• 방송공학회논문지
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• 제19권2호
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• pp.195-204
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• 2014

이 논문에서는 순환정상 프로세스의 고차 통계 특성을 바탕으로 2-FSK, 4-FSK, 8-FSK, MSK, BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM, 64-QAM 등 10개의 기저대역 디지털 변조신호를 자동으로 인식하는 방법을 제안하였다. 변조신호의 고유한 성질을 나타내는 특징변수로는 1차 순환 모멘트와 고차 순환 큐뮬런트를 이용하였다. 제안한 변조인식기는 크게 두 단계로 구성되며, 첫 번째 단계에서는 1차 순환 모멘트가 나타내는 첨두치를 이용하여 M-FSK와 비FSK로 변조신호를 분류한다. 두 번째 단계에서는 비FSK를 분류하기 위해 고차 순환 큐뮬런트 값을 이용하는 Gaussian 혼합 모델 기반의 분류기를 적용하였다. 제안한 방법의 성능을 검증하기 위해서 모의실험을 실시하였다. 모의실험 결과 제안한 분류기는 주파수와 위상 옵셋이 존재하는 환경에서도 우수한 분류확률을 나타내었다.

• Management Science and Financial Engineering
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• 제4권2호
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• pp.15-42
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• 1998

A joint problem of order delivery, setup reduction, and cost-sharing in a two-echelon inventory system in which a vendor supplies multiple products to a group of buyers is studied here. The basic premise is that buyers have independently implemented setup reduction programs to acquire benefits from small order sizes. Doing so, however, causes the buyers' individually optimal order cycles to be differ from that of the vendor. In conjunction with this, two models are considered. In the first model, a multi-buyers single product situation is considered in which the vendor implements a joint supply cycle policy. However, buyers, as the dominant party, insist after implementing the individually optimal setup reduction that the vendor accept their individually optimal order schedules. In the second model. a multi-products, single buyer situation is considered in which the buyer implements a joint order policy. Here, the vendor, as the dominant party, refuses to cooperate fully with the buyer's individually reduced joint order schedule, and designs his own individually optimal setup reduction mix for each product under a given budget constraint. This led to a study of an integrated Setup Reduction/Break-even Pricing Policy for each situation to eliminate mismatches in individually optimal cycle times.

• Structural Engineering and Mechanics
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• 제6권7호
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• pp.727-746
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• 1998

Finite element models and numerical results are presented for bending and natural vibration using the unified third-order plate theory developed in Part 1 of this paper. The unified third-order theory contains the classical, first-order, and other third-order plate theories as special cases. Analytical solutions are developed using the Navier and L$\acute{e}$vy solution procedures (see Part 1 of the paper). Displacement finite element models of the unified third-order theory are developed herein. The finite element models are based on $C^0$ interpolation of the inplane displacements and rotation functions and $C^1$ interpolation of the transverse deflection. Numerical results of bending and natural vibration are presented to evaluate the accuracy of various plate theories.

• Smart Structures and Systems
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• 제5권5호
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• pp.531-546
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• 2009

In the present analysis, the spline finite strip with higher-order shear deformation is formulated for the static analysis of piezoelectric composite plates. The proposed method incorporates Reddy's third-order shear deformation theory, Touratier's "Sine" model, Afaq's exponential model, Cho's higher-order zigzag laminate theory, as well as the classic plate theory and the first-order plate theory. Thus, the analysis can be conducted based on any of the above-mentioned theories. The selection of a specific method is done by simply changing a few terms in a 2 by 2 square matrix and the results, obtained according to different plate theories, can be compared to each other. Numerical examples are presented for piezoelectric composite plates subjected to mechanical loading. The results based on different shear deformation theories are compared with the three-dimensional solutions. The behaviours of piezoelectric composite plates with different length-to-thickness ratios, fibre orientations, and boundary conditions are also investigated in these examples.

• Structural Engineering and Mechanics
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• 제10권4호
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• pp.337-357
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• 2000

Analytical formulations and solutions for the first time, to the stability analysis of a simply supported composite and sandwich plates based on a higher order refined theory, developed by the first author and already reported in the literature are presented. The theoretical model presented herein incorporates laminate deformations which account for the effects of transverse shear deformation, transverse normal strain/stress and a nonlinear variation of inplane displacements with respect to the thickness coordinate - thus modelling the warping of transverse cross sections more accurately and eliminating the need for shear correction coefficients. The equations of equilibrium are obtained using the Principle of Minimum Potential Energy (PMPE). The comparison of the results using this higher order refined theory with the available elasticity solutions and the results computed independently using the first order and the other higher order theories developed by other investigators and available in the literature shows that this refined theory predicts the critical buckling load more accurately than all other theories considered in this paper. New results for sandwich laminates are also presented which may serve as a benchmark for future investigations.

• 한국식품과학회지
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• 제33권1호
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• pp.66-71
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• 2001

가열에 의한 품종별 고구마 조직의 변화에 대한 반응속도론적 상수를 biphasic model과 fractional conversion method를 사용하여 결정하였다. Biphasic model에 따라 고구마의 가열에 의한 조직의 변화는 2단계의 연속적인 1차 반응식으로 표시할 수 있었으며, 활성화에너지는 고구마의 품종에 따라 $71.0{\sim}75.1\;kJ/mol$ 및 $48.4{\sim}59.6\;kJ/mol$이었다. 또한 고구마의 가열에 의한 조직변화를 fractional conversion method를 사용하여 1개의 1차 반응식으로 표시할 수 있었는데, 이 때의 활성화에너지는 $67.5{\sim}75.3\;kJ/mol$로서 biphasic model에 의한 제 1단계의 반응에 대한 값과 유사한 값을 나타냈다. 이들 방법으로 결정된 반응속도론적 상수들 사이에는 kinetic compensation 효과가 있었으며, 두 방법 모두 고구마의 가열에 의한 조직변화에 대한 반응속도론적 상수들을 결정하는데 적용할 수 있음을 알 수 있었다.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.12-17
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• 2018

가상환경에 대한 현실감을 증강시키기 위해서는 햅틱 시스템의 안정성을 유지하면서 가상환경 모델의 강성을 최대한 크게 할 수 있는 방법이 필요하다. 이에 기존 연구에서 영차홀드 대신 일차홀드를 적용하는 방법이 제시되었고, 영차홀드를 이용할 때보다 가상 스프링의 안정성 영역을 더 크게 확보할 수 있음을 시뮬레이션을 통해 제시했다. 그렇지만 실제로 시스템을 구현하는 측면에서 보면, 영차홀드가 일반적이고 손쉬운 방법이다. 이에 본 논문에서는 영차홀드를 사용하지만, 일차홀드와 동등한 안정성 영역을 확보하기 위한 방법으로 외삽법과 고주파 영차홀드 출력 방법을 제안한다. 제안된 방법에 대한 시뮬레이션을 통해 고주파 영차홀드의 샘플링 주기가 작아질수록 가상 스프링의 안정성 영역이 일차홀드를 적용한 경우와 거의 같아짐을 보였고, 기존 연구에서 제시된 영차홀드만을 적용한 경우보다는 수 배에서 수십 배 안정성 영역이 더 커질수 있음을 보였다. 따라서 제안된 방법을 통해 가상 환경 속 강체에 대한 현실감을 증강시킬 수 있을 것으로 기대된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1201-1204
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• 2004

This paper suggests a DCS (Distributed Control System) model for steam temperature system of the thermal power plant. The model calculated within sectional range is linear. In order to calculate mathematical models, the system is partitioned into two or three sectors according to its thermal conditions, that is, saturated water/steam and superheating state. It is divided into three sections; water supply, steam generation and steam heating loop. The steam heating loop is called 'superheater' or steam temperature system. Water spray supply is the control input. A first order linear model is extracted. For linear approach, sectional linearization is achieved. Modeling methodology is a decomposition-synthetic technique. Superheater is composed of several tube-blocks. For this block, linear input-output model is to be calculated. Each tiny model has its transfer function. By expanding these block models to total system, synthetic DCS linear models are derived. Control instrument include/exclude models are also considered. The resultant models include thermal combustion conditions, and applicable to practical plant engineering field.

• 한국경영과학회지
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• 제19권2호
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• pp.57-73
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• 1994

KADS is currently a best known methodology for expert system development is Europe. KADS world sees the expert system development as a modeling activity and uses models to control complexity of the development process. Four layers KADS expertise model is used to describe expert knowledge. But this expertise model in high abstraction level is conceptual and not formalized. This paper has formalized KADS expertise model using set theory and mathematical semantics combined in order to reduce the ambiguity of informal models of expertise, provide a precise means of communication about the model of expertise and point out incompleteness and inconsistency of the model of expertise. Instead of first order predicate calculs, set theory and mathematical semantics are used because they are a more general and have compositive quality.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.310-315
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• 2003

This paper presents the effect of boundary condition of failure pressure model for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with various corrosion defects for long exposure periods in years. A failure pressure model based on a failure function composed of failure pressure and operation pressure is adopted for the assessment of pipeline failure. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the corrosion pipeline.