Large-scale manufacturing of aluminum alloy plate extruded from subsize billet by new porthole-equal channel angular processing technique

To manufacture plate by the combination of equal channel angular processing （ECAP） and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing （P-ECAP）, was studied. Extrusion of AL6005A plate used for the bullet train plate was investigated by finite element method. The relevant porthole dies involving ECAP technique in channels were designed. Dimensional changes in the scrap part of the extrudate obtained after extrusion from the P-ECAP die, with different channel angles, were predicted. Effects of the channel angle and extrusion speed on the maximum temperature of the workpiece and other field variables were evaluated. At the channel angle of 160° of P-ECAP dies, the extrudate exhibited the optimal performance and the least amount of extrudate scrap was obtained. The optimal extrusion speed was 3-5 mm/s. Moreover, with the increase in ram speed from 1 to 9 mm/s, the peak extrusion load increased by about 49% and the maximum temperature was increased by about 70 ℃. The effective strain exhibited ascending trend in the comer of the ECAP deformation zone. In the solder seam and the side of die bearing of extrudate, the maximum principal stresses were tensile stress.

A new method of characterizing equivalent strain for equal channel angular processing

In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing （ECAP）, a new approach to characterize the equivalent strain was proposed. The results show that there exists better accordance between mechanical property （such as hardness or strength） and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as：ε=k0exp[-（k1M-k2）^2], where M is the strength or hardness of the material, k1 is the modified coefficient （k1∈ （0, 1））, ko and k2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material, respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter relating to material property rather than the classical geometry equation.

Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion in semi-solid isothermal treatment

Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angularextrusion(ECAE) in semi-solid isothermal treatment was investigated. The results show that withincreasing semi-solid isothermal treatment temperature, the a phase solid grain size of processedMg-Al-Zn alloy by ECAE increases firstly due to coarsening of a phase solid grains, then decreasesdue to melting of a phase solid grains. With the increase of extrusion passes during ECAE, the aphase solid grain size in the following semi-solid isothermal treatment decreases. The a phase solidgrain size of processed Mg-Al-Zn alloy by ECAE under route B_C is the smallest, while the a phasesolid grain size of processed material by ECAE under route A is the largest. The primary mechanismof spheroid formation depends on the melting of recrystallizing boundaries and diffusion of soluteatoms in the semi-solid state.

A Survey of Wi-Fi Sensing Techniques with Channel State Information

A review of signal processing algorithms employing Wi-Fi signals for positioning and recognition of human activities is presented.The principles of how channel state information(CSI)is used and how the Wi-Fi sensing systems operate are reviewed.It provides a brief introduction to the algorithms that perform signal processing,feature extraction and recognitions,including location,activity recognition,physiological signal detection and personal identification.Challenges and future trends of Wi-Fi sensing are also discussed in the end.

Microstructural Development of Fe-20mass%Cr Alloys and Pure Copper Processed by Equal-Channel Angular Pressing

Microstructural development of ultra low C, N, Fe-Cr alloy and pure copper processed by equal-channel angular pressing (ECAP) have been examined focusing on the initial stage of the formation of ultrafine grain structure. Fe-Cr alloys were pressed at 423 K while pure copper at room temperature for 1 to 3 passes via the route Bc to compare at the equivalent homologous temperature. Microstructural evolutions were characterized by electron backscatter diffraction (EBSD) image and transmission electron microscopy (TEM). It was found that deformation structures were mostly deformation-induced subboundaries in both the materials after one pass, but the fraction of high-angle grain boundary became higher in the Fe-Cr alloys than in pure copper in subsequent passes by increasing misorientation of the boundaries. The more enhanced formation of high angle boundaries in Fe-Cr alloys was discussed in terms of the nature of crystal slip of FCC and BCC structures.

Mechanical responses, texture and microstructural evolution of high purity aluminum deformed by equal channel angular pressing

Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively refine metals. The microstructure and microtexture evolutions and grain boundary characteristics of the high purity aluminum(99.998%) processed by ECAP at room temperature are investigated by means of TEM and EBSD. The results indicate that the shear deformation resistance increases with repeated EACP passes, and equiaxed grains with an average size of 0.9 μm in diameter are formed after five passes. Although the orientations distribution of grains tends to evolve toward random orientations, and microtextures(80°, 35°, 0°),(40°, 75°, 45°) and(0°, 85°, 45°) peak in the sample after five passes. The grain boundaries in UFG aluminum are high-angle geometrically necessary boundaries. It is suggested that the continuous dynamic recrystallization is responsible for the formation of ultrafine grains in high purity aluminum. Microstructure evolution in the high purity aluminum during ECAP is proposed.

An Orthogonal Wavelet Transform Fractionally Spaced Blind Equalization Algorithm Based on the Optimization of Genetic Algorithm

An orthogonal wavelet transform fractionally spaced blind equalization algorithm based on the optimization of genetic algorithm(WTFSE-GA) is proposed in viewof the lowconvergence rate,large steady-state mean square error and local convergence of traditional constant modulus blind equalization algorithm(CMA).The proposed algorithm can reduce the signal autocorrelation through the orthogonal wavelet transform of input signal of fractionally spaced blind equalizer,and decrease the possibility of CMA local convergence by using the global random search characteristics of genetic algorithm to optimize the equalizer weight vector.The proposed algorithm has the faster convergence rate and smaller mean square error compared with FSE and WT-FSE.The efficiency of the proposed algorithm is proved by computer simulation of underwater acoustic channels.

Blind Equalization Using a Hybrid Algorithm of Multilayer Neural Network

A novel blind equalization scheme based on multilayer neural network and Higher OrderCumulants(HOC)is proposed in the paper.The training of the neural network uses a newhybrid algorithm which has strict convex character(after a threshold)and converges muchfaster than the CMA algorithm.The inverse channel is built on the basis of the estimatedchannel and the training of neural network.The scheme can be used in nonlinear and timevarying channel and to deal with PAM or QAM signals.Simulation results Show that it per-forms well for blind equalization.

Real-time Parallel Processing System Design and Implementation for Underwater Acoustic Communication Based on Multiple Processors

ADSP-TS101 is a high performance DSP with good properties of parallel processing and high speed.According to the real-time processing requirements of underwater acoustic communication algorithms,a real-time parallel processing system with multi-channel synchronous sample,which is composed of multiple ADSP-TS101s,is designed and carried out.For the hardware design,field programmable gate array(FPGA)logical control is adopted for the design of multi-channel synchronous sample module and cluster/data flow associated pin connection mode is adopted for multiprocessing parallel processing configuration respectively.And the software is optimized by two kinds of communication ways:broadcast writing way through shared bus and point-to-point way through link ports.Through the whole system installation,connective debugging,and experiments in a lake,the results show that the real-time parallel processing system has good stability and real-time processing capability and meets the technical design requirements of real-time processing.

经络信息系统穴位及传导区结构特征的理论模型

目的:现代科学技术实验初步证明了经络的客观存在,但无法得到明确专一的经络生物组织结构支持,经络需要更多的深入研究。本研究从理论上分析经络的特征结构。方法:基于符合物理化学原理和生物遗传变异信息原理的经络信息产生传导方程,及经络通过的生理组织特性进行研究。结果:理论表明经络必须存在穴位和信息传导区,经典经络理论中的感传一体为感传交替过程。经络穴位之间的传导区域大小主要决定于经络物质信息在经络组织侧面渗漏率。相同或相似生理组织区域,经络穴位间距相近。而不同生理组织区域,经络穴位之间的尺度变化明显。经络中的生物信息传感器高密度集中于穴位的近点状区域,而传导线上的密度极低。结论:本研究首次从理论上证明了经络结构的基本特征。同时建立了穴位之间尺度的定量变化规律。证明及修正了传统的经络信息产生传导假说。这也从理论上证明了经络的客观存在。

城市环境信息公开服务均等化的测度研究

可持续推动生态文明建设,是中华民族永续发展的大计。为保障城市居民都能享有大致均等的信息公开服务,以环境知情权理论、信息不对称理论为依托,根据相关法律和通过大量阅读文献提取了影响城市信息公开均等化的因素,采用层次分析法进而构建城市环境信息公开服务均等化评价指标体系。最终结果证实,城市环境信息公开均等化准则层四维度的重要排序:环境信息公开水平>环境信息互动回应>环境监管信息>环境污染源自行检测。

基于Wi-Fi Sensing的无感检测技术

随着智能家居的推广普及,对于移动物体的行为感知成为热点技术。相比于传统的信息检测技术,新型的基于Wi-Fi信号的设备无关被动入侵检测,能够在无需用户做任何干预也不影响人员隐私安全的情况下实现对于行为的检测判断,这和使用摄像头或红外检测形成显著差异,成为研究热点。该文基于Wi-Fi芯片平台采集物理层信道状态信息,构建与移动载体信息相关的检测模型,结合大数据分析和智能算法,给出相关的实现方案,并基于实验验证实现从无线信道中捕捉波形特征,验证方案的有效性,结合结果分析也为后续精度的进一步提升提供改进方向。

面向医学影像报告生成的门归一化编解码网络

医学影像报告的自动生成可以减轻医生的工作强度,减少误诊或漏诊的情况发生。由于医学影像的独特性,通常病灶比较小,与正常区域灰度差异难以分辨,导致文本生成时关键词的缺失,报告不够准确。对此提出一种面向医学影像报告生成的门归一化编解码网络,通过门控通道变换单元优化视觉特征提取,加强特征间的差异,自动筛选关键特征;提出门归一化算法,沿通道维度整合上下文信息,在浅层网络激活、深层网络抑制通道间神经元活性,过滤无效特征,使文本和视觉语义充分交互,提高报告生成质量。在2种广泛使用的基准数据集IU X-Ray和MIMIC-CXR上的试验结果表明,模型能够取得先进的性能,生成的影像报告也具有更好的视觉语义一致性。

工艺参数对7075铝合金室温等通道转角拉伸载荷的影响

为探讨拉伸载荷在等通道转角拉伸过程中的变化规律,以7075铝合金为研究对象,基于上限法推导圆柱试样等通道转角拉伸峰值载荷的解析式;利用载荷测量系统分析了7075铝合金拉伸载荷的分布特征,揭示了工艺参数对拉伸载荷变化和各阶段拉伸载荷峰值的影响。结果表明,等通道转角拉伸理论计算峰值载荷与实验峰值载荷的相对误差在10%以内,表明解析式具有较高的可信度;等通道转角拉伸载荷经历了弹性阶段(Ta)、屈服阶段(Tb)、稳定阶段(Tc)和卸荷阶段(Td),其中峰值载荷出现在弹性阶段的末尾;峰值载荷随着模具内角和外角的增大出现下降的趋势,但下降的幅度有所放缓;峰值载荷随着拉伸道次的增加而减小;拉伸路径对峰值载荷影响的顺序为路径C>路径B>路径A,并且第2道次的路径B在拉伸时会出现载荷失稳现象;高速拉伸对拉伸峰值载荷的影响不大,但在低速拉伸时拉伸载荷曲线会出现“爬行”抖动现象。

基于DSP算法的广播电视发射基站信号实时信道均衡系统设计

设计一种应用于广播电视发射基站的信号实时信道均衡系统,该系统基于数字信号处理(Digital Signal Processing,DSP)算法,旨在提高信号传输质量并降低误码率。系统由信号预处理、信道估计、自适应均衡3个关键模块组成。信号预处理模块采用自适应滤波技术去除噪声和干扰;信道估计模块利用频域分析技术精确估计信道参数;自适应均衡模块则通过最小均方误差(Least Mean Square,LMS)算法动态调整均衡器系数,以补偿信道失真。实验结果表明,该系统在城市、郊区、山区环境下均能显著提高信号质量,降低误码率,并提供足够的信道容量,满足广播电视信号的高质量实时传输需求。

高铁环境下基于循环神经网络的无线传播信道模型研究

为了解决高铁高移速带来的无线通信传播中的信号不稳定问题,提出利用LSTM循环神经网络来设计均衡器,辅助信道搭建。为此建立基本的信道模型,根据高铁环境带来的信号变化,利用LSTM循环神经网络设计自适应均衡器对信道进行跟踪。结果中显示,LSTM循环神经网络均衡器最低信号符号错误率可降至0.4%以下。以上结果说明面对高移速的无线信号,基于LSTM循环神经网络设计均衡器可帮助信道搭建,实现信号远程无差别传播,有助于高铁网络的发展。

Microstructure and Properties of Mg-12Gd-3Y-0.5Zr Alloys Processed by ECAP and Extrusion

Equal channel angular pressing （ECAP） processing and conventional extrusion （Ex） were applied to the Mg-12Gd-3Y-0.5Zr （wt%） magnesium alloy in order to evaluate the potential improvement in the mechanical properties. The ECAP experiment was conducted at 380 ℃ in a die having an included angle of 90° between two channels by the Bc route with the billet rotated by 90° about its longitudinal axis. Subsequently, some billets were processed by conventional extrusion at 300 ℃. The microstructures were examined by X-ray diffraction （XRD）, optical microscopy and transmission electron microscopy （TEM）. The experimental results indicate that the grain size is refined effectively, but the basal planes are highly inclined （about 40o） from the extrusion axis introduced by ECAP, which impairs the grain boundary strengthening effect. The conventional extrusion, following the ECAP, can modify the grains in hard orientation. Based on grain boundary strengthening due to ECAP and texture strengthening due to Ex, the strength is improved effectively. The enhanced activity of the non-basal slips, due to the refined grains and the reduction in c/a ratio, is responsible for good ductility and high strain hardening rate in samples obtained by the two-step process.

信息获取能力会影响果农的销售渠道选择吗?

进入数字经济时代后,信息逐步成为影响农户行为决策的关键因素。本研究基于行为转变理论和计划行为理论,利用来自中国黄土高原优势产区1074户微观数据,通过运用Ordered Probit模型,实证检验信息获取能力对果农销售渠道选择的影响,并进一步运用条件混合过程估计法(CMP方法)对模型进行了内生性检验。研究结果表明:(1)当前,传统销售渠道的中间商(果贩)仍然是果农销售农产品的主要方式;(2)信息获取能力对果农销售渠道的选择有显著正向影响,即信息工具使用水平对果农进入市场壁垒更高的销售渠道具有促进作用;(3)信息获取能力正向显著影响新、中生代苹果户群体对销售渠道的选择。因此,政府应在完善农村信息基础设施和信息服务体系的同时,优化升级农产品流通体系,重点对新生代农户开展信息技术培训,提升其信息获取能力。

综合射频一体化系统技术发展综述

综合射频一体化系统的研究起源于20世纪八九十年代,是伴随着联合作战需求和电子器件的发展而发展起来的,尤其适用于舰载、机载等平台。综合射频一体化系统具备功能一体、软硬件通用、高度集成、协同高效等典型特征,既符合平台装备发展的需求,又满足联合作战任务的需求。综合射频一体化系统是当前射频领域的研究重点,也是射频系统未来的发展趋势之一,具有良好的应用前景。文中将从发展历程、系统架构、关键技术及未来发展方向等多个方面对综合射频一体化系统展开全面且深入的研究分析,希望可以为相关研究提供参考。