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Erasure coding for distributed storage: an overview

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Science China(Information Sciences) 2018年第10期61卷 7-51页

作者： S.B.BALAJI M.Nikhil KRISHNAN Myna VAJHA Vinayak RAMKUMAR Birenjith SASIDHARAN P.Vijay KUMAR department of electrical Communication engineering Indian Institute of Science ming hsieh department of electrical engineering University of Southern California

In a distributed storage system, code symbols are dispersed across space in nodes or storage units as opposed to time. In settings such as that of a large data center, an important consideration is the efficient repair of a failed node. Efficient repair calls for erasure codes that in the face of node failure,are efficient in terms of minimizing the amount of repair data transferred over the network, the amount of data accessed at a helper node as well as the number of helper nodes contacted. Coding theory has evolved to handle these challenges by introducing two new classes of erasure codes, namely regenerating codes and locally recoverable codes as well as by coming up with novel ways to repair the ubiquitous Reed-Solomon code. This survey provides an overview of the efforts in this direction that have taken place over the past decade.

关键词： distributed storage regenerating codes locally recoverable codes codes with locality erasure codes node repair

DAWN: A Density Adaptive Routing for Deadline-Based Data Collection in Vehicular Delay Tolerant Networks

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Tsinghua Science and Technology 2013年第3期18卷 230-241页

作者： Qiao Fu Bhaskar Krishnamachari Lin Zhang the department of Electronic engineering Tsinghua University the ming hsieh department of electrical engineering University of Southern California

Vehicular Delay Tolerant Networks （DTN） use moving vehicles to sample and relay sensory data for urban areas, making it a promising low-cost solution for the urban sensing and infotainment applications. However, routing in the DTN in real vehicle fleet is a great challenge due to uneven and fluctuant node density caused by vehicle mobility patterns. Moreover, the high vehicle density in urban areas makes the wireless channel capacity an impactful factor to network performance. In this paper, we propose a local capacity constrained density adaptive routing algorithm for large scale vehicular DTN in urban areas which targets to increase the packet delivery ratio within deadline, namely Density Adaptive routing With Node deadline awareness （DAWN）. DAWN enables the mobile nodes awareness of their neighbor density, to which the nodes＇ transmission manners are adapted so as to better utilize the limited capacity and increase the data delivery probability within delay constraint based only on local information. Through simulations on Manhattan Grid Mobility Model and the real GPS traces of 4960 taxi cabs for 30 days in the Beijing city, DAWN is demonstrated to outperform other classical DTN routing schemes in performance of delivery ratio and coverage within delay constraint. These simulations suggest that DAWN is practically useful for the vehicular DTN in urban areas.

关键词： delay tolerant networks node density adaptive routing deadline-based data collection channel capacity

Thickness bound for nonlocal wide-field-of-view metalenses

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Light(Science & Applications) 2022年第12期11卷 3018-3027页

作者： Shiyu Li Chia Wei Hsu ming hsieh department of electrical and Computer engineering University of Southern CaliforniaLos AngelesCA 90089USA

Metalenses—flat lenses made with optical metasurfaces—promise to enable thinner,cheaper,and better imaging *** a sufficient angular field of view(FOV)is crucial toward that goal and requires a tailored incidentangle-dependent ***,we show that there is an intrinsic trade-off between achieving a desired broad-angle response and reducing the thickness of the *** the memory effect in disordered media,this thickness bound originates from the Fourier transform duality between space and *** can write down the transmission matrix describing the desired angle-dependent response,convert it to the spatial basis where its degree of nonlocality can be quantified through a lateral spreading,and determine the minimal device thickness based on such a required lateral *** approach is *** applied to wide-FOV lenses,it predicts the minimal thickness as a function of the FOV,lens diameter,and numerical *** bound is tight,as some inverse-designed multi-layer metasurfaces can approach the minimal thickness we *** work offers guidance for the design of nonlocal metasurfaces,proposes a new framework for establishing bounds,and reveals the relation between angular diversity and spatial footprint in multi-channel systems.

关键词： desired angular field

Synthesis and Device Applications of High-Density Aligned Carbon Nanotubes Using Low-Pressure Chemical Vapor Deposition and Stacked Multiple Transfer

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Nano Research 2010年第12期3卷 831-842页

作者： Chuan Wang Koungmin Ryu Lewis Gomez De Arco Alexander Badmaev Jialu Zhang Xue Lin Yuchi Che Chongwu Zhou ming hsieh department of electrical engineering University of Southern CaliforniaLos AngelesCalifornia 90089USA

For nanotube-based electronics to become a viable alternative to silicon technology,high-density aligned carbon nanotubes are *** this paper,we report the combined use of low-pressure chemical vapor deposition and stacked multiple transfer to achieve high-density aligned *** using an optimized nanotube synthesis recipe,we have achieved high-density aligned carbon nanotubes with density as high as 30 tubes/μ*** addition,a facile stacked multiple transfer technique has been developed to further increase the nanotube density to 55 tubes/μ***,high-performance submicron carbon nanotube field-effect transistors have been fabricated on the high-density aligned *** removing the metallic nanotubes by electrical breakdown,the devices exhibit on-current density of 92.4μA/μm and normalized transconductance of 13.3μS/μ***,benchmarking with the aligned carbon nanotube transistors in the literature indicates that our devices exhibit the best performance so far,which is attributed to both the increased nanotube density and scaling down of channel *** study shows the great potential of using such high-density aligned nanotubes for high performance nanoelectronics and analog/RF applications.

关键词： Aligned carbon nanotubes chemical vapor deposition high-density high performance transistors

Plasmonic mode mixing in nanoparticle dimers with nm-separations via substrate-mediated coupling

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Nano Research 2014年第9期7卷 1344-1354页

作者： Jesse Theiss Mehmet Aykol Prathamesh Pavaskar Stephen B. Cronin ming hsieh department of electrical engineering University of Southern California Los Angeles CA 90089 USA

We fabricate arrays of metallic nanoparticle dimers with nanometer separation using electron beam lithography and angle evaporation. These ＂nanogap＂ dimers are fabricated on thin silicon nitride membranes to enable high resolution transmission electron microscope imaging of the specific nanoparticle geometries. Plasmonic resonances of the pairs are characterized by dark-field scattering micro-spectroscopy, which enables the optical scattering from individual nano- structures to be measured by using a spatially-filtered light source to illuminate a small area. Scattering spectra from individual dimers are correlated with transmis- sion electron microscope images and finite-difference time-domain simulations of their electromagnetic response, with excellent agreement between simulation and experiment. We observe a strong polarization dependence with two dominant scattering peaks in spectra taken with the polarization aligned along the dimer axis. This response arises from a unique Fano interference, in which the bright hybridized modes of an asymmetric dimer are able to couple to the dark higher- order hybridized modes through substrate-mediated coupling. The presence of this interference is strongly dependent on the nanoparticle geometry that defines the plasmon energy profile but also on the intense localization of charge at the dielectric surface in the nanogap region for separations smaller than 6 nm.

关键词： plasmonics fano interference transmission electron microscopy (TEM) nanogapdark-field spectroscopy

Quasi-two-dimensionalβ-Ga2O3 field effect transistors with large drain current density and low contact resistance via controlled formation of interfacial oxygen vacancies

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Nano Research 2019年第1期12卷 143-148页

作者： Zhen Li Yihang Liu Anyi Zhang Qingzhou Liu Chenfei Shen Fanqi Wu Chi Xu mingrui Chen Hongyu Fu Chongwu Zhou ming hsieh department of electrical engineering Mork Family Department of Chemical Engineering and Material ScienceDepartment of Physics and AstronomyUniversity of Southern CalifomiOy Los AngelesCalifornia 90089USA

Quasi-two-dimensi on al(2D)β-Ga2O3 is a rediscovered metal-oxide semiconductor with an ultra-wide bandgap of *** has been reported to be a promising material for next-generation power and radio frequency *** effect transistors(FETs)that can switch at high voltage are key compone nts in power and radio frequency devices,and reliable Ohmic con tacts are essential for high FET ***,obtaining low contact resistance onβ-Ga2O3 FETs is difficult since reactions betweenβ-Ga2O3 and metal contacts are not fully ***,we experimentally demonstrate the importanee of reactions at the metal/β-Ga2O3 interface and the corresponding effects of these reactions on FET *** Ti is employed as the metal contact,annealing ofβ-Ga2O3 FETs in argon can effectively transform Schottky contacts into Ohmic contacts and permit a large drain current density of-3.1 mA//μ*** contact resistance(Rcontact)between the Ti electrodes andβ-Ga2O3 decreased from^430 to^0.387Ω·mm after annealing.X-ray photoelectron spectroscopy(XPS)confirmed the formation of oxygen vacancies at the Ti/β-Ga2O3 interface after annealing,which is believed to cause the improved FET *** results of this study pave the way for greater application ofβ-Ga2O3 in electronics.

关键词： quasi-two-dimensional material metal-oxides field effect transistor β-Ga2O3 contact resistanee

Gold-vapor-assisted chemical vapor deposition of aligned monolayer WSe2 with large domain size and fast growth rate

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Nano Research 2020年第10期13卷 2625-2631页

作者： mingrui Chen Anyi Zhang Yihang Liu Dingzhou Cui Zhen Li Yu-Han Chung Sai Praneetha Mutyala Matthew Mecklenburg Xiao Nie Chi Xu Fanqi Wu Qingzhou Liu Chongwu Zhou Mork Family department of Chemical engineering and Materials Science Ming Hsieh Department of Electrical EngineeringCore Center of Excellence in Nano Imaging and Department of Physics and AstronomyUniversity of Southern CaliforniaLos AngelesCA 90089USA

Orientation-controlled growth of two-dimensional(2D)transition metal dichalcogenides(TMDCs)may enable many new electronic and optical ***,previous studies reporting aligned growth of WSe2 usually yielded very small domain ***,we introduced gold vapor into the chemical vapor deposition(CVD)process as a catalyst to assist the growth of WSe2 and successfully achieved highly aligned monolayer WSe2 triangular flakes grown on c-plane sapphire with large domain sizes(130μm)and fast growth rate(4.3μm·s^−1).When the aligned WSe2 domains merged together,a continuous monolayer WSe2 was formed with good *** transferring to Si/SiO2 substrates,field effect transistors were fabricated on the continuous monolayer WSe2,and an average mobility of 12 cm^2·V^−1·s−1 was achieved,demonstrating the good quality of the *** report paves the way to study the effect of catalytic metal vapor in the CVD process of TMDCs and contributes a novel approach to realize the growth of aligned TMDC flakes.

关键词： two-dimensional materials transition metal dichalcogenides tungsten diselenide(WSe2) chemical vapor deposition aligned growth

Optoelectronic devices based on two-dimensional transition metal dichalcogenides

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Nano Research 2016年第6期9卷 1543-1560页

作者： He Tian Matthew L. Chin Sina Najmaei Qiushi Guo Fengnian Xia Hart Wang Madan Dubey ming hsieh department of electrical engineering University of Southern California Los Angeles California 90089 USA United States Army Research Laboratory Maryland 20783-1197 USA department of electrical engineering Yale University Connecticut 06511 USA

In the past few years, two-dimensional （2D） transition metal dichalcogenide （TMDC） materials have attracted increasing attention of the research community, owing to their unique electronic and optical properties, ranging from the valley-spin coupling to the indirect-to-direct bandgap transition when scaling the materials from multi-layer to monolayer. These properties are appealing for the development of novel electronic and optoelectronic devices with important applications in the broad fields of communication, computation, and healthcare. One of the key features of the TMDC family is the indirect-to-direct bandgap transition that occurs when the material thickness decreases from multilayer to monolayer, which is favorable for many photonic applications. TMDCs have also demonstrated unprecedented flexibility and versatility for constructing a wide range of heterostructures with atomic-level control over their layer thickness that is also free of lattice mismatch issues. As a result, layered TMDCs in combination with other 2D materials have the potential for realizing novel high-performance optoelectronic devices over a broad operating spectral range. In this article, we review the recent progress in the synthesis of 2D TMDCs and optoelectronic devices research. We also discuss the challenges facing the scalable applications of the family of 2D materials and provide our perspective on the opportunities offered by these materials for future generations of nanophotonics technology.

关键词： transition metaldichalcogenides (TMDCs),optoelectronic device,molybdenum disulfide(MoS2) photodetector,light-emitting diode (LED)

Single-step flash-heat synthesis of red phosphorus/ graphene flame-retardant composite as flexible anodes for sodium-ion batteries

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Nano Research 2018年第7期11卷 3780-3790页

作者： Yihang Liu Anyi Zhang Chenfei Shen Qingzhou Liu Jiansong Cai Xuan Cao Chongwu Zhou ming hsieh department of electrical engineering University of Southern California Los Angeles California 90089 USA Mork Family department of Chemical engineering and Materials Science University of Southern California Los Angeles California 90089 USA

Red phosphorus （RP） has attracted considerable attention as the anode for high-performance Na-ion batteries, owing to its low cost and high theoretical specific capacity of -2,600 mAh/g. In this study, a facile single-step flash-heat treatment was developed to achieve the reduction of graphene oxide （GO） and the simultaneous deposition of RP onto the reduced graphene oxide （rGO） sheets. The resulting RP/rGO composite was shown to be a promising candidate for overcoming the issues associated with the poor electronic conductivity and large volume variation of RP during cycling. The RP/rGO flexible film anode delivered an average capacity of 1,625 mAh/g during 200 cycles at a charge/ discharge current density of 1 A/g. Average charge capacities of 1,786, 1,597, 1,324, and 679 mAh/g at 1, 2, 4, and 6 A/g current densities were obtained in the rate capability tests. Moreover, owing to the RP component, the RP/rGO film presented superior flame retardancy compared to an rGO film. This work thus introduces a highly accessible synthesis method to prepare flexible and safe RP anodes with superior electrochemical performance toward Na-ion storage.

关键词： sodium-ion batteries red phosphorus facile synthesis flexible flame-retardant reduced graphene oxide