Novel Sum-of-Sinusoids Simulation Channel Modeling for 6G Multiple-Input Multiple-Output Vehicle-to-Everything Communications

In this paper,a statistical cluster-based simulation channel model with a finite number of sinusoids is proposed for depicting the multiple-input multiple-output(MIMO)communications in vehicleto-everything(V2X)environments.In the proposed sum-of-sinusoids(SoS)channel model,the waves that emerge from the transmitter undergo line-of-sight(LoS)and non-line-of-sight(NLoS)propagation to the receiver,which makes the model suitable for describing numerous V2X wireless communication scenarios for sixth-generation(6G).We derive expressions for the real and imaginary parts of the complex channel impulse response(CIR),which characterize the physical propagation characteristics of V2X wireless channels.The statistical properties of the real and imaginary parts of the complex CIRs,i.e.,autocorrelation functions(ACFs),Doppler power spectral densities(PSDs),cross-correlation functions(CCFs),and variances of ACFs and CCFs,are derived and discussed.Simulation results are generated and match those predicted by the underlying theory,demonstrating the accuracy of our derivation and analysis.The proposed framework and underlying theory arise as an efficient tool to investigate the statistical properties of 6G MIMO V2X communication systems.

AZ31镁合金和7050铝合金ECAP过程的数值模拟研究

利用Abaqus有限元软件分别对AZ31镁合金和7050铝合金进行等通道转角挤压(ECAP)数值模拟研究。利用有限元(FE)模拟得到应力场、应变场及载荷-位移曲线,分析了在不同挤压温度、挤压速度、摩擦条件和不同截面下等通道转角挤压的变形规律。结果表明,挤压温度升高可以降低挤压载荷,这有利于AZ31镁合金挤压,在摩擦较小情况下进行变形有利于降低挤压载荷,提高变形均匀性;在不考虑变形过程中温升效应的情况下,挤压速度对挤压载荷影响较小,当挤压速度提高时,最大等效应变值有所提高;圆形截面比方形截面更适合进行等通道转角挤压。

Artificial neural network-based subgrid-scale models for LES of compressible turbulent channel flow

Fully connected neural networks(FCNNs)have been developed for the closure of subgrid-scale(SGS)stress and SGS heat flux in large-eddy simulations of compressible turbulent channel flow.The FCNNbased SGS model trained using data with Mach number Ma=3.0 and Reynolds number Re=3000 was applied to situations with different Mach numbers and Reynolds numbers.The input variables of the neural network model were the filtered velocity gradients and temperature gradients at a single spatial grid point.The a priori test showed that the FCNN model had a correlation coefficient larger than 0.91 and a relative error smaller than 0.43,with much better reconstructions of SGS unclosed terms than the dynamic Smagorinsky model(DSM).In a posteriori test,the behavior of the FCNN model was marginally better than that of the DSM in predicting the mean velocity profiles,mean temperature profiles,turbulent intensities,total Reynolds stress,total Reynolds heat flux,and mean SGS flux of kinetic energy,and outperformed the Smagorinsky model.

Influence of bed elevation discordance on flow patterns and head losses in an open-channel confluence

Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics.This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections.A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others.Four configurations with different bed discordance ratios were investigated.The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces.The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step.Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio.It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently.

Fluid Flow and Mixed Heat Transfer in a Horizontal Channel with an Open Cavity and Wavy Wall

Heat exchangers are utilized extensively in different industries and technologies.Consequently,optimizing heat exchangers has been a major concern among researchers.Although various studies have been conducted to improve the heat transfer rate,the use of a wavy wall in the presence of different types of heat transfer mechanisms has not been investigated.This study thus investigates the mixed heat transmission behavior of fluid in a horizontal channel with a cavity and a hot,wavy wall.The fluid flow in the channel is considered laminar,and the governing equations including continuity,momentum,and energy are all solved numerically.The numerical solution is stabilized by using a first-order multi-dimensional characteristic-based scheme in combination with a fifth-order Runge-Kutta method.The flow and heat transfer effects of varying Richardson numbers,Reynolds numbers,wave amplitude,wavelength,channel height,and cavity width are examined.The results indicate that the mean Nusselt number increases with an increase in Reynolds number,wave amplitude,and cavity width,while it decreases with an increase in Richardson number,wavelength,and channel height.The minimum Nusselt number is calculated to be 0.7,whereas the maximum Nusselt number is 27.09.The Nusselt number has only increased by 40%in the higher depths of the cavity,despite the Richardson number being 10,000 times larger.But this figure increases to 130%at lower depths.The mean Nusselt number is thus significantly influenced by channel height and cavity width.The influence of wave amplitude on the mean Nusselt number is twice that of wavelength.

A Rigorous Analysis of Vehicle-to-Vehicle Range Performance in a Rural Channel Propagation Scenario as a Function of Antenna Type and Location via Simulation and Field Trails

Vehicle-to-Everything(V2X) communications will be an essential part of the technology in future autonomous drive decision systems.A fundamental procedure is to establish a robust communication channel between end-to-end devices.Due to the antenna placed at different positions on vehicles,the existing cellular electro-magnetic(EM) wave propagation modelling does not fit properly for V2X direct communication application.In order to figure out a feasible understanding of this problem,this paper focuses on the propagation channel analysis in a rural Vehicle-to-Vehicle(V2V) scenario for vehicular communication with antenna position experiments at different heights.By adopting the ray-tracing algorithm,a rural scenario simulation model is built up via the use of a commercial-off-the-shelf(COTS) EM modelling software package,that computes the path loss received power and delay spread for a given propagation channel.Next,a real-world vehicle measurement campaign was performed to verify the simulation results.The simulated and measured receiver power was in good agreement with each other,and the results of this study considered two antenna types located at three different relative heights between the two vehicles.This research provides constructive guidance for the V2V antenna characteristics,antenna placement and vehicle communication channel analysis.

Deterministic and Stochastic Simulators for Non-Isotropic V2V-MIMO Wideband Channels

In this paper, we consider a novel two-dimensional(2D) geometry-based stochastic model(GBSM) for multiple-input multiple-output(MIMO) vehicle-to-vehicle(V2V) wideband fading channels. The proposed model employs the combination of a two-ring model and a multiple confocal ellipses model, where the signal is sum of the line-of-sight(Lo S) component, single-bounced(SB) rays, and double-bounced(DB) rays. Based on the reference model, we derive some expressions of channel statistical properties, including space-time correlation function(STCF), Doppler spectral power density(DPSD), envelope level crossing rate(LCR) and average fade duration(AFD). In addition, corresponding deterministic and stochastic simulation models are developed based on the reference model. Moreover, we compare the statistical properties of the reference model and the two simulation models in different scenarios and investigate the impact of different vehicular traffic densities(VTDs) on the channel statistical properties of the proposed model. Finally, the great agreement between simulation models and the reference model demonstrates not only the utility of simulation models, but also the correctness of theoretical derivations and simulations.

Principle and key technology of generalized high precision simulation of TT&C channel

A generalized simulation method of the tracking,telemetry and control（TT＆C） channel,which is applicable to wideband and arbitrary radio frequency（RF） signal,is proposed.It can accurately simulate the dynamic transmission delay of the arbitrary RF signal in channels,especially regardless of any prior knowledge including signal form,signal parameters,and so on.The proposed method orthogonally demodulates the wideband and arbitrary RF signal to complex baseband by a known local oscillator（LO） signal.Whereafter,it takes measures to obtain the delay reconstruction signal of baseband signals based on the dynamic transmission delay between a ground station and a responder.Meanwhile,it manages to obtain the delay reconstruction signal of LO signals.The simulation output signal（the delayed RF signal） can be achieved through the synthesis of the two delay reconstruction signals mentioned above.The principle and its related key technology are described in detail,and the realizable system architecture is given.

New Channel Simulator for Adaptive HF Communication Systems

The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-varying delay spread is introduced into the channel simulators to simulate the transition states between two channel modes of CCIR520-1. Two signals, including a 500 Hz and a 1 000 Hz bandwidth signal are respectively input into the standard Watterson HF channel model and the proposed channel model with time-varying parameters. Some simulation results prove that the proposed HF channel model with time-varying parameters can reflect the time-varying characteristics of frequency selected fading of HF channel.

基于CFD的泵站进水流道优化

受限于用地规模、地形等因素,我国排水泵站流道的设计趋于复杂,普遍具有流道深、狭长的特点。这导致泵站进水流道存在回流、流速分布不均匀等不良流态,影响泵站安全稳定运行。以某泵站为实例,采用计算流体力学(computational fluid dynamics,CFD)技术,通过改变肘形流道的弯曲段长度、底边线倾角和喉管高度,拟定优化设计方案,采用基于CFD的数值模拟方法分析流道内部流场分布,并根据流道出口的流速分布均匀度、速度加权平均角度和流道水力损失等水力指标比选,优选出最优方案。该研究为进水流道设计提供了更精细的优化手段,弥补了传统经验设计方法只能定性分析的不足,得到的最优设计方案可供类似工程参考,保障泵站机组的稳定运行。

Dual-Channel Communication of Column Plasma Antenna Excited by a Surface Wave——Actualization and Simulation of Radiation Pattern

Along with the introduction of the concept of dual-channel communication,we utilized the finite-difference time-domain（FDTD） method to simulate and measure the radiation pattern under certain plasma densities and plasma collision frequencies.Results show that under certain settings,the radiation pattern of a plasma antenna resembles that of a metallic antenna.In contrast to a metallic antenna,a plasma antenna possesses other functionalities,such as dynamic reconfiguration and digital controllability.The data from simulation are similar to the measurement results,indicating that column plasma antenna can realize dual-channel communication.This work confirms the viability of realizing dual-channel communication by column plasma antenna,which adds a new but promising method for modern intelligent communication.

Design of Fading Channel Simulator Based on IIR Filter Using Genetic Algorithm

This article designs a Rayleigh fading channel simulator using IIR filter (called Doppler filter), which is used to approximate the Jakes Doppler spectrum. We mainly focus on the design of Doppler filter and model it as an optimization problem. Non-convexity of the problem is proved in this paper and genetic algorithm (GA) is used to optimize it, which has never been used before in this area. Simulation result shows that GA converges at the solution corresponding to very accurate approximation of Jakes PSD. Finally, several statistical characteristics of the simulator are verified, including correlation functions and level-crossing rate (LCR), all of which match the theoretical predictions pretty well.

基于欧拉-欧拉方法的CO_(2)电解池水气传输特性

为研究CO_(2)电解还原过程中的水-气传输特性,基于欧拉-欧拉方法,建立CO_(2)电解池中多相传质过程与电化学相耦合的计算模型,搭建CO_(2)电解池试验测试平台,基于试验数据对仿真模型进行验证;在此基础上分别基于单通道模型和大尺寸单蛇形流场模型对电解池工作特性进行模拟分析。仿真结果表明:较大的水流速度可以加快生成气体的排出,利于催化层电化学反应进行;在大尺寸流场中,由于水排出不及时,有相当一部分水通过质子交换膜传递到阴极侧,导致阴极发生水淹,降低阴极侧液态水含量可在一定程度上改善阴极侧的气体传输;为避免阴极水量过多,应合理设计流场结构和供水供气策略。

Influence of tool deflection on micro channel pattern of 6:4 brass with rectangular tool

Machining experiment of micro channel structure with 6:4 brass was carried out by shaping process using a single crystal diamond tool. FEM simulation using solid cantilever beam model was analyzed. In result of experiment, tool deflection is observed as machining characteristics through result of experiments such as surface roughness, cutting force and burr formations. And the influence of tool deflection is experimentally proved.

NUMERICAL SIMULATION OF ATTENUATION OF LOVE-TYPE CHANNEL WAVES IN VISCOELASTIC MEDIA

Proceeding from wave equations, the paper strictly deduced the dispersion relation equation of Love-type channel waves in Standard Linear Solid model. The e quation is a complex one with its real part signifying the dispersion characteristics of the channel wave while the imaginary part, the attenuation characteristics. In calcu lating the attenuation value, the author has set up a mathematical model of a horizon tal symmetric sequence (a three layer sequence of rock-coal-rock), given out some physical parametersl and adopted the dichotomy method that is more of ten used in root resolving of an equatlon. The calculation indicates that the influence of non-elas tic absorption on the attenuation of the propagation of channel wave varies with the frequency. In the frequency band of the Airy phase, the attenuation increases steep like, which is unfavorable for the channel wave seismic prospecting. The study of channel wave attenuation has provided a theoretical basis for the compensation of at tenuation.

应用于中继卫星通信系统的16QAM-TCM技术研究

网格编码调制技术可以在不改变信息传输频谱带宽的条件下,改善信噪比,减少发射功率,降低误码率,其实现的方法是分割星座图形成子集,逐步增大星座图中信号点之间的最小欧氏距离。本论文在项目组自研的中继卫星通信系统仿真平台上,仿真了8PSK与16QAM-TCM两种调制技术的解调性能,仿真曲线反映了误比特率需求与所需信噪比之间的关系。仿真结果表明:(1)在理想信道条件、I/Q(Inphase/Quadrature,同相/正交)幅相不平衡、幅频特性、群时延、相位噪声、功率放大器饱和点条件下,假设误比特率需求为1E-7,16QAM-TCM技术的信噪比需求与8PSK调制技术的信噪比需求相比,分别可节省8.85 dB、9.04 dB、8.45 dB、10.2 dB、8.5 dB、14.6 dB的信噪比;(2)在非线性信道条件下,当信噪比增大时,8PSK调制技术的误比特率在1E-3数量级附近波动,不再变化;(3)假设需求的误比特率为1E-7,16QAMTCM调制技术非线性信道信噪比仿真值与理想信道信噪比仿真值相比,损失了4.8 dB。

面向快速散热的HTCC基板微流道性能研究

随着微波组件向着大功率、高密度集成方向的快速发展,组件中大功率芯片的散热问题已影响到组件的可靠性,解决大功率微波组件的散热问题需要采用高效的散热技术。作为新兴的快速散热技术之一,微流道具有低热阻、高效率以及可集成等众多优势。建立了基于大功率微波组件的微流道陶瓷基板有限元分析模型并对其进行热仿真,分析了不同微流道构型、占空比、扰流柱半径以及流速对组件散热的影响,并基于仿真结果制备了实物组件,实测温升下降60℃,实现了超大功率芯片的快速散热。

Fiber Channel协议中CRC编码的硬件实现

介绍了光缆通道(Fiber Channel)协议中CRC校验编码的原理和硬件的实现。并结合仿真结果对面向字节的CRC-32编码器进行了论述。