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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

Embracing connected intelligence with the YuanOS architecture:one OS kit for all

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Frontiers of Computer Science 2024年第1期18卷 1-3页

作者： Haibo CHEN ning jia Jie YIN Institute of Parallel and Distributed Systems School of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China OS Kernel Lab Huawei Technologies Co.Ltd.Beijing 100085China

Operating system abstracts hardware and creates application execution environment,and thus is the key pillar for IT *** its first invention in 1956,operating system has been evolved over three main stages:Mainframe,PC&Internet,Mobile Internet[1].Now,the entire society is firmly stepping towards the connected intelligence era[2],how should operating system be evolved to embrace this new era?

关键词： hardware execution connected

Numerical investigation of the dynamics of flexible vegetations in turbulent open-channel flows

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Journal of Hydrodynamics 2022年第4期34卷 681-699页

作者： Dong Xu jia-ning Liu Yun-feng Wu Chun-ning Ji State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

Aquatic vegetations widely exist in natural rivers and play an essential role in the evolution of the water environment and ecosystem by changing the river’s hydrodynamic characteristics and transporting sediments and *** reality,most aquatic vegetations are highly flexible,which invalidates the“rigid-cylinder”assumption widely adopted in many *** explore the dynamics of submerged flexible vegetation in open-channel flows and its feedback to turbulent flow structures,numerical simulations are carried out using an in-house fluid-structure interaction(FSI)*** the simulations,the geometry of vegetation plants is grid-resolved,the turbulent flow is simulated using the large eddy simulation(LES),the dynamics of the flexible plants are solved using the vector form intrinsic finite element(VFIFE)method,and the turbulent flow and the plants are two-way coupled using the immersed boundary(IB)*** dynamic responses of the flexible vegetation with different plant flexibility,spacing,and submergence are *** results show that flexible plants are subjected to complex flow-induced vibrations(FIVs)rather than static *** FIV involves both streamwise and cross-flow motions driven by the small-scale vortex shedding around the plants and the large-scale Kelvin-Helmholtz(K-H)vortices developed in the vegetation canopy *** vegetations exhibit pulsive wave motion of different patterns in relatively long and narrow open *** with the open-channel flows with static plants with equivalent bending deformation,the dynamic responses of flexible plants may increase the turbulent Reynolds stress of the open-channel flow by 70%–100%and increase the invasion depth of the K-H vortices by 30%–50%.

关键词： Flexible vegetation dynamic responses flow-induced vibration(FIV) fluid-structure interaction(FSI)

Online belief propagation algorithm for probabilistic latent semantic analysis

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Frontiers of Computer Science 2013年第4期7卷 526-535页

作者： Yun YE Shengrong GONG Chunping LIU jia ZENG ning jia YiZHANG School of Computer Science & Technology Soochow University Suzhou 215006 China Feng Chao Revenue Baidu Online Network Technology Co. LTD Beijing 100000 China

Probabilistic latent semantic analysis （PLSA） is a topic model for text documents, which has been widely used in text mining, computer vision, computational biology and so on. For batch PLSA inference algorithms, the required memory size grows linearly with the data size, and handling massive data streams is very difficult. To process big data streams, we propose an online belief propagation （OBP） algorithm based on the improved factor graph representation for PLSA. The factor graph of PLSA facilitates the classic belief propagation （BP） algorithm. Furthermore, OBP splits the data stream into a set of small segments, and uses the estimated parameters of previous segments to calculate the gradient descent of the current segment. Because OBP removes each segment from memory after processing, it is memoryefficient for big data streams. We examine the performance of OBP on four document data sets, and demonstrate that OBP is competitive in both speed and accuracy for online ex- pectation maximization （OEM） in PLSA, and can also give a more accurate topic evolution. Experiments on massive data streams from Baidu further confirm the effectiveness of the OBP algorithm.

关键词： probabilistic latent semantic analysis topicmodels expectation maximization belief propagation

Unique Solvability for a Class of Non-newtonian Fluids for a Reacting Mixture with Vacuum

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Acta Mathematicae Applicatae Sinica 2016年第4期32卷 833-850页

作者： Hong-jun YUAN jia-ning XIE College of Mathematics Jilin University School of Mathematics and Quantitative Economics Dongbei University of Finance and Economics

In this paper,we consider a class of non-Newtonian fluids for a reacting mixture in one-dimensional bounded interval, provided the initial data satisfying a compatibility condition. The main ingredient is that we allo... 详细信息

关键词： existence and uniqueness reactive gas flow vacuum non-Newtonian

Spatio-temporal Characteristics of Disturbance of Land Use Change on Major Ecosystem Function Zones in China

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Chinese Geographical Science 2015年第5期25卷 523-536页

作者： ning jia LIU Jiyuan ZHAO Guosong Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences University of Chinese Academy of Sciences

In recent years, because of increasing human activities, ecosystems have been substantially disturbed and their service functions have been greatly compromised. Based on the effect of land use changes on the major ecosystem services, we estimated the ecosystem comprehensive anthropogenic disturbance index(ECADI) and analyzed the spatio-temporal characteristics of changes in the ECADI in China from 1990 to 2010. The average ECADI of the major ecosystem function zones in China in 2010 is approximately 0.382. The ECADI of Northeast China and North China is slightly higher than that of Northwest China and Southwest China. Most zones have slight changes in the ECADI. The average increases of ECADI in the major ecosystem function zones in China from 1990 to 2000 and from 2000 to 2010 are 0.0024 and 0.0002, respectively. The increase is mainly due to reclamation and urbanization, whereas the decrease is due to the implementation of ecosystem protection policies. During the last 20 years, the ECADI of water resources conservation zones increased first, and then stopped. The ECADI of soil conservation zones increased first, and then declined. The ECADI of sandstorm prevention zones, biodiversity conservation zones and flooding mitigation zones increased continuously. Our results may provide proposals to the government regarding land use planning and ecosystem protection plans in the major ecosystem zones. The major ecosystem function zones in the western part of China have been protected effectively. However, the major ecosystem function zones in the eastern part of China require more protection in the future.

关键词： land use change major ecosystems services disturbance spatiotemporal patterns China

An approximately analytical solution method for the cable-driven parallel robot in FAST

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Research in Astronomy and Astrophysics 2021年第2期21卷 169-179页

作者： jia-ning Yin Peng jiang Rui Yao National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the largest single-dish aperture telescope with a cable-driven parallel robot introduced to achieve the highest sensitivity in the ***,to realize the high-precision,mechanical equations of such a robot are always complicated,so that it is difficult to achieve real-time control by the traditional iterative *** this regard,this paper proposes an approximately analytical solution method,which uses the approximately linear relationship between the main parameters of FAST to bypass some *** the coefficients of the relationship extracted,static or quasi-static mechanical equations can be analytically *** this paper’s example,this method saves at least 90%of the calculating time and the calculated values are consistent with the experimental *** such huge efficiency improvements,real-time and high-precision control of the FAST will no longer be difficult ***,all the work in this paper is expected to be used in the FAST.

关键词： telescopes-methods analytical-instrumentation miscellaneous

Formation of multiple trimethylsilyl derivatives in the derivatization of 17α-ethinylestradiol with BSTFA or MSTFA followed by gas chromatography-mass spectrometry determination

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Journal of Environmental Sciences 2007年第7期19卷 879-884页

作者： ZHOU Yi-qi WANG Zi-jian jia ning Sate Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China. College of Environment and Energy Engineering Beijing University of Technology Beijing 100022 China

N,O-bis（trimethylsily）trifluoroacetamide （BSTFA） and N-methyl-N（trimethylsily） trifluoroacetamide （MSTFA） are common derivatization reagents used in the GC-MS analysis of estrogen steroids such as estrone （El） and 17α-ethinylestradiol （EE2）. In this study, three trimethylsilyl （TMS） steroid derivatives, mono- and di-trimethylsilyl EE2 and mono-trimethylsilyl El, were observed during the derivatization of EE2 with BSTFA or MSTFA and/or GC separation. Factors influencing the production of multiple TMS derivatives and their relative abundance were examined. It was found that both methanol and bisphenol A competed with estrogenic esteroids when reacting with silylation reagents, and thus affected the formation of TMS derivatives and their relative abundance in the derivatization products. Methanol was found to be more reactive than bisphenol A with the BSTFA reagent. None of the three solvents tested in this study could prevent the generation of multiple TMS derivatives during the derivatization of EE2 with BSTFA, followed by GC analysis. A similar result was observed using MSTFA as the derivative reagent followed by GC analysis. Thus, the suitability of BSTFA or MSTFA as the derivatization reagent for the determination of E1 and EE2 by GC-MS, under the conditions reported here, is questionable. This problem can be solved by adding trimethylsilylimidaz （TMSI） in the BSTFA reagent as recommended, and the performance of the method has been proved in this study.

关键词： estrogens water sample GC/MS determination trimethylsilyl steroid derivatives

The Effect of Topologies and Refilling Short-chain PEG on Protein Adsorption

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Chinese Journal of Polymer Science 2023年第12期41卷 1879-1888,I0007页

作者： Chi Li jia-ning Zhang Jing Jin Wei jiang State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of Applied Chemistry and Engineering University of Science and Technology of ChinaHefei 230026China

PEGylation is the gold standard for constructing protein resistance ***,grafting mPEG-SH and SH-PEG-SH with varied molecular weights(Mw=5K,10K,and 20K)on a gold chip,and the subsequent lysozyme adsorptions of the PEG layers are evaluated using quartzcrystal microbalance based on dissipation(QCM-D).The lysozyme resistance depends on the features of grafting density and chain conformation,i.e.,linear and looped ***,long-chain PEG(Mw≥10K)is insufficient to form a dense layer to resist protein due to large steric ***-chain PEG(Mw=1K)with linear and looped structures is used to refill onto the long-chain PEG layer to increase the grafting density of PEGs and improve protein *** refilling process and the subsequent protein adsorption depend on conformation rather than the density of the long-chain PEG ***,the long-chain PEG looped substrates significantly improve protein resistance,attributing to the high viscoelasticity of the looped substrate and an increase in grafting density after ***,refilling short-chain PEG improves protein resistance and the substrate conformation-dependence gives insight into the impact of topology,providing new ideas for how to increase chain density and select suitable topology to resist protein adsorption and demonstrating a potential application in biomedical fields.

关键词： Poly(ethylene glycol) Refilling Protein adsorption Conformation QCM-D