Hera and other extensions of Erato

The MHD stability code ERATO has been modified in order to study helically symmetric equilibria. The resulting new code is called HERA. A new formulation to calculate the vacuum contribution has been added to the spectral codes ERATO and HERA. The finite hybrid element approach is equivalent to that in the plasma region. The stability problem including a conducting wall is now done in one step. The fast angular variation of high n modes has been eliminated by a change of variables. With this new quasi-mode representation it is possible to study unstable modes with nq values up to 1000 in the case of high β, high shear equilibria. It applies equally well to internal and external modes.     

Chaos control of a bounded 4D chaotic system

This paper is concerned with the problem of optimal and adaptive control for controlling chaos in a novel bounded four-dimensional (4D) chaotic system. This system can display hyperchaos, chaos, quasiperiodic and periodic behaviors, and may have a unique equilibrium, three equilibria and five equilibria for the different system parameters. An optimal control law is designed for the novel bounded chaotic system, based on the Pontryagin minimum principle. Furthermore, we propose Lyapunov stability conditions to control the new bounded 4D chaotic system with unknown parameters by a feedback control approach. Numerical simulations are presented to show the effectiveness of the proposed chaos control scheme.     

Development of a parallelized 2D/2D-axisymmetric Navier–Stokes equation solver for all-speed gas flows

A parallelized 2D/2D-axisymmetric pressure-based, extended SIMPLE finite-volume Navier–Stokes equation solver using Cartesians grids has been developed for simulating compressible, viscous, heat conductive and rarefied gas flows at all speeds with conjugate heat transfer. The discretized equations are solved by the parallel Krylov–Schwarz (KS) algorithm, in which the ILU and BiCGStab or GMRES scheme are used as the preconditioner and linear matrix equation solver, respectively. Developed code was validated by comparing previous published simulations wherever available for both low- and high-speed gas flows. Parallel performance for a typical 2D driven cavity problem is tested on the IBM-1350 at NCHC of Taiwan up to 32 processors. Future applications of this code are discussed briefly at the end.     

Dynamic R&D with strategic behavior

We consider a two-player infinite-horizon discrete-time game where the players invest in R&D in order to develop a new technology to reduce production costs. We compute firms’ equilibrium R&D investment strategy as a function of the level of knowledge in the economy. The latter changes endogenously with firms’ decisions to invest in R&D. We show that firms do not invest in R&D if the knowledge level is too low, while both firms do R&D when the level of knowledge is high. However, there is an intermediate knowledge region where there are two pure Nash equilibria: either no firm does R&D or both firms do R&D. Multiplicity of equilibria leads generally to a challenging selection problem. In our context, it is shown that the case of both firms investing in R&D can be Pareto-dominating for both players. It follows that government actions which allow an economy to increase the level of knowledge above a threshold may be welfare enhancing.     

A parallel multiphase flow code for the 3D simulation of explosive volcanic eruptions

A new parallel code for the simulation of the transient, 3D dispersal of volcanic particles in the atmosphere is presented. The model equations, describing the multiphase flow dynamics of gas and solid pyroclasts ejected from the volcanic vent during explosive eruptions, are solved by a finite-volume discretization scheme and a pressure-based iterative non-linear solver suited to compressible multiphase flows. The solution of the multiphase equation set is computationally so demanding that the simulation of the transient 3D dynamics of eruptive columns would not be cost-effective on a single workstation. The new code has been parallelized by adopting an ad hoc domain partitioning scheme that enforces the load balancing in the presence of a large number of topographic blocking-cells. An optimized communication layer has been built over the Message-Passing Interface. It is shown that the present code has a remarkable efficiency on several high-performance platforms and makes it possible, for the first time, to simulate fully 3D eruptive scenarios on realistic volcano topography.     

基于二维码和信息隐藏的物流系统隐私保护方案

针对现有物流系统中的用户隐私信息容易泄露的问题,提出了一种基于二维码和信息隐藏的物流系统隐私保护方案。该方案使用信息隐藏技术将用户隐私信息嵌入快递面单上的二维码中,完成对隐私信息的访问权限控制。为了提升用户隐私信息的安全性,在该方案中设计了一种用于二维码的JPEG图像隐写算法。实验结果表明,该算法使在二维码图像中嵌入的用户隐私信息具有较高的抗检测性能,同时不影响载密二维码的正确扫描和解码。使用本文所提方案,在物流系统中具有访问权限的机构或个人才能够获取这些重要的隐私信息,既确保了快件的正确投递,也保障了用户的隐私安全。     

标刻在金属零件上的二维条码识别

直接零件标识(DPM)技术是实现产品标识的重要手段,二维条码技术是其关键技术之一。DPM标识是以金属作为背景用激光在其上面打上二维条码,与印刷品上的二维条码识读相比,基于金属背景下的二维条码识读更为复杂。改进了传统的识别方法,综合运用最大连通域提取、改进的霍夫变换定位边界、基于最大匹配度的网格化分和基于灰度图像的无损信息提取等方法来实现条码图像的粗定位、精定位、校正、条码分割和数据提取。实验表明,本方案对于磨损、轻度污染、畸变及光照不均的金属上的二维条码图像的识读具有较强的抗干扰性,并取得可靠的识读结果。     

Simulation of anomalous transport in tokamaks using the FACETS code

The development of a new parallel framework for integrated modeling of tokamak plasmas is a primary objective of the SciDAC Framework Architecture for Core-Edge Transport Simulations (FACETS) project. The FACETS code will be used to predict the performance of tokamak discharges and to optimize tokamak discharge scenarios. Novel parallel numerical algorithms and solvers have been developed in the FACETS project in order to simulate the multi-scale dynamics of tokamak plasmas. The status of development of modules for anomalous transport in the FACETS code is described in this paper. Mechanisms that are used for coupling 1D anomalous transport in the plasma core together with 2D transport in the plasma edge (in near separatrix and scrape-off-layer regions) are considered. Results of the first verification studies based on predictive modeling of several analytical and experimental equilibria are presented.     

基于改进D*算法的无人机室内路径规划

针对多旋翼飞行器室内无GPS信号时的导航问题,本文采用二维码阵列构建室内定位系统,基于改进D*算法实现无人机室内路径规划,从而实现飞行器在室内的自主导航和避障。基于ArUco二维码设计了地面阵列为无人机提供了全局精确定位信息,使用改进D*算法保证了无人机在飞行过程中能自主进行路径规划和飞行。通过设计实验对改进D*算法进行了数值仿真验证,并在实际无人机的飞行中应用。实验结果证明:所提改进算法较传统D*算法能更好地保证无人机的飞行安全,同时基于二维码阵列的定位方式不但具有较高精度同时成本低易于实现。     

A new relative chain code in 3D

A new chain code to represent 3D discrete curves is proposed. The method is based on a search for relative changes in the 3D Euclidean space, composed of three main vectors: a reference vector, a support vector, and a change direction vector, utilized to obtain a directed simple path in a grid of 26 connected components. A set of rotation transformations is defined in the 3D Euclidean space, and an alphabet of only 25 symbols is required to represent any face, edge or vertex-connected discrete curve. Important properties of this code are found: independence under translation, rotation and mirror transformations, as well as high compression levels. A set of 3D curve-skeletons and digital elevation model data to study the terrain were utilized to prove the proposed code. Compared with the state-of-the-art, our method has more advantages: at first, it represents voxelized paths independently of vicinity, also it gives better representation for the tested objects and detects better the redundant parts. This fact is shown in the entropy calculated for 3D curve-skeletons: our method gives 3.03 bits/symbol, whereas the state-of-the-art method gives 4.35 bits/symbol. On the other hand, our proposed chain code uses 23% less memory than the well known Freeman code of 26 directions. In case of digital elevation models, our method improves memory for 36.1% regarding Freeman code and 10.7% regarding the well known relative code called orthogonal direction change chain code. Finally, average length of the chain code proposed is 14% shorter than the relative code of the state-of-the-art.     

Matrix Cubic Splines for Progressive 3D Imaging

Mathematical theory of matrix cubic splines is introduced, then adapted for progressive rendering of images. 2D subsets of a 3D digital object are transmitted progressively under some ordering scheme, and subsequent reconstructions using the matrix cubic spline algorithm provide an evolving 3D rendering. The process can be an effective tool for browsing three dimensional objects, and effectiveness is illustrated with a test data set consisting of 93 CT slices of a human head. The procedure has been implemented on a single processor PC system, to provide a platform for full 3D experimentation; performance is discussed. A web address for the complete, documented Mathematica code is given.     

Twins: A Practical Vision-based 3D Mouse

A novel scheme is introduced that uses a mirror and a single camera to restore the 3D position of a finger tip. The camera is positioned in such a way that it captures both the hand as well as its mirror image. The captured images are then processed to extract the contour of the hand. This extraction process is done using a fast algorithm that integrates Bayesian estimation in the traditional chain code generation algorithm. The algorithm works well with a complex, albeit fixed, background. In addition, we have integrated the smoothness assumption into the algorithm so as to obtain a smoother hand contour, thus improving the accuracy of our tracking process. Tolerance to noise can be improved by utilizing the constraints imposed by our system setting to eliminate false signals. A prototype system has been implemented and the performance of the 3D mouse before different backgrounds has been analysed.     

A study on automatic on-machine inspection system for 3D modeling and measurement of cutting tools

A 3D model of the maximum rotating envelope of a milling cutter with tool holder is required for Computer Aided Manufacturing (CAM) process design and machining simulation. The user may define the 3D model of the whole tool assembly in the tool library of CAM software. However, it is not convenient and reliable. Considering these problems, a new method based on single view 3D reconstruction algorithm has been proposed in previous research work, which is able to quickly reconstruct the 3D model of a cutter with tool holder while they are installed onto the spindle. As the extension of this work, this paper focuses on the recent progresses in order to improve the automation, accuracy, efficiency and reliability of tool modeling system. First, an improved flexible on-machine camera calibration procedure is proposed. The accurate motion of machine tool axis is used to calibrate the camera on machine tool instead of a physical calibration board. The whole procedure of calibration can be conducted automatically by running NC code. Therefore, the automation of vision system can be guaranteed. Second, the contour extraction module is improved by using a method of silhouette image composition. This method is applied to solve the problem of translucent and fuzzy cutter profile induced by motion blur. Third, the new algorithm for contour partitioning and classification are proposed, which is more reliable and robust. The reliability and accuracy of the vision system can be guaranteed. Finally, the vision system with an 8 mm lens and 1 mm extensions has been tested on different type of machine tool with smaller cutters. The average measurement accuracy is about 35 microns verified by comparison with a commercial tool setting system.     

A new 3D parallel SPH scheme for free surface flows

We propose a new robust and accurate SPH scheme, able to track correctly complex three-dimensional non-hydrostatic free surface flows and, even more important, also able to compute an accurate and little oscillatory pressure field. It uses the explicit third order TVD Runge-Kutta scheme in time, following Shu and Osher [Shu C-W, Osher S. Efficient implementation of essentially non-oscillatory shock-capturing schemes. J Comput Phys 1988;89:439-71], together with the new key idea of introducing a monotone upwind flux for the density equation, thus removing any artificial viscosity term. For the discretization of the velocity equation, the non-diffusive central flux has been used. A new flexible approach to impose the boundary conditions at solid walls is also proposed. It can handle any moving rigid body with arbitrarily irregular geometry. It does neither produce oscillations in the fluid pressure in proximity of the interfaces, nor does it have a restrictive impact on the stability condition of the explicit time stepping method, unlike the repellent boundary forces of Monaghan [Monaghan JJ. Simulating free surface flows with SPH. J Comput Phys 1994;110:399-406]. To asses the accuracy of the new SPH scheme, a 3D mesh-convergence study is performed for the strongly deforming free surface in a 3D dam-break and impact-wave test problem providing very good results.Moreover, the parallelization of the new 3D SPH scheme has been carried out using the message passing interface (MPI) standard, together with a dynamic load balancing strategy to improve the computational efficiency of the scheme. Thus, simulations involving millions of particles can be run on modern massively parallel supercomputers, obtaining a very good performance, as confirmed by a speed-up analysis. The 3D applications consist of environmental flow problems, such as dam-break flows and impact flows against a wall. The numerical solutions obtained with our new 3D SPH code have been compared with either experimental results or with other numerical reference solutions, obtaining in all cases a very satisfactory agreement.     

二维彩色条码打印系统软件的设计与实现

介绍了利用VB设计并实现的一种二维彩色条码的打印系统。该彩色条码相对于传统的黑白条码在第三维增加了信息容量,实现了在条空横向宽度、条空纵向排列和条空颜色三方面传载信息,可得到远大于目前黑白条码的容量。文中对编码软件系统框架进行整体介绍,实现了条码码字集的编码入库,二维彩色条码字符的打印及条码模块属性设置等关键技术,并附有关键代码。通过对软件系统的测试,效果良好。表明该二维彩色条码编码系统实现了比二维条码更高的信息容量和信息密度,具有广泛的应用前景。     

基于Direct 3D的3维自由立体显示软件双视点设置

如何生成具有适当水平位差的左右眼平面图片是自由立体显示软件设计的核心问题。针对该问题，首先以双眼能够舒适地融合显示屏上的最大水平位差为依据，在Microsoft Direct 3D构建的3维模型空间体系内，寻找模型空间的视点与显示屏上水平位差之间的理论关系；然后，以视者在真实空间浏览3维模型真实感强、视觉舒适为原则来确定模型空间视点位置和投射表面平移量；最后，还提出了调整立体视觉效果的参数，并阐述了它们对立体视觉效果的影响机制。该研究成果已经投入使用，并获得了理想的立体视觉效果。     

基于二维码的数据传输系统设计

基于二维码的数据传输系统面向涉密场景,旨在实现涉密信息系统之间的自动数据传输。文中设计了涉密信息系统之间的数据通信流程,即发送端将传输数据按二维码帧容量切分为多帧,按序合成并显示二维码图像序列,接收端使用摄像头等设备采集二维码图像信息,合成传输数据,并按预定规则对接收情况进行反馈,完成收发两端之间的数据通信。与现有采用人工交互或安全铰链设备的方案相比,基于二维码的数据传输系统解决了自动化程度低、传输效率低、设备昂贵等问题,实现了网络隔离条件下自动高效的数据传输,适用于涉密信息系统中具有较高时效性要求的信息交互。