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Effects of temperature distribution and level on heat transfer on a rotating free disk

航空动力学报 2011年第6期26卷 1310-1320页

作者： ZHAO xi xu Guo-qiang LUO xiang National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics School of Jet Propulsion Beijing University of Aeronautics and Astronautics Beijing 100191 China

In gas turbine engines,with the existence of the intense forced convection and significant buoyancy effects,temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics *** this paper,numerical simulations were performed to analyze these influences for a free disk,with the laminar and turbulent flow *** influences of temperature distribution on the heat transfer were observed by using incompressible cooling air,and temperature profiles of nth order monomial and polynomial were assumed on the *** analysis revealed that the heat transfer for two flow states on the free disk is determined by the exponent n of the monomial profile when specifying the rotating Reynolds number;for an arbitrary polynomial profile,the local Nusselt number can be deduced from results of monomial *** study the effects of temperature level on heat transfer singly,monomial profiles were used and the local Nusselt number of compressible and incompressible cooling air were *** both for two flow states,the following conclusions could be drawn: the relative difference of local Nusselt number is mainly controlled by nondimensional local temperature difference,and almost independent of the monomial's coefficient C,exponent n and the rotating Reynolds ***,a correction method for heat transfer of the free disk is presented and verified computationally,with which the local Nusselt number,obtained with a uniform and low temperature profile,can be revised by arbitrary distribution and high temperature magnitude.

关键词： thermal boundary condition temperature boundary condition rotating disk free disk heat transfer

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Vegetation Cover Variation in the Qilian Mountains and its Response to Climate Change in 2000-2011

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Journal of Mountain Science 2013年第6期10卷 1050-1062页

作者： DENG Shao-fu yang Tai-bao ZENG Biao ZHU xi-fen xu Hao-jie Key Laboratory of Western China’s Environmental System (Ministry of Education) Research School of Arid Environment & Climate Change Lanzhou University Institute of Glaciology and Ecogeography College of Earth and Environmental Sciences Lanzhou University Geological Team No. 135 Sichuan Bureau of Coal Geology

An understanding 0f variati0ns in vegetati0n c0ver in resp0nse t0 climate change is critical f0r predicting and managing future terrestrial ec0system dynamics. Because scientists anticipate that m0untain ec0systems will be m0re sensitive t0 future climate change c0mpared t0 0thers, 0ur 0bjectives were t0 investigate the impacts 0f climate change 0n variati0n in vegetati0n c0ver in the Qilian M0untains （QLM）, China, between 2000 and 2011. T0 acc0mplish this, we used linear regressi0n techniques 0n 250-m MODIS N0rmalized Difference Vegetati0n Index （NDVI） datasets and mete0r0l0gical rec0rds t0 determine spati0temp0ral variability in vegetati0n c0ver and climatic fact0rs （i.e. temperature and precipitati0n）. Our results sh0wed that temperatures and precipitati0n have increased in this regi0n during 0ur study peri0d. In additi0n, we f0und that gr0wing seas0n mean NDVI was mainly distributed in the vertical z0ne fr0m 2,700 m t0 3,600 m in elevati0n. In the study regi0n, we 0bserved significant p0sitive and negative trends in vegetati0n c0ver in 26.71% and 2.27% 0f the vegetated areas. C0rrelati0n analyses indicated that rising precipitati0n fr0m May t0 August was resp0nsible f0r increased vegetati0n c0ver in areas with p0sitive trends in gr0wing seas0n mean NDVI. H0wever, there was n0 similar significant c0rrelati0n between gr0wing seas0n mean NDVI and precipitati0n in regi0ns where vegetati0n c0ver declined thr0ugh0ut 0ur study peri0d. Using spatial statistics, we f0und that veeetati0n c0ver freauentlvdeclined in areas within the 2,500-3,100 m vertical z0ne, where it has steep sl0pe, and is 0n the sunny side 0f m0untains. Here, the p0sitive influences 0f increasing precipitati0n c0uld n0t 0ffset the drier c0nditi0ns that 0ccurred thr0ugh warming trends. In c0ntrast, in higher elevati0n z0nes （3,900-4,500 m） 0n the shaded side 0f the m0untains, rising temperatures and increasing precipitati0n impr0ved c0nditi0ns f0r vegetati0n gr0wth. Increased precipitati0n als0 faci

关键词： NDVI Temperature Precipitation Topography

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Clinical significance of germline copy number variation in susceptibility of human diseases

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Journal of Genetics and Genomics 2018年第1期45卷 3-12页

作者： Liwen Hu xinyue Yao Hairong Huang Zhong Guo xi Cheng yang xu Yi Shen Biao xu Demin Li Department of Cardiothoracic Surgery Jinling Hospital School of Clinical Medicine Nanjing University Institute of Laboratory Medicine Jinling Hospital School of Clinical Medicine Nanjing University

Germline copy number variation （CNV） is considered to be an important form of human genetic poly- morphisms. Previous studies have identified amounts of CNVs in human genome by advanced technologies, such as comparative genomic hybridization, single nucleotide genotyping, and high-throughput sequencing. CNV is speculated to be derived from multiple mechanisms, such as nonallelic homologous recombination （NAHR） and nonhomologous end-joining （NHEJ）. CNVs cover a much larger genome scale than single nucleotide polymorphisms （SNPs）, and may alter gene expression levels by means of gene dosage, gene fusion, gene disruption, and long-range regulation effects, thus affecting individual phenotypes and playing crucial roles in human pathogenesis. The number of studies linking CNVs with common complex diseases has increased dramatically in recent years. Here, we provide a comprehensive review of the current understanding ofgermline CNVs, and summarize the association of germline CNVs with the susceptibility to a wide variety of human diseases that were identified in recent years. We also propose potential issues that should be addressed in future studies.

关键词： Copy number variation Susceptibility Risk Cancer Neuropsychological disorders

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Case Report:Bacteremia due to Rhodococcus equi:a case report and review of the literature

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2009年第12期10卷 933-936页

作者： xi-yuan CHEN Feng xu Jing-yan xiA Yu-sheng CHENG Yan yang Department of Respiratory Medicine the Second Affiliated Hospital School of Medicine Zhejiang University Hangzhou 310009 China Department of Radiotherapy the Second Affiliated Hospital School of Medicine Zhejiang University Hangzhou 310009 China

Rhodococcus equi, previously known as Corynebacterium equi, is one of the most important causes of zoonotic infections in grazing animals. Increased cases of human infection with R. equi have been reported, especially in immunocompromised patients, within recent years. We present a case of R. equi bacteremia in a 51-year-old man with diabetes and liver cirrhosis, on long-term corticosteroid therapy after skin-grafting surgery. The patient recovered soon after he was treated with vancomycin. This review focuses on the microbiological characteristics of this organism, and the diagnosis and treatment of this infection.

关键词： Rhodococcus equi Bacteremia Opportunistic pathogen

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Hot deformation behavior and microstructure evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment

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Rare Metals 2013年第4期32卷 338-346页

作者： Yan xu Lian-xi Hu Yu Sun School of Materials Science and Engineering Harbin Institute of Technology School of Mechanical Engineering Beihua University

The deformation behavior and the microstruc-ture evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment were systematically inves-tigated. The flow stress behavior was studied by com-pression tests in strain rate range of 0.001-1.000 s^-1 and deformation temperature range of 220-380 ℃ with a maximum deformation strain of 60 %. The dependence of flow stress on deformation temperature and strain rate was described by hyperbolic sine constitutive equation. Through regression analysis, the average apparent activa- tion energy and coefficient of strain rate sensitivity were estimated to be 181.98 ***^-1 and 0.14, respectively. The results also reveal that the variation of peak stress depends on strain rate and deformation temperature. Microstructure observation shows that, at temperatures higher than 300 ℃ and strain rates lower than 0.01 s^-1, DRX developed extensively at the grain boundaries and in the core of coarse grains, resulting in a more homogeneous microstructure. Furthermore, the effects of strain, defor-mation temperature, strain rate, and eutectic β phase on the microstructure evolution of as-cast AZ91D magnesium alloy were discussed.

关键词： AZ91D magnesium alloy Isothermalcompression Constitutive equation Peak stress Microstructure evolution

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Volume expansion rates of seismic landslides and influencing factors: A case study of the 2008 Wenchuan earthquake

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Journal of Mountain Science 2019年第8期16卷 1731-1742页

作者： MA Si-yuan xu Chong xu xi-wei Key Laboratory of Active Tectonics and Volcano Institute of GeologyChina Earthquake AdministrationBeijing 100029China Institute of Crustal Dynamics China Earthquake AdministrationBeijing 100085China

When a big landside occurs, source material can change into loose deposit during its runout, causing the increase of the total landslide volume to some extent. Such changes can influence the quantification of seismic landslides. The objective of this paper was to study the volume expansion rate of landslides based on the data of 1417 co-seismic landslides triggered by the 2008 Wenchuan, China Mw 7.9 earthquake. We also analyzed the correlations between this rate and landslide geometric parameters(volume, height(H), length-width ratio(L/W), length-height ratio(L/H)), and environmental factors(peak ground acceleration(PGA), lithology, slope angle and aspect). The results show that the total source volume of the 1417 landslides is 1248 million m3, while the total volume of the deposit is 1501 million m3, which means the total volume expanding rate(Et) is 20.3% with the average volume expansion rate(Ea) 22.6%. The analysis indicates that volume expansion rate generally decreases with the increasing volume and height of landslides, while becoming larger with increasing L/H and L/W. Besides, the volume expansion rate is closely related to the landslide type and the volume scale of landslides. This study analyses volume change of co-seismic landslides deeply, permitting to help the correct quantification of the source volume and deposit volume of seismic landslide and a useful reference for the correct quantification of landslide volume.

关键词： Landslide volume Volume expansion rate Wenchuan earthquake Influencing factors

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A novel gene R049 identified in uropathogenic Escherichia coli provides partial protection in mice from colonization

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Chinese Science Bulletin 2011年第8期56卷 755-761页

作者： CHEN JinYing GE xin ZHANG YuMei LIN xu ZHANG Wei yang xi Department of Medical Microbiology Tianjin Medical University Tianjin 300070 China Research Center of Molecular Medicine Fujian Medical University Fuzhou 350004 China Department of Medical Microbiology Faculty of Medicine University of Manitoba Winnipeg Manitoba R3E OW3 Canada

Uropathogenic Escherichia coli(UPEC) is the most common causative organism of human urinary tract infection(UTI).Several UPEC virulence factors have been identified,but more are yet to be *** previously identified a novel 789-bp-long DNA fragment(named R049) in UPEC strain 132 using a suppressive subtractive hybridization *** the present study,we used genome walking to elongate the sequence of this fragment to obtain the whole gene sequence and examined the role of this gene product in generating protective *** bioinformatic analysis,we predicted that this gene is a 1311-bp open reading frame(ORF),which we designated ORFR049(GenBank accession No.:EF488001).We further constructed a prokaryotic expression system to express full recombinant R049 protein and isolated and purified the protein through IPTG induction and nickel affinity *** mouse immunosera generated by the purified protein,we confirmed the natural expression and outer membrane localization of the protein in wild-type strain UPEC132 by Western *** test the potential of this protein as a vaccine candidate,we immunized mice with the recombinant protein before challenging them with UPEC132 through the urinary *** results showed significantly reduced bacterial colonization in the urine and kidneys of the immunization group compared with the control ***,the degree of renal pathological damage was not significantly improved in the immunized *** study has identified a novel gene of UPEC which can generate protective immunity against *** novel gene provides a promising new vaccine candidate.

关键词：保护性免疫免疫小鼠大肠杆菌基因组肾炎定植抑制消减杂交技术 GenBank

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Effects of Root Pruning on Non-Hydraulic Root-Sourced Signal, Drought Tolerance and Water Use Efficiency of Winter Wheat

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Journal of Integrative Agriculture 2013年第6期12卷 989-998页

作者： MA Shou-chen LI Feng-min yang Shen-jiao LI Chun-xi xu Bing-cheng ZHANG xu-cheng State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Ministry of Water Resources/Institute of Soil and Water Conservation Chinese Academy of Sciences School of Surveying and Land Information Engineering Henan Polytechnic University Key Laboratory of Efficient Utilization of Water in Dry Farming Gansu Province College of Life Science Henan Normal University

Two pot experiments were conducted to study the effects of root pruning at the stem elongation stage on non-hydraulic root-sourced signals （nHRS）, drought tolerance and water use efficiency of winter wheat （Triticum aestivum）. The root pruning significantly reduced the root weight of wheat, but had no effect on root/shoot ratio at the two tested stages. At booting stage, specific root respiration of root pruned plants was significantly higher than those with intact roots （1.06 and 0.94 mmol g-1 s-1, respectively）. The soil water content （SWC） at which nHRS for root pruned plants appeared was higher and terminated lower than for intact root plants, the threshold range of nHRS was markedly greater for root pruned plants （61.1-44.6% field water capacity） than for intact root plants （57.9-46.1% field water capacity）. At flowering stage, while there was no significant difference in specific root respiration. The SWCs at which nHRS appeared and terminated were both higher for root pruned plants than for intact root plants. The values of chlorophyll fluorescence parameters, i.e., the effective photosystem II quantum yield （F PS II ）, the maximum photochemical efficiency of PS II （F v /F m ）, coefficient of photochemical quenching （qP）, and coefficient of non-photochemical quenching （NPQ）, in root pruned plants were significantly higher than in intact root plants, 7 d after withholding of water. Root pruned plants had significantly higher water use efficiency （WUE） than intact root plants in well-watered and medium drought soil, but not in severe drought condition. In addition, root pruning had no significant effect on grain yield in well-watered and medium drought soil, but significantly decreased grain yield in severe drought condition. In conclusion, the current study showed that root pruning significantly altered nHRS sensitivity and improved WUE of winter wheat in well-watered and medium drought soil, but lowered drought tolerance of winter wheat in severe drought soil

关键词： winter wheat root pruning non-hydraulic root-sourced signal (nHRS) root activity drought tolerance

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P-doped electrode for vanadium flow battery with high-rate capability and all-climate adaptability

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Journal of Energy Chemistry 2019年第8期28卷 55-59,I0003页

作者： Lihong Yu Feng Lin Lin xu Jingyu xi School of Applied Chemistry and Biological Technology Shenzhen PolytechnicShenzhen 518055 Guangdong China Institute of Green Chemistry and Energy Graduate School at Shenzhen Tsinghua UniversityShenzhen 518055 Guangdong China

A phosphorous-doped graphite felt(PGF) is fabricated and examined as electrode for vanadium flow battery(VFB). P doping improves the electrolyte wettability of GF and induces more defect sites on its surface, resulting in significantly enhanced activity and reversibility towards VO2^+/VO2^+ and V^2+/V3^+couples. VFB with PGF electrode demonstrates outstanding performance such as high-rate capability under 50–400 mA cm^-2, wide-temperature tolerance at-20 °C–60 °C, and excellent durability over 1000 charge–discharge cycles. These merits enable PGF a promising electrode for the next-generation VFB,which can operate at high-power and all-climate conditions.

关键词： Vanadium flow battery Graphite felt P doping High-power electrode All-climate

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Energy Absorption Characteristics of a Novel Asymmetric and Rotatable Re-entrant Honeycomb Structure

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Acta Mechanica Solida Sinica 2021年第4期34卷 550-560页

作者： Huifeng xi Jiachu xu Shende Cen Shiqing Huang MOE Key Laboratory of Disaster Forecast and Control in Engineering and School of Mechanics and Construction Engineering Jinan UniversityGuangzhou510632China

Based on the symmetric re-entrant honeycomb(S-RH)structure with negative Poisson’s ratios,a novel asymmetric and rotatable re-entrant honeycomb(AR-RH)structure was *** the S-RH structure and AR-RH structure were produced by the 3D printing *** experimental test and finite element simulation,the deformation mechanism and energy absorption characteristics of the AR-RH structure and the S-RH structure with negative Poisson’s ratios at different impact velocities were *** experimental test and finite element simulation results show that the novel AR-RH structure with negative Poisson’s ratios has stronger energy absorption capacity than the S-RH structure,and it has been verified that the rotatability of AR-RH can indeed absorb ***,the degree of asymmetry of the AR-RH structure was discussed.

关键词： Asymmetric and rotatable re-entrant honeycomb structure Dynamic compression Energy absorption characteristics Metal 3D printing technology

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