• Journal of Navigation and Port Research
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• v.37 no.1
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• pp.63-69
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• 2013

Since most merchant vessels are mainly influenced by the added resistance in an actual sea, they could be navigated more efficiently if this added resistance could be precisely predicted and then effectively reduced. In this paper, we have computed the effective horsepower based on the resistance performance in still water and then calculated the added resistance in regular wave in order to estimate a ship's propulsion performance on a voyage. Firstly, we have performed experiments using a model of KCS in a circulating water channel to estimate the flow characteristics around a container ship and the ship's resistance in still water. Then we have calculated the motion response function in regular wave as well as the values for the increase in resistance, and evaluated the ship's motion performance in waves according to the calculated response function. It was found that the resistance in waves increased because the ship's motion response value became larger as the ship's speed increased in the case of head sea. The effect of the added resistance could be reduced by maneuvering the ship to the encounter angle of $120^{\circ}$ in areas of long wavelengths and to head sea in areas of short wavelengths.

• The Pure and Applied Mathematics
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• v.20 no.4
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• pp.251-258
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• 2013

We define an ${\varepsilon}$-regular function in dual quaternions. From the properties of ${\varepsilon}$-regular functions, we represent the Taylor series of ${\varepsilon}$-regular functions with values in dual quaternions.

• Journal of Korean Public Health Nursing
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• v.27 no.1
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• pp.5-15
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• 2013

Purpose: The purpose of this study was to determine factors related to regular walking exercise in the elderly using KNHNES data. Method: The study subjects, a total of 1437 adults over age 65, were classified into two groups based on their type of walking exercise: regular walking exercise group or irregular walking exercise group. The study variables were measured using scale physiological function, mental health status, chronic disease and quality of life. Results: The data was analyzed by $x^2$-test, t-test, and logistic regression using the SPSS 18.0 program. The factors related to regular walking exercise were male (OR=0.628, 95%CI=0.503-0.783), subjective health state (OR=0.832, 95%CI=0.751-0.921), thoughts of suicide (OR=0.753, 95%CI=0.586-0.967), hypoHDL-cholesterolemia (OR=0.742, 95%CI=0.591-0.930), and stroke (OR=0.604, 95%CI=0.366-0.997). Conclusion: The findings indicate that regular walking exercise in the elderly is related to physiological function, mental health status, and chronic disease. Therefore, providing for the education and awareness of health promotion for the elderly will may improve the quality of life in old age.

• Journal of Mechanical Science and Technology
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• v.20 no.1
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• pp.94-109
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• 2006

An improved meshfree method called the Petrov-Galerkin natural element (PG-NE) method is introduced in order to secure the numerical integration accuracy. As in the Bubnov-Galerkin natural element (BG-NE) method, we use Laplace interpolation function for the trial basis function and Delaunay triangles to define a regular integration background mesh. But, unlike the BG-NE method, the test basis function is differently chosen, based on the Petrov-Galerkin concept, such that its support coincides exactly with a regular integration region in background mesh. Illustrative numerical experiments verify that the present method successfully prevents the numerical accuracy deterioration stemming from the numerical integration error.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1066-1073
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• 1993

Using regular finite elements and infinite elements simultaneously, elastic boundary value problems with infinite domain can be analyzed more effectively and accurately. In this paper, two dimensional infinite elements have been formulated by means of applying the derived mapping function to the coordinates and multiplying the regular displacement shape functions by a decay function. Orders(m, n) of the mapping and decay functions are found for the purpose of obtaining the convergent solutions without respect to the various decay lengthes. As a result of numerical tests for an infinite plate with a hole under internal pressure, two sets of function orders are obtained as follows. (a) n=0, m=1.5 (b) n=m=0.65

• Journal of the Korean Mathematical Society
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• v.46 no.3
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• pp.551-560
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• 2009

A theorem of Robert Blumenthal is used here in order to obtain a sufficient condition for a function between two Finsler manifolds to be a fibre bundle map. Our study is connected with two possible constructions: 1) a Finslerian generalization of usually Kaluza-Klein theories which use Riemannian metrics, the well-known particular case of Finsler metrics, 2) a Finslerian version of reduction process from geometric mechanics. Due to a condition in the Blumenthal's result the completeness of Euler-Lagrange vector fields of Finslerian type is discussed in detail and two situations yielding completeness are given: one concerning the energy and a second related to Finslerian fundamental function. The connection of our last framework, namely a regular Lagrangian having the energy as a proper (in topological sense) function, with the celebrated $Poincar{\acute{e}}$ Recurrence Theorem is pointed out.

• Kyungpook Mathematical Journal
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• v.32 no.1
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• pp.21-30
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• 1992

• Korean Journal of Mathematics
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• v.27 no.4
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• pp.861-877
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• 2019

The aim of this paper is to extend some existing fixed point results for asymptotically regular mappings to fuzzy metric spaces. For this purpose some contractive type conditions with respect to an altering distance function are used. Some new common fixed point results have been derived for such mappings. We provide suitable examples to justify our study.

• Journal of the Korean Mathematical Society
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• v.56 no.2
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• pp.475-484
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• 2019

We study the set of critical exponents of discrete groups acting on regular trees. We prove that for every real number ${\delta}$ between 0 and ${\frac{1}{2}}\;{\log}\;q$, there is a discrete subgroup ${\Gamma}$ acting without inversion on a (q+1)-regular tree whose critical exponent is equal to ${\delta}$. Explicit construction of edge-indexed graphs corresponding to a quotient graph of groups are given.

• Journal of Korean Public Health Nursing
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• v.30 no.2
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• pp.337-348
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• 2016

Purpose: This study was to examine the factors (depression, level of health status, physical function, depression) influence health related quality of life (EQ5D) in community dwelling elderly according to sex. Methods: A total of 226 elderly subjects over the age of 65 years in community were included. Data were collected by measuring the physical function (muscle endurance, flexibility, balance, and cardiovascular endurance) and by using a questionnaire about EQ5D, depression, health status. Data were analyzed by SPSS 18.0 and AMOS 18.0. Results: The major findings of this study are as follows. Explained variance of EQ5D by regular exercise, physical function, and level of health status was 19% for male elderly subjects and 26.0% for female elderly subjects. The effect was different according to sex. Depression has the effect on EQ5D (${\beta}=-.356$, p<.001) in females, while the level of health status has the effect (${\beta}=.314$, p=.027) in males. Conclusion: The results of this study indicate that the effect of regular exercise, physical function, and level of health status were different on EQ5D according to sex. Thus, different health programs according to sex are necessary to increase the quality of life in elderly individuals.