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26th International Congress on Sound and Vibration, ICSV 2019

作者： Musafir, Ricardo E. Schor, Fabio J. Avital, Eldad J. Dept. of Mechanical Engineering COPPE and Water Resources and Environmental Eng Dept./EP Rio de Janeiro Brazil Dept. of Mechanical Engineering COPPE Brazil Queen Mary University of London School of Engineering and Materials Science United Kingdom

ISBN: (纸本)9781999181000

A relationship between the spectrum of a cold jet at 90° and the spectra at arbitrary angles and temperature ratios is explored, by combining limiting forms of analytical solutions of Lilley's equation for the high and low frequency limits. The model, which extends that presented previously at ICSV13 (2006), considers the sources are as compact. For angles inside the cone of silence, refraction is explicitly included. For the hot jet, it is shown that new components which exist in addition to those contributing to the cold one, can show both dipole and quadrupole efficiency. Predictions are compared with experimental results and it is shown that the model achieves, in general, good to reasonable agreement both for cold and hot jets. For the hot jet, at 30°, however, the model over-predicts the spectra. Empirical corrections are proposed to enhance the prediction capability of the model © Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.

关键词： Forecasting

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Transport Study of Charge Carrier Scattering in Monolayer WSe2

arXiv

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arXiv 2023年

作者： Joe, Andrew Y. Pistunova, Kateryna Kaasbjerg, Kristen Wang, Ke Kim, Bumho Rhodes, Daniel A. Taniguchi, Takashi Watanabe, Kenji Hone, James Low, Tony Jauregui, Luis A. Kim, Philip Department of Physics Harvard University CambridgeMA02138 United States Department of Physics and Astronomy University of California RiversideCA92521 United States Department of Physics Technical University of Denmark Kongens LyngbyDK-2800 Denmark Department of Mechanical Engineering Columbia University New YorkNY10027 United States National Institute for Materials Science Tsukuba Japan Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Dept. of Physics and Astronomy The University of California IrvineCA92697 United States

Employing flux-grown single crystal WSe2, we report charge carrier scattering behaviors measured in h-BN encapsulated monolayer field effect transistors. We perform quantum transport measurements across various hole densities and temperatures and observe a non-monotonic change of transport mobility µ as a function of hole density in the degenerately doped sample. This unusual behavior can be explained by energy dependent scattering amplitude of strong defects calculated using the T-matrix approximation. Utilizing long mean-free path (>500 nm), we demonstrate the high quality of our electronic devices by showing quantized conductance steps from an electrostatically-defined quantum point contact. Our results show the potential for creating ultra-high quality quantum optoelectronic devices based on atomically thin semiconductors. © 2023, CC BY.

关键词： Monolayers

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Energy storage for a high penetration of renewables

Energy storage for a high penetration of renewables

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2019 Offshore Energy and Storage Summit, OSES 2019

作者： Cardenas, Bruno Swinfen-Styles, Lawrie Rouse, James P. Hoskin, Adam Xu, Weiqing Garvey, Seamus D. Dept. of Mechanical Materials and Manufacturing Engineering University of Nottingham Nottingham United Kingdom School of Automation Science and Electrical Engineering Beihang University Beijing China

ISBN: (纸本)9781728123172

This paper explores how the energy storage capacity required by an electric grid increases with the penetration of renewable generation. The paper uses the UK as a case study and aims to quantify the amount and duration of energy storage that the country will need to fully decarbonize its electric supply. The paper also studies the effect that the mix of renewables (wind + solar) has on the storage capacity needed and highlights that a greater mismatch between the generation and demand profiles will require a larger energy storage capacity. Therefore the right generation mix for the region should be used. Results show that the UK will need a storage capacity of approximately 7.63 TWh (4 days) to achieve an overall renewable penetration of 100%. Two important considerations are made: i) the mix between wind and solar is 79-21% and ii) a 5% of over-generation (and curtailment) is allowed. Assuming that the storage capacity is provided by compressed air systems (CAES) and considering the current costs of renewable generation, this scenario attains a levelized cost of electricity of 61 £/MWh. This scenario achieves the lowest possible LCOE despite the fact that 5% of the generated electricity is wasted and still paid-for. If a strict rule of zero-net curtailment was in place, the storage capacity required would almost double (14.93 TWh) and the final cost of electricity would be 2.3% higher. © 2019 IEEE.

关键词： Electric power transmission networks

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Quality index design for online monitoring injection molding process 77

Quality index design for online monitoring injection molding...

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77th Annual Technical Conference of the Society of Plastics Engineers, ANTEC 2019

作者： Chen, Jian-Yu Huang, Ming-Shyan Nian, Shih-Chih Tseng, Chien-Chou Bachelor Program of Precision System Design Feng Chia University Taiwan Dept. of Mechanical and Automation Engineering National Kaohsiung University of Science and Technology Taiwan Dept. of Power Mechanical Engineering National Taitung College Taiwan

Quality control is a crucial issue in the injection molding process with target of obtaining a high yield rate and reducing production cost. However, conventional injection molding acts like a black-box in which the flowing behavior of polymer melt within cavities is unseen, and the tuning of process parameters is heavily relied on operators' experience, design of experimental methods, or even trial- and-error. Such approaches are not only time-consuming but also lack of assuring consistent injection molding qualities and quality control is then required. Nowadays with the advance of sensing technology, many sensors are available to detect the flowing behavior of polymer melt within mold cavities. Particularly the pressure, velocity, and temperature that affect the flowing ability of polymer melt can be detected in time. In other words, injection molding now has been transformed into a grey-box and a scientific viewpoint to tune process parameters can be realized. In this research, a quality index extracted from pressure profile is aimed for online quality monitoring. In addition, the clamping force increment quality index extracted from the tie-bar elongation which is detected by strain gauges attached on tie bars, free of invading injection mold structure, is paid much attention. To verify the feasibility of the designed quality index using to prediction the injection molded quality, varying barrel temperature, back pressure and rotational speed of plasticizing screw those can affect the plasticizing quality of raw materials are conducted in this investigation. Experimental results reveals that the clamping force increment as well as pressure peak index extracted from injection system pressure, nozzle pressure, end-of-filling cavity pressure profiles during injection molding are highly correlated with injection-molded qualities and thereby are feasible to be a good quality indicator. © 2019 Society of Plastics Engineers. All rights reserved.

关键词： Polymer melts

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Tie-bar elongation based prediction of injection molding quality 77

Tie-bar elongation based prediction of injection molding qua...

引用

77th Annual Technical Conference of the Society of Plastics Engineers, ANTEC 2019

作者： Huang, Ming-Shyan Nian, Shih-Chih Chen, Jian-Yu Dept. of Mechanical and Automation Engineering National Kaohsiung University of Science and Technology Taiwan Dept. of Power Mechanical Engineering National Taitung College Taiwan Bachelor Program in Precision System Design Feng Chia University Taiwan

Filling-to-packing switchover (also called as V/P switchover) is critical for assuring injection molding quality. An improper filling-to-packing switchover setting may result in various defects of injection-molded parts, such as excessive residual stress, flash, short shot, and warpage, etc. To enhance consistent molding quality, recent V/P switchover approach applies cavity pressure profiles requiring sensors embedded in mold cavities, which is invasive to mold cavities and even expensive. Instead of using cavity pressure sensors, this study thereby proposes a novel approach of identifying ideal V/P switchover timing using a tie-bar elongation profile. In this investigation, a dumbbell testing specimen mold is applied to experimentally verify the feasibility of the proposed method. The results showthat the mold filling and packing stages can be observed along the tie-bar elongation profile detected by mounting strain gauges on tie bars. Moreover, the varying process parameter settings including injection speed, filling-to-packing switchover point, and holding pressure, can be reflected in these profiles. By extracting their characteristics, the decision of filling-to-packing switchover is proved to be realistic. © 2019 Society of Plastics Engineers. All rights reserved.

关键词： Filling

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Fabrication of Surface Nitridation Mask on GaAs Substrate for Nano-Lithography

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MRS Online Proceedings Library 2020年第1期843卷 351-354页

作者： Yo Yamamoto Kohji Saito Toshiyuki Kondo Takahiro Maruyama Shigeya Naritsuka Meijo Univ. 21st Century COE Program Nagoya Japan Dept. of Materials Science & Engineering Meijo University Nagoya Japan

The surface nitridation of GaAs substrate under various conditions were performed and its surface morphology was studied by using atomic force microscope. The RMS roughness of the surfaces was closely related to formation of the particles which was formed by As evaporation and subsequent Ga migration, which was enhanced by higher substrate temperature.

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Review: Topology of solitons and singular defects in chiral liquid crystals

arXiv

引用

arXiv 2021年

作者： Wu, Jin-Sheng Smalyukh, Ivan I. Department of Physics and Chemical Physics Program University of Colorado BoulderCO80309 United States Dept. of Electrical Computer and Energy Engineering and Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

Widely known for their uses in displays and electro-optics, liquid crystals are more than just technological marvels. They vividly reveal the topology and structure of various solitonic and singular field configurations, often markedly resembling the ones arising in many field theories and in the areas ranging from particle physics to optics, hard condensed matter and cosmology. In this review, we focus on chiral nematic liquid crystals to show how these experimentally highly accessible systems provide valuable insights into the structure and behavior of fractional, full, and multi-integer two-dimensional skyrmions, dislocations and both abelian and non-abelian defect lines, as well as various three-dimensionally localized, often knotted structures that include hopfions, heliknotons, torons and twistions. We provide comparisons of some of these field configurations with their topological counterparts in chiral magnets, discussing close analogies between these two condensed matter systems. Copyright © 2021, The Authors. All rights reserved.

关键词： Topology

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High-voltage high-current vertical geometry Ga2O3 rectifiers 11

High-voltage high-current vertical geometry Ga2O3 rectifiers

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Oxide-based materials and Devices XI 2020

作者： Xian, Minghan Fares, Chaker Carey, Patrick Ren, Fan Tadjer, Marko Liao, Yu-Te Chang, Chin-Wei Lin, Jenshan Sharma, Ribhu Law, Mark E. Raad, Peter E. Komarov, Pavel L. Islam, Zahabul Haque, Aman Kuramata, Akito Pearton, S.J. Dept. of Chemical Engineering University of Florida GainesvilleFL32611 United States Naval Research Laboratory WashingtonDC United States Dept. of Electrical and Computer Engineering National Chiao Tung University Hsinchu Taiwan Department of Electrical and Computer Engineering University of Florida GainesvilleFL32611 United States Department of Materials Science and Engineering University of Florida GainesvilleFL32611 United States Department of Mechanical Engineering Southern Methodist University DallasTX United States TMX Scientific Inc. RichardsonTX75081 United States Department of Mechanical Engineering Penn State University University ParkPA United States Tamura Corporation and Novel Crystal Technology Inc. Saitama350-1328 Japan

ISBN: (纸本)9781510633254

There are continuing rapid developments in vertical geometry Ga2O3 for high voltage switching applications. Ga2O3 is emerging as a viable candidate for certain classes of power electronics with capabilities beyond existing technologies due to its large bandgap, controllable doping and the availability of large diameter, relatively inexpensive substrates. These include power conditioning systems, including pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors and advanced power management and control electronics. There are already cases where the performance exceeds the theoretical values for SiC. Existing Si, SiC (vertical devices), and heteroepitaxial GaN (lateral devices) enjoy tremendous advantages in terms of process maturity, an advantage that is especially true for Si, where the ability to precisely process the material has resulted in devices such as super-junctions that surpass the unipolar "limit". Continued development of low defect substrates, optimized epi growth and surface treatments and improved device design and processing methods for Ga2O3 are still required to push the experimental results closer to their theoretical values. Even 3 μm epi layers with doping concentration of 1016 cm-3 should have a theoretical breakdown voltage of ∼1800V. The actual experimental value of VB is currently well below the theoretical predictions. Thermal management is a key issue in Ga2O3 power devices for practical high current devices and initial studies have appeared on both the experimental and theoretical fronts. We summarize progress in edge termination design, temperature measurement using thermoreflectance-based thermography to measure the thermal rise and decay of the active diodes, failure under forward bias and development of large current (up to 130A) arrays. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

关键词： Wide band gap semiconductors

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On the martensitic transformation in FexMn80−xCo10Cr10 high-entropy alloy

arXiv

引用

arXiv 2021年

作者： Singh, Prashant Picak, Sezer Sharma, Aayush Chumlyakov, Y.I. Arroyave, Raymundo Karaman, Ibrahim Johnson, Duane D. Ames Laboratory U.S. Department of Energy Iowa State University AmesIA50011 United States Dept. of Mechanical Engineering Texas A&M University College StationTX77843 United States Dept. of Materials Science & Engineering Texas A&M University College StationTX77843 United States Sandvik Coromant R&D Stockholm12679 Sweden Tomsk State University Siberian Physical Technical Institute Novosobornay Square 1 Tomsk634050 Russia Dept. of Materials Science & Engineering Iowa State University AmesIA50011 United States

High-entropy alloys (HEAs), and even medium-entropy alloys (MEAs), are an intriguing class of materials in that structure and property relations can be controlled via alloying and chemical disorder over wide ranges in the composition space. Employing density-functional theory combined with the coherent-potential approximation to average over all chemical configurations, we tune free energies between face-centered-cubic (fcc) and hexagonal-close-packed (hcp) phases in FexMn80−xCo10Cr10 systems. Within Fe-Mn-based alloys, we show that the martensitic transformation and chemical short-range order directly correlate with the fcc-hcp energy difference and stacking-fault energies, which are in quantitative agreement with recent experiments on a x=40 at.% polycrystalline HEA/MEA. Our predictions are further confirmed by single-crystal measurements on ax=40at.% using transmission-electron microscopy, selective-area diffraction, and electronbackscattered-diffraction mapping. The results herein offer an understanding of transformation-induced/twinning-induced plasticity (TRIP/TWIP) in this class of HEAs and a design guide for controlling the physics behind the TRIP effect at the electronic level. Copyright © 2021, The Authors. All rights reserved.

关键词： Entropy

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Distortion mitigation in additive manufacturing of AlSi10Mg by multilayer laser peening

引用

Procedia CIRP 2020年 95卷 133-137页

作者： G. Madireddy J.F. Liu M.P. Sealy Dept. of Mechanical & Materials Engineering University of Nebraska Lincoln NE 68588 USA Sentient Science Corporation 672 Delaware Avenue Buffalo NY 14209 USA

Distortion in metal additive manufacturing remains an industry barrier due to the inadequate thermal management that gives rise to residual stresses. Mitigation strategies primarily involve developing a print recipe based on the build material; however, variability among machine platforms, build strategies, and raw material stock inhibit development of universal print recipes that eliminate distortion. There is a need for a universal manufacturing technology that enables distortion free additive manufacturing. A solution to provide distortion free parts that are machine platform and build strategy independent is coupling additive manufacturing with multilayer peening. Peening enables favorable redistribution of residual stresses that drive distortion using mechanical means rather than thermal management. The cumulative nature of residual stress during layer-by-layer peening and the compounding effect on distortion is poorly understood. Thus, the research objective of this work was to measure residual stress and distortion after multilayer laser peening on AlSi10Mg printed by laser powder bed fusion on the Matsuura Lumex Avance-25. Residual stress was measured for several interlayer peening frequencies. An optimum condition was identified and evaluated for distortion mitigation. To measure deflection, bridge samples based on NIST AMB2018-01 were printed and interlayer peened. Results indicated that laser peening reduced distortion 45% over an as-printed sample.

关键词： additive manufacturing laser peening residual stress AlSi10Mg distortion powder bed fusion hybrid

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