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针对无线光通信（WOC）技术高频谱效率以及低误码率的需求，文章提出了一种脉冲幅度调制（PAM）与脉冲位置调制（PPM）联合的调制方法，在传统调制技术的基础上充分利用无线通信带宽资源提高了传输速率。系统采用空域映射（SM）方式将不同幅度脉冲映射至特定激光器，并通过映射关系完成多链路分层传输。与传统单调制方式相比，联合调制技术通过编码机制的协调配合，利用脉冲的幅度以及所在时隙位置的变化来传递信息。实验测试证明，采用联合调制分层传输技术，通过同时发送和检测每个数据脉冲的时隙位置及幅度信息，不仅提升了系统频谱效率和传输速率，误码性能也得到了有效改善，实验结果为后续应用研究提供了一种新的技术途径。

针对声光偏转效应相干探测信号光斑随射频信号变化的偏移特性,利用光斑重叠物理模型,研究了光斑结构与探测效率的关系,分析了光束准直、探测器有效光敏面半径以及本振光能量匹配等因素对相干光探测效率的影响。计算机仿真和实验测试验证表明,以能量分布均匀的光斑作为本振光斑,对信号光斑在一定范围内漂移的光斑重叠相干探测效率改善十分有利,空间失配角在±0.5rad内,重叠效率下降不到5%;采用光斑压缩准直处理能有效保证系统混频光束准直性,并且重叠光斑能量利用率高,系统光学匹配好。

利用modtran大气传输模型对低空信道紫外光传输特性进行分析,研究了近地短距离传输的大气吸收和散射的数学模型。在实验室环境下,系统采用视场角为80°的紫外LED（发光二极管）发射,在传输距离为5～8m的情况下进行了模拟信号的散射传输测试。结果表明:利用一定的有效散射体,收发俯仰角从10°增加到65°时,能有效实现短距离紫外散射传输。散射体浓度过大对紫外光存在强烈的吸收作用,传输距离将减小,单个紫外LED发射功率低,实际通信应用中,可采用阵列LED来提高发射功率,增加传输距离。

文章用几何光学原理分析了反射光强与表面涂层厚度及均匀度的关系,提出一种用于检测物体表面涂层均匀度的方法。该传感器能针对物体表面涂层的随机性实现不同区域涂层均匀度的在线测试。在理论分析的基础上,构建了实验测试系统。数据表明,采用该传感器进行测试能反映表面涂层均匀度的变化,测试精度可达10μm,具有良好的应用前景。

Thermal compression deformation experiments were conducted on a novel cobalt-based Co-Al-V superalloy. The deformation temperature was in the period of 800°C and 1050°C, and the strain rate varied from 0.001 to 1 s-1. The experimental results indicate that twins occurred after dynamic recrystallization of the alloy at low temperatures and low strain rates (800℃,0.001 s-1), at moderate temperatures and higher strain rates (950℃, 0.1 s-1), as well as at higher temperatures and higher strain rates (1050°C,1 s-1). The flow stress curves exhibited a trend of initially decreasing after reaching a peak, followed by an increase. At 800°C and 950°C, twins were more easily formed under high strain rates. As the strain rate decreased, the degree of dynamic recrystallization gradually increased. At 1050°C, twins were prone to formation at low strain rates, and the degree of dynamic recrystallization also decreased as the strain rate decreased. With the increase of deformation temperature, the degree of dynamic recrystallization increased, and the grain size of the recrystallized grains gradually became larger. Analysis of the EBSD test results revealed that the grain size of the recrystallized grains under high-temperature and low strain rates (1 050°C, 0.001 s-1) conditions was larger compared to that under high-temperature and high strain rates (1050℃,1 s-1) conditions. The twin boundaries at high temperatures were majorly 23 boundaries, and the fraction of 23 boundaries increased with decreasing strain rate at high temperatures. These findings provide a theoretical basis for optimizing the processing technology of the novel cobalt-based high-temperature alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The existing centrifugal simulation technology for piled embankments contains many simplifications and neglects the similarity of model stress history. Fully considering the similarity of geometric pile layout, material characteristics, loading and stress history, a centrifuge model test protocol for piled embankments with high gravity field in-flight consolidation, pile construction, and embankment loading was optimized and designed. A numerical simulation method corresponding to the in-flight loading process was proposed, and a single pile finite element model of piled embankments was established at the corresponding model scale and prototype scale, respectively. Comparative analysis shows that the pile-soil settlement curve, load sharing law, load transfer of embankments and pile shaft, and excess pore water pressure distribution of the model scale and prototype scale numerical models are consistent, verifying the correctness and rationality of the similarity design of centrifuge model of the piled embankments. The centrifuge modeling plan can reflect the deformation development, soil arching effect, and load transfer characteristics of piled embankments, laying an important preliminary research foundation for the centrifuge model test of piled embankments under in-flight loading conditions. [ABSTRACT FROM AUTHOR]

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Using a Gleeble-3500 thermal simulation testing machine, the thermal deformation behavior of Co-7Al-7Mo and Co-30Ni-7Al-7Mo subjected to vacuum arc melting and solid solution treatment (1 300 °C) was studied at deformation temperatures ranging from 700 °C to 900 °C and strain rates ranging from 0. 001 to 0. 1 s-1. Analyzing the true stress-strain curves, the results show that the deformation process of Co-7Al-7Mo and Co-30Ni-7 Al-7Mo at 900 °C with a strain rate of 0. 001 s-1 includes work hardening + dynamic recovery, which is divided into 4 stages, namely I (work hardening stage), Ⅱ (transition stage), III (softening stage) and IV (stable stage). When the deformation temperature is low or the strain rate is high, because the y' strengthening phase in the alloy hinders recrystallization, there is no obvious recovery softening stage, and the hardening effect continues until fracture occurs. When the solution temperature of y' phase is below, the flow stress under the same loading condition increases obviously with the increase of the volume fraction of y' phase and solution temperature with the addition of 30% atomic percentage Ni. The Arrhenius constitutive equations of the two alloys were established, and combined with the analysis of the thermal processing diagram, the good processing zones of the two alloys were obtained when the deformation temperature was 700 °C to 900 °C and the strain rate was 0. 001 to 0. 01 s-1. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Computer Engineering & Applications is the property of Beijing Journal of Computer Engineering & Applications Journal Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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