• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.9-18
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• 2004

The IEEE 802.11 Distributed Coordination Function(DCF) protocol provides a contention-based distribution channel access mechanism for stations to share the wireless medium. However, the performance of the DCF drops dramatically in terms of throughput, delay and delay jitter as the number of active stations becomes large. In this paper, we propose a simple and effective scheme, called DCF/VG(Distributed Coordination Function with Virtual Group), for improving the performance of the IEEE 802.11 DCF mechanism. In this scheme, each station independently decides the virtual group cycle using the information provided by the carrier sensing mechanism. The virtual group cycle consists of one or more virtual groups and a virtual group includes an idle period and a busy period. Each station operates in only one out of several virtual groups of the virtual group cycle and does not operate in the others. In other words, each station decreases its backoff counter and tries to transmit a packet only in its virtual group like the IEEE 802.11 DCF. Performance of the proposed scheme is investigated by numerical analysis and simulation. Numerical and simulation results show that the proposed scheme is very effective and has high throughput and low delay and jitter under a wide range of contention level.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.63-70
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• 2017

The purpose of this study was compare to the patient setup deviation of two different type thermoplastic immobilization masks for glottis cancer in the intensity-modulated radiation therapy (IMRT). A total of 16 glottis cancer cases were divided into two groups based on applied mask type: standard or alternative group. The mean error (M), three-dimensional setup displacement error (3D-error), systematic error (${\Sigma}$), random error (${\sigma}$) were calculated for each group, and also analyzed setup margin (mm). The 3D-errors were $5.2{\pm}1.3mm$ and $5.9{\pm}0.7mm$ for the standard and alternative groups, respectively; the alternative group was 13.6% higher than the standard group. The systematic errors in the roll angle and the x, y, z directions were $0.8^{\circ}$, 1.7 mm, 1.0 mm, and 1.5 mm in the alternative group and $0.8^{\circ}$, 1.1 mm, 1.8 mm, and 2.0 mm in the alternative group. The random errors in the x, y, z directions were 10.9%, 1.7%, and 23.1% lower in the alternative group than in the standard group. However, absolute rotational angle (i.e., roll) in the alternative group was 12.4% higher than in the standard group. For calculated setup margin, the alternative group in x direction was 31.8% lower than in standard group. In contrast, the y and z direction were 52.6% and 21.6% higher than in the standard group. Although using a modified thermoplastic immobilization mask could be affect patient setup deviation in terms of numerical results, various point of view for an immobilization masks has need to research in terms of clinic issue.

• Korean Journal of Social Welfare
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• v.66 no.1
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• pp.61-85
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• 2014

Lately, as the problem of the aged poverty becomes a big social issue, this paper studies the problem of financial stability with respect to the income and consumption of before-and-after retirement generations. After dividing the data in Korean Longitudinal Study of Ageing(KLoSA) into retired and non-retired groups, this study compares the difference among ageing groups by cross analysis and t-test. First, the result tells that the total personal income of retired group is lower than the one of non-retired group. Second, the public pension income benefit ratio of retired group is only 30% of it's total income, and the amount of public pension appears to be 40% of the total pension income. The benefit ratio of the personal pension income is low as about 1% in both groups, The private transfer income of the retired group takes relatively large portion in its total personal income. Third, as people gets older, financial stability gets worse because consumption does not decrease as much as the income decreases. Fourth, it is turned out that the expectation of old life supporting from nation is low in both groups. Fifth, the factors that affects the income of the public pension in the retired group are gender, age, education, and health status, when compared with the factors to the personal total income of the non-retired group. In terms of policy, this paper emphasizes the needs of the intensification of the public pension and the support for the revitalization of the personal pension.

• Journal of Marine Life Science
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• v.1 no.1
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• pp.56-62
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• 2016

In the present study, to clarify a possible relevance of blind-side hypermelanosis to chronic stress in cultured flounders, P. olivaceus, a serial experiment was tried with comparison of biochemical stress factors between wild type and hypermelanic type in cultured olive flounders. The mean size of experimental animal was total length 21.5±0.42 cm and body weight 87.5±6.1 g. The initial malpigmented area rate on the blind side skin was 0.63±0.12% and 16.7±4.7%, respectively, in the wild type and the hypermelanic type. The stress factors surveyed in the experiment were glucose (GLU), total protein (TP), cortisol, free type-thyroid hormones (FT₃ and FT₄) in plasma, and also moisture, crude protein, crude lipid, and crude ash in body muscle. As a result, GLU and TP were higher in hypermelanic type than in wild type. Plasma cortisol was also higher in hypermelanic type than in wild type. In FT₃ and FT₄, any difference between two groups was not observed. In body nutrient factors, the moisture and the crude ash in body composition were not different between two groups, but the crude protein was low and the crude lipid was high in the hypermelanic type. Therefore, it is concluded that the blind-side hypermelanosis of cultured flounders could be related with a chronic stress.

• Journal of the Korea Computer Industry Society
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• v.2 no.2
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• pp.203-210
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• 2001

To estimate relational models and test the theoretical hypotheses of binary tree search algorithms, we built binary search trees with random permutations of n (number of nodes) distinct numbers, which ranged from three to seven. Probabilities for building binary search trees corresponding to each possible height and balance factor were estimated. Regression models with variables of number of nodes, height, and average number of comparisons were estimated and the theorem of O(1g(n)) was accepted experimentally by a Lack of Test procedure. Analysis of Variance model was applied to compare the average number of comparisons with three groups by height and balance factor of the trees to test theoretical hypotheses of a binary search tree performance statistically.

• The Korean Journal of Applied Statistics
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• v.26 no.6
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• pp.889-902
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• 2013

Several goodness-of-fit test statistics have been proposed for a multinomial logit regression model; however, the properties of the proposed tests were not adequately studied. This paper evaluates three different goodness-of-fit tests using grouping strategies, proposed by Fagerland et al. (2008), Bull (1994), and Pigeon and Heyse (1999). In addition, Pearson (1900)'s method is also examined as a reference. Simulation studies were conducted to evaluate the four methods in terms of null distribution and power. A real data example is presented to illustrate the methods.

• Proceedings of the Korea Contents Association Conference
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• 2012.05a
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• pp.97-98
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• 2012

본 연구의 목적은 치료면의 질에 따른 복합균형운동프로그램이 균형능력에 어떠한 영향을 미치는지 알아보기 위해 본 연구를 실시하였다. 정상 성인 21명을 대상으로 연구를 진행하였으며 복합균형 운동을 실시한 Aero-step군(ASG)과 평지면군(Flat floor group;FFG) 그리고 처치 없이 실시한 대조군에게 Biodex balance system을 이용하여 전체안정성지수(Overall stability index;OSI), 전후안정성지수(Anteroposterior index;APSI), 좌우안정성지수(Mediolateral stability index;MLSI)를 측정하였다. 본 연구 결과에서 전체안정성지수와 전후안정성지수는 Aero-step군의 그룹 내 비교에서 유의한 차이가 있었으며 좌우안정성지수는 평지면군의 그룹 내 비교에서 유의한 차이가 있었다. 전후안정성지수의 그룹간 비교에서 유의한 차이가 있었다. 본 연구의 결과에 따라 치료면의 질에 따른 복합균형운동이 안정된 지지면 보다는 불안정한 지지면의 균형능력 향상에 더 효과적이라 사료된다.

• The Korean Journal of Nuclear Medicine Technology
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• v.20 no.2
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• pp.54-61
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• 2016

Purpose Precocious Puberty is defined as the development of secondary sexual characteristics in girls younger than 8 years, and boys 9 years. Cause premature closure of the epiphysis is a disease that eventually decreases the final adult height. In this study, we retrospectively analyzed to evaluate the diagnostic difference the GnRH (Gonado-tropin-releasing Hormone) stimulation test results with medical records of precocious puberty in girls. Materials and Methods From February 2015 to December 2015 it was enrolled in the girls 118 people who visited the Seoul National University Bundang Hospital, Pediatrics, Endocrinology Internal Medicine. True precocious puberty group (n=57), early puberty group (n=39), were divided into Premature thelarche (n=22) group. A Tanner stage, chronological age, bone age, height, body weight for each group was determined by examining the mean${\pm}$standard deviation. GnRH test result was compared LH (Basal, 30 min, 45 min, 60 min), FSH (Basal, 30 min, 60 min) for each group, Each group LH, FSH Peak value distribution, the mean${\pm}$standard deviation was calculated for the peak LH/LH basal ratio, peak LH/Peak FSH ratio. The significance probability (P-value) between the value of each third group was determined. Results The average height of the true precocious puberty group $131{\pm}14.85$, the mean weight was $28.80{\pm}4.93$, the average chronological age $7.1{\pm}0.81$, the mean bone age was $9.9{\pm}0.9$, The average height of early puberty group was $134{\pm}5.10$, the average weight $28.50{\pm}4.43$, the average chronological age $8.05{\pm}0.03$, the mean bone age was $10.0{\pm}0.62$, The average height of Premature thelarche $129{\pm}6,01$, the average weight was $28.65{\pm}5.98$, the average chronological age $7.02{\pm}0.58$, the mean bone age was $8.04{\pm}1.29$. There was no significant difference when compared to the height and weight. There was a significant difference between the groups in the chronologic age and bone age difference (P <0.0002) True precocious puberty group showed peak LH levels at 30'(82.5%), 45'(12.3%), 60'(5.3%), in Peak FSH 30'(8.8%), 60'(91.2%). Early Puberty group showed high values in Peak LH at 30'(79.5%), 45'(17.9%), 60'(2.6%), in peak FSH levels at 30'(7.7%), 60'(92.32%). In Premature thelarche Group it showed the Peak LH levels at 30'(30%), 45'(59%), 60'(9.09%), Peak FSH levels at 30'(0%) 60'(100%). When compared with the The Peak LH/basal LH ratio, True precocious puberty group was $19.09{\pm}17.15$, early puberty group was $15.23{\pm}10.88$, Premature thelarche group showed significant differences between the three groups as $4.93{\pm}4.36$.(P <0.0001) LH Peak/FSH Peak ratio, true precocious puberty group was $1.222{\pm}0.77$, early puberty group was $1.34{\pm}1.23$, Premature thelarche group showed significant differences between the three groups as $0.3{\pm}0.09$(P <0.0001) Conclusion In order to diagnose the true precocious puberty have a diagnostic value when the LH peak after GnRH stimulation is increased by more than two to three times compared to baseline or a predetermined level or more than 5~10 IU/L increases. GnRH Test is a test for a long time and the patient discomfort due to repeated blood sampling, but the hypothalamus-pituitary gland- gonad axis activity evaluate and is the most basic accurate test in the differential diagnosis of precocious puberty disorders.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.300-306
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• 2013

Purpose: This study was to evaluate the accuracy of how to use the Mechanical Torque-Limiting Devices. Materials and methods: Three different implant manufacturers (Dentium, Osstem, Shinhung) were prepared for each two implant torque controllers. Divided into two groups depending on the method used for removal torque was measured. Repeated measures of ANOVA test (${\alpha}=.05$) was used as statistics to evaluate the effect of repeated loading number on the removal torque. Independent t-test was used to evaluate the difference in removal torque of two groups. Results: The removal torque significantly decreased as the number of loading repetition increased (P<.05). There was significant difference between two groups. Conclusion: Loosen the handle part of the implant torque controllers spring resilience to recover one group compared to the group that did not, showed a little more closed to the reference value.

• Journal of Service Research and Studies
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• v.11 no.4
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• pp.43-55
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• 2021

This study analyzed the efficiency of medical services in OECD member countries by dividing it into operational efficiency and quality efficiency. For this purpose, data from 2017-2019 OECD Health Statistics were used. As the analysis method, super efficiency was measured by applying an output-oriented Variable Returns to Scale (VRS) model. As a result of the analysis, Switzerland, Korea, and Italy were included in the high group of operational efficiency, Canada, Greece, Denmark, etc. in the medium group, and Belgium, Germany, and Spain in the low group. Based on quality efficiency, Norway, Switzerland, and Spain are in the high group, and Greece, Denmark, Mexico, etc. are in the medium group, and the Netherlands, Germany, Belgium, etc. were included in the low group. As a result of comparative analysis of efficiency by OECD member countries as of 2018, it was found that Korea's operational efficiency was the most efficient and quality efficiency was inefficient. Korea (0.998) should improve life expectancy by 0.2 (0.2%) and subjective health perception by 44.2 (138.1%) by benchmarking Greece (0.422), Switzerland (0.207), and Spain (0.371) to improve quality efficiency. Unlike most previous studies that focused on operational efficiency, this study measured quality efficiency together and analyzed the efficiency of the medical service industry in each OECD member country. Through this, this study has implications in that it confirmed the international competitiveness of the domestic medical service industry and suggested ways to improve efficiency.