检索结果-南通市图书馆

Performance of soft-hard-soft （SHS） cement based composite subjected to blast loading with consideration of interface properties

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2015年第3期9卷 323-340页

作者： Jun WU Xuemei Liu College of Urban Railway Transportation Shanghai University of Engineering Science Shanghai 201620 China Department of Civil and Environmental Engineering National University of Singapore Singapore 119077 Singapore School of Civil Engineering and Built Environment Queensland University of Technology Brisbane QLD 4072 Australia

This paper presents a combined experimental and numerical study on the damage and performance of a soft-hard-soft （SHS） multi-layer cement based composite subjected to blast loading which can be used for protective structures and infrastructures to resist extreme loadings, and the composite consists of three layers of construction materials including asphalt concrete （AC） on the top, high strength concrete （HSC） in the middle, and engineered cementitious composites （ECC） at the bottom. To better characterize the material properties under dynamic loading, interface properties of the composite were investigated through direct shear test and also used to validate the interface model. Strain rate effects of the asphalt concrete were also studied and both compressive and tensile dynamic increase factor （DIF） curves were improved based on split Hopkinson pressure bar （SHPB） test. A full-scale field blast test investigated the blast behavior of the composite materials. The numerical model was established by taking into account the strain rate effect of all concrete materials. Furthermore, the interface properties were also considered into the model. The numerical simulation using nonlinear finite element Both the numerical and field blast test indicated that the software LS-DYNA agrees closely with the experimental data SHS composite exhibited high resistance against blast loading

关键词： high strength concrete （SHS） engineered cementitious composite interface blast test strain rate effect

Outstanding high-temperature oxidation-and wear-resistance of WC based cermets

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 2023年第24期155卷 33-46页

作者： Wentao Jiang Hao Lu Xuemei Liu Haibin Wang Dongyang Li Chao liu Mingsheng Wang Xiaoyan Song Faculty of Materials and Manufacturing Key Laboratory of Advanced Functional Materials Ministry of Education of China Beijing University of Technology Beijing 100124 China Department of Chemical & Materials Engineering University of Alberta Edmonton Alberta T6G 2H5 Canada Xiamen Tungsten Co. Ltd. Xiamen 361009 China

The interaction between oxidation and frictional load can greatly deteriorate the performance of ceramic-metal composites.In this work,we used WC-Co cermet as a representative of ceramic-metal composites to study its wear failure behavior and protection effectiveness.It is found that a transition of wear mechanism from mechanical wear to oxidative wear occurs with increasing temperature.The addition of zirconia can significantly improve the anti-oxidation performance and load-bearing capacity of the cermet under the frictional load.This is mainly attributed to the modulation of the tribo-oxide layer constitutions and changes in surface morphology.The zirconia component facilitates the formation of a dense protective oxide layer and reduces the content of brittle oxides on the worn surface.Based on the understanding of the temperature-and oxidation-induced compositional and microstructural evolutions at the sliding contact surface and subsurface,a promising approach is proposed for developing ceramic-metal composites with high wear resistance and anti-oxidation capability.

关键词： Cermet Anti-oxidation performance Wear mechanism Zirconia

Rapid quantitative analysis of 12 chemical constituents in wild-simulated and cultivated Astragali Radix based on UHPLC-MS

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 Herbal Medicines 2022年第3期14卷 464-469页

作者： Dan Li Yuetao liu xuemei Qin Modern Research Center for Traditional Chinese Medicine Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of EducationShanxi UniversityTaiyuan 030006China Shanxi Key Laboratory of Effective Substances Research and Utilization in Traditional Chinese Medicine Taiyuan 030006China

Objective:Astragali Radix(AR)is one of the most widely used traditional Chinese medicines(TCMs)for tonic,which can be divided into wild-simulated and cultivated AR according to its cultivation method.However,whether cultivated AR can replace wild-simulated AR has always been a concern.Methods:In this study,a rapid,highly sensitive and specific analytical method using ultra-high performance liquid chromatography tandem mass spectrometry(UHPLC-MS)was developed to quantitatively measure 12 chemical constituents of AR in the different cultivation methods.Results:AR samples were analyzed with a good linear regression relationship(R2,0.9983–0.9995),precisions(relative standard deviation(RSD),1.31%-2.36%),repeatability(RSD,2.65%-4.92%),stability(RSD,1.50%-4.05%),and recovery(95.13%-106.52%).Through the determination of AR samples,we found the components of favonoids in wild-simulated AR were higher than cultivated AR,the saponins in cultivated AR were higher,the ratio of saponins/favonoids in cultivated AR was higher than wildsimulated AR.Conclusion:Based on this research,it could provide guidance for the quality control of AR.

关键词： Astragali Radix chemical constituent cultivation method quantification UHPLC-MS

Recognition of cotton growth period for precise spraying based on convolution neural network

在线全文

学校读者我要写书评

暂无评论

Information Processing in Agriculture 2021年第2期8卷 219-231页

作者： Shanping Wang Yang Li Jin Yuan Laiqi Song Xinghua liu Xuemei Liu College of Mechanical&Electronic Engineering Shandong Agricultural UniversityTai’an 271018China Shandong Provincial Key Laboratory of Horticultural Machinery and Equipment Tai’an 271018China

Dynamic acquisition of crop morphology is beneficial to real-time variable decision of precise spraying operations in fields.However,the existing spraying quantity regulation has high tolerance on the statistical characteristics of regional morphology,so expensive LiDAR and ultrasonic radar can’t make full use of their high accuracy,and can reduce decision speed because of too much detail of branches and leaves.Therefore,designing a novel recognition system embedded machine learning with low-cost monocular vision is more feasible,especially in China,where the agricultural implements are medium sizes and cost-sensitive.In addition,we found that the growth period of crops is an important reference index for guiding spraying.So,taking cotton as a case study,a cotton morphology acquisition by a single camera is established,and a cotton growth period recognition algorithm based on Convolution Neural Network(CNN)is proposed in this paper.Through the optimization process based on confusion matrix and recognition efficiency,an optimized CNN model structure is determined from 9 different model structures,and its reliability was verified by changing training sets and test sets many times based on the idea of kfold test.The accuracy,precision,recall,F1-score and recognition speed of this CNN model are 93.27%,95.39%,94.31%,94.76%and 71.46 ms per image,respectively.In addition,compared with the performance of VGG16 and AlexNet,the convolution neural network model proposed in this paper has better performance.Finally,in order to verify the reliability of the designed recognition system and the feasibility of the spray decision-making algorithm based on CNN,spraying deposition experiments were carried out with 3 different growthperiods of cotton.The experiments’results validate that after the optimal spray parameters were applied at different growth periods respectively,the average optimum index in 3 growth periods was 42.29%,which was increased up to 62.24%than the operations without distinguishing growth periods.

关键词： Precision spraying Growth period of cotton Target perception Convolution neural network Image classification

High-temperature mechanical behavior of ultra-coarse cemented carbide with grain strengthening

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 2022年第9期104卷 8-18页

作者： Huaxin Hu Xuemei Liu Jinghong Chen Hao Lu Chao liu Haibin Wang Junhua Luan Zengbao Jiao Yong liu Xiaoyan Song Faculty of Materials and Manufacturing Key Laboratory of Advanced Functional MaterialsMinistry of Education of ChinaBeijing University of TechnologyBeijing 100124China Xiamen Tungsten Co. Ltd.Xiamen 361009China Department of Materials Science and Engineering City University of Hong KongHong KongChina Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong KongChina State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Ultra-coarse grained cemented carbides are often used under conditions of concurrently applied stress and high temperature.Improvement of high-temperature mechanical performance of ultra-coarse grained cemented carbides is highly desirable but still a big challenge.In this study,it is proposed that the hightemperature compression strength of ultra-coarse cemented carbides can be enhanced by modulating hard matrix grains by activated Ta C nanoparticles,through solid solution strengthening of Ta atoms.Based on the designed experiments and microstructural characterizations combined with finite element simulations,the grain morphology,stress distribution and dislocation configuration were studied in detail for ultra-coarse grained cemented carbides.The mechanisms of Ta dissolving in WC crystal and strengthening ultra-coarse grains through interaction with dislocations were disclosed from the atomic scale.This study opens a new perspective to modulate hard phases of cemented carbides for improving their hightemperature performance,which will be applicable to a variety of cermet and ceramic-based composite materials.

关键词： Ultra-coarse cemented carbides High-temperature compressive behavior Strengthening of hard-phase grains Dislocation motion

A Two-point Method for Multiaxial Fatigue Life Prediction

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2022年第2期35卷 316-327页

作者： Jianhui liu xuemei Pan Youtang Li Xiaochuang Chen School of Mechanical and Electrical Engineering Lanzhou University of TechnologyLanzhou 730050China Lanzhou Jinchuan Advanced Materials Technology Co. Ltd.Lanzhou 730101China

Fatigue fracture is one of the most common failure modes of engineering compo-nents,and the combined action of geometrie discontinuity and multiaxial loading is more likely to cause severe fatigue damage of components.This work focuses on the fatigue behavior of U-notched Q345 steel specimens with differen t notch sizes under proportional cyclic tension-torsion.Firstly,based on the concept of strain energy,the calculation method of critical plane is given and the equivalent stress of the specified path on the critical plane is extracted to char-acterize the equivalent stress distribution state and the stress gradient effect.Then,based on the high stress volume method and theory of critical distance,a simple method for determining the critical distance is given considering the contribution of stress at the dangerous point and the critical point.In addition,based on the idea of stress-distance normalization,a new stress gradient impact factor is defined and a new method for predicting the multiaxial fatigue life of notched specimens is given.The prediction results of the proposed model,the local stress-strain method and the point method of theory of critical distance are compared with the experimental results.The comparisons show that the prediction results of the proposed model are closer to experimentai life,and the calculation accuracy is higher.

关键词： Multiaxial fatigue Stress gradient Life prediction Critical distance method Local stress-strain method

Subrecoil cooling of ^(6)Li atoms by 2S→3P ultraviolet narrow transition

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 36-41页

作者： Yang Rui Liang Zhang Rui Li Pengyue liu Xuemei Liu Chunyang Duan Shichuan Yu Yuelong Wu Haibin Wu State Key Laboratory of Precision Spectroscopy Institute of Quantum Science and Precision MeasurementEast China Normal UniversityShanghai 200062China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China Shanghai Research Center for Quantum Sciences Shanghai 201315China

Laser cooling of atoms and molecules is crucial to exhibiting excellent features in the field of low-temperature physics.Cooling ^(6)Li atoms to very low temperatures is difficult due to their partially resolved D_(2) line of excited states.Here we report an observation of cooling ^(6)Li atom samples to 16μK with an ultraviolet(UV)laser in a magneto-optical trap,which breaks the Doppler cooling limit and approaches half of the photon-recoil limit.The essential mechanism of cooling results is that the natural linewidth is comparable to the recoil frequency in such a 2S→3P ultraviolet narrow transition.Laser frequency stability is important in the cooling process,and thus,the UV laser was locked to an optical frequency comb referenced to an ultrastable optical cavity.The cooling was numerically simulated to explain the cooling forces.The results can provide an ideal platform in the field of precision measurements and ultracold Fermi gases.

关键词： cold atom narrow-line UV cooling photon-recoil limit

Rapid report of source parameters of 2023 M6.2 Jishishan,Gansu earthquake sequence

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2024年第2期8卷 436-443页

作者： ZhiGao Yang Jie liu YingYing Zhang Wen Yang xuemei Zhang China Earthquake Networks Center Beijing 100045China

The M6.2 earthquake in Jishishan,Gansu Province,on December 18,2023,caused extraordinary earthquake disasters.It was located in the northern part of the north−south seismic zone,which is a key area for earthquake monitoring in China.The newly built dense strong motion stations in this area provide unprecedented conditions for high-precision earthquake relocation,especially the earthquake focal depth.This paper uses the newly built strong motion and traditional broadband seismic networks to relocate the source locations of the M3.0 and above aftershocks and to invert their focal mechanisms.The horizontal error of earthquake location is estimated to be 0.5−1 km,and the vertical error is 1−2 km.The focal depth range of aftershocks is 9.6−14.6 km,distributed in a 12-km-long strip with SSE direction.Aftershocks in the south are more concentrated horizontally and vertically,while aftershocks in the north are more scattered.The focal mechanisms of the main shock and aftershocks are relatively consistent,and the P-axis orientation is consistent with the regional strain direction.There is a seismic blank area of M3.0 and above,about 3−5 km between the main shock and aftershocks.It is suggested that the energy released by the main shock rupture is concentrated in this area.Based on the earthquake location and focal mechanism of the main shock,it is inferred that the Northern Lajishan fault zone is the seismogenic structure of the main shock,and the main shock did not occur on the main fault,but on a secondary fault.The initial rupture depth and centroid depth of the main shock were 12.8 and 14.0 km,respectively.The source rupture depth may not be the main reason for the severe earthquake disaster.

关键词： Jishishan earthquake earthquake relocation focal mechanism strong motion data

RNA Quality Control as a Key to Suppressing R Silencing of Endogenous Genes in Plants

在线全文

学校读者我要写书评

暂无评论

Molecular Plant 2016年第6期9卷 826-836页

作者： Lin liu xuemei Chen Guangdong Provincial Key Laboratory for Plant Epigenetics College of Life Sciences and Oceanography Shenzhen University Shenzhen 518060 P.R. China Department of Botany and Plant Sciences Institute of Integrative Genome Biology University of California Riverside CA 92521 USA Howard Hughes Medical Institute University of California Riverside CA 92521 USA

RNA quality control of endogenous RNAs is an integral part of eukaryotic gene expression and often relies on exonucleolytic degradation to eliminate dysfunctional transcripts. In parallel, exogenous and selected endogenous RNAs are degraded through RNA silencing, which is a genome defense mechanism used by many eukaryotes. In plants, RNA silencing is triggered by the production of double-stranded RNAs （dsRNAs） by RNA-DEPENDENT RNA POLYMERASEs （RDRs） and proceeds through small interfering （si） RNA-directed, ARGONAUTE （AGO）-mediated cleavage of homologous transcripts. Many studies revealed that plants avert inappropriate posttranscriptional gene silencing of endogenous coding genes by using RNA surveillance mechanisms as a safeguard to protect their transcriptome profiles. The tug of war between RNA surveillance and RNA silencing ensures the appropriate partitioning of endogenous RNA substrates among these degradation pathways. Here we review recent advances on RNA quality control and its role in the suppression of RNA silencing at endogenous genes and discuss the mechanisms underlying the crosstalk among these pathways.

关键词： gene silencing RNA quality control aberrant RNA siRNA