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RISS 인기검색어
- 검색키워드
- 저자 : Xiaoping Cui (검색결과 4 건)
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Preparation and Characterization of Polyimide/Alumina Composite Films as Improved Solid Dielectrics
Xiaoping Cui,Guangming Zhu,Wenyuan Liu 한국고분자학회 2016 폴리머 Vol.40 No.4
Polyimide/alumina (PI/Al₂O₃) nanocomposite films were prepared by incorporating different nano-sized Al₂O₃ contents into PI which derived from pyromellitic dianhydride (PMDA) and a flexible diamine 4,4-bis(3-aminophenoxy) biphenyl (4,3-BAPOBP). The micromorphology, chemical structure, dielectric, mechanical properties and glass transition temperatures (Tg) of prepared films were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), LCR metry, electronic tensile testing and differential scanning calorimetry (DSC). SEM images show uniform distribution of Al₂O₃ nanoparticles in matrix. FTIR spectra indicate that Al₂O₃ nanoparticles are functionalized with γ-aminopropyl triethoxysilane (γ-APS) and the imidization was complete. XRD patterns reveal the peaks of PI/Al₂O₃ composite films were similar to those of Al₂O₃, indicating that the crystal structure of Al₂O₃ remains unchanged and stable after being doped into PI matrix. Meanwhile, the effects of additives on the dielectric and mechanical properties of composite films were also studied. The results show the dielectric constant and dielectric loss of hybrid materials increase with the addition of Al₂O₃ nanoparticles. The electrical breakdown strength and tensile strength of PI/Al₂O₃ can be markedly improved by the addition of appropriate amounts of Al₂O₃ to the PI matrix.
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Gong, Jian,Cui, Weijiu,Yuan, Yong,Wu, Xiaoping Council on Tall Building and Urban Habitat Korea 2015 International journal of high-rise buildings Vol.4 No.4
Crack control remains a primary concern for mass concrete structures, where the majority of cracking is caused by temperature changes during the hydration process. One-time pouring is a useful construction method for mass concrete structures. The suitability of this method for constructingon of the Shanghai Tower's mass concrete foundation slab of Shanghai Tower is considered here by a numerical simulation method based on a 6- meter- thick slab. Some of the conclusions, which can be verified by monitoring results conducted during construction, are as follows. The temperature gradient is greater in the vertical direction than in the radial direction, therefore, the vertical temperature gradient should be carefully considered for the purpose of crack control. Moreover, owing to cooling conditions at the surfaces and the cement mortar content of the slab, the temperatures and temperature gradients with respect to time vary according to the position within the slab.
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Weak compressibility effects on the pressure fluctuation at RSI in a high-speed centrifugal pump
Shaolong Wang,Xiaoping Chen,Xiaojun Li,BaoLing Cui,Zu-chao Zhu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.10
This study presents large eddy simulation of high-speed centrifugal pump at approximate quarter load (0.23 Q d ) and design load (Q d ) conditions. Two liquid models, including weak compressible and incompressible assumptions, are considered to investigate the weak compressibility effects (WCE) on the pressure fluctuation at rotor-stator interaction (RSI). Researches show that the performance is slightly increased by the WCE at both the flow rates, which deviate from the experimental data within 5 %. There is a phase deviation between the pressure fluctuation of the two assumptions. The amplitudes of pressure fluctuation and pressure spectra are affected by the WCE, especially in the guide vane channel far away from the tongue. The first and second frequencies of pressure spectra are 12 and 6 times the rotation frequency, respectively, which are insensitive to the WCE. The influence of WCE on the pressure fluctuation and pressure spectra is significant at 0.23 Q d and gradually weakened at Q d .
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Numerical simulation and analysis of flow characteristics in the front chamber of a centrifugal pump
Yang Wu,Xiaoping Chen,Hua-Shu Dou,Lulu Zheng,ZuChao Zhu,BaoLing Cui,Boo Cheong Khoo 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11
We performed numerical simulations to study the flow characteristic in a centrifugal pump based on the RANS equations and the RNG k-ε turbulent model. The flow field, including the front and back pump chambers, the impeller wear-ring, the impeller passage, the volute casing, the inlet section and outlet section was calculated to obtain accurate numerical results of fluid flow in a centrifugal pump. The flow characteristic was studied from the internal flow structure in pump chambers, the radial velocity at impeller outlet as well as the pressure inside of the pump, the circumferential velocity and the radial velocity in front pump chamber. The variation of flow parameters in internal flow versus flow rate in the centrifugal pump was analyzed. The results show that the overall performance of the pump is in good agreement with the experimental data. The simulation results show that the distribution of flow field in the front pump chamber is axial asymmetry. The energy dissipation at the impeller outlet is larger than other areas. The distribution of the circumferential velocity and that of radial velocity are similar along the axial direction in the front pump chamber, but the distribution of flow is different along the circumferential and the radial directions. It was also found that the vorticity is large at the impeller inlet compared with other areas.
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