• Korean Journal of Health Education and Promotion
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• v.25 no.2
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• pp.1-18
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• 2008

Objectives: The objective of this study is to identify the gender differences of risk factors for falls among the elderly in community dwellings. Methods: We analyzed the data on 3,278(male 1,255, female 2,023) persons, including 497 persons who have experienced falls, drawn from the 2004 National Elderly Survey. We conducted a cross-tabulation analysis, $X^2$-test and hierarchical regression analysis of the impact of the socio-economical characteristics, environmental characteristics, the number of chronic diseases, usage of supplementary devices, activities of daily living, dementia, and the severity of problem behavior. Results: For the entire sample of the elderly, gender, age, the size of the cities of residence, the number of chronic diseases, and the severity of problem behavior were identified as risk factors for falls. The number of chronic diseases and the severity of problem behavior were found to be significant for the male subsample, while age, the size of cities of residence, dwelling types, and the number of chronic diseases were found to be significant for the female subsample. Conclusion: The number of chronic diseases was identified as a common risk factor for falls in the male and female elderly. Chronic diseases were also found to aggravate the risk for falls when they concur with other diseases.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.145-156
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• 1993

An improved analysis model for material nonlinearity induced by elasto-plastic deformation and damage including large strain response was proposed. The elasto-plastic-damage constitutive model based on the continuum damage mechanics approach was adopted to overcome limitations of the conventional plastic theory, which can manage the anisotropic tonsorial damages evolved during time-independent plastic deformation process of materials. Updated Lagrangian finite element formulation for elasto-plastic damage coupling problem including large deformation, large rotation and large strain problems was completed to develop a numerical model which can predict all kinds of structural nonlinearities and damage rationally. Finally, a finite element analysis code for the 2-dimensional plane problem was developed and the applicability and validity of the numerical model was investigated through some numerial examples. Calculations showed reasonable results in both geometrical nonlinear problem due to large deformation and material nonlinearity including the damage effect.

• Korean Management Science Review
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• v.31 no.1
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• pp.27-40
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• 2014

Tour products have been recognized as a perishable asset. For tour operation companies (TOCs), improving profitability is a core decision problem for their business. Since package tour products, typical products of TOCs, are perishable after the tour was departed, TOCs have been tried to increase their sales before the departure date with various marketing strategies including price discounts. The pricing problem for perishable assets have been studied in Revenue Management for a long time. However, it is hard to find a research on pricing decisions for tour products. In this paper, we focus on a pricing problem for tour products. In particular, we will consider the pricing scheme with customer preference values on purchasing conditions. With conjoint analysis, we can use the part-worth value as a preference value for each level of purchasing conditions. To construct various discount prices, we use an enumeration method and suggest a mathematical optimization model. With experimental analysis for a sample tour package, we will show that our pricing process is very helpful for designing customer-oriented pricing decision.

• Korean Journal of Environment and Ecology
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• v.19 no.2
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• pp.139-143
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• 2005

The purpose of this study was to provide basic data for developing effective park management. For this, satisfaction factors and estimated model by satisfaction variables of user were analyzed through a questionnaire survey in Woraksan National Park, Korea. In the evaluation of the satisfaction, variables of the 'fee', 'lack and cleanness of facility', 'exorbitant pay', 'littering problem' were more unsatisfied than any other variables. Satisfaction factors by Factor Analysis were loaded with 'usual management'. In estimated model of satisfaction by Multiple Regression Analysis order of 'safety for recreation activities', 'parking problem', 'littering problem' were shown.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.17-27
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• 2009

Water jet impingement cooling is used to remove heat from high-temperature surfaces such as hot steel plates in the steel manufacturing process (thermo-mechanical cooling process; TMCP). In those processes, uniform cooling is the most critical factor to ensure high strength steel and good quality. In this study, experiments are performed to measure the heat transfer coefficient together with the inverse heat conduction problem (IHCP) analysis for a plate cooled by planar water jet. In the inverse heat transfer analysis, spatial and temporal variations of heat transfer coefficient, with no information regarding its functional form, are determined by employing the conjugate gradient method with an adjoint problem. To estimate the two dimensional distribution of heat transfer coefficient and heat flux for planar waterjet cooling, eight thermo-couple are installed inside the plate. The results show that heat transfer coefficient is approximately uniform in the span-wise direction in the early stage of cooling. In the later stage where the forced-convection effect is important, the heat transfer coefficient becomes larger in the edge region. The surface temperature vs. heat flux characteristics are also investigated for the entire boiling regimes. In addition, the heat transfer rate for the two different plate geometries are compared at the same Reynolds number.

• Structural Engineering and Mechanics
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• v.58 no.4
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• pp.731-743
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• 2016

Plastic behaviors, based on the von Mises yield criterion, of circular discs containing a purely elastic, circular inclusion under uniform temperature loading are studied with the finite element analysis. Temperature-dependent mechanical properties are considered for the matrix material only. In addition to analyzing the plane stress and plane strain disc, a 3D thin disc and cylinder are also analyzed to compare the plane problems. We determined the elastic irreversible temperature and global plastic collapse temperature by the finite element calculations for the plane and 3D problem. In addition to the global plastic collapse, for the elastically hard case, the plane stress problem and 3D thin disc may exhibit a local plastic collapse, i.e. significant pile up along the thickness direction, near the inclusion-matrix interface. The pileup cannot be correctly modeled by the plane stress analysis. Furthermore, due to numerical difficulties originated from large deformation, only the lower bound of global plastic collapse temperature of the plane stress problem can be identified. Without considerations of temperature-dependent mechanical properties, the von Mises stress in the matrix would be largely overestimated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1070-1077
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• 2006

In the present study, sizing and shape optimizations are performed based on the reduced system of large-scaled problem. In the analysis part to achieve efficiency and reliability of computation, two-level condensation scheme is applied. In the construction of reduced system of large scaled problems, it is much more efficient to use sub-domain method. Thus, in the present paper, two-level reduction method combined with sub-domain method is employed. Once the reduced system is constructed, it is straightforward to obtain design sensitivities from the analysis results of the reduced system We use semi-analytic method to obtain design sensitivities. Performance of the efficiency and reliability of the present reduction method in the structural optimization problem is demonstrated through the numerical examples. The present framework of reduction method should serve as a fast and reliable design tool in analysis and design of large-scaled dynamic problems.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.4
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• pp.253-259
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• 2013

Investment scenarios in the transportation network design problem usually contain installation or expansion of multi-mode transportation links. When one applies the mode choice analysis and traffic assignment sequentially for each investment scenario, it is possible that the travel impedance used in the mode choice analysis is different from the user equilibrium cost of the traffic assignment step. Therefore, to estimate the travel impedance and mode choice accurately, one needs to develop a combined model for the mode choice and traffic assignment. In this paper, we derive the inverse demand and the excess demand functions for the multi-mode multinomial logit mode choice function and develop a combined model for the multi-mode variable demand traffic assignment problem. Using data from the regional O/D and network data provided by the KTDB, we compared the performance of the partial linearization algorithm with the Frank-Wolfe algorithm applied to the excess demand model and with the sequential heuristic procedures.

• Journal of Korean Academy of Nursing
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• v.50 no.6
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• pp.822-836
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• 2020

Purpose: This study aimed to identify latent classes of behavioral problem trajectories in children with allergic diseases and investigate their predictors. Methods: This study used data from the 5th to 7th Panel Study of Korean Children. The participants included 840 children aged 4~6 years with allergic diseases. Statistical analyses were conducted using latent class growth analysis and multinomial logistic regression. Results: The trajectories of both internalizing and externalizing behavioral problems in children with allergic diseases were classified into five groups, that is deteriorative, recovering, changing 1 (decreasing-increasing), changing 2 (increasing-decreasing), and low state persistent group. For the internalizing behavioral problems, predictors were temperament, father's education, family interaction, and disconnection in peer interaction. For the externalizing behavioral problems, predictors child's gender, temperament, marital conflict, parenting stress, family interaction, and parenting environment. Conclusion: Deteriorative group has high-risk behavioral problems in children with allergic diseases. We suggest to provide interventions considering latent problem trajectories based on ecological environments for allergic children.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.11
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• pp.771-781
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• 2022

Sequential convex programming based performance analysis of the designed UAV is performed. The nonlinear optimization problems generated by aerodynamics are approximated to socond order program by discretization and convexification. To improve the performance of the algorithm, the solution of the relaxed problem is used as the initial trajectory. Dive trajectory optimization problem is analyzed through iterative solution procedure of approximated problem. Finally, the maximum final velocity according to the performance of the actuator model was compared.