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Exploiting Unlabeled Data for Neural Grammatical Error Detection

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Journal of Computer Science & Technology 2017年第4期32卷 758-767页

作者： Zhuo-ran liu Yang liu School of Software Beihang University Beijing 100191 China State Key Laboratory of Intelligent Technology and Systems Tsinghua University Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Jiangsu Collaborative Innovation Center for Language Competence Xuzhou 221009 China

Identifying and correcting grammatical errors in the text written by non-native writers have received increasing attention in recent years. Although a number of annotated corpora have been established to facilitate data-driven grammatical error detection and correction approaches, they are still limited in terms of quantity and coverage because human annotation is labor-intensive, time-consuming, and expensive. In this work, we propose to utilize unlabeled data to train neural network based grammatical error detection models. The basic idea is to cast error detection as a binary classification problem and derive positive and negative training examples from unlabeled data. We introduce an attention-based neural network to capture long-distance dependencies that influence the word being detected. Experiments show that the proposed approach significantly outperforms SVM and convolutional networks with fixed-size context window.

关键词： unlabeled data grammatical error detection neural network

INVESTIGATION ON APPLICABILITY OF VARIOUS STRESS DEFINITIONS IN ATOMISTIC SIMULATION

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Acta Mechanica Solida Sinica 2009年第6期22卷 644-649页

作者： ran Xu Bin liu AML Department of Engineering Mechanics Tsinghua University Beijing 100084 China

How to correctly extract Cauchy stress from the atomistic simulations is a crucial issue in studying the mechanical behaviours of atomic systems, but is still in controversy. In this paper, three typical atomistic simulation examples are used to validate various existing stress definitions. It is found that the classical virial stress fails in predicting the stresses in these examples, because the velocity depends on the choice of the local average volume or the reference frame velocity and other factors. In contrast, the Lagrangian cross-section stress and Lagrangian virial stress are validated by these examples, and the instantaneous Lagrangian atomic stress definition is also proposed for dynamical problems.

关键词： atomic stress virial stress atomistic simulation

LES investigation of the tip vortex cavitating flow with special emphasis on the interaction between cavitation and vorticity by a modified cavitation model

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Journal of Hydrodynamics 2023年第3期35卷 594-606页

作者： Xin-ran liu Tao Wang Xiao-yang Zhao Tai-ran Chen School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China Vehicle Engineering Department Army Academy of Armored ForcesBeijing 100072China China Ship Research and Development Academy Beijing 100085China

Cavitation within the tip vortex(TV)flow remains a challenging issue in the design of high-speed and low-noise hydraulic *** this paper,the TV cavitating flow around an elliptical hydrofoil is calculated by using large eddy simulation(LES)combined with a modified Schnerr-Sauer(S-S)cavitation *** original S-S cavitation model is modified by taking into account the typical effect of vortex *** partial pressure term which can describe the vortex quantitatively and qualitatively is confirmed asρ_(m)ω^(2) x r _(c)^(2) ,and is considered into the R-P equation of the modified S-S cavitation *** between the numerical and experimental results shows good agreement in the form and evolution of cavities,including attached cavities(AC)and tip vortex cavities(TVC).The vorticity transport equation is utilized to investigate the dynamic mechanisms of the vortex development around the *** analyses indicate that cavitation in the TV flow influences the pressure in the core of the cavity and the local flow *** vortex structures in the TV cavitating flow include TV,secondary vortex(SV)and wake vortex(WV).The direction and magnitude of the rotation effect can be described by axial vorticity which is drawn on the iso-surface of Q=1×105 s−*** development of the TV cavitating flow can be divided into two stages:Stage I,the development and fusion of TV,SV,stage II,the dissipation of *** stretching term dominates the evolution of TV,and the dilatation term is the main reason in the mergence process of SV.

关键词： Cavitating flow tip vortex(TV) large eddy simulation(LES) cavitation model

Classifying and clustering in negative databases

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Frontiers of Computer Science 2013年第6期7卷 864-874页

作者： ran liu Wenjian LUO Lihua YUE School of Computer Science and Technology University of Science and Technology of China Hefei 230027 China Anhui Province Key Laboratory of Software Engineering in Computing and Communication University of Science and Technology of China Hefei 230027 China

Recently, negative databases （NDBs） are proposed for privacy protection. Similar to the traditional databases, some basic operations could be conducted over the NDBs, such as select, intersection, update, delete and so on. However, both classifying and clustering in negative databases have not yet been studied. Therefore, two algorithms, i.e., a k nearest neighbor （kNN） classification algorithm and a k-means clustering algorithm in NDBs, are proposed in this paper, respectively. The core of these two algorithms is a novel method for estimating the Hamming distance between a binary string and an NDB. Experimental results demonstrate that classifying and clustering in NDBs are promising.

关键词： negative databases classification clustering k nearest neighbor k-means hamming distance

Prescribed-time stabilization and inverse optimal control of stochastic high-order nonlinear systems

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Science China(Information Sciences) 2024年第2期67卷 144-156页

作者： ran liu Hui WANG Wuquan LI School of Mathematics and Statistics Science Ludong University

This paper investigates the prescribed-time state-feedback stabilization and prescribed-time inverse optimality problems for stochastic high-order nonlinear systems. First, a time-varying controller is designed by developing scaled quartic Lyapunov functions, which can guarantee that the system has a unique strong solution almost surely on the prescribed interval for any system initial conditions and that the states and the control converge to the origin in a mean-square form within the prescribed time. Then, the controller is redesigned to address the problem of prescribed-time inverse optimal mean-square stabilization. Finally,a concrete example is provided to confirm the efficiency of the proposed design schemes.

关键词： stochastic high-order nonlinear systems prescribed-time stabilization the scaled design inverse optimality

Locomotion Optimization and Manipulation Planning of a Tetrahedron-Based Mobile Mechanism with Binary Control

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Chinese Journal of Mechanical Engineering 2018年第1期31卷 78-99页

作者： ran liu Yan-An Yao Wan Ding Xiao-Ping liu School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University Department of Mechanism Theory and Dynamics of Machines RWTH Aachen University Department of Systems and Computer Engineering Carleton University

Locomotion and manipulation optimization is essential for the performance of tetrahedron-based mobile mechanism. Most of current optimization methods are constrained to the continuous actuated system with limited degree of freedom(DOF), which is infeasible to the optimization of binary control multi-DOF system. A novel optimization method using for the locomotion and manipulation of an 18 DOFs tetrahedron-based mechanism called 5-TET is proposed. The optimization objective is to realize the required locomotion by executing the least number of *** control strategy is adopted, and forward kinematic and tipping dynamic analyses are performed, *** on a developed genetic algorithm(GA), the optimal number of alternative struts between two adjacent steps is obtained as 5. Finally, a potential manipulation function is proposed, and the energy consumption comparison between optimal 5-TET and the traditional wheeled robot is carried out. The presented locomotion optimization and manipulation planning enrich the research of tetrahedron-based mechanisms and provide the instruction to the successive locomotion and operation planning of multi-DOF mechanisms.

关键词： Tetrahedron-based mobile mechanism Binary control GA Locomotion optimization Manipulation planning

A Rigorous Analysis of Vehicle-to-Vehicle range Performance in a Rural Channel Propagation Scenario as a Function of Antenna Type and Location via Simulation and Field Trails

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China Communications 2023年第11期20卷 131-141页

作者： ran liu Daniel N.Aloi School of Engineering and Computer Science Oakland UniversityRochester HillsMI-48309USA

Vehicle-to-Everything(V2X) communications will be an essential part of the technology in future autonomous drive decision systems.A fundamental procedure is to establish a robust communication channel between end-to-end *** to the antenna placed at different positions on vehicles,the existing cellular electro-magnetic(EM) wave propagation modelling does not fit properly for V2X direct communication *** order to figure out a feasible understanding of this problem,this paper focuses on the propagation channel analysis in a rural Vehicle-to-Vehicle(V2V) scenario for vehicular communication with antenna position experiments at different *** adopting the ray-tracing algorithm,a rural scenario simulation model is built up via the use of a commercial-off-the-shelf(COTS) EM modelling software package,that computes the path loss received power and delay spread for a given propagation ***,a real-world vehicle measurement campaign was performed to verify the simulation *** simulated and measured receiver power was in good agreement with each other,and the results of this study considered two antenna types located at three different relative heights between the two *** research provides constructive guidance for the V2V antenna characteristics,antenna placement and vehicle communication channel analysis.

关键词： antenna simulation and measurement propagation channel modeling ray-tracing simula-tion V2V scenario propagation

Development and Analysis of a Closed-Chain Wheel-Leg Mobile Platform

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Chinese Journal of Mechanical Engineering 2020年第5期33卷 62-74页

作者： Chaoran Wei Yanan Yao Jianxu Wu ran liu School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

Current research concerning legged platforms and wheeled platforms primarily focuses on terrain adaptive capability and speed capability,*** with wheeled platforms,legged platforms with a closed-chain mechanism still present deficiencies regarding speed *** integrate the advantages of these two types of platforms,a wheel-leg mobile platform with two modes based on a closed-chain mechanism is ***,a closed-chain mechanism that generates a high-knee trajectory in legged mode is designed and analyzed based on kinematic *** improve the platform’s obstacle-surmounting performance,the dimensional parameters of the closedchain mechanism are optimized and the design requirements for the platform’s frame are *** addition,the particular structure of the leg group is designed to realize transformation between legged mode and wheeled *** mobility of the constructed platform is calculated through an obstacle-surmounting probability *** performances of the two motion modes are analyzed and compared by conducting dynamic ***,experiments are carried out to verify both the theoretical analyses and the prototype *** study proposes a new approach to designing wheel-leg platforms with prominent speed ability and mobility based on a closed-chain mechanism.

关键词： Wheel-leg mobile platform Closed-chain leg mechanism High-knee trajectory Obstacle-surmounting probability

Continuous-Variable Quantum Network Coding Based on Quantum Discord

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Computers, Materials & Continua 2020年第9期64卷 1629-1645页

作者： Tao Shang ran liu Jianwei liu Yafei Hou School of Cyber Science&Technology Beihang UniversityBeijing100083China Graduate School of Natural Science and Technology Okayama UniversityOkayama Prefecture700-8530Japan

Establishing entanglement is an essential task of quantum communication *** entanglement,quantum discord,as a measure of quantum correlation,is a necessary prerequisite to the success of entanglement *** realize efficient quantum communication based on quantum discord,in this paper,we consider the practical advantages of continuous variables and propose a feasible continuous-variable quantum network coding scheme based on quantum *** means of entanglement distribution by separable states,it can achieve quantum entanglement distribution from sources to targets in a butterfly *** with the representative discrete-variable quantum network coding schemes,the proposed continuous-variable quantum network coding scheme has a higher probability of entanglement distribution and defends against eavesdropping and forgery ***,the deduced relationship indicates that the increase in entanglement is less than or equal to quantum discord.

关键词： Continuous variable quantum network coding quantum discord entanglement distribution Gaussian cloning