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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 1089-1097页

作者： jianjun xu Hanlin Ding Xin Lin Feng Liu Analytical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples subjected to IDED under 1050℃ preheating with and without hot isostatic pressing(HIP,1190℃,105 MPa,and 3 h).Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ’ phases in interdendritic and dendritic core *** HIP,grain morphology changed negligibly,whereas the size of the γ’ phase became increasingly *** further heat treatment(HT,1070℃,2 h + 845℃,24 h),the γ’ phase in the as-deposited and HIPed samples presented a bimodal size distribution,whereas that in the as-deposited sample showed a size that remained *** comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%,respectively,due to the synergistic deformation of bimodal γ’phases,especially large cubic γ’ ***,the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.

关键词： directed energy deposition Ni-based superalloys high-temperature preheating hot isostatic pressing microstructure tensile properties

Mathematical modelling study for water uptake of steadily growing plant root

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Science China(Physics,Mechanics & Astronomy) 2008年第2期51卷 184-205页

作者： CHU JiaQiang JIAO WeiPing xu jianjun School of Mathematical Sciences Nankai UniversityTianjin 300071China Department of Mathematics and Statistics McGill UniversityMontreal H3A 2K6Canada

The root system of plant is a vitally important organ for living plant. One of the major functions of the root system is uptaking water and nutrients from the soil. The present paper analyzes the whole process of water uptake from soil by a steadily growing plant with a single slender root. We start from the basic principles of physics and fluid-dynamics, consider the structure characteristics of the water transport channel formed by the tiny xylems tubes inside plant, and establish a simplified coherent mathematical model to describe the water transport in the complete system consisting of soil, individual plant, including root, stem and leaves-atmosphere, on the basis of the plant physiology. Moreover, we resolve the proposed mathematical model for a simple artificial plant model under a variety of conditions, in terms of the numerical approach as well as analytical approach. It is shown that the results obtained by both approaches are in very good agreement; the theoretical predictions are qualitatively consistent with the practical experi-ences very well. The simplified mathematical model established in the present pa-per may provide a basis for the further investigations on the more sophisticated mathematical model.

关键词： plant root water uptake Poiseuille flow asymptotic expansion solution

Interannual and Interdecadal Variability of Winter Precipitation over China in Relation to Global Sea Level Pressure Anomalies

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Advances in Atmospheric Sciences 2002年第5期19卷 914-926页

作者： jianjun xu Johnny C.L Chan Department of Physics&Materials Science City University of Hong KongChina Department of Earth&Environmental Science New Mexico Tech801 Leroy PlaceSocorro87801 New MexicoUSA

Based on the method of rotated principal component (RPC) analysis and wavelet transforms, the winter precipitation from 36 stations over China for the period 1881-1993 is examined. The results show that the three leading space-time modes correspond, in sequence, to winter rainfall anomalies over the reaches of the Yangtze River, the bend of the Yellow River, and the northeastern region of China. The three modes exhibit interannual oscillations with quasi-biennial and 8-year periods as well as interdecadal oscillations with 16- and 32-year periods. The interannual oscillation (< 10 years) occurs in phase over the different areas, and its maximum amplitude migrates northward considerably with prominent interdecadal variations. However, the interdecadal oscillations (10-32 years) are out of phase over the different regions, and the amplitude variations have the characteristics of stationary waves. The rainfall anomalies appear to be closely related to the anti-phase changes of mean sea-level pressure (SLP) over the Asian mainland and the North Pacific. When the SLP rises over the North Pacific and decreases over the Asian mainland, the precipitation over East China increases noticeably. The linkage between the rainfall over China and the SLP anomalies apparently results from the strength of the East Asian winter monsoon and its associated temperature and moisture advection.

关键词： wavelet transform winter precipitation China SLP

Relationship between the Tibetan Plateau-tropical Indian Ocean thermal contrast and the South Asian summer monsoon

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Frontiers of Earth Science 2021年第1期15卷 151-166页

作者： Xiaoqing LUO jianjun xu Yu ZHANG Kai LI South China Sea Institute of Marine Meteorology Guangdong Ocean UniversityZhanjiang 524088China College of Ocean and Meteorology Guangdong Ocean UniversityZhanjiang 524088China Maritime College Guangdong Ocean UniversityZhanjiang 524088China

The impact of land-sea thermal contrast on the South Asian summer monsoon(SASM)was investigated by calculating the atmospheric heat sources(AHS)and baroclinic component with ERA5 data for the period *** diagnostic and statistical methods,it was found that the thermal contrast between the Tibetan Plateau(TP)and the tropical Indian Ocean(TIO)affects the South Asian monsoon circulation through the meridional temperature gradient in the upper *** seasonal changes of the AHS of the TP and TIO are *** summer,the TP is the strongest at the same latitude whereas the TIO is the weakest,and the thermal contrast is the most *** heat sources of the TP and TIO are located on the north and south side of the strong baroclinic area of the SASM region,respectively,and both of which are dominated by deep convective heating in the upper *** TP-TIO regional meridional thermal contrast index(QI)based on the AHS,and the SASM index(MI)based on baroclinicity were found to be strongly positively *** years of abnormally high QI,the thermal contrast between the TP and TIO is strong in summer,which warms the upper troposphere over Eurasia and cools it over the *** stronger temperature gradient enhances the baroclinicity in the troposphere,which results in a strengthening of the low-level westerly airflow and the upper-level easterly *** anomalous winds strengthen the South Asian high(SAH),with the warmer center in the upper troposphere,and the enhanced Walker circulation over the equatorial Indian ***,the anomalous circulation leads to much more precipitation over the SASM *** influence of abnormally low QI is almost the opposite.

关键词： Tibetan Plateau tropical Indian Ocean atmosphere heat sources South Asian summer monsoon atmosphere baroclinic component

An Adaptive Semi-Lagrangian Level-Set Method for Convection-Diffusion Equations on Evolving Interfaces

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Advances in Applied Mathematics and Mechanics 2017年第6期9卷 1364-1382页

作者： Weidong Shi jianjun xu Shi Shu School of Mathematical and Computational Sciences Xiangtan UniversityXiangtanHunan 411105China Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 400714China

A new Semi-Lagrangian scheme is proposed to discretize the surface convection-diffusion *** other involved equations including the the levelset convection equation,the re-initialization equation and the extension equation are also solved by S-L *** S-L method removes both the CFL condition and the stiffness caused by the surface Laplacian,allowing larger time step than the Eulerian *** method is extended to the block-structured adaptive *** examples are given to demonstrate the efficiency of the S-L method.

关键词： Convection-diffusion equation semi-Lagrangian method level-set method blockstructured adaptive mesh finite difference method

The assimilation experimentin the southwestern South China Sea in summer 2000

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Chinese Science Bulletin 2006年第B12期51卷 31-37页

作者： XIAO Xianjun WANG Dongxiao xu jianjun Key Laboratory of Tropical Marine Environmental Dynamics (LED) South China Sea Institute of Oceanology (SCSIO) Chinese Academy of Sciences Guangzhou 510301 China Joint Center for Satellite Data Assimilation NOAA/NASA/DOD USA

We performed an assimilation experiment of the southern South China Sea in summer 2000, and the altimeter data were assimilated into Princeton Ocean Model (POM). The result was evaluated with the in situ data. There were obvious improvements of the currents in the southern South China Sea, and the modeling uncertainty coming from the error of wind stress forcing was reduced. This experiment provides us a new idea about improving the modeling of the ocean currents.

关键词： 2000年夏季南海西南部海域洋流同化试验

Interdecadal variability in the tropical Indian Ocean and its dynamic explanation

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Chinese Science Bulletin 1999年第17期44卷 1620-1627页

作者： Dongxiao Wang Guoxiong Wu jianjun xu Chinese Acad Sci Inst Atmospher Phys Beijing 100080 Peoples R China

Interdecadal variability in the tropical Indian Ocean has been analyzed based on the long-term climatic observational data. Case study showed that strong interannual signals formed at the surface can penetrate the depth of seasonal thermocline, where the anomalies last a couple of years. Artificial time series based on damping with exponential decay of selected strong events agree well with the detected interdecadal variability in the tropical Indian Ocean.

关键词： tropical Indian Ocean interdecadal variability memory.

Sandwich ELISA for detecting urinary Survivin in bladder cancer

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Chinese Journal of Cancer Research 2013年第4期25卷 375-381页

作者： xuefeng Li Yaming Wang jianjun xu Qingyun Zhang Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education) Department of Clinical LaboratoryPeking University Cancer Hospital&Institute

Objective： Survivin as a tumor marker in the diagnosis of bladder cancer has not been completely confirmed yet and there are few reports about using Survivin enzyme-linked immunosorbent assay （ELISA） kit to detect the urine of bladder cancer patients. This study aimed to develop a Survivin ELISA and validate its value in the detection of bladder cancer. Methods： Through square matrix titration, different combinations of coating antibody and detecting antibody, a Survivin ELISA was constructed. This assay was evaluated according to intra-assay precision, inter-assay precision and minimum detectable dose （MDD）. Survivin levels were detected and analyzed in 102 bladder cancer patients and 102 healthy people by established ELISA. Then cutoff value was defined according to the analysis of receiver operating characteristic （ROC） curve. The sensitivity and specificity of detection were calculated on the basis of cutoff value to diagnose bladder cancer patients. Furthermore, the value of Survivin expression detected by ELISA among different clinicopathological characteristics of patients was also compared. Results： Through optimization of different conditions, intra-assay precision was 8.39%, inter-assay precision 8.57% and MDD 0.0625 ng/mL in this assay. When the optical density at 450 nm （OD 450 ） was 0.09, it could get the optimized diagnostic cutoff value. According to this value, the sensitivity and specificity of diagnosis in bladder cancer patients were 70.6% and 89.2%, respectively. The associations between patients＇ clinical variables and OD 450 were not significant except tumor numbers in patients. Conclusions： This experiment has preliminarily developed a Survivin ELISA and confirmed Survivin as a biomarker which owned a practical and significant value in the diagnosis of bladder cancer.

关键词： Survivin bladder cancer enzyme-linked immunosorbent assay (ELISA) tumor marker diagnosis

Sensitivity of Typhoon Lingling(2019)simulations to horizontal mixing length and planetary boundary layer parameterizations

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Frontiers of Earth Science 2022年第2期16卷 304-322页

作者： Siqi CHEN Feng xu Yu ZHANG Guiling YE jianjun xu Chunlei LIU College of Ocean and Meteorology Guangdong Ocean UniversityZhanjiang 524088China South China Sea Institute of Marine Meteorology Zhanjiang 524088China Shenzhen Institute of Guangdong Ocean University Shenzhen 518120China

Forecasting the intensity of typhoons is a difficult problem in numerical weather *** is subject to many factors,among which the selection of physical parameterization schemes for the model is a hot topic of *** this study,the effects of horizontal mixing length(represented by h_diff)and planetary boundary layer(PBL)schemes were *** idealized and four operational sensitivity experiments were designed based on simulation of the typhoon Lingling,which occurred over the western Pacific in 2019,using the Hurricane Weather Research and Forecasting *** results of the idealized experiments showed that,as h_diff was increased,the slope of the typhoon eye area also increased,and its intensity became *** the other hand,the results of the sensitivity experiments indicated that the intensity of the simulated typhoon was sensitive to the choice of PBL scheme,with the forecast bias of the QNSE(Quasi-Normal Scale Elimination)scheme being smaller than that of the GFDL(Geophysical Fluid Dynamics Laboratory)*** momentum budget analyses indicated that,when increasing the h_diff,the convergence of angular momentum was larger in the boundary layer,which led to a faster spin-up of the vortex,further increasing the intensity of the *** the calculated horizontal and vertical vortex spread it was found that,when the h_diff was increased,the corresponding horizontal and vertical diffusion eddies also showed an increasing trend,which was also the reason for the strengthening of the ***,the forecast bias decreased significantly with increasing horizontal mixing length when using the same PBL scheme.

关键词： Hurricane Weather Research and Forecasting model planetary boundary layer western Pacific typhoon horizontal diffusion

Large-scale characteristics of landfalling tropical cyclones with abrupt intensity change

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Frontiers of Earth Science 2019年第4期13卷 808-816页

作者： Qianqian JIU Feng xu jianjun xu Mei LIANG Shifei TU Siqi CHEN South China Sea Institute of Marine Meteorology Guangdong Ocean UniversityZhanjiang 524088China College of Ocean and Meteorology Guangdong Ocean UniversityZhanjiang 524088China Southern Marine Science and Engineering Guangdong Laboratory Zhanjiang 524088China

Data from the China Meteorological Administration and ERA-Interim are used to examine the environmental characteristics of landfalling tropical cyclones(TCs)with abrupt intensity *** results show that,of all 657 landfalling TCs during 1979-2017,71%,70%and 65%of all landfalling TDs,TSs and TYs,respectively,*** all the 16595 samples,4.0%and 0.2%of typhoons and tropical storms,respectively,experience over-water rapid intensification(RI)process during their life ***,4.5%and 0.6%of typhoons and tropial storms,respectively,undergo overwater rapid decay(RD).These two kinds of cases,i.e.,RI and RD,are used to analyze their associated large-scale *** show that the RI cases are generally on the south side of the strong western Pacific subtropical high(WPSH);warm sea surface temperatures(SSTs)and sufficient water vapor fluxes existing in RI samples is a dominant feature that is conducive to the development of ***,the moderate low-level relative vorticity is favorable for TC *** the contrary,the RD TCs are located on the west side of the WPSH;significant decreasing SSTs and low-level water vapor transport may synergistically contribute to ***,low-level relative vorticity seems to be unfavorable for the development of TCs.

关键词： landfalling tropical cyclone abrupt intensity change environmental factors dynamic composite analysis