检索结果-南通市图书馆

Water hammer prediction and control:the Green's function method

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2012年第2期28卷 266-273页

作者： Li-Jun xuan Feng mao Jie-Zhi Wu State Key Laboratory of Turbulence and Complex System College of EngineeringPeking University100871 BeijingChina

By Green＇s function method we show that the water hammer （WH） can be analytically predicted for both laminar and turbulent flows （for the latter, with an eddy vis- cosity depending solely on the space coordinates）, and thus its hazardous effect can be rationally controlled and mini- mized. To this end, we generalize a laminar water hammer equation of Wang et al. （J. Hydrodynamics, B2, 51, 1995） to include arbitrary initial condition and variable viscosity, and obtain its solution by Green＇s function method. The pre- dicted characteristic WH behaviors by the solutions are in excellent agreement with both direct numerical simulation of the original governing equations and, by adjusting the eddy viscosity coefficient, experimentally measured turbulent flow data. Optimal WH control principle is thereby constructed and demonstrated.

关键词： Water hammer Two-dimensional analytical theory - Pressure transients Pipe-valve flow control

Role of in-situ formed free carbon on electromagnetic absorption properties of polymer-derived SiC ceramics

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2020年第5期9卷 617-628页

作者： Zhaoju YU xuan LV Kangwei mao Yujing YANG Anhua LIU College of Materials Key Laboratory of High Performance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen 361005China College of Materials Fujian Key Laboratory of Advanced Materials(Xiamen University)Xiamen 361005China Shenzhen Research Institute of Xiamen University Shenzhen 518000China

In order to enhance dielectric properties of polymer-derived SiC ceramics,a novel single-source-precursor was synthesized by the reaction of an allylhydrido polycarbosilane(AHPCS)and divinyl benzene(DVB)to form carbon-rich *** expected,the free carbon contents of resultant SiC ceramics annealed at 1600℃are significantly enhanced from 6.62 wt%to 44.67 wt%.After annealing at 900-1600℃,the obtained carbon-rich SiC ceramics undergo phase separation from amorphous to crystalline feature where superfine SiC nanocrystals and turbostratic carbon networks are dispersed in an amorphous SiC(O)*** dielectric properties and electromagnetic(EM)absorption performance of as-synthesized carbon-rich SiC ceramics are significantly improved by increasing the structural order and content of free *** the 1600℃ ceramics mixed with paraffin wax,the minimum reflection coefficient(RCmin)reaches-56.8 dB at 15.2 GHz with the thickness of 1.51 mm and a relatively broad effective bandwidth(the bandwidth of RC values lower than-10 dB)of 4.43 GHz,indicating the excellent EM absorption *** carbon-rich SiC ceramics have to be considered as harsh environmental EM absorbers with excellent chemical stability,high temperature,and oxidation and corrosion resistance.

关键词： polymer-derived ceramics(PDCs) microstructural evolution dielectric properties electromagnetic properties

Preparation,crystallization,and wetting of ZnO-Al_2O_3-B_2O_3-SiO_2 glass-ceramics for sealing to Kovar

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2009年第5期16卷 586-591页

作者： mao Wu Xin-bo He Zhuo-shen Shen xuan-hui Qu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

A novel type of ZnO-Al2O3-B2O3-SiO2 glass-ceramics sealing to Kovar in electronic packaging was developed, whose thermal expansion coefficient and electrical resistance are 5.2× 10^-6/℃ and over 1×10^13 Ω·cm, respectively. The major crystalline phases in the glass-ceramic seals were ZnAl2O4, ZnB2O4, and NaSiAl2O4. The dielectric resistance of the glass-ceramic could be remarkably enhanced through the control of alkali metal ions into crystal lattices. It was found that crystallization happened first on the surface of the sample, leaving the amorphous phase in the inner, which made the glass suitable for sealing. The glass-ceramic showed better wetting on the Kovar surface, and sealing atmosphere and temperature had great effect on the wetting angle. Strong interracial bonding was obtained, which was mainly attributed to the interracial reaction between SiO2 and FeO or Fe3O4.

关键词： electronic packaging materials glass-ceramic crystallization wetting sealing

Optimization Study on Expansion Energy Used Air-Powered Vehicle with Pneumatic-Hydraulic Transmission

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2018年第1期31卷 220-229页

作者： Xiang-Heng Fu mao-Lin Cai Yi-xuan Wang Yan Shi School of Automation Science and Electrical Engineering Beihang University The State Key Laboratory of Fluid Power & Mechatronic Systems Zhejiang University

Pneumatic-hydraulic transmission has been developed for years. However, its dynamic properties are not good enough for application. In this paper, in order to increase the output characteristics, a late-model air-powered vehicle using expansion energy is proposed which can boost energy through a pneumatic-hydraulic transmission. The dynamic characteristics of the air-powered vehicle is modeled and verified by conducting experiment. In addition,the influence of the key parameters of the air-powered vehicle is researched for the optimization of the system performance. Through the results, the author got the conclusion that, firstly, comparison of the results of model and experiment proves the built model to be effective; secondly, input air pressure should be set according to the request of the practical loads, and range of 0.65 to 0.75 MPa can be chosen; thirdly, as a key structure parameter of the airpowered vehicle, ratio of the areas is considered to be set to approximate 8; what’s more, a bigger orifice with a limit will promote the system dynamic characteristic property, and the limit is about 3.5 mm; last but not the least, not too farther position of the rings will increase the quality of output dynamic characteristics. This paper can be a reference for system design of air-powered vehicle and dynamic improvement.

关键词： Air-powered vehicle Expansion energy Pneumatic-hydraulic transmission Output dynamic characteristics

Evaluation Method of Software Reliability Based on SPN Model

在线全文

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2016年第3期21卷 242-248页

作者： PAN Ping mao Xinyue ZHU xuan College of Computer Science and Technology Guizhou University

As a significant measure of software security evaluation, software reliability evaluation is also the basis of software safe operation. Traditional software system security evaluation methods are qualitative evaluation based on the functional and structural measurements, and it often ignores quantitative research based on invalidity and fault. This paper propose a stochastic transition function as a measure parameters of the reliability of stochastic Petri nets （SPN） theory. By calculating the probability of stability of the system, failure and mean time to first failure, it establishes an evaluation and measurement method for software reliability. With example analysis, the method can conduct effective evaluation on the software reliability index quickly and accurately, and meanwhile provides a new method for the software security evaluation.

关键词： stochastic Petri nets (SPN) software reliability evaluation

Perturbation of autophagy pathways in murine alveolar macrophage by 2D TMDCs is chalcogen-dependent

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2024年第1期135卷 97-107页

作者： Xiaofei Zhou Weitao Jin Rui Zhang xuan.mao Jianbo Jia Hongyu Zhou College of Science&Technology Hebei Agricultural UniversityHuanghua 061100China Institute of Environmental Research at Greater Bay Area Key Laboratory for Water Quality and Conservation of the Pearl River DeltaMinistry of EducationGuangzhou UniversityGuangzhou 510006China

Increasing risks of incidental and occupational exposures to two-dimensional transition metal dichalcogenides(2D TMDCs)due to their broad application in various areas raised their public health *** the composition-dependent cytotoxicity of 2D TMDCs has been well-recognized,how the outer chalcogenide atoms and inner transition metal atoms differentially contribute to their perturbation on cell homeostasis at non-lethal doses remains to be *** the present work,we compared the autophagy induction and related mechanisms in response to WS_(2),NbS_(2),WSe_(2)and Nb Se_(2)nanosheets exposures in MH-S murine alveolar *** these 2D TMDCs had comparable physicochemical properties,overall cytotoxicity and capability in triggering autophagy in MH-S cells,but showed outer chalcogen-dependent subcellular localization and activation of autophagy ***,WS_(2)and NbS_(2)nanosheets adhered on the cell surface and internalized in the lysosomes,and triggered m TOR-dependent activation of ***,WSe_(2)and Nb Se_(2)nanosheets had extensive distribution in cytoplasm of MH-S cells and induced autophagy in an m TOR-independent ***,the 2D TMDCs-induced perturbation on autophagy aggravated the cytotoxicity of respirable benzo[a]*** findings provide a deeper insight into the potential health risk of environmental 2D TMDCs from the perspective of homeostasis perturbation.

关键词： Chalcogen group Autophagy pathway Cell function Endosomal escape Inhalation toxicity

On the governing equations for the compressing process and its coupling with other processes

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第6期54卷 1154-1167页

作者： mao Feng SHI YiPeng xuan LiJun SU WeiDong WU JieZhi State Key Laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing 100871China University of Tennessee Space Institute TullahomaTN 37388USA

As a continuation of a recent linear analysis by mao et al.(Acta Mech Sin,2010,26:355),in this paper we propose a general theoretical formulation for the compressing process in complex Newtonian fluid flows,which covers gas dynamics,aeroacoustics,nonlinear thermoviscous acoustics,viscous shock layer,etc.,as its special *** principle on which our formulation is based is the maximally natural and dynamic Helmholtz decomposition of the Navier-Stokes equation,along with the kinematic Helmholtz decomposition of the velocity *** central results are the new dilatation equation and velocity-potential equation,which are the counterparts of vorticity transport equation and vector stream-function equation for the shearing process,*** couplings of the compressing process with shearing and thermal processes,including its physical sources,are carefully *** the possible applications and influences of the new formulation are yet to be explored,our preliminary discussion on the pros and cons of previous formulations pertain to acoustic analogy and that on the process splitting and coupling in highly compressible turbulence indicates that at least the formulation can serve as a new frame of reference by which one may gain some additional insight and thereby develop new approaches to the multi-process complex flow problems.

关键词： longitudinal (compressing) process transversal (shearing) process Helmholtz decomposition aeroacoustics compressible turbulence

Supramolecular Vesicles Based on Water-Soluble 2,6-Helic[6]arene:High Affinity Binding,Stimuli Responsiveness and Delivery of Doxorubicin to Cancer Cells

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2019年第6期37卷 575-580页

作者： xuan Yang Weipeng mao Yamin Liu Libai Li Da Ma Department of Chemistry Fudan University220 Handan RoadShanghai 200433China

Water-soluble 2,6-helic[6]arene was used to construct supramolecular vesicles via host-guest interaction. Water-soluble 2,6-helic[6]arene was discovered to be high affinity host for suitable biomarkers. Supramolecular vesicles were responsive to multiple stimuli types, including temperature, pH, Ca^2+, CO2 bubbling and biomarker displacement. Supramolecular vesicles were used to load and deliver anti-tumor drug doxorubicin to HeLa cells in vitro.

关键词： host-guest systems nanostructures molecular recognitions self-assembly supramolecular vesicles

Preparation of Agarose Sulfate and Its Antithrombogenicity

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2012年第1期27卷 110-114页

作者： JIE Youping ZHANG Lingmin CHEN Peng mao xuan TANG Shunqing Biomedical Engineering Institute Jinan UniversityGuangzhou 510632China

As one of the seaweed polysaccharide, agarose has received much attention because of its biocompatibility. However, its application in biomedical field was limited with its biological inertia. Modification with some functional groups is needed to obtain agarose derivatives with biological activity and expand its applications. Consequently, agarose was sulfated with chlorosulfonic acid-pyridine with formamide as dispersing agent. The orthogonal test result showed that the optimal reaction condition was the reaction time being 4 h, the reaction temperature 65 ℃ and the ratio of chlorosulfonic acid to agarose 1-4（mL/g）. Two kinds of the insoluble agarose sulfate （below 37 ℃） were synthesized with degree of substitution （DS） being 0.17 and 0.43 respectively. Infrared spectroscopy （IR） and tac nuclear magnetic resonance （13C-NMR） spectroscopy results proved that C3_6 in agarose was sulfated. Their hydrophobic property and BSA adsorption capacity rose with increasing DS, while the adsorption of lib was reduced. The anti-clotting properties of agarose sulfate were significantly improved, and agarose sulfate could protect red blood cells from deformation after adsorption of BSA. These findings demonstrate that the cold-water insoluble agarose sulfate has a promise for applications as heoarin-like material in anticoagulation or endothelial re^enera＇Lion scaffold.

关键词： coal gangue copper tailings XRD oxygen-rich minerals