• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.169-175
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• 2015

Recently, a stone is preferred as a cladding materials because of its outstanding durability and luxurious character. However, because of running out of natural resources and restriction of production, it is expected that difficulty of stable supply, and thus alternative cladding materials for concrete wall is needed. Therefore, in this research, as an alternative cladding materials, exposed-aggregate concrete is studied using saccharin based retarder. For evaluating factors, changing water-to-cement ratio, dosages of saccharin-based retarder, and timing of water jet washing were tested on the surface properties of exposed-aggregate concrete. As a result, the most favorable surface performance was obtained at 0.75 day after the placing in 25% of water-to-cement ratio, and at one day after the placing in 35 and 55% of water-to-cement ratio, 1.5 day after the placing in 65% of water-to-cement ratio with $24m{\ell}/m^2$ of retarder application.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.417-422
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• 2009

Tunnels that have recently been constructed are characterized by longer length than ever before and furthermore they frequently go through the ground area with poor conditions such as fractured zones. If ground strength is weak, plastic deformation of tunnel occurs, and occasionally a big fall may be brought about. Up to now, the construction work of tunneling has been executed as a sequential method placing the lining concrete after completion of excavation. Such a method requires a long time and much money to complete the tunnel. It is hard to ensure the stability of tunnel if tunnel is left undone for a long time after excavation in fracture zones or plastic grounds. For this reason, we tried to take simultaneous construction of tunnel excavation and lining concrete in order to not only shorten construction schedule but also stabilize the tunnel at the highly fractures zone as soon as possible. As preliminary consideration for simultaneous construction, in-situ tests are performed to calculate the isolation distance over which blasting vibration does not influence the strength of lining concrete. Improvement of ling form, placing method of concrete, ventilation using a dust collector, together with equipment arrangement, was made to assure the simultaneous construction work.

• Clinics in Shoulder and Elbow
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• v.18 no.1
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• pp.13-20
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• 2015

Background: The purpose of this study is to assess the range of shoulder motion using an indirect evaluation method without physical examinations of patients based on questionnaires regarding several specific arm postures referenced by patient's own body parts. Methods: Nine criteria of specific shoulder motion including 4 forward flexion, 2 external rotation, and 3 internal rotation were decided as reference position which can represent a certain shoulder motion. Flexion contains postures such as lifting arm to waist-height, shoulder-height, eye-height, and raising arm above head with arm touching ears. External rotation comprises grasping ears and placing hands on back of the head. Vertebral height in internal rotation is determined by calculating the samples' motions, which are holding on to trouser belts, opposite-elbow, and scapula. These postures are included in questionnaires for patients to evaluate the validity and effectiveness of this indirect method. Results: The range of flexion was $77^{\circ}$ ($60^{\circ}$ to $100^{\circ}$), $96^{\circ}$ ($87^{\circ}$ to $115^{\circ}$), $135^{\circ}$ ($115^{\circ}$ to $150^{\circ}$), and $167^{\circ}$ ($150^{\circ}$ to $175^{\circ}$) when arms go up to waist, shoulder, eye, and high vertically. Range of external rotation was $39.6^{\circ}$ ($30^{\circ}$ to $50^{\circ}$) when grasping ears and $69.2^{\circ}$ ($60^{\circ}$ to $80^{\circ}$) with the hands on the back of the head. Range of internal rotation was L4 when placing trouser belts, T12 for holding opposite elbow, and T9 for reaching scapula. The mismatch rates of flexion, external rotation, and internal rotation were 11.6%, 9.6%, and 7.8%. Conclusions: The range of shoulder motion using this method is expected to be applied to an established shoulder scoring system which included shoulder motion evaluation item.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.921-924
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• 2008

Several techniques, including transmission X-ray photography and AC-impedance spectroscopy, are available for evaluating the fiber dispersion in a fiber reinforced concrete Evaluating the fiber dispersion in fiber reinfored concrete needs since the fibers bridge crackseffectively. However, these equipment is very expensive. Therefore this paper presents the quantitative evaluation method based on the image analysis of sectional image taken using an ordinary digital camera. After detecting the fiber accurately, the fiber dispersion characteristics are represented by the coefficient such as the fiber dispersion coefficient, the number of fibers in unit area, and the distribution of the fiber orientation. Test were performed to evaluate the effectiveness of proposed method and the dispersion characteristics of fibers according placing method and flow direction. Additionally, the effect of fiber dispersion characteristics on mechanical properties was investigated. Test results shows that fiber aligned along the flow direction and more fibers placed and dispersion was better on the section parallel to the flow direction. And about 50% difference in the flexural tensile strength according to the placing method occured.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.11-20
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• 2013

PURPOSES : This study is to suggest time to spray curing compound, the amount of curing compound, and the number of times to spray curing compound based on indoor tests. METHODS : Based on the literature review, two methods are used in this study, One is test for water retention of concrete curing material and the other is test for abrasion resistance of concrete surfaces by the rotating-cutter method. Through those methods, curing compound was evaluated. RESULTS : The result of the laboratory experiment for time to spray curing compound indicates that 30 minutes after placing concrete is optimal. For the amount of curing compound, $0.5{\ell}/m^2$ is the minimum quantity for both concretes. Through test of the number of times to spray curing compound, method to spray the whole amount of curing compound in twice is more efficient than it to spray the whole amount at a time. Also, method of separately 30-50 minutes spray is better than method of separately 10-30 minutes spray. CONCLUSIONS : From the testing results, it can be proposed that optimum time to curing compound is $30{\pm}15$ minutes, $0.5{\ell}/m^2$ is efficient for spraying the whole amount of curing compound at a time, and $0.4{\ell}/m^2$ is the best for spraying the whole amount of curing compound in twice, which sprays it in 20 minutes after 30 minutes from placing concrete.

• Journal of the Korea Safety Management & Science
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• v.14 no.1
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• pp.129-136
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• 2012

This study proposes a collaboration system framework on the web service in a supply chain to implement an efficient virtual supply chain and improve an ability to fulfill received orders over a supply chain. The system based on the framework proposed in this paper plays an important role for automatic order negotiation and placing/receiving an order noticed in web service by the main system. Furthermore, it can evaluate the fulfillment of received orders over a supply chain by using the transaction results from hierarchically related vendors and establish efficient manufacturing plans. In a word, this system is the automated system for creating manufacturing plans, placing and receiving orders. A little more important main function of this system is that it has a dynamic evaluation capability about fulfillment with received orders over a supply chain, and improves the evaluation method of fulfillment ability with received orders with related to direct dealing vendors, which is a main problem in existing system. As a result, this system is able to reduce the work load of the sales and purchasing materials, production control division, to manage accurate inventory promptly, to maintain the optimal inventory level by analyzing the information of fulfillment ability with received orders, and to enhance the level of service for customers.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.253-254
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• 2021

In the field of construction, research on smart construction technology is being actively pursued as a measure to increase productivity and efficiency. The technology that links 3D scanning and BIM of smart construction technology is in the limelight as a technology for checking the state of buildings in the field of architecture. It is thought that these techniques will be of great help in solving problems when the amount of inspection targets is large, such as confirmation of the rebar arrangement intervals, and therefore a large number of human resources are required. Therefore, in this study, we would like to apply 3D scanning to rebar construction to confirm whether the rebar arrangement can be confirmed according to the design drawing. In the study, the wall rebar of the rebar placed at the actual construction site was directly scanned to extract data, and the rebar placing status was confirmed through type analysis. As a result of analyzing the reinforcing bar arrangement state based on the data obtained by 3D scanning, it was found that the technology can be utilized.

• Journal of the Korea Institute of Building Construction
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• v.20 no.3
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• pp.213-221
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• 2020

The aim of the research is to provide thixotropy on cement-based materials. For this purpose, the linkage between polyvinyl alcohol (PVA) and borax was used. Namely, adding the suspensions of PVA and borax in cement paste, the thixotropy of cement paste was confirmed. The thixotropy of cement-based materials can have various advantages on construction process, especially, the placing method using pipe can have advantages. As a result of this research, the linkage between PVA and borax is valid inside of cement paste. Therefore, using PVA and borax, it is confirmed that the cement-based materials can have thixotropy with this method, and it can be expected to contribute on developing new method of placing cement-based materials with thixotropy.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.6 s.312
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• pp.85-96
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• 2006

This paper deal with a method for efficient placing 2 dimensional virtual labels on the view plane. The proposed method has suitable computational costs for realtime processing and it overcomes the local minima problem which is not solved in previous automatic label placement algorithms, and also it enhances readability by placing labels in less congestion area on the view plane. Background analysis must be considered for label placement. However previous works do not concern with this problem seriously. And furthermore, automatic label placement algorithm and background analysis algorithm have been studied separately in their own field. This paper proposed the background analysis method using background color and texture component to enhance readability, and it is the first research about analyzing the background of color image and applying it in automatic label placement field. This paper shown improved placement performance through combining automatic label placement algorithm and background analysis algorithm organically, and various experiments verified it.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.3
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• pp.131-137
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• 1996

The existing digital governors are in the beginning stage. Placing the focus on the marine site, most of the digital governors developed are still using the simple PID algorithm. But, the performance of a diesel engine is widely changed according to the parameters of the PID controller. So, this article describes a new method to adjust the parameters of the PID controller in a marine digital governor. In this paper, the diesel engine is considered as a nonoscillatory second order system. A new method to adjust the parameters of the PID controller for speed control of a diesel engine is proposed by means of the model matching method. Also, the simulations by numerical methods are carried out in cases of the exact understanding or out of the parameters of a diesel engine respectively. And this paper confirms that the proposed new method here is superior to Ziegler & Nichols's method through the comparisons and analysis of the characteristics of indicial responses.