基于ECT图像的微胶囊消化道轨迹三维重建方法

为了重建微型胶囊在人体肠道内的三维空间运动轨迹,运用核医学成像原理,通过ECT拍摄原始实验图像,在Visual C＋＋6．0环境下编写程序,运用矩阵变换进行图像数据处理,计算出微型胶囊的三维坐标。重建出了连续时间内,微型胶囊的人体肠道运动轨迹。与人体消化道钡餐造影图片对比,重建图能够较好地描绘出肠道走向。     

Three-dimensional finite element models based on in vivo microfocus computed tomography: Elimination of metal artefacts in a small laboratory animal model by registration with artefact-free reference images

A method is presented to generate metal-artefact-free finite element (FE) models based on in vivo micro-CT images of bone–implant structures in the case of the Guinea Pig’s tibiae. A bone–implant composite FE model was constructed based on both pre- (just before implant insertion) and post-operative (4 days after implant insertion) sets of micro-CT scans. Definition of bone geometry and attribution of material properties to the volumetric elements was based on pre-operative images while post-operative scans were mainly used for registration. Standard Triangulation Language (STL) representations of implant and bone were generated after segmentation of CT images in MIMICS^® (Materialise). Registration was performed in 3-matic^® (Materialise). By taking two sets of scans at a 4 days interval, undisturbed bone geometry before implant insertion and implant position after insertion were recorded. After adequate validation, FE models constructed with this method can be used to study bone adaptive response to controlled mechanical loading.     

An integrative software package for gastrointestinal biomagnetic data acquisition and analysis using SQUID magnetometers

The study of bioelectric and biomagnetic activity in the human gastrointestinal (GI) tract is of great interest in clinical research due to the proven possibility to detect pathological conditions thereof from electric and magnetic field recordings. The magnetogastrogram (MGG) and magnetoenterogram (MENG) can be recorded using superconducting quantum interference device (SQUID) magnetometers, which are the most sensitive magnetic flux-to-voltage converters currently available. To address the urgent need for powerful acquisition and analysis software tools faced by many researchers and clinicians in this important area of investigation, an integrative and modular computer program was developed for the acquisition, processing and analysis of GI SQUID signals. In addition to a robust hardware implementation for efficient data acquisition, a number of signal processing and analysis modules were developed to serve in a variety of both clinical procedures and scientific investigations. Implemented software features include data processing and visualization, waterfall plots of signal frequency spectra as well as spatial maps of GI signal frequencies. Moreover, a software tool providing powerful 3D visualizations of GI signals was created using realistic models of the human torso and internal organs.     

A CAE system for micromachines: Its application to electrostatic micro wobble actuator

This paper describes a new computer-aided engineering (CAE) system for micromachines 10⁻⁶−10⁻³ m in size. An automatic finite-element (FE) mesh-generation technique, which is based on the fuzzy knowledge processing and computational geometry techniques, is incorporated into the system, together with a commercial FE analysis code, MARC, and a commercial solid modeler, DESIGNBASE. The system allows a geometry model of interest to be automatically converted to different FE models, depending on the physical phenomena of the micromachines to be analyzed, i.e., electrostatic analysis, stress analysis, modal analysis, and so on. The FE models are then automatically analyzed using the FE analysis code. Out of the whole process of analysis, the definition of a geometry model, the designation of local node patterns and the assignment of material properties and boundary conditions to the geometry model are the only interactive processes to be done by the user. The interactive operations can be processed in a few minutes. The other processes, which are time consuming and labour intensive in conventional CAE systems, are fully automatically performed in a popular engineering workstation environment. With the aid of multilayer neural networks, the present system also allows us to obtain automatically a design window in which a number of satisfactory design solutions exist in a multi-dimensional design parameter space, considering coupled multiple phenomena such as static and dynamic deformation, thermal conduction, electrostatics, and so on. This CAE system is successfully applied to evaluate an electrostatic micro wobble actuator. As a typical CAE evaluation, we identify the quantitative conditions for operating the micro wobble actuator, considering both structural and electrostatic phenomena.     

Process monitoring in stamping operations through tooling integrated sensing

This paper introduces a new sensing method for stamping process monitoring based on the measurement of contact pressure distribution across the sheet metal-tooling interface, by means of an array of tooling-integrated force sensors. The role of numeric surface methods in estimating the contact pressure distribution on the sheet metal-tooling interface has been studied through finite element analysis and experiments. A finite element model is set up to model the contact interactions, based on the geometry of a customized stamping test fixture. Discrete samples of contact pressure taken from the FE model have been used to recreate continuous-pressure surfaces based on the Thin Plate Splines (TPS) and Bezier surface algorithms. It is shown that the temporal–spatial contact pressure distribution across the sheet metal-tooling interface can be effectively reconstructed through interpolation using spatially discrete sensor data. Comparison of surface-based pressure estimates with the FEA field solution indicates that the TPS-based method is more accurate than the Bezier method. The effectiveness of the surface modeling scheme is also evaluated experimentally by comparing the net press force calculated from numerical integration of the TPS surfaces with the experimentally measured value under different press speeds. The effectiveness of the new sensing method is further demonstrated by detection of slide misparallelism through analysis of the tooling interface pressure distribution. The study presents a new approach to enhancing process observability in manufacturing operations.     

Finite element-based probabilistic analysis tool for orthopaedic applications

Orthopaedic implants, as well as other physical systems, contain inherent variability in geometry, material properties, component alignment, and loading conditions. While complex, deterministic finite element (FE) models do not account for the potential impact of variability on performance, probabilistic studies have typically predicted behavior from simplified FE models to achieve practical solution times. The objective of this research was to develop an efficient and versatile probabilistic FE tool to quantify the effect of uncertainty in the design variables on the performance of orthopaedic components under relevant conditions. Key aspects of the computational tool developed include parametric and automated FE model creation for changes in dimensional variables, efficient solution using the advanced mean-value (AMV) reliability method, and identification of the most significant design variables. Two orthopaedic applications are presented to demonstrate the ability of the computational tool to efficiently and accurately represent component performance.     

Three dimensional shape optimization of total knee replacements for reduced wear

This paper presents the design optimization of a total knee replacement (TKR) using a parametric three-dimensional finite element (FE) model, considering wear of the ultra high molecular weight polyethylene (UHMWPE) insert. A framework has been developed to generate three-dimensional FE models of the femoral component and UHMWPE insert of a TKR design in a batch mode process, then simulate an ISO standard TKR wear test. A modified version of Archard’s wear model calculates abrasive wear as a function of contact pressure, sliding distance and an experimentally determined wear factor. The UHMWPE wear was reduced by modifying the contact geometry of both components in the frontal and sagittal planes. Wear was reduced by 18.5%, from 55.248 to 45.013 mm³ per year by reducing the radii of curvature of the femoral condyles in the sagittal planes, increasing the radii in the frontal plane, and reducing conformity between the implant components.     

Development of the object-oriented finite element modeling system — MODIFY

In this paper we present a new concept of FE modeling, based on the object-oriented principle, and develop the prototype program MODIFY (MODeling tool for Integrated Finite element analYsis). MODIFY has three novel features: (1) FE modeling by the part object concept, (2) a fully object-oriented data structure, and (3) a part-by-part fully automated mesh subdivision. When using MODIFY it is necessary to define and assemble part objects, which consist of geometry objects, analytical condition objects and relation objects, to describe the continuity between adjacent part objects.MODIFY automatically generates an appropriate FE model for each geometry object, satisfying continuity conditions with adjacent parts by referring to relation objects. If some part of the model is to be modified, the user needs only to change the corresponding part objects. Because of the object-oriented data structure, MODIFY also has a powerful capability for adaptive meshing. The existing version of MODIFY is applicable to FE models for3-D shell structures.     

Gastrointestinal fluids proteomics

Seventy million people suffer from diseases of the gastrointestinal tract annually in US, translating to US$85.5 billion in direct healthcare costs. The debilitating effects of these gastrointestinal (GI) diseases can be circumvented with good biomarkers for early detection of these disorders, which will greatly increase the success of curative treatments. GI fluids represent a potential reservoir of biomarkers for early diagnosis of various GI and systemic diseases since these fluids are the most proximal fluid bathing diseased cells. They are anticipated to have proteomes that closely reflect the ensemble of proteins secreted from the respective GI tissues. Most importantly, the disease markers present in GI fluids should be present in higher concentrations than in sera, thus offering greater sensitivity in their detection. However, proteome analysis of GI fluids can be complex mainly due to the dynamic range of protein content and the numerous PTMs of proteins in each specialized GI compartment. This review attempts to discuss the physiology of the various GI fluids, the special technical considerations required for proteome analysis of each fluid, as well as to summarize the current state of knowledge of biomarker discoveries and clinical utility of GI fluids such as salivary, gastric, pancreatic, and biliary secretions.     

An intelligent system for automatic layout routing in aerospace design

This paper discusses the development of an intelligent routing system for automating design of electrical wiring harnesses and pipes in aircraft. The system employs knowledge based engineering (KBE) methods and technologies for capturing and implementing rules and engineering knowledge relating to the routing process. The system reads a mesh of three dimensional structure and obstacles falling within a given search space and connects source and target terminals satisfying a knowledge base of design rules and best practices. Routed paths are output as computer aided design (CAD) readable geometry, and a finite element (FE) mesh consisting of geometry, routed paths and a knowledge layer providing detail of the rules and knowledge implemented in the process. Use of this intelligent routing system provides structure to the routing design process and has potential to deliver significant savings in time and cost.     

Identification of new material model for machining simulation of Inconel 718 alloy and the effect of tool edge geometry on microstructure changes

Johnson–Cook (J-C) material model is often used for Finite Element (FE) modeling of cutting processes and it affects significantly the results of simulation. Since experimentally determination of J-C equation parameters is an expensive and time-consuming task, in this paper, a new and efficient methodology was implemented based on the evolutionary optimization algorithm to identify new J-C material constants for Inconel 718 superalloy. Then, orthogonal cutting process of Inconel 718 was simulated using the new material models. The results of simulation were compared extensively with experimental results of cutting forces, chip geometry, and maximum temperature to select and then validate the most suitable material model. After that, a user subroutine was implemented in FE code to model microstructure changes using the dynamic recrystallization mechanism in cutting process of Inconel 718. The Zener–Hollomon and Hall–Petch equations were used to respectively predict the grain size and hardness. The results of simulation were verified successfully with corresponding experiments in terms of near-surface profile. At the end, the effect of tool edge geometry including honed and chamfered tool edge was investigated on microstructure changes.     

Hybrid plate vibration models for coarse-mesh analysis

Hybrid FE combined membrane + bending rectangular plate vibration models (7 + 11)βC⁰ and (7 + 17)βC¹ are proposed for computer assisted identification of vibration modes for high degree efficient coarse-mesh analysis. Accurate yet cost effective hierarchial FE matrix generation capability is provided through the expedient of an exact analytical integration algorithm, which circumvents many time consuming steps and associated controversies of the numerical quadrature interactions, while yielding computational economy comparable to that required by the single-point Gaussian rule. Samples of numerical experiments corroborate the present development and confirm the high accuracy with rapid convergence characteristics.     

泡沫铝部分填充薄壁梁弯曲吸能特性研究

为了研究泡沫铝填充帽型薄壁梁横向弯曲时的吸能特性,建立了泡沫铝填充双帽型薄肇粱的有限元模型,采用非线性有限元软件LS-DYNA进行了横向弯曲工况下的仿真.首先进行了空心帽型薄壁梁和泡沫铝填充帽型薄壁梁的横向弯曲仿真,分析了材料参数、几何参数对其比吸能(单位质量吸收的能量)的影响;然后为降低结构重量并保持薄壁梁吸能效果,对部分填充泡沫铝薄壁梁进行了横向弯曲仿真,考察了不同泡沫铝填充长度对结构吸能特性的影响.研究结果表明:填充泡沫铝后,帽型薄壁梁在横向弯曲中吸能特性有明显的改善;在吸收相同的能量时,泡沫铝填充薄壁梁的质量要比空心薄壁梁的质量少.     

基于SOPC的井喷预测系统设计

介绍了SOPC技术为核心逻辑模块的井喷预测系统,对井喷预兆、原因和相关参量变化规律进行了分析;描绘了系统组成结构,给出了硬件原理框图,并对系统进行了分解;系统应用计算机对钻井过程中相关参量的变化进行实时监测,研究智能决策方法,实现了对钻井过程中可能发生的溢流、井涌、井喷等进行科学的预测和预报;实际应用证明,系统有效并可靠地完成井喷的预测预报任务;系统的研制成功,对确保油气勘探开发作业安全起到重要作用,具有广阔的推广应用前景.     

Child head injury criteria investigation through numerical simulation of real world trauma

Finite element modelling has been used for decades in the study of adult head injury biomechanics and determination of injury criteria. Interest is recently growing in investigation on pediatric head injury which requires elaboration of biofidelic models that take into account child's head particularities in terms of size, geometry, and mechanical properties. In this study, a finite element model of a 3-year-old child head is proposed. The model is reconstructed from real CT scan images and mechanical properties are extracted from available data in the literature. A large number of real accidents (25 falls) are reconstructed with proposed model using different brain constitutive relationships in order to investigate their influence on model response. Mechanical output parameters (HIC, pressure, shearing stress) are calculated from these simulations. Statistical analysis was performed in order to evaluate predictive capability of the parameters. Von Mises stress appears to be clearly the most predictive parameters, allowing clear distinction between injured and non-injured cases. To the authors' knowledge, this study proposes for the first time a statistically based neurological injury criterion for a pediatric population using finite element modelling.     

Texturing 3D Models of Real World Objects from Multiple Unregistered Photographic Views

As the efficiency of computer graphic rendering methods is increasing, generating realistic models is now becoming a limiting factor. In this paper we present a new technique to enhance already existing geometry models of real world objects with textures reconstructed from a sparse set of unregistered still photographs. The aim of the proposed technique is the generation of nearly photo-realistic models of arbitrarily shaped objects with minimal effort. In our approach, we require neither a prior calibration of the camera nor a high precision of the user's interaction. Two main problems have to be addressed of which the first is the recovery of the unknown positions and parameters of the camera. An initial estimate of the orientation is calculated from interactively selected point correspondences. Subsequently, the unknown parameters are accurately calculated by minimising a blend of objective functions in a 3D-2D projective registration approach. The key point of the proposed method of registration is a novel filtering approach which utilises the spatial information provided by the geometry model. Second, the individual images have to be combined yielding a set of consistent texture maps. We present a robust method to recover the texture from the photographs thereby preserving high spatial frequencies and eliminating artifacts, particularly specular highlights. Parts of the object not seen in any of the photographs are interpolated in the textured model. Results are shown for three complex example objects with different materials and numerous self-occlusions.     

电子车长测试平台气路模糊控制的实现

介绍了电子车长测试平台中广泛采用人工控制测试气压方式精度差、效率低的问题。提出了采用模糊控制策略及CAN总线、RS232、RS485等多种通讯方式,应用上位机软件将系统集成,控制测试系统中气压的方法与实现,达到了提高测试精度、效率和稳定性的目的。     

Geometry Textures and Applications†

Geometry textures are a novel geometric representation for surfaces based on height maps. The visualization is done through a graphics processing unit (GPU) ray casting algorithm applied to the whole object. At rendering time, the fine‐scale details (mesostructures) are reconstructed preserving original quality. Visualizing surfaces with geometry textures allows a natural level‐of‐detail (LOD) behaviour. There are numerous applications that can benefit from the use of geometry textures. In this paper, besides a mesostructure visualization survey, we present geometry textures with three possible applications: rendering of solid models, geological surfaces visualization and surface smoothing.     

Serial 3D model reconstruction for machining evolution of rotational parts by merging semantic and graphic process planning information

The manufacturing of a mechanical part is a dynamic evolution process from a raw workpiece to the final part, in which the generation of serial 3D models reflecting the changes on geometric shapes is especially critical to digital manufacturing. In this paper, an approach driven by the process planning course, the machining semantics and the machining geometry to reconstruct incrementally the serial 3D models for rotational part’s dynamic evolution is proposed. The two major techniques involved are: (1) extraction of machining semantics based on process planning language understanding; (2) 3D reconstruction from 2D procedure working drawings guided by machining semantics and visualization for the reconstructed series of 3D models. Compared with the conventional 3D reconstruction methods, this approach introduced the process planning course and relevant information to implement a dynamic, incremental and knowledge-based reconstruction which can greatly reduce the efforts in reconstruction and extend the collection of geometric shapes to be reconstructed.