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Yang, Dang-Wei,Ma, Zhan-Guo,Qi, Fu-Zhou,Gong, Peng,Liu, Dao-Ping,Zhao, Guo-Zhen,Zhang, Ray Ruichong Techno-Press 2017 Geomechanics & engineering Vol.13 No.2
This paper proposes gob-side entry retaining by roof break and filling in thick-layer soft rock conditions based on the thick-layer soft rock roof strata migration law and the demand for non-pillar gob-side entry retaining projects. The functional expressions of main roof subsidence are derived for three break roof direction conditions: lateral deflection toward the roadway, lateral deflection toward the gob and vertically to the roof. These are derived according to the load-bearing boundary conditions of the main roadway roof stratum. It is concluded that the break roof angle is an important factor influencing the stability of gob-side entry retaining surrounding rock. This paper studies the stress distribution characteristics and plastic damage scope of gob-side entry retaining integrated coal seams, as well as the roof strata migration law and the supporting stability of caving structure filled on the break roof layer at the break roof angles of $-5^{\circ}$, $0^{\circ}$, $5^{\circ}$, $10^{\circ}$ and $15^{\circ}$ are studied. The simulation results of numerical analysis indicate that, the stress concentration and plastic damage scope to the sides of gob-side entry retaining integrated coal at the break roof angle of $5^{\circ}$ are reduced and shearing stress concentration of the caving filling body has been eliminated. The disturbance of coal mining to the roadway roof and loss of carrying capacity are mitigated. Field tests have been carried out on air-return roadway 5203 with the break roof angle of $5^{\circ}$. The monitoring indicates that the break roof filling section and compaction section are located at 0-45 m and 45-75 m behind the working face, respectively. The section from 75-100 m tends to be stable.
Wei Bangzheng,Zhou Rui,Xu Dang,Chen Ruizhi,Yu Xinxi,Chen Pengqi,Cheng Jigui 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12
The thermal stress between W plasma-facing material (PFM) and Cu heat sink in fusion reactors can be significantly reduced by using a WeCu functionally graded material (WeCu FGM) interlayer. However, there is still considerable stress at the joining interface between W and WeCu FGM in the W/WeCu FGM/Cu portions. In this work, we fabricate W skeletons with continuous gradients in porosity by a modified sedimentation method. Sintering densification behavior and pore characteristics of the sedimented W skeletons at different sintering temperatures were investigated. After Cu infiltration, the final WeCu FGM was obtained. The results indicate that the pore size and porosity in the W skeleton decrease gradually with the increase of sintering temperature, but the increase of skeleton sintering temperature does not reduce the gradient range of composition distribution of the final prepared WeCu FGM. And WeCu FGM with composition distribution from pure W to W-20.5wt.% Cu layer across the section was successfully obtained. The thickness of the pure W layer is about one-fifth of the whole sample thickness. In addition, the prepared WeCu FGM has a relative density of 94.5 % and thermal conductivity of 185 W/ (m K). The WeCu FGM prepared in this work may provide a good solution to alleviate the thermal stress between W PFM and Cu heat sink in the fusion reactors.
Naian Wang,Dan Luo,Yujing Wu,Yangwei Zhou,Dange Guo,Diangui Huang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3
Surge and blockage are relatively common problems in compressors. To improve the aerodynamic performance of the compressor and expand the range of stable operating conditions, this paper proposes a new passive control method to improve the internal flow field of the compressor by adding tiny flat plates near the leading edge of blades. The effect of the tiny plate and its placement on the transonic compressor (NASA Rotor 37) was investigated by numerical simulations. The results show that, in the range of operating conditions studied in this paper, this passive control method, which puts the micro-plate at the leading edge of the blade, will form a micro-acceleration channel that can effectively reduce the flow separation in the suction surface of the blade. Although this makes the adiabatic efficiency of the compressor slightly decrease (the absolute reduction value is about 2 %), but it improves the blocking flow of the compressor (about 2 % increase), reduces the surge flow (about 4.9 % decrease) and also improves the pressure ratio of the compressor. Thus, this passive flow control method can effectively expand the range of stable operating conditions of the compressor, with certain theoretical and practical research value.
A Privacy-preserving Data Aggregation Scheme with Efficient Batch Verification in Smart Grid
( Yueyu Zhang ),( Jie Chen ),( Hua Zhou ),( Lanjun Dang ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.2
This paper presents a privacy-preserving data aggregation scheme deals with the multidimensional data. It is essential that the multidimensional data is rarely mentioned in all researches on smart grid. We use the Paillier Cryptosystem and blinding factor technique to encrypt the multidimensional data as a whole and take advantage of the homomorphic property of the Paillier Cryptosystem to achieve data aggregation. Signature and efficient batch verification have also been applied into our scheme for data integrity and quick verification. And the efficient batch verification only requires 2 pairing operations. Our scheme also supports fault tolerance which means that even some smart meters don’t work, our scheme can still work well. In addition, we give two extensions of our scheme. One is that our scheme can be used to compute a fixed user’s time-of-use electricity bill. The other is that our scheme is able to effectively and quickly deal with the dynamic user situation. In security analysis, we prove the detailed unforgeability and security of batch verification, and briefly introduce other security features. Performance analysis shows that our scheme has lower computational complexity and communication overhead than existing schemes.
Lairong Yin,Lei Tian,Long Huang,Juan Huang,Dang Zhou,Anwei Jiang 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2
We present a solution-region based approach for the synthesis of straight-line linkages, which is based on the stationary curvature point on curve and higher order stationery point theory of infinite approximation geometry. The selection of the Ball-Burmester point and the distribution of the solution-regions are discussed in this work. Further, two alternative cases have been analyzed for finding the Ball-Burmester point positions of the crank-rocker straightline mechanism, when one side-link is collinear with the frame. The distribution diagrams of the Ball-Burmester point positions are depicted to help the designers extract complete solutions. Infinite solu-tions for the mechanism can be expressed for each case on a diagram by employing the solution-region method. These diagrams will help the designers find the inherent mechanism intuitively and streamline the selection of results. The results indicate that the efficiency of design and reliability have been effectively improved owing to the implementation of these methods.