• Title/Summary/Keyword: approximation function

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Conformational Analysis of Sulfonylureas (술포닐 우레아 유도체들의 형태분석)

  • Kang, Kee-Long;Lee, Sung-Hee;Chung, Uoo-Tae
    • YAKHAK HOEJI
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    • v.36 no.6
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    • pp.518-528
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    • 1992
  • To determine the optimal conformation of sulfonylureas, the correlation between conformation and hypoglycemic activity of the two sulfonylureas of tolbutamide and chlorpropamide as hypoglycemic agent was studied using an empirical potential function (ECEPP/2) and the hydration shell model in the unhydrated and hydrated states. The conformational energy was minimized from several starting conformations with possible torsion angles in each molecule. The conformational entropy change of each conformation was computed using a harmonic approximation. To understand the hydration effect on the conformation of the molecules in aqueous solution, the contribution of water-accessible volume of each group or atom in the lowest-free-energy conformation was calculated and compared each other. From comparison of the computed lowest-free-energy conformations of two sulfonylureas, it could be suggested that the hydration of sulfonylurea moiety is related to increase the hypoglycemic activity. From the calculation results, it was known that the conformational entropy is the major contribution to stabilize the low-free-energy conformations of two sulfonylureas in unhydrated state. Whereas, in hydrated state, the hydration free energy largely contributes to the total free energies of low-free-energy conformations of tolbutamide and conformational entropy contributes to stabilize the low-free-energy conformations of chlorpropamide. The torsion angles from phenyl ring to urea moiety of the low-free-energy conformations of the two sulfonylureas were shown the nearly regular trend. On the basis of these results, the conformation exhibiting the optimal hypoglycemic activity of sulfonylureas and the binding direction to pancreatic receptor site A could be predicted. Also, according to the side chain lengthening of urea moiety, tolbutamide showed various conformational change. Therefore, steric effect may be important factor in the interaction between sulfonylureas and the putative pancreatic receptor.

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Genetically Optimized Self-Organizing Polynomial Neural Networks (진화론적 최적 자기구성 다항식 뉴럴 네트워크)

  • 박호성;박병준;장성환;오성권
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.53 no.1
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    • pp.40-49
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    • 2004
  • In this paper, we propose a new architecture of Genetic Algorithms(GAs)-based Self-Organizing Polynomial Neural Networks(SOPNN), discuss a comprehensive design methodology and carry out a series of numeric experiments. The conventional SOPNN is based on the extended Group Method of Data Handling(GMDH) method and utilized the polynomial order (viz. linear, quadratic, and modified quadratic) as well as the number of node inputs fixed (selected in advance by designer) at Polynomial Neurons (or nodes) located in each layer through a growth process of the network. Moreover it does not guarantee that the SOPNN generated through learning has the optimal network architecture. But the proposed GA-based SOPNN enable the architecture to be a structurally more optimized network, and to be much more flexible and preferable neural network than the conventional SOPNN. In order to generate the structurally optimized SOPNN, GA-based design procedure at each stage (layer) of SOPNN leads to the selection of preferred nodes (or PNs) with optimal parameters- such as the number of input variables, input variables, and the order of the polynomial-available within SOPNN. An aggregate performance index with a weighting factor is proposed in order to achieve a sound balance between approximation and generalization (predictive) abilities of the model. A detailed design procedure is discussed in detail. To evaluate the performance of the GA-based SOPNN, the model is experimented with using two time series data (gas furnace and NOx emission process data of gas turbine power plant). A comparative analysis shows that the proposed GA-based SOPNN is model with higher accuracy as well as more superb predictive capability than other intelligent models presented previously.

Sensitivity of Seepage Behavior of Dam to Unsaturated Soil Properties (불포화 수리특성에 대한 댐체 침투 거동의 민감도 분석)

  • Cho Sung-Eun
    • Journal of the Korean Geotechnical Society
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    • v.21 no.3
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    • pp.119-131
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    • 2005
  • Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. The behavior of dam such as seepage rate and the pore water pressure distribution is different according to the unsaturated hydraulic properties, but nevertheless simply assumed properties have been used due to insufficient data from domestic soils. In this paper, the effect of unsaturated hydraulic properties on the behavior of dam was studied through a series of numerical analyses, and then the results were discussed. It is observed that water table moves at a (aster rate, as the values of unsaturated soil parameter a and n increase. The value of m showed opposite trend. The sensitivity calculated using the approximation form showed maximum values near the water table. And the value of n that is related to the slope of soil water characteristic curve gives greatest influence on the change of sensitivity with time.

Transient Analysis of General Dispersive Media Using Laguerre Functions (라게르 함수를 이용한 일반적인 분산 매질의 시간 영역 해석)

  • Lee, Chang-Hwa;Kwon, Woo-Hyen;Jung, Baek-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.10
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    • pp.1005-1011
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    • 2011
  • In this paper, we present a marching-on-in-degree(MOD) finite difference method(FDM) based on the Helmholtz wave equation for analyzing transient electromagnetic responses in a general dispersive media. The two issues related to the finite difference approximation of the time derivatives and the time consuming convolution operations are handled analytically using the properties of the Laguerre functions. The basic idea here is that we fit the transient nature of the fields, the flux densities, the permittivity with a finite sum of orthogonal Laguerre functions. Through this novel approach, not only the time variable can be decoupled analytically from the temporal variations but also the final computational form of the equations is transformed from finite difference time-domain(FDTD) to a finite difference formulation through a Galerkin testing. Representative numerical examples are presented for transient wave propagation in general Debye, Drude, and Lorentz dispersive medium.

The Calculation of the Energy Band Gaps of Zincblende GaP1-X NX (질화물계 반도체 GaP1-X NX의 에너지 밴드갭 계산)

  • Chung, Ho-Yong;Kim, Dae-Ik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.12 no.5
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    • pp.783-790
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    • 2017
  • The energy band gaps and the bowing parameters of zincblende GaP1-xNx on the variation of temperature and composition are determined by using an empirical pseudopotential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter calculated is 13.1eV and the energy band gaps are decreased rapidly for GaP1-xNx ($0{\leq}x{\leq}0.05$, 300K). A refractive index n and a function of real dielectric constant ${\varepsilon}$ are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

Structural Optimization for LMTT-Mover Using Sequential Kriging Approximation Model (순차적 크리깅 근사모델을 이용한 LMTT 이동체의 구조최적설계)

  • Lee Kwon-Hee;Park Hyung-Wook;Han Dong-Seop;Han Geun-Jo
    • Journal of Navigation and Port Research
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    • v.30 no.1 s.107
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    • pp.105-111
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    • 2006
  • A LMTT (Linear Motor-based Transfer Technology) is a horizontal transfer system for the yard automation This system is based on PMLSM (Permanent Magnetic Linear Synchronous Motor) that consists of stator modules on the rail and shuttle car. In this research, the kriging interpolation method using sequential sampling is utilized to find the optimum design of a mover in LMTT. The design variables are considered as the transverse, longitudinal and wheel beam's thicknesses. The objective function is set up as weight, while the constant functions are set up as the stresses generated by four loading conditions. The optimum results obtained by the suggested method are compared with those determined by the GENESIS.

An Analytical Solution for Regular Progressive Water Waves

  • Shin, JangRyong
    • Journal of Advanced Research in Ocean Engineering
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    • v.1 no.3
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    • pp.157-167
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    • 2015
  • In order to provide simple and accurate wave theory in design of offshore structure, an analytical approximation is introduced in this paper. The solution is limited to flat bottom having a constant water depth. Water is considered as inviscid, incompressible and irrotational. The solution satisfies the continuity equation, bottom boundary condition and non-linear kinematic free surface boundary condition exactly. Error for dynamic condition is quite small. The solution is suitable in description of breaking waves. The solution is presented with closed form and dispersion relation is also presented with closed form. In the last century, there have been two main approaches to the nonlinear problems. One of these is perturbation method. Stokes wave and Cnoidal wave are based on the method. The other is numerical method. Dean's stream function theory is based on the method. In this paper, power series method was considered. The power series method can be applied to certain nonlinear differential equations (initial value problems). The series coefficients are specified by a nonlinear recurrence inherited from the differential equation. Because the non-linear wave problem is a boundary value problem, the power series method cannot be applied to the problem in general. But finite number of coefficients is necessary to describe the wave profile, truncated power series is enough. Therefore the power series method can be applied to the problem. In this case, the series coefficients are specified by a set of equations instead of recurrence. By using the set of equations, the nonlinear wave problem has been solved in this paper.

Analysis of Dimension Dependent Subthreshold Swing for FinFET Under 20nm (20nm이하 FinFET의 크기변화에 따른 서브문턱스윙분석)

  • Jung, Hak-Kee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.10
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    • pp.1815-1821
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    • 2006
  • In this paper, the subthreshold swing has been analyzed for FinFET under channel length of 20nm. The analytical current model has been developed , including thermionic current and tunneling current models. The potential distribution by Poisson equation and carrier distribution by Maxwell-Boltzman statistics are used to calculate thermionic emission current and WKB(Wentzel-Kramers-Brillouin) approximation to tunneling current. The cutoff current is obtained by simple adding two currents since two current is independent. The subthreshold swings by this model are compared with those by two dimensional simulation and two values agree well. Since the tunneling current increases especially under channel length of 10nm, the characteristics of subthreshold swing is degraded. The channel and gate oxide thickness have to be fabricated as am as possible to decrease this short channel effects, and this process has to be developed. The subthreshold swings as a function of channel doping concentrations are obtained. Note that subthreshold swings are resultly constant at low doping concentration.

The Comparative Software Development Cost Model Considering the Change in the Shape Parameter of the Erlang Distribution (어랑분포의 형상모수 변화에 따른 소프트웨어 개발 비용모형에 관한 비교 연구)

  • Yang, Tae-Jin
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.9 no.6
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    • pp.566-572
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    • 2016
  • Software Reliability implemented in software development is one of the most important issues. In finite failure NHPP software reliability models for software failure analysis, the hazard function that means a failure rate may have constant independently for failure time, non-increasing or non-decreasing pattern. In this study, software development cost analysis considering the variable shape parameter of Erlang distribution as the failure life distribution in the software product testing process was studied. The software failure model was applied finite failure Non-Homogeneous Poisson Procedure and the parameters approximation using maximum likelihood estimation was accompanied. Thus, this paper was presented comparative analysis by applying a software failure time data to the software, considering the shape parameter of Erlang distribution for development cost model analysis. When compared to the cost curve in accordance with the shape parameter, the model of smaller shape can be seen that the optimal software release time delay and more cost. Through this study, it is thought that it can serve as a preliminary information which can basically help the software developers to search for development cost according to software shape parameters.

Study on Stokes Flow Past Circular Cylinder in Two-Dimensional Channel (2차원 채널 내의 원형실린더를 지나는 스톡스 유동에 대한 연구)

  • Yoon, Seok-Hyun;Jeong, Jae-Tack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.10
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    • pp.895-900
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    • 2013
  • A two-dimensional Stokes flow past a circular cylinder in a channel is analyzed. The circular cylinder is located at the center of the channel, and a plane Poiseuille flow exists upstream and downstream far from the circular cylinder. The Stokes approximation is used, and the flow is investigated analytically by using the eigenfunction expansion and the least square methods. From the analysis, the stream function and pressure distribution are obtained, and the pressure and shear stress distributions on the circular cylinder and channel wall are calculated. The additional pressure drop induced by the circular cylinder and the force exerted on it are calculated as functions of the length of the radius of the circular cylinder. For a typical length of the radius of the circular cylinder, the streamline pattern and pressure distribution are shown.