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2015

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Articles 1 - 30 of 38

Full-Text Articles in Other Engineering Science and Materials

Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles Nov 2015

Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles

Department of Mechanical and Materials Engineering: Faculty Publications

The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. …

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Umass Amherst Green Building Guidelines 2013, Ludmilla Pavlova-Gillham, Ted Mendoza, Ezra Small, Patricia O'Flaherty, Nariman Mostafavi, Mohamed Farzinmoghadam, Somayeh Tabatabaee Pozveh Oct 2015

Umass Amherst Green Building Guidelines 2013, Ludmilla Pavlova-Gillham, Ted Mendoza, Ezra Small, Patricia O'Flaherty, Nariman Mostafavi, Mohamed Farzinmoghadam, Somayeh Tabatabaee Pozveh

Ludmilla D Pavlova

Facilities & Campus Services, Sustainable UMass and Campus Planning support sustainability and energy conservation initiatives by providing in-house resources to campus staff as well as designers and contractors working with the University. The UMass Amherst Green Building Guidelines provide a framework for approaching new construction and major renovation projects at UMass Amherst that are undergoing LEED certification by focusing the conversation on green building aspects that are most important to the campus. They are intended to be the beginning of a dynamic conversation between designers, environmental consultants and constructors, university stakeholders, and users of new high performance buildings.

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Elevated Test Pressure Significantly Reduces Dynamic Accumulation Oxygen Transmission Rate (Astm F3136) Measurement Time For Barrier Packaging Films, Bruce A. Welt Sep 2015

Elevated Test Pressure Significantly Reduces Dynamic Accumulation Oxygen Transmission Rate (Astm F3136) Measurement Time For Barrier Packaging Films, Bruce A. Welt

Journal of Applied Packaging Research

Measurement of gas transmission rates of materials is important for successful package design. The dynamic accumulation (DA) method (ASTM F3136) is becoming increasingly popular for measuring oxygen transmission rate (OTR) due to its simplicity and low cost. However, measurement time increases with barrier properties of materials, limiting measurement throughput. A dynamic accumulation measurement prototype capable of operating up to 1,000 psig was developed in order to accelerate gas transfer by boosting concentration gradients via elevated absolute pressures. Results show that measurement results were independent of test pressure while measurement times were substantially reduced. These results also suggest that gas transmission …

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System And Method For Estimating States Of Spacecraft In Planet-Moon Environment, Piyush Grover Aug 2015

System And Method For Estimating States Of Spacecraft In Planet-Moon Environment, Piyush Grover

Department of Mechanical and Materials Engineering: Faculty Publications

A method estimates a state of a spacecraft in a planet-moon environment by executing iteratively a particle filter. The particle filter comprising integrates individually states of each particle of the particle filter according to a probability-evolution equation using a model of the state of the spacecraft represented as a planar circular restricted three-body problem and determines a prior probability of each particle as a previous posterior probability of a corresponding particle during a previous iteration. A joint probability distribution of the state of the spacecraft is determines using the states of each particle and the prior probabilities of each particle …

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An Estimate Of The Second-Order In-Plane Acceleration Sensitivity Of A Y-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, John A. Kosinski Aug 2015

An Estimate Of The Second-Order In-Plane Acceleration Sensitivity Of A Y-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, John A. Kosinski

Department of Mechanical and Materials Engineering: Faculty Publications

We perform a theoretical analysis of the second-order in-plane acceleration sensitivity of a Y-cut quartz thick-ness-shear mode resonator. The second-order nonlinear theory of elasticity for anisotropic crystals is used to determine the biasing fields in the resonator under in-plane acceleration. The acceleration-induced frequency shift is determined from a per-turbation analysis based on the plate equations for small-amplitude vibrations superposed on a finite bias. We show that, whereas the first-order acceleration-induced frequency shift is zero for a structurally symmetric resonator under in-plane ac-celeration, the second-order frequency shift is nonzero and is quadratic in the acceleration. As the fourth-order nonlinear elastic constants …

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Biodegradable Medical Device Having An Adjustable Degradation Rate And Methods Of Making The Same, Yuebin Guo, Michael Sealy, Meisam Salahshoor Pirsoltan Jul 2015

Biodegradable Medical Device Having An Adjustable Degradation Rate And Methods Of Making The Same, Yuebin Guo, Michael Sealy, Meisam Salahshoor Pirsoltan

Department of Mechanical and Materials Engineering: Faculty Publications

Disclosed herein are biodegradable medical devices comprising biodegradable material (e.g., magnesium-calcium alloys) having an adjustable rate of degradation that can be used in various applications, including, but not limited to, drug delivery applications, cardiovascular applications, and orthopedic applications to make biodegradable and biocompatible devices. Also disclosed herein are methods of making biodegradable medical devices comprising biodegradable materials by using, for instance, hybrid dry cutting/hydrostatic burnishing.

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Non-Wetting Surface-Driven High-Aspect-Ratio Crystalline Grain Growth For Efficient Hybrid Perovskite Solar Cells, Cheng Bi, Qi Wang, Yongbo Yuan, Zhengguo Xiao, Jinsong Huang Jun 2015

Non-Wetting Surface-Driven High-Aspect-Ratio Crystalline Grain Growth For Efficient Hybrid Perovskite Solar Cells, Cheng Bi, Qi Wang, Yongbo Yuan, Zhengguo Xiao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Large-aspect-ratio grains are needed in polycrystalline thin-film solar cells for reduced charge recombination at grain boundaries; however, the grain size in organolead trihalide perovskite (OTP) films is generally limited by the film thickness. Here we report the growth of OTP grains with high average aspect ratio of 2.3–7.9 on a wide range of non-wetting hole transport layers (HTLs), which increase nucleus spacing by suppressing heterogeneous nucleation and facilitate grain boundary migration in grain growth by imposing less drag force. The reduced grain boundary area and improved crystallinity dramatically reduce the charge recombination in OTP thin films to the level in …

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Predictive Modeling Of Oxygen Transmission Through Micro-Perforations For Packaging Applications, Ayman Abdellatief, Bruce A. Welt, Jason Butler, Eric Mclamore, Arthur Teixeira, Sanjay Shukla May 2015

Predictive Modeling Of Oxygen Transmission Through Micro-Perforations For Packaging Applications, Ayman Abdellatief, Bruce A. Welt, Jason Butler, Eric Mclamore, Arthur Teixeira, Sanjay Shukla

Journal of Applied Packaging Research

Methods for creating precise perforations in respiring produce packaging are being increasingly adopted. Knowledge of oxygen transfer through perforated packaging and oxygen distribution in packages is necessary for successful packaging design of fresh produce. An approach to modeling perforated packaging performance was developed using a cylindrical chamber with precision perforations using Fick’s second law. The model was simulated using two techniques including Finite Element Method (FEM) using commercially available software and Finite Volume Method (FVM) through programming. Perforations were approximated as a source term in the second method. Both simulation techniques showed trends similar to experimental data.

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Local Control Robotic Surgical Devices And Related Methods, Eric Markvicka, Tom Frederick, Jack Mondry, Joe Bartels, Shane Farritor Apr 2015

Local Control Robotic Surgical Devices And Related Methods, Eric Markvicka, Tom Frederick, Jack Mondry, Joe Bartels, Shane Farritor

Department of Mechanical and Materials Engineering: Faculty Publications

The various robotic medical devices include robotic devices that are disposed within a body cavity and positioned using a support component disposed through an orifice or opening in the body cavity. Additional embodiments relate to devices having arms coupled to a device body wherein the device has a minimal profile such that the device can be easily inserted through smaller incisions in comparison to other devices without such a small profile. Further embodiments relate to methods of operating the above devices.

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Development Of A Metal-Printing 3d Printer At The University Of North Dakota, Benjamin Kading, Michaela Kegley, Tiana Delzer, Jeremy Straub, Scott Kerlin Mar 2015

Development Of A Metal-Printing 3d Printer At The University Of North Dakota, Benjamin Kading, Michaela Kegley, Tiana Delzer, Jeremy Straub, Scott Kerlin

Jeremy Straub

Three-dimensional (3D) printing is being used for numerous applications: from consumer hobbies to the development of aircraft parts. However, inexpensive 3D printers have been constrained in material selection to plastic. These printer use the fused deposition modeling (FDM) method of printing, which is a relatively new technology that utilizes computer numerical control (CNC) techniques to deposit melted material at specific places. Other methods, for example, include laser sintering and stereolithography. With 3D printing, layers are stacked upon each other and via this compilation of layers, a 3D object is formed. Currently there are a variety of materials that can be …

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Methods And Systems For Handling Or Delivering Materials For Natural Orifice Surgery, Carl Nelson, Jeff Midday, Dimitry Oleynikov, Alan Goyzueta Mar 2015

Methods And Systems For Handling Or Delivering Materials For Natural Orifice Surgery, Carl Nelson, Jeff Midday, Dimitry Oleynikov, Alan Goyzueta

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical systems, including systems that can be used in conjunction with medical devices used in endoscopic surgery. Certain embodiments include various material handling devices that can transport materials between the inside and the outside of an endoscopic surgery patient.

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Development And Preliminary Evaluation Of A Spray Deposition Sensing System For Improving Pesticide Application, Melissa A. Kesterson, Joe D. Luck, Michael P. Sama Jan 2015

Development And Preliminary Evaluation Of A Spray Deposition Sensing System For Improving Pesticide Application, Melissa A. Kesterson, Joe D. Luck, Michael P. Sama

Department of Mechanical and Materials Engineering: Faculty Publications

An electronic, resistance-based sensor array and data acquisition system was developed to measure spray deposition from hydraulic nozzles. The sensor surface consisted of several parallel tin plated copper traces of varying widths with varying gap widths. The system contained an embedded microprocessor to monitor output voltage corresponding to spray deposition every second. In addition, a wireless module was used to transmit the voltage values to a remote laptop. Tests were conducted in two stages to evaluate the performance of the sensor array in an attempt to quantify the spray deposition. Initial tests utilized manual droplet placement on the sensor surface …

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Enhanced Pool-Boiling Heat Transfer And Critical Heat Flux On Femtosecond Laser Processed Stainless Steel Surfaces, Cory M. Kruse, Troy Anderson, Chris Wilson, Craig Zuhlke, Dennis Alexander, George Gogos, Sidy Ndao Jan 2015

Enhanced Pool-Boiling Heat Transfer And Critical Heat Flux On Femtosecond Laser Processed Stainless Steel Surfaces, Cory M. Kruse, Troy Anderson, Chris Wilson, Craig Zuhlke, Dennis Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper, we present an experimental investigation of pool boiling heat transfer on multiscale (micro/nano) functionalized metallic surfaces. Heat transfer enhancement in metallic surfaces is very important for large scale high heat flux applications like in the nuclear power industry. The multiscale structures were fabricated via a femtosecond laser surface process (FLSP) technique, which forms self-organized mound-like microstructures covered by layers of nanoparticles. Using a pool boiling experimental setup with deionized water as the working fluid, both the heat transfer coefficients and critical heat flux were investigated. A polished reference sample was found to have a critical heat flux …

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Quantification Of Plaque Stiffness By Brillouin Microscopy In Experimental Thin Cap Fibroatheroma, Giuseppe Antonacci, Ryan M. Pedrigi, Avinash Kondiboyina, Vikram V. Mehta, Ranil De Silva, Carl Paterson, Rob Krams, Peter Torok Jan 2015

Quantification Of Plaque Stiffness By Brillouin Microscopy In Experimental Thin Cap Fibroatheroma, Giuseppe Antonacci, Ryan M. Pedrigi, Avinash Kondiboyina, Vikram V. Mehta, Ranil De Silva, Carl Paterson, Rob Krams, Peter Torok

Department of Mechanical and Materials Engineering: Faculty Publications

Plaques vulnerable to rupture are characterized by a thin and stiff fibrous cap overlaying a soft lipid-rich necrotic core. The ability to measure local plaque stiffness directly to quantify plaque stress and predict rupture potential would be very attractive, but no current technology does so. This study seeks to validate the use of Brillouin microscopy to measure the Brillouin frequency shift, which is related to stiffness, within vulnerable plaques. The left carotid artery of an ApoE-/- mouse was instrumented with a cuff that induced vulnerable plaque development in nine weeks. Adjacent histological sections from the instrumented and control arteries …

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The Examination Of Stress Corrosion Cracking In High Strength Carbon Steel Through Combined Mechanical-Electrochemical Testing, Jacob Sines Jan 2015

The Examination Of Stress Corrosion Cracking In High Strength Carbon Steel Through Combined Mechanical-Electrochemical Testing, Jacob Sines

Williams Honors College, Honors Research Projects

Through the analysis of materials and environments seen in industry a better understanding of the fundamentals behind degradation mechanisms can be observed. The scope of this project was to better understand the fundamentals behind the degradation of high strength pipeline steels in a lab setting to simulate an environment seen in industry. Specifically the degradation mechanisms of high and nearly neutral pH stress corrosion cracking were examined in environments that simulated oil and gas pipelines buried in soil. Experimentation was carried out utilizing X65 carbon steel specimen, a Gamry potentiostat, a CORTEST proof ring, a CORTEST slow strain rate machine, …

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Magnus Effect In Duct Flow, Cameron W. Clarke, Jesse S. Batko, Kenneth W. Smith Jr. Jan 2015

Magnus Effect In Duct Flow, Cameron W. Clarke, Jesse S. Batko, Kenneth W. Smith Jr.

Williams Honors College, Honors Research Projects

The following research paper details the preliminary research carried out by this team. The project was originally conceived to determine if Magnus Lift could be utilized in an unconventional way to assist rockets during takeoff. Several conceptual designs were proposed, but the idea was scrapped when it became apparent that the team would not be able to generate the desired lift without inducing significant amounts of drag and additional weight on a rocket. Instead, the team focused on researching an interesting topic that hasn’t been previously explored: Magnus lift on a cylinder within a duct. An experimental procedure that could …

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Quantification Of Ultraprecision Surface Morphology Using An Algebraic Graph Theoretic Approach, Prahalad Rao, Satish T. S. Bukkapatnam, Zhenyu (James) Kong, Omer F. Beyca, Kenneth Case, Ranga Komanduri Jan 2015

Quantification Of Ultraprecision Surface Morphology Using An Algebraic Graph Theoretic Approach, Prahalad Rao, Satish T. S. Bukkapatnam, Zhenyu (James) Kong, Omer F. Beyca, Kenneth Case, Ranga Komanduri

Department of Mechanical and Materials Engineering: Faculty Publications

Assessment of progressive, nano-scale variation of surface morphology during ultraprecision manufacturing processes, such as fine-abrasive polishing of semiconductor wafers, is a challenging proposition owing to limitations with traditional surface quantifiers. We present an algebraic graph theoretic approach that uses graph topological invariants for quantification of ultraprecision surface morphology. The graph theoretic approach captures heterogeneous multi-scaled aspects of surface morphology from optical micrographs, and is therefore valuable for in situ real-time assessment of surface quality. Extensive experimental investigations with specular finished (Sa ~ 5 nm) blanket copper wafers from a chemical mechanical planarization (CMP) process suggest that the proposed method was …

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Asphalt Composition, David Allen, Flavio Souza, Yong-Rak Kim, Roberto Soares Jan 2015

Asphalt Composition, David Allen, Flavio Souza, Yong-Rak Kim, Roberto Soares

Department of Mechanical and Materials Engineering: Faculty Publications

A computational method is provided for predicting roadway failure due to degradation of the roadway over time as a function of the input loads, the roadway geometry, the material properties of the constituents in the asphaltic pavement, the shape, distribution, orientation and volume fractions of the constituents, and environmental conditions. The unique and new feature of the method is that it employs several physically based predictive methodologies simultaneously.

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Extracting Continuum-Like Deformation And Stress From Molecular Dynamics Simulations, Lili Zhang, John Jasa, George Gazonas, Antoine Jerusalem, Mehrdad Negahban Jan 2015

Extracting Continuum-Like Deformation And Stress From Molecular Dynamics Simulations, Lili Zhang, John Jasa, George Gazonas, Antoine Jerusalem, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We present methods that use results from molecular dynamics (MD) simulations to construct continuum parameters, such as deformation gradient and Cauchy stress, from all or any part of an MD system. These parameters are based on the idea of minimizing the difference between MD measures for deformation and traction and their continuum counterparts. The procedures should be applicable to non-equilibrium and inhomogeneous systems, and to any part of a system, such as a polymer chain. The resulting procedures provide methods to obtain first and higher order deformation gradients associated with any subset of the MD system, and associated expressions for …

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Evaluation Of Peritoneal Microbubble Oxygenation Therapy In A Rabbit Model Of Hypoxemia, Nathan D. Legband, Jameel A. Feshitan, Mark A. Borden, Benjamin S. Terry Jan 2015

Evaluation Of Peritoneal Microbubble Oxygenation Therapy In A Rabbit Model Of Hypoxemia, Nathan D. Legband, Jameel A. Feshitan, Mark A. Borden, Benjamin S. Terry

Department of Mechanical and Materials Engineering: Faculty Publications

Alternative extrapulmonary oxygenation technologies are needed to treat patients suffering from severe hypoxemia refractory to mechanical ventilation. We previously demonstrated that peritoneal microbubble oxygenation (PMO), in which phospholipid-coated oxygen microbubbles (OMBs) are delivered into the peritoneal cavity, can successfully oxygenate rats suffering from a right pneumothorax. This study addressed the need to scale up the procedure to a larger animal with a splanchnic cardiac output similar to humans. Our results show that PMO therapy can double the survival time of rabbits experiencing complete tracheal occlusion from6.6 ± 0.6 min for the saline controls to 12.2 ± 3.0 min for the …

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Electronic Structure Evolution Of Fullerene On Ch3Nh3Pbi3, Chenggong Wang, Congcong Wang, Xiaoliang Liu, John Kauppi, Yuchuan Shao, Zhengguo Xiao, Cheng Bi, Jinsong Huang, Yongli Gao Jan 2015

Electronic Structure Evolution Of Fullerene On Ch3Nh3Pbi3, Chenggong Wang, Congcong Wang, Xiaoliang Liu, John Kauppi, Yuchuan Shao, Zhengguo Xiao, Cheng Bi, Jinsong Huang, Yongli Gao

Department of Mechanical and Materials Engineering: Faculty Publications

The thickness dependence of fullerene on CH3NH3PbI3 perovskite film surface has been investigated by using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital and highest occupied molecular orbital (HOMO) can be observed directly with IPES and UPS. It is observed that the HOMO level in fullerene shifts to lower binding energy. The XPS results show a strong initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskite film to fullerene molecules. Further deposition of fullerene …

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Improving The Sensitivity Of A Near-Infrared Nanocomposite Photodetector By Enhancing Trap Induced Hole Injection, Liang Shen, Yanjun Fang, Qingfeng Dong, Zhengguo Xiao, Jinsong Huang Jan 2015

Improving The Sensitivity Of A Near-Infrared Nanocomposite Photodetector By Enhancing Trap Induced Hole Injection, Liang Shen, Yanjun Fang, Qingfeng Dong, Zhengguo Xiao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

We report the enhancement of the photoconductive gain of nanocomposite near-infrared photodetectors by a zinc oxide nanoparticles (ZnO NPs) rich surface at the nanocomposite/cathode interface. An argon plasma etching process was used to remove polymer at the surface of nanocomposite films, which resulted in a ZnO NPs rich surface. The other way is to spin-coat a thin layer of ZnO NPs onto the nanocomposite layer. The ZnO NPs rich surface, which acts as electron traps to induce secondary hole injection under reverse bias, increased hole injection, and thus the external quantum efficiency by 2–3 times. The darkcurrent declined one order …

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Efficiency Enhancement In Polymer Solar Cells With A Polar Small Molecule Both At Interface And In The Bulk Heterojunction Layer, Zhengguo Xiao, Qingfeng Dong, Qi Wang, Wenjing Tian, Hui Huang, Jinsong Huang Jan 2015

Efficiency Enhancement In Polymer Solar Cells With A Polar Small Molecule Both At Interface And In The Bulk Heterojunction Layer, Zhengguo Xiao, Qingfeng Dong, Qi Wang, Wenjing Tian, Hui Huang, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The polar molecules, including ferroelectric materials with large dipole moments, have been applied as interfacial layers to increase the efficiency of organic solar cells by increasing the bounded charge separation, tuning the energy levels, etc. Here, we report a small polar molecule 2-cyano-3- (4-(diphenylamino) phenyl)acrylic acid (TPACA) that can be either blended in the active layer or at the polymer/electrode interface to increase the efficiency of organic solar cell devices after poling. It is found that the built-in potential of the device is increased by 0.2 V after poling under negative bias. Blending TPACA into the active layer has shown …

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Electron-Hole Diffusion Lengths >175 Μm In Solution-Grown Ch3Nh3Pbi3 Single Crystals, Qingfeng Dong, Yanjun Fang, Yuchuan Shao, Padhraic Mulligan, Jie Qiu, Lei Cao, Jinsong Huang Jan 2015

Electron-Hole Diffusion Lengths >175 Μm In Solution-Grown Ch3Nh3Pbi3 Single Crystals, Qingfeng Dong, Yanjun Fang, Yuchuan Shao, Padhraic Mulligan, Jie Qiu, Lei Cao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in polycrystalline CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We report that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 μm under 1 sun illumination and exceed 3 mm under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3 mm-thick single crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, lifetime and dramatically smaller trap densities in …

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Relevance Of Blood Vessel Networks In Blast-Induced Traumatic Brain Injury, Yi Hua, Shengmao Lin, Linxia Gu Jan 2015

Relevance Of Blood Vessel Networks In Blast-Induced Traumatic Brain Injury, Yi Hua, Shengmao Lin, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Cerebral vasculature is a complex network that circulates blood through the brain. However, the role of this networking effect in brain dynamics has seldom been inspected. This work is to study the effects of blood vessel networks on dynamic responses of the brain under blast loading. Voronoi tessellations were implemented to represent the network of blood vessels in the brain. The brain dynamics in terms of maximumprincipal strain (MPS), shear strain (SS), and intracranial pressure (ICP) weremonitored and compared. Results show that blood vessel networks significantly affected brain responses.The increased MPS and SS were observed within the brain embedded with …

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Role Of Interphase In The Mechanical Behavior Of Silica/Epoxy Resin Nanocomposites, Yi Hua, Linxia Gu, Sundaralingam Premaraj, Xiaodong Zhang Jan 2015

Role Of Interphase In The Mechanical Behavior Of Silica/Epoxy Resin Nanocomposites, Yi Hua, Linxia Gu, Sundaralingam Premaraj, Xiaodong Zhang

Department of Mechanical and Materials Engineering: Faculty Publications

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had significant influence on the effective stiffness of nanocomposites, while its sensitivities with respect to both the thickness and the gradient property of the interphase was minimal. The stiffer interphase demonstrated a higher load-sharing capacity, which also increased the stress distribution uniformity within the resin nanocomposites. Under the condition of imperfect interfacial bonding, the effective stiffness of nanocomposites …

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Towards Tuning The Mechanical Properties Of Three-Dimensional Collagen Scaffolds Using A Coupled Fiber-Matrix Model, Shengmao Lin, Lauren A. Hapach, Cynthia Reinhart-King, Linxia Gu Jan 2015

Towards Tuning The Mechanical Properties Of Three-Dimensional Collagen Scaffolds Using A Coupled Fiber-Matrix Model, Shengmao Lin, Lauren A. Hapach, Cynthia Reinhart-King, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Scaffold mechanical properties are essential in regulating the microenvironment of three-dimensional cell culture. A coupled fiber-matrix numerical model was developed in this work for predicting the mechanical response of collagen scaffolds subjected to various levels of non-enzymatic glycation and collagen concentrations. The scaffold was simulated by a Voronoi network embedded in a matrix. The computational model was validated using published experimental data. Results indicate that both non-enzymatic glycation-induced matrix stiffening and fiber network density, as regulated by collagen concentration, influence scaffold behavior. The heterogeneous stress patterns of the scaffold were induced by the interfacial mechanics between the collagen fiber network …

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In Situ Longitudinal Pre-Stretch In The Human Femoropopliteal Artery, Alexey Kamenskiy, Andreas Seas, Grant Bowen, Paul Deegan, Anastasia Desyatova, Nick Bohlim, William Poulson, Jason N. Mactaggart Jan 2015

In Situ Longitudinal Pre-Stretch In The Human Femoropopliteal Artery, Alexey Kamenskiy, Andreas Seas, Grant Bowen, Paul Deegan, Anastasia Desyatova, Nick Bohlim, William Poulson, Jason N. Mactaggart

Department of Mechanical and Materials Engineering: Faculty Publications

In situ longitudinal (axial) pre-stretch (LPS) plays a fundamental role in the mechanics of the femoropopliteal artery (FPA). It conserves energy during pulsation and prevents buckling of the artery during limb movement. We investigated how LPS is affected by demographics and risk factors, and how these patient characteristics associate with the structural and physiologic features of the FPA. LPS was measured in n=148 fresh human FPAs (14–80 years old). Mechanical properties were characterized with biaxial extension and histopathological characteristics were quantified with Verhoeff-Van Gieson Staining. Constitutive modeling was used to calculate physiological stresses and stretches which were then analyzed …

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Multiscale Modeling Of Skeletal Muscle Active Contraction In Relation To Mechanochemical Coupling Of Molecular Motors, Jiangcheng Chen, Xiaodong Zhang, Shengmao Lin, He Wang, Linxia Gu Jan 2015

Multiscale Modeling Of Skeletal Muscle Active Contraction In Relation To Mechanochemical Coupling Of Molecular Motors, Jiangcheng Chen, Xiaodong Zhang, Shengmao Lin, He Wang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, a mathematical model was developed to relate the mechanochemical characterizations of molecular motors with the macroscopic manifestation of muscle contraction. Non-equilibrium statistical mechanics were used to study the collective behavior of myosin molecular motors in terms of the complex conformation change and multiple chemical states in one working cycle. The stochastic evolution of molecular motor probability density distribution during the contraction of sarcomere was characterized by the Fokker-Planck Equation. Quick muscle contraction was demonstrated by the collective dynamic behavior of myosin motors, the muscle contraction force, and the muscle contraction velocity-force relation. Our results are validated against …

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Color And Texture Morphing With Colloids On Multilayered Surfaces, Ziguang Chen, Shumin Li, Andrew Arkebauer, George Gogos, Li Tan Jan 2015

Color And Texture Morphing With Colloids On Multilayered Surfaces, Ziguang Chen, Shumin Li, Andrew Arkebauer, George Gogos, Li Tan

Department of Mechanical and Materials Engineering: Faculty Publications

Dynamic morphing of marine species to match with environment changes in color and texture is an advanced means for surviving, self-defense, and reproduction. Here we use colloids that are placed inside a multilayered structure to demonstrate color and texture morphing. The multilayer is composed of a thermal insulating base layer, a light absorbing mid layer, and a liquid top layer. When external light of moderate intensity (∼0.2 W cm−2) strikes the structure, colloids inside the liquid layer will be assembled to locations with an optimal absorption. When this system is exposed to continuous laser pulses, more than 18 000 times …

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