12453473
A feature-based topological optimization for structure design
The feature-based modeling technology in computer aided design (CAD) has been widely studied, which greatly facilitates the manufacture of the design. We have incorporated the standard idea into topology optimization, and developed a feature-based structure topology optimization method. The method applies a real valued function to implicitly represent complex material interfaces of a design structure, and employs constructive solid geometry (CSG) to describe the design structure based on a set of simple geometric primitives during the topological optimization process. Meanwhile, the topological derivative analysis is adopted to determine where a simple geometric primitive is inserted in the current structure, and the morphing technology is used to determine which is chosen among the given geometric primitives by combining with the sensitivity analysis. In addition, Boolean operations on the geometric primitives are implemented by R-function method, which guarantees the regularity of the structure representation function, and which meets the need of the structure boundary smoothness for finite element analysis in the fixed Euler meshes. Finally, in order to further simplify the design structure, the shape matching technique is applied to merge the given geometric primitives so that each connected perforation is only constructed by one based geometric primitive.
17025259
A level-set based variational method for design and optimization of heterogeneous objects
Abstract A heterogeneous object is referred to as a solid object made of different constituent materials. The object is of a finite collection of regions of a set of prescribed material classes of continuously varying material properties. These properties have a discontinuous change across the interface of the material regions. In this paper, we propose a level-set based variational approach for the design of this class of heterogeneous objects. Central to the approach is a variational framework for a well-posed formulation of the design problem. In particular, we adapt the Mumford–Shah model which specifies that any point of the object belongs to either of two types: inside a material region of a well-defined gradient or on the boundary edges and surfaces of discontinuities. Furthermore, the set of discontinuities is represented implicitly, using a multi-phase level set model. This level-set based variational approach yields a computational system of coupled geometric evolution and diffusion partial differential equations. Promising features of the proposed method include strong regularity in the problem formulation and inherent capabilities of geometric and material modeling, yielding a common framework for optimization of the heterogeneous objects that incorporates dimension, shape, topology, and material properties. The proposed method is illustrated with several 2D examples of optimal design of multi-material structures and materials.
8207565
An intelligent software-integrated environment of IC test
The migration and simulation of IC test programs among the heterogeneous ATE systems are a very difficult task. An unifying IC test software-integrated environment from simulation to test for digital circuit has been developed. The environment, TeDS which is designed by using object-oriented paradigm, supports two kinds of CAD systems and three kinds of ATE (Automatic Test Equipment). The paper focuses on issues and techniques in developing TeDS based on object-oriented paradigm.
3433910
Residual-Based Measurement of Peer and Link Lifetimes in Gnutella Networks
Existing methods of measuring lifetimes in P2P systems usually rely on the so-called create-based method (CBM), which divides a given observation window into two halves and samples users "created" in the first half every Delta time units until they die or the observation period ends. Despite its frequent use, this approach has no rigorous accuracy or overhead analysis in the literature. To shed more light on its performance, we flrst derive a model for CBM and show that small window size or large Delta may lead to highly inaccurate lifetime distributions. We then show that create-based sampling exhibits an inherent tradeoff between overhead and accuracy, which does not allow any fundamental improvement to the method. Instead, we propose a completely different approach for sampling user dynamics that keeps track of only residual lifetimes of peers and uses a simple renewal-process model to recover the actual lifetimes from the observed residuals. Our analysis indicates that for reasonably large systems, the proposed method can reduce bandwidth consumption by several orders of magnitude compared to prior approaches while simultaneously achieving higher accuracy. We finish the paper by implementing a two-tier Gnutella network crawler equipped with the proposed sampling method and obtain the distribution of ultrapeer lifetimes in a network of 6.4 million users and 60 million links. Our experimental results show that ultrapeer lifetimes are Pareto with shape a alpha ap 1.1; however, link lifetimes exhibit much lighter tails with alpha ap 1.9.
16394530
Resonance Characteristic Analysis for Spur Gear Servo Mechanism
Spur gear servomechanism is widely used in photoelectric stabilization platform and other weapon system, its resonance characteristic directly determines the bandwidth, gain and stability of the whole subsystem. Taking Spur gear servo mechanisms as research aim, three degrees of freedom vibration differential equation of gear mesh is theorized, and the resonance equation of the servo mechanism is obtained through Laplace transform, and then the vibration characteristic of stabilization platform is analyzed by numerical analysis. A new kind of resonance frequency analysis method is proposed based on virtual test technology. The digital simulation model of mechanism is created in MATLAB, and then the virtually frequency sweep method is used to excite the resonance characteristic of servo mechanism. The resonance frequency was obtained by analysis of curve of servo mechanism in time domain and frequency domain. Result of numerical analysis and virtual test show that the inertia moment of high speed axes and the mesh stiffness of gear are key assembly and sensitive parameter of the Spur gear servomechanism.
8432652
Study on Embedded System Grid
The center of gravity of the computer industry is now moving from personal computing into embedded computing. At present, the key to realize intellectual control and network control of manufacturing equipments is to embed the embedded system into manufacturing equipment and extend the control method of manufacturing equipments to the remote network through the network function of the embedded system. In this paper, the characteristic of embedded system and the architecture of embedded system grid are introduced firsty. Then, the interface method between embedded system and grid are discussed. The control model of embedded system resources under the grid environment, the method of overall sharing embedded system and its equipment are also describled. After that, the embedded system grid technology of sharing and controlling embedded resources are presented. 1. Interface of Embedded System Grid The embedded system grid provides a single integrated system that receives, processes, displays, maintains, and assesses the controlled devices information. To achieve sharing embedded system resource under grid environment, it is in the first place to release embedded resource to grid by means of grid interface. OGSA defines standard behaviors and associated interfaces [1]. Service Data is used to express these data that embody state of serve instance [2]. In order to set up grid service node, the key problem lies in defining one or more essential interfaces for various kinds of resource; each interface is able to provide a certain operation and describe essential attribute of resource and service data. 2. Embedded System Grid Architecture Embedded system grid means that embedded system is integrated into the grid as a grid node or grid resource. The Embedded system grid integrates key Grid technologies with Web services mechanisms to create a distributed system framework based around the Grid service. Using OGSA to introduces standard factory and registration interfaces for creating and discovering embedded system grid services. In the embedded system grid architecture, GRAM offers a simple interface for the remote system for users, is responsible for resource request for remote application. GARA expands the resource management of Globus, introduces resource target and reserve mechanism, provide QoS of application. The architecture consists of three main components: an information service, local resource managers, and various types of co-allocation agents. Co-reservation and co-allocation agents lie on top of GRAM and the standardized information services enable the dynamic construction of collections of independently administered resources that satisfy QoS requirements of applications. Embedded system grid technology realize sharing and controlling for embedded system and its equipment.
120708868
An energy equation for the weakly damped driven nonlinear Schro¨dinger equations and its application to their attractors
Abstract In this note we present an energy equation concerning the H 2 norm of a forced one-dimensional nonlinear Schrodinger equation. As an application we are able to corroborate recent results on attractors of weakly damped forced nonlinear Schrodinger equation, by proving that the attractor is an attractor in the strong topology of H 2 and its Hausdorff and fractal dimensions are finite in H 2 . The energy equation for the H 1 norm can be derived in the same fashion and it implies corresponding results for the attractor in H 1 .