检索结果-南通市图书馆

数字经济如何影响绿色全要素生产率?——来自中国地级市的证据

在线全文

学校读者我要写书评

暂无评论

软科学 2024年第3期38卷 44-52页

作者：邹静王强鄢慧丽邓晓军浙江财经大学金融学院杭州310018 浙江财经大学经济学院杭州310018 杭州国际城市学研究中心/浙江省城市治理研究中心杭州311121 华东师范大学城市与区域科学学院上海200241 海南大学旅游学院海口570228

基于2011—2020年中国地级市面板数据,运用多种计量方法探究了数字经济对绿色全要素生产率具的影响及作用机制。研究发现,数字经济对绿色全要素生产率具有显著正向影响,主要推动绿色技术进步。产业结构升级和要素配置扭曲缓解在其中发... 详细信息

基于2011—2020年中国地级市面板数据,运用多种计量方法探究了数字经济对绿色全要素生产率具的影响及作用机制。研究发现,数字经济对绿色全要素生产率具有显著正向影响,主要推动绿色技术进步。产业结构升级和要素配置扭曲缓解在其中发挥中介作用。数字经济是资源型城市打破“资源诅咒”的关键因素,但数字经济发展不均衡会导致中心城市与外围城市存在“数字鸿沟”。从时间效应来看,产业数字化和数字产业化等数字经济细分维度的发展是绿色全要素生产率提升的持久动力。最后,基于DID模型评估政策效应表明,数字化经济政策也有利于提升绿色全要素生产率。

关键词：数字经济绿色全要素生产率产业结构升级要素配置扭曲工具变量法

区域企业孵化系统资源配置效率评价及解构——基于中国内地28个省级行政区的经验数据分析

在线全文

学校读者我要写书评

暂无评论

科学决策 2024年第8期 94-112页

作者：张玲张慧敏常红锦闫慧丽山西财经大学

当前我国的企业孵化产业正遭遇低效运作与资源配置失衡的双重困境,严重阻碍了创业经济的发展进程。论文建立了区域企业孵化系统资源配置的二阶段理论模型并完成28个省域系统的效率评价和分阶段解构,使用Malmquist指数模型探索各区域效... 详细信息

当前我国的企业孵化产业正遭遇低效运作与资源配置失衡的双重困境,严重阻碍了创业经济的发展进程。论文建立了区域企业孵化系统资源配置的二阶段理论模型并完成28个省域系统的效率评价和分阶段解构,使用Malmquist指数模型探索各区域效率的纵向演化规律。研究发现:①近年来我国各省域企业孵化系统资源配置平均效率整体偏低,东北地区的效率长期低迷,提升空间巨大。②省域效率按两阶段维度划分为四大类型,只有少数省份属于两阶段双高效率区域,多数省份面临阶段间资源配置能力衔接不畅的挑战。③我国区域企业孵化系统资源配置效率下降的根本原因在于创业孵化在众多关键技术领域难以取得实质性的突破。

关键词：区域企业孵化系统资源配置效率评价

CYP1A2基因多态性与前列腺增生术后尿路感染的关联及MCP-1、SP-A/D、U-HBP和LEU的预测价值

在线全文

学校读者我要写书评

暂无评论

中华医院感染学杂志 2024年第10期34卷 1512-1516页

作者：王娜高岩林张晓萌潘丽丽何雪洁闫丽辉邢台市人民医院泌尿外科河北邢台054000

目的探讨CYP1A2基因多态性与前列腺增生术后尿路感染的关联及单核细胞趋化蛋白1(MCP-1)、表面活性蛋白(SP)-A/D、尿肝素结合蛋白(U-HBP)、白细胞酯酶(LEU)的预测价值。方法选取268例邢台市人民医院2020年3月-2023年6月收治的前列腺增生... 详细信息

目的探讨CYP1A2基因多态性与前列腺增生术后尿路感染的关联及单核细胞趋化蛋白1(MCP-1)、表面活性蛋白(SP)-A/D、尿肝素结合蛋白(U-HBP)、白细胞酯酶(LEU)的预测价值。方法选取268例邢台市人民医院2020年3月-2023年6月收治的前列腺增生患者,根据术后尿路感染情况分组,包括51例感染组和217例未感染组,统计术后尿路感染的病原菌分布;检测MCP-1、U-HBP、SP-A/D和LEU水平;受试者工作特征(ROC)曲线分析各指标对前列腺增生术后尿路感染的诊断价值。采用限制性片段长度多态性聚合酶链反应(PCR-RFLP)检测两组患者CYP1A2基因多态性。结果前列腺增生术后尿路感染发生率为19.03%;共分离病原菌63株,革兰阴性菌居多;感染组LEU阳性表达率及MCP-1、SP-A/D、U-HBP水平均高于未感染组(P<0.05);MCP-1、U-HBP、SP-A/D、LEU四者联合预测前列腺增生术后尿路感染的曲线下面积(AUC)为0.955;感染组CYP1A2 rs20695143859位点AA基因型频率和A等位基因频率较未感染组升高(P<0.05),GG基因型频率和G等位基因频率低于未感染组(P<0.05)。结论前列腺增生术后尿路感染发生率较高,其中革兰阴性菌占比较大;前列腺增生术后尿路感染MCP-1、SP-A/D、U-HBP呈高表达,LEU阳性表达率升高,联合检测有助于诊断前列腺增生术后尿路感染;CYP1A2基因多态性可能参与前列腺增生术后尿路感染病情进展。

关键词：前列腺增生尿路感染病原菌基因多态性单核细胞趋化蛋白1 表面活性蛋白尿肝素结合蛋白白细胞酯酶

Effects of Sm content on crystallized structure and magnetic properties of Co80-xSmxb20 amorphous alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2020年第4期27卷 471-476页

作者： Lei-qiang Lai yan-hui li Feng Bao Wei Zhang Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of Materials Science and EngineeringDalian University of TechnologyDalian 116024LiaoningChina

The formation,thermal stability,crystallized structure,and magnetic properties of melt-spun Co80-xSmxB20(x=0–20)amorphous alloys have been investigated.A single amorphous phase is formed for the alloys with x=0–*** first crystallization temperature gradually increases from 670 to 955 K as x increases from 0 to 10,and decreases to 836K when x=*** optimum annealing,the nanocomposite structure consisting of SmCo12B6+fcc-Co+Sm2Co17 phases is formed for the alloys with x=5 and 7.5,and SmCo12B6+Sm2Co17+SmCo3,SmCo12B6+Sm2Co17+SmCo4B,and SmCo12B6+SmCo4B phases are formed for the alloys with x=10,12.5,and 15,*** coercivity of the annealed alloys increases remarkably from 103.5 to 1249.4 kA m^-1 as x increases from 5 to 15,while the magnetization at the applied field of 2.0T decreases from 0.51 to *** improved magnetic hardness with rising Sm content is attributed to the formation of the hard magnetic phases with higher magnetocrystalline anisotropy and the increase in their volume fraction.

关键词： Co-Sm-B alloy Melt-spun Amorphous alloy Crystallized structure Magnetic property

Kinetic study on the direct nitridation of silicon powders diluted with α-Si_3N_4 at normal pressure

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

International Journal of Minerals,Metallurgy and Materials 2013年第5期20卷 493-498页

作者： Shao-wu Yin li Wang li-ge Tong Fu-ming yang yan-hui li School of Mechanical Engineering University of Science and Technology Beijing Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry University of Science and Technology Beijing

Silicon nitride （Si3N4） powders were prepared by the direct nitridation of silicon powders diluted with a- Si3N4 at normal pressure. Silicon powders of 2.2 μm in average diameter were used as the raw materials. The nitriding temperature was from 1623 to 1823 K, and the reaction time ranged from 0 to 20 min. The phase compositions and morphologies of the products were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The effects of nitriding temperature and reaction time on the conversion rate of silicon were determined. Based on the shrinking core model as well as the relationship between the conversion rate of silicon and the reaction time at different temperatures, a simple model was derived to describe the reaction between silicon and nitrogen. The model revealed an asymptotic exponential trend of the silicon conversion rate with time. Three kinetic parameters of silicon nitridation at atmospheric pressure were calculated, including the pre-exponential factor （2.27 cm.s^-1） in the Arrhenius equation, activation energy （114 kJ·mol^-1）, and effective diffusion coefficient （6.2×10-s cm2.s^-1）. A formula was also derived to calculate the reaction rate constant.

关键词： silicon nitride powders nitridation reaction kinetics activation energy

Enhancement of glass-forming ability and thermal stability of a soft magnetic Co_(75)B_(25)metallic glass by micro-alloying Y and Nb

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2021年第5期28卷 597-603页

作者： Feng Bao yan-hui li Zheng-wang Zhu Xin-yu liang yan Zhang Wei Zhang Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of Materials Science and EngineeringDalian University of TechnologyDalian 116024LiaoningChina Institute of Metal Research Chinese Academy of SciencesShenyang 110016LiaoningChina Institute for Materials Research Tohoku UniversitySendai 980-8577MiyagiJapan

Soft magnetic Co-based Co-Y-Nb-B bulk metallic glasses(BMGs)without Fe have been developed by micro-alloying Y and Nb into a C075B25 ***,addition of 3^at.%Y promotes the occurrence of glass transition and increases the supercooled liquid stability and magnetic softness.C0_(71.5)Y_(35)B_(25) metallic glass possesses a large supercooled liquid region(△T_(x))of 33 K and low coercivity(H_(c))of l.5 A/*** alloying 2-4 at.% Nb into C0_(71.5)Y_(35)B_(25) alloy further enlarges △T_(x) to 50 K,lowers H_(c) to 0.9 A/m,and enables the formation of BMGs with a critical sample diameter up to 2.0 *** alloying Nb causes the formation of complex(Co,Nb,Y)_(23)B_(6) competing phase during crystallization and widens the melt undercooling during solidification,which improves the supercooled liquid stability and glass-forming ability,***-Y-Nb-B BMGs also exhibit good soft magnetic and mechanical properties,i.e.,lowH_(c)of 0.9-1.2 A/m,relatively high saturation magnetic flux density of 0.36-0.57 T,high yielding strength of 3877-3930 MPa with plastic strain of 0.2%-0.3%,and high Vickers hardness of *** developed soft magnetic Co-based BMGs are promising for applications as structural and functional materials.

关键词： Co-based bulk metallic glass Glass-forming ability Thermal stability Soft magnetic property Micro-alloying

Relationship Between Microstructure and Corrosion Behavior of Cr12Ni3Co12Mo4W Ultra-High-Strength Martensitic Stainless Steel

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

Acta Metallurgica Sinica(English Letters) 2016年第11期29卷 1064-1072页

作者： hui-yan li Chao-Fang Dong Kui Xiao Xiao-Gang li Ping Zhong Corrosion and Protection Center Key Laboratory for Corrosion and Protection (MOE) University of Science and Technology Beijing Beijing 100083 China Beijing Institute of Aeronautical Materials Beijing 100095China

The effect of tempering temperature on the microstructure and corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel was investigated using transmission electron microscopy, atomic force microscopy, X-ray diffraction, and electrochemical tests. The microstructures of the ultra-high-strength martensitic stainless steel consisted of some retained austenite and lath/plant martensite with the carbides distributed within the matrix and at the grain boundaries. Tempering of the steel for 4 h at various temperatures resulted in various carbide grain sizes and different amounts of the retained austenite. The results showed that larger carbide grains led to diminished corrosion resistance, whereas larger amounts of the retained austenite resulted in improved corrosion resistance. The steels exhibited good corrosion resistance in 0.017 mol/L NaCl solution and exhibited pitting corrosion in 0.17 mol/L Na Cl solution. The martensite and prior austenite crystal boundaries dissolved in solution with pH 1.

关键词： Heat treatment Martensite Retained austenite Carbide Corrosion behavior

Effects of chloride ion concentration and pH values on the corrosion behavio of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2016年第11期23卷 1286-1293页

作者： hui-yan li Chao-fang Dong Kui Xiao Xiao-gang li Ping Zhong Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing 100083 China Beijing Institute of Aeronautical Materials Beijing 100095 China

The effects of Cl ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel（UHSMSS） were investigated by a series of electrochemical tests combined with observations by stereology microscopy and scanning electron microscopy. A critical Cl- ion concentration was found to exist（approximately 0.1wt%）, above which pitting occurred. The pitting potential decreased with increasing Cl- ion concentration. A UHSMSS specimen tempered at 600°C exhibited a better pitting corrosion resistance than the one tempered at 400°C. The corrosion current density and passive current density of the UHSMSS tempered at 600°C decreased with increasing pH values of the corrosion solution. The pits developed a shallower dish geometry with increasing polarization potential. A lacy cover on the pits of the UHSMSS tempered at 400°C accelerated pitting, whereas corrosion products deposited in the pits of the UHSMSS tempered at 600°C hindered pitting.

关键词： martensitic stainless steel steel corrosion chloride ions pitting potential

Effects of Ribbon Thickness on Structure and Soft Magnetic Properties of a High-Cu-Content FeBCuNb Nanocrystalline Alloy

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2022年第2期35卷 235-242页

作者： li-Cheng Wu yan-hui li Xing-Jie Jia Ai-Na He Wei Zhang Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of Materials Science and EngineeringDalian University of TechnologyDalian 116024China Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology CAS Key Laboratory of Magnetic Materials and DevicesNingbo Institute of Materials Technology&EngineeringChinese Academy of SciencesNingbo 315201China

The effects of ribbon thickness(t)on the structure and magnetic properties of a Fe_(82.3)B_(13)Cu_(1.7)Nb_(3) alloy in melt-spun and annealed states have been *** the t from 15 to 23μm changes the structure of the melt-spun ribbons from a single amorphous phase to a composite with denseα-Fe nanograins embedded in the amorphous *** grain size(D_(α-Fe))of theα-Fe near the free surface of the ribbon is about 6.7 nm,and it gradually decreases along the cross section toward the wheel-contacted *** increasing the t to 32μm coarsens the D_(α-Fe) near the free surface to 15.2 nm and aggravates the D_(α-Fe) ramp along the cross *** annealing,the ribbon with t=15μm has relatively largeα-Fe grains with D_(α-Fe)>30 nm,while the thicker ribbons possessing the pre-existing nanograins form a finer nanostructure with D_(α-Fe)lity at 1 kHz of 15,*** ribbon with t=32μm has a slightly larger coercivity due to the lower structural *** formation mechanism of the fine nanostructure for the ribbons with suitable t has been discussed in terms of the competitive growth effect among the pre-existingα-Fe nanograins.

关键词： Fe-based nanocrystalline alloy Microstructure Pre-existingα-Fe nanograin Soft magnetic properties Ribbon thickness