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Stability Analysis of Hybrid-Driven Underwater Glider

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China Ocean Engineering 2017年第5期31卷 528-538页

作者： NIU wen-dong WANG Shu-xin WANG Yan-hui SONG Yang zhu Ya-qiang Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education School of Mechanical EngineeringTianjin University The Joint Laboratory of Ocean Observing and Detecting Qingdao National Laboratory for Marine Science and Technology

Hybrid-driven underwater glider is a new type of tmmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steady- state operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and *** to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.

关键词： hybrid-driven underwater glider stability analysis numerical simulation field trials

Ultrasound features of hepatocellular adenoma and the additional value of contrast-enhanced ultrasound

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Hepatobiliary & Pancreatic Diseases International 2016年第1期15卷 48-54页

作者： Yi dong Zheng zhu wen-Ping Wang Feng Mao Zheng-Biao Ji Department of Ultrasound Zhongshan HospitalFudan University Department of Ultrasound Taicang First People’s Hospital

BACKGROUNI）： Hepatocellular adenoma （HCA） is a rare benign tumor of the liver. It is of clinical importance to dif- ferentiate HCA from other liver tumors, especially hepatocel- lular carcinoma （HCC）. This study aimed to evaluate the char- acteristic features of HCA by conventional ultrasound and contrast-enhanced ultrasound （CEUS） findings. METHODS： Twenty-six patients （10 males and 16 females; mean age 36.2＋5.0 years） with 26 histopathologically proven HCAs were retrospectively identified. According to the maxi- mum diameter of HCAs, they were divided into three groups：〈30 mm, 30-50 mm, and 〉50 mm. Ultrasound examinations were performed with C5-2 broadband curved transducer of Philips iU22 unit （Philips Bothell, WA, USA）. For each lesion, a dose of 2.4 mL SonoVue~ （Bracco Imaging Spa, Milan, Italy） was injected as a quick bolus into the cubital vein. Lesions＇ echogenicity, color-Doppler flow imaging and contrast en- hancement patterns were recorded. RESULTS： Grayscale ultrasound revealed that most of HCAs were hypoechoic （73.1%, 19/26）. Spotty calcifications were detected in 26.9% （7/26） of the lesions. Color-Doppler flow imaging detected centripetal bulky color flow in 46.2% （12/26） of the HCAs. CEUS showed that 73.1% （19/26） of the HCAs displayed as rapid, complete and homogenous enhancement, and 53.8% （14/26） showed decreased contrast enhancement in the late phase. There was no significant difference in enhance- ment patterns among different sizes of HCAs （P〉0.05）. Centripetal enhancement with subcapsular tortuous arteries was common in larger HCAs.

关键词： contrast-enhanced ultrasound hepatocellular adenoma ultrasound diagnosis

Cuttings transport: Back reaming analysis based on a coupled layering-sliding mesh method via CFD

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Petroleum Science 2023年第6期20卷 3673-3686页

作者： Na zhu Shi-dong Ding Xiao-Lei Shi wen-Jun Huang De-Li Gao MOE Key Laboratory of Petroleum Engineering China University of PetroleumBeijing102249China SINOPEC Research Institute of Petroleum Engineering Co.Ltd No.197 Baisha RoadChangping DistrictBeijing102206China

Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach *** mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this *** this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established *** dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe *** back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been *** results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings *** addition,the cuttings concentration is observed to decrease significantly with the pipe rotation ***,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the ***,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings ***“bulldozer”effect of the connector causes a more severe impact on hole *** both cases,increasing the tripping velocity only mildly affects the cuttings *** is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming ***,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passe

关键词： Drill cuttings transport Back reaming Layering-sliding mesh Hole cleaning Connector

Modification and investigation of silica particles as a foam stabilizer

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International Journal of Minerals,Metallurgy and Materials 2017年第2期24卷 208-215页

作者： Qian zhu Hua-lei Zhou Ying-xiao Song Zhi-dong Chang wen-jun Li School of Chemistry and Biological Engineering University of Science and Technology Beijing Beijing 100083 China

As a solid foam stabilizer, spherical silica particles with diameters ranging from 150 to 190 nm were prepared via an improved Stober methOd and were subsequently modified using three different silane coupling agents to attain the optimum surface hydrophobicity of the particles. Fourier transform infrared （FTIR） spectra and the measured contact angles were used to characterize the surface properties of the prepared particles. The foam stability was investigated by the foam drainage half-life and the expansion viscoelastic modulus of the liquid film. The results demonstrate that all of the modified silica nanoparticles effectively improve the foam stability. The surface hydrophobicity of the modified particles is found to be a key factor influencing the foam stability. The optimum contact angle of the particles lies in the ap- proximate range from 50° to 55°. The modifier molecular structure used can also influence the stabilizing foam property of the solid particles The foam system stabilized by （CH3）2SiCl2-modified silica particles exhibits the highest stability; its drainage half-life at maximum increases by 27% compared to that of the blank foam system and is substantially greater than those of the foam systems stabilized by KH570- and KH550-modified particles.

关键词： silica nanoparticles surface modification hydrophobicity foam stability viscoelasticity

Analysis of Amino Acids in a Single Human Red Blood Cell by Capillary Zone Electrophoresis with Intracellular NDA- derivatization and Electrochemical Detection

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Chinese Chemical Letters 2002年第7期13卷 655-657页

作者： Qian dong Xiao Lei WANG Lan Lan zhu wen Rui JIN School of Chemistry and Chemical Engineering Shandong UniversityJinan 250100

A novel method for determination of amino acids in individual human red blood cells has been developed. In this method, the derivatization reagents (NDA and CN-) are introduced into living cells by electroporation. After completion of derivatization, the amino acids in a single cell is determined by capillary zone electrophoresis with end-column amperometric detection.

关键词： Capillary electrophoresis electrochemical detection single cell analysis amino acid.

Preparation and properties of poly(lactic acid)/cellulolytic enzyme lignin/PGMA ternary blends

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Chinese Chemical Letters 2012年第3期23卷 351-354页

作者： wen zhu Ouyang Yong Huang Hong Jun Luo dong Shan Wang Laboratory of Cellulose and Lignocellulosics Chemistry Guangzhou Institute of ChemistryChinese Academy of SciencesGuangzhou 510650China National Engineering Research Center for Engineering Plastics Technical Institute of Physics&ChemistryChinese Academy of SciencesBeijing 100190China

Poly（lactic acid）-based ternary blends consisting of poly（lactic acid）（PLA）,cellulolytic enzyme lignin（CEL）,and polyolefine grafting maleic anhydride（PGMA） were prepared by extrusion blending and the mechanical properties and the morphology of the ternary blends were *** was found that the mechanical properties varied with various loading of the components in the *** to neat PLA,the tensile strength and the Young＇s modulus of the ternary blends were decreased,but the elongation at break and the impact strength were effectively *** electron microscope observations revealed that the CEL plays a bridging role between PLA and PGMA,enhancing the miscibility between them and resulting in the improvement of ductility and toughness of the ternary *** the cost and performance,we obtained the optimal blend PLA/CEL/ PGMA（80/20/20,w/w/w）,of which the impact strength and the elongation at break were doubled as that of neat PLA,and the tensile strength remained moderate.

关键词： Polycaprolactone Cellulolytic enzyme lignin Tougher Blends

Low lighting image enhancement using local maximum color value prior

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Frontiers of Computer Science 2016年第1期10卷 147-156页

作者： Xuan dong Jiangtao wen Department of Computer Science and Technology Tsinghua University Beijing 100084 China

We study the problem of low lighting image en- hancement. Previous enhancement methods for images un- der low lighting conditions usually fail to consider the factor of image degradation during image formation. As a result, the lost contrast could not be recovered after enhancement. This paper will adaptively recover the contrast and adjust the exposure for low lighting images. Our first contribution is the modeling of image degradation in low lighting con- ditions. Then, the local maximum color value prior is pro- posed, i.e., in most regions of well exposed images, the lo- cal maximum color value of a pixel will be very high. By combining the image degradation model and local maximum color value prior, we propose to recover the un-degraded im- ages under low lighting conditions. Last, an adaptive expo- sure adjustment module is proposed to obtain the final result. We show that our approach enables better enhancement com- paring with popular image editing tools and academic algo- rithms.

关键词： low lighting enhancement image degradationmodel

A pixel-based outlier-free motion estimation algorithm for scalable video quality enhancement

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Frontiers of Computer Science 2015年第5期9卷 729-740页

作者： Xuan dong Jiangtao wen Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Scalable video quality enhancement refers to the process of enhancing low quality frames using high quality ones in scalable video bitstreams with time-varying qualities. A key problem in the enhancement is how to search for correspondence between high quality and low quality frames. Previous algorithms usually use block-based motion estimation to search for correspondences. Such an approach can hardly estimate scale and rotation transforms and always in- troduces outliers to the motion estimation results. In this paper, we propose a pixel-based outlier-free motion estimation algorithm to solve this problem. In our algorithm, the motion vector for each pixel is calculated with respect to estimate translation, scale, and rotation transforms. The motion relationships between neighboring pixels are considered via the Markov random field model to improve the motion estimation accuracy. Outliers are detected and avoided by taking both blocking effects and matching percentage in scale- invariant feature transform field into consideration. Experiments are conducted in two scenarios that exhibit spatial scalability and quality scalability, respectively. Experimental results demonstrate that, in comparison with previous algorithms, the proposed algorithm achieves better correspondence and avoids the simultaneous introduction of outliers, especially for videos with scale and rotation transforms.

关键词： motion estimation scalable video coding videosuper resolution.

Light tuning CO/H_(2)composition on Ag:Unraveling CO_(2)mass transfer and electron-phonon coupling in plasmon-enhanced electrocatalysis

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Nano Research 2025年第1期18卷 173-185页

作者： Rui Lin dong Fan Luca MBerger Thomas Possmayer Yu Zhou Jiexin zhu Xingbao Chen wen Luo Lars Allmendinger Andreas Tittl Leonardo de Souza Menezes Guillaume Maurin Shihe Yang and Stefan AMaier Nanoinstitute Munich Faculty of PhysicsLudwig-Maximilians-Universität München80539 MunichGermany Institut Charles Gerhardt Montpellier UMR 5253 CNRS ENSCM UniversitéMontpellierPlace E.Bataillon34090 MontpellierFrance Guangdong Provincial Key Lab of Nano-Micro Material Research School of Advanced MaterialsPeking University Shenzhen Graduate SchoolShenzhen 518055China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Faculty of Chemistry and Pharmacy Ludwig-Maximilians-Universität München81377 MunichGermany Departamento de Física Universidade Federal de Pernambuco50670-901 Recife-PEBrazil School of Physics and Astronomy Monash University Clayton CampusMelbourneVictoria 3800Australia Department of Physics Imperial College LondonSW72AZ LondonUK

Plasmon-enhanced electrocatalysis(PEEC)is an emerging approach to mitigate CO_(2)*** mechanisms behind CO_(2)adsorption and reduction at the catalyst-electrolyte interface in PEEC still need to be further ***,we employ a well-defined Ag nanostructure to elucidate these pivotal *** shining light with wavelengths of 625,525,405 nm on Ag,an adjustable CO/H_(2)ratio from 35 to 1 can be *** reaction pathway changing under plasmonic excitation does not originate from the lowered CO_(2)mass transfer in the vicinity of Ag,as the electrochemical quartz crystal microbalance results unravel that a slightly elevated temperature in bulk electrolyte caused by light irradiation cannot weaken the CO_(2)adsorption at the Ag catalyst-electrolyte *** calculations reveal that optical excitation towards shorter wavelengths leads to a progressive lowered energy barrier for H_(2)formation together with an enhanced energy barrier for^(*)COOH *** thermodynamically suppressed,CO_(2)reduction can still be improved kinetically by optimizing the excitation wavelength and intensity,being accompanied with the enhanced *** absorption spectroscopy results further correlate the higher photocurrent with a prolonged electron-phonon coupling time,verifying that the improvement of CO_(2)reduction kinetics in PEEC can be realized by hot electron harnessing.

关键词： plasmonic catalysis photoelectrochemical CO_(2)reduction CO/H_(2)ratio hot electron generation electronphonon coupling thermal effect