Similarity-Based Decision Support for Internet Enabled Supply-Web Interactions

New approaches for decision making are emerging to support the use of the Internet for supply-web interactions in the manufacturing industry. In this paper, we discuss one such paradigm, namely similarity-based decision support. It recognizes that knowledge of similar experiences can support rapid and effective decision making in various forms of supply-web interactions. We illustrate this approach using two prototype systems, WebScout (an agent-based system for customer–supplier matchmaking in the job-shop machining industry context) and TOME (Treasury of Manufacturing Experiences — an Intranet application to aid manufacturability assessment in foundries).

A Computational Study of the Interaction of Melting Soil With Moisture Transport in the Native Soil

The current paper describes a computer model designed to analyze the moisture transport in the unmelted, porous soil neighboring a convecting melt. The time-dependent fluid and heat flow in the soil melt is simulated implicitly using the SIMPLE method generalized to predict viscous fluid motion and heat transfer on boundary-fitted, non-orthogonal coordinates which adapt with time. TOUGH2, a general-purpose computer code for multiphase fluid and heat flow developed by K. Pruess at Lawrence Berkekey Laboratory, has been modified for use on time-adaptive, boundary-fitted coordinates to predict heat transfer, moisture and air transport, and pressure distribution in the porous, unmelted soil. The soil melt model is coupled with the modified TOUGH2 model via an interface (moving boundary) whose shape is determined implicitly with the progression of time. The computer model’s utility is demonstrated in the present study with a special two-dimensional study. A soil initially at 20°C and partially-saturated with either a 0.2 or 0.5 relative liquid saturation is contained in a box two meters wide by ten meters high with impermeable bottom and sides. The upper surface of the soil is exposed to a 20°C atmosphere to which vapor and air can escape. Computation begins when the soil, which melts at 1700°C, is heated from one side (maintained at constant temperatures ranging from 1700°C to 4000°C). Heat from the hot wall causes the melt to circulate in such a way that the melt interface grows more rapidly at the top of the box than at the bottom. As the upper portion of the melt approaches the impermeable wall it creates a bottle neck for moisture release from the soil’s lower regions. The pressure history of the trapped moisture is examined as a means for predicting the potential for moisture penetration into the melt. The melt’s interface movement and moisture transport in the unmelted, porous soil are also examined.

Feature-Based Machining Precedence Reasoning and Sequence Planning

This paper presents a feature-based method to support machining sequence planning. Precedence relations among machining operations are systematically generated based on geometric information, tolerance specifications, and machining expertise. The feature recognition method using Alternating Sum of Volumes With Partitioning (ASVP) Decomposition is applied to obtain a Form Feature Decomposition (FFD) of a part model. Form features are classified into a taxonomy of atomic machining features, to which machining process information has been associated. Geometry-based precedence relations between features are systematically generated using the face dependency information obtained by ASVP Decomposition and the features’ associated machining process information. Multiple sets of precedence relations are generated as alternative precedence trees, based on the feature types and machining process considerations. These precedence trees are further enhanced with precedence relations from tolerance specifications and machining expertise. Machining sequence planning is performed for each of these precedence trees, applying a matrix-based method to reduce the search space while minimizing the number of tool changes. The precedence trees may then be evaluated based on machining cost and other criteria. The precedence reasoning module and operation sequence planning module are currently being implemented within a comprehensive Computer-Aided Process Planning system.

Structural Analysis by the Differential Quadrature Method Using Modified Weighting Matrices

The differential quadrature method has lately been more and more often used for analysis of engineering problems as an alternative for the finite element method or finite difference method. In this paper, static, dynamic and buckling analyses of structural components are performed by the differential quadrature method. To improve the accuracy of this method, an approach is proposed for selecting the sampling points which include base points and conditional points. The base points are taken as the roots of the Legendre polynomials. Accuracy of the problems analyzed will be increased by using the base points. The conditional points are determined according to boundary conditions and specified conditions of external load. A modified algorithm is proposed for applying two or more boundary conditions in a sampling point at boundary of domain, such that the higher-order partial differential equation can be solved without adding new sampling points. By applying this approach to variety problems, such as deflections of beam under nonuniformly distributed loading, vibration and buckling analyses of beam and plate, it is found that numerical results of the present approach are more accurate than those obtained by the equally-spaced differential quadrature method and is computationally efficient.

Influence of Imperfections in the Working Media on Diesel Engine Indicator Process: Part 2 — Results

In the companion Part 1 of this two-part series paper several improvements to the mathematical model of the energy conversion processes, taking place in a diesel engine cylinder, have been proposed. Analytical mathematical dependencies between thermal parameters (pressure, temperature, volume) and caloric parameters (internal energy, enthalpy, specific heat capacities) have been obtained. These equations have been used to provide an improved mathematical model of diesel engine indicator process. The model is based on the first law of thermodynamics, by taking into account imperfections in the working media which appear when working under high pressures and temperatures. The numerical solution of the simultaneous differential equations is obtained by Runge-Kutta type method. The results show that there are significant differences between the values calculated by equations for ideal gas and real gas under conditions of high pressures and temperatures. These equations are then used to solve the desired practical problem in two different two-stroke turbo-charged engines (8DKRN 74/160 and Sulzer-RLB66). The numerical experiments show that if the pressure is above 8 to 9 MPa, the working medium imperfections must be taken into consideration. The mathematical model presented here can also be used to model combustion process of other thermal engines, such as advanced gas turbine engines and rockets.

An Automated CFD Design and Analysis Tool for Inlet-Bleed Systems

A pre-processor was developed to assist CFD experts and non-experts in performing steady, three-dimensional Navier-Stokes analysis of a class of inlet-bleed problems involving oblique shock-wave/ boundary-layer interactions on a flat plate with bleed into a plenum through rows of circular holes. With this pre-processor, once geometry (e.g., hole dimensions and arrangement) and flow conditions (e.g., Mach number, boundary-layer thickness, incident shock location) are inputted, it will automatically generate every file needed to perform a CFD analysis from the grid system to initial and boundary conditions. This is accomplished by accessing a knowledge base established by experts who understand both CFD and the class of problems being analyzed. For experts in CFD, this tool greatly reduces the amount of time and effort needed to setup a problem for CFD analysis. It also provides experts with knobs to make changes to the setup if desired. For non-experts in CFD, this tool enables reliable and correct usage of CFD. A typical session on a workstation from data input to the generation of all files needed to perform a CFD analysis involves less than ten minutes. This pre-processor, referred to as AUTOMAT-V2, is an improved version of a code called AUTOMAT. Improvements made include: (1) multi-block structured grids can be patched in addition to being overlapped; (2) embedded grids can be introduced near bleed holes to reduce the number of grid points/cells needed by a factor of up to four; (3) grid systems generated allow up to three levels of multigrid; (4) CFL3D is supported in addition to OVERFLOW, two well-known and highly regarded Navier-Stokes solvers developed at NASA’s Langley and Ames Research Centers; (5) all files needed to run RONNIE for patched grids and MAGGIE for overlapped grids are also generated; and (6) more design parameters can be investigated including the study of micro bleed and effects of flow/hole misalignments.

Internet-Based Concurrent Engineering: An Interactive 3D System With Markup

Although Concurrent Engineering can offer substantial benefits, and hence many companies take a strong interest in the collaborative approach, it is not yet clear how it can best be implemented, particularly for a geographically distributed Concurrent Engineering team that may be using a disparate range of computer systems. The recent rise in the number connected to the Internet would offer the possibility of using Internet standards to allow for collaboration over the Internet. Central to the use of Internet standards for Concurrent Engineering is the key area of transmitting and viewing CAD and engineering information, and of communication between team members. This paper is concerned with addressing this issue and describes the how 3D CAD files can be viewed, and engineering information exchanged, by geographically distributed team members in an interactive manner using Internet standards. In particular this paper is concerned with the issue of storing STEP data so that it can be retrieved efficiently, how this data can be converted from STEP data to the Virtual Reality Modeling Language (VRML) to allow the product to be viewed in interactive 3-D on a wide number of platforms using the Internet, and is concerned with the issue of how team members can markup the VRML worlds, with other team members being able to examine the markup comments of others. An algorithm for converting STEP data to VRML is described and an overview of the implementation of this approach, in a system called CyberView, is given. The result of this is that users from disparate functions, on a wide variety of platforms, can view products in interactive 3-D through the Internet, can comment on aspects of the design, and can examine the markup comments of other team members on particular aspects of the design. Such an approach offers the promise of improved communication and hence for enhancing the product development process.

A Temporal Process Specification Language for Virtual Manufacturing Engineering

A process specification language is being developed for virtual manufacturing that provides a structured portable definition of a given manufacturing process as well as the ability to specify the temporal relationships between individual operation steps that compose a process. Based on the concepts embodied in markup languages such as HTML, SGML and XML, a portable process definition structure is defined. This structure provides a template from which virtual process specifications can be created. Subsequently, these structures can be exchanged between development environments for virtual process engineering and the actualized manufacturing facilities where processes are implemented. In addition, dependencies in time between the operation steps of a process such as common start times and operation serialization can be represented to allow for a complete specification of temporal behavior of a given manufacturing process. By providing this explicit mechanism for representing temporal constraints, a virtual manufacturing process can be viewed and utilized both in a localized application on a single virtual factory floor as well as distributed across multiple, interlinked virtual environments.

Features and Constraints in Architectural Design

The concepts of the experimental design system that are discussed are feature modeling and geometrical constraints. The main technique for creating the user environment is Virtual Reality. Feature modeling forms the basis for managing the design data. To start with, data storage is implemented in a Relational Data Base Management System. Along with this a (traditional) interface is developed for managing the data. Data management consists of feature type creation and feature type instancing. Features are used to define building elements, their relationships and additional constraints. Apart from the design data, geometrical data are stored. The system contains a library of parameterized geometrical objects which format is in coherence with the geometrical modeling environment (VR). Possible design solutions can be limited using geometrical constraints. Specifying connection types between building elements result in a set of solutions for the position of the bounding boxes of the building elements in space.

Some Comments on the Differential Model of Hysteresis

The differential model of hysteresis has found general acceptance in computational mechanics. Shapes of hysteresis loops generated by the model depend on both the loop parameters and external excitation. In this paper, sensitivity of the differential model to various constituent parameters is studied. A more robust model of hysteresis can be constructed if sensitivity to loop parameters and excitation can be better understood.