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LES investigation of the tip vortex cavitating flow with special emphasis on the interaction between cavitation and vorticity by a modified cavitation model

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Journal of Hydrodynamics 2023年第3期35卷 594-606页

作者： Xin-ran Liu Tao Wang Xiao-yang Zhao Tai-ran chen School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China Vehicle Engineering Department Army Academy of Armored ForcesBeijing 100072China China Ship Research and Development Academy Beijing 100085China

Cavitation within the tip vortex(TV)flow remains a challenging issue in the design of high-speed and low-noise hydraulic *** this paper,the TV cavitating flow around an elliptical hydrofoil is calculated by using large eddy simulation(LES)combined with a modified Schnerr-Sauer(S-S)cavitation *** original S-S cavitation model is modified by taking into account the typical effect of vortex *** partial pressure term which can describe the vortex quantitatively and qualitatively is confirmed asρ_(m)ω^(2) x r _(c)^(2) ,and is considered into the R-P equation of the modified S-S cavitation *** between the numerical and experimental results shows good agreement in the form and evolution of cavities,including attached cavities(AC)and tip vortex cavities(TVC).The vorticity transport equation is utilized to investigate the dynamic mechanisms of the vortex development around the *** analyses indicate that cavitation in the TV flow influences the pressure in the core of the cavity and the local flow *** vortex structures in the TV cavitating flow include TV,secondary vortex(SV)and wake vortex(WV).The direction and magnitude of the rotation effect can be described by axial vorticity which is drawn on the iso-surface of Q=1×105 s−*** development of the TV cavitating flow can be divided into two stages:Stage I,the development and fusion of TV,SV,stage II,the dissipation of *** stretching term dominates the evolution of TV,and the dilatation term is the main reason in the mergence process of SV.

关键词： Cavitating flow tip vortex(TV) large eddy simulation(LES) cavitation model

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Research on the Critical Conditions for Clay Particle Release During Saline Aquifer Freshening Process

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Journal of Ocean University of China 2014年第4期13卷 628-636页

作者： ZHENG Xilai chen ran Key Laboratory of Marine Environment and Ecology Ministry of Education Ocean University of China College of Environmental Science and Engineering Ocean University of China

Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to find out the factors and mechanisms for clay particle release, laboratory column infiltration experiments simulating saline aquifer freshening process were designed to measure the critical conditions(critical flow velocity, critical salt concentration and critical ionic strength) and force analysis for clay particle according to DLVO electric double layer theory was employed to illustrate the mechanisms for particle release. The research results showed that critical flow velocity for clay particle release is influenced by salt concentration of injecting solution. When salt concentration of injecting solution is very high, clay particles are not released, indicating that there does not exist a critical flow velocity in this situation. As salt concentration of injecting solution decreases, particles start to be released. The critical salt concentration for clay particle release is 0.052 mol L-1 in our work, which was determined by a constant-flux experiment for stepwise displacement of high concentration Na Cl solution. The critical ionic strength for clay particle release decreases as Ca2+ molar content percentage of the mixed solution of Na Cl and Ca Cl2 increases following the first-order exponential decay equation y = 0.0391e-0.266 x + 0.0015.

关键词： seawater intrusion area clay particle release critical flow velocity critical salt concentration critical ionic strength

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Object-Based Classification Method for PolSAR Images with Improved Scattering Powers and Contextual Features

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Chinese Journal of Electronics 2017年第4期26卷 803-809页

作者： YUAN Zhengwu chen ran chen Cuiping LUO Xiaobo LIU Minghao College of computer science and technology Chongqing University of Posts and Telecommunications

This paper proposes a new object-based classification method for Polarimetric synthetic aperture radar(Pol SAR) images, which considers scattering powers from an improved model-based polarimetric decomposition approach, as well as the spatial and textural features. With the decomposition, the scattering ambiguities between oriented buildings and vegetation are reduced. Furthermore,various contextual features are extracted from the object and incorporated into the K-nearest neighbors(k-NN)based classification. To reduce the feature redundancy, a new Supervised locally linear embedding(S-LLE) dimensionality reduction method is introduced to map the high dimensional polarimetric signatures into the most compact low-dimensional structure for classification. Experimental results with Airborne synthetic aperture rada(AIRSAR)C-band Pol SAR image demonstrate the superior performance to other methods.

关键词： Object-based Polarimetric decomposi tion Contextual features Supervised locally linear embed ding(S-LLE) Polarimetric synthetic aperture radar(PolSAR)

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Two-stage robust optimization of power cost minimization problem in gunbarrel natural gas networks by approximate dynamic programming

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Petroleum Science 2022年第5期19卷 2497-2517页

作者： Yi-Ze Meng Ruo-ran chen Tian-Hu Deng Department of Industrial Engineering Tsinghua UniversityBeijing100084China

In short-term operation of natural gas network,the impact of demand uncertainty is not *** address this issue we propose a two-stage robust model for power cost minimization problem in gunbarrel natural gas *** demands between pipelines and compressor stations are uncertain with a budget parameter,since it is unlikely that all the uncertain demands reach the maximal deviation *** solving the two-stage robust model we encounter a bilevel problem which is challenging to *** formulate it as a multi-dimensional dynamic programming problem and propose approximate dynamic programming methods to accelerate the *** results based on real network in China show that we obtain a speed gain of 7 times faster in average without compromising optimality compared with original dynamic programming *** results also verify the advantage of robust model compared with deterministic model when facing *** findings offer short-term operation methods for gunbarrel natural gas network management to handle with uncertainties.

关键词： Natural gas Gunbarrel gas pipeline networks Robust optimization Approximate dynamic programming

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The Legitimacy of Pretrial Detention

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学术界 2014年第4期 260-268页

作者： Ding Huanxiang chen ran Law School Zhejiang Wanli University Ningbo Zhejiang 315100 People' s PrOrate Zhenhai District Ningbo Ningbo Zhejiang 315200

The utilization of pretrial detention,which constrains and expropriates the human rights of citizens,should be of legitimacy. That is to say,the implementation of pretrial detention must follow the standards of legitimacy and legal procedures. To guarantee the legitimacy,the process of pretrial detention should stick to three principles,the presumption of innocence,judicial inspection and proportion. The legitimacy benefits constructing the system of detention,preventing the alienation of pretrial detention,saving the judicial resources,perfecting the litigation structure,and improving non-costidal measures. Aiming at the deficiency of the legitimacy of pretrial detention in present China,there are necessities of promoting the constitution awareness of protection of human rights in criminal process,of constructing factual standard systems of legitimacy,and of perfecting the due procedural mechanism of pretrial detention.

关键词：合法性事实标准体系法定程序生活必需品利用率人权司法拘留

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Model-based in-situ measurement of pakchoi leaf area

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International Journal of Agricultural and Biological Engineering 2015年第4期8卷 35-42页

作者： Gong Liang chen ran Zhao Yuanshen Liu chengliang School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

Leaf area measurement is of great significance in plant growth process *** poses challenges to perform an unattended in-situ measurement,arising from quantifying the 3-dimensional pakchoi leaf *** non-destructive measurement techniques,which usually take its projection on the horizon plane of the leaf area,inevitably cause considerable measurement *** order to improve the measurement precision for leaf area,the exemplar pakchoi leaf was modeled as a complete or a piecewise spatial plane to approximate the actual leaf surface,and a machine-vision based ad hoc measuring platform was developed to conduct the in-situ ***,the leaf image was captured by a stereo vision system and segmented via a semi-automatic process to obtain its projective area and spatial inclination ***,pakchoi leaves were modeled as spatial surfaces regarding to their projected ***,leaf areas were calculated according to the established planar spatial model,acquired inclination angles and projective *** experimental comparison among the lattice-based monotype method,projection method,and the model-based method,whose results are denoted as MA,PA,and EA respectively,showed that the proposed framework could simultaneously meet the accuracy and non-destructive measurement *** constructed platform also provided a cost-effective semi-automatic measurement approach for continuously in-situ monitoring of pakchoi growth during its whole cultivation *** is further suggested from the experimental results that the proposed methodology can offer a generic measurement solution to various kinds of plant physiological and ecological studies in future researches.

关键词： leaf area in-situ measurement non-destructive measurement stereo vision image processing

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Synthesis of Three-Dimensional Agaric-like Biomorphic TiO_2 by a Facile Method with Coscinodiscus ***

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Journal of Ocean University of China 2012年第4期11卷 507-510页

作者： ZHANG Qianqian chen ran LI Ling Department of Chemistry and Chemical Engineering Ocean University of ChinaQingdao 266100P.R.China

The paper aims to expand the application of natural marine algae. Marine diatoms, which have intricate frustule struc- tures, can serve as bio-template for preparing three-dimensional materials. A simple and effective approach to synthesize the corru- gated agaric-like biomorphic TiO2 templated with frustule of Coscinodiscus sp. is reported. In the sol-gel preparation process, the titania-coating on the frustule is prepared through the deposition and condensation with the aid of acetylacetone （acac） as a control- ling agent to make the precursor Ti（BuO）4 hydrolyze slowly. The as-prepared titania-coated frustule and biomorphic TiOz is charac- terized by scanning electron microscopy （SEM） attached with energy dispersive X-ray spectrometer （EMAX） and X-ray diffraction （XRD）. The microstructure of the corresponding titania nanoparticles appears to be sphere with the diameters distributed around 10-20nm. The templating process is repeated for three cycles. Subsequently, the three-dimensional freestanding corrugated aga- ric-like biomorphic TiO2 structure is obtained by a selective removal in the NaOH solution. As far as we known, the 3D freestanding corrugated agaric-like biomorphic TiOz with greatly increased surface area is obtained for the first time.

关键词： marine diatoms frustule Coscinodiscus sp. biomorphic Ti02 microstructure

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Image Augmentation-Based Food Recognition with Convolutional Neural Networks

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Computers, Materials & Continua 2019年第4期59卷 297-313页

作者： Lili Pan Jiaohua Qin Hao chen Xuyu Xiang Cong Li ran chen College of Computer Science and Information Technology Central South University of Forestry and TechnologyChangsha410004China College of Computer Science and Electronic Engineering Hunan UniversityChangsha410082China

Image retrieval for food ingredients is important work,tremendously tiring,uninteresting,and *** vision systems have extraordinary advancements in image retrieval with CNNs *** it is not feasible for small-size food datasets using convolutional neural networks *** this study,a novel image retrieval approach is presented for small and medium-scale food datasets,which both augments images utilizing image transformation techniques to enlarge the size of datasets,and promotes the average accuracy of food recognition with state-of-the-art deep learning ***,typical image transformation techniques are used to augment food *** transfer learning technology based on deep learning is applied to extract image ***,a food recognition algorithm is leveraged on extracted deepfeature *** presented image-retrieval architecture is analyzed based on a smallscale food dataset which is composed of forty-one categories of food ingredients and one hundred pictures for each *** experimental results demonstrate the advantages of image-augmentation architecture for small and medium datasets using deep *** novel approach combines image augmentation,ResNet feature vectors,and SMO classification,and shows its superiority for food detection of small/medium-scale datasets with comprehensive experiments.

关键词： Image augmentation small-scale dataset deep feature deep learning convolutional neural network

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Research Progress of Catalysts and Initiators for Promoting the Cracking of Endothermic Hydrocarbon Fuels

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Transactions of Tianjin University 2022年第3期28卷 199-213页

作者： Yiyao Liu ran chen Jie Liu Xiangwen Zhang School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China Academic Journal Publishing Center of Tianjin University Tianjin 300072China Key Laboratory for Advanced Fuel and Chemical Propellant of Ministry of Education Tianjin 300072China

Catalytic/initiated cracking of endothermic hydrocarbon fuels is an eff ective technology for cooling a hypersonic aircraft with a high Mach number(over 5).Catalysts and initiators can promote fuel cracking at low temperatures,increase fuel conversion and the heat sink capacity,and suppress coke deposition,thereby reducing waste *** mainly include metal oxide catalysts,noble metal catalysts and metal nanoparticles,zeolite catalysts,nanozeolite catalysts,and coating ***,initiators roughly include nitrogenous compounds,oxygenated compounds,and hyperbranched polymer *** this review,we aim to summarize the catalysts and initiators for cracking endothermic hydrocarbon fuels and their mechanisms for promoting *** review will facilitate the development of the synthesis and exploration of catalysts and initiators.

关键词： Endothermic hydrocarbon fuels Cracking Catalysts Initiators

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Deformation Temperature and Lamellar Thickness Dependency of FormⅠto Form Ⅲ Phase Transition in Syndiotactic Polypropylene during Tensile Stretching

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Chinese Journal of Polymer Science 2014年第9期32卷 1210-1217页

作者： Ying Lu Ying-ying Sun ran chen Xiu-hong Li 门永锋 State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences University of Chinese Academy of Sciences SSRF Shanghai Institute of Applied Physics Chinese Academy of Sciences

Phase transition from form Ⅰ to form Ⅲ in syndiotactic polypropylene crystallized at different conditions during tensile deformation at different temperatures was investigated by using in situ synchrotron wide angle X-ray diffraction technique. In all cases, the occurrence of this phase transition was observed. The onset strain of this transition was found to be crystalline thickness decided by crystallization temperature and drawing temperature dependent. The effect of drawing temperature on this phase transition is understood by the changes in mechanical properties with temperature. Moreover, crystalline thickness dependency of the phase transition reveals that this form Ⅰ to from Ⅲ phase transition occurs first in those lamellae with their normal along the stretching direction which have not experienced stress induced melting and recrystallization.

关键词： Tensile deformation Phase transition Syndiotactic polypropylene WAXD.

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