• 한국방재학회:학술대회논문집
• /
• 2007.02a
• /
• pp.340-343
• /
• 2007

The temperature variation of concrete pavement at early-age significantly affects the initiation and movement of joint cracks. For this analysis, we have built on IIA(Incheon International Airport) concrete pavement construction zone, and we measured the temperature and movement of the concrete slabs by using thermocouples, moisture sensors, V/W strain gages, and Demac discs. The analysis results showed that pavement's temperature significantly affected the joint movement. The widths of the joint cracks increased at evening and early in the morning when the temperature dropped but, those decreased in the day time when the temperature rose because of the effect of thermal expansion of the concrete slabs. The movements of the joints where the cracks never developed showed opposite trend to the cracked joints.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2009.05b
• /
• pp.53-56
• /
• 2009

This study reviewed the characteristics of concrete made of performance improving mixture materials based on KOH as a means to resolve the problems of initial quality reduction that result in concretes with blast furnace slag powder. Summarizing the results, first as the characteristics of fresh concrete, liquidity was found to reduce in general with increased BS substitution ratio. Objective range of liquidity was not satisfied in all mixes according to the use of performance improving mixture materials. Air capacity was satisfied to the objective range in all mixes. As the characteristics of hardened concrete, while compressive strength showed a decreasing trend with increasing BS substitution ratio at early age, increasing trend was shown by the plain with increasing BS substitution ratio at later age. On the other hand, K1 and K2 were only effective among mixture materials at early age, but K1F30 showed excellent strength at both early and later ages.

• Neonatal Medicine
• /
• v.25 no.3
• /
• pp.96-101
• /
• 2018

Purpose: We aimed to evaluate the respiratory illness-related hospital visits (out-patient clinics, emergency room, and re-admission) of preterm infants, and compare them according to corrected age and prematurity. Methods: We reviewed the medical records of preterm infants born at <37 weeks of gestation admitted to the neonatal intensive care unit (NICU) at Inha University Hospital between January 2012 and June 2015. Infant follow-up appointments in both neonatology and pulmonology out-patient clinics occurred for at least 2 years after NICU discharge. Results: The proportion of infants who visited the hospital due to any respiratory illness was as high as 50% until 12 months of corrected age, and subsequently decreased over time. Hospital admission was significantly higher in early preterm infants (<34 weeks of gestation) compared to late preterm infants (${\geq}34$ and <37 weeks of gestation). The proportion of infants who were re-admitted due to lower respiratory tract illness was significantly higher until 6 months of corrected age compared to the later, and did not differ between early and late preterm infants. Conclusion: The proportion of hospital visits of preterm infants due to respiratory disease was high until 12 months of corrected age. Most notably, the re-admission proportion from lower respiratory tract illness was high under 6 months in both early and late preterm infants. Preterm infants within this age that are visiting the hospital with respiratory symptoms should be carefully observed and followed up.

• Journal of Korean Society of Forest Science
• /
• v.84 no.3
• /
• pp.356-360
• /
• 1995

Korean white pine(Pinus koraiensis S.et Z.) is one of the important silvicultural species due to its quality timber in addition to edible pine - nut production. Selective breeding method is under progress to improve growth and nut production for this species. This study was carried out to obtain genetic information necessary for establishing advanced generation seed orchard, such as genetic parameters and efficiency of early selection. Open - pollinated cones were collected from 50 plus trees. In the spring of 1986, test plantations were established at 3 different sites with 4 - year - old seedlings. Seedling height was measured from age 5 to 10 in plantations. Genetic and phenotypic correlations based on the log of the ratio of two ages (LAK) were expressed as simple regression with statistical significance($r^2=0.7862$ and 0.8256, respectively). If 20 years is presumed to mature, the most efficient age for early selection is 3 years after planting with efficiency of 1.96.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.741-744
• /
• 2008

Quality control of early age concrete significantly influences the long term performance. Primary factors for early age concrete quality control should include the relative humidity and temperature variation, and these are more important as structures become massive and huge. Temperature raise due to cement hydration causes stress, which can develop to cracking with internal and/or external restraints. Exposure conditions including ambient temperature, humidity and wind also significantly affect the cracking behavior of early age concrete. Among many of studies on the early age concrete behavior, investigation on the variation of temperature and relative humidity internal of concrete is not common. That is in part because the difficulties in measuring the relative humidity and temperature inside the concrete. This study used a digital sensor with an appropriate logger to measure internal temperature and relative humidity. This direct measuring method is expected to provide more reliable and comprehensive data acquisition on the early age behavior of concrete.

• Nuclear Engineering and Technology
• /
• v.44 no.5
• /
• pp.523-534
• /
• 2012

The objective of this study was to experimentally investigate the effect of heat curing methods on the temperature history and strength development of slab concrete exposed to $-10^{\circ}C$. The goal was to determine proper heat curing methods for the protection of nuclear power plant structures against early-age frost damage under adverse (cold) conditions. Two types of methods were studied: heat insulation alone and in combination with a heating cable. For heat curing with heat insulation alone, either sawdust or a double layer bubble sheet (2-BS) was applied. For curing with a combination of heat insulation and a heating cable, an embedded heating cable was used with either a sawdust cover, a 2-BS cover, or a quadruple layer bubble sheet (4-BS) cover. Seven different slab specimens with dimensions of $1200{\times}600{\times}200$ mm and a design strength of 27 MPa were fabricated and cured at $-10^{\circ}C$ for 7 d. The application of sawdust and 2-BS allowed the concrete temperature to fall below $0^{\circ}C$ within 40 h after exposure to $-10^{\circ}C$, and then, the temperature dropped to $-10^{\circ}C$ and remained there for 7 d owing to insufficient thermal resistance. However, the combination of a heating cable plus sawdust or 2-BS maintained the concrete temperature around $5^{\circ}C$ for 7 d. Moreover, the combination of the heating cable and 4-BS maintained the concrete temperature around $10^{\circ}C$ for 7 d. This was due to the continuous heat supply from the heating cable and the prevention of heat loss by the 4-BS. For maturity development, which is an index of early-age frost damage, the application of heat insulation materials alone did not allow the concrete to meet the minimum maturity required to protect against early-age frost damage after 7 d, owing to poor thermal resistance. However, the combination of the heating cable and the heat insulating materials allowed the concrete to attain the minimum maturity level after just 3 d. In the case of strength development, the heat insulation materials alone were insufficient to achieve the minimum 7-d strength required to prevent early-age frost damage. However, the combination of a heating cable and heat insulating materials met both the minimum 7-d strength and the 28-d design strength owing to the heat supply and thermal resistance. Therefore, it is believed that by combining a heating cable and 4-BS, concrete exposed to $-10^{\circ}C$ can be effectively protected from early-age frost damage and can attain the required 28-d compressive strength.

• Journal of Animal Environmental Science
• /
• v.4 no.1
• /
• pp.1-8
• /
• 1998

The objective of this study was conducted to develope a mobile pig nursery(MPN) for segregation of early weaned piglet. The units of MPN was consisted of 4 rectangle-type pens, 1 workroom, 2 doors, 3 windows, 1 air-inlet, 1 exhaust fan, and 1 cooling and heating system. Total of 40 piglet were weaned at 7 days of age. The period of the feeding test was 63 days. The results obtained are as follows: 1. The insulation thickness was 70, 70 and 50 mm of roof, floor and wall, respectively. R-value was 15.32 and 10.32 of roof and wall, respectively. 2. Exhaust fan( 30.48) was installed near back door 40cm from the bottom. When exhaust fan speeds were 15, 20, 30 and 35%, Air ventilation was required 9.75, 7.07, 1.72, 1.45 minutes of respectively. 3. Average temperature in the MPN was able to maintain 27∼28$^{\circ}C$ from 7∼28 days of age, 24∼25$^{\circ}C$ from 35∼56 days of age and 20∼21.5$^{\circ}C$ from 56∼70 days of age. 4. Average daily gain, feed intake and feed conversion were 420.6g, 761.5g, 1.81 respectively.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04b
• /
• pp.531-537
• /
• 1998

Recently, the pile driving or blasting works are increasingly done in many areas to perform large scale construction projects. The vibrations from these blasting works may affect the properties of concrete, especially young concrete. The purpose of present study is to explore the effects of vibration at early ages on the properties of concrete. To this end, comprehensive experimental study is conducted in the present study. The major test variables are peak particle velocity or vibration velocity and the age at vibration. The compressive strengths and bond strengths are measured for all the specimens at 28days after casting. The duration of vibration is fixed to 30 minutes for all cases. The results indicate that the strength increases for vibration velocity less than about 0.25cm/sec and decreases for vibration velocity larger than 0.5cm/sec. The effect of age at vibration is not pronounced and shows almost similar behavior for the age at vibration of 0 to 12 hours range. The present study provides some important guidelines to control the construction or vehicle vibrations for the concrete at very early ages.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.23 no.7
• /
• pp.941-952
• /
• 1999

The purposes of this study were to provide the fundamental data on elementary school girls' somatotype for their clothing construction by contemplating the stage of physical growth dividing into the period of school age and characterizing the variation of body type according to the school age. The results are as follows : 1. Form the results of one-way variables analysis and multiple comparson test(Duncan's test) classification of the period school age can be divided into 'early grade(1 2 grade)' ' middle grade(3 4 grade)' and 'later grade(5 6 grade)' 2. As the results of analyzing Mean Coefficient of Variation and Standard Deviation graph for direct and indirect measurments and index especially of the Coefficient Variation that explain individual difference of growth the items of height indicates individual difference related with height of lower body of early grade group the items of length individual difference related with length of upper body of later grade group and the items of circumference make little difference. The items of anagle makes pretty higher value that direct measurements and especially in lower angle of chest make a distinctive difference, This fact proves that children's somatotype change from the belly part extruded forwards of early and middle grade to the upper body part slanted slightly forward of later grade.

• Journal of Home Health Care Nursing
• /
• v.25 no.1
• /
• pp.96-104
• /
• 2018

Purpose: This study compared factors related to fear of falling among women in the early phase of old age based on hand grip strength. Methods: Researchers obtained data of 1,071 women who had participated in the 4th Korean Longitudinal Study of Aging. Data were analyzed using multiple regression analysis. Results: In both groups, fear of falling was positively correlated with falling experience within two years, osteoarthritis-related leg pain, depression, and instrumental daily life abilities; however, self-rated health was negatively correlated. In the low hand grip strength group, self-rated health, osteoarthritis-related leg pain, and hand grip strength accounted for 21.3% of the variance regarding fear of falling. In the normal hand grip strength group, age, self-rated health, fall experience within two years, osteoarthritis-related leg pain, and depression significantly accounted for 16.6% of the variance regarding fear of falling. Conclusion: In applying interventions to prevent falling in women in the early phase of old age, health care workers must verify if women have low hand grip strength and determine whether to focus on fitness improvement through exercise interventions or consider psychological interventions for depression.