检索结果-南通市图书馆

Mixed finite element for two-dimensional incompressible convective Brinkman-Forchheimer equations

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2019年第6期40卷 889-910页

作者： demin liu Kaitai LI College of Mathematics and System Sciences Xinjiang UniversityUrumqi 830046China School of Mathematics and Statistics Xi’an Jiaotong UniversityXi’an 710049China

In this work, the two-dimensional convective Brinkman-Forchheimer equa- tions are considered. The well-posedness for the variational problem and its mixed finite element approximation is established, and the error estimates based on the conforming approximation are obtained. For the computation, a one-step Newton (or semi-Newton) iteration algorithm initialized using a fixed-point iteration is proposed. Finally, numerical experiments using a Taylor-Hood mixed element built on a structured or unstructured triangular mesh are implemented. The numerical results obtained using the algorithm are compared with the analytic data, and are shown to be in very good agreement. Moreover, the lid-driven problem at Reynolds numbers of 100 and 400 is considered and analyzed.

关键词： Brinkman-Forchheimer equations finite element method Newton iteration

Experimental Investigation of Inter-Blade Vortices in a Model Francis Turbine

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2017年第4期30卷 854-865页

作者： demin liu Xiaobing liu Yongzhi ZHAO Key Laboratory of Fluid and Power Machinery of Ministry of Education Xihua University Dongfang Electric Machinery Co. Ltd

The inter-blade vortex in a Francis turbine becomes one of the main hydraulic factors that are likely to cause blade erosion at deep part load operating con- ditions. However, the causes and the mechanism of inter- blade vortex are still under investigation according to present researches. Thus the causes of inter-blade vortex and the effect of different hydraulic parameters on the inter-blade vortex are investigated experimentally. The whole life cycle of the inter-blade vortex is observed by a high speed camera. The test results illustrate the whole life cycle of the inter-blade vortex from generation to separation and even to fading. It is observed that the inter- blade vortex becomes stronger with the decreasing of flow and head, which leads to pressure fluctuation. Meanwhile, the pressure fluctuations in the vane-less area and the draft tube section become stronger when inter-blade vortices exist in the blade channel. The turbine will be damaged if operating in the inter-blade vortex zone, so its operating range must be far away from that zone. This paper reveals the main cause of the inter-blade vortex which is the larger incidence angle between the inflow angle and theblade angle on the leading edge of the runner at deep part load operating conditions.

关键词： Inter-blade vortex Francis turbine Highspeed photography

Numerical predictions and stability analysis of cavitating draft tube vortices at high head in a model Francis turbine

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2014年第11期57卷 2106-2114页

作者： ZUO ZhiGang liu ShuHong liu demin QIN DaQing State Key Laboratory of Hydro Science and Engineering Department of Thermal Engineering Tsinghua University Research & Test Center Dongfang Electric Machinery Co. Ltd State Key Laboratory of Hydro-Power Equipment

Draft tube vortex is one of the main causes of hydraulic instability in hydraulic reaction turbines,in particular Francis turbines.A method of cavitation calculations was proposed to predict the pressure fluctuations induced by draft tube vortices in a model Francis turbine,by solving RANS equations with RNG k-turbulence model and ZGB cavitation model,with modified turbulence *** cases with different flow rates at high head were *** the study case of part load,two modes of revolutions with the same rotating direction,revolution around the axis of the draft tube cone,and revolution around the core of the vortex rope,can be *** elliptical shaped vortex rope causes anisotropic characteristics of pressure fluctuations around the centerline of the draft tube *** analyzing the phase angles of the pressure fluctuations,the role of the vortex rope as an exciter in the oscillating case can be *** analysis of Batchelor instability,*** in q-vortex like flow structure,has been carried out on the draft tube vortices in these three *** can be concluded that the trajectory for study case with part load lies in the region of absolute instability(AI),and it lies in the region of convective instability(CI)for study case with design flow *** for study case with over load lies in the AI region at the inlet of the draft tube,and enters CI region near the end of the elbow.

关键词： draft tube vortices pressure fluctuations Francis turbine cavitation Batchelor instability

Unstable flow characteristics in a pump-turbine simulated by a modified Partially-Averaged Navier-Stokes method

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2019年第3期62卷 406-416页

作者： YANG Dandan LUO XianWu liu demin HUANG RenFang ZHU ZuChao State Key Laboratory of Hydroscience and Engineering Department of Energy and Power Engineering Tsinghua University Dongfang Electric Machinery Corporation Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech University

Positive slope characteristics are very important for the safe and stable operation of a pump-turbine. In this study, the unsteady flows in a pump-turbine at pump mode are investigated numerically. To predict the positive slope characteristics with an improved accuracy, a modified Partially-Averaged Navier-Stokes(MPANS) model is employed to capture the unstable physics in a pump-turbine. It is confirmed that the present numerical method predicts the positive slope characteristics in the pumpturbine fairly well compared with the experimental data. It is noted that at the drooping point of the performance curve(positive slope), there are three sets of rotating stall cells in the flow passages of both the guide vanes and stay vanes. In the guide vane region, the flow is completely shut off by the rotating stall, whereas in the stay vane region, the flow passage is partly blocked at the drooping point. The numerical results also reveal that the remarkable variation and high angle of attack(AOA) values upstream the leading edge of the guide vane contribute to the flow separation at the vane suction side and induce rotating stall in the flow passage within the positive slope region. Furthermore, the propagation of the rotating stall is depicted by both Eulerian and Lagrangian viewpoints: the rotating stall blocks the flow passage between two neighboring guide vanes and pushes the flow toward the leading edge of the subsequent guide vane. The rotating stall cell shifts along the rotational direction with a much lower frequency(0.146 f_n) compared with the runner rotational frequency, f_n.

关键词： pump-turbine positive slope modified Partially-Averaged Navier-Stokes(MPANS) model angle of attack(AOA) Lagrangian coherent structure(LCS)

Structure of different types of coal metamorphism by HTEM

在线全文

学校读者我要写书评

暂无评论

Mining Science and Technology 2010年第6期20卷 835-838页

作者： LI Xiaoming CAO Daiyong liu demin College of Safety Engineering North China Institute of Science and Technology Beijing 101601 China College of Geoscience and Surveying Engineering China University of Mining & Technology Beijing 100083 China

In order to discuss the effect of tectonic stress on the structural evolution of coal, given the importance attached to High-resolution Transmission Electron Microscopy (HTEM), we investigated several aspects of material structures of high-rank Carboniferous period coal, located in the northern foreland basin of the Dabie orogenic belt in eastern China. High powered crystal lattice images of Bright Fields (BF) and Selected Area Diffraction patterns (SAD) of different types of metamorphism in coal were obtained. The results show that the Basic Structural Units (BSU) become increasingly more compact as a function of rising tem-perature and pressure. Under pressure, the local orientation of molecules is strengthened, the arrangement of BSU speeds up and the degree of order is clearly enhanced.

关键词： Dabie orogenic belt high-rank coal high-resolution transmission electron microscopy tectonic stress

Tectonic Landform of Quaternary Lakes and Its Implications for Deformation in the Northern Qinghai-Tibet Plateau

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2009年第1期83卷 121-129页

作者： WANG An WANG Guocan LI Dewei XIE Defan liu demin Faculty of Earth Sciences China University ofGeosciences Wuhan Hubei 430074 China State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Wuhan Hubei 430074 China

The Hohxil region in the northern Qinghai-Tibet Plateau is occupied by numerous plateau lakes, which have long been inferred as being tectonic products. However, so far little evidence has been found to support this tentative inference. Field survey and morphotectonic analysis of TM satellite images in the eastern segment of the Hohxil region revealed that Kusai Lake and Yelusu Lake are S- shaped pull-apart basins, which were dominated by left strike-slip master faults trending WNW-ESE. The pull-apart distances of the two lakes are analyzed to be 〈15-20 km and 15 km respectively. Based on studies of the faulting rate, the initiation ages of the pull-apart basins are suggested to be approximately in the Early Pleistocene. The pull-apart basin tectonics is further regarded as a common mechanism for the widely distributed large lake basins in the northern Qinghai-Tibet Plateau. Regional distribution of these pull-apart basins and their substantial intra-block slip suggest that a sinistral shear stress, which is independent of the distinguished strike-slip faults, has been imposed on across the northern Qinghai-Tibet Plateau. Thus, the intra-block slip may be an important expression of the eastward extrusion of the Plateau crustal material in accommodating the ongoing continent-continent convergence between India and Eurasia. The revelation of pull-apart tectonics within the Plateau hinterland provides field evidence and a possible style of deformation for the newly proposed continuous deformation by the global positioning system （GPS） measurement across the northern Qinghai-Tibet Plateau. A model, with respect to systematic tectonic landform development, for pull- apart basins is finally proposed.

关键词： lake pull-apart basin Quaternary tectonic landform Qinghai-Tibet Plateau

Late Jurassic Intracontinental Extension and Related Mineralisation in Southwestern Fujian Province of SE China:Insights from Deformation and Syn-Tectonic Granites

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2021年第1期32卷 158-173页

作者： Rui Cao Xinghua Ma Leon Bagas Yongbao Gao demin liu Zailai Mou Kay Laboratory of Earth Exploration and Information Techniques Ministry of educationChengdu University of TechnologyChengdu 610059China State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesBeijing 100083China Xi'an Center of China Geological Survey Xi'an 710054China Centre for Exploration Targeting the University of Western AustraliaCrawley WA 6009Australia MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China School of Earth Sciences China University of GeosciencesWuhan 430074China

Late Mesozoic igneous intrusions and extensional structures in Carboniferous to Permian sequences in the SW Fujian region acted as important controls on the localisation of Fe-polymetallic *** we document the identification of extensional deformation at shallow crustal levels and syn-tectonic granites related to normal *** on spatial distribution and structural features,the extensional deformation can be divided into cover-only and basement-intersecting styles.A series of syn-tectonic plutons were emplaced into the footwall of normal *** samples of the Tangquan Granite have high SiO2(66.4 wt.%-73.9 wt.%)assays and Mg#values(37-59).The samples also have relatively homogenous initial 87Sr/86Sr(0.7083-0.7089)andεNd(-9.2--10.2)*** and isotopic evidences indicate that the Tangquan granite originates from a hybrid source including lower crustal-derived felsic and lithospheric mantle-derived mafic *** U-Pb dating indicates that the granodiorite phase from the pluton crystallised at 161±4 Ma and the monzogranite phase crystallised at 159±1 *** with the granitic rocks in a wider region of SE China,the widespread granitic magmatism and polymetallic mineralisation have been synchronous during the Late Mesozoic,probably resulting from extensional tectonics related to the lithospheric thinning.

关键词： extensional tectonic intracontinental deformation granitic magmatism mineralisation SE China

Paleo-Earthquakes along the Zheduotang Fault,Xianshuihe Fault System,Eastern Tibet:Implications for Seismic Hazard Evaluation

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2022年第5期33卷 1233-1245页

作者： Guifan Chen Mervin Bartholomew demin liu Kai Cao Minxuan Feng Dun Wang School of Earth Sciences China University of GeosciencesWuhan 430074China Three Gorges Geotechnical Consultants Co. Ltd.Wuhan 430074China Department of Earth Sciences University of MemphisMemphisTN38152USA Xi’an Center of Geological Survey China Geological SurveyXi’an710054China

The Kangding City in eastern Tibet is at high risk due to frequent strong earthquakes along the Xianshuihe sinistral strike-slip fault bounding the Chuandian Block to the *** knowledge of paleo-seismicity recurrence along this fault system is key to the evaluation of earthquake hazards in this region;thus,more accurate paleoseismic information are *** examined the paleo-seismicity along the Zheduotang fault in the central segment of the Xianshuihe fault system by applying the field investigation,trenching,and Quaternary dating methods(e.g.,OSL and ^(14)C).Field observations found~8.5 m offset of stream by sinistral slip along the Zheduotang *** trenched the central fault zone of the Zheduotang fault and found that the colluvial wedges and five buried,discontinuous,A-soil horizons progressively have been offset in the shallow graben on the SW-side of the main fault indicative of the *** dating results of OSL and ^(14)C,in line with existing data,enable us to establish the paleo-seismic history of the Zheduotang *** shows at least eight surface ruptures in the last 7500 years identified from displaced buried soils,colluvial wedges and *** study reveals~100 years minimum paleo-earthquake recurrence,suggesting potential large earthquakes in the Kangding area in the future.

关键词： Tibetan Plateau Xianshuihe fault system paleo-seismicity trench recurrence geophysics

同方期刊数据库

CD38 deficiency alleviates Ang II-induced vascular remodeling by inhibiting small extracellular vesicle-mediated vascular smooth muscle cell senescence in mice

在线全文

学校读者我要写书评

暂无评论

Signal Transduction and Targeted Therapy 2021年第7期6卷 2172-2185页

作者： Lu Gan demin liu Jing liu Erya Chen Chan Chen Lian liu Hang Hu Xiaohui Guan Wen Ma Yanzi Zhang Yarong He Bofu liu Songling Tang Wei Jiang Jianxin Xue Hongbo Xin Research Laboratory of Emergency Medicine Department of Emergency MedicineNational Clinical Research Center for GeriatricsWest China HospitalSichuan UniversityChengduPeopled Republic of China Cardiology Department The Second Hospital of Hebei Medical UniversityShijiazhuangPeopled Republic of China Department of Endocrinology The Second Hospital of Shanxi Medical UniversityTaiyuanPeople’s Republic of China Department of Anesthesiology Laboratory of Anesthesia and Critical Care MedicineTranslational Neuroscience CenterWest China HospitalSichuan UniversityChengduPeople's Republic of China The National Engineering Research Center for Bioengineering Drugs and the Technologies Institute of Translational MedicineNanchang UniversityNanchangPeople's Republic of China State Key Laboratory of Biotherapy West China HospitalSichuan UniversityChengduPeopled Republic of China Department of Thoracic Oncology Cancer CenterWest China HospitalSichuan UniversityChengduPeople’s Republic of China

CD38 is the main enzyme for nicotinamide adenine dinucleotide(NAD)degradation in mammalian *** NAD levels are closely related to metabolic syndromes and aging-related *** study showed that CD38 deficiency significantly alleviated angiotensin II(Ang ll)-induced vascular remodeling in mice,as shown by decreased blood pressures;reduced vascular media thickness,media-to-lumen ratio,and collagen deposition;and restored elastin ***,our bone marrow transplantation assay showed that CD38 deficiency in lymphocytes led to lack of protection against Ang ll-induced vascular remodeling,suggesting that the effects of CD38 on Ang ll-induced vascular remodeling might rely primarily on vascular smooth muscle cells(VSMCs),not *** addition,we observed that CD38 deficiency or NAD supplementation remarkably mitigated Ang ll-induced vascular senescence by suppressing the biogenesis,secretion,and internalization of senescence-associated small extracellular vesicles(SA-sEVs),which facilitated the senescence of neighboring non-damaged ***,we found that the protective effects of CD38 deficiency on VSMC senescence were related to restoration of lysosome dysfunction,particularly with respect to the maintenance of sirtuin-mediated mitochondrial homeostasis and activation of the mitochondria-lysosomal axis in *** conclusion,our findings demonstrated that CD38 and its associated intracellular NAD decline are critical for Ang ll-induced VSMC senescence and vascular remodeling.

关键词： CD38 Ang remodeling