检索结果-南通市图书馆

A New Ductile Fracture Criterion and Its Application to the Prediction of Forming limit in Deep Drawing

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 2003年第z1期19卷 217-219页

作者： yuying YANG Zhongqi yu Xuechun li Zhenzhong sun School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China

With considering the influence of equivalent plastic strain on void-damage and taking Lemaitre damage equivalent stress as plastic potential, based on continuous damage mechanics theory, a new criterion for ductile fracture is derived. The two key material constants in the criterion are determined by the combination of tension tests with FE (finite element) simulation. On the basis of the values of stress and strain calculated from commercial finite element software, the forming limit in cylindrical deep drawing of annealed aluminum alloy LY12(M) is predicted by means of the new ductile fracture criterion. Experiments verify that the predicted results are in agreement with the experimental ones. Hence, it is reliable to predict the forming limit in deep drawing by means of the new ductile fracture criterion.

关键词： Sheet metal forming, Ductile fracture criterion, FEM, Forming limit

Mechanism of brittle-ductile transition of a glass-ceramic rigid substrate

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 2011年第2期18卷 229-233页

作者： yu-li sun Dun-wen Zuo Hong-yu Wang Yong-wei Zhu Jun li Jiangsu Key Laboratory of Precision and Micro-manufacturing Technology College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The hardness, elastic modulus, and scratch resistance of a glass-ceramic rigid substrate were measured by nanoindentation and nanoscratch, and the fracture toughness was measured by indentation using a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 200 nm are 9.04 and 94.70 GPa, respectively. These values reflect the properties of the glass-ceramic rigid substrate. The fracture toughness value of the glass-ceramic rigid substrate is 2.63 MPa？m1/2. The material removal mechanisms are seen to be directly related to normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after scratching and the friction profile are 268.60 mN and 335.10 nm, respectively. If the load and scratch depth are under the critical values, the glass-ceramic rigid substrate will undergo plastic flow rather than fracture. The formula of critical depth of cut described by Bifnao et al. is modified based on the difference of critical scratch depth

关键词： brittle-ductile transition critical conditions glass ceramics nanoindentation nanoscratch

Silicon-mediated enantioselective synthesis of structurally diverseα-amino acid derivatives

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2020年第8期63卷 1082-1090页

作者： Jun-Han Ma li li yu-li sun Zheng Xu Xing-Feng Bai Ke-Fang Yang Jian Cao yu-Ming Cui Guan-Wu Yin li-Wen Xu Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education and Key Laboratory of Organosilicon Material Technology of Zhejiang ProvinceHangzhou Normal UniversityHangzhou 311121China State Key Laboratory for Oxo Synthesis and Selective Oxidation Suzhou Research Institute(SRI)and Lanzhou Institute of Chemical Physics(LICP)University of Chinese Academy of Sciences(UCAS)Lanzhou 730000China

The catalytic asymmetric synthesis of novel and chiral amino acid derivatives with unconventional chemo-,diastereo-,and enantio-selectivity remains a paramount *** we reported a novel protocol for the use of highly enantioselective copper-catalyzed cycloaddition ofα,β-unsaturated acylsilanes as a springboard reaction for the facile synthesis of structurally diversified pyrrolidines and complicatedα-amino esters by *** newly developed process could provide a wide range of synthetically useful acylsilane-substituted pyrrolidines(ASiP)in high yields and excellent diastereo-and enantioselectivities with Cu/(R)-XylBINAP complex as the *** the downstream desilylation transformation enables to expand the potntial applications of 1,3-dipolar cycloaddition in the construction of structurally unique amino acid derivatives,in which an unprecedented and concerted fluoride anion-promoted C–X(X=H,Si,N,C)bond cleavage occurred to the enantioselective construction of aldehyde-substituted pyrrolidines,linear cinnamaldehyde or alkene-substituted amino esters in high ee values.

关键词： (3+2)cycloaddition asymmetric catalysis acylsilane pyrrolidine amino aldehyde amino acids

Exploring changes of precipitation extremes under climate change through global variable-resolution modeling

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2024年第2期69卷 237-247页

作者： Wei sun Jian li Rucong yu Nina li Yi Zhang State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China Institute of Tibetan Plateau Meteorology China Meteorological AdministrationChengdu 610072China Department of Atmospheric Science Yunnan UniversityKunming 650091China National Meteorological Center China Meteorological AdministrationBeijing 100081China 2035 Future Laboratory PIESAT Information Technology Co.Ltd.Beijing 100105China

Understanding the responses of precipitation extremes to global climate change remains limited owing to their poor representations in models and complicated interactions with multi-scale *** we take the record-breaking precipitation over China in 2021 as an example,and study its changes under three different climate scenarios through a developed pseudo-global-warming(PGW)experimental framework with 60-3 km variable-resolution global ensemble *** to the present climate,the precipitation extreme under a warmer(cooler)climate increased(decreased)in intensity,coverage,and total amount at a range of 24.3%-37.8%(18.7%-56.1%).With the help of the proposed PGW experimental framework,we further reveal the impacts of the multi-scale system interactions in climate change on the precipitation *** the warmer climate,large-scale water vapor transport converged from double typhoons and the subtropical high marched into central China,enhancing the convective energy and instability on the leading edge of the transport *** a result,the mesoscale convective system(Mcs)that directly contributed to the precipitation extreme became stronger than that in the present *** the contrary,the cooler climate displayed opposite changing characteristics relative to the warmer climate,ranging from the large-scale systems to local environments and to the *** summary,our study provides a promising approach to scientifically assess the response of precipitation extremes to climate change,making it feasible to perform ensemble simulations while investigating the multi-scale system interactions over the globe.

关键词： Precipitation extreme Climate change Pseudo-global-warming experiment Variable-resolution modeling Multi-scale system interaction

System Strength Assessment Based on Multi-task Learning

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2024年第1期10卷 41-50页

作者： Baoluo li Shiyun Xu Huadong sun Zonghan li lin yu Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education Shandong UniversityJinan 250014China China Electric Power Research Institute Beijing 100192China

Increase in permeability of renewable energy sources(RESs)leads to the prominent problem of voltage stability in power system,so it is urgent to have a system strength evaluation method with both accuracy and practicability to control its access scale within a reasonable ***,a hybrid intelligence enhancement method is proposed by combining the advantages of mechanism method and data driven ***,calculation of critical short circuit ratio(CSCR)is set as the direction of intelligent enhancement by taking the multiple renewable energy station short circuit ratio as the quantitative ***,the construction process of CSCR dataset is proposed,and a batch simulation program of samples is developed accordingly,which provides a data basis for subsequent ***,a multi-task learning model based on progressive layered extraction is used to simultaneously predict CSCR of each RESs connection point,which significantly reduces evaluation error caused by weak *** performance and anti-noise performance of the proposed method are verified on the CEPRI-FS-102 bus system,which provides strong technical support for real-time monitoring of system strength.

关键词： Critical short circuit ratio hybrid intelligence enhancement multi-task learning system strength

A Cooperative Schema between Web Sever and Search Engine for Improving Freshness of Web Repository

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2006年第1期11卷 11-14页

作者： WEN Kun-mei LU Zheng-ding li yu-hua sun Xiao-lin College of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074Hubei China

Because the web is huge and web pages are updated frequently, the index maintained by a search engine has to refresh web pages periodically. This is extremely resource consuming because the search engine needs to crawl the web and download web pages to refresh its index, Based on present technologies of web refreshing, we present a cooperative schema between web server and search engine for maintaining freshness of web repository. The web server provides metadata defined through XML standard to describe web sites. Before updating the web page the crawler visits the meta-data files. If the meta-data indicates that the page is not modified, then the crawler will not update it. So this schema can save bandwidth resource. A primitive model based on the schema is implemented. The cost and efficiency of the schema are analyzed.

关键词： search engine freshness cooperative schema

De-biased knowledge distillation framework based on knowledge infusion and label de-biasing techniques

在线全文

学校读者我要写书评

暂无评论

Journal of Electronic Science and Technology 2024年第3期22卷 57-68页

作者： Yan li Tai-Kang Tian Meng-yu Zhuang yu-Ting sun School of Economics and Management University of Electronic Science and Technology of ChinaChengdu611731China School of Economics and Management Beijing University of Posts and TelecommunicationBeijing100876China School of Electrical Engineering and Computer Science The University of QueenslandBrisbane4072Australia

Knowledge distillation,as a pivotal technique in the field of model compression,has been widely applied across various ***,the problem of student model performance being limited due to inherent biases in the teacher model during the distillation process still *** address the inherent biases in knowledge distillation,we propose a de-biased knowledge distillation framework tailored for binary classification *** the pre-trained teacher model,biases in the soft labels are mitigated through knowledge infusion and label de-biasing *** on this,a de-biased distillation loss is introduced,allowing the de-biased labels to replace the soft labels as the fitting target for the student *** approach enables the student model to learn from the corrected model information,achieving high-performance deployment on lightweight student *** conducted on multiple real-world datasets demonstrate that deep learning models compressed under the de-biased knowledge distillation framework significantly outperform traditional response-based and feature-based knowledge distillation models across various evaluation metrics,highlighting the effectiveness and superiority of the de-biased knowledge distillation framework in model compression.

关键词： De-biasing Deep learning Knowledge distillation Model compression

Solubility of iron(Ⅲ) and nickel(Ⅱ) acetylacetonates in supercritical carbon dioxide

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1期65卷 29-34页

作者： Haixin sun Jianlei Qi Jianfei sun lin li Kunpeng yu Jintao Wu Jianzhong Yin State Key Laboratory of Fine Chemicals School of Chemical EngineeringDalian University of TechnologyDalian 116024China College of Chemical Engineering Inner Mongolia University of TechnologyHohhot 010051China

As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of ***,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic *** this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility *** was measured using a static weight loss *** semi-empirical models proposed by Chrastil and sung et *** used to correlate the solubility data of Fe(acac)3 and Ni(acac)*** equations obtained can be used to predict the solubility of the same system in the experimental range.

关键词： Iron(III)acetylacetonate Nickel(II)acetylacetonate Supercritical carbon dioxide Solubility measurement Correlation model Phase equilibrium

Rapid chemical recycling of waste polyester plastics catalyzed by recyclable catalyst

在线全文

学校读者我要写书评

暂无评论

Green Chemical Engineering 2024年第2期5卷 257-265页

作者： yu-Ji Luo Jia-Yin sun Zhi li School of Physical Science and Technology ShanghaiTech UniversityShanghai201210China

Waste plastics are serious environmental threats due to their low degradability and low recycling *** and efficient waste plastics recycling technologies are urgently demanded for a sustainable ***,we report a rapid,closed-loop,and streamlined process to convert polyesters such as poly(ethylene terephthalate)(PET)back to its purified *** trifluoromethanesulfonic acid or metal triflates as the recyclable catalyst,polyesters such as PET can be completely depolymerized by simple carboxylic acids within 1 *** coupling this acidolysis with a subsequent hydrogenolysis process,the consumed carboxylic acid was recovered and the closed-loop of PET depolymerization could be *** catalysts and depolymerization agents are fully recycled while only PET and hydrogen are consumed.

关键词： Chemical recycling Waste polyester plastics Acidolysis Recyclable catalyst