检索结果-南通市图书馆

Retrieval of Eddy Thermal Conductivity in the Weakly Nonlinear Prandtl Model for Katabatic Flows

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 Meteorological Research 2017年第5期31卷 965-975页

作者： bing yan Sixun HUANG Jing FENG Institute of Meteorology and Oceanography National University of Defense Technology State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration

Because the nonlinearity of actual physical processes can be expressed more precisely by the introduction of a non- linear term, the weakly nonlinear Prandtl model is one of the most effective ways to describe the pure katabatic flow （no backgrotmd flow）. Features of the weak nonlinearity are reflected by two factors： the small parameter c and the gradually varying eddy thermal conductivity. This paper first shows how to apply the Wentzel-Kramers-Brillouin （WKB） method for the approximate solution of the weakly nonlinear Prandtl model, and then describes the retrieval of gradually varying eddy thermal conductivity from observed wind speed and perturbed potential temperature. Gradually varying eddy thermal conductivity is generally derived from an empirical parameterization scheme. We utilize wind speed and potential temperature measurements, along with the variational assimilation technique, to de- rive this parameter. The objective function is constructed by the square of the differences between the observation and model value. The new method is validated by numerical experiments with simulated measurements, revealing that the order of the root mean squre error is 10-2 and thus confirming the method＇s robustness. In addition, this me- thod is caoable of anti-interference, as it effectivelv reduces the influence of observation error.

关键词： weakly nonlinear Prandtl model parameter retrieval variational method Wentzel-Kramers-Brillouin(WKB) method

Self-lubricated Array Film of Amorphous Carbon Nanorods on an Aluminum Substrate

在线全文

学校读者我要写书评

暂无评论

材料热处理学报 2004年第05B期25卷 1253-1256页

作者： JIANGChun-xi TUJiang-ping GUOShao-yi FUMing-fu ZHAOxin-bing DepartmentofMechanicalElectronicandEngineering NanchangUniversityNanchanChina DepartmentofMaterialsScienceandEngineering ZhejiangUniversityHangzhouChina DepartmentofMechanicalEngineering ZhejiangUniversityofScienceHangzhouChina DepartmentofMechanicalElectronicandEngineering NanchangUniversityNanchanChina／／DepartmentofMaterialsScienceandEngineeringZhejiangUniversityHangzhouChina

A self-lubricated array film of amorphous carbon nanorods was prepared by chemical catalytic pyrolysis of acetylene on the anodic aluminum oxide membrane fabricated by two-step anodization of aluminum. The tribological properties of the array film of amorphous carbon nanorods in ambient air were investigated using a ball-on-disk tester at applied loads range from 245 mN to 1960 mN at a sliding velocity of 0.2 m/s. The self-lubricated array film exhibited a small value of the friction coefficient as well as good wear resistance. The friction coefficient of array film of amorphous carbon nanorods decreased gradually with increasing the applied load. The approach proposed demonstrated a new efficient route towards enhanced the friction and wear performances of aluminum.

关键词：铝合金磨损性能毫微不定形碳棒自动润滑阵列薄膜

Preparation and characterization of porous ceramics prepared by kaolinite gangue and Al(OH)_3 with double addition of MgCO_3 and CaCO_3

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2011年第4期18卷 450-454页

作者： Wen yan Nan Li bing-qiang Han The Key State Laboratory Breeding Base of Refractories and Ceramics Wuhan University of Science and Technology Wuhan 430081 China

Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ *** characterizations of porous ceramics were investigated by X-ray diffractometry,scanning electron microscopy,and mercury porosimetry measurements,*** is found that although the decomposition of MgCO3 and CaCO3 has little contribution to the porosity,the double addition of MgCO3 and CaCO3 strongly affects the formation of liquid phase,and then changes the phase compositions,pore characterization,and *** appropriate mode is the sample containing 1.17wt% MgCO3 and 1.17wt% CaCO3,which has high apparent porosity（41.0%）,high crushing strength（53.5 MPa）,high mullite content（76wt%）,and small average pore size（3.24 μm）.

关键词： porous ceramics characterization kaolinite aluminum hydrxide additives

Analysis of wave propagation in micro/nanobeam-like structures: A size-dependent model

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2012年第6期28卷 1659-1667页

作者： bing-Lei Wang Jun-Feng Zhao Shen-Jie Zhou xi Chen Department of Engineering Mechanics Shandong University School of Mechanical Engineering Shandong University Department of Earth and Environmental Engineering Columbia University International Center for Applied Mechanics SV Lab School of Aerospace Xi'an Jiaotong University

By incorporating the strain gradient elasticity into the classical Bernoulli-Euler beam and Timoshenko beam models, the size-dependent characteristics of wave propaga- tion in micro/nanobeams is studied. The formulations of dis- persion relation are explicitly derived for both strain gradi- ent beam models, and presented for different material length scale parameters （MLSPs）. For both phenomenological size- dependent beam models, the angular frequency, phase veloc- ity and group velocity increase with increasing wave num- ber. However, the velocity ratios approach different values for different beam models, indicating an interesting behavior of the asymptotic velocity ratio. The present theory is also compared with the nonlocal continuum beam models.

关键词： Strain gradient elasticity theory ~ Bernoulli-Euler beam theory. Timoshenko beam theory Wave propa-gation

Investigation of three different cooling treatments on dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling

在线全文

学校读者我要写书评

暂无评论

Underground Space 2022年第5期7卷 847-861页

作者： Lifeng Fan Han Li yan xi Beijing University of Technology Beijing 100124China

Underground thermal engineering such as geothermal exploitation usually involves the response of impact loads due to the drilling operation and blasting *** study investigated the dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling under natural cooling,water cooling,and liquid nitrogen ***,split Hopkinson pressure bar tests were performed on granite under three different cooling methods to study the dynamic mechanical parameters with thermal ***,the damage factors were calculated to evaluate the damage on granite and the relationship between damage and ***,the granite fragments after impact were sieved,and the fractal dimension and average fragment size were introduced to analyze the fragmentation *** results demonstrate that the degradation of dynamic mechanical properties mainly occurs in the first four thermal cycles;with the increase of damage factor,the stress decreases linearly under the three cooling methods,and the damage caused by liquid nitrogen cooling to granite is the most significant,followed by water *** of granite change from axial splitting failure to a more complex composite failure *** addition,with the decrease of the average fragment size,the fractal dimension of the granite gradually increases,resulting in the higher fragmentation degree and the better uniformity of fragmentation.

关键词： Split Hopkinson pressure bar Dynamic mechanical properties Fragmentation characteristics Cooling treatment

Prevalence of gene mutations in a Chinese 46,XY disorders of sex development cohort detected by targeted next-generation sequencing

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2021年第1期23卷 69-73页

作者： bing-Qing Yu Zhao-xiang Liu Yin-Jie Gao xi Wang Jiang-Feng Mao Min Nie Xue-yan Wu NHC Key Laboratory of Endocrinology Department of EndocrinologyPeking Union Medical College HospitalPeking Union Medical CollegeChinese Academy of Medical SciencesBeijing 100730China

46,XY disorders of sex development(DSD)is characterized by incomplete masculinization genitalia,with gonadal dysplasia and with/without the presence of Mullerian *** least 30 genes related to 46,XY DSD have been ***,the clinical phenotypes of patients with different gene mutations overlap,and accurate diagnosis relies on gene sequencing ***,this study aims to determine the prevalence of pathogenic mutations in a Chinese cohort with 46,XY DSD by the targeted nextgeneration sequencing(NGS)***-seven 46,XY DSD patients were enrolled from the Peking Union Medical College Hospital(Beijing,China).A total of fifty-four rare variants were identified in 60 patients with 46,XY *** incidence of these rare variants was approximately 69.0%(60/87).Twenty-five novel variants and 29 reported variants were *** on the American College of Medical Genetics and Genomics(ACMG)guidelines,thirty-three variants were classified as pathogenic or likely pathogenic variants and 21 variants were assessed as variants of uncertain *** overall diagnostic rate was about 42.5%based on the pathogenic and likely pathogenic *** receptor{AR),steroid 5-alpha-reductase 2(SRD5A2)and nuclear receptor subfamily 5 Group A member 1(NR5A1)gene variants were identified in 21,13 and 13 patients,*** incidence of these three gene variants was about 78.3%(47/60)in patients with rare *** is concluded that targeted NGS is an effective method to detect pathogenic mutations in 46,XY DSD patients and AR,SRD5A2,and NR5A1 genes were the most common pathogenic genes in our cohort.

关键词： 46,XY disorders of sex development mutations targeted next-generation sequencing

Reconstruction of deep fluid chemical constituents for estimation of geothermal reservoir temperature using chemical geothermometers

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 Groundwater Science and Engineering 2017年第2期5卷 173-181页

作者： LIU yan-guang LIU bing LU Chuan ZHU xi WANG Gui-ling Institute of Hydrogeology and Environmental Geology CAGS Shijiazhuang 050061 China

This paper elaborates the chemical constituent change principles of deep geothermal fluid during the process of upward movement. It summarizes research methods of hydrochemistry, isotope and numerical modelling technique for the physiochemical processes such as decreasing temperature, shallow groundwater infusion, and degassing. The multi-component chemical geothermometry methods including gas geochemical method are discussed. High-temperature geothermal fields in China are mostly located in the southwest with frequent new tectonic movements, especially in Tibet high-temperature geothermal areas. Therefore the paper also focuses the status of high-temperature geothermal fluid research. At last, it's pointed out in the paper that in the future we can start from typical high-temperature geothermal zones and geothermal fields to explore optimization of the multi-component geothermometry method and use it in the reconstruction and analogue of the formation mechanism and internal relevancy of regional geothermal systems.

关键词： High temperature geothermal fluid Multi-component geothermometer optimization Geothermal gases Analogue

Numerical simulations of turbulent flows in aeroramp injector/gas-pilot flame scramjet

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 Aeronautics 2017年第4期30卷 1373-1390页

作者： bing CHEN Xu XU Baoxi WEI yan ZHANG School of Astronautics Beihang University Science and Technology on Scramjet Laboratory Beijing Power Machinery Institute

To uncover the internal flow characteristics in an ethylene-fueled aeroramp injector/gaspilot（ARI/G-P）flame scramjet,a Reynolds-averaged Navier-Stokes（RANS）solver is constructed under a hybrid polyhedral cell finite volume *** shear stress transport（SST）k-x model is used to predict the turbulence,while the Overmann’s compressibility corrected laminar flamelet model is adopted to simulate the turbulent *** computations for Case 1（G-P jet on）,Case 2（ARI jets on）,and Case 3（both ARI and G-P jets on）were conducted to analyze the mixing mechanism,while reactive Cases 4–7 at equivalent ratios of 0.380,0.278,0.199 and0.167 respectively were calculated to investigate the flame structure and combustion *** numerical results are compared well to those of the *** is shown that the G-P jet plays significant role in both the fuel/air mixing and flame holding processes;the combustion for the four reactive cases takes place intensively in the regions downstream of the ARI/G-P unit;Cases 4 and 5are under subsonic combustion mode,whereas Cases 6 and 7 are mode transition critical and supersonic combustion cases,respectively;the mode transition equivalent ratio is approximately 0.20.

关键词： Combustion mode Laminar flamelet model Menter's SST k-ω model Scramjet Turbulent combustion

Recent advances in molecular biology research of a rice pest, the brown planthopper

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2019年第4期18卷 716-728页

作者： BAO yan-yuan ZHANG Chuan-xi State Key Laboratory of Rice Biology and Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insects Institute of Insect Sciences Zhejiang University

The brown planthopper, Nilaparvata lugens St?l, has become a major threat in tropical Asian and China since the rice green revolution of the 1960 s. Currently, insecticide application remains the primary choice for controlling this rice insect pest, but heavy use of insecticides poses dangerous risks to beneficial natural enemies and pollinators, and stimulates N. lugens reproductivity, and has caused a resurgence of the pest in the major rice-planting regions throughout Asia. Achieving the long-lasting goal of sustainable management of N. lugens requires understanding of the molecular basis of outbreaks of the pest and the development of environment-friendly pest-control strategies. Here, we review the recent molecular advances in N. lugens research on the aspects of its endosymbionts, virus transmission, insecticide resistance, and interaction between N. lugens and rice plants. We also put forward further research directions that may shed some lights on management of the rice pest.

关键词： Nilaparvata lugens endosymbionts virus transmission insecticide resistance interaction with rice biological management