• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.209-217
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• 2021

This paper investigates the effect of high strength hooked-end steel fiber content and aspect ratio on the compressive and flexural performance of concrete. A total of ten mixtures were prepared and tested. Concretes with specific compressive strength of 30 MPa were reinforced with three different aspect ratios (l/d) of steel fibers 64, 67, and 80 and three different percentages of steel fibers 0.25, 0.50, and 0.75% by volume of concrete. Tensile strengths of steel fibers with l/d of 64, 67, and 80 are 2,000, 2,400, and 2,100 MPa, respectively. The compressive and flexural properties of plain and steel fiber-reinforced concrete (SFRC) mixtures were evaluated and compared. The experimental results indicated that the incorporation of high-strength hooked-end steel fibers had significant effects on the compressive and flexural performance of concrete. With the increase of steel fiber content, compressive performances, such as Poisson's ratio and toughness, of concrete were improved. The steel fibers with the least l/d of 67 resulted in a larger enhancement of compressive performances. The residual flexural strength, that is, post-cracking flexural resistance and toughness, of concrete is mainly depended on the dosage and aspect ratio of steel fibers. The residual flexural strength at serviceability (SLS) and ultimate limit state (ULS) defined in fib Model Code 2010 (MC2010) is increased as the fiber content and aspect ratio increase.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.1-8
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• 2019

Phase change material(PCM) has the capacity to absorb or release energy in heat when the phase changes. This study conducted to investigate the effect of strontium-based PCM on the hydration heat and mechanical properties of mortar with fly ash and blast furnace slag. The amounts of PCM were 1%, 2%, 3%, 4%, and 5% by the cementitious materials weight. The tests about mortar flow, semi-adiabatic temperature rise, compressive and flexural strength tests were carried out for twelve types of mortar mixtures. The test results indicated that the use of PCM was effective to reduce hydration heat and retard hydration of mortar with industrial by-products. In particular, the heat generation rate of mortars with fly ash was lower than that of mortars with blast furnace slag. The compressive strength of mortar with fly ash and blast furnace slag were decreased with increasing PCM ratio.

• Journal of the Korea Institute of Construction Safety
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• v.6 no.1
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• pp.27-32
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• 2024

In this study, based on accident cases of manned and unmanned tower cranes, the types and causes of accidents were analyzed and tower crane accident prevention measures were proposed accordingly. As a result, 'lack of communication' was commonly analyzed as the biggest cause of accidents. Therefore, in this study, we investigated domestic and international systems and laws regarding signalmen responsible for communication between tower crane operators and workers and proposed the following three improvement methods. First, the signalman system must be legally and institutionally reestablished. Second, national agencies and private organizations with expertise should create standardized training manuals and distribute them to signalman educators, and create checklists to manage educators. Third, in the case of a site using a tower crane, the employer must mandatorily deploy a signalman with professional qualifications. Lastly, the results of this study are expected to highlight the differences in accident types and causes of manned and unmanned tower cranes and the need for legal and institutional improvement in the signal system.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.1
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• pp.17-21
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• 2015

There have been sustained developments of advanced technologies using traffic safety facilities recently and techniques for identifying failure modes and devices which could result in fatal outcomes. The purpose of this research is aimed at improving the driving conditions in advance through analyzing the IT convergence, driving education, researches for vehicles, field of construction and robotics. The researchers evaluate on usability tests of the driving with 26 candidates through focusing on safety, convenience, efficiency, effectiveness. Using specialized LED panel to enhance driving performances of disabled people are for cautious road conditions like foggy weather or heavy rain. As a result, there were improvements in the driving conditions, and candidates reported this system was helpful. It allows them for maintaining proper driving all times and was especially informative for people with low vision or visually impaired. This system plays a pivotal role as a prevention mechanism not only for regular drivers but also for further delict of traffic violations or accident offenders who already have former record on tort.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.207-207
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• 2019

최근 우리나라는 지역 특성 및 기후변화의 영향으로 인해 수문학적 요소의 변동성이 커지고 수자원의 지속적인 관리에 있어 유출량은 중요한 문제로 여겨지고 있다. 특히 일부 소하천 또는 접경지역과 같은 미계측유역은 수문학적 요소에 대한 자료가 부족하고 수문모형의 초기치 설정과 과거 유출량 자료를 통하여 최적화한 매개변수를 결정해야하므로 장기유출분석이 어렵다. 본 연구의 적용유역으로 미계측유역인 임진강상류 유역에 대한 유출량 추정을 위해 계측 유역의 자료를 활용하여 모형의 매개변수 등을 추정하는 지역화 기법인 다중선형회귀분석과 공간근접분석을 활용하여 유출량을 산정 및 검증하였다. 또한, 확률론적 예측이 가능한 앙상블 기법 적용을 통한 유출량 예측을 하였고, 이를 예측 정확성 평가지표를 통해 효율성 검토를 수행하여 미계측유역의 유출량에 대해 확률론적 예측을 수행하였다. 대표적 지역화 기법의 적용성을 검토한 결과, 계측유역을 통해 다중선형회귀분석과 공간근접분석을 abcd 모형에 적용하였다. 모의유출량을 산정하고 실측 유출량과 비교 분석 결과 모의정확성이 높게 분석되었다. 이와 같은 검증 결과를 토대로 미계측유역의 유출량을 추정하였다. 또한, 지역화 기법을 앙상블 기법에 적용하여 확률론적 유출량 예측의 효율성을 검토하였다. 적용유역과 같은 지류를 포함하고 있는 임진강하류 유역을 대상으로 수행하였다. 검증기간(2013년~2017년) 동안의 월 예측 유출량 앙상블 생성을 위해 과거 강우량와 증발량(1988년~2012년) 자료를 사용하였으며, 지역화 기법을 적용한 abcd 모형을 이용하였다. 예측 유출량의 정확성 평가를 실시하였으며, 정확성이 비교적 높게 분석되었다. 이와 같은 결과를 토대로 미계측유역의 확률론적 유출량을 예측하였다. 따라서, 대표적 지역화 기법을 앙상블 기법에 적용하여 확률론적 유출량을 예측할 경우 보다 정확한 유출량 예측이 가능하다.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.129-134
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• 2018

This is about the CCTV hacking which is one of the recently emerging privacy-spilling crime. Recently, the usage of CCTV is being increased, and Black Hat Hackers spill the individual's privacy by hacking it. However, That crime is being increased. However, most users rarely fulfill the security management, and the government's measures are insufficient. Therfore, this research report implies some security technologies including user authentication protocols such as SSH Tunneling and Media Encryption Algorithm. and recently developed technologies including Wookyeong Information Technology's SecuWatcher for CCTV, Norma's CCTV Care App, and MarkAny's Password SAFERTM for CCTV.

• Korean Journal of Construction Engineering and Management
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• v.20 no.2
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• pp.95-104
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• 2019

EPC plant projects are large and complex, requiring systematic working methodologies, accumulated data, and thorough planning through communications between the entities. In this study, the method of extracting the process planning information using asset data of the plant project and using it to present the initial process plan is presented through the concept of IAP(Interactive Planning). In order to carry out the effective IAP at the early stage of the project, this study extracted the schedule element information from the asset data, created the process plan for each work package, and applied it to the sample project case. Through the proposed IAP methodology, it is possible to promote the utilization of asset data, to identify schedule risks, and to develop countermeasures, which can form the basis for establishing the process management strategy to successfully complete the project.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.11
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• pp.155-162
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• 2019

The construction industry is the highest safety accident causing industry as 28.55% portion of all industries' accidents in Korea. In particular, falling is the highest accidents type composed of 60.16% among the construction field accidents. Therefore, we analyzed the factors of major disaster affecting the fall accident and then derived feature importances by considering various variables. We used data collected from Korea Occupational Safety & Health Agency (KOSHA) for learning and predicting in the proposed model. We have an effort to predict the degree of occupational fall accidents by using the machine learning model, i.e., Adaboost, short for Adaptive Boosting. Adaboost is a machine learning meta-algorithm which can be used in conjunction with many other types of learning algorithms to improve performance. Decision trees were combined with AdaBoost in this model to predict and classify the degree of occupational fall accidents. HyOperpt was also used to optimize hyperparameters and to combine k-fold cross validation by hierarchy. We extracted and analyzed feature importances and affecting fall disaster by permutation technique. In this study, we verified the degree of fall accidents with predictive accuracy. The machine learning model was also confirmed to be applicable to the safety accident analysis in construction site. In the future, if the safety accident data is accumulated automatically in the network system using IoT(Internet of things) technology in real time in the construction site, it will be possible to analyze the factors and types of accidents according to the site conditions from the real time data.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.265-277
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• 2019

The objective of this study was to develop and verify an effective vortex typed nonfilter nonpoint source pollution reduction device. To verify this pollution reduction device, a total of twelves scenarios (three rainfall intensities${\times}$two states${\times}$two steps) of experiments were conducted using pollutants. First, simulated inflow (rainfall intensity 2.5 mm/hr: $0.00152m^3/s$, rainfall intensity 3.395 mm/hr: $0.00206m^3/s$, rainfall intensity 6.870 mm/hr: $0.00326m^3/s$) was calculated. Second, pollutants (mixture of 25% of four particle sizes) were selected and injected. Third, pollutant removal efficiencies of this device at its initial state and operating states were measured. As a result of analysis based on rainfall intensity, the concentration of pollutants was decreased by the device at initial and operating states at all rainfall intensities. Its pollutant removal efficiency was more than 80%, the standard set by the Ministry of Environment. Its pollutant removal efficiency was gradually increased over time, reaching approximately 90%. Its pollutant removal efficiency was higher in its operating state than that in its initial state. Therefore, nonpoint source pollutants can be effectively removed by this vortex typed nonpoint source pollution reduction device developed in this study.

• Journal of the Korean Vacuum Society
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• v.19 no.6
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• pp.423-431
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• 2010

In order to teach the accumulated knowledge of nanoscience, nanoengineering and nanotechnology to graduate school students and young scientists with the sense of public engagement, Osaka University started from 2004 to prepare and offer various kinds of education and training programs such as trans-disciplinary graduate-school minor program, evening course refresher program, short-term international research training program, etc. It offers a series of lectures, partly broadcasted live to satellite classrooms. In addition, the students can join intensive hands-on training programs using modern facilities, allowing them to design, fabricate, measure, characterize and functionalize nanomaterials and nanodevices. In addition, there are four specially designed lectures and research training programs aimed for nanocommunication including social, legal and ethical relationship: "Nanotechnology Career-up Lectures", "Social Engagement on Nanotechnology", "Road Map Design on Nanotechnology", and "Project-Aimed Learning and Training Programs (PAL)". The outline of the whole programs is described together with the specialized programs for nanocommunication.