• Honam Mathematical Journal
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• v.45 no.3
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• pp.542-554
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• 2023

Given a real number α, the Lagrange number of α is the supremum of all real numbers L > 0 for which the inequality |α - p/q| < (Lq²)^-1 holds for infinitely many rational numbers p/q. All Lagrange numbers less than 3 can be arranged as a set {l_p/q : p/q ∈ ℚ ∩ [0, 1]} using the Farey index. The present paper considers a function C(α) devised from Sturmian words. We demonstrate that the function C(α) contains all information on Lagrange numbers less than 3. More precisely, we prove that for any real number α ∈ (0, 1], the value C(α) - C(0) is equal to the sum of all numbers 3 - l_p/q where the Farey index p/q is less than α.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.842-849
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• 2000

In this paper, We analyzed the protocol to improve the performance of the multicast traffic processing in WDM networks. In the protocol, control channels are devided into contention-less minislots and contention minislots. And the packets which fail to have successful reservation in the present time slot have priority to have successful reservation in the contention-less minislots of the next time slot. Therefore, control channel contentions and destination conflicts can be reduced with the use of contention-less minislots. For the multicast traffic processing, the theoretical analysis and computer simulation are important to estimate the network performance and to calculate the optimized number of contention-less minislots. In this paper, the state transition probability of the number of contention-less minislots and arrival packets are calculated using 4-dimension matrix. The maximum number of contention-less minislots is equal to the number of channels for maximum performance improvement of the system. It is theoretical analysis and prove to computer simulation the performance of the protocol.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.3
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• pp.216-223
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• 2006

The high efficiency full-bridge LLC resonant converter using a contact-less transformer Is proposed for the photovoltaic power generation system. For the series resonance with a series capacitor, the LLC resonant converter utilizes the leakage inductance and magnetizing inductance of a contact-less transformer Unlike the conventional series resonant converter operated to the continuous resonant current at above resonance frequency, the proposed converter operates to the discontinuous resonant current at the narrow frequency control range below resonance frequency. Due to the discontinuous mode resonant current, the proposed converter can be achieved the zero voltage switching (ZVS) in the primary switches and the zero current switching (ZCS) in the secondary rectification diodes without my auxiliary circuit. In this paper, the experimental results of the proposed full-bridge LLC resonant converter using a contact-less transformer are verified on the simulation based on the theoretical analysis and the 150W experimental prototype.

• Journal of the Korean Home Economics Association
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• v.36 no.9
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• pp.49-62
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• 1998

This paper investigates the parenting stress of fathers who have preschooler. At first, a causal model constructed, including the parenting stress as a dependent variable and the psychological characteristics of paternal self-esteem and parenting efficacy as parameters. Based on the change of parenting stress, self-esteem and parenting efficacy according to various pertinent to fathers, the causal effect of various variables effecting on the paternal parenting stress is analyzed. The SPSS PC program was used for the statistical analysis, where fully exploited were frequencies, percentages, means, standard deviations, Cronbach α, one-way analysis(ANOVA), path analysis. The results can be summarized into 3 parts, in conclusion: 1) The younger a father is, the higher paternal self-esteem becomes. Paternal self-esteem trend was there, for a father who is a member of large family, and for a father whose education level is high, and for a father whose occupation is professional. Regarding parenting sense of competence, a father shows confidence when he has more income, more educated and less children. 2) The variable analysis effecting on the parenting stress dut to the paternal environment shows that a father feels more stress when his income is less and his spouse is working. The sub-factor analysis on the parenting stress shows that 'typical stress dut to the parenting' increases when his income is less and his spouse is working, and 'pressures pertaning to the parental role and distress' increases for a father with less income, working spouse, less educated and non-professional job. Further 'guilty to the parenting by others' shows higher for a father with less income and a working spouse. 3) The path analysis, which were performed to check the causality of the parenting stress dut to various variables, shows that the self-esteem and the parenting efficacy are significant factors directly effecting on the paternal parenting stress, and the job-satisfaction and marriage-satisfaction are significantly effecting on the parenting stress both directly and indirectly.

• Korean Journal of Community Nutrition
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• v.10 no.6
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• pp.825-834
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• 2005

This study was to investigate the effects of the body fat $\%$ on life styles and self-recognition of health conditions in hotel culinary college students. This survey was conducted using the questionnaires for 144 students (110 males, 34 female) in Hongseung-located college. More exercise time and less frequency of alcoholic beverage they intake, lowered their body fat $\%$. Males did stronger exercise and had lower body fat $\%$ than females. The stronger exercise they did, the lower body fat $\%$ they had, and were more satisfied with their present weight. Since they had more alcoholic beverage, they smoked more. Less smoking, more abdominal obesity they were. The less satisfaction with their body weights, the higher body fat $\%$ they had. The obese less were content with their weights. More recognition of obese shape, higher body fat $\%$ they had and abdominal obesity they were. Female had higher body fat $\%$ and were more abdominal obesity, did weak action, less smoke and weak exercise than male. Higher body fat $\%$ they had, more abdominal obesity they were. The more part time jobs they had, they did not smoke or were not satisfied with their body weights. Female students in culinary arts division had higher body fat $\%$ and were dissatisfied with their body weights and did less exercise or subnormal exercises. (Korean J Communty Nutrition 10(6) : $825\∼834$, 2005)

• Journal of Environmental Impact Assessment
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• v.7 no.1
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• pp.11-22
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• 1998

In Korea, the Demilitarized Zone(Hereafter DMZ) and the vicinity have special importance for a natural ecosystem research. However, We have difficulty in studying this region due to the access control. The purpose of this study is to analyze the landcover and the vegetation status of DMZ and the vicinity using remote sensing and GIS techniques. The site was divided into two regions; less than 2km from DMZ and less than 10 km from DMZ. The analyzed results of this study are as follow. First, the result of vegetation analysis is that the region of South and North Korea are similar in the area less than 2km from DMZ. However, the region of South Korea have good vegetation status than the region of South Korea in the area less than 10km from DMZ. Second, the result of landcover analysis is that the ratio of the landcover of South and North Korea decreased forest, agricultural and grass, built-up, barren area by turns in the area less than 2km from DMZ. However, the built-up area of South Korea increased as much as the forest area decreased and the other areas of North Korea increased as much as the forest area decreased in the area less than 10 km from DMZ. There are some differences in landcover between analyzed result and an existing statistical data. The causes are using one season setellite images, and an existing statistical data with landuse types. The analysis using remote sensing and GIS techniques is the most suitable method to understand the landcover and vegetation status of DMZ and the vicinity. Further studies are expected to overcome the limitation of this study.

• Pediatric Infection and Vaccine
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• v.15 no.1
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• pp.5-11
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• 2008

Primary rotavirus gastroenteritis infection usually occurs in infants under 2 years of age worldwide regardless of level of hygiene, quality of water, food or sanitation or type of behavior. In Korea, the disease mostly occurred in infants under 2 year old, and usually in late fall to early winter with the highest incidence shown in November until early 1990s. However, since then, relatively the age incidence of this infection has increased in children over 2 years old, and it has mainly occurred in late winter to early spring with the highest incidence shown between February and March. And rotavirus gastroenteritis serotypes varied year to year as well as varied by year within the same region in our country. The comparison of severity scores between age groups in Korea showed that severity score was lowest in infants less than 3 months and highest in infants more than 6 months and less than 12 months, and hospitalization period between age groups was longest in infants older than 3 months and less than 3 months and highest in infants more than 6 months and less than 12 months and less than 6 months. In this aspect, rotavirus vaccines should be given to infants less than 2 years of age in whom the incidence of rotavirus gastroenteritis is the highest, and vaccination should be ideally started before 3 months considering hospitalization period and severity of rotavirus gastroenteritis. However, It should be careful for the introduction of new rotavirus vaccine, and the effectiveness of rotavirus vaccines should be assessed by long-term post marketing surveillance. And we guess an multivalent vaccine may be an ideal rotavirus vaccine to prevent primary infection caused by variable rotavirus strains in Korea. In addition, clinical epidemiology studies on rotavirus gastroenteritis which evaluate the age and serotypes related severity should be continuously conducted in various regions.

• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.119-142
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• 2003

In the present work the knowledge of dental health as well as dental prosthesis has been studied on the basis of analysis of current dental prosthetic treatments for dental diseases prophylaxis and the final decision for dental prosthetic appliance. The results have been analyzed by the current dental health care and the subjective acknowledgement from 700 people of urban as well as rural inhabitance in our country. The results from the present work have been summarized as following: Depending dental status has been shown worse to be in the cases of divorce and bereavement, age and less educated or jobless. It is also interesting to note that the dental status has shown to be even worse than health status. It has been shown that the dental prosthetic treatments have been mainly caused by the oral disease (62.2%) and depend on the age and the educational level. According to the actual status of dental prosthetic treatments, the fixed partial denture was the most case (78.9%) that increased as divorced, bereavement and as less educated, less income, retired and jobless as well as from urban to rural. As a clinic for the dental prosthetic treatments, dental clinics have been most frequent visited as indicated by 59.6%, then the un-licensed dentist (6.5%), then the hospitals (3.7%), then the public health centers (2.2%). Most of those who are older in age, less educated and jobless have been treated by the un-licensed dentists. In point of view on the cost for dental prosthetic treatments, 93.1% have claimed to be too expensive, in as the divorced and the bereaved, the older age, the less educated and the jobless. About satisfaction of dental prosthetic treatments, 51.4% was satisfied, 39.4% was normal and 9.2% was dissatisfied. Most of people experienced increasing levels of satisfaction as their income increase. Most in the age range of 40-60 have wanted to be insured for the dental prosthetic treatments. It is also interesting to note that the older age and the less educated wanted to apply this kind of insurance.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.98-102
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• 2012

These days, Uncooled IR Systems are more popular in the area of defense and aerospace than before. Uncooled IR Systems are widely used as core technology for making unmanned systems and detecting enemy objects during the day and night in the distance. Recently, researches on TEC-less IRFPA have been increased to minimize the power consumption and to make a smaller system than before. For this, it needs to find adequate NUC(Non-Uniformity Correction) coefficients as FPA(Focal Plane Array) temperature changes. In this paper, we propose a new NUC coefficient estimating technique, DCCE-LI(Dynamic Calibration Coefficients Estimation with Linear Interpolation), for TEC-less IRFPA. It is based on a linear interpolation method and it can estimate NUC coefficients in real-time. So, by testing and evaluating it with some IR images, we conclude that the quality of IR images using proposed method is better than applying static coefficients.

• Journal of Korea Foundry Society
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• v.33 no.5
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• pp.215-225
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• 2013

The alloys required for fossil power plants are altered from stainless steel that has been used below $600^{\circ}C$ to Ni-based alloys that can operate at $700^{\circ}C$ for Hyper Super Critical (HSC) steam turbine. The IN740 alloy (Special Metals Co. USA) is proposed for improved rupture strength and corrosion resistance at high temperature. However, previous studies with experiments and simulations on stable phases at about $700^{\circ}C$ indicated the formation of the eta phase with the wasting of a gamma prime phase, which is the most important reinforced phase in precipitation hardened Ni alloys, and this resulted in the formation of precipitation free zones to decrease the strength. On the basis of thermodynamic calculation, the new Ni-based superalloy named LESS 1 (Low Eta Sigma Superalloy) was designed in this study to improve the strengthening effect and structure stability by depressing the formation of topologically close packed phases, especially sigma and eta phases at high temperature. A thermal exposure test was carried out to determine the microstructure stability of LESS 1 in comparison with IN740 at $800^{\circ}C$ for 300 hrs. The experimental results show that a needle-shaped eta phase was formed in the grin boundary and it grew to intragrain, and a precipitation free zone was also observed in IN740, but these defects were entirely controlled in LESS 1.