• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.237-247
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• 1999

Flight parameters of a light aircraft in normal category named ChangGong-91 we identified from flight tests. Modified Maximum Likelihood Estimation (MMLE) is used to produce aerodynamic coefficients, stability and control derivatives. A Flight Training Device (FTD) has been developed based on the identified flight parameters. Flat earth, rigid body, and standard atmosphere are assumed in the FTD model. Euler angles are adapted for rotational state variables to reduce computational load. Variations in flight Mach number and Reynolds number are assumed to be negligible. Body, stability and inertial axes allow 6 second-order linear differential equations for translational and rotational motions. The equations of motion are integrated with respect to time, resulting in good agreements with flight tests.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.158-163
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• 1996

In the conventional GaAs MESFET circuit simulation, the DC and transient simulation results are often failed due to the discontrinuities of the first and second order derivatives arising from the use of separate C-V models in linear, satruration, and transition regions. In this paper, we propose a unified capacitance model for linear, transition, and saturation regions by using a unified channel length modulation effect that is derived by extending the channel length modulation effect in the saturation region to the linear region. Calculated resutls from the proposed capacitance model agree well with 2-D device simulation resutls. Thus, the proposed model is expected to be useful in circuit simulation.

• Korean Journal of Optics and Photonics
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• v.28 no.2
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• pp.68-74
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• 2017

To minimize chromatic variations across a wavelength band, we suggest a new design that corrects the first- and second-order wavelength derivatives of the refractive power. Based on this method, a diffraction-limited collimator is designed. The design is very stable against wavelength change, as expected. The chromatic change of the effective focal length is less than 0.002% in the wavelength range from 360 to 410 nm.

• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.49-65
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• 2006

A robust numerical method for a singularly perturbed second-order ordinary differential equation having two parameters with a discontinuous source term is presented in this article. Theoretical bounds are derived for the derivatives of the solution and its smooth and singular components. An appropriate piecewise uniform mesh is constructed, and classical upwind finite difference schemes are used on this mesh to obtain the discrete system of equations. Parameter-uniform error bounds for the numerical approximations are established. Numerical results are provided to illustrate the convergence of the numerical approximations.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.2
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• pp.263-267
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• 2001

Beef samples of loin eye area from New Zealand, USA and three quality grades of Hanwoo were analyzed using near infrared spectrophotometer with reference values from laboratory optical Chromameter to determine effective spectrum range and mathematical treatment for determination of color values. $R^2s$ of prediction models were not improved much by calibrating with whole light range (400~2500 nm) compared to using visible range (400~1100 nm). Standard errors of calibration and prediction were influenced by possible bias due to sampling non-homogeneous sample sources. However, partial differentiation in the first order was more stable against sampling biases than second derivatives of the spectra. Lightness value was little different among the five sample sources of beef. Beef samples from USA were brighter and more reddish than beefs of Hanwoo or from New Zealand (p<0.05). Yellowness of USA beef was the highest followed by beef from New Zealand, which was also higher than Hanwoo beefs of three quality grades (p<0.05).

• Journal of the Korean Mathematical Society
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• v.41 no.6
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• pp.1049-1070
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• 2004

We classify all partial differential equations with polynomial coefficients in $\chi$ and y of the form A($\chi$) $u_{{\chi}{\chi}}$ ＋ 2B($\chi$, y) $u_{{\chi}y}$ ＋ C(y) $u_{yy}$ ＋ D($\chi$) $u_{{\chi}}$ ＋ E(y) $u_{y}$ = λu, which has weak orthogonal polynomials as solutions and show that partial derivatives of all orders are orthogonal. Also, we construct orthogonal polynomials in d-variables satisfying second order partial differential equations in d-variables.s.

• Structural Engineering and Mechanics
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• v.17 no.1
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• pp.87-97
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• 2004

In gradient-dependent plasticity theory, the yield strength depends on the Laplacian of an equivalent plastic strain measure (hardening parameter), and the consistency condition results in a differential equation with respect to the plastic multiplier. The plastic multiplier is then discretized in addition to the usual discretization of the displacements, and the consistency condition is solved simultaneously with the equilibrium equations. The disadvantage is that the plastic multiplier requires a Hermitian interpolation that has four degrees of freedom at each node. Instead of using a Hermitian interpolation, in this article, a 3-node incompatible (trigonometric) interpolation is proposed for the plastic multiplier. This incompatible interpolation uses only the function values of each node, but it is continuous across element boundaries and its second-order derivatives exist within the elements. It greatly reduces the degrees of freedom for a problem, and is shown through a numerical example on localization to yield good results.

• Korean Journal of Construction Engineering and Management
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• v.11 no.2
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• pp.54-63
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• 2010

Domestic construction companies suffer from the difficulty in financing in the wake of economic slump at home and abroad. In the periods of this economic slump, which hit the nation REITs, the facilitator of fluid financing and the stimulating of construction economic, has increasingly been expanded since its introduction in 2001. But, REITs relatively falls behinds any other nations, in terms of its growth speed and marketing volume. The purpose of this research thesis is to suggest the method for composing a portfolio using Markowitz portfolio selection models for stimulating REITs. Main contents are as follows. First, the thesis made the comparative analysis on profit increase in REITs investment in application of models by Markowitz and REITs derivatives from 2007/07/03 to 2008/07/21 during investment analysis periods. The result showed that total profits by Markowitz model amounted to about 10 percent higher than average profits of REITs derivatives. Second, this thesis made the analysis on sensitivity of data-gathering and portfolio change periods of the existing profits, in order to measure the both periods and yield optimum profits. The six month data-collecting periods of profits accounted for some 16% higher profits than profits of REITs derivatives. In case when the two week periods of portfolio change accounted for some 11% higher profits than profits of REITs derivatives.

• Journal of Sensor Science and Technology
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• v.19 no.1
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• pp.17-24
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• 2010

This paper describes a real time reliable monitoring method and analysis system using wrist type oximeter for ubiquitous healthcare service based on IEEE 802.15.4 standard. Photoplethysmograph(PPG) is simple and cost effective technique to measure blood volume change. In order to obtain and monitor physiological body signals continuously, a small size and low power consumption wrist type oximeter is designed for the measurement of oxygen saturation of a patient unobtrusively. The measured data is transferred to a central PC or server computer by using wireless sensor nodes in wireless sensor network for storage and analysis purposes. LabVIEW server program is designed to monitor stress indicator from heart rate variability(HRV) and process the measured PPG to accelerated plethysmograph(APG) by appling second order derivatives in server PC. These experimental results demonstrate that APG can precisely describe the features of an individual's PPG and be used as estimation of vascular elasticity for blood circulation.

• Journal of KIISE
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• v.42 no.6
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• pp.764-768
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• 2015

Requirement of effective image handling methods such as image retrieval has been increasing with the rising production and consumption of multimedia data. In this paper, a method of constructing more effective descriptor is proposed for robust keypoint based image retrieval. The proposed method uses information embedded in the first order and second order derivative images, in addition to the scale space image, for the descriptor construction. The performance of multi-image descriptor is evaluated in terms of the similarities in keypoints with a public domain image database that contains various image transformations. The proposed descriptor shows significant improvement in keypoint matching with minor increase of the length.