• 수산해양기술연구
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• 제46권1호
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• pp.50-55
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• 2010

The ship's heading information of hybrid GPS/EM compass were applied to the AIS of fishing vessel and examined the possibility of accuracy improvement. It is observed 453 each in AIS receiver of land among 3,982 each in AIS Rx/Tx transponder of the test ship at sea, and transmission interval according to the speed of ship is determined the 11.4% good transmitting data of the all information. In results, maximum compass error for the ship's heading of an EM compass was $19.1^{\circ}$. The variance of ship's heading owing to the speed of ship is surveyed. The COG (Course Over Ground) was changed extremely in $180^{\circ}W-179^{\circ}E$ range under 4.9knots, and in $24^{\circ}W-23^{\circ}E$ range over 4.9knots. Finally, using the ship's heading of EM compass and the COG from GPS for the autopilot system of a small fishing boat and the ship's heading information of AIS results in danger on the own ship's navigation safety and leads to make confusion both the others and VTS (Vessel Traffic Service) center. Therefore, the hybrid GPS/EM compass is identified as the best system for a small fishing boat and is allowed to offer continuously a ship's heading information with high accuracy and stability.

• Communications for Statistical Applications and Methods
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• 제30권1호
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• pp.95-107
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• 2023

Purpose: The statistical analysis of point processes on linear networks is a recent area of research that studies processes of events happening randomly in space (or space-time) but with locations limited to reside on a linear network. For example, traffic accidents happen at random places that are limited to lying on a network of streets. This paper applies techniques developed for point processes on linear networks and the tools available in the R-package spatstat to estimate the intensity of traffic accidents in Leon County, Florida. Methods: The intensity of accidents on the linear network of streets is estimated using log-linear Poisson models which incorporate cubic basis spline (B-spline) terms which are functions of the x and y coordinates. The splines used equally-spaced knots. Ten different models are fit to the data using a variety of covariates. The models are compared with each other using an analysis of deviance for nested models. Results: We found all covariates contributed significantly to the model. AIC and BIC were used to select 9 as the number of knots. Additionally, covariates have different effects such as increasing the speed limit would decrease traffic accident intensity by 0.9794 but increasing the number of lanes would result in an increase in the intensity of traffic accidents by 1.086. Conclusion: Our analysis shows that if other conditions are held fixed, the number of accidents actually decreases on roads with higher speed limits. The software we currently use allows our models to contain only spatial covariates and does not permit the use of temporal or space-time covariates. We would like to extend our models to include such covariates which would allow us to include weather conditions or the presence of special events (football games or concerts) as covariates.

• 대한수학회보
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• 제48권3호
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• pp.469-474
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• 2011

The Kauffman bracket skein module $K_t$(M) of a 3-manifold M becomes an algebra for t = -1. We prove that this algebra has no non-trivial nilpotent elements for M being the exterior of the twist knot in 3-sphere and, therefore, it is isomorphic to the $SL_2(\mathbb{C})$-character ring of the fundamental group of M. Our proof is based on some properties of Chebyshev polynomials.

• 대한수학회보
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• 제50권6호
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• pp.1989-2000
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• 2013

We show that for any given closed orientable 3-manifold M with a Heegaard surface of genus g, any positive integers b and n, there exists a knot K in M which admits a (g, b)-bridge splitting of distance greater than n with respect to the Heegaard surface except for (g, b) = (0, 1), (0, 2).

• 대한수학회지
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• 제36권1호
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• pp.51-71
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• 1999

We classify all conjugacy classes of 3-braids that are related by flypes on representatives. Among them we determine which classes have representatives that admit both (+) and (-) flypes as an effort to search for a potential example of a pair of transversal knots that are topologically isotopic and have the same Bennequin number but are not transversally isotopic.

• 대한수학회논문집
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• 제38권3호
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• pp.913-924
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• 2023

We consider the number of colors for colorings of links by the symmetric group S₃ of degree 3. For knots, such a coloring corresponds to a Fox 3-coloring, and thus the number of colors must be 1 or 3. However, for links, there are colorings by S₃ with 4 or 5 colors. In this paper, we show that if a 2-bridge link admits a coloring by S₃ with 5 colors, then the link also admits such a coloring with only 4 colors.

• East Asian mathematical journal
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• 제35권3호
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• pp.285-288
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• 2019

Let $F_n$, $n{\in}{\mathbb{N}}$ be the n - th Fibonacci number, and let (p, q) be one of ordered pairs ($F_{n+2}$, $F_n$) or ($F_{n+1}$, $F_n$). Then we show that the multiplicative inverse of q mod p as well as that of p mod q are again Fibonacci numbers. For proof of our claim we make use of well-known Cassini, Catlan and dOcagne identities. As an application, we determine the number $N_{p,q}$ of nonzero term of a polynomial ${\Delta}_{p,q}(t)=\frac{(t^{pq}-1)(t-1)}{(t^p-1)(t^q-1)}$ through the Carlitz's formula.

• 대한조선학회논문집
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• 제49권6호
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• pp.478-483
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• 2012

The speed performances of ice sea trial on the Arctic(2010 & 2011) area were shown different results depend on the ice floe size. Penetration phenomena of level ice was not happened on medium ice floe and tore up by the impact force because the mass of medium ice floe is similar to the mass of Araon which is Korean ice breaking research vessel and did not shut up by the ice ridge or iceberg. The sea trial on the Amundsen sea was performed at the big floe which is classified by WMO(World Meteorological Organization). Three measurements of ice properties and five results of speed trial were obtained with different ice thicknesses and engine powers. To evaluate speed of level ice trial and model test results at the same ice thickness and engine power, the correction method of HSVA(Hamburg Ship Model Basin) was used. The thickness, snow effect, flexural strength and friction coefficient were corrected to compare the speed of sea trial. The analyzed speed at 1.03m thickness of big floe was 5.85 knots at 10MW power and it's 6.10 knots at 1.0m ice thickness and the same power. It's bigger than the results of level ice because big floe was also slightly tore up by the impact force of vessel based on the observation of recorded video.

• 한국항해항만학회지
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• 제37권2호
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• pp.149-154
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• 2013

이 논문은 파공봉쇄장치(Liquid Spill Stopper) 성능 검증 실험에 대한 문제를 다룬다. 실험을 통해 선체에 파공이 발생한 경우 파공 봉쇄장치를 사용하여 신속하고 효율적으로 대응 및 봉쇄할 수 있는지를 가늠할 수 있다. 이 연구에서 쓰인 방법은 선체의 파공으로 해수가 유입할 때 발생하는 압력에 대한 실험 장치와 선박에 부착한 후 운항 중 분리 속도에 대한 실험이다. 이 논문의 주요 결과는 다음과 같다. 첫째, 직경 40mm 및 100mm 파공에서 1.0bar의 압력에도 제 성능을 발휘했다. 둘째, 선체 중앙에서 선미 방향으로 흘수선상 300mm, 흘수선, 흘수선하 300mm에 각각 2개씩 6개의 파공봉쇄장치를 부착한 채 항속을 높이기 시작한 결과, 해군 작전속도(18knots)를 상회하였으며 최초로 선수 흘수선에 부착한 것이 20.2knots에서 분리하였으므로 함정의 작전속도에 지장이 없을 뿐만 아니라 일반 선박의 선체 파공에서도 침수 방지 기능을 제공할 수 있다.

• 대한조선학회논문집
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• 제31권1호
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• pp.1-13
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• 1994

30만톤 초대형 유조선을 대상으로 하여 전류고정날개 추진시스템을 개발하기 위한 일련의 과정을 서술하였다. 전류고정날개 추진시스템은 프로펠러 후류 유동에서의 회전 운동에너지의 손실을 회수하여 추진 효율향상을 도모하기 위한 복합추진 장치이다. 에너지 절약형 복합추진 장치중 전류고정날개 추진시스템은 명확한 유체역학적 원리에 의하여 작동될뿐 아니라 기계적 구조가 간단하여 초기 설치비가 저렴하고 신뢰성이 높은 추진 장치이다. 선체와 기존 프로펠러를 고려하여 5개의 고정날개를 설계하였으며, 모형시험에 의하여 성능을 검증하였다. 공동수조의 모형시험 결과 전류고정날개 추진시스템의 단독 추진효율이 단독 프로펠러에 비하여 $4{\sim}6%$ 증가됨을 확인하였다. 또한 예인수조에서의 자항추진 시험결과 설계속도(15.5 Knots)에서 전달마력이 최대 6.5% 감소되었다. 일련의 설계 및 모형시험에 의한 검증 과정을 통하여 전류고정날개는 선체후류에 맞추어 설계되어야 큰 마력 절감효과를 낼 수 있음을 밝혔다.