PURPOSES : To efficiently manage pavements, a systematic pavement management system must be established based on regional characteristics. Suppose that the future conditions of a pavement section can be predicted based on data obtained at present. In this case, a more reasonable road maintenance strategy should be established. Hence, a prediction model of the annual surface distress (SD) change for national highway pavements in Gangwon-do, Korea is developed based on influencing factors. METHODS : To develop the model, pavement performance data and influencing factors were obtained. Exploratory data analysis was performed to analyze the data acquired, and the results show that the data were preprocessed. The variables used for model development were selected via correlation analysis, where variables such as surface distress, international roughness index, daily temperature range, and heat wave days were used. Best subset regression was performed, where the candidate model was selected from all possible subsets based on certain criteria. The final model was selected based on an algorithm developed for rational model selection. The sensitivity of the annual SD change was analyzed based on the variables of the final model. RESULTS : The result of the sensitivity analysis shows that the annual SD change is affected by the variables in the following order: surface distress ˃ heat wave days ˃ daily temperature range ˃ international roughness index. CONCLUSIONS : An annual SD change prediction model is developed by considering the present performance, traffic volume, and climatic conditions. The model can facilitate the establishment of a reasonable road maintenance strategy. The prediction accuracy can be improved by obtaining additional data, such as the construction quality, material properties, and pavement thickness.

PURPOSES : The surface distress of asphalt pavements is one of the major factors affecting the safety of road users. The aim of this study was to analyze the factors influencing the occurrence of surface distress and statistically predict its annual change to contribute to more reasonable asphalt pavement management using the data periodically collected by the national highway pavement data management system. METHODS : In this study, the factors that were expected to influence the surface distress were determined by reviewing the literature. The normality was secured by changing the forms of the variables to make the distribution of the variables got closer to normal distribution. In addition, min-max normalization was performed to minimize the effect of the unit and magnitude of the candidate independent variables on the dependent variable. The final candidate independent variables were determined by analyzing the correlation between the annual surface distress change and each candidate independent variable. In addition, a prediction model was developed by performing data grouping and multi-regression analysis. RESULTS : An annual surface distress change prediction model was developed using present surface distress, age, and below 0 ℃ days as the independent variables. As a result of sensitivity analysis, the surface distress affected the annual surface distress change the most. The positive correlation between the dependent variable and each independent variable demonstrated engineering and statistical meaningfulness of the prediction model. CONCLUSIONS : The surface distress in the future can be predicted by applying the annual surface distress prediction model to the national highway asphalt pavement sections with survey data. In addition, the prediction model can be applied to the national highway pavement condition index (NHPCI) evaluating the national highway asphalt pavement conditions to be used in the prediction of future NHPCI.

목적: 본 연구는 연령증가에 따른 안경굴절검안에 있어서 조절반응과 조절지체 간의 변화량의 영향 관계를 검정하는데 있다. 방법 : 연령증가에 따른 원점과 근점의 자극에 대응하는 조절 반응점 (ARf, ARn)을 연구하기 위해서, 선조 검영기를 사용하여 정시 74개 (남: 37, 여: 37)의 단안을 대상으로 굴절검사를 진행하였다. MEM 0.4 시력카드의 스넬린 (Snellen chart) E 단일문자를 검영기헤드 (No 18235, WelchAllyn, USA) 전면에 부착한 선조 검영기를 사용하여 조절 반응을 확인하였다. 결과 : 연령증가에 따른 원점 조절반응의 경우Ⅰ>Ⅱ, Ⅲ, Ⅳ의 유의한 결과를 보였고, 나머지 근점 조절반응과 조절지체는 Ⅰ, Ⅱ, Ⅲ<Ⅳ의 결과를 보여주었다. 연령증가에 따른 원점 조절반응과 조절지체 간의 통계적 조절효 과는 Ⅰ·Ⅱ〉Ⅰ·Ⅲ〉Ⅰ·Ⅳ의 유의한 결과를 보였다. 결론 : 40대 이후 연령의 증가에 따른 시축상의 원점 조절반응의 절댓값과 조절지체는 각각 감소하고 증가함에 따라 원거리 안경굴절검사를 위한 안와 내 조절반응의 기준점을 달리 적용하여야 한다.

PURPOSES : Rut depth of asphalt pavements is a major factor that affects the maintenance of pavements as well as the safety of drivers. The purpose of this study was to analyze the factors influencing rut depth, using data collected periodically on national highways by the pavement management system and, consequently, predict annual rut depth change, to contribute to improved asphalt pavement management. METHODS : The factors expected to influence rut depth were determined by reviewing relevant literature, and collecting the related data. Further, the correlations between the annual rut depth change and the influencing factors were analyzed. Subsequently, the annual rut depth change model was developed by performing regression analysis using age, present rut depth, and annual average maximum temperature as independent variables. RESULTS : From the sensitivity analysis of the developed model, it was found that age affected the annual rut depth change the most. Additionally, the relationship between the dependent and independent variables was statistically significant. The model developed in this study could reasonably predict the change in the rut depth of the national highway asphalt pavements. CONCLUSIONS : In summary, it was verified that the model developed in this study could be used to predict the change in the National Highway Pavement Condition Index (NHPCI), which represents comprehensive conditions of national highway pavements. Development of other models that predict changes in surface distress as well as international roughness index is required to predict the change in NHPCI, as they are the independent variables of the NHPCI prediction model.

본 연구의 목적은 청소년의 운동시간의 변화가 자아존중감의 변화로 이어지는 관계에서 그릿의 변화의 매개효과를 검증하는 것이다. 한국아동·청소년패널 2018의 중1 코호트 2개년도 자료 중 결측치를 포함한 케이스를 제외한 2,438명(남=1,327명, 여=1,111명)의 자료가 분석에 활용되었다. 각 변인의 변화량 간의 관계를 검증하기 위해 1차년도 측정값과 2차년도 측정값의 회귀분석에서 생성된 표준화잔차점수를 변화량 변수로 활용하였다. 상관관계 분석 결과, 운동시간의 변화량과 자아존중감의 변화량, 그릿의 변화량은 모두 서로 유의한 정적상관이 있는 것으로 나타났다. 위계적 회귀분석을 통한 매개효과 검증 결과, 운동 시간의 변화가 그릿의 변화를 통해 자아존중감의 변화에 직·간접적으로 영향을 미치는 부분매개효과가 유의한 것으로 확인되었다. 이러한 결과는 운동시간의 감소가 청소년의 그릿과 자아존중감의 감소에 영향을 미친다는 것을 의미한다.

Heatwaves are one of the most common phenomena originating from changes in the urban thermal environment. They are caused mainly by the evapotranspiration decrease of surface impermeable areas from increases in temperature and reflected heat, leading to a dry urban environment that can deteriorate aspects of everyday life. This study aimed to calculate daily maximum ground surface temperature affecting heatwaves, to quantify the effects of urban thermal environment control through water cycle restoration while validating its feasibility. The maximum surface temperature regression equation according to the impermeable area ratios of urban land cover types was derived. The estimated values from daily maximum ground surface temperature regression equation were compared with actual measured values to validate the calculation method’s feasibility. The land cover classification and derivation of specific parameters were conducted by classifying land cover into buildings, roads, rivers, and lands. Detailed parameters were classified by the river area ratio, land impermeable area ratio, and green area ratio of each land-cover type, with the exception of the rivers, to derive the maximum surface temperature regression equation of each land cover type. The regression equation feasibility assessment showed that the estimated maximum surface temperature values were within the level of significance. The maximum surface temperature decreased by 0.0450˚C when the green area ratio increased by 1% and increased by 0.0321˚C when the impermeable area ratio increased by 1%. It was determined that the surface reduction effect through increases in the green area ratio was 29% higher than the increasing effect of surface temperature due to the impermeable land ratio.

PURPOSES : Road sectors contribute approximately 16 % of total GHG emission rates in South Korea. Engineers and experts expend significant efforts to identify countermeasures for the reduction of carbon emission. This study aims to determine how total carbon emission rates change depending on whether or not there is speed limit enforcement.METHODS: In this study, Lamm’s travel speed profile theory is first adopted to select the hazard road, which sections are designated as speed limit enforcement. Second, Motor Vehicle Emission Simulator (MOVES) was used to simulate the carbon emission on the road.RESULTS : The total carbon emission rate under speed limit enforcement was 10,773 g higher than the condition without speed limit enforcement in the designated road. This might affect acceleration, which can lead to increased emissions.CONCLUSIONS : There would be no researches about proving the relationship how speed limit enforcement has an effect on carbon emission. The result of our study can provide valuable guidelines regarding road safety and eco-friendly roads.

Background: A forward head posture (FHP) is one of the most common types of poor head posture in patients with neck disorder. A prolonged FHP might increase pressure on the posterior cranio-cervical structure and exhibit reduced performance on a cranio-cervical flexion test (CCFT). CCFT is included to activate deep cervical flexor muscles and inhibit excessive activation of superficial cervical flexor muscles. Therefore, the selective activation of deep cervical flexors is needed for effective exercise for FHP. Objects: The purpose of this study was to compare muscle thickness between longus colli (Lco) and sternocleidomastoid (SCM) using ultrasonography in subjects with FHP depending on head support. Methods: This was a cross-sectional, case-control research design study. The ultrasonographic images of Lco and SCM were taken in 17 subjects with FHP during the 5 phases of the CCFT with and without a head support. Towel was used for supporting head to make the neutral head position in supine. Changes in muscle thickness during the test were calculated to infer muscle activation. Data were analyzed using repeated measures of two-way analysis of variance with the significance level of .05. Results: When subjects performed the CCFT with head support, there was a significant difference in muscle thickness of Lco and SCM (p<.05). According to a post hoc paired t-test, change of thickness of Lco was greater at all phases, and change of thickness of SCM muscle was less at phase 4 and 5 in condition with head support (p<.01) compared to condition without head support (p<.01). Conclusion: The result of this study suggest that applying head support for neutral head position during CCFT could be a useful method for activating Lco muscle without excessive activation of SCM muscle.

The lower trapezius muscle is an important stabilizer and primary mover of the scapula. The potential use of ultrasound imaging to evaluate scapular muscle function warrants investigation. The purpose of this study is to use ultrasound imaging for determining the effectiveness of 4 different isometric exercises for maximally activating the lower trapezius muscles in healthy subjects. Twenty-eight (14 men and 14 women) volunteers were recruited for this study. Thickness measurements of the lower trapezius muscles were recorded during 4 exercises: latissimus pulldown (LP), prone V-raise (PV), prone row (PR), and modified prone cobra (MP). Lower trapezius muscle thickness was measured 3 times by 2 investigators at a point 3 cm lateral to the lateral edge of the T8 spinous process. The order of 4 exercise execution was randomized for each participant. To identify statistical significance, one-way ANOVA with repeated measures was used with the significance level of .05. Intraclass correlation coefficient (ICC) for intra-reliability was .86~.98 and inter-rater reliability .83~.96 for the lower trapezius, respectively (p<.01). Thickness changes in the lower trapezius muscles between the relaxed and contracted states in men were as follows: LP (, 182%), MP (, 167%), PV (, 149%), and PR (, 133%). In women the values were as follows: LP (, 163%), MP (, 131%), PV (, 129%), and PR ( mm, 100%). Thickness of the lower trapezius muscles significantly differed between exercises in both the gender (p<.01). The LP was the most effective exercise for increasing the activation of the lower trapezius muscle in both the gender. We recommend performing the LP exercise for strengthening the lower trapezius muscles.

목적: 근시발생 시점에 따른 굴절이상도와 안광학상수의 차이를 분석하여 근시 발생의 요인을 알아보고, 1년간의 변화를 분석하여 각 그룹의 근시진행 원인을 알아보고자 한다. 방법: 2008년 3월과 2009년 3월 2회에 걸쳐 76명(남 23명, 여 53명)을 대상으로 기본신체검사, 자동굴절검사, 각막곡률반경, 전방깊이, 안축장을 조절마비 상태에서 측정하고 등가구면 굴절이상도가 -0.50D 이상인 피검자(46명, 92안)를 대상으로 안경이나 콘택트렌즈로 교정한 시기에 따라 조기발생 근시군과 만기발생 근시군으로 구분하였다. 결과: 조기발생 근시군의 등가구면 굴절이상도는 -4.25±2.05D로 만기발생 근시군의 -2.63±1.69D보다 근시도가 컸으며 안축길이도 조기발생 근시군이 25.464±1.059 mm로 만기발생 근시군의 24.850±0.867mm보다 더 길었다. 1년간의 등가구면 굴절이상도 변화는 조기발생 근시군이 -0.08±0.28D, 만기발생 근시군이 -0.32±0.36D로 만기발생 근시군에서 근시도가 더 증가하였다. 조기발생 근시군에서 등가구면 굴절이상도 변화와 각막곡률반경 사이에는 양의 상관성(r=0.627, p=0.000)이 있었고 AL/CR비 변화와는 음의 상관성(r=0.487, p=0.000)이 있었다. 만기발생 근시군의 등가구면 굴절이상도 변화와 각막곡률반경 사이에는 양의 상관성을(r=0.651, p=0.000), AL/CR비 사이에는 음의 상관성을 보였다(r=0.710, p=0.000). 결론: 이상으로부터 근시발생 시점이 빠를수록 안축길이가 더 길었으며 근시도가 더 큰 것으로 나타났다. 근시도 증가는 조기발생 근시군에 비해 만기발생 근시군에서 더 크게 나타났다.

We investigated heat stability of epoxy resin products and epoxy resin according to the influence hardener. The heat flow which shows the degree of thermal decomposition of the epoxy resin product and epoxy resin measured by using the differential scanning calorimeter (DSC). As a result, we found that in the case of heat stability for epoxy resin as hardener was added, the ratio of one to one (epoxy resin : hardener) was the most suitable in air condition and nitrogen atmosphere.

The purpose of this study was to establish modified physiological cost index (PCI) for predicting energy consumption by heart rate (HR) at isokinetic ergometer exercise testing. The subjects were twenty-eight healthy men in their twenties. All of them performed upper and lower extremity isokinetic ergometer exercise tests which had six loads (400, 500, 600, 700, 800, and 900 kg-m/min) and five loads (400, 500, 600, 700, and 800 kg-m/min) respectively. The exercise sessions were finished when HR was in plateau. HR and oxygen consumption were determined during the final minute. Resting heart rate and oxygen consumption were used for calculating heart rate, oxygen consumption changes and modified PCI. Regression analysis established the relationship between each variable to work load, HR and oxygen consumption. The results were as follows: 1) In the lower extremity ergometer exercise test, oxygen consumption increased continuously as work load increased, but in the upper extremity ergometer test, oxygen consumption only increased until work load was 700 kg-m/min. 2) HR increased as work load increased in both exercise tests, but in the upper extremity ergometer test, HR decreased from the 700 kg-m/min. 3) The modified PCI increased as work load mcreased until the 700 kg-m/min point in the lower extremity ergometer test and until the 500 kg-m/min point in the upper extremity ergometer test when it started to decrease in both tests. 4) In the lower extremity ergometer exercise test, regression analysis established the relation as = -.0215HR - .2141 where is given in l/min and HR in beat/min ( = .2677, p = .000). ln the upper extremity ergometer exercise test. regression analysis established the relation as = -.0115HR + .2746 ( = .1308, p = .000). The results of this study were similar to previous studies but were different under high work load conditions. So modified PCI should be used with only low intensity work load testing. Subjects for upper extremity ergometer exercise testing should complete a prescribed training course prior to testing, and only low intensity work load should be used for safety considerations.