动态饱和鉴相鉴频器

在鉴相鉴频器的复位路径中插入可变延迟单元,利用反馈动态调节延迟时间,可消除死区并且不受环境变化的影响;采用多级鉴相鉴频器,可扩展鉴相鉴频器的工作范围,改善输入输出的非线性,提高鉴相鉴频性能。文章综合两者的优势,提出了一种动态饱和鉴相鉴频器,并把其应用在锁相环中,结果表明该电路在增加的功耗开销小于0.44%的情况下,使得锁相环的锁定时间减小了14%。     

Separation of nanocolloids driven by dielectrophoresis: A molecular dynamics simulation

The nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separation of colloids driven by dielectrophoresis (DEP) could be seen clearly under a strong electric field at low temperatures. Analyzing the ratio of DEP velocities of colloids to thermal velocities of neutral solvent particles showed that when the ratio was correspondingly big, collision between colloids and solvent particles would be intense, making the DEP velocity of colloids fluctuate frequently. By changing the electric field strength, it was found that the enhancement of electric field strength would quicken the separation of colloids. But when the electric field strength increased to a certain degree, the separation motion would be slow because of the strong friction resistance of the solvent particles to the colloids. Moreover, studying the separation reason of colloids based on the potential energy showed that after colloids were polarized, the attractive potential energy among the colloids would be weaker than before, while the increase of temperature would reduce the attractive potential energy and increase the repulsive potential energy, which accorded with the DLVO theory. Supported by the National Hi-Tech Research and Derelopment Program of China (“863” Project) (Grant No. 2006AA04Z351) and the National Natural Science Foundation of China (Grant Nos. 50675033, 30770553)     

Rapid prediction method for nonlinear expansion process of medical vascular stent

A neural network model with high nonlinear recognition capability was constructed to describe the relationship between the deformation impact factors and the deformation results of vascular stent.Then,using the weighted correction method with the attached momentum term,the network training algorithm was optimized by introducing learning factor η and momentum factor ψ,so the speed of the network training and the system robustness were enhanced.The network was trained by some practi-cal cases,and the statisti...     

煤矿工作面无线全覆盖通信系统设计

根据煤矿工作面无线通信的需求,分析了现有工作面有线通信和无线通信技术的优缺点,提出了一种基于无线网状网和ZigBee技术的煤矿工作面无线全覆盖通信系统设计方案,并介绍了综合基站和WiFi网关的设计。测试结果表明,该系统能够满足工作面数据、语音、视频等不同信息的无线传输需求,实现了工作面无线信号的全覆盖。     

Fractional partial differential equation denoising models for texture image

In this paper,a set of fractional partial differential equations based on fractional total variation and fractional steepest descent approach are proposed to address the problem of traditional drawbacks of PM and ROF multi-scale denoising for texture image.By extending Green,Gauss,Stokes and Euler-Lagrange formulas to fractional field,we can find that the integer formulas are just their special case of fractional ones.In order to improve the denoising capability,we proposed 4 fractional partial differential equation based multiscale denoising models,and then discussed their stabilities and convergence rate.Theoretic deduction and experimental evaluation demonstrate the stability and astringency of fractional steepest descent approach,and fractional nonlinearly multi-scale denoising capability and best value of parameters are discussed also.The experiments results prove that the ability for preserving high-frequency edge and complex texture information of the proposed denoising models are obviously superior to traditional integral based algorithms,especially for texture detail rich images.     

VB与Matlab混合编程在梯度胶片制作中的应用

在梯度胶片制作系统的设计中,为了完成制胶系统上位机数据计算、图形显示、系统管理软件的设计,采用Matlab函数根据采样数据合出步进电机进给控制曲线,结合VB将曲线和数据显示在人机交互界面上,将所计算的参数提供给下位控制系统,系统通过曲线插补计算对步进电机进行控制来完成胶片制作.经实践检验,这种方法所设计的监控程序功能完善、界面良好、操作方便.     

油气井钻进钻铤进动特性仿真研究

油气井钻进破岩过程发生于地下几千米,难以获取井底钻具组合的运动状态.井底钻具组合与岩石的相互作用产生多种形式的振动及振动的耦合.为进一步研究破岩引发钻进中振动的产生机理,建立了井底钻具组合钻铤段非线性动力学模型,通过数值仿真,分析了破岩过程中转速、钻井液、井底钻具组合偏心距、摩擦等对钻铤段旋转进动的影响.数值研究表明,系统参数的变化导致井底钻具组合进动轨迹的多样性和不可预测性;井底钻具组合受到外力作用,导致钻铤进动出现混沌;钻进过程中钻铤与井壁间会发生周期性碰摩现象,为研究钻进引发钻柱黏滑振动提供新的研究思路.     

结合CNN与双向LSTM的心律失常分类

心律失常是心血管疾病中常见的病症之一,实现心律失常的自动分类对心血管疾病的诊治具有重要意义.基于一维心电信号的心律失常分类方法以若干节拍作为输入,通过模型提取特征并用于分类.针对现有方法预处理时间成本高以及未按医疗仪器促进协会(AAMI)标准分类等问题,提出了一种基于原始一维心电信号并按照AAMI推荐标准类别进行心律失常自动分类的方法.该方法首先利用卷积神经网络(CNN)学习心电信号的形态特征,之后通过双向长短期记忆网络(BLSTM)获取特征中的上下文依赖关系,最后借助softmax函数完成分类任务.方法采用mish函数作为激活函数,使得模型在训练中更为稳定.在公开数据库MIT-BIH上进行五折交叉验证,评估结果达到了99.11％的平均准确率,表明该模型可以有效地提取心电信号的特征,适用于监测系统中心律失常疾病的诊断.     

Effects of CaO and Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the reduction of high silicon iron ores

The effects of CaO and Na₂CO₃ on the reduction of high silicon iron ores at 1 250 °C were studied. The experimental results showed that the metallization rate was significantly hindered by the addition of CaO and Na₂CO₃, particularly at the early stage of roasting, compared to the rate without additives. In the absence of additives, iron oxides were quickly reduced to metallic iron, and fayalite was difficult to form. When CaO and Na₂CO₃ were added, the low reducible iron-containing silicate compounds formed and melted, subsequently retarding the metallization process. The inhibition of Na₂CO₃ was more noticeable than that of CaO, and higher Na₂CO₃ doses resulted in stronger inhibition of the increased metallization rate. However, when Na₂CO₃ was added prior to CaO, the liquid phase formed, which facilitated the growth of the metallic phase. To reinforce the separation of the metallic phase and slag, an appropriate amount of liquid phase generated during the reduction is necessary. It was shown that when 10% CaO and 10% Na₂CO₃ were added, a high metallization rate and larger metallic iron particles were obtained, thus further decreasing the required Na₂CO₃ dosage.     

Probabilistic and interval reliability design of the composite pressure vessel

Considering the randomness or interval character of physical parameters and applied loads of composite pressure vessels (COPV), the COPV reliability-analyzing model is built. And then the computational expressions for the mean value, standard deviation and deviation of fiber stress are deduced by the random factor method. The probabilistic and interval reliability designs on COPV are implemented by utilizing the probabilistic method and interval method combined with the improved particle swarm optimization (PSO) algorithm, respectively. The influence of fluctuation of structure uncertain parameters on COPV design thickness is inspected. Finally, examples are given to demonstrate that both probabilistic and interval reliability methods can satisfy the safety requirement and both are of higher rationality than the traditional safety factor method. And probabilistic method has a lower relative error but a higher computational complexity contrasted with the interval method.