Geometric surface patches without twist constraints

An interpolation scheme which assumes position values, derivatives and curvature values on the boundary of an arbitrary triangle is presented. The development of this interpolant is based upon univariate interpolation using a geometric Hermite-operator along line segments joining a vertex and a side.     

Complex dynamics through fuzzy chains

This paper gives a new contribution to characterize a class of complex systems build as arrays of coupled fuzzy logic based chaotic oscillators and investigates their dynamical features. Different spatio-temporal dynamics have been reproduced using interconnected fuzzy chaotic cells in order to study the effects, due to the variation of some parameters and network topologies, in the collective behavior and to highlight the synchronization capability of the complex fuzzy systems under consideration. The synchronization characteristics have been focused by defining a behavioral index.     

利用空间几何信息的改进PMVS算法

基于多视图像的立体重建是计算机视觉的核心问题之一. 由Furukawa提出的PMVS算法是目前为止表现最好的多视立体重建算法之一. 但该算法仍存在一些不足.一方面, PMVS不能保证重建表面的几何形状与重建 面片法向保持好的一致性, 特别是在一些特定拍摄角度下,如大场景重建经常 碰到的俯仰拍摄,情况尤为严重.另外, PMVS算法时间和空间复杂度高,特别是在 利用高分辨率图像重建时,往往要付出巨大的时间和空间代价.针对这些不足, 本文提出了一种基于空间几何信息的面片调整和多分辨率分层扩散重建的改进 策略,一方面提高了重建精度和表面的光滑性,另一方面,在尽量保持场景细节 的同时,提高了重建效率.文中的实验证实了改进策略的有效性和实用性.     

松弛状态圆截面螺旋细杆的弹性波传播

研究松弛状态下的圆截面弹性螺旋细杆,即带有原始曲率和挠率的非圆截面弹性杆的动力学问题.基于Kirchhoff动力学比拟,建立欧拉角表达的弹性杆动力学方程.考虑截面的线加速度和角加速度的惯性效应.在一次近似意义下讨论松弛状态圆截面螺旋杆的静态和动态稳定性.证明在空间域内保持静态稳定,在波数大于1条件下亦满足时域内的动态稳定性条件.讨论弯扭变形弹性波在螺旋杆内的传播,导出波速与波数之间的对应关系.     

Inter-organizational relationships and the flow of information through value chains

I developed a framework that can identify types of inter-organizational relationships. Various kinds of information exchanged between trading partners were grouped into two broad types: transactional and managerial. I then examined the effects of inter-organizational information systems (IOS) and traditional communication media (TCM) on the amount of information exchanged. Stepwise regression analyses showed that the use of value chains was the most significant factor influencing the exchange of both types of information. In examining the impact of the information exchanged to improve production performance, it appeared that different kinds of information influenced different aspects. Depending on the usage level of the media and the types of information exchanged, four categories of inter-organizational relationships and their particular characteristics were defined: traditional links for coordination, strategic alliances, electronic links for coordination, and virtual organizations.     

Axis-coupled trajectory generation for chains of integrators through smoothing splines

Integrator based model is used to describe a wide range of systems in robotics. In this paper, we present an axis-coupled trajectory generation algorithm for chains of integrators with an arbitrary order. Special notice has been given to problems with pre-existing nominal plans, which are common in robotic applications. It also handles various type of constraints that can be satisfied on an entire time interval, including non-convex ones which can be transformed into a series of convex constraints through time segmentation. The proposed approach results in a linearly constrained quadratic programming problem, which can be solved effectively with off-the-shelf solvers. A closed-form solution is achievable with only the boundary constraints considered. Finally, the proposed method is tested in real experiments using quadrotors which represent high-order integrator systems.     

Diagnosis of multi-operational machining processes through variation propagation analysis

It is a very challenging task to develop effective process control methodologies for multi-operational manufacturing processes. Although Statistical Process Control (SPC) has been widely used as the primary method in the control of quality, it mainly serves as a change detection tool rather than a method to identify root causes of process changes. This paper proposes a systematic approach to overcome the limitations faced by SPC. In this method, a state space variation propagation model is derived from the product and process design information. The virtual machining concept is applied to isolate faults between operations, and further used in the root cause determination. The detailed methodology is presented, and a case study is conducted to illustrate and verify the developed diagnosis method.     

Laser beams propagation through photopolymerizable composite containing non-polymerizable component

The process of optical formation of dielectric waveguiding structures in transparent photo-polymerizable composition containing non-polymerizable component is considered. It is shown, that using NC does not break modes of initiating radiation self-channeling, and allows to create stable graded-index polymeric structures. We discuss results of studying of diffusion and nonlinear wave processes in liquid photopolymerizable mediums occurring under the influence of optical radiation.     

Coordinating static and dynamic supply chains with advertising through two-part tariffs

Zaccour (2008) analyses a marketing channel where firms invest in advertising to increase brand equity, showing that an exogenous two-part tariff cannot replicate the vertically integrated performance. I revisit the model proving that a multiplicity of efficient franchising contracts exists. I characterise an optimal two-part tariff specified as a linear function of the upstream firm’s advertising effort, performing this task both in the static and in the dynamic games. An analogous result emerges both in the static game, writing the fixed component of the two-part tariff as a non-linear function of the manufacturer’s advertising effort, and in the dynamic game, using a contract which is linear in the brand equity.     

Combating Web spam through trust–distrust propagation with confidence

Semi-automatic anti-spam algorithms propagate either trust through links from a set of good seed pages or distrust through inverse-links from a set of bad seed pages to the entire Web. It has been mentioned that a combined usage of both trust and distrust propagations can lead to better results. However, little work has been known to realize this insight successfully. In this paper, we view that each Web page has both a trustworthy side and an untrustworthy side, and propose to assign two scores for each Web page to denote its trustworthy side and untrustworthy side, respectively. We then propose the Good-Bad Rank (GBR) algorithm for propagating trust and distrust simultaneously from both directions. In GBR, the propagation of a page’s trust/distrust is decided by its probability of being trust/distrust. GBR takes advantages from both trust and distrust propagations, thus is more powerful than propagating only trust or distrust. Experimental results show that GBR outperforms other typical link-based anti-spam algorithms that propagates only trust or distrust. GBR achieves comparable performance than another algorithm that propagates both trust and distrust, TDR, but is much more efficient than TDR.     

The propagation of whole plant oscillations through a chemical process plant

The change in harmonic content of oscillations as they propagate through a plant is modelled by examining ratios of observed signals. Heuristics are then proposed to enable these models to be characterised without recourse to detailed plant identification. This results in a harmonic-content based procedure to isolate the source of an oscillation. The procedure is tested on bi-amplitude ratio data generated from measurements obtained from a real industrial plant.     

Acceleration of the back propagation through dynamic adaptation of the learning rate

Standard backpropagation, as with many gradient based optimization methods converges slowly as neural networks training problems become larger and more complex. In this paper, we present a new algorithm, dynamic adaptation of the learning rate to accelerate steepest descent. The underlying idea is to partition the iteration number domain into n intervals and a suitable value for the learning rate is assigned for each respective iteration interval. We present a derivation of the new algorithm and test the algorithm on several classification problems. As compared to standard backpropagation, the convergence rate can be improved immensely with only a minimal increase in the complexity of each iteration.     

共形几何代数与几何不变量的代数运算

几何不变量的使用是计算机视觉和图形学的一个重要手段.发现一个不变量后,如何找到它与其他不变量的关系,是实际应用中的一个重要问题,这种关系的探讨主要依靠在不变量层次上的代数运算.文中介绍了共形几何代数中的基本、高级和有理不变量如何在几何问题中自然出现,它们之间如何进行代数运算,以及如何通过不变量的化简,自然地得到几何条件的充分必要化和几何定理的完全化.几何定理的机器证明作为几何定理完全化的副产品,被发展成几何定理的关系定量化,这种量化的几何还原就是几何定理的自然推广.几何不变量之间的几何关系的计算是这些技术的一个具体应用.     

Inverse propagation of uncertainties in finite element model updating through use of fuzzy arithmetic

A fuzzy finite element model updating (FFEMU) method is presented in this study for the damage detection problem. The uncertainty caused by the measurement noise in modal parameters is described by fuzzy numbers. Inverse analysis is formulated as a constrained optimization problem at each α-cut level. Membership functions of each updating parameter which correspond to reduction in bending stiffness of the finite elements is determined by minimizing an objective function using a hybrid version of genetic algorithms (GA) and particle swarm optimization method (PSO) which is very efficient in terms of accuracy and robustness. Practical evaluation of the approximate bounds of the interval modal parameters in FFEMU iterations is addressed. A probabilistic analysis is performed using Monte Carlo simulation (MCS) and the results are compared with presented FFEMU method. It is apparent from numerical simulations that the proposed method is well capable in finding the membership functions of the updating parameters within reasonable accuracy. It is also shown that the results obtained by FFEMU are in good agreement with the MCS results while FFEMU is not as computationally expensive as the MCS method. Nevertheless, the proposed FFEMU do not required derivatives of the objective function like existing methods except in the deterministic case.     

Assessment and propagation of uncertainties in input terms through an ocean-color-based model of primary productivity

Net primary productivity (NPP) fields, derived from satellite observations of ocean color, are commonly published without relevant information on uncertainties. In this study, we assessed the uncertainty in NPP estimates of the Vertically Generalized Productivity Model using a Monte Carlo approach. We did not consider the uncertainty stemming from the basic model formulation, but restricted the uncertainty analysis to input terms, which were generated by, or related to, remote sensing. The study was based on global monthly remote sensing data from 2005. We found that the typical distribution of uncertainty around the model output could be approximated by a lognormal probability density function. On average, NPP value in a grid cell was overestimated by 6%, relative to the mean of the corresponding uncertainty distribution. The random component of uncertainty in NPP, expressed as the coefficient of variation, amounted to an average of 108%. The systematic positive errors in individual grid cells built up to an overestimate of 2.5 Pg C in the annual global NPP of 46.1 Pg C. The largest individual contributor to the random uncertainty in NPP was the input term that describes the physiological state of phytoplankton. However, the biggest contribution to the systematic uncertainty in the model output came from the parameter that represents changes in the rate of chlorophyll-normalized photosynthesis with depth. Therefore, improvements in the accuracy of these two terms would have the largest potential to decrease the input-related uncertainty in the model NPP estimates.     

Back propagation through adjoints for the identification ofnonlinear dynamic systems using recurrent neural models

In this paper, back propagation is reinvestigated for an efficient evaluation of the gradient in arbitrary interconnections of recurrent subsystems. It is shown that the error has to be back-propagated through the adjoint model of the system and that the gradient can only be obtained after a delay. A faster version, accelerated back propagation, that eliminates this delay, is also developed. Various schemes including the sensitivity method are studied to update the weights of the network using these gradients. Motivated by the Lyapunov approach and the adjoint model, the predictive back propagation and its variant, targeted back propagation, are proposed. A further refinement, predictive back propagation with filtering is then developed, where the states of the model are also updated. The convergence of this scheme is assured. It is shown that it is sufficient to back propagate as many time steps as the order of the system for convergence. As a preamble, convergence of online batch and sample-wise updates in feedforward models is analyzed using the Lyapunov approach.     

Computer-Aided Construction of Finite Geometric Spaces: Automated Verification of Geometric Constraints

The category of noncommutative geometric spaces is a rather new and wide field in geometry that provides a rich source of hard computer applications. In this contribution we give a short summary of the basic notions of geometric spaces. The so-called parallel map that describes a space will play a fundamental role because, in terms of the parallel map, a geometric space can be represented in such a way that geometric conditions/axioms (which form the structure of a space) are expressible by certain equations. To verify a configuration amounts to showing the solvability of a corresponding equation or a system of equations, respectively. This is a computational aspect that opens the whole field naturally to computer applications by means of automated deduction in geometry, verification of geometric constraints, computer-aided construction of finite geometries. We give motivation why we use specific declarative programming languages for doing all the implementations and computer applications.     

基于几何配准的三维模型几何比对方法研究

针对设计师在进行协同建模时无法快速查看模型变更信息的问题,提出了快速比 对两个模型几何差异的方法。首先,通过等步长采点获取两个模型的点云数据;然后,利用主 元分析法计算两个点云的特征向量从而获取点云的参考坐标系,推导两个点云参考坐标系的坐 标变换,将两个点云调整到一致,即可实现点云的初始配准;最后,利用最近点迭代法对两个 点云进行精确配准,记录配准后两个点云中的非重叠区域,可获取两个点云的几何差异区域。 测试结果表明该方法可以有效识别两个模型的几何差异。     

Stability-beta limit of helical equilibria

Investigation of helical, net longitudinal currentless equilibria with the help of the high-n number ballooning criterion and with the 2D spectral code HERA of m = 1, 2, 3 (2m poloidal node number) internal and external modes suggests that the MHD stability limit of helical equilibria exceeds 〈β〉 = 0.1.