• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.6-12
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• 2018

Recently, The use of the curtain wall method is increasing in construction. The curtain wall construction is widely applied to the exterior wall of the building for shortening construction period and economical efficiency. However, the replacement of deterioration of the weather resistance and structural behavior of the sealing material connecting the curtain wall method and the glass frame is necessary for introduction of the stable curtain wall method and quality improvement in accordance with KS F 4910 standard. In this study, the elastic restoring force test was performed in the external environment. In this study, the deterioration of the sealant was evaluated for structural sealants. In Korea, studies on the variable displacement behavior of structural sealants are lacked. In this study, the reproduced results in laboratory conditions are compared with the deteriorating conditions exposed to the external environment, and they are reflected in the design of sealing materials in the future. According to the results of the study, it was confirmed that the existing structure sealant meets the quality standard of KS F 4910, but in the conditions performed in this study, adhesion failure of the specimen and cracking of the surface occurred. Especially, in the weather resistance test, it is necessary to evaluate the long-term durability performance of the structural sealant used in the curtain wall method by checking the insoluble state of all the test pieces. Therefore, in order to apply a conventional structural sealant to the site, it is necessary to introduce another durability performance evaluation.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.467-475
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• 2015

The Deokjin Pond is one of the places representing Jeonju City's history but has the poor water quality. The pond has a storage of $88,741m^3$ and a drainage area of $3.77km^2$. It has been maintained only by the groundwater pumped from the upstream wells and the direct rainfalls on the water surface since the old streams replenishing the pond were turned into a part of the sewer system due to indiscreet urbanization. The lack of replenishing water as well as the organic-rich bottom sediment were suggested as two main causes deteriorating the water-ecosystem. In this study, possible measures obtaining waters for restoration of Deokjin Pond ecosystem are discussed. It is estimated that the present pond can be replenished about 32 times a year by the runoff when the drainage system in the watershed is recovered to a state before urbanization. To support this, the drainage system is compared with that of nearby Osong Pond, which shows relatively better water-ecosystem. Even though Osong Pond has a drainage area one-seventh of that of Deokjin Pond, its storage is more than the half of it. It is because its watershed has a near natural drainage system where the rain mostly infiltrates into soil and slowly discharges into the pond. Therefore, it is believed that the low impact development (LID), which is known as a technique restoring the water circulating system to a condition before development, would be helpful in obtaining waters required for Deokjin Pond ecosystem management.

• Applied Microscopy
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• v.12 no.2
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• pp.11-22
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• 1982

The morphological development of Mycoplasma pneumoniae attached to solid surfaces was examined by light and electron microscopies. Critical point drying and carbon replication techniques revealed that during the growth cycle of developing microcolonies, the morphological form coincided with the pH of the culture. M. pneumoniae appeared to have a well defined morphology associated with age of the culture. The organisms were dimorphic, with round cells capable of reproduction and segments consisting of a spindle shaped body with one pointed and one knob-like end. Starting with single cells, there were the following stages in the development of a culture: replication stage through binary fission and segmentation, stage of confluency, and a degeneration stage into rough spherical forms. The round cells appearrd to replicate by binary fission during the lag and early log phases of growth, while spindle segments replicated by segmentation during most of the logarithmic growth. The growth of the filaments and replication of the segments occured at the knob-like ends, showing a type of polarity, and formed a meshwork across the surface. This development could be cycled under favorable growth conditions, but the culture aged and when the conditions became adverse(e.g. pH 6.8 or lower), filamentous cells converted to spherical forms, losing their reproductive capability.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.213-226
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• 2004

The present study was conducted to analyze the pattern of eutrophication of Korean reservoir with Chl. a concentration and morpho-physical parameters, and to valuate water quality characteristics of the classified types. The collected data from 486 reservoirs were classified as four types, with the Chl- a concentration (25 ${\mu}g\;L^{-1}$) and the ratio of water storage/surface area (mean depth, 7.5 m). According to OECD criteria and trophic state index based on Chl-a concentration, 34.3 and 72.8% of selected reservoirs appeared to be eutrophic, respectively. Characteristics of TYPE ll reservoirs generally showed high Chl-a concentration, relatively old age, small DA/LA ratio, short Hydraulic retention time, large paddy field and field to watershed ratio, and high pollutant loading compared to other types of reservoirs. The difference of TP concentration was greater than that of TN concentration in reservoir water among classified four types. Based on TN/TP ratio (by weight), phosphorus was limiting nutrient in all types and more closely related with Chl- a concentration than nitrogen. Significant decrease of Chl- a concentration with increase of TN/TP ratio observed only in reservoirs with Chl-a concentration > 25${\mu}g\;L^{-1}$. Although drainage area is believed to be a factor that is related to the generation load of pollutants in the watershed, it did not show any significant relationship with water quality parameters. Morphometric characteristics such as depth and age of reservoir as well as type of land use patterns in the watershed was among important parameters for the assessment of water quality characteristics in Korean reservoirs.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.539-544
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• 2020

A three-dimensional (3D) porous polyaniline (PANI) film was fabricated by a combined photo-and soft-lithography technique based on a large-area nanopillar array, followed by a controlled chemical dilute polymerization. The as-obtained 3D PANI film consisted of hierarchically interconnected PANI nanofibers, resulting in a 3D hierarchical nanoweb film with a large surface and open porous structure. Using electrochemical measurements, the resulting 3D PANI film was demonstrated as a flexible pH sensor electrode, exhibiting a high sensitivity of 60.3 mV/pH, which is close to the ideal Nernstian behavior. In addition, the 3D PANI electrode showed a fast response time of 10 s, good repeatability, and good selectivity. When the 3D PANI electrode was measured under a mechanically bent state, the electrode exhibited a high sensitivity of 60.4 mV/pH, demonstrating flexible pH sensor performance.

• Geotechnical Engineering
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• v.10 no.2
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• pp.25-40
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• 1994

In order to investigate behavior of lateral flow by plasticity of soils and construction control due to it, in the case of unsymmetrical surcharge load on the soft soils, we examine the existing theoretical background, and compared and analysed the experimental results by model test. After model test fabricated by model test apparatus, which made full remolding samples of soft soils, we observed the state of behavior for deformation with increasing load step to constant time interval. The critical surcharge and ultimate capacity showed tendency to approach to the proposed value of Jaky and Meyerhof, and the lateral flow pressure of which the maximum value was acted on the depth calculated by z/H=0.26+1.71cu and one third value of the maximum lateral flow pressure acted on the ground surface, approach the trapezoid distribution And maximum lateral flow pressure will be calculated by proposed equation of Hong or simple equation which($\alpha=0.4$) the flow pressure coefficient . of proposed equation by Tschebotarioff exchanged to($\alpha=K_0$) . Basides, the failure surcharge by [(q/$y_m$)-q] and [$S_y-(y_m/S_y)$] showed the smaller than ultimate bearing capacity, especially failure criteria line of control diagram of [$S_y(y_m/S_y)$] will be calculated by following equation. $S_y.=3.15exp[-0.58(y_m/S_y)$

• Journal of The Korean Association For Science Education
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• v.20 no.4
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• pp.527-541
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• 2000

The purpose of this study was to find out the characteristics of learning contents structure of K-12 science textbooks. The characteristics are related to 7 main concepts of matter properties; reaction rate, other reaction, density, solution, state change, absorption, and surface property. The contects are analyzed into 5 types of characteristics; type of concept extension, type of concept deepness, type of same level concept, type of confusion with other concepts, and type of concept interruption. First two types are positive content structures, but the others are negative structures. The findings are as follows. First, a lot of learning contents have the characteristic of 'type of same level concept'. There are few which have the characteristic of 'type of concept deepness'. Second, there are a lot of concepts related to 'properties of matter' which are not represented any more in middle and high school science textbooks. Those concepts are importantly taught in early childhood education and elementary school science. Most of the learning contents don't represent 'type of concept deepness'. Therefore the science textbooks needs to be restructuring.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.183-190
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• 2009

The aim of this study is to find the condition of forming the favorable nanotubes by anodizing with NaF and $H_3PO_4$. Machined Ti discs were used for anode, and Platinum net was used for cathode. For electrolyte, $H_3PO_4$ and NaF solution were mixed. We controlled voltage, electrolyte concentration, anodizing time and formed nanotubes on Ti discs. After that, these were washed with distilled water for 24 hours and dried in the $40^{\circ}C$ oven for 24 hours. The surface structure of specimens were analyzed. The results were as follows : At 0.5 wt % NaF, according as increasing voltage and anodizing time, early state of nucleating pores were generated. At 1.0 wt % NaF, 20 V, 20 & 25 min, well-formed nanotubes were observed. At 1.0 wt % NaF, 30 V, structure of nanotube became bigger and interconnected. At 2.0 wt % NaF, no nanotubes were formed and it was unrelated with voltage and time. At 1.0 wt % NaF, 20 V, 20 - 25 min, well-ordered nanotubes were generated on Ti discs. For the formation of favorable nanotubes, it is considered that proper parameters such as electrolyte concentration, voltage, anodizing time are necessary according to the kind of electrolytes.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.271-277
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• 2014

To overcome the limitations of the solid oxide fuel cells (SOFCs) due to the high temperature operation, there has been increasing interest in proton conducting fuel cells (PCFCs) for reduction of the operating temperature to the intermediate temperature range. In present work, the perovskite $BaCe_{0.85-x}Zr_xY_{0.15}O_{3-\delta}$ (BCZY, x = 0.1, 0.3, 0.5, and 0.7) were synthesized via solid state reaction (SSR) and adopted as an electrolyte materials for PCFCs. Powder characteristics were examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer, Emmett and Teller (BET) surface area analysis. Single phase BCZY were obtained in all compositions, and chemical stability was improved with increasing Zr content. Anode-supported cell with $Ni-BaCe_{0.55}Z_{0.3}Y_{0.15}O_{3-\delta}$ (BCZY3) anode, BCZY3 electrolyte and BCZY3-$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-\delta}$ (BSCF) composite cathode was fabricated and electrochemically characterized. Open-circuit voltage (OCV) was 1.05 V, and peak power density of 370 ($mW/cm^2$) was achieved at $650^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.1
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• pp.61-65
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• 2012

Once oil has spilled, oil spill responders use a variety of countermeasures to reduce the adverse effects of spilled oil on the environment. Mechanical methods of containment and recovery are preferred as the first response when the use of other methods fail or are ineffective. In these cases, the application of oil dispersants shall be use only as a last resort. While effectiveness of dispersants in removing oil form the sea surface is proven, the use of dispersants is controlled in almost all countries due to the toxicity of their active agents and the dispersed oil on the marine environment. However, according to reports, after dispersant application, no significant toxicity to fish or shrimp was observed in the field-collected samples. Moreover, the results also indicate that dispersant-oil mixtures are generally no more toxic to the aquatic test species than oil alone. During the Deepwater Horizon Incident, dispersants were applied to floating oil and injected into the oil plume at depth. These decisions were carefully considered by state and federal agencies, as well as BP, to prevent as much oil as possible from reaching sensitive shoreline habitats. Net Environmental Benefit Analysis for dispersant use assumed that dispersants appear to prevent long-term contamination resulting absence of oil in the substrate and will benefit marine wildlife by decreasing the risk of significant contamination to feathers or fur. Further study to use dispersants with scientific baseline is needed for our maritime environment which consistently threaten huge oil spill incidents occurrence.