检索结果-南通市图书馆

The role of crystallinity on differential attachment/ proliferation of osteoblasts and fibroblasts on poly （caprolactone-co-glycolide） polymeric surfaces

在线全文

学校读者我要写书评

暂无评论

Frontiers of Materials Science 2012年第1期6卷 47-59页

作者： Helen cui Patrick j.SINKO Advanced Technology and Regenerative Medicine(ATRM) LLCSomervilleNJ 08876USA Department of Pharmaceutics Ernest Mario School of PharmacyRutgersThe State University of New JerseyPiscatawayNJ 08854USA

The objective of the present study is to systematically evaluate the role of polymer crystallinity on fibroblast and osteoblast adhesion and proliferation using a series of poly（caprolactone-co-glycolide）（PCL/PGA） polymers. PCL/PGA polymers were selected since they reflect both highly crystalline and amorphous materials. PCL/PGA polymeric materials were fabricated by compression molding into thin films. Five compositions, from PCL or PGA to intermediate copolymeric compositions of PCL/PGA in ratios of 25：75, 35：65 and 45：55, were studied. Pure PCL and PGA represented the crystalline materials while the copolymers were amorphous. The polymers/copolymers were characterized using DSC to assess crystallinity, contact angle measurement for hydrophobicity, and AFM for nanotopography. The PCL/PGA films demonstrated similar hydrophobicity and nanotopography whereas they differed significantly in crystallinity. Cell adhesion to and proliferation on PCL/PGA films and proliferation studies were performed using osteoblasts and NIH-3T3 fibroblasts. It was observed that highly crystalline and rigid PCL and PGA surfaces were significantly more efficient in supporting fibroblast growth, whereas amorphous/flexible PCL/PGA 35：65 was significantly more efficient in supporting growth of osteoblasts. This study demonstrated that while chemical composition, hydrophobicity and surface roughness of PCL/PGA polymers were held constant, crystallinity and rigidity of PCL/PGA played major roles in determining cell responses.

关键词： crystallinity attachment proliferation osteoblast fibroblast PCL-PGA

Constitutive equation and model validation for a 31 vol.% B_4Cp/6061Al composite during hot compression

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

journal of Materials Science & Technology 2018年第10期34卷 1730-1738页

作者： L. zhou C. cui Q.z. Wang C. Li B.L. Xiao z.Y. Ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of B4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% B4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in B4C/AI composites.

关键词： Composites B4C/AI Constitutive equation Hot compression Finite element simulation

Partition method and experimental validation for impact dynamics of flexible multibody system

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2018年第3期34卷 482-492页

作者： j.Y.Wang z.Y.Liu j.z.Hong School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University

The impact problem of a flexible multibody system is a non-smooth, high-transient, and strong-nonlinear dynamic process with variable boundary. How to model the contact/impact process accurately and efficiently is one of the main difficulties in many engineering applications. The numerical approaches being used widely in impact analysis are mainly from two fields： multibody system dynamics （MBS） and computational solid mechanics （CSM）. Approaches based on MBS provide a more efficient yet less accurate analysis of the contact/impact problems, while approaches based on CSM are well suited for particularly high accuracy needs, yet require very high computational effort. To bridge the gap between accuracy and efficiency in the dynamic simulation of a flexible multibody system with contacts/impacts, a partition method is presented considering that the contact body is divided into two parts, an impact region and a non-impact region. The impact region is modeled using the finite element method to guarantee the local accuracy, while the non-impact region is modeled using the modal reduction approach to raise the global efficiency. A three-dimensional rod-plate impact experiment is designed and performed to validate the numerical results. The principle for how to partition the contact bodies is proposed： the maximum radius of the impact region can be estimated by an analytical method, and the modal truncation orders of the non-impact region can be estimated by the highest frequency of the signal measured. The simulation results using the presented method are in good agreement with the experimental results. It shows that this method is an effec-rive formulation considering both accuracy and efficiency. Moreover, a more complicated multibody impact problem of a crank slider mechanism is investigated to strengthen this conclusion.

关键词： Partition method Impact dynamics Experimental investigation Efficiency and accuracy Partition principle

职业使命感对大学生幸福感的影响及边界条件:一项元分析

在线全文

学校读者我要写书评

暂无评论

黑龙江高教研究 2025年第1期43卷 140-146页

作者：崔小雨李辉苏涛广东警官学院广东广州510230 中国人民公安大学北京100038 广东工业大学广东广州510520

为明晰职业使命感对大学生幸福感的影响及边界条件,基于29篇实证文献的44个独立研究、53个效应值、41819个独立样本,通过元分析方法对职业使命感与大学生幸福感的关系进行了系统量化综述。结果发现,就主效应而言,职业使命感对大学生幸... 详细信息

为明晰职业使命感对大学生幸福感的影响及边界条件,基于29篇实证文献的44个独立研究、53个效应值、41819个独立样本,通过元分析方法对职业使命感与大学生幸福感的关系进行了系统量化综述。结果发现,就主效应而言,职业使命感对大学生幸福感具有显著正向影响,且相较主观幸福感,职业使命感对大学生心理幸福感的影响更强。就边界条件而言,职业使命感对大学生幸福感的影响会因其所处地域、院校、年级而异:相较西方地域文化,职业使命感对东方地域文化下大学生幸福感、主观幸福感、心理幸福感的影响均更强;相较普通院校,职业使命感对行业特色院校大学生幸福感、主观幸福感、心理幸福感的影响均更强;相较高年级,职业使命感对低年级大学生心理幸福感的影响更强。

关键词：大学生职业使命感幸福感元分析调节效应

基于多尺度融合金字塔焦点网络的接触网零部件检测

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

工程科学学报 2025年第2期47卷 315-327页

作者：朱新宇崔浩锐宋洋中国民用航空飞行学院航空电子电气学院广汉618307 西南交通大学利兹学院成都611756

作为高铁牵引供电系统的重要组成部分,接触网系统承担着向动车组传输电能的重要功能.实际工程运营表明,受弓网交互产生的持续冲击以及外部环境的影响,接触网支撑部件可能会出现“松、脱、断、裂”等缺陷,导致接触网结构可靠性下降,严重... 详细信息

作为高铁牵引供电系统的重要组成部分,接触网系统承担着向动车组传输电能的重要功能.实际工程运营表明,受弓网交互产生的持续冲击以及外部环境的影响,接触网支撑部件可能会出现“松、脱、断、裂”等缺陷,导致接触网结构可靠性下降,严重影响接触网系统稳定运行.因此,及时精确定位接触网支撑部件(CSCs),对保障高铁安全运行和完善接触网检修维护策略具有重大意义.然而,CSCs的检测通常面临着零部件种类多、尺度差异大、部分零部件微小的问题.针对以上问题,本文提出一种基于多尺度融合金字塔焦点网络的接触网零部件检测算法,将平衡模块和特征金字塔模块相结合,提高对小目标的检测性能.首先,设计了可分离残差金字塔聚合模块(SRPAM),用于优化模型多尺度特征提取能力、扩大感受野,缓解CSCs检测的多尺度问题;其次,设计了一种基于平衡特征金字塔的路径聚合网络(PA-BFPN),用于提升跨层特征融合效率和小目标检测性能.最后,通过对比试验、可视化实验和消融实验证明了所提方法的有效性和优越性.其中,所提的MFPFCOS在CSCs数据集上的检测精度(mAP)能够在达到48.6%的同时,实现30的FLOPs(Floating point operations per second),表明所提方法能够在检测精度和检测速度之间保持良好的平衡.

关键词：深度学习目标检测接触网支撑组件(CSCs) 路径聚合特征金字塔(PA-FPN) 空洞空间卷积池化金字塔(ASPP)

KINETICS OF TEMPER EMBRITTLEMENT IN 2.25Cr-1Mo STEEL USED FOR HOT-WALL HYDROFINING REACTORS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2004年第2期17卷 139-146页

作者： j.z.Tan CollegeofMechanicalandPowerEngineering NanjingUniversityofTechnologyNanjing210009China

Based on the theory of grain boundary segregation, a kinetics model of temper em-brittlement caused by long-term service for hot-wall hydrofining reactors was *** kinetics model was applied to phosphorus (P) segregation in 2.25Cr-1Mo steelused for a hot-wall hydrofining reactor, and the kinetics of grain boundary segrea-tion of impurity P in the steel exposed to the process environment of the hydrofiningreactor was calculated on the basis of the model. The Auger electron spectroscopytest was performed in order to determine the grain boundary concentration of P. Theexperimental result is agreement with the theoretical calculated data. The results showthat the kinetics equation is reasonable for predicting the levels of grain boundarysegregation of impurity P in 2.25Cr-1Mo steel used for hot-wall hydrofining reactors.

关键词： hydrofining reactor 2.25Cr-1Mo steel temper embrittlement kinetics

Polydopamine wrapped polyaniline nanosheets:Synthesis and anticorrosion application for waterborne epoxy coatings

在线全文

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2024年第9期176卷 155-166页

作者： X.P.Hu Y.H.zhang C.B.Liu H.z.cui School of Materials Science and Engineering Shandong University of Science and TechnologyQingdao 266590China School of Materials Science and Engineering Ocean University of ChinaQingdao 266100China

Two-dimensional materials have been proved to be effective in improving the performance of anticorrosive ***,most of the reported two-dimensional materials only have the ability to passively block corrosive media and cannot effectively inhibit localized corrosion reactions at the metal/coating ***,we first synthesized a novel polyaniline(PANI)nanosheet with both barrier and passivation functions for *** addition,polydopamine(PDA)wrapped PANI nanosheets(PANI@PDA)were obtained by in situ self-polymerization reaction of dopamine on the PANI surface,which enhance its interfacial interaction with polymeric *** chemical structure,morphology and corrosion inhibition properties of the nanosheets were systematically *** incorporated PANI@PDA nanosheets in composite coating provide a longer penetration path for corrosive ***,the uniformly dispersed two-dimensional nanosheets induce the formation of passivation film on the metal *** protective effect of PANI@PDA nanosheets on coatings was verified by electrochemical impedance spectroscopy(EIS).Results indicated that the prepared composite coating exhibited excellent corrosion resistance throughout the test *** simple and effective modification strategy based on conductive polymers provides a new insight into the development of environmentally adaptive composite coatings with active and passive protection.

关键词： Corrosion prevention Polyaniline Polydopamine Nanosheet Active protection

THERMODYNAMICS OF CERIUM CARBIDE Fe_4Ce_4C_7 IN 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) 1998年第2期11卷 150-156页

作者： j.z.zhang D.z.Li Guizhou Univ of Technology Guiyang China

The thermodynamics and the properties of the cerium carbide Fe4 Ce4 C7 in steel have been studied by means of metallography, electron microprobe, X-ray diffraction technique and electrolytic separation. The main results obtained can be summarized as follows: The cerium carbide CeC2 can be precipitated in cast steel and distributed along the grain boundaries. Heat treating the steel as austenite, the CeC2 transformed into ternary compound Fe4Ce4 C7, its thermodynamics of formation in steel being expressed as: ac exp(6400/T-6. 28), where 1015Kzed light, opaque in dark field and a little greyer than iron matrix in bright field. Its Vickers hardness is about 420kg/mm2 (annealed) and 750kg/mm2 (quenched). This phase in steel is stable in basic and organic solutions and can be seperated from the matrix by electrolysis. Moreover, the LaC2 in steel can not be transformed into Fe-La-C ternary compound in present investigation.

关键词： cerium carbide electrolytic separation thermodynamics

Effect of Variable Selection on Multidisciplinary Design Optimization:a Flight Vehicle Example

在线全文

学校读者我要写书评

暂无评论

Chinese journal of Aeronautics 2007年第1期20卷 86-96页

作者： j.Roshanian z.Keshavarz MDO Laboratory Aerospace Engineering Department of K.N. Toosi University of Technology East Vafadar blvd 4th Tehranpars sq. 16579 Tehran Iran.

Different multidisciplinary design optimization （MDO） problems are formulated and compared. Two MDO formulations are applied to a sounding rocket in order to optimize the performance of the rocket. In the MDO of the referred vehicle, three disciplines have been considered, which are trajectory, propulsion and aerodynamics. A special design structure matrix is developed to assist data exchange between disciplines. This design process uses response surface method （RSM） for multidisciplinary optimization of the rocket. The RSM is applied to the design in two categories： the propulsion model and the system level. In the propulsion model, RSM determines an approximate mathematical model of the engine output parameters as a function of design variables. In the system level, RSM fits a surface of objective function versus design variables. In the first MDO problem formulation, two design variables are selected to form propulsion discipline. In the second one, three new design variables from geometry are added and finally, an optimization method is applied to the response surface in the system level in order to find the best result. Application of the first developed multidisciplinary design optimization procedure increased accessible altitude （performance index） of the referred sounding rocket by twenty five percents and the second one twenty nine.

关键词： multidisciplinary design optimization sounding rocket central composite design response surface method equation of motion of a rocket