检索结果-南通市图书馆

The near-Surface Region of Cubic Boron Nitride Single Crystal from the Li3N-hBN System

维普期刊数据库评论

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 Physics Letters 2014年第4期31卷 182-184页

作者： guo xiao-fei XU Bin WEN Zhen-Xing FAN xiao-Hong TIAN Bin School of Materials Science and Engineering Shandong University Jinan 250061 School of Materials Science and Engineering Shandong Jianzhu University Jinan 250101

Cubic boron nitride single crystals are synthesized with lithium nitride as a catalyst under high pressure and high temperature. The main phases in the near-surface region, which around the single crystal are determined as a mixture of hexagonal boron nitride （hBN）, cubic boron nitride （cBN） and lithium boron nitride （Li3BN2）. High resolution transmission electron microscopy examinations show that there exist lots of nanometer-sized cubic boron nitride nuclei in this region. The interface phase structures of cubic boron nitride crystal and its near-surface region are investigated by means of transmission electron microscopy. The growth mechanism of cubic boron nitride crystal is analyzed briefly. It is supposed that LisBN2 impels the direct conversion of hBN to cBN as a real catalyst, and cBN is homogeneously nucleated in the molten state under high pressure and high temperature.

关键词： BORON nitride SINGLE crystals -- Spectra LITHIUM nitrides HIGH resolution spectroscopy NUCLEATION TRANSMISSION electron microscopy

结构阻尼比对超高层建筑顺风向风振响应的影响

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

建材世界 2024年第1期45卷 97-100页

作者：郭小飞袁哲峰王瑞牛方义中国建筑科学研究院有限公司北京100013 建研院检测中心有限公司北京100013

以某超高层建筑结构为工程研究背景,主要研究了阻尼比对风振响应(基底剪力、楼层位移、加速度)的影响,结果表明:阻尼比较大时,其对结构顺风向的风振响应影响较小;随着阻尼比的增加,风振响应(基底剪力、楼层位移)最大值减小幅度较大,而... 详细信息

以某超高层建筑结构为工程研究背景,主要研究了阻尼比对风振响应(基底剪力、楼层位移、加速度)的影响,结果表明:阻尼比较大时,其对结构顺风向的风振响应影响较小;随着阻尼比的增加,风振响应(基底剪力、楼层位移)最大值减小幅度较大,而均方根值和平均值减小幅度较小,几乎无太大变化;随着阻尼比的增加,顶层加速度最大值、最小值和均方根值变化量比较大,而平均值几乎无变化。

关键词：风振系数阻尼比超高层建筑风振响应

维普期刊数据库博看期刊

在线全文

学校读者我要写书评

暂无评论

输电塔纵向地震作用下抗震简化模型研究

建材世界 2024年第2期45卷 115-118页

作者：袁哲峰牛方义郭小飞朱建金中国建筑科学研究院有限公司北京100013 建研院检测中心有限公司北京100013

纵向地震作用下,将输电塔简化为了广义单自由度模型。采用Newmark法的增量形式进行杆塔地震响应分析,并与实际输电塔结构的有限元模型在相同纵向地震作用下计算得到的响应进行比较。计算结果表明,简化模型通过逐步积分计算出的塔顶位移... 详细信息

纵向地震作用下,将输电塔简化为了广义单自由度模型。采用Newmark法的增量形式进行杆塔地震响应分析,并与实际输电塔结构的有限元模型在相同纵向地震作用下计算得到的响应进行比较。计算结果表明,简化模型通过逐步积分计算出的塔顶位移,略大于精细化模型在通用有限元软件中计算出的塔顶位移,差别较小;说明在纵向地震作用下,采用输电塔广义单自由度简化模型可以很好地替代原模型。

关键词：输电塔纵向地震作用简化模型有限元模型

西双版纳热带森林恢复对土壤反硝化N_(2)O排放的影响

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

西北林学院学报 2024年第2期39卷 97-105页

作者：张路路王邵军张昆凤樊宇翔解玲玲肖博王郑钧郭志鹏郭晓飞罗双李瑞夏佳慧杨胜秋兰梦杰西南林业大学生态与环境学院云南昆明650224

为探明热带森林恢复对土壤反硝化N_(2)O排放时空动态的影响,选择西双版纳热带森林不同恢复阶段白背桐(Mallotus paniculatus)、崖豆藤(Mellettia leptobota)、高檐蒲桃(Syzygium oblatum)群落为研究对象,反硝化N_(2)O排放及微生物多样... 详细信息

为探明热带森林恢复对土壤反硝化N_(2)O排放时空动态的影响,选择西双版纳热带森林不同恢复阶段白背桐(Mallotus paniculatus)、崖豆藤(Mellettia leptobota)、高檐蒲桃(Syzygium oblatum)群落为研究对象,反硝化N_(2)O排放及微生物多样性分别采用“纯氧法抑制反硝化”和高通量测序测定,并分析其与土壤化学性质之间的关联特征。结果表明,1)热带森林恢复显著影响土壤反硝化N_(2)O排放速率(P崖豆藤(251.38±28.37)>白背桐(193.45±26.76)。2)反硝化N_(2)O排放速率具有显著的时空变化,季节动态表现为湿季(6月和9月)显著高于干季(3月和12月),且干湿季变幅表现为白背桐(2.94倍)>高檐蒲桃(2.50倍)>崖豆藤(2.22倍);垂直变化随土层加深逐渐降低。3)不同恢复阶段土壤水分、微生物生物量碳及Shannon多样性对反硝化N_(2)O排放速率的解释量随恢复年限呈增加趋势,其大小顺序分别为:高檐蒲桃(68.77%,70.45%,97.87%)>崖豆藤(62.54%,57.16%,96.8%)>白背桐(54.56%,46.46%,93.17%)。4)主成分分析表明,土壤有机碳、易氧化有机碳、Shannon指数、含水率、微生物量碳是调控土壤反硝化N_(2)O排放的主控因子,而全氮、硝态氮、铵态氮、水解氮、Chao指数、Simpson指数的贡献次之。热带森林恢复通过影响土壤反硝化微生物Shannon多样性、水分及碳库组分含量,进而调控反硝化过程的N_(2)O排放的时空动态。

关键词：热带森林次生演替反硝化作用反硝化微生物 N_(2)O排放

Determination of Metamizole Sodium by Cyclic Voltammetry Under Microwave Activation

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2010年第4期26卷 537-540页

作者： LI Li-jun CHENG Long-jun CAI Zhuo LAN Su-mei guo xiao-fei LI Yan-qing Department of Biological and Chemical Engineering Guangxi University of Technology Liuzhou 545006 P. R. China College of Chemistry and Chemical Engineering Guangxi University Nanning 530004 P. R. China

Microwave radiation was applied to the detection of metamizole sodium by cyclic voltammetry. The electrochemical characteristics of metamizole sodium were studied by cyclic voltammetry at GC electrode under microwave radiation and a considerable current enhancement was observed for metamizole sodium in aqueous 0.05 mol/L H2SO4. Under the optional conditions, metamizole sodium was determined in the absence and presence of microwave activation. In the absence of microwave activation cyclic voltammogram of metamizole sodium shows good linear relationship in a concentration range of 8.0×10^-5-1.0×10^-3 mol/L in aqueous 0.05 mol/L H2SO4 with a detection limit of 6.75× 10^-6 mol/L（S/N=3） and the equation of linear regression is Ip=12.973c-0.1905（R^2=0.9996, n=6）; in the presence of 80 W microwave activation cyclic voltammogram of metamizole sodiumin shows good linear relationship in a concentration range of 4.0× 10^-5-1.0×10^-3 mol/L in aqueous 0.05 mol/L H2SO4 with a detection limit of 4,41 × 10^-6 mol/L（S/N=3） and the equation of linear regression is Ip=25.107c-0.1193（R^2=0.9973, n=7）. The current in the presence of 80 W microwave activation increases to about 2 orders of magnitude compared with that in the absence of microwave activation. The proposed method in the presence of microwave activation showed high selectivity and sensitivity, and the sampling of the disposal method is simple. The method was verified by the determination of Metamizole Sodium tablet with satisfactory results.

关键词： Microwave Metamizole sodium Cyclic voltammetry

Characteristics and stability of oxide+carbonitride in H13 steel at 1250℃

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2024年第1期31卷 134-142页

作者： xiao-lin Sun Han-jie guo Jing guo fei Wang Dong Xu Gao-yang Song Shuai Wang School of Materials Science and Engineering Hebei University of EngineeringHandan056038HebeiChina School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China High Temperature Materials Research Institute Central Iron and Steel Research Institute Co.Ltd.Beijing100081China Technology Innovation Center for High Quality Cold Heading Steel of Hebei Province Hebei University of EngineeringHandan056038HebeiChina

The morphology,size,quantity,and composition of complex oxide+carbonitride in H13 steel held at 1250℃for 5,10,and 15 h were *** results show that the ratio and number of complex carbonitrides with cores in H13 steel are gradually increased when holding at 1250℃compared with those in the original H13 steel,and the core size *** are one or more oxide cores in(Ti_(x),V_(1-x))(Cy,N_(1-y)),including xCaO·zAl_(2)O_(3),xCaO·yMgO·zAl_(2)O_(3),and CaO after holding at 1250℃,in addition to MgO·Al_(2)O_(3)and Al_(2)O_(3)in the original *** equilibrium temperature for(Ti_(x),V_(1-x))(Cy,N_(1-y))precipitation at the solidification front and decomposition in the solid state was theoretically analyzed,which was affected by the x value and the product of Ti and N contents in H13 ***,the composition of(Ti_(x),V_(1-x))(Cy,N_(1-y))is influenced by the oxide *** is convinced that(Ti_(x),V_(1-x))(Cy,N_(1-y))with oxide cores has a higher stability,especially for oxides with a high Al_(2)O_(3)*** treatment at high temperature facilitates a more reasonable analysis of oxide+carbonitride,and the generation mechanism of oxide+carbonitride was discussed.

关键词： Complex carbonitride Decomposition Oxide core Characteristic Stability

Surface Polarization Effects on Collapse Transition of Polyelectrolyte Brushes

维普期刊数据库评论

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 2024年第9期42卷 1313-1320,I0006页

作者： xiao-fei Xu State Key Laboratory of Chemical Engineering and School of Chemical Engineering East China University of Science and TechnologyShanghai200237China

Polyelectrolyte brushes(PEBs)are commonly used to modify surface that have attracted great research *** dielectric permittivity of the grafted surface is typically significantly different from that of solution,which results in surface polarization(SP)effect with a jump of electric *** is thus important to study how SP alters the PEB’s structure and *** this work,the SP effects on PEB structure was studied using a statistical thermodynamic *** free energy functional to describe SP effect was constructed by using the image-charge ***,the electrostatic potential was solved from a modified Poisson-Boltzmann equation taking the ion solvation effect into *** the absence of SP,the thickness of PEB exhibited a continuous collapse transition when decreasing the solvent *** the presence of SP,the collapse became a jump-like *** energy analysis showed that the long-range Coulombic interaction dominated the transition because of the enhanced counterion condensation in the presence of *** theory provides an effective tool to study SP effect on PEBs,and the results explain the underlying physics in PEB collapse transition.

关键词： Surface polarization Polyelectrolyte brush Image charge Ion solvation Polyelectrolyte collapse transition

Quercetin Alleviates Lipopolysaccharide-Induced Cardiac Inflammation via Inhibiting Autophagy and Programmed Cell Death

在线全文

学校读者我要写书评

暂无评论

Biomedical and Environmental Sciences 2024年第1期37卷 54-70页

作者： YU Jin Hai HU guo Liang guo xiao Quan CAO Hua Bin XIA Zhao fei AMIN Buhe Jiangxi Provincial Key Laboratory for Animal Health Institute of Animal Population HealthCollege of Animal Science and TechnologyJiangxi Agricultural UniversityNanchang 330045JiangxiChina Internal Medicine Laboratory Department of Veterinary Clinical MedicineCollege of Veterinary MedicineChina Agricultural UniversityBeijing 100091China Department of Cancer Surgery Beijing Shijitan Hospital Affiliated with Capital Medical UniversityBeijing 100038China

Objective The aim of this study is to explore the potential modulatory role of quercetin against Endotoxin or lipopolysaccharide(LPS)induced septic cardiac *** Specific pathogen-free chicken embryos(n=120)were allocated untreated control,phosphate buffer solution(PBS)vehicle,PBS with ethanol vehicle,LPS(500 ng/egg),LPS with quercetin treatment(10,20,or 40 nmol/egg,respectively),Quercetin groups(10,20,or 40 nmol/egg).Fifteenday-old embryonated eggs were inoculated with abovementioned solutions via the allantoic *** embryonic day 19,the hearts of the embryos were collected for histopathological examination,RNA extraction,real-time polymerase chain reaction,immunohistochemical investigations,and Western *** They demonstrated that the heart presented inflammatory responses after LPS *** LPS-induced higher mRNA expressions of inflammation-related factors(TLR4,TNFα,MYD88,NF-κB1,IFNγ,IL-1β,IL-8,IL-6,IL-10,p38,MMP3,and MMP9)were blocked by quercetin with three *** significantly decreased immunopositivity to TLR4 and MMP9 in the treatment group when compared with the LPS *** significantly decreased protein expressions of TLR4,IFNγ,MMP3,and MMP9 when compared with the LPS *** treatment prevented LPS-induced increase in the mRNA expression of Claudin 1 and ZO-1,and significantly decreased protein expression of claudin 1 when compared with the LPS *** significantly downregulated autophagyrelated gene expressions(PPARα,SGLT1,APOA4,AMPKα1,AMPKα2,ATG5,ATG7,Beclin-1,and LC3B)and programmed cell death(Fas,Bcl-2,CASP1,CASP12,CASP3,and RIPK1)after LPS *** significantly decreased immunopositivity to APOA4,AMPKα2,and LC3-II/LC3-I in the treatment group when compared with the LPS *** significantly decreased protein expressions of AMPKα1,LC3-I,and *** significantly decreased the protein expression to CASP1 and CASP3 by immunohistochemical investigation or

关键词： Quercetin Lipopolysaccharide Inflammation Autophagy Programmed cell death Myocardiocytes permeability

Temporal-Spatial Variability of Soil Organic Carbon Stocks in a Rehabilitating Ecosystem

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2004年第4期14卷 501-508页

作者： ZHANGShi-Rong SUNBo ZHAOQi-guo xiaoPeng-fei SHUJian-Ying InstituteofSoilScience ChineseAcademyofSciencesNanjing210008（China）. CollegeofResourcesandEnvironment SichuanAgriculturalUniversityYa＇an625014（China）

In global change research, changes of soil organic carbon (SOC) reservoirs intropical and subtropical regions are still unknown. The temporal-spatial variability of SOC stockswas determined in a basin of over 579 km^2 in subtropical China from 1981to 2002. ArcGIS8.l softwarewas utilized for spatial analysis of semivariance, ordinary kriging (OK), and probability kriging(PK). Grid and hierarchical approaches were employed for the sampling scenario in 2002 with 106Global Position System (GPS) established spots sampled. Bulk topsoil samples (0—30 cm) werecollected at three random sites on each spot. The SOC content for 1981 came from the SOC map of theSecond National Soil Survey. Geostatistical results of the nugget to sill ratio (0.215-0.640)in therehabilitating ecosystem indicated a moderate spatial dependence for SOC on this large scale. Therange of SOC changed from 2.04 km in 1981 to 7.15 km in 2002. The mean topsoil SOC increased by 4.6%from 10.63 g kg^(-1) (1981) to 11.12 g kg^(-1)(2002). However, during this 21-year period 25.2% ofthe total basin area experienced a decrease in SOC. Also, the probability kriging results showedthat the geometric mean probabilities of SOC 15.0 gkg^(-1) were 0.188, 0.534 and 0.378, respectively in 2002, comparing to 0.234, 0.416 and 0.234 inthat order in 1981, respectively. The SOC storage in the topsoil increased by 17.0% during this timewith the main increase occurring in forests and cultivated land,which amounted to 82.5% and 17.0%of the total increase, respectively.

关键词： ordinary kriging probability kriging rehabilitating ecosystem soil organiccarbon temporal-spatial variability