编码协作系统准循环重复累积码的联合设计与性能分析

重复累积(RA)码是一种特殊结构的低密度奇偶校验(LDPC)码,不仅具有LDPC码的优点,还能实现差分编码。针对LDPC编码协作系统编码复杂度高、时延长的问题,该文引入准循环RA(QC-RA)码,推导出信源节点和中继节点采用的QC-RA码对应的联合校验矩阵,基于公差构造方法设计该联合校验矩阵,并证明该方法设计的联合校验矩阵不存在围长为girth-4, girth-6的短环。理论分析和仿真结果表明,同等条件下该系统比相应点对点系统具有更优异的误码率性能。仿真结果同时表明,与采用一般构造QC-RA码或基于Z型构造QC-RA码相比,采用基于公差构造的联合设计QC-RA码的多信源多中继协作均可获得更高的编码增益。     

管状带式输送机设计及调试难点分析

本文对管状带式输送机设计及调试难点作了简要分析，比较了其与普通带式输送机的不同，为设计和调试提供技术支撑。     

Asymptotic analysis soot model and experiment for a directed injection engine

The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many researchers within the error range in the current computer speed. On the basis of the latest experimental results, TP (temperature phases) model is presented as a new soot model to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature and excess air factor are the most important two parameters in this model. When zone temperature T?1 500 K and excess air factor Ф?0.6, only the soot precursors-polycyclic aromatic hydrocarbons(PAH) is created and there is no soot emission. When zone temperature T ≥ 1 500 K and excess air factor Ф?0.6, PAHs and soot source terms (particle inception, surface growth, oxidation, coagulation) are calculated. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. KIVA standard model and experimental data are analyzed for the results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP models. The experimental results indicate that the TP model can carry out optimization and computational fluid dynamics can be a tool to calculate for a high-pressure common rail directed injection diesel engine. The TP model result is closer than the use of the original KIVA-3V results of soot model accuracy by about 50% and TP model gives a new method for engine researchers.     

梅钢1420mm冷轧机液压压下系统的设计计算

液压压下系统是现代高速冷连轧机的核心设备。在梅山钢铁公司1420 mm酸轧机组自主集成建设过程中,根据产品的质量和生产要求,在对以往引进轧机压下系统深入剖析的基础上,通过理论计算最终确定了压下缸、伺服阀的型号,以此为重点完成了1420 mm轧机液压压下系统的设计,并在随后的调试和使用中验证,达到了设计效果。     

旋流-静态微泡浮选柱在某金矿的工业试验

通过工业分流条件试验,研究了旋流-静态微泡浮选柱在山东某金矿应用的最佳工艺条件参数.试验结果表明:用浮选柱的一次粗选、一次精选工艺流程与生产中用浮选机的一次粗选、二次精选、二次扫选的工艺流程相比,在尾矿品位接近的情况下,精矿品位可提高12.69g/t.     

大型机械结构的分层动态优化方法

针对大型机械结构动态优化设计维数高,同时涉及外形尺寸和截面尺寸两类变量,采用整体优化策略,存在收敛困难的问题,提出了采用分层优化结合子结构方法的机械结构动态优化策略。以有限元方法为基础,将外形尺寸和截面尺寸分离到两个相对独立的设计空间,从而将整体优化问题分解为整体层优化和局部层优化两个子优化问题。在整体层以整体结构动态特性最优为目标,完成对外形尺寸的优化;在局部层以子结构动态特性最优为目标,完成对截面尺寸的优化;两层优化交替进行直至问题最后收敛。某型大跨自动扶梯金属结构的动态优化工程实例表明,该方法优化效果良好且优化效率高。     

Hot Compression Mechanical Behavior of Solution Heat-Treated and Pre-aged Mg-Zn-Gd-Er Alloys

The mechanical behavior of solution heat-treated and pre-aged Mg-6Zn-1Gd-1Er alloys during hot compression (from 180 to 330 °C) has been investigated. The results showed that the flow stress curves of the pre-aged sample (PAS) intersected with that of the solution heat-treated sample (SHTS) during hot compression. At 180 °C, when the true strain is 0.27 and 0.47, the PAS showed larger and smaller stress (210.80 MPa vs. 207.58 MPa and 205.67 MPa vs. 207.93 MPa) than the SHTS, respectively. These phenomena were due to the stronger interaction of W phase and dislocations/twins under the strain of 0.27, while dynamic recrystallization softening occurred under the strain of 0.47. When the temperature increased to 330 °C, the flow stress of PAS and SHTS showed an opposite trend to that of 180 °C. Continuous dynamic recrystallization and particle stimulated nucleation based on slip operations are the main deformation mechanisms under 330 °C. At the true strain is 0.33 and 0.53, the PAS has smaller and larger stress (61.32 MPa vs. 63.69 MPa and 58.75 MPa vs. 57.09 MPa) than the SHTS, respectively. The increasing deformation resistance of dynamic precipitation improved the flow stress under smaller strain and dynamic recrystallization decreased the flow stress under high strain, which resulted the opposite phenomena of SHTS.     

基于多尺度卷积特征融合的癫痫脑电信号识别

脑电信号(electroencephalography,EEG)已成为医生诊断神经系统疾病最 广泛使用的工具,实现癫痫EEG的自动识别对 于癫痫患者的临床诊断和治疗具有重要意义。为了提高癫痫EEG的识别精度,提出了一 种基于多尺 度卷积特征融合的癫痫EEG自动识别模型。首先采用多尺度卷积特征融合方法提取多粒 度数据特征, 实现卷积神经网络(convolutional neural network,CNN)中不同层次的信息互补;然后经过长短期记忆网络(long short-term memory network,LSTM)提取时间 特征,利用 softmax分类器给出最终的识别结果。为了评估提出方法的识别性能,在波恩大学癫痫病研 究中心数据集 中进行实验,并与CNN-LSTM模型、单一的LSTM等模型的识别性能进行了比较,实验结果表 明,提出 方法的识别精度明显高于其余方法, 平均可达到99.19%。该模型能够 有效识别癫痫EEG类别,具有较高的识别性能和临床应用潜力。     

煤矸石热活化及相变分析

系统研究了不同温度下热处理活化煤矸石的物相组成和活性组分溶出的变化规律.用差热分析、X射线衍射、红外光谱、核磁共振、电感耦合等离子原子发射光谱和扫描电镜等仪器测试分析煤矸石原矿和不同煅烧温度制备的样品的矿物组成、分子结构、29Si和27Al化学位移、活性Si4 和Al3 溶出量及微观结构.结果表明:煤矸石的活化程度随不同温度下矿物相组成及铝配位情况的变化而改变.连续性的相转变与活性硅、铝的溶出量相对应.     

C_9闪蒸油加氢及切割分馏

裂解C9馏分作为裂解乙烯的副产物,可以采用成熟的加氢技术及精馏技术,生产市场需求量大且附加值较高的芳烃溶剂油及高辛烷值汽油调和组分,对于提高C9装置的整体效益以及C9原料的深加工利用都具有十分重要的意义。