检索结果-南通市图书馆

Analysis of limit cycle oscillations of a typical airfoil section with freeplay

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2013年第4期29卷 583-592页

作者： Si-Jin Zhang Gui-Lin Wen fan peng Zi-Qiang Liu School of Mechanical and Vehicle Engineering Hunan University Institute of Astronautic Aero-Dynamics and Technology

A typical airfoil section system with freeplay is investigated in the paper. The classic quasi-steady flow model is applied to calculate the aerodynamics, and a piecewise-stiffness model is adopted to characterize the non- linearity of the airfoil section＇s freeplay. There are two crit- ical speeds in the system, i.e., a lower critical speed, above which the system might generate limit cycle oscillation, and an upper critical one, above which the system will flutter. Then a Poincar6 map is constructed for the limit cycle os- cillations by using piecewise-linear solutions with and with- out contact in the system. Through analysis of the Poincar6 map, a series of equations which can determine the frequen- cies of period-1 limit cycle oscillations at any flight veloc- ity are derived. Finally, these analytic results are compared to the results of numerical simulations, and a good agree- ment is found. The effects of freeplay value and contact stiffness ratio on the limit cycle oscillation are also analyzed through numerical simulations of the original system. More- over, there exist multi-periods limit cycle oscillations and even complicated ＂chaotic＂ oscillations may occur, which are usually found in smooth nonlinear dynamic systems.

关键词： Freeplay nonlinearity ~ Typical airfoil section ~Limit cycle oscillations ~ Poincar6 map

Design and calculation of low infrared transmittance and low emissivity coatings for heat radiative applications

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2012年第2期19卷 179-184页

作者： Cruang-hai Wang Yue Zhang Da-hai Zhang Jin-peng fan School of Materials Science and Engineering Beihang University Beijing 100191 China National Defence Science ＆ Technology Key Laboratory of Advanced Functional Composites Aerospace Research Institute of Materials and Processing Technology Beijing 100076 China

The infrared transmittance and emissivity of heat-insulating coatings pigmented with various structural particles were studied using Kubelka-Munk theory and Mie theory. The primary design purpose was to obtain the low transmittance and low emissivity coatings to reduce the heat transfer by thermal radiation for high-temperature applications. In the case of silica coating layers constituted with various structural titania particles （solid, hollow, and core-shell spherical）, the dependence of transmittance and emissivity of the coating layer on the particle structure and the layer thickness was investigated and optimized. The results indicate that the coating pigmented with core-shell titania particles exhibits a lower infrared transmittance and a lower emissivity value than that with other structural particles and is suitable to radiative heat-insulating applications.

关键词： scattering pigments coatings transmittance emissivity

Species bias and spillover effects in scientific research on Carnivora in China

在线全文

学校读者我要写书评

暂无评论

Zoological Research 2021年第3期42卷 354-361页

作者： Zhi-Ning Wang Li Yang peng-Fei fan Lu Zhang School of Life Sciences Sun Yat-Sen UniversityGuangzhouGuangdong 510275China

Scientific research provides essential information for conservation of threatened *** deficiency due to insufficient research impedes the design of conservation plans,and research bias may mistakenly direct limited resources to low biodiversity regions or less threatened ***,we conducted a systematic review of published papers,grants,and graduate student training on carnivorans in China to identify species bias and research ***,we collected intrinsic and extrinsic features of carnivorans,and identified features that impact research intensity using generalized linear *** found that the amount of research on carnivorans increased markedly after 2000,but species bias *** and big cats received the greatest research attention,while most small-and medium-sized carnivorans received little attention,thus showing the 80-20 *** with a higher level of endemism and protection under Chinese law received more *** an animal conservation icon in China,the giant panda(Ailuropoda melanoleuca)attracted more than 50%of overall carnivoran research ***,the giant panda also showed spillover effects,i.e.,post-doctoral graduates who studied the giant panda shifted their research focus to other species after graduation,which may help improve research on other ***,to improve and strengthen Carnivora research and conservation,we suggest investing greater effort in species of less concern,training of more graduate students,and reinforcing academic *** such actions are not taken,many carnivoran species will continue being data deficient and threatened.

关键词： Ailuropoda melanoleuca Carnivora Conservation Research bias 80-20 phenomenon

Two New Dihydroflavanoids from Patrinia villosa Juss

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2006年第2期17卷 218-220页

作者： Jin Yong peng Guo Rong fan Yu Tian WU Shanghai Key Laboratory for Pharmaceutical Metabolite Research School of Pharmacy Second Military Medical University Shanghai 200433

Two new dihydroflavonoids were obtained from the traditional Chinese medicinal herb Patrinia villosa Juss. Their structures were elucidated as （2S）-5, 7, 2＇, 6＇-tetrahydroxy-6, 8-di （γ, γ-dimethylallyl） flavanone （1） and （2S）-5, 7, 2＇, 6＇-tetrahydroxy-6-1avandulylated flavanone （2） by spectroscopic methods including UV, IR, HR-TOF-MS, 1D NMR and 2D NMR techniques.

关键词： Patrinia villosa Juss prenylated flavonoids.

Surgical intervention for malignant bowel obstruction caused by gastrointestinal malignancies

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastrointestinal Oncology 2020年第3期12卷 323-331页

作者： peng-Ju Chen Lin Wang Yi-fan peng Nan Chen Ai-Wen Wu Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education) Department of Gastrointestinal Cancer Center Unit Ⅲ Peking University Cancer Hospital and Institute

BACKGROUND Malignant bowel obstruction(MBO)is a common event for end-stage gastrointestinal cancer *** studies had demonstrated manifestations and clinical management of MBO with mixed *** still lack reports of the surgical treatment of *** To analyze the short-term outcomes and prognosis of palliative surgery for MBO caused by gastrointestinal *** A retrospective chart review of 61 patients received palliative surgery between January 2016 to October 2018 was performed,of which 31 patients underwent massive debulking surgery(MDS)and 30 underwent ostomy/by-pass surgery(OBS).The 60-d symptom palliation rate,30-d morbidity and mortality,and overall survival rates were compared between the two *** The overall symptom palliation rate was 75.4%(46/61);patients in the MDS group had significantly higher symptom palliation rate than OBS group(90%vs 61.2%,P=0.016).Patients with colorectal cancer who were in the MDS group showed significantly higher symptom improvement rates compared to the OBS group(overall,76.4%;MDS,61.5%;OBS,92%;P=0.019).However,patients with gastric cancer did not show a significant difference in symptom palliation rate between the MDS and OBS groups(OBS,60%;MDS,80%;P=1.0).The median survival time in the MDS group was significantly longer than in the OBS group(10.9 mo vs 5.3 mo,P=0.05).CONCLUSION For patients with MBO caused by peritoneal metastatic colorectal cancer,MDS can improve symptom palliation rates and prolong survival,without increasing mortality and morbidity rates.

关键词： Gastrointestinal neoplasms Malignant bowel obstruction Metastasis Palliative surgery Prognosis Quality of life

M-estimation for Periodic GARCH Model with High-frequency Data

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2017年第3期33卷 717-730页

作者： peng-ying fan Si-xin WU Zi-long ZHAO Min CHEN School of Economics Beijing Technology and Business University Academy of Mathematics and Systems Science Chinese Academy of Sciences

This paper studies an M-estimator of a proxy periodic GARCH （p, q） scaling model and establishes its consistency and asymptotic normality. Simulation studies are carried out to assess the performance of the estimator. The numerical results show that our M-estimator is more efficient and robust than other estimators without the use of high-frequency data.

关键词： asymptotic normality consistency high-frequency data PGARCH model M-estimator

Monitoring the green evolution of vernacular buildings based on deep learning and multi-temporal remote sensing images

在线全文

学校读者我要写书评

暂无评论

Building Simulation 2023年第2期16卷 151-168页

作者： Baohua Wen fan peng Qingxin Yang Ting Lu Beifang Bai Shihai Wu Feng Xu School of Architecture and Planning Hunan UniversityChangsha 410082China Hunan Key Laboratory of Sciences of Urban and Rural Human Settlements at Hilly Areas Changsha 410082China College of Electrical and Information Engineering Hunan UniversityChangsha 410082China School of Architecture Changsha University of Science and TechnologyChangsha 410004China

The increasingly mature computer vision(CV)technology represented by convolutional neural networks(CNN)and available high-resolution remote sensing images(HR-RSIs)provide opportunities to accurately measure the evolution of natural and artificial environments on Earth at a large *** on the advanced CNN method high-resolution net(HRNet)and multi-temporal HR-RSIs,a framework is proposed for monitoring a green evolution of courtyard buildings characterized by their courtyards being roofed(CBR).The proposed framework consists of an expert module focusing on scenes analysis,a CV module for automatic detection,an evaluation module containing thresholds,and an output module for data *** on this,the changes in the adoption of different CBR technologies(CBRTs),including light-translucent CBRTs(LT-CBRTs)and non-lighttranslucent CBRTs(NLT-CBRTs),in 24 villages in southern Hebei were identified from 2007 to *** evolution of CBRTs was featured as an inverse S-curve,and differences were found in their evolution stage,adoption ratio,and development speed for different ***-CBRTs are the dominant type but are being replaced and surpassed by NLT-CBRTs in some villages,characterizing different preferences for the technology type of *** proposed research framework provides a reference for the evolution monitoring of vernacular buildings,and the identified evolution laws enable to trace and predict the adoption of different CBRTs in a particular *** work lays a foundation for future exploration of the occurrence and development mechanism of the CBR phenomenon and provides an important reference for the optimization and promotion of CBRTs.

关键词： courtyard buildings evolution deep learning high-resolution network remote sensing images

A Unified Thermodynamic Model of Flow-induced Crystallization of Polymer

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 Journal of Polymer Science 2021年第11期39卷 1489-1495页

作者： Cui Nie fan peng Ting-Yu Xu Jun-fang Sheng Wei Chen Liang-Bin Li National Synchrotron Radiation Laboratory Anhui Provincial Engineering Laboratory of Advanced Functional Polymer FilmCAS Key Laboratory of Soft Matter ChemistryUniversity of Science and Technology of ChinaHefei 230026China

We propose a unified thermodynamic model of flow-induced crystallization of polymer(uFIC),which incorporates not only the conformational entropy reduction but also the contributions of flow-induced chain orientation,the interaction of ordered segments,and the free energy of crystal nucleus and crystal ***,it clarifies the determining parameters of the critical crystal nucleus size,and is able to account for the acceleration of nucleation,the emergence of precursor,different crystal morphologies and structures induced by *** on the nucleation barrier under flow,we analyze at which condition precursor may occur and how flow affects the competition among different crystal forms such as orthorhombic and hexagonal phases of *** to the uFIC model,the different crystal morphologies and structures in the flow-temperature space have been clarified,which give a good agreement with experiments of FIC.

关键词： Flow-induced crystallization Unified thermodynamic model Flow-induced chain orientation

Response of ocean climate to different heat-flux perturbations over the North Atlantic in FAFMIP

在线全文

学校读者我要写书评

暂无评论

Advances in Climate Change Research 2023年第4期14卷 546-559页

作者： Wen-Yu YIN Xin GAO Run GUO peng fan Guang-Qing ZHOU International Center for Climate and Environment Sciences Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

The diversity of surface-flux perturbations,especially for heat-flux perturbations,notably leads to uncertainties surrounding the responses of ocean climate under global warming scenarios projected by climate/Earth system ***,when imposing heat-flux perturbations on the models,strong feedback persists between the atmosphere and the ocean,resulting in nearly doubled heat-flux perturbation over the North Atlantic(NA).Herein,quantitative evaluation of the influences of magnitude change of heat-flux perturbations over the NA on the changes in the Atlantic Meridional Overturning Circulation(AMOC),ocean heat uptake(OHU)and dynamic sea level(DSL)has been conducted by analysis of eight coupled model responses to the heat-flux perturbation experiments in the Flux-Anomaly-Forced Model Inter-comparison *** has been demonstrated that the magnitude of the AMOC change is extremely sensitive to the magnitude change of imposed NA heat-flux perturbation,and the weakening amplitude of the AMOC is nearly halved as the imposed heat-flux perturbation F is halved over the *** most remarkable responses of both DSL and OHU to the magnitude changes of NA heat-flux perturbation have been primarily found in the Atlantic and Arctic basins,especially for the NA *** the added ocean heat uptake(OHUa)and redistributed ocean heat uptake(OHUr)play key roles in OHU changes among the various NA heat-flux perturbation *** magnitude change of NA-mean OHUa is almost linearly related to the imposed NA heat-flux perturbation,while the magnitude change of NA-mean OHUr,which is primarily caused by AMOC change and redistributed heat flux,is not proportional to the imposed NA heat-flux *** is a nearly linear relationship between the magnitude of AMOC change and the OHUr in tropical regions,including the regions in the low-latitude South Atlantic,the tropical Pacific Ocean and the Indian Ocean.

关键词： Heat-flux perturbation Ocean heat uptake North Atlantic Atlantic meridional overturning circulation Coupled general circulation model