一种Delaunay三角网数模快速定位算法

逐点插入法是构建Delaunay三角网的主流算法之一，在众多三角形中快速定位目标三角形是影响逐点插入法构网速度的一个重要因素，同时也是影响高程内插速度的关键。在分析多种已有定位法特点的基础上提出区域定位法，给出了详细的判断条件，并加以证明。通过对几种定位方法进行分析比较，在两种投点方式下用逐点插入法对四种算法进行了TIN的构网实验，结果表明均匀投点的构网速度都要快于任意投点的构网速度，区域定位法搜索方向唯一，算法稳健，具有较快的定位速度。     

一种基于H.26L的自适应差错掩盖方法

利用解码帧的特征及其相关参数，提出了一种基于H．26L的自适应差错掩盖方法．该方法对不同的差错特征分别采用以下3种掩盖方法：边界匹配(BMA)、空间插值(SI)和频域插值(FI)．与采用单一方法相比，用本方法的仿真结果的主客观质量都显著提高，尤其是在场景转换和剧烈运动的时候。     

蜂窝移动通信系统中信道借用指配策略的优化

分析了蜂窝移动通信系统信道指配策略中的一个重要策略－信用策略,包括最早出现的简单借用策略,到后来在此基础上发展而来的带信道序号的借用策略（ＢＣＯ）和带方向锁定的借用策略（ＢＤＣＬ）。在原指配策略的基础上,增加了共道信道中的被锁定信道在信道表中的位置和处理,澄清了原策略中在这一点上的模糊不清。同时,通过两个方面的措施优化了ＢＣＯ和ＢＤＣＬ算法,仿真结果表明优化的算法可以显著降低原算法的复杂性。     

Joint Tomlinson-Harashima source and linear relay precoder design in amplify-and-forward multiple-input multiple-output two-way relay systems

Existing minimum-mean-squared-error (MMSE) transceiver designs in amplified-and-forward (AF) multiple-input multiple-output (MIMO) two-way relay systems all assume a linear precoder at the sources. Nonlinear source precoders in such a system have not been considered yet. In this paper, we study the joint design of source Tomlinson-Harashima precoders (THPs), relay linear precoder and MMSE receivers in two-way relay systems. This joint design problem is a highly nonconvex optimization problem. By dividing the original problem into three sub-problems, we propose an iterative algorithm to optimize precoders and receivers. The convergence of the algorithm is ensured since the updated solution is optimal to each sub-problem. Numerical simulation results show that the proposed iterative algorithm outperforms other algorithms in the high signal-to-noise ratio (SNR) region.     

Five-Axis Interpolation of Continuous Short Linear Trajectories for 3[PP]S-XY Hybrid Mechanism by Dual Bezier Blending

A novel five-axis real-time interpolation algorithm for 3[PP]S-XY hybrid mechanism is proposed in this paper. In the algorithm, the five-axis tool path for controlling this hybrid mechanism is separated into two sub-paths. One sub-path describes the movement of 3[PP]S parallel kinematic mechanism module, and the other one describes the movement of XY platform. A pair of cubic Bezier curves is employed to smooth the corners in those two sub-paths. Based on the homogenous Jacobian matrix of 3[PP]S mechanism, a relationship between the position errors of every driving joint in hybrid mechanism and the position deviation of the tool tip center point at the moving platform is established. This relationship is used to estimate the approximation error for the corners smoothing according to the accuracy requirement of tool tip center in interpolation. Due to the high computational efficiency of this corner smoothing method, it is integrated into the look-ahead module of computer numerical control(CNC) system to perform online tool path smoothing. By performing the speed planning based on a floating window scheme, a jerk limited S-shape speed profile can be generated efficiently. On this basis, a realtime look-ahead scheme, which is comprised of path-smoothing and feedrate scheduling, is developed to acquire a speed profile with smooth acceleration. A monotonic cubic spline is employed for synchronization between those two smoothed sub-paths in tool path interpolation. This interpolation algorithm has been integrated into our own developed CNC system to control a 3PRS-XY experimental instrument(P, R and S standing for prismatic,revolute and spherical, respectively). A club shaped trajectory is adopted to verify the smoothness and efficiency of the five-axis interpolator for hybrid mechanism control.     

基于混沌系统的量子彩色图像加密算法

为了提高图像安全性,将混沌系统引入到量子图像加密领域. 首先通过Chen混沌将图像按位异或;然后将彩色图像表示为量子的叠加态,通过Logistic混沌序列产生幺正矩阵对量子图像进行置乱;再次产生一个混沌序列对每个像素的红绿蓝三基色进行随机互换,达到对量子图像加密的目的;最后,在经典计算机上进行了模拟实验,结果表明加密后图像直方图更为平滑,像素平均分布在0～255范围内,图像相邻像素相关性低,加密图像红绿蓝像素相关系数平均值分别为0.001 6、0.001 7和0.003 8,并且密钥敏感性高,能有效抵抗穷举攻击和统计攻击,算法具有良好的有效性和可行性.      

An Adaptive Joint Source/Channel Coding Using Error Correcting Arithmetic Codes

An approximately optimal adaptive arithmetic coding (AC) system using a forbidden symbol (FS) over noisy channels was proposed which allows one to jointly and adaptively design the source decoding and channel correcting in a single process, with superior performance compared with traditional separated techniques. The concept of adaptiveness is applied not only to the source model but also to the amount of coding redundancy. In addition, an improved branch metric computing algorithm and a faster sequential searching algorithm compared with the system proposed by Grangetto were proposed. The proposed system is tested in the case of image transmission over the AWGN channel, and compared with traditional separated system in terms of packet error rate and complexity. Both hard and soft decoding were taken into account.     

A New Wireless Packet Scheduling Algorithm Based on EDF and Its Application in Multi-bottleneck Networks

Most of current wireless packet scheduling algorithms aim at resource allocation as fairly as possible or maximizing throughput. This paper proposed a new packet scheduling algorithm that aims at satisfying delay requirement and is the improvement of earliest due first (EDF) algorithm in wired networks. The main idea is to classify the packets based on their delay bound, scheduling the most "urgent" class of user and the users that have the best channel condition with higher priority. This algorithm can easily integrate with common buffer management algorithms, when buffer management algorithm cannot accept new arrival packets, try to modify scheduling policy. Packet scheduling algorithms in multiple bottleneck wireless networks were also discussed. A new variable multi-hop factor was defined to estimate the congestion situation (including channel condition) of future hops. Multi-hop factor can be integrated into packet scheduling algorithms as assistant and supplement to improve its performance in multi-bottleneck wireless networks.     

Five-axis interpolation of continuous short linear trajectories for 3[PP]S-<Emphasis Type="Italic">XY</Emphasis> hybrid mechanism by dual Bezier blending

A novel five-axis real-time interpolation algorithm for 3[PP]S-XY hybrid mechanism is proposed in this paper. In the algorithm, the five-axis tool path for controlling this hybrid mechanism is separated into two sub-paths. One sub-path describes the movement of 3[PP]S parallel kinematic mechanism module, and the other one describes the movement of XY platform. A pair of cubic Bezier curves is employed to smooth the corners in those two sub-paths. Based on the homogenous Jacobian matrix of 3[PP]S mechanism, a relationship between the position errors of every driving joint in hybrid mechanism and the position deviation of the tool tip center point at the moving platform is established. This relationship is used to estimate the approximation error for the corners smoothing according to the accuracy requirement of tool tip center in interpolation. Due to the high computational efficiency of this corner smoothing method, it is integrated into the look-ahead module of computer numerical control (CNC) system to perform online tool path smoothing. By performing the speed planning based on a floating window scheme, a jerk limited S-shape speed profile can be generated efficiently. On this basis, a realtime look-ahead scheme, which is comprised of path-smoothing and feedrate scheduling, is developed to acquire a speed profile with smooth acceleration. A monotonic cubic spline is employed for synchronization between those two smoothed sub-paths in tool path interpolation. This interpolation algorithm has been integrated into our own developed CNC system to control a 3PRS-XY experimental instrument (P, R and S standing for prismatic, revolute and spherical, respectively). A club shaped trajectory is adopted to verify the smoothness and efficiency of the five-axis interpolator for hybrid mechanism control.     

A novel vertical handoff algorithm based on fuzzy logic in aid of grey prediction theory in wireless heterogeneous networks

To coordinate the various access technologies in the 4G communication system, intelligent vertical handoff algorithms are required. This paper mainly deals with a novel vertical handoff decision algorithm based on fuzzy logic with the aid of grey theory and dynamic weights adaptation. The grey prediction theory (GPT) takes 4 sampled received signal strengths as input parameters, and calculates the predicted received signal strength in order to reduce the call dropping probability. The fuzzy logic theory based quantitative decision algorithm takes 3 quality of service (QoS) metric, received signal strength (RSS), available bandwidth (BW), and monetary cost (MC) of candidate networks as input parameters. The weight of each QoS metrics is adjusted along with the networks changing to trace the network condition. The final optimized vertical handoff decision is made by comparing the quantitative decision values of the candidate networks. Simulation results demonstrate that the proposed algorithm provides high performance in heterogeneous as well as homogeneous network environments.     

数控系统插补算法的研究

本文提出了一种用于数控系统的粗、精插补算法,粗插补采用时间分割精确算法,精插补采用参数三次样条插值算法。     

Improvement of efficiency and flexibility in multi-slice helical CT

One of the main aspects in computed tomography (CT) development is to make CT rapidly scan a large longitudinal volume with high z-axis resolution. The combination of helical scanning with multi-slice CT is a promising approach. Image reconstruction in multi-slice CT becomes, therefore, the major challenge. Known algorithms need to derive the complementary data or work only for certain range of pitches. A reconstruction algorithm was presented that works with the direct data as well as arbitrary pitches. Filter interpolation based on the proposed method was implemented easy. The results of computer simulations under kinds of conditions for four-slice CT were presented. The proposed method can obtain higher efficiency than the conventional method.     

基于目的层预约的改进型粒子群电梯群控调度策略

针对单一粒子群算法的派梯策略优化运算过程中容易陷入局部极值点的状况,结合模拟退火理论,提出一种改进型的粒子群电梯群控派梯策略,应用到目的层预约的电梯群控系统中.通过仿真和对比试验可知,基于目的层预约的电梯群控系统能有效地提高服务的各项指标,改进型的粒子群电梯群控调度策略可有效减小乘客候梯时间和电梯启停次数,改善电梯运行性能.     

基于三维高斯混合码本模型的运动目标检测算法

为解决智能视觉监控中码本模型参数调节困难和高斯混合模型概率分布计算的复杂性,提出了一种基于三维高斯混合码本模型的运动目标检测算法.该算法基于RGB空间建立码本模型,然后基于码字中的R、G、B分量建立三维高斯模型,从而使整个码本具有三维高斯混合模型的特征.实验结果表明:该算法具有较高的实时性(该算法的平均帧率约23.0帧/s,而iGMM(improved Gaussian mixture model)算法约9.0帧/s,BM(Bayesmodel)算法约6.2帧/s,CBM(codebook model)算法约10.7帧/s),且具有良好的检测质量.     

分形方法在地形数据内插中的应用

简述了分形、迭代函数系统（ＩＦＳ）及分形布朗运动的基本概念,介绍了基于迭代函数系统和分形布朗运动的分形内插方法,并给出了具体算法和应用实例。     

Accelerating BP-Based Iterative Low-Density Parity-Check Decoding by Modified Vertical and Horizontal Processes

Two modified BP algorithms related to vertical and horizontal processes are proposed to accelerate iterative low-density parity-check (LDPC) decoding over an additive white Gaussian noise (AWGN) channel, where the newly updated extrinsic information is immediately used in the current decoding round. Theoretical analysis and simulation results demonstrate that both the modified approaches provide significant performance improvements over the traditional BP algorithm with almost no additional decoding complexity. The proposed algorithm with modified horizontal process offers even better performance than another algorithm with the modified horizontal process. The two modified BP algorithms are very promising in practical communications since both can achieve an excellent trade-off between the performance and decoding complexity.     

Switching between antenna subset selection and quasi-orthogonal space-time block code in presence of correlation

We address the problem of adaptive modulation and coding scheme (AMCS) for a multi-input multioutput (MIMO) system in presence of time-varying transmitting correlation. Antenna subset selection and quasiorthogonal space-time block code (QOSTBC) have different error performances with different signal-to-noise ratios (SNRs) and in different spatial correlation scenarios. The error performance can be improved by selecting an appropriate transmission scheme to adapt to various channel conditions. The maximum distance criterion is the simplest and very effective algorithm for the antenna subset selection without needs of complex calculation and channel state information at transmitter (CSIT). The minimum error performance criteria and the simplified linear decision strategy are developed for constant transmission rate traffic to select the optimal transmission scheme. It can dramatically decrease algorithm complexity for obtaining error probability according to the known quantities comparing with using instant CSIT. Simulation results show that, remarkable performances including low SNR and weak spatial correlation at the expense of simple calculation and almost no bandwidth loss by adopting AMCS can be achieved. The proposed AMCS improves robustness of slowly varying spatial correlated channels.     

求解旅行商问题的一种新方法

目前关于旅行商问题的启发式算法主要分为两类:环路构造算法和环路改进算法.通过对两类近似算法的深入研究,提出了一种新的方法――简化模型法来求解旅行商问题.该方法通过排序和选择操作得到原网络图的简化模型,对简化模型中的路径进行重构得到旅行商问题的解.通过测试TSPLIB中的实例,表明用简化模型法求解旅行商问题解的质量高、收敛快,时耗小,该算法是实用的.     

A new algorithm to automatically extract the drainage networks and catchments based on triangulation irregular network digital elevation model

A new algorithm to automatically extract drainage networks and catchments based on triangula- tion irregular networks （TINs） digital elevation model （DEM） was developed. The flow direction in this approach is determined by computing the spatial gradient of triangle and triangle edges. Outflow edge was defined by comparing the contribution area that is separated by the steepest descent of the triangle. Local channels were then tracked to build drainage networks. Both triangle edges and facets were considered to con- struct flow path. The algorithm has been tested in the site for Hawaiian Island of Kaho＇olawe, and the results were compared with those calculated by ARCGIS as well as terrain map. The reported algorithm has been proved to be a reliable approach with high efficiency to generate well-connected and coherent drainage networks.     

Joint user and antenna selection for multiuser MIMO downlink with block diagonalization

User selection is necessary for multiuser multiple-input multiple-output (MIMO) downlink systems with block diagonalization (BD) due to the limited free spatial transmit dimensions. The pure user selection algorithms can be improved by performing receive antenna selection (RAS) to increase sum rate. In this paper, a joint user and antenna selection algorithm, which performs user selection for sum rate maximization in the first stage and then performs antenna selection in the second stage, is proposed. The antenna selection process alternately drops one antenna with the poorest channel quality based on maximum determinant ranking (MDR) from the users selected during the first stage and activates one antenna with the maximum norm of projected channel from the remaining users. Simulation results show that the proposed algorithm significantly outperforms the algorithm only performing user selection as well as the algorithm combining user selection with MDR receive antenna selection in terms of sum rate.