Satellite communications have attracted significant interests due to its advantages of large footprint and massive access.However,the commonly used onboard beamforming is hard to achieve reliable security because of t...Satellite communications have attracted significant interests due to its advantages of large footprint and massive access.However,the commonly used onboard beamforming is hard to achieve reliable security because of the highly correlated legitimate and wiretap downlink channels.We exploit the benefits of satellite-terrestrial integrated network(STIN)and a novel absorptive reconfigurable intelligent surface(RIS)for improving the security of satellite downlink communications(SDC)in the presence of eavesdroppers(Eves).This paper aims to maximize the achievable secrecy rate of the earth station(ES)while satisfying the signal reception constraints,harvested power threshold at the RIS,and total transmit power budget.To solve this nonconvex problem,we propose a penalty-function based dual decomposition scheme,which firstly transforms the original problem into a two-layer optimization problem.Then,the outer layer and inner problems are solved by utilizing the successive convex approximation,Lagrange-dual and Rayleigh quotient methods to obtain the beamforming weight vectors and the reflective coefficient matrix.Finally,simulation results verify the effectiveness of the proposed scheme for enhancing the SDC security.展开更多
Currently,model tests are increasingly being used to simulate the construction of mountain tunnels,but the support structure of the model tests does not show the composite lining,and the force laws of the composite li...Currently,model tests are increasingly being used to simulate the construction of mountain tunnels,but the support structure of the model tests does not show the composite lining,and the force laws of the composite lining are not yet clear.In this research,the force variation of composite lining under three cases in model tests of deep-buried tunnels were carried out with the surrounding rock grade and installation time as the variation factors.The test results reveal that:(1)The suitable method to reduce the contact load between the secondary lining and primary support is to enhance the primary support in the soft and weak surrounding rock.Correspondingly,for ClassⅢsurrounding rock and better quality of surrounding rock,the primary support can lag behind the excavation face a certain distance.(2)The axial forces of the bolts tend to rise with concentration of 0.4 kN-0.7 kN after the secondary lining was installed.(3)With or without two to three excavation cycles delayed,the load sharing ratio of the secondary lining of the Class III surrounding rock is less than 10%.Finally,the numerical simulation verifies the feasibility of the model tests.展开更多
目的:以具有抗肿瘤活性的穿山龙乙酸乙酯层提取物(extract from Discorea nipponica Makino,DNM)和蒺藜提取物哈尔满碱为研究对象,采用体内裸鼠肿瘤HepG2模型实验探究两药联合应用是否具有协同抗肿瘤的作用。方法:通过建立裸鼠肿瘤HepG...目的:以具有抗肿瘤活性的穿山龙乙酸乙酯层提取物(extract from Discorea nipponica Makino,DNM)和蒺藜提取物哈尔满碱为研究对象,采用体内裸鼠肿瘤HepG2模型实验探究两药联合应用是否具有协同抗肿瘤的作用。方法:通过建立裸鼠肿瘤HepG2模型,灌胃给药两周,观察穿山龙乙酸乙酯层提取物组、哈尔满碱组和联合用药组的对肿瘤细胞的抑制情况;通过经统计学分析和采用金正均法计算分析验证结果;对肿瘤组织进行HE切片染色,观察联合用药对肿瘤组织中肿瘤细胞生长的影响。结果:穿山龙乙酸乙酯层提取物组、哈尔满碱组和联合用药组抑瘤率分别为3.36%、45.31%、59.59%,经统计学分析后有显著性差异(P<0.05),表明联合用药抑瘤率高于单独用药组。显微镜下观察联合用药组肿瘤组织出现大面积坏死,且出现肿瘤细胞核质比降低,异型性减小等现象。结论:说明穿山龙乙酸乙酯层提取物和蒺藜提取物哈尔满碱联合用药在裸鼠体内具有协同抗肿瘤的作用。展开更多
基金supported by the National Natural Science Foundation of China(No.62201592)the Research Plan Project of NUDT(ZK21-33)the Young Elite Scientist Sponsorship Program of CAST,China(2021-JCJQ-QT-048)。
文摘Satellite communications have attracted significant interests due to its advantages of large footprint and massive access.However,the commonly used onboard beamforming is hard to achieve reliable security because of the highly correlated legitimate and wiretap downlink channels.We exploit the benefits of satellite-terrestrial integrated network(STIN)and a novel absorptive reconfigurable intelligent surface(RIS)for improving the security of satellite downlink communications(SDC)in the presence of eavesdroppers(Eves).This paper aims to maximize the achievable secrecy rate of the earth station(ES)while satisfying the signal reception constraints,harvested power threshold at the RIS,and total transmit power budget.To solve this nonconvex problem,we propose a penalty-function based dual decomposition scheme,which firstly transforms the original problem into a two-layer optimization problem.Then,the outer layer and inner problems are solved by utilizing the successive convex approximation,Lagrange-dual and Rayleigh quotient methods to obtain the beamforming weight vectors and the reflective coefficient matrix.Finally,simulation results verify the effectiveness of the proposed scheme for enhancing the SDC security.
基金the Scientific Research Project of Zhejiang Provincial Transportation Department(2021050)for the preparation of this manuscript。
文摘Currently,model tests are increasingly being used to simulate the construction of mountain tunnels,but the support structure of the model tests does not show the composite lining,and the force laws of the composite lining are not yet clear.In this research,the force variation of composite lining under three cases in model tests of deep-buried tunnels were carried out with the surrounding rock grade and installation time as the variation factors.The test results reveal that:(1)The suitable method to reduce the contact load between the secondary lining and primary support is to enhance the primary support in the soft and weak surrounding rock.Correspondingly,for ClassⅢsurrounding rock and better quality of surrounding rock,the primary support can lag behind the excavation face a certain distance.(2)The axial forces of the bolts tend to rise with concentration of 0.4 kN-0.7 kN after the secondary lining was installed.(3)With or without two to three excavation cycles delayed,the load sharing ratio of the secondary lining of the Class III surrounding rock is less than 10%.Finally,the numerical simulation verifies the feasibility of the model tests.
文摘目的:以具有抗肿瘤活性的穿山龙乙酸乙酯层提取物(extract from Discorea nipponica Makino,DNM)和蒺藜提取物哈尔满碱为研究对象,采用体内裸鼠肿瘤HepG2模型实验探究两药联合应用是否具有协同抗肿瘤的作用。方法:通过建立裸鼠肿瘤HepG2模型,灌胃给药两周,观察穿山龙乙酸乙酯层提取物组、哈尔满碱组和联合用药组的对肿瘤细胞的抑制情况;通过经统计学分析和采用金正均法计算分析验证结果;对肿瘤组织进行HE切片染色,观察联合用药对肿瘤组织中肿瘤细胞生长的影响。结果:穿山龙乙酸乙酯层提取物组、哈尔满碱组和联合用药组抑瘤率分别为3.36%、45.31%、59.59%,经统计学分析后有显著性差异(P<0.05),表明联合用药抑瘤率高于单独用药组。显微镜下观察联合用药组肿瘤组织出现大面积坏死,且出现肿瘤细胞核质比降低,异型性减小等现象。结论:说明穿山龙乙酸乙酯层提取物和蒺藜提取物哈尔满碱联合用药在裸鼠体内具有协同抗肿瘤的作用。
