• 한국지하수토양환경학회지:지하수토양환경
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• 제23권1호
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• pp.41-53
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• 2018

Comprehensive statistical analysis for the 127 groundwater monitoring stations in Jeju Island during 2005~2015 was carried out for the re-establishment of management groundwater level. Three probability distribution functions such as normal distibution, GEV (General Extreme Value) distribution, and Gumbel distribution were applied and the maximum likelihood method was used for parameter estimation of each distribution. AIC (Akaike information criterion) was calculated based on the estimated parameters to determine the proper probability distribution for all 127 stations. The results showed that normal distribution and Gumble distribution were found in 11 stations. Whereas GEV distribution were found in 105 stations, which covered most of groundwater monitoring stations. Therefore, confidence levels should be established in accord with the proper probability distribution when groundwater level management is determined.

• 정보저장시스템학회논문집
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• 제3권1호
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• pp.5-12
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• 2007

This paper investigates the design of disturbance observer for rotational vibration suppression in disk drive systems. The design aims to provide an optimal controller which satisfies both vibration performance and robust stability. It consists of an inversion method, a special filter, and optimization scheme. Firstly a new inversion method is introduced, which provides more accurate inversion compared to conventional zero phase error method. The inversion is to deal with unstable zeros in the plant model. Secondly a special filter for disturbance selection is given, which features adjustable gain and band pass characteristics so that it enables flexible shaping of the loop considering the trade-off between performance and stability margins. And finally the parameters of disturbance observer are optimized in conjunction with external disturbance model. Simulation and experiment on commercial hard disk drives confirm that the design is very effective to such disturbance which is hard to be handled by conventional approach.

• 한국환경과학회지
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• 제24권4호
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• pp.425-435
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• 2015

A number of projects for development have been done continuously due to the increase of tourist in Jeju Island. However flood disaster countermeasure due to urbanization is not considered during this development projects. This study is to make basic process for the flood estimation in Han stream of Jeju Island. The variation of stream discharge due the every 5 years' land use change from 1980 to 2005. Data for flood events (rainfall and discharge) were collected for HEC-HMS model. Clark method was used for unit hydrograph analysis. For the estimation of Clark unit hydrograph parameters, Kraven II and Sabol's empirical equations were applied. The peak discharge increased 9.9~33.67% and total discharge amount increased 12.53~30.21%. Also, time of concentration for peak discharge was reduced by 10 minutes for each event.

• Nuclear Engineering and Technology
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• 제40권5호
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• pp.327-348
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• 2008

A risk-informed regulatory approach implies that risk insights be used as supplement of deterministic information for safety decision-making purposes. In this view, the use of risk assessment techniques is expected to lead to improved safety and a more rational allocation of the limited resources available. On the other hand, it is recognized that uncertainties affect both the deterministic safety analyses and the risk assessments. In order for the risk-informed decision making process to be effective, the adequate representation and treatment of such uncertainties is mandatory. In this paper, the risk-informed regulatory framework is considered under the focus of the uncertainty issue. Traditionally, probability theory has provided the language and mathematics for the representation and treatment of uncertainty. More recently, other mathematical structures have been introduced. In particular, the Dempster-Shafer theory of evidence is here illustrated as a generalized framework encompassing probability theory and possibility theory. The special case of probability theory is only addressed as term of comparison, given that it is a well known subject. On the other hand, the special case of possibility theory is amply illustrated. An example of the combination of probability and possibility for treating the uncertainty in the parameters of an event tree is illustrated.

• 한국강구조학회 논문집
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• 제23권1호
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• pp.83-97
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• 2011

본 논문에서는 콘크리트 채움 U형 강재보와 철근콘크리트 기둥으로 구성된 접합부의 내진 상세를 개발하였다. 접합부 내진성능을 평가하기 위하여 세 개의 보-기둥 접합부 실험체를 반복주기하중에 대하여 실험하였다. 보춤과 기둥 단면 형상을 실험 변수로 하였다. 합성보의 춤은 슬래브 두께를 포함하여 610mm, 710mm이며, 철근콘크리트 기둥은 사각단면과 원형단면이 사용되었다. 접합부를 보강시키기 위하여 사각단면 기둥과 원형단면 기둥에 각각 대각 철근과 외다이어프램 강판을 사용한 특수 상세가 사용되었다. 실험 결과 실험체는 강도와 변형능력, 에너지 소산에 있어서 우수한 성능을 보여주었다. 변형능력은 특수모멘트골조 기준인 4% 이상의 층간변위각을 발휘하였다.

• Journal of the Korean Data and Information Science Society
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• 제24권6호
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• pp.1275-1283
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• 2013

다변량 통합공정관리의 기본절차는 잡음이 내재하는 공정에 수정조치를 취하여 공정편차벡터를 백색잡음벡터로 전환하도록 하여 공정제곱편차벡터를 최소화하게 되는 것이며, 이러한 다변량 통합공정관리의 수정활동을 하는 경우 공정에 이상원인이 발생하면 관리도를 통해 이를 탐지하고 제거하게 된다. 수정된 공정은 이상원인 발생 전에는 백색잡음이지만, 이상원인 발생 후 다양한 형태의 시계열 모형으로 변환하게 된다. 만약 수정된 공정을 탐지하여 이상원인의 신호가 발생한 경우 교정활동을 통하여 이를 제거해야 하지만, 구조적으로 교정이 불가능 하거나 교정활동의 비용이 많이 발생하는 경우에는 이상원인의 효과를 감안하여 수정활동을 재조정해야할 것이다. 이 논문에서는 공정모형으로 다변량 IMA(1,1)모형을 가정하고 다변량 통합공정관리 절차를 수행하는 경우 이상신호가 발생한 후 재수정 절차에서 필요한 모수추정을 하고자 한다.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1945-1955
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• 2018

High frequency signal injection (HFI) is an alternative method for estimating rotor position of interior permanent magnet synchronous motor (IPMSM). The general method of frequency and amplitude selection is based on error tolerance and experiments, and is usually set with only one group of HF parameters, which is not efficient for different working modes. This paper proposes a novel rotor position estimation scheme by HFI with optimized frequency and amplitude, based on the mathematic model of IPMSM. The requirements for standstill and low-speed operational modes are met by applying this novel scheme. Additionally, the effects of the frequency and amplitude of the injected HF signal on the position estimation results under different operating conditions are analyzed. Furthermore, an optimization method for HF parameter selection is proposed to make the estimation process more efficient under different working conditions according to error tolerance. The effectiveness of the propose scheme is verified by the experiments on an IPMSM motor prototype.

• 한국산학기술학회논문지
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• 제10권9호
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• pp.2210-2220
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• 2009

대형 특수차량용 독립현가형 액슬은 극소수 전문업체에서 생산되며 설계, 제작, 시험평가 등 세부기술은 제공되지 않고 있다. 또한 액슬 제작을 위한 설계기준 설정에는 시작품을 실제 차량에 탑재하여 수년 이상 소요되는 내구성 시험이 필수적이다. 본 연구는 독립현가형 액슬의 핵심부품인 스루드라이브를 역설계방법으로 개발하였으며 개발목표 달성 확인에 필요한 시험평가기준을 제안하였다. 또한 CAD/CAE 도구를 사용하여 제품을 설계하고 설계검증을 거쳐 시제품을 제작하였다. 본 연구에 적용된 개발절차 및 방법은 차량의 동력전달계통 개발에 유용할 것이다.

• Advances in materials Research
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• 제8권1호
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• pp.47-73
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• 2019

Joining of Mg/Ti hybrid structures by welding for automotive and aerospace applications has attracted great attention in recent years due mainly to its potential benefit of energy saving and emission reduction. However, joining them has been hampered with many difficulties due to their physical and metallurgical incompatibilities. Different joining processes have been employed to join Mg/Ti, and in most cases in order to get a metallurgical bonding between them was the use of an intermediate element at the interface or mutual diffusion of alloying elements from the base materials. The formation of a reaction product (in the form of solid solution or intermetallic compound) along the interface between the Mg and Ti is responsible for formation of a metallurgical bond. However, the interfacial bonding achieved and the joints performance depend significantly on the newly formed reaction product(s). Thus, a thorough understanding of the interaction between the selected intermediate elements with the base metals along with the influence of the associated welding parameters are essential. This review is timely as it presents on the current paradigm and progress in welding and joining of Mg/Ti alloys. The factors governing the welding of several important techniques are deliberated along with their joining mechanisms. Some opportunities to improve the welding of Mg/Ti for different welding techniques are also identified.

• International Journal of Computer Science & Network Security
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• 제24권8호
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• pp.184-190
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• 2024

The research involved children and parents of primary school-aged children with cognitive development disorder, as well as scientific and pedagogical workers who organized the psychological and pedagogical principles for organizing distance learning. The purpose of the research lies in establishing how effectively children, parents and their teachers cope with online distance learning during the pandemic, as well as investigating the extent to which such educational technology affects the emotional and behavioural state of the child. The research methodology is based on complexity. In the course of the research, the method of pedagogical experiment was used; observation and questionnaire methods were also introduced; the descriptive method, analysis and synthesis were used to review the theoretical material. The hypothesis lies in the fact that distance online education increases academic difficulties, changes the behavioural and emotional picture of a child with cognitive development disorder; consequently, the behaviour and emotional background will be limited by certain parameters, and this requires the active involvement of parents and teachers in the distance work process. The results of the research have revealed that distance education causes a number of restrictions for children with cognitive development disorder, namely: concentration of attention has decreased, anxiety has increased, and sleep has worsened. Behavioural changes predicted increased restlessness and aggression. Parents and teachers have had methodological, academic and everyday difficulties; all participants in the educational process have been more limited in the conditions of online distance learning. difficulties and improving the behaviour and emotional states of all participants in the educational process.