1,721,460 research outputs found
ABSOLUTE MINIMIZATION OF COMPLETELY SPECIFIED SWITCHING-FUNCTIONS
No full textFor the automated design of PLA's with a minimum size, we need computationally efficient procedures that can minimize functions of a large number of variables. For such minimization procedures, excessively long processing time and excessively large memory requirement are major problems to overcome. This paper presents a new absolute minimization procedure for standard PLA's with reduced computation time and memory space. The improvement of the procedure, which is based on the decomposition of ratio sets, is mainly due to the detection of all essential prime implicants during the derivation of inclusion functions and also the merger of two separate procedures previously published by Cutler and Muroga [7] into one efficient procedure.X119sciescopu
Approximating 3D general sweep boundary using depth-buffer
No full textThis paper presents a. practical technique for approximating the boundary surface of the volume swept out by three-dimensional objects using the depth-buffer. Objects may change their geometries and orientations while sweeping. The sweep volume is approximated as a union of volume elements, which are just rendered inside appropriate viewing frusta of virtual cameras and mapped into screen viewports with depth-buffer. From. the depth of each pixel in the screen spare of each rendering, the corresponding point in the original world space can be computed. Appropriately connecting these points yields polygonal faces forming polygonal surface patches approximately covering some portion of the sweep volume. Each view frustum adds one or more surface patches in this way, and these presumably overlapped polygonal surface patches approximately enclose the whole sweep volume. These patches may further be processed to yield non-overlapped polygonal surfaces as an approximation to the boundary of the original 3D sweep volume.X11sciescopu
New circuits for XOR and XNOR functions
No full textTwo new circuit designs are proposed to implement the exclusive-OR (XOR) and exclusive-NOR (XNOR) functions on the transistor level. The first circuit uses three transistors and non-complementary signal inputs. The other circuit improves the performance of the prior circuit, hut needs two more transistors. Computer simulations using HSPICE show that the proposed designs realize the expected logic functions and achieve a reasonable performance.X116sciescopu
Dual-mode r-reliable task model for flexible scheduling in reliable real-time systems
No full textRecent research in real-time systems has much focused on new task models for flexible scheduling and fault-tolerant real-time systems. In this paper, we propose a novel task model for the purpose of flexible scheduling in reliable real-time systems. In the proposed dual-mode r-reliable task model, a task periodically releases fast mode jobs or reliable mode jobs with the constraint that reliable mode jobs must be executed at least once for any r consecutive periods to guarantee the reliability of task. We also propose scheduling algorithms and compare performance through simulation results.110sciescopu
A new approach to through-the-lens camera control
No full textThe through-the-lens camera control technique originally proposed by M. Gleicher and A. Witkin [Comput. Graphics 26(2), 1992, 331-340], provides a powerful user interface for the control of the virtual camera in 3D computer graphics and animation. Their technique is based on locally inverting the nonlinear perspective viewing transformation. However, given tn image control points, the Jacobian matrix is derived as a quite complex 2m X 8 matrix; furthermore, the Jacobian matrix always has at least one redundant column since its rank can be 7 at most. For the overconstrained case of m greater than or equal to 4, the Lagrange equation is always singular since its 2m x 2m square matrix has rank 7 at most. All these complications result from removing the constraint q(w)(2), + q(x)(2) + q(y)(2) + q(z)(2) = 1 for unit quaternions (qw, qx, qy, qz) is an element of S-3 which represent the camera rotations. In this paper, we interpret the problem as a target tracking problem and formulate it as a constrained nonlinear inversion problem. The problem is then solved by integrating a tangent vector field defined on the configuration space of the virtual camera. The vector field is given by the least-squares solutions of the Jacobian matrix equations. The row and column weighting scheme for the Jacobian matrix provides a convenient way to control the desired least-squares solutions and the associated vector held. The Lie group structure of the unit quaternion space S-3 enables us to derive a simple 2m x 7 Jacobian matrix, which improves both the computational efficiency and numerical stability of the overall algorithm. For the overconstrained case of m greater than or equal to 4, the Jacobian matrix equation is solved (in the least-squares sense) by using an efficient projection method with O(m) time complexity. (C) 1996 Academic Press, Inc.X1110sciescopu
Polygonal boundary approximation for a 2D general sweep based on envelope and boolean operations
No full textThis paper presents an algorithm that approximates (using polygons) the boundary of a general sweep for an arbitrary 2D curved object (possibly with holes). Based on set-theoretic properties of the general sweep, our algorithm generates the polygonal sweep boundary incrementally, where envelope approximations and union operations are repeatedly applied to intermediate boundaries of the sweep and consecutive instances of the moving object at sampled locations of the motion. For approximation, each instance of the object is polygonized along the motion, where the object may experience dynamic shape transformation with topological changes such as creating and/or destroying internal holes. The incremental nature of the proposed algorithm makes the boundary construction of a general sweep useful for applications in interactive shape design, collision detection, and mechanical part design. Our algorithm generates a precise approximation of the boundary of a general sweep with real-time performance in computing unsweeps, Minkowski sums and differences, and constant radius offsets. Some experimental results are also given in this paper.X119sciescopu
Mobile multicast routing protocol using prediction of dwelling time of a mobile host
No full textWe propose a mobile multicast routing protocol based on the timer-based mobile multicast (TBMOM). A mobile host that stays in a foreign network receives multicast datagrams from a foreign multicast agent (FMA) through tunneling. When a mobile host hands off, the foreign agent in the foreign network where it moves calculates the expected dwelling time for which the mobile host will stay in the foreign network. The foreign agent decides whether it will be included in the multicast tree using the expected dwelling time during hand-off. The proposed protocol reduces the tunnel length from FMA to the foreign network by predicting the expiration of the timer of a mobile host. Simulation results show that the proposed protocol provides a multicast delivery path closer to the optimal path than TBMOM.110sciescopu
A design methodology of a soft sensor based on local models
No full textA soft sensor is an empirical model, which estimates variables that is infeasible to measure on-line from other correlated variables. Because constructing a soft sensor is a process of data based empirical modeling, the homogeneity in the training data set is very important. If a process experiences a wide operation range or lasting significant disturbances, the data homogeneity is damaged and frequently results in several sub-clusters, which causes the prediction power of a soft sensor to be degraded. In this paper, we proposed a modeling procedure,that involves classification of training data and subclass modeling. PLS and NLPLS are adopted selectively as the subclass modeling algorithm and wavelet coefficients thresholding is used to remove noises contained in signals without severe distortion of the signals. Also, weighted X variables based on Variable Importance to Projection(VIP) through exploratory PLS are used to enhance the performance of the subclass models. The proposed methodology has been illustrated using an application to the development of a soft sensor for composition estimation of a binary distillation column simulated with HYSYS. The soft sensor based on the proposed scheme has shown better performance and robustness.X115sciescopu
Approximation of optimal moving paths of huge robot reclaimer with a 3D range finder
No full textThis paper proposes a simple method for approximating the optimal moving paths of a huge robot reclaimer located in the outdoor material stock yard with emphasis on safety, energy consumption, and transfer time. The reclaimer is equipped with a 3D range finder to measure the shape of material piles in the yard, and the material yard is modeled into 3D space where 2D section of grid type is constructed in several layers. To define a safety function against moving between grids, a simplified Voronoi diagram that has a minimized extension error of vertex is used. In addition, the function of energy consumption and transfer time required when the control point of the reclaimer moves between 3D grids is defined. This is used as a cost evaluation factor of path optimization along with the safety function. The proposed method can be readily applied to low-performance industrial control devices.X116sciescopu
On-line scheduling of scalable real-time tasks on multiprocessor systems
No full textThe computation time of scalable tasks depends on the number of processors allocated to them in multiprocessor systems. As more processors are allocated to a scalable task, the overall computation time of the task decreases but the total amount of processors' time devoted to the execution of the task, called workload, increases due to parallel execution overhead. In this paper, we propose a task scheduling algorithm that utilizes the property of scalable tasks for on-line and real-time scheduling. In the proposed algorithm, the total workload of all scheduled tasks is reduced by managing processors allocated to the tasks as few as possible without missing their deadlines. As a result, the processors in the system have less load to execute the scheduled tasks and can execute more newly arriving tasks before their deadlines. Simulation results show that the proposed algorithm performs significantly better than the conventional algorithm based on a fixed number of processors to execute each task. (C) 2003 Elsevier Inc. All rights reserved.X1118sciescopu
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