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Excellent Strengthening of Low-Carbon Steel by Severe Free-End Torsion
Shijun Tan,Bo Song,Hongbing Chen,Xiaodong Tan,Risheng Qiu,Tingting Liu,Ning Guo,Shengfeng Guo 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.8
In this work, the effects of free-end torsion on microstructure and tensile property of low-carbon steel were investigated indetail. Low-carbon steels exhibited exceptionally high yield strength through severe torsion deformation. Such high hardeningeffect was mainly attributed to the severe lattice distortion, high density of dislocations and the change in grain shape. Moreover, a gradient deformation structure can be introduced by torsion deformation. The gradient-structure can generate ahigh hetero-deformation induced strengthening, which can increase the strain hardening capacity and remain high plasticity/toughness. Therefore, with increasing torsion angle from 700 to 2800 deg., the uniform elongation and the peak strength werelargely enhanced. After twisting 2800 deg., yield strength and peak strength can achieve 524 MPa and 675 MPa, respectively,and good tensile elongations (εf = 9.6%, εu = 7.4%) are remained.
Personal Remittances and Financial Development for Economic Growth in Economic Transition Countries
Shijun Cao,Sung Jin Kang 한국국제경제학회 2020 International Economic Journal Vol.34 No.3
This study investigates the effect of personal remittance inflows and financial development on the economic growth of 29 economic transition countries for the period of 2000–2015. Dynamic panel system GMM estimation results show that there is a positive relationship between remittance inflows and economic growth. It also shows that remittances and the level of financial development have a substitute relationship in promoting economic growth. So the remittance inflows have a positive effect on economic growth for the countries with low levels of financial development, but they have a negative effect on such growth for countries with moderate to high levels of financial development.
ShiJun Chen,Qi Zhang,Biao He,SuRong Huang,Dou-Dou Hui 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.1
In order to meet the thermal performance analysis accuracy requirements of high density permanent magnet synchronous motor (PMSM), a method of multi physical domain coupling thermal analysis based on control circuit, electromagnetic and thermal is presented. The circuit, electromagnetic, fluid, temperature and other physical domain are integrated and the temperature rise calculation method that considers the harmonic loss on the frequency conversion control as well as the loss non-uniformly distributed and directly mapped to the temperature field is closer to the actual situation. The key is to obtain the motor parameters, the realization of the vector control circuit and the accurate calculation and mapping of the loss. Taking a 48 slots 8 poles high density PMSM as an example, the temperature rise distribution of the key components is simulated, and the experimental platform is built. The temperature of the key components of the prototype machine is tested, which is in agreement with the simulation results. The validity and accuracy of the multi physical domain coupling thermal analysis method are verified.
Shijun Ji,Chengxin Jiang,Ji Zhao,Jilong Yang,Jili Wang,Handa Dai 한국물리학회 2019 Current Applied Physics Vol.19 No.11
In this paper, a dual-band metamaterial absorber (MMA) with wide-angle and polarization-insensitivity is proposed. The MMA consists of two copper layers with a layer of FR-4 between them. And its top layer consists of a cross-shaped resonator and a square ring resonator. The calculation result demonstrates that there are two distinct absorption peaks, whose absorptivity are 99.933% at 3.8441 GHz and 99.99% at 9.1094 GHz. And its thickness is only 1.34% of the wavelength of the lowest absorption frequency. The dual-band MMA shows polarization-insensitivity for normal incident wave and shows high absorptivity in a wide incident angle for both TE and TM polarization wave. In addition, we discuss the working mechanism. The influences of main parameters on the dual-band MMA's absorption are also analyzed. The proposed ultra-thin MMA has simple structure and high absorptivity, which has many potential applications, such as thermal radiometer, detection sensor, stealth technology.
Song Shijun,Xiong Chao,Yin Junhui,Yang Zhaoshu,Wang Lu 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.2
In this study, a hierarchical composite Kagome honeycomb sandwich (HCKHS) structure was manufactured based on the interlocking method, and its uniaxial compression performance was explored. Through experiments, the compressive strength, stiffness, energy absorption, and failure process of HCKHS specimens of seven different sizes were determined and compared. Mechanical analytical models were established, and the variation trend in the specific strength was predicted and compared with those of other advanced sandwich structures. The size effect of the HCKHS specimens was analyzed. The influence of a single variable on the core modulus, failure strength, and failure modes was discussed, and failure mechanism maps were drawn. The structure was optimized based on the maximum specific strength and engineering application, and the optimal size design ratio was obtained. The results showed that the HCKHS specimens exhibited excellent compressive properties with a convenient manufacturing process, making them suitable for lightweight applications in engineering. The optimization ideas presented herein are also applicable to other two-dimensional hierarchical or normal composite honeycomb sandwich structures with diamond, triangular, and hexagonal shapes.
Chen, ShiJun,Zhang, Qi,He, Biao,Huang, SuRong,Hui, Dou-Dou The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.1
In order to meet the thermal performance analysis accuracy requirements of high density permanent magnet synchronous motor (PMSM), a method of multi physical domain coupling thermal analysis based on control circuit, electromagnetic and thermal is presented. The circuit, electromagnetic, fluid, temperature and other physical domain are integrated and the temperature rise calculation method that considers the harmonic loss on the frequency conversion control as well as the loss non-uniformly distributed and directly mapped to the temperature field is closer to the actual situation. The key is to obtain the motor parameters, the realization of the vector control circuit and the accurate calculation and mapping of the loss. Taking a 48 slots 8 poles high density PMSM as an example, the temperature rise distribution of the key components is simulated, and the experimental platform is built. The temperature of the key components of the prototype machine is tested, which is in agreement with the simulation results. The validity and accuracy of the multi physical domain coupling thermal analysis method are verified.
Li, Shijun,Huang, Jianying,Cook, Timothy R.,Pollock, J. Bryant,Kim, Hyunuk,Chi, Ki-Whan,Stang, Peter J. American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.6
<P>We describe the formation of a suite of [3]catenanes via multicomponent coordination-driven self-assembly and host–guest complexation of a rectangular scaffold comprising a 90° Pt-based acceptor building block with a pseudorotaxane bis(pyridinium)ethane/dibenzo-24-crown-8 linear dipyridyl ligand and three dicarboxylate donors. The doubly threaded [3]catenanes are formed from a total of 10 molecular components from four unique species. Furthermore, the dynamic catenation process is reversible and can be switched off and on in a controllable manner by successive addition of KPF<SUB>6</SUB> and 18-crown-6, as monitored by <SUP>1</SUP>H and <SUP>31</SUP>P NMR spectroscopy.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-6/ja3118812/production/images/medium/ja-2012-118812_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja3118812'>ACS Electronic Supporting Info</A></P>
The Applications and Energy Saving Analysis of Straw Board Buildings in Cold Rural Regions of China
Sun Shijun,Zhao Yunduo,LuanYm. gTao 국제온돌학회 2014 International Journal of Ondol Vol.7 No.1
Straw board is renewable natural building material with the advantages of green environmental protection, strong applicability. But it hadn't been promoted because of many reasons such as technology and economy. Through the analysis ofthe unique advantages and the recent new cases of straw board buildings in Harbin, and the current obstacles to application. The effective ways and the feasible solutions to promote sustainable straw board buildings are summarized.
Influence mechanism of silicon surface generation in ultraprecision turning
Zhang Shijun 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4
A quantificational approach was proposed to analyze the discrepancy of monocrystalline silicon surface roughness along different crystal orientations in diamond turning on Statistical Product and Service Solutions software. This work aimed to understand how crystal orientation affects surface generation in the cutting behavior of monocrystalline silicon. In this study, the measured surface roughness data were first processed in advance to eliminate some adverse effects of outliers. The average values of surface roughness distributions were obtained. The surface roughness values of different measurement directions were compared, and the influences of crystal orientations on surface roughness were analyzed. Results indicate that the crystal orientation and the cutting parameters have much influence on machined surface roughness. Finding some special crystal orientations using Euclidean distance analysis with average analysis is effective. The vibration induced by crystallographic orientation is the main reason to make surface nonuniform roughness in single-point diamond turning. This finding is verified by analyzing the surface generation mechanism.