检索结果-南通市图书馆

Attitude stabilization of a pico-satellite by momentum wheel and magnetic coils

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第11期10卷 1617-1623页

作者： Tao MENG hao wang zhong-he jin ke han Department of lnformation Science & Electronic Engineering Zhejiang University Hangzhou 310027 China

The three-axis active attitude control method with a momentum wheel and magnetic coils for a pico-satellite is considered. The designed satellite is a 2.5 kg class satellite stabilized to nadir pointing. The momentum wheel performs a pitch-axis momentum bias, nominally spinning at a particular rate. Three magnetic coils are mounted perpendicularly along the body axis for precise attitude control through the switch control mechanism. Momentum wheel start up control, damping control and attitude acquisition control are considered. Simulation results show that the proposed combined control laws for the pico-satellite is reliable and has an appropriate accuracy under different separation conditions. The proposed strategy to start up the wheel after separation from the launch vehicle shows that its pitch momentum wheel can start up successfully to its nominal speed from rest, and the attitude convergence can be completed within several orbits, depending on separation conditions.

关键词： Pico-satellite Attitude control Magnetic coils Momentum wheel

Magnetometer Compensation Scheme and Experimental Results on ZDPS-1A Pico-satellite

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2012年第3期25卷 430-436页

作者： han ke wang hao XIANG Tian jin zhonghe Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027China

In a pico-satellite with small volume, measurements from on-board three-axis magnetometer （TAM） are not accurate, as it can be easily disturbed by other electronic systems. To improve its accuracy, a scheme of compensation methods is introduced in this article. The scheme is based on an improved meast, rement model of pico-satellite TAM, and it mainly consists of three steps. First, in satellite design stage, several techniques are recommended to simplify the afterwards compensations. Then after satellite assembly, TAM ground tests and pre-launch calibration with least-square batch filter are introduced to improve magnetometer performance. At the end, a post-launch calibration with unscented Kalman filter （UKF） is implemented with in-orbit data. The compensation scheme is used in the development of Chinese pico-satellite ZDPS-1A made by Zhejiang University. Results show that with the introduced compensation scheme, the maximum error of ZDPS-1A TAM can be reduced from 80 mG to 6 naG （1 G=10^-4T）.

关键词： pico-satellite magnetometers calibration: least-square filter Kalman filter

Pico-satellite Autonomous Navigation with Magnetometer and Sun Sensor Data

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2011年第1期24卷 46-54页

作者： han ke wang hao TU Binjie jin zhonghe Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

This article presents a near-Earth satellite orbit estimation method for pico-satellite applications with light-weight and low-power requirements. The method provides orbit information autonomously from magnetometer and sun sensor, with an extended Kalman filter （EKF）. Real-time position/velocity parameters are estimated with attitude independently from two quantities： the measured magnitude of the Earth’s magnetic field, and the measured dot product of the magnetic field vector and the sun vector. To guarantee the filter’s effectiveness, it is recommended that the sun sensor should at least have the same level of accuracy as magnetometer. Furthermore, to reduce filter’s computation expense, simplification methods in EKF’s Jacobian calculations are introduced and testified, and a polynomial model for fast magnetic field calculation is developed. With these methods, 50% of the computation expense in dynamic model propagation and 80% of the computation burden in measurement model calculation can be reduced. Tested with simulation data and compared with original magnetometer-only methods, filter achieves faster convergence and higher accuracy by 75% and 30% respectively, and the suggested simplification methods are proved to be harmless to filter’s estimation performance.

关键词： pico-satellite autonomous navigation orbit estimation magnetometer Kalman filter

Evolution of nC_(16)H_(34)-water-mineral systems in thermal capsules and geological implications for deeply-buried hydrocarbon reservoirs

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2022年第2期13卷 139-158页

作者： Guang-Hui Yuan Zi-hao jin Ying-Chang Cao ke-Yu Liu Jon Gluyas Yan-zhong wang ke-Lai Xi key Laboratory of Deep Oil and Gas School of GeosciencesChina University of PetroleumQingdao 266580China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyNo.62Fuzhou South RoadQingdao 266071China Department of Earth Sciences Durham UniversityDurham DH13LEUK

Organic-inorganic interactions between hydrocarbons and most minerals in deeply buried reservoirs remain *** this study,gold capsules and fused silica capillary capsules(FSCCs)with different com-binations of nC_(16)H_(34),water(distilled water,CaCl_(2) water)and minerals(quartz,feldspar,calcite,kaolinite,smectite,and illite)were heated at 340℃ for 3-10 d,to investigate the evolution and reaction pathways of the organic-inorganic interactions in different hot *** heating,minerals exhibited little alteration in the anhydrous *** alterations,how-ever,occurred obviously in the hydrous *** inorganic components affected nC_(16)H_(34) degra-dation ***,water promoted the free-radical thermal-cracking reaction and step oxidation reaction but suppressed the free-radical cross-linking *** impact of CaCl_(2) water on the nC_(16)H_(34) degradation was weaker than the distilled water as high Ca^(2+)concentration suppressed the formation of free *** presence of different waters also affects the impact of different minerals on nC_(16)H_(34) degradation,via its impact on mineral *** the anhydrous nC_(16)H_(34)-mineral systems,calcite and clays catalyzed generation of low-molecular-weight(LMW)alkanes,particularly the ***,feldspar,and calcite catalyzed generation of high-molecular-weight(HMW)alkanes and PAHs,whereas clays catalyzed the generation of LMW alkanes and mono-bicyclic aromatic hydrocarbons(M-BAHs).In the hydrous nC_(16)H_(34)-distilled water-mineral systems,all minerals but quartz promoted nC_(16)H_(34) degra-dation to generate more LMW alkanes,less HMW alkanes and *** the nC_(16)H_(34)-CaCl_(2) water-mineral systems,the promotion impact of minerals was weaker than that in the systems with distilled *** study demonstrated the generation of different hydrocarbons with different fluorescence colors in the different nC_(16)H_(34)-water-mineral systems after heating for t

关键词： nC_(16)H_(34)-water-mineral systems Organic-inorganic interactions Hydrocarbon degradation Mineral alteration Deeply buried hot reservoirs

Adaptive Trajectory Tracking Control for Nonholonomic Wheeled Mobile Robots:A Barrier Function Sliding Mode Approach

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 1007-1021页

作者： Yunjun Zheng jinchuan Zheng ke Shao han Zhao hao Xie Hai wang the School of Mechanical Engineering Hefei University of TechnologyHefei 230009China the School of Science Computing and Engineering TechnologiesSwinburne University of TechnologyHawthorn VIC 3122Australia the School of Civil Aviation Northwestern Polytechnical UniversityXi’an 710072China the Shanghai Aerospace Control Technology Institute Shanghai 201109 the School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China the College of Science HealthEngineering and EducationMurdoch UniversityPerth WA6150Australia

The trajectory tracking control performance of nonholonomic wheeled mobile robots(NWMRs)is subject to nonholonomic constraints,system uncertainties,and external *** paper proposes a barrier function-based adaptive sliding mode control(BFASMC)method to provide high-precision,fast-response performance and robustness for *** with the conventional adaptive sliding mode control,the proposed control strategy can guarantee that the sliding mode variables converge to a predefined neighborhood of origin with a predefined reaching time independent of the prior knowledge of the uncertainties and disturbances *** advantage of the proposed algorithm is that the control gains can be adaptively adjusted to follow the disturbances amplitudes thanks to the barrier *** benefit is that the overestimation of control gain can be eliminated,resulting in chattering ***,a modified barrier function-like control gain is employed to prevent the input saturation problem due to the physical limit of the *** stability analysis and comparative experiments demonstrate that the proposed BFASMC can ensure the prespecified convergence performance of the NWMR system output variables and strong robustness against uncertainties/disturbances.

关键词： Adaptive sliding mode barrier function nonholonomic wheeled mobile robot(NWMR) trajectory tracking control

Signal-background discrimination with convolutional neural networks in the PandaX-Ⅲ experiment using MC simulation

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2018年第10期61卷 51-59页

作者： hao Qiao ChunYu Lu Xun Chen ke han XiangDong Ji SiGuang wang School of Physics and State key Laboratory of Nuclear Physics and Technology and Center for High Energy Physics Peking University Beijing 100871 China Institute of Particle and Nuclear Physics and School of Physics and Astronomy Shanghai Jiao Tong University Shanghai Laboratory for Particle Physics and Cosmology Shanghai 200240 China Tsung-Dao Lee Institute Shanghai 200240 China

The PandaX-Ⅲ experiment will search for neutrinoless double beta decay of 136Xe with high pressure gaseous time projection chambers at the China jin-Ping underground Laboratory. The tracking feature of gaseous detectors helps suppress the background level, resulting in the improvement of the detection sensitivity. We study a method based on the convolutional neural networks to discriminate double beta decay signals against the background from high energy gammas generated by 214Bi and 2^208 T1 decays based on detailed Monte Carlo simulation. Using the 2-dimensional projections of recorded tracks on two planes, the method successfully suppresses the background level by a factor larger than 100 with a high signal efficiency. An improvement of 62% on the efficiency ratio of Еs/√Еb is achieved in comparison with the baseline in the PandaX-Ⅲ conceptual design report.

关键词： neutrino double beta decay convolutional neural networks background suppression

Emerging pro-drug and nano-drug strategies for gemcitabine-based cancer therapy

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Pharmaceutical Sciences 2022年第1期17卷 35-52页

作者： Haijie han Su Li Yueyang zhong Yue Huang Kai wang Qiao jin Jian Ji ke Yao Eye Center the Second Affiliated HospitalSchool of MedicineZhejiang UniversityHangzhou 310009China Zhejiang Provincial key Lab of Ophthalmology the Second Affiliated HospitalSchool of MedicineZhejiang UniversityHangzhou 310009China MOE key Laboratory of Macromolecule Synthesis and Functionalization of Ministry of Education Department of Polymer Science and EngineeringZhejiang UniversityHangzhou 310027China

Gemcitabine has been extensively applied in treating various solid tumors. Nonetheless,the clinical performance of gemcitabine is severely restricted by its unsatisfactory pharmacokinetic parameters and easy deactivation mainly because of its rapid deamination, deficiencies in deoxycytidine kinase (DCK), and alterations in nucleoside transporter. On this account, repeated injections with a high concentration of gemcitabine are adopted, leading to severe systemic toxicity to healthy cells. Accordingly, it is highly crucial to fabricate efficient gemcitabine delivery systems to obtain improved therapeutic efficacy of gemcitabine. A large number of gemcitabine pro-drugs were synthesized by chemical modification of gemcitabine to improve its biostability and bioavailability. Besides,gemcitabine-loaded nano-drugs were prepared to improve the delivery efficiency. In this review article, we introduced different strategies for improving the therapeutic performance of gemcitabine by the fabrication of pro-drugs and nano-drugs. We hope this review will provide new insight into the rational design of gemcitabine-based delivery strategies for enhanced cancer therapy.

关键词： Gemcitabine Pro-drug Nano-drug Cancer therapy

A Stochastic Filtering Algorithm Using Schr¨odinger Equation

在线全文

学校读者我要写书评

暂无评论

自动化学报 2014年第10期40卷 2370-2376页

作者： WU hao-han jin Fu-Jiang LAI Lian-You wang Liang College of Information Science and Engineering Huaqiao Universityxiamen 361021China College of Mechanical Engineeringand Automation Huaqiao University Xiamen 361021 China

This paper provides a new adaptive algorithm for single-step prediction by modeling the potential field of a one dimension Schrodinger wave equation using neural *** new architecture is referred to as the recurrent quantum neural network (RQNN).The RQNN can filter the signal embedded with non-stationary noise without any priori knowledge of the shape of the signal and statistical properties of the *** compared the simulation results of the RQNN with a classical adaptive stochastic *** is shown that the RQNN is much more efficient in denoising signals embedded with Gaussian stationary,non-Gaussian stationary and Gaussian nonstationary noise such as DC,sinusoid,staircase and speech *** RQNN can enhance the signal to noise rate (SNR) by 20 dB,which is more than 10 dB given by the traditional technology when it denoising sinusoid signal.

关键词：波动方程滤波算法随机模拟神经网络自适应算法非平稳噪声语音信号量子神经网络

A high precision computing method for heat transfer in the process of oil-water displacement

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2021年第5期33卷 958-969页

作者： Pan-pan han ke Chen Dong-xi Liu Yun-xiang You jin wang State key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China Yazhou Bay Institute of Deepsea Technology Shanghai Jiao Tong UniversitySanya 572000China College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China COTEC Offshore Engineering Solutions Beijing 100011China

The process of oil-water displacement is one of the key technologies in offshore underwater *** hot oil is contacting the normal-temperature water,the interfacial heat transfer should be investigated as the heat loss may result in wax precipitation and solidification which will reduce the flowing of oil and thus affect the *** for the numerical simulation of heat transfer,the calculation is costly as the underwater tank is usually large and the displacement period is long.A high precision computing method would greatly reduce the mesh ***,this research is performed to establish a high precision computing *** on volume of fluid(VOF),a new form of energy equation is *** equation is derived from temperature equation and the variable internal energy per volume is *** variable is additive and has a close relationship with volume *** algorithm implantation to OpenFOAM,two non-isothermal VOF solvers are established corresponding to temperature equation and the new equation *** an analytical solution is built,the two solvers are *** solver based on the new equation presents far more accurate results than the solver based on temperature *** energy weighted scheme is more reasonable than a linear temperature distribution for the mixture phase.

关键词： Multi-phase flow energy equation heat transfer oil-water displacement volume of fluid(VOF)