今年的 BIRTV 上,Sony 公司将有两个新的举动。一是 Sony 今年将不在国贸展厅里搭设展台,而将所有展示活动都迁多到临近的中国大饭店宴会厅。关于这一点,主要是配合组委会缓解场地供求矛盾,同时也希望在一个独立的,不受限制的,排除其它...今年的 BIRTV 上,Sony 公司将有两个新的举动。一是 Sony 今年将不在国贸展厅里搭设展台,而将所有展示活动都迁多到临近的中国大饭店宴会厅。关于这一点,主要是配合组委会缓解场地供求矛盾,同时也希望在一个独立的,不受限制的,排除其它干扰的场地里给用户提供更好的参观环境。另一个大的举动是,Sony 在今年展览会上推出的主题:Digital Reality——数字化现实。作为"数字化",相信这几年用户们都已成熟于心,那么何以在今年 Sony 公司有信心宣布数字化成了一种"现实"?您不妨先听我们大致介绍一下今年 Sony 准备展出的系统和设备,有个总体印象。展开更多
The emerging deployment of large-scale Low Earth Orbit(LEO)satellite constellations provides seamless global coverage.However,the increasing number of satellites also introduces significant security challenges,such as...The emerging deployment of large-scale Low Earth Orbit(LEO)satellite constellations provides seamless global coverage.However,the increasing number of satellites also introduces significant security challenges,such as eavesdropping and illegal communication behavior detection.This paper investigates covert wireless communication over uplink satellite-terrestrial network,focusing on scenarios with warden satellites.By accounting for shot noise generated by ambient signals from terrestrial interferers,the terrestrial transmitter Alice can effectively hide its signal from warden satellites.Leveraging stochastic geometry,the distributions of distances between transmitter and satellites are analyzed,enabling the assessment of uplink performance and interference within a satellite’s coverage area.Approximate expressions for detection error probability and transmission outage probability are derived.Based on the theoretical analysis,an optimal scheme is proposed to maximize covert throughput under the constraint of the average detection error probability of the most detrimental warden satellite.Extensive Monte Carlo simulations experiments are conducted to validate the accuracy of analytical methods for evaluating covert performance.展开更多
Nonlinear wavefront shaping is crucial for advancing optical technologies,enabling applications in optical computation,information processing,and imaging.However,a significant challenge is that once a metasurface is f...Nonlinear wavefront shaping is crucial for advancing optical technologies,enabling applications in optical computation,information processing,and imaging.However,a significant challenge is that once a metasurface is fabricated,the nonlinear wavefront it generates is fixed,offering little flexibility.This limitation often necessitates the fabrication of different metasurfaces for different wavefronts,which is both time-consuming and inefficient.To address this,we combine evolutionary algorithms with spatial light modulators(SLMs)to dynamically control wavefronts using a single metasurface,reducing the need for multiple fabrications and enabling the generation of arbitrary nonlinear wavefront patterns without requiring complicated optical alignment.We demonstrate this approach by introducing a genetic algorithm(GA)to manipulate visible wavefronts converted from near-infrared light via third-harmonic generation(THG)in a silicon metasurface.The Si metasurface supports multipolar Mie resonances that strongly enhance light-matter interactions,thereby significantly boosting THG emission at resonant positions.Additionally,the cubic relationship between THG emission and the infrared input reduces noise in the diffractive patterns produced by the SLM.This allows for precise experimental engineering of the nonlinear emission patterns with fewer alignment constraints.Our approach paves the way for self-optimized nonlinear wavefront shaping,advancing optical computation and information processing techniques.展开更多
文摘今年的 BIRTV 上,Sony 公司将有两个新的举动。一是 Sony 今年将不在国贸展厅里搭设展台,而将所有展示活动都迁多到临近的中国大饭店宴会厅。关于这一点,主要是配合组委会缓解场地供求矛盾,同时也希望在一个独立的,不受限制的,排除其它干扰的场地里给用户提供更好的参观环境。另一个大的举动是,Sony 在今年展览会上推出的主题:Digital Reality——数字化现实。作为"数字化",相信这几年用户们都已成熟于心,那么何以在今年 Sony 公司有信心宣布数字化成了一种"现实"?您不妨先听我们大致介绍一下今年 Sony 准备展出的系统和设备,有个总体印象。
基金supported in part by the National Natural Science Foundation of China under Grant No.U22B2006.
文摘The emerging deployment of large-scale Low Earth Orbit(LEO)satellite constellations provides seamless global coverage.However,the increasing number of satellites also introduces significant security challenges,such as eavesdropping and illegal communication behavior detection.This paper investigates covert wireless communication over uplink satellite-terrestrial network,focusing on scenarios with warden satellites.By accounting for shot noise generated by ambient signals from terrestrial interferers,the terrestrial transmitter Alice can effectively hide its signal from warden satellites.Leveraging stochastic geometry,the distributions of distances between transmitter and satellites are analyzed,enabling the assessment of uplink performance and interference within a satellite’s coverage area.Approximate expressions for detection error probability and transmission outage probability are derived.Based on the theoretical analysis,an optimal scheme is proposed to maximize covert throughput under the constraint of the average detection error probability of the most detrimental warden satellite.Extensive Monte Carlo simulations experiments are conducted to validate the accuracy of analytical methods for evaluating covert performance.
基金support from the Biotechnology and Biological Council Doctoral Training Programme(BBSRC DTP)the support from the Royal Society and Wolfson Foundation(RSWF\FT\191022).
文摘Nonlinear wavefront shaping is crucial for advancing optical technologies,enabling applications in optical computation,information processing,and imaging.However,a significant challenge is that once a metasurface is fabricated,the nonlinear wavefront it generates is fixed,offering little flexibility.This limitation often necessitates the fabrication of different metasurfaces for different wavefronts,which is both time-consuming and inefficient.To address this,we combine evolutionary algorithms with spatial light modulators(SLMs)to dynamically control wavefronts using a single metasurface,reducing the need for multiple fabrications and enabling the generation of arbitrary nonlinear wavefront patterns without requiring complicated optical alignment.We demonstrate this approach by introducing a genetic algorithm(GA)to manipulate visible wavefronts converted from near-infrared light via third-harmonic generation(THG)in a silicon metasurface.The Si metasurface supports multipolar Mie resonances that strongly enhance light-matter interactions,thereby significantly boosting THG emission at resonant positions.Additionally,the cubic relationship between THG emission and the infrared input reduces noise in the diffractive patterns produced by the SLM.This allows for precise experimental engineering of the nonlinear emission patterns with fewer alignment constraints.Our approach paves the way for self-optimized nonlinear wavefront shaping,advancing optical computation and information processing techniques.
