• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.159-163
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• 2004

This study was conducted to calculate the permeability coefficient in a single fracture while taking the true fracture geometry into consideration. The fracture geometry was measured using the confocal laser scanning microscope (CLSM). The CLSM geometry data were used to reconstruct a fracture model for numerical analysis using a homogenization analysis (HA) method. The HA is a new type of perturbation theory developed to characterize the behavior of a micro-inhomogeneous material that involves periodic microstructures. The HA permeability was calculated based on the local geometry and local material properties (water viscosity in this case). The results show that the permeability coefficients do not follow the theoretical relationship of the cubic law.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.956-957
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• 2015

This paper analyzes a operating characteristic for maximum power point tracking (MPPT) of photovoltaic generation system. MPPT methods are used to maximize PV array output power by tracking maximum power point(MPP) continuously. To increase the output efficiency of PV system, it is important to have more efficient MPPT. MPPT algorithm is widely used the control method such as the perturbation and observation(PO) method, incremental conductance(IC) method and constant voltage(CV) method. In case of the radiation is changed, this paper proposes a response characteristic with MPPT control algorithms. Also, it proposes the direct for a novel MPPT control algorithm development through the analyzed data, hereby proves the effectiveness of this paper.

• 대한수학회지
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• 제34권3호
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• pp.695-706
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• 1997

We investigate the bahivor of the gradient of solutions to the refraction equation $div(( 1+ (k - 1)_\chi D)\nabla u) = 0$ under perturbation of domain D. If $u_h$ are solutions to the refraction equation corresponding to subdomains D and $D_h$ of a domain $\Omega$ in 2 dimensional plane with the same Neumann data on $\partial\Omega$, respectively, we prove that $\left\$\mid$ \nabla(u - u_h) \right\$\mid$_{L^2(\Omega)} \leq C\sqrt{dist(D, D_h)}$ where $dist(D, D_h)$ is the Hausdorff distance between D and $D_h$. We also show that this is the best possible result.

• 대한수학회보
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• 제52권6호
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• pp.1945-1962
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• 2015

This paper is mainly concerned with the formation of delta standing wave for the scalar conservation law with a linear flux function involving discontinuous coefficients by using the self-similar viscosity vanishing method. More precisely, we use the self-similar viscosity to smooth out the discontinuous coefficient such that the existence of approximate viscous solutions to the delta standing wave for the Riemann problem is established and then the convergence to the delta standing wave solution is also obtained when the viscosity parameter tends to zero. In addition, the Riemann problem is also solved with the standard method and the instability of Riemann solutions with respect to the specific small perturbation of initial data is pointed out in some particular situations.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.144-144
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• 2011

Diagnostics of plasma density and temperature play an important role for monitoring plasma processing and Laser Thomson scattering is a one of the most accurate diagnostic technique for measuring plasma density and temperature because of none-perturbation to plasma among various diagnostic techniques invented to measure plasma density and temperature. I will briefly review Laser Thomson scattering experiment performed in KRISS and difficulties for measuring the electron velocity distribution such as Gaussian due to low signal-to-noise ratio with showing results that we got until now. This work is an intermediate step in a process that we will get a reliable data which shows physical phenomenon of plasma compared with other diagnostic techniques and results.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.414-421
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• 1998

The content of this paper consists of two related subjects. One is the assessment of damages in the existing structure and the other is the evaluation of seismic capacity of the structure with damage. A method is presented for damage assessment of existing structures using the modal data measured at limited points by the inverse medal perturbation technique. For efficient damage assessment, the number of the unknown probable damaged members is reduced for each damage identification by grouping the members in the large structure. The aseismic capacity is evaluated for the structure using the results of damage assessment. An example analysis is carried out for a building structure subjected to different earthquake excitations.

• Bulletin of the Korean Chemical Society
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• 제13권4호
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• pp.429-440
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• 1992

The second order ab initio effective valence shall Hamiltonian ($H^v$) which is based on quasidegenerate many-body perturbation theory is applied to the SiH, PH, and their positive ions. A singie Hv computation for the neutral molecule is used for a whole set of valence states of a molecule and its ion simultaneously. The low-lying valence state potential energy curves of SiH, PH and their positive ions are computed. And various spectroscopic constants of the low-lying bound valence states are determined from the potential energy curves. The $H^v$ results are found to be in good agreement with other theoretical and experimental data.

• 천문학회보
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• 제44권1호
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• pp.41.1-41.1
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• 2019

We consider dynamical dark energy models based on a minimally coupled scalar field with three different potentials: the inverse power-law, SUGRA and double exponential potentials. For each model, we derived perturbation initial conditions in the early epoch and performed the Markov Chain Monte Carlo (MCMC) analysis to explore the parameter space that is favored by the current cosmological observations like Planck CMB anisotropy, type Ia supernovae, and baryon acoustic oscillation data. The analysis has been done by using the modified CAMB/COSMOMC code in which the dynamical evolution of the scalar field perturbations are fully considered. The MCMC constraints on the cosmological as well as potential parameters are derived. In the talk we will present a progress report.

• 한국정밀공학회지
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• 제13권12호
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• pp.54-62
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• 1996

To get the time response characteristics of the hydrostatic transmission, seaborne winch is modelde by using bond graphs. After modeling of its basic elements, it is represented as power flow, and the determination of variable causality. The state equations are derived by using CAMP. As dynamic stabilites and solutions are investigated by perturbation method and direct integration, winch system is stable. Simulations are performed under the conditions of low speed, high speed, and maximum tension. The pressure and flow rate of the hydrostatic transmission have a big overshoot. But when it is comparaed to the empirical data with simulation results, it is similar to each other. When a lead compensator is applied to improve response characteristics of the hydrostatic transmission, rise time and overshoot of the system are improved.

• Advances in aircraft and spacecraft science
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• 제11권1호
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• pp.1-21
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• 2024

The stiffness reduction of cross-ply composite laminates featuring a transverse cracking and delamination within the mid-layer is predicted through utilization of a modified shear-lag model, incorporating a stress perturbation function. Good agreement is obtained by comparing the prediction models and experimental data. The material characteristics of the composite are affected by fluctuations in temperature and transient moisture concentration distribution in desorption case, based on a micro-mechanical model of laminates. The transient and non-uniform moisture concentration distribution induces a stiffness reduction. The obtained results demonstrate the stiffness degradation dependence on factors such as cracks density, thickness ratio and environmental conditions. The present study underscores the significance of comprehending the degradation of material properties in the failure progression of laminates, particularly in instances of extensive delamination growth.