• 전자공학회논문지A
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• 제30A권8호
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• pp.63-71
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• 1993

To verify validity of the steady-state Nyquist theorem and the steady-state Nyquist theorem with hot carrier effects in semiconductor devices, we calculate thermal noise in n-i-n structures using both the steady-state Nyquist theorem and the Monte-Carlo method, and compare the results from these two-methods. When the carrier temperature is not far from the lattice temperature, the results from both methods agree with each other very well, but in the hot carrier regime there are some discrepancies. Our results support the argument that for MOSFETs and MESFETs operating in the linear region, the channel thermal noise should be explained by the steady-state Nyquist theorem rather than by the existing theories.

• Journal of Advanced Research in Ocean Engineering
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• 제3권4호
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• pp.193-203
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• 2017

This study investigated the steady-flow effects present in the numerical computation of the resistance added to a ship in waves. For a ship advancing in the forward direction, a time-domain 3D Rankine panel method is applied to solve the ship motion problem, and the added resistance due to waves is calculated using a near-field method, with the direct integration of the second-order pressure on the hull surface. In the linear potential theory, the steady flow is approximated by the basis potential of a uniform flow or double-body flow in order to linearize the boundary conditions. By applying these two different linearization schemes, the coupling effects between steady and unsteady solutions were examined. Furthermore, in order to analyze the steady-flow effects on the hull geometry, the computation results for two realistic hull forms, a KVLCC2 tanker and DTC containership, were compared. In particular, the mj term, which represents the coupling effects under the body boundary condition, was evaluated considering the geometry of a non-wall-sided ship. Lastly, the characteristics of the linearization schemes were examined in relation to the disturbed waves around a ship and the components of added resistance.

• Bulletin of the Korean Chemical Society
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• 제11권6호
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• pp.557-560
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• 1990

The transition from one stable steady state branch to another stable steady state branch in a simple metabolic system with positive feedback is discussed with the aid of the bimodal Gaussian probability distribution method. Fluctuations lead to transitions from one stable steady state branch to the other, so that the bimodal Gaussian evolves to a new distribution. We also obtain the fractional occupancies in the two stable steady states in terms of a parameter characterizing conditions of the system.

• 소성∙가공
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• 제24권3호
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• pp.161-166
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• 2015

The finite element method has been widely used in the analysis of ring rolling. For ring rolling it requires a high computational expense due to the non-steady state material flow characteristics of the process. The high computational expense causes the finite element analysis to be impractical for industrial applications. In the current study, we aim to develop a practical implicit finite element modeling method for ring rolling. This method uses a step-wise steady state assumption and is called the “Stepped method”. The stepped method divides the whole process time of unsteady-state flow model into a finite number of steady-state models. It then solves the process at several specific time steps until convergence is reached. In order to confirm the performance and validity of the newly proposed stepped method, the result from the stepped method were compared to the results from a Lagrangian finite element method and to results from experiments reported in the literature.

• International Journal of Automotive Technology
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• 제7권1호
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• pp.101-107
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• 2006

The force and moment simulation of a steady-state rolling tire taking the effect of tread pattern into account is described using a steady-state transport method with ABAQUS. Tread meshes can not fully consider a tread pattern because detailed tread meshes are not allowed in the steady-state transport method. Therefore, the tread elements are modeled to have orthotropic property instead of isotropic property. The force and moment simulation has been carried out for the cases of both isotropic and orthotropic properties of tread elements. Both cases of simulation results are then compared with the experimental results. It is verified that the orthotropic case is in a better agreement with the experimental result than the isotropic case. Angle effects of tread pattern have been studied by changing the orientation angle of orthotropic property of tread. It is shown that the groove angle in the tread shoulder region has a more effect on force and moment of a tire than that in the tread center region.

• International Journal of Aerospace System Engineering
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• 제7권1호
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• pp.21-27
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• 2020

Quasi steady stall is a phenomenon to characterize the aerodynamic behavior of aircraft at high angle of attack region. Generally, it is exercised from a steady state level flight to stall and its recovery to the initial flight in a calm weather. For a theoretical study, such maneuver is demonstrated in the form of aerodynamic model which consists of aircraft's stability and control derivatives. The current research paper is focused on the appropriate selection of aerodynamic model for the maneuver and estimation of the unknown model coefficients using least-square method. The statistical accuracy of the estimated parameters is presented in terms of standard deviations. Finally, the validation has been presented by comparing the measured data to the simulated data from different models.

• 산업기술연구
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• 제15권
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• pp.203-208
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• 1995

This paper suggests the three dimensional steady state searching techniques of hard disk/head system, which has some skew angle with flexure. In order to analyze the steady state behaviors of magnetic head slider, the localized Knudsen number and the localized bearing numbers are sued. For finding the steady state of magnetic head slider under the pre-loaded condition, I proposed multi-dimensional Newton-Raphson method which traces the equilibrium position of magnetic head slider, which has 3-degrees of freedom, using Jacobian matrix. The multi-dimensional Newton-Raphson method is very efficient technique for finding the steady state position of magnetic head slider because it approaches to the equilibrium position with changing three parameters simultaneously.

• 대한수학회지
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• 제57권1호
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• pp.249-281
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• 2020

A reaction-diffusion model with spatiotemporal delay modeling the dynamical behavior of a single species is investigated. The parameter regions for the local stability, global stability and instability of the unique positive constant steady state solution are derived. The conditions of the occurrence of Turing (diffusion-driven) instability are obtained. The existence of time-periodic solutions, the existence and nonexistence of nonconstant positive steady state solutions are proved by bifurcation method and energy method. Numerical simulations are presented to verify and illustrate the theoretical results.

• 대한기계학회논문집B
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• 제30권9호
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• pp.898-904
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• 2006

A new method measuring thermal conductivity of fluids is proposed in this research. It is based on the steady state heat transfer from a hot central cylinder to a cold outer cylinder located concentrically. This method guarantees more stable measurement than conventional THM(transient hot-wire method) due to its simplicity of theoretical principle. Measurements was made for the three nanofluid samples with different particle concentration of pure, 2% and 4%. Nanofluids are made by mixing the pure transformer oil with AlN nano particles. Design of the sensor module and experimental procedures are explained and comparison of the measuring data between present method and THM was made in detail.

• 전력전자학회논문지
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• 제23권6호
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• pp.373-380
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• 2018

This study proposes a new islanding detection method that uses the phase shift of feed-forward voltage and evaluates the performance of an existing method and the proposed method when the grid frequency changes within the allowable range under steady-state conditions. The investigated existing method, which is slip mode frequency shift (SMS), uses current phase shift to detect islanding. The SMS method supplies reactive current to the grid under this condition, but the proposed method does not generate additional reactive power because it does not depend on the current control loop. The performance in steady-state grid condition is evaluated through simulations and experiments.