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RISS 인기검색어
- 검색키워드
- 저자 : Liu Dazhao (검색결과 4 건)
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Numerical simulation of pressure relief in hard coal seam by water jet cutting
Song, Dazhao,Wang, Enyuan,Xu, Jiankun,Liu, Xiaofei,Shen, Rongxi,Xu, Wenquan Techno-Press 2015 Geomechanics & engineering Vol.8 No.4
The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.
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Simulation of Conceptual Designs of a Three-Surface Stealth Strike Fighter
Yue Kuizhi,Chen ShiChun,Liu Wenlin,Yu Dazhao 한국항공우주학회 2014 International Journal of Aeronautical and Space Sc Vol.15 No.4
A conceptual design of a three-surface strike fighter was studied and stealth performance was taken into account to enhance survivability and battle effectiveness. CATIA was used to design the aircraft’s three-dimensional prototype model and the weapon carriage arrangement was also studied. The aircraft’s RCS characteristics and distributions under X, S, C, and L bands were simulated using the RCSPlus software, which is based on the PO method. Pressure and velocity distributions of the flow field were also simulated using CFD. A turbulence model was based on standard k-ε function and N-S functions were used during the CFD computation. Lift coefficients, drag coefficients, and lift-to-drag ratio were obtained by aerodynamic simulation. The results showed that: (1) the average value of head-on RCS between ±30° is below -3.197 ㏈sm, and (2) the lift coefficient is 0.34674, the drag coefficient is 0.04275, and the lift-to-drag ratio is 8.11087 when the attack angle is 2.5°.
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Simulation of Conceptual Designs of a Three-Surface Stealth Strike Fighter
Kuizhi, Yue,ShiChun, Chen,Wenlin, Liu,Dazhao, Yu The Korean Society for Aeronautical and Space Scie 2014 International Journal of Aeronautical and Space Sc Vol.15 No.4
A conceptual design of a three-surface strike fighter was studied and stealth performance was taken into account to enhance survivability and battle effectiveness. CATIA was used to design the aircraft's three-dimensional prototype model and the weapon carriage arrangement was also studied. The aircraft's RCS characteristics and distributions under X, S, C, and L bands were simulated using the RCSPlus software, which is based on the PO method. Pressure and velocity distributions of the flow field were also simulated using CFD. A turbulence model was based on standard $k-{\varepsilon}$ function and N-S functions were used during the CFD computation. Lift coefficients, drag coefficients, and lift-to-drag ratio were obtained by aerodynamic simulation. The results showed that: (1) the average value of head-on RCS between ${\pm}30^{\circ}$ is below -3.197 dBsm, and (2) the lift coefficient is 0.34674, the drag coefficient is 0.04275, and the lift-to-drag ratio is 8.11087 when the attack angle is $2.5^{\circ}$.
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Study on the pore/scratch-strength response of ZrB2–SiC ceramic via laser processing
Wang Anzhe,Wang Shuai,Yin Huimin,Zhou Peng,Liu Dazhao 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.6
Defects, such as pores and scratches, are inevitably introduced during preparation and processing of ceramics. How they aff ect the mechanical properties of materials is worthy of attention. Here, artifi cial surface pores and notches introduced by femtosecond/nanosecond lasers are regarded as inherent pore- and scratch-like defects. Bending test results indicated that a small-sized fl aw with the length and depth of ~ 10 μm could lead to a strength reduction up to ~ 40% in sharp fl aw case, while only slight attenuation (< 10%) occurs in blunt fl aw case. Linear extrapolation result reveals that the maximum strength in notch cases, when the depth reaches the atomic scale, is ~ 34 GPa, which is in the range of the theoretical value of 24–48 GPa. Furthermore, the calculated critical fl aw size ( ac) may tend to be overestimated, given that the artifi cial defect, which is smaller than the ac value, also results in signifi cant strength decay. This study could provide guidance for strength evalu- ation and high-strength design of ceramics.
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