• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.409-410
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• 2023

In this study, the compressive strength and ultrasonic pulse velocity were evaluated according to the elapsed time on concrete mixed with normal and lightweight aggregates at early age. For evaluation in various strength ranges, the design compressive strength was set to 30, 45, and 60MPa and evaluated. As a result of the experiment, the compressive strength of concrete mixed with lightweight aggregates developed 5MPa earlier compared to normal aggregate concrete, and the UPV showed a similar tendency.

• 한국생활과학회지
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• 제19권4호
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• pp.589-599
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• 2010

When the Korean government announced the lowering of the school entrance age from 6 to 5 years in an effort to increase the fertility rate, one candidate for the Seoul mayor rode on the slogan, 'one dong, one public kindergarten'. This study attempted to show the introduction of a preschool class for six-year-olds being used as analternative to lowering school entrance age in Sweden. First, the current state of preschool class, the Early Childhood Education and Care, and the education system in Sweden were described. Next, the background for the introduction of the preschool classes was analyzed. Thirdly, the effects of preschool class were evaluated from the perspectives of 6 year-olds as well as the institutiona land social status of the ECEC. Results from this study imply not only that the lower school entrance age policy should be abolished but also preschool classes could be considered as an alternative.

• 한국건축시공학회지
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• 제7권1호
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• pp.71-77
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• 2007

This paper is to investigate the effect of the curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of the compressive strength of the concrete was conducted using the equivalent age equation and the rate constant model proposed by Carino. Correction of Carino model was studied to secure the accuracy of strength development estimation by introducing correction factors regarding rate constant and age. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of BS has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• 콘크리트학회논문집
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• 제13권5호
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• pp.447-456
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• 2001

그 동안 많은 연구자들은 콘크리트의 응력-변형률 관계의 비선형 거동을 적절한 수식으로 나타내기 위해 많은 노력을 해 왔다. 그러나 이 응력-변형률 관계에 대한 대부분의 경험식은 경화된 콘크리트에 촛점을 맞추어 왔으며, 초기재령에서의 콘크리트의 거동을 잘 나타내지 못하였다. 여기서 초기재령에서 경화시까지 걸친 전 콘크리트의 재령에 대한 폭 넓은 이해는 콘크리트구조물의 내구성과 잔존수명을 평가하는데 있어서 매우 중요하다. 본 논문에서는 5가지의 강도수준과 12시간에서 28일까지의 재령에 대하여 응력-변형률 관계를 검토하였으며, 20$\pm$3$^{\circ}C$ 에서 수중양생된 ø100$\times$200mm의 원주공시체에 대하여 1축압축강도실험을 수행했다. 실험결과에 대한 회귀분석을 수행하여 강도와 재령에 따른 응력-변형률 관계의 모델식을 제시하였으며, 제시된 모델식의 검증을 위하여 실험결과와 기존의 실험결과와 모델식에 대한 해석적 검토도 수행하였다. 해석결과, 제시된 모델식이 실험결과와 잘 맞으며 응력-변형률 관계에 강도와 재령이 미치는 영향을 잘 나타내고 있음을 알 수 있었다.

• Journal of Nutrition and Health
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• 제35권1호
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• pp.69-77
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• 2002

The purpose of this study was to determine the probability of overweight throughout childhood in relation to the presence of overweight at birch or in early childhood, and presence of overweight in children's parents. Weight and height measures were collected at birth and at ages of 7, 10, 12 years from 655 6th grade primary schoolchildren. Childhood overweight was defined as a body mass index at or above the 85th percentile for age and sex, and overweight in children's parents as a body mass index at or above 27. The prevalence of overweight increased with age of the children. Overweight at birth was not associated with overweight at 12 years of ages. However, overweight at 12 years old was already related to overweight at 7 years old. In comparison to non-overweight peers, overweight children at ages 7(OR = 7.64, 95% CI = 4.32-13.51) and 10 years(OR = 19.69, 95% CI = 11.42-33.94) had a higher rick of becoming overweight at 12 years of age. Among children who was overweight at age 7years, 60.7% remained overweight 5 years later, Yearly increment in BMI of overweight children was larger than that of non-obese children (1.15-1.65kg/m$^2$vs 0.50-0.71kg/m$^2$. As compared with the lower case in mealy increment of BMI, the probability of being overweight at age of 12 years was greater in higher case. BMI values at age 7years were positively correlated with BMI values at age of 10 and 127ear,i, and with annual increments in BMI. But those relationships with birth weight were not observed. Children were at greater risk for overweight if at least ogle parent was overweight. The odds ratio for child overweight associated with maternal overweight was 2.41(95% CI = 1,13-5.IS), and those associated with paternal overweight 1.70(95% CI = 0.92-3.17). And parents' BMIs were positively correlated with children's BMI values and yearly BMI increment. In conclusion, overweight at early childhood and annual inclement in BMI can be important in predicting the prevalence of overweight and the risk that overweight will remain after 7 years of age. The risk of being overweight throughout the childhood increases by the parents'overweight.

• 한국보육지원학회지
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• 제13권5호
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• pp.65-91
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• 2017

Objective: This study aims to investigate early childhood teachers' perception of STEAM and suggest activation measures for STEAM according to teachers' background variables. Methods: The researchers conducted a pilot study, and then did survey research for 5 weeks. The participants of this study included 523 teachers of early childhood education institutions in Gwangju metropolitan city and Jeollanam-do Province. Results: The results of this study were as follows. First, early childhood teachers perceived the necessity of STEAM differently according to their age, experience, and academic background. The higher their age, experience, and academic background were, the more they wanted to participate in further teacher training and education. In particular, early childhood teachers' perception and activation measures were very different according to their workplace. These results come from the fact that the conditions in conducting STEAM are different according to their workplace. Conclusion/Implications: In order to activate STEAM, a teacher training program including practical contents and methods should be conducted. Also, it is necessary to carefully organize the content and structure of the teacher training program according to their workplace. This study is meaningful in terms of suggesting activation measures for STEAM by showing how early childhood teachers think about STEAM and what they demand.

• Journal of Oral Medicine and Pain
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• 제21권2호
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• pp.225-242
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• 1996

The author studied to determine the sex and age of 8 ancient human skeletal remains, which had excavated from ancient tombs located in Yeanri, Kimhae. Some kinds of personal identification methods their skulls and teeth were used for this study and the results were obtained as follows : 1. Sex determination was possible in ancient teeth from 4th to 5th century, using detection of X-Y homologous amelogenin gene by polymerase chain reaction. 2. DNA analysis proved that the materials examined were all male, but which always did not coincide with the results from other methods for sex determination including comparison of sexual differentiation of cranium and teeth and use of discriminant functions in the dental measurement. 3. There was little difference of the estimated ages between the methods by regression of pulp cavity and attrition in teeth. The ages from these two methods always did not coincide with ones from evaluation closure of cranial and palatal sutures. 4. Sex and age of the materials were determined as follows ; $\cdot$ Y9 was estimated to be male in early sixties. $\cdot$ Yl2 was estimated to be male in late twenties to early thirties. $\cdot$ Y37 was estimated to be male in early forties. $\cdot$ Y70 was estimated to be male in early sixties. $\cdot$ Y87 was estimated to be male in late forties. $\cdot$ Y109 was estimated to be male in early forties. $\cdot$ Yl29 was estimated to be male in late thirties to early forties. $\cdot$ Yl42 was estimated to be male in late fifties to early sixties.

• Journal of Periodontal and Implant Science
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• 제49권5호
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• pp.287-298
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• 2019

Purpose: The aim of this retrospective study was to determine the prevalence of early implant failure using a single implant system and to identify the factors contributing to early implant failure. Methods: Patients who received implant treatment with a single implant system ($Luna^{(R)}$, Shinhung, Seoul, Korea) at Dankook University Dental Hospital from 2015 to 2017 were enrolled. The following data were collected for analysis: sex and age of the patient, seniority of the surgeon, diameter and length of the implant, position in the dental arch, access approach for sinus-floor elevation, and type of guided bone regeneration (GBR) procedure. The effect of each predictor was evaluated using the crude hazard ratio and the adjusted hazard ratio (aHR) in univariate and multivariate Cox regression analyses, respectively. Results: This study analyzed 1,031 implants in 409 patients, who comprised 169 females and 240 males with a median age of 54 years (interquartile range [IQR], 47-61 years) and were followed up for a median of 7.2 months (IQR, 5.6-9.9 months) after implant placement. Thirty-five implants were removed prior to final prosthesis delivery, and the cumulative survival rate in the early phase at the implant level was 95.6%. Multivariate regression analysis revealed that seniority of the surgeon (residents: aHR=2.86; 95% confidence interval [CI], 1.37-5.94) and the jaw in which the implant was placed (mandible: aHR=2.31; 95% CI, 1.12-4.76) exerted statistically significant effects on early implant failure after adjusting for sex, age, dimensions of the implant, and type of GBR procedure (preoperative and/or simultaneous) (P<0.05). Conclusions: Prospective studies are warranted to further elucidate the factors contributing to early implant failure. In the meantime, surgeons should receive appropriate training and carefully select the bone bed in order to minimize the risk of early implant failure.

• Asian-Australasian Journal of Animal Sciences
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• 제14권11호
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• pp.1585-1591
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• 2001

The present study was conducted to evaluate the effect of early feed restriction on growth, fat accumulation and meat composition in unsexed broiler chickens. Five hundred 7-day old unsexed broiler chickens were distributed into ten treatment groups with 5 pens of 10 broilers each group. One group was fed ad libitum as the control group and other nine groups were fed 25% ad libitum for 3, 6 or 9 days, 50% ad libitum for 3, 6 or 9 days, and 75% ad libitum for 3, 6 or 9 days, respectively. Thereafter, they were fed ad libitum to 56 days of age. The present results showed that broilers showed compensatory growth when they were restrict-refed. Feed conversion ratio was significantly lower in broilers fed 25% ad libitum for 9 days (p<0.05). Triglyceride concentration of serum was significantly lower in restricted unsexed broilers (p <0.01), whereas cholesterol concentration was not significantly different. Abdominal fat was significantly lower in broilers fed 25% ad libitum for 9 days, 50% ad libitum for 3 days and 75% ad libitum for 6 or 9 days (p<0.05). Moisture and protein contents of meats were not significantly affected. Ash content of meat was significantly higher in restricted broilers. Fat content of meat was lower in broilers fed 25% ad libitum for 9 days, 75% ad libitum for 3 to 9 days. In conclusion, broilers showed compensatory growth when they were restrict-refed at an early age. In order to achieve the success of early feed restriction (namely reduce fat accumulation and improve feed conversion ratio with comparable body weight at market age), unsexed broilers should be fed at level of 25 ad libi=tum for 9 days starting at 7 days of age.

• 콘크리트학회논문집
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• 제14권3호
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• pp.331-340
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• 2002

본 연구에서는 해사를 사용한 초기재령 콘크리트의 자기 및 건조 수축의 구속에 의한 균열발생을 재현하기 위해 유한요소 해석을 실시하였다. 이를 위해 미시역학적 관점에서 열역학적 평형관계를 토대로 해사를 사용한 초기재령 콘크리트의 수화발열 모델, 수분이동 모델 및 건조수축 예측 모델 등의 재료 모델을 정립하여 해석알고리즘을 제안하였고 초기재령에서 해사를 사용 한 콘크리트의 자기 및 건조수축의 구속에 의해서 발생하는 구속응력의 경시변화와 그에 따른 균열발생 및 시기에 관한 균열평가를 목적으로 염분 함유량을 변화시킨 콘크리트의 시편에 대하여 일축 방향 변형구속 실험을 실시하였다. 실험결과 초기재령 콘크리트내 염분 함유량의 증가가 강도발현에 큰 영향을 미치지 못하는 반면 건조수축량을 증가시키므로 일축 방향 변형 구속시 동일 재령에서 높은 구속인장력이 발생하고 그로 인해 균열발생시기를 앞당기는 것을 밝혔다. 또한 구속시험과 동일한 조건으로 해사를 사용한 콘크리트 시편에 대한 응력해석을 실시하여 부재내부에 도입된 건조수축 응력 및 균열 발생의 시간 의존적 변화를 재현하여 그 타당성을 실험결과와 비교를 통해 검증하였다.