检索结果-南通市图书馆

复式钢管混凝土墩柱轴压性能及承载力提高分析

在线全文

学校读者我要写书评

暂无评论

Ni-Ag双原子团簇催化甲烷干法重整反应的理论研究

工程力学 2025年第1期42卷 209-222页

作者：张玉芬郝圣旺李栋磊方永坚燕山大学建筑工程与力学学院秦皇岛066099 河北工业大学土木与交通学院天津300401 河北省土木工程绿色建造与智能运维重点实验室秦皇岛066099

为提升矩形钢管混凝土独柱墩的工作性能，在其截面内套异心双圆钢管形成新型复式钢管混凝土墩柱。该文进行了7个墩柱轴压荷载试验，通过对比空钢管柱、矩形墩柱和夹层墩柱分析了新型墩柱的破坏形态、钢管应变发展及承载力和延性差异，... 详细信息

为提升矩形钢管混凝土独柱墩的工作性能，在其截面内套异心双圆钢管形成新型复式钢管混凝土墩柱。该文进行了7个墩柱轴压荷载试验，通过对比空钢管柱、矩形墩柱和夹层墩柱分析了新型墩柱的破坏形态、钢管应变发展及承载力和延性差异，最后利用钢管和混凝土的组合效应原理进行组合墩柱轴压承载力提高分析。研究得出新型复式钢管混凝土墩柱轴压破坏形态为鼓曲破坏，其极限承载力较夹层墩柱提高20%，较矩形墩柱提高22%，延性提高效果更为明显;新型墩柱内、外钢管应变发展充分，说明钢管较好地发挥了竖向承载和横向约束混凝土的能力;根据钢板的正则化宽厚比和屈曲后强度计算得出，内、外钢管在混凝土的支撑下承载力提高15%，混凝土在钢管的约束下承载力提高49%;根据约束组合效应得出，新型墩柱整体承载力提高31%;采用等效套箍系数计算的新型墩柱承载力与试验值绝对误差在4%以内，说明新型复式钢管混凝土墩柱符合钢管混凝土统一理论。研究结果表明，新型复式钢管混凝土墩柱在约束混凝土效应方面明显提高，构件的承载力较高、延性较好，具有较强的工程应用前景。

关键词：新型复式钢管混凝土墩柱轴压性能破坏形态承载力套箍系数

来源：博看期刊评论

在线全文

博看期刊

学校读者我要写书评

暂无评论

原子与分子物理学报 2025年第3期42卷 13-20页

作者：刘佳慕红梅张明明李文雅李东东张建辉兰州资源环境职业技术大学黄河流域生态环境产教融合研究院兰州730021 贵州民族大学化学工程学院贵阳550025

甲烷干重整制合成气是将温室气体转换为合成气的有效途径,兼具环境效益和经济效益.本文采用密度泛函理论方法对Ni-Ag双原子团簇催化甲烷干重整反应的体系进行理论研究,对势能面上各驻点进行了全几何参数优化,通过频率分析确认了过渡态,... 详细信息

甲烷干重整制合成气是将温室气体转换为合成气的有效途径,兼具环境效益和经济效益.本文采用密度泛函理论方法对Ni-Ag双原子团簇催化甲烷干重整反应的体系进行理论研究,对势能面上各驻点进行了全几何参数优化,通过频率分析确认了过渡态,并通过内禀反应坐标方法进行了验证,得出各基元反应的能量最低路径.研究结果对于理解在Ni上引入第二种金属Ag形成双原子团簇催化甲烷干法重整的理论研究有一定的意义,并为下一步实验研究提供理论基础.

关键词：甲烷干重整 Ni-Ag双原子团簇密度泛函理论活化能

维普期刊数据库博看期刊

Numerical study on evolution of subharmonic varicose low-speed streaks in turbulent channel flow

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2016年第3期37卷 325-340页

作者： jian li Gang dong jianlei zhang National Key Laboratory of Transient Physics Nanjing University of Science and Technology

The evolution of two spanwise-aligned low-speed streaks in a wall turbulent flow, triggered by the instability of the subharmonic varicose （SV） mode, is studied by a direct numerical simulation （DNS） method in a small spatial-periodic channel. The results show that the SV low-speed streaks are self-sustained at the early stage, and then transform into subharmonic sinuous （SS） low-speed streaks. Initially, the streamwise vortex sheets are formed by shearing, and then evolve into zigzag vortex sheets due to the mutual induction. As the intensification of the SV low-speed streaks becomes prominent, the tilted streamwise vortex tubes and the V-like streamwise vortex tubes can be formed simultaneously by increasing ＋~. When the SV low-speed streaks break down, new zigzag streamwise vortices will be generated, thus giving birth to the next sustaining cycle of the SV low-speed streaks. When the second breakdown happens, new secondary V-like streamwise vortices instead of zigzag streamwise vortices will be generated. Because of the sweep motion of the fluid induced by the secondary V-like streamwise vortices, each decayed low-speed streak can be divided into two parts, and each part combines with the part of another streak, finally leading to the formation of SS low-speed streaks.

关键词： low-speed streak subharmonic varicose mode turbulent boundary layer,direct numerical simulation

Effect of Cooling Rate on Microstructure and Mechanical Properties of 20CrNi2MoV Steel

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2016年第4期29卷 353-359页

作者： jian zhang Chang-Sheng li Bin-Zhou li Zhen-Xing li Xue-dong Pang State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China Fushun Special Steel Co. Ltd Fushun 110003 China

Thermo-mechanical process and continuous cooling process were carried out on 20CrNi2MoV steel. Three cooling rates were implemented to optimize the mechanical properties. The microstructure evolution, precipitation behavior, and strengthening mechanisms were systematically investigated, and the fracture mechanisms were analyzed via combination of impact fracture morphologies and deflection-load curves. The experimental results indicate that the transformed microstructure of experimental steel is all complex consisting of granular bainitic ferrite and bainitic ferrite with dispersed martensite/austenite （M/A） constituents in the matrix at cooling rates of 13, 21, and 29 ℃/s. When the cooling rate increases, the grain of the steel is obviously refined. The sizes of the bainitic ferrite are 5.8, 4.7, and 3.1 μm under cooling rates of 13, 21, and 29 ℃/s, respectively. The refinement of the bainitic ferrite plays a dominant role in strength increasing and also contributes to high crack propagation energy. However, the morphologies of M/A constituents obtained under different cooling rates contribute to different crack initiation energies and then affect the impact property.

关键词： 20CrNi2MoV steel Microstructure Cooling rate Mechanical properties

阿尔茨海默病患者MRI表现与认知功能的关系

在线全文

学校读者我要写书评

暂无评论

中国CT和MRI杂志 2025年第1期23卷 28-29,32页

作者：李方建陈飞董从松李新黄锋盐城市第三人民医院(南通大学第六附属医院)影像科江苏盐城224008

目的探究阿尔茨海默病(AD)患者磁共振成像(MRI)表现与认知功能的关系。方法回顾性分析2021年5月至2023年5月收治的78例AD患者的临床资料,患者均进行MRI检查,并使用简易智力状态检查量表(MMSE)对患者认知功能进行评估,将MMSE得分<20分... 详细信息

目的探究阿尔茨海默病(AD)患者磁共振成像(MRI)表现与认知功能的关系。方法回顾性分析2021年5月至2023年5月收治的78例AD患者的临床资料,患者均进行MRI检查,并使用简易智力状态检查量表(MMSE)对患者认知功能进行评估,将MMSE得分<20分的患者纳入中重度组(n=37),将MMSE得分≥20分的患者纳入轻度组(n=41),分析两组患者脑室结构体积(左海马体积、右海马体积、胼胝体体积、侧脑室体积)、侧脑室颡角宽度(左侧脑室颞角宽度、右侧脑室颞角宽度)、外侧裂宽度水平、MRI诊断结果差异。结果中重度组患者左海马体积、右海马体积、胼胝体体积、侧脑室体积均低于轻度组(P均<0.05);中重度组患者左侧脑室颞角宽度、右侧脑室颞角宽度、外侧裂宽度均高于轻度组(P均<0.05);中重度组患者海马萎缩、脑萎缩、脑室改变发生率均高于轻度组(P均<0.05)。结论AD患者中认知功能损害严重的患者进行M RI检查后发现存在明显海马体萎缩、脑萎缩、脑室改变,AD患者MRI表现与认知功能存在联系。

关键词：阿尔茨海默病磁共振成像认知功能海马体

NUMERICAL SOLUTIONS OF REYNOLDS AVERAGED NAVIER-STOKES EQUATIONS FOR 3-D TURBULENT FLOW OVER CONCAVE SURFACES OF DISCHARGING STRUCTURES

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

Journal of Hydrodynamics 2000年第4期12卷 120-126页

作者： Wei Wen-li li jian-zhong zhang dong-sheng Xi′an University of Technology Xi′an 710048P.R.China

This paper is conserned with a numerical method for the solution of complete Reynolds averaged Navier Stokes equations for three dimensional flows over the concave surfaces of discharging structures. A non orthogonal body fitted coordinate system was used to deal with the complex physical geometry, and finite volume method (FVM) was employed to solve the convective transport equations for mean velocities and turbulence parameters (k, ε). It is indicated through the numerical example that the calculated results are in good agreement with the experimental ones, and it is also proved that this numerical method used to predict the characteristics of turbulent flow over the concave surfaces of discharging structures is feasible.

关键词： non-orthogonal body fitted coordinate system turbulent flow concave surface of discharging structure

Synthesis and analysis of new humidity-controlling composite materials

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2017年第5期24卷 594-602页

作者： jian-li Shang Zhi-fang Zong Hao zhang College of Materials and Mineral Resources Xi’an University of Architecture and TechnologyXi’an 710055China

Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added liCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of liCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.

关键词： composite materials gypsum humidity control sol-gel processing adsorption desorption

TD-DFT Study on Pyrazoline Derivatives

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Structural Chemistry 2005年第10期24卷 1169-1175页

作者： MIAO Ti-fang zhang jian-Fu li Shuang Department of Chemistry Huaibei Coal Teachers College Huaibei 235000 China Department of Chemistry Zhoukou Teachers College Zhoukou 466000 China

The molecular structures of ground state and first single excited state for pyrazoline derivatives are optimized with DFT B3LYP method and ab initio “configuration interaction with single excitations”（CIS） method, respectively. The frontier molecular orbital characteristics have been analyzed systematically, and the electronic transition mechanism has been discussed. Electronic spectra are calculated by using TD-DFT method. These results are consistent with those from the experiment.

关键词： pyrazoline derivatives electron transfer time-dependent density functional theory (TD-DFT) electronic spectrum

Better Choice:linear Long Chains Rather than Branched Ones to Improve Mechanical Performance of Polyethylene through Generating Shish-Kebabs

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2020年第7期38卷 715-729,I0006页

作者： Lu-Feng Deng Xi-Xi zhang dong Zhou jian-Hua Tang Jun Lei Jun-fang li Zhong-Ming li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu 610065China College of Chemical Engineering Sichuan UniversityChengdu 610065China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

We utilized two structurally different long chains(linear and branched ultra-high molecular weight polyethylene)to reveal the dependence of flow-induced crystallization on long chain architecture,and prepared two bi-disperse systems of 98 wt%short chain and 2 wt%long chain.A flow field was applied to the bi-disperse polyethylene melt by a modified injection-molding machine,known as oscillation shear injection molding(OSIM).For the first time,the structural influence of long chains on flow-induced shish-kebab formation was systematically *** the intermediate layer of OSIM samples,the branched long chains were better than the linear long chains at inducing shish-kebab formation,agreeing with the reported literatures,because the branches can maintain their oriented conformations *** unexpectedly,the reverse is the case for the core layer of OSIM samples,where the shear flow was much weaker than the intermediate *** understand the unexpected phenomenon,the lifetime of shishes induced by different long chains was *** demonstrated that the linear-induced shishes possessed higher thermal stability than the branched-induced ones so that the linear-induced shishes could survive in the core layer of OSIM ***,unlike other methods for flow-induced crystallization,OSIM could create samples for measuring mechanical properties,and thus offer the chance to reveal the relationship between structure and *** mechanical results demonstrated that both long chains remarkably enhanced the mechanical properties because of the significant promoting effect of long chains and intense flow fields on shish-kebab ***,the linear long chains induced more stable and flawless shishes with higher tensile strength and modulus(80.4 and 1613.5 Mpa,respectively)than the branched ones(74.4 and 1489.3 Mpa).Our research not only helps elucidate the mechanism of shish-kebab formation but also provides a better choice to reinforce

关键词： Polyethylene Crystallization Shear-induced Long chain Short chain