气体开关串级环形间隙放电相互影响机制研究

针对中空和非中空触发电极结构的两间隙开关，进行了触发击穿特性实验，对比两个间隙的击穿抖动和通道数，分析了串级两间隙的相互影响机制。实验结果表明：两只开关触发间隙击穿抖动和通道数变化规律基本一致；非中空开关自击穿间隙击穿抖动随工作系数的增大而减小，最小约3 ns，中空开关自击穿间隙击穿抖动始终约1 ns；非中空开关自击穿间隙难形成多通道放电，中空开关自击穿间隙通道数明显多于其他间隙。触发间隙首先放电产生紫外光，通过触发电极中空通孔预先照射自击穿间隙产生初始电子，是自击穿间隙击穿抖动减小、通道数增加的主要作用机制。     

基于多通道的ICU脑血管疾病死亡风险预测模型

死亡风险预测指根据病人临床体征监测数据来预测未来一段时间的死亡风险。对于ICU病患，通过死亡风险预测可以有针对性地对病人做出临床诊断，以及合理安排有限的医疗资源。基于临床使用的MEWS和Glasgow昏迷评分量表，针对ICU病人临床监测的17项生理参数，提出一种基于多通道的ICU脑血管疾病死亡风险预测模型。引入多通道概念应用于BiLSTM模型，用于突出每个生理参数对死亡风险预测的作用。采用Attention机制用于提高模型预测精度。实验数据来自MIMIC [Ⅲ]数据库，从中提取3?080位脑血管疾病患者的16?260条记录用于此次研究，除了六组超参数实验之外，将所提模型与LSTM、Multichannel-BiLSTM、逻辑回归（logistic regression）和支持向量机（support vector machine, SVM）四种模型进行了对比分析，准确率Accuracy、灵敏度Sensitive、特异性Specificity、AUC-ROC和AUC-PRC作为评价指标，实验结果表明，所提模型性能优于其他模型，AUC值达到94.3%。     

多通道低频电磁传感器的仿真及优化

针对金属板构件内外壁损伤的检测问题,通过数值仿真与试验优化的方法,研制了一种适用于金属板构件内外壁损伤缺陷检测的多通道低频电磁传感器。建立了低频电磁检测三维有限元仿真计算模型,研究当圆形线圈切向放置在金属板导体上方时对缺陷的检测能力。进行对比试验,优化激励线圈匝数、检测线圈内径、高度等影响传感器灵敏度的参数,通过对含有人工缺陷金属板的检测验证了传感器的灵敏度与实用性。结果表明,研制的多通道低频电磁传感器可以实现对?12 mm埋深9.6 mm的304不锈钢缺陷及?12 mm埋深8 mm的20#碳钢缺陷的有效检测。     

基于分数阶Hilbert变换的多路加密

基于分数阶Hilbert变换的单边带通信可以同时将分数阶旋转角度作为加密密钥,从而保证通信安全。但基于分数阶Hilbert变换的单边带通信加密技术只能让信号使用一个加密密钥。为了达到增大密钥空间以更有效地保证信息安全的目的,采用多通道滤波器组分路处理的方法,在减少了系统计算复杂度的基础上增大了密钥空间。     

汽车点焊超声波检测技术发展与趋势

电阻点焊在汽车工业是一种最常用的焊接方式。电阻点焊焊接过程短暂而复杂,焊接过程中熔核的形成不可见,容易出现各种不同类型的焊接缺陷。因此,对点焊接头进行监测和检测是非常必要的。点焊无损检测中最重要的手段是超声波检测。首先对汽车车身点焊的质量检测与监测手段进行综述,然后着重论述点焊超声波检测技术、点焊超声波检测系统的分类与产品现状、点焊超声波检测的信号处理方法、成像技术等关键问题,最后总结当前面临的主要难题,并预测未来的发展趋势。     

CAWR: Buffer Replacement with Channel‐Aware Write Reordering Mechanism for SSDs

A typical solid‐state drive contains several independent channels that can be operated in parallel. To exploit this channel‐level parallelism, a variety of works proposed to split consecutive write sequences into small segments and schedule them to different channels. This scheme exploits the parallelism but breaks the spatial locality of write traffic; thus, it is able to significantly degrade the efficiency of garbage collection. This paper proposes a channel‐aware write reordering (CAWR) mechanism to schedule write requests to different channels more intelligently. The novel mechanism encapsulates correlated pages into a cluster beforehand. All pages belonging to a cluster are scheduled to the same channels to exploit spatial locality, while different clusters are scheduled to different channels to exploit the parallelism. As CAWR covers both garbage collection and I/O performance, it outperforms existing schemes significantly. Trace‐driven simulation results demonstrate that the CAWR mechanism reduces the average response time by 26% on average and decreases the valid page copies by 10% on average, while achieving a similar hit ratio to that of existing mechanisms.     

Joint channel assignment and routing in multiradio multichannel wireless mesh networks with directional antennas

The aggregate capacity of a wireless mesh network (WMN) is severely affected by interflow interference. In this paper, we propose a network architecture that incorporates directional antennas with multiple orthogonal channels to effectively enhance the performance of WMNs. First, a sectored connectivity graph is introduced to model multiradio multichannel WMNs with directional antennas. Next we formulate the topology design, directional interface assignment, channel allocation, and routing mathematically as a mixed integer linear programming problem. This problem is solved using an iterated local search algorithm to obtain optimized network resource allocation. Simulation results indicate that the proposed architecture can achieve higher packet delivery ratio while providing better network fairness. Copyright © 2014 John Wiley & Sons, Ltd.     

A robust mixed‐conducting multichannel hollow fiber membrane reactor

To accelerate the commercial application of mixed‐conducting membrane reactor for catalytic reaction processes, a robust mixed‐conducting multichannel hollow fiber (MCMHF) membrane reactor was constructed and characterized in this work. The MCMHF membrane based on reduction‐tolerant and CO₂‐stable SrFe_0.8Nb_0.2O_3‐δ (SFN) oxide not only possesses a good mechanical strength but also has a high oxygen permeation flux under air/He gradient, which is about four times that of SFN disk membrane. When partial oxidation of methane (POM) was performed in the MCMHF membrane reactor, excellent reaction performance (oxygen flux of 19.2 mL min^?1 cm^?2, hydrogen production rate of 54.7 mL min^?1 cm^?2, methane conversion of 94.6% and the CO selectivity of 99%) was achieved at 1173 K. And also, the MCMHF membrane reactor for POM reaction was operated stably for 120 h without obvious degradation of reaction performance. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2592–2599, 2015     

Two-phase flow instability in a parallel multichannel system

The two-phase flow instabilities observed in through parallel multichannel can be classified into three types, of which only one is intrinsic to parallel multichannel systems. The intrinsic instabilities observed in parallel multichannel system have been studied experimentally. The stable boundary of the flow in such a parallel-channel system are sought, and the nature of inlet flow oscillation in the unstable region has been examined experimentally under various conditions of inlet velocity, heat flux, liquid temperature, cross section of channel and entrance throttling. The results show that parallel multichannel system possess a characteristic oscillation that is quite independent of the magnitude and duration of the initial disturbance, and the stable boundary is influenced by the characteristic frequency of the system as well as by the exit quality when this is low, and upon raising the exit quality and reducing the characteristic frequency, the system increases its instability, and entrance throttling effectively contributes to stabilization of the system.     

基于8051F410的多路高精度测力装置设计

设计了一种新型高精度多路测力装置,它集压力传感器信号变送、实时采集、大容量数据存储和串行计算机通信于一体,前端采集器基于8051F410单片机和18位高精度数模转化器FS511,采样稳定分辨率可以达到16位,与计算机之间通过CAN或RS485物理协议通信。该装置具有功耗低、精度较高、实时性强、数据处理量大、数据处理方便、数据安全可靠和移动灵活等特点,以适应现在对机械工程设备的各种要求。