Open Access. Powered by Scholars. Published by Universities.®

Mechanical Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Discipline
Keyword
Publication Year

Articles 271 - 300 of 1144

Full-Text Articles in Mechanical Engineering

Fast Reversible Phase Change Silicon For Visible Active Photonics, Letian Wang, Matthew Eliceiri, Yang Deng, Yoonsoo Rho, Wan Shou, Heng Pan, Jie Yao, Costas P. Grigoropoulos Apr 2020

Fast Reversible Phase Change Silicon For Visible Active Photonics, Letian Wang, Matthew Eliceiri, Yang Deng, Yoonsoo Rho, Wan Shou, Heng Pan, Jie Yao, Costas P. Grigoropoulos

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Both amorphous and crystalline silicon are ubiquitous materials for electronics, photonics, and microelectromechanical systems. On-demand control of Si crystallinity is crucial for device manufacturing and to overcome the limitations of current phase-change materials (PCM) in active photonics. Fast reversible phase transformation in silicon, however, has never been accomplished due to the notorious challenge of amorphization. It is demonstrated that nanostructured Si can function as a PCM, since it can be reversibly crystallized and amorphized under nanosecond laser irradiation with different pulse energies. Reflection probing on a single nano disk's phase transformations confirms the distinct mechanisms for crystallization and amorphization. The …

Go to article

A Molecular Dynamics Study Of Transient Evaporation And Condensation, Zhi Liang, Anirban Chandra, Eric Bird, Pawel Keblinski Mar 2020

A Molecular Dynamics Study Of Transient Evaporation And Condensation, Zhi Liang, Anirban Chandra, Eric Bird, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We Use Molecular Dynamics (MD) Simulations to Study the Transient Evaporation and Condensation of a Pure Fluid Ar in a Nanochannel. in the MD Model, the Evaporation and Condensation of Fluid Ar is Initiated by a Sudden Increase of the Temperature or Periodically Varying the Temperature in the Solid Substrate on One Side of the Nanochannel. in Both Cases, We Find the Transient Evaporation and Condensation Rates Obtained Directly from MD Simulations Are in Good Agreement with the Predictions from the Schrage Relationships. Furthermore, Our Analyses Show that the Kinetics of the Transient Heat and Mass Transfer between the Evaporating …

Go to article

Laser-Assisted Micromachining Systems And Methods, Yung C. Shin, Xiangyang Dong Feb 2020

Laser-Assisted Micromachining Systems And Methods, Yung C. Shin, Xiangyang Dong

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser-assisted micromachining methods and systems capable of providing flexible beam positioning and low incident angles. Such laser-assisted micromachining systems preferably include a laser beam source, a cutting tool, means for engaging a workpiece with the cutting tool, optical elements arranged to define a path of a laser beam emitted by the laser beam source wherein the optical elements include at least a first mirror mounted in fixed relation to the laser beam source, and means for adjustably mounting a second mirror to project the laser beam onto the workpiece in proximity to the cutting tool and at an incidence angle …

Go to article

Angular Correlation Using Rogers-Szego-Chaos, Christine Schmid, Kyle J. Demars Feb 2020

Angular Correlation Using Rogers-Szego-Chaos, Christine Schmid, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Polynomial chaos expresses a probability density function (pdf) as a linear combination of basis polynomials. If the density and basis polynomials are over the same field, any set of basis polynomials can describe the pdf; however, the most logical choice of polynomials is the family that is orthogonal with respect to the pdf. This problem is well-studied over the field of real numbers and has been shown to be valid for the complex unit circle in one dimension. The current framework for circular polynomial chaos is extended to multiple angular dimensions with the inclusion of correlation terms. Uncertainty propagation of …

Go to article

Frequency-Selective Metasurface Integrated Uncooled Microbolometers, Mahmoud Almasri, Edward C. Kinzel Jan 2020

Frequency-Selective Metasurface Integrated Uncooled Microbolometers, Mahmoud Almasri, Edward C. Kinzel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A metasurface integrated microbolometer having a sensing layer (e.g., SixGeyO1-x-y). The presence of the metasurface provides selectivity with respect to wavelength, polarization and angle-of-incidence. The presence of the metasurface into the microbolometer affects conversion of electromagnetic to thermal energy, thermal response, electrical integration of the microbolometer, and the tradeoff between resistivity and temperature coefficient of resistance, thereby allowing the ability to obtain a sensing with high temperature coefficient of resistance with lower resistivity values than that of films without the metasurface. The presence of the metasurface removes the need for a Fabry-Perot cavity.

Go to article

Aluminum Parts Fabricated By Laser-Foil-Printing Additive Manufacturing: Processing, Microstructure, And Mechanical Properties, Chia Hung Hung, Yingqi Li, Austin Sutton, Wei Ting Chen, Xiangtao Gong, Heng Pan, Hai Lung Tsai, Ming-Chuan Leu Jan 2020

Aluminum Parts Fabricated By Laser-Foil-Printing Additive Manufacturing: Processing, Microstructure, And Mechanical Properties, Chia Hung Hung, Yingqi Li, Austin Sutton, Wei Ting Chen, Xiangtao Gong, Heng Pan, Hai Lung Tsai, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Fabrication of dense aluminum (Al-1100) parts (>99.3% of relative density) by our recently developed laser-foil-printing (LFP) additive manufacturing method was investigated as described in this paper. This was achieved by using a laser energy density of 7.0 MW/cm2 to stabilize the melt pool formation and create sufficient penetration depth with 300 μm thickness foil. The highest yield strength (YS) and ultimate tensile strength (UTS) in the LFP-fabricated samples reached 111 ± 8 MPa and 128 ± 3 MPa, respectively, along the laser scanning direction. These samples exhibited greater tensile strength but less ductility compared to annealed Al-1100 samples. Fractographic …

Go to article

Metal Additive Manufacturing Parts Inspection Using Convolutional Neural Network, Wenyuan Cui, Yunlu Zhang, Xinchang Zhang, Lan Li, Frank W. Liou Jan 2020

Metal Additive Manufacturing Parts Inspection Using Convolutional Neural Network, Wenyuan Cui, Yunlu Zhang, Xinchang Zhang, Lan Li, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Metal additive manufacturing (AM) is gaining increasing attention from academia and industry due to its unique advantages compared to the traditional manufacturing process. Parts quality inspection is playing a crucial role in theAMindustry, which can be adopted for product improvement. However, the traditional inspection process has relied on manual recognition, which could suffer from low efficiency and potential bias. This study presented a convolutional neural network (CNN) approach toward robust AM quality inspection, such as good quality, crack, gas porosity, and lack of fusion. To obtain the appropriate model, experiments were performed on a series of architectures. Moreover, data augmentation …

Go to article

Impartial Sensor Tasking Via Forecasted Information Content Quantification, Matthew J. Gualdoni, Kyle J. Demars Jan 2020

Impartial Sensor Tasking Via Forecasted Information Content Quantification, Matthew J. Gualdoni, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The consistently increasing population of space debris in orbit about the Earth is becoming an increasingly unavoidable problem, necessitating a proper handling of the problem of sensor tasking to effectively and efficiently obtain observations of space objects to maintain catalogs of their positions and velocities. A variety of approaches have been explored to achieve this in an autonomous fashion, assisting with space traffic management. This work presents new statistical analysis of the Kullback–Leibler divergence justifying the use of its expected value in generating sensor schedules. This divergence's use as an objective measure is extended to simultaneously consider, in an impartial …

Go to article

Optimization Strategies For Myopic And Forecasted Divergence-Based Sensor Tasking Objectives, Matthew J. Gualdoni, Kyle J. Demars Jan 2020

Optimization Strategies For Myopic And Forecasted Divergence-Based Sensor Tasking Objectives, Matthew J. Gualdoni, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In light of the ever-increasing value of space assets operating in the presence of a continuously growing population of space objects in orbit about Earth, space situational awareness is becoming more crucial than ever. The process of tracking and maintaining estimates for the numerous assets and space objects is a complex and highly demanding problem, as it requires robust state estimates in the presence of sparse data. As the number of space objects greatly outweighs the number of available sensors, a sensor tasking policy is necessary to properly utilize the available sensor resources in a way that ensures targets are …

Go to article

Impact Of Considering And Neglecting States On Descent-To-Landing Navigation, Kyle J. Demars, Kari C. Ward Jan 2020

Impact Of Considering And Neglecting States On Descent-To-Landing Navigation, Kyle J. Demars, Kari C. Ward

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a novel square-root formulation of the consider/neglect Kalman filter for navigation applications. The proposed filter partitions system parameters into three distinct categories: those to be estimated by the filter, those whose contribution to the system can be considered without explicitly estimating them, and those with sufficiently low effect on the system such that their contribution can be neglected altogether. Discussion on appropriate selection of consider and neglect parameters is provided with specific attention given to descent-to-landing navigation. Monte Carlo simulations and analysis are performed to assess the performance of the square-root consider/neglect filter.

Go to article

Robustness Metric For Robust Design Optimization Under Time-And Space-Dependent Uncertainty Through Metamodeling, Xinpeng Wei, Xiaoping Du Jan 2020

Robustness Metric For Robust Design Optimization Under Time-And Space-Dependent Uncertainty Through Metamodeling, Xinpeng Wei, Xiaoping Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Product performance varies with respect to time and space in many engineering applications. This paper discusses how to measure and evaluate the robustness of a product or component when its quality characteristics (QCs) are functions of random variables, random fields, temporal variables, and spatial variables. At first, the existing time-dependent robustness metric is extended to the present time-and space-dependent problem. The robustness metric is derived using the extreme value of the quality characteristics with respect to temporal and spatial variables for the nominal-the-better type quality characteristics. Then, a metamodel-based numerical procedure is developed to evaluate the new robustness metric. The …

Go to article

Design And Analysis Of Descent-To-Landing Navigation Incorporating Terrain Effects, Kari C. Ward, Gunner S. Fritsch, J. Cameron Helmuth, Kyle J. Demars, James S. Mccabe Jan 2020

Design And Analysis Of Descent-To-Landing Navigation Incorporating Terrain Effects, Kari C. Ward, Gunner S. Fritsch, J. Cameron Helmuth, Kyle J. Demars, James S. Mccabe

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This study investigated the ability of a navigation filter to process multiple terrain-based sensors, such as slant-range, slant-speed, and terrain relative navigation sensors, during a descent-to-landing scenario to estimate the state of a landing vehicle. The filtering technique leveraged was based upon a factorized form of the multiplicative extended Kalman filter, and terrain-based measurements were fused with star camera and inertial measurement unit sensor returns to estimate the position, velocity, and attitude of the landing vehicle. Monte Carlo simulations were carried out to assess the performance of the navigation filter along a lunar descent trajectory, as well as the consistency …

Go to article

A Brief Review On 3d Bioprinted Skin Substitutes, Fateme Fayyazbakhsh, Ming-Chuan Leu Jan 2020

A Brief Review On 3d Bioprinted Skin Substitutes, Fateme Fayyazbakhsh, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Global Escalating Cases of Skin Donor Shortage for Patients with Severe Wounds Warn the Vital Need for Alternatives to Skin Allografts. over the Last Three Decades, Research in the Skin Regeneration Area Has Addressed the Unmet Need for Artificial Skin Substitutes. 3D Bioprinting is a Promising Innovative Technology to Accurately Fabricate Skin Constructs based on Natural or Synthetic Bioinks, Whether Loaded or Not Loaded with Native Skin Cells (I.e., Keratinocytes and Fibroblasts) or Stem Cells in the Prescribed 3D Hierarchal Structure to Create Artificial Multilayer and Single Cell-Laden Construct. in This Paper, the Recent Developments in 3D Bioprinting for …

Go to article

Propagation Of Errors Through Coning, Sculling, And Scrolling Correction Algorithms, James D. Brouk, Kyle J. Demars Jan 2020

Propagation Of Errors Through Coning, Sculling, And Scrolling Correction Algorithms, James D. Brouk, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper investigates the propagation of estimation errors through a common coning, sculling, and scrolling architecture used in modern day inertial navigation systems. Coning, sculling, and scrolling corrections often have an unaccounted-for effect on the error statistics of inertial measurements used to describe the state and uncertainty propagation for position, velocity, and attitude estimates. Through the development of an error analysis for a set of coning, sculling, and scrolling algorithms, mappings of the measurement and estimation errors through the correction term are adaptively generated. Using the developed mappings, an efficient and consistent propagation of the state and uncertainty, within the …

Go to article

Simulation And Modeling Of Cold-Wall Hypersonic Turbulent Boundary Layers On Flat Plate, Junji Huang, Gary L. Nicholson, Lian Duan, Meelan M. Choudhari, Rodney D.W. Bowersox Jan 2020

Simulation And Modeling Of Cold-Wall Hypersonic Turbulent Boundary Layers On Flat Plate, Junji Huang, Gary L. Nicholson, Lian Duan, Meelan M. Choudhari, Rodney D.W. Bowersox

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct numerical simulations (DNS) of flat-plate, zero-pressure-gradient turbulent boundary layers are presented for nominal freestream Mach numbers of 11 and 14 and a highly cooled wall (wall-to-recovery temperature of approximately 0.2). The flow conditions of the DNS are representative of the experimental data for a Mach 11.1 turbulent boundary layer on a flat plate that was tested at Calspan–University of Buffalo Research Center (CUBRC) and the operational conditions of the AEDC Hypervelocity Tunnel No. 9 at Mach 14. The wall shear stress and turbulent heat flux predicted by DNS show good comparisons with those measured at CUBRC and those modeled …

Go to article

Erratum: Minimization Of The Kullback-Leibler Divergence For Nonlinear Estimation (Journal Of Guidance, Control, And Dynamics, (2017), 10.2514/1.G002282), Jacob E. Darling, Kyle J. Demars Jan 2020

Erratum: Minimization Of The Kullback-Leibler Divergence For Nonlinear Estimation (Journal Of Guidance, Control, And Dynamics, (2017), 10.2514/1.G002282), Jacob E. Darling, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Erratum Notice In the original article [https://doi.org/10.2514/1.G002282], Eqs. (16b) and (18b) were typeset as (Formula Presented) which incorrectly show that the posterior covariance at time tk, denoted by Pk, is calculated about the prior mean, m−k. The correct forms of these equations are given by (Formula Presented) which show that Pk is calculated about the posterior mean, mk. All resulting analyses and simulations reported in the article were performed using the correct forms of the equations.

Go to article

Information-Based Particle Flow For High Uncertainty Estimation, Kari C. Ward, Kyle J. Demars Jan 2020

Information-Based Particle Flow For High Uncertainty Estimation, Kari C. Ward, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This work presents a new formulation of the Gaussian particle flow filter derived using an information theoretic approach. The developed information flow addresses two problems with Gaussian particle flow: the lack of inherent meaning in the flow parameters and the inability to easily include modifications for a non-Bayesian update. Equivalency between Gaussian particle flow and information flow is established using a linear, Gaussian example. An orbit determination simulation with high initial uncertainty is used to demonstrate the consistent, robust performance of the information flow filter in situations where the extended Kalman filter fails.

Go to article

Direct Numerical Simulations Of Acoustic Disturbances In Various Rectangular Nozzle Configurations, Nathaniel Hildebrand, Meelan M. Choudhari, Lian Duan Jan 2020

Direct Numerical Simulations Of Acoustic Disturbances In Various Rectangular Nozzle Configurations, Nathaniel Hildebrand, Meelan M. Choudhari, Lian Duan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We perform Direct Numerical Simulations (DNS) to study the acoustic freestream disturbances radiating from the turbulent boundary layers along the contoured nozzle walls of a hypersonic wind tunnel with a rectangular test section. To begin with, the effects of the spanwise end walls are suppressed by confining the spanwise computational domain to a finite segment of the overall nozzle cross section and by imposing periodic boundary conditions across that spanwise domain. Besides providing a building-block configuration to reveal partial effects of the enclosed acoustic environment within the wind tunnel, these computations serve as a steppingstone toward the goal of fully-3D …

Go to article

Direct Numerical Simulation Of Turbulent Pressure Fluctuations Over A Cone At Mach 8, Junji Huang, Lian Duan, Katya M. Casper, Ross M. Wagnild, Neal P. Bitter Jan 2020

Direct Numerical Simulation Of Turbulent Pressure Fluctuations Over A Cone At Mach 8, Junji Huang, Lian Duan, Katya M. Casper, Ross M. Wagnild, Neal P. Bitter

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct numerical simulations (DNS) were conducted to characterize the pressure fluctuations under the turbulent portion of the boundary layer over a sharp 7◦ half-angle cone at a nominal freestream Mach number of 8 and a unit Reynolds number of Reunit = 13.4 x 106/m. The axisymmetric cone geometry and the flow conditions of the DNS matched those measured in the Sandia Hypersonic Wind Tunnel at Mach 8 (Sandia HWT-8). The DNS-predicted wall pressure statistics, including the root-mean-square (r.m.s.) fluctuations and the power spectral density (PSD), were compared with those measured in the Sandia HWT-8. A good comparison between the DNS …

Go to article

Real-Time Assembly Operation Recognition With Fog Computing And Transfer Learning For Human-Centered Intelligent Manufacturing, Wenjin Tao, Md Al-Amin, Haodong Chen, Ming-Chuan Leu, Zhaozheng Yin, Ruwen Qin Jan 2020

Real-Time Assembly Operation Recognition With Fog Computing And Transfer Learning For Human-Centered Intelligent Manufacturing, Wenjin Tao, Md Al-Amin, Haodong Chen, Ming-Chuan Leu, Zhaozheng Yin, Ruwen Qin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In a human-centered intelligent manufacturing system, every element is to assist the operator in achieving the optimal operational performance. The primary task of developing such a human-centered system is to accurately understand human behavior. In this paper, we propose a fog computing framework for assembly operation recognition, which brings computing power close to the data source in order to achieve real-time recognition. For data collection, the operator's activity is captured using visual cameras from different perspectives. For operation recognition, instead of directly building and training a deep learning model from scratch, which needs a huge amount of data, transfer learning …

Go to article

Thermodynamic Properties Of Hydroxylammonium Nitrate-Based Electric Solid Propellant Plasma, Matthew S. Glascock, Patrick D. Drew, Joshua L. Rovey, Kurt A. Polzin Jan 2020

Thermodynamic Properties Of Hydroxylammonium Nitrate-Based Electric Solid Propellant Plasma, Matthew S. Glascock, Patrick D. Drew, Joshua L. Rovey, Kurt A. Polzin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Electric solid propellants are advanced solid chemical rocket propellants controlled by electric current. An electric solid propellant may also be used in an electric propulsion system: specifically, an ablative pulsed plasma thruster. Previous experiments with the electric solid propellant known as high-performance electric propellant, or HIPEP, suggest its ablation processes are similar to the traditional propellant polytetrafluoroethylene (C2 F4). Better understanding of the ablation and the resulting propulsion performance of HIPEP requires a model of its vapor composition, bulk plasma quantities, and thermodynamic properties. Such a model was developed and favorably compared with previous analogous model predictions found in the …

Go to article

A Brief Review On 3d Bioprinted Skin Substitutes, Fateme Fayyazbakhsh, Ming-Chuan Leu Jan 2020

A Brief Review On 3d Bioprinted Skin Substitutes, Fateme Fayyazbakhsh, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The global escalating cases of skin donor shortage for patients with severe wounds warn the vital need for alternatives to skin allografts. Over the last three decades, research in the skin regeneration area has addressed the unmet need for artificial skin substitutes. 3D bioprinting is a promising innovative technology to accurately fabricate skin constructs based on natural or synthetic bioinks, whether loaded or not loaded with native skin cells (i.e., keratinocytes and fibroblasts) or stem cells in the prescribed 3D hierarchal structure to create artificial multilayer and single cell-laden construct. In this paper, the recent developments in 3D bioprinting for …

Go to article

Impact Of Isolated Atmospheric Aging Processes On The Cloud Condensation Nuclei Activation Of Soot Particles, Franz Friebel, Prem Lobo, David Neubauer, Ulrike Lohmann, Saskia Drossaart Van Dusseldorp, Evelyn Mühlhofer, Amewu A. Mensah Dec 2019

Impact Of Isolated Atmospheric Aging Processes On The Cloud Condensation Nuclei Activation Of Soot Particles, Franz Friebel, Prem Lobo, David Neubauer, Ulrike Lohmann, Saskia Drossaart Van Dusseldorp, Evelyn Mühlhofer, Amewu A. Mensah

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted into the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of 1 week, requiring tailored experiments that cover this time span. This work presents results on the ability of two types of soot, obtained using a miniCAST soot generator, to act …

Go to article

Generation Of Polarization Singularities With Geometric Metasurfaces, Yuchao Zhang, Xiaodong Yang, Jie Gao Dec 2019

Generation Of Polarization Singularities With Geometric Metasurfaces, Yuchao Zhang, Xiaodong Yang, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The polarization singularities are directly generated by using plasmonic metasurfaces with the geometric phase profiles designed to form the Poincaré beams. Different morphologies of polarization topological structures of lemon, star, monstar, spiral, dipole and quadrupole are created by the superpositions of Laguerre-Gauss modes with different orders under orthogonal circular or linear polarization basis. The polarization ellipse patterns and topological features of the produced optical vector fields are analyzed to reveal the properties of the polarization singularities of C-points and L-lines, and the orbital angular momentum states are also measured. The demonstrated polarization singularities generated from the geometric metasurfaces will promise …

Go to article

3d Janus Plasmonic Helical Nanoapertures For Polarization-Encrypted Data Storage, Yang Chen, Xiaodong Yang, Jie Gao Dec 2019

3d Janus Plasmonic Helical Nanoapertures For Polarization-Encrypted Data Storage, Yang Chen, Xiaodong Yang, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Helical structures have attracted considerable attention due to their inherent optical chirality. Here, we report a unique type of 3D Janus plasmonic helical nanoaperture with direction-controlled polarization sensitivity, which is simply fabricated via the one-step grayscale focused ion beam milling method. Circular dichroism in transmission of as large as 0.72 is experimentally realized in the forward direction due to the spin-dependent mode coupling process inside the helical nanoaperture. However, in the backward direction, the nanoaperture acquires giant linear dichroism in transmission of up to 0.87. By encoding the Janus metasurface with the two nanoaperture enantiomers having specified rotation angles, direction-controlled …

Go to article

Orbital Angular Momentum Transformation Of Optical Vortex With Aluminum Metasurfaces, Yuchao Zhang, Xiaodong Yang, Jie Gao Dec 2019

Orbital Angular Momentum Transformation Of Optical Vortex With Aluminum Metasurfaces, Yuchao Zhang, Xiaodong Yang, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The orbital angular momentum (OAM) transformation of optical vortex is realized upon using aluminum metasurfaces with phase distributions derived from the caustic theory. The generated OAM transformation beam has the well-defined Bessel-like patterns with multiple designed topological charges from -1 to +2.5 including both the integer-order and fractional-order optical vortices along the propagation. The detailed OAM transformation process is observed in terms of the variations of both beam intensity and phase profiles. The dynamic distributions of OAM mode density in the transformation are further analyzed to illustrate the conservation of the total OAM. The demonstration of transforming OAM states arbitrarily …

Go to article

Pore Elimination Mechanisms During 3d Printing Of Metals, S. Mohammad H. Hojjatzadeh, Niranjan D. Parab, Wentao Yan, Lianyi Chen, For Full List Of Authors, See Publisher's Website. Dec 2019

Pore Elimination Mechanisms During 3d Printing Of Metals, S. Mohammad H. Hojjatzadeh, Niranjan D. Parab, Wentao Yan, Lianyi Chen, For Full List Of Authors, See Publisher's Website.

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser powder bed fusion (LPBF) is a 3D printing technology that can print metal parts with complex geometries without the design constraints of traditional manufacturing routes. However, the parts printed by LPBF normally contain many more pores than those made by conventional methods, which severely deteriorates their properties. Here, by combining in-situ high-speed high-resolution synchrotron x-ray imaging experiments and multi-physics modeling, we unveil the dynamics and mechanisms of pore motion and elimination in the LPBF process. We find that the high thermocapillary force, induced by the high temperature gradient in the laser interaction region, can rapidly eliminate pores from the …

Go to article

Spatial Variation Of Vector Vortex Beams With Plasmonic Metasurfaces, Yuchao Zhang, Jie Gao, Xiaodong Yang Dec 2019

Spatial Variation Of Vector Vortex Beams With Plasmonic Metasurfaces, Yuchao Zhang, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The spatial variation of vector vortex beams with arbitrary polarization states and orbital angular momentum (OAM) values along the beam propagation is demonstrated by using plasmonic metasurfaces with the initial geometric phase profiles determined from the caustic theory. The vector vortex beam is produced by the superposition of deflected right- and left-handed circularly polarized component vortices with different helical phase charges, which are simultaneously generated off-axially by the single metasurface. Besides, the detailed evolution processes of intensity profile, polarization distribution and OAM value along the beam propagation distance is analyzed. The demonstrated arbitrary space-variant vector vortex beam will pave the …

Go to article

Spontaneous Emission Rate Enhancement With Aperiodic Thue-Morse Multilayer, Ling Li, Cherian J. Mathai, Shubhra Gangopadhyay, Xiaodong Yang, Jie Gao Dec 2019

Spontaneous Emission Rate Enhancement With Aperiodic Thue-Morse Multilayer, Ling Li, Cherian J. Mathai, Shubhra Gangopadhyay, Xiaodong Yang, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The emergence of multilayer metamaterials in the research field of enhancing spontaneous emission rates has recently received extensive attention. Previous research efforts mostly focus on periodic metal-dielectric multilayers in hyperbolic dispersion region; however, the influence of lattice order in subwavelength multilayers on spontaneous emission is rarely studied. Here, we observe the stronger Purcell enhancement of quantum dots coupled to the aperiodic metal-dielectric multilayer with Thue-Morse lattice order from elliptical to hyperbolic dispersion regions, compared to the periodic multilayer with the same metal filling ratio. This work demonstrates the potential of utilizing quasiperiodic metamaterial nanostructures to engineer the local density of …

Go to article

Publisher Correction: Pore Elimination Mechanisms During 3d Printing Of Metals (Nature Communications, (2019), 10, 1, (3088), 10.1038/S41467-019-10973-9), S. Mohammad H. Hojjatzadeh, Niranjan D. Parab, Wentao Yan, Qilin Guo, Lianghua Xiong, Cang Zhao, Mimglei Qu, Luis I. Escano, Xianghui Xiao, Kamel Fezzaa, Wes Everhart, Tao Sun, Lianyi Chen Dec 2019

Publisher Correction: Pore Elimination Mechanisms During 3d Printing Of Metals (Nature Communications, (2019), 10, 1, (3088), 10.1038/S41467-019-10973-9), S. Mohammad H. Hojjatzadeh, Niranjan D. Parab, Wentao Yan, Qilin Guo, Lianghua Xiong, Cang Zhao, Mimglei Qu, Luis I. Escano, Xianghui Xiao, Kamel Fezzaa, Wes Everhart, Tao Sun, Lianyi Chen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The original version of this Article contained an error in Fig. 4. The x-axis labels in Fig. 4a, b were incorrectly labelled 'Diameter (mm)', rather than the correct 'Diameter (µm)'. This has been corrected in both the PDF and HTML versions of the Article.

Go to article

First Prev Next Last