卫星下行链路因其开放性、广域覆盖性而面临严峻的窃听威胁,传统以加密技术为核心的卫星下行链路防窃听方案在计算复杂度与抗量子攻击能力上存在双重瓶颈,且现有卫星下行链路物理层安全防窃听方案的应用场景存在局限性。针对以上问题,...卫星下行链路因其开放性、广域覆盖性而面临严峻的窃听威胁,传统以加密技术为核心的卫星下行链路防窃听方案在计算复杂度与抗量子攻击能力上存在双重瓶颈,且现有卫星下行链路物理层安全防窃听方案的应用场景存在局限性。针对以上问题,通过基于动态扩展因子的扰码与编码级联设计,提出一种基于信道状态信息(Channel State Information,CSI)和协作中继的卫星下行链路防窃听方案。首先,通过部署地面中继基站,建立基于协作中继的卫星下行链路通信模型,扩大合法链路与窃听链路的CSI随机性差异;其次,通过合法链路CSI对准循环低密度奇偶校验码扩展因子进行动态调控,增加编码随机性,进而增加窃听者译码难度;最后,通过动态扩展因子与合法链路CSI在卫星端与用户端构建加扰与解扰机制,使窃听者因缺乏合法链路CSI而无法解扰保密信息。仿真结果表明,在用户端误码率低至10-6的情况下,利用扰码对CSI的依赖性构建窃听者解扰壁垒,可使窃听者误码率接近0.5。所提方案凭借对CSI与地面协作中继的协同设计,既具备抵御量子计算攻击的潜在能力,又契合卫星通信网络工程部署对高效低耗的需求,能够有效平衡卫星下行链路信息传输可靠性与安全性的矛盾,可为未来6G空天地一体化场景下的信息安全传输提供具备工程实践价值的技术参考路径。展开更多
[目的/意义]"亚洲海事透明倡议"(Asia Maritime Transparency Initiative,AMTI)是由美国智库"战略与国际研究中心"(Center for Strategic and International Studies,CSIS)专门围绕东海、南海问题而建立的网站,从A...[目的/意义]"亚洲海事透明倡议"(Asia Maritime Transparency Initiative,AMTI)是由美国智库"战略与国际研究中心"(Center for Strategic and International Studies,CSIS)专门围绕东海、南海问题而建立的网站,从AMTI的报道可以了解美国政府在相关问题上的立场,但目前国内尚无关于该网站的相关分析。[方法/过程]收集了AMTI网站近一年多共一万多字的英文专题报道,建成一小型语料库;采用Ant Conc软件统计词频,分析搭配模式或词汇共现模式。[结果/结论]该网站明显偏袒日本、越南等国,宣扬所谓的"中国威胁",目的是维护美国在亚太地区的经济政治利益。中国迫切需要成立专门的海洋话语权研究机构,应对外媒不利宣传,打赢东海、南海的舆论之战。展开更多
With the growing advancement of wireless communication technologies,WiFi-based human sensing has gained increasing attention as a non-intrusive and device-free solution.Among the available signal types,Channel State I...With the growing advancement of wireless communication technologies,WiFi-based human sensing has gained increasing attention as a non-intrusive and device-free solution.Among the available signal types,Channel State Information(CSI)offers fine-grained temporal,frequency,and spatial insights into multipath propagation,making it a crucial data source for human-centric sensing.Recently,the integration of deep learning has significantly improved the robustness and automation of feature extraction from CSI in complex environments.This paper provides a comprehensive review of deep learning-enhanced human sensing based on CSI.We first outline mainstream CSI acquisition tools and their hardware specifications,then provide a detailed discussion of preprocessing methods such as denoising,time–frequency transformation,data segmentation,and augmentation.Subsequently,we categorize deep learning approaches according to sensing tasks—namely detection,localization,and recognition—and highlight representative models across application scenarios.Finally,we examine key challenges including domain generalization,multi-user interference,and limited data availability,and we propose future research directions involving lightweight model deployment,multimodal data fusion,and semantic-level sensing.展开更多
In this paper,we focus on the detection of prohibited items with small size,and establish an automatic detection model based on feature fusion single shot multibox detector(FSSD)architecture.Two modifications are carr...In this paper,we focus on the detection of prohibited items with small size,and establish an automatic detection model based on feature fusion single shot multibox detector(FSSD)architecture.Two modifications are carried out to improve the detection accuracy.Firstly,the semantic enrichment module(SEM)with dilated convolution is applied to extract the low level feature with strong semantic information.Secondly,a residual module(Res)with residual blocks is added in the multibox detection architecture in order to extract more adequate features for target detection.The simulation results have demonstrated a better performance of the proposed detection model for prohibited items with small size compared with the state-of-the-arts.展开更多
In recent times, mathematical models have been developed to describe various scenarios obtainable in the management of inventories. These models usually have as objective the minimizing of inventory costs. In this res...In recent times, mathematical models have been developed to describe various scenarios obtainable in the management of inventories. These models usually have as objective the minimizing of inventory costs. In this research work we propose a mathematical model of an inventory system with time-dependent three-parameter Weibull deterioration and a stochastic type demand in the form of a negative exponential distribution. Explicit expressions for the optimal values of the decision variables are obtained. Numerical examples are provided to illustrate the theoretical development.展开更多
In intercontinental trade and economics goods are bought from a global supplier.On occasion,the expected lot may include a fraction of defective items.These imperfect items still have worth and can be sold to customer...In intercontinental trade and economics goods are bought from a global supplier.On occasion,the expected lot may include a fraction of defective items.These imperfect items still have worth and can be sold to customers after repair.It is cost-effective and sustainable to rework such items in nearby repair workshops rather than return them.The reworked items can be returned from the workshop to the buyer when shortages are equal to the quantity of imperfect items.In the meantime,the supplier correspondingly deals a multi-period delay-in-payments strategy with purchaser.The entire profit has been maximized with paybacks for interim financing.This study aims to develop a synergic inventory model to get the most profit by making an allowance for reworking,multi-period delay-in-payments policy,and shortages.The findings of the proposed model augment inventory management performance by monitoring cycle time as well as fraction of phase with optimistic inventory for a supply chain.The results demonstrate that profit is smaller if the permitted period given by supplier to buyer is equal to or greater than the cycle time,and profit is greater if the permitted period is smaller than the cycle time.The algebraic method is engaged to make a closed system optimum solution.The mathematical experiment of this study is constructed to provide management insights and tangible practices.展开更多
文摘卫星下行链路因其开放性、广域覆盖性而面临严峻的窃听威胁,传统以加密技术为核心的卫星下行链路防窃听方案在计算复杂度与抗量子攻击能力上存在双重瓶颈,且现有卫星下行链路物理层安全防窃听方案的应用场景存在局限性。针对以上问题,通过基于动态扩展因子的扰码与编码级联设计,提出一种基于信道状态信息(Channel State Information,CSI)和协作中继的卫星下行链路防窃听方案。首先,通过部署地面中继基站,建立基于协作中继的卫星下行链路通信模型,扩大合法链路与窃听链路的CSI随机性差异;其次,通过合法链路CSI对准循环低密度奇偶校验码扩展因子进行动态调控,增加编码随机性,进而增加窃听者译码难度;最后,通过动态扩展因子与合法链路CSI在卫星端与用户端构建加扰与解扰机制,使窃听者因缺乏合法链路CSI而无法解扰保密信息。仿真结果表明,在用户端误码率低至10-6的情况下,利用扰码对CSI的依赖性构建窃听者解扰壁垒,可使窃听者误码率接近0.5。所提方案凭借对CSI与地面协作中继的协同设计,既具备抵御量子计算攻击的潜在能力,又契合卫星通信网络工程部署对高效低耗的需求,能够有效平衡卫星下行链路信息传输可靠性与安全性的矛盾,可为未来6G空天地一体化场景下的信息安全传输提供具备工程实践价值的技术参考路径。
文摘[目的/意义]"亚洲海事透明倡议"(Asia Maritime Transparency Initiative,AMTI)是由美国智库"战略与国际研究中心"(Center for Strategic and International Studies,CSIS)专门围绕东海、南海问题而建立的网站,从AMTI的报道可以了解美国政府在相关问题上的立场,但目前国内尚无关于该网站的相关分析。[方法/过程]收集了AMTI网站近一年多共一万多字的英文专题报道,建成一小型语料库;采用Ant Conc软件统计词频,分析搭配模式或词汇共现模式。[结果/结论]该网站明显偏袒日本、越南等国,宣扬所谓的"中国威胁",目的是维护美国在亚太地区的经济政治利益。中国迫切需要成立专门的海洋话语权研究机构,应对外媒不利宣传,打赢东海、南海的舆论之战。
基金supported by National Natural Science Foundation of China(NSFC)under grant U23A20310.
文摘With the growing advancement of wireless communication technologies,WiFi-based human sensing has gained increasing attention as a non-intrusive and device-free solution.Among the available signal types,Channel State Information(CSI)offers fine-grained temporal,frequency,and spatial insights into multipath propagation,making it a crucial data source for human-centric sensing.Recently,the integration of deep learning has significantly improved the robustness and automation of feature extraction from CSI in complex environments.This paper provides a comprehensive review of deep learning-enhanced human sensing based on CSI.We first outline mainstream CSI acquisition tools and their hardware specifications,then provide a detailed discussion of preprocessing methods such as denoising,time–frequency transformation,data segmentation,and augmentation.Subsequently,we categorize deep learning approaches according to sensing tasks—namely detection,localization,and recognition—and highlight representative models across application scenarios.Finally,we examine key challenges including domain generalization,multi-user interference,and limited data availability,and we propose future research directions involving lightweight model deployment,multimodal data fusion,and semantic-level sensing.
基金supported by the National Natural Science Foundation of China(No.61806208)the Fundamental Research Funds for the Central Universities(No.3122018S008)the Tianjin Education Committee Research Project(No.2018KJ246)。
文摘In this paper,we focus on the detection of prohibited items with small size,and establish an automatic detection model based on feature fusion single shot multibox detector(FSSD)architecture.Two modifications are carried out to improve the detection accuracy.Firstly,the semantic enrichment module(SEM)with dilated convolution is applied to extract the low level feature with strong semantic information.Secondly,a residual module(Res)with residual blocks is added in the multibox detection architecture in order to extract more adequate features for target detection.The simulation results have demonstrated a better performance of the proposed detection model for prohibited items with small size compared with the state-of-the-arts.
文摘In recent times, mathematical models have been developed to describe various scenarios obtainable in the management of inventories. These models usually have as objective the minimizing of inventory costs. In this research work we propose a mathematical model of an inventory system with time-dependent three-parameter Weibull deterioration and a stochastic type demand in the form of a negative exponential distribution. Explicit expressions for the optimal values of the decision variables are obtained. Numerical examples are provided to illustrate the theoretical development.
文摘In intercontinental trade and economics goods are bought from a global supplier.On occasion,the expected lot may include a fraction of defective items.These imperfect items still have worth and can be sold to customers after repair.It is cost-effective and sustainable to rework such items in nearby repair workshops rather than return them.The reworked items can be returned from the workshop to the buyer when shortages are equal to the quantity of imperfect items.In the meantime,the supplier correspondingly deals a multi-period delay-in-payments strategy with purchaser.The entire profit has been maximized with paybacks for interim financing.This study aims to develop a synergic inventory model to get the most profit by making an allowance for reworking,multi-period delay-in-payments policy,and shortages.The findings of the proposed model augment inventory management performance by monitoring cycle time as well as fraction of phase with optimistic inventory for a supply chain.The results demonstrate that profit is smaller if the permitted period given by supplier to buyer is equal to or greater than the cycle time,and profit is greater if the permitted period is smaller than the cycle time.The algebraic method is engaged to make a closed system optimum solution.The mathematical experiment of this study is constructed to provide management insights and tangible practices.
