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Full-Text Articles in Engineering

Dislocations Interaction Induced Structural Instability In Intermetallic Al2cu, Qing Zhou, Jian Wang, Amit Misra, Ping Huang, Fei Wang, Kewei Xu Jan 2018

Dislocations Interaction Induced Structural Instability In Intermetallic Al2cu, Qing Zhou, Jian Wang, Amit Misra, Ping Huang, Fei Wang, Kewei Xu

Department of Mechanical and Materials Engineering: Faculty Publications

Intermetallic precipitates are widely used to tailor mechanical properties of structural alloys but are often destabilized during plastic deformation. Using atomistic simulations, we elucidate structural instability mechanisms of intermetallic precipitates associated with dislocation motion in a model system of Al2Cu. Interaction of non-coplanar <001> dislocation dipoles during plastic deformation results in anomalous reactions—the creation of vacancies accompanied with climb and collective glide of <001> dislocation associated with the dislocation core change and atomic shuffle—accounting for structural instability in intermetallic Al2Cu. This process is profound with decreasing separation of non-coplanar dislocations and increasing temperature and is likely to be …


Mechanical Performance Of Plla Stent, Longzhen Wang, Junfei Tong, Pengfei Dong, David L. Wilson, Hiram G. Bezerra, Linxia Gu Jan 2018

Mechanical Performance Of Plla Stent, Longzhen Wang, Junfei Tong, Pengfei Dong, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Stent implantation is widely used to treat blocked lumen. Stents were meshed structure made of polymers and metal alloys, including stainless steel, cobalt chrome and nitinol [1]. Clinical studies had demonstrated that stents helped to scaffold the diseased lesion up to one year when tissue adapted to the stented environment [2]. However, the permanently implanted stents inside artery were associated with complications such as stent fracture, tissue inflammation, in-stent restenosis and thrombosis [3]. Currently, biodegradable stents are attracting more attention due to its potential long-term efficacy in treating blocked lumens. The detailed characterizations of biodegradable stents are essential for the …


Tissue Stresses In Stented Coronary Arteries With Different Geometries: Effect Of The Relation Between Stent Length And Lesion Length, Xiang Shen, Song Ji, Yong-Quan Deng, Hong-Fei Zhu, Jia-Bao Jiang, Linxia Gu Jan 2018

Tissue Stresses In Stented Coronary Arteries With Different Geometries: Effect Of The Relation Between Stent Length And Lesion Length, Xiang Shen, Song Ji, Yong-Quan Deng, Hong-Fei Zhu, Jia-Bao Jiang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In-stent restenosis after stent deployment remains an obstruction in the long-term benefits of stenting. This study sought to investigate the influence of the relation between stent length and lesion length on the mechanics of the arterial wall with different geometries, including straight and tapered vessels. Results showed that when the length of the stent was longer than the lesion length, the maximum stress in plaque and vessel increased as the length of stent increased. When the length of the stent was shorter than the lesion length, the vessel stress induced by stent inflation was lower; both ends of the stenosis …


Scaffold Structural Microenvironmental Cues To Guide Tissue Regeneration In Bone Tissue Applications, Xuening Chen, Hongyuan Fan, Xiaowei Deng, Lina Wu, Tao Yi, Linxia Gu, Changchun Zhou, Yujiang Fan, Xingdong Zhang Jan 2018

Scaffold Structural Microenvironmental Cues To Guide Tissue Regeneration In Bone Tissue Applications, Xuening Chen, Hongyuan Fan, Xiaowei Deng, Lina Wu, Tao Yi, Linxia Gu, Changchun Zhou, Yujiang Fan, Xingdong Zhang

Department of Mechanical and Materials Engineering: Faculty Publications

In the process of bone regeneration, new bone formation is largely affected by physico-chemical cues in the surrounding microenvironment. Tissue cells reside in a complex scaffold physiological microenvironment. The scaffold should provide certain circumstance full of structural cues to enhance multipotent mesenchymal stem cell (MSC) differentiation, osteoblast growth, extracellular matrix (ECM) deposition, and subsequent new bone formation. This article reviewed advances in fabrication technology that enable the creation of biomaterials with well-defined pore structure and surface topography, which can be sensed by host tissue cells (esp., stem cells) and subsequently determine cell fates during differentiation. Three important cues, including scaffold …


Heat Transfer Across A Nanoscale Pressurized Air Gap And Its Application In Magnetic Recording, Jinglin Zheng, Yung-Kan Chen, Qin Zhou Jan 2018

Heat Transfer Across A Nanoscale Pressurized Air Gap And Its Application In Magnetic Recording, Jinglin Zheng, Yung-Kan Chen, Qin Zhou

Department of Mechanical and Materials Engineering: Faculty Publications

In this study, we investigated how a thermally actuated air bearing slider heats up a fast-spinning storage disk through a highly pressurized nanoscale air gap in a magnetic recording system. A Euleriandescription- based computational approach is developed considering heat conduction through a pressurized air film and near-field radiation across the gap. A set of field equations that govern the air bearing dynamics, slider thermo-mechanics and disk heat dissipation are solved simultaneously through an iterative approach. A temperature field on the same order as the hot slider surface itself is found to be established in the disk. The effective local heat …


Interfacial Characterization By Pull-Out Test Of Bamboo Fibers Embedded In Poly(Lactic Acid), Quentin Viel, Antonella Esposito, Jean-Marc Saiter, Carlo Santulli, Joseph A. Turner Jan 2018

Interfacial Characterization By Pull-Out Test Of Bamboo Fibers Embedded In Poly(Lactic Acid), Quentin Viel, Antonella Esposito, Jean-Marc Saiter, Carlo Santulli, Joseph A. Turner

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, the apparent shear strength at the interface between a bamboo fiber and the surrounding poly(lactic acid) (PLA) matrix is quantified. A method for processing pull-out test samples within a controlled embedded length is proposed and the details of the test procedure are presented, along with a critical discussion of the results. Two series of samples are considered: untreated and mercerized bamboo fibers from the same batch, embedded in the same polyester matrix. Electron and optical microscopy are used to observe the fiber–matrix interface before and after the test, and to identify the failure mode of each sample, …


Plaque Burden Influences Accurate Classification Of Fibrous Cap Atheroma By In-Vivo Optical Coherence Tomography In A Porcine Model Of Advanced Coronary Atherosclerosis., Christian B. Poulsen, Ryan M. Pedrigi, Nilesh Pareek, Ismail D. Kilic, Niels R. Holm, Jacob F. Bentzon, Hans Erik Botker, Erling Falk, Rob Krams, Ranil De Silva Jan 2018

Plaque Burden Influences Accurate Classification Of Fibrous Cap Atheroma By In-Vivo Optical Coherence Tomography In A Porcine Model Of Advanced Coronary Atherosclerosis., Christian B. Poulsen, Ryan M. Pedrigi, Nilesh Pareek, Ismail D. Kilic, Niels R. Holm, Jacob F. Bentzon, Hans Erik Botker, Erling Falk, Rob Krams, Ranil De Silva

Department of Mechanical and Materials Engineering: Faculty Publications

Advanced coronary atherosclerosis assessed by in-vivo optical coherence tomography (OCT) has not been directly compared with histology. In a porcine model with human-like coronary atherosclerosis we compared in-vivo OCT images with histology in five animals. We found a high sensitivity but modest specificity of OCT in classifying fibrous cap atheroma (FCA). The modest specificity was caused by misclassification of FCA lesions as pathological intimal thickening. The misclassification most frequently occurred when plaque burden exceeded ~20%. Compared with histology, OCT has high sensitivity but modest specificity for identifying FCA. The study suggests that plaque burden should be considered when interpreting OCT …


Experimental Measurement Of Dolphin Thrust Generated During A Tail Stand Using Dpiv, Frank E. Fish, Terrie M. Williams, Erica Sherman, Yae Eun Moon, Vicki Wu, Timothy Wei Jan 2018

Experimental Measurement Of Dolphin Thrust Generated During A Tail Stand Using Dpiv, Frank E. Fish, Terrie M. Williams, Erica Sherman, Yae Eun Moon, Vicki Wu, Timothy Wei

Department of Mechanical and Materials Engineering: Faculty Publications

Estimation of force generated by dolphins has long been debated. The problem was that indirect estimates of force production for dolphins resulted in low values that could not be validated. Bubble digital particle image velocimetry (DPIV) measured hydrodynamic force production for swimming dolphins and demonstrated high force production. To validate the bubble DPIV and reconcile force production measurements, two bottlenose dolphins (Tursiops truncatus) performing tail stands were measured with bubble DPIV. Microbubbles were generated from a finely porous hose and compressed air source. Displacement of the bubbles by the propulsive motions of the dolphin was tracked with a …


Neuroprotective And Anti-Inflammatory Effects Of Rhus Coriaria Extract In A Mouse Model Of Ischemic Optic Neuropathy, Saba Khalilpour, Ghazaleh Behnammanesh, Fouad Suede, Mohammed O. Ezzat, Jayadhisan Muniandy, Yasser Tabana, Mohamed B. K. Ahamed, Ali Tamayol, Amin Malik Shah Majid, Enrico Sangiovanni, Mario Dell'agli, Aman Shah Majid Jan 2018

Neuroprotective And Anti-Inflammatory Effects Of Rhus Coriaria Extract In A Mouse Model Of Ischemic Optic Neuropathy, Saba Khalilpour, Ghazaleh Behnammanesh, Fouad Suede, Mohammed O. Ezzat, Jayadhisan Muniandy, Yasser Tabana, Mohamed B. K. Ahamed, Ali Tamayol, Amin Malik Shah Majid, Enrico Sangiovanni, Mario Dell'agli, Aman Shah Majid

Department of Mechanical and Materials Engineering: Faculty Publications

Modulating oxidative stresses and inflammation can potentially prevent or alleviate the pathological conditions of diseases associated with the nervous system, including ischemic optic neuropathy. In this study we evaluated the anti-neuroinflammatory and neuroprotective activities of Rhus coriaria (R. coriaria) extract in vivo. The half maximal inhibitory concentration (IC50) for DPPH, ABTS and B-carotene were 6.79 ± 0.009 µg/mL, 10.94 ± 0.09 µg/mL, and 6.25 ± 0.06 µg/mL, respectively. Retinal ischemia was induced by optic nerve crush injury in albino Balb/c mice. The anti-inflammatory activity of ethanolic extract of R. coriaria (ERC) and linoleic acid (LA) on …


Methods, Systems, And Devices For Surgical Access And Procedures, Shane M. Farritor, Mark Rentschler, Amy Lehman, Stephen R. Platt, Jeff Hawks Jan 2018

Methods, Systems, And Devices For Surgical Access And Procedures, Shane M. Farritor, Mark Rentschler, Amy Lehman, Stephen R. Platt, Jeff Hawks

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incorporated into robotic and/or in vivo medical devices. Certain embodiments include various actuation system embodiments, including fluid actuation systems, drive train actuation systems, and motorless actuation systems. Additional embodiments include a reversibly lockable tube that can provide access for a medical device to a patient's cavity and further provides a reversible rigidity or stability during operation of the device. Further embodiments include various operational components for medical devices, including medical device arm mechanisms that have both axial and rotational movement while maintaining a relatively compact …


Methods, Systems, And Devices Relating To Force Control Surgical Systems, Shane M. Farritor, Thomas Frederick, Kearney Lackas, Joe Bartels, Jacob Greenburg Jan 2018

Methods, Systems, And Devices Relating To Force Control Surgical Systems, Shane M. Farritor, Thomas Frederick, Kearney Lackas, Joe Bartels, Jacob Greenburg

Department of Mechanical and Materials Engineering: Faculty Publications

The various embodiments herein relate to robotic surgical systems and devices that use force and/or torque sensors to measure forces applied at various components of the system or device. Certain implementations include robotic surgical devices having one or more force/torque sensors that detect or measure one or more forces applied at or on one or more arms. Other embodiments relate to systems having a robotic surgical device that has one or more sensors and an external controller that has one or more motors such that the sensors transmit information that is used at the controller to actuate the motors to …


Multifunctional Operational Component For Robotic Devices, Shane M. Farritor, Amy Lehman, Mark Rentschler Jan 2018

Multifunctional Operational Component For Robotic Devices, Shane M. Farritor, Amy Lehman, Mark Rentschler

Department of Mechanical and Materials Engineering: Faculty Publications

The various embodiments disclosed herein relate to modular medical devices, including various devices with detachable modular components and various devices with pivotally attached modular components. Additional embodiments relate to procedures in which various of the devices are used cooperatively. Certain embodiments of the medical devices are robotic in vivo devices.


Frequency Dependent Deformation Reversibility During Cyclic Loading, Shuai Shao, Michael M. Khonsari, Jian Wang, Nima Shamsaei, Nan Li Jan 2018

Frequency Dependent Deformation Reversibility During Cyclic Loading, Shuai Shao, Michael M. Khonsari, Jian Wang, Nima Shamsaei, Nan Li

Department of Mechanical and Materials Engineering: Faculty Publications

High-frequency testing (HFT) is useful for accelerated fatigue testing of conventional materials that typically serve under low-frequency loading conditions, as well as for the assessment of the robustness of microelectromechanical systems which typically experience high-frequency service conditions. Using discrete dislocation dynamics, we attempt to elucidate the effect of loading frequency on the reversibility of cyclic deformation. We demonstrate that the HFT induces a higher fraction of reversible cyclic deformation because of a larger portion of elastic/anelastic deformation due to limited dislocation mobility, and a higher degree of reversibility in plastic deformation owing to the less occurrence of cross-slip.