PURPOSES : This paper presents a foundational study aimed at strengthening the competitiveness of future overseas construction engineering projects, efficiently guiding investment decisions for the government or private sectors and establishing policy suggestions for areas that need to be supplemented and linked. METHODS : The data envelopment analysis (DEA) model was used to measure the operational efficiency for individual types of work. The DEA model for measuring efficiency uses the representative Charnes, Cooper, and Rhode (CCR) and Banker, Charnes, and Cooper (BCC) models. RESULTS : By using statistics of overseas construction projects and conducting DEA, it was revealed that construction management was most needed in the energy facility sector of overseas construction projects. CONCLUSIONS : Although the capabilities of our country's companies are excellent, it was evident that the energy and industrial facilities sectors, which need to be supplemented to enhance their competitiveness, require policy support that incorporates construction management (CM). Consequently, it was confirmed that the construction management sector needs investment that should continue to be activated in the future. Additional research is needed that considers variables and environments related to overseas construction projects’ on-site conditions. To this end, the government should continue to promote research and government investment linked to CM to make progress in overseas construction sectors.

The n-type Bi2-xSbxTe3 compounds have been of great interest due to its potential to achieve a high thermoelectric performance, comparable to that of p-type Bi2-xSbxTe3. However, a comprehensive understanding on the thermoelectric properties remains lacking. Here, we investigate the thermoelectric transport properties and band characteristics of n-type Bi2-xSbxTe3 (x = 0.1 – 1.1) based on experimental and theoretical considerations. We find that the higher power factor at lower Sb content results from the optimized balance between the density of state effective mass and nondegenerate mobility. Additionally, a higher carrier concentration at lower x suppresses bipolar conduction, thereby reducing thermal conductivity at elevated temperatures. Consequently, the highest zT of ~ 0.5 is observed at 450 K for x = 0.1 and, according to the single parabolic band model, it could be further improved by ~70 % through carrier concentration tuning.

PURPOSES : The primary objective of this study is to analyze the relationship between the factors that affect traffic incident duration in the mainline, tunnel, and ramp segments of an expressway. In addition, this study derived the most suitable statistical prediction model based on various incident duration distributions. METHODS : South Korean expressway crash data for 11 years, from 2011 to 2021, were analyzed. The incident durations on the mainline, tunnel, and ramp segments were selected using the accelerated failure time model, which is a parametric survival analysis approach. RESULTS : The mainline segment showed that the incident duration increased during accidents, including guard pipe collisions, multivehicle collisions, and snowfall. In particular, collisions in a tunnel with shoulder facilities increase the incident duration, while decreasing the time in the ramp segment. CONCLUSIONS : The incident duration model for each segment type yielded the most accurate results when applying a log-logistic distribution.

In stream ecosystem assessment, RIVPACS, which makes a simple but clear evaluation based on macroinvertebrate community, is widely used. In this study, a preliminary study was conducted to develop a RIVPACS-type model suitable for Korean streams nationwide. Reference streams were classified into two types (upstream and downstream), and a prediction model for macroinvertebrates was developed based on each family. A model for upstream was divided into 7 (train): 3 (test), and that for downstream was made using a leave-one-out method. Variables for the models were selected by non-metric multidimensional scaling, and seven variables were chosen, including elevation, slope, annual average temperature, stream width, forest ratio in land use, riffle ratio in hydrological characteristics, and boulder ratio in substrate composition. Stream order classified 3,224 sites as upstream and downstream, and community compositions of sites were predicted. The prediction was conducted for 30 macroinvertebrate families. Expected (E) and observed fauna (O) were compared using an ASPT biotic index, which is computed by dividing the BMWPK score into the number of families in a community. EQR values (i.e. O/E) for ASPT were used to assess stream condition. Lastly, we compared EQR to BMI, an index that is commonly used in the assessment. In the results, the average observed ASPT was 4.82 (±2.04 SD) and the expected one was 6.30 (±0.79 SD), and the expected ASPT was higher than the observed one. In the comparison between EQR and BMI index, EQR generally showed a higher value than the BMI index.

PURPOSES : The objective of this study is to develop an optimal placement of the overturning prevention device based on a 3D object model during the development of the girder-type overturning prevention device for the remote control construction of bridges METHODS : Based on existing construction methods and literature research, a detailed design model of a phase-optimized conduction prevention device is presented. The 3D-object model data, optimal placement, and an operating range of the equipment developed for the remote control construction of bridge girders were considered. RESULTS : The shape of the overturning prevention device was selected taking into account the dimensions and operating range of numerous devices developed for the remote control construction of the bridge. In particular, the detachable device was chosen to allow a trouble-free construction considering the spacing between the pier cap of the bridge and the girders. The overturning prevention device presented based on this 3D object model will be manufactured as a mock-up and used for a demonstration project on remote control bridge construction. CONCLUSIONS : This will enable easy and economical construction as this development will support remote control construction of bridge girders to avoid accidents such as workers falling from high places like piers.

KAERI has planned to carry out a series of dynamic tests using a shaking table and time-history analyses for a channel-type concrete shear wall to investigate its seismic performance because of the recently frequent occurrence of earthquakes in the south-eastern parts of Korea. The overall size of a test specimen is ×× 2500 mm×3500 mm×4500 mm, and it consists of three stories having slabs and walls with thicknesses of 140 mm and 150 mm, respectively. The system identification, FE model updating, and time-history analysis results for a test shear wall are presented herein. By applying the advanced system identification, so-called pLSCF, the improved modal parameters are extracted in the lower modes. Using three FE in-house packages, such as FEMtools, Ruaumoko, and VecTor4, the eigenanalyses are made for an initial FE model, resulting in consistency in eigenvalues. However, they exhibit relatively stiffer behavior, as much as 30 to 50% compared with those extracted from the test in the 1st and 2nd modes. The FE model updating is carried out to consider the 6-dofs spring stiffnesses at the wall base as major parameters by adopting a Bayesian type automatic updating algorithm to minimize the residuals in modal parameters. The updating results indicate that the highest sensitivity is apparent in the vertical translational springs at few locations ranging from 300 to 500% in variation. However, their changes seem to have no physical meaning because of the numerical values. Finally, using the updated FE model, the time-history responses are predicted by Ruaumoko at each floor where accelerometers are located. The accelerograms between test and analysis show an acceptable match in terms of maximum and minimum values. However, the magnitudes and patterns of floor response spectra seem somewhat different because of the slightly different input accelerograms and damping ratios involved.

해양공간 이용 수요와 중요도의 지속적인 증가에 따라 국내에서의 해양탐사 및 해양조사활동이 활발히 수행중이다. 이러한 활 동을 위해 운항되는 해양탐사조사선은 목적 및 탐사선박에 따라 특수한 운항패턴을 가지므로 해상교통위험도를 고려한 연구가 필요하다. 본 연구에서는 해양탐사·조사선의 운항이 해상교통에 미치는 영향을 각 요인별 상관관계로 파악하고자 하였다. 우리나라에서 활동중인 해양탐사·조사선 현황을 파악하였고 일부 해양물리탐사선의 특수한 운항실태를 식별하였다. 운항자부담감의 결과를 비교하기 위해서 운 항요인 중 각 2가지를 독립변수로하여 ES Model 기반의 해상교통류시뮬레이션을 수행하였다. 분석결과 교통량, 선박 길이, 속력 순으로 운항자 부담감이 두드러지게 변화하는 것을 확인하였다. 또한 인근 해상교통흐름과 선수방위(침로)가 거의 유사한 운항 침로를 설정할 경 우 운항자 부담감이 다소 감소하는 것을 확인하였다. 이에 따라 해양탐사·조사선이 운항계획을 설정할 단계에서 인근 해상교통현황을 파 악하여 운항방식에 반영한다면 운항자 부담감을 감소시키는데 기여할 것이다.

The current study identified risk factors associated with porcine circovirus type 2 (PCV2) infection on pig farms in the Republic of Korea using a multinomial logistic regression model to evaluate the PCV2 infection status of pigs at different growth stages. Compulsory disinfection of visitors (odds ratio [OR]: 0.019, 95% confidence interval [CI]: <0.001–0.378, p=0.0095), compulsory registration of visitors (OR: 0.002, 95% CI: <0.001–0.184, p=0.0070), regular blood testing (OR: 0.012, 95% CI: <0.001–0.157, p=0.0007), and running on-farm biosecurity learning programs for workers (OR: 0.156, 95% CI: 0.040–0.604, p=0.0072 and OR: 0.201, 95% CI: 0.055–0.737, p=0.0155, respectively) were identified as factors which could reduce the risk of PCV2 infection. However, visitation by a regular veterinarian (OR: 32.733, 95% CI: 3.768–284.327, p=0.0016) was associated with PCV2 infection.

In this paper, an experimental study was carried out for vibration control of cable bridges with structurally flexible characteristics. For the experiment on vibration control, a model bridge was constructed by reducing the Seohae Grand Bridge and the shear type MR damper was designed using the wind load response measured at Seohae Grand Bridge. The shear type MR damper was installed in the vertical direction at the middle span of the model bridge, and dynamic modeling was performed using the power model. The tests of the vibration control were carried out by non-control, passive on/off control and Lyapunov control method on model bridge with scaled wind load response. The performance of the vibration control was evaluated by calculating absolute maximum displacement, RMS displacement, absolute maximum acceleration, RMS acceleration, and size of applied power using the response (displacement, acceleration, etc.) from the model bridge. As a result, the power model was effective in simulating the nonlinear behavior of the MR damper, and the Lyapunov control method using the MR damper was able to control the vibration of the structure and reduce the size of the power supply.

As the fourth industry revolution is starting, most of the fields including education are rapidly being changed. In parituclar, research on IT or SW fusion in each field is being performed. This paper discusses novel approaches to improve previous education services through IT fusion. First, I propose a way to converge IT into global education, which focuses on students of the college of education who are interested in becoming teachers. Due to internationalization demands in the field of education, the necessity of global education is increasing rapidly. However, a general consensus of the definition and model for global education is not clear yet and the actual performance falls short of our expectations owing to high cost, low effectiveness, and lack of persistence in the process of global education. To overcome the limits of global education and develop an efficient education system, this research suggests an IT-fusion-based education system for training global teachers. Second, it is difficult for an instructor to grasp instantly how much learners understand learning content in class in a typical education environment. In case of a class, which consists of possibly dozens of students at various levels ; trying to understand degree and learning achievement of the learners in a broad spectrum, depending on the learning contents. Therefore, it is almost impossible for an instructor to let all of the learners reach a specific learning objective. In this paper, I propose an approach that enables the arbitrary rate of learners, who reach a learning goal, to be set by an instructor. I describe an instruction support system combined with an instant response system, dynamic formative evaluation scheme, and confidence level. I expect that this approach can make an instructor set the ratio of learners, who reach the learning objective, as the instructor wants, and brings about effective instruction. Third, this study proposes a new learning model for improving problem solving and programming skills. To solve a real world problem using IT, problem solving and programming skills are important. In this study, I describe a learning model that can help to improve problem solving and programming skills, based on computational thinking. The feature of the learning model proposed is to offer learners challenges and spur interest by presenting the questions into learning games of an intercompetition type after developing the questions that improve problem solving and programming skills. Another feature is to present the questions about algorithms and programming in various forms and generate them dynamically. Especially, by providing an inter-competition game type, due to increase of competition between learners, learners will feel relatively less difficulty in problem solving and programming, and enable them to naturally improve problem solving abilities and programming skills through the competition.

The purpose of this study is to make a generalized analytical based on the proposed experiments on reinforced concrete(RC) partially infilled frames by U-type precast concrete(PC) wall panels with openings. RC frame and PC wall panels were connected with different strengths. Therefore, we developed modified strut-tie model(STM) with two seismic retrofitting specimens and conducted a nonlinear analysis by using a computer analysis program. Based on the test results, truss member of modified STM was designed, applying the strut-tie model theory of ACI 318M-11 Appendix- A. As a result, the modified STM analysis results were very similar to the experimental results. As a result of the load-displacement curve comparison, the failure load were similar within 5∼17% of error range. In particular, the experimental results and the results of modified STM analysis show that the failure behavior almost matched.

Cyclic loading test was performed on the partially infilled reinforced concrete(RC) frames by L-type precast concrete(PC) wall panels with the connections of two different strength. Based on the results of experimental test, the nonlinear analysis was practiced with modified strut-tie model(STM) method by using a computer program. Truss member of modified STM was designed, applying the strut-tie model theory of ACI 318M-11 Appendix-A. Modified STM was designed with two ways according to the test result. PC wall panel and RC frame were assumed to composite when push loading applied. The PC and RC structures were also assumed to behave non-composite and those two structures connected with link(top connector) when pull loading applied. The connection was designed by using elastic link of program. The results of analytical modified STM process generally conform to the experimental results. The failure load and the failure mode of the specimens could be predicted using modified STM. The ratio of failure load measured in specimens to analytical values were between 0.83∼1.16. The member or connection which was failed in experiment yield in the results of modified STM. The failure mode perfectly matched.

본 연구는 난지형 마늘 ‘남도’의 적정 생육 온도 구명과 일 평균온도를 이용한 구중 예측을 위하여 수행되었다. 온도처리는 주간 16시간 야간 8시간 처리로 11/7oC, 14/10oC, 17/12oC, 20/15oC, 23/18oC, 28/23oC 로 설정하였다. 구의 생체중과 건물중은 20oC/15oC 처리구에서 가장 높았으며 고온이나 저온으로 갈수록 감소하였다. 엽수와 총엽면적은 저온인 처리구가 고온처리구보다 생장이 느렸으나, 최종적으로는 최고온도인28/23oC을 제외하고 유사한 경향을 보였다. 구의 생체중으로 6종의 함수를 개발하였으며 이를 통해 ‘남도’ 마늘의 적정 생육온도와 한계온도, 온도에 따른 구생장량을 확인할 수 있었다. 분석 결과 ‘남도’ 마늘의 적정 생육온도는 18~20oC 이며 GDD 기본온도와 한계온도는 7.1oC와 31.7oC로 추정할 수 있었다. 일 평균온도를 이용한 수확기 기준 구 생체중 모델을 검증하기 위하여 온도구배터널의 기상자료를 이용하여 예측하였다. 선형함수를 이용한 예측은 79.0~95.0%, 2차 함수를 이용한 예측은 77.2~92.3%, 로 지스틱분포 함수를 이용한 예측은 80.0~95.8% 예측도를 보였다. 이중 가장 예측력이 좋은 함수는 로지스틱분포 함수이며 생육적정온도와 한계온도도 잘 표현하였다.

OBJECTIVES : The objective of this study is to develop a traffic accident model of a roundabout based on the type of land use. METHODS : The traffic accident data from 2010 to 2014 were collected from the“ traffic accident analysis system (TAAS)”data set of the Road Traffic Authority. A multiple linear regression model was utilized in this study to analyze the accidents based on the type of land use. Variables such as geometry and traffic volume were used to develop the accident models based on the type of land use. RESULTS : The main results are as follows. First, the null hypothesis that the type of land use does not affect the number of accidents is rejected. Second, four accident models based on the type of land use have been developed, which are statistically significant (high R2 values). Finally, the total entering and circulating volumes, area of the central island, number of speed breakers, mean number of entry lanes, diameter of the inscribed circle, mean width of the entry lane, area of the roundabout, bus stops, and number of circulatory roadways are analyzed to see how they affect the accident for each type of land use. CONCLUSIONS: The development of the accident models based on the type of land use has revealed that the accident factors at a roundabout are different for each case. Thus, more speed breakers in commercial areas and an inscribed circle of proper diameter in commercial and residential areas are determined to be important for reducing the number of accidents. Additionally, expanding the width of the entry lanes, decreasing the area of the roundabouts in residential areas, and reducing the conflict factors such as bus stops in green spaces are determined to be important.