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Effect of the number of irradiation holes on rock breaking under constant laser energy

Petroleum Science 2022年第6期19卷 2969-2980页

作者： Hai-Zeng pan Yi Hu Yong Kang Ze-feng Wang jia-Wei Liu Hao Chen Meng-Da Zhang Hubei Key Laboratory of Waterjet Theory and New Technology Wuhan UniversityWuhan430072HubeiChina School of Power and Mechanical Engineering Wuhan UniversityWuhan430072HubeiChina The Institute of Technological Sciences Wuhan UniversityWuhan430072HubeiChina School of Urban Construction Wuhan University of Science and TechnologyWuhan430081HubeiChina jianghan Machinery Research Institute Limited Company of CNPC Wuhan430000HubeiChina

The use of mechanical drilling in accessing energy resources stored in deep and hard rock formations is becoming increasingly ***,laser irradiation has emerged as a novel drilling method with considerable in this *** study examines the variation of rock fracture length,fracture tortuosity,hole size,and rock breaking efficiency for a different number of holes and laser power,based on the constant total energy of laser *** indicated by the results,increasing the laser power increases the laser intensity,which helps increase the hole diameter and ***,for the same laser power,increasing the number of irradiated holes reduces the laser energy absorbed by each hole,which is not conducive to increasing the hole *** the number of holes increases,the mass loss of the rock also increases,while both specific energy(SE)and modified specific energy(MSE)*** the number of holes remains the same,the mass of the shale removed by low power is less than that removed by high power,while SE and MSE have an inverse relation with ***,high laser power and multiple-hole irradiation are more conducive to rock ***,the fracture length and fracture tortuosity of the rock irradiated by the low laser power will increase first and then decrease with the increase in the number of holes,and reach the peak value when the irradiation takes place through three *** a high-power laser irradiates the rock,the fracture length and tortuosity will increase with the increase in the number of irradiation *** is because a rock irradiated by low power dissipates more energy,with the result that the energy absorbed by the sample with four irradiation holes is not enough to break the rock *** study is expected to provide some guidance to break rock for drilling deep reservoirs and hard rock formations using laser irradiation.

关键词： Number of irradiation holes Rock breaking Fracture tortuosity Macrofracture

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The Law of Logarithm for Arrays of Random Variables under Sub-linear Expectations

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Acta Mathematicae Applicatae Sinica 2020年第3期36卷 670-688页

作者： jia-pan XU Li-xin ZHANG School of Mathematical Sciences Zhejiang UniversityHangzhou310027China

Under the framework of sub-linear expectation initiated by Peng,motivated by the concept of extended negative dependence,we establish a law of logarithm for arrays of row-wise extended negatively dependent random variables under weak ***,the law of logarithm for independent and identically distributed arrays is derived more precisely and the sufficient and necessary conditions for the law of logarithm are obtained.

关键词： sub-linear expectation capacity exponential inequality extended negative dependence the law of logarithm

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Shim coil design for Halbach magnet by equivalent magnetic dipole method

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Chinese Physics B 2018年第10期27卷 300-307页

作者： jia-Min Wu Zheng Xu pan Guo Jin-feng Qi Yu-Cheng He State Key Laboratory of Power Transmission Equipment and System Security and New Technology Chongqing UniversityChongqing 400044China School of Physics and Electronic Engineering Chongqing Normal UniversityChongqing 401331China

Low-field nuclear magnetic resonance magnet（2 MHz） is required for rock core analysis. However, due to its low field strength, it is hard to achieve a high uniform B0 field only by using the passive shimming. Therefore, active shimming is necessarily used to further improve uniformity for Halbach magnet. In this work, an equivalent magnetic dipole method is presented for designing shim coils. The minimization of the coil power dissipation is considered as an optimal object to minimize coil heating effect, and the deviation from the target field is selected as a penalty function term. The lsqnonlin optimization toolbox of MATLAB is used to solve the optimization problem. Eight shim coils are obtained in accordance with the contour of the stream function. We simulate each shim coil by ANSYS Maxwell software to verify the validity of the designed coils. Measurement results of the field distribution of these coils are consistent with those of the target *** uniformity of the B0 field is improved from 114.2 ppm to 26.9 ppm after using these shim coils.

关键词： equivalent magnetic dipole method shim coils magnetic resonance Halbach magnet

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(Nd_(0.9)Dy_(0.1))_(16)Co_(5)Fe_(70)Nb_(2)B_(7) PERMANENT MAGNETIC ALLOY AND BEHAVIOUR OF Nb

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Transactions of Nonferrous Metals Society of China 1996年第1期6卷 67-71页

作者： pan Shuming pan feng Ma Ruzhang General Research Institute of Non-ferrous Metals Beijing 100088 Beijing Tape Recorder Factory Beijing 100080 University of Science and Technology Beijing Beijing 100083

The magnetic properties of (Nd_(0.9)Dy_(0.1))_(16)Co_(5)Fe_(70)Nb_(2)B_(7) permanent magnetic alloy prepared by powder metallurgy are:Br=1.08T,_(1)H_(C)=1620kA/m,(BH)_(max)=208kJ/m^(3).The behaviour of Nb in this alloy was studied by joint methods of dynamic observation by high voltage electron microscope(HVEM)and Mossbauer *** Nb and Co substituting parts of Fe and adding a little Dy,practical magnetic alloy with excellent properties can be *** thermal stability of it is 80 ℃ higher than that of ternary Nd-Fe-13 *** study shows that adding Nb into Nd-Fe-B can make the intrinsic coercivity appear peak value at about Nb=2%(in mole fraction).Nb mainly enters into Nd-rich and B-rich phases,a little into Nd_(2)Fe_(14)B phase.

关键词： (Nd_(0.9)Dy_(0.1))_(16)Co_(5)Fe_(70)Nb_(2)B_(7) permanent magnetic alloy magnetic properties

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Efficient Configuration Space Construction and Optimization for Motion Planning

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Engineering 2015年第1期1卷 46-57页

作者： jia pan Dinesh Manocha Department of Computer Science The University of Hong Kong Department of Computer Science University of N.Carolina

The configuration space is a fundamental concept that is widely used in algorithmic robotics. Many applications in robotics, computer-aided design, and related areas can be reduced to computational problems in terms of configuration spaces. In this paper, we survey some of our recent work on solving two important challenges related to configuration spaces： ~ how to efficiently compute an approximate representation of high-dimensional configuration spaces; and how to efficiently perform geometric proximity and motion planning queries （n high-dimensional configuration spaces. We present new configuration space construction algorithms based on machine learning and geometric approximation techniques. These algorithms perform collision queries on many configuration samples. The collision query results are used to compute an approximate representation for the configuration space, which quickly converges to the exact configuration space. We also present parallel GPU-based algorithms to accelerate the performance of optimization and search computations in configuration spaces. In particular, we design efficient GPU-based parallel k-nearest neighbor and parallel collision detection algorithms and use these algorithms to accelerate motion planning.

关键词： configuration space motion planning GPUparallel algorithm

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State Classification and Motion Description for the Lower Extremity Exoskeleton SJTU-EX

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Journal of Bionic Engineering 2014年第2期11卷 249-258页

作者： Yunjie Miao feng Gao Dalei pan State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University Shanghai 200240 P. R. China

A lower extremity exoskeleton, SJTU-EX, is proposed, which mainly aims to help soldiers and workers to support a payload in motions. To solve the issues of the exoskeleton-environment and exoskeleton-human interactions, four types of foot contact are proposed based on their different kinematic characteristics. By the combination of single leg states, sixteen exo- skeleton states are presented using a series of meaningful notations from the topological point of view. The generalized function set （GF set） theory is employed to achieve the kinematic characteristics of the end effectors in different states. Moreover six mathematical formulations of the dynamics of the exoskeleton and its interactions with the human wearer are developed for different exoskeleton states. The applicability and potential of the proposed classification method are demonstrated by analyzing common lower limb motions, which are described concisely by a sequence of notations. Finally, a new concept of characteristic state is put forward to uniquely indicate the type of motion.

关键词： exoskeleton topological states lower limb motions dynamics GF set

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Fault detection and diagnosis for data incomplete industrial systems with new Bayesian network approach

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Journal of Systems Engineering and Electronics 2013年第3期24卷 500-511页

作者： Zhengdao Zhang Jinlin Zhu feng pan Key Laboratory of Advanced Process Control for Light Industry(Ministry of Education) Jiangnan University

For the fault detection and diagnosis problem in largescale industrial systems, there are two important issues： the missing data samples and the non-Gaussian property of the data. However, most of the existing data-driven methods cannot be able to handle both of them. Thus, a new Bayesian network classifier based fault detection and diagnosis method is proposed. At first, a non-imputation method is presented to handle the data incomplete samples, with the property of the proposed Bayesian network classifier, and the missing values can be marginalized in an elegant manner. Furthermore, the Gaussian mixture model is used to approximate the non-Gaussian data with a linear combination of finite Gaussian mixtures, so that the Bayesian network can process the non-Gaussian data in an effective way. Therefore, the entire fault detection and diagnosis method can deal with the high-dimensional incomplete process samples in an efficient and robust way. The diagnosis results are expressed in the manner of probability with the reliability scores. The proposed approach is evaluated with a benchmark problem called the Tennessee Eastman process. The simulation results show the effectiveness and robustness of the proposed method in fault detection and diagnosis for large-scale systems with missing measurements.

关键词： fault detection and diagnosis Bayesian network Gaussian mixture model data incomplete non-imputation.

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Magnetoresistive sensors with hybrid Co/insulator/ZnO:Co junctions

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International Journal of Minerals,Metallurgy and Materials 2013年第2期20卷 160-165页

作者： Guang Chen Cheng Song feng pan Laboratory of Advanced Materials Department of Materials Science and EngineeringTsinghua University

Magnetic tunnel junctions （MTJs）, as the seminal spintronic devices, are expected for applications in magne- toresistive sensors due to their large magnetoresistance （MR） and high field sensitivity. Two hybrid Co/insulator/ZnO：Co junctions were fabricated with two different barriers to investigate the magneto-transport properties. Experimental results indicate that, both Co/MgO/ZnO：Co and Co/ZnO/ZnO：Co junctions show the positive and nearly linear MR, and their tunnel magnetoresistances （TMR） are 21.8% and 13.6%, respectively, when the current is applied perpendicular to the film plane under the magnetic field of 2 T at 4 K. The nonlinearity of MR is less than 1% within the magnetic field （H） of 1 kOe 〈 H 〈 12 kOe at low temperature, making them attractive as magnetoresistive sensors. The higher MR of Co/MgO/ZnO：Co junctions is due to the superior spin filtering effect and larger effective barrier height of the MgO barrier. This linear MR characteristic of Co/insulator/ZnO：Co structures shows a promising future on the applications of diluted magnetic semiconductors in magnetoresistive sensors.

关键词： magnetoresistance sensors zinc oxide magnesia cobalt doping magnetic semiconductors

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Research on variance of subnets in network sampling

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Journal of Systems Engineering and Electronics 2014年第6期25卷 1098-1106页

作者： Qi Gao Xiaoting Li feng pan School of Automation Beijing Institute of Technology

In the recent research of network sampling, some sampling concepts are misunderstood, and the variance of subnets is not taken into account. We propose the correct definition of the sample and sampling rate in network sampling, as well as the formula for calculating the variance of subnets. Then, three commonly used sampling strategies are applied to databases of the connecting nearest-neighbor（CNN） model, random network and small-world network to explore the variance in network sampling. As proved by the results, snowball sampling obtains the most variance of subnets, but does well in capturing the network structure. The variance of networks sampled by the hub and random strategy are much smaller. The hub strategy performs well in reflecting the property of the whole network, while random sampling obtains more accurate results in evaluating clustering coefficient.

关键词： complex network sampling sample variance of sub-nets

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Improved resistive switching stability of Pt/ZnO/CoO_x /ZnO/Pt structure for nonvolatile memory devices

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Rare Metals 2013年第6期32卷 544-549页

作者： Guang Chen Cheng Song feng pan Laboratory of Advanced Materials Science and Engineering Tsinghua University

For Pt(Ag)/ZnO single-layer/Pt structure,random 10 formation and rupture of conductive filaments composed by oxygen vacancies or metallic ions often cause dispersion problems of resistive switching(RS)parameters,which is disadvantageous to devices *** this study,ZnO/CoOx/ZnO(ZCZ)tri-layers were utilized as the switching layers to investigate their RS properties as compared with ZnO-based single-layer *** is interestingly noted that Pt/ZCZ/Pt devices show quite stable bipolar RS behaviors with little resistance value fluctuations compared to Ag/ZCZ/Pt devices and Pt(Ag)/ZnO/Pt devices,which minimize the dispersion of the resistances of *** highly stable RS effect of Pt/ZCZ/Pt structure would be promising for high density memory devices.

关键词： Resistive random access memory Conductive filaments ZnO CoO x

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