• Korean Journal of Environment and Ecology
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• v.31 no.2
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• pp.252-265
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• 2017

This study aims to analyze the landscape ecological characteristics of green spaces within built up area of high density and evaluate the potential applicability of green patches, thereby introducing urban garden for generating green networks in residence areas. To this end, Yeoksam-Dong was selected as the site area since it is classified as both green initiative zone and alienated area of park service in Seoul. First, the current condition of green spaces in Yeoksam-Dong was identified by five categories: Street trees, private garden, public pocket garden, rooftop garden, and park. Then, the landscape index analysis through FRAGSTATS and connectivity assessment via multi-buffer zone analysis were carried out for analyzing the green networks and evaluating the potential value of green space. The results showed that the degree to which green areas in the site were distributed is arranged in the order of street tree, private garden, public pocket garden, park, and rooftop garden. In case of the street trees whose total core area (TCA, $1,618m^2$) is as high as the park's ($1,128m^2$). Private garden has potential for green network in built up area of high density by gardening since the shape of the patches are irregular (ED = 78.1m/ha) and the average distance among the patches is close (ENN=33.9m). Public pocket garden has also potential for gardening according to the result that it was found to be distributed evenly (LPI=5.7%, SHEI=0.9) with exposing external disturbance ($TCA=66m^2$). For the green network, 84% of all the study site is covered by small green network in 50m butter range of connected green area. The effect of green network was expected through gardening in public pocket garden (27%) and street tree (26%). Accordingly, it is encouraged to actively utilize street tree, private gardens, and rooftop gardens and to establish the urban gardens like local-based community gardens in public pocket garden where a variety of activities can be carried out near residential areas. By doing so, green networks can effectively be established in built up area with high density. The results of this study can contribute positively to fostering the creation of various types of urban gardens.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.538-543
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• 2008

Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.479-499
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• 2019

State assessment of an operational tunnel is usually done by performing visual inspection and durability tests by following the detailed guideline for safety inspection (SI) and/ or precision inspection for safety and diagnosis (PISD). In this study, 12 NATM tunnels, which have been operational for more than 10 years, were inspected to figure out the cause of longitudinal cracks for the purpose of modifying the scoring items in the state assessment NATM tunnel related to the longitudinal crack and the thickness of concrete lining. All investigated tunnels were classified into four groups depending on the shape and usage of each tunnel. The causes of longitudinal crack occurrence were analyzed by investigating the correlations between the longitudinal crack and the following four factors: the patterns of ground excavation; construction state of primary support system; characteristics of material properties of the concrete lining; and thickness of lining which was obtained by Ground Penetration Radar (GPR) tests. It was found that influencing factors causing longitudinal cracks in the lining were closely related with the construction condition of the primary support system, i.e. shotcrete, rockbolt, and steel-rib; crack occurrences were not much affected by the excavation patterns. As for the properties of concrete lining materials, occurrence of the longitudinal crack was mostly affected by the following three items: w/c ratio; contents of cement; and strength of lining. When estimating the lining thickness of the concrete lining by GPR tests and taking thickness effect into account in the statement assessment, it was concluded that increase of the index score by an average of 0.03 (ranging from 0.01 up to 0.071) is needed; a more realistic way of state assessment should be proposed in which the increased index score caused by lack of lining thickness should be taken into account.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1061-1071
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• 2018

A subsea tunnel, being a super-sized underground structure must ensure safety at the time of earthquake, as well as at ordinary times. At the time of earthquake, in particular, of a subsea tunnel, a variety of response behaviors are induced owing to relative rigidity to the surrounding ground, or difference of displacement, so that the behavior characteristics can be hardly anticipated. The investigation aims to understand the behavior characteristics switched by earthquake of an imaginary subsea tunnel which passes through a fault zone having different physical properties from those of the surrounding ground. In order to achieve the aim, dynamic response behaviors of a subsea tunnel which passes through a fault zone were observed by means of indoor experiments. For the sake of improved earthquake resistance, a shape of subsea tunnel to which flexible segments have been applied was considered. Afterward, it is believed that a D/B can be established through 3-dimensional earthquake resistance interpretation of various grounds, on the basis of verified results from the experiments and interpretations under various conditions. The present investigation performed 1 g shaking table test in order to verify the result of 3-dimensional earthquake resistance interpretation. A model considering the similitude (1:100) of a scale-down model test was manufactured, and tests for three (3) Cases were carried out. Incident seismic wave was introduced by artificial seismic wave having both long-period and short-period earthquake properties in the horizontal direction which is rectangular to the processing direction of the tunnel, so that a fault zone was modeled. For numerical analysis, elastic modulus of the fault zone was assumed 1/5 value of the modulus of individual grounds surround the tunnel, in order to simulate a fault zone. Resultantly, reduced acceleration was confirmed with increase of physical properties of the fault zone, and the result from the shaking table test showed the same tendency as the result from 3-dimensional interpretation.

• Journal of Korea Water Resources Association
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• v.52 no.9
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• pp.627-635
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• 2019

In Korea, snow damage has been happened in the region with no snowfalls in history. Also, casual damage was caused by heavy snow. Therefore, policy about the Natural Disaster Reduction Comprehensive Plan has been changed to include the mitigation measures of snow damage. However, since heavy snow damage was not frequent, studies on snowfall have not been conducted in different points. The characteristics of snow data commonly are not same to the rainfall data. For example, some parts of the southern coastal areas are snowless during the year, so there is often no values or zero values among the annual maximum daily snow accumulation. The characteristics of this type of data is similar to the censored data. Indeed, Busan observation sites have more than 36% of no data or zero data. Despite of the different characteristics, the frequency analysis for snow data has been implemented according to the procedures for rainfall data. The frequency analysis could be implemented in both way to include the zero data or exclude the zero data. The fitness of both results would not be high enough to represent the real data shape. Therefore, in this study, a methodology for selecting a probability density function was suggested considering the characteristics of snow data in Korea. A method to select probability density function using conditional joint probability distribution was proposed. As a result, fitness from the proposed method was higher than the conventional methods. This shows that the conventional methods (includes 0 or excludes 0) overestimated snow depth. The results of this study can affect the design standards of buildings and also contribute to the establishment of measures to reduce snow damage.

• Korean Journal of Heritage: History & Science
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• v.38
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• pp.329-358
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• 2005

The Three storied Stone pagoda in Gameunsa Temple site, one of the early staged stone pagodas, has been known as a standard for Silla stone pagodas. A stone pagoda is not only a stone art work and but also a stone structure. Most studies and investigation of the stone pagoda has done mainly based on style and chronological research according to an art historical view. However, there is not an attempt to research the stone pagoda as a stone architecture. Most Korean experts at the stone pagoda has art history in their background. Engineers who can understand the structure of the stone pagoda are very limited. More architectural and engineering approach is need to research not only art historial understanding but also safety as a structure. We can find many technical know-how from our ancestors who made stone pagodas. 1. To reduce any deformation such as relaxation and sinking of BuJae which is caused by a heavy load, the BuJae (consist of a foundation stone and lower stereobates) should be enlarged. 2. A special construction method for connection between Myonsuk and Tangjoo was invented. This unique method is not used any longer after the Three storied Stone pagoda in Gameunsa Temple site. 3. The upper BuJae and the lower BuJae are missed each other by making a difference of Okgaesuk and Okgaebatchim in size. It is done for a distribution of perpendicular load and a prevention for relaxation of BuJae. 4. The center of gravity in the BuJae is located to the center of the stone pagoda by trimming the upper surface of the Okgaebatchim into a convex shape. The man who made stone pagodas had excellent knowledge on the engineering and techniques to understand the structure of the stone pagodas. We can confirm it as follows: the enlarged BuJae, dislocated connection between upper Bujae and lower BuJae, and moving the center of gravity close to the center of the stone pagoda.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.3
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• pp.133-149
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• 2021

This study aims to report the behavioral mechanism of steel pipe reinforcement grouting, which is being actively used to ensure the stability of the excavation surface during tunnel excavation, based on measurements taken at the actual site. After using a 12 m steel pipe attached with a shape displacement meter and a strain gauge to reinforce the actual tunnel surface, behavioral characteristics were identified by analyzing the measured deformation and stress of the steel pipe. Taking into account that the steel pipes were overlapped every 6 m, the measured data up to 7 m of excavation were used. In addition, the behavioral characteristics of the steel pipe reinforcement according to the difference in strength were also examined by applying steel pipes with different allowable stresses (SGT275 and SGT550). As a result of analyzing the behavior of steel pipes for 7 hours after the first excavation for 1 m and before proceeding with the next excavation, the stress redistribution due to the arching effect caused by the excavation relaxation load was observed. As excavation proceeded by 1 m, the excavated section exhibited the greatest deformation during excavation of 4 to 6 m due to the stress distribution of the three-dimensional relaxation load, and deformation and stress were generated in the steel pipe installed in the ground ahead of the tunnel face. As a result of comparing the behavior of SGT275 steel pipe (yield strength 275 MPa) and SGT550 steel pipe (yield strength 550 MPa), the difference in the amount of deformation was up to 18 times and the stress was up to 12 times; the stronger the steel pipe, the better it was at responding to the relaxation load. In this study, the behavior mechanism of steel pipe reinforcement grouting in response to the arching effect due to the relaxation load was identified based on the measured data during the actual tunnel excavation, and the results were reported.

• The Journal of Engineering Geology
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• v.32 no.3
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• pp.411-420
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• 2022

Recently, research using remote sensing has been active in various fields such as environment, science, and society. The results of research using remote sensing are not only numerical results, but also play an important role in solving and preventing social and scientific problems. The purpose of this thesis is to tell the correlation between the data provided and each data by using remote sensing technology for the tidal flat environment. The purpose of this study is to obtain high-resolution data using artificial satellites during remote sensing to find out information on tidal flat currents. Tidal flats created by erosion, sedimentation, low tide, and high tide contain information about the tidal flat slope and information about the ecosystem. Therefore, it can be considered as one of the very important studies to analyze the overall tidal flow channel. This paper creates a DEM (Digital Elevation Model) through TanDEM-X, and DEM is used as the most basic data to create a tidal channel. The research area is a tidal flat located in the middle of the west coast of Ganghwado tidal flat. By analyzing the tidal channel created, various information such as the slope direction of Ganghwado tidal flat and the shape of the tidal channel can be grasped. It is expected that the results of this study will increase the importance and necessity of using DEM data for tidal flat research in the future, and that high-quality results can be obtained.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.594-605
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• 2022

CaO was prepared by calcining for oyster shells using a microwave kiln. It was analyzed to Ca(OH)₂ synthed on hydration reaction from prepared CaO. The synthesized Ca(OH)₂ was formulated as an external water paint. Oyster shells (325 mesh, 43 ㎛) were decarbonized for (a) 950 ℃/1 hr and (b) 1,150 ℃/1 hr to prepare CaO. In the calcination condition of (a), CaO was 56.7 wt%, and in the calcination condition of (b), CaO was 100 wt%. To compare CaO by calcination of oyster shells with that of limestone, limestone (25~30 mm) was decarbonized at 950 ℃/1 hr to prepare CaO, and as a result of the analysis(XRD), it was analyzed as CaO 100 wt%. CaO was prepared under the calcining conditions of oyster shells (b) 1,150 ℃/1 hr, and Ca(OH)₂ was synthesized through hydration. Hydration conditions of the prepared CaO were (a) CaO : H₂O(100 g : 200 g) and (b) CaO : H₂O(100 g : 400 g). As a result of the hydration reaction, it was confirmed as low reactivity. 100 wt% of Ca(OH)₂ was synthesized. In particular, Ca(OH)₂ synthesized under the hydration condition of (a) was analyzed in a plate shape. An external water paint was formulated with Ca(OH)₂ synthesized from oyster shells as the main component. When 15 items of the external water paint standard specification (KS M 6010) were analyzed, it was confirmed that all other criteria were satisfied except for freezing stability.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.399-409
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• 2021

In order to utilize dolomite as a calcium/magnesium compound material, it was prepared highly reactive calcined dolomite(CaO·MgO) using a microwave kiln (950 ℃, 60 min). The experiment was performed according to the standard of the hydration test (ASTM C 110) and hydration reactivity was analyzed as medium reactivity (max 74.1 ℃, 5 min). Experiments were performed with calcined dolomite and salt (MgCl₂·6H₂O) (a) 1:1, (b) 1:1.5, and (c) 1:2 wt% based on the hydration reaction of calcined dolomite. The result of X-ray diffraction analysis confirmed that MgO of calcined dolomite increased to Mg(OH)₂ as the salt addition ratio increased. After the separating reaction, calcium was stirred at 80 ℃, 24 hr that produced CaCl₂ of white crystal. XRD results, it was confirmed calcium chloride hydrate (CaCl₂·(H₂O)x) and CaO of calcined dolomite and salt additional reaction was separated into CaCl₂. And it was synthesized with Ca(OH)₂ 99 wt% by NaOH adding reaction to the CaCl₂ solution, and the synthesized Ca(OH)₂ was manufactured CaO through the heat treatment process. In order to prepare calcium carbonate, CaCO₃ was synthesized by adding Na₂CO₃ to CaCl₂ solution, and the shape was analyzed in cubic form with a purity of 99 wt%.