A Retrodirective Array Enabled by CMOS Chips for Two-Way Wireless Communication with Automatic Beam Tracking

This article proposes and demonstrates a retrodirective array(RDA)for two-way wireless communication with automatic beam tracking.The proposed RDA is enabled by specifically designed chips made using a domestic complementary metal-oxide semiconductor(CMOS)process.The highly integrated CMOS chip includes a receiving(Rx)chain,a transmitting(Tx)chain,and a unique tracking phaselocked loop(PLL)for the crucial conjugated phase recovery in the RDA.This article also proposes a method to reduce the beam pointing error(BPE)in a conventional RDA.To validate the above ideas simply yet without loss of generality,a 2.4 GHz RDA is demonstrated through two-way communication links between the Rx and Tx chains,and an on-chip quadrature coupler is designed to achieve a nonretrodirective signal suppression of 23 dBc.The experimental results demonstrate that the proposed RDA,which incorporates domestically manufactured low-cost 0.18 lm CMOS chips,is capable of automatically tracking beams covering±40with a reduced BPE.Each CMOS chip in the RDA has a compact size of 4.62 mm^(2) and a low power consumption of 0.15 W.To the best of the authors’knowledge,this is the first research to demonstrate an RDA with a fully customized CMOS chip for wireless communication with automatic beam tracking。

Reference-frame-independent quantum key distribution with two-way classical communication

The data post-processing scheme based on two-way classical communication(TWCC)can improve the tolerable bit error rate and extend the maximal transmission distance when used in a quantum key distribution(QKD)system.In this study,we apply the TWCC method to improve the performance of reference-frame-independent quantum key distribution(RFI-QKD),and analyze the influence of the TWCC method on the performance of decoy-state RFI-QKD in both asymptotic and non-asymptotic cases.Our numerical simulation results show that the TWCC method is able to extend the maximal transmission distance from 175 km to 198 km and improve the tolerable bit error rate from 10.48%to 16.75%.At the same time,the performance of RFI-QKD in terms of the secret key rate and maximum transmission distance are still greatly improved when statistical fluctuations are considered.We conclude that RFI-QKD with the TWCC method is of practical interest.

Beamforming Design for IRS-and-UAV-Aided Two-Way Amplify-and-Forward Relay Networks in Maritime IoT

In this paper,an intelligent reflecting surface(IRS)-and-unmanned aerial vehicle(UAV)-assisted two-way amplify-and-forward(AF)relay network in maritime Internet of Things(IoT)is proposed,where ship1(S1)and ship2(S2)can be viewed as data collecting centers.To enhance the message exchange rate between S1 and S2,a problem of maximizing minimum rate is cast,where the variables,namely AF relay beamforming matrix and IRS phase shifts of two time slots,need to be optimized.To achieve a maximum rate,a low-complexity alternately iterative(AI)scheme based on zero forcing and successive convex approximation(LC-ZF-SCA)algorithm is presented.To obtain a significant rate enhancement,a high-performance AI method based on one step,semidefinite programming and penalty SCA(ONSSDP-PSCA)is proposed.Simulation results show that by the proposed LC-ZF-SCA and ONS-SDP-PSCA methods,the rate of the IRS-and-UAV-assisted AF relay network surpass those of with random phase and only AF relay networks.Moreover,ONS-SDP-PSCA perform better than LC-ZF-SCA in aspect of rate.

Investigating the Efficiency Coefficient of Pile Group in Clay Under Two-Way Lateral Load

This research investigates the behavior of a 2×2 pile group under two-directional lateral loads in addition to the vertical load.Through three-dimensional numerical modeling based on Flac 3D software,the study examines the total bearing capacity and efficiency coefficient of the pile group,considering factors such as the angle of lateral load,relative pile spacing,and relative stiffness of the pile-soil system.The findings highlight the significance of these factors in understanding and predicting the response of pile groups to changing lateral load directions.The results reveal that increasing the angle of the lateral load from 0°to 45°enhances both the maximum total lateral load and the efficiency coefficient of the pile group.When the relative stiffness of the pile-soil system significantly increases,soil stiffening occurs and reducing the relative spacing of the piles from 7 to 3 times the diameter of the piles diminishes the influence of the pile group.Consequently,the response of the pile group to lateral loads becomes more linear,with only a slight alteration in the maximum total lateral load and the efficiency coefficient when the lateral load is angled from 0°to 45°.Conversely,increasing the relative distance between the piles,specifically from 3 to 7 times the diameter of the piles,amplifies the influence of the pile group.Both the maximum total lateral load and the efficiency coefficient of the pile group exhibit an observed increase.These provide insights for designing pile groups and optimizing their performance under lateral loading conditions.

Secrecy Outage Probability for Two-Way Integrated Satellite Unmanned Aerial Vehicle Relay Networks with Hardware Impairments

In this paper,we investigate the secrecy outage performance for the two-way integrated satellite unmanned aerial vehicle relay networks with hardware impairments.Particularly,the closed-form expression for the secrecy outage probability is obtained.Moreover,to get more information on the secrecy outage probability in a high signalto-noise regime,the asymptotic analysis along with the secrecy diversity order and secrecy coding gain for the secrecy outage probability are also further obtained,which presents a fast method to evaluate the impact of system parameters and hardware impairments on the considered network.Finally,Monte Carlo simulation results are provided to show the efficiency of the theoretical analysis.

Two-way中继系统中的双向中继选择及功率分配策略

通过中继选择和功率分配,可以达到提高two-way中继系统总速率的目的。综合考虑中继节点处的接收信噪比和中继节点到目的节点间的信道增益,提出了two-way AF中继系统中的双向中继选择策略(BRS);同时,在总功率受限的条件下,建立了two-way AF中继系统中的优化功率分配模型,通过对模型进行数学分析求解,提出了一种自适应的最优功率分配策略(OPA)。仿真结果证明两种策略均能提高系统总速率。

Two-way中继系统中基于最小化中断概率的功率分配策略

为了降低Two-way中继系统中断概率,提出了一种Two-way中继系统中基于最小化中断概率的功率分配策略。首先推导了Two-way中继系统中断概率的闭合表达式,然后在总功率受限的条件下,提出了一种最小化中断概率的最优功率分配策略(OPA),通过拉格朗日乘数法对该优化模型进行了求解。仿真结果证明了该策略能够有效降低系统的中断概率,提高系统性能。

Securing Forwarding Layers from Eavesdropping Attacks Using Proactive Approaches

As an emerging network paradigm,the software-defined network(SDN)finds extensive application in areas such as smart grids,the Internet of Things(IoT),and edge computing.The forwarding layer in software-defined networks is susceptible to eavesdropping attacks.Route hopping is amoving target defense(MTD)technology that is frequently employed to resist eavesdropping attacks.In the traditional route hopping technology,both request and reply packets use the same hopping path.If an eavesdropping attacker monitors the nodes along this path,the risk of 100%data leakage becomes substantial.In this paper,we present an effective route hopping approach,called two-day different path(TDP),that turns communication paths into untraceable moving targets.This technology minimizes the probability of data leakage by transmitting request data and reply data through different paths.Firstly,a brief introduction to the network model and attack model involved in this paper is given.Secondly,the algorithm and processingmethod of the TDP are proposed.Thirdly,the paper proposes three differentmetrics tomeasure the effectiveness of the proposed approach.Finally,theoretical analysis and simulation results show that the TDP can effectively reduce the percentage of data exposure,decrease eavesdropping attack success probability,and improve the unpredictability of the path.

基于ISAPI协议的语音对讲在巡视系统中的应用

巡视系统是使用监控设备(摄像头、机器人和无人机)等对巡视设备进行周期性巡视,并将巡视的产物(图片和视频)等进行算法解析,找出其中的异常和缺陷,在此基础上需要在监控设备中对现场的操作人员以及陌生人员进行语音交互。语音交互过程中使用监控设备自带的摄像头语音功能可以很好实现上述功能,不需要额外的设备支持。基于ISAPI协议,将麦克风中的语音流发送到摄像头并接收摄像头中的语音流发送到前端播放,从而实现语音对讲在巡视系统中的应用。实验证明,基于ISAPI协议的语音对讲功能可以在巡视系统中广泛且高效地使用,并提高运维人员工作效率。

Assessment of plant diversity of endemic species of the Saharo-Arabian region in Egypt

Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emirates, Oman, Yemen, southern Jordan, Syria, Iraq, Iran, Afghanistan, Pakistan, and northern India. Its neighboring regions, the Sudano-Zambezian region belonging to the Paleotropical Kingdom and the Mediterranean and Irano-Turanian regions included in the Holarctic Kingdom, share a large portion of their flora with the Saharo-Arabian region. Despite the widespread acknowledgment of the region's global importance for plant diversity, an up to date list of the Saharo-Arabian endemics is still unavailable. The available data are frequently insufficient or out of date at both the whole global and the national scales. Therefore, the present study aims at screening and verifying the Saharo-Arabian endemic plants and determining the phytogeographical distribution of these taxa in the Egyptian flora. Hence, a preliminary list of 429 Saharo-Arabian endemic plants in Egypt was compiled from the available literature. Indeed, by excluding the species that were recorded in any countries or regions outside the Saharo-Arabian region based on different literature, database reviews, and websites, the present study has reduced this number to 126 taxa belonging to 87 genera and 37 families. Regarding the national geographic distribution, South Sinai is the richest region with 83 endemic species compared with other eight phytogeographic regions in Egypt, followed by the Isthmic Desert(the middle of Sinai Peninsula, 53 taxa). Sahara regional subzone(SS1) distributes all the 126 endemic species, Arabian regional subzone(SS2) owns 79 taxa, and Nubo-Sindian subzone(SS3) distributes only 14 endemics. Seven groups were recognized at the fourth level of classification as a result of the application of the two-way indicator species analysis(TWINSPAN) to the Saharo-Arabian endemic species in Egypt, i.e., Ⅰ Asphodelus refractus group, Ⅱ Agathophora alopecuroides var. papillosa group, Ⅲ Anvillea garcinii group, Ⅳ Reseda muricata group, V Agathophora alopecuroides var. alopecuroides group, Ⅵ Scrophularia deserti group, and Ⅶ Astragalus schimperi group. It's crucial to clearly define the Saharo-Arabian endemics and illustrate an updated verified database of these taxa for a given territory for providing future management plans that support the conservation and sustainable use of these valuable species under current thought-provoking devastating impacts of rapid anthropogenic and climate change in this region.

多种通信方式融合的矿用广播系统设计

针对现有矿用广播系统因通信方式不灵活,从而导致煤矿井下覆盖面有限,功能不完善等问题,研究设计了一种融合以太网、CAN(控制器局域网络)总线和模拟音频传输等通信方式的矿用广播系统设计方案,并阐述该系统的系统架构,软硬件设计及核心技术。该系统硬件由广播终端和广播对讲音箱组成:广播终端采用以太网通信实现网络IP电话,完成远距离通话;广播对讲音箱通过CAN总线,结合模拟音频实现双向对讲和流媒体在线播放,自带CAN中继功能,可无限级联,可部署在光纤无法覆盖的地方。整套广播系统可实现煤矿井下语音全覆盖,具有安装方便、硬件成本低等优势,为煤矿日常安全生产调度和防灾避险提供了有力的支持。

关于消防员电梯的几点思考

结合相关规范条文,针对电气设计人员对于消防员电梯井道照明、机房空调配电及五方通话等方面存在的疑惑或争议进行探讨,并提出笔者的见解。

扩音对讲系统在LNG接收站的应用及发展综述

分析适用于LNG接收站的扩音对讲系统设计方法。从系统结构、工作原理、传输方式、功能特点等方面详细论述了无主机型扩音对讲系统、有主机型扩音对讲系统、全数字IP型扩音对讲系统和5G型扩音对讲系统这四种扩音对讲系统的功能特点和差异性。通过对四种扩音对讲系统在LNG接收站中应用的优缺点和发展局限性分析对比,提出了在我国现阶段LNG接收站中应用最为广泛的扩音对讲系统设计方案为全数字IP型扩音对讲系统。通过介绍扩音对讲系统的功能和全数字IP型扩音对讲系统在LNG接收站应用案例,详细介绍了数字IP型扩音对讲系统在LNG接收站中的设计方法。阐述了基于5G网络技术的5G型扩音对讲系统在LNG接收站应用的局限性并对其发展进行了展望。

应急指挥对讲系统在企业安全生产中的应用

酒钢集团公司原有模拟对讲机品牌众多、无法互联互通,有些厂矿没有基站,对讲机只能点对点通话,通话距离有限,尤其在相对封闭的钢结构厂房内无法与厂房外通信,不能作为应急指挥使用。文章以酒泉钢铁集团公司应急指挥对讲系统建设为案例,论述了系统建设的背景,系统建设的目标,系统建设的内容,建设方案,系统实现的功能,以及系统运行的效果评价。文章对大型工矿企业应急指挥对讲系统的建设和企业数字化转型升级推动工厂智能化建设具有一定的借鉴意义。

利用同轴电缆和对讲机在室内覆盖施工现场通信的研究

室内覆盖项目的施工现场通信是工程建设者们经常遇到的一个难题,为解决在大型综合楼、深层地下室、地铁及隧道等室内覆盖参建人员之间的通信交流问题,耗费建设者们大量的时间和精力。使用同轴电缆和对讲机组成的即时通信系统,较好地解决这一问题,改善室内覆盖参建者们在施工现场的通信交流状况,大幅提升室内覆盖施工现场的工作效率。主要介绍了同轴电缆和对讲机组成通信系统的技术要点与相关注意事项。

星地一体融合应急通信保障系统设计

利用天通卫星和北斗系统的优势,充分结合地面数字对讲系统和移动通信系统的特点,设计了一种星地融合、互联互通的应急通信保障系统。该系统由各类通信终端、地面和卫星通信网络及中心应用系统组成。星地通终端为中心站构建区域对讲系统,实现区域内终端通信;通过星地通终端申请的卫星信道远程转发区域内终端业务,完成跨区域终端间、终端和中心应用系统之间信息交互。中心应用系统包括业务接入层和应用层,完成各通信网内终端数据接入及用户应用,提供音视频、位置、短息等通信业务,实现应急通信保障。

Buckling-controlled two-way shape memory effect in a ring-shaped bilayer

Shape memory polymers(SMPs)usually have a one-way shape memory effect.In this paper,an easy-operating method to realize a two-way shape memory effect was demonstrated in a ring-shaped bilayer structure where the two layers are SMPs with different thermal transition temperatures.By designing specific thermomechanical processes,the mismatched deformation between the two layers leads to a morphology change of ring-shaped bilayer structures from a smooth ring to a gear-like buckling shape under cooling and a reversible recovery to the smooth shape under heating.Such a morphology change is ascribed to occurrence and recovery of thermoelastic buckling.This method was validated by finite element simulation.We experimentally investigated the influence of pre-strain on buckling,and it was found that both the buckling occurrence and recovery temperature vary with pre-strain.Furthermore,considering a ring-shaped SMP-SMP bilayer structure,finite element analysis was conducted to study the influence of film thickness and modulus ratio of two layers on buckling behavior.The results showed that the critical buckling wavelength was greatly influenced by film thickness and modulus ratio.W e made a theoretical analysis that accorded well with the numerical results.

3D Two-way Coupled TEHD Analysis on the Lubricating Characteristics of Thrust Bearings in Pump-turbine Units by Combining CFD and FEA

The thermal elastic hydro dynamic （TEHD） lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis （FEA）. But it is still a problem to conduct the computation by combining computational fluid dynamics （CFD） and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.

Simulation and Analysis of China Climate Using Two-Way Interactive Atmosphere-Vegetation Model (RIEMS-AVIM)

In this paper, an Atmosphere-Vegetation Interaction Model （AVIM） is coupled to the Regional Integrated Environment Model System （RIEMS）, and a 10-year integration for China is performed using the RIEMS-AVIM. The analysis of the results of the 10-year integration shows that the characters of the spatial distributions of temperature and precipitation over China are well simulated. The patterns of simulated surface sensible and latent heat fluxes match well with the spatial climatological atlas： the values of winter surface sensible and latent heat fluxes are both lower than climatological values over the whole country. Summer surface sensible heat flux is higher than climatological values in western China and lower in eastern China, while summer surface latent heat flux is higher than climatological values in the eastern and lower in the western. Seasonal variations of simulated temperature and precipitation of RIMES-AVIM agree with those of the observed. Simulated temperature is lower than the observed in the Tibetan Plateau and Northwest China for the whole year, slightly lower in the remaining regions in winter, but consistent with the observed in summer. The simulated temperature of RIEMS-AVIM is higher in winter and lower in summer than that of RIEMS, which shows that the simulated temperature of RIEMS-AVIM is closer to the observed value. Simulated precipitation is excessive in the first half of the year, but consistent with the observed in the second half of the year. The simulated summer precipitation of RIEMS-AVIM has significant improvement compared to that of RIEMS, which is less and closer to the observed value. The interannual variations of temperature and precipitation are also fairly well simulated, with temperature simulation being superior to precipitation simulation. The interannual variation of simulated temperature is significantly correlated with the observed in Northeast China, the Transition Region, South China, and the Tibetan Plateau, but the correlation between precipitation simulation and observation is only significant in Northwest China.

A Novel Forwarding Method for Full-Duplex Two-Way Relay Networks

An estimate-and-forward(EF) scheme for single-input single-output(SISO) and multiple-input multiple-output(MIMO) full-duplex two-way relay networks is proposed and analyzed. The relay estimates the received signal from two terminal nodes by a minimum mean squared error(MMSE) estimation and forwards a scaled version of the MMSE estimate to the destination. The proposed EF outperforms conventional amplify-and-forward(AF) and decode-and-forward(DF) across all signal-to-noise ratio(SNR) region. Because its computational complexity is high for relays with a large number of antennas(large MIMO) and/or high order constellations, an approximate EF scheme, called list EF, are thus proposed to reduce the computational complexity. The proposed list EF computes a candidate list for the MMSE estimate by using a sphere decoder, and it approaches the performance of the exact EF relay at a negligible performance loss. The proposed forwarding approach also could be used to other relay networks, such as half-duplex, one-way or massive MIMO relay networks.