• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.2
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• pp.1-17
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• 2021

As population concentration, high-rise, and high-density progresses amid rapid industrialization and urbanization in Korea, green areas in the city have decreased significantly and the natural environment has deteriorated day by day due to various development projects. In order to cope with these social changes, many studies related to park and green areas have been conducted, but in the case of Gwangju-si, only studies on green areas such as vegetation structures, street facilities, and recreation forests have been conducted on park green areas. The situation is not losing. Therefore, in this study, a survey was conducted on Gwangju citizens to understand the usage behavior and satisfaction of park green areas, and to provide basic data for future park development and reorganization. As a result, first, to induce a variety of static and dynamic activities in order to increase the park satisfaction of Gwangju citizens, it is possible to create a park that has not been formed as soon as possible, and by planning programs with various themes. Second, it is necessary to expand green space services in marginalized areas by creating water streams, flower pots, and rooftop greening around the lives of Gwangju citizens, and create park green spaces with themes using cultural and historical resources for each administrative district. Third, in order to solve the dry landscape in some urban areas, it is necessary to establish a three-dimensional landscape plan by creating a variety of green areas such as potted plants, green areas, and street trees, and by giving functions of park green areas such as expanding leisure and convenience facilities.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1023-1037
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• 2018

The interest in the use of shield TBM (Tunnel Boring Machine) on the tunnel excavation has been increased rapidly in Korea. The shield TBM tunnel is generally designed as non-drainage tunnel. Consequently, if water leakage through the segment joints happens, big problems on the usage and stability of tunnel can be occurred. In this study, the variation of waterproof capacity of hydrophilic rubber waterstop and gasket, respectively by the construction error and excessive displacement of segment was studied. The test results show that hydrophilic rubber waterstop has favorable on the offset, however unfavorable on the gap. On the other hand, gasket has unfavorable on the offset, however favorable on the gap.

• Advances in concrete construction
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• v.8 no.1
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• pp.21-31
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• 2019

The rich recipe of ultra high performance concrete (UHPC) offers the higher mechanical, durability and dense microstructure property. The variable like cement/sand ratio, amount of supplementary cementitious material, water/binder ratio, amount of fiber etc. alters the UHPC hardened properties to any extent. Therefore, to understand the effects of these variables on the performance of UHPC, inevitably a stage-wise development is required. In the present experimental study, the effect of sand/cement ratio, the addition of finer material (fly ash and quartz powder) and, hybrid fiber on the fresh, compressive and microstructural property of UHPC is evaluated. The experiment is conducted in three phases; the first phase evaluates the flow value and strength attainment of ingredients, the second phase evaluates the efficiency of finer materials (fly ash and quartz powder) to develop the UHPC and the third phase evaluate the effect of hybrid fiber on the flow value and strength of ultra high performance hybrid fiber reinforced concrete (UHP-HFRC). It has been seen that the addition of fly ash improves the flow value and compressive strength of UHPC as compared to quartz powder. Further, the usage of hybrid fiber in fly ash contained matrix decreases the flow value and improves the strength of the UHP-HFRC matrix. The dense interface between matrix and fiber and, a higher amount of calcium silicate hydrate (CSH) in fly ash contained UHP-HFRC is revealed by SEM and XRD respectively. The dense interface (bond between the fiber and the UHPC matrix) and the higher CSH formation are the reason for the improvement in the compressive strength of fly ash based UHP-HFRC. The differential thermal analysis (DTA/TGA) shows the similar type of mass loss pattern, however, the amount of mass loss differs in fly ash and quartz powder contained UHP-HFRC.

• Korean Journal of Heritage: History & Science
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• v.36
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• pp.69-86
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• 2003

This article introduce the manufacturing technique of Silla potteries based on the result excavated from Songogdong and Mulchunri site in Gyungju. As a result, we selected the kiln-site to produce Silla potteries and knew the feature which following to make them. 1. The Environmental elements to take a kiln-site were abundant fuel, plenty water and suitable soil. In particular, efficient usage of refracted winds and reserved space of forepart in the kiln-site were importantly applied to select place of kiln-site. 2. The structure of the kiln-body have been changing according to the time. It could be massproduced by produce-group from the middle and end of sixth centry which the fireplace-kiln was generalized. 3. The work center of equipments were related kiln-site. It consisted of mixed wheel, keepingpit and ditch. We knew that a look-out shed had been appeared according to utility purpose variously. 4. It sees as trimming trace of inner and outter aspects in excavated potteries and we knew that wheel had been turn to the contrast watch direction. For producing pottery of the good guality, various kiln-tools had been used already at Silla period and they used for the different purpose. 5. We intended to know method for laying the potteries in the kiln through the example of the adherent pottery to be melted. Finally, manufature and tomb-site are separated by the time through current situation of Songokdong and Mulchonri site. At the same time, we could know that group of Chounbuk kiln-site moved from the south to the north step by step.

• Korean Journal of Remote Sensing
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• v.35 no.3
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• pp.389-400
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• 2019

Level meters are non-invasively capable of measuring the level of the medium, and a growing variety of level meters are being used in the industry in connection with safety and maintenance. The level meter can be measured according to various kinds of medium such as solid medium such as coal, flour, rice and liquid medium such as water and petroleum. In order to reduce the error depending on the medium, the measurement using the Doppler Effect can compensate the measurement error, However, the number of signal processing steps is increased, the operation speed is further increased, the hardware complexity increases, and a high cost structure is required. In this paper, we propose a method to improve the signal processing operation structure of the remote measurement level meter to reduce the amount of computation and the resource usage of the required FPGA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.600-606
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• 2018

A class D fire or combustible metal fire is characterized by the presence of burning metals. Only certain metals or metal compounds are flammable, including sodium and lithium. General fire extinguishing agents, such as dry chemical powder, water-based fire extinguish agents, and carbon dioxide, cannot be used in class D fires. This is because these agents cause adverse reactions or are ineffective. In addition, the amount of usage of combustible metals is increasing due to continuous development of the semiconductor and fuel cell industries. Despite this, Korea does not have standards and laws related to combustible metal fires. This paper suggests directions of the class D fire management policies to reduce the class D fire risk and impact by analyzing the standards and laws related to class D fires and combustible metal fire cases. The factors to make laws on class D fire prevention and response systems, and management system of dry sand were determined. These results may be used to help reduce the risk of class D fires and improve the response abilities.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.2
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• pp.75-82
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• 2018

Green roof in Korea has been recognized as part of landscape area and local governments enacted municipal ordinance for supporting green roof thereby assisting part of expenses spent for green roof within a range of budget for buildings which are eligible for the green roof support of existing buildings. However, it is necessary to enforce a regulation of mandatory green roof for new buildings in order to expand green roof application and provide a variety of assistances such as subsidy payment, tax relief, and mitigation of floor area ratio-related regulation as done in other advanced nations. In particular, LEED(Leadership in Environmental and Energy Design) in the USA applies additional point directly for green roof in terms of the reduction in heat island effects. For example, the following items are beneficial to have additional points: habitat preservation or restoration, external space, rainwater management, reduction in outdoor water usage, minimum energy performance, and optimum energy performance. In addition, the BREEAM(Building Research Establishment Environmental Assessment Method) in the UK specifies green roof as one of assessment items to be complied in terms of diversity of species. As such, LEED and BREEAM reflect direct and indirect effects of green roof on assessment criteria, which suggest a direction to green building certification criteria in Korea where only additional points are given for green roof according to soil depth.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.449-455
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• 2022

Concrete is the most widely used construction material. The heavy self-weight of concrete may offer an advantage when developing high compressive strength and good dimensional stability. However, it is limited in the construction of super-long bridges or very high skyscrapers owing to the substantially increased self-weight of the structure. For developing lightweight concrete, various lightweight aggregates have typically been utilized. However, due to the porous characteristics of lightweight aggregates, the strength at the composite level is generally decreased. To overcome this intrinsic limitation, this study aims to develop a construction material that satisfies both lightweight and high strength requirements. The developed cementitious composite was manufactured based on a high volume usage of hollow glass microspheres in a matrix with a low water-to-cement ratio. Regardless of the tested hollow glass microspheres from among four different types, compressive strength outcomes of more than 60 MPa and 80 MPa with a density of 1.7 g/cm³ were experimentally confirmed under ambient and high-temperature curing, respectively.

• The Journal of Advanced Prosthodontics
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• v.14 no.6
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• pp.360-368
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• 2022

PURPOSE. This study assessed the physical and mechanical properties of interim crown materials fabricated using various digital techniques after accelerated aging. MATERIALS AND METHODS. Three groups of interim dental restorative materials (N = 20) were tested. The first group (CO) was fabricated using a conventional manual method. The second group (ML) was prepared from prefabricated resin blocks for the milling method and cut into specimen sizes using a cutting disc. The third group (3D) was additively manufactured using a digital light-processing (DLP) 3D printer. Aging acceleration treatments using toothbrushing and thermocycling simulators were applied to half of the specimens corresponding to three years of usage in the oral environment (N = 10). Surface roughness (Ra), Vickers microhardness, 3-point bending, sorption, and solubility tests were performed. A 2-way analysis of variance (ANOVA) and Fisher's multiple comparison test were used to compare the results among the groups. RESULTS. The mean surface roughness (Ra) of the resin after accelerated aging was significantly higher in the CO and ML groups than that before aging, but not in the 3D group. All groups showed reduced hardness after accelerated aging. The flexural strength values were highest in the 3D group, followed by the ML and CO groups after accelerated aging. Accelerated aging significantly reduced water sorption in the ML group. CONCLUSION. According to the tested material and 3D printer type, both 3D-printed and milled interim restoration resins showed higher flexural strength and modulus, and lower surface roughness than those prepared by the conventional method after accelerated aging.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.1
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• pp.55-66
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• 2022

In this study, forty corrugated fiberboard (CF) boxes for fresh produce were collected from farms located in Gyeongsan city and evaluated its characterizations and physical properties according to Korean Standard (KS). The basis weight, flute, and paperboard combination were determined for the characterizations of CF boxes. The measured basis weights of all samples were within the tolerance limit referred to KS and the flutes were B/F, EB/F, and AB/F flute, respectively. The bursting strength (BS), edgewise crush resistance (ECR), and compression strength (CS) were tested to evaluate the physical properties. There are four single-walled (SW) CF boxes showed BS and ECR higher than 638 kPa and 3.30 kN/m, respectively. One SW CF boxes showed BS and ECR higher than 785 kPa and 3.43 kN/m, respectively. In case of double-walled (DW) CF boxes, sixteen CF boxes showed BS and ECR higher than 785 kPa, 4.96 kN/m (AB flute), or 4.90 (EB flute), respectively. The other nineteen CF boxes showed BS and ECR higher than 981 kPa, 5.29 kN/m (AB flute), or 5.20 (EB flute), respectively. All the CF boxes except two samples showed the acceptable compression strength in reference to the guideline of KS.