• 산업경영시스템학회지
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• 제27권2호
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• pp.114-122
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• 2004

In statistical process control applications, variable sample size (VSS) $\bar{X}$ chart is often used to detect the assignable cause quickly. However, it is usually assumed that only one assignable cause results in the out-of-control in the process. In this paper, we propose the algorithm to minimize the function of cost per unit time and compare the economic design and the statistical design by use of the value of cost per unit time. We consider double assignable causes to occur with compound in the process and adopt the Markov chain approach to investigate the statistical properties of VSS $\bar{X}$ chart. A procedure that can calculate the control chart's parameters is proposed by the economic design.

• 응용통계연구
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• 제24권4호
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• pp.609-622
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• 2011

The pattern of methylation draws significant attention from cancer researchers because it is believed that DNA methylation and gene expression have a causal relationship. As the interest in the role of methylation patterns in cancer studies (especially drug resistant cancers) increases, many studies have been done investigating the association between gene expression and methylation. However, a model-based approach is still in urgent need. We developed a finite mixture model in the Bayesian framework to find a possible relationship between gene expression and methylation. For inference, we employ Expectation-Maximization(EM) algorithm to deal with latent (unobserved) variable, producing estimates of parameters in the model. Then we validated our model through simulation study and then applied the method to real data: wild type and hydroxytamoxifen(OHT) resistant MCF7 breast cancer cell lines.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.740-741
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• 2015

This paper presents the design and dynamic analysis of surface-mounted type variable flux permanent magnet(VFPM) machines. VFPM machines with a low-coercive-force (LCF) magnetic material have been studied extensively for their potential to improve the efficiency and extend the flux-weakening range of permaennt magnet (PM) machines. In order to implement the design of the VFPM machines effectively, we perform a characteristic analysis of the LCF magnet with respect to design parameters. The analysis results of the designed VFPM machines are compared with measured results, and the validity of the design of the VFPM machines is confirmed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.736-741
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• 1998

It is well known that an encoder or a resolver is necessary to obtain the position data for speed or position control Generally utilized speed sensors are mal-affected by the EMI, dusty, and high temperature surroundings. Therefore, the speed and position sensorless controls using observers have been studied widely. In this paper, the binary observer which is composed of two feedback regulation loops to control the speed of SRM(Switched Reluctance Motor) is applied. One loop compensates the control input directly like the sliding mode control, and the other one compensates the system parameters indirectly. This observer is constructed on the foundation of variable structure control on the foundation of variable structure control theory and has the inertial term for the varying parameter. The validities of this proposed method is proved by experiments.

• Journal of Biosystems Engineering
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• 제17권4호
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• pp.396-403
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• 1992

In order to operate a combine harvester at the optimum conditions and maximum performance, a forward speed control system(FSCS) was designed and develped. The FSCS consisted of engine, continuously variable V-belt transmission, threshing unit, traveling unit, detecting unit, and controller. Each components of the system were mathematically modeled. By a computer simulation, the effects of control parameters such as hydraulic piston speed, speed ratio, dead band of engine speed on the system performance were analysed, and the optimum control conditions were identified. The system appeared to be the most stable at the hydraulic piston speed of 10.6mm/s and the speed ratio of 0.4. The proper dead band of engine speed appeared to be 30rpm through the simulation and verification tests.

• 한국경영과학회지
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• 제17권2호
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• pp.91-106
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• 1992

It an inventory control system, the demand over time are often assumed to be independently identically distributed (i. i. d.). However, the demands may well be correlated over time in many situations. The estimation of reorder points is not simple for correlated demands with variable lead time. In this paper, a general class of autoregressive and moving average processes is considered for modeling the demands of an inventory item. The first four moments of the lead-time demand (L) are derived and used to approximate the distribution of L. The reorder points at given service level are then estimated by the three approximation methods : normal approximation, Charlier series and Pearson system. Numerical investigation shows that the Pearson system and the Charlier series performs extremely well for various situations whereas the normal approximation show consistent underestimation and sensitive to the distribution of lead time. The same conclusion can be reached when the parameters are estimated from the sample based on the simulation study.

• 품질경영학회지
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• 제30권2호
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• pp.99-117
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• 2002

Variable sampling interval(VSI) and variable sample size(VSS) control charts vary the sampling rate for the next sample depending on the current chart statistic. This paper develops EWMA charts with the VSI and VSS features, and investigates the effectiveness of these charts in context of an economic model. The economic properties of these charts are evaluated by using Markov chain methods. The model contains cost parameters which allow the specification of the costs associated with sampling, false alarms, and operating off target. This economic model can be used to quantify the cost saving that can be obtained by using control charts with the VSI and VSS features instead of with the fixed sampling rate(FSR) feature, and can also be used to gain insight into the way that control charts with the VSI and VSS features should be designed to achieve optimal economic performance. The economic performance of X charts with the VSI and VSS features is also considered.

• International Journal of Precision Engineering and Manufacturing
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• 제8권3호
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• pp.3-7
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• 2007

There have been numerous studies directed toward the development of driving mechanisms for off-road mobility and rescue robots. To achieve surveillance, reconnaissance, and rescue, it is necessary for robots to have a driving mechanism that can handle off-road environments, We propose a new type of single-track driving mechanism with a variable geometry for a rescue robot, This mechanism has a symmetric configuration so that the robot can advance in two directions and also remain operable when overturned. By transforming its geometry, the robot can reduce energy consumption in steering and rotating as well as maximize its ability to climb obstacles such as stairs. The robot is also designed to have a compact size and low center of gravity to facilitate driving when on a set of stairs. In this paper, we analyzed the design parameters of the robot for the four phases of climbing stairs and determined the specifications needed to enhance its adaptability.

• 품질경영학회지
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• 제36권1호
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• pp.49-61
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• 2008

The classical IT-Outsourcing studies have focused on the factors which a company decides for the IT-Outsourcing strategy. But the main concerns of recent researches are more about the Critical Success Factors determining the Success of the IT-Outsourcing service. Especially, the factors, which enhance the level of Success during and after the implementation of IT-Outsourcing services, are the main field of the recent researches. The study about the Partnership between Outsourcer and Outsourcee are also one of the most frequently researched themes. The result of these studies shows us that the "Reliability" and "Communication" are the main factors for the successful partnership. In this paper we try to find out how the IT-Outsourcing factors (independent variable) have influenced on the Success of IT-Outsourcing strategy (dependent variable) with 4 kinds of parameters. These moderate variables are the 4-types of Partnership by FORT, that is, "Support", "Reliance", "Alignment" and "Alliance".

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.36.2-36.2
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• 2011

In variable-speed variable-pitch wind turbines, the conventional approach for controlling power-production operation relies on a generator-torque controller and a rotor-collective blade-pitch controller. Both controllers use the generator speed measurement as the sole feedback input. In order to mitigate unwanted excitation of the control system, many filters are adopted. In this study, the characteristics of some filters for signal processing are investigated based on frequency response function. They include low-pass filters, band-pass filters, and notch filters. Especially, this study focuses on design parameters of their filters.