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Microstructure and corrosion resistance of vanadium films deposited at different target-substrate distance by HPPMS

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Rare Metals 2014年第5期33卷 587-593页

作者： Chun-wei Li Xiu-Bo tian tian-wei liu Jian-wei Qin Chun-Zhi Gong State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology College of Engineering and Technology Northeast Forestry University State Key Laboratory of Surface Physics and Chemistry China Academy of Engineering Physics

High power pulsed magnetron sputtering（HPPMS）, a novel physical vapor deposition technology, was applied to prepare vanadium films on aluminum alloy substrate in this paper. The influence of target–substrate distance（Dt–s）（ranging from 8 to 20 cm） on phase structure, surface morphology, deposition rate, and corrosion resistance of vanadium films was investigated. The results show that the vanadium films are textured with a preferential orientation in the（111） direction except for that fabricated at 20 cm. With Dt–sincreasing, the intensity of（111） diffraction peak of the films decreases and there exists a proper distance leading to the minimum surface roughness of 0.65 nm. The deposition rate decreases with Dt–sincreasing. All the V-coated aluminum samples possess better corrosion resistance than the control sample. The sample fabricated at Dt–sof 12 cm demonstrates the best corrosion resistance with the corrosion potential increasing by 0.19 V and the corrosion current decreasing by an order of magnitude compared with that of the substrate. The samples gain further improvement in corrosion resistance after annealing, and if compared with that of annealed aluminum alloy, then the corrosion potential of the sample fabricated at 20 cm increases by 0.415 V and the corrosion current decreases by two orders of magnitude after annealed at 200 °C. If the annealing temperature further rises to 300 °C, then the corrosion resistance of samples increases less obviously than that of the control sample.

关键词： High power pulsed magnetron sputtering Vanadium films Target–substrate distance Microstructure Corrosion resistance

Irreversibility and transformation randomness of thermoelastic martensitic transformation in Ni–Ti alloys

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Rare Metals 2015年第12期34卷 833-837页

作者： tian-wei liu Yan-Jun Zheng Li-Shan Cui Department of Materials Science and Engineering China University of Petroleum

In this work, the in situ optical observation was carried out in complete and incomplete transformation cycles of Ni–Ti alloys. In complete transformation cycles, initial martensite plates nucleate randomly in austenite. However, in a partial transformation cycle, the existing martensite plates have an influence on guiding the formation of subsequent martensite plates. And the randomness decreases with the decrease in transformation volume involved in the partial cycle. It is suggested that the randomness of transformations contributes to the introduction of defects, and the irreversibility associates with transformation randomness of martensite plates. For instance, a higher randomness in transformations could introduce more defects and more obvious irreversibility. On the other hand, defects generated in thermoelastic martensitic transformation are responsible for the hysteresis of transformations. Therefore, the randomness of transformations also contributes to the transformation hysteresis. These results could help further understanding on some martensitic transformation phenomena of shape memory alloys, such as the nonlinear and history-dependent characteristic.

关键词： Thermoelastic martensitic transformation Shape memory alloys Transformation sequence Hysteresis

Transformation Sequence Rule of Martensite Plates and Temperature Memory Effect in Shape Memory Alloys

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Acta Metallurgica Sinica(English Letters) 2015年第10期28卷 1286-1290页

作者： tian-wei liu Yan-Jun Zheng Li-Shan Cui Department of Materials Science and Engineering China University of Petroleum

In thermoelastic martensitic transformation, it is well established that the first martensite plate appearing upon cooling becomes the final one during reverse transformation to austenite upon heating. The results obtained from this work show that the transformation sequence of the martensite appears to be random. Newly formed martensite plates can modify the elastic strain energy level stored in the already existing martensite. Additionally, the elastic strain energy stored in newly formed martensite is not necessarily to be higher than the remaining martensite. The obtained results may assist in understanding phenomena related to partial transformation of shape memory alloys, such as temperature memory effect.

关键词： Phase transformation Shape memory alloys TEM Transformation sequence

Effect of Alloying Tin on the Corrosion Characteristics of Austenitic Stainless Steel in Sulfuric Acid and Sodium Chloride Solutions

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Acta Metallurgica Sinica(English Letters) 2015年第9期28卷 1089-1096页

作者： Min Sun Ming Luo Chao Lu tian-wei liu Yan-Ping Wu Lai-Zhu Jiang Jin Li Department of Materials Science Fudan University Research and Development Center Baosteel Co. Ltd. Science and Technology on Surface Physics and Chemistry Laboratory

The effect of tin on general and pitting corrosion behaviors of the austenitic stainless steel in sulfuric acid and sodium chloride solutions was investigated by potentiostatic critical pitting temperature, cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy. The results showed that there is an optimal tin addition which is around （0.062-0.1） wt%, and the general corrosion resistance of B316LX with 0.08 wt% tin addition in boiling H2SO4 increased remarkably with a corrosion rate of an order of magnitude lower than that of 316L. Hydrolyzation of tin ions induces more metastable pit occurrence on the material surface. However, the pitting resistance of B316LX increases because tin oxides improve the density and uniformity of the passive film, and hydroxide and oxide of tin inhabit the process of pit growing. The effect of tin on pitting corrosion process is illustrated schematically.

关键词： Stainless steel Corrosion resistance Passivation Pitting corrosion

A novel interpretable multilevel wavelet decomposition deep network for actual heartbeat classification

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Science China(Technological Sciences) 2024年第6期67卷 1842-1854页

作者： JIN YanRui LI ZhiYuan tian YuanYuan wei XiaoYang liu ChengLiang School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China

Arrhythmias may lead to sudden cardiac death if not detected and treated in time.A supraventricular premature beat(SPB)and premature ventricular contraction(PVC)are important categories of arrhythmia ***,deep learning methods have been applied to the PVC/SPB heartbeats ***,most researchers have focused on time-domain information of the electrocardiogram and there has been a lack of exploration of the interpretability of the *** this study,we design an interpretable and accurate PVC/SPB recognition algorithm,called the interpretable multilevel wavelet decomposition deep network(IMWDDN).Wavelet decomposition is introduced into the deep network and the squeeze and excitation(SE)-Residual block is designed for extracting time-domain and frequency-domain ***,inspired by the idea of residual learning,we construct a novel loss function for the constant updating of the multilevel wavelet decomposition ***,the IMWDDN is evaluated on the Third China Physiological Signal Challenge Dataset and the MIT-BIH Arrhythmia *** comparison results show IMWDDN has better detection performance with 98.51%accuracy and a 93.75%F1-macro on average,and its areas of concern are similar to those of an expert diagnosis to a certain ***,the IMWDDN has good application value in the clinical screening of PVC/SPB heartbeats.

关键词： actual heartbeat classification electrocardiogram interpretable deep network multilevel discrete wavelet decomposition layer SE-Residual block

Impact of Mo/Ni alloying on microstructural modulation and low-temperature toughness of high-strength low-alloy steel

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Journal of Iron and Steel Research International 2024年第7期31卷 1746-1762页

作者： wei liu Hong-li Zhao Bing-xing Wang Yong tian State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819LiaoningChina

The high-strength low-alloy steel plates with varying Ni/Mo contents were manufactured using the thermos-mechanical control *** investigation was conducted to explore the effect of Ni/Mo microalloying on microstructure evolution and mechanical properties of the *** results revealed that the increase in Ni content from 1 to 2 wt.%reduced the transition temperature of ferrite and the growth range of ferritic grain was narrowed,which promoted grain *** optimized combination of grain size,high-angle grain boundaries(HAGBs),and martensite-austenite(M-A)islands parameter contributed to the excellent impact toughness of S1 steel at-100℃(impact absorbed energy of 218.2 J at-100℃).As the Mo increases from 0 to 2 wt.%,the matrix structure changes from multiphase structure to granular bainite,which increases the average effective grain size to~4.62 pm and reduces HAGBs proportion to~36.22%.With these changes,the low-temperature impact toughness of S3 steel is *** addition,based on the analysis of the characteristics of crack propagation path,it was found that M-A islands with low content(~2.21%)and small size(~1.76 pm)significantly retarded crack propagation,and the fracture model of M-A islands with different morphologies was further ***,correlation between behaviour of delamination and toughness was further analysed by observing delamination size and impact energy parameters.

关键词： High-strength low-alloy steel Microstructural regulation Ni addition Mo addition Crack propagation Low-temperature toughness

Eutectic high entropy alloy syntactic foam

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Journal of Materials Science & Technology 2023年第18期149卷 177-189页

作者： Jin Meng Yu Qiao tian-wei liu Yuan-Yuan Tan Fu-Hua Cao Yan Chen Hai-Ying Wang Lan-Hong Dai State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of Sciences(CAS)Beijing 100190China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei 230027China

High-strength metallic foams have a wide range of applications in engineering as lightweight structural and energy-absorbing ***,it is challenging to obtain metallic foam with both good energy absorption performance and high ***,we developed a novel metal matrix syntactic foam fabri-cated with AlCoCrFeNi_(2.1) eutectic high entropy alloy and alumina cenospheres that exhibits a remarkable combination of high strength and energy absorption performance under both quasi-static and dynamic *** porous structure of syntactic foam fully exploits the properties of the AlCoCrFeNi_(2.1) alloy matrix with a unique FCC/B2 dual-phase eutectic microstructure and thus yields exceptional *** discovered that this dual-phase microstructure not only provides high strength but also allows the pores to collapse in a progressive and diffusive way,which enables the formation of a high and smooth energy absorption *** is found that the heterogeneity between the two phases in the matrix can provide back stress strengthening,and it also induces multiple micro shear bands and microcracks as additional energy dissipation modes as the deformation *** unique mechanism ensures the strength of microstructures and makes them fracture promptly,which causes the balance of strengthening and softening on the macro *** work opens the avenue for developing advanced high-strength lightweight structural and energy-absorbing materials.

关键词： Eutectic high entropy alloy Foams Metal matrix composites(MMCs) Energy absorption

Robust adaptive radar beamforming based on iterative training sample selection using kurtosis of generalized inner product statistics

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Journal of Systems Engineering and Electronics 2024年第1期35卷 24-30页

作者： tian Jing ZHANG wei School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China National Key Laboratory of Electromagnetic Space Security Chengdu 610036China

In engineering application,there is only one adaptive weights estimated by most of traditional early warning radars for adaptive interference suppression in a pulse reputation interval(PRI).Therefore,if the training samples used to calculate the weight vector does not contain the jamming,then the jamming cannot be removed by adaptive spatial *** the weight vector is constantly updated in the range dimension,the training data may contain target echo signals,resulting in signal cancellation *** cope with the situation that the training samples are contaminated by target signal,an iterative training sample selection method based on non-homogeneous detector(NHD)is proposed in this paper for updating the weight vector in entire range *** principle is presented,and the validity is proven by simulation results.

关键词： adaptive radar beamforming training sample selection non-homogeneous detector electronic jamming jamming suppression

Regulating CRISPR/Cas9 Using Streptavidin-Biotin Interactions

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Chinese Journal of Chemistry 2024年第12期42卷 1387-1393页

作者： wei Shen wei Xiong Qianqian Qi Xingyu liu Zhongpao Xie Yuanyuan Zhang Jinxuan Hou tian tian Xiang Zhou College of Chemistry and Molecular Sciences Wuhan UniversityWuhanHubei 430072China Department of Thyroid&Breast Surgery Zhongnan Hospitalof Wuhan University Wuhan Hubei43001Chin

Comprehensive Summary Currently,CRISPR/Cas9 technology has found widespread applications across various ***,the utility of CRISPR/Cas9 is encumbered by issues pertaining to its reliability and safety,primarily stemming from the uncontrolled activity of the ***,the design and development of CRISPR/Cas9 systems with controllable activity is of paramount ***,characterized by its small molecular weight,and streptavidin,distinguished by its substantial spatial steric hindrance,can be harnessed as an ideal OFF switch(termed a"bioactivity brake")due to their interaction *** this work,we present a strategy that employs the streptavidin-biotin interaction as a"brake system"for CRISPR/Cas9,effectively allowing for the shutdown of the enzymatic activity of CRISPR/Cas9.

关键词： Streptavidin-biotin CRISPR/Cas9 CRISPR-OFF Guide RNA 2'-OH acylation Gene technology DNA cleavage