非接触式章动减速电机一体化设计

针对电机和章动减速传动机构分体使用状态下,存在着结构不紧凑、使用不便利的问题,提出并设计一种非接触式章动减速电机。该设计是探索部分零件共用实现非接触式章动传动机构与直流电机有机融合,达到进一步减少等效轴向尺寸、部分零件的目的。采用三维建模软件完成三维模型信息构建、虚拟装配等,为3D打印快速制作和调试样机提供了保证,最后对样机进行减速比实验。结果表明,该减速电机减速比稳定,也为机电集成设计提供了一种思路。     

Parametric design of a part with free-form surfaces

INTRODUCTION A 3D solid model is used in various processes such as design, engineering evaluation, drafting, manufacturing, and so on. It is a time-consuming and skill-required job to create a complicated 3D solid model. Most commercial CAD tools support func- tions to generate engineering drawings from solid models automatically. However, adjusting layouts, dimensioning, and inserting annotations are required and they are tedious and time-consuming work. Most current CAD/CAM/CAE so…     

Pattern design on 3D triangular garment surfaces

This paper focuses on a pattern design method for a 3D triangular garment surface. Firstly, some definitions of 3D style lines are proposed for designing the boundaries of patterns as drawing straight lines or splines on the triangular surface. Additionally some commonly used style lines are automatically generated to enhance design efficiency. Secondly, after style lines are preprocessed, a searching method is presented for quickly obtaining the boundaries and patches of a pattern on the 3D trian- gular surface. Finally a new pattern design reuse method is introduced by encoding/decoding the style line information. After style lines are encoded, the pattern design information can be saved in a pattern template and when decoding this template on a new garment surface, it automates the pattern generation for made-to-measure apparel products.     

基于Solidworks三维建模的制图测绘教学改革探索

针对高职院校机械类专业开设的制图测绘实训课程,分析了目前制图测绘教学中出现的学生忽视测量准确性、零部件表达不准确、疲于完成图纸绘制等问题,提出了将三维建模引入制图测绘教学,利用三维模型与二维图纸的转换提升零部件表达的准确性、利用三维装配来约束零件尺寸测量的准确性,同时由三维模型直接生成二维工程图,大大提高了绘图的速度和准确度,也符合现代设计理念。     

RA码编译码算法

本文介绍了重复累积码 -RA码 ,该码分为规则RA码和不规则RA码 .RA码具有线性时间编码算法 .使用积和译码算法 ,可以实现线性时间译码 .本文对RA码的编译码算法进行了分析 ,并进行了系统仿真 .仿真结果表明 ,随着信息长度的增加 ,系统的误码率降低 ,性能接近信道容量 .     

基于投影图与直方图的机械零件模型检索

为实现资源重复利用与产品创新,通过检索出数据库中的相似零件给设计者提供帮助。首先对机械零件模型进行方位归一化与预处理,以起始点为圆心作最大内切圆,划分连通区,在连通区内根据距离变换值判定邻域像素,进而确定新的骨架点,迭代生成完整骨架。将骨架转换成直方图曲线,划分网格生成骨架点数矩阵,根据矩阵特征值和之间的差计算两模型间的差异度,从而判定机械零件相似度。通过实例验证以及与 D2形状分布算法及递归分割算法的比较,该方法检索速度高于递归分割算法,准确性高于 D2 形状分布算法和递归分割算法。     

A level set based segmentation approach for point-sampled surfaces

Segmenting a complex 3D surface model into some visually meaningful sub-parts is one of the fundamental problems in digital geometry processing. In this paper, a novel segmentation approach of point-sampled surfaces is proposed, which is based on the level set evolution scheme. To segment the model so as to align the patch boundaries with high curvature zones, the driven speed function for the zero level set inside narrow band is defined by the extended curvature field, which approaches zero speed as the propagating front approaches high curvature zone. The effectiveness of the proposed approach is demonstrated by our ex- perimental results. Furthermore, two applications of model segmentation are illustrated, such as piecewise parameterization and local editing for point-sampled geometry.     

一种三维数值方法及其应用分析

为了提高包含有交界面的三维复杂流动问题的求解精度，将二维坐标系中的Youngs算法公式推广到三维坐标系应用，根据流体体积分数的定义，在二维直角坐标系Youngs算法的基础上，把介质分界面近似为平面，通过引入修正系数，实现了Youngs算法在三维坐标系中的应用，给出计算方法，并编写程序进行算例验证，数值模拟了具有复杂边界的空中爆炸形成冲击波的形成和传播过程，通过数值试验，证明了Youngs算法在三维坐标系中成功的应用．     

一种改进的快速分形图像压缩编码算法

在深入分析PIFS分形图像压缩编码原理的基础上,明确了影响分形编码速度的四个因素,分别针对各因素提出了改进方法。实验证明本文方法在提高编码速度和压缩比方面是有效的。     

基于EXIT图的TET-LDPC码优化分析

两边类型低密度奇偶校验码（ two-edge type low density parity check, TET-LDPC码）是一种高效的信道纠错码,其性能受到删余变量节点度（ punctured variable node degree, PVN度）的影响。为了分析PVN度对TET-LDPC码纠错性能的影响,基于外信息转移图（ extrinsic information transfer, EXIT图）估算了TET-LDPC码在不同PVN度情况下的门限值,利用门限值的好坏来分析纠错性能的优劣,进而通过选取门限值好的PVN度优化TET-LDPC码。仿真结果显示,经过EXIT图优化的TET-LDPC码具有更好的纠错性能。利用EXIT图优化分析TET-LDPC码的方法,比现有的仿真试值法更加简捷、直观。     

单校验码为子码的多维Turbo乘积码性能分析

Turbo乘积码是一类易于硬件实现高速迭代译码的分组码,本文对单校验码为子码的高维Turbo乘积码的软输入软输出迭代译码算法进行了详细的分析。进而将其与QAM调制结合起来,提出了一种简化的、便于硬件实现的联合解调译码方案,充分利用了高维Turbo乘积码优越的纠错性能。仿真结果表明这种简化方案在高斯和衰落信道下的译码性能很好。     

Human motion recognition using ultra-wideband radar and cameras on mobile robot

Cameras can reliably detect human motions in a normal environment, but they are usually affected by sudden illumination changes and complex conditions, which are the major obstacles to the reliability and robustness of the system. To solve this problem, a novel integration method was proposed to combine bi-static ultra-wideband radar and cameras. In this recognition system, two cameras are used to localize the object’s region, regions while a radar is used to obtain its 3D motion models on a mobile robot. The recognition results can be matched in the 3D motion library in order to recognize its motions. To confirm the effectiveness of the proposed method, the experimental results of recognition using vision sensors and those of recognition using the integration method were compared in different environments. Higher correct-recognition rate is achieved in the experiment.     

基于自动生成技术的三维动画型微课场景设计

微课作为一种新型的网络学习方式,其理论设计、开发制作以及应用创新是研究热点。当前构建三维动画型微课场景存在制作周期长、工作量大等问题。通过研究场景规划,提出一种基于模型标注与区域布局的场景设计规划方法,包括模型数据处理、预规划与计算实现几个步骤,对模型进行数据预处理与标注存储,通过基于知识的方法推导出场景预规划方案,并对模型位置进行动态计算。实验结果表明,该方法能自动生成三维动画型微课场景,场景模型位置规划正确率达到85%。     

使用试错法加快扩频通信伪随机码捕获

An optimun search algorithm for the coherent acquisition in direct-sequence spread-spectrum （DSSS） receivers is proposed and analyzed in this paper. The system consists of two major parts： a phase region estimator and a phase alignment detector. We use an auxiliary sequence to correlate the incoming signal in the phase region estimator. Since the cross-correlation value between the auxiliary sequence and the incoming PN signal has linear magnitude, and can provide the direction for the phase updating, an optimum search algorithm, try and error method, can be adopted to obtain the phase region information of the incoming signal. The mean acquisition time is derived through the signal flow graph theory. The time is compared with that of the conventional serial search scheme, and the results show that the proposed scheme can achieve coarse acquisition significantly faster than the conventional scheme.     

An immune-tabu hybrid algorithm for thermal unit commitment of electric power systems

This paper presents a new method based on an immune-tabu hybrid algorithm to solve the thermal unit commitment （TUC） problem in power plant optimization. The mathematical model of the TUC problem is established by analyzing the generating units in modem power plants. A novel immune-tabu hybrid algorithm is proposed to solve this complex problem. In the algorithm, the objective function of the TUC problem is considered as an antigen and the solutions are considered as antibodies, which are determined by the affinity computation. The code length of an antibody is shortened by encoding the continuous operating time, and the optimum searching speed is improved. Each feasible individual in the immune algorithm （IA） is used as the initial solution of the tabu search （TS） algorithm after certain generations of IA iteration. As examples, the proposed method has been applied to several thermal unit systems for a period of 24 h. The computation results demonstrate the good global optimum searching performance of the proposed immune-tabu hybrid algorithm. The presented algorithm can also be used to solve other optimization problems in fields such as the chemical industry and the power industry.     

国家标准下服装标签的应用问题与对策

服装标签是是每件服饰不可或缺的一个组成部分。国家标准对服装标签在内容和安全信息方面都有明确的规定,但当前服装标签应用在真实性和准确性方面仍存在诸多问题,需要通过行政部门完善监管、技术部门加强监测、企业规范生产和消费者重视等对策加以解决。     

Reconstruction of symmetric models composed of analytic curves and surfaces from point cloud

This paper presents a method to reconstruct symmetric geometric models from point cloud with inherent symmetric structure. Symmetry types commonly found in engineering parts, i.e., translational, reflectional and rotational symmetries are considered. The reconstruction problem is formulated as a constrained optimization, where the objective function is the sum of squared distances of points to the model, and constraints are enforced to keep geometric relationships in the model. First, the explicit representations of symmetric models are presented. Then, by using the concept ofparameterized points （where the coordinate components are represented as functions rather than constants）, the distances of points to symmetric models are deduced. With these distance functions, symmetry information, for both 2D and 3D models, is uniformly represented in the process of reconstruction. The constrained optimization problem is solved by a standard nonlinear optimization method. Owing to the explicit representation of symmetry information, the computational complexity of our method is reduced greatly. Finally, examples are given to demonstrate the application of the proposed method.     

The Analysis Method of Time Reversal for Defect Diagnosis of Concealed Structure

本文基于结构声波检测技术及走时反演理论,提出了一种用于隐蔽结构缺陷诊断的走时反演分析方法,建立了联合高差异步测试的波速结构走时反演递推公式．该方法可以对隐蔽结构的波速结构进行网格化反演重建,实现了隐蔽结构的二维波速诊断．并以模型试验进行了验证．     

Iterative Decoding of Parallel concatenated Block Codes and Coset Based MAP Decoding Algorithm for F24 Code

A multi-dimensional concatenation scheme for block codes is introduced.in which information symbols are interleaved and re-encoded for nmore than once.It provides a convenient platform to design high performance codes with flexible interleaver size,Coset based MAP soft-in/soft-out decoding algorithms are presented for the F24 code.Simulation results show that the propsed coding scheme can achieve high coding gain with flexible interleaver length and very low decoding complexity.     

Visual Short‐Term Memory for Complex Objects in 6‐ and 8‐Month‐Old Infants

Infants' visual short‐term memory (VSTM) for simple objects undergoes dramatic development: Six‐month‐old infants can store in VSTM information about only a simple object presented in isolation, whereas 8‐month‐old infants can store information about simple objects presented in multiple‐item arrays. This study extended this work to examine the development of infants' VSTM for complex objects during this same period (N = 105). Using the simultaneous streams change detection paradigm, Experiment 1 confirmed the previous developmental trajectory between 6 and 8 months. Experiment 2 showed that doubling the exposure time did not enhance 6‐month‐old infants' change detection, demonstrating that the developmental change is not due to encoding speed. Thus, VSTM for simple and complex objects appears to follow the same developmental trajectory.