• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.409-417
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• 1998

The 123 left hand-wrist radiographs and menarcheal ages attained by direct questioning to patients or her mothers are used, in order to exploit the relationship between the bone maturity and the menarcheal age of girls in adolescence. The results were as follows, 1. The mean age at menarche was $12.31{\pm}0.99$. 2. The onset of menarche occurred at SMI 7 and SMI 8 ($73.33\%$). The onset of menarche was correlated with skeletal age rather than chronological age. 3. There was statistically significant difference among the time passed from menarche according to skeletal maturity level. 4. The distal epiphyseal union of radius began at about 20 months after menarche. 5. In comparision of the time intervals from menarche to radial epiphyseal fusion among early, average, and late menarcheal age groups, late group had lesser time interval than other two groups.

• The korean journal of orthodontics
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• v.25 no.4
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• pp.415-423
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• 1995

In order to investigate the relationship between the menarche and the bone maturity of growing girls, the author interviewed about the date of menarche of 70 girls and assessed their bone maturity by hand-wrist radiographs. The results and conclusion were as iollows ; 1. The mean menarcheal age was $12.04{\pm}0.82$ year. 2. There was significant correlation between the time interval after menarche and the ossification stage. 3. The skeletal maturation level at menarche was stage SMI 7 and SMI 8. 4. There was statistically different among the time intervals after menarche according to the ossification stage. 5. The epiphyseal union of radius began about 2 years after menarche. According to this study, the probability of clinical use can be accepted in some range. In another words, skeletal age can be predicted by just interviewing the date and time interval of menarche without hand-wrist radiograph, also, with this information, the level of maxillofacial growth can be assessed.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.319-327
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• 2016

The objective of this study is to identify the secular trend in age at menarche and to investigate the factors influence the early menarche(<12 years old) among Korean middle and high school girls. We analyzed data from the Korean Youth Risk Behavior Web-based Survey(KYRBWS) 2006-2014. This study was a descriptive study of 216,917 Korean middle and high school girls born between 1988 and 2002. Linear trends test performed to assess the trend age at menarche and percentage of early menarche. Multiple logistic regression analysis was to assess the risk factors influence the early menarche. Mean age at menarche decreased from $12.61{\pm}1.32$ years for middle and high school girls born 1988 to $11.88{\pm}0.75$ years for those born 2002(p for trends<.001). Percentage of early menarche increased from 19.7% to 25.2% between 1988 and 2002(p for trends<.001). Living in city, higher stress level, short sleep duration, and higher body mass index were associated with an early menarche among middle and high school girls(all p<.001). We found that age at menarche is still falling in the Korean adolescents, and it need intervention strategies to control the early menarche.

• Clinical and Experimental Pediatrics
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• v.49 no.6
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• pp.610-616
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• 2006

Purpose : The purpose of this study was to evaluate the timing of sexual maturation and secular trends of menarchial age in Korean adolescents. Methods : Nine hundred eighty two school students and 119 university female students were included. Tanner's pubertal assessment method was applied using a self-assessment sheet with pictures for their developmental stages. A medical checkup database from 1,156,022 women was also used to analyze the age of menarche from the year 1900 to 1980. Results : Onset of puberty was at $11.3{\pm}1.3$ years(y) in girls and $12.1{\pm}1.5$ y in boys and total pubertal duration was 3.6 y in girls and 3.3 y in boys. Height at the onset of puberty was $146.1{\pm}7.9cm$ in girls and $152.7{\pm}9.8cm$ in boys. Weight at the onset of puberty was $39.3{\pm}6.9kg$ in girls and $47.7{\pm}14.4kg$ in boys. The mean age of menarche was $12.0{\pm}1.0y$ and mean age at nocturnal emission was $12.3{\pm}1.8y$. By age ten, 3.0 percent of girls experienced menarche, which increased to 41.1 percent by age 12, and 98.0 percent by age over 15. By SMR 2 breast stage, 18.2 percent of girls experienced menarche, which increased to 66.1 percent and 91.7 percent by SMR stages 3 and 4, respectively. By SMR 2 pubic hair stage, 52.0 percent and by SMR 3, 93.8 percent of girls experienced menarche. While the menarchial age of women born around 1980 was $12.4{\pm}1.1y$, the menarchial age of women born around 1990 was $12.0{\pm}1.1y$. Age at menarche has been advanced approximately by 2 years between 1900 and 1980 birth cohorts. Conclusion : There was a downward secular trend in pubertal timing. Age at menarche has been advanced by 2 years during the last 80 years. Further large scale, prospective studies, including inspection by specialists, are needed to provide reference data for pubertal timing in Korean adolescents.

• Journal of the Korean Data and Information Science Society
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• v.20 no.1
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• pp.139-148
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• 2009

The present study was conducted for analyzing changes in physique of at menarche of athletic and non-athletes. The maximum growth age of height and weight during menarche was not different between non-athletes and the athletes. Second, among non-athletes, those who had menarche late were taller and heavier than those who did early, and among the athletes, those who had menarche late were taller but lighter. The development rate of height was higher and the development duration was longer in the athletes than in the non-athletes. The development rate of weight was similar between the non-athletes and the athletes, but the maximum rate was higher in the athletes.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.28-35
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• 2009

Objective: The purpose of this study was to investigate the relationship between menarche and cervical vertebral maturation. Methods: Lateral cephalograms of 67 young korean girls within the range of 1 year before or after their menarche were gathered. The concavity of the cervical vertebrae base and the ratio of the base length to the 3rd and 4th cervical vertebrae anterior height were measured and analyzed. Results: The mean measured values were as follows, concavity of the 3rd cervical vertebrae base: 1.27(${\pm}0.18$) mm, concavity of the 4th cervical vertebrae base: 1.06(${\pm}0.15$) mm, ratio of the base length to the 3rd cervical vertebrae anterior height: 0.73(${\pm}0.06$) and ratio of the base length to the 4th cervical vertebrae anterior height: 0.70(${\pm}0.05$). There was a significant increase in the ratio of the base length to the 3rd vertebrae anterior height and the base concavity of the 3rd and 4th cervical vertebrae during the period of 1 year before to 1 year after their menarche. Conclusions: These characteristics of the 3rd and 4th cervical vertebrae on the lateral cephalogram can provide useful clues on evaluating the growth stage.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.485-492
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• 2008

Computers used fer light-weight computing environments are considerably limited in resources and performance running in ubiquitous environment. Because of the limited resources, it is difficult to apply existing security technologies to the light-weight computers. In this paper, light-weight security software is implemented using RC-5 encryption and SHA-1 authentication algorithm which is appropriate for light-weight computing environments. The design of components based on security software of a light-weight computer application and the test-bed for security software are presented. The simulation verifies the correctness of the security software. The architecture of the light-weight and reconfigurable security software for light-weight computer applications is proposed. The proposed security software is small size and provides reconfigurable security library based on the light-weight component and the software manager that configures software platform is loaded with the library at the time it is needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.248-248
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• 2004

초경합금재 (cemented carbides)는 WC(텅스텐 카바이드, 탄화텅스텐)과 Co(코발트)를 주성분으로 한 복합재료로서 저온경도와 고온경도가 뛰어 나며, 압축강도와 강성이 높은 것 등, 제반 물리적 성질이 안정되어 있다 이와 같은 우수한 특징을 이용하여, 초경합금재는 다양한 분야에 이용되고 있는데, 크게 나누어 절삭 공구용으로 뿐만 아니라 IT 관련, 환경 관련 산업용, 광산용 공구, 건설 공구, 철강의 압연 롤러 등의 내마멸, 내충격용 재료에도 많이 사용된다. 이들 가운데, 내마멸, 내충격용으로 사용되는 것은 절삭 공구용 초경합금재에 비해 결합제인 코발트를 많이 함유하며 경질 성분의 텅스텐 카바이드의 입자 지름도 거칠고 크다.(중략)

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.255-255
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• 2013

WC-Co 초경합금은 실온경도, 고온경도, 강도, 내마모, 내충격 등 기계적 특성이 우수하여 공구재료, 절삭공구 및 고압용 부품 등 다양한 응용분야를 가지고 있으며 WC-Co 분말 코팅같은 경우 항공분야, 일반 공업 분야에 내마모 특성 및 내열특성 향상을 위한 코팅용 소재로서 활용되어 지고 있다. 활용분야가 넓은 WC-Co 초경합금의 제조방법은 WC, Co 분말을 혼합하여 약 900도에서 1차 예비소결 후 원하는 형상 가공 후 약 1,300~1,600도에서 2차 소결을 진행한다. 지금 현재 초경분말의 조성, 크기와 같은 변수들에 따른 초경합금의 기계적 특성 변화에 대한 연구가 계속적으로 진행되고 있다. 본 연구에서는 WC-Co 분말의 소결 특성을 향상시키고자 Planetary ball mill 장비를 활용하여 볼 밀링 공정을 진행하였고 Spark plasma sintering 장비를 활용하여 빠른 소결을 진행하였다. WC-Co 분말의 미세구조, 입도, 조성 및 분산의 변화를 관찰하기 위해 볼 밀링 전, 후 분말을 분석하였고 제조된 분말의 소결 특성을 확인하기 위해 상용화 된 WC-Co 분말의 소결 특성과 비교 평가하였다. 분석 결과 볼 밀링 공정 후 분말은 약 15 ${\mu}m$에서 4.4 ${\mu}m$로 미세해지는 것을 확인하였고 밀링 후 분말로 초경합금을 제작하였을 때 기존 상용화 초경합금제작 온도보다 약 100~400도 낮아지면서 경도 값은 약 20% 향상된 것을 확인할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5737-5744
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• 2013

This study was performed to identify the association between the menarche experience and mental health in middle school girls aged 14. The subjects were selected using data from the 8th Korean Youth Risk Behavior Web-based Survey (KYRBWS-V), which included 5,991 girls in 1st grade of middle school. Data were analyzed using the PASW 18.0 program for frequency analysis, t-test, chi square and logistic regression analysis. As to results, we found 4,473 girls who had experienced menarche (mean age, 12.8 0.9 years) and 1,518 girls hadn't experienced menarche. In the logistic regression analysis between the menarche experience and mental health behaviors, the odds ratio (OR) [95% confidence interval (CI)] for perceived stress (OR=1.39, 1.20-1.62, p<0.001), perceived depression (OR=1.25, 1.10-1.42, p<0.05), suicide thinking (6OR=1.60, 1.38-1.87, <0.001), suicide planning (OR=1.66, 1.33-2.81, p<0.001) and suicide trial (OR=1.42, 1.09-1.86, p<0.05) were higher in the menarche experience group than in the menarche non-experience group. Our results indicate, a viable association between the menarche experience and mental health in the 1st grade of middle school girls, and suggests that the menarche experience is an important factor influencing adolescent girls' mental health.