In recent years,in order to improve the destructive effectiveness of munitions,the use of new types of destructive elements is an important way to improve destructive effectiveness.As a new type of reactive material,r...In recent years,in order to improve the destructive effectiveness of munitions,the use of new types of destructive elements is an important way to improve destructive effectiveness.As a new type of reactive material,reactive alloy contains a large portion of reactive metal elements(Al,Mg,Ti,Zr,etc.),which breaks up under high-velocity impact conditions,generating a large number of high-temperature combustible fragments,which undergo a violent combustion reaction with air.Compared with traditional metal polymers(Al-PTFE)and other reactive composites,it has higher density and strength,excellent mechanical properties and broader application prospects.Currently,researchers have mainly investigated the impact energy release mechanism of reactive alloys through impact tests,and found that there are several important stages in the process of the material from fragmentation to reaction,i.e.,impact fragmentation of the material,rapid heating and combustion reaction.This paper focuses on three problems that need to be solved in the impact-induced energy release process of reactive alloys,namely:the fragmentation mechanism and size distribution law of the fragments produced by the impact of the material on the target,the relationship between the transient temperatures and the size of the fragments,and the reaction temperatures and size thresholds of the fragments to undergo the chemical reaction.The current status of the research of the above problems is reviewed,some potential directions to reveal the impact induced reaction mechanism of reactive alloy is discussed.展开更多
Under the background of the big data era,the education of big data majors is undergoing a profound teaching reform and innovation.With the increasing role of big data technology in analysis and decision-making,updatin...Under the background of the big data era,the education of big data majors is undergoing a profound teaching reform and innovation.With the increasing role of big data technology in analysis and decision-making,updating and expanding the teaching content of big data majors has become particularly important.In the era of big data,modern enterprises have put forward new and higher demands for big data talents,which not only include traditional data analysis skills but also knowledge of data visualization and information technology.To address these challenges,big data education needs to reform and innovate in the development and utilization of teaching content,methods,and resources.This paper proposes teaching models and reform methods for big data majors and analyzes corresponding teaching reforms and innovations to meet the requirements of the new development of big data majors.The traditional classroom teaching method is no longer sufficient to meet the learning needs of students,and more dynamic and interactive teaching methods,such as case studies,flipped classrooms,and project-based learning,are becoming increasingly essential.These innovative teaching methods can more effectively cultivate students’practical operation skills and independent thinking while allowing them to better learn advanced knowledge in a real big-data environment.In addition,the paper also discusses the construction of big data processing and analysis platforms,as well as innovative teaching management and evaluation systems to improve teaching quality.展开更多
A forest fire is a severe threat to forest resources and human life, In this paper, we propose a forest-fire detection system that has an artificial neural network algorithm implemented in a wireless sensor network （...A forest fire is a severe threat to forest resources and human life, In this paper, we propose a forest-fire detection system that has an artificial neural network algorithm implemented in a wireless sensor network （WSN）. The proposed detection system mitigates the threat of forest fires by provide accurate fire alarm with low maintenance cost. The accuracy is increased by the novel multi- criteria detection, referred to as an alarm decision depends on multiple attributes of a forest fire. The multi-criteria detection is implemented by the artificial neural network algorithm. Meanwhile, we have developed a prototype of the proposed system consisting of the solar batter module, the fire detection module and the user interface module.展开更多
This paper provides a comprehensive review of advanced radio fre-quency(RF)filter technologies available in miniature chip or inte-grated circuit(IC)form for wireless communication applications.The RF filter technolog...This paper provides a comprehensive review of advanced radio fre-quency(RF)filter technologies available in miniature chip or inte-grated circuit(IC)form for wireless communication applications.The RF filter technologies were organized according to the time-line of their introduction,in conjunction with each generation of wireless(cellular)communication standards(1G to 5G).This ap-proach enabled a clear explanation of the corresponding invention history,working principles,typical applications and future develop-ment trends.The article covered commercially successful acoustic filter technologies,including the widely used surface acoustic wave(SAW)and bulk acoustic wave(BAW)filters,as well as electromag-netic filter technologies based on low-temperature co-fired ceramic(LTCC)and integrated passive device(IPD).Additionally,emerg-ing filter technologies such as IHP-SAW,suspended thin-film lithium niobate(LiNbO3 or LN)resonant devices and hybrid were also dis-cussed.In order to achieve higher performance,smaller form factor and lower cost for the wireless communication industry,it is believed that fundamental breakthroughs in materials and fabrication tech-niques are necessary for the future development of RF filters.展开更多
Microwave photonics,a field that crosscuts microwave/millimeter-wave engineering with optoelectronics,has sparked great interest from research and commercial sectors. This multidisciplinary fusion can achieve ultrawid...Microwave photonics,a field that crosscuts microwave/millimeter-wave engineering with optoelectronics,has sparked great interest from research and commercial sectors. This multidisciplinary fusion can achieve ultrawide bandwidth and ultrafast speed that were considered impossible in conventional chip-scale microwave/millimeterwave systems. Conventional microwave-to-photonic converters,based on resonant acousto-optic modulation,produce highly efficient modulation but sacrifice bandwidth and limit their applicability for most real-world microwave signal-processing applications. In this paper,we build highly efficient and wideband microwaveto-photonic modulators using the acousto-optic effect on suspended lithium niobate thin films. A wideband microwave signal is first piezoelectrically transduced using interdigitated electrodes into Lamb acoustic waves,which directly propagates across an optical waveguide and causes refractive index pertp urbation through the photoelastic effect. This approach is power-efficient,with phase shifts up to 0.0166 rad∕m W over a 45μm modulation length and with a bandwidth up to 140 MHz at a center frequency of 1.9 GHz. Compared to the state-ofthe-art,a 9×more efficient modulation has been achieved by optimizing the acoustic and optical modes and their interactions.展开更多
文摘In recent years,in order to improve the destructive effectiveness of munitions,the use of new types of destructive elements is an important way to improve destructive effectiveness.As a new type of reactive material,reactive alloy contains a large portion of reactive metal elements(Al,Mg,Ti,Zr,etc.),which breaks up under high-velocity impact conditions,generating a large number of high-temperature combustible fragments,which undergo a violent combustion reaction with air.Compared with traditional metal polymers(Al-PTFE)and other reactive composites,it has higher density and strength,excellent mechanical properties and broader application prospects.Currently,researchers have mainly investigated the impact energy release mechanism of reactive alloys through impact tests,and found that there are several important stages in the process of the material from fragmentation to reaction,i.e.,impact fragmentation of the material,rapid heating and combustion reaction.This paper focuses on three problems that need to be solved in the impact-induced energy release process of reactive alloys,namely:the fragmentation mechanism and size distribution law of the fragments produced by the impact of the material on the target,the relationship between the transient temperatures and the size of the fragments,and the reaction temperatures and size thresholds of the fragments to undergo the chemical reaction.The current status of the research of the above problems is reviewed,some potential directions to reveal the impact induced reaction mechanism of reactive alloy is discussed.
基金Teaching Reform Project of Beijing Union University“Exploration of Teaching Reform of Big Data Analysis and Visualization Course under the Background of New Engineering”(JJ2024Y025)。
文摘Under the background of the big data era,the education of big data majors is undergoing a profound teaching reform and innovation.With the increasing role of big data technology in analysis and decision-making,updating and expanding the teaching content of big data majors has become particularly important.In the era of big data,modern enterprises have put forward new and higher demands for big data talents,which not only include traditional data analysis skills but also knowledge of data visualization and information technology.To address these challenges,big data education needs to reform and innovate in the development and utilization of teaching content,methods,and resources.This paper proposes teaching models and reform methods for big data majors and analyzes corresponding teaching reforms and innovations to meet the requirements of the new development of big data majors.The traditional classroom teaching method is no longer sufficient to meet the learning needs of students,and more dynamic and interactive teaching methods,such as case studies,flipped classrooms,and project-based learning,are becoming increasingly essential.These innovative teaching methods can more effectively cultivate students’practical operation skills and independent thinking while allowing them to better learn advanced knowledge in a real big-data environment.In addition,the paper also discusses the construction of big data processing and analysis platforms,as well as innovative teaching management and evaluation systems to improve teaching quality.
文摘A forest fire is a severe threat to forest resources and human life, In this paper, we propose a forest-fire detection system that has an artificial neural network algorithm implemented in a wireless sensor network （WSN）. The proposed detection system mitigates the threat of forest fires by provide accurate fire alarm with low maintenance cost. The accuracy is increased by the novel multi- criteria detection, referred to as an alarm decision depends on multiple attributes of a forest fire. The multi-criteria detection is implemented by the artificial neural network algorithm. Meanwhile, we have developed a prototype of the proposed system consisting of the solar batter module, the fire detection module and the user interface module.
基金supported in part by the National Natural Science Foundation of China 62231023in part by the USTC Center for Micro and Nanoscale Research and Fabrication,in part by the USTC Institute of Advanced Technology,in part by the CAS Key Laboratory of Wireless-Optical Communications and in part by the Hong Kong Research Grant Council under Grant 26202122.
文摘This paper provides a comprehensive review of advanced radio fre-quency(RF)filter technologies available in miniature chip or inte-grated circuit(IC)form for wireless communication applications.The RF filter technologies were organized according to the time-line of their introduction,in conjunction with each generation of wireless(cellular)communication standards(1G to 5G).This ap-proach enabled a clear explanation of the corresponding invention history,working principles,typical applications and future develop-ment trends.The article covered commercially successful acoustic filter technologies,including the widely used surface acoustic wave(SAW)and bulk acoustic wave(BAW)filters,as well as electromag-netic filter technologies based on low-temperature co-fired ceramic(LTCC)and integrated passive device(IPD).Additionally,emerg-ing filter technologies such as IHP-SAW,suspended thin-film lithium niobate(LiNbO3 or LN)resonant devices and hybrid were also dis-cussed.In order to achieve higher performance,smaller form factor and lower cost for the wireless communication industry,it is believed that fundamental breakthroughs in materials and fabrication tech-niques are necessary for the future development of RF filters.
文摘Microwave photonics,a field that crosscuts microwave/millimeter-wave engineering with optoelectronics,has sparked great interest from research and commercial sectors. This multidisciplinary fusion can achieve ultrawide bandwidth and ultrafast speed that were considered impossible in conventional chip-scale microwave/millimeterwave systems. Conventional microwave-to-photonic converters,based on resonant acousto-optic modulation,produce highly efficient modulation but sacrifice bandwidth and limit their applicability for most real-world microwave signal-processing applications. In this paper,we build highly efficient and wideband microwaveto-photonic modulators using the acousto-optic effect on suspended lithium niobate thin films. A wideband microwave signal is first piezoelectrically transduced using interdigitated electrodes into Lamb acoustic waves,which directly propagates across an optical waveguide and causes refractive index pertp urbation through the photoelastic effect. This approach is power-efficient,with phase shifts up to 0.0166 rad∕m W over a 45μm modulation length and with a bandwidth up to 140 MHz at a center frequency of 1.9 GHz. Compared to the state-ofthe-art,a 9×more efficient modulation has been achieved by optimizing the acoustic and optical modes and their interactions.
