bluuebunny/crossref_metadata_2025 huggingface dataset:
Language, Social Cognitive Processing, and Behavioral Characteristics of Psychiatrically Disturbed Children with Previously Identified and Unsuspected Language Impairments
Authors: Cohen Nancy J. , Menna Rosanne , Vallance Denise D. , Barwick Melanie A. , Im Nancie , Horodezky Naomi B.
Published: July 2003

This study examined characteristics of social cognitive processing, psychiatric disorder, and behavioral ratings of 380 children aged 7 to 14 years who had been referred consecutively for child psychiatric services with identified and unsuspected language impairments and with normally developing language. The results indicated that children with language impairments generally exhibited greater deficits in social cognitive processing, and particularly emotion decoding and social problem solving, than children who have language that is developing normally. Differences in psychiatric diagnosis and behavior problems were observed only between children with previously identified language impairments and children with normally developing language; children with previously identified language impairments were more likely to be diagnosed as having Attention Deficit Hyperactivity Disorder (ADHD) and to be rated by both parents and teachers as having more severe attentional problems. In addition, teachers rated them as more socially withdrawn. The results suggest that it is important to incorporate measures of both social cognition and language functioning routinely into clinical assessment, something that currently is rarely done.
Practitioner Review: Routes from Research to Clinical Practice in Child Psychiatry: Retrospect and Prospect
Authors: Rutter Michael
Published: July 2003

The last 40 years has seen a virtual revolution in both medical research and medical practice. Child psychiatry has been part of that revolution. The situation in the 1950s is briefly noted and seven examples are used to illustrate how causal research in the past has led to changes in clinical practice. The areas used as examples comprise: autism, hyperactivity/attention deficit syndromes, conduct disorders, depressive conditions, genetic research, organic brain dysfunction, and psychosocial risk processes. Prospects for the future with respect to the impact of research on clinical practice are discussed in relation to molecular genetics, environmental risks, cognitive and affective processing of experiences, links across the lifespan, and functional brain imaging. Attention is drawn to implications for training as well as for practice.
The Emanuel Miller Memorial Lecture 1997: Change and Continuity in the Development of Children with Autism
Authors: Sigman Marian
Published: July 2003

The developmental approach to childhood psychopathology identifies deviations from typical patterns of development and stability of individual characteristics over time, and precursors in early life of later functions. The application of this approach to the social, communicative, and cognitive development of children with autism is discussed. Results from a longitudinal study of children with autism and other developmental disorders are described, indicating that children with autism have stable deficits in joint attention, representational play, and responsiveness to the emotions of others, and that early variations in these abilities are important for concurrent and subsequent language development and for peer engagement many years later.
Information Processing Deficits Associated with Developmental Coordination Disorder: A Meta‐analysis of Research Findings
Authors: Wilson Peter H. , McKenzie Beryl E.
Published: July 2003

A meta‐analysis was conducted to identify information processing factors that characterise children with Developmental Coordination Disorder (DCD). A total of 50 studies yielded 374 effect sizes based on 983 DCD and 987 control children. A mild generalised performance deficit was indicated, since motor‐impaired children were inferior on almost all measures of information processing. There were, however, several areas where their deficiencies were more pronounced. The greatest deficiency was in visual‐spatial processing. This was evident regardless of whether or not the tasks involved a motor component. Most other deficiencies were in the small‐to‐moderate range and included kinaesthetic and cross‐modal processing. The findings support the notion that perceptual problems, particularly in the visual modality, are associated with difficulties in motor coordination.
Inattention, Impulsivity, and Hyperactivity from Preschool to School Age: Performance of Hard‐to‐manage Boys on Laboratory Measures
Authors: Marakovitz Susan E. , Campbell Susan B.
Published: July 2003

Boys identified as hard‐to‐manage at age 4 and age‐matched controls were assessed on laboratory measures of inattention, impulsivity, and hyperactivity at ages 4, 6, and 9. Hard‐to‐manage boys still exhibited some behavioral difficulties at age 9, but were not more inattentive or impulsive than controls. Boys with Attention Deficit Disorder (ADD) at age 9 showed performance deficits in each symptom‐related domain relative to problem boys without ADD and controls. However, hard‐to‐manage problem boys with and without ADD did not differ on most earlier measures of inattention, impulsivity, and hyperactivity, suggesting that symptoms specific to ADD emerged more clearly between ages 6 and 9.
Language, Achievement, and Cognitive Processing in Psychiatrically Disturbed Children with Previously Identified and Unsuspected Language Impairments
Authors: Cohen Nancy J. , Barwick Melanie A. , Horodezky Naomi B. , Vallance Denise D. , Im Nancie
Published: July 2003

This study examined the language, achievement, and cognitive characteristics of 380 children, aged 7 to 14 years, consecutively referred to child psychiatric services. Among those children referred solely for psychiatric problems, 40% had a language impairment that had never been suspected. Children with previously identified and unsuspected language impairments were similar with respect to receptive and expressive language and on measures of cognitive processing. Although both groups of children with language impairments exhibited poorer academic achievement than children with normal language, children with previously identified language impairments had the lowest achievement. The milder achievement problems of children with unsuspected language impairment may explain why their problems had not been suspected. Both the clinical and theoretical implications of the findings are discussed. Heightened awareness concerning the high frequency of language impairment and other cognitive processing problems in children referred for psychiatric assessment and treatment should lead to more systematic examination of language functioning and evaluation of the impact of language and communication functioning on therapeutic outcomes.
Development of the Children's Communication Checklist (CCC): A Method for Assessing Qualitative Aspects of Communicative Impairment in Children
Authors: Bishop D. V. M.
Published: July 2003

The Children's Communication Checklist (CCC) was developed to assess aspects of communicative impairment that are not adequately evaluated by contemporary standardised language tests. These are predominantly pragmatic abnormalities seen in social communication, although other qualitative aspects of speech and language were also included. Some items covering social relationships and restricted interests were incorporated, so that the relationship between pragmatic difficulties and other characteristics of pervasive developmental disorders could be explored. Checklist ratings were obtained for 76 children aged 7 to 9 years, all of whom had received special education for language impairment. In 71 cases, 2 raters (usually a teacher and speech‐language therapist) independently completed the checklist, making it possible to establish inter‐rater reliability. From an initial pool of 93 items, 70 items, grouped into 9 scales, were retained. Five of the subscales were concerned with pragmatic aspects of communication. A composite pragmatic impairment scale formed from these subscales had inter‐rater reliability and internal consistency of around .80. This composite discriminated between children with a school diagnosis of semantic‐pragmatic disorder and those with other types of specific language impairment (SLI). The majority of children with pragmatic language impairments did not have any evidence of restricted interests or significant difficulties in the domains of social relationships.
Are There Subgroups within the Autistic Spectrum? A Cluster Analysis of a Group of Children with Autistic Spectrum Disorders
Authors: Prior Margot , Leekam Susan , Ong Ben , Eisenmajer Richard , Wing Lorna , Gould Judith , Dowe David
Published: July 2003

Comprehensive data on the developmental history and current behaviours of a large sample of high‐functioning individuals with diagnoses of autism, Asperger's syndrome, or other related disorder were collected via parent interviews. This provided the basis for a taxonomic analysis to search for subgroups. Most participants also completed theory of mind tasks. Three clusters or subgroups were obtained; these differed on theory of mind performance and on verbal abilities. Although subgroups were identified which bore some relationship to clinical differentiation of autistic, Asperger syndrome, and Pervasive Developmental Disorder Not Otherwise Specified (PDD‐NOS) cases, the nature of the differences between them appeared strongly related to ability variables. Examination of the kinds of behaviours that differentiated the groups suggested that a spectrum of autistic disorders on which children differ primarily in term of degrees of social and cognitive impairments could explain the findings.
The Development of Theory of Mind in Deaf Children
Authors: Russell P. A. , Hosie J. A. , Gray C. D. , Scott C. , Hunter N. , Banks J. S. , Macaulay M. C.
Published: July 2003

Deaf children aged 4 to 16 years were given a false‐belief test of theory of mind. Although the children experienced difficulty with the test, relative to hearing children, confirming a report by Peterson and Siegal (1995), performance was age‐related, with a significantly higher proportion of 13‐ to 16‐year‐olds passing the test. It was concluded that deaf children raised in a spoken language environment show a developmental delay in theory of mind acquisition. This delay is consistent with the assumption that their early opportunities for learning about mental states are relatively restricted and that the normal development of theory of mind is dependent upon such opportunities.
Diagnostic Rules for Children with PDD‐NOS and Multiple Complex Developmental Disorder
Authors: Buitelaar Jan K. , Van Der Gaag Rutger Jan
Published: July 2003

This study was designed to examine the classification performance of diagnostic rules for pervasive developmental disorder not otherwise specified (PDD‐NOS) and multiple complex developmental disorder (McDD), with clinical diagnosis as the gold standard. McDD is an heuristic concept of a developmental disorder characterised by social impairments, affective dysregulation, and thought disturbance. Detailed information on the symptoms, reliably extracted from the charts of 103 children with PDD‐NOS and McDD, 32 with autistic disorder, and 96 with non‐PDD disorders, was used to determine the presence of the DSMIV criteria of autistic disorder and the criteria of McDD. A scoring rule for PDD‐NOS based on a short set of seven DSM‐IV criteria with a cut‐off point of three items and one social interaction item set as mandatory had the best balance between high sensitivity and high specificity. The most effective and simple rule based on McDD criteria had a cut‐off of three items, out of six items of anxieties and thought disturbance.
Sociometric Classification Methods in School Peer Groups: A Comparative Investigation
Authors: Frederickson Norah L. , Furnham Adrian F.
Published: July 2003

The categorical consequences and psychometric properties of different sociometric classification methods were evaluated. Children aged 9 to 12 years (N=254) completed three sociometric questionnaires and a peer assessment measure on two occasions 5 weeks apart. The sociometric data were analysed using 13 different methods. Analysis of kappa values indicated relatively poor agreement across methods on subject classification. Temporal stability of the classifications was also poor. Assessment of construct validity involved analysis of the peer assessment items, using MANOVA to test hypotheses based on ideas from social exchange theory. Cross‐sex rating biases and difficulties with the neglected and controversial classifications are discussed as indicating a need for the application of theoretically based approaches which consider features of the peer group social system and a need for caution in selecting methods for clinical use.
Equity Market Liberalization in Emerging Markets
Authors: Bekaert Geert , Harvey Campbell R. , Lundblad Christian T.
Published: July 2003

Equity market liberalizations, if effective, lead to important changes in both the financial and real sectors as the economy becomes integrated into world capital markets. The study of market integration is complicated because one can liberalize in many ways and many countries have taken different routes. To study the effectiveness of particular liberalization policies, the sequencing of liberalizations, and the impact on the real economy, systematic methods must be developed to date the liberalization of emerging equity markets. We provide a synthesis of the current methods and show the impact of liberalization on the real sector.
Competition For Order Flow, Market Quality, And Price Discovery In The Nasdaq 100 Index Tracking Stock
Authors: Tse Yiuman , Erenburg Grigori
Published: July 2003

We investigate competition for order flow, market quality, and price discovery in the Nasdaq 100 Index Tracking Stock (QQQ). The QQQ, an AMEX‐listed, exchange‐traded fund, is the most actively traded security in the U.S. equities market. On July 31, 2001, the NYSE began trading the QQQ, marking the first time it traded securities of companies it does not list. The greatest volume of trading takes place on electronic communication networks (ECNs), following by trading on the AMEX and the NYSE. Most of the block trades are executed on the AMEX, where the bid‐ask spreads are narrower. We find that ECNs contribute the most to the price‐discovery process. The spreads on all trading platforms have decreased and market quality and price discovery have improved since QQQ shares have traded on the NYSE.
The Effects of Unanticipated Macroeconomic News on Debt Markets
Authors: Christie‐David Rohan , Chaudhry Mukesh , Lindley James T.
Published: July 2003

We examine the effects of unanticipated macroeconomic news on two interest rate futures using intraday data. The surprises are identified on the basis of their potential effects on debt markets (positive or negative) and by their size (large, medium, or small). The results show distinct ex‐post return patterns associated with different categories of news surprises. For example, large surprises have the strongest immediate effects whereas negative surprises have the longest persisting effects. Tests that examine the separate effects of each announcement suggest that debt responses vary with the size and potential effect of the news surprise in each announcement.
Ceo Compensation And The Transformation Of Banking
Authors: Harjoto Maretno A. , Mullineaux Donald J.
Published: July 2003

We examine the compensation strategies of commercial bank holding companies (BHCs) during 1992–2000. In particular, we analyze whether CEO compensation is more closely tied to the presence of growth options and to risk than is revealed in earlier research. We also examine whether BHC entry into investment banking has influenced compensation policies. Our evidence shows a stronger link between growth options and CEO compensation in the 1990s than observed in earlier studies and that pay‐for‐performance sensitivities are substantially larger for BHCs that have entered the underwriting business. We also find that BHC leverage and variability in returns have positive effects on CEO incentive pay. Finally, we find some evidence supporting the hypothesis that pay‐for‐performance sensitivities decline generally at BHCs as return variability increases, as agency theory predicts.
Do Emerging Market Firms Follow Different Dividend Policies From U.S. Firms?
Authors: Aivazian Varouj , Booth Laurence , Cleary Sean
Published: July 2003

We find that emerging market firms exhibit dividend behavior similar to U.S. firms, in the sense that dividends are explained by profitability, debt, and the market‐to‐book ratio. However, empirical dividend policy equations are structurally different, indicating different sensitivities to these variables. Additionally, emerging market firms seem to be more affected by asset mix, which seems to be due to their greater reliance on bank debt. Overall, country factors are as important in dividend policies as previous studies find them to be in capital structure decisions.
Nonlinear Drift And Stochastic Volatility: An Empirical Investigation Of Short‐Term Interest Rate Models
Authors: Sun Licheng
Published: July 2003

In this article I provide new evidence on the role of nonlinear drift and stochastic volatility in interest rate modeling. I compare various model specifications for the short‐term interest rate using the data from five countries. I find that modeling the stochastic volatility in the short rate is far more important than specifying the shape of the drift function. The empirical support for nonlinear drift is weak with or without the stochastic volatility factor. Although a linear drift stochastic volatility model fits the international data well, I find that the level effect differs across countries.
Membership On Editorial Boards And Finance Department Rankings
Authors: Chan Kam C. , Fok Robert C. W.
Published: July 2003

We examine membership on editorial boards of sixteen leading finance journals in 1985, 1990, 1995, and 2000. Membership on a board of a high‐quality journal is highly selective. Editors and members of editorial boards of quality journals are trusted by their peers who submit their research for publication consideration. Thus, the number of faculty represented on editorial boards of quality journals should provide a quality indication of the finance department. We use membership representation to provide a ranking of finance departments adjusted for department size and journal quality.
Mawdūd?'s Contribution to the Development of Modern Islamic Thinking in the Arabic‐Speaking World
Authors: Osman Fathi
Published: July 2003

Sayyid Abu al‐A‘la Mawdūd? (1903–1979) was one of the most influential and prolific of contemporary Muslim thinkers. His interpretive reading of Islam has contributed greatly to the articulation of Islamic revivalist thought and has influenced Muslim thinkers and activists from Morocco to Indonesia. His impact is evident in the exegesis of Sayyid Qu⃛b of Egypt, as well as in the ideas and actions of Algerian, Iranian, Malaysian and Sudanese revivalist activists.
Extraction of Three-Dimensional Parameters for Weld Pool Surface in Pulsed GTAW With Wire Filler
Authors: Zhao D. B. , Yi J. Q. , Chen S. B. , Wu L. , Chen Q.
Published: July 2003

By viewing the topside of a weld pool, a skilled operator can estimate the weld joint penetration. The weld pool shape or the solidified bead shape is crucial for weld quality. Automatic control of pulsed GTAW with wire filler is achieved by recording the image of the weld pool with an optical sensing method and then calculating shape parameters with an image processing algorithm. Three-dimensional shape parameters of the weld pool were determined that uniquely and accurately describe various weld pool shapes. Two-dimensional shape parameters were extracted from a two-dimensional image processing algorithm. Finally, a shape from shading (SFS) algorithm on a single image was used to recover the surface height from a single weld pool image. The extracted three-dimensional parameters for the weld pool surface were verified and used for double-sided shape control.
Investigation of Layer Thickness and Surface Roughness in Rapid Freeze Prototyping
Authors: Sui Guanghua , Leu Ming C.
Published: July 2003

Rapid Freeze Prototyping (RFP) builds three-dimensional ice parts according to CAD models by depositing and freezing water droplets in a layer-by-layer manner. This paper studies the layer thickness and surface roughness of ice parts built by the RFP process. The equations governing the water line formed by a sequence of water droplets are developed, and then a model of the water line is proposed by simplifying these equations based on our experimental condition. The analysis using this model shows that the cross-section of an ice line is circular, which is verified by experimental observations. Based on the analysis, equations for predicting layer thickness as a function of nozzle scanning speed, water feed rate, and water-ice contact angle in building vertical and slant walls by the RFP are derived and the predictions from these equations are shown to agree well with experimental measurements. The surface roughness of ice parts built by the RFP process is also studied.
3D Double-Vision Inspection Based on Structured Light
Authors: Zhang Guangjun , Wei Zhenzhong , Li Xin
Published: July 2003

3D double-vision inspection is very necessary. It has a larger field of view, and can solve the problem of “blind area” for 3D measurement, as proposed by 3D single-vision inspection. At the beginning of this paper, the principle of structured-light based 3D vision inspection is introduced. Then, a method of gaining calibration points for 3D double-vision inspection system is proposed in detail. In order to gain calibration points with high precision, a double-directional photoelectric aiming device is designed as well, and a method for compensating the position-setting error of the aiming device is described. The coordinates of all calibration points are precisely unified in a world coordinate system. The application of RBF (radial basis function) neural network in establishing the inspection model of structured-light based 3D vision is described in detail. Finally, with the use of the calibration points, the inspection model of 3D double-vision based on RBF neural network is successfully established. The model’s training accuracy is 0.078 mm, and the testing accuracy is 0.084 mm.
Deposition of Diamond in Copper by Triboadhesion
Authors: Rodrı´guez Lelis J. M. , Colı´n Ocempo J. , Porcayo Caldero´n J. , Robles J. M.
Published: July 2003

In the present work, it is shown that friction can be used to deposit diamond in a substrate of copper. Here it was found through electronic scan microscopy that a composite material film that varies from 27 to 30 microns depth can be formed. This film has particles from 10 to 1 microns and the concentration of diamond decreases with depth. A change on the crystalline structure caused by temperatures closer to the melting point achieved by the process was also found.
Gate Effectiveness in Controlling Resin Advance in Liquid Composite Molding Processes
Authors: Gokce Ali , Advani Suresh G.
Published: July 2003

In Liquid Composite Molding (LCM) processes, the flow pattern of the resin in the mold cavity during mold filling dictates the quality of the composite part. Disturbances such as uncertainty in the fiber preform permeability, variations in the resin viscosity, and racing of the resin along the mold walls may create unexpected and unanticipated flow patterns that could result in dry spots in the preform. Process control with sensor feedback can potentially provide the ability to make fully impregnated parts despite various disturbances by manipulating the flow front movement during resin impregnation through modification of the injection conditions at the gates. Studies have shown that under certain conditions, the flow front shape is not influenced by even large changes in the flow rate or the pressure at the injection gates. This study investigates gate effectiveness in modifying the flow front shape by analyzing the flow dynamics and conducting a parametric study in a simulation environment.
Fracture Mechanism of Laser Cutting With Controlled Fracture
Authors: Tsai Chwan-Huei , Liou Chi-Sheng
Published: July 2003

Laser cutting using the controlled fracture technique has great potential to be used for the machining of brittle materials. In this technique, the applied laser energy produces a mechanical stress that causes the material to separate along the moving path of the laser beam. The material separation is similar to a crack extension and the fracture growth is controllable. The fracture mechanism of laser cutting with controlled fracture is studied in this paper. The temperature and stress distributions are obtained by using the finite element software ANSYS. The laser heat first induces compressive stress around the laser spot. After the passage of the laser beam, the compressive stress is relaxed, and then a residual tensile stress is induced, which makes the fracture grow from upper surface to lower surface of the substrate. The stable separation of the brittle material is due to the local residual tensile stress. However, if the tensile stress is distributed throughout the thickness around the crack tip, the crack will extend unstably. The experimental materials in this study are alumina ceramic and the laser source is CO2 laser. It is found that the crack propagation is non-uniform and the speed is variable during the cutting process. The relationships between laser power, cutting speed, diameter of laser spot, and specimen geometry are obtained from the experimental analysis, and the phenomena are also explained from the results of stress analysis.
Review of studies on geometrically nonlinear vibrations and dynamics of circular cylindrical shells and panels, with and without fluid-structure interaction
Authors: Amabili Marco , Paı¨doussis Michael P.
Published: July 2003

This literature review focuses mainly on geometrically nonlinear (finite amplitude) free and forced vibrations of circular cylindrical shells and panels, with and without fluid-structure interaction. Work on shells and curved panels of different geometries is but briefly discussed. In addition, studies dealing with particular dynamical problems involving finite deformations, eg, dynamic buckling, stability, and flutter of shells coupled to flowing fluids, are also discussed. This review is structured as follows: after a short introduction on some of the fundamentals of geometrically nonlinear theory of shells, vibrations of shells and panels in vacuo are discussed. Free and forced vibrations under radial harmonic excitation (Section 2.2), parametric excitation (axial tension or compression and pressure-induced excitations) (Section 2.3), and response to radial transient loads (Section 2.4) are reviewed separately. Studies on shells and panels in contact with dense fluids (liquids) follow; some of these studies present very interesting results using methods also suitable for shells and panels in vacuo. Then, in Section 4, shells and panels in contact with light fluids (gases) are treated, including the problem of stability (divergence and flutter) of circular cylindrical panels and shells coupled to flowing fluid. For shells coupled to flowing fluid, only the case of axial flow is reviewed in this paper. Finally, papers dealing with experiments are reviewed in Section 5. There are 356 references cited in this article.
Review of hypersingular integral equation method for crack scattering and application to modeling of ultrasonic nondestructive evaluation
Authors: Bostro¨m Anders
Published: July 2003

The scattering of elastic waves by cracks in isotropic and anisotropic solids has important applications in various areas of mechanical engineering and geophysics, in particular in ultrasonic nondestructive testing and evaluation. The scattering by cracks can be investigated by integral equation methods, eg, boundary element methods, but here we are particularly concerned with more analytically oriented hypersingular integral equation methods. In these methods, which are only applicable to very simple crack shapes, the unknown crack opening displacement in the integral equation is expanded in a set of Chebyshev functions, or the like, and the integral equation is projected onto the same set of functions. This procedure automatically takes care of the hypersingularity in the integral equation. The methods can be applied to cracks in 2D and 3D, and to isotropic or anisotropic media. The crack can be situated in an unbounded space or in a layered structure, including the case with an interface crack. Also, problems with more than one crack can be treated. We show how the crack scattering procedures can be combined with models for transmitting and receiving ultrasonic probes to yield a complete model of ultrasonic nondestructive testing. We give a few numerical examples showing typical results that can be obtained, also comparing with some experimental results. This review article cites 78 references.
Wave-induced sea floor dynamics
Authors: Jeng Dong S
Published: July 2003

This article reviews recent developments in the interaction between water waves, seabed, and coastal structures. The scope of the review covers theoretical approaches and physical modeling for the wave-induced soil response, wave damping, and sea floor instability around coastal structures. Important advances in this field of study are summarized and scope for future studies is suggested. There are 208 references cited in this review article.
Recent developments in geometrically nonlinear and postbuckling analysis of framed structures
Authors: Yang Yeong-Bin , Yau Jong-Dar , Leu Liang-Jenq
Published: July 2003

Geometric nonlinear analysis of structures is not a simple extension from its counterpart of linear analysis. In this article, some research works conducted primarily in the past two decades on the geometric nonlinear analysis of framed structures that are readily available to the authors, including, in particular, those conducted by the senior author and coworkers, will be briefly reviewed. To highlight the key features of geometric nonlinear analysis, each of the papers cited will be reviewed according to one or more of the following categories: a) analytical or semi-analytical works, b) formulation of incremental nonlinear theory, c) discrete vs connected element and procedure of assembly, d) joint equilibrium conditions in the deformed configuration, e) rigid body test for nonlinear finite elements, f) key phases in incremental-iterative analysis, g) force recovery procedure, h) strategy for incremental-iterative approaches, i) rigid body-qualified geometric stiffness matrix, j) formulation and simulation for curved beam problems, k) special considerations for truss structures, and l) other related considerations. Throughout this article, emphasis will be placed on the theories and procedures leading to solution of the load-deflection response of structures, which may involve multi-looping curves in the postbuckling range. In fact, a nonlinear analysis using incremental-iterative schemes need not be as complicated as we think. If due account can be taken of the rigid body behaviors at each stage, then the whole process of incremental-iterative analysis can be made simpler and more efficient. Even when the postbuckling behavior of structures is of concern, the use of an accurate elastic stiffness matrix plus a rigid-body-qualified geometric stiffness matrix can always yield satisfactory results. There are 122 references cited in this review article.
Analysis of the Influence of Fixture Locator Errors on the Compliance of Work Part Features to Geometric Tolerance Specifications
Authors: Marin Rodrigo A. , Ferreira Placid M.
Published: July 2003

A machining fixture controls position and orientation of datum references (used to define important functional features of the geometry of a mechanical part) relative the reference frame for an NC program. Inaccuracies in fixture’s location scheme result in a deviation of the work part from its nominal specified geometry. For a part to be acceptable this deviation must be within the limits allowed by the geometric tolerances specified. This paper addresses the problem of characterizing the acceptable level of inaccuracy in the location scheme so that the features machined on the part comply with the limits associated with its geometric tolerances. First we solve the “forward problem” that involves predicting the tolerance deviation resulting at a feature from a known set of errors on the locators. However, the paper concentrates on solving the “inverse” problem that involves establishing bounds on the errors of the locators to ensure that the limits specified by geometric tolerances at a feature are not violated.
A Real-Time Predictor-Corrector Interpolator for CNC Machining
Authors: Tsai Mi-Ching , Cheng Chung-Wei
Published: July 2003

This paper presents a predictor-corrector interpolator (PCI) for the CNC machining of parts with parametric curves or surfaces. In contrast to existing parametric interpolators, the proposed method uses a simple algorithm as a predictor and the current feedrate command feedback compensation scheme as the corrector. The predictor adjusts itself according to the current feedrate command feedback, it also has the capability of predicting the next reference point of the parametric curves from the current reference point. As a result, the deviations between the current and desired feedrate commands will always fall within the specified feedrate command tolerances. This study aims at developing the mathematical analysis of the PCI, where the convergence condition is derived for the corrector. In this present approach, the user can specify either constant or variable federate and also its feedrate command accuracy. Both the simulation and experiment results are presented to demonstrate the feasibility of the proposed PCI for machining the parametric curves represented in the Non-Uniform Rational B-Spline (NURBS) form.
Modeling Chip-Evacuation Forces in Drilling for Various Flute Geometries
Authors: Mellinger Jeffrey C. , Ozdoganlar O. Burak , DeVor Richard E. , Kapoor Shiv G.
Published: July 2003

In this paper, a chip-evacuation force model is presented to predict the torque and thrust required to evacuate the chips during drilling for various flute geometries. The model considers the chips in the flutes as granular solids and determines the chip-evacuation thrust and torque from the normal and lateral pressure distributions in the chips that fill the flutes. The model requires two coefficients of friction that are established via a calibration procedure. The critical depth for the process is determined by setting a threshold value on the chip-evacuation torque, which is based on the onset of chip-clogging. The effectiveness of the chip-evacuation force model in determining the chip-evacuation thrust and torque and predicting the critical depth has been assessed via a set of validation experiments using both standard and parabolic drills. The parabolic drill produced lower chip-evacuation forces and increased critical depths relative to the standard drill. While the standard drill has a modestly larger effective flute cross-sectional area for most of the flute length, the parabolic drill has a significantly smaller contact area between the chips and the flute surface, which is the main reason for the superior chip-evacuation performance of the parabolic drill.
Close-Loop Cost Equation for Objects Manufactured by Milling
Authors: Kulkarni Uday A. , Bao Han P.
Published: July 2003

One of the major drawbacks of present cost estimation models is their incapability of embracing effectively complete product development stage. Parametric estimation works well in early design stage, but when it comes to detail design stage, a more complete estimation is provided by process model based and detail estimation techniques. A major paradigm shift is proposed in this paper whereby “Cost” is to be considered as a design parameter from scientific perspective and it is to be treated as a design consequence rather than as an operational outcome. A comprehensive framework using System Analysis fundamentals is designed to study ‘’Process Cost” aspects of a part or a design. The paper gives detailed implementation of this new approach for objects manufactured largely by milling operation. The paper also suggests a methodology to extend this approach to other manufacturing processes. The proposed Generic Cost Estimation Model shows good agreement with cost estimation by commercial estimation software when applied to the objects manufactured by milling process. It also promises integration of “Cost” with other disciplines in Multidisciplinary Optimization and Collaborative Engineering. The integration is achievable through new information technology interface tools.
The Effect of Lamps Radius on Thermal Stresses for Rapid Thermal Processing System
Authors: Chao Ching-Kong , Hung Shih-Yu , Yu Cheng-Ching
Published: July 2003

The concept of rapid thermal processing has many potential applications in microelectronics manufacturing, but the details of chamber design remains an active area of research. In this work the influence of lamps radius on the thermal stresses in a wafer during the cooling process is studied in detail. Since the equations governing the present thermal-elastic system are coupled in nature, the solution for the temperature and stresses must proceed simultaneously by using a fully implicit finite difference method. After the thermal stresses are obtained, the optimum lamps radii for various heights of the chamber under the constant power ramp-down control scheme are determined based on the maximum shear stress failure criterion. The shortest cooling time that can significantly reduce the thermal budget and dopant redistribution is also predicted by applying the maximum stress control scheme. The result obtained is useful in the design of a reliable rapid thermal processor based on a more practical consideration, thermal stress.
On the Critical Plunger Speed and Three-Dimensional Effects in High-Pressure Die Casting Injection Chambers
Authors: Lo´pez J. , Faura F. , Herna´ndez J. , Go´mez P.
Published: July 2003

During the initial slow stage of the injection process in high-pressure die casting machines with horizontal cold chamber, a plunger pushes the molten metal which partially fills the injection chamber, causing the formation of a gravity wave. The evolution of the wave surface profile, which depends on the plunger acceleration law, may trap air in the molten metal, causing porosity when the metal solidifies. In this work, a one-dimensional shallow-water model, which is solved numerically using the method of characteristics, and a three-dimensional numerical model, based on a finite element formulation and the volume of fluid (VOF) method for treating the free surface, are used to analyze the flow of molten metal in an injection chamber of circular cross section. The results for the evolution of the free surface obtained from both models for different plunger motion laws and initial filling fractions of the injection chamber were in good agreement for broad ranges of operating conditions. The existence of a critical plunger speed, above which the reflection of the wave of molten metal against the chamber ceiling might appreciably increase air entrapment effects, is investigated. The results for the wave profiles in chambers of circular cross section are compared with those obtained in an equivalent two-dimensional configuration of the injection chamber, for which the shallow-water model is solved analytically. It is shown how the results obtained by applying the one-dimensional model to a two-dimensional chamber configuration can be used to reproduce, with an acceptable degree of accuracy, the salient characteristics of the flow of molten metal in a real injection chamber of circular cross section.
Tribological Issues in the Tube Hydroforming Process—Selection of a Lubricant for Robust Process Conditions for an Automotive Structural Frame Part
Authors: Koc¸ Muammer
Published: July 2003

In this paper, an overall review of tribological issues in the tube hydroforming process is presented. Guidelines for the selection of lubricants under the hydroforming process conditions are summarized following a description of existing testing methods and apparatus. A methodology of combined experiments and FEA was presented to determine the coefficient of friction in the hydroforming process in addition to selecting a proper lubricant for a given part and process design. Experimental results showed that thickness of the final part at critical regions, amount of axial feeding and axial force are strong indicators of lubricant performance whereas effect of lubrication on the part flatness, corner radius formation and box dimensions are found to be negligible.
A Computational Mechanics Model for the Brim Forming Process in Paperboard Container Manufacturing
Authors: Ramasubramanian M. K. , Muthuraman K.
Published: July 2003

The manufacturing process of brim forming in paperboard containers consists of taking a thin paperboard shell and forming a brim to provide additional stiffness to the structure. A paper cup is an example of such a structure manufactured at rates exceeding 300 units per minute. A realistic model for the manufacturing process is not available and the effects of process and material parameters are not well understood. In this study, a finite element model of this highly nonlinear problem is presented. The model takes into account the material orthotropy and nonlinear elastic-plastic behavior, die paperboard contact interaction during loading and unloading, and friction between the metal die and paperboard, die geometry, and environmental conditions. Model predictions of the force-displacement curve agree well with the experimentally observed results.
A Shape Error Metric for Sheet Metal Forming and Its Application to Springback
Authors: Rolfe B. F. , Cardew-Hall M. J. , Abdallah S. M. , West G. A. W.
Published: July 2003

There are many variations within sheet metal forming, some of which are manifest in the final geometry of the formed component. It is important that this geometric variation be quantified and measured for use in a process or quality control system. The contribution of this paper is to propose a novel way of measuring the geometric difference between the desired shape and an actual formed “U” channel. The metric is based upon measuring errors in terms of the significant manufacturing variations. The metric accords with the manually measured errors of the channel set. The shape error metric is then extended to develop a simple empirical, whole-component, springback error measure. The springback error measure combines into one value all the angle springback and side wall curl geometric errors for a single channel. Two trends were observed: combined springback decreases when the blank holder force is increased; and the combined springback marginally decreases when the die radii is increased.
Effect of Mechanical Alignment System on Assembly Accuracy
Authors: Lee Neville K. S. , Yu Grace H. , Chen J. Y. , Joneja Ajay
Published: July 2003

Mechanical means of positioning are frequently used in mechanical assembly processes. However, very little attention has been paid to the proper design and selection of mechanical alignment systems (MAS) for assembly processes. In this paper, we study the performance of different MAS in terms of assembly accuracy in the presence of the form error, surface waviness and surface roughness of the references surfaces. In particular, simulation models are used to investigate how the datum pin configuration, datum pin location and datum geometry of the MAS would affect the assembly accuracy in the presence of surface errors of the workpieces. Our investigation can provide insight into how to design MAS for optimum performance for assembly accuracy. Our analysis shows that over an order of magnitude of difference in assembly accuracy can exist between using properly designed MAS and poorly design MAS.
Robust Machining Force Control With Process Compensation
Authors: Kim Sung I. , Landers Robert G. , Ulsoy A. Galip
Published: July 2003

Force control is an effective means of improving the quality and productivity of machining operations. Metal cutting force models are difficult to accurately generate and, thus, there is large uncertainty in the model parameters. This has lead to investigations into robust force control techniques; however, the approaches reported in the literature include known process changes (e.g., a change in the depth-of-cut) in the model parameters variations. These changes create substantial variations in the model parameters; thus, only loose performance bounds may be achieved. A novel robust force controller is presented in this paper that explicitly compensates for known process effects and accounts for the force-feed nonlinearity inherent in metal cutting operations. The controller is verified via simulation and experimental studies and the results demonstrate that the proposed controller is able to maintain tighter performance bounds than robust controllers that include known process changes in the model parameter variations.
Simulation of Particle Migration of Powder-Resin System in Injection Molding
Authors: Lam Y. C. , Chen X. , Tam K. C. , Yu S. C. M.
Published: July 2003

Powder injection molding is an important processing method for producing precision metallic or ceramic parts. Experience, intuition and trial-and-error have been the practice for the design and process optimization of such molding operations. However, this practice is becoming increasingly inefficient and impractical for the molding of larger, more complicated and more costly parts. In this investigation, a numerical method for simulating the mold-filling phase of powder injection molding was developed. The flow was modelled using the Hele-Shaw approach coupled with particle diffusion transport equation for the calculation of powder concentration distribution. The viscosity of the feedstock was evaluated using a power-law type rheological model to account for the viscosity dependency on shear rate and powder concentration. A numerical example is presented and discussed to demonstrate the capabilities and limitations of the simulation algorithm, which has the potential as an analytical tool for the mold designer. The variation of powder density distribution can be predicted, which is ignored by the existing simulation packages. Preliminary simulation indicated that powder concentration variation could be significant. Non-isothermal analysis indicated that most of the key parameters for filling process would change due to a change in powder concentration distribution.
Surface Profile Analysis for Conformable Interfaces
Authors: Malburg Mark C.
Published: July 2003

This paper presents a novel method for the analysis of solid surfaces in contact with a conformable component. These applications are common in many engine and hydraulic applications, wherein conformable seals, gaskets, bushings, etc. are employed to prevent unwanted flow across an interface or provide a uniform load distribution. The proposed analysis method employs a combination of meanline (m-system) filtering and envelope (e-system) or morphological filtering. Through this analysis, a simulation of contact area and the associated voids or gaps can be assessed.