• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.3A
• /
• pp.227-234
• /
• 2011

Recently, a high strength concrete of more than 40 MPa has been increasingly used in practice. However, use of the high strength concrete may influence on design parameters, particularly stress distribution. This is very true since the current everyday practice employs equivalent rectangular stress distribution that is derived from normal strength concrete. Subsequently, the stress distribution seems to be reevaluated and then a new distribution with new parameters needs to be suggested for the high strength concrete. For this purpose, linear and multiple regression analyses have been carried out in term of using experimental data for the high strength concrete of 40 to 80 MPa available in literatures. Accordingly, new parameters associated with the stress distribution have been proposed and employed for the design of flexural and compressive members. Comparative design examples indicate that designs with new parameters reduce section dimensions compared to those with the current code parameters for concrete strengths of 40 to 70 MPa. In particular, for compressive members, design with new parameters exhibit conservative compressive force compared to those with the current code parameters.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.3
• /
• pp.347-362
• /
• 2019

Underground excavation using TBM machines has been increasing to reduce complaints caused by noise, vibration, and traffic congestion resulted from the urban underground construction in Korea. However, TBM excavation design and construction still need improvement because those are based on standards of the technologically advanced countries (e.g., Japan, Germany) that do not consider geological environment in Korea at all. Above all, although TBM performance is a main factor determining the TBM machine type, duration and cost of the construction, it is estimated by only using UCS (uniaxial compressive strength) as the ground parameters and it often does not match the actual field conditions. This study was carried out as part of efforts to predict penetration rate suitable for Korean ground conditions. The effective parameters were defined through the correlation analysis between the penetration rate and the geotechnical parameters or TBM performance parameters. The effective parameters were then used as variables of the multiple regression analysis to derive a regression model for predicting TBM penetration rate. As a result, the regression model was estimated by UCS and joint spacing and showed a good agreement with field penetration rate measured during TBM excavation. However, when this model was applied to another site in Korea, the prediction accuracy was slightly reduced. Therefore, in order to overcome the limitation of the regression model, further studies are required to obtain a generalized prediction model which is not restricted by the field conditions.

• Korean Journal of Social Welfare
• /
• v.66 no.1
• /
• pp.251-276
• /
• 2014

This study scrutinizes the common sense in the field of disability employment that the bigger the size of a firm, the lower the employment rate of people with disabilities. This common sense has been established by conventional cross-tabulation and multiple regression analyses without taking into account possible interactions between the sizes of firms and the industries in which they operate. This study shows that the distribution of the disability employment rate violates the linearity and homoscedasticity assumptions of the OLS. In an effort to find models that explain the data better, this study fits the OLS model, the weighted linear regression model, and the multinomial logit model as well as the path analysis which is meant to examine the relationships between firm size and other variables relevant to disability employment. The result shows that, when an interaction term between firm size and industry is added to the model, firm size does not have any significant effect on disability employment rate for those firms with 100 or more regular employees, to the contrary of the findings of prior studies. It also demonstrates that other factors such as job setting, the extent of helpfulness of disability employment employers perceive, employers' care for disability, and employers' awareness of disability policies may matter more than does firm size. This study proposes that future research and policy implementation for disability employment should pay no less attention to industry and other factors mentioned above than to firm size.

• Journal of Climate Change Research
• /
• v.4 no.4
• /
• pp.359-369
• /
• 2013

In this paper, correlations between driving parameters and $CO_2$ of light-duty vehicles have been analyzed. Three test vehicles equipped with PEMS (Portable Emission Measurement System) have been driven in real-road in urban areas of Seoul. Averaged vehicle speed, RPA(Relative Positive Acceleration) and stop ratio have been selected as main driving parameters. The analysis have been conducted in interrupted and uninterrupted road types. Averaged values in various driving conditions have been calculated with distance based moving averaging window method. The multiple linear regression method have been applied to account for correlation between driving parameters and $CO_2$ emissions. This approach has shown statistically that $CO_2$ emission per distance (g/km) have tendencies to be increased as decreased averaged vehicle speed and increased RPA and stop ratio. Compared with uninterrupted traffic, interrupted traffic have shown the lower vehicle speed and the higher RPA and stop ratio. These characteristics of driving parameters in interrupted traffic should cause the higher $CO_2$ emission per distance.

• Korean Journal of Remote Sensing
• /
• v.30 no.1
• /
• pp.61-73
• /
• 2014

This study reviewed an application of water quality estimation using an Airborne Hyperspectral Imagery (A-HSI) and tested a part of Han River water quality (especially suspended solid) estimation with available in-situ data. The estimation of water quality was processed two methods. One is using observation data as downwelling radiance to water surface and as scattering and reflectance into water body. Other is linear regression analysis with water quality in-situ measurement and upwelling data as at-sensor radiance (or reflectance). Both methods drive meaningful results of RS estimation. However it has more effects on the auxiliary dataset as water quality in-situ measurement and water body scattering measurement. The test processed a part of Han River located Paldang-dam downstream. We applied linear regression analysis with AISA eagle hyperspectral sensor data and water quality measurement in-situ data. The result of linear regression for a meaningful band combination shows $-24.847+0.013L_{560}$ as 560 nm in radiance (L) with 0.985 R-square. To comparison with Multispectral Imagery (MSI) case, we make simulated Landsat TM by spectral resampling. The regression using MSI shows -55.932 + 33.881 (TM1/TM3) as radiance with 0.968 R-square. Suspended Solid (SS) concentration was about 3.75 mg/l at in-situ data and estimated SS concentration by A-HIS was about 3.65 mg/l, and about 5.85mg/l with MSI with same location. It shows overestimation trends case of estimating using MSI. In order to upgrade value for practical use and to estimate more precisely, it needs that minimizing sun glint effect into whole image, constructing elaborate flight plan considering solar altitude angle, and making good pre-processing and calibration system. We found some limitations and restrictions such as precise atmospheric correction, sample count of water quality measurement, retrieve spectral bands into A-HSI, adequate linear regression model selection, and quantitative calibration/validation method through the literature review and test adopted general methods.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2016.05a
• /
• pp.412-427
• /
• 2016

댐의 건설은 자연하천에서 퇴적과 침식의 유사 순환과정에 영향을 주고 저수지 퇴사(reservoir sedimentation)를 야기한다. 이러한 현상은 댐의 건설 이후 장기간 축적되면서 이수와 취수에 대한 영향을 가져오기 때문에 댐 관리와 설계를 위해 정확한 추정이 필요하다. 퇴사량을 산정하는 방법에는 실측자료를 방법과 실제 유사량 자료를 이용하는 방법 그리고 경험공식을 이용하는 방법 등이 있으나, 가용한 자료의 부족으로 주로 경험 공식에 의존하고 있다. 이에 본 연구에서는 국내 대규모 다목적댐에 적합한 비퇴사량 산정 경험 공식을 제안하고자 하였다. 이를 위해 먼저 기존의 공식을 조사 및 검토하여 비퇴사량에 영향을 미칠 만한 여러 인자들을 선정하였다. 총 8개 국내 대규모 다목적댐의 비퇴사량 자료와 제원을 이용하여 다중 회귀분석을 실시하여 최종적인 식을 제안하였다. 그 결과, 대규모 다목적댐의 비퇴사량에 영향을 미치는 인자로 연평균 강우량(P, mm),연평균 유입량(I, cms), 유역 평균경사(S, %),저수지 길이(L, km),저수용량/유역면적(C/A, $m^3/km^2$)을 채택하였으며, 제안된 식을 이용하여 산정한 비퇴사량과 실측 비퇴사량의 상관계수와 결정계수는 각각 0.985, 0.970으로 확인되었다. 아울러, 다중 공선성 분석에서도 모두 일반적인 기준치를 범위 안에 존재함을 확인하면서, 선정된 독립변수들이 통계적으로 유의함을 확인하였다. 허나, 가용 자료의 부족과 불확실성으로 인해 여전히 한계점이 존재한다. 충분한 비퇴사량 실측 자료가 구축된다면, 보다 신뢰도 높고 발전된 형태의 경험 공식의 제안이 가능할 것이다.

• The korean journal of orthodontics
• /
• v.39 no.2
• /
• pp.112-119
• /
• 2009

Objective: To develop a mixed dentition analysis method in consideration of the normal variation of tooth sizes. Methods: According to the tooth-size of the maxillary central incisor, maxillary 1st molar, mandibular central incisor, mandibular lateral incisor, and mandibular 1st molar, 307 normal occlusion subjects were clustered into the smaller and larger tooth-size groups. Multiple regression analyses were then performed to predict the sizes of the canine and premolars for the 2 groups and both genders separately. For a cross validation dataset, 504 malocclusion patients were assigned into the 2 groups. Then multiple regression equations were applied. Results: Our results show that the maximum errors of the predicted space for the canine, 1st and 2nd premolars were 0.71 and 0.82 mm residual standard deviation for the normal occlusion and malocclusion groups, respectively. For malocclusion patients, the prediction errors did not imply a statistically significant difference depending on the types of malocclusion nor the types of tooth-size groups. The frequency of prediction error more than 1 mm and 2 mm were 17.3% and 1.8%, respectively. The overall prediction accuracy was dramatically improved in this study compared to that of previous studies. Conclusions: The computer aided calculation method used in this study appeared to be more efficient.

• Journal of Korean Society of Transportation
• /
• v.35 no.4
• /
• pp.321-331
• /
• 2017

The objective of this study is to analyze the factors affecting the pedestrian accidents of roundabout near schools. To this end, this study has focus on the comparative analysis of pedestrian accidents across different school areas. The traffic accident data from 2007 to 2014 are collected from TAAS data set of Road Traffic Authority. To develop the pedestrian accident rate model, the linear regression model has been utilized in this study. 28 explanatory variables such as geometry and traffic volume factors are used. The main results are summarized as follows. First, the null hypotheses that the number of pedestrian accidents are the same are rejected. Second, 5 multiple linear regression accident models with higher statistical significance (adjusted $R^2$ of 0.651~0.788) have been developed. Third, while the common variables of 3 models (model I~III) related to school location are evaluated to be the pedestrian island, crosswalk, types of roundabout, elementary school and bus stop. Fourth, while the common variable of 3 models (model III~V) related to near school area or not is evaluated to be pedestrian island, type of roundabout, sidewalk, elementary school, speed hump, speed limit sign and number of entry lane. As a result, the installation of pedestrian islands and crosswalk might be expected to decrease the number of pedestrian accidents near schools.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.3
• /
• pp.544-552
• /
• 2019

The purpose of this study was to find concrete measures to improve the subjective health level, happiness and quality of life of the elderly according to economic level and to propose social and policy alternatives accordingly. As a research method, 63,929 elderly people aged 65 or older were surveyed using the Community Health Survey (Indicator Bank) _v09, and the frequency of health use by economic level, subjective health level, euphoria and quality of life Analysis and Chi square analysis and independent t-test. Multi variate logistic regression analysis was performed with subjective health level as a dependent variable and multiple linear regression analysis was performed to determine the factors affecting euphoria and quality of life. The results of the study are as follows. In the case of recipients, medical use was lower than that of non-recipients, lower education level, female age of 75 years or older, and less stress, In case of present or past recipients, the result of non - receipt increased as the subjective health level was worse, and the non - recipient had higher euphoria and quality of life. As a result, there is a need for alternatives to increase opportunities for medical use among the recipients, with particular attention being paid to women and elderly people over 75 years old. It is expected to be used as a basic data to effectively improve the health promotion, happiness and quality of life of the elderly people of low income group.

• Journal of Korean Society of Transportation
• /
• v.32 no.4
• /
• pp.315-326
• /
• 2014

This paper analyzes and compares the pedestrian characteristics of 5 urban communities with 2012 Seoul floating population survey data. First of all, differences in total pedestrian volumes and time distribution of the volumes are compared across the 5 urban communities and the effects of pedestrian road properties are investigated. Then, we conduct a regression analysis to find factors influencing pedestrian volume according to the type of urban community and day of week. As results, the urban community had the greatest volume and the volume increased significantly at lunch time. Center bus lane, bus stop, and crosswalk lead to more trips in the urban community, while opposite patterns occurred in the other communities. Less slopes and commercial region areas caused more trips in all communities. Regression analysis results showed that a variety of variables including demographic indices, land use type and pedestrian road properties differently affect pedestrian volumes in individual urban communities. The research can be used as basic data to establish polices for pedestrian environment improvement.