• Journal of the Korean Mathematical Society
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• v.45 no.2
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• pp.405-423
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• 2008

By using critical point theorem, we study a higher order difference system, and obtain some new sufficient conditions ensuring the existence of periodic solutions for such a system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.279-286
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• 2020

In this study, we investigate the accuracy of higher order derivatives in the moving least square (MLS) difference method. An interpolation function is constructed by employing a Taylor series expansion via MLS approximation. The function is then applied to the mixed variational theorem in which the displacement and stress resultants are treated as independent variables. The higher order derivatives are evaluated by solving simply supported beams and cantilevers. The results are compared with the analytical solutions in terms of the order of polynomials, support size of the weighting function, and number of nodes. The accuracy of the higher order derivatives improves with the employment of the mean value theorem, especially for very high-order derivatives (e.g., above fourth-order derivatives), which are important in a classical asymptotic analysis.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.52-57
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• 2001

Laminar two-dimensional time-dependent flow past a circular cylinder is numerically investigated using direct numerical simulation for the low Reynolds number (Re=164∼280). The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. The convection term is applied by the 7th order up wind scheme and the pressure and viscosity terms are applied by the 4th order central difference. The grid system makes use of the regular grid system and it is generated by an equation. The calculated results of drag coefficients, lift coefficients, pressure distributions, and vorticity contours and other information are compared with experimental and numerical ones. These results obtained by the present DNS show good agreement with the previous studies.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.94-101
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• 1994

To develope the new simulator for the analysis of fluid flow information, the influence of various convective difference schemes were evaluated. General curvilinear coordinate system with nonorthogonal grids was adopted for the successful analysis of various complex geometries. Computation results show that if we can not obtain full grid numbers within available computational environment, we need to use higher order finite difference schemes to keep the prediction accuracy.

• Smart Structures and Systems
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• v.14 no.6
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• pp.1081-1103
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• 2014

Real-time hybrid simulation (RTHS) has emerged as an important tool for testing large and complex structures with a focus on rate-dependent specimen behavior. Due to the real-time constraints, accurate dynamic control of servo-hydraulic actuators is required. These actuators are necessary to realize the desired displacements of the specimen, however they introduce unwanted dynamics into the RTHS loop. Model-based actuator control strategies are based on linearized models of the servo-hydraulic system, where the controller is taken as the model inverse to effectively cancel out the servo-hydraulic dynamics (i.e., model-based feedforward control). An accurate model of a servo-hydraulic system generally contains more poles than zeros, leading to an improper inverse (i.e., more zeros than poles). Rather than introduce additional poles to create a proper inverse controller, the higher order derivatives necessary for implementing the improper inverse can be calculated from available information. The backward-difference method is proposed as an alternative to discretize an improper continuous time model for use as a feedforward controller in RTHS. This method is flexible in that derivatives of any order can be explicitly calculated such that controllers can be developed for models of any order. Using model-based feedforward control with the backward-difference method, accurate actuator control and stable RTHS are demonstrated using a nine-story steel building model implemented with an MR damper.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.47 no.1
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• pp.1-8
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• 2024

This study analyzed the impact of Higher-order resources on profit sustainability for domestic companies using a mathematical statistical model. Higher-order resources refer to resources that do not directly affect profits but influence other resources that directly contribute to profits. As a result of analysis using 30 years of actual data from more than 650 domestic companies, the average duration of competitive advantage including high-order resources was found to be about twice as long as the period suggested by the autoregressive model excluding high-order resources. Through this, if companies want to earn more profits over a long period of time than their competitors, they must not only possess resources that are more valuable, rare, difficult to imitate, and non-substitutable compared to their competitors, but also that higher-order resources can contribute to changes in these resources over time. It was confirmed that it must lead the long-term profit difference. High-level resources include strategic planning, mergers and acquisitions (M&A) capabilities, and good forecasting.

• Ocean Systems Engineering
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• v.10 no.2
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• pp.201-226
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• 2020

A systematic numerical comparative study of the performance of semicircular and rectangular submerged breakwaters interacting with solitary waves is the basis of this paper. To accomplish this task, Nwogu's extended Boussinesq model equations are employed to simulate the interaction of the wave with breakwaters. The finite difference technique has been used to discretize the spatial terms while a fourth-order predictor-corrector method is employed for time discretization in our numerical model. The proposed computational scheme uses a staggered-grid system where the first-order spatial derivatives have been discretized with fourth-order accuracy. For validation purposes, five test cases are considered and numerical results have been successfully compared with the existing analytical and experimental results. The performances of the rectangular and semicircular breakwaters have been examined in terms of the wave reflection, transmission, and dissipation coefficients (RTD coefficients) denoted by K_R, K_T, K_D. The latter coefficient K_D emerges due to the non-energy conserving K_R and K_T. Our computational results and graphical illustrations show that the rectangular breakwater has higher reflection coefficients than semicircular breakwater for a fixed crest height, but as the wave height increases, the two reflection coefficients approach each other. un the other hand, the rectangular breakwater has larger dissipation coefficients compared to that of the semicircular breakwater and the difference between them increases as the height of the crest increases. However, the transmission coefficient for the semicircular breakwater is greater than that of the rectangular breakwater and the difference in their transmission coefficients increases with the crest height. Quantitatively, for rectangular breakwaters the reflection coefficients K_R are 5-15% higher while the diffusion coefficients K_D are 3-23% higher than that for the semicircular breakwaters, respectively. The transmission coefficients K_T for rectangular breakwater shows the better performance up to 2.47% than that for the semicircular breakwaters. Based on our computational results, one may conclude that the rectangular breakwater has a better overall performance than the semicircular breakwater. Although the model equations are non-dissipative, the non-energy conserving transmission and reflection coefficients due to wave-breakwater interactions lead to dissipation type contribution.

• Korea Journal of Hospital Management
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• v.10 no.1
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• pp.93-114
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• 2005

The prenatal care is the preventive medical service to help the pregnant mother deliver the healthy baby. It's regular examines give some chances to check-up the healthy conditions. This thesis concentrates on the CRM system to support an effective prenatal care system and prove the effectiveness of it. As CRM is the adapted management related to the customer's own information, it is important to develop the CRM model classified by the patients characteristics. A general hospital in Busan operated the CRM system to carry out the effective prenatal care and there is an analysis to ensure the effectiveness of CRM system for the pregnant women in our maternity ward. The results can be summarized as follows: 1) According to the comparisons with the CRM system, we can conclude the system is desirable. (1) Maternal Age : In the age distribution, the prenatal visit frequency, triple marker freqency, oral GTT and targeted ultrasonography in the experimental group in 30 to 34 years old is higher on the whole. For over 35 years old group, the higher frequency comes out in the oral GTT and targeted ultrasonography and for 25 to 29 years old group the different figure shows just in the targeted ultrasonography. (2) Area of residence: There is a clear difference in all the items in Busan and near area but no sign of difference in prenatal visits and oral GTT in other residencial area. Especially in the targeted ultrasonography the higher figure shows in the experimental group located in the both areas. The targeted ultrasonography is known as the specific examination which should be examined by the specialists, on the contrary the other examinations can be operated in the small clinic. So the public information and seminars related with ultrasonography increases the check-up frequency. The clinic requests some ultrasonographical examinations to the specialists in general hospital. (3) Parity: The clear difference shows that the CRM system causes the prenatal visit frequency to become higher in experimental group. The figure is 9.7 times and 8.6 times each. This is opposite that the past study said multiparity reduced the average prenatal visits. But the result of CRM is considered as the method to help the multiparity understand the importance of the prenatal care. (4) Obstetrical history: In the experimental group of the spontaneous delivery group, the figure is higher in the prenatal visit frequency, triple marker, oral GTT and targeted ultrasonography but the Caesarean section delivery group has higher figure in targeted ultrasonography. (5) In the first check-up, the rate of targeted ultrasonography in under 16 week pregnancy, in the 16 week pregnancy to 32 week pregnancy and the over 32 week pregnancy in the experimental group is upper than the compared one. For the oral GTT, there is a difference in under 16 week pregnancy but no difference in prenatal visits and triple marker. 2) The analysis of characteristics of prenatal care through the decision tree resulted in the fact that the most important variable is the residential area. After the delivery frequency is following, the obstetrical history and maternal age are in order. It is the same result in the triple marker and oral GTT. Consequently it is the same order of important variables in CRM system. The effectiveness of CRM system is proved in this study. The CRM system is a marketing method to control and lead the customers through the segmentation of customer data. It increases the new customer aquisition, maintenance of loyal customers, augmentation of customers value, activation of potential customers and creation of life time customers. So eventually it can enlarge the customers value. The medical institution should make efforts to establish the data base enforced by the customer's information on the underlying ordinary data system to carry out the CRM system effectively. In addition, it should develop the a variety of marketing strategy in order to set up one to one marketing satisfying the needs of individual patients.

• Journal of Korean Academy of Nursing
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• v.11 no.2
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• pp.105-123
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• 1981

This study was carried out during the month of September 1976 to analyse and compare the health complaints of two groups of the university women, those who lived at home and those who lived in the university dormitory. The purpose of the study was to provide basic data required by the university health program for planning related to the health need of women students. The study sample consisted of 434 students living in the dormitory and 381 students living at home enrolled for the fall semester 1976 in a womens university in Seoul. The instrument used for the collection of data was an abridged version of a modified Cornell Medical Index. The questionarre included 35 items related to physical health complaint and 22 items related to mental health complaints. The data was treated by a computer (SPSS) using one way analysis, the Fishers' ratio and Chi-Square test at the 5％ level were used for the test for statistical significance. The interpretation of this study is limited due to the sample which was restricted to one university and not randomly selected. To guide the direction of the study, it was hypothesized that the rate of expressed health problems of students living in the dormitory would be Venter than that of students living at home. The hypothesis was tested and rejected. The following is a summary of the findings; 1. Total health (physical and mental) complaints a. There was no statistically significant difference between the home and dormitory groups with regard to total health complaints expressed. b. The rate of total complaints expressed by the home group significantly higher than dormitory group only among third year students. c. There was no statistically significant between the home and dormitory groups in their satisfaction with their economic situation. d. The home group showed a significantly higher rate of complaints related to the Nervous System compared to that of the dormitory group. 2. Physical health complaints a. Students living at home showed a significantly higher rate of physical complaints than the dormitory group. b. When the year variable was controlled, the third year was the only group which showed a different rate between home and dormitory groups; the home group presented a higher rate. c. Since the year variable seemed to affect the physical complaints those data were further analysed to see whether the specific system areas were operating as variables in each year. The results were as follow: Among the home group, First year students showed a higher rate in Family History of Disease, while the third year students more Nervous System and Cardiovascular System complaints. Among the dormitory group, only fourth year students showed a higher rate in the Skeletal-Muscular System. This was the only area the dormitory group though only for the fourth year students supported the hypothesis. d. When the economic satisfaction variable was controlled, the satisfied group was the only group which showed a different rate between home and dormitory groups; the home group presented higher rate. e. Since the economic satisfaction variable seemed to affect the physical complaints those data were further analyzed to see whether the specific system areas were operating as variables in each economic satisfaction level, but there was no statistically significant difference between home and dormitory groups. 3. Mental health complaints a. There was no significantly difference between home and dormitory groups with regard to mental health complaints expressed. b. When the year variable was controlled the third year group was the only group which showed a different rate between home and dormitory groups; the home group presented a higher rate. c. Since the year variable seemed to affect the mental complaints, those data were further analyzed to see whether the specific system areas were operatings variables in each economic satisfaction level. The result were as follows: Among the home group, the third year students showed higher rates in Inadequacy and Anxiety. d. When the economic satisfaction variable was controlled, the very satisfied group was the only group which showed a different rate between home and dormitory groups: the home group presented a higher rate. Since the economic satisfaction variable seemed to affect the mental complaints, those data were further analysed to see whether the specific system areas were operating as variables in each economic satisfaction level, but there was no statistical significant difference between the home and dormitory groups. Although the social environment of dormitory life differs from family life, there was no difference in the rate of total health problem complaints between the home and dormitory groups but the home group showed a higher rate of physical health complaints than the dormitory group. Possible positive factors influencing dormitory life and negative factors influencing family life affecting health complaints must be explored in order to relate to the health needs of the university health program. This study could not define the causes for the fewer physical complaints of dormitory students living at home. Further study of such causal factors recommended in order to provide the data needed to contribute to a more effective health program.

• Health Policy and Management
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• v.24 no.2
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• pp.128-135
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• 2014

Background: With ageing and growing importance of disease management system, it is necessary to investigate the extent of regional difference in service utilization for chronic diseases among the elderly and to reflect it in designing the system. Methods: A multiple regression analysis and descriptive statistics analyses were employed using patient survey, which covers nationwide health facilities and their users. Results: While the differences in the rate of service utilization/utilization outside living area between urban and rural areas or between income levels are not large, considerable variations are observed within urban or rural areas and within income groups. Conclusion: This results suggest that it is important to subsidize economically disadvantaged segments of the population and residents of less-favored areas to be better-equipped for chronic disease management in order to prevent the development of severe ailments and the need for treatment at higher-level medical institutions. Improvements to the service infrastructure in vulnerable regions are essential.