• 산업경영시스템학회지
• /
• 제39권1호
• /
• pp.123-129
• /
• 2016

In the manufacturing industry fields, thousands of quality characteristics are measured in a day because the systems of process have been automated through the development of computer and improvement of techniques. Also, the process has been monitored in database in real time. Particularly, the data in the design step of the process have contributed to the product that customers have required through getting useful information from the data and reflecting them to the design of product. In this study, first, characteristics and variables affecting to them in the data of the design step of the process were analyzed by decision tree to find out the relation between explanatory and target variables. Second, the tolerance of continuous variables influencing on the target variable primarily was shown by the application of algorithm of decision tree, C4.5. Finally, the target variable, loss, was calculated by a loss function of Taguchi and analyzed. In this paper, the general method that the value of continuous explanatory variables has been used intactly not to be transformed to the discrete value and new method that the value of continuous explanatory variables was divided into 3 categories were compared. As a result, first, the tolerance obtained from the new method was more effective in decreasing the target variable, loss, than general method. In addition, the tolerance levels for the continuous explanatory variables to be chosen of the major variables were calculated. In further research, a systematic method using decision tree of data mining needs to be developed in order to categorize continuous variables under various scenarios of loss function.

• 한국지구과학회지
• /
• 제28권1호
• /
• pp.87-104
• /
• 2007

소형망원경을 이용하여 산개성단 내 단주기 미세 변광성을 체계적으로 탐사하기 위한 보현산 천문대 측광 모니터링 프로그램 Short Period Variability Survey(SPVS)의 일환으로, 젊은 산개성단 NGC 129의 $90'{\times}60'$ 영역에 대한 V필터 시계열 측광 관측을 수행하였다. 성단의 관측은 보현산 천문대 155mm 소형 굴절 망원경과 $3K{\times}2K$ CCD 카메라를 이용하여 2004년 10월 12일부터 2005년 11월 3일까지 총 11일간 수행되었으며, 그 결과 전체 2400장의 V 필터시계열 CCD 영상자료 및 성단의 색-등급도를 얻었다. 시계열 자료의 기기등급을 표준등급으로 변환하기 위하여 앙상블정규화 기법(ensemble normalization technique)을 사용하였다. 측광 후 총 9537개별의 시간에 따른 광도변화를 조사한결과 총 66개의 새로운 변광성을 발견 하였다. 새롭게 찾아낸 변광성들은 DFT(Discrete Fourier Transform) 분석과 위상 맞추기 방법(phase-matching technique)을 이용하여 변광 주기를 결정하였다. 결정된 변광성의 주기 및 진폭 변화, 색-등급도 상에서의 변광성의 위치 등을 고려하여 변광 유형을 조사한 결과 9개의 SPB형 변광성과 9개의 ${\delta}$ Scuti형 변광성, 29개의 식변광성, 17개의 장주기 변광성과 기타 2개의 변광성으로 분류할 수 있었다. 본 연구를 통해, 산개성단에서의 변광성 탐사 연구에 소형망원경이 유용하게 활용될 수 있음을 확인하였다.

• Structural Engineering and Mechanics
• /
• 제55권3호
• /
• pp.655-674
• /
• 2015

In this paper, a new and simplified method is presented in which the natural frequencies of the uniform and non-uniform beams are calculated through simple mathematical relationships. The various vibration problems such as: Rayleigh beam under variable axial force, axial vibration of a bar with and without end discrete spring, torsional vibration of a bar with an attached mass moment of inertia, flexural vibration of the beam with laterally distributed elastic springs and also flexural vibration of the beam with effects of viscose damping are investigated. The governing differential equations are first obtained and then; according to a harmonic vibration, are converted into single variable equations in terms of location. Through repetitive integrations, the governing equations are converted into weak form integral equations. The mode shape functions of the vibration are approximated using a power series. Substitution of the power series into the integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of a non-trivial solution for system of equations. The efficiency and convergence rate of the current approach are investigated through comparison of the numerical results obtained with those obtained from other published references and results of available finite element software.

• 대한기계학회논문집A
• /
• 제41권1호
• /
• pp.63-68
• /
• 2017

이 논문에서는 열간 사상압연 공정에서 스트립 통판성의 안정성과 판 품질 향상을 위하여 새로운 선진율 학습모델 개발에 관한 연구를 수행한다. 먼저 기존의 선진율 해석모델에 대한 고찰을 통해 스트립 장력, 루퍼 각도 그리고 롤 주속이 선진율 학습에 크게 영향을 미치는 주요 압연 인자들임을 보인다. 두 번째로는 선진율 학습의 주요 압연 인자들을 이용하여 새로운 선진율 학습모델을 도출한 후, 보조변수 규명 알고리즘을 이용하여 이산시간계 학습모델을 규명한다. 끝으로 컴퓨터 시뮬레이션을 통해 이 논문에서 제안한 새로운 학습모델이 기존의 학습모델보다 유용함을 보인다.

• 대한수학회지
• /
• 제55권1호
• /
• pp.101-129
• /
• 2018

From an analytical perspective, we introduce a sequence of Cartier operators that act on the field of formal Laurent series in one variable with coefficients in a field of positive characteristic p. In this work, we discover the binomial inversion formula between Hasse derivatives and Cartier operators, implying that Cartier operators can play a prominent role in various objects of study in function field arithmetic, as a suitable substitute for higher derivatives. For an applicable object, the Wronskian criteria associated with Cartier operators are introduced. These results stem from a careful study of two types of Cartier operators on the power series ring ${\mathbf{F}}_q$[[T]] in one variable T over a finite field ${\mathbf{F}}_q$ of q elements. Accordingly, we show that two sequences of Cartier operators are an orthonormal basis of the space of continuous ${\mathbf{F}}_q$-linear functions on ${\mathbf{F}}_q$[[T]]. According to the digit principle, every continuous function on ${\mathbf{F}}_q$[[T]] is uniquely written in terms of a q-adic extension of Cartier operators, with a closed-form of expansion coefficients for each of the two cases. Moreover, the p-adic analogues of Cartier operators are discussed as orthonormal bases for the space of continuous functions on ${\mathbf{Z}}_p$.

• 한국통신학회논문지
• /
• 제25권6A호
• /
• pp.782-793
• /
• 2000

본 논문은 10GHz이상의 주파수 대역을 사용하는 위성 통신 링크에서 강우에 의해 감쇠된 신호 레벨을 동적으로 예측하기 위한 비교적 간단한 예측 기법을 제시한다. 예측 기법은 이산시간 저역 통과 필터링, 기울기에 근거한 예측, 평균 오차 보정, 고정 및 가변 혼합 예측 여유 할당의 4가지 기능 블록을 갖는다. Ku 대역의 측정 데이터로부터 주파수 스케일링에 의해 얻어진 Ka 대역 강우 감쇠 데이터를 이용하여 시뮬레이션을 수행하였다. 평균 오차 보정을 갖는 기울기 예측 기법은 1dB 이하의 표준 편차를 가지며, 평균 오차 보정에 의해 약 1.5~2.5 배의 예측 오차 감소를 보인다. 요구되는 평균 여유 면에서, 혼합 예측 여유 할당은 고정 여유 방법과 가변 여유 방법에 비해 더 적은 평균 여유를 요구한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1989년도 하계종합학술대회 논문집
• /
• pp.571-575
• /
• 1989

A position control system of D.C. Servo motor based on discrete variable structure system with sliding mode is presented. The sliding mode has been designed for a continuous system, but it is often realized in digital fashion because the complex switching logic can be easily carried out. In digital control system, the ideal sliding mode does not occur since the structure can't be switched during sampling interval. However, there can be exist a motion which is confined to a regoin including the sliding surface and proceeds to the origin along the surface. This notion is called quasisliding mode. In this paper, we introduce this control scheme to the D.C. Servo motor position control in order to reduce the chattering phenonenon.

• 한국지능시스템학회논문지
• /
• 제26권4호
• /
• pp.273-278
• /
• 2016

본 논문에서는 로렌츠 카오스 회로를 곱셈기, 커패시터, 연산증폭기, 제어저항 등을 이용하여 설계하였다. 제안하는 회로는 SPICE 프로그램을 통하여 시간파형, 주파수 특성, 위상특성 등을 해석하였고, 로렌츠 하드웨어를 구현하여서 시간파형, 주파수 특성, 위상특성, 분기도 특성을 측정하였다. 측정결과, $500k{\Omega}$ 가변 제어 저항의 조건에 따라, 로렌츠 회로는 제어저항의 특정 영역 ($10{\sim}100k{\Omega}$)에서 카오스 신호가 생성됨을 확인하였다. SPICE 모의실험 결과와 일치함을 보였고, 하드웨어의 가변저항을 변화주면서 분기도 특성을 측정하여서 저항 변화에 따라 카오스와 주기적인 분기도 형태를 나타내는 것을 확인하였다.

• ETRI Journal
• /
• 제28권3호
• /
• pp.301-310
• /
• 2006

In mobile communications, a class of variable-complexity algorithms for convolutional decoding known as sequential decoding algorithms is of interest since they have a computational time that could vary with changing channel conditions. The Fano algorithm is one well-known version of a sequential decoding algorithm. Since the decoding time of a Fano decoder follows the Pareto distribution, which is a heavy-tailed distribution parameterized by the channel signal-to-noise ratio (SNR), buffers are required to absorb the variable decoding delays of Fano decoders. Furthermore, since the decoding time drawn by a certain Pareto distribution can become unbounded, a maximum limit is often employed by a practical decoder to limit the worst-case decoding time. In this paper, we investigate the relations between buffer occupancy, decoding time, and channel conditions in a system where the Fano decoder is not allowed to run with unbounded decoding time. A timeout limit is thus imposed so that the decoding will be terminated if the decoding time reaches the limit. We use discrete-time semi-Markov models to describe such a Fano decoding system with timeout limits. Our queuing analysis provides expressions characterizing the average buffer occupancy as a function of channel conditions and timeout limits. Both numerical and simulation results are provided to validate the analytical results.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권3호
• /
• pp.741-750
• /
• 2021

The budget deficit is closely related to expansionary fiscal policy as a fiscal instrument to encourage economic growth. This study aims to apply optimal control theory in the Keynesian macroeconomic model for the economy, so that optimal growth can be found. Macroeconomic variables include GDP, consumption, investment, exports, imports, and budget deficit as control variables. This study uses secondary data in the form of time series, the time period 1990 to 2018. Performing optimal control will result in optimal fiscal policy. The optimal determination is done through simulation, for the period 2019-2023. The discrete optimal control problem is to minimize the objective function in the form of a quadratic function against the deviation of the state variable and control variable from the target value and the optimal value. Meanwhile, the constraint is Keynes' macroeconomic model. The results showed that the optimal value of macroeconomic variables has a deviation from the target values consisting of: consumption, investment, exports, imports, GDP, and budget deficit. The largest deviation from the average during the simulation occurs in GDP, followed by investment, exports, and the budget deficit. Meanwhile, the lowest average deviation is found in imports.