检索结果-南通市图书馆

Effects of diamond particle size on microstructure and properties of diamond/Al-12Si composites prepared by vacuum-assisted pressure infiltration

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第4期21卷 360-368页

作者： Jia-ping Fu can-xu zhou Guo-fa Mi Yuan Liu School of Materials Science and Engineering Henan Polytechnic UniversityJiaozuo 454100HenanChina School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

Diamond/aluminium composites have attracted attention in the field of thermal management of electronic packaging for their excellent *** order to solve the interfacial problem between diamond and aluminium,a novel process combining pressure infiltration with vacuum-assisted technology was proposed to prepare diamond/aluminum *** effect of diamond particle size on the microstructure and properties of the diamond/Al-12Si composites was *** results show that the diamond/Al-12Si composites exhibit high relative density and a uniform *** thermal conductivity and coefficient of thermal expansion increase with increasing particle size,while the bending strength exhibits the opposite *** the average diamond particle size increases from 45μm to 425μm,the thermal conductivity of the composites increases from 455 W·m^(-1)·K^(-1)to 713 W·m^(-1)·K^(-1)and the coefficient of thermal expansion increases from 4.97×10^(-6)K^(-1)to 6.72×10^(-6)K^(-1),while the bending strength decreases from 353 MPa to 246 *** research demonstrates that high-quality composites can be prepared by the vacuum-assisted pressure infiltration process and the thermal conductivity of the composites can be effectively improved by increasing the diamond particle size.

关键词： diamond/aluminum composites thermal conductivity electronic packaging vacuum-assisted pressure infiltration

Highly Improved Creep Resistance in Polypropylene Through Thermally Reduced Graphene Oxide and Its Creep Lifetime Prediction

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第2期42卷 256-266,I0010页

作者： can-can Zhang Jun-Long Yang Ya-Jiang Huang Guang-Xian Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials Engineering of ChinaSichuan UniversityChengdu610065China

Polypropylene(PP) exhibits suboptimal creep resistance due to the presence of methyl groups on its main chain, leading to irregular chain segment distribution, diminished inter-chain interaction, and crystallinity. This structural feature causes chain slippage in PP under stress,significantly constraining its service lifetime. In this study, thermally reduced graphene oxide(TrGO) nanosheets were incorporated into the PP matrix, yielding a nanocomposite with exceptional creep resistance performance. Results demonstrated that at a stress of 25 MPa, a 2.0 wt% TrGO content could enhance the creep failure lifetime of PP by 21.5 times compared to neat PP. Rheology, transmission electron microscopy(TEM),and scanning electron microscopy(SEM) characterization techniques were employed to analyze the mechanism of TrGO's influence on PP's creep behavior. It was observed that when TrGO content exceeded 1.0 wt%, an effective particle network structure formed within the PP matrix. This homogeneously dispersed TrGO-formed particle network structure restricted the migration and rearrangement of PP molecular chains, enabling prolonged stress resistance without structural failure. By combining the time-strain superposition method with the critical failure strain as a criterion, generalized creep compliance curves for PP and its composites were established, facilitating the prediction of material creep failure lifetimes, with a strong agreement between experimental and predicted lifetime values. This research proposes a novel strategy aimed at developing polypropylene materials and products with enhanced long-term stability and durability, thus extending service life, reducing failure risk, and broadening their potential across various application domains.

关键词： Thermally reduced graphene oxide Polypropylene Creep failure and lifetime prediction

Highly Hydrolysis-Resistant Polyimide Fibers Prepared by Thermal Crosslinking with Inherent Carboxyl Groups

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第2期42卷 247-255,I0010页

Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chains. In this work, crosslinked polyimide fibers(CPI fibers) were produced by intrinsic carboxyl decarboxylation for the first time. The thermal stability of the polyimide fibers containing the intrinsic carboxyl groups(PIC fibers) was studied, and the temperature of the decarboxylation-crosslinking reaction was determined to be 450 ℃. The PIC fibers were hotdrawn to initiate thermal crosslinking of the carboxyl groups and molecular chain orientation at high temperature. The CPI fibers had high tensile strengths(0.72-1.46 GPa) and compressive strengths(401-604 MPa). The oriented macromolecules and chemically crosslinked structure improved the tightness of the molecular chains and endowed the CPI fibers with excellent hydrolytic resistance. The CPI-50 fiber did not dissolve in a 0.5 wt% NaOH solution during heating at 90 ℃ for 10 h, and the tensile strength retention reached 87% when treated in 0.5 wt% NaOH solutions at 90 ℃ for 1 h, providing a guarantee for its application in alkaline corrosive environments.

关键词： Polyimide Carboxyl group Crosslinking Hydrolysis-resistance

Stereochemical editing:Catalytic racemization of secondary alcohols and amines

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2024年第5期35卷 17-31页

作者： Jun Zhang Zhiyao Zheng can Zhu Department of Chemistry Fudan UniversityShanghai 200438China Department of Organic Chemistry Arrhenius LaboratoryStockholm UniversityStockholm 10691Sweden

Chiral alcohols and amines are important structural units widely existing in pharmaceuticals,agrochemicals,and food *** kinetic resolution(DKR)is an efficient strategy to deliver optically active alcohols and amines from their *** the development of DKR method,racemization catalyst plays as a crucial element with the requirement of compatibility with the kinetic resolution(KR)*** this paper,recent advance in the catalytic racemization of secondary alcohols and amines is summarized based on different types of racemizing intermediates,which are redox racemization via ketone/imine intermediates,racemization via radical intermediates,and racemization via carbocation *** racemization of secondary alcohols and amines is also enclosed.

关键词： Racemization Secondary alcohols Amines Kinetic resolution Dynamic kinetic resolution

Ytterbium modified birnessite MnO_(2) for improving deep oxidation of toluene

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第4期42卷 668-675页

作者： Linjiang Sun Yan Cheng Yujie Liu can Yi Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengdu611756China

A series of rare earth metals modified birnessite manganese dioxides(RE-Mn)was synthesized by hydrothermal method and their catalytic degradation of toluene was ***-Mn shows the best toluene oxidation activity with the conversion of T50%and T99%at 196 and 226℃,*** physiochemical characterizations identified that the high catalytic performance and excellent stability of Yb-Mn are mainly associated with its higher molar ratios of Mn^(4+)/Mn^(3+),more lattice oxygen(Olatt),and better mobility of surface adsorbed oxygen(O_(ads)).Moreover,it is confirmed that introduction of Yb into birnessite MnO_(2) facilitates the production of acetic acid at lower *** results can aid the design of high-efficiency manganese oxide catalysts for the catalytic combustion of VOCs.

关键词： Manganese oxide Rare earth metal doping Toluene Catalytic combustion

Performance of iron-air battery with iron nanoparticle-encapsulated C-N composite electrode

在线全文

学校读者我要写书评

暂无评论

Frontiers in Energy 2024年第1期18卷 42-53页

作者： can FANG Xiangmei TANG Jiaoyan WANG Qingfeng YI School of Chemistry and Chemical Engineering Hunan University of Science and TechnologyXiangtan 411201China Hunan Provincial Key Laboratory of Advanced Materials for New Energy Storage and Conversion Xiangtan 411201China

Highly efficient and stable iron electrodes are of great significant to the development of iron-air battery(IAB).In this paper,iron nanoparticle-encapsulated C–N composite(NanoFe@CN)was synthesized by pyrolysis using polyaniline as the C–N *** performance of the NanoFe@CN in different electrolytes(alkaline,neutral,and quasi-neutral)was investigated via cyclic voltammetry(CV).The IAB was assembled with NanoFe@CN as the anode and IrO_(2)+Pt/C as the *** effects of different discharging/charging current densities and electrolytes on the battery performance were also *** K_(2)SO_(4)electrolyte can effectively suppress the passivation of iron electrode,and the battery showed a good cycling stability during 180 charging/discharging *** to the pure nano-iron(NanoFe)battery,the NanoFe@CN battery has a more stable cycling stability either in KOH or NH_(4)Cl+KCl electrolyte.

关键词： energy storage and conversion metallic composites nanocomposites iron-air battery iron anode

Current status of early gastric cancer screening research

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

cancer Biology & Medicine 2024年第3期21卷 218-222页

作者： can Hu Li Yuan Xiangdong Cheng Department of Gastric surgery Zhejiang Cancer HospitalHangzhou Institute of Medicine(HIM)Chinese Academy of SciencesHangzhouZhejiang 310022China Key Laboratory of Prevention Diagnosis and Therapy of Upper Gastrointestinal Cancer of Zhejiang ProvinceHangzhou 310022China Zhejiang Provincial Research Center for Upper Gastrointestinal Tract cancer Zhejiang Cancer HospitalHangzhou 310022China

Gastric cancer is a predominant threat to the health and well-being of China's residents. Data from the World Health Organization(WHO) in 2020 revealed that gastric cancer in China notably accounted for 44.0% of new c... 详细信息

关键词： cancer Gastric gastric

Assessment of large-scale multiple forest disturbance susceptibilities with AutoML framework: an Izmir Regional Forest Directorate case

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2024年第4期35卷 73-88页

作者： Remzi Eker Kamber can Alkiş Abdurrahim Aydın Department of Forest Engineering Faculty of ForestryIzmir KatipÇelebi University35620 IzmirTurkey Graduate School of Natural and Applied Sciences Izmir KatipÇelebi University35620 IzmirTurkey Department of Forest Engineering Faculty of ForestryDüzce University81620 DüzceTurkey

Disturbances such as forest fires,intense winds,and insect damage exert strong impacts on forest ecosystems by shaping their structure and growth dynamics,with contributions from climate ***,there is a need for reliable and operational methods to monitor and map these disturbances for the development of suitable management *** susceptibility assessment using machine learning methods has increased,most studies have focused on a single ***,there has been limited exploration of the use of“Automated Machine Learning(AutoML)”in the *** this study,susceptibility assessment for multiple forest disturbances(fires,insect damage,and wind damage)was conducted using the PyCaret AutoML framework in the Izmir Regional Forest Directorate(RFD)in *** AutoML framework compared 14 machine learning algorithms and ranked the best models based on AUC(area under the curve)*** extra tree classifier(ET)algorithm was selected for modeling the susceptibility of each disturbance due to its good performance(AUC values>0.98).The study evaluated susceptibilities for both individual and multiple disturbances,creating a total of four susceptibility maps using fifteen driving factors in the *** to the results,82.5%of forested areas in the Izmir RFD are susceptible to multiple disturbances at high and very high ***,a potential forest disturbances map was created,revealing that 15.6%of forested areas in the Izmir RFD may experience no damage from the disturbances considered,while 54.2%could face damage from all three *** SHAP(Shapley Additive exPlanations)methodology was applied to evaluate the importance of features on prediction and the nonlinear relationship between explanatory features and susceptibility to disturbance.

关键词： AutoML Forest disturbances Forest fire Insect Susceptibility Wind

Cas13d-mediated gene knockdown in CAR T cells:towards off-the-shelf cancer treatment

在线全文

学校读者我要写书评

暂无评论

Signal Transduction and Targeted Therapy 2024年第5期9卷 1796-1798页

作者： Midori Johnston Nadine Urban can Dincer FIT Freiburg Centre for Interactive Materials and Bioinspired Technology University of FreiburgFreiburgGermany IMTEK-Department of Microsystems Engineering University of FreiburgFreiburgGermany

In a recent study published in Cell,Tieu et *** RfxCas13d to dynamically enhance performance and longevity of chimeric antigen receptor(CAR)T cells by massively multiplexed gene knockdown and thereby,move the treatmen... 详细信息

关键词： treatment shelf