• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.505-517
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• 2008

A numerical analysis method was studied to predict the nonlinear behavior of slender double skin composite walls. For convenience in numerical analysis, the model for the double skin composite wall was developed as a macroscopic model that can predict nonlinear behavior with relatively simplified models. For the wall showing flexure-dominant behavior, a multiple layer model was used. Each layer was modeled with composite elements of concrete and steel plate. An X-type truss model was used for coupling beams showing shear-dominant behavior. To describe the cyclic behavior of concrete and steel elements, simplified cyclic models for the materials were proposed. The proposed analysis model was applied to isolated walls and coupled walls with rectangular or T-shaped cross-sections. The analytical results were compared with existing test results.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.139-145
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• 2009

An analytical solution of groundwater flow is applied to design soil vacuum extraction for removing volatile organic compounds from the unsaturation zone. The governing equation of gas or vapor flow in porous media is nonlinear in that gas density depends on gas pressure. A linear equation suggested by researcher is similar to that of groundwater flow. The pressure drawdowns of confined and leaky aqufiers are calculated using Massmann's field data, and the pressure drawdowns are compared. A solution of Theis equation calculated by Massmann is modified using GASSOLVE9 program in this paper. The pressure drawdown using Hantush's analytical solution for leaky aquifer also compared to that of Massmann. Hantush's analytical solution gives good approximations to pressure drawdown.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.109-113
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• 2007

We investigated the magnetic properties of VRu(001) surface by using the all electron full-potenial linearized augmented planewave (FLAPW) energy band method within the GGA. We consider two different configurations, V and Ru surface layers, respectively. The V atoms in surface layer was calculated to have large magnetic moment of $1.71_{{\mu}_B}$ while the Ru surface layer to have nearly nonmagnetic state. The calculated spin-polarized density of states. spin density contour, and charge density were discussed in relation to the magnetic properties of VRu(001) surface.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.217-220
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• 2005

The electronic structure and magnetism of Fe chain along the [110] direction on Ag(001) were investigated by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within generalized gradient approximation (GGA). The magnetic moment of Fe atom in Fe chain is calculated to be $3.02\;{\mu}_B$, which is slightly larger than that ($2.99\;{\mu}_B$) of the Fe[110] chain on Cu(001). The reduced coordination number for the Fe chain induced the Fe-d band narrowing and exchange-splitting enhancement, which are responsible for the large magnetic moment of the Fe chain. The calculated band width of the Fe-d band and the exchange-splitting are 1.7 eV and 3.2 eV, respectively.

• Journal of the Korean Magnetics Society
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• v.23 no.4
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• pp.117-121
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• 2013

In this study we investigated magnetism and magnetostriction of B2-structured FeX (X = Al, Si, Ni, Ga, Ge, and Sn) using a first-principles method, in order to survey the possibility of developing a transition metal based magnetostriction material. The Full-potential Linearized Augmented Plane Wave method was employed for solving the Kohn-Sham equation within the generalized gradient approximation for exchange-correlation interaction between electrons. FeX alloys are stabilized in ferromagnetic states except for the FeSi and FeGe alloys. Magnetostrcition coefficients of FeX (X = Al, Ni, Ga, and Sn) were calculated to be -5, +6, -84, -522ppm, respectively. It is noteworthy that the magnetostriction coefficient (-522ppm) of FeSn is larger than that (+400ppm) of Gafenol.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.145-152
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• 2016

Recently, we can find news about toxic and combustible gas accident. So, we have to develop gas detector that can measure gas at dangerous area for preventing gas accidents. In this paper, we calculate a approximation function from sensor's output using the linear regressiong. And we develop software algorithm using Neville's algorithm for measuring gas concentration. Finally, we compare our algorithm with combustible gas detectors that are already developed, by using standard gas samples manufactured Korea Gas Safety. As a result of this experiment, we confirm that performance of our algorithm is more improved than performance of already developed combustible gas detectors. In the future, we'll research how to improve reliability from using count, temperature and humidity. And we'll design hardware applied explosion proof for safety.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.438-447
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• 2008

This study is focused on reliability based design optimization (RBDO) using moving least squares. A response surface is used to derive a limit-state equation for reliability based design optimization. Response surface method (RSM) with least square method (LSM) or Kriging will be used as a response surface. RSM is fast to make the response surface. On the other hand, RSM has disadvantage to make the response surface of nonlinear equation. Kriging can make the response surface in nonlinear equation precisely but needs considerable amount of computations. The moving least square method (MLSM) is made of both methods (RSM with LSM+Kriging). Numerical results by MLSM are compared with those by LMS in Rosenbrock function and six-hump carmel back function. The RBDO of engine duct of smart UAV is pursued in this paper. It is proved that RBDO is useful tool for aerospace structural optimal design problems.

• Journal of the Korean Institute of Intelligent Systems
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• v.7 no.2
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• pp.70-78
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• 1997

Proportional-integral-derivative(P1D) controllers have been still widely used in industrial processes due to their simplicity, effectiveness, robustness for a wide range of operating conditions, and the familiarity of control engineers. And a number of recent papers in fuzzy systems are showing that fuzzy systems are universal approximators. That is, fuzzy controllers are capable of approximating any real continuous function on a compact set of arbitrary accuracy. In this paper, we derive the linear PID control law from the fuzzy control algorithm where all fuzzy sets for representing plant state variables and a control variable use common triangular types. We first lead a linear PD control law from a fuzzy logic control with only two fuzzy sets for error and change-of-error. And then we derive the linear PID control law from a fuzzy controller. We here assumed that the intervals of error, change-of-error, and integral error could be partitioned into arbitrary numbers, respectively. As a result, a linear PID controller is only a sort of various fuzzy logic controls.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.39-47
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• 2017

Precipitation is an important component for hydrological and water control study. In general, AWS data provides more accurate but low dense information for precipitation while radar data gives less accurate but high dense information. The objective of this study is to construct adjusted precipitation field based on hierarchical spatial model combining radar data and AWS data. Here, we consider a Bayesian hierarchical model with spatial structure for hourly accumulated precipitation. In addition, we also consider a redistribution of hourly precipitation to 2.5 minute precipitation. Through real data analysis, it has been shown that the proposed approach provides more reasonable precipitation field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1013-1021
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• 1994

The stiffness and mass matrices are developed for free torsional vibration analysis in linearly tapered thin-walled I-beams that takes into account the effect of warping torsion. The approximate shape functions are used for formulating stiffness and mass matrices. Significant improvements of accuracy and efficiency of free vibration analysis are achieved by using the stiffness and mass matrices developed in this study. Frequencies of free vibration of tapered members are compared with solutions based upon stepped representation of beam element and also are verified with model tests. The stiffness and mass matrices presented in this study can be used for the free vibration analysis of tapered and prismatic thin walled I-beams and space structures involving warping torsion.