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Full-Text Articles in Other Mechanical Engineering

Floating-Gate Transistor Photodetector, Jinsong Huang, Yongbo Yuan Oct 2017

Floating-Gate Transistor Photodetector, Jinsong Huang, Yongbo Yuan

Department of Mechanical and Materials Engineering: Faculty Publications

A field effect transistor photodetector that can operate in room temperature includes a source electrode , a drain electrode , a channel to allow an electric current to flow between the drain and source electrodes , and a gate electrode to receive a bias voltage for controlling the current in the channel . The photodetector includes a light - absorbing mate rial that absorbs light and traps electric charges . The light absorbing material is configured to generate one or more charges upon absorbing light having a wavelength within a specified range and to hold the one or more charges …

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Software For Extracting Deformation Gradient And Stress From Md Simulations: Simulations Using The Charmm Force Field, Mehrdad Negahban, Lili Zhang, Zesheng Zhang, John Jasa, Antoine Jérusalem Aug 2017

Software For Extracting Deformation Gradient And Stress From Md Simulations: Simulations Using The Charmm Force Field, Mehrdad Negahban, Lili Zhang, Zesheng Zhang, John Jasa, Antoine Jérusalem

Department of Mechanical and Materials Engineering: Faculty Publications

Software was developed, and is provided under a general use license, to calculate continuum level deformation gradient and stress for any group of atoms in an MD simulation that uses the Charmm force fields. This software can also calculate the interaction stress applied by one group of atoms on any other group. To obtain deformation gradient and stress, the user needs to provide the selected group(s) of atoms in an atom group identification file, and provide the associated LAMMPS format files and force field parameter file. An example is included to demonstrate the use of the software.

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Energy Absorbing Guardrail System, John R. Rohde, John D. Reid, King K. Mak, Dean L. Sicking Aug 2017

Energy Absorbing Guardrail System, John R. Rohde, John D. Reid, King K. Mak, Dean L. Sicking

Department of Mechanical and Materials Engineering: Faculty Publications

A highway crash attenuation system having W - beam rail elements attached to a plurality of vertical posts . An impact terminal with a feeder chute guides one or more of the W - beam rail elements through the impact terminal . The feeder chute has an impact shield extending along a traffic facing side of the chute from an upstream - most end to a downstream - most end of the chute closing the traffic - facing side of the chute . The system also has an anchor cable release mechanism for releasing the cable downstream of the first …

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Shape-Adaptive Mechanism For Robotic Grasping, Carl A. Nelson Aug 2017

Shape-Adaptive Mechanism For Robotic Grasping, Carl A. Nelson

Department of Mechanical and Materials Engineering: Faculty Publications

A grapser can include a first pantograph cell and a second pantograph cell coupled with the first pantogrpah cell. The first and second pantograph cells can be coupled together at a first pivot and a second pivot. The grasper can also include a finger extendable in a direction extending between the first pivot and the second pivot. The grasper can include a support base, where one or more links of the first pantograph cell can be slidably coupled with the support base for extending the grasper. In some embodiment, the grasper can be configured to extend along a curved path. …

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Simulating Dynamic Failure Of Polymer-Bonded Explosives Under Periodic Excitation, Rachel Kohler, Camilo Duarte Cordon, Marisol Koslowski Aug 2017

Simulating Dynamic Failure Of Polymer-Bonded Explosives Under Periodic Excitation, Rachel Kohler, Camilo Duarte Cordon, Marisol Koslowski

The Summer Undergraduate Research Fellowship (SURF) Symposium

Accidental mishandling of explosive materials leads to thousands of injuries in the US every year. Understanding the mechanisms behind the detonation process is crucial to prevent such accidents. In polymer-bonded explosives (PBX), high-frequency mechanical excitation generates thermal energy and can lead to an increase in temperature and vapor pressure, and potentially the initiation of the detonation process. However, the mechanisms behind this energy release, such as the effects of dynamic fracture and friction, are not well understood. Experimental data is difficult to collect due to the different time scales of reactions and vibrations, so research is aided by running simulations …

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Meniscus-Assisted Solution Printing Of Largegrained Perovskite Films For High-Efficiency Solar Cells, Ming He, Bo Li, Xun Cui, Beibei Jiang, Yanjie He, Yihuang Chen, Daniel O'Neil, Paul Szymanski, Mostafa A. El-Sayed, Jinsong Huang, Zhiqun Lin Jul 2017

Meniscus-Assisted Solution Printing Of Largegrained Perovskite Films For High-Efficiency Solar Cells, Ming He, Bo Li, Xun Cui, Beibei Jiang, Yanjie He, Yihuang Chen, Daniel O'Neil, Paul Szymanski, Mostafa A. El-Sayed, Jinsong Huang, Zhiqun Lin

Department of Mechanical and Materials Engineering: Faculty Publications

Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics. However, this remains particularly challenging for solution-printed devices due to the complex crystallization kinetics of semiconductor materials within dynamic flow of inks. Here we report a simple yet effective meniscus-assisted solution printing (MASP) strategy to yield large-grained dense perovskite film with good crystallization and preferred orientation. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparts the transport of perovskite solutes, thus facilitating the growth of micrometre-scale perovskite grains. The growth kinetics of perovskite …

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Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban Jun 2017

Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its …

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Multiple Scattering Theory For Heterogeneous Elastic Continua With Strong Property Fluctuation: Theoretical Fundamentals And Applications, Huijing He Jun 2017

Multiple Scattering Theory For Heterogeneous Elastic Continua With Strong Property Fluctuation: Theoretical Fundamentals And Applications, Huijing He

Department of Mechanical and Materials Engineering: Faculty Publications

Scattering of elastic waves in heterogeneous media has become one of the most important problems in the field of wave propagation due to its broad applications in seismology, natural resource exploration, ultrasonic nondestructive evaluation and biomedical ultrasound. Nevertheless, it is one of the most challenging problems because of the complicated medium inhomogeneity and the complexity of the elastodynamic equations. A widely accepted model for the propagation and scattering of elastic waves, which properly incorporates the multiple scattering phenomenon and the statistical information of the inhomogeneities is still missing. In this work, the author developed a multiple scattering model for heterogeneous …

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A Strategy To Optimize Recovery In Orthopedic Sports Injuries, Michael P. Sealy, Ziye Liu, Chao Li, Yuebin Guo, Ben White, Mark Barkey, Brian Jordon J, Luke N. Brewer, Dale Feldman Jun 2017

A Strategy To Optimize Recovery In Orthopedic Sports Injuries, Michael P. Sealy, Ziye Liu, Chao Li, Yuebin Guo, Ben White, Mark Barkey, Brian Jordon J, Luke N. Brewer, Dale Feldman

Department of Mechanical and Materials Engineering: Faculty Publications

An important goal for treatment of sports injuries is to have as short a recovery time as possible. The critical problem with current orthopedic implants is that they are designed to be permanent and have a high complication rate (15%) that often requires removal and replacement with a second surgery; and subsequently a second rehabilitation cycle. This study was designed to test the feasibility of having a device that could provide the needed mechanical properties, while promoting healing, for a specified amount of time and then degrade away, to shorten the recovery time. The specific strategy was to create a …

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Bear Minimum: Ultralight Composite Bear Canister, Rama B. Adajian, Adam C. Eisenbarth Jun 2017

Bear Minimum: Ultralight Composite Bear Canister, Rama B. Adajian, Adam C. Eisenbarth

Mechanical Engineering

The ultralight backpacking community needs a strong, easy to use, safe bear canister that is lighter than current market products for trekking in the backcountry. A full design of the lid for the bear canister is to be completed. This includes the locking mechanism to ensure it is bear proof, the interface between the lid and the canister, and the structure of the lid so it passes the strength and weight specifications. The lid, along with the already designed canister body, is to be manufactured with formal documentation. The lid will initially be tested separately and then with the canister …

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Development Of 3d Compression Molded Composite Primary Structure, Sean D. Tischler, Jacob H. Goldstein, Alea A. Perez Jun 2017

Development Of 3d Compression Molded Composite Primary Structure, Sean D. Tischler, Jacob H. Goldstein, Alea A. Perez

Mechanical Engineering

The work accomplished by the Black Gold team improved upon the carbon fiber compression molding research and information available on the Cal Poly San Luis Obispo campus. The team used the rear suspension rocker arm off a Ventana Alpino mountain bike as a design goal for this project. This research and body of work includes the methods used to design a compression molded part for complex part loading and shape. This extends to the process of choosing an appropriate layup process, in addition to benefits and drawbacks of the use of chopped fibers in compression molding. The research includes the …

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Deployable Antenna For Cubesat, Mackenzie Thomas Lennon, Caleb Andrew Barber, David Matthew Galves Jun 2017

Deployable Antenna For Cubesat, Mackenzie Thomas Lennon, Caleb Andrew Barber, David Matthew Galves

Mechanical Engineering

This project is a proof-of-concept ground model of a large deployable antenna designed for the small space requirements of CubeSats. This small deployment module is designed to fit a 2 m by 1 m reflective antenna inside a storage volume of with the dimensions 20 cm by 20 cm x 40 cm. The reflector will be deployed to a parabolic shape with the goal of modeling the reflector necessary for high frequency communication. Because this module is designed as a proof-of-concept for the deployable parabolic reflector specifically, no electrical components will be incorporated and will just focus on the deployment …

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Primary Blast Waves Induced Brain Dynamics Influenced By Head Orientations, Yi Hua, Yugang Wang, Linxia Gu Apr 2017

Primary Blast Waves Induced Brain Dynamics Influenced By Head Orientations, Yi Hua, Yugang Wang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

There is controversy regarding the directional dependence of head responses subjected to blast loading. The goal of this work is to characterize the role of head orientation in the mechanics of blast wave-head interactions as well as the load transmitting to the brain. A three-dimensional human head model with anatomical details was reconstructed from computed tomography images. Three different head orientations with respect to the oncoming blast wave, i.e., front-on with head facing blast, back-on with head facing away from blast, and side-on with right side exposed to blast, were considered. The reflected pressure at the blast wave-head interface positively …

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Dirichlet Process Gaussian Mixture Models For Real-Time Monitoring And Their Application To Chemical Mechanical Planarization, Jia (Peter) Liu, Omer F. Beyca, Prahalad K. Rao, Zhenyu (James) Kong, Satish T. S. Bukkapatnam Jan 2017

Dirichlet Process Gaussian Mixture Models For Real-Time Monitoring And Their Application To Chemical Mechanical Planarization, Jia (Peter) Liu, Omer F. Beyca, Prahalad K. Rao, Zhenyu (James) Kong, Satish T. S. Bukkapatnam

Department of Mechanical and Materials Engineering: Faculty Publications

The goal of this work is to use sensor data for online detection and identification of process anomalies (faults). In pursuit of this goal, we propose Dirichlet process Gaussian mixture (DPGM) models. The proposed DPGM models have two novel outcomes: 1) DP-based statistical process control (SPC) chart for anomaly detection and 2) unsupervised recurrent hierarchical DP clustering model for identification of specific process anomalies. The presented DPGM models are validated using numerical simulation studies as well as wireless vibration signals acquired from an experimental semiconductor chemical mechanical planarization (CMP) test bed. Through these numerically simulated and experimental sensor data, we …

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Strained Hybrid Perovskite Thin Films And Their Impact On The Intrinsic Stability Of Perovskite Solar Cells, Jingjing Zhao, Yehao Deng, Haotong Wei, Xiaopeng Zheng, Zhenhua Yu, Yuchuan Shao, Jeffrey E. Shield, Jinsong Huang Jan 2017

Strained Hybrid Perovskite Thin Films And Their Impact On The Intrinsic Stability Of Perovskite Solar Cells, Jingjing Zhao, Yehao Deng, Haotong Wei, Xiaopeng Zheng, Zhenhua Yu, Yuchuan Shao, Jeffrey E. Shield, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane …

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The Effect Of Number Of Corrugation On Crashworthiness Of Aluminum Corrugated Tube Under Lateral Loading, Hozhabr Mozafari, Arameh Eyvazian, Abdel Magid Hamouda Jan 2017

The Effect Of Number Of Corrugation On Crashworthiness Of Aluminum Corrugated Tube Under Lateral Loading, Hozhabr Mozafari, Arameh Eyvazian, Abdel Magid Hamouda

Department of Mechanical and Materials Engineering: Faculty Publications

Thin-walled tubes have been developed and are growing in use as new energy absorber structures. The objective of this study is to investigate the energy absorption and crushing characteristics of corrugated tubes with different number of corrugation in a specific length exposed to lateral loading. At the first step, experimental tests were carried out on a corrugated tube with three con'ugations (two inner and one outer) and a tube without corrugation. After that, a finite element model was developed by means of ABAQUS software in order to study the effect of corrugation number on crushing properties of thin-walled tubes. The …

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Methods, Systems, And Devices For Surgical Visualization And Device Manipulation, Shane M. Farritor, Mark Rentschler, Amy Lehman, Nathan A. Wood, Adam Bock, Reed Prior Jan 2017

Methods, Systems, And Devices For Surgical Visualization And Device Manipulation, Shane M. Farritor, Mark Rentschler, Amy Lehman, Nathan A. Wood, Adam Bock, Reed Prior

Department of Mechanical and Materials Engineering: Faculty Publications

A surgical device includes a console having a visual display and a manipulator arm, a robotic device having a camera and a connection component. The robotic device is configured to be positioned completely within a body cavity. The camera is configured to transmit visual images to the visual display. The connection component operably couples the console and the robotic device. The manipulator arm is positioned relative to the visual display so as to appear to be penetrating the visual display.

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Local And Segmental Motions Of The Mobile Amorphous Fraction In Semi-Crystalline Polylactide Crystallized Under Quiescent And Flow-Induced Conditions, Xavier Monnier, Laurence Chevalier, Antonello Esposito, Lucia Fernandez-Ballester, Allisson Saiter, Eric Dargent Jan 2017

Local And Segmental Motions Of The Mobile Amorphous Fraction In Semi-Crystalline Polylactide Crystallized Under Quiescent And Flow-Induced Conditions, Xavier Monnier, Laurence Chevalier, Antonello Esposito, Lucia Fernandez-Ballester, Allisson Saiter, Eric Dargent

Department of Mechanical and Materials Engineering: Faculty Publications

The molecular dynamics of the constrained and unconstrained mobile amorphous fractions in semicrystalline polylactide (PLA) was investigated in the presence of both flow-induced crystalline structures and spherulites by fast scanning calorimetry (FSC) through cooperativity and physical aging concepts. First, the shear rate conditions leading to flow-induced crystallization were characterized by examining the relaxation of shear-induced precursors. At a temperature of 150 °C, the critical relaxation time is so long that cooling down the sheared melt to the crystallization temperature does not affect significantly the precursors. Therefore, highly oriented structures develop. The arrangement of the crystalline fraction, either in flow-induced crystalline …

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Experimental Study Of Corrugated Metal-Composite Tubes Under Axial Loading, Arameh Eyvazian, Hozhabr Mozafari, Abdel Magid Hamouda Jan 2017

Experimental Study Of Corrugated Metal-Composite Tubes Under Axial Loading, Arameh Eyvazian, Hozhabr Mozafari, Abdel Magid Hamouda

Department of Mechanical and Materials Engineering: Faculty Publications

In this study, crushing behavior of corrugated metal-composite tube was examined experimentally under axial loading condition. Six types of specimens, classified into two groups of metal and metal-composite, were tested under quasi static axial loading. The failure mechanism and failure history of the specimens were presented and discussed. The experimental result showed that corrugated metal composite tubes demonstrate perfect energy absorption characteristics in terms of uniformity of load-displacement diagram, reduction of initial peak load and controlling failure mechanism. Moreover, it was also found that adding filament wound layer of composite on the surface of metallic corrugated tube compensated weakness of …

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Disturbed Cyclical Stretch Of Endothelial Cells Promotes Nuclear Expression Of The Pro-Atherogenic Transcription Factor Nf-Kb, Ryan M. Pedrigi, Konstantinos I. Papadimitriou, Avinash Kondiboyina, Sukhjinder Sidhu, James Chau, Miten B. Patel, Daniel C. Baeriswyl, Emmanuel M. Drakakis, Rob Krams Jan 2017

Disturbed Cyclical Stretch Of Endothelial Cells Promotes Nuclear Expression Of The Pro-Atherogenic Transcription Factor Nf-Kb, Ryan M. Pedrigi, Konstantinos I. Papadimitriou, Avinash Kondiboyina, Sukhjinder Sidhu, James Chau, Miten B. Patel, Daniel C. Baeriswyl, Emmanuel M. Drakakis, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

Exposure of endothelial cells to low and multidirectional blood flow is known to promote a pro-atherogenic phenotype. The mechanics of the vessel wall is another important mechano-stimulus within the endothelial cell environment, but no study has examined whether changes in the magnitude and direction of cell stretch can be pro-atherogenic. Herein, we developed a custom cell stretching device to replicate the in vivo stretch environment of the endothelial cell and examined whether low and multidirectional stretch promote nuclear translocation of NF-kB. A fluid–structure interaction model of the device demonstrated a nearly uniform strain within the region of cell attachment and …

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Built-In Bicycle Rack For Cars, Scott A. Hansberry Jan 2017

Built-In Bicycle Rack For Cars, Scott A. Hansberry

All Undergraduate Projects

Transporting a bicycle after riding somewhere and then needing to be pickup can be problematic. Bicycles will not fit in most vehicles without removing components. There is also the risk of damaging the inside of the vehicle. Expecting everyone to have a bike rack for their vehicle is unrealistic because the bike rack could be considered unappealing visually, take up to much space in the trunk, or limit the vehicle owner’s access to the trunk. The solution to this problem is a bike rack that mounts onto your car and then mounts your bike onto the rack. Most people don’t …

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Quantification Of Re-Absorption And Re-Emission Processes To Determine Photon Recycling Efficiency In Perovskite Single Crystals, Yanjun Fang, Haotong Wei, Qingfeng Dong, Jinsong Huang Jan 2017

Quantification Of Re-Absorption And Re-Emission Processes To Determine Photon Recycling Efficiency In Perovskite Single Crystals, Yanjun Fang, Haotong Wei, Qingfeng Dong, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Photon recycling, that is, iterative self-absorption and re-emission by the photoactive layer itself, has been speculated to contribute to the high open-circuit voltage in several types of high efficiency solar cells. For organic–inorganic halide perovskites that have yielded highly efficient photovoltaic devices, however, it remains unclear whether the photon recycling effect is significant enough to improve solar cell efficiency. Here we quantitatively evaluate the re-absorption and re-emission processes to determine photon recycling efficiency in hybrid perovskite with its single crystals by measuring the ratio of the re-emitted photons to the initially excited photons, which is realized by modulating their polarization …

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Target Lesion Calcium Arc Influence The Performance Of Stenting, Pengfei Dong, Shengmao Lin, David L. Wilson, Hiram G. Bezerra, Linxia Gu Jan 2017

Target Lesion Calcium Arc Influence The Performance Of Stenting, Pengfei Dong, Shengmao Lin, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Percutaneous coronary intervention (PCI) is the most common revascularization procedure, in which, fibrocalcific plaques are found in 17–35% of patients undergoing PCI [1]. Numbers will rise with population aging and prolonged statin treatment. Calcifications often lead to stent under expansion and strut malapposition, with increased risk of thrombosis and in-stent restenosis [2]. Presence of calcium strongly inhibits stent performance, a well-documented metric for outcome [3]. The goal of this work is to develop the finite element models for inspecting the influence of the calcium arc extent on the stenting outcomes, such as the stress and strain distribution within the plaque, …

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Growth Mechanisms Of Multiscale, Mound-Like Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Ryan Bell, Craig A. Zuhlke, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield Jan 2017

Growth Mechanisms Of Multiscale, Mound-Like Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Ryan Bell, Craig A. Zuhlke, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Femtosecond laser surface processing (FLSP) can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophobicity/- hydrophilicity. In this study, the subsurface microstructure of a series of mound-like FLSP structures formed on commercially pure titanium using five combinations of laser fluence and cumulative pulse counts was studied. Using a dual beam Scanning Electron Microscope with a Focused Ion Beam, the subsurface microstructure for each FLSP structure type was revealed by cross-sectioning. The microstructure of the mounds formed using the lowest fluence value consists of the original Ti grains. This is evidence that preferential …

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Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban Jan 2017

Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its …

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Narrowband Nanocomposite Photodetector, Jinsong Huang, Fawen Guo, Liang Shen Jan 2017

Narrowband Nanocomposite Photodetector, Jinsong Huang, Fawen Guo, Liang Shen

Department of Mechanical and Materials Engineering: Faculty Publications

A photodetector includes an anode that is transparent or partially transparent to light, a cathode and an active layer disposed between the anode and the cathode. The active layer includes a nanocomposite material that has a polymer blended with nanoparticles or organic electron trapping particles. The photodetector has a low dark current when not illuminated by light and has a high conductivity when illuminated by light, in which the light passes the anode and is absorbed by the active layer. The active layer has a thickness selected such that the photodetector has a narrowband spectral response.

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Role Of Copper Oxide Layer On Pool Boiling Performance With Femtosecond Laser Processed Surfaces, Corey Kruse, Edwin Peng, Craig Zuhlke, Jeff Shield, Dennis Alexander, Sidy Ndao, George Gogos Jan 2017

Role Of Copper Oxide Layer On Pool Boiling Performance With Femtosecond Laser Processed Surfaces, Corey Kruse, Edwin Peng, Craig Zuhlke, Jeff Shield, Dennis Alexander, Sidy Ndao, George Gogos

Department of Mechanical and Materials Engineering: Faculty Publications

Copper pool boiling surfaces are tested for pool boiling enhancement due to femtosecond laser surface processing (FLSP). FLSP creates self-organized micro/nanostructures on metallic surfaces and creates highly wetting and wicking surfaces with permanent surface features. In this study two series of samples were created. The first series consists of three flat FLSP copper surfaces with varying microstructures and the second series is an open microchannel configuration with laser processing over the horizontal surfaces of the microchannels. These microchannels range in height from 125 microns to 380 microns. Each of these surfaces were tested for pool boiling performance. It was found …

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Atomically Informed Nonlocal Semidiscrete Variational Peierls-Nabarro Model For Planar Core Dislocations, Guisen Liu, Xi Cheng, Jian Wang, Kaiguo Chen, Yao Shen Jan 2017

Atomically Informed Nonlocal Semidiscrete Variational Peierls-Nabarro Model For Planar Core Dislocations, Guisen Liu, Xi Cheng, Jian Wang, Kaiguo Chen, Yao Shen

Department of Mechanical and Materials Engineering: Faculty Publications

Prediction of Peierls stress associated with dislocation glide is of fundamental concern in understanding and designing the plasticity and mechanical properties of crystalline materials. Here, we develop a nonlocal semi-discrete variational Peierls-Nabarro (SVPN) model by incorporating the nonlocal atomic interactions into the semi-discrete variational Peierls framework. The nonlocal kernel is simplified by limiting the nonlocal atomic interaction in the nearest neighbor region, and the nonlocal coefficient is directly computed from the dislocation core structure. Our model is capable of accurately predicting the displacement profile, and the Peierls stress, of planar-extended core dislocations in face-centered cubic structures. Our model could be …

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Photoluminescence From Radiative Surface States And Excitons In Methylammonium Lead Bromide Perovskites, Dengyang Guo, Davide Bartesaghi, Haotong Wei, Eline M. Hutter, Jinsong Huang, Tom J. Savenije Jan 2017

Photoluminescence From Radiative Surface States And Excitons In Methylammonium Lead Bromide Perovskites, Dengyang Guo, Davide Bartesaghi, Haotong Wei, Eline M. Hutter, Jinsong Huang, Tom J. Savenije

Department of Mechanical and Materials Engineering: Faculty Publications

In view of its band gap of 2.2 eV and its stability, methylammonium lead bromide (MAPbBr3) is a possible candidate to serve as a light absorber in a subcell of a multijunction solar cell. Using complementary temperature-dependent time-resolved microwave conductance (TRMC) and photoluminescence (TRPL) measurements, we demonstrate that the exciton yield increases with lower temperature at the expense of the charge carrier generation yield. The low-energy emission at around 580 nm in the cubic phase and the second broad emission peak at 622 nm in the orthorhombic phase originate from radiative recombination of charges trapped in defects with …

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Helium Irradiation And Implantation Effects On The Structure Of Amorphous Silicon Oxycarbide, Qing Su, Shinsuke Inoue, Manabu Ishimaru, Jennifer A. Gigax, Tianyao Wang, Hepeng Ding, Michael J. Demkowicz, Lin Shao, Michael Nastasi Jan 2017

Helium Irradiation And Implantation Effects On The Structure Of Amorphous Silicon Oxycarbide, Qing Su, Shinsuke Inoue, Manabu Ishimaru, Jennifer A. Gigax, Tianyao Wang, Hepeng Ding, Michael J. Demkowicz, Lin Shao, Michael Nastasi

Department of Mechanical and Materials Engineering: Faculty Publications

Despite recent interest in amorphous ceramics for a variety of nuclear applications, many details of their structure before and after irradiation/implantation remain unknown. Here we investigated the short-range order of amorphous silicon oxycarbide (SiOC) alloys by using the atomic pair-distribution function (PDF) obtained from electron diffraction. The PDF results show that the structure of SiOC alloys are nearly unchanged after both irradiation up to 30 dpa and He implantation up to 113 at%. TEM characterization shows no sign of crystallization, He bubble or void formation, or segregation in all irradiated samples. Irradiation results in a decreased number of Si-O bonds …

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