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Framework for atomic-level characterisation of quantum computer arrays by machine learning

npj computational Materials 2020年第1期6卷 1513-1520页

作者： Muhammad Usman Yi zheng Wong charles D.Hill Lloyd c.L.Hollenberg center for Quantum computation and communication Technology University of MelbourneParkvilleVIC 3010Australia School of Physics University of MelbourneParkvilleVIC 3010Australia School of computing and Information Systems Melbourne School of EngineeringUniversity of MelbourneParkvilleVIC 3010Australia School of Mathematics and Statistics University of MelbourneParkvilleVIC 3010Australia

Atomic-level qubits in silicon are attractive candidates for large-scale quantum computing;however,their quantum properties and controllability are sensitive to details such as the number of donor atoms comprising a qubit and their precise *** work combines machine learning techniques with million-atom simulations of scanning tunnelling microscopic(STM)images of dopants to formulate a theoretical framework capable of determining the number of dopants at a particular qubit location and their positions with exact lattice site precision.A convolutional neural network(cNN)was trained on 100,000 simulated STM images,acquiring a characterisation fidelity(number and absolute donor positions)of>98% over a set of 17,600 test images including planar and blurring noise commensurate with experimental *** formalism is based on a systematic symmetry analysis and feature-detection processing of the STM images to optimise the computational *** technique is demonstrated for qubits formed by single and pairs of closely spaced donor atoms,with the potential to generalise it for larger donor *** method established here will enable a high-precision post-fabrication characterisation of dopant qubits in silicon,with high-throughput potentially alleviating the requirements on the level of resources required for quantum-based characterisation,which will otherwise be a challenge in the context of large qubit arrays for universal quantum computing.

关键词： quantum character donor

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PHASE TRANSFORMATION BEHAVIOR AND MIcROSTRUcTURE OBSERVATION OF Nb-Ru HIGH TEMPERATURE SHAPE MEMORY ALLOY

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Acta Metallurgica Sinica(English Letters) 2003年第5期16卷 401-406页

作者： X.Gao Y.F.zheng W.cai L.c.Zhao SchoolofMaterialsScienceandEngineering HarbinInstituteofTechnologyHarbin150001China 不详

The phase transformation behavior and micro structure of Nb-Ru alloys have been studied by DSc, X-ray diffraction, optical microscopy, transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). Two-step phase transformation of cscl (β) →face-centered tetragonal (β)→ monoclinic (β') occurs during cooling from high temperature to room temperature. The lattice parameters of marten-sites of Nb-Ru alloys were found to increase with the increase of Nb content. The martensite variants exhibit triangular self-accommodating morphology, with alternating regular bands inside. The twinning relationship between the sub structural bands was found to be (101) type I mode, and this kind of twinning interface was straight, well-defined and coherent.

关键词： Nb-Ru alloy shape memory alloy (SMA) phase transformation micro structure.

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Semantic Segmentation of Sorghum Using Hyperspectral Data Identifies Genetic Associations

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Plant Phenomics 2020年第1期2卷 14-24页

作者： chenyong Miao Alejandro Pages zheng Xu Eric Rodene Jinliang Yang James c.Schnable center for Plant Science Innovation University of Nebraska-LincolnLincolnNEUSA Department of Agronomy and Horticulture University of Nebraska-LincolnLincolnNEUSA Quantitative Life Sciences Initiative University of Nebraska-LincolnLincolnNEUSA Department of Mathematics and Statistics Wright State UniversityDaytonOHUSA

This study describes the evaluation of a range of approaches to semantic segmentation of hyperspectral images of sorghum plants,classifying each pixel as either nonplant or belonging to one of the three organ types(leaf,stalk,panicle).While many current methods for segmentation focus on separating plant pixels from background,organ-specific segmentation makes it feasible to measure a wider range of plant *** scored training data for a set of hyperspectral images collected from a sorghum association population was used to train and evaluate a set of supervised classification *** algorithms show acceptable accuracy for this classification *** trained on sorghum data are able to accurately classify maize leaves and stalks,but fail to accurately classify maize reproductive organs which are not directly equivalent to sorghum *** measurements extracted from semantic segmentation of sorghum organs can be used to identify both genes known to be controlling variation in a previously measured phenotypes(e.g.,panicle size and plant height)as well as identify signals for genes controlling traits not previously quantified in this population(e.g.,stalk/leaf ratio).Organ level semantic segmentation provides opportunities to identify genes controlling variation in a wide range of morphological phenotypes in sorghum,maize,and other related grain crops.

关键词： Sorghum classify organs

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Simulation of Wave-Flow-cavitation Interaction Using a compressible Homogenous Flow Method

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communications in computational Physics 2013年第7期14卷 328-354页

作者： J.G.zheng B.c.Khoo Z.M.Hu Department of Mechanical Engineering National University of SingaporeSingapore 119260 Singapore-MIT Alliance National University of SingaporeSingapore 117576 Temasek Laboratories National University of SingaporeSingapore 117411

A numerical method based on a homogeneous single-phase flow model is presented to simulate the interaction between pressure wave and flow *** account for compressibility effects of liquid water,cavitating flow is assumed to be compressible and governed by time-dependent Euler equations with proper equation of state(EOS).The isentropic one-fluid formulation is employed to model the cavitation inception and evolution,while pure liquid phase is modeled by Tait equation of *** of large stiffness of Tait EOS and great variation of sound speed in flow field,some of conventional compressible gasdynamics solvers are unstable and even not applicable when extended to calculation of flow *** overcome the difficulties,a Godunov-type,cell-centered finite volume method is generalized to numerically integrate the governing equations on triangular *** boundary is treated specially to ensure stability of the *** method proves to be stable,robust,accurate,time-efficient and *** numerical experiments are designed to investigate unsteady dynamics of the cavitating flow impacted by pressure wave,which is of great interest in engineering applications but has not been studied systematically so *** simulation indicates that cavity over cylinder can be induced to collapse if the object is accelerated suddenly and extremely high pressure pulse results almost ***,however,may be avoided by changing the traveling speed *** accompanying huge pressure increasemay damage underwater ***,cavity formed at relatively high upstream speed may be less distorted or affected by shock wave and can recover fully from the initial *** is observed that the cavitating flow starting from a higher freestream velocity is more stable and more resilient with respect to perturbation than the flow with lower background *** findings may shed some light on how to control cavitation development

关键词： cavitating flow isentropic cavitation model shock-flow-cavitation interaction

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Ignition enhancement of ethylene/air by NO_x addition

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chinese Journal of Aeronautics 2013年第4期26卷 876-883页

作者： Guo Peng chen zheng State Key Laboratory for Turbulence and complex Systems College of Engineering Peking University

Recently, non-equilibrium plasma assisted combustion （PAc） has been found to be promising in reducing the ignition delay time in hypersonic propulsion system. NO x produced by non-equilibrium plasma can react with intermediates during the fuel oxidation process and thereby has influence on the combustion process. In this study, the effects of NO x addition on the ignition process of both the homogeneous ethylene/air mixtures and the non-premixed diffusion layer are examined numerically. The detailed chemistry for ethylene oxidization together with the NO x sub-mechanism is included in the simulation. Reaction path analysis and sensitivity analysis are conducted to give a mechanistic interpretation for the ignition enhancement by NO x addition. It is found that for both the homogenous and non-premixed ignition processes at normal and elevated pressures, NO 2 addition has little influence on the ignition delay time while NO addition can significantly promote the ignition process. The ignition enhancement is found to be caused by the promotion in hydroxyl radical production which quickly oxidizes ethylene. The promotion in hydroxyl radical production by NO addition is achieved in two ways：one is the direct production of OH through the reaction HO2＋NO = NO2＋OH, and the other is the indirect production of OH through the reactions NO＋O2=NO2＋O and c2H4＋O = c2H3＋OH. Moreover, it is found that similar to the homogeneous ignition process, the acceleration of the diffusion layer ignition is also controlled by the reaction HO2＋NO = NO2＋OH.

关键词： Ethylene/air Ignition enhancement NO x addition Reaction path analysis Sensitivity analysis

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DPM dispersion inside a single straight entry using dynamic mesh model

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International Journal of coal Science & Technology 2017年第3期4卷 234-244页

作者： Yi zheng Ying Li Magesh Thiruvengadam Hai Lan Jerry c. Tien Missouri University of Science and Technology Rolla MOUSA clean Air Power Inc. Poway CA 92064 USA Monash University clayton campus Wellington RoadClayton VIC 3800 Australia

Three-dimensional simulations of diesel particulate matter （DPM） distribution inside a single straight entry for the Load-Haul-Dump loader （LHD）-truck loading and truck hauling operations were conducted by using ANSYS FLUENT computational fluid dynamics software. The loading operation was performed for a fixed period of 3 min. The dynamic mesh technique in FLUENT was used to study the impact of truck motion on DPM distribution. The resultant DPM distributions are presented for the cases when the truck were driving upstream and downstream of the loading face. Interesting phenomena were revealed in the study including the piston effect, layering of DPM in the roof region, and backflow of diesel exhaust against ventilation. The results from the simulation can be used to determine if the areas inside the face area and straight entry exceed the current U.S. regulatory requirement for DPM concentration （〉160 pg/m3）. This research can guide the selection of DPM reduction strategies and improve the working practices for the underground miners.

关键词： cFD · DPM · Dynamic meshing ·Piston effect · Backflow · Buoyancy effect · Layering of DPM

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Synthesis and Electrochemical Properties of Snco_(1-x)Fe_x/c composite

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Journal of Materials Science & Technology 2010年第7期26卷 653-659页

作者： zheng Liang Shaobin Yang college of Materials Science and Engineering Liaoning Technical University Fuxin 123000 China University of Michigan-Shanghai Jiao Tong University Joint Institute Shanghai 200240 China

The Snco1-xFex/c （x=0.1, 0.2, 0.3, 0.4） composites as novel anode materials for lithium-ion batteries with large capacity were prepared by ball milling first and then solid-state sintering. The influences of the partial substitution of inert metal Fe for co on material structures and the electrochemical properties were investigated. Structure analyses show that the uniform solid dissolution of Fe into coSn phase promotes the formation of coSn2 impurity phase. With the growth of x, the cell volumes of coSn phase is enlarged, the grain size decreases and the content of coSn2 increases. carbon black is mainly physically mixed with other phases on the surface of particles. Electrochemical analyses reveal that the reversible capacity and cycle performance are both improved through the introduction of Fe. When x is 0.2, the cycle performance is up to the maximum, 85.1% of the reversible capacity after 50 cycles. During cycling, among Snco/c, Snco0.8Fe0.2/c and Snco0.6Fe0.4/c samples, the grain size of coSn phase for Snco0.8Fe0.2/c sample increases leastly. It is usually believed that the comprehensive effects of grain size, structure stability and impurity-phase content lead to the maximum of the cycle performance at appropriate content of Fe （x=0.2）.

关键词： Lithium-ion batteries Snco/c Fe cycle performance Grain refinement

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Resistance Torque Based Variable Duty-cycle control Method for a Stage Ⅱ compressor

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chinese Journal of Mechanical Engineering 2017年第4期30卷 876-887页

作者： Meipeng ZHONG Shuiying zheng college of Mechanical and Electrical Engineering Jiaxing University Institute of chemical Machinery Zhejiang University

The resistance torque of a piston stage II com- pressor generates strenuous fluctuations in a rotational period, and this can lead to negative influences on the working performance of the compressor. To restrain the strenuous fluctuations in the piston stage II compressor, a variable duty-cycle control method based on the resistance torque is proposed. A dynamic model of a stage II com- pressor is set up, and the resistance torque and other characteristic parameters are acquired as the control tar- gets. Then, a variable duty-cycle control method is applied to track the resistance torque, thereby improving the working performance of the compressor. Simulated results show that the compressor, driven by the proposed method, requires lower current, while the rotating speed and the output torque remain comparable to the traditional vari- able-frequency control methods. A variable duty-cycle control system is developed, and the experimental results prove that the proposed method can help reduce the specific power, input power, and working noise of the compressor to 0.97 ***-1, 0.09 kW and 3.10 dB, respectively, under the same conditions of discharge pressure of 2.00 MPa and a discharge volume of 0.095 m3/rain. The proposed variable duty-cycle control method tracks the resistance torque dynamically, and improves the working performance of a Stage II compressor. The pro- posed variable duty-cycle control method can be applied to other compressors, and can provide theoretical guidance for the compressor.

关键词： Stage II compressor Resistance torque Variable duty-cycle control Variable frequency control

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Priority access for QoS support in distributed wireless networks

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Journal of Systems Engineering and Electronics 2019年第6期30卷 1202-1211页

作者： ZHOU Xin zheng changwen Institute of Software Chinese Academy of Sciences

Guaranteed quality of service(QoS) support has been an open issue of distributed wireless networks for years. The IEEE802.11 e provides a valuable method for this purpose. However, it could only provide service differentiation, rather than service guarantee, for multi-priority traffic. Many studies have tried to improve its QoS ability, but still leave some problems. This paper investigates these problems and proposes a scheme called the priority access based on busy tone(PABT) to improve the Qo S performance. To guarantee the priority channel access, this scheme uses an in-band busy tone to limit the transmission of lower-priority traffic when higher-priority traffic has packets to send. Based on that, it also optimizes the contention window tuning according to the flows number of each traffic type individually, in order to improve the throughput as well as the traffic capacity. Simulation results show that the proposed scheme significantly improves the real-time traffic capacity, throughput, delay, fairness and packet loss rate.

关键词： 802.11e quality of service(QoS) busy tone priority access traffic capacity contention window

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Novel Magnesium Alloys Developed for Biomedical Application:A Review

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Journal of Materials Science & Technology 2013年第6期29卷 489-502页

作者： Nan Li Yufeng zheng State Key Laboratory for Turbulence and complex System and Department of Materials Science and Engineering College of EngineeringPeking University

There is an increasing interest in the development of magnesium alloys both for industrial and biomedical applications. Industrial interest in magnesium alloys is based on strong demand of weight reduction of transportation vehicles for better fuel efficiency, so higher strength, and better ductility and corrosion resistance are required. Nevertheless, biomedical magnesium alloys require appropriate mechanical properties, suitable degradation rate in physiological environment, and what is most important, biosafety to human body. Rather than simply apply commercial magnesium alloys to biomedical field, new alloys should be designed from the point of view of nutriology and toxicology. This article provides a review of state-of-the-art of magnesium alloy implants and devices for orthopedic, cardiovascular and tissue engineering applications. Advances in new alloy design, novel structure design and surface modification are overviewed. The factors that influence the corrosion behavior of magnesium alloys are discussed and the strategy in the future development of biomedical magnesium alloys is proposed.

关键词： Biomaterials Magnesium alloys Biodegradation Mechanical property Biocompatibility

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