• 한국기계가공학회지
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• 제18권11호
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• pp.103-108
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• 2019

The cooling rate and the uniformity of mold temperature, in the injection molding process, possess great influences on the productivity and quality of replications. The conformal cooling channel, which is of a uniform spacing from the mold cavity by the metal additive manufacturing process, receives much attention recently. The purpose of this study is to develop a mold core with a curved conformal cooling channel for a pottery-shaped thick-wall cosmetic container through the hybrid method of direct metal tooling (DMT) process. In this study, we design a mold core that contains the curved cooling channel for the container. A method that divides the cavity is proposed and the DMT process is carried out to form the curved cooling channel. The test mold core, with the curved conformal cooling channel, has been fabricated by the proposed method to confirm the feasibility of the design concept. We show that no leakage is observed for the additive manufactured test mold core, and its physical properties demonstrate that it can be sufficiently used as the injection mold core.

• 한국해양공학회지
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• 제33권3호
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• pp.222-228
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• 2019

An extreme value analysis (EVA) is essential to obtain a design value for highly nonlinear variables such as long-term environmental data for wind and waves, and slamming or sloshing impact pressures. According to the extreme value theory (EVT), the extreme value distribution is derived by multiplying the initial cumulative distribution functions for independent and identically distributed (IID) random variables. However, in the position mooring of DNVGL, the sampled global maxima of the mooring line tension are assumed to be IID stochastic variables without checking their independence. The ITTC Recommended Procedures and Guidelines for Sloshing Model Tests never deal with the independence of the sampling data. Hence, a design value estimated without the IID check would be under- or over-estimated because of considering observations far away from a Weibull or generalized Pareto distribution (GPD) as outliers. In this study, the IID sampling data are first checked in an EVA. With no IID random variables, an automatic resampling scheme is recommended using the block maxima approach for a generalized extreme value (GEV) distribution and peaks-over-threshold (POT) approach for a GPD. A partial autocorrelation function (PACF) is used to check the IID variables. In this study, only one 5 h sample of sloshing test results was used for a feasibility study of the resampling IID variables approach. Based on this study, the resampling IID variables may reduce the number of outliers, and the statistically more appropriate design value could be achieved with independent samples.

• 예술인문사회 융합 멀티미디어 논문지
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• 제9권2호
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• pp.737-744
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• 2019

연구는 한국의 익스트림 스포츠 참여자들의 여가지지가 여가제약과 생활만족에 미치는 영향을 분석하였다. 본 연구의 대상자는 서울, 인천, 경기, 충청도에 거주하는 성인남녀 368명으로 편의표본추출법을 사용하여 모집하였다. 본 연구의 목적을 규명하기 위하여 SPSS 18.0과 AMOS 18.0 프로그램을 사용하여 빈도분석, 신뢰도 분석, 확인적 요인분석, 상관관계 분석, 구조방정식모형 분석 등을 사용하였다. 위와 같은 연구 과정을 거쳐 다음과 같은 연구결과를 도출하였다. 첫째, 익스트림 스포츠참여자의 여가지지는 여가제약에 영향을 미치지 않았다. 둘째, 익스트림 스포츠 참여자의 여가지지는 생활만족에 영향을 미쳤다. 셋째, 익스트림 스포츠 참여자의 여가제약은 생활만족에 영향을 미치지 않았다. 스포츠 활동과 같은 여가활동은 참여자들에게 높은 만족을 주고 있다는 것을 다시 확인할 수 있었다. 특히 참여자들의 여가지지는 생활만족과 밀접한 관계가 있음을 밝혀졌다. 따라서 익스트림 스포츠 활동에 대한 장점을 적극적으로 홍보하여 지속적인 참여를 유도할 필요가 있다.

• 충청수학회지
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• 제21권1호
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• pp.99-106
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• 2008

In this paper, we establish some recurrence relations which is satisfied by the quotient moments of the lower record values from the standard generalized extreme value (GEV) distribution.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.300-302
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• 2005

We employ a new technique to account for extreme values when using the generalized autoregressive conditionally heteroskedastic (GARCH) methodology to forecast day-ahead electricity prices in New York City.

• International Journal of Automotive Technology
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• 제6권1호
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• pp.37-44
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• 2005

The creation of automotive systems of active safety with intelligent functions needs the use of new control principles for the wheel and automobile. One of such directions is the pre-extreme control strategy. Its aim is the ensuring of wheel's work in pre-extreme, stable area of tire grip wheel slip dependence. The simplest realization of pre-extreme control in automotive anti-lock brake systems consists in the threshold and gradient algorithms. A comparative analysis of these algorithms, which has been made on 'hardware in-the-loop' simulation results of the braking for bus with various anti-lock brake systems (ABS), indicated their high efficiency.

• 대한산업공학회지
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• 제33권4호
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• pp.410-418
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• 2007

This article suggests the methods to investigate adverse movement across global stock markets arising from insolvency of subprime mortgage in U.S. Our application deals with asymptotic tail dependence of daily stock index returns (KOSPI, DJIA, Shanghai Composite) of three countries; Korea, U.S., and China, over specific period via extreme value theory and copula functions. Daily stock index returns among three countries show higher extremal dependence during the period exposed to systematic shock. We confirm that extreme value theory and copula functions have potential to well describe the extreme dependence between three countries' daily stock index returns.

• 한국해양공학회지
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• 제16권5호
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• pp.1-6
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• 2002

Extreme waves are generated in a model basin based on directional wave focusing. The targeted wave field is described by double summation method and it is applied to serpent-type wavemaker system. The extreme crest amplitude at a designed location is obtained by syncronizing the phases and focusing the directions of wave components. Two distinguished spectrums of constant wave amplitude and constant wave steepness are adapted to describe the frequency distribution of component waves. The surface profile of generated wave packets is measured by wave guage array and the effects of dominant spectral parameters governing extreme wave characteristics are investigated. It is found that frequency bandwidth, center frequency, shape of frequency spectrum and directional range play a significant role in the wave focusing. In particular, the directional effect significantly enhances the wave focusing efficiency.

• 디지털산업정보학회논문지
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• 제8권1호
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• pp.47-53
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• 2012

Sensor networks and car networks that have different structure from that of conventional TCP/IP network require extreme network environment due to frequent change of connectivity. Because such extreme network environment has characteristics like unreliable link connectivity, long delay time, asymmetrical data transfer rate, and high error rate, etc., it is difficult to perform normally with the conventional TCP/P-based routing. DTNs (delay and disruption tolerant network) was designed to support data transfer in extreme network environment with long delay time and no guarantee for continuous connectivity between terminals. This study suggests an algorithm that limits the maximum number of copying transferred message to L by improving the spray and wait routing protocol, which is one of the conventional DTNs routing protocols, and using the azimuth and density data of the mobile nods. The suggested algorithm was examined by using ONE, a DTNs simulator. As a result, it could reduce the delay time and overhead of unnecessary packets compared to the conventional spray and wait routing protocol.

• Communications for Statistical Applications and Methods
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• 제18권5호
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• pp.615-623
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• 2011

이항비율에 대한 구간추정에 다양한 신뢰구간들이 사용된다. 그러나 대부분의 신뢰구간들은 모비율 p가 0이나 1에 근사할 때 포함확률이 신뢰수준(또는 명목수준, 1 - ${\alpha}$)을 크게 벗어난다. 이는 극단적인 관찰값의 영향 때문이다. Vollset (1993), Agresti와 Coull (1998), Newcombe (1998), Brown 등 (2001) 등은 극단값의 조정을 통해서 이러한 문제를 해결하는 방법들을 제시하였다. 본 연구에서는 극단값들이 이항비율에 대한 신뢰구간에 어느 정도 영향을 미치는지를 6개의 신뢰구간들에 대해서 수치적으로 비교해 보았다.