• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.259-264
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• 1999

The aim of this study of to compare the development of compressive strength of high-strength concrete with maturity and investigate the applicability the strength prediction models. An experiment was attempted on the high-strength concrete mixes using portland cement replaced by silica fume of 10% by weight of cement, the water-binder ratios of mixes being 0.30 and 0.35, the curing temperatures being 30, 20, 10, 5$^{\circ}C$. Test results of mixes are statistically analyzed to infer the correlation coefficient between the maturity and the compressive strength of high-strength concrete. The constant of strength prediction equation were determined from test results, and the equation was adopted to predict the strength of slab(W80$\times$D100$\times$H20cm). The slab was cast in the laboratory from the same batch water-binder ratio of 0.30, and cores were cut from slab in order to estimate the actual strength. These values are used to compare with predicted value. The present study allows more realistic determination of early age compressive strength of high-strength concrete and can be efficiently used to control the quality in actual construction.

• 한국건축시공학회지
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• 제4권2호
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• pp.113-118
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• 2004

This study is a basic experiment on quality management of the compression strength of high strength concrete, aiming. at quality management of high strength mass concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Different from ordinary concrete, high strength concrete generally shows the temperature high rising caused by hydration heat inside the concrete. It is known that, in mass concrete, thermal stress occurs due to the difference in temperature between the inside and the outside, which causes a significant difference in compression strength between structure beams and managerial test pieces. It is also reported that there is a large difference between the compression strength of cylindrical managerial test pieces of standard underwater curing and the strength of structure beam concrete. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created thermal insulation curing box and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.

• 한국건설순환자원학회논문집
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• 제8권3호
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• pp.325-332
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• 2020

화재피해 콘크리트 구조물의 안전진단 시, 기존 내구성 평가 방법으로는 고온으로 인한 강도감소 및 재료의 변화 등을 정량화하기가 어렵다. 특히, 두께별 손상도가 다른 공시체의 압축강도를 부재의 압축강도 저하의 대표 값으로 사용하고 있어 콘크리트의 깊이에 따른 손상도 변화를 반영하지 못하고 있다. 이 연구에서는 고온에 노출된 콘크리트의 손상깊이를 정량적으로 평가하기 위하여 400℃-800℃ 온도로 콘크리트 공시체를 전면 가열과 일면 가열 조건으로 가열실험을 수행하였다. 가열 후 전면 가열 공시체의 압축실험과, 일면 가열 공시체를 고온 노출면부터 20mm두께의 절편을 만든 후 각각에 대해 쪼갬 인장실험과 색조분석을 실시하였다. 실험결과, 공시체 절편의 쪼갬 인장강도로부터 산정된 압축강도 감소율이 전면 가열공시체의 압축강도 값과 평균 10% 이내로 나타났고, 색조분석 결과 400℃-600℃에서 빨강 색상, 700℃이상에서는 회색계열로 변색되는 일관적인 색상 값이 관찰된 바, 이 연구에서 제안한 기법은 수열온도의 추정과 콘크리트 잔존 압축강도와 손상깊이를 합리적으로 평가할 수 있는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.75-79
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• 2006

Recently, more highly effective construction materials are needed for the reasonable and economical structure system is required as the construction structures become more multi storied, large-sized and diversified. That is to say, the highly qualified concrete is positively promoted as a part of plan to establish the effective space according to the dead load of structures and diminish of segment profile and to build up the economic structures. However, the high strength concrete has the problems such high brittleness and low ductility. Specially, for the high strength concrete, it has different strength from normal concrete as the internal temperature goes up steadily due to high heat of hydration by the quantities of highly level of cement, so the concrete which is mixed with various miscible materials is used. As the development and study for high strength concrete (more than $100N/mm^2$) is under way actively and the strength of high strength concrete increases, the strength different from the existing high strength concrete of ten than $100N/mm^2$, but the study for this is not adequate and indefinite. In addition, the study and report to apply the strength expression and analysis results of internal structure. Therefore, this study is an experiment about using the miscible materials affects what happens to the longitudinal physical property.

• 한국건축시공학회지
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• 제13권4호
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• pp.351-359
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• 2013

고로슬래그는 콘크리트의 적용시 효율적인 가치향상과 관련하는 많은 장점도 있으나, 고로슬래그의 사용량 증대에 따른 부작용도 나타나고 있다. 따라서 고로슬래그 미분말의 활용성 증대를 위해 High Volume Slag를 자극제 종류별, 치환율별, 조강제 혼입율별, NaOH, $Na_2SiO_3$ 혼합사용시, 폐알칼리자극제 혼입율별 특성을 알아보기 위해 실험하였다. 실험결과, 압축강도의 경우 수산화나트륨을 제외한 모든 알칼리자극제에서 치환율이 증가함에 따라 강도가 증진되었다. 알칼리자극제 중 규산나트륨이 동탄성계수와 흡수율 등에서 높게 나타났으며, 조강제의 경우 혼입율 1.5%와 고로슬래그 치환율 75%가 높은 강도증진을 나타내었다. 폐알칼리 자극제의 경우 모든 실험에서 각기 다른 결과를 나타내었다.

• 농업과학연구
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• 제46권3호
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• pp.569-577
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• 2019

The current experiment was conducted to compare nutrient utilization in the aged laying hens with different eggshell strengths or different intensities of brown eggshell color. Two metabolic trials with 96-week-old Hy-Line Brown laying hens were conducted. Twelve hens with a strong eggshell strength (SES) and 12 hens with a weak eggshell strength (WES) were selected and used in the first experiment, whereas 12 hens with dark brown eggshells (DBE) and 12 hens with light brown eggshells (LBE) were selected and used in the second experiment. All hens were fed a common commercial layer diet. Diets included chromic oxide as an indigestible marker to determine the apparent total tract retention (ATTR) of the gross energy (GE), dry matter, acid-hydrolyzed ether extract, nitrogen, neutral detergent fiber, acid detergent fiber, ash, and minerals. The results indicate that the ATTR of Ca in the aged laying hens with SES (59.7%) was greater (p < 0.05) than in the aged laying hens with WES (48.6%). However, the ATTR of the GE and other nutrients was not different between the hens with SES or WES. There were no differences in the ATTR of GE and nutrients between the hens with DBE or LBE. In conclusion, aged laying hens with SES have a greater ability to utilize dietary Ca than those with WES, indicating that the extent of dietary Ca utilization determines the eggshell strength of aged laying hens. However, nutrient utilization in diets may have little impact on eggshell brown coloration in aged laying hens.

• Ecology and Resilient Infrastructure
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• 제10권1호
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• pp.1-10
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• 2023

제방은 기본적으로 물이 넘치지 않도록 하기 위하여 조성되는 구조물이다. 개발된 제방보강 기술은 바이오폴리머와 골재를 혼합하여 제방의 붕괴로 발생되는 대규모 재난을 방지하기 위한 기술로 제방의 세굴 및 붕괴 등을 억제하는데 목적이 있다. 개발된 기술은 호안 사면 등에도 활용이 가능하지만 시공성이 수월하여 월류파괴에 대한 대응 기술로 적용하기 용이하다. 개발된 기술을 현장에 적용하기 위해서는 기술의 안전성을 확보해야 하므로 현장시범사업 등 실제 적용에 대한 연구가 필요하다. 하지만 월류 파괴는 현장에서 시범사업을 수행할 수 없으므로 본 연구에서는 실규모 실험을 통해 현장 적용성 연구를 수행하였다. 실규모실험은 안동에 위치한 하천실험센터에서 수행하였으며, 인위적인 월류를 통하여 제방 세굴 및 붕괴 상황을 검토하였다. 실험결과 개발기술이 월류파괴에 대해 대응 가능하고 붕괴를 억제할 수 있는 기술로의 실증을 수행하였다.

• 지역사회간호학회지
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• 제6권1호
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• pp.55-73
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• 1995

An Effect of Muscle Strength Training Program on Muscle Strength, Muscle Endurance, Instrumental Activities of Daily Living and Quality of Life in the Institutionalized Elderly Recent statistics shows that the aged are the fastest growing segment of our population by increasing life span. The age group of over 60 shows multiple health problems and the most serious handicapping problem of these. are related to the changes in muscular skeletal system. With aging, people lose. their muscle mass and muscle strength resulting from biological changes and physical inactivity. Studies documented a 30-50% loss of muscle mass in an advanced age and thus, ordinary life activities can be seriously affected due to weakened muscle strength. Preservation of muscle strength of lower limb is especially important in the aged. Since it is readily affected from reduced physical activity in old age, sometimes to the detriment of moving or walking. So muscle strength exercise program designed for the elderly to improve leg muscle strength and leg muscle endurance. The research design used was nonequivalent control group pretest - protest design. The purposes of this study were to test the effect of muscle strength exercise program utilizing Leg Press on muscle strength, muscle endurance, instrumental activities of daily living(IADL), cognitive perceptual variables and quality of life. Forty nine subjects participating in this study consisted of twenty four male and twenty five female. Twenty four experimental group subjects were selected from C-institution in Chung Buk province, and twenty five control group subjects were selected from O-institution in Chung Nam province. The mean age of subjects was 72.8 years. Muscle strength training program utilizing Leg Press for the experimental group was carried out three times a week for 9 weeks. The data was collected from August, 1993 to October, 1993. Data were analyzed with $X^2-test$, t-test, ANCOVA test, Kruskal Wallis 1-Way ANOVA test using SPSS PC program. Results were obtained as follows : 1) The experimental group showed significantly higher scores on muscle strength (leg lift strength, back lift strength and grip strength) and muscle endurance than control group after the experiment $\ulcorner$F=52.35(p=.001), F=54.07(p=.001), F=6.97(p=.011), F=18.17(p=.001)$\lrcorner$ 2) Experimental group were significantly higher scores on IADL than control group(F=7.51, p=.009). 3) Experimental group showed significantly higher scores on economical state and self esteem aspects of the quality of life scale than control group $\ulcorner$F=10.59(p=.002), F=6.97(p=.011)$\lrcorner$. But there were no differences in emotional state, physical and functional state and relationship with reatives in the quality of life between groups. 4) Scores on IADL showed a significant difference with the level of muscle strength and muscle endurance $\ulcornerx^2=7.73(p=.025),\;x^2=8.86\;(p=.011)\lrcorner$ 5) Scores on self esteem and physical and functional state aspects of the quality of life scale showed a significant difference with the level of IADL $\ulcornerx^2=11.39(p=.003),\;x^2=9.02(p=.011)\lrcorner$. 6) Scores of experimental group after the experiment in cognitive perceptual variables (perceived benefit on exercise, perceived health status, self efficacy, emotion on exercise) were significantly higher than those of control group $\ulcorner$F=32.09(p=.001), F=5.07(p=.029), F=20.63 (p=.001), F=30.38(p=.001)$\lrcorner$. As a result of this study, the effect of strength training exercise program with Leg. Press had improved muscle strength, muscle endurance, IADL, and the perception of self esteem, physical and funtional state, and economical state. Thus strength training program could be beneficially applied for the prevention of disablity and promotion of health and wellbeing in the aged easily and safely. The subjects in the experimental group have maintained their exercises till six months after the cessation of the experiment. This seem to illustrate that changes in cognitive perceptual variables and the improvement in health status have reinforced motivation for the continuation of voluntary exercises. A further study is necessary to determine the factors affecting maintainance of muscle strength exercise and to assess the effect of weight training program on bone density.

• Geomechanics and Engineering
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• 제24권5호
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• pp.471-478
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• 2021

Water damage is one of the five disasters that affect the safety of coal mine production. The erosion of rocks by water is a very important link in the process of water inrush induced by fault activation. Through the observation and experiment of fault filling samples, according to the existing rock classification standards, fault sediments are divided into breccia, dynamic metamorphic schist and mudstone. Similar materials are developed with the characteristics of particle size distribution, cementation strength and water rationality, and then relevant tests and analyses are carried out. The experimental results show that the water-rock interaction mainly reduces the compressive strength, mechanical strength, cohesion and friction Angle of similar materials, and cracks or deformations are easy to occur under uniaxial load, which may be an important process of water inrush induced by fault activation. Mechanical experiment of similar material specimen can not only save time and cost of large scale experiment, but also master the direction and method of the experiment. The research provides a new idea for the failure process of rock structure in fault activation water inrush.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.77-86
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• 2002

In this study we intended to investigate properties of cement mortar with recycled PET fiber, PE fiber, and PP fiber such as slump flow, compressive strength, tensile strength, and flexural strength. As results of experiment, several properties of specimen with recycled PET fiber were little low comparing those of specimen with PE fiber and PP fiber. But if we see from point of economy and recycle of industrial wastes, it has enough reason to be used. Compressive strength of specimen with recycled PET fiber at 56 days was about 10% higher, but tensile strength and flexural strength were lower than that of no-fiber.