检索结果-南通市图书馆

Porous nanofibrous dressing enables mesenchymal stem cell spheroid formation and delivery to promote diabetic wound healing

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 Chemical Engineering 2024年第4期68卷 156-164页

作者： Kexin Zhang Wenmin Zhang Heng An Zhe Huang Yanzhen Wen Xiangyu Jiao Yongqiang Wen College of Chemical Engineering and Technology Taiyuan University of Science and TechnologyTaiyuan 030024China Beijing Key Laboratory for Bioengineering and Sensing Technology Daxing Research InstituteSchool of Chemistry&Biological EngineeringUniversity of Science&Technology BeijingBeijing 100083China

Delayed and nonhealing of diabetic wounds imposes substantial economic burdens and physical pain on patients.Mesenchymal stem cells(MSCs)promote diabetic wound healing.Particularly when MSCs aggregate into multicellular spheroids,their therapeutic effect is enhanced.However,traditional culture platforms are inadequate for the efficient preparation and delivery of MSC spheroids,resulting in inefficiencies and inconveniences in MSC spheroid therapy.In this study,a three-dimensional porous nanofibrous dressing(NFD)is prepared using a combination of electrospinning and homogeneous freeze-drying.Using thermal crosslinking,the NFD not only achieves satisfactory elasticity but also maintains notable cytocompatibility.Through the design of its structure and chemical composition,the NFD allows MSCs to spontaneously form MSC spheroids with controllable sizes,serving as MSC spheroid delivery systems for diabetic wound sites.Most importantly,MSC spheroids cultured on the NFD exhibit improved secretion of vascular endothelial growth factor,basic fibroblast growth factor,and hepatocyte growth factor,thereby accelerating diabetic wound healing.The NFD provides a competitive strategy for MSC spheroid formation and delivery to promote diabetic wound healing.

关键词： Electrospinning homogenization Biomedical engineering Nanomaterials Stem cell spheroids Diabetic wound healing

homogenization with the Quasistatic Tresca Friction Law:Qualitative and Quantitative Results

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

Chinese Annals of Mathematics,Series B 2023年第5期44卷 781-802页

作者： Changqing YE Eric T.CHUNG Jun-zhi CUI Department of Mathematics the Chinese University of Hong KongShatinHong Kong SARChina LSEC Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China

Modeling of frictional contacts is crucial for investigating mechanical performances of composite materials under varying service environments.The paper considers a linear elasticity system with strongly heterogeneous coefficients and quasistatic Tresca friction law,and studies the homogenization theories under the frameworks of H-convergence and small ε-periodicity.The qualitative result is based on H-convergence,which shows the original oscillating solutions will converge weakly to the homogenized solution,while the author’s quantitative result provides an estimate of asymptotic errors in H^(1)-norm for the periodic homogenization.This paper also designs several numerical experiments to validate the convergence rates in the quantitative analysis.

关键词： homogenization Frictional contact mechanics Quasistatic Tresca frictionlaw

Thermo-Mechanical Calculation of Printed Circuit Heat Exchanger Using homogenization

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2022年第6期31卷 2309-2328页

作者： GARNIER Christophe VINCENT Sébastien LAMAGNERE Pierre LEJEAIL Yves CACHON Lionel CEA DESIRESNENuclear Technology DepartmentCadarache F-13108 Saint-Paul-Lez-DuranceFrance

The Finite-Element Method(FEM) is mainly used to design Compact Heat Exchanger structures. However, the narrow channel structures require fine mesh to accurately compute stress and strain. Combined with the dimensions of the overall component, this leads to an excessively large numerical model and therefore long computing time. This is especially true for transient thermal analyses, which require taking into account the full geometry. It is therefore interesting to reduce the size of the mesh. Periodic homogenization is an efficient method for achieving this goal. It can be applied to the core of the structure when periodic patterns(identified on basis of the arrangement of the channels) exist. A method based on this technique, with some improvements, is proposed in this paper for thermal loading without internal pressure. In addition to the Equivalent Homogenous Medium(EHM) replacing the periodic patterns, some explicit channels are interposed between the EHM and the cover plates. This has two advantages. The first is to smooth the transition of stiffness between the cover plates and the homogenized medium. The second one is to be able to directly compute stress and strain on the most critical channels located in this area. This paper assesses the method’s effectiveness for thermal loadings in order to conduct thermal stress analyses. First, the equivalent elastic constants of the EHM are obtained with a numerical Finite Elements Method. Then, two 2D cases using EHM are compared against a 2D explicit model(i.e. explicit geometry for the core channels). These cases are chosen to validate the EHM itself and its effectiveness for a real section of the heat exchanger. Results show very good agreement with a relative difference lower than 1%. In addition, the sensitivity to the number of layers added between the EHM and the cover plates is analysed. It is recommended interposing at least two layers of patterns to obtain converged results for the considered configuration. Finally, a triangular mesh is considered to re

关键词： compact heat exchanger thermal stress finite element method homogenization

Microstructural strengthening and toughening mechanisms in Fe-containing Ti-6Al-4V:A comparison between homogenization and aging treated states

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第4期99卷 114-126页

作者： Yu Liao Junhua Bai Fuwen Chen Guanglong Xu Yuwen Cui Tech Institute for Advanced Materials&College of Materials Science and Engineering Nanjing Tech UniversityNanjing 211816China

Microalloying of Ti–6Al–4V alloy by Fe addition has attracted interest as a promising way to improve castability and comprehensive mechanical performance.The mission of this work is twofold by employing the experimental examination and the phenomenological analysis,(1)to investigate the effect of Fe addition on the microstructure features and mechanical properties of the Fe-containing Ti–6Al–4V(TC4-xF)alloys subjected to casting and homogenization treatment,and(2)to unveil the critical microstructure features in homogenization,hot-worked and aging treated alloys,respectively,that benefit the yield strength and the fracture toughness.Experimental observations evidence that the addition of 0.5 wt.%Fe is most effective in enhancing the tensile ductility and the modeⅠfracture toughness.Further Fe addition up to 0.7–0.9 wt.%results in plateau values of yield and ultimate strengths with some fluctuations.Phenomenological analyses screen out the microstructural strengthening and toughening determinants which exhibit distinct sensitivities on Fe content under different processing conditions.The solid solution strengthening is confirmed as the primary effect that governs the yield strength of the homogenization treated TC4-xF alloys,followed by the refined size of colony andαlamella,so does it for the hot-worked and the aging-treated alloys.The strengthening effect of Fe could be further promoted by hot-working but impaired by a prolonged annealing time or a lowered cooling rate.The type of crack propagation path and theαmorphology are discerned to play their own leading roles in different cases to influence the performance of fracture toughness.A long crack propagation distance that traverses broadα/βlamellae embraces a high crack propagation resistance and gives rise to enhanced fracture toughness.The experimental results enrich the dataset of microstructure features and mechanical properties of Ti–6Al–4V relevant alloys.While upon the phenomenological analysis,the discovered microstructural strengthening and toughening

关键词： Ti-6Al-4V Fe microalloying homogenization Yield strength Fracture toughness Microstructural strengthening/toughening factors

Effects of homogenization temperature on microstructure and mechanical properties of high-speed-extruded Mg–5Bi–3Al alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2022年第10期10卷 2833-2846页

作者： Jae Won Cha Sang-Cheol Jin Jae-Gil Jung Sung Hyuk Park School of Materials Science and Engineering Kyungpook National University80 DaehakroDaegu 41566Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effects of billet homogenization temperature on the dynamic recrystallization behavior during high-speed extrusion and resultant microstructure and tensile properties of the Mg–5Bi–3Al(BA53,wt%)alloy.Two billets homogenized at 350 and450℃(350H and 450H billets)are extruded at a high speed of 69 m/min.The 350H billet has a relatively smaller grain size and a higher abundance of fine Mg3Bi2particles compared to the 450H billet.During extrusion of the 350H billet,enhanced dynamic recrystallization occurs as a result of its finer grains and abundance of particles,while the growth of recrystallized grains is suppressed by the grain-boundary pinning effect of particles.Ultimately,the extruded 350H material is characterized by smaller grains,relatively greater number of Mg3Bi2particles,and a higher internal strain energy than the extruded 450H material.The tensile strength of the extruded 350H material is higher than that of the extruded 450H material owing to stronger grain-boundary hardening,particle hardening,and strain hardening effects.The extruded 350H material also exhibits a higher tensile elongation as its smaller grains inhibit the formation of crack-inducing undesirable twins during tension.The results from this study demonstrate that a decrease in the homogenization temperature from 450 to 350℃leads to improved strength and ductility in the high-speed-extruded BA53 material.

关键词： Mg–Bi–Al alloy High-speed extrusion homogenization Dynamic recrystallization Tensile properties

Oxidation and internal nitridation behaviors of a Ni-based superalloy Rene 65 during high-temperature homogenization

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2023年第8期30卷 1622-1632页

作者： Xian-guang Zhang Jia-jun Chen Yang Zhou Lang Shui Dong-ping Xiao Jian-hui Fu Wen-chao Yang Huan Liu Ying-jie Ren Peng Shi Jian Zhang State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing(USTB)Beijing 100083China School of Metallurgical and Ecological Engineering University of Science and Technology Beijing(USTB)Beijing 100083China Chengdu Advanced Metal Materials Industrial Technology Institute Co. Ltd.Chengdu 610300SichuanChina Iron and State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114009LiaoningChina Pangang Group Research Institute Co. Ltd.Panzhihua 617000SichuanChina

homogenization heat treatment is a key process to remove the micro-segregation and re-dissolve the undesired phases for wrought superalloy.The oxidation behavior of the wrought superalloy during the high-temperature homogenization process,however,was rarely studied.The oxidation film evolution and growth kinetics of an as-cast superalloy Rene 65 during the homogenization were systematically studied.The oxide film consists of Cr_(2)O_(3) external oxidation layer and dendritic TiO_(2) and Al_(2)O_(3) internal oxidation layer.And the growth kinetics of the oxide film followed a parabolic law.Internal nitridation occurs during the oxidation process,and TiN is apparently formed at the tip of internal oxidation layer.The originally formed TiN can be transformed into TiO_(2) or retained with the progress of oxidation.Meanwhile,the TiN is newly formed in the deeper matrix at the new oxidation-layer tip.Thermodynamic analyses revealed that there is a competition between the oxidation and nitridation.Nitridation can occur when the partial pressure of nitrogen exceeds the threshold of nitridation and the critical partial pressure ratio of nitrogen and oxygen.

关键词： Nickel-based superalloy homogenization Oxidation Kinetics Internal nitridation Thermodynamics

A local homogenization approach for simulating the reinforcement effect of the fully grouted bolt in deep underground openings

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 Mining Science and Technology 2022年第2期32卷 247-259页

作者： Dingping Xu Xiuyang Liu Quan Jiang Shaojun Li Yangyi Zhou Shili Qiu Fei Yan Hong Zheng Xiang Huang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines Northeastern UniversityShenyang 110819China

Fully grouted bolts are a key component of the support system for underground openings.Although considerable effort has been made in the simulation of the reinforcement effect of the fully grouted bolts on the rock masses surrounding underground openings,most of the work has limited significance since the structural element approach is used.This study proposes a local homogenization approach(L-H approach)that integrates elastoplastic mechanics,composite mechanics,and analytical approaches with numerical simulation to effectively simulate the reinforcement effect of the fully grouted bolt on deep surrounding rock masses.In the L-H approach,the representative volume of bolted rock mass(RVBRM)with a fully grouted bolt is established based on the original mesh model utilized in the rockbolt element approach.The RVBRM is a regular quadrangular prism with a cross-sectional size equal to the bolt spacing and a length equal to the bolt length.The RVBRM is homogenized by the L-H approach from a unidirectional bolt-reinforced composite into a homogeneous transversely isotropic medium whose mechanical properties are described by a new transversely isotropic elastoplastic model.The L-H parameters for the RVBRM are obtained using analytical approaches,composite mechanics,and known parameters of the rock mass and bolt.Using the L-H approach,the reinforcement effect of the fully grouted bolt on the bolted rock specimen and the surrounding rock mass in Jinping II Diversion Tunnel#2 with a depth greater than 2000 m is simulated.The results show that the predictions of the L-H approach are more in agreement with the physical model results of bolted rock specimen and provide a more realistic response of the bolted surrounding rock mass.The L-H approach demonstrates that fully grouted bolts with common bolt spacings and diameters substantially enhance the elastic modulus,shear strength,and tensile strength of the rock mass in the direction of the bolt axis.

关键词： Fully grouted bolt Reinforcement effect Representative volume Transverse isotropy homogenization

Enhanced ultrasonic total focusing imaging of CFRP corner with ray theory-based homogenization technique

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2023年第1期36卷 434-443页

作者： Zhongbing LUO Jinli KANG Huanqing CAO Li LIN NDT&E Laboratory Dalian University of TechnologyDalian 116024China Shenzhen Key Laboratory of Smart Sensing and Intelligent Systems Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesShenzhen 518055China

Ultrasonic testing is effective in defect characterization and quality assurance of Carbon Fiber Reinforced Plastic(CFRP) components in the aerospace industry. Due to the coupling between complex shape and elastic anisotropy, the Phased Array Ultrasonic Testing(PAUT) and time-based Total Focusing Method(TFM) face significant challenges in the calculation of wave propagation. A wave velocity distribution model is established for a multidirectional convex corner of CFRP based on a homogenization theory and the above coupling effects are also incorporated. A ray-tracing method is proposed based on Dijkstra’s shortest path search algorithm. The predicted time of flight ensures that this technique, the homogenized TFM, could synthesize a high-quality focused image by post-processing on the full matrix capture data. Experiments on a laminate with three φ1.5 mm Side-Drilled Holes(SDHs) in different circumferential directions confirm a successful homogenized TFM imaging that all SDHs can be effectively detected. As compared to the isotropic scenario, the maximum positioning error is reduced to 0.12, 0.08, and 0.38 mm, and the Signal-to-Noise Ratios(SNRs) are increased by 2.1, 1.1, and 11.8 dB, respectively. It is suggested that the ray-tracing assisted TFM technique can effectively improve the imaging of corners in CFRP components.

关键词： Carbon fiber reinforced plastic Complex shape homogenization Imaging Time of Flight(TOF)

Effects of homogenization and heat treatment on fatty acids in milk from five dairy species

在线全文

学校读者我要写书评

暂无评论

Food Quality and Safety 2023年第1期7卷 13-19页

作者： Rongbo Fani Runjia Shi Zhongyuan Ji Qijing Du Jun Wang Hongning Jiang Rongwei Han Yongxin Yang College of Food Science and Engineering Qingdao Agricultural UniversityQingdaoChina Institute of Nutrition and Health Qingdao UniversityQingdaoChina

Milk fatty acids significantly contribute to human nutrition and clinical health.However,previous evidence for changes in the fatty acid profiles of different dairy species following homogenization and heat treatment is lacking.Here,changes in fat globule particle size and fatty acids in samples of Holstein,goat,buffalo,yak,and camel milk following homogenization(20 MPa)and heat treatment(63℃for 30 min and 90℃for 15 min)were investigated using a laser particle sizer and gas chromatography approach.The results indicated that the milk fat globule particle size of all studied dairy species significantly decreased after homogenization and heat treatment,in which there was no difference.The fatty acid composition of C10:0 and medium-chain fatty acid in goat milk,Ci8:0 and long-chain fatty acid in camel milk,and C16:0 in buffalo and yak milk served as the characteristic traits of these milks.Changes in the relative contents of several fatty acids(C4:0,C10:0,C16:0,C18:0,C18:1n9c,and C18:3n3)were dependent on homogenization,heat treatment,and the type of dairy species.In particular,C18:3n3 significantly decreased in goat and camel milk after homogenization and heat treatment.These findings provide new insights into how homogenization and heat treatment affect the fatty acid profile and can be used to further improve the heat treatment of milk from minor dairy species.

关键词： Dairyanimals fattyacid homogenization heattreatment