• Journal of KIBIM
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• v.8 no.2
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• pp.29-40
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• 2018

Recently, the free-form buildings are continuously increasing in the world. However, due to the shortage of experience and technology in the project of the free-form buildings, problems such as increase of construction cost, increase of air and deterioration of construction quality are occurring. In this study, data on the 27 free-form projects in Korea and abroad using digital fabrication were collected through the journals, reports, articles, and websites of the institutes and case studies were conducted based on the collected data. Based on the following case analysis, we conducted evaluation of case data analysis based on the knowledge domain specified in PMBOK. Evaluation of case data analysis shows that the application of digital fabrication is divided into positive and negative effects for each knowledge area in the free-form building project. Using the results of the analysis, we can confirm the knowledge field showing the positive effect on the free-form building project by using digital fabrication. However, the data scale of the project using the digital fabrication is not realized at present and research is insufficient. In Korea, a small number of specialists were interviewed and verified because experts do not exist much in korea. Therefore, this study is expected to suggest the necessity of applying digital fabrication in the free-form building projects in the construction industry.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.2
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• pp.124-137
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• 2018

Due to the decrease in coastal productivity and deterioration in the quality of ecosystem which result from the excessive overfishing of fisheries resources and the environmental pollution, fisheries resources in the Korean waters hit the dangerous level in respect of quantity and quality. In order to manage sustainable and effective fisheries resources, it is necessary to suggest the potential yield (PY) for clarifying available fisheries resources in the Korean waters. So far, however, there have been few studies on the estimation methods for PY in Korea. In addition, there have been no studies on the comparative analysis of the estimation methods and the substantial estimation methods for PY targeted for large marine ecosystem (LME) For the reasonable management of fisheries resources, it is necessary to conduct a comprehensive study on the estimation methods for the PY which combines population dynamics and ecosystem dynamics. To reflect the research need, this study conducts a comparative analysis of estimation methods for the PY in the Korean waters of the East Sea to understand the advantages and disadvantages of each method, and suggests the estimation method which considered both population dynamics and ecosystem dynamics to supplement shortcomings of each method. In this study, the maximum entropy (ME) model of the holistic production method (HPM) is considered to be the most reasonable estimation method due to the high reliability of the estimated parameters. The results of this study are expected to be used as significant basic data to provide indicators and reference points for sustainable and reasonable management of fisheries resources.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.15-21
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• 2010

Structural analysis used to evaluate the load carrying capacity of a bridge should implement behavioral characteristics similar to the actual behaviors of the structure through loading tests, but it is not feasible in many cases due to the behavioral characteristics of points, inadequate modeling method in structural analysis, errors in loading tests, changes in strength and rigidity resulting from cross-sectional damage, etc. This problem can be more serious if bridge bearings have been damaged or were not installed and, consequently, the bearings do not function properly. This study produced results similar to actual behaviors using a structural analysis model built with support moment derived from the difference $\Delta{\delta}$ between measured deflection obtained by confining the cantilever segment of a solid beam and calculated deflection under a unrestrained condition. When the load carrying capacity of a bridge in operation was evaluated in consideration of the confinement condition of supports, the result was 15~19% lower than load carrying capacity calculated by the existing method.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.2
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• pp.26-34
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• 2011

Hybrid powertrain systems have been developed to improve the fuel efficiency of internal combustion engines. In the case of a parallel hybrid powertrain system, an engine and a motor are directly coupled. Because of the hardware configuration of the parallel hybrid system, friction and the pumping losses of internal combustion engines always exists. Such losses are the primary factors that result in the deterioration of fuel efficiency in the parallel-type hybrid powertrain system. In particular, the engine operates as a power consumption device during the fuel-cut condition. In order to improve the fuel efficiency for the parallel-type hybrid system, cylinder deactivation (CDA) technology was developed. Cylinder deactivation technology can improve fuel efficiency by reducing pumping losses during the fuel-cut driving condition. In a CDA engine, there are two operating modes: a CDA mode and an SI mode according to the vehicle operating condition. However, during the mode change from CDA to SI, a serious fluctuation of the air-fuel ratio can occur without adequate control. In this study, an air-fuel ratio control algorithm during the mode transition from CDA to SI was proposed. The control algorithm was developed based on the mean value CDA engine model. Finally, the performance of the control algorithm was validated by various engine experiments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.128-138
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• 2015

Carbonation is one of the most critical deterioration phenomena to concrete structures exposed to high $CO_2$ concentration, sheltered from rain. Lots of researches have been performed on evaluation of carbonation depth and changes in hydrate compositions, however carbonation modeling is limitedly carried out due to complicated carbonic reaction and diffusion coefficient. This study presents a simplified carbonation model considering diffusion coefficient, solubility of $Ca(OH)_2$, porosity reduction, and carbonic reaction rate for low concentration. For verification, accelerated carbonation test with varying temperature and MIP (Mercury Intrusion Porosimetry) test are carried out, and carbonation depths are compared with those from the previous and the proposed model. Field data with low $CO_2$ concentration is compared with those from the proposed model. The proposed model shows very reasonable results like carbonation depth and consuming $Ca(OH)_2$ through reduced diffusion coefficient and porosity compared with the previous model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.29-39
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• 2012

The main objective is to predict the future degradation and maintenance budget for a suspension bridge system. Bayesian inference is applied to find the posterior probability density function of the source parameters (damage indices and serviceability), given ten years of maintenance data. The posterior distribution of the parameters is sampled using a Markov chain Monte Carlo method. The simulated risk prediction for decreased serviceability conditions are posterior distributions based on prior distribution and likelihood of data updated from annual maintenance tasks. Compared with conventional linear prediction model, the proposed quadratic model provides highly improved convergence and closeness to measured data in terms of serviceability, risky factors, and maintenance budget for bridge components, which allows forecasting a future performance and financial management of complex infrastructures based on the proposed quadratic stochastic regression model.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.569-575
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• 2015

The current Total Pollution Load Control (TPLC) sets the Target Water Quality (TWQ) by utilizing the delivery ratio, unit loads, and water quality modeling, it also allocates the watershed's permitted discharge load. Currently, common target pollutants of every unit watershed in TPLC are BOD and T-P. This study has reviewed the 1th and 2th of TWQ setting process for the Nakdong River 3th TWQ setting in Total Pollution Load Control (TPLC). As a result of review, 1th and 2th were divided into one management basin (mulgeum) for setting management goals. However, 3th was divided into six management basins (mulgeum, gnagjeong, geumho river, nam river, miryang river, end of nakdong river). The principle of management goal setting were to achieve the objective criteria of Medium Areas for the linkage of the water environment management policy. And Anti-Degredation (principle of preventing deterioration) were applied to the 3th TWQ. Also, additional indicators were considered in accordance with the reduction scenarios for the final management goals.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.5
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• pp.721-731
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• 2018

Manpower in domestic construction sites is becoming more and more aging. Various methods have been devised to prevent productivity and quality deterioration of construction due to absence of skilled workers and difficulty in supplying manpower. Especially, many researchers study various methods such as Machine Guidance (MG) and Remote Machine Control to improve productivity and quality. Although many prior studies have been conducted since the advent of MG, There is lack of field test in a difficult site to stakeout. In this study, field test of MG excavator was carried out at difficult site to stakeout, and productivity analysis and quality evaluation were conducted. As a result of the analysis of productivity, the minimum value was 20.5%, the maximum value was 56.9%, and the average productivity in 4 days was 38.3% higher than the standard product. As a result of the analysis of quality, the horizontal error ${\pm}1cm$ and the vertical error ${\pm}2cm$ confirmed in the previous study were verified.

• Structural Engineering and Mechanics
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• v.54 no.6
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• pp.1135-1152
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• 2015

Most of current bridge decks are made of reinforced concrete and often deteriorate at a relatively rapid rate in operational environments. The quick deterioration of the deck often impacts other critical components of the bridge. Another disadvantage of the concrete deck is its high weight in long-span bridges. Therefore, it is essential to examine new materials and innovative designs using hybrid system consisting conventional materials such as concrete and steel with FRP plates which is also known as composite deck. Since these decks are relatively new, so it would be useful to evaluate their performances in more details. The present study is dedicated to Hat-Shape composite girder with concrete slab. The structural performance of girder was evaluated with nonlinear finite element method by using ABAQUS and numerical results have been compared with experimental results of other researches. After ensuring the validity of numerical modeling of composite deck, parametric studies have been conducted; such as investigating the effects of constituent properties by changing the compressive strength of concrete slab and Elasticity modulus of GFRP materials. The efficacy of the GFRP box girders has been studied by changing GFRP material to steel and aluminum. In addition, the effect of Cross-Sectional Configuration has been evaluated. It was found that the behavior of this type of composite girders can be studied with numerical methods without carrying out costly experiments. The material properties can be modified to improve ultimate load capacity of the composite girder. strength-to-weight ratio of the girder increased by changing the GFRP material to aluminum and ultimate load capacity enhanced by deformation of composite girder cross-section.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.6
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• pp.703-710
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• 2018

Although various efforts have been made every year to reduce electric fire accidents such as accident analysis and inspection for electric fire accidents, there is no effective countermeasure due to lack of effective decision support system and existing cumulative data utilization method. The purpose of this study is to develop an algorithm for predicting electric fire based on data such as electric safety inspection data, electric fire accident information, building information, and weather information. Through the pre-processing of collected data for each institution such as Korea Electrical Safety Corporation, Meteorological Administration, Ministry of Land, Infrastructure, and Transport, Fire Defense Headquarters, convergence, analysis, modeling, and verification process, we derive the factors influencing electric fire and develop prediction models. The results showed insulation resistance value, humidity, wind speed, building deterioration(aging), floor space ratio, building coverage ratio and building use. The accuracy of prediction model using random forest algorithm was 74.7%.