NEPTUNE:并行三维全电磁粒子模拟软件

为求解具有复杂几何的高功率微波电磁场问题,本文研制了一个三维全电磁粒子并行软件NEPTUNE。本文介绍了该并行软件的基本结构和采用的一些并行算法。目前,该软件已经成功模拟了多种高功率源器件,并可扩展到数千台处理器核上运行。     

三维空间对象拓扑关系的研究

在数字地球、数字城市、地理信息系统等涉及地理数据等许多应用中,三维空间对象的拓扑关系的研究是一个十分重要的问题;弄清三维空间对象的拓扑关系,对于三维空间对象的操作以及操作的算法研究至关重要。由于三维空间对象的复杂性,它们之间拓扑关系的判定大多只是从简单的概念来进行判断,还没有从理论上全面地给定它的判定准则。该文试图在三维空间中,详细地研究空间对象之间拓扑关系成立的条件与结论,利用这些规则,可以全面地得到三维空间对象之间可能存在的所有拓扑关系。     

Three-dimensional shape reconstruction of abdominal aortic aneurysm

This paper presents an effective computational technique for reconstructing a three-dimensional shape of an abdominal aortic aneurysm (AAA), from a limited number of computed tomography (CT) images. The three-dimensional template geometry of a healthy abdominal aorta is used as a priori knowledge, and the template geometry is deformed by extended free-form deformation (EFFD), to generate a patient-specific AAA geometry. A two-step optimization scheme is devised to find an optimal set of EFFD parameters that match the cross-section of a deformed template with an AAA contour shown in a CT image. The geometric continuity of a deformed model is maintained by raising the order of the polynomial function used in EFFD. Experimental results show that the proposed method creates the three-dimensional shape of AAA suitable for structural finite element analysis and computational fluid dynamics for medical diagnosis.     

Combining formal verification and conformance testing for validating reactive systems

This paper presents a combination of verification and conformance testing techniques to support the formal validation of reactive systems. The idea is to use symbolic test selection techniques to extract subgraphs (components) from a specification, and to perform the verification on the components rather than on the whole specification. Under reasonable sufficient conditions, this constitutes a sound compositional verification technique, in the sense that a property verified on the components also holds on the whole specification. This may considerably reduce the global verification effort. Moreover, once verified, a component forms the basis of an adequate test case, i.e. when executed on an implementation, it will not issue false positive or negative verdicts with respect to the verified properties. The approach has been implemented using the STG test selection tool and the PVS theorem prover. It is demonstrated here on a smart‐card application: the Common Electronic Purse System. Copyright © 2003 John Wiley & Sons, Ltd.     

节流装置应用中的误差分析

以标准孔板作为节流件的节流装置，在工业计量各种介质流量中广泛地得到应用。本文对流量计量的节流装置在应用中的误差分析进行了论证。对工业流量测量的节流装置符合制造和安装标准情况下的标准误差相对值的估算和工艺参数偏离设计条件时误差分析提出修正方法。     

Surface extraction from multi-material components for metrology using dual energy CT

This paper describes a novel method for creating surface models of multi-material components using dual energy computed tomography (DECT). The application scenario is metrology and dimensional measurement in industrial high resolution 3D x-ray computed tomography (3DCT). Based on the dual source / dual exposure technology this method employs 3DCT scans of a high precision micro-focus and a high energy macro-focus x-ray source. The presented work makes use of the advantages of dual x-ray exposure technology in order to facilitate dimensional measurements of multi-material components with high density material within low density material. We propose a workflow which uses image fusion and local surface extraction techniques: a prefiltering step reduces noise inherent in the data. For image fusion the datasets have to be registered. In the fusion step the benefits of both scans are combined. The structure of the specimen is taken from the low precision, blurry, high energy dataset while the sharp edges are adopted and fused into the resulting image from the high precision, crisp, low energy dataset. In the final step a reliable surface model is extracted from the fused dataset using a local adaptive technique. The major contribution of this paper is the development of a specific workflow for dimensional measurements of multi-material industrial components, which takes two x-ray CT datasets with complementary strengths and weaknesses into account. The performance of the workflow is discussed using a test specimen as well as two real world industrial parts. As result, a significant improvement in overall measurement precision, surface geometry and mean deviation to reference measurement compared to single exposure scans was facilitated.     

Registration of CAD mesh models with CT volumetric model of assembly of machine parts

X-ray CT (computed tomography) has experienced tremendous growth in industrial application in recent years, and acquiring information about the mechanical parts from CT data has been a great challenge for researchers. This paper presents a new method for the registration of a CT volumetric model of an assembly of parts with a CAD mesh model of a part of the assembly using ICP (iterative closest point) registration method. A few steps to extract feature points should be done as a preprocessing step of the volumetric model and the mesh model before applying the ICP registration algorithm, since the volumetric model and the mesh model are different in their data representation. This preprocessing step is important in order to unify the input of the ICP algorithm, and contributes to the robustness and the speed of the registration process.     

Efficient Techniques for Automatic Verification-Oriented Test Set Optimization

Most Systems-on-a-Chips include a custom microprocessor core, and time and resource constraints make the design of such devices a challenging task. This paper presents a simulation-based methodology for the automatic completion and refinement of verification test sets. The approach extends the μGP, an evolutionary test program generator, with the possibility to enhance existing test sets. Already devised test programs are not merely included in the new set, but assimilated and used as a starting point for a new test-program cultivation task. Reusing existing material cuts down the time required to generate a verification test set during the microprocessor design. Experimental results are reported on a small pipelined microprocessor, and show the effectiveness of the approach. Additionally, the use of the proposed methodology enabled to experimentally analyze the relationship of the different code coverage metrics used in the test program generation     

Real-time limit analysis of vaulted masonry buildings

This paper presents new structural analysis tools based on limit state analysis for vaulted masonry buildings. Thrust lines are used to visualize the forces within the masonry and to predict possible collapse modes. The models are interactive and parametric to explore relationships between building geometry and possible equilibrium conditions in real time. Collapse analysis due to applied displacements is determined by combining kinematics and statics. The approach is largely two dimensional, though more complex three-dimensional problems are analyzed using the same methods. This paper presents a series of analytical tools that are fast and easy to use in real time, but at the same time rigorous and highly accurate. This work represents a significant improvement over traditional methods of thrust line analysis performed by hand, which are often tedious and time-consuming.     

A Metric-Based Approach to Detect Abstract Data Types and State Encapsulations

This article presents an approach to identify abstract data types (ADT) and abstract state encapsulations (ASE, also called abstract objects) in source code. This approach, named similarity clustering, groups together functions, types, and variables into ADT and ASE candidates according to the proportion of features they share. The set of features considered includes the context of these elements, the relationships to their environment, and informal information. A prototype tool has been implemented to support this approach. It has been applied to three C systems (each between 30–38 Kloc). The ADTs and ASEs identified by the approach are compared to those identified by software engineers who did not know the proposed approach or other automatic approaches. Within this case study, this approach has been shown to have a higher detection quality and to identify, in most of the cases, more ADTs and ASEs than the other techniques. In all other cases its detection quality is second best. N.B. This article reports on work in progress on this approach which has evolved since it was presented in the original ASE97 conference paper.     

3D scanning of cultural heritage with consumer depth cameras

Three dimensional reconstruction of cultural heritage objects is an expensive and time-consuming process. Recent consumer real-time depth acquisition devices, like Microsoft Kinect, allow very fast and simple acquisition of 3D views. However 3D scanning with such devices is a challenging task due to the limited accuracy and reliability of the acquired data. This paper introduces a 3D reconstruction pipeline suited to use consumer depth cameras as hand-held scanners for cultural heritage objects. Several new contributions have been made to achieve this result. They include an ad-hoc filtering scheme that exploits the model of the error on the acquired data and a novel algorithm for the extraction of salient points exploiting both depth and color data. Then the salient points are used within a modified version of the ICP algorithm that exploits both geometry and color distances to precisely align the views even when geometry information is not sufficient to constrain the registration. The proposed method, although applicable to generic scenes, has been tuned to the acquisition of sculptures and in this connection its performance is rather interesting as the experimental results indicate.     

Autostereoscopic Rendering of Multiple Light Fields

Light fields were introduced a decade ago as a new high‐dimensional graphics rendering model. However, they have not been thoroughly used because their applications are very specific and their storage requirements are too high. Recently, spatial imaging devices have been related to light fields. These devices allow several users to see three‐dimensional (3D) images without using glasses or other intrusive elements. This paper presents a light‐field model that can be rendered in an autostereoscopic spatial device. The model is viewpoint‐independent and supports continuous multiresolution, foveal rendering, and integrating multiple light fields and geometric models in the same scene. We also show that it is possible to examine interactively a scene composed of several light fields and geometric models. Visibility is taken care of by the algorithm. Our goal is to apply our models to 3D TV and spatial imaging.     

Representation and analysis of additively manufactured parts

Representations of solid models were initially formulated partially in response to the need to support automation for numerically controlled machining processes. The assumed equivalence between shape, topology, and material properties of manufactured components and their computer representations led to the practice of modeling and simulating the behavior of physical parts before manufacture. In particular, representations of shape and material properties are treated in distinct nominal models for most unit manufacturing processes. Additively manufactured parts usually exhibit deviations from their nominal geometry in the form of stair-stepping artifacts and topological irregularities in the vicinity of small features. Furthermore, structural properties of additively manufactured parts have experimentally been shown to be dependent on the build orientation defining the cross sections where material is accumulated. Therefore geometric models of additively manufactured parts cannot be decoupled from the manufacturing process plan.In this paper we show that as-manufactured shapes may be represented in terms of the convolution operation to capture the additive deposition of material, measure the conformance to nominal geometry in terms of overlap volume, and model uncertainties involved in material flow and process control. We then demonstrate a novel interoperable approach to physical analysis on as-manufactured part geometry represented as a collection of machine-specific cross sections augmented with boundary conditions defined on the nominal geometry. The analysis only relies on fundamental queries of point membership classification and distance to boundary and therefore does not involve the overhead of model preparation required in approaches such as finite element analysis. Results are shown for non-trivial geometries to validate the proposed approach.     

Efficient weakest preconditions

Desired computer-program properties can be described by logical formulas called verification conditions. Different mathematically-equivalent forms of these verification conditions can have a great impact on the performance of an automatic theorem prover that tries to discharge them. This paper presents a simple weakest-precondition understanding of the ESC/Java technique for generating verification conditions. This new understanding of the technique spotlights the program property that makes the technique work.     

Transfer of small structures by bonding

The work presented in this paper deals with the bonding of small structures, down to 1 μm. Its aim is to evaluate the dimensional limits of anodic bonding between silicon and pyrex 7740 glass. Test structures consisting in silicon pillars with controlled radii have been developed. The silicon pillars have been fabricated by deep reactive ion etching to allow a good geometry control of the structures. A collection of matrices of 3×3 identical silicon test structures with dimensions from 200 to 1 μm has been fabricated to determine the smallest area that can bond anodically. The test results have been applied to the transfer of small structures from one wafer to another wafer by bonding, with the final objective of transferring tips for AFM probes. From the test results, a new test for bonding has been defined, based on the pull test of small structures with controlled dimensions. Preliminary simulations by FEM of the pull test of the test structures are in agreement with the experimental results. The test has been used to determine the effect of the voltage and temperature conditions during the anodic bonding on the bond strength.     

大规模存储系统可靠性参数最优化分析

在大规模存储系统中,数据的可靠性越来越受到人们的关注。已有的研究分析了在系统规模已知的条件下,某些系统参数,如副本分布策略、存储对象数目等,对可靠性的粗略影响,但较少提及它们的最优值或者最优组合。提出了一种基于对象粒度恢复的可靠性新模型;基于该模型,在分析三种主流的副本分布策略的基础上,分别计算出了各个系统参数的独立最优值及其组合最优值。与已有模型相比,该模型更易于求解,且获得了更加综合实用的最优值,这些最优参数值能直接有效地指导系统设计者构建更可靠的大规模存储系统。     

Admissible transformation volume for part dimensional quality gauging

Coordinate metrology aims to answer two questions: whether a manufactured part meets design tolerance specifications and how well the manufactured part meets the specifications. Existing methods for analyzing measured coordinate data are not adequate or effective for parts of complex tolerance zones.This paper presents a new approach to dimensional qualification of manufactured parts. In this paper, we view the part qualification problem as an issue of finding an admissible point in transformation space. Based on the concept of admissible point, we develop theories and algorithms for part geometric dimensioning and tolerancing (GD&T) conformance check. A formulation based on containment fit for tolerance check is developed. An admissible transformation volume (ATV) is used to quantitatively characterize the quality of manufactured parts with respect to design tolerance specifications.We examine our approach in three tolerance examples and conclude that admissible transformation volume is an effective metric for part dimensional quality gauging and it is especially useful for multi-tolerance zone check where traditional methods fail to address it effectively.     

An evolutionary approach to automatic synthesis of high-performance analog integrated circuits

This paper presents an analog integrated circuit synthesis system based on an evolutionary approach. The system contains several novel features. One of these is the high-performance optimization algorithm, which is a combination of evolutionary strategies and simulated annealing. Modeling of dc parameters is done via a fast dc simulator developed for this purpose whereas modeling of ac parameters can be done either with user-defined equations or with neural-fuzzy performance models trained from SPICE simulations. Another novel feature of the system is the incorporation of matching properties of devices. This way, the optimized circuit becomes tolerant to process variations. The synthesis system has been tested on several independent examples and synthesized circuits have been verified functionally with SPICE simulations. Finally, a prototype chip composed of the three examples has been manufactured. The measurement results have demonstrated the validity of the synthesis system on silicon.     

A virtual reality-based experimentation environment for the verification of human-related factors in assembly processes

This paper investigates the use of virtual reality (VR)-based methods for the verification of performance factors related to manual assembly processes. An immersive and interactive virtual environment has been created to provide functionality for realistic process experimentation. Ergonomic models and functions have been embedded into the VR environment to support verification and constrain experimentation to ergonomically acceptable conditions. A specific assembly test case is presented, for which a semi-empirical time model is developed employing statistical design experimentation in the virtual environment. The virtual experimentation results enable the quantification and prediction of the influence of a number of process parameters and their combination at the process cycle time.     

星载计算机软硬件协同验证技术的研究

在星载计算机LYRA的设计和验证过程中,采用System Verilog的DPI建立了完整的、低成本的、高效的SOC系统软硬件协同验证的系统仿真平台;利用这种技术使得可以在实际硬件可用前进行C/C++代码的开发和测试,同时又可以利用真实的软件对硬件进行验证;在早期软硬件可以公用测试平台进行并行开发,不仅大大减少软硬件开发的重复工作,加快了验证速度,还能对软硬件之间的边角情况进行完整的验证;验证方法已经成功的应用于星载计算机LYRA的开发中,取得了良好的效果。