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A user-friendly yield criterion for metals exhibiting tension-compression asymmetry

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Chinese Journal of Aeronautics 2020年第10期33卷 2602-2609页

作者： Lei chen Weidong wen Hongjian ZHANG Faculty of Civil Engineering&Mechanics Jiangsu UniversityZhenjiang 212013China College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The aim of this paper is to model the yielding asymmetry of pressure-insensitive metals,including but not limited to Ni3 Al *** main focuses are put on the flexibility and manipulative *** parameters of theory are kept to a minimum and can be determined by as few tests as *** requirements are fulfilled by constructing a yield function using the second and third-invariants of a linearly transformed stress *** proposed yield criterion has a simple mathematical form and has only seven parameters when used in three-dimensional *** with existing theories,the new yield criterion has much fewer parameters,which makes it very convenient for practical *** coefficients of the criterion are identified by an error minimization *** to a Ni3 Al based intermetallic alloy as well as a Cu-Al-Be shape memory alloy and comparison to other criteria show that the proposed criterion has nearly the same predictive ability and flexibility with other *** proposed yield criterion can estimate the coefficients by using less data,which is a big advantage compared with other similar theories,especially when there is a limited number of experimental data.

关键词： Ni3Al based alloy Plastic anisotropy Plastic deformation Tension-compression asymmetry Yield criterion Yield stress

RFC:a feature selection algorithm for software defect prediction

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Journal of Systems Engineering and Electronics 2021年第2期32卷 389-398页

作者： XU Xiaolong chen wen WANG Xinheng Jiangsu Key Laboratory of Big Data Security&Intelligent Processing Nanjing University of Posts and TelecommunicationsNanjing 210023China Institute of Big Data Research at Yancheng Nanjing University of Posts and TelecommunicationsYancheng 224000China School of Computing and Engineering University of West LondonLondon W55RFUK

Software defect prediction(SDP)is used to perform the statistical analysis of historical defect data to find out the distribution rule of historical defects,so as to effectively predict defects in the new ***,there are redundant and irrelevant features in the software defect datasets affecting the performance of defect *** order to identify and remove the redundant and irrelevant features in software defect datasets,we propose ReliefF-based clustering(RFC),a clusterbased feature selection ***,the correlation between features is calculated based on the symmetric *** to the correlation degree,RFC partitions features into k clusters based on the k-medoids algorithm,and finally selects the representative features from each cluster to form the final feature *** the experiments,we compare the proposed RFC with classical feature selection algorithms on nine National Aeronautics and Space Administration(NASA)software defect prediction datasets in terms of area under curve(AUC)and *** experimental results show that RFC can effectively improve the performance of SDP.

关键词： software defect prediction(SDP) feature selection cluster

Covert communication with beamforming over MISO channels in the finite blocklength regime

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Science China(Information Sciences) 2021年第9期64卷 187-201页

作者： Xinchun YU Yuan LUO wen chen School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University

This paper considers beamforming techniques for covert communication over multiple input single output(MISO) channels with finite blocklength. We first show that the optimal input distribution for covert communication over complex Gaussian channels is circular symmetric complex Gaussian. By reviewing our previous results on the throughput of Gaussian random coding over additive white Gaussian noise(AWGN) channels, the achievability and converse bounds on the attainable throughput over MISO channels are analyzed. Then, the optimal beamforming strategies and their relationship with the transmitting power are thoroughly investigated in a variety of situations in terms of several types of channel state information available at both ends of the system. We reveal the fact that the maximal allowable transmit power is not constrained by covertness requirement when there is full channel information of the adversary, while there is an upper bound of the transmit power which is based on beamforming and an outage-based covertness criterion if there is only partial channel information of the adversary. Finally, numerical results are presented to show that the throughput of covert communication can be increased notably by adopting a proper beamforming strategy in MISO channels in comparison with the single antenna case.

关键词： beamforming circular symmetric complex Gaussian covert communication MISO channels power control

Impact of Planetary Wave Reflection on Tropospheric Blocking over the Urals–Siberia Region in January 2008

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Advances in Atmospheric Sciences 2016年第3期33卷 309-318页

作者： Debashis NATH wen chen Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences

Planetary wave reflection from the stratosphere played a significant role in changing the tropospheric circulation pattern over Eurasia in mid-January 2008. We studied the 2008 event and compared with composite analysis （winters of 2002/2003, 200412005, 200612007, 200712008, 201012011 and 2011/2012）, when the downward coupling was stronger, by employing time-lagged singular value decomposition analysis on the geopotential height field. In the Northern Hemisphere, the geopo- tential fields were decomposed into zonal mean and wave components to compare the relative covariance patterns. It was found that the wavenumber 1 （WN1） component was dominant compared with the wavenumber 2 （WN2） component and zonal mean process. For the WNI field, the covariance was much higher （lower） for the negative （positive） lag, with a prominent peak around ＋15 days when the leading stratosphere coupled strongly with the troposphere. It contributed to the downward coupling due to reflection, when the stratosphere exhibited a partially reflective background state. We also analyzed the evolution of the WNI anomaly and heat flux anomaly, both in the troposphere and stratosphere, during January- March 2008. The amplitude of the tropospheric WN 1 pattern reached a maximum and was consistent with a downward wave coupling event influenced by the stratospheric WN1 anomaly at 10 hPa. This was consistent with the reflection of the WN1 component over Eurasia, which triggered an anomalous blocking high in the Urals-Siberia region. We further clarified the impact of reflection on the tropospheric WNI field and hence the tropospheric circulation pattern by changing the propagation direction during and after the event.

关键词： planetary wave reflection singular value decomposition (SVD) Eliassen-Palm (EP) flux blocking circulation

Evolution of microstructure and texture of cold-drawn polycrystalline Ag with low stacking fault energy

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Science China(Technological Sciences) 2015年第7期58卷 1146-1153页

作者： MA XiaoGuang chen Jian chen Zheng YAN wen State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University School of Materials Science and Chemical Engineering Xi'an Technological University

The evolution of microstructure and texture for drawn polycrystalline Ag was investigated by transmission electron microscopy and electron backscattering *** results show that there are deformation twins and some un-tangled discrete dislocations at low *** the strain is increased to 0.58,a lot of high density dislocation walls and microbands come into *** the same time,some twins lose the twinning relationship of 60°.At a strain of 0.94,both dislocation boundaries and twin boundaries will rotate to the axis direction of wires and the shear bands start to *** the strain is higher than 1.96,most of the boundaries are parallel to the drawn *** analysis indicates that with the strain increasing,the volume fraction of complex texture component decreases,butandtexture components ***,the variation in the volume fraction of each texture component as strains is not evident when the strains are higher than *** polycrystalline Ag with low stacking fault energy,complex texture components are easily formed.

关键词： polycrystalline Ag cold-drawn deformation microstructure deformation twinning stacking fault energy

RESERVOIR SEDIMENTATION AND TRANSFORMATION OF MORPHO-LOGY IN THE LOWER YELLOW RIVER DURING 10 YEAR'S INITIAL OPERATION OF THE XIAOLANGDI RESERVOIR

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Journal of Hydrodynamics 2012年第6期24卷 914-924页

作者： chen Jian-guo ZHOU wen-hao chen Qiang International Research and Training Center on Erosion and Sedimentation(IRTCRS) China Institute of Water Resources and Hydropower Research(IWHR)

The Xiaolangdi Hydro-Project is one of the large projects on the main stem of the Middle Yellow River. It has been operated for more than 10 years, since its impoundment in October, 1999. The reservoir has trapped 2.833 × 10^9 m3 of sediment, and caused the total erosion of 1.891 × 10^9t in the Lower Yellow River from October, 1999 through October, 2010. Not only the serious atrophied situation of the Lower Yellow River （LYR） has been resuscitating, but also many new phenomena of sediment transport and behaviors of channel re-establishing are coming into being. They are illustrated and discussed in detail in this paper.

关键词： reservoir sedimentation density current water-sediment regulation artificial flood channel siltation and erosion,erosion efficiency river configuration

New key pre-distribution scheme using symplectic geometry over finite fields for wireless sensor networks

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The Journal of China Universities of Posts and Telecommunications 2017年第5期24卷 16-22,76页

作者： chen Shangdi wen Jiejing College of Science Civil Aviation University of China Tianjin 300300 China The Chern Institute of Mathematics Nankai University Tianjin 300071 China

To achieve secure communication in wireless sensor networks （WSNs）, where sensor nodes with limited computation capability are randomly scattered over a hostile territory, various key pre-distribution schemes （KPSs） have been proposed. In this paper, a new KPS is proposed based on symplectic geometry over finite fields. A fixed dimensional subspace in a symplectic space represents a node, all 1-dimensional subspaces represent keys and every pair of nodes has shared keys. But this naive mapping does not guarantee a good network resiliency. Therefore, it is proposed an enhanced KPS where two nodes have to compute a pairwise key, only if they share at least q common keys. This approach enhances the resilience against nodes capture attacks. Compared with the existence of solution, the results show that new approach enhances the network scalability considerably, and achieves good connectivity and good overall performance.

关键词： pre-dislribution scheme symplectic geometry WSNs

Preparation of mesoporous silica microspheres with multi-hollow cores and their application in sustained drug release

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Particuology 2010年第5期8卷 447-452页

作者： chen Zhang Tian Hou Jianfeng chen Lixiong wen Key Lab for Nanomaterials Ministry of Education Beijing University of Chemical Technology Beijing 100029 China Research Center of the Ministry of Education for High Gravity Engineering & Technology Beijing University of Chemical Technology Beijing 100029 China

Mesoporous silica microspheres with multi-hollow cores （MSMMCs） were prepared by an O1/W/O2 double emulsion technique. When tetraethyl orthosilicate （TEOS） was hydrolyzed in the O1/W/O2 double emulsion with P123 （a triblock copolymer with a formula of HO（CH2CH20）20（CH2CH（CH3）O）70（CH2CH2O）20H） dissolved in the aqueous phase, the internal oil droplets would serve as templates for the empty hollow cores, P123 function as templates for the mesopores in the shell, and the aqueous phase act as space-limiting micro-reactors for the hydrolysis process, thus forming MSMMCs with controllable size and hollow cores. After further modification by a high-temperature aging process, the prepared MSMMCs had a diameter of 2-10 μm, with macromulti-hollow cores with a size of 100-1000 nm, mesopores in the shell with a size of 3.8-4.4 nm, and a surface area of 383-735 m2/g. In addition, MSMMCs were used as carriers to load avermectin through an immersing and evaporating process, and the loaded avermectin showed a well sustained release behavior from the MSMMCs matrix. This study demonstrated a promising and simple method for preparing silica micro-particles with porous multi-hollow core structure for sustained release applications.

关键词： SilicaPreparationHollow structureSustained release

A Phenol-containing α-Diimine Ligand for Nickel-and Palladium-Catalyzed Ethylene Polymerization

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Chinese Journal of Polymer Science 2019年第10期37卷 974-980,I0003页

作者： chen Tan wen-Min Pang Chang-Le chen Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Soft Matter Chemistry Department of Polymer Science and Engineering University of Science and Technology of China

A phenol-containing dibenzhydryl-based α-diimine ligand bearing hydroxy group on para-position of aniline moiety was designed, synthesized, and investigated in Ni-and Pd-catalyzed ethylene polymerization. The Ni complex bearing hydroxy groups resulted in not only high polyethylene molecular weight(Mn up to 1.5 × 10^~6), but also significantly increased melting temperature(Tm up to 123℃) and greatly decreased branching density(33/1000 C) versus the Ni catalyst bearing OMe group on para-position of aniline moiety. This is consistent with the hypothesis that the deprotonation of the phenol moiety generated a phenoxide bearing strong electrondonating O-substituent by methylaluminoxane(MAO) cocatalyst. The Pd complexes bearing hydroxy groups exhibited similar catalytic properties to those of the Pd catalyst bearing OMe groups did.

关键词： α-Diimine Ethylene polymerization Electronic effect Palladium Nickel