检索结果-南通市图书馆

A high-resolution numerical investigation of unsteady wake vortices for coaxial rotors in hover

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第11期37卷 278-299页

作者： Shaoqiang HAN Wenping SONG Zhonghua HAN jianhua xu Tianfu Engineering-oriented Numerical&Software Innovation Center College of Computer ScienceSichuan UniversityChengdu 610065China National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of AeronauticsNorthwestern Polytechnical UniversityXi’an 710072China

High-resolution numerical simulations for wake vortical flows have long been a challenge in rotor aerodynamics.A novel spectrum-optimized sixth-order Weighted Essentially NonOscillatory(WENO)scheme is proposed to discretize inviscid fluxes on moving overset grids,and the Improved Delayed Detached Eddy Simulation(IDDES)is employed to resolve turbulent *** integration of these methods facilitates a comprehensive numerical investigation into the unsteady vortical flows over coaxial rotors in *** results highlight the substantial improvement in numerical resolution,in terms of both spatial structure and temporal evolution of unsteady multiscale wake *** rotors in hover manifest three primary scales of wake vortex structures:(A)the helical evolution of primary blade tip vortices and the periodic occurrence of strong Blade-Vortex Interactions(BVI);(B)the continuous shedding of small-scale horseshoeshaped vortices from the trailing edges of rotor blades,forming the vortex sheets;(C)the emergence of small-scale secondary vortex braids induced by interactions between rotor tip vortices and the vortex *** vortex structures and their interactions cause high-frequency oscillations in rotor disk loads and induce unsteady perturbations in the local flow *** among these primary vortices,coupled with the generation of secondary vortices,result in the dissipation,distortion,and breakup of the rotor tip vortices,ultimately forming a vortex ***,a substantial quantity of seemingly weak small-scale secondary vortex braids significantly contribute to energy dissipation during the evolution of wake vortices for coaxial rotors in hover.ó2024 Chinese Society of Aeronautics and *** and hosting by Elsevier *** is an open access article under the CC BY-NC-ND license(http://***/licenses/by-nc-nd/4.0/).

关键词： Coaxial rotor Blade tip vortex Secondary vortex High-order scheme IDDES Moving overset grid

Long-range cross-correlation between urban impervious surfaces and land surface temperatures

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

Frontiers of Earth Science 2016年第1期10卷 117-125页

作者： Qin NIE jianhua xu Wang MAN Department of Spatial Information Science and Engineering Xiamen University of Technology Xiamen 361024 China The Research Center for East-West Cooperation in China The Key Laboratory of GIScience Ministry of Education of China East China Normal University Shanghai 200241 China

The thermal effect of urban impervious surfaces （UIS） is a complex problem. It is thus necessary to study the relationship between UIS and land surface temperatures （LST） using complexity science theory and methods. This paper investigates the long-range cross- correlation between UIS and LST with detrended cross- correlation analysis and multifractal detrended cross- correlation analysis, utilizing data from downtown Shanghai, China. UIS estimates were obtained from linear spectral mixture analysis, and LST was retrieved through application of the mono-window algorithm, using Landsat Thematic Mapper and Enhanced Thematic Mapper Plus data for 1997-2010. These results highlight a positive long-range cross-correlation between UIS and LST across People＇s Square in Shanghai. LST has a long memory for a certain spatial range of UIS values, such that a large increment in UIS is likely to be followed by a large increment in LST. While the multifractal long-range cross- correlation between UIS and LST was observed over a longer time period in the W-E direction （2002-2010） than in the N-S （2007-2010）, these observed correlations show a weakening during the study period as urbanization increased.

关键词： urban impervious surface land surface temperature long-range cross-correlation Shanghai

Deep oxidation in propane oxidative dehydrogenation to propene over V_2O_5/γ-Al_2O_3 studied by in-situ DRIFTS

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2009年第3期18卷 359-364页

作者： Yunbing He Hongbing Ji jianhua xu Lefu Wang School of Chemistry and Chemical Engineering South China University of Technology Guangzhou 510640 Guangdong China

In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150-250℃ with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.

关键词： propane propene oxidative dehydrogenation in-situ DRIFTS deep oxidation

Preparation and Characteristics of Stearic Acid/PEDOT(PSS) Langmuir-Blodgett Films

在线全文

学校读者我要写书评

暂无评论

稀有金属材料与工程 2006年第A03期35卷 176-177页

作者： Yang Yajie Jiang Yadong xu jianhua School of Optoeletrocnic Information University of Electronic Science and Technology of China Chengdu 610054 China

Mixed Stearic acid and poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) Langmuir- Blodgett(LB) films were successfully fabricated by the conventional vertical dipping *** acid and PEDOT/PSS was dissolved in chloroform and spread on subphase containing 0.04wt% FeCl_*** Y-type mixed LB films was successfully prepared under the condition of surface pressure with 30 mN/m,pH 3.8,and 19℃.UV-VIS spectrum showed that well ordered layer-by-layer fabrication of mixed films were obtained and thickness of single layer film with about 5 nm was *** morphology image of mixed LB film was observed by atomic force microscopy (AFM).The conductivity of mixed LB film was about 1.8×10^(-5)S/cm and the film showed sensitivity to NH_3 at the same time.

关键词： Langmuir-Blodgett PEDOT/PSS AFM mixed LB film

Remote sensing of spatial patterns of urban renewal using linear spectral mixture analysis： A case of central urban area of Shanghai （1997-2000）

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2006年第8期51卷 977-986页

作者： YUE Wenze xu jianhua WU Jiawei xu Lihua College of Southeast Land Management Zhejiang University Hangzhou 310029 China Department of Geography East China Normal University Shanghai 200062 China Zhejiang Forest University Lin'an 311300 China

It is very important to integrate remote sensing with urban geography that the spectral mix- ture analysis technique is applied to urban land cover evolvement and its eco-environmental effect. Urban land cover is mainly composed of complicated artifi- cial materials, which is the key factor to limit the de- velopment of the spectral mixture analysis technique. There are two main aspects in which the technique of spectral mixture analysis is applied to urban geog- raphy: one is to calculate vegetation fraction; the other is to build quantitative model of the urban im- pervious surface obtained from the combination be- tween high albedo fraction and low albedo fraction. The technique of spectral mixture analysis is firstly applied to study urban renewal pattern, scale and mode which happened in Shanghai City from 1997 to 2000.

关键词：遥感分布类型城市更新上海线性光谱分析

Long-term Trend and Fractal of Annual Runoff Process in Mainstream of Tarim River

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2008年第1期18卷 77-84页

作者： xu jianhua CHEN Yaning LI Weihong DONG Shan Key Laboratory of Geographic Information Science Ministry of Education Shanghai 200062 China Department of Geography East China Normal University Shanghai 200062 China The Key Laboratory of Oasis Ecology and Desert Environment Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences Urumqi 830011 China

Based on the time series data from the Aral hydrological station for the period of 1958-2005,the paper re-veals the long-term trend and fractal of the annual runoff process in the mainstream of the Tarim River by using the wavelet analysis method and the fractal *** main conclusions are as follows:1)From a large time scale point of view,*** time scale of 16(24)years,the annual runoff basically shows a slightly decreasing trend as a whole from 1958 to *** the time scale is reduced to 8(23)or 4(22)years,the annual runoff still displays the basic trend as the large time scale,but it has fluctuated more obviously during the period.2)The correlation dimension for the annual runoff process is 3.4307,non-integral,which indicates that the process has both fractal and chaotic *** correlation dimension is above 3,which means that at least four independent variables are needed to describe the dynamics of the annual runoff process.3)The Hurst exponent for the first period(1958-1973)is 0.5036,which equals 0.5 approximately and indicates that the annual runoff process is in *** Hurst exponents for the second(1974-1989)and third(1990-2005)periods are both greater than 0.50,which indicate that the annual runoff process showed a long-enduring characteristic in the two *** Hurst exponent for the period from 1990 to 2005 indi-cates that the annual runoff will show a slightly increasing trend in the 16 years after 2005.

关键词： annual runoff, wavelet fractal Tarim River

Study on Conductivity Properties of PEDOT Prepared through a Modified LB Film Method

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2011年第3期29卷 415-421页

作者： Zheng, Huajing Jiang, Yadong xu, jianhua Yang, Yajie State Key Laboratory of Electronic Thin Films & Integrated Devices School of Optoelectronic Information University of Electronic Science and Technology of China Chengdu Sichuan 610054 China

Adopting LB film method, an arachidic acid （AA）/PEDOT multilayer LB film was chosen, and polymerized EDOT monomers in hydrophilic group of LB to prepare arachidic acid （AA）/PEDOT multilayer LB film. UV-Vis, FT-IR and XPS analyses implied that EDOT was effectively polymerized in film, and thus PEDOT conducting polymer was produced. Analyses of XRR and SIMS indicated that film had a well-arranged lamella structure, and further research showed that polymerization of EDOT in AA film destroyed the orderliness of the original LB film. This phenomenon could be related to the destructive effect of polymerization on layered structure. We used four-point probe and semiconductor instrument to study the conductivity property of the film, and observed that the conductivity of AA/PEDOT film had sudden changes with the processing time of changes in effective conduction network. That was caused by ＂permeability＂ in conducting channel of multilayer film. The test results also indicated that the conductivity of AA/PEDOT film was obviously better than that of spin-coating PEDOT/PSS film or that of ODA-SA/PEDOT-PSS film, which was due to the higher π structure of PEDOT structure and ordered film structure.

关键词： PEDOT LB film method conductivity properties measurement

Climate Change and Its Effects on Runoff of Kaidu River, Xinjiang, China:A Multiple Time-scale Analysis

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

Chinese Geographical Science 2008年第4期18卷 331-339页

作者： xu jianhua CHEN Yaning JI Minhe LU Feng Key Laboratory of Geographic Information Science Ministry of Education Shanghai 200062 China The Research Center for East-West Cooperation in China East China Normal University Shanghai 200062 China The Key Laboratory of Oasis Ecology and Desert Environment Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences Urumqi 830011 China

This paper applied an integrated method combining grey relation analysis, wavelet analysis and statistical analysis to study climate change and its effects on runoff of the Kaidu River at multi-time scales. Major findings are as follows: 1) Climatic factors were ranked in the order of importance to annual runoff as average annual temperature, average temperature in autumn, average temperature in winter, annual precipitation, precipitation in flood season, average temperature in summer, and average temperature in spring. The average annual temperature and annual precipi- tation were selected as the two representative factors that impact the annual runoff. 2) From the 32-year time scale, the annual runoff and the average annual temperature presented a significantly rising trend, whereas the annual precipita- tion showed little increase over the period of 1957-2002. By changing the time scale from 32-year to 4-year, we ob- served nonlinear trends with increasingly obvious oscillations for annual runoff, average annual temperature, and annual precipitation. 3) The changes of the runoff and the regional climate are closely related, indicating that the runoff change is the result of the regional climate changes. With time scales ranging from 32-year, 16-year, 8-year and to 4-year, there are highly significant linear correlations between the annual runoff and the average annual temperature and the annual precipitation.

关键词： runoff temperature precipitation nonlinear trend time scale Kaidu River

Payments for Watershed Services and Practices in China:Achievements and Challenges

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2018年第5期28卷 873-893页

作者： LU Yan xu jianhua QIN Fen WANG Jiayao Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions Ministry of EducationHenan University School of Water Conservancy & Environment Zhengzhou University Henan Industrial Technology Academy of Spatio-Temporal Big Data Henan University College of Environment and Planning Henan University School of Geographic Sciences East China Normal University

Implementation of payments for watershed services(PWS) has been regarded as a promising approach to coordinating the interests of upstream and downstream ecosystem services stakeholders. There is growing concern about whether PWS programs have achieved their original environmental goals of improving water quality and quantity, as well as the ancillary objective of increasing the welfare of local people. We start with an overview of PWS schemes and focus on their particularity and implementation mechanisms in China. We proceed to review 62 active PWS cases and examine their environmental performance in detail. The resulting findings show that PWS schemes have been able to reduce water pollution to some extent by establishing collaborative upstream/downstream watershed management policies, thereby improving water quality and quantity, as well as by making government officials more responsible for water resource management. In addition, their continued effectiveness in light of present challenges such as water-quality data availability is discussed. Chinese PWS schemes and their implementation mechanisms also provide information useful in monitoring environmental outcomes and guiding future designs of PWS programs in other regions.

关键词： payments for watershed services(PWS) environmental impacts water pollution socioeconomic impacts watershed management