out.
文摘The key techniques of modular design of heavy duty NC mathine tools are described. Amodule definition modelfor modular design and manufacturing of heavy duty NC machine tools isbulit and the essential composition of the module definition model (MDM) is discussed in detail. Itis composed of two models: the part definition model (PDM) and the module assembly model(MAM). The PDM and MAM are built and their structures are given. Using object-oriented know-ledge representation and based on these models, an intelligent support system of modular design forheavy duty NC machine tools is developed and implemented This system has been applied to thepractical use of Wuhan Heavy Duty Machine Tool Works
文摘The demand for quality software expands as the business environment grows internationally. Common to all software development methodologies is a design phase that focuses on the physical software model. Design criteria used to evaluate these models are important for refinement and improvement. The purpose of this research is to apply transformations of McCabe’s cyclomatic complexity as a means for improving software design and assessing risks within a design. In this research, two metrics, the management (<em>C<sub>MGT</sub></em>) and maintenance (<em>C<sub>MN</sub></em>) coefficients are introduced, and they are used to address the architectural, size, and quality dimensions of a software design.
基金This project is supported by National Natural Science Foundation of China (No.50275019, No.50335040, No.50575031).
文摘To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against the background of an international commercial communication satellite (INTELSAT-Ⅲ) module. Three improvements are developed, including multi-population search based on pyramid model, adaptive collision avoidance among particles, and mutation of degraded particles. In the numerical examples of the layout design of this simplified satellite module, the performance of PPSO is compared to global version PSO and local version PSO (ring and Neumann PSO). The results show that PPSO has higher computational accuracy, efficiency and success ratio.
文摘Over the past decade, open-source software use has grown. Today, many companies including Google, Microsoft, Meta, RedHat, MongoDB, and Apache are major participants of open-source contributions. With the increased use of open-source software or integration of open-source software into custom-developed software, the quality of this software component increases in importance. This study examined a sample of open-source applications from GitHub. Static software analytics were conducted, and each application was classified for its risk level. In the analyzed applications, it was found that 90% of the applications were classified as low risk or moderate low risk indicating a high level of quality for open-source applications.
基金supported by the Self-deployment Project of Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZZ104)the Fujian Province STS Project(Nos.2020T3002 and 2022T3012)。
文摘Thin-film lithium niobate electro-optical modulator will become the key device in the future optical communication,which has the advantages of high modulation rate,low half-wave voltage,large bandwidth,and easy integration compared with conventional bulk lithium niobate modulator.However,because the electrode gap of the lithium niobate film modulator is very narrow,when the microwave frequency gets higher,it leads to higher microwave loss,and the electro-optical performance of the modulator will be greatly reduced.Here,we propose a thin film lithium niobate electro-optic modulator with a bimetallic layer electrode structure to achieve microwave loss less than 8 dB/cm in the range of 200 GHz,exhibiting a voltage-length product of 1.1 V·cm and a 3 dB electro-optic bandwidth greater than 160 GHz.High-speed data transmission test has been performed,showing good performance.
文摘This paper applies software analytics to open source code. Open-source software gives both individuals and businesses the flexibility to work with different parts of available code to modify it or incorporate it into their own project. The open source software market is growing. Major companies such as AWS, Facebook, Google, IBM, Microsoft, Netflix, SAP, Cisco, Intel, and Tesla have joined the open source software community. In this study, a sample of 40 open source applications was selected. Traditional McCabe software metrics including cyclomatic and essential complexities were examined. An analytical comparison of this set of metrics and derived metrics for high risk software was utilized as a basis for addressing risk management in the adoption and integration decisions of open source software. From this comparison, refinements were added, and contemporary concepts of design and data metrics derived from cyclomatic complexity were integrated into a classification scheme for software quality. It was found that 84% of the sample open source applications were classified as moderate low risk or low risk indicating that open source software exhibits low risk characteristics. The 40 open source applications were the base data for the model resulting in a technique which is applicable to any open source code regardless of functionality, language, or size.
基金This research comes from the Tianwen-1 Mars exploration mission.The authors gratefully acknowledge the contributions of the entire Tianwen-1 design team.
文摘The clear differences between the atmosphere of Mars and the Earth coupled with the lack of a domestic research basis were significant challenges for the aerodynamic prediction and verification of Tianwen-1.In addition,the Mars entry,descent,and landing(EDL)mission led to specific requirements for the accuracy of the aerodynamic deceleration performance,stability,aerothermal heating,and various complex aerodynamic coupling problems of the entry module.This study analyzes the key and difficult aerodynamic and aerothermodynamic problems related to the Mars EDL process.Then,the study process and results of the design and optimization of the entry module configuration are presented along with the calculations and experiments used to obtain the aerodynamic and aerothermodynamic characteristics in the Martian atmosphere.In addition,the simulation and verification of the low-frequency free oscillation characteristics under a large separation flow are described,and some special aerodynamic coupling problems such as the aeroelastic buffeting response of the trim tab are discussed.Finally,the atmospheric parameters and aerodynamic characteristics obtained from the flight data of the Tianwen-1 entry module are compared with the design data.The data obtained from the aerodynamic design,analysis,and verification of the Tianwen-1 entry module all meet the engineering requirements.In particular,the flight data results for the atmospheric parameters,trim angles of attack,and trim axial forces are within the envelopes of the prediction deviation zones.
文摘A new module design concept that integrates materials engineering with thermoelectric module optimization is proposed.This concept transforms the gaps between thermoelements and couples into internal space/pores within the elements to eliminate heat loss and thus to enhance module performance.The effect of the internal pore structure on module performance was studied using two effective medium models.The modeling results demonstrated that the power generation of the proposed module design increased by~8%and the efficiency increased>20%compared to those of the traditional module design.The effect of the inclusion of the second solid phase in the composite on module performance was also studied using nine different high-efficiency thermoelectric materials as the inclusions.The modeling results showed that further increase in module performance up to~50%that of the traditional module design can be achieved.
基金The project is supported by Basic Research Foundation of Tsinghua University, No: JZ2000005.
文摘Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.