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水流作用下桩基局部水沙动力特征数值模拟

水利水运工程学报 2024年第5期 42-53页

作者：伍志元李昂蒋昌波高凯陈杰邓斌长沙理工大学水利与环境工程学院湖南长沙410114 水沙科学与水灾害防治湖南省重点实验室湖南长沙410114 湖南工业大学土木工程学院湖南株洲412007

基于VOF方法追踪水气界面,利用不可压缩流体连续方程和运动方程对流体进行描述,通过嵌套网格技术建立三维数值水槽,湍流采用RNG k–ε模型,泥沙运动基于van Rijn方法。基于验证后的数值水槽模型,开展水流作用下高桩承台结构局部水动力... 详细信息

基于VOF方法追踪水气界面,利用不可压缩流体连续方程和运动方程对流体进行描述,通过嵌套网格技术建立三维数值水槽,湍流采用RNG k–ε模型,泥沙运动基于van Rijn方法。基于验证后的数值水槽模型,开展水流作用下高桩承台结构局部水动力和冲刷规律研究,讨论不同来流条件下桩基桩周流场分布、泥沙输运和床面局部冲刷特征。结果表明,桩基冲刷特征受冲刷时间、流速、水位、水流攻角等来流条件的影响,同时也受桩间距的影响。当流速较小时,高桩承台桩基各桩之间相互作用较小,泥沙冲淤形态彼此独立,与单桩冲刷特征相似。流速较大时,前桩对后桩出现较为明显的遮蔽作用,前桩水流涡旋影响后桩,后桩周围流速明显降低,此时泥沙冲刷坑彼此相连构成群桩整体冲刷坑,且在最后排桩桩间形成条状冲刷坑,冲刷深度最大。

关键词：桩基结构高桩承台局部冲刷水沙动力

Lower Bifidobacteria counts in both duodenal mucosa-associated and fecal microbiota in irritable bowel syndrome patients

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World Journal of Gastroenterology 2009年第23期15卷 2887-2892页

作者： angèle PM Kerckhoffs Melvin Samsom Michel E van der Rest Joris de Vogel Jan Knol Kaouther Ben-Amor Louis MA Akkermans Gastrointestinal Research Unit Department of Gastroenterology and Surgery University Medical Center Utrecht Heidelberglaan 100 F02.618 3584CX Utrecht The Netherlands BioVisible BV LJ Zielstraweg 1 9713 GX Groningen The Netherlands Danone Research-Centre for Specialized Nutrition Bosrandweg 20 6704PH Wageningen The Netherlands

AIM: to determine the composition of both fecal and duodenal mucosa-associated microbiota in irritable bowel syndrome (IBS) patients and healthy subjects using molecular-based techniques. MEtHODS: Fecal and duodenal mucosa brush samples were obtained from 41 IBS patients and 26 healthy subjects. Fecal samples were analyzed for the composition of the total microbiota using fluorescent in situ hybridization (FISH) and both fecal and duodenal brush samples were analyzed for the composition of bif idobacteria using real-time polymerase chain reaction. RESULtS: the FISH analysis of fecal samples revealed a 2-fold decrease in the level of bifidobacteria (4.2 ± 1.3 vs 8.3 ± 1.9, P tients compared to healthy subjects, whereas no major differences in other bacterial groups were observed. At the species level, Bifidobacterium catenulatum levels were significantly lower (6 ± 0.6 vs 19 ± 2.5, P the IBS patients in both fecal and duodenal brush samples than in healthy ***: Decreased bifidobacteria levels in both fecal and duodenal brush samples of IBS patients compared to healthy subjects indicate a role for microbiotic composition in IBS pathophysiology.

关键词： Irritable bowel syndrome Gut microbiota Bifidobacteria Bifidobacterium catenulatum

Optimization of sodium hydroxide for securing high thermoelectric performance in polycrystalline Sn1−xSe via anisotropy and vacancy synergy

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InfoMat 2020年第6期2卷 1201-1215页

作者： Xiao-Lei Shi Wei-Di Liu ang-Yin Wu van tNguyen Han Gao Qiang Sun Raza Moshwan Jin Zou Zhi-Gang Chen Centre for Future Materials University of Southern QueenslandSpringfield CentralQueenslandAustralia Materials Engineering The University of QueenslandBrisbaneQueenslandAustralia Centre for Microscopy and Microanalysis The University of QueenslandBrisbaneAustralia

the morphology and composition are two key factors to determine the thermoelectric performance of aqueously synthesized tin selenide(SnSe)crystals;however,their controlling is still under *** this study,we report a high figure-of-merit(Zt)of1.5 at 823 K in p-type polycrystalline Sn1−xSe resulted from a synergy of morphology control and vacancy optimization,realized by carefully tuning the sodium hydroxide(NaOH)concentration during solvothermal *** a comprehensive investigation on various NaOH concentrations,it was found that an optimized NaOH amount of 10 mL with a concentration of 10 mol L^−1 can simultaneously achieve a large average crystal size and a high Sn vacancy concentration of2.5%.the large microplate-like crystals lead to a considerable anisotropy in the sintered pellets,and the high Sn vacancy level contributes to an optimum hole concentration to the level of2.3×10^19 cm^−3,and in turn a high power factor of7.4μW cm^−1 K^−2 at 823 K,measured along the direction perpendicular to the sintering *** addition,a low thermal conductivity of0.41 W m^−1 K^−1 is achieved by effective phonon scattering at localized crystal imperfections including lattice distortions,grain boundaries,and vacancy domains,as observed by detailed structural ***,a competitive compressive strength of52.1 MPa can be achieved along the direction of high thermoelectric performance,indicating a mechanically robust *** study provides a new avenue in achieving high thermoelectric performance in SnSe-based thermoelectric materials.

关键词： anisotropy sodium hydroxide thermoelectric tin selenide vacancy

Diffusion of Solar Energy Use in the Built Environment Supported by New Design

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Journal of Civil Engineering and Architecture 2014年第2期8卷 253-260页

作者： Marina van Geenhuizen Joop Schoonman angèle Reinders Faculty of technology Policy and Management Delft University of Technology Delft 2628 CE The Netherlands Faculty of Applied Sciences Delft University of Technology Delft 2628 CE The Netherlands Faculty of Engineering technology Univiversity of Twente Enschede 7500 AR The Netherlands Faculty of lndustrial Design Engineering Delft University of Technology Delft 2628 CE The Netherlands

Places of large potentials of sustainable energy production and places of large energy consumption are often very different and separated by large distances across the globe. this paper first discusses potentials of solar technology in terms of global availability using PV （photovoltaic） technology and actual energy production. Solar energy is widely under-used and one way to reduce this is to improve production in low-energy places with high demand： large cities. According to this option, about 40% of the electricity consumption in the built environment could be produced by solar PV systems and energy storage systems. this paper discusses conditions in the built environment and functional and design qualities enabling an increased diffusion of the technologies In a comparative analysis of PV technologies, the criteria taken into account encompass efficiency of the type of solar cell and commercial availability. Special attention is paid to the design features of different PV systems, like flexibility, colour and transparency that might help in their utilization as integrated in building material and ornaments in modem architecture. the same procedure is followed for electricity storage devices. the preliminary conclusion is that at present the freedom of design is largest for a combination of crystalline silicon PV cells and Li-ion batteries.

关键词： Solar PV energy systems battery storage systems design qualities built environment.

Anomalously enhanced thermal stability of phosphorene via metal adatom doping: An experimental and first-principles study

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Nano Research 2016年第9期9卷 2687-2695页

作者： Xuewei Feng Vadym V.Kulish Ping Wu xinke Liu Kah-Wee ang Department of Electrical and Computer Engineering National University of Singapore4 Engineering Drive 3Singapore 117583Singapore Entropic Interface Group(EIG) Engineering Product DevelopmentSingapore University of Technology and Design(SUTD)8 Somapah RoadSingapore 487372Singapore College of Materials Science and Engineering Shenzhen Engineering Laboratory for Advanced Technology of CeramicsNanshan District Key Lab for Biopolymer and Safety EvaluationShenzhen University3688 Nanhai AvenueShenzhen 518060China

Atomically thin black phosphorus, also known as phosphorene, is an emerging two-dimensional (2D) material, which has attracted increasing attention due to its unique electronic and optoelectronic properties. However, the reduced thermal stability of phosphorene limits its suitability for high-temperature fabrication processes, which could be detrimental for the performance of phosphorenebased devices. Here, we investigate the impact of doping by Al and Hf transition metal adatoms on the thermal stability of phosphorene. the formation of Al–P covalent bonds was found to significantly improve the thermal coefficients of the Ag1, B2g, and Ag2phonon modes to 0.00044, 0.00081, and 0.00012 cm–1·°C–1, respectively, which are two orders of magnitude lower than those observed for pristine P–P bonds (~0.01 cm–1·°C–1). First-principles calculations within the density functional theory framework reveal that the observed thermal stability enhancement in the Al-doped material reflects a significantly higher Al binding energy, due to the stronger Al–P bonds compared to the weak van der Waals interactions between adjacent P atoms in the undoped material. the present work thus paves the way towards phosphorene materials with improved structural stability, which could be promising candidates for potential nanoelectronic and optoelectronic applications. [Figure not available: see fulltext.] © 2016, tsinghua University Press and Springer-Verlag Berlin Heidelberg.

关键词： phosphorene black phosphorus adatom doping transition metals thermal stability

Static Crack Propagation of Carbon Nanotube through Non-Bonded Interface of Nanocomposites

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World Journal of Nano Science and Engineering 2014年第2期4卷 42-49页

作者： Khondaker Sakil Ahmed ang Kok Keng Department of Civil & Environmental Engineering National University of Singapore Singapore City Singapore

this study presents an analytical shear-lag model to illustrate the interface crack propagation of carbon nanotube (CNt) reinforced polymer-matrix composites (PMCs) using representative volume element (RVE). In the model, a 3D cylindrical RVE is picked to present the nanocomposite in which CNt/polymer chemically non-bonded interface is taken into consideration. In the non-bonded interface, the stress transfer of CNt is generally considered to be controlled by the combined contribution of mechanical interlocking, thermal residual stress, Poisson’s contraction and van der Waals (vdW) interaction. Since CNt/matrix interface becomes debonded due to crack propagation, vdW interaction which is a function of relative radial displacement of the CNt/matrix interface makes the modeling of the interface tricky and challenging. In order to solve this complexity, an iterative approach is proposed to calculate the vdW interaction for debonded CNt/matrix interface accurately. the analytical results aim to obtain the characteristics load displacement relationship in static crack propagation for CNt reinforced PMCs.

关键词： Polymer-Matrix Composites (PMCs) Interface Computational Modelling Crack Propagation

Coaxial boron nitride nanotubes as interfacial dielectric layers to lower interface trap density in carbon nanotube transistors

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Nano Research 2023年第11期16卷 12840-12848页

作者： Keigo Otsuka taiki Sugihara taiki Inoue Weijie Jia Satoru Matsushita takanobu Saito Minhyeok Lee takashi taniguchi Kenji Watanabe Gregory Pitner Ming-Yang Li tzu-ang Chao Rong Xiang Shohei Chiashi Shigeo Maruyama Department of Mechanical Engineering The University of TokyoTokyo 113-8656Japan Department of Applied Physics Osaka UniversityOsaka 565-0871Japan Research Center for Materials Nanoarchitectonics National Institute for Materials ScienceTsukuba 305-0044Japan Research Center for Electronic and Optical Materials National Institute for Materials ScienceTsukuba 305-0044Japan Corporate Research Taiwan Semiconductor Manufacturing CompanySan JoseCA 95134USA Corporate Research Taiwan Semiconductor Manufacturing CompanyHsinchu 30078

A semiconductor/dielectric interface is one of the dominant factors in device characteristics,and a variety of oxides with high dielectric constants and low interface trap densities have been used in carbon nanotube *** the crystal structure of nanotubes with no dangling bonds,there remains room to investigate unconventional dielectric ***,we fabricate carbon nanotube transistors with boron nitride nanotubes as interfacial layers between channels and gate dielectrics,where a single semiconducting nanotube is used to focus on switching behaviors at the subthreshold *** subthreshold swing of 68 mV·dec^(−1)is obtained despite a 100-nm-thick Sio_(2)dielectric,corresponding to the effective interface trap density of 5.2×10^(11)cm^(−2)·eV^(−1),one order of magnitude lower than those of carbon nanotube devices without boron nitride *** interfacial layers also result in the mild suppression of threshold voltage variation and *** achieve Ohmic contacts through the selective etching of boron nitride nanotubes with XeF2 gas,overcoming the trade-off imposed by wrapping the inner *** impacts of fluorinating carbon nanotubes on device performances are also confirmed as long as the etching is applied exclusively at source/drain *** results represent an important step toward nanoelectronics that exploit the advantage of one-dimensional van der Waals heterostructures.

关键词： carbon nanotubes hexagonal boron nitride van der Waals interfaces field-effect transistors subthreshold swing selective etching

Dual-sized hollow particle incorporated fibroin thermal insulating coatings on catheter for cerebral therapeutic hypothermia

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Bioactive Materials 2023年第8期26卷 116-127页

作者： Ming Li Yuan Gao Miaowen Jiang Hongkang Zhang Yang Zhang Yan Wu Wenhao Zhou Di Wu Chuanjie Wu Longfei Wu Luzi Bao Xiaoxiao Ge Zhengfei Qi Ming Wei ang Li Yuchuan Ding Jicheng Zhang Guangzhen Pan Yu Wu Yan Cheng Yufeng Zheng Xunming Ji China-America Institute of Neuroscience and Beijing Institute of Geriatrics Xuanwu HospitalCapital Medical UniversityBeijing100053China School of Instrumentation and Optoelectronic Engineering Beihang UniversityBeijing100191China Beijing Institute for Brain Disorders Capital Medical UniversityBeijing100069China School of Materials Science and Engineering Peking UniversityBeijing100871China Shaanxi Key Laboratory of Biomedical Metallic Materials Northwest Institute for Nonferrous Metal ResearchXi’an710016China Department of Biomedical Engineering Columbia UniversityNew York CityNY10027USA Department of Neurosurgery Wayne State University School of MedicineDetroitMI48201USA Gong Yi van-research Innovation Composite Material Co.Ltd Zheng Zhou451299China Department of Neurosurgery Xuanwu HospitalCapital Medical UniversityBeijing100053China

Selective endovascular hypothermia has been used to provide cooling-induced cerebral neuroprotection,but current catheters do not support thermally-insulated transfer of cold infusate,which results in an increased exit temperature,causes hemodilution,and limits its cooling ***,air-sprayed fibroin/silica-based coatings combined with chemical vapor deposited parylene-C capping film was prepared on *** coating features in dual-sized-hollow-microparticle incorporated structures with low thermal *** infusate exit temperature is tunable by adjusting the coating thickness and infusion *** peeling or cracking was observed on the coatings under bending and rotational scenarios in the vascular *** efficiency was verified in a swine model,and the outlet temperature of coated catheter(75μm thickness)was 1.8-2.0◦C lower than that of the uncoated *** pioneering work on catheter thermal insulation coatings may facilitate the clinical translation of selective endovascular hypothermia for neuroprotection in patients with acute ischemic stroke.

关键词： Silk fibroin thermal insulation coating Catheter Stroke Hypothermia

Graphene-based catalysts for electrochemical carbon dioxide reduction

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Carbon Energy 2020年第2期2卷 158-175页

作者： Amirhossein Hasani Mahider Asmare teklagne Ha Huu Do Sung Hyun Hong Quyet van Le Sang Hyun Ahn Soo Young Kim School of Chemical Engineering and Materials Science Integrative Research Center for Two-Dimensional Functional MaterialsInstitute of Interdisciplinary Convergence ResearchChung-Ang UniversitySeoulRepublic of Korea Department of Materials Science and Engineering Korea UniversitySeoulRepublic of Korea Institute of Research and Development Duy Tan UniversityDa NangVietnam

Electrochemical carbon dioxide(CO2)reduction is considered to be an efficient strategy to produce usable fuels and overcome the concerns regarding global *** this purpose,an efficient,earth abundant,and a low cost catalyst has to be *** has been found that graphene-based materials could be promising candidates for CO2 conversion because of their unique physical,mechanical,and electronic *** addition,the surface of graphenebased materials can be modified by using different strategies,including doping,defect engineering,producing composite structures,and wrapping *** this review,the fundamentals of electrochemical CO2 reduction and recent progress of graphene-based catalysts are ***,recent studies on graphene-based materials for CO2 reduction are summarized.

关键词： catalyst CO2 reduction electrochemical graphene