bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapidly dissolving dense bodies in an inviscid fluid
Authors: Eames I
Published: July 2008

We study the rapid dissolution of a dense rigid body (a cylinder or sphere; density
ρ
p
), fixed in a uniform flow of speed
U
(density
ρ
f
), within an inviscid framework. The body consists of
N
shells, and dissolves through a series of discrete steps, where after each shell dissolves, it is pushed out by a radial flow. The flow through the surface of the body pushes bound vorticity into the ambient flow, creating free vorticity and satisfying, at the same time, Kelvin's circulation theorem. The circulation of each shell is described by a Lagrangian equation describing the position of each shell and an integral relationship between the circulation of the shells dissolved and the bound vorticity. The thermal component is neglected from this analysis.

The impulse of the exterior fluid increases to compensate for the decrease in the momentum of the body. The bodies are fixed as they dissolve so that the sum of the flow impulse and body momentum is only approximately conserved. The impulse of the vorticity field created after the body has disappeared,
I
T
, is approximately equal to the initial momentum of the body,
ρ
p
UV
(where
V
is the initial volume of the body). The total circulation in the upper half-plane is
Γ
≈
Γ
0
+
C

Γ

(
ρ
p
/
ρ
f
)

1/
N

a
0
U
, where
N
=2, 3 for a cylinder, sphere, respectively, and
C

Γ

∼
O
(1) a constant. The total kinetic energy associated with the vorticity field after the body has disappeared is
T
∼(1/2)
ρ
p
C

T

VU
2
, where
C

T

<1. The sum of the kinetic energy of the flow and body is not conserved.

After the cylinder/sphere has disappeared, the vorticity distribution rolls up to produce a dipolar vortex/vortex ring. The properties of these dipolar structures are estimated assuming a final form and the conservation of
T
,
Γ
and
I
T
. A dense cylinder dissolves to create a vortex that has a radius 1.3
a
0
(
ρ
p
/
ρ
f
)
1/2
and moves with a speed 0.28
U
, while a dense sphere dissolves to create a vortex of radius 0.65
a
0
(
ρ
p
/
ρ
f
)
1/3
, which moves with a speed 0.50
U
.
Nasal architecture: form and flow
Authors: Doorly D.J , Taylor D.J , Gambaruto A.M , Schroter R.C , Tolley N
Published: July 2008

Current approaches to model nasal airflow are reviewed in this study, and new findings presented. These new results make use of improvements to computational and experimental techniques and resources, which now allow key dynamical features to be investigated, and offer rational procedures to relate variations in anatomical form. Specifically, both replica and simplified airways of a single subject were investigated and compared with the replica airways of two other individuals with overtly differing geometries. Procedures to characterize and compare complex nasal airway geometry are first outlined. It is then shown that coupled computational and experimental studies, capable of obtaining highly resolved data, reveal internal flow structures in both intrinsically steady and unsteady situations. The results presented demonstrate that the intimate relation between nasal form and flow can be explored in greater detail than hitherto possible. By outlining means to compare complex airway geometries and demonstrating the effects of rational geometric simplification on the flow structure, this work offers a fresh approach to studies of how natural conduits guide and control flow. The concepts and tools address issues that are thus generic to flow studies in other physiological systems.
Cryocrystallography in capillaries: critical glycerol concentrations and cooling rates
Authors: Warkentin Matthew , Stanislavskaia Valentina , Hammes Katherine , Thorne Robert E.
Published: June 2008

Capillary tubes have many advantages over multi-well plates for macromolecular crystal growth and handling, including the possibility ofin situstructure determination. To obtain complete high-resolution X-ray data sets, cryopreservation protocols must be developed to prevent crystalline ice formation and preserve macromolecular crystal order. The minimum glycerol concentrations required to vitrify aqueous solutions during plunging into liquid nitrogen and liquid propane have been determined for capillary diameters from 3.3 mm to 150 µm. For the smallest diameter, the required glycerol concentrations are 30%(w/v) in nitrogen and 20%(w/v) in propane, corresponding to cooling rates of ∼800 and ∼7000 K s−1, respectively. These concentrations are much larger than are required in current best practice using crystals in loops or on microfabricated mounts. In additon, the relation between the minimum cooling rate for vitrification and glycerol concentration has been estimated; this relation is of fundamental importance in developing rational cryopreservation protocols.
Treating nerves: a call to arms
Authors: Hughes Richard A. C.
Published: June 2008

Abstract  The process of proving that new treatments for peripheral nerve diseases work has often been slow and inefficient. The lack of adequate evidence for some existing treatments has been highlighted by Cochrane systematic reviews. This article uses four different conditions to illustrate the need for more research. Both corticosteroid injections and surgical decompression of the median nerve are efficacious in carpal tunnel syndrome, but whether corticosteroid injections avoid the need for operation needs to be discovered. Corticosteroids are efficacious for Bell’s palsy, but the role of antiviral agents needs clarification, which should come from ongoing trials. Intravenous immunoglobulin (IVIg) and plasma exchange are both efficacious in Guillain‐Barré syndrome, but corticosteroids are not. More trials are needed to discover the best dose of IVIg in severe cases and whether mild cases need treatment. In chronic inflammatory demyelinating polyradiculoneuropathy, corticosteroids, IVIg and plasma exchange are all efficacious, at least in the short term, but trials are needed to discover whether and which other immunosuppressive agents help. The Peripheral Nerve Society has formed a standing committee, the Inflammatory Neuropathy Consortium (http://pns.ucsd.edu/INC.htm), to facilitate the trials needed to answer the remaining questions in the inflammatory neuropathies.
Automated Symmetry Exploitation in Engineering Analysis
Authors: Suresh Krishnan
Published: June 2008

It is well known that one can exploit symmetry to speed-up engineering analysis and improve accuracy, at the same time. Not surprisingly, most CAE systems have standard ‘provisions’ for exploiting symmetry. However, these provisions are inadequate in that they needlessly burden the design engineer with time consuming and error-prone tasks of symmetry detection, symmetry cell construction and reformulation. In this paper, we propose and discuss an automated methodology for symmetry exploitation. First, we briefly review the theory of point symmetry groups that symmetry exploitation rests on. We then address symmetry detection and ‘symmetry cell’ construction. We then address an important concept of boundary mapping of symmetry cells, and relate it to the irreducible representations of point symmetry groups. By formalizing these concepts, we show how automated symmetry exploitation can be achieved, and discuss an implementation of the proposed work within the FEMLAB CAE environment.
On the Design Synthesis of Multistable Equilibrium Systems
Authors: King Carey W. , Campbell Matthew I. , Beaman Joseph J.
Published: June 2008

Multistable equilibrium (MSE) systems are a type of adaptable system that can have multiple mechanical configurations requiring no power to maintain the stable configurations. Thus, power is only needed to move among the stable states, and each stable configuration represents a level of adaptability. Since stable equilibrium configurations can be defined by potential energy minima, we base the design of MSE systems on shaping the potential energy curve at desired equilibrium configurations. This view allows one to construct a performance space defined by how well candidate systems meet a desired potential energy curve. By using a Monte Carlo mapping to link the performance space to the design space in tandem with stochastic optimization methods, the designer determines whether or not a certain system topology can be designed as a MSE system. Qualitative and quantitative mapping procedures enable the designer to decide whether or not the desired design lies near the center or periphery of a performance space. This dictates how the optimization is to be executed which in turn informs the designer as to whether or not a feasible limit in the system performance has indeed been reached.
Concurrent Parameter Design Based on Constraint Network
Authors: Fan Wenhui , Li Tao , Xiong Guangleng
Published: June 2008

A Concurrent Parameter Design (CPD) based on constraint network method is proposed. Since concurrent design emphasizes solving downstream problems early in the design period, the constraint network, which is used to collect the constraints from the multidisciplinary teams, uses the consistency algorithm to verify the design process early in the process and to assist the designers in determining design variables to reduce the multidisciplinary iterations in concurrent design. A consistency algorithm which is designed using interval arithmetic to refine the intervals is used to obtain a feasible solution space for the designers. Then, the designers choose the parameters in the solution space using their expertise. The constraint network can reduce the modification iterations among the multidisciplinary teams during the concurrent design. The quantitative effect of the downstream constraints can be analyzed before determining the design parameters and potential conflicts can be predicted. A parameter design example about Bogie of Railway Rolling Stock is given to show the validity of the method.
An Efficient Weighting Update Method to Achieve Acceptable Consistency Deviation in Analytical Target Cascading
Authors: Michalek Jeremy J. , Papalambros Panos Y.
Published: June 2008

Weighting coefficients are used in Analytical Target Cascading (ATC) at each element of the hierarchy to express the relative importance of matching targets passed from the parent element and maintaining consistency of linking variables and consistency with designs achieved by subsystem child elements. Proper selection of weight values is crucial when the top level targets are unattainable, for example when “stretch” targets are used. In this case, strict design consistency cannot be achieved with finite weights; however, it is possible to achieve arbitrarily small inconsistencies. This article presents an iterative method for finding weighting coefficients that achieve solutions within user-specified inconsistency tolerances and demonstrates its effectiveness with several examples. The method also led to reduced computational time in the demonstration examples.
Task Scheduling of Parallel Development Projects Using Genetic Algorithms
Authors: Zhuang Miao , Yassine Ali A.
Published: June 2008

Resources for development projects are often scarce in the real world. Generally, many projects are to be completed that rely on a common pool of resources. Besides resource constraints, there exists data dependency among tasks within each project. A genetic algorithm approach with one-point uniform crossover and a refresh operator is proposed to minimize the overall duration or makespan of multiple projects in a resource constrained multi project scheduling problem (RCMPSP) without violating inter-project resource constraints or intra-project precedence constraints. The proposed GA incorporates stochastic feedback or rework of tasks. It has the capability of capturing the local optimum for each generation and therefore ensuring a global best solution. The proposed Genetic Algorithm, with several variants of GA parameters is tested on sample scheduling problems with and without stochastic feedback. This algorithm demonstrates to provide a quick convergence to a global optimal solution and detect the most likely makespan range for parallel projects of tasks with stochastic feedback.
Modeling and Design of Materials for Controlled Wave Propagation in Plane Grid Structures
Authors: Ma Liangkai , Diaz Alejandro , Haddow Alan
Published: June 2008

Formulations for the optimal design of plane grids with maximum band gaps are presented. Periodic band-gap structures prevent waves in certain frequency ranges from propagating. Materials or structures with band gaps have many applications, including frequency filters, vibration protection devices and wave guides. Here, a simple model of a periodic plane grid structure is presented and then an optimization problem is formulated where the structure’s band gap above a particular frequency is maximized by the selective addition of non-structural masses. Numerical implementation issues are discussed and examples are presented.
An Efficient Pareto Set Identification Approach for Multi-Objective Optimization on Black-Box Functions
Authors: Wang G. Gary , Shan Songqing
Published: June 2008

Both multiple objectives and computation-intensive black-box functions often exist simultaneously in engineering design problems. Few of existing multi-objective optimization approaches addresses problems with expensive black-box functions. In this paper, a new method called the Pareto set pursing (PSP) method is developed. By developing sampling guidance functions, this approach progressively provides a designer with a rich and evenly distributed Pareto optimal points. This work describes PSP in detail with analysis of its properties. From testing and design application, PSP demonstrates considerable efficiency, accuracy, and robustness. Theoretical proof of convergence of PSP is also given. It is believed that PSP has a great potential to be a practical tool for multi-objective optimization problems.
A Parametric Approach to Vehicle Seating Buck Design
Authors: Wang Nanxin , Wan Jian , Gomez-Levi Gianna
Published: June 2008

Vehicle package development is an important part of the entire vehicle design. It consists of determining the occupant’s spatial environment, the vehicle’s mechanical spatial configuration and the overall exterior/interior dimensions while meeting the engineering requirements, including packaging, structure, manufacturing, etc. Developing and verifying the occupant compartment configuration is usually conducted by using a seating buck. To build a seating buck, vehicle interior surfaces are generated in CAD using vehicle exterior surfaces, package layouts and master sections. During early program stages, this information is scattered, incomplete and constantly changing, which makes the seating buck creation challenging and the package design decision-making more difficult. A new method has been developed to quickly generate the seating buck surfaces from scattered information. It has shown to significantly reduce the time conventionally required for the seating buck surface modeling. This paper documents the method and process and summarizes the potential of the method and its impact on vehicle package design.
Design of Components With Optimized Microstructure
Authors: Stahl Douglas C. , Batdorff Mark
Published: June 2008

The ability to optimize shape and microstructure creates tremendous potential for designing lightweight high-performance structural components, but this potential can only be realized if design procedures are effectively linked to fabrication techniques. In this paper we describe such links. The key to this work is to base the topology optimization on a unit cell that matches the physical unit cell used in the fabricated object. Distortion and rotation of the unit cell can control effective material properties at all locations within the component by affecting changes in density, degree of anisotropy, and orientation of principle material axes. Advances in solid freeform fabrication (SFF) and related hybrid fabrication techniques make production of components with complex microstructures feasible. This paper describes the complete design process, from specializations of topology optimization to interpretation of optimization results and communication of design information to SFF machines. The process includes a new procedure to establish the orientation of an orthotropic material for multiple loading cases.
An Integrated Design Support Environment for a Micro-Scale Portable Absorption Cooling System
Authors: Daniels Brian J. , Ballal Ashutosh , Ge Ping , Drost Kevin
Published: June 2008

Portable cooling systems play an important role in assisting human operations in unfriendly environments, such as soldiers continuously working in a desert area for long hours. Typical cooling system designs utilizing a vapor compression cycle driven by electrical power usually have high weights due to batteries and as a result, compromise the effectiveness of the portable cooling system. A self-contained absorption cycle cooling system design based on micro-scale thermal technology has demonstrated unique advantages in minimizing system weight while providing reasonable thermal efficiency. This system adopts a heat actuated absorption/desorption thermal cycle to raise the pressure of the refrigerant vapor without a heavy battery load. Design challenges exist: 1) multi-physics considerations when integrating the thermodynamic and transport models for the heat pump and peripheral component devices; 2) trade-off among multi-functional design requirements of system weight and thermal efficiency, using the inputs of cooling load, heat rejection temperature, and heat transfer characteristics based on the micro-channel geometry. No existing design automation tools are available on the market to directly support these design tasks. In this work, physics-based system-level models are developed and validated against state-of-the-art prototypes. The use of these models is demonstrated through the design of a 150-watt portable cooling system, typically used by the military in desert training. The system modeling methodology is implemented in Java as a part of an Integrated Design Support Environment, and has been used to generate trade-off study results. These results show that the current implementation is effective, and is a significant step toward a complete integrated design support environment to analyze and synthesize high-quality micro-scale portable cooling systems.
Geometric Containment Analysis for Rotational Parts
Authors: Karnik Mukul , Gupta Satyandra K. , Magrab Edward B.
Published: June 2008

This paper describes a system and underlying algorithms to perform geometric containment analysis to determine if a newly designed rotational part can be manufactured from a part in an existing database of rotational parts. Only material removal of the database part is considered in order to obtain the newly designed part from the database part. The system uses a three-step algorithm to test for containment. The first step analyzes feasibility of containment using bounding cylinders. If the bounding cylinder of the query part is bigger than the part in the database, then the database part cannot contain the query part and it is eliminated from consideration. The second step analyzes feasibility of containment by ignoring off-axis features. Any part that fails to satisfy containment at this stage is eliminated from consideration. The third step analyzes the remaining parts from the database for feasibility of containment by including the off-axis features. Finally, the system rank-orders all the database parts that can contain the query part based on their volume differences with the query part. The system described in this paper can be used to find an existing part from which to manufacture a newly designed part. This capability is expected to significantly reduce proliferation of parts, to improve manufacturing responsiveness, and to reduce the cost of new products.
A New Approach for Simultaneous Shape and Topology Optimization Based on Implicit Topology Description Functions
Authors: Guo Xu , Zhao Kang , Wang Michael Yu
Published: June 2008

In the present paper, a new approach for structural topology optimization based on implicit topology description function (TDF) is proposed. TDF is used to describe the shape/topology of a structure, which is approximated in terms of the nodal values. Then a relationship is established between the element stiffness and the values of the topology description function on its four nodes. In this way and with some non-local treatments of the design sensitivities, not only the shape derivative but also the topological derivative of the optimal design can be incorporated in the numerical algorithm in a unified way. Numerical experiments demonstrate that by employing this approach, the computational efforts associated with TDF (and level set) based algorithms can be saved. Clear optimal topologies and smooth structural boundaries free from any sign of numerical instability can be obtained simultaneously and efficiently.
On Electrochemical Deposition for Layered Manufacturing
Authors: Anderson Rhonda , Ganter Mark , Schwartz Dan , Storti Duane , Whitaker John
Published: June 2008

This paper describes the initial results from new research in the area of electrochemical deposition applied to rapid layered manufacturing with heterogeneous materials. Our interest in electrochemical layered manufacturing stems from earlier collaborative projects on heterogeneous modeling and fabrication [1–4]. The current work focuses on employing electrochemical deposition of binder into layers sequentially added to a powder bed as a method for additive fabrication of working parts. We show that electrodeposition provides a feasible approach to (1) eliminating the need for a fugitive binder system, (2) reducing thermal postprocessing operations for three-dimensional printing of working parts, and (3) achieving a room temperature fabrication process minimizing the need for thermal postprocessing thereby eliminating residual thermal stresses and dimensional inaccuracies from thermal expansion/contraction associated with processing at elevated temperatures. We also demonstrate the feasibility of direct, single-step fabrication of fully dense parts.
Robustness and Performance Optimization of Engine Bearing System Using Computer Model and Surrogate Noise
Authors: Ejakov Mikhail , Sudjianto Agus , Pieprzak John
Published: June 2008

Designing an internal combustion engine involves compromising among multiple performance metrics and targets with multiple control and noise factors. The main challenges are in determining the critical performance metrics, finding the optimal compromise between these metrics, and correctly represent the most important control and noise factors through CAE modeling and optimization. This paper presents a methodology for practical application of robustness and performance optimization using a CAE model. The key element of the methodology is a concept of surrogate noise. With this concept, the multiple noise factors affecting the system performance are represented through a limited number of noise factors for CAE modeling. The other part of the methodology is to substitute complicated and computationally time intensive CAE modeling with a cheap-to-compute Gaussian Kriging model through Optimal Sampling and Design of Experiment. The final part of the methodology is performing multi-criteria robustness and performance optimization as well as performance and robustness confirmation of the optimal design point. The proposed methodology has been applied to a practical problem of designing the IC engine main bearing system. The results of the analysis have provided practical recommendations and directions to drive the main bearing system design. In this paper, the methodology is demonstrated through the presentation of a simplified form of this investigation.
Design Optimization of Enclosed Liquid Containers With Baffles for Sloshing and Impact
Authors: Kingsley T. C. , Craig K. J.
Published: June 2008

A multidisciplinary optimization method is presented to support the design process of partially-filled liquid containers subject to the disciplines of sloshing and impact analysis. This paper represents a part of a study on Multidisciplinary Design and Optimization of liquid containers, and shows experimental techniques used to try to better understand sloshing as a phenomenon and to evaluate the capabilities of the commercial Computational Fluid Dynamics (CFD) code in question. Experimental validation includes qualitative comparison of visual free-surface behavior and quantitative comparisons of pressure measurements in the time and frequency domain. The liquid motion exhibits good comparisons in time with some deviations in wave amplitude due to a modification of the low frequency content of the input signal to the CFD simulation. This modification was caused by both the experimental signal filtration process and deficiencies in the low-frequency measurement capability of the accelerometer. In the frequency domain the first two odd oscillatory modes are accurately captured. A candidate objective function for the quantitative evaluation of the sloshing phenomenon is proposed. Using the response surface method in LS-OPT, various single (sloshing or impact only) and multidisciplinary optimization formulations are presented and results are examined. As expected, the multidisciplinary optimum proved to be a compromise between the optima obtained when considering the two single disciplines independently.
A Formal Approach to Handling Conflicts in Multiattribute Group Decision Making
Authors: See Tung-King , Lewis Kemper
Published: June 2008

The Hypothetical Equivalents and Inequivalents Method (HEIM) has been developed to support decision making in multiattribute problems where one decision maker is making the decision. In this paper HEIM is modified to support group decision making in multiattribute problems, resulting in the Group Hypothetical Equivalents and Inequivalents Method (G-HEIM). Instead of aggregating attribute weights or overall alternative values from each individual as is common in other group decision methods, G-HEIM operates by aggregating individual preferences. It is recognized that in group decision making, common preferences among group members can rarely be guaranteed, unless individual freedom is greatly limited. G-HEIM instead allows individuals to freely express preferences over a number of hypothetical alternatives and then explores the level of conflict or differences from the aggregated group preferences. The relationship between the level of conflicting preferences and the usability of the resulting decision is also directly studied using the G-HEIM. An automotive selection example is used to illustrate the approach.
Purely Declarative Feature-Based Design With Feature Type Property Maintenance
Authors: Lokagariwar Dhaval , Bettig Bernhard
Published: June 2008

Commercial feature-based design systems are based on describing the design model in some form of sequential representation of primitive shapes and operations called features. In these systems, the overall design process, the behavior of building blocks and the characteristics of the final model, are governed by the construction sequence. These systems do not check for the conformity of the final shape with the actual design intent of features, and allow their design and engineering intent to be altered during the design process. The research work presented here describes a new design methodology and feature representation for facilitating a design environment that is independent of any construction order or constraint-based dependencies and provides a mechanism for maintaining design and engineering intent of the design features. The methodology works by dynamically evaluating the features using a planning algorithm such that the validity of each feature is maintained. These are intended to serve as a generic template that can be used to design and develop specific design features and CAD software systems.
Text and Illustration Based Scenario Expressions for Conveying Failure Knowledge
Authors: Hatamura Yotaro , Tsuchiya Kensuke
Published: June 2008

Our “Study of Failure” has shown the effects of failure case illustration and text based diagonal scenario expression to successfully convey the essence of failure cases to the reader. A well drawn failure case illustration generates a good image of the failure event in the readers mind, thus succeeds in passing the failure knowledge to the reader. A carefully produced diagonal scenario expression has the same effect. We demonstrated the power of these two fundamentally different representations through an experiment: A failure case illustration alone was shown to a group of people who were asked to define a diagonal scenario expression for the case. The reverse test started from a diagonal scenario expression to reach an illustration that the group had no prior knowledge about. Our tests showed that people can produce a fairly good representation in the other form starting from either an illustration or a diagonal scenario alone.
A Process-Oriented Approach for Management of Product Configuration Models
Authors: Mesihovic Samir , Malmqvist Johan
Published: June 2008

Efficient product configuration systems have been widely recognized by industrial companies as an important tool for meeting increasing customer requirements for specifically adapted products according to their needs/requirements. The main obstacle in this area has been the long-term maintenance of the product configuration models with the new product definition information generated throughout the product lifecycle. Much of the work in this area has focused on product architecture issues, data modelling techniques and software tools. However, in order to be useful, the models and software applications must be put into the right business process context that is supported by the proper organizational framework. Thus, the paper presents a generic process-oriented approach for change management of product configuration-related information in industrial companies. The process contains steps for identification of new and/or changed product configuration knowledge, request of a change in the product configuration model, evaluation of the request, and finally an update of the product configuration model in the system. In addition, there is a description of employees’ competence profile descriptions and the organizational roles needed to support an effective product configuration management process in an industrial company.
Objective Function Based Pattern Search: A Computationally Efficient Algorithm for 3D Component Layout
Authors: Aladahalli Chandankumar , Cagan Jonathan , Shimada Kenji
Published: June 2008

A new class of pattern search algorithms called Objective Function-based Pattern Search is proposed for 3D Layout. These algorithms are driven by decreasing expected change in objective function rather than by decreasing step size. Current pattern search algorithms rely on decreasing step size of all patterns at the same rate. Also, all translation and rotation patterns are active at all step sizes of patterns. The new class of algorithms decreases the step sizes of the patterns based on the expected change in objective function value due to that pattern. Also, whether a pattern is active or inactive at a particular step size is decided by the expected change in objective function due to that pattern at that step size. The new algorithm is found to be up to 50% faster in runtime compared to previous pattern search based algorithms.
Economics of Sacrificial Fixturing for CNC Machining and Rapid Manufacturing
Authors: McBrearty Kevin , Wysk Richard A. , Frank Matthew C.
Published: June 2008

This paper presents a fixturing method for sacrificial fixturing machining using CNC equipment. The focus of the paper is not on the method itself, but on the economics of sacrificial fixturing CNC machining, which defines the domain of use for the results described in the paper. The paper presents an economic model of machining, and then analyzes the use of the method as a function of: the number of parts to be produced, the ratio of material removed to final part volume, the number of features on the part, and the basic part geometry. We conclude that sacrificial fixturing is a very practical method that should be seriously considered when machining small batches of parts, rapid prototyping with CNC machining and parts with some particular geometric characteristics.
A Benchmark Comparison of CAD 5-Axis Machining Packages
Authors: Cheng Zhenyu , Cheatham Robert , Wang Jianguo , Jensen C. Greg , Chen Yifan , Bowman Brian
Published: June 2008

In this paper, parts from Ford GT were machined based on tool path created using Curvature Matched Machining and three other popular CAD systems. Five-axis flat end mill methods are used as the baseline of comparison. The performance of these CAD packages was compared using the benchmark of tool path density, surface finish, and post-machining finishing time. Results show that CM2 has advantage over today’s leading CAM capability in terms of both machining efficiency and tool path computation time.
The Performance Moment Integration Method for Reliability-Based Robust Design Optimization
Authors: Youn Byeng D. , Choi Kyung K.
Published: June 2008

Reliability-based robust design optimization deals with two objectives of structural design methodologies subject to various uncertainties: reliability-based design and robust design. A reliability-based design optimization deals with the probability of failure, while a robust design optimization minimizes the product quality loss. In general, the product quality loss is described by using the first two statistical moments: mean and standard deviation. In this paper, a performance moment integration (PMI) method is proposed by using numerical integration scheme for output response to estimate the product quality loss. For the reliability part of the reliability-based robust design optimization, the performance measure approach (PMA) and its numerical method, hybrid-mean value (HMV) method, are used. New formulations of reliability-based robust design optimization are presented for three different types of robust objectives, such as smaller-the-better, larger-the-better, and nominal-the-better types. Examples are used to demonstrate the effectiveness of reliability-based robust design optimization using the proposed PMI method for different types of robust objective.
Development of a J2EE Web Application for STEP-Based Design Conformance Checking
Authors: Yang Q. Z. , Lu W. F.
Published: June 2008

Product design needs great team efforts from multi-disciplinary participants, even external partners, for collaborative problem solving. Design conflicts within and between functional teams do occur in such a collaborative design process. Detection and resolution of design conflicts through design conformance checking therefore becomes a critical activity in the joint design problem solving. This paper presents the development of a J2EE application prototype to support the STEP-based design conformance checking. A STEP-compliant information model has been specified to represent 3D CAD objects and other design information, while a knowledge representation model been proposed to describe design rules and constraints. The STEP objects and rule objects are managed and processed by the enterprise Java beans of a J2EE application server, which continuously applies the rule objects to the STEP objects and finally draws a conclusion for the design conformance checking. Application scenarios are discussed in the paper to illustrate the effectiveness of both the STEP/rule objects modeling approaches and the prototype system for support of the design compliance checking in distributed environment.
An Exploration-Estimation Algorithm for Synthesis and Analysis of Engineering Systems Using Minimal Physical Testing
Authors: Lipson Hod , Bongard Josh
Published: June 2008

We describe a new general algorithm for the automated design, analysis and repair of nonlinear physical systems. The process iterates a two-phase exploration-estimation cycle. The exploratory phase seeks a new improvement or test to perform to the system based on some initial internal model. The estimation phase performs the suggested operation and observes the outcomes; it then improves the internal model so as to explain all observations so far. This process relies on very few, targeted, and carefully planned interactions with the physical systems. We describe an implementation of this method using two evolutionary algorithms, where the exploratory phase uses a simulator to evolve improvements or tests, and the estimation phase uses observations to evolve the simulator itself. We demonstrate this algorithm for analysis, design and repair of electromechanical systems.
Using the Compromise Decision Support Problem in Microsystem Design: A Formulation for a Miniature Parylene Gas Chromatographic Column
Authors: Schnell Andrew R. , Mistree Farrokh , Noh Hongseok Moses , Hesketh Peter J.
Published: June 2008

The concurrent consideration of design and manufacturing requirements at the early stages of design is one of the cited challenges in microsystem design. In this paper, we take the first steps, through an example, towards addressing these issues through the use of the compromise Decision Support Problem (cDSP). The cDSP is a domain-independent hybrid multiobjective decision support formulation utilized in engineering design. The design of a parylene microchannel for a microscale gas chromatography system is refined using the cDSP. The objective is to adjust the geometry of the microchannel to create a satisficing design for one fabrication goal and two performance goals. The cDSP is utilized for five scenarios, one in which all three goals are given equal priority, one for each of three goals when they are given first priority, and one in which the performance goals are given equal priority. We are more interested in demonstrating the method than the results per se. Our goal is to show how microsystem designers can use the cDSP to gain some insight into how these goals interact and how design decisions can be made with this insight.
A Constraint Satisfaction Problem in Real-Time Collaborative Assembly Modeling
Authors: Song Zhijie , Chen Li
Published: June 2008

Collaborative assembly modeling has emerged as a stream of collaborative CAD research and development. Yet, it is still not clear how constraint satisfaction should be implemented in real-time collaborative assembly modeling, even though intensive research in geometric constraint satisfaction has been extensively conducted. To this end, this paper formally describes the constraint satisfaction problem in the context of real-time collaborative assembly modeling, and presents a method for the problem solving in support of collaborative assembly computation for constraint satisfaction. Overall, this method consists of a proposal of computing protocol and an incremental constraint satisfaction approach. In particular, the rule-based computing protocol is deliberately designed to safeguard model consistency via an incremental modeling sequence. Governed upon the computing protocol, a two-phase incremental constraint satisfaction approach of new contents is introduced to enhance computation efficiency in the multi-user involved modeling process. The proposed method has been incorporated into the implementation of an Internet-based real-time collaborative assembly modeling system.
Using Spreadsheet Modules to Augment Tolerance Dimensioning
Authors: Shoup Terry E.
Published: June 2008

This paper presents an easy-to-use spreadsheet module in Microsoft Excel to handle the implementation of the ANSI standards for tolerance fits for shafts and collars. The module makes use of drop-down menus and an embedded Visual Basic numerical algorithm to locate the correct tolerance ranges for a shaft and collar combination for the entire range of tolerances handled by the tables published in the ANSI standard. This module allows the quick implementation of designs and features a process that is less subject to errors associated with the traditional method of reading of the tolerance tables and transferring this information manually. The method is particularly helpful to students and inexperienced designers who first encounter the need to utilize tolerances in engineering designs. The paper presents an example application to illustrate the overall utility of the module.
Algorithm of Non-Interference Tool Path Generation for Manufacturing Integral Impeller
Authors: Sun Chun-Hua
Published: June 2008

This study focuses on algorithm for generation non-interference tool-path for manufacturing blades of integral impeller. The interference is classified into three kinds according to occurring area. The algorithm mentioned in the paper can be used to check not only interference between the cutter and the machined area of an integral impeller part, but also interference between the cutter and the tip area of blades, including the machining blade and the adjacent blade. The correction for tool-path is done to avoid the interference. Computer simulations of machining an integral impeller and correction for tool path are conducted to verify the efficiency of the algorithm.
Fuzzy Declaration Modeling of Data Models Using EXPRESS
Authors: Ma Z. M.
Published: June 2008

Information with imprecision and uncertainty is inherently presented in engineering design and manufacturing. The nature of imprecision and uncertainty is incompleteness. Product data model, being a core of intelligent manufacturing system, consists of all concerned data in the product life cycle. It is possible that crisp data as well as incomplete data are involved in product data model. So EXPRESS, being a powerful tool to develop a product data model, should be extended for this purpose. This paper extends the declaration in EXPRESS to make it possible to model fuzzy engineering information.
MIVAS: A Multi-Modal Immersive Virtual Assembly System
Authors: Wan Huagen , Gao Shuming , Peng Qunsheng , Dai Guozhong , Zhang Fengjun
Published: June 2008

Evaluation and planning of assembly processes in virtual environments have become an active research area in engineering community. However, planning of complex assemblies in virtual environments, especially large-scale virtual environments, is still hindered by limitations like unnatural user interaction, insufficient frame rates, and deficiencies in processing of assembly constraints. In this paper, we present MIVAS, a Multi-modal Immersive Virtual Assembly System. By viewing the virtual assembly system as a finite state machine, we incorporate tracked devices, force feedback dataglove, voice commands, human sounds, fully immersive 4-sided CAVE, together with optimization techniques for both complex assembly models and assembly operations to provide for engineers an intuitive and natural way of assembly evaluation and planning. Testing scenarios on disassembling different components of an intelligent hydraulic excavator are described. Special attention is paid upon such technical issues as interface between CAD packages and the CAVE virtual environment, natural and intuitive user interaction including realistic virtual hand interaction and force feedback, intelligent navigation for assembly operations, and real-time display of complex assemblies.
PDA Based Anywhere — Anytime Collaborative CAD for Conceptual Design
Authors: Siddique Zahed , Chen Zhiqiang
Published: June 2008

Advances in handheld computers are providing a device that is pocket-sized, ultra-light, and wireless. The new handheld computers are providing an opportunity to not only access information from electronic repositories, but also to run software to perform activities and to collaborate with experts “anywhere/anytime”. The confluence of ubiquitous wireless networking and powerful handheld computers provide a powerful technology base for providing an environment, which can support distributed and mobile usage and enhance collaboration during different product design and development stages. Graphics, which include geometric modeling, is one of the most widely used methods of communication during the design phase. In this paper we present a framework and tool to provide CAD support during conceptual design stage for a distributed and collaborative design environment. The HCAD framework, is based on a combination of handheld computers and servers, interconnected by wireless and wired networks. An agent based approach is utilized to allow collaboration during concept development. The applicability of the HCAD framework is demonstrated through the development of a concept for an automotive center console.
Use of JView in 3D Digital Color Image Reconstruction and Visualization
Authors: Vira Naren
Published: June 2008

The paper describes a comprehensive approach to first reconstruct and then visualize three-dimensional image models created from a pair of two-dimensional digital color images. The method integrates an interactive output data manipulation capability of JView, a Java based API (Application Programming Interface) engineered by US Air Force (AFRL/IFSB) with newly developed more accurate procedure of recreating texture mapped 3D-models using a stereo triangulation technique. Though several procedures have been proposed in literature on how to generate 3D models from 2D stereo pairs by recovering the image depth, they are limited in predicting an accurate pixel matching between image correspondences. Furthermore, the majority of papers lack depicting the reconstructed 3D-image geometry to show how well their adopted techniques have been able to recover the scene depth at every pixel. We have employed a region-based block matching methodology for color image analysis. The reconstructed 3D image models can be viewed and maneuvered on a computer screen by moving up and down, rotating around, and zooming in and out with the help of mouse buttons. This interactive viewing capability is an aid to the visualization process and facilitates algorithm designers to test step-by-step their codes and make appropriate judgments as to the accuracy of the underlining reconstruction techniques (sort of a visual debugger). Example presented shows detailed disparity map and reconstructed geometries.
Some Examples of Real Masonry Structures Modelling by 3D-NSCD Discrete Element Method
Authors: Chetouane Brahim , Bohatier Claude , Vinches Marc
Published: June 2008

The aim of this paper is to provide answers to some questions of the archaeologists and leaders of cultural heritage agencies in charge of structures affected by structural problems and instabilities with emphasis on the Arles roman aqueduct in the South of France. The modeling is performed with NSCD discrete element method. The 3D geometric decomposition of the two structures is realistic and is obtained by a conversion from (DXF) CAO format to LMGC90 discrete element code which is dealing with the NSCD method. A comparison with continuous modeling shows the unique possibilities of discrete modeling to account for observed failure phenomena on the real structures.
B-Spline Based Free Form Solutions of Nonlinear Systems
Authors: Venkataraman P.
Published: June 2008

B-spline parametric curves provide alternative solutions to multipoint nonlinear systems. They solve the problem with less effort than traditional numerical techniques. The new approach demonstrated in this paper is natural and direct. It uses the least squared error technique to identify curves that satisfy the differential relations and boundary conditions. No state space integration is required. No Euler-Lagrange relations are to be satisfied and the Hamiltonian principle is not necessary. In addition, the solution can have properties that are currently not investigated or encouraged. This solution can also be analytically described. The problem set up is simple and is uniform over different classes of problems. The casual nature of problem definition and set up are demonstrated through three examples of increasing complexity: (i) Blassius two-point boundary-value problem (fluids); (ii) Brachistochrone problem (calculus of variation); and (iii) Planar trajectory interception problem (optimal control).