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Vision-based aerial image mosaicking algorithm with object detection

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Journal of Systems Engineering and Electronics 2022年第2期33卷 259-268页

作者： HAN Jun LI Weixing feng Kai pan feng School of Automation Beijing Institute of TechnologyBeijing 100081China

Aerial image sequence mosaicking is one of the chal-lenging research fields in computer *** obtain large-scale orthophoto maps with object detection information,we propose a vision-based image mosaicking algorithm without any extra location *** to object detection results,we define a complexity factor to describe the importance of each input ima-ge and dynamically optimize the feature extraction *** feature points extraction and matching processes are mainly guided by the speeded-up robust features(SURF)and the grid motion statistic(GMS)algorithm respectively.A robust refer-ence frame selection method is proposed to eliminate the trans-formation distortion by searching for the center area based on ***,the sparse Levenberg-Marquardt(LM)al-gorithm and the heavy occluded frames removal method are ap-plied to reduce accumulated errors and further improve the mo-saicking *** proposed algorithm is performed by using multithreading and graphics processing unit(GPU)accel-eration on several aerial image *** experiment results demonstrate that our algorithm outperforms most of the existing aerial image mosaicking methods in visual quality while guaranteeing a high calculation speed.

关键词： image mosaicking object detection grid motion statistic(GMS) mapping

dCompaction： Speeding up Compaction of the LSM-Tree via Delayed Compaction

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Journal of Computer Science & Technology 2017年第1期32卷 41-54页

作者： feng-feng pan Yin-Liang Yue Jin Xiong State Key Laboratory of Computer Architecture Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China Institute of Information Engineering Chinese Academy of Sciences Beijing 100093 China

Key-value （KV） stores have become a backbone of large-scale applications in today＇s data centers. Write- optimized data structures like the Log-Structured Merge-tree （LSM-tree） and their variants are widely used in KV storage systems like BigTable and RocksDB. Conventional LSM-tree organizes KV items into multiple, successively larger components, and uses compaction to push KV items from one smaller component to another adjacent larger component until the KV items reach the largest component. Unfortunately, current compaction scheme incurs significant write amplification due to repeated KV item reads and writes, and then results in poor throughput. We propose a new compaction scheme, delayed compaction （dCompaction） that decreases write amplification, dCompaction postpones some compactions and gathers them into the following compaction. In this way, it avoids KV item reads and writes during compaction, and consequently improves the throughput of LSM-tree based KV stores. We implement dCompaction on RocksDB, and conduct extensive experiments. Validation using YCSB framework shows that compared with RocksDB, dCompaction has about 40% write performance improvements and also comparable read performance.

关键词： key-value store Log-Structured Merge-tree (LSM-tree) write amplification delayed compaction

(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

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

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

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.

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

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

Compound Pendulum Modeling and Resonant Frequency Analysis of the Lower Limbs for the Wearer and Exoskeleton

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Journal of Bionic Engineering 2015年第3期12卷 372-381页

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

An innovative lower extremity exoskeleton with hybrid leg structures is proposed in this paper. The compound pendulum model is applied to analyze the swing motion during walking for the wearer and the exoskeleton respectively. The expression of the resonant period for the human lower limb is obtained and the optimum stride frequency, at which the energy expenditure for walking is the least, coincides with the stride frequency of strolling well. As for the exoskeleton, the relationship between the inertial parameters and the resonant period of the hybrid leg is established. To minimize the walking energy cost for the exoskeleton, the inertial parameter design must guarantee that the resonant period of the hybrid leg coincides with the actual stride period of the wearer. The resonant period of the hybrid leg is also influenced by the scissor angle which determines the distance between the hip and the ankle of the lower extremity exoskeleton （SJTU-EX） and can be adjusted to match different stride frequencies of various motions by the proper scissor angle planning.

关键词： compound pendulum exoskeleton inertial parameter stride frequency