10565448
Singularity analysis of the HALF parallel manipulator with revolute actuators
This paper concerns the singularity of the half parallel manipulator, a novel three degrees of freedom (DOFs) mechanism, with revolute actuators. The parallel manipulator, proposed previously, consists of a base plate, a movable platform, and three connecting legs. It has the advantages in terms of only single-DOF joints and high rotational capability. The parallel manipulator has wide application in the fields of industrial robots, simulators, parallel machine tools and any other manipulating devices that high rotational capability is required. The inverse kinematics problem and Jacobian matrices are recalled firstly. And then all possible singularities of the manipulator are analyzed in detail. The results of the paper are very useful for the apprehension and the application of the manipulator.
18685518
A novel 2-DOF parallel mechanism based design of a new 5-axis hybrid machine tool
In this paper, the concept of a new 5-axis hybrid machine tool is proposed. The machine is a tool being with both parallel and serial structures, which is based on a novel 2-DOF parallel platform and serial orientations. The machine tool has advantages in terms of high stiffness, high dexterity, high speed, and being capable of long components manufacturing. The kinematics characteristics, such as inverse and forward kinematics, conditioning indices, of the novel 2-DOF parallel platform are studied. The dimensional synthesis based on the workspace and conditioning indices is presented. The results of the paper are very useful for the design of the hybrid machine tool.
1211146
Multi-hop probing asymptotics in available bandwidth estimation: stochastic analysis
This paper analyzes the asymptotic behavior of packet-train probing over a multi-hop network path P carrying arbitrarily routed bursty cross-traffic flows. We examine the statistical mean of the packet-train output dispersions and its relationship to the input dispersion. We call this relationship the response curve of path P. We show that the real response curve Z is tightly lower-bounded by its multi-hop fluid counterpart F, obtained when every cross-traffic flow on P is hypothetically replaced with a constant-rate fluid flow of the same average intensity and routing pattern. The real curve Z asymptotically approaches its fluid counterpart F as probing packet size or packet train length increases. Most existing measurement techniques are based upon the single-hop fluid curve S associated with the bottleneck link in P. We note that the curve S coincides with F in a certain large-dispersion input range, but falls below F in the remaining small-dispersion input ranges. As an implication of these findings, we show that bursty cross-traffic in multi-hop paths causes negative bias (asymptotic underestimation) to most existing techniques. This bias can be mitigated by reducing the deviation of Z from S using large packet size or long packet-trains. However, the bias is not completely removable for the techniques that use the portion of S that falls below F.
36065326
Learning short multivariate time series models through evolutionary and sparse matrix computation
Multivariate time series (MTS) data are widely available in different fields including medicine, finance, bioinformatics, science and engineering. Modelling MTS data accurately is important for many decision making activities. One area that has been largely overlooked so far is the particular type of time series where the data set consists of a large number of variables but with a small number of observations. In this paper we describe the development of a novel computational method based on Natural Computation and sparse matrices that bypasses the size restrictions of traditional statistical MTS methods, makes no distribution assumptions, and also locates the associated parameters. Extensive results are presented, where the proposed method is compared with both traditional statistical and heuristic search techniques and evaluated on a number of criteria. The results have implications for a wide range of applications involving the learning of short MTS models.
7988049
Word Sense Disambiguation for Cross-Language Information Retrieval
We have developed a word sense disambiguation algorithm, following Cheng and Wilensky (1997), to disambiguate among WordNet synsets. This algorithm is to be used in a cross-language information retrieval system, CINDOR, which indexes queries and documents in a language-neutral concept representation based on WordNet synsets. Our goal is to improve retrieval precision through word sense disambiguation. An evaluation against human disambiguation judgements suggests promise for our approach.
15044185
The Dark Side of Risk (what your mother never told you about Time Warp)
This paper is a reminder of the danger of allowing ``risk'' when synchronizing a parallel discrete-event simulation: a simulation code that runs correctly on a serial machine may, when run in parallel, fail catastrophically. This can happen when Time Warp presents an ``inconsistent'' message to an LP, a message that makes absolutely no sense given the LP's state. Failure may result if the simulation modeler did not anticipate the possibility of this inconsistency. While the problem is not new, there has been little discussion of how to deal with it; furthermore the problem may not be evident to new users or potential users of parallel simulation. This paper shows how the problem may occur, and the damage it may cause. We show how one may eliminate inconsistencies due to lagging rollbacks and stale state, but then show that so long as risk is allowed it is still possible for an LP to be placed in a state that is inconsistent with model semantics, again making it vulnerable to failure. We finally show how simulation code can be tested to ensure safe execution under a risk-free protocol. Whether risky or risk-free, we conclude that under current practice the development of correct and safe parallel simulation code is not transparent to the modeler; certain protections must be included in model code or model testing that are not rigorously necessary if the simulation were executed only serially.
11755901
Interactive mesh deformation with pseudo material effects
This paper presents a novel interactive mesh deformation method that can achieve various dynamic material effects, including elastic membrane and cloth effects. In our framework, a mesh is encoded by some differential quantities based on edge length and dihedral angle; and the deformation is formulated as a least square problem for preserving the edge length and dihedral angle via the differential quantities. In order to obtain anisotropic material effects, we further propose an edge-weighting scheme based on a user-specified vector field. To avoid specifying the local transformations, we set up an iterative scheme for solving the deformation. At last, several examples are presented to show that our approach can interactively generate visually pleasing deformations. Copyright © 2006 John Wiley & Sons, Ltd.