• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.427-436
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• 2010

Much oyster shell is breeding by character and conduct of oyster-industry for a long time among them. An experimental study was carried out to investigate the recycling possibility of waste oyster shells, which induce environmental pollutions by piling up out at the open or the temporary reclamation. The purpose of this study is to develope eco-friendly binder using waste oyster shells, and to reinforce soils fur soft soil improvement. In this paper, a series of laboratory tests including compressive pot tests were performed to evaluate characteristics of soils treated by developed waste oyster shells with different water content of soils. Based on test results, eco-friendly Supporter manufactured from waste oyster shells were estimated as good resource materials for soft soil improvements. We got the conclusion by a series of experiment, It is verified that change of pH of soil is improved by mixing with oyster shells. The homogenization method for deducing apparent of oyster shells, which can consider micro-structure of mixed soil, is introduced. The improvement treatment leaded to enlarge fluctuation of soil moisture content. The effect of calcium concentration was good though improvement treatment of physical property. In addition, the crop yield in amelioration plots increased. It means that the increase of crop yield was caused by improvement of soil physical properties rather than improvement of calcium concentration.

• Journal of the Korean GEO-environmental Society
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• v.9 no.3
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• pp.51-60
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• 2008

Soil nailing systems are generally many used to the temporary structure in underground excavations and reinforcements of slopes in Korea. However, large-scaled experimental studies related to soil nailing systems are mostly studies related to performance monitoring and field pullout tests. Specially, there are no researches related in the large scaled load tests of soil nailed walls in Korea. In this study, a case study on the large scaled load tests of soil nailed walls is introduced and the behavior characteristic of them is investigated. Also, they are proposed allowable deformation corresponding to the serviceability limit of soil nailed walls and ultimate deformation corresponding to the collapse state of the walls. These results can be applied to the maintenance management of soil nailed walls. And analysis on the required minimum factor of safety of soil nailed walls using the relation curve of load ratio and deformation ratio are carried out.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.559-566
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• 2017

This paper proposes a new composite deckplate system reinforced with inverted triangular truss girders(called 'D Deck'), which does not require the use of temporary supports at construction stage. The proposed system retains increased stiffness and strength while keeping the absolute floor height change to a minimum level and can be utilized as floor systems of various types beam members such as the conventional wide-flange and U-shaped composite beams. In order to evaluate the performance of the proposed system, five specimens with a span of 5.5 m were fabricated and tested under field loading conditions consisting of several intermediate steps. The load-deflection curves of each specimen were plotted and compared with the nonlinear three-dimensional finite element analysis results. The comparison showed that the effective load sharing between the truss girders and floor deck occurs and the maximum deflection under construction stage loading is well below the limit estimated by the provisions in Korea Building Code.

• Smart Structures and Systems
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• v.15 no.3
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• pp.769-785
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• 2015

Although timber structures have been extensively used in underground temporary supporting system, their actual performance is poorly understood, resulting in potentially conservative and over-engineered design. In this paper, a novel wireless sensor technology, SmartPlank, is introduced to monitor the field performance of timber structures during underground construction. It consists of a wooden beam equipped with a streamlined wireless sensor node, two thin foil strain gauges and two temperature sensors, which enables to measure the strain and temperature at two sides of the beam, and to transmit this information in real-time over an IPv6 (6LowPan) multi-hop wireless mesh network and Internet. Four SmartPlanks were deployed at the London Underground's Tottenham Court Road (TCR) station redevelopment site during the Stair 14 excavation, together with seven relay nodes and a gateway. The monitoring started from August 2013, and will last for one and a half years until the Central Line possession in 2015. This paper reports both the short-term and long-term performances of the monitored timber structures. The grouting effect on the short-term performance of timber structures is highlighted; the grout injection process creates a large downward pressure on the top surface of the SmartPlank. The short and long term earth pressures applied to the monitored structures are estimated from the measured strains, and the estimated values are compared to the design loads.

• Journal of architectural history
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• v.23 no.1
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• pp.7-19
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• 2014

This study considers the proper repair techniques by examining the most representative repair cases of the Korean arch bridges and proposes the constructional manual which can apply similar occasions. The cases are Seonamsa Seungseongyo and Songgwangsa Geukrockgyo where this researcher had taken part in the repair works. This Study proposes the maintenance construction manual about the performance degradation drew by performance degradation of the both Korean arch bridges in the maintenance process. First, arch bridge maintenance should be carried out in the dry season, when water is impermeable in the bottom surface of the bridge. Moreover, risk factors of the maintenance should be excluded to secure the water vally flow, the bypass and the temporary bridge. Second, prior to repair, it has to precede (1)3D shooting (2)formal examination (3)structure safety test (4)geological and lithic surveys (5)arch curvature establishment and makeshift frame settlement before transformation (6)relationship expert comments. Third, if the baduk and the foundation stones are inevitable to replace due to performance degradation on the foundation, it should use the high quality stones and secure greater stress by extending the standard range. The foundation on irregular rock needs to be flattened and underside on the replaced materials require Grengyijil to deliver the equal loads. Fourth, In the process of dismantling the stones of the arched bridge, it could make heavy weathering degree and not reuse the materials. Charge should converge the expert advices to choose the reuseable, the conservate and the alternative materials, and increase the reutilization of the raw materials by preservation and reinforcement treatments. Fifth, the side wall should be repaired by the rubble work technique which is not able to pile compost satiety, so it must use long depth of masonary stones for reinforcement. It is considered to reinforce the stone wall in shore as much as possible and protect the abutment and the side wall on the upstream for the arch bridge maintenance works.

• The Journal of the Korea Contents Association
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• v.13 no.9
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• pp.28-38
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• 2013

During the past decades, the B+-tree has been most widely used as an index file structure for disk-resident databases. For the disk based B+-tree, a node update can be cheaply performed just by modifying its associated disk page in place. However, in case that the B+-tree is stored on flash memory, the traditional algorithms of the B+-tree come to be useless due to the prohibitive cost of in-place updates on flash memory. For this reason, the earlier schemes for flash memory B+-trees usually take an approach that saves B+-tree changes from real-time updates into extra temporary storage. Although that approach can easily prevent frequent in-place updates in the B+-tree, it can suffer from a waste of storage space and prolonged search times. Particularly, it is not allowable to process range searches on the leaf node level. To resolve such problems, we devise a new scheme in which the leaf nodes and their parent node are stored together in a single flash block, called the p-node block.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.4
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• pp.299-308
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• 2001

The company invests its time and money for temporary maintenance to satisfy the fast change of the computer use environment and the user's demands. Therefore, various problems occur including low performance because of duplication of codes and unstable structures from the restructuring and redevelopment. Furthermore, if a developer, who did not participate in initial process of development, wrote additional program codes to upgrade or restructure, it would cause many problems such as lack or lose of development documentation, understanding of documentation and reuse of existing program language. This study, Object-oriented Refactoring Process, suggests that the developers can reuse object unit to overcome the limit of the reusing code. In addition, this paper shows case study to verify our process by adjusting the project called "D2D", which is a case tool for developing windows system from Company D. Our works get positive results such as improvement of system pelfonnance, decreased cost of development and maintenance and optimizing structure and class.

• Korea journal of population studies
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• v.3 no.1
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• pp.62-77
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• 1979

The purpose of this study is to explain the increasing trend of the aged population and its demographic characteristics. This study is based on the data for the aged population above 65 years old published by the Bureau of Statistics, Economic Planning Board. The increasing trend of the aged population has been analyzed and projected from 1955 to the year 2000. Some demographic charicteristics of the aged population including marital status, educational status and status of economic activities have also been analyzed in order to identify the problems associated with aging of population in Korea. The study offers the following conclusion. 1. The aged population index, the proportion of aged population to total population was 3.6 in 1975 and projected to be 6.6 in 2000. There has been steady increase of the aged population is reflected in changes of population structure. The proportional change of the aged population index was 100.0 in 1955, 109.0 in 1975 and 200.0 in 2000 respectively. 2. As for marital status of the aged population 77.6 per cent of male were married while 24.3 per cent of female were married in 1975. 22 per cent of male were widowed while it spouses died declined remarkable the mortality rate declined. 3. As the educational status of the aged, 77 per cent never attended school and 18 per cent attended from a primary school. This is very low and the number of educated men is higher than that of educated women. The rank ordering of schooling is city, Eub and Myeon in that aged. 4. The dependency ratio of the aged population was 5.9 in 1955, 6.1 in 1975 and will be 9.8 in 2000. It is gradually increasing as indicated above 20 per cent of aged population was economically active of these, they are employed in the following occupations as listed in order of the magnitude of the aged population employed. The employment status of the aged workers shows that a greater number of persons are self-employed than workers for another employer. In particular, temporary employees comprise 56.0 per cent of those employed.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.271-278
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• 2021

This paper is a study on the implementation of smart filter system that recognizes the external environment and automatically removes pollutants according to pollution level. Recently, the occurrence of various pollutants in indoor and outdoor space has adversely affected the human body. Especially, various fine dust generated in the atmosphere becomes worse in closed residential space or office space. Although air pollution can be temporary lowered through ventilation, it is difficult to respond to fine dust changes in real time, and such problems become serious in the space where many people reside, such as at home or industry. Therefore, it is necessary to measure the pollution level of fine dust inside the residential space in real time and to reduce the pollution of indoor ventilation through automatic ventilation with the outside. To improve these problems, this paper proposes the implementation of smart filter system for external environment recognition. The structure of smart filter system that automatically measures air quality inside and outside, removes pollutants, implements the function, and confirms the operability by manufacturing prototypes. Finally, the effectiveness of the smart filter system for solving fine dust problems was examined.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.5
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• pp.35-42
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• 2018

In order to seek out methods to reduce safety accidents caused by construction machinery and equipment, this study collects data about safety accidents and draws main risk factors by construction from the data, through SNA. It aimed to suggest safety management points to be used in future construction fields, by analyzing risk index of such factors. The finding can be summarized: First, Backhoe Bucket is the risk factor for crash accidents of average workers in earth works; boring machines-maintenance is the risk factor for fall accidents of construction machinery operators in foundation works; bending machine-reinforcing rod processing is the risk factor for jamming accidents of reinforcing rod engineers in frame works; and mobile crane-hook is the risk factor for crash accidents of average workers in lifting works. Second, works can be arranged in turn, according to the risk index: earth, lifting, frame and foundation works. Risk factors can be also arranged according to the risk index: Backhoe in earth works, pile drivers in foundation works, bending machines in frame works and mobile cranes in lifting works. This study has some limits, in that it only analyzed main machinery/equipment, among various kinds of them, for earth, foundation, frame and temporary works (lifting works) and used data collected over three years. Therefore, it is necessary to conduct an analysis using big data, by collecting additional data about a lot of machinery/equipment in future construction fields.