• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.2
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• pp.130-136
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• 1982

Experiments were conducted to establish a measuring method of the stomatal aperture in the leaves of the wheat plant, and to find the diurnal movements of the stomate in leaves of different position and tillers. The measurement methods used were the infiltration and the microrelief impression methods. The aperture of the stomate in the infiltration method was expressed in terms of the solutions pent ration into the leaf and this was refered to as the infiltration score. A score I represents injection with 10% iso-butyl alcohol＋90% ethylene glycol solution and a score 7 represents injection with 70% iso-butyl alcohol +30% ethlene glycol solution. A linear relationship was obtained between the infiltration score and average pore width in a large number. of the stomata observed in the leaves of the adaxial and abaxial epidermis. The aperature of the stomate of flag and the 1st leaf were exhibited diurnal change with the maximum aperture at 10 A.M. but that of 2nd leaf reached maximum aperture 2 hours later than upper two leaves. After reaching the maximum aperture the stomata gradually closed and then completely closed at 6 P.M. The aperture of the stomate in the adaxial epidermis and the base part of the leaf were larger than those in the abaxial and top part of the leaf, and aperture of the stomate in the leaves of the main stem was larger than those on the tillers.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.309-315
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• 2012

Metal foam has many excellent properties, such as light weight, incombustibility, good thermal insulation, sound absorption, energy absorption, and environmental friendliness. It has two types of macrostructure, a closed-cell foam with sealed pores and an open-cell foam with open pores. The open-cell foam has a complex macrostructure consisting of an interconnected network. It can be exploited as a degradable biomaterial and a heat exchanger material. In this paper, open cell Mg alloy foams have been produced by infiltrating molten Mg alloy into porous pre-forms, where granules facilitate porous material. The granules have suitable strength and excellent thermal stability. They are also inexpensive and easily move out from open-cell foamed Mg-Al alloy materials. When the melt casting process used an inert gas, the molten magnesium igniting is resolved easily. The effects of the preheating temperature of the filler particle mould, negative pressure, and granule size on the fluidity of the open cell Mg alloy foam were investigated. With the increased infiltration pressure, preheat temperature and granule sizes during casting process, the molten AZ31 alloy was high fluidity. The optimum casting temperature, preheating temperature of the filler particle mould, and negative pressure were $750^{\circ}C$, $400-500^{\circ}C$, and 5000-6000 Pa, respectively, At these conditions the AZ31 alloy had good fluidity and castability with the longest infiltration length, fewer defects, and a uniform pore structure.

• Geotechnical Engineering
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• v.14 no.3
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• pp.123-134
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• 1998

To analyse the stability of a slope composed of waste material produced in a closed lead mine, numerical modeling has been carried out in two dimension using FLAC, finite difference program. The research was focused on the effect of the earthquake as well as a rise of water table upon slope stability. The numerical results have shown that the slope would not be safe against earthquake event and that the increase of pore pressure due to a rise of water table up to the ground level may result in a failure of the slope. On the basis of numerical analyses and site investigation, two sorts of measures have been taken. In short term, removal of a part of materials deposited on the top of the pile is required to increase immediately safety factor of the slope even a little. In ling term, it is necessary to repair drainage facilities and dam which covers waste material so that the slope is prevented from failure in a radical manner. It has been confirmed by numerical analyses that an improvenment of the stability can be in a great extent expected after such measures have been performed.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.553-559
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• 2003

PDP rib is one of the important parts of manufacturing process and the sintering degree of rib plays an important role to prevent some problems such as cross talk. Nowadays, the screen-printing method, which is a low price and high production, is used to make a rib. However, it is hard to judge and value the sintering ratio of sintered body itself. In this study, we measured the sintering degree by the dielectric breakdown of pores with the potentiostat. We conformed that this has similar tendency to density of sintered samples and an error being expected by open and closed pores was inspected by change of the microstructure to scanning electron microscope. This result showed that the sintering degree of PDP rib could be analyzed into the electro-chemical method.

• Resources Recycling
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• v.9 no.2
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• pp.33-39
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• 2000

Low density ceramic supporter was prepared by using fly ash as a starting material for the application to the biological aerated filter system. Wheat powders were used to control the porosity of the supporter and the carbon content of the raw material. Apparent density of 1.6~1.8 g/$\textrm{cm}^3$ was obtained when the fly ash was sintered at $1200^{\circ}C$ in a weak reducing atmosphere. By maintaining the reducing atmosphere and sintering at a high heating rate, the liquid phase was formed from the reduced composition of fly ash. This resulted in the closed pore formation which enabled the low apparent density.

• Nuclear Engineering and Technology
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• v.42 no.5
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• pp.576-581
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• 2010

KAERI (Korea Atomic Energy Research Institute) fabricated MOX (Mixed Oxide) fuel pellets as a cooperation project with PSI (Paul Scherrer Institut) for an irradiation test in the Halden reactor. The MOX pellets were fitted into fuel rods that included instrumentation for measurement in IFE (Institutt for Energiteknikk). The fuel rods were assembled into the test rig and irradiated in the Halden reactor up to 50 MWd/kgHM. The irradiated fuel rods were transported to the IFE, where ceramography was carried out. The fuel rods were cut transversely at the relatively higher burn-up locations and then the radial cross sections were observed. Micrographs were analyzed using an image analysis program and grain sizes along the radial direction were measured by the linear intercept method. Radial cracks in the irradiated MOX were observed that were generally circumferentially closed at the pellet periphery and open in the hot central region. A circumferential crack was formed along the boundary between the dark central and the outer regions. The inner surface of the cladding was covered with an oxide layer. Pu-rich spots were observed in the outer region of the fuel pellets. The spots were surrounded by many small pores and contained some big pores inside. Metallic fission product precipitates were observed mainly in the central region and in the inside of the Pu spots. The average areal fractions of the metallic precipitates at the radial cross section were 0.41% for rod 6 and 0.32% for rod 3. In the periphery, pore density smaller than 2 ${\mu}m$ was higher than that of the other regions. The grain growth occurred from 10 ${\mu}m$ to 12 ${\mu}m$ in the central region of rod 6 during irradiation.

• Korean Journal of Materials Research
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• v.28 no.9
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• pp.506-510
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• 2018

Nitrogen is a serious contaminant in natural gas because it decreases the energy density. The natural gas specification in South Korea requires a $N_2$ content of less than 1 mol%. Thus, cost-effective $N_2$ removal technology from natural gas is necessary, but until now the only option has been energy-intensive processes, e.g., cryogenic distillation. Using porous materials for the removal process would be beneficial for an efficient separation of $CH_4/N_2$ mixtures, but this still remains one of the challenges in modern separation technology due to the very similar size of the components. Among various porous materials, metal-organic frameworks (MOFs) present a promising candidate for the potential $CH_4/N_2$ separation material due to their unique structural flexibility. A MIL-53(Al), the most well-known flexible metal-organic framework, creates dynamic changes with closed pore (cp) transitions to open pores (ops), also called the 'breathing' phenomenon. We demonstrate the separation performance of $CH_4/N_2$ mixtures of MIL-53(Al) and its derivative $MIL-53-NH_2$. The $CH_4/N_2$ selectivity of $MIL-53-NH_2$ is higher than pristine MIL-53(Al), suggesting a stronger $CH_4$ interaction with $NH_2$.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.63-73
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• 2009

Recently, the use of lightweight panels in building structures has been increasing. Of the various lightweight panel types, styrofoam sandwich panels are inexpensive and are excellent in terms of their insulation capacity and their constructability. However, sandwich panels that include organic material are quite vulnerable to fire, and thus can numerous casualties in the event of a fire due to the lack of time to vacate and their emission of poisonous gas. On the other hand, lightweight foamed concrete is excellent, both in terms of its insulation ability and its fire resistance, due to its Inner pores. The properties of lightweight concrete is influenced by foaming agent type. Accordingly, this study investigates the insulation properties by foaming agent type, to evaluate the possibility of using light-weight foamed concrete instead of styrene foam. Our research found thatnon-heating zone temperature of lightweight foamed concrete using AP (Aluminum Powder) and FP (animal protein foaming agent) are lower than that of light-weight foamed concrete using AES (alkyl ether lactic acid ester). Lightweight foamed concrete using AES and FP satisfied fire performance requirements of two hours at a foam ratio 50, 100. Lightweight foamed concrete using AP satisfied fire performance requirements of two hours at AP ratio 0.1, 0.15. The insulation properties were better in closed pore foamed concrete by made AP, FP than with open pore foamed concrete made using AES.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.113-120
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• 2007

In this study, researches for the development of antibiotics and antimicrobial concrete were conducted to reduce biochemical corrosion of sewage concrete. First of all, desired performance, such as watertightness, antibiosis, homogeneity, workability and harmlessness, was proposed and performance of antibiotics and antimicrobial concrete were evaluated by them. As results of this study, dispersibility and antibiosis of liquid antibiotics superior to powdery antibiotics. Antibiosis of antimicrobial concrete was verified, and amount of elution of harmful and effective ingredients was little. In workability, setting time of antimicrobial concrete was delayed. Compressive strength and resistance to carbonation of antimicrobial concrete were more increased than ordinary concrete. Also, as little pore volume and closed structure of antimicrobial concrete were observed, watertightness of it was verified. Finally artificial accelerating test for biochemical corrosion was proposed, and its suitability was experimentally proved.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.30-35
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• 2016

Rice cultivation in paddy field affects the global balance of methane ($CH_4$) as a key greenhouse gas. To evaluate a potential use of by-product gypsum fertilizer (BGF) in reducing $CH_4$ emission from paddy soil, $CH_4$ fluxes from a paddy soil applied with BGF different levels (0, 2, 4 and $8Mg\;ha^{-1}$) were investigated by closed-chamber method during rice cultivation period. $CH_4$ flux significantly decreased (p<0.05) with increasing level of BGF application. $8Mg\;ha^{-1}$ of BGF addition in soil reduced $CH_4$ flux by 60.6% compared to control. Decreased soil redox potential (Eh) resulted in increasing $CH_4$ emission through a $CO_2$ reduction reaction. The concentrations of dissolved calcium (Ca) and sulfate ion (${SO_4}^{2-}$) in soil pore water were significantly increased as the application rate of BGF increased and showed negatively correlations with $CH_4$ flux. Decreased $CH_4$ flux with BGF application implied that ${SO_4}^{2-}$ ion led to decreases in electron availability for methanogen and precipitation reaction of Ca ion with inorganic carbon including carbonate and bicarbonate as a source of $CH_4$ formation under anoxic condition. BGF application also increased rice grain yield by 16% at $8Mg\;ha^{-1}$ of BGF addition. Therefore, our results suggest that BGF application can be a good soil management practice to reduce $CH_4$ emission from paddy soil and to increase rice yield.