• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.86-95
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• 2006

Brillouin backscatter is a type of reflection that occurs when light is shone into an optical fibre. Brillouin reflections are very sensitive to changes in the fibre arising from external effects, such as temperature, strain and pressure. We report here several case studies on the measurement of strain using Brillouin reflections. A mechanical bending test of an I beam, deployed with both fiber optic sensors and conventional strain gauge rosettes, was performed with the aim of evaluating: (1) the capability and technical limit of the DTSS technology for strain profile sensing; (2) the reliability of strain measurement using fiber optic sensor. The average values of strains obtained from both DTSS and strain gauges (corresponding to the deflection of I beam) showed a linear relationship and an excellent one-to-one match. A practical application of DTSS technology as an early warning system for land sliding or subsidence was examined through a field test at a hillside. Extremely strong, lightweight, rugged, survivable tight-buffered cables, designed for optimal strain transfer to the fibre, were used and clamped on the subsurface at a depth of about 50cm. It was proved that DTSS measurements could detect the exact position and the progress of strain changes induced by land sliding and subsidence. We also carried out the first ever distributed dynamic strain measurement (10Hz) on the Korean Train eXpress(KTX) railway track in Daejeon, Korea. The aim was to analyse the integrity of a section of track that had recently been repaired. The Sensornet DTSS was used to monitor this 85m section of track while a KTX train passed over. In the repaired section the strain increases to levels of 90 microstrain, whereas in the section of regular track the strain is in the region of 30-50 microstrain. The results were excellent since they demonstrate that the DTSS is able to measure small, dynamic changes in strain in rails during normal operating conditions. The current 10km range of the DTSS creates a potential to monitor the integrity of large lengths of track, and especially higher risk sections such as bridges, repaired track and areas at risk of subsidence.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.442-449
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• 2017

In this study, a method to inject small amount of activation agent from the outside of the pipeline to the inside wall of the pipe was newly proposed to enhance pumping efficiency of cementitious materials. The activation agent is injected into the slip-layer, which is generally formed in the vicinity of the inside wall of the pipe during pumping cementitous materials. Through the injections, it is expected to decrease viscosity of slip-layer, namely, the friction between the mateirals and the pipe. The proposed method was verified by lab-scale pumping tests with mortars having water to cement ratio of 47%. The tests were performed with two different type of activation agents(superplasticizer and anionic surfactant) and three different amount of the agents(0.14, 0.28, 0.42% of the mortar volume). The compressive strength were measured with and without injecting the activation agent, and the internal pressures of pipeline were measured. When the anionic surfactant was used, there was no change in the compressive strength. As the amount of anionic surfactant increased, the pumping pressure decreased up to 71.4% at the maximum.

• The Journal of the Korea Contents Association
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• v.12 no.5
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• pp.227-242
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• 2012

This study is to experientially verify that market orientation affect organizational performance toward social service marketization. social service marketization put pressure upon financial environment in nonprofit human service organizations and exacerbate competition between nonprofit human service organizations and profit organizations each other. For survival, nonprofit human service organizations in social service market where various supply organization participate needs sensitivity to the environment. For this purpose the need of introduction of market orientation is being raised. At this point this study is useful that measure the level of market orientation and analysis impact of market orientation toward organizational performance in nonprofit human service organizations. Data was collected from busan nonprofit human service organizations in participate voucher program, number of total organization is 92. The level of market orientation was 3.63. Analysis of the impact of market orientation to organizational performance used regression analysis through structural equation modelling. As a result of the analysis, market orientation was affected by organizational performance. Based on the results, this study suggests that nonprofit human service organizations should need market orientation centered organization management and sensitive response toward external environment.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.482-490
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• 2006

Deep caries in primary molars without early intervention frequently induce a pulpal disease and consequent abscess lesion in surrounding tissue. Especially in many furcation radiolucent lesions of primary molars, accessory canals in furcation areas of primary molars play an important role in theses pathological progress. Although the studies of these communication canals in furcation area of human permanent molar well documented, there has been little research showing their existence in primary molar. For the purpose of understanding the morphological characteristics of accessory canals at furcation areas of primary molars and examining its frequency and patency, 52 specimen teeth were observed under the scanning electro-microscope and tested with dye penetration under vacuum pressure, and obtained the results as follows : 1. In SEM study, the frequency of accessory foramina viewed from the external and internal furcation area was 60% and 35% respectively. Likewise the diameter of the accessory canals was within the range of $11{\sim}107{\mu}m$ and $12{\sim}62{\mu}m$ respectively. 2. The frequency of patent accessory canals evidenced by the dye penetrated under the vacuum suction at furca areas in primary molars was 50% among the 20 specimen teeth tested.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.522-528
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• 2006

When tooth is displaced within the alveolar bone, it could apply pressure and rupture the apical vessels. Pulpal reaction in such case is affected by the stage of root formation, amount of intrusion and pulpal infection. Determining the need of pulp treatment depends on the pulp vitality. Therefore, periodic vitality tests, coronal color changes and radiographic root resorption signs should be observed through periodic post-trauma follow-up. Pulp necrosis, pulp canal obliteration, external root resorption, root ankylosis and marginal bone loss could result from periodontal injuries. Negative sign changes from positive signs of vitality tests suggest pulp necrosis. In this case, pulp treatment should be held before root resorption occurs. By comparing the following two cases, complications of intrusion and factors producing them could be confirmed, thus we propose to report these two cases.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.651-668
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• 2017

For initial stability of the tunnel, the primary support, Shotcrete and rockbolt shall be placed in the most appropriate time. This is because the role of such support plays a vital role in long-term and short-term tunnel stability. In this study, the rock bolt is an important supporting system that receives the external pressure generated by the stress relaxation during tunnel excavation as axial force and transmits it to the shotcrete on the tunnel excavation surface. Until now, most of the materials of rock bolts have been used in the field, but there have been many problems such as uncertain quality of Chinese materials entering the market, poor packing due to falling down of rock bolts when filled with mortar, and corrosion due to water. Therefore, in this study, we have developed a high strength steel pipe rock bolt using Autobeam material to solve and improve various problems of existing rock bolts. In order to evaluate the performance of the developed bolt, field tests were carried out and the existing mortar filler in order to improve the performance of the rock bolt, the design and construction criteria were studied and the results were included in this paper.

• Journal of the Korean Institute of Landscape Architecture
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• v.44 no.5
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• pp.92-102
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• 2016

While there have many completions of large parks recently under development, there has been a dearth of quality assessments. Studies focused on post-evaluation have been made to resolve this, but most of these are biased toward user satisfaction after completion and therefore behaviour analysis has limitations on solving problemsduring the actual design implementation processes. Therefore, this study examined the internal phenomenon and structure of the implementation process of design competition through the ground theory and microscopic independent perspective. As a result, maintaining the identity and differentiation of parks derived from the preserved design competition scheme contributed greatly to completeness and satisfaction. Outcomes were mainly caused by the trust of public officials as the ordering organization, the will of policy decision-makers, and the competence of operational enterprises, etc. Negative factors such as undermining the whole concept of the park and landscape occurred as external pressure and related subjects intruded on change design factors due to variations in social conditions. Additionally, illogical construction processes occurred, such as a reinvestigation of the budget for restoration after damaging on original landscape. There have been needs for the improvement of the work processing system. On balance, an interventional role is very important in the park construction process, especially the PA and operation committee in terms of maintaining the basic direction, landscape design supervision for detailed designs, and expert construction management on LA in terms of rational work management in the field. The study, using the microscopic perspective of the designer and ground theory, deliver significant meaning as an early study by suggesting alternative methods for the after-evaluation of large parks and structurally looking into main influence factors driven during the construction process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.730-736
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• 2019

The demand for natural gas, which is considered an environmentally friendly energy source, is increasing, and at the same time, the market share of large pipelines for natural gas supply is increasing continuously. On the other hand, the corrosion of such large pipelines reduces the efficiency of natural gas transportation. Therefore, this study aims to establish a strategy for securing the patent rights of related technologies through quantitative analysis of patents on energy-independent high-efficiency corrosion prevention technology for large-scale pipelines for natural gas supply. In this patent technology trend study, Korean, US, Japanese, and European patents filed, published, and registered by June 2018 were analyzed, and a technical classification system and classification criteria were prepared through expert discussion. To use fuel cells as an external power source to prevent the corrosion of natural gas large-scale pipelines, it is believed that rights can be claimed using an energy control system and methods having 1) branch structures of pipeline and facility designs (decompressor/compressor/heat exchanger) and 2) decompression/preheating and pressurization/cooling technology of high pressure natural gas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.793-798
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• 2017

In modern naval ships, an infrared signature suppression (IRSS) system is used to reduce the metal surface temperature of the heated exhaust pipe and high-temperature exhaust gases generated from the propulsion system. Generally, the IRSS systems used in Korean naval ships consist of an eductor, mixing tube, and diffuser. The diffuser reduces the temperature of the metal surface by creating an air film due to a pressure difference between the internal gas and the external air. In this study, design variables were selected by analyzing the shapes of a diffuser designed by an advanced overseas engineering company. The characteristics of the design variables that affect the performance of the IRSS were investigated through the Taguchi experimental method. A heat flow analysis technique for IRSS systems established in previous studies was used analyze the performance of the diffuser. The performance evaluation was based on the area-averaged value of the metal surface temperature and exhaust gas temperature at the outlet of the diffuser, which are directly related to the intensity of the infrared signature. The results show that the temperature of the exhaust gas was significantly affected by changes in the diameter of the diffuser outlet, and the temperature of the diffuser's metal surface was significantly affected by changes in the number of diffuser rings.

• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.87-93
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• 2001

Pressure-balanced external Ag/AgCl electrode has been extensively used for both Pressurized Water Reactor (PWR) and Boiling Water Reactor (PWR) environments. The use of KCI-based buffer solution often becomes the source of electrode potential drift due to slow leakage through its porous plug, typically made of zirconia. It is reported that results of our effort to improve the stability of electrode potential by using high purity water as the filling solution in which $Cl^-$ ion activity can be established and maintained at the solubility of AgCl even with the sustained leakage for a long period. Stability tests have been made in boron and lithium mixture solution at $288^{\circ}C$. The electrode potential remained stable within 10 mV over one week period. And after a thermal cycle between 288 to $240^{\circ}C$ the potential shift of Ag/AgCl electrodes did not exceed 15 mV By using the limiting equivalent ionic conductances and Agar's hydrodynamic theory, the thermal liquid junction potential (TLJP) of the electrode has been predicted. The calculated values for the water-fiued Ag/AgCl electrode potential, in which the chlorine concentration in the filling solution was derived from the measured data at ambient temperature, had a good agreement with the experimental values.