• 한국도로학회논문집
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• 제15권4호
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• pp.85-94
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• 2013

PURPOSES: The performance of tack coat, commonly used for layer interface bonding, is affected by application rate and curing time. In this study, bonding strength tests were performed according to the application rate and curing time of asphalt emulsion. Based on finding from this study, optimum application rates and curing times are proposed. METHODS: In order to investigate bonding characteristic of asphalt emulsion, tests were performed on both asphalt concrete pavement and portland concrete pavement. Also, asphalt emulsions were tested at the application rate of 0, 0.2, 0.4, 0.6, and $0.8{\ell}/m^2$ and at the curing time of 0, 0.5, 1, 2, and 24 hours. Pull-off test and shear bonding strength test, which commonly used for bonding strength measurement of asphalt emulsion, were adopted for this study. To assess field performance under different testing condition, asphalt emulsions were applied to in-service pavement. Throughout coefficient of determination analysis between material index properties from asphalt emulsion and mechanical response from bonding strength tests, performance correlativity was analyzed. RESULTS: Test results show that optimum application rate for asphalt overlay on asphalt concrete pavement (AOA) and asphalt overlay on concrete pavement (AOC) was $0.4{\sim}0.5{\ell}/m^2$ and $0.3{\sim}0.5{\ell}/m^2$, respectively. According to the curing time increment, tensile strength and shear strength of AOC were increased to 22~44% and 20~39%, respectively. AOA case also show strength increment in tensile strength (42%) and shear strength (9%). We tested the applicability of tack coat materials at the field sites, and our findings demonstrated that the bonding (for D and E) and rapid curing (for B, C, and D, E) performances were superior than others. Among material index properties, there was a high correlation between penetration ratio and bonding strength test result. CONCLUSIONS : Result show that interlayer bonding strength was affected by asphalt emulsion type, application rate and curing time. AOC required slightly higher application ($0.1{\ell}/m^2$) than AOA. Both AOA and AOC cases show higher strength at longer curing time. Up to 2hours of curing, rapid strength increments were observed, but strength increment ratio was decreased after 2hours of curing. From the observed correlation between penetration ratio and bonding strength, it is expected that penetration ratio can be used as one of important factors affecting bonding strength analysis.

• 보건행정학회지
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• 제29권3호
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• pp.303-311
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• 2019

Background: Cerebrovascular disease is included in four major diseases and is a disease that has high rates of prevalence and mortality around the world. Moreover, it is a disease that requires a high cost for long-term hospitalization and treatment. This study aims to figure out the correlation between grip strength, which was presented as a simple, cost-effective, and relevant predictor of cerebrovascular disease, and cerebrovascular disease based on the results of a prior study. And furthermore, our study compared model suitability of the model to measuring grip strength and relative grip strength as a predictor of cerebrovascular disease to improve the quality of cerebrovascular disease's predictor. Methods: This study conducted an analysis based on the generalized linear mixed model using the data from the Korea Longitudinal Study of Ageing from 2006 to 2016. The research subjects consisted of 9,132 middle old age people aged 45 years or older at baseline with no missing information of education level, gender, marital status, residential region, type of national health insurance, self-related health, smoking status, alcohol use, and economic activity. The grip strength was calculated the average which measured 4 times (both hands twice), and the relative grip force was divided by the body mass index as a variable considering the anthropometric figure that affects the cerebrovascular disease and the grip strength. Cerebrovascular diseases, a dependent variable, were investigated based on experiences diagnosed by doctors. Results: An analysis of the association between grip strength and found that about 0.972 (odds ratio [OR], 0.972; 95% confidence interval [CI], 0.963-0.981) was the incidence of cerebral vascular disease as grip strength increased by one unit increase and the association between relative grip strength and cerebrovascular disease found that about 0.418 (OR, 0.418; 95% CI, 0.342-0.511) was the incidence of cerebral vascular disease as relative grip strength increased by unit. In addition, the model suitability of the model for each grip strength and relative grip strength was 11,193 and 11,156, which means relative grip strength is the better application to the predictor of cerebrovascular diseases, irrespective of other variables. Conclusion: The results of this study need to be carefully examined and validated in applying relative grip strength to improve the quality of predictors of cerebrovascular diseases affecting high mortality and prevalence.

• 터널과지하공간
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• 제24권4호
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• pp.325-333
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• 2014

대표적인 비재래에너지자원인 셰일가스 생산을 위해서는 수압파쇄가 핵심적인 기술이다. 암석의 취성도는 셰일가스 생산을 위한 수압파쇄 효율결정의 가장 중요한 물성 중 하나이며, 셰일의 취성도가 클수록 셰일가스 생산량이 증가하는 관계를 보인다. 암석의 취성은 다양하게 정의되며 표준화된 정의가 없어 혼란이 존재한다. 본 논문에서는 취성도의 다양한 개념들을 살펴보고 실내 실험값을 이용하여 취성도를 측정하고 각기 다르게 정의된 취성도간의 상관관계에 대해서 고찰해보았다. 일반적으로 일축압축강도와 인장강도의 비율로 나타내는 취성도와, 탄성계수와 포아송비를 이용한 취성도를 비교하였을 때 같은 암석에 대한 취성도 간에 매우 약한 양의 상관관계를 가지고 있는 것을 확인할 수 있었다. 또한 포아송비의 경우 취성도에 미치는 영향이 명확하지 않은 것으로 나타났다. 수압파쇄 결과를 예측하기 위한 지표로써 취성도를 적용하기 위해서는 취성도의 개념의 표준화가 필요한 것을 알 수 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.615-618
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• 2005

This study concerns the equation of high strength concrete by schmidt hammer test. There are not only few prediction strength equations of concrete by schmidt hammer test, but also many problems to apply them because of time, cost, easiness, structural damage, reliability and so on. For this study, there performed a series of schmidt hammer test with in existing 1,095days' concrete structures and proposed equations as follows ; Linear: ${\Large f}_{ck}=-45.35+2.44R(r^2=72.7\%)$ Quadratic: ${\Large f}_{ck}=-502.08+24.0R-0.25R^2(r^2=82.4\%)$ here, $f_{ck}$ : Estimated compressive strength of concrete by MPa, R : Rebound index of concrete

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.475-480
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• 2003

Latex modification of concrete provides the material with higher flexural strength. This increase in flexural strength can attribute to the crack-arresting action of polymer in concrete, and also to the bonding they provide between the matrix and aggregates. This experimental study presents the fracture behavior of 12 flexural reinforced concrete beams repaired or strengthened by latex-modified concrete with the main experimental variables such as overlay thickness, strength thickness, and shear reinforcement. The results are as follow: All beam specimens having shear reinforcement were failed by delamination rupture at concrete interface at about 80% of ultimate loading after flexural cracking. All specimens overlayed and strengthened by latex-modified concrete (LMC) showed higher ultimate flexural strength than OPC control specimen, but lower than LMC control specimen. This increase in flexural strength could attribute to the high bonding they provide between the matrix and aggregates. All specimens except two shear unreinforced showed quite similar and consistent displacement behavior. The effect of overlay and strength thickness on the load-displacement relationship were a small at this study.

• 한국재난정보학회 논문집
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• 제2권1호
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• pp.129-137
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• 2006

The present work is attempt to evaluate the temperature dependence of blast furnace slag concrete(BFSC) based on the concrete strength cured with different curing temperatures and ages. A equivalent substitution index(ESI) was induced to explain temperature dependence of concrete quantitatively as well as concrete strength. The results from compressive strength showed substantial crossover effect. which is the phenomenon that the compressive strength cured at low temperature becomes stronger than the one cured at high temperature. The crossover effect found more definitely on BFSC than plain concrete.. The ESI became 1.1 and 1.0 for the BFSC cured at $20^{\circ}C$ and $30^{\circ}C$ after age of 56 days, respectively. Which means that the contribution to strength development of blast furnace slag per unit mass is stronger than that of the Portland cement. It was considered therefore that the optimum curing temperature for BFSC is $20^{\circ}C$.

• 한국광학회지
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• 제17권6호
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• pp.548-555
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• 2006

양 단면 반사율과 단면 회절격자 위상, 위상 조정 영역의 위상이 두 개의 DFB 영역과, 가운데 위상 조정 영역을 가진 다중 영역 Index-Coupled DFB 레이저의 Self-Pulsation동작 특성에 미치는 영향을 수율 관점에서 살펴보았다. 결합세기가 작을수록 양 단면 반사율이 증가할 때 양 단면과 다른 DFB 영역에서 반사되는 필드가 모드의 특성에 미치는 영향이 커져 양 단면 회절격자 위상 변화에 따른 발진 모드의 호핑이 많이 발생하고 수율이 감소한다. 결합세기가 클수록 양 단면 반사율이 증가하여도 양 단면과 다른 DFB 영역에서 반사되는 필드가 모드의 특성에 미치는 영향이 작아 양 단면 회절격자 위상 변화에 따른 모드의 호핑은 적게 발생하나 Spatial Hole Burning 효과가 증가하여 수율이 감소하는 것을 볼 수 있었다. 결합세기에 상관없이 단면 반사율이 증가할수록 최대 수율과 수율이 40% 이상 되는 위상 조정 영역의 위상 범위가 감소함을 볼 수 있었다. 또한 결합세기가 클수록 위상 조정 영역의 위상 변화에 따른 수율의 변화가 커지고 단면 반사율의 변화에 따른 최대 수율을 주는 위상 조정 영역의 위상 값의 변화가 작음을 볼 수 있었다. 결합세기가 2와 3일 경우가 1.2와 4인 경우에 비하여 수율 특성이 좋음을 볼 수 있었다.

• 한국지반공학회논문집
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• 제29권1호
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• pp.23-27
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• 2013

기후변화에 따른 토석류 발생과 그로 인한 피해가 세계적으로 증가 추세에 있다. 토석류 연구는 역학적 관점에서 파괴 후(post-failure) 거동에 해당하며 지반강도와 유동특성을 분석함으로써 특성화할 수 있다. 본 연구는 국내의 토석류 발생지역인 상주(화강암 풍화토), 인제(편마암 풍화토), 포항(이암 및 셰일) 지역을 대상으로 지반의 물성-전단강도 상관관계와 토석류의 유동특성을 평가하였다. 본 연구지역을 대상으로 스웨덴 낙하 콘(Swedish Fall cone) 시험장치를 이용하여 지반의 물성 및 지반강도 사이에 일정한 상관관계가 있음을 밝혔다. 실험결과에 따르면, 인제, 상주, 포항지역에서 채취된 시료에 대해 액성지수(IL)와 비배수 전단강도($C_{ur}$) 사이에 $C_{ur}=(1.2/I_L)^{3.3}$의 관계식이 성립한다. 토석류 흐름을 지배하는 항복응력은 재성형 비배수 전단강도에 상응하는 것으로 간주하고, Bingham 모델과 액성지수-항복응력 관계식을 이용하여 토석류의 유동성을 조사하였다. 유동해석은 국내 풍화토와 낮은 활성점토를 구분하여 적용하였다. 이때 액성지수는 액성한계를 기준으로 $I_L=1$, 1.5, 3.0으로 구분하여 비교분석하였다. 동일한 액성지수($I_L=1$)에 대해, 토석류의 발생 5분 경과 후 최대 이동거리는 250m에 다다른다. 액성지수가 3으로 증가 될 경우, 토석류의 이동거리를 5분까지 살펴본 결과, 국내 풍화토는 낮은 활성점토에 비해 2배 이상 큰 유동성이 있음을 알 수 있었다. 본 유동성 평가기술은 토석류 피해저감기술 전략수립에 활용할 수 있을 것으로 기대된다.

• Computers and Concrete
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• 제11권2호
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• pp.93-104
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• 2013

The use of rock wool waste, an industrial by-product, in cement-based composites has positive effects on the environment because it reduces the problems associated rock wool disposal. The experiments in this study tested cement-based composites using various rock wool waste contents (10, 20, 30 and 40% by weight of cement) as a partial replacement for Portland cement in mortars. The pozzolanic strength activity test, flow test, compressive strength test, dry shrinkage test, absorption test, initial surface absorption test and scanning electron microscope observations were conducted to evaluate the properties of cement-based composites. Test results demonstrate that the pozzolanic strength activity index for rock wool waste specimens is 103% after 91 days. The inclusion of rock wool waste in cement-based composites decreases its dry shrinkage and initial surface absorption, and increases its compressive strength. These improved properties are the result of the dense structure achieved by the filling effect and pozzolanic reactions of the rock wool waste. The addition of 30% and 10% rock wool wastes to cement is the optimal amount based on the results of compressive strength and initial surface absorption for a w/cm of 0.35 and 0.55, respectively. Therefore, it is feasible to utilize rock wool waste as a partial replacement of cement in cement-based composites.

• 대한간호학회지
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• 제36권1호
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• pp.5-14
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• 2006

Purpose: This study was done to analyze the effects of an exercise program on body composition and physical fitness of obese female college students. Method: Data was collected from September 29, 2003 to December, 29, 2003. The research design was arandomized control group pretest-posttest experimental design. The subjects were college nursing students at K University. Forty four students, 20 in the experimental group and 24 ina control group, with more than $30\%$ body fat were randomly assigned. The subjects in the experimental group participated in an exercise program for 12 weeks, sixty minutes per session, five times per week. Body composition and physical fitness was measured by a body composition analyzer, cardiovascular endurance, muscle endurance, muscle strength(grip strength, back strength), flexibility, balance, agility(whole body reaction time) and power(standing long jump). Result: Body weight(F=4.76, p=0.035), body fat(kg)(F=5.68, p=0.022) and body mass index(F=5.73, p=0.021) of the experimental group were significantly different from the control group, but there were no significant differences in body fat($\%$), lean body mass, muscle mass and WHR. Back strength(F=6.50, p=0.015), flexibility(F=14.62, p=0.000), muscle endurance(F=7.98, p=0.007), power(F=5.76, p=0.02l) and balance(F=2.46, p=0.018) of the experimental group were significantly different from the control group, but there were no significant differences in cardiovascular endurance, grip strength or agility. Conclusiton: The exercise program was effective in improving body weight, body fat(kg), body mass index, back strength, muscle endurance, flexibility, balance and power of obese female college students.