The Experts below are selected from a list of 104595 Experts worldwide ranked by ideXlab platform
Jeong Whan Yoon - One of the best experts on this subject based on the ideXlab platform.
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the effect of plastic anisotropy on compressive instability in sheet metal forming
International Journal of Plasticity, 2000Co-Authors: Jongbong Kim, Jeong Whan Yoon, Dong-yol Yang, Frédéric BarlatAbstract:Abstract The wrinkling behavior of a thin sheet with perfect geometry is associated with compressive instability. The compressive instability is influenced by many factors such as stress state, mechanical properties of the sheet material, geometry of the body, contact conditions and plastic anisotropy. The Analysis of compressive instability in a plastically deforming body is difficult considering all the factors because the effects of the factors are very complex and the instability behavior may show a wide variation for a small deviation of the factors. In this study, the bifurcation theory is introduced for the finite element Analysis of puckering initiation and growth of a thin sheet with perfect geometry. All the above mentioned factors are conveniently considered by the finite-element method. The instability limit is found by the Incremental Analysis and the post-bifurcation behavior is analyzed by introducing the branching scheme proposed by Riks. The finite-element formulation is based on the Incremental deformation theory and elastic–plastic material modeling. The finite-element Analysis is carried out using the continuum-based resultant shell elements considering the anisotropy of the sheet metal. In order to investigate the effect of plastic anisotropy on the compressive instability, a square plate that is subjected to compression in one direction and tension in the other direction is analyzed by the above-mentioned finite-element Analysis. The critical stress ratios above which buckling does not take place are found for various plastic anisotropic modeling methods and discussed. Finally, the effect of plastic anisotropy on the puckering behavior in the spherical cup deep drawing process is investigated. From the results of the finite-element Analysis, it is shown that puckering behavior of sheet metal is largely affected by plastic anisotropy.
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elasto plastic finite element method based on Incremental deformation theory and continuum based shell elements for planar anisotropic sheet materials
Computer Methods in Applied Mechanics and Engineering, 1999Co-Authors: Jeong Whan Yoon, Dong-yol Yang, Kwansoo ChungAbstract:Abstract An implicit approach for the Incremental Analysis of planar anisotropic sheet forming processes is developed based on the Incremental deformation theory. The Incremental deformation theory based on the minimum plastic work path enables convenient decoupling of deformation and rotation by the polar decomposition. The mathematical description of a constitutive law for the Incremental deformation theory is obtained from the flow theory along the minimum plastic work path. The resulting constitutive law is then incorporated in an elasto-plastic finite element Analysis code. In the elasto-plastic formulation, continuum based resultant (CBR) shell element is employed. The CBR shell allows large rotation and large membrane/bending strain. The laminar coordinate system is taken to coincide with planar anisotropic material axes. Then, planar anisotropic axes during deformation are updated using a newly developed algorithm based on the polar decomposition. An iterative solving method based on the Incremental deformation theory is also developed for an accurate and stable stress integration. The planar anisotropy is incorporated into the formulation for sheet forming by introducing non-quadratic Barlat's yield function. For verification purposes, two examples have been simulated and compared with experimental results. The good verification results show that the present elasto-plastic formulation for planar anisotropic sheet materials can provide a good theoretical basis for more extended analyses of sheet forming processes.
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A general elasto-plastic finite element formulation based on Incremental deformation theory for planar anisotropy and its application to sheet metal forming
International Journal of Plasticity, 1999Co-Authors: Jeong Whan Yoon, Dong-yol Yang, Kwansoo Chung, Frédéric BarlatAbstract:Abstract A new implicit approach for the Incremental Analysis of planar anisotropic elasto-plastic sheet forming processes was developed based on the Incremental deformation theory of plasticity. The Incremental deformation theory based on minimum work paths enables convenient decoupling of deformation and rotation by the polar decomposition. The mathematical description of a constitutive law for the Incremental deformation theory has been previously derived from the flow theory along the minimum plastic work path. The resulting Incremental constitutive law is frame-indifferent (objective) since the theory uses the materially-embedded coordinate system. Utilizing the natural convected coordinate system in the Incremental variational formulation, the geometrical evolution of materials and the rotation of planar anisotropic axes were effectively incorporated. Planar anisotropy was represented using a nonquadratic yield function. For verification purposes, the onset of necking as well as the earing of aluminum alloy sheet samples were simulated for circular cup drawing and NUMISHEET'93 square cup drawing. The simulated results were compared with experimental results. Simulation was also carried out for NUMISHEET'93 front fender in order to show a computational efficiency and robustness.
Sean D Sullivan - One of the best experts on this subject based on the ideXlab platform.
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cost effectiveness Analysis alongside clinical trials ii an ispor good research practices task force report
Value in Health, 2015Co-Authors: Scott D Ramsey, Richard J Willke, Henry A Glick, Shelby D Reed, Federico Augustovski, Bengt Jonsson, Andrew Briggs, Sean D SullivanAbstract:Clinical trials evaluating medicines, medical devices, and procedures now commonly assess the economic value of these interventions. The growing number of prospective clinical/economic trials reflects both widespread interest in economic information for new technologies and the regulatory and reimbursement requirements of many countries that now consider evidence of economic value along with clinical efficacy. As decision makers increasingly demand evidence of economic value for health care interventions, conducting high-quality economic analyses alongside clinical studies is desirable because they broaden the scope of information available on a particular intervention, and can efficiently provide timely information with high internal and, when designed and analyzed properly, reasonable external validity. In 2005, ISPOR published the Good Research Practices for Cost-Effectiveness Analysis Alongside Clinical Trials: The ISPOR RCT-CEA Task Force report. ISPOR initiated an update of the report in 2014 to include the methodological developments over the last 9 years. This report provides updated recommendations reflecting advances in several areas related to trial design, selecting data elements, database design and management, Analysis, and reporting of results. Task force members note that trials should be designed to evaluate effectiveness (rather than efficacy) when possible, should include clinical outcome measures, and should obtain health resource use and health state utilities directly from study subjects. Collection of economic data should be fully integrated into the study. An Incremental Analysis should be conducted with an intention-to-treat approach, complemented by relevant subgroup analyses. Uncertainty should be characterized. Articles should adhere to established standards for reporting results of cost-effectiveness analyses. Economic studies alongside trials are complementary to other evaluations (e.g., modeling studies) as information for decision makers who consider evidence of economic value along with clinical efficacy when making resource allocation decisions.
Frédéric Barlat - One of the best experts on this subject based on the ideXlab platform.
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the effect of plastic anisotropy on compressive instability in sheet metal forming
International Journal of Plasticity, 2000Co-Authors: Jongbong Kim, Jeong Whan Yoon, Dong-yol Yang, Frédéric BarlatAbstract:Abstract The wrinkling behavior of a thin sheet with perfect geometry is associated with compressive instability. The compressive instability is influenced by many factors such as stress state, mechanical properties of the sheet material, geometry of the body, contact conditions and plastic anisotropy. The Analysis of compressive instability in a plastically deforming body is difficult considering all the factors because the effects of the factors are very complex and the instability behavior may show a wide variation for a small deviation of the factors. In this study, the bifurcation theory is introduced for the finite element Analysis of puckering initiation and growth of a thin sheet with perfect geometry. All the above mentioned factors are conveniently considered by the finite-element method. The instability limit is found by the Incremental Analysis and the post-bifurcation behavior is analyzed by introducing the branching scheme proposed by Riks. The finite-element formulation is based on the Incremental deformation theory and elastic–plastic material modeling. The finite-element Analysis is carried out using the continuum-based resultant shell elements considering the anisotropy of the sheet metal. In order to investigate the effect of plastic anisotropy on the compressive instability, a square plate that is subjected to compression in one direction and tension in the other direction is analyzed by the above-mentioned finite-element Analysis. The critical stress ratios above which buckling does not take place are found for various plastic anisotropic modeling methods and discussed. Finally, the effect of plastic anisotropy on the puckering behavior in the spherical cup deep drawing process is investigated. From the results of the finite-element Analysis, it is shown that puckering behavior of sheet metal is largely affected by plastic anisotropy.
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A general elasto-plastic finite element formulation based on Incremental deformation theory for planar anisotropy and its application to sheet metal forming
International Journal of Plasticity, 1999Co-Authors: Jeong Whan Yoon, Dong-yol Yang, Kwansoo Chung, Frédéric BarlatAbstract:Abstract A new implicit approach for the Incremental Analysis of planar anisotropic elasto-plastic sheet forming processes was developed based on the Incremental deformation theory of plasticity. The Incremental deformation theory based on minimum work paths enables convenient decoupling of deformation and rotation by the polar decomposition. The mathematical description of a constitutive law for the Incremental deformation theory has been previously derived from the flow theory along the minimum plastic work path. The resulting Incremental constitutive law is frame-indifferent (objective) since the theory uses the materially-embedded coordinate system. Utilizing the natural convected coordinate system in the Incremental variational formulation, the geometrical evolution of materials and the rotation of planar anisotropic axes were effectively incorporated. Planar anisotropy was represented using a nonquadratic yield function. For verification purposes, the onset of necking as well as the earing of aluminum alloy sheet samples were simulated for circular cup drawing and NUMISHEET'93 square cup drawing. The simulated results were compared with experimental results. Simulation was also carried out for NUMISHEET'93 front fender in order to show a computational efficiency and robustness.
Scott D Ramsey - One of the best experts on this subject based on the ideXlab platform.
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cost effectiveness Analysis alongside clinical trials ii an ispor good research practices task force report
Value in Health, 2015Co-Authors: Scott D Ramsey, Richard J Willke, Henry A Glick, Shelby D Reed, Federico Augustovski, Bengt Jonsson, Andrew Briggs, Sean D SullivanAbstract:Clinical trials evaluating medicines, medical devices, and procedures now commonly assess the economic value of these interventions. The growing number of prospective clinical/economic trials reflects both widespread interest in economic information for new technologies and the regulatory and reimbursement requirements of many countries that now consider evidence of economic value along with clinical efficacy. As decision makers increasingly demand evidence of economic value for health care interventions, conducting high-quality economic analyses alongside clinical studies is desirable because they broaden the scope of information available on a particular intervention, and can efficiently provide timely information with high internal and, when designed and analyzed properly, reasonable external validity. In 2005, ISPOR published the Good Research Practices for Cost-Effectiveness Analysis Alongside Clinical Trials: The ISPOR RCT-CEA Task Force report. ISPOR initiated an update of the report in 2014 to include the methodological developments over the last 9 years. This report provides updated recommendations reflecting advances in several areas related to trial design, selecting data elements, database design and management, Analysis, and reporting of results. Task force members note that trials should be designed to evaluate effectiveness (rather than efficacy) when possible, should include clinical outcome measures, and should obtain health resource use and health state utilities directly from study subjects. Collection of economic data should be fully integrated into the study. An Incremental Analysis should be conducted with an intention-to-treat approach, complemented by relevant subgroup analyses. Uncertainty should be characterized. Articles should adhere to established standards for reporting results of cost-effectiveness analyses. Economic studies alongside trials are complementary to other evaluations (e.g., modeling studies) as information for decision makers who consider evidence of economic value along with clinical efficacy when making resource allocation decisions.
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good research practices for cost effectiveness Analysis alongside clinical trials the ispor rct cea task force report
Value in Health, 2005Co-Authors: Scott D Ramsey, Richard J Willke, Henry A Glick, Andrew Briggs, Ruth E Brown, Martin Buxton, Anita Chawla, John R Cook, Bengt Liljas, Diana B PetittiAbstract:Objectives: A growing number of prospective clinical trials include economic end points. Recognizing the variation in methodology and reporting of these studies, the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) chartered the Task Force on Good Research Practices: Randomized Clinical Trials— Cost-Effectiveness Analysis. Its goal was to develop a guidance document for designing, conducting, and reporting cost-effectiveness analyses conducted as a part of clinical trials. Methods: Task force cochairs were selected by the ISPOR Board of Directors. Cochairs invited panel members to participate. Panel members included representatives from academia, the pharmaceutical industry, and health insurance plans. An outline and a draft report developed by the panel were presented at the 2004 International and European ISPOR meetings, respectively. The manuscript was then submitted to a reference group for review and comment. Results: The report addresses issues related to trial design, selecting data elements, database design and management, Analysis, and reporting of results. Task force members agreed that trials should be designed to evaluate effectiveness (rather than efficacy), should include clinical outcome measures, and should obtain health resource use and health state utilities directly from study subjects. Collection of economic data should be fully integrated into the study. Analyses should be guided by an Analysis plan and hypotheses. An Incremental Analysis should be conducted with an intention-to-treat approach. Uncertainty should be characterized. Manuscripts should adhere to established standards for reporting results of costeffectiveness analyses. Conclusions: Trial-based cost-effectiveness studies have appeal because of their high internal validity and timeliness. Improving the quality and uniformity of these studies will increase their value to decision makers who consider evidence of economic value along with clinical efficacy when making resource allocation decisions.
Maja Pantic - One of the best experts on this subject based on the ideXlab platform.
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Building autonomous sensitive artificial listeners (Extended abstract)
2015 International Conference on Affective Computing and Intelligent Interaction ACII 2015, 2015Co-Authors: Marc Schröder, Sathish Pammi, Gary Mckeown, Elisabetta Bevacqua, Mark Ter Maat, Roddy Cowie, Dirk Heylen, Hatice Gunes, Florian Eyben, Maja PanticAbstract:This paper describes a substantial effort to build a real-time interactive multimodal dialogue system with a focus on emotional and nonverbal interaction capabilities. The work is motivated by the aim to provide technology with competences in perceiving and producing the emotional and nonverbal behaviors required to sustain a conversational dialogue. We present the Sensitive Artificial Listener (SAL) scenario as a setting which seems particularly suited for the study of emotional and nonverbal behavior since it requires only very limited verbal understanding on the part of the machine. This scenario allows us to concentrate on nonverbal capabilities without having to address at the same time the challenges of spoken language understanding, task modeling, etc. We first report on three prototype versions of the SAL scenario in which the behavior of the Sensitive Artificial Listener characters was determined by a human operator. These prototypes served the purpose of verifying the effectiveness of the SAL scenario and allowed us to collect data required for building system components for analyzing and synthesizing the respective behaviors. We then describe the fully autonomous integrated real-time system we created, which combines Incremental Analysis of user behavior, dialogue management, and synthesis of speaker and listener behavior of a SAL character displayed as a virtual agent. We discuss principles that should underlie the evaluation of SAL-type systems. Since the system is designed for modularity and reuse and since it is publicly available, the SAL system has potential as a joint research tool in the affective computing research community.
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building autonomous sensitive artificial listeners
IEEE Transactions on Affective Computing, 2012Co-Authors: Marc Schröder, Sathish Pammi, Gary Mckeown, Elisabetta Bevacqua, Mark Ter Maat, Roddy Cowie, Dirk Heylen, Hatice Gunes, Florian Eyben, Maja PanticAbstract:This paper describes a substantial effort to build a real-time interactive multimodal dialogue system with a focus on emotional and nonverbal interaction capabilities. The work is motivated by the aim to provide technology with competences in perceiving and producing the emotional and nonverbal behaviors required to sustain a conversational dialogue. We present the Sensitive Artificial Listener (SAL) scenario as a setting which seems particularly suited for the study of emotional and nonverbal behavior since it requires only very limited verbal understanding on the part of the machine. This scenario allows us to concentrate on nonverbal capabilities without having to address at the same time the challenges of spoken language understanding, task modeling, etc. We first report on three prototype versions of the SAL scenario in which the behavior of the Sensitive Artificial Listener characters was determined by a human operator. These prototypes served the purpose of verifying the effectiveness of the SAL scenario and allowed us to collect data required for building system components for analyzing and synthesizing the respective behaviors. We then describe the fully autonomous integrated real-time system we created, which combines Incremental Analysis of user behavior, dialogue management, and synthesis of speaker and listener behavior of a SAL character displayed as a virtual agent. We discuss principles that should underlie the evaluation of SAL-type systems. Since the system is designed for modularity and reuse and since it is publicly available, the SAL system has potential as a joint research tool in the affective computing research community.
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Come and have an emotional workout with sensitive artificial listeners!
2011 IEEE International Conference on Automatic Face and Gesture Recognition and Workshops FG 2011, 2011Co-Authors: Marc Schröder, Sathish Pammi, Gary Mckeown, Mark Ter Maat, Roddy Cowie, Dirk Heylen, Hatice Gunes, Maja Pantic, Florian EybenAbstract:This demonstration aims to showcase the recently completed SEMAINE\nsystem. The SEMAINE system is a publicly available, fully autonomous\nSensitive Artificial Listeners (SAL) system that consists of virtual\ndialog partners based on audiovisual Analysis and synthesis (see\nhttp://semaine.opendfki.de/wiki). The system runs in real-time, and\ncombines Incremental Analysis of user behavior, dialog management,\nand synthesis of speaker and listener behavior of a SAL character,\ndisplayed as a virtual agent. The SAL characters intend to engage\nthe user in a conversation by paying attention to the user's emotions\nand nonverbal expressions. The characters have their own emotionally\ndefined personality. During an interaction, the characters attempt\nto create an emotional workout for the user by drawing her/him towards\ntheir dominant emotion, through a combination of verbal and nonverbal\nexpressions.
