Low complexity carrier phase estimation for m-QAM optical communication systems

Photonic Network Communications - A low complexity carrier phase estimation (CPE) algorithm for M-ary quadrature amplitude modulation (m-QAM) optical communication systems is investigated in this...     

多分量数据全波形反演在气藏检测中的关键问题——以苏里格气田为例

苏里格气田是中国典型的致密砂岩气藏，构造简单、平缓，横向非均质性强，有效储层与围岩声学特征差别小，地震响应不明显，常规地震监测方法预测难度大，但气田含气砂岩泊松比低，是地震气藏检测的有效参数。利用弹性全波形反演精度高和能处理复杂非均质介质的优势，反演地层拉梅常数、剪切模量和密度，并计算泊松比，从而进行气藏预测。重点阐述了苏里格气田多分量数据全波形反演初始模型建模、先验模型建模和地震数据预处理3个关键问题的处理方法。二维三分量数据反演和"甜点"预测结果表明：①对于具有强非均质性的苏里格气田，利用全波形反演获得精度较高的地层弹性参数能显著提高气藏预测的准确度；②苏里格地区构造简单、平缓，利用常规叠加速度并结合构造解释可以建立比较好的初始模型，从而有效地解决了周波跳跃和局部极小的难题；③先验知识的约束和地震数据的预处理是全波形反演成功应用于苏里格气田气藏检测的关键。     

固体碳直接还原钢铁厂含锌固废的理论与实践

 钢铁厂内的含锌固废数量巨大，同时富含铁、碳等元素，是可循环再利用的二次资源。通过固体碳直接还原ZnO和FeO的热力学分析，发现在非标准状态下，ZnO的还原条件要优于FeO。为此，在实验室条件下设计了含锌固废在不同温度和时间下的还原试验，发现在还原温度为1 423 K、还原时间为15 min以上时，脱锌率可达到90%，而铁的金属化率需要在1 573 K时才能接近90%；在还原温度低于1 423 K时，还原时间对脱锌率的影响较大；在还原温度高于1 473 K时，还原温度对脱锌率影响较小，同时脱锌率可达到95%。这些结果对国内当前处理含锌固废主要工艺(回转窑、转底炉)的操作制度设置具有重要的参考价值，也为如何选择合理的工艺路线，以低投入、低运营成本实现含锌固废的再利用提供了理论依据。     

考虑关节角加速度约束的仿人机器人偏摆力矩控制方法

针对仿人机器人步行过程中存在的机器人关节角加速度约束影响控制性能的问题，提出一种考虑关节角加速度约束的仿人机器人偏摆力矩控制方法.该方法充分考虑了双臂在摆动过程中对偏摆力矩的影响，根据力矩平衡条件得到需要抵消的偏摆力矩的大小与方向，将偏摆力矩的控制问题转化为带约束条件的二次规划问题，并设计了一种在线变步长迭代算法计算得到优化后的双臂摆动轨迹.实验表明，该方法能有效抵消机器人步行中产生的偏摆力矩，避免控制过程中的"削峰"现象，有效提高机器人的步行稳定性.     

Study of MW-scale biogas-fed SOFC-WGS-TSA-PEMFC hybrid power technology as distributed energy system: Thermodynamic,exergetic and thermo-economic evaluation

Advanced biogas power generation technology has been attracting attentions, which contributes to the waste disposal and the mitigation of greenhouse gas emissions. This work proposes and models a novel biogas-fed hybrid power generation system consisting of solid oxide fuel cell, water gas shift reaction, thermal swing adsorption and proton exchange membrane fuel cell (SOFC-WGS-TSA-PEMFC). The thermodynamic, exergetic, and thermo-economic analyses of this hybrid system for power generation were conducted to comprehensively evaluate its performance. It was found that the novel biogas-fed hybrid system has a gross energy conversion efficiency of 68.63% and exergy efficiency of 65.36%, indicating high efficiency for this kind of hybrid power technology. The market sensitivity analysis showed that the hybrid system also has a low sensitivity to market price fluctuation. Under the current subsidy level for the distributed biogas power plant, the levelized cost of energy can be lowered to 0.02942 $/kWh for a 1 MW scale system. Accordingly, the payback period and annual return on investment can reach 1.4 year and about 20%, respectively. These results reveal that the proposed hybrid system is promising and economically feasible as a distributed power plant, especially for the small power scale (no more than 2 MW).     

Rapid screening of DON contamination in whole wheat meals by Vis/NIR spectroscopy and computer vision coupling technology

This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s⁻¹ on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg⁻¹ as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing.     

推土机低温适应性研究及应用

推土机在低温环境下使用,常出现发动机启动困难,传动、液压、电气系统故障率高等问题.为解决推土机低温环境下使用问题,通过分析影响推土机低温使用性能的因素,提出了提升推土机低温性能措施,并对相关措施进行了实际应用.应用结果证明了提升推土机低温性能措施的有效性,使推土机可以在低温环境下正常使用.     

基于变量决策层的启发式变量选择策略

启发式分支策略是SAT求解器中不可或缺的一部分，直接影响求解器的效率。早期的启发式分支决策需要遍历整个子句数据库，效率比较低。随着独立变量状态衰减和（Variable State Independent Decaying Sum, VSIDS）分支策略的出现，SAT求解器的效率有所提高，但VSIDS策略以及它的延伸策略中变量的增量都只是与变量的冲突次数有关，没有考虑变量的决策层在分支策略中的影响。因此当发生冲突时，如果与冲突有关的变量的得分相同而决策层不同时，对于变量的选择就具有随机性。基于此，本文在阐述变量的决策层的重要性之后在VSIDS策略的基础上，提出一种基于变量决策层的启发式变量选择策略--HSVDL策略。然后通过实例显示HSVDL策略在变量决策阶段选择决策层低的变量的可能性比选择决策层高的变量的可能性要大，而且得分比较小，减少了内存的占用。最后通过实验表明HSVDL策略能够求解出更多的实例，求解器的效率也有所提高，说明该策略有一定的优势。     

Ductile-brittle transition mechanisms of amorphous glass subjected to taper grinding experiment

Taper grinding experiments were conducted in this paper to investigate the continuous and complete ductile-brittle transition process of two kinds of amorphous glass: high purity fused silica (HPFS) which is silica rich glass and soda-lime silica glass (SLSG) which is low silica glass. The grinding force, ground surface morphology, surface roughness, and subsurface damage depth induced during different stages of taper grinding were all analyzed. A mathematical model describing the cutting force of a grit and micro-crack length was established to clarify the ductile-brittle transition mechanisms of isotropic material. The model revealed that material removal mechanisms and grinding force were mainly determined by the crack equivalent length in front of the grit and its equivalent cutting force. The ground surface roughness and subsurface damage depth were mainly affected by the cutting force of the grit and length of cracks behind it. The ductile machinability of SLSG was better than that of HPFS due to the bonding of metallic atoms in SLSG with nonbridging oxygens, as well as their packing into free volume in SiO₂ network.     

Structural,optical and electrical properties of indium doped Cu2ZnSn(S,Se)4 thin films synthesized by the DC and RF reactive magnetron cosputtering

Element doping into the Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber is an effective method to optimize the performance of thin film solar cells. In this study, the Cu₂In_xZn_1-xSn(S,Se)₄ (CIZTSSe) precursor film was deposited by magnetron cosputtering technique using indium (In) and quaternary Cu₂ZnSnS₄ (CZTS) as targets. Meanwhile, the In content was controlled using the direct current (DC) power on In target (P_In). A single kesterite CIZTSSe alloy was formed by successfully doping a small number of In³⁺ into the main lattice of CZTSSe. The partial Zn²⁺ cations were substituted by In³⁺ ions, resulting in improving properties of CZTSSe films. Morphological analysis showed that large grain CIZTSSe films could be obtained by doping In. The well-distributed, smooth, and dense film was obtained when the P_In was 30 W. The band gap of CIZTSSe could be continuously adjusted from 1.27 to 1.05 eV as P_In increased from 0 to 40 W. In addition, the CIZTSSe alloy thin film at P_In = 30 W exhibited the best p-type conductivity with Hall mobility of 6.87 cm²V^?1s^?1, which is a potential material as the absorption layer of high-performance solar cells.