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Flow structures of gaseous jets injected into water for underwater propulsion

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Acta Mechanica Sinica 2011年第4期27卷 461-472页

作者： Jia-Ning Tang Ning-Fei Wang wei Shyy School of Aerospace Engineering Beijing Institute of Technology 100081 Beijing China Department of Aerospace Engineering University of Michigan Ann Arbor MI 48109 USA

Gaseous jets injected into water are typically found in underwater propulsion, and the flow is essentially unsteady and turbulent. Additionally, the high water-to-gas density ratio can result in complicated flow structures; hence measuring the flow structures numerically and experimentally remains a challenge. To investigate the performance of the underwater propulsion, this paper uses detailed NavierStokes flow computations to elucidate the gas-water interactions under the framework of the volume of fluid （VOF） model. Furthermore, these computations take the fluid compressibility, viscosity, and energy transfer into consideration. This paper compares the numerical results and experimental data, showing that phenomena including expansion, bulge, necking/breaking, and back-attack are highlighted in the jet process. The resulting analysis indicates that the pressure difference on the rear and front surfaces of the propul- sion system can generate an additional thrust. The strong and oscillatory thrust of the underwater propulsion system is caused by the intermittent pulses of the back pressure and the nozzle exit pressure. As a result, the total thrust in underwater propulsion is not only determined by the nozzle geometry but also by the flow structures and associated pressure distri- butions.

关键词： Gaseous jets - Underwater propulsion Highdensity ratio Gas-water interactions

Innovative developments in lunar and planetary science promoted by China's lunar exploration

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Science China Earth Sciences 2023年第11期66卷 2399-2418页

作者： Chunlai LI wei YAN Jianjun LIU Ziyuan OUYANG Key Laboratory of Lunar and Deep Space Exploration National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Institute of Geochemistry Chinese Academy of SciencesGuiyang 550002China

As the only natural satellite of the earth, the Moon has always been the first choice for human exploration of the solar system. China's lunar exploration project(Chang'e project) was launched in 2004. At present, it has created a perfect end to the three phases of “orbiting, landing and returning”. A series of remarkable research achievements have been made on the basic issues of current lunar scientific research, such as the Earth-Moon space environment, lunar surface material, morphology,geological structure, lunar subsurface and internal structure, and the origin and evolution of the Moon, further deepening the human understanding of the Moon. This paper briefly reviews the development process of China's lunar exploration project,summarizes the main research results and scientific understanding, and finally prospects to the future development of China's lunar and planetary exploration.

关键词： Lunar exploration Lunar science Chang'e project Scientific achievements Future prospects

Advanced sodium-ion capacitor based on antimony-carbon composite anode

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Rare Metals 2022年第10期41卷 3360-3369页

作者： wei-Qing Yu Chun-Yan Zhu Ru-Tao Wang Jian-Chao Chen Qing-Yuan Liu Shu-Xian Zhang Zhi-Jie Gao Cheng-Xiang Wang Zhi-wei Zhang Long-wei Yin Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationSchool of Materials Science and EngineeringShandong UniversityJinan250061China Suzhou Institute of Shandong University Suzhou215123China College of Chemical Engineering and Safety Binzhou UniversityBinzhou256603China

Alloy-type materials with the characteristics of high theoretical capacity,low sodiation/desodiation potential,and good conductivity are considered as one of the most promising anodes for sodium-ion batteries or ***,the large volume change during the sodiation leads to poor cyclability and slow kinetics,thus presenting the main issue impeding the practical ***,we propose a facile wet chemistry and pyrolysis method to synthesize Sb-carbon composite that Sb nanoparticles or single atoms are confined and/or dispersed in the wrinkled carbon framework with high nitrogen *** unique architecture of Sb-carbon composite increases atomic interface contact/interaction with Na~+,facilitating ion diffusion and alleviating the volume change of Sb during the charge/discharge ***-cell test shows that Sb-carbon composite exhibits a high-rate capability and stable cycling ***,sodium-ion capacitors fabricated by employing Sb-carbon composite as anode and home-made active carbon as cathode,deliver both high-energy density of 157 Wh·kg^(-1)and high-power density of 25 kW·kg^(-1)as well as excellent cycling performance exceeding 4000 cycles.

关键词： Antimony Nitrogen doping carbon Alloy-type anode Sodium-ion capacitor

Nickel-titanium shape memory alloys made by selective laser melting:a review on process optimisation

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Advances in Manufacturing 2022年第1期10卷 24-58页

作者： Omar Ahmed Mohamed Syed Hasan Masood wei Xu School of Engineering Deakin UniversityGeelongVIC 3216Australia Department of Mechanical Engineering The Higher Institute of Engineering TechnologyBani WaledLibya Department of Mechanical and Product Design Engineering Swinburne University of TechnologyHawthornVIC 3122Australia

Selective laser melting(SLM)is a mainstream powder-bed fusion additive manufacturing(AM)process that creates a three-dimensional(3D)object using a high power laser to fuse fine particles of various metallic powders such as copper,tool steel,cobalt chrome,titanium,tungsten,aluminium and stainless *** the past decade,SLM has received significant attention due to its capability in producing dense parts with superior mechanical *** a premier shape memory alloy,the nickel-titanium(NiTi)shape memory alloy is attractive for a variety of biomedical applications due to its superior mechanical properties,superelasticity,corrosion resistance and *** paper presents a comprehensive review of the recent progress in NiTi alloys produced by the SLM process,with a particular focus on the relationship between processing parameters,resultant microstructures and *** research gaps,challenges and suggestions for future research are also addressed.

关键词： Additive manufacturing(AM) Selective laser melting(SLM) Microstructure NiTi alloy Mechanical properties

Frequency and Offset Online Estimation of Sinusoidal Signals Based on High-Order Nonlinear Continuous Differentiator

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Chinese Journal of Electronics 2017年第3期26卷 579-584页

作者： WANG Hongwei ZHANG wei ZUO Junyi WANG Heping School of Aeronautics Northwestern Polytechnical University

Real-time parameter identification of sinusoidal signals is an essential research topic due to its broad utilization in both theoretical studies and engineering practice.A tracking differentiator based online estimation framework has been proposed to simultaneously identify frequencies and offset of given multi-sinusoidal *** differentiator is exploited in presented framework to track the time derivatives of measurements which are then utilized to estimate the frequencies and *** introduce a tracking differentiator called high-order nonlinear continuous differentiator into the framework,giving birth to a new estimation *** experiments on both single and two sinusoidal signal are simulated,indicating the superiority of proposed method on both convergent speed and estimation accuracy.

关键词： Frequency estimation Offset estimation High-order nonlinear continuous differentiator Sinusoidal signal Multi-sinusoidal signal

An improved numerical method for constructing Halo/Lissajous orbits in a full solar system model

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Chinese Journal of Aeronautics 2018年第6期31卷 1362-1374页

作者： Yingjing QIAN Xiaodong YANG Wuxing JING wei ZHANG Beijing Key Laboratory of Nonlinear Vibrations and Strength of Mechanical Structures College of Mechanical Engineering Beijing University of Technology Department of Aerospace Engineering Harbin Institute of Technology

An improved numerical method that can construct Halo/Lissajous orbits in the vicinity of collinear libration points in a full solar system model is investigated. A full solar system gravitational model in the geocentric rotating coordinate system with a clear presentation of the angular velocity relative to the inertial coordinate system is proposed. An alternative way to determine patch points in the multiple shooting method is provided based on a dynamical analysis with Poincare′sections. By employing the new patch points and sequential quadratic programming, Halo orbits for L1, L2, and L3points as well as Lissajous orbits for L1and L2points in the EarthMoon system are generated with the proposed full solar system gravitational model to verify the effectiveness of the proposed method.

关键词： Full solar system model Halo orbit Libration motion Lissajous orbit Poincare section

A novel unsupervised method for new word extraction

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Science China(Information Sciences) 2016年第9期59卷 11-21页

作者： Lili MEI Heyan HUANG Xiaochi wei Xianling MAO Beijing Engineering Research Center of High Volume Language Information Processing and Cloud Computing Applications Department of Computer Science and TechnologyBeijing Institute of Technology

New words could benefit many NLP tasks such as sentence chunking and sentiment analysis. However, automatic new word extraction is a challenging task because new words usually have no fixed language pattern, and even appear with the new meanings of existing words. To tackle these problems, this paper proposes a novel method to extract new words. It not only considers domain specificity, but also combines with multiple statistical language knowledge. First, we perform a filtering algorithm to obtain a candidate list of new words. Then, we employ the statistical language knowledge to extract the top ranked new words. Experimental results show that our proposed method is able to extract a large number of new words both in Chinese and English corpus, and notably outperforms the state-of-the-art methods. Moreover, we also demonstrate our method increases the accuracy of Chinese word segmentation by 10% on corpus containing new words.

关键词： new word extraction word segmentation domain specificity statistical language knowledge domain word extraction

Investigation Into Vibration Characteristic in Vibrothermography

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Photonic Sensors 2019年第2期9卷 108-114页

作者： Yin LI Anbo MING Ruimin ZHANG wei ZHANG Rocket Force University of Engineering Xi'an 710025China High-tech Institute Fan Gong-ting South Street on the 12thQingzhou 262550China

Vibration characteristic plays an important role in vibrothermography, which directly affects the heating during the test. In this work, involving all the contacts in the vibrothermography, the "double-mass-thiree-spring" model is established to explore the vibration characteristic. The obtained results show that ultrasonic gun vibrates at fundamental frequency (FF), while the specimen vibrates at multi-frequencies including FF, 2FF, 3FF, and 4FF, which is validated through experimental investigation results. Additionally, the model proposed in this work reveals a high order harmonics in the vibrothermography test and makes the specimen conduct the steady vibration, which indicates that the model is closer to the practical equipment and can ensure the heating efficiency induced by vibration of specimen to improve the detection capability.

关键词： Vibrothermography vibration characteristic “double-mass-three-spring” model

Binary Image Steganalysis Based on Symmetrical Local Residual Patterns

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Chinese Journal of Electronics 2022年第4期31卷 752-763页

作者： LUO Junwei YU Mujian YIN Xiaolin LU wei School of Computer Science and Engineering Guangdong Province Key Laboratory of Information Security TechnologyMinistry of Education Key Laboratory of Machine Intelligence and Advanced Computing Sun Yat-sen University

Residual computation is an effective method for gray-scale image steganalysis. For binary images, the residual computation calculated by the XOR operation is also employed in the local residual patterns(LRP) model for steganalysis. A binary image steganalytic scheme based on symmetrical local residual patterns(SLRP) is proposed. The symmetrical relationships among residual patterns are introduced that make the features more compact while reducing the dimensionality of the features set. Multi-scale windows are utilized to construct three SLRP submodels which are further merged to construct the final features set instead of a single *** with higher probability to be modified after embedding are emphasized and selected to construct the feature sets for training the support vector machine classifier. The experimental results show that the proposed steganalytic scheme is effective for detecting binary image steganography.

关键词： Information hiding Steganalysis Symmetrical local residual patterns Multi-scale model