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2008

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Articles 31 - 60 of 531

Full-Text Articles in Mechanical Engineering

Edge-Stress Induced Warping Of Graphene Sheets And Nanoribbons, Ashwin Ramasubramaniam, Y. W. Zhang, C. D. Reddy, V. B. Shenoy Nov 2008

Edge-Stress Induced Warping Of Graphene Sheets And Nanoribbons, Ashwin Ramasubramaniam, Y. W. Zhang, C. D. Reddy, V. B. Shenoy

Ashwin Ramasubramaniam

We show that edge stresses introduce intrinsic ripples in freestanding graphene sheets even in the absence of any thermal effects. Compressive edge stresses along zigzag and armchair edges of the sheet cause out-of-plane warping to attain several degenerate mode shapes. Based on elastic plate theory, we identify scaling laws for the amplitude and penetration depth of edge ripples as a function of wavelength. We also demonstrate that edge stresses can lead to twisting and scrolling of nanoribbons as seen in experiments. Our results underscore the importance of accounting for edge stresses in thermal theories and electronic structure calculations for freestanding ...


Diagnostic Analysis Of A Small-Scale Incinerator By The Garson Index, Wei-Hsin Chen Nov 2008

Diagnostic Analysis Of A Small-Scale Incinerator By The Garson Index, Wei-Hsin Chen

Wei-Hsin Chen

No abstract provided.


Product Family Design Using Smart Pareto Filters, Jonathan D. Yearsley Nov 2008

Product Family Design Using Smart Pareto Filters, Jonathan D. Yearsley

Theses and Dissertations

Product families are frequently used to provide consumers with a variety of appealing products and to help maintain reasonably low production costs for manufacturers. Three common objectives in the design of product families are used to balance the interests of both consumers and manufacturers. These objectives are to maximize (i) product performance, (ii) product distinctiveness as perceived by the consumer, and (iii) product commonality as seen by the manufacturer. In this thesis, three methods are introduced that use multiobjective optimization and Smart Pareto filtering to satisfy the three objectives of product family design. The methods are progressive in nature and ...


Design And Testing Of A Pumpless Microelectromechanical System Nanoinjector, Quentin Theodore Aten Nov 2008

Design And Testing Of A Pumpless Microelectromechanical System Nanoinjector, Quentin Theodore Aten

Theses and Dissertations

A deeper understanding of human development and disease is made possible partly through the study of genetically modified model organisms, such as the common mouse (Mus musculus). By genetically modifying such model organisms, scientists can activate, deactivate, or highlight particular characteristics. A genetically modified animal is generated by adding exogenous (foreign) genetic material to one or more embryonic cells at their earliest stages of development. Frequently, this exogenous genetic material consists of specially engineered DNA, which is introduced into a fertilized egg cell (zygote). When successfully introduced into the zygote, the exogenous DNA will be incorporated into the cell's ...


Ecad To Mcad Interoperability For Automated Enclosure Design, Adam C. Wilcox Nov 2008

Ecad To Mcad Interoperability For Automated Enclosure Design, Adam C. Wilcox

Theses and Dissertations

Enclosure design is the process of creating a package that will support and protect enclosed circuitry. Electronic enclosures are used in almost all industries, such as aerospace, automotive, naval, computer, toy, etc. Many designers use computer aided design (CAD) packages to aid them in creating these enclosures. Enclosure creation involves a working knowledge of the physics behind electrical and mechanical systems. Each of these engineering disciplines has separate CAD packages with their own set of rules, programming language, and interfaces. This creates a barrier for communication flow between electrical CAD (ECAD) and mechanical CAD (MCAD). The purpose of this thesis ...


Design Of A Three-Passage Low Reynolds Number Turbine Cascade With Periodic Flow Conditions, Daniel R. Rogers Nov 2008

Design Of A Three-Passage Low Reynolds Number Turbine Cascade With Periodic Flow Conditions, Daniel R. Rogers

Theses and Dissertations

A numerical method for modeling a low Reynolds number turbine blade, the L1M, is presented along with the pitfalls encountered. A laminar solution was confirmed to not accurately predict the flow features known in low Reynolds number turbine blade flow. Three fully turbulent models were then used to try to predict the separation and reattachment of the flow. These models were also found to be insufficient for transitioning flows. A domain was created to manually trip the laminar flow to turbulent flow using a predictive turbulence transition model. The trip in the domain introduced an instability in the flow field ...


Dynamic Responses Of Marine Risers/Pipes Transporting Fluid Subject To Top End Excitations, J. Leklong, S. Chucheepsakul, S. Kaewunruen Nov 2008

Dynamic Responses Of Marine Risers/Pipes Transporting Fluid Subject To Top End Excitations, J. Leklong, S. Chucheepsakul, S. Kaewunruen

Faculty of Engineering - Papers (Archive)

This paper deals with the dynamic responses to top end excitation of marine risers/pipes conveying internal fluid. The marine riser is often used as a flexible link between undersea bore head and subsurface offshore platform. The tidal waves and the changes of sea level consistently excite its top end connected to a floating vessel. In order to carry out the performance-based design of the marine risers, the evaluation of their dynamic responses to top end excitations is imperative. In this study, the marine riser is simulated using twodimensional beam elements. Energy functional of the marine risers conveying fluids is ...


Techniques For Developing Large Scale Fuzzy Logic Systems, Jon C. Ervin, Sema E. Alptekin Nov 2008

Techniques For Developing Large Scale Fuzzy Logic Systems, Jon C. Ervin, Sema E. Alptekin

Sema E. Alptekin

In this paper, we describe various techniques used to make Intuitionistic Fuzzy Logic Systems amenable to operating on applications with large numbers of inputs. A rule reduction technique known as Combs method is combined with an automated tuning process based on Particle Swarm Optimization. A second stage of tuning on rule weights results in improved performance and further reduction in the size of the rule-base. The entire process has been developed to operate within the Matlab software environment. The technique is tested against the Wisconsin Breast Cancer Database. The use of these tools shows great promise in significantly expanding the ...


Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn Nov 2008

Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn

Mechanical Engineering Faculty Publications

A micromechanics model is developed to predict Young’s modulus of perfluorosulfonic acid (PFSA) membranes at various temperatures and water contents. The morphology of PFSA membranes is characterized by a two-phase structure, where hydrophilic clusters expand to hold water molecules during swelling, whereas the hydrophobic polymer network maintains the structural stability. A representative volume element (RVE) is proposed based on the descriptions for the nanostructure of PFSA membranes available in the literature. On the basis of mechanics model, we estimate Young’s modulus in tension of PFSA membranes as a function of water volume fraction for various temperatures. The results ...


Lean Six Sigma As A Source Of Competitive Advantage, Alessandro Giorgio Cavallini Nov 2008

Lean Six Sigma As A Source Of Competitive Advantage, Alessandro Giorgio Cavallini

Theses and Dissertations

Anecdotal data affirms that companies applying Lean Six Sigma in their operations not only deliver higher quality products and services, but also obtain superior financial results. The goal of this research was to empirically verify anecdotal data. The study proposed to analyze a group of publicly traded manufacturing companies with the intent of verifying if a correlation exists between companies being lean and the attainment of superior returns on investments. The researcher performed a series of statistical tests comparing key Financial Performance Indicators (FPI) extracted from annual reports (10-K) from a large pool of companies. The outcome of this study ...


Modified Predator-Prey (Mpp) Algorithm For Single-And Multi-Objective Optimization Problems, Souma Chowdhury Nov 2008

Modified Predator-Prey (Mpp) Algorithm For Single-And Multi-Objective Optimization Problems, Souma Chowdhury

FIU Electronic Theses and Dissertations

The aim of this work is to develop an algorithm that can solve multidisciplinary design optimization problems. In predator-prey algorithm, a relatively small number of predators and a much larger number of prey are randomly placed on a two dimensional lattice with connected ends. The predators are partially or completely biased towards one or more objectives, based on which each predator kills the weakest prey in its neighborhood. A stronger prey created through evolution replaces this prey. In case of constrained problems, the sum o f constraint violations serves as an additional objective.

Modifications of the basic predator-prey algorithm have ...


Development Of A Dual-Handed Haptic Assembly System: Sharp, Abhishek Seth, Hai-Jun Su, Judy M. Vance Nov 2008

Development Of A Dual-Handed Haptic Assembly System: Sharp, Abhishek Seth, Hai-Jun Su, Judy M. Vance

Mechanical Engineering Publications

Virtual reality (VR) technology holds promise as a virtual prototyping (VP) tool for mechanical assembly; however, several developmental challenges still need to be addressed before VP applications can successfully be integrated into the product realization process. This paper describes the development of System for Haptic Assembly and Realistic Prototyping (SHARP), a portable virtual assembly system. SHARP uses physics-based modeling for simulating realistic part-to-part and hand-to-part interactions in virtual environments. A dual-handed haptic interface for a realistic part interaction using the PHANToM® haptic devices is presented. The capability of creating subassemblies enhances the application’s ability to handle a wide variety ...


تعيين عرض تختال در ورودي كوره هاي پيش گرم ناحيه نورد گرم مجتمع فولاد مباركه با استفاده از پردازش ديجيتال تصاوير, Eaman Alibeigi, Rasoul Amirfattahi, Masoud Harooni, Hamid Montazerolghaem Nov 2008

تعيين عرض تختال در ورودي كوره هاي پيش گرم ناحيه نورد گرم مجتمع فولاد مباركه با استفاده از پردازش ديجيتال تصاوير, Eaman Alibeigi, Rasoul Amirfattahi, Masoud Harooni, Hamid Montazerolghaem

Masoud Harooni

هر يك از تختال هاي توليد شده در بخش ريخته گري مداوم ناحيه فولاد سازي، پس از مارك زني و تعيين مشتري به يكي از دو صورت هوايي يا سيالي خنك شده و در زمان مقرر به وسيله غلطك هايي وارد كوره پيش گرم مي شوند. در اين مرحله، 1/6 mm تختال تا حرارت 1100 درجه سانتيگراد گرم شده و عمليات نورد گرم بر روي آن به منظور تهيه ورق فولاد با ضخامت صورت مي گيرد. تعيين دقيق مشخصات ابعادي تختال ها از جمله طول، عرض و ضخامت آنها قبل از ورود به كوره هاي پيش گرم و تطبيق ...


Drop Impact Dynamic Response Study Of Jedec Jesd22-B111 Test Board, Michael Krist, Jianbiao Pan, Andrew Farris, Nicolas Vickers Nov 2008

Drop Impact Dynamic Response Study Of Jedec Jesd22-B111 Test Board, Michael Krist, Jianbiao Pan, Andrew Farris, Nicolas Vickers

Industrial and Manufacturing Engineering

Mobile and handheld electronic devices are prone to being dropped. This drop event may result in failure of solder joints inside these devices. The need for RoHS compliant boards coupled with the demand for reliable electronics has resulted in the development of the JEDEC Standard JESD22-B111 to standardize the method of drop testing surface mount electronic components. However, there has been little study on the effects of additional mass on the board and rigidity of the board on drop test reliability. This paper examines the drop impact dynamic responses of the JEDEC JESD22-B111 board. Of interest are the effects of ...


The Effect Of Ultrasonic Frequency On Gold Wire Bondability And Reliability, Jianbiao Pan, Minh-Nhat Le, Cuong Van Pham Nov 2008

The Effect Of Ultrasonic Frequency On Gold Wire Bondability And Reliability, Jianbiao Pan, Minh-Nhat Le, Cuong Van Pham

Industrial and Manufacturing Engineering

This paper presents a systematic study on the effect of 120KHz ultrasonic frequency on the bondability and reliability of fine pitch gold wire bonding. The study was carried out on a thermosonic ball bonder that is allowed to easily switch between ultrasonic frequency of 60KHz and 120 KHz by changing the ultrasonic transducer and the ultrasonic generator. Bonding parameters were optimized through design of experiment methodology for four different cases: 25.4 μm wire at 60 kHz, 25.4 μm wire at 120 kHz, 17.8 μm wire at 60 kHz, and 17.8 μm wire at 120 kHz. The ...


Board Level Failure Analysis Of Chip Scale Package Drop Test Assemblies, Nicholas Vickers, Kyle Rauen, Andrew Farris, Jianbiao Pan Nov 2008

Board Level Failure Analysis Of Chip Scale Package Drop Test Assemblies, Nicholas Vickers, Kyle Rauen, Andrew Farris, Jianbiao Pan

Industrial and Manufacturing Engineering

This paper presents the failure analysis results of board level drop tests. In this study, the test vehicle was designed according to the requirements of the Joint Electron Device Engineering Council (JEDEC) drop test board. The test vehicle was assembled with 15 chip scale packages (CSPs) each having 228 daisy-chained 0.5 mm pitch solder joints using Sn-3.0 wt% Ag-0.5 wt% Cu (SAC305) lead free solder. Assemblies were drop tested using three different peak accelerations of 900 G, 1500 G, 2900 G, with 0.7 ms, 0.5 ms, and 0.3 ms pulse durations, respectively. Scanning electron ...


Image Analyses Of Two Crustacean Exoskeletons And Implications Of The Exoskeletal Microstructure On The Mechanical Behavior, Liang Cheng, Liyun Wang, Anette M. Karlsson Nov 2008

Image Analyses Of Two Crustacean Exoskeletons And Implications Of The Exoskeletal Microstructure On The Mechanical Behavior, Liang Cheng, Liyun Wang, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The microstructures of exoskeletons from Homarus americanus (American lobster) and Callinectes sapidus (Atlantic blue crab) were investigated to elucidate the mechanical behavior of such biological composites. Image analyses of the cross-sectioned exoskeletons showed that the two species each have three well-defined regions across the cuticle thickness where the two innermost regions (exocuticle and endocuticle) are load bearing. These regions consist of mineralized chitin fibers aligned in layers, where a gradual rotation of the fiber orientation of the layers results in repeating stacks. The exocuticle and endocuticle of the two species have similar morphology, but different thicknesses, number of layers, and ...


A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai Nov 2008

A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

It remains a big challenge to theoretically predict the material removal mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of nonmetals have been based on the free electron density distribution without the actual consideration of the phase change mechanism. However, this widely used key assumption needs further theoretical and experimental confirmation. by combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through nonthermal processes (the Coulomb explosion and electrostatic ablation). The predicted ...


Real-Time Vertical Track Deflection Measurement System, Sheng Lu Nov 2008

Real-Time Vertical Track Deflection Measurement System, Sheng Lu

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Track quality is a major factor in railroad safety, and one accepted indicator of track quality is the vertical track deflection. Measuring track deflection from a moving railcar is difficult because there is no stable reference for the measurements. A system developed by researchers at the University of Nebraska to measure track deflection from a moving railcar in real-time is described in detail. The system consists of a loaded hopper with a camera/laser sensor system to detect the vertical deflection of the rail relative to the wheel/rail contact point. Modeling and simulation of the system is also presented ...


Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai Nov 2008

Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such ...


Progress Toward Meeting The Challenges Of Our Coastal Urban Future, Juile Pullen, Jason Ching, David J. Sailor, William Thompson, Bob Bornstein, Darko Koracin Nov 2008

Progress Toward Meeting The Challenges Of Our Coastal Urban Future, Juile Pullen, Jason Ching, David J. Sailor, William Thompson, Bob Bornstein, Darko Koracin

Mechanical and Materials Engineering Faculty Publications and Presentations

The article provides information on the Seventh Conference on Coastal Atmospheric and Oceanic Prediction and Processes, and the Seventh Symposium on the Urban Environment in San Diego, California on September 9-13, 2008. Topics include the heterogeneity of urban areas, coastal vulnerabilities, urban planning, and emergency response modeling. The conference featured several speakers including Walter Dabberdt and James Voogt.


Localised Galvanic Corrosion Processes In Thermal Spray Coated/Cast Aluminium Alloy Systems, David Culliton, Tony Betts, David Kennedy Nov 2008

Localised Galvanic Corrosion Processes In Thermal Spray Coated/Cast Aluminium Alloy Systems, David Culliton, Tony Betts, David Kennedy

Conference Papers

Cast Aluminium Alloys, because of the propensity of aluminium to react with impurities and alloying elements, are prone to developing IM impurities during the solidification process. These IM phases can act, in some fluids, as initiation sites for localised corrosion processes, resulting in degradation phenomena, such as pitting. Whilst Thermal Spray coatings can improve the wear resistance of Cast Aluminium Alloys, their corrosion performance may be hampered by the presence of through porosity within the coating.

The present work details some preliminary studies of the localised corrosion processes occurring at the interface area between a Thermal Spray coating and a ...


Flush-Mounted Steady-Periodic Heated Film With Application To Shear-Stress Measurement, Kevin D. Cole Nov 2008

Flush-Mounted Steady-Periodic Heated Film With Application To Shear-Stress Measurement, Kevin D. Cole

Mechanical & Materials Engineering Faculty Publications

Surface-mounted heated films have been used for fluid-flow measurement for many years. Recently unsteady heating of such surface films has been explored experimentally. In this paper steady-periodic heating of a surface-mounted film is studied analytically. Wall effects and axial heat conduction in the fluid are included. The temperature is found as an exact integral expression constructed from separate Green’s function formulations in the fluid flow and in the solid wall that are matched at the fluid-solid interface. Results for temperature, obtained by quadrature, are reported for several flow speeds and several steady-periodic frequencies. The results show that steady-periodic heating ...


Modeling And Simulation Of Hydrogen Generation From Hightemperature And Low-Temperature Water Gas Shift Reactions, Wei-Hsin Chen Oct 2008

Modeling And Simulation Of Hydrogen Generation From Hightemperature And Low-Temperature Water Gas Shift Reactions, Wei-Hsin Chen

Wei-Hsin Chen

No abstract provided.


Gtaw ايجادشده با روش جوشکاری Tini-Tic و Tini بررسی ريزساختاری پوشش, Masoud Harooni, Morteza Shamanian, Alireza Fadaei Tehrani Oct 2008

Gtaw ايجادشده با روش جوشکاری Tini-Tic و Tini بررسی ريزساختاری پوشش, Masoud Harooni, Morteza Shamanian, Alireza Fadaei Tehrani

Masoud Harooni

هدف از انجام اين پژوهش بهبود سختي سطحي و ريزساختار فولاد ساده کربنی از نوع 52 و مقايسه ريز ساختار اين دو با هم GTAW ايجاد شده به روش جوشکاری TiNi-TiC و TiNi پوششی از بترتيب با نسبت استوکيومتری مساوي و نسبت ۲۰ Ti-Ni-C و Ti-Ni است. بدين منظور مخلوط پودری به طور جداگانه توسط روش فعال سازی مکانيکی فعال شد و سپس بر سطح TiC درصد تقويت کننده به ضخامت ۱ ميليمتر پيش نشانده شده با استفاده از روش جوشکاری قوسی St نمونه های فولادی 52 تنگستن- گاز ذوب و با فلز پايه امتزاج يافته است. جهت بررسي نوع ...


Work In Progress - Enhancing Student-Learning Through State-Of-The-Art Systems Level Design And Implementation, Albert A. Liddicoat, Jianbiao Pan, James G. Harris, Dominic J. Dal Bello, Lynne A. Slivovsky Oct 2008

Work In Progress - Enhancing Student-Learning Through State-Of-The-Art Systems Level Design And Implementation, Albert A. Liddicoat, Jianbiao Pan, James G. Harris, Dominic J. Dal Bello, Lynne A. Slivovsky

Industrial and Manufacturing Engineering

The curriculum for undergraduate engineering programs is often partitioned into several courses that are taught in isolation followed by a single culminating senior design or capstone project experience. In the senior design class students being to synthesize the knowledge and skills that they acquired through the engineering curriculum. This paper presents lower and upper division course and curricular changes made to accommodate learning objectives that better prepare students for project-based learning. These learning experiences and skills include: systems level design, experience with state-of-the-art Computer Aided Design (CAD) tools, printed circuit board (PBC) design, design for manufacturability, electronics assembly, project management ...


Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner Oct 2008

Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner

Faculty Publications from the Department of Engineering Mechanics

We present a quantitative method for determining the viscoelastic properties of materials with nanometer spatial resolution. The approach is based on the atomic force acoustic microscopy technique that involves the resonant frequencies of the atomic force microscopy cantilever when its tip is in contact with a sample surface. We derive expressions for the viscoelastic properties of the sample in terms of the cantilever frequency response and damping loss. We demonstrate the approach by obtaining experimental values for the storage and loss moduli of a poly(methyl methacrylate) film using a polystyrene sample as a reference material. Experimental techniques and system ...


Enhancing Co−Water Mass Transfer By Functionalized Mcm41 Nanoparticles, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel Oct 2008

Enhancing Co−Water Mass Transfer By Functionalized Mcm41 Nanoparticles, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel

Mechanical Engineering Publications

Organic groups are grafted to 250-nm-diameter MCM41 nanoparticles with a spherical morphology to enhance the CO−water volumetric mass-transfer coefficient (kLa) for synthesis gas fermentation. The results indicate that (i) 250-nm MCM41 nanoparticles show a higherkLa value than large silica particles (1.4 and 7 μm), (ii) surface hydroxyl groups on MCM41 nanoparticles play an important role in mass-transfer enhancement, (iii) organic groups grafted to MCM41 modify the mass-transfer enhancement, and (iv) mercaptan groups grafted to MCM41 show the most mass-transfer enhancement of 1.9 times that of no nanoparticle addition. The CO−water mass-transfer ...


A Mechanistic Investigation Of Nitrogen Evolution In Pulverized Coal Oxy-Fuel Combustion, Andrew John Mackrory Oct 2008

A Mechanistic Investigation Of Nitrogen Evolution In Pulverized Coal Oxy-Fuel Combustion, Andrew John Mackrory

Theses and Dissertations

Oxy-fuel combustion is an enabling technology for capture of CO2 from coal combustion, the economics of which depends strongly on the ability of the process to produce low NOX emissions. The literature contains many reports of lower NOX emissions from oxy-fuel combustion but the reasons for this are not fully understood. The objective of this work was to gain understanding of nitrogen evolution under pulverized coal oxy-fuel conditions. Pulverized coal was burned in a once-through, down-fired, laminar flow reactor. Nitrogen compounds and other combustion species were measured at the reactor centerline as a function of distance from the burner. Dry ...


A Variational Shape Optimization Approach For Image Segmentation With A Mumford-Shah Functional, Günay Doğam, Pedro Morin, Ricardo H. Nochetto Oct 2008

A Variational Shape Optimization Approach For Image Segmentation With A Mumford-Shah Functional, Günay Doğam, Pedro Morin, Ricardo H. Nochetto

Departmental Papers (MEAM)

We introduce a novel computational method for a Mumford–Shah functional, which decomposes a given image into smooth regions separated by closed curves. Casting this as a shape optimization problem, we develop a gradient descent approach at the continuous level that yields nonlinear PDE flows. We propose time discretizations that linearize the problem and space discretization by continuous piecewise linear finite elements. The method incorporates topological changes, such as splitting and merging for detection of multiple objects, space–time adaptivity, and a coarse-to-fine approach to process large images efficiently. We present several simulations that illustrate the performance of the method ...