• Korean Journal of Construction Engineering and Management
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• v.13 no.6
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• pp.121-132
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• 2012

The current estimation system of construction equipment cost was first introduced in 1960's when general contractors had ownership of equipment. However, most of construction equipment in construction sites has been rented from equipment leasing company these days. Therefore, the improvement of current cost estimation system is therefore inevitable in order to advance domestic construction industry. This study is aimed to suggest the improved system by analyzing nationwide market rental rates of major construction equipment. A user friendly prototype of actual database grounded on actual market rental rates collected from over 200 leasing companies in the nation was proposed. The database includes various rates and statistics analyzed by different form of contract as well as different region. Using the collected data, "The Cost Estimate System in Construction Equipment Database" was developed by using VBA(Visual Basic for Applications). The system makes users convenient to utilize the rental rates by choosing equipment and region, and various types of contract.

• Journal of the Korean Institute of Gas
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• v.19 no.3
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• pp.1-8
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• 2015

In this study, we performed risk assessment of chloroprene by hazard evaluation and workplace investigation. The chemical is used to manufacture of shoes, tires, adhesives, and classified as IARC category 2B (possibly carcinogenic to humans) and target organ systemic toxicity. It is used about 1,300 tons per year in 27 sites. It was calculated the risk of carcinogenesis with chloroprene by Monte-carlo simulation that the averages are 2,199 and 26,404 in each case of working less than 15 minutes per day with local exhaust ventilation and over 4 hours per day without local exhaust ventilation. The risk of target organ systemic toxicity are 4.10 and 169.06 with high correlation with working time to be longer and with ventilation system. Therefore, it is recommended that the local exhaust ventilation and respirators to prevent occupational cancer and target organ systemic toxicity with chloroprene. Especially it is determined that there is a need to strengthen the workplace exposure limit (TWA 10 ppm) in Korea since it is managed with TWA less than 5 ppm ($18mg/m^3$) by the United States Occupational Safety and Health Administration (OSHA) as well as it has carcinogenicity, reproductive toxicity.

• Elastomers and Composites
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• v.52 no.2
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• pp.114-130
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• 2017

Enhancing the properties of rubber, such as the tensile strength, modulus, and wear abrasion, by the addition of carbon black and silica as fillers is very important for improving the performance of rubber products. In this review, we summarize the general features of 'the reinforcement of rubber by fillers' and the equations for representing the reinforcement phenomena. The rubber reinforcement was attributed to enhancement of the following: the rubber, bound rubber, formation of networks, and combination between rubber chains and silica followed by entanglement. The reinforcement capability of silica species with different surface and networked states demonstrated the importance of the connection between the silica particles and the rubber chains in achieving high reinforcement. The model involving combination followed by entanglement can provide a plausible explanation of the reinforcement of rubber by carbon black and silica because the combination facilitates the concentration of rubber chains near the filler particles, and entanglement of the rubber chains around the filler particles enforces the resistance against deformation and breakage of rubber compounds, resulting in high reinforcement.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.1
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• pp.21-27
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• 2022

Traditional automobile or 2-wheeled robot have limitations on mobility because of their mechanical structure. As traditional automobile is being replaced by electric cars, robot technology is applied to the car industry. In robotics, many researchers worked on omnidirectional mobile robot and produced lots of noticeable results. However in many of the results, specialized wheels such as Mecanum wheels are required. That imposes restrictions on robot speed and outdoor driving. We proposed a 2-wheeled modular robot that has omnidirectional mobility without using specialized wheels. In this paper, we propose a 4-wheeled omnidirectional mobile robot that consists of those two modular robots. The proposed robot adopts electric brakes to combine wheel housings and the robot body or to separate wheel housings from the robot body. Two absolute-type encoders and four incremental encoders are used to control the position of the wheel housing and velocities of the wheels. The proposed robot has omnidirectional mobility and can move fast and outdoor with normal tire wheels. We implemented the proposed robot and the feasibility and stability of the robot is verified by two separate experiments.

• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.837-845
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• 2017

A recirculating integrated system composed of a fluidized biofilter filled with waste-tire crumb media fixed with return sludge from wastewater treatment facility of D dyeing industrial center, and a UV/photocatalytic reactor packed with calcined $TiO_2$ coated-glass beads as photocatalyst-support, was constructed and was run to treat authentic textile-dyeing wastewater from D-dyeing industrial center, which was mixed with an alkaline polyester-weight-reducing wastewater and a wastewater from sizing process. As a result, its total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were ca. 81% and 55%, respectively. The synergy effect of the recirculating integrated system to enhance total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were evaluated at most ca. 7% and 3%, respectively. The fluidized biofilter and the UV/photocatalytic reactor were responsible for ca. 94% and 6% of the total $COD_{cr}$ removal efficiency, respectively, and were also responsible for ca. 86% and 14% of the total color-removal efficiency, respectively. Thus, the degree of the UV/photocatalytic reactor-unit process's contribution to RE(tot) of color, was about 2.4 times of that to RE(tot) of $COD_{cr}$. Therefore, the UV/photocatalytic reactor facilitated the more effective elimination of colors by breaking down the chemical bonds oriented from colors of dyes such as azo-bond, than $COD_{cr}$. In addition, the effect of the removal efficiency of each unit process(i.e., the fluidized biofilter or the UV/photocatalytic reactor) of the recirculating integrated system on RE(tot) of $COD_{cr}$ and colors, was analysed by establishing its model equation with an analytic correlation.