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- 저자 : Youquan Feng (검색결과 2 건)
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Juan Feng,Xiang Li,Xiaolan Yang,Chun Zhang,Yonghua Yuan,Jun Pu,Yunsheng Zhao,Yanling Xie,Huidong Yuan,Youquan Bu,Fei Liao 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.11
The use of uricase-deficient mammals to screen formulations of engineered uricases as potential drugs for hyperuricemia involves heavy costs and presents a technical bottleneck. Herein, a new practical system was investigated to evaluate the pharmacological significance of a bacterial uricase based on its ability to eliminate uric acid in plasma in vitro, its pharmacokinetics in vivo in healthy rats, and the modeled pharmacodynamics in vivo. This uricase, before and after modification with the monomethyl ether of poly(ethylene glycol)-5000, effectively eliminated uric acid in vitro in rabbit plasma, but its action was susceptible to xanthine inhibition. After intravenous injection of the modified uricase without purification, a bi-exponential model fit well to uricase activities in vivo in the plasma of healthy rats; the half-life of the modified uricase was estimated without interference from the unmodified uricase leftover in the sample and was nearly 100-fold longer than that of the unmodified uricase. Using a model of the elimination of uric acid in vivo taking into account of uricase pharmacokinetics and xanthine inhibition, modeled pharmacodynamics supported that the half-life of uricase and its susceptibility to xanthine are crucial for the pharmacological significance of uricase. Hence,this practical system is desirable for doing preliminary screening of formulations of engineered uricases as potential drugs for hyperuricemia.
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An Improved Solution for Beam on Elastic Foundation using Quintic Displacement Functions
Tongji Univ,Youquan Feng,Wenya Shu 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2
The theory of beam on elastic foundation is a simple and popular analytic approach for computing the response of laterally loaded piles. For a laterally loaded pile with constant subgrade reaction coefficient, an analytical solution can be easily deduced based on the theory of beam on elastic foundation when the load distribution and boundary condition are simple. However, when the subgrade reaction coefficient increases linearly with the depth or when the constraint condition is complex, an approximate solution can only be obtained by numerical method. At present, the node-spring simulation method and the modifying stiffness matrix method are two main solution methods for beam on elastic foundation with a nonuniform distribution of subgrade reaction coefficient, but a large number of elements are necessary for obtaining a sufficient calculation accuracy. Based on the Winkler elastic foundation model, an improved Finite Element (FE) method for the laterally loaded pile on an elastic foundation with a linearly distributed modulus of the subgrade reaction is proposed. A quintic displacement function is proposed as an approximate solution, and the weighted residual method is used for solving differential equations. The corresponding element stiffness matrix and nodal force vector are derived, and a more accurate nodal displacement, element internal force and displacement distribution can then be obtained by employing fewer elements. Three beams on elastic foundations under different boundaries and loading conditions are taken as typical examples to compare the difference of the calculation accuracy between the improved method and the node-spring simulation method. A laterally loaded pile is analyzed by the improved method, and the numerical results show that two elements for one soil layer can provide a sufficient calculation accuracy.
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