• 대한인간공학회지
• /
• 제22권2호
• /
• pp.1-13
• /
• 2003

In general, causal relationship for theoretical concepts is hypothesized based on precedent studies and tested by a structural equation model. However, when theoretical backgrounds are scarce or absent, the causal relationship is hypothesized operatively by the purpose and scope of research and tested by overall goodness-of-fit indices such as GFI and RMR. Such a causal relationship can't be most appropriate statistically because it is selected as specific relationship from researcher's view among possible causal relationships. Therefore, this study is to propose a procedure for identifying the causal relationship that produces the best GFI among possible causal relationships for theoretical concepts.

• Journal of the Korean Physical Society
• /
• 제73권9호
• /
• pp.1211-1218
• /
• 2018

Within the framework of the modified factorization method, we solve the $Schr{\ddot{o}}dinger$ equation with the modified Yukawa potential. The energy spectrum is obtained using the Pekeris approximation scheme for the centrifugal term. The thermodynamic properties, including the vibrational partition function, vibrational mean energy, vibrational mean free energy, vibrational specific heat capacity and vibrational entropy, are calculated. As a special case, we compare our result with that work of Dong [Int. J. Quant. Chem. 107, 366 (2007)] and find good agreement.

• 한국수자원학회논문집
• /
• 제48권4호
• /
• pp.299-308
• /
• 2015

본 연구의 목적은 하천에서 흐름방향 유속의 횡분포식에 기반하여 1차원 종분산계수를 이론적으로 유도하고 이들의 타당성을 검증하는 것이다. 이를 위해 본 논문의 전편 "I. 흐름방향 유속의 횡포식"에서는 SKM을 도입하여 삼각형 단면수로에서 횡분포식을 해석적으로 유도하였다. 본 논문의 후편 "II. 종분산계수"에서는 전편에서 유도된 유속의 횡분포식을 기반으로 1차원 종분산계수 이론식을 새롭게 개발하였다. 개발된 종분산계수 이론식을 검증하기 위해 전편과 동일한 하천에서 수행된 추적자 농도 실험 결과를 이용한 관측 종분산계수와 비교 분석하였다. 또한 개발된 종분산 계수식을 기존의 식들과 비교하여 본 연구에서 개발된 식의 차별점 및 우수성을 검토하였다. 결과적으로 무차원 종분산계수는 무차원 횡확산계수에 반비례하고, 하폭 대 수심비의 제곱에 비례하였다. 그리고 Manning의 조도계수의 제곱에 반비례함을 확인할 수 있었다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.93-96
• /
• 2007

This paper presents a theoretical approach to describe the vibration characteristics in the 1-3 piezoelectric composite arrayed on a cylindrical surface. By homogenizing the composite composed of a piezoelectric ceramic and a polymer the physically useful parameters were defined and then used to derive the governing equation of radial motion for the cylindrical 1-3 piezoelectric composite. Applying mechanical and electric boundary conditions has yielded a characteristic equation for radial vibration of the composite. Theoretical calculations of the resonance frequency have been compared with those obtained by the finite-element analysis and have shown a good agreement.

• 대한기계학회논문집A
• /
• 제27권8호
• /
• pp.1317-1323
• /
• 2003

In this paper, In-air and in-water vibration characteristics of Rotary Specimen Rack(RSR) are estimated through 3D finite element analysis by using ANSYS software. Added mass is calculated by using Blevins' equation. To confirm the accuracy of the results presented in this study, obtained results are compared to those of using a theoretical equation. It is confirmed that in-water natural frequencies of the RSR are lower than in-air ones due to tile added mass effect of the fluid. Also, good agreement is founded between natural frequency ratios obtained by a theoretical equation and those of using ANSYS.

• Journal of Information Display
• /
• 제10권4호
• /
• pp.143-148
• /
• 2009

The theoretical current density equations for organic semiconductors was derived according to the internal carrier emission equation based on the diffusion model at the Schottky barrier contact and the mobility equation based on the field dependence model, the so-called "Poole-Frenkel mobility model." The electric field becomes constant because of the absence of a space charge effect in the case of a higher injection barrier height and a lower sample thickness, but there is distribution in the electric field because of the space charge effect in the case of a lower injection barrier height and a higher sample thickness. The transition between the injection- and bulk-limited currents was presented according to the Schottky barrier height and the sample thickness change.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 1997년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
• /
• pp.159-166
• /
• 1997

The purpose of this thesis is to derive a theoretical model of the hysteretic resistance of the visco-elastic damper based on test results of harmonic excitation and to investigate of the basis of theory and experiment the effect of vibration control and response characteristics of portal frames degree vibration systems provided with the damper. The behaviour of a visco-elastic degree under dynamic loading is idealized by a model of the theory of visco-elasticity, i.e. a four-parameter model formed as a parallel combination of Maxwell fluid and Kelvin-Voigh models and its constitutive equation is derived. The model parameters are determined for a tested damper from the datas of harmonic excitation tests. The theoretical model of the damper is incorporated in equation fo motion of single degree of freedom. A computer program for solving the equation is written using Runge-kuttas's numerical integration scheme. Using this analysis program test cases of the earthquake excitation are simulated and the results of the simulation are the results of the simulation are the results of the simulation are compared with the test results.

• Bulletin of the Korean Chemical Society
• /
• 제34권12호
• /
• pp.3709-3714
• /
• 2013

Based on the Debye-H$\ddot{u}$ckel equation, a semi-empirical equation for activity coefficients was derived through empirical and theoretical trial and error efforts. The obtained equation included two parameters: the proportional factor and the effective radius of an ionic sphere. These parameters were used in the empirical and regression parameter fitting of the calculated values to the experimental results. The activity coefficients calculated from the equation agreed with the data. Transforming to a semi-empirical form, the equation was expressed with one parameter, the ion radius. The ion radius, ${\alpha}$, was divided into three parameters, ${\alpha}_{cation}$, ${\alpha}_{anion}$ and ${\delta}_{cation}$, representing parameters for the cation, anion and combination, respectively. The advantage of this equation is the ability to propose a semi-empirical equation that can easily determine the activity coefficient with just one parameter, so the equation is expected to be used more widely in actual industry applications.

• 대한기계학회논문집B
• /
• 제41권10호
• /
• pp.675-683
• /
• 2017

본 연구에서 원자력 발전용 비상노심냉각 장치인 안전주입탱크의 재충수 단계에 대한 유량에 대한 이론해석을 수행했다. 이론해석을 통해 재충수 단계 유동에 대한 이론 모형을 정립하고 재충수 단계에 대한 비선형 유량방정식을 구하고, 테일러 급수 전개법을 통해 근사유량방정식과 냉각수의 자유표면 높이변화와 유량변화를 예측할 수 있는 이론해들을 구했다. 기존연구에 나와 있는 실험과 비교하여 이론해의 유용성을 검증했다.

• 동력기계공학회지
• /
• 제22권6호
• /
• pp.58-66
• /
• 2018

The use of external gear pumps is an effective way to achieve adequate performance at low cost when composing hydraulic systems. The biggest drawback, on the other hand, is the accompanying noise. Gears of continuous contact shape are actively used for the pump recently. The continuous contact shape must be the helical type due to the nature of the gear pump that is driven only by the drive gear. In this paper the theoretical shape of continuous contact gear is analyzed using simple rack shape of straight lines and two circular arcs. Using such geometry, the theoretical equation will be developed by envelope curves according to the conjugate gear shape rules. After checking the validity of the theory by the shape of gear rules, the grinding shape was also developed. The 3D shapes using equation can be also drawn. It was also shown that contact ratio and radius of curvature are easily developed by the theoretical equations.