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Experimental observation of high intrinsic thermal conductivity of AlN

Physical Review Materials 2020年第4期4卷 044602-044602页

作者： Zhe Cheng Yee Rui Koh Abdullah Mamun Jingjing Shi Tingyu Bai Kenny Huynh Luke Yates Zeyu Liu Ruiyang Li Eungkyu Lee Michael E. Liao Yekan Wang Hsuan Ming Yu Maki Kushimoto Tengfei Luo Mark S. Goorsky Patrick E. Hopkins Hiroshi Amano Asif Khan Samuel Graham George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta Georgia 30332 USA Department of Mechanical and Aerospace Engineering University of Virginia Charlottesville Virginia 22904 USA Department of Electrical Engineering University of South Carolina Columbia South Carolina 29208 USA Materials Science and Engineering University of California Los Angeles Los Angeles California 90095 USA Department of Aerospace and Mechanical Engineering University of Notre Dame Notre Dame Indiana 46556 USA Department of Electrical Engineering and Computer Science Nagoya University Furo-cho Chikusa-ku 464–8603 Nagoya Japan Department of Materials Science and Engineering University of Virginia Charlottesville Virginia 22904 USA Department of Physics University of Virginia Charlottesville Virginia 22904 USA Institute of Materials and Systems for Sustainability Nagoya University Furo-cho Chikusa-ku 464–8601 Nagoya Japan School of Materials Science and Engineering Georgia Institute of Technology Atlanta Georgia 30332 USA

Wurtzite AlN is an ultrawide bandgap semiconductor that has been developed for applications including power electronics and optoelectronics. Thermal management of these applications is the key for stable device performance and allowing for long lifetimes. However, the intrinsic high thermal conductivity of bulk AlN predicted by theoretical calculations has not been experimentally observed because of the difficulty in producing high-quality materials. This work reports the growth of thick (>15 μm) AlN layers by metal-organic chemical vapor deposition and experimental observation of intrinsic thermal conductivity from 130 to 480 K that matches density-functional-theory calculations for single crystal AlN, producing some of the highest values ever measured. Detailed material characterizations confirm the high quality of these AlN samples with one or two orders of magnitude lower impurity concentrations than commercially available bulk AlN. The thermal conductivity of these commercially available bulk AlN substrates are also measured as comparison. To interpret the reduced thermal conductivity, a simple Callaway model is built. This work demonstrates the possibility of obtaining theoretically high values of thermal conductivity in AlN and will impact the thermal management and reliability of future electronic and optoelectronics devices.

关键词： Defects Phonons Thermal conductivity Thermal properties

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An optimality gap test for a semidefinite relaxation of a quadratic program with two quadratic constraints

arXiv

引用

arXiv 2019年

作者： Cheng, Sheng Martins, Nuno C. Department of Electrical and Computer Engineering and Institute for Systems Research University of Maryland College ParkMD United States

We propose a necessary and sufficient test to determine whether a solution for a general quadratic program with two quadratic constraints (QC2QP) can be computed from that of a specific convex semidefinite relaxation, in which case we say that there is no optimality gap. Originally intended to solve a nonconvex optimal control problem, we consider the case in which the cost and both constraints of the QC2QP may be nonconvex. We obtained our test, which also ascertains when strong duality holds, by generalizing a closely-related method by Ai and Zhang. An extension was necessary because, while the method proposed by Ai and Zhang also allows for two quadratic constraints, it requires that at least one is strictly convex. In order to illustrate the usefulness of our test, we applied it to two examples that do not satisfy the assumptions required by prior methods. Our test guarantees that there is no optimality gap for the first example-a solution is also computed from the relaxation-and we used it to establish that an optimality gap exists in the second. Copyright © 2019, The Authors. All rights reserved.

关键词： Quadratic programming

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Fast, composable rescue mission planning for uavs using metric temporal logic

arXiv

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arXiv 2019年

作者： Fiaz, Usman A. Baras, John S. Department of Electrical & Computer Engineering Institute for Systems Research University of Maryland College ParkMD United States

We present a hybrid compositional approach for real-time mission planning for multi-rotor unmanned aerial vehicles (UAVs) in a time critical search and rescue scenario. Starting with a known environment, we specify the mission using Metric Temporal Logic (MTL) and use a hybrid dynamical model to capture the various modes of UAV operation. We then divide the mission into several sub-tasks by exploiting the invariant nature of safety and timing constraints along the way, and the different modes (i.e., dynamics) of the UAV. For each sub-task, we translate the MTL specifications into linear constraints and solve the associated optimal control problem for desired path, using a Mixed Integer Linear Program (MILP) solver. The complete path for the mission is constructed recursively by composing the individual optimal sub-paths. We show by simulations that the resulting suboptimal trajectories satisfy the mission specifications, and the proposed approach leads to significant reduction in computational complexity of the problem, making it possible to implement in real-time. Our proposed method ensures the safety of UAVs at all times and guarantees finite time mission completion. It is also shown that our approach scales up nicely for a large number of UAVs. Copyright © 2019, The Authors. All rights reserved.

关键词： Decision making

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Blockchain for COVID-19: Review, opportunities and a trusted tracking system

TechRxiv

引用

TechRxiv 2020年

作者： Marbouh, Dounia Abbasi, Tayaba Maasmi, Fatema Omar, Ilhaam A. Debe, Mazin S. Salah, Khaled Jayaraman, Raja Ellahham, Samer Department of Industrial & Systems Engineering Khalifa University of Science and Technology Abu Dhabi127788 United Arab Emirates Department of Electrical & Computer Engineering Khalifa University of Science and Technology Abu Dhabi127788 United Arab Emirates Heart & Vascular Institute Cleveland Clinic Abu Dhabi United Arab Emirates

The sudden development of the COVID-19 pandemic has exposed the limitations in modern healthcare systems to handle public health emergencies. It is evident that adopting innovative technologies such as blockchain can help in effective planning operations and resource deployments. Blockchain technology can play an important role in the healthcare sector, such as improved clinical trial data management by reducing delays in regulatory approvals, streamline the communication between diverse stakeholders of the supply chain, etc. Moreover, the spread of misinformation has intensely increased during the outbreak, and existing platforms lack the ability to validate the authenticity of data, leading to public panic and irrational behavior. Thus, developing a blockchain-based tracking system is important to ensure that the information received by the public and government agencies are reliable and trustworthy. In this paper, we review various blockchain applications and opportunities in combating the COVID-19 pandemic and develop a tracking system for the COVID-19 data collected from various external sources. We propose, implement, and evaluate a blockchain-based system using Ethereum smart contracts and oracles to track reported data related to the number of new cases, deaths, and recovered cases obtained from trusted sources. We present detailed algorithms that capture the interactions between stakeholders in the network. We present security analysis and the cost incurred by the stakeholders, and we highlight the challenges and future directions of our work. Our work demonstrates that the proposed solution is economically feasible and ensures data integrity, security, transparency, data traceability among stakeholders. © 2020, CC BY-NC-SA.

关键词： Coronavirus

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Silicon slot metasurface supporting a multitude of bound states in the continuum: theoretical and experimental studies

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Optics & Laser Technology 2025年 192卷

作者： G. Nousios J.F. Algorri W. Fuscaldo F. Dell’Olio S. Romano G. Zito B. Miranda Y. Ding V. Dmitriev L.C. Andreani M. Galli O. Tsilipakos E.E. Kriezis D.C. Zografopoulos Consiglio Nazionale delle Ricerche Istituto per la Microelettronica e Microsistemi (CNR-IMM) Rome 00133 Italy Photonics Engineering Group University of Cantabria Santander 39005 Spain CIBER-bbn Instituto de Salud Carlos III Madrid 28029 Spain Instituto de Investigación Sanitaria Valdecilla (IDIVAL) Santander 39011 Spain Department of Electrical and Information Engineering Polytecnic University of Bari Bari 70125 Italy CNR ISASI Institute of Applied Sciences and Intelligent Systems Naples 80078 Italy SiPhotonIC ApS Virum Stationsvej 207 Virum 2830 Denmark Department of Electrical and Photonics Engineering Technical University of Denmark Ørsteds Plads Bygning 343 Kongens Lyngby 2800 Denmark Electrical Engineering Department Federal University of Pará Belém 66075-900 Brazil Dipartimento di Fisica Università di Pavia Pavia 27100 Italy Theoretical and Physical Chemistry Institute National Hellenic Research Foundation Athens GR-11635 Greece School of Electrical and Computer Engineering Aristotle University of Thessaloniki (AUTH) Thessaloniki GR-54124 Greece

A dielectric metasurface supporting a variety of quasi-bound states in the continuum (qBICs), including the intricate dark toroidal dipole and toroidal quadrupole Mie modes, is theoretically and experimentally investigated in the near-infrared. The metasurface consists of square slots etched into a thin silicon layer and periodically arrayed in a subdiffractive lattice residing on a sapphire substrate. The modal properties of the qBICs, i.e., the quality factors alongside the near- and far-field characteristics, are comprehensively assessed through a set of theoretical tools, including eigenfrequency simulations and multipolar expansion analysis. The results are corroborated by experimental studies verifying the existence of the qBICs. The investigated metasurface may serve as an ideal platform for nonlinear applications, such as third-harmonic generation, when leveraging the Kerr effect of silicon, as well as for lasing when the slot is filled with a low-index material hosting organic dye molecules.

关键词： Silicon metasurfaces Bound states in the continuum Nanofabrication Multipole analysis Metasurface lasers Nonlinear nanophotonics

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Self-Propelled Detachment upon Coalescence of Surface Bubbles

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Physical Review Letters 2021年第23期127卷 235501-235501页

作者： Pengyu Lv Pablo Peñas Hai Le The Jan Eijkel Albert van den Berg Xuehua Zhang Detlef Lohse State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science Beijing Innovation Center for Engineering Science and Advanced Technology College of Engineering Peking University Beijing 100871 People’s Republic of China Physics of Fluids group Faculty of Science and Technology Max Planck—University of Twente Center for Complex Fluid Dynamics MESA+Institute and J. M. Burgers Centre for Fluid Dynamics University of Twente P.O. Box 217 7500 AE Enschede Netherlands BIOS Lab-on-a-Chip group Faculty of Electrical Engineering Max Planck—University of Twente Center for Complex Fluid Dynamics Mathematics and Computer Science MESA+Institute University of Twente P.O. Box 217 7500 AE Enschede Netherlands Department of Chemical & Materials Engineering University of Alberta Edmonton Alberta T6G1H9 Canada Max Planck Institute for Dynamics and Self-Organization 37077 Göttingen Germany

The removal of microbubbles from substrates is crucial for the efficiency of many catalytic and electrochemical gas evolution reactions in liquids. The current work investigates the coalescence and detachment of bubbles generated from catalytic decomposition of hydrogen peroxide. Self-propelled detachment, induced by the coalescence of two bubbles, is observed at sizes much smaller than those determined by buoyancy. Upon coalescence, the released surface energy is partly dissipated by the bubble oscillations, working against viscous drag. The remaining energy is converted to the kinetic energy of the out-of-plane jumping motion of the merged bubble. The critical ratio of the parent bubble sizes for the jumping to occur is theoretically derived from an energy balance argument and found to be in agreement with the experimental results. The present results provide both physical insight for the bubble interactions and practical strategies for applications in chemical engineering and renewable energy technologies like electrolysis.

关键词： Drops & bubbles

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Multiple-association supporting htc/mtc in limited-backhaul capacity Ultra-Dense Networks

arXiv

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arXiv 2020年

作者： Elbayoumi, Mohammed Hamouda, Walaa Youssef, Amr Concordia Institute for Information Systems Engineering Concordia University MontrealQCH3G 1M8 Canada The Department of Electrical and Computer Engineering Concordia University MontrealQCH3G 1M8 Canada

Coexistence of Human-Type Communications (HTCs) and Machine-Type Communications (MTCs) is inevitable. Ultra-Dense Networks (UDNs) will be efficacious in supporting both types of communications. In a UDN, a massive number of low-power and low-cost Small Cells (SCs) are deployed with density higher than that of the HTC users. In such a scenario, the backhaul capacities constitute an intrinsic bottleneck for the system. Hence, we propose a multiple association scheme where each HTC user associates to and activates multiple SCs to overcome the backhaul capacity constraints. In addition, having more active cells allows for more MTC devices to be supported by the network. Using tools from stochastic geometry, we formulate a novel mathematical framework investigating the performance of the limited-backhaul capacity UDN in terms of Area Spectral Efficiency (ASE) for both HTC and MTC and the density of supported MTC devices. Extensive simulations were conducted to verify the accuracy of the mathematical analysis under different system parameters. Results show the existence of an optimum number of SCs to which an HTC user may connect under backhaul capacity constraints. Besides, the proposed multiple association scheme significantly improves the performance of MTC in terms of both ASE and density of supported devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Geometry

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Modeling differentiation-state transitions linked to therapeutic escape in triple-negative breast cancer (vol 15, e1006840, 2019)

引用

PLOS COMPUTATIONAL BIOLOGY 2019年第10期15卷 e1006840-e1006840页

作者： Chapman, Margaret P. Risom, Tyler Aswani, Anil J. Langer, Ellen M. Sears, Rosalie C. Tomlin, Claire J. Department of Electrical Engineering and Computer Sciences University of California Berkeley Berkeley California United States of America Department of Molecular and Medical Genetics Oregon Health and Science University Portland Oregon United States of America Department of Industrial Engineering and Operations Research University of California Berkeley Berkeley California United States of America Knight Cancer Institute Oregon Health and Science University Portland Oregon United States of America Center for Spatial Systems Biomedicine Oregon Health and Science University Portland Oregon United States of America

Drug resistance in breast cancer cell populations has been shown to arise through phenotypic transition of cancer cells to a drug-tolerant state, for example through epithelial-to-mesenchymal transition or transition to a cancer stem cell state. However, many breast tumors are a heterogeneous mixture of cell types with numerous epigenetic states in addition to stem-like and mesenchymal phenotypes, and the dynamic behavior of this heterogeneous mixture in response to drug treatment is not well-understood. Recently, we showed that plasticity between differentiation states, as identified with intracellular markers such as cytokeratins, is linked to resistance to specific targeted therapeutics. Understanding the dynamics of differentiation-state transitions in this context could facilitate the development of more effective treatments for cancers that exhibit phenotypic heterogeneity and plasticity. In this work, we develop computational models of a drug-treated, phenotypically heterogeneous triple-negative breast cancer (TNBC) cell line to elucidate the feasibility of differentiation-state transition as a mechanism for therapeutic escape in this tumor subtype. Specifically, we use modeling to predict the changes in differentiation-state transitions that underlie specific therapy-induced changes in differentiation-state marker expression that we recently observed in the HCC1143 cell line. We report several statistically significant therapy-induced changes in transition rates between basal, luminal, mesenchymal, and non-basal/non-luminal/non-mesenchymal differentiation states in HCC1143 cell populations. Moreover, we validate model predictions on cell division and cell death empirically, and we test our models on an independent data set. Overall, we demonstrate that changes in differentiation-state transition rates induced by targeted therapy can provoke distinct differentiation-state aggregations of drug-resistant cells, which may be fundamental to the design of improved

关键词： DRUG resistance in cancer cells CANCER stem cells TRIPLE-negative breast cancer EPIGENETICS BREAST tumors PHENOTYPES

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Verification of AA-Diagnosability in Probabilistic Finite Automata is PSPACE-Hard

Verification of AA-Diagnosability in Probabilistic Finite Au...

引用

IEEE Annual Conference on Decision and Control

作者： Christoforos Keroglou Christoforos N. Hadjicostis Division of Decision and Control Systems School of Electrical Engineering and Computer Science KTH Royal Institute of Technology Stockholm Sweden Department of Electrical and Computer Engineering University of Cyprus Nicosia Cyprus

ISBN: (数字)9781728113982

ISBN: (纸本)9781728113999

In this paper we consider the complexity of verifying the property of AA-diagnosability in probabilistic finite automata and establish that AA-diagnosability is, in general, a PSPACE-hard problem. In deterministic and nondeterministic finite automata, the property of diagnosability captures our ability to determine, based on our observation of the activity in a given finite automaton, the occurrence of any fault event, at least if we wait for at most a finite number of events (following the occurrence of the unobservable fault event). In stochastic settings where the underlying system is a probabilistic finite automaton under partial observation, there is not a prevalent notion of diagnosability and many variations have been proposed, including A-diagnosability and AA-diagnosability. Earlier work has shown that the verification of A-diagnosability (also referred to as strong stochastic diagnosability) for a given probabilistic finite automaton is a PSPACE-hard problem. In this paper, we establish that the verification of AA-diagnosability (also referred to as stochastic diagnosability) is a PSPACE-hard problem.

关键词： Automata Hidden Markov models Probabilistic logic Markov processes Complexity theory Fault diagnosis

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Power Minimization Via Rate Splitting in Downlink Cloud-Radio Access Networks

Power Minimization Via Rate Splitting in Downlink Cloud-Radi...

引用

IEEE International Conference on Communications Workshops, ICC

作者： Alaa Alameer Ahmad Hayssam Dahrouj Anas Chaaban Aydin Sezgin Tareq Y. Al-Naffouri Mohamed-Slim Alouini Institute of Digital Communication Systems Ruhr-Universität Bochum Germany Department of Electrical and Computer Engineering Effat University Saudi Arabia School of Engineering The University of British Columbia Kelowna Canada Communication Theory Lab King Abdullah University of Science and Technology Thuwal Saudi Arabia

ISBN: (数字)9781728174402

ISBN: (纸本)9781728174419

Minimizing the power consumption in mobile communication networks while guaranteeing quality of service (QoS) requirements is essential in light of the unprecedented increase in the number of connected devices and the associated data traffic. Conventional cloud-radio access networks (C-RAN) assume treating interference as noise (TIN) while dealing with the provisioning of wireless interference. This paper considers a C-RAN system, where a central processor (CP) at the cloud is connected to several base-stations (BSs) via limited capacity fronthaul links. The paper then assumes a communication scheme where the CP applies rate splitting (RS) to the messages requested by the users, and enables common message decoding (CMD) at the receivers side. The paper addresses the problem of minimizing the weighted transmit power subject to minimum QoS and fronthaul capacity constraints, which is generally a non-convex and difficult problem to solve. We, therefore, propose an iterative approach based on inner-convex approximations (ICA) to obtain a stationary point of the optimization problem. The simulations show the power savings achieved by the proposed RS-CMD scheme as compared to the conventional TIN, especially at high QoS requirements.

关键词： Quality of service Decoding Interference Receivers Cloud computing Array signal processing Downlink

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