• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.96-98
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• 2001

In this paper, the equivalent magnetic circuit and FEM are used to calculate force density of linear BLDC motor. The equivalent magnetic circuit is hard to exact compose for analysis model and it is just applied to linear system. To flexible design and reducing the calculated and analyzed time, magnetic circuit has to be used for designing the linear BLDC motor and deducing equation of force density. Force density as parameter of permanent magnet and coil-side width that are important to determined force density can be estimated using equation of force density. FEM is used to prove reliability of equation of force density and to consider the nonlinear system. Equivalent magnetic circuit and result of FEM are similar, but it is little different by friction loss at the experiment.

• 한국농공학회지
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• 제30권4호
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• pp.109-116
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• 1988

This study was aimed at determining a regime of flow through rubble mound dike consisted of all sized quarrystons, and deriving a relationship between hydraulic gradient (I) and mean flow velocity (V) through the dike. The analysis was carried out with the data observed after final gap closing of the Haenam Sea dike from May, 6 to May, 14, 1987. The resu]ts are summarized as follows: 1. The regime of flow would be defined as the turbulent flow. 2. As to the relationships, two kinds of formula that are exponential and binomial were obtained. Exponential formula: I=2.099V 1.2888 Binomial formula: I=0.6113V+5.5235V$^2$ 3. Correlation coefficient of the former was 0.824 and that of the latter was 0.821, and the deviations between observed data and estimated were 0.0070 and 0.0064 respectively. 4. Comparing the correlation coefficient, both the equations have the same correlation coefficients, but in case of the deviation the binomial equation was better than the exponential equation. Therefore, the binomial equation is proposed for analyzing the flow through rubble mound dike.

• 콘크리트학회논문집
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• 제11권4호
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.897-899
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• 2000

This paper deals with the dynamic characteristic analysis of Linear Oscillatory Actuator (LOA) considering Sine Pulse Width Modulation (SPWM) method with H-bridge driver. The input current shape obtained by the driver has great influence on the driving performance of LOA. Therefore, according to the various current shapes, the analysis is achieved by using the combined equation between kinetic and electric circuit equation. Moreover, the parameters in the electric circuit equation are accurately estimated by using FEM.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.129-132
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• 2004

This study concerns the new strength equation of concrete by ultrasonic pulse velocity test. There are not only few estimate strength equations of concrete by ultrasonic pulse velocity test, but also many problems to apply them because of time, cost, easiness, structural damage, reliability and so on. For this study, there performed a series of test and proposed equations as follows; $$Linear\;:\;f_{kc}=65.43Vp-207.18\;r^2=80.8\%$$ $$Quadratic\;:\;f_{ck}=42.35Vp^2-250.71Vp+378.8\;r^2=83.7\%$$ here, fck : Estimated compressive strength of concrete by MPa Vp: Ultrasonic Pulse Velocity of concrete by km/sec.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.133-136
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• 2004

This study concerns the. new equation of concrete strength by schmidt hammer test. There are not only few estimate strength equations of concrete by schmidt hammer test, but also many problems to apply them because of time, cost, easiness, structural damage, reliability and so on. For this study, there performed a series of schmidt hammer test with in existing 730days' concrete structures and proposed equations as follows; $$Linear\;:\;f_{ck}=2.18R-40.54\;(r^2=77.7\%)$$ $$Quadratic\;:\;f_{ck}=0.076R^2-2.92R+40.04\;(R^2= 85.5\%)$$ here, fck : Estimated compressive strength of concrete by MPa, R : Rebound index of concrete.

• 대한전기학회논문지
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• 제38권3호
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• pp.193-200
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• 1989

The errors of activation energy calculated by the initial rise method from the characteristics of thermally stimulated current have been estimated and an equation for the correction of the error is proposed. The coefficients needed in the proposed equation are determined by the numerical method. It is shown that the activation energy calculated by the conventional initial rise method contains errors of 0.7-10% depending on the location of the data points of the interval on which the method is applied. However, the error can be reduced to less than 0.5% when corrected by using the proposed equation. It is finally concluded that the activation energy determined by the initial rise method can approach the true value by adapting the proposed error correction method which is effective and reliable.

• 한국정밀공학회지
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• 제22권5호
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• pp.55-62
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• 2005

This paper presents mainly a procedure to get the mathematical form of the manufactured aspherical lens. Generally Schulz formula describes the aspherical lens profile. Therefore, the base curvature, conic constant. and high-order polynomial coefficient should be set to get the approximated design equation. To find the best-approximated aspherical form, lens profile is measured by a commercial stylus profiler, which has a sub-micrometer measurement resolution. The optimization tool is based on the minimization of the root mean square of error sum to get the estimated aspherical surface equation from the scanned aspherical profile. Error minimization step uses the Nelder-Mead simplex (direct search) method. The result of the lens refractive power measurement shows the experimental consistency with the curvature distribution of the best-approximated aspherical surface equation

• 한국정밀공학회지
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• 제15권7호
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• pp.167-174
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• 1998

This paper presents an unoccluded cylindrical object pose measurement using a slit beam laser in which a robot recognizes all of the unoccluded objects from the top of jumbled objects, and picks them up one by one. The elliptical equation parameters of a projected curve edge on a slice are calculated using LSM. The coefficients of standard elliptical equation are compared with these parameters to estimate the object pose. The hamming distances between the estimated coordinates and the calculated ones are extracted as measures to evaluate a local constraint and a smoothing surface curvature. The edges between slices are linked using error function based on the edge types and the hamming distances. The linked edges on slices are compared with the model object's length to recognize the unoccluded object. This proposed method may provide a solution to the automation of part handling in manufacturing environments such as punch press operation or part assembly.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.145-153
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• 1997

Dynamic characteristics are investigated when a nonlinear system showing periodic and chaotic responses under harmonic excitation is exposed to random perturbation. About two well potential problem, probability of homoclinic bifurcation is estimated using stochastic generalized Meinikov process and quantitive characteristics are investigated by calculation of Lyapunov exponent. Critical excitaion is calculated by various assumptions about Gaussian Melnikov process. To verify the phenomenon graphically Fokker-Planck equation is solved numerically and the original nonlinear equation is numerically simulated. Numerical solution of Fokker-Planck equation is calculated on Poincare section and noise induced chaos is studied by solving the eigenvalue problem of discretized probability density function.