检索结果-南通市图书馆

Flat jet electrochemical milling of TC4 alloy with tailoring backward parallel flow

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第4期37卷 574-592页

作者： Huanghai KONG Ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool *** on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed ***, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.

关键词： Flat jet electrochemical milling TC4 alloy Surface roughness Micro-hardness Material removal rate

Pathways toward a pollution-free planet and challenges

在线全文

学校读者我要写书评

暂无评论

Frontiers of Environmental Science & Engineering 2024年第6期18卷 3-8页

作者： Jiuhui qu Jiaping Chen School of Environment Tsinghua UniversityBeijing 100084China College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060China

The mission of“Establishment of Zero-Pollution Earth”defined by United Nations Environment Programme aims at creation of a clean,safe and prosperous home for all human *** is of rational choice from each individual to protect our environment and demonstrates our great ambition to achieve our *** key message given in this article is that,zero pollution does not mean no discharge of pollutants and instead it can be achievable through optimizing and controlling a sound balance between pollutants discharge and capacities of decontamination through treatment and natural environmental accumulation,which can be termed as“Principle of Equilibrium”between pollution and *** on this principle,we propose and illustrate several key factors and synergistic pathways toward a pollution-free planet:quantitative determination on purification and wastewater;source control through green measures;minimization of negative side-effects;precise management through digitalized systems;and keeping sound balance between pollutants and natural *** should be noted that we would face a series of difficulties and challenges in moving forward to“Zero-Pollution Earth”.We should further develop theories,principles and tools to achieve the balance between quantity of pollutants and decontamination *** should work together to break through the bottleneck limited by“Principle of equilibrium”to establish new environmental remediation systems leading to“Zero-Pollution Earth”.

关键词： Wastewater treatment Resources Recovery Greenhouse gases Energy Pollution-free

Design of a Passive Gait‑based Ankle‑foot Exoskeleton with Self‑adaptive Capability

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

Chinese Journal of Mechanical Engineering 2020年第3期33卷 86-96页

作者： Xiangyang Wang Sheng Guo Bojian qu Majun Song Haibo qu Robotics Institute School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Key Laboratory of Vehicle Advanced Manufacturing Measuring and Control TechnologyMinistry of EducationBeijing Jiaotong UniversityBeijing 100044China School of Engineering Science KTH Royal Institute of Technology10044 StockholmSweden.

Propulsion during push-off is the key to realizing human *** have evolved a way of walking with high energy utilization,but it can be further *** inspiration from the muscle-tendon unit,a passive spring-actuated ankle-foot exoskeleton is designed to assist with human walking and to lengthen walking duration by mechanically enhancing walking *** of the gait events is realized using a smart clutch,which is designed to detect the contact states between the shoe sole and the ground,and automatically switch its working *** engagement of a suspended spring behind the human calf muscles is hence controlled and is in synchrony with *** device is completely passive and contains no external power *** is stored and returned passively using the *** our walking trials,the soleus electromyography activity is reduced by as much as 72.2%when the proposed ankle-foot exoskeleton is worn on the human *** influence of the exoskeleton on walking habits is also *** results show the potential use of the exoskeleton in humans’daily life.

关键词： Ankle-foot exoskeleton Energy cost Self-adaptiveness Human augmentation

Inclusion Size Effect on Mechanical Properties of Particle Hydrogel Composite

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2019年第5期32卷 643-651页

作者： Xiaocheng Hu Shaoxing qu State Key Laboratory of Fluid Power and Mechatronic System Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceDepartment of Engineering Mechanics38 Zheda RoadHangzhou 310027China

Particle hydrogel composite(PHC)combines the characteristics of at least two mat erials and has pot ential applications in many *** functions require the particle size to range from nanometer to millimeter,which has a noticeable effect on the mechanical properties of the hydrogel *** this paper,the mechanical properties of silica-inlaid PAAM hydrogel are measured with various particle diameters from 75 nm to 50|*** results show no obvious size effect on the mechanical properties of PHC when the particle diameter falls in micron ***,as the particle size decreases to nanoscale,the modulus of the PHC begins to increase *** size-irrelevant moduli and stress fields of PHCs with random and uniform particle distributions under different loading conditions are obtained based on the finite element ***,the toughening mechanism and the failure of the PHC are *** size-irrelevant modulus of the PHC is also predicted by the equivalent inclusion ***,the interaction between the hydrogel polymer chains and the particles is described from the microscopic point of view,requiring the nanoscale size-dependent theory and new experimental approach to further explore the mechanical proper ties of PHC.

关键词： Particle hydrogel composite Size effect Finite element method

Stochastic Iterative Learning Control With Faded Signals

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

IEEE/CAA Journal of Automatica Sinica 2019年第5期6卷 1196-1208页

作者： Ganggui qu Dong Shen the College of Information Science and Technology Beijing University of Chemical TechnologyBeijing 100029China

Stochastic iterative learning control(ILC) is designed for solving the tracking problem of stochastic linear systems through fading channels. Consequently, the signals used in learning control algorithms are faded in the sense that a random variable is multiplied by the original signal. To achieve the tracking objective, a two-dimensional Kalman filtering method is used in this study to derive a learning gain matrix varying along both time and iteration axes. The learning gain matrix minimizes the trace of input error covariance. The asymptotic convergence of the generated input sequence to the desired input value is strictly proved in the mean-square sense. Both output and input fading are accounted for separately in turn, followed by a general formulation that both input and output fading *** examples are provided to verify the effectiveness of the proposed schemes.

关键词： Fading channels iterative learning control (ILC) Kalman filtering, mean-square convergence stochastic systems

Effects of mean-field and pairing correlations on the Bogoliubov quasiparticle resonance

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2019年第11期62卷 93-101页

作者： XiaoYing qu Ying Zhang School of Physics and Nuclear Energy Engineering Beihang UniversityBeijing 100191China School of Mechatronics Engineering Guizhou Minzu UniversityGuiyang 550025China Department of Physics School of ScienceTianjin UniversityTianjin 300072China

The quasiparticle resonances are investigated by examining three kinds of quasiparticle spectra, i.e., the density of quasiparticle states, the occupation number density, and the pair number density in the continuum Skyrme Hartree-Fock-Bogoliubov theory with the Green’s function method. Taking the weakly bound nucleus 66Ca as an example, the quasiparticle resonant energies and widths extracted from these three kinds of quasiparticle spectra are compared. For the narrow resonances, the extracted resonant energy and the width are consistent with each other. However, it is difficult to use the density of quasiparticle states to identify the broad resonances due to the background of nonresonant continuum. By switching off the pairing potential and/or the Hartree-Fock(HF) potential respectively in the calculation of these quasiparticle spectra, the roles of HF mean-field and pairing correlations in the quasiparticle resonances are demonstrated clearly. It turns out that all the quasiparticle resonances corresponding to the deeply bound, weakly bound and positive-energy single-particle resonant states, are mainly contributed by the HF potential. The pairing potential helps to slightly increase the resonant energy and the width. However, the pairing potential is important to make the nucleons occupy the low-lying nonresonant continuum states near the threshold and take part in the pairing correlations here,especially for the partial waves with small angular momentum ?.

关键词： quasiparticle resonance mean-field pairing correlations Skyrme Hartree-Fock-Bogoliubov theory Green’s function method

The progress of catalytic technologies in water purification:A review

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2009年第6期21卷 713-719页

作者： LI Dapeng qu Jiuhui National Natural Science Foundation of China Beijing 100085 China Research Center for Eeo-Envrionmental Sciences Chinese Academy of Sciences Beijing 100085 China

Catalytic technologies have been paid increasing attention in refractory pollutants abatement due to its practical and potential values in water purification. As effective and efficient approaches for water purification, Fenton＇s reagent, ozonation, electrochemical and photocatalytic methods have been widely studied and applied in different aspects and have been reviewed by several articles. In recent years, some novel catalytic processes based on above processes have been developed for enhancing the efficiency of removing the organics from water. This review emphasized on the recent development of heterogeneous catalytic ozonation, electrocatalysis in respect of novel electrodes and electro-Fenton method, photoelectrocatalysis process and photoelectron-Fenton in water purification. It was also an attempt to propose general ideas about mechanism and principle enhancing the catalytic efficiency for the degradation and the mineralization of organics in water.

关键词： catalytic technology water purification heterogeneous catalytic ozonation electrocatalysis electro-Fenton photoelectro- catalysis photoelectro-Fenton

Experimental study on effect of inclination angles to ammonia pulsating heat pipe

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2014年第5期27卷 1122-1127页

作者： Xue Zhihu qu Wei China Academy of Aerospace Aerodynamics (CAAA)

In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter. The filling ratio is50%. The visualization investigation is conducted to observe the oscillation and circulation flow in the CLPHP. In order to investigate the effects of inclination angles to thermal performance in the ammonia CLPHP, four case tests are studied. The trends of temperature fluctuation and thermal resistance as the input power increases at different inclination angles are highlighted. The results show that it is very easy to start up and circulate for the ammonia CLPHP at an inclining *** thermal resistance is low to 0.02 K/W, presenting that heat fluxes can be transferred from heating section to cooling section very quickly. It is found that the thermal resistance decreases as the inclination angle increases. At the horizontal operation, the ammonia CLPHP can be easy to start up at low input power, but hard to circulate. In this case, once the input power is high,the capillary tube in heating section will be burnt out, leading to worse thermal performance with high thermal resistance.

关键词： Ammonia Inclination angles Pulsating heat pipe Thermal performance Thermal resistance

Cooperative localization against GPS signal loss in multiple UAVs flight

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2011年第1期22卷 103-112页

作者： Yaohong qu Youmin Zhang School of Automation Northwestern Polytechnical University Xi'an 710072 P. R. China Department of Mechanical and Industrial Engineering Concordia University Montreal H3G 1M8 Canada

Based on multiple unmanned aerial vehicles（UAVs） flight at a constant altitude,a fault-tolerant cooperative localization algorithm against global positioning system（GPS） signal loss due to GPS receiver malfunction is *** to the traditional means with single UAV,the proposed method is based on the use of inter-UAV relative range measurements against GPS signal loss and more suitable for the small-size and low-cost UAV ***,for re-localizing an UAV with a malfunction in its GPS receiver,an algorithm which makes use of any other three healthy UAVs in the cooperative flight as the reference points for re-localization is ***,by using the relative ranges from the faulty UAV to the other three UAVs,its horizontal location can be determined after the GPS signal is *** order to improve an accuracy of the localization,a Kalman filter is further exploited to provide the estimated location of the UAV with the GPS signal *** Kalman filter calculates the variance of observations in terms of horizontal dilution of positioning（HDOP） ***,during each discrete computing time step,the best reference points are selected adaptively by minimizing the ***,two simulation examples in Matlab/Simulink environment with five UAVs in cooperative flight are shown to evaluate the effectiveness of the proposed method.

关键词： unmanned aerial vehicle(UAV) cooperative localization Kalman filter horizontal dilution of positioning(HDOP).