Algorithm For Automatic Generation Research Articles

A posteriori dual-mixed adaptive finite element error control for Lamé and Stokes equations

A unified and robust mathematical model for compressible and incompressible linear elasticity can be obtained by rephrasing the Herrmann formulation within the Hellinger-Reissner principle. This quasi-optimally converging extension of PEERS (Plane Elasticity Element with Reduced Symmetry) is called Dual-Mixed Hybrid formulation (DMH). Explicit residual-based a posteriori error estimates for DMH are introduced and are mathematically shown to be locking-free, reliable, and efficient. The estimator serves as a refinement indicator in an adaptive algorithm for effective automatic mesh generation. Numerical evidence supports that the adaptive scheme leads to optimal convergence for Lamé and Stokes benchmark problems with singularities.

Automatic cuts for magnetic scalar potential formulations

The approach of magnetic scalar potential T/sub 0//spl phi/-/spl phi/ is widely popular for solving magnetic problems coupled with electric circuits. However, cuts are required to preserve the Ampere's law for the case of ferromagnetic circuits with holes surrounded by coils. The manual definition of cuts might not be evident even for experimented finite-element (FE) users. This paper presents a new automatic cuts generation algorithm. First, we present a tool that allows determining if a ferromagnetic region has holes or not. If holes are found, the region is then inflated to get automatically needed cuts. The presented algorithm is also applicable to generate electric cuts in massive conductors.

Optimal Interconnect ATPG Under a Ground-Bounce Constraint

In order to prevent ground bounce, Automatic Test Pattern Generation (ATPG) algorithms for wire interconnects have recently been extended with the capability to restrict the maximal Hamming distance between any two consecutive test patterns to a user-defined integer, referred to as the Simultaneously-Switching Outputs Limit (SSOL). The conventional approach to meet this SSOL constraint is to insert additional test patterns between consecutive test patterns if their Hamming distance is too large; this approach often leads to substantially more test patterns than strictly necessary. This paper presents an algorithm that generates, for a user-defined number of interconnect wires, a minimal set of test patterns that respects a user-defined SSOL constraint. Experimental results show that, in comparison to the conventional approach, our algorithm leads to a significant reduction of up to 60% in the test pattern count and corresponding test application time.

Computational Electrochemistry: A Model to Studying Ohmic Distortion of Voltammetry in Multiple Working Electrode, Microfluidic Devices, an Adaptive FEM Approach

AbstractCharacteristics of mass transport and potential distribution applicable to microfluidic electrochemical flow cell devices has been modelled using the finite element method. A flexible, automatic grid generation algorithm has been combined with an a‐posteriori error indication technique presented by Nann and Heinze to allow irregular cell geometries to be modelled. The code has been applied to the problem of steady state generator – detector linear sweep voltammetry in a channel flow cell showing the effects of IR drop on the voltammetric response of each electrode.

On Multigrid for Overlapping Grids

The solution of elliptic partial differential equations on composite overlapping grids using multigrid is discussed. An approach is described that provides a fast and memory efficient scheme for the solution of boundary value problems in complex geometries. The key aspects of the new scheme are an automatic coarse grid generation algorithm, an adaptive smoothing technique for adjusting residuals on different component grids, and the use of local smoothing near interpolation boundaries. Other important features include optimizations for Cartesian component grids, the use of over-relaxed red-black smoothers, and the generation of coarse grid operators through Galerkin averaging. Numerical results in two and three dimensions show that very good multigrid convergence rates can be obtained for Dirichlet, Neumann, and mixed boundary conditions. A comparison to Krylov-based solvers shows that the multigrid solver can be much faster and require significantly less memory.

영역기반 해쉬구조를 이용한 효율적 삼각형 자동 요소망 생성 알고리듬 개발

In this work, a domain-wise hash structure is developed for efficient data handling, and by using the developed domain-wise hash structure, an automatic triangular mesh generation algorithm is proposed. To generate the optimal nodal points and triangles efficiently, the advancing layer method and Delaunay triangulation method are utilized. To investigate the performance of the proposed algorithm, benchmarking tests are carried out for various models including convex, concave and complicated shapes through the developed object oriented C++ mesh generation code.

Scan Architecture With Mutually Exclusive Scan Segment Activation for Shift- and Capture-Power Reduction

Power dissipation during scan testing is becoming an important concern as design sizes and gate densities increase. While several approaches have been recently proposed for reducing power dissipation during the shift cycle (minimum-transition don't care fill, special scan cells, and scan chain partitioning), limited work has been carried out toward reducing the peak power during test response capture and the few existing approaches for reducing capture power rely on complex automatic test pattern generation (ATPG) algorithms. This paper proposes a scan architecture with mutually exclusive scan segment activation which overcomes the shortcomings of previous approaches. The proposed architecture achieves both shift and capture-power reduction with no impact on the performance of the design, and with minimal impact on area and testing time (typically 2%-3%). An algorithmic procedure for assigning flip-flops to scan segments enables reuse of test patterns generated by standard ATPG tools. An implementation of the proposed method had been integrated into an automated design flow using commercial synthesis and simulation tools which was used on a wide range of benchmark designs. Reductions up to 57% in average power, and up to 44% and 34% in peak-power dissipation during shift and capture cycles, respectively, were obtained when using two scan segments. Increasing the number of scan segments to six leads to reductions of 96% and 80% in average power and, respectively, maximum number of simultaneous transitions.

VIRTUAL WOODWORK: MAKING TOYS FROM GEOMETRIC MODELS

Shape idealization techniques provide a simplified description of a geometric model. Idealized descriptions are useful for recognition, animation, and other applications, providing a compact and efficient alternative to manipulating the complete model. Often idealized models are visually interesting in their own right and provide an appealing artistic impression of the models. We describe an algorithm for automatic generation of idealized bead figures from recognizable 3D models (animals, humans, etc.). The bead figures approximate the model by a set of cylindrical shapes threaded onto a skeleton of the model. As such, they provide volumetric shape information in addition to the skeleton. The bead figures can be used by applications requiring a simple and compact description of the shapes. They also provide a visually appealing, toy-like description which can be used in artistic applications. The input models are given as 3D triangulated meshes. A bead figure is generated using the skeleton of the model, often referred to as the stick figure. The skeleton reflects the structure of the original mesh and its features, using a small number of edges. Once the skeleton is computed, beads are threaded onto it to create the final model. Computation of a compact and concise skeleton which captures the features of the model is crucial for realistic bead figure generation. The figure making process involves voxelization of the model; computation of the 3D Euclidean distance transform (DT); extraction of the skeleton from the DT data (combined with the model's curvature information); and threading the beads over the skeleton. In addition to the generation of the beaded figures, our work also introduces a novel skeleton construction algorithm. The algorithm has several advantages over existing methods and may be used in other applications which utilize skeletons.

A fast automatic VOP generation using boundary block segmentation

With the increase of multimedia applications and content-based functionalities, efficient video coding methods are necessary. The moving picture experts group-4 (MPEG-4) provides content-based functionalities by introducing the concept of the video object plane (VOP). Each frame of the input sequence is segmented into a number of arbitrarily shaped image regions or VOP's so that each VOP describes a semantically meaningful object or video content of interest. For real-time applications of MPEG-4, a fast automatic object segmentation method of video sequences is needed. We propose a fast automatic VOP generation algorithm composed of two parts: object block segmentation and boundary block segmentation. The former defines block-based object regions in a frame and the latter generates the pixel-based object mask. Block-based object region search and restriction of segmentation regions to boundary blocks reduce a computational load. Experimental results with two test sequences show the effectiveness of the proposed algorithm in terms of the visual quality of segmentation results and the computation time.

A divide-and-conquer-based algorithm for automatic simulation vector generation

Testbenches play one of the most important roles in simulation-based design verification. Given a simulation scenario, a testbench provides specific vectors to simulate the design, then collects responses from the design to monitor whether the simulation has satisfied the scenario. The major bottleneck in writing testbenches is generating valid simulation vectors. Many current automatic-vector-generation methods focus on exploring a design's state space. Due to memory or runtime limitations, these methods cannot keep up with the rapid growth of design complexity. We propose a novel algorithm based on the divide-and-conquer paradigm that helps these methods decompose the design's complexity. The algorithm uses a partitioning method that recursively divides a design into smaller, more manageable components. Other approaches handle the divided components while maintaining the entire design's proper functioning. Random simulation generates sets of simulation vectors by randomly assigning the logic values to the design's primary inputs (Pis) one cycle at a time. Unlike random simulation, which uses only a single trace, symbolic solvers attempt to simultaneously enumerate all possible primary inputs to explore the entire state space. They typically use binary decision diagrams (BDDs) or satisfiability (SAT) solvers as their core engine.

XID: Don't Care Identification of Test Patterns for Combinational Circuits

Given a test set for stuck-at faults of a combinational circuit or a full-scan sequential circuit, some of the primary input values may be changed to the opposite logic values without losing fault coverage. We can regard such input values as don't care (X). In this paper, we propose a method for identifying the X inputs of test vectors in a given test set. While there are many combinations of X inputs in the test set generally, the proposed method finds one including as many X inputs as possible, by using fault simulation and procedures similar to implication and justification of automatic test pattern generation (ATPG) algorithms. Experimental results for ISCAS benchmark circuits show that approximately 69% of the inputs of uncompacted test sets could be X on the average. Even for highly compacted test sets, the method found that approximately 48% of inputs are X.

Advanced automatic generation scheme of prestressing tendons for efficient FE analysis of PSC shell structures

In finite element analysis of the prestressed concrete (PSC) shell structures, preparation of the tendon data including the intersection points with the shell elements is very time-consuming. In this respect, automatic generation scheme of these points can be very effective. The purpose of this study is to propose an efficient method that can improve the existing automatic generation algorithm of the tendon data for the shell elements. Here, some useful techniques are proposed that can accelerate the procedure and overcome cases of singularity. Numerical examples are presented to verify the enhanced speed as well as the accuracy of the proposed scheme in comparison with the previous algorithms.

RTGEN-an algorithm for automatic generation of reservation tables from architectural descriptions

Reservation Tables (RTs) have long been used to detect conflicts between operations that simultaneously access the same architectural resource. Traditionally, these RTs have been specified explicitly by the designer. However, the increasing complexity of modern processors makes the manual specification of RTs cumbersome and error prone. Furthermore, manual specification of such conflict information is infeasible for supporting rapid architectural exploration. In this paper, we present an algorithm to automatically generate RTs from a high-level processor description with the goal of avoiding manual specification of RTs, resulting in more concise architectural specifications and also supporting faster turnaround time in design space exploration. We demonstrate the utility of our approach on a set of experiments using the TI C6201 very long instruction word digital signal processor and DLX processor architectures, and a suite of multimedia and scientific applications.

Optimization of Ply Drop-offs in Bonded Patch to Cylindrical Shell Structures

Ply drop-off is a technique widely used to achieve gradual thickness change in composite laminate, and it can be utilized to form boundary tapering of a composite patch bonded to a parent structure. This paper firstly presents a new adhesive element formulation with a nonneutral reference plane that takes into account the geometrical features of ply drop-off and can be applied to conduct 2.5-D simplified stress analysis of bonded repairs to curved structures. The new formulation is numerically validated by comparing results calculated using both the present formulation and a full three-dimensional finite element formulation available in commercial software. Sequential Linear Programing (SLP) method is then employed in conjunction with a fully implemented automatic mesh generation algorithm to minimize adhesive stresses, namely, the peak peel, shear or Von Mises stresses, through optimally selecting ply drop-off parameters. The objective of this paper is to ensure effective bonding between a patch and an undamaged parent shell structure via minimizing maximum stress along the boundary of adhesive layer. Several numerical examples are presented to demonstrate that an optimum ply drop-off in a bonded patch can dramatically reduce peak stresses in the adhesive layer, particularly the peak positive peel stress.

Automatic metric 3D surface mesh generation using subdivision surface geometrical model. Part 1: Construction of underlying geometrical model

AbstractThis paper proposes a new automatic mesh generation algorithm for 3D surface mesh generation. The algorithm is based on the metric specification approach and can generate anisotropic meshes on 3D surfaces. It is based on a new geometrical model using the interpolating subdivision surface concept. By using the subdivision surface concept, the new mesh generator can generate finite element meshes to model a wide range of surfaces which may contain sharp features such as cusp points and crease lines. When comparing with other traditional algorithms which use analytical surface patches as the underlying geometrical model, the new mesh generation scheme can be used in applications such as large deformation or crack analyses in which the domains to be gridded are not well defined or involve changing boundaries. The presentation of the work is divided into two parts. In Part 1, a detailed description of the underlying geometrical model used will be given, while in Part 2, attention will be focused on the mesh generation algorithms and the performance of the mesh generator developed. Copyright © 2003 John Wiley & Sons, Ltd.

Adaptive finite element analysis of electrostatic interactions: a sphere between two charged walls and two isolated spheres

In the process and particle technology-based industries, a number of processing steps involve the separation of a dispersed phase from a continuous phase. The dispersed phase may be in the form of solid and/or liquid particles, for which the use of high electric fields provides a number of electric forces to cause its separation from the continuous phase. Therefore, an analysis of the effect of the applied electric field on the particles is important in order to improve the separation efficiency. In this work, a finite element method, combining an automatic error estimator and an automatic mesh generation algorithm, has been applied to calculate electrical-induced forces in a number of physical systems. These systems include the interaction of a charged sphere between two charged walls, and the interaction between two charged spheres. The finite element formulation, utilising nine-node quadrilateral elements, has been shown to be more accurate than the currently available approximate analytical solutions when the sphere–wall separation distance or sphere–sphere separation distance is smaller than the radius of the sphere. The FE formulation reported here can also produce more accurate results with minimum predetermined error, compared with other numerical solutions. The FE formulation in the present work can be extended to more complicated geometries and structures, including more complex particle shapes and/or drop shapes and non-uniform electric fields. This gives a more complete simulation for real physical systems in the particle technology and separation industries.

An algorithm for automatic 2D quadrilateral mesh generation with line constraints

Finite element method (FEM) is a fundamental numerical analysis technique widely used in engineering applications. Although state-of-the-art hardware has reduced the solving time, which accounts for a small portion of the overall FEM analysis time, the relative time needed to build mesh models has been increasing. In particular, mesh models that must model stiffeners, those features that are attached to the plate in a ship structure, are imposed with line constraints and other constraints such as holes. To automatically generate a 2D quadrilateral mesh with the line constraints, an extended algorithm to handle line constraints is proposed based on the constrained Delaunay triangulation and Q-Morph algorithm. The performance of the proposed algorithm is evaluated, and numerical results of our proposed algorithm are presented.

Verified Code Generation for Embedded Systems

Digital signal processors provide specialized SIMD (single instruction multiple data) operations designed to dramatically increase performance in embedded systems. While these operations are simple to understand, their unusual functions and their parallelism make it difficult for automatic code generation algorithms to use them effectively. In this paper, we present a new optimizing code generation method that can deploy these operations successfully while also verifying that the generated code is a correct translation of the input program.

T-Ω formulation for eddy-current problems in multiply connected regions

When using t-/spl Omega/ formulation for solving eddy-current problems in multiply connected regions, cuts have to be introduced to avoid multivalued problems of scalar potential. In this paper, the vector potential is used in both the conducting region and cutting domains. The cutting domains are composed of one layer of elements that fill the holes of conductors. In the cutting domains, the zero curl condition of the vector potential is strongly imposed by a constraint function. Such a method avoids the introduction of a fake conductor in the holes. To generate the cutting domains, an automatic cut generation algorithm is developed.

Finite-element method adapted to AC problems

An analysis of the use of the Finite-Element Method for modeling high-frequency steady-state AC problems is presented. A specific skin depth automatic mesh generation algorithm in two dimensions (2D) has been developed. For the calculation of global quantities as impedance, three kinds of current equilibration algorithms are presented. Their use on Flux-Expert package is compared on two-dimensional (2-D) axisymmetrical geometry with Integral method results.