• 한국해양공학회지
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• 제36권2호
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• pp.91-100
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• 2022

In general, the effect of roll motion is not considered in the study on maneuverability in calm water. However, for high-speed twin-screw ships such as the DTMB 5415, the coupling effects of roll and other motions should be considered. Therefore, in this study, the estimation of maneuverability using a 4-degree-of-freedom (DOF; surge, sway, roll, yaw) maneuvering mathematical group (MMG) model was conducted for the DTMB 5415, to improve the estimation accuracy of its maneuverability. Furthermore, a study on the change in turning performance according to the fin angle was conducted. To accurately calculate the lift and drag forces generated by the fins, it is necessary to consider the three-dimensional shape of the wing, submerged depth, and effect of interference with the hull. First, a maneuvering simulation model was developed based on the 4-DOF MMG mathematical model, and the lift force and moment generated by the side fins were considered as external force terms. By employing the CFD model, the lift and drag forces generated from the side fins during ship operation were calculated, and the results were adopted as the external force terms of the 4-DOF MMG mathematical model. A 35° turning simulation was conducted by altering the ship's speed and the angle of the side fins. Accordingly, it was confirmed that the MMG simulation model constructed with the lift force of the fins calculated through CFD can sufficiently estimate maneuverability. It was confirmed that the heel angle changes according to the fin angle during steady turning, and the turning performance changes accordingly. In addition, it was verified that the turning performance could be improved by increasing the heel angle in the outward turning direction using the side fin, and that the sway speed of the ship during turning can affect the turning performance. Hence, it is considered necessary to study the effect of the sway speed on the turning performance of a ship during turning.

• Industrial Engineering and Management Systems
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• 제7권2호
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• pp.160-170
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• 2008

This paper proposes a mathematical model for converting conveyor assembly line to cellular manufacturing in complex production environments. Complex production environments refer to the situations with multi-products, variant demand, different batch sizes and the worker abilities varying with work stations and products respectively. The model proposed in this paper aims to determine (1) how many cells should be formatted; (2) how many workers should be assigned in each cell; (3) and how many workers should be rested in shortened conveyor line when a conveyor assembly line should be converted, in order to optimize system performances which are defined as the total throughput time and total labor power. We refer the model to a new production system. Such model can be used as an evaluation tool in the cases of (i) when a company wants to change its production system (usually a belt conveyor line) to a new one (including cell manufacturing); (ii) when a company wants to evaluate the performance of its converted system. Simulation experiments based on the data collected from the previous documents are used to estimate the marginal impact that each factor change has had on the estimated performance improvement resulting from the conversion.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제12권4호
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• pp.251-258
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• 2008

This paper deals with factors discriminating mathematically gifted and non-gifted students. Discussion of some characteristics of mathematically gifted students is done in the first session. Several factors distinguish mathematically gifted from the non-gifted students. High mathematical creativity, high intelligence and opinion of teachers are some of the key factors that can be used for discriminating mathematically gifted and non-gifted students. Research studies have revealed that cognitive as well as affective factors will enhance giftedness. In this study the investigator wishes to look in detail about the characteristics of mathematically gifted students and how they can be identified. Anyway, teachers can change environmental factors and maximum outcome of giftedness can be ensured."

• 한국수학사학회지
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• 제29권6호
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• pp.353-363
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• 2016

In mathematical population ecology which is an academic field that studies how populations of biological species change as times flows at specific locations in their habitats, PDE models have been studied in many aspects and found to have different properties from the classical ODE models. And different approaches to PDE type models in mathematical biology are still being tried currently. This article investigate various forms to express diffusion effects and review the history of PDE models involving diffusion terms in mathematical ecology. Semi-linear systems representing the spatial movements of each individual as random simple diffusion and quasi-linear systems describing more complex diffusions reflecting interspecific interactions are studied. Also it introduce a few of important problems to be solved in this field.

• 대한수학회보
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• 제44권4호
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• pp.795-806
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• 2007

We investigate F-traceless component of the conformal curvature tensor defined by (3.6) in $K\ddot{a}hler$ manifolds of dimension ${\geq}4$, and show that the F-traceless component is invariant under concircular change. In particular, we determine $K\ddot{a}hler$ manifolds with parallel F-traceless component and improve some theorems, provided in the previous paper([2]), which are concerned with the traceless component of the conformal curvature tensor and the spectrum of the Laplacian acting on $p(0{\leq}p{\leq}2)$-forms on the manifold by using the F-traceless component.

• East Asian mathematical journal
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• 제32권1호
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• pp.139-152
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• 2016

Inflammatory Bowel Disease(IBD) is chronic, relapsing, immune mediated disorder. The exact cause of IBD is still unknown. The immune system is known to play important role in the dynamics of IBD. We focus on relation between T cells and cytokines in immune system that leads to IBD. In this paper, we propose a mathematical model describing IBD under considering immune mediated disorder by using ordinary differential equations. The existence and stability of the model are established, where an applicable basin of attraction are calculated and examined. Some numerical simulations are presented to verify the proposed results and as changing parameter values given by sensitivity analysis, we show how to change dynamic behaviors of the model.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제19권4호
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• pp.261-276
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• 2016

본 연구는 동료 멘토링을 활용한 수학 수업에서 학생들의 수학적 인성과 수학 학업성취도에 미치는 영향을 분석하는데 목적이 있다. 본 연구 결과 동료 멘토링을 활용한 수학 수업에서 선행 연구들과는 달리 수학적 인성의 하위요소인 존중심, 배려심, 공유심, 개방심 영역에서 멘토 집단과 멘티 집단 사이에 통계적으로 유의미한 차이는 보이지 않았다. 그러나 수학 일기와 학습지 분석을 통해서는 동료 멘토링 수업으로 인한 수학적 인성의 변화를 각 하위 요소별로 구체적으로 확인해 볼 수 있었고, 학생들의 수학 학업성취도에도 통계적으로 유의한 차이를 보이는 것으로 나타났다. 이러한 결과를 바탕으로 동료 멘토링을 활용한 수업은 학생들의 수학적 인성 함양과 수학 학업성취도 향상에 도움을 주고, 멘토보다는 멘티에게 보다 큰 변화가 있음을 알 수 있었다. 초등 수학 수업에서 동료 멘토링에 대한 다양한 학년 수준에서의 후속 연구를 제언하였다.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제19권1호
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• pp.19-41
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• 2015

Previous studies indicated that students tended to hold less satisfactory beliefs about the discipline of mathematics, beliefs about themselves as learners of mathematics, and beliefs about mathematics teaching and learning. However, only a few studies had developed curricular interventions to change students' beliefs. This study aimed to examine the effect of a problem-solving curriculum (i.e., Mathematical Problem Solving for Everyone, MProSE) on Singaporean Grade 7 students' beliefs about mathematical problem solving (MPS). Four classes (n =142) were engaged in ten lessons with each comprising four stages: understand the problem, devise a plan, carry out the plan, and look back. Heuristics and metacognitive control were emphasized during students' problem solving activities. Results indicated that the MProSE curriculum enabled some students to develop more satisfactory beliefs about MPS. Further path analysis showed that students' attitudes towards the MProSE curriculum are important predictors for their beliefs.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제26권1호
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• pp.29-50
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• 2012

이 연구의 목적은 우수학력 학생들과 기초학력 미달 학생들의 수학과 학업성취도를 비교하는 데 있다. 이러한 연구 목적을 수행하기 위해 이 연구에서는 학교급별로 우수학력과 기초학력 미달 학생들의 비율, 우수학력과 기초학력 미달 학생들의 전체, 내용 영역별, 행동 영역별 수학 학업성취도를 비교하였다. 이를 통해 우수학력과 기초학력 미달 학생들의 변화 추이를 파악할 수 있을 뿐만 아니라 내용 영역별, 행동 영역별, 문항 유형별(서답형 문항)로 우수학력과 기초학력 미달 학생들의 특성을 파악할 수 있었다.

• 대한수학회보
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• 제48권3호
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• pp.475-489
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• 2011

In this paper, we use a generalized Brownian motion to define a generalized analytic Feynman integral. We then obtain some results for the generalized analytic Feynman integral of bounded cylinder functionals of the form F(x) = $\hat{v}$(($g_1,x)^{\sim}$,..., $(g_n,x)^{\sim}$) defined on a very general function space $C_{a,b}$[0,T]. We also present a change of scale formula for function space integrals of such cylinder functionals.