摘要：The use of a reconfigurable intelligent surface(RIS)in the enhancement of the rate performance is considered to involve the limitation of the RIS being a passive *** address this issue,we propose a RIS-aided amplify-and-forward(AF)relay network in this *** jointly optimizing the beamforming matrix at AF relay and the phase-shift matrices at RIS,two schemes are put forward to address a maximizing signal-to-noise ratio(SNR)***,aiming at achieving a high rate,a high-performance alternating optimization(AO)method based on Charnes–Cooper transformation and semidefinite programming(CCT-SDP)is proposed,where the optimization problem is decomposed into three subproblems solved using CCT-SDP,and rank-one solutions can be recovered using Gaussian ***,the optimization variables in the CCT-SDP method are matrices,leading to extremely high *** reduce the complexity,a low-complexity AO scheme based on Dinkelbachs transformation and successive convex approximation(DT-SCA)is proposed,where the variables are represented in vector form,and the three decoupling subproblems are solved using *** results verify that compared to three benchmarks(i.e.,a RIS-assisted AF relay network with random phase,an AF relay network without RIS,and a RIS-aided network without AF relay),the proposed CCT-SDP and DT-SCA schemes can harvest better rate ***,it is revealed that the rate of the low-complexity DT-SCA method is close to that of the CCT-SDP method.

摘要：为了确定第二脉冲点火药量对双脉冲发动机点火过程的影响规律,以某双脉冲固体火箭发动机为模型,采用轴对称非定常Navier-Stokes方程和标准k-ε湍流模型,对第二脉冲点火过程进行了仿真,研究了点火装置工作持续时间和点火燃气流量对于点火延迟的影响。研究结果表明:点火燃气流量相同时,增加点火装置工作持续时间可以有效减小第二脉冲点火延迟,该点火延迟存在一个极限值即最小点火延迟。不同点火燃气流量对应不同的最小点火延迟,点火燃气流量越大,最小点火延迟越小,两者之间存在着负指数关系。在设计第二脉冲点火药量时,自由容积应选取为第一、二脉冲自由容积之和更加合理。

摘要：针对由于鸡毒支原体(Mycoplasma gallisepticum,MG)不同毒株(针对TS-11、6/85、F株疫苗株和S6、R株野毒株)的特定序列,设计出特异性检测引物,对临床免疫MG疫苗株TS-11的鸡群以及父母代(A^H场)鸡群和祖代(I场)鸡群采集毛蛋气囊拭子,A场父母代种鸡群和I场祖代鸡群同时采集咽喉拭子进行MG的PCR鉴别诊断,对临床送检免疫6/85的客户鸡群(J场)采集病料,F株疫苗株进行MG的鉴别诊断,同时采集SPF鸡群咽喉拭子作为阴性对照群,验证该鉴别引物的特异性。结果显示:鉴别引物具有非常好的特异性,SPF鸡群MG的检测均为阴性,不存在假阳性的弊端;临床免疫MG疫苗株6/85的鸡群(J场)存在MG野毒株S6的感染,在免疫后1个月左右采集病料中仍能检出MG 6/85疫苗株。对免疫TS-11的父母代种鸡群(A^H场)和祖代种鸡群(I场)死亡的毛蛋气囊拭子,用PCR检测MG阳性率,结果显示:祖代鸡群(I场)后代死亡的毛蛋气囊评估结果为优,毛蛋气囊拭子MG的PCR鉴别引物检测均为阴性;而父母代鸡群后代死亡的毛蛋气囊从50周龄开始出现浑浊,MG的PCR鉴别引物可同时检出TS-11疫苗毒和野毒株,部分鸡群同时存在R株和S6株两种野毒感染;采集A场父母代种鸡群的咽喉拭子和后代啄壳死亡毛蛋气囊拭子,PCR检测结果显示种鸡群和后代可同时检出野毒株S6和疫苗株TS-11。这表明种鸡群MG的感染,可通过垂直传播感染其后代。本研究设计的MG鉴别引物,可将不同MG疫苗株(TS-11、F株、6/85)与野毒株(S6株、R株)区分,为临床MG的鉴别诊断和种鸡群的MG感染状态评估提供积极的指导意义。

摘要：基材土-岩接触面剪切力学性能是生态护坡体系长久稳定的关键,相关研究可为解决基材脱落难题、完善生态防护技术体系提供必要依据和指导。采用自制的原位剪切仪对4种不同粗糙起伏的基材土-岩接触面进行了原位剪切试验,结果表明,基材土-岩接触面剪切应力-位移表现出典型的软化特性,具有明显的初始线弹性变形、弹塑性变形、峰后软化以及残余剪切变形4个阶段。分析发现,文中试验条件下凸起高度算数平均偏差Ra在4 mm以下时,峰值剪切强度增加速度较快,随后呈逐渐减弱趋势;残余剪切强度、峰值剪切位移以及进入残余阶段的剪切位移与粗糙凸起高度算数平均偏差呈近线性正相关关系。可见实施生态护坡时合理地控制坡面粗糙起伏,有助于提高土-岩接触面峰值剪切强度和残余剪切强度,改善其变形性能,对防护体系的长期整体稳定具有促进作用。