• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.127-132
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• 2009

We have investigated the intrinsic defects remaining in epitaxial GaSb layers grown on SI-GaAs substrates compared to those in bulk GaSb crystal substrate, which is a basic material of Sb-based strained-layer superlattice infrared photodetectors. From the functional dependence of the band-to-band transition energy of the photomuminescence (PL) spectra observing up to near room-temperature (250 K), the temperature parameters of [$E_o$, $\alpha$, $\beta$] of undoped GaSb crystal are determined by using the Varshni empirical equation describing the temperature variation of the bandgap energy. Additionally to the antisite-Ga ([$Ga_{Sb}$]) with an ionization energy of 29 meV that is well known to a major intrinsic defect in GaSb, epitaxial GaSb layers show a pair of deep states at the emission energy of 732/711 meV that may be related with a complex of two antisite-Ga and antisite-Sb ([$Ga_{Sb}-Sb_{Ga}$]). Based on the analysis of the temperature and the excitation-power dependences of PL, it suggests that excess-Sb substitutes Ga-site by self-diffusion and two anti sites of [$Ga_{Sb}$] and [$Sb_{Ga}$] could form as a complex of [$Ga_{Sb}-Sb_{Ga}$] in GaSb epilayers grown under Sb-rich condition.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.107-116
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• 2017

When drilling operation is being performed, many physical and chemical changes are occurred near wellbore. To handle various changes of well condition and keep drilling process safe, additives of bulk, such as bentonite for increasing density of drilling mud, barite for increasing viscosity of drilling mud, polymer for chemical control, or surfactant, are added into drilling mud through a mud shear mixer. Because the achievement of the required material property through mud mixing system is essential to stabilize drilling system, it is of importance to analyze multi-phase flow during mud mixing process, which is directly related to increase mixing performance of the system and guarantee the safety of the whole drilling system. In this study, a series of liquid-solid flow simulation based on a computational fluid dynamics (CFD) are performed with comparing to solid concentration in experiment by Gilles et al. [2004] to understand the characteristics of liquid-solid mixing in a mud shear mixer. And then, the simulation-based design of shear mixer are carried out to improve mixing performance in a mud handling system.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.4 s.117
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• pp.96-104
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• 2006

Impervious pavement is primary contributor to the malfunctioning of the urban water circulation system. The aim of this research is to provide basic information and data for new pavement materials and paving technology which could enhance the urban water circulation system. For the study purposes, physical properties of soils sampled from 16 stations were analyzed. The sampling spots were paved with grass block porous pavement material. The findings from the analysis are as follows. The hardness of soils under the pavement was $17{\sim}22mm$ for thoroughfare and $6{\sim}32mm$ for parking areas. The bulk density was $1.42{\sim}1.81g/cm^{3}$ for thoroughfare and $1.38{\sim}1.75g/cm^{3}$ for parking area. The solid phase ration was $46.9{\sim}62.5m^{3}/m^{3}$ for thoroughfare and $45.6{\sim}61.3m^{3}/m^{3}$ for parking area. The porosity was $37.5{\sim}53.1m^{3}/m^{3}$ for thoroughfare and $38.7{\sim}54.4m^{3}/m^{3}$ for parking area. The saturated hydraulic conductivity was $8{\sim}164mm/hr$ for thoroughfare and $14{\sim}201mm/hr$ for parking area. The saturated hydraulic conductivity of the H sample area (the area was completed three months ago) and that of the other area were compared. There was up to 80% decreases of the saturated hydraulic conductivity within one year after the completion of pavement. After the first year, decrease in the saturated hydraulic conductivity was modest. Also there are changes in both surface and under soil physical properties of the grass block porous pavement depending on compaction. The extent of change depends on the degree of compaction. All these factors are combined to influence the permeability of the soil under the pavements. The results of this suggest that it is required to develop a new pavement technology which ensures both the durability and porosity of the pavement to improve the water circulation system by applying Ecological Area Rate.

• Korean Journal of Food Science and Technology
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• v.39 no.2
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• pp.146-151
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• 2007

Resistant starch (RS) content, paste viscosity, water solubility and absorption index, bulk density, color, compression force, and bowl life of Goami flakes manufactured by extrusion process were determined to evaluate Goami (high fiber rice) as a food material. Various extrusion process conditions included barrel temperature (90, 110, $130^{\circ}C$) and moisture content (50, 55%). RS content in the extruded pellet and defatted flake ranged from $8.00{\sim}8.56%$ and $6.57{\sim}9.53%$ respectively. RS content increased as moisture increased from 50% to 55%. Peak viscosity, trough viscosity, final viscosity, and setback viscosity of the extruded pellet and defatted flake decreased with steeping for 1 hr, and the breakdown viscosity significantly increased. The water solubility and absorption index increased in the flake compared to Goami and extruded pellet. The water solubility index of the extruded pellet was lower than that of Goami, while its water absorption index was higher than Goami. The bulk density of the flake ranged from $0.35{\sim}0.44$ g/mL. The bowl life of the flake was $12.4{\sim}19.4$ min, which was longer than commercial breakfast cereals on the market.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.2
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• pp.196-208
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• 1998

To improve the quality of environmental measurements and evaluation of the workplace air in the pigment manufacturing industries, we analyzed metal(chromium, cadmium, lead, iron, cobalt, manganese, antimony, titanium, arsenic, and selenium) concentrations by ICP-AES in sixty seven samples of inorganic bulk pigments which are produced and/or used in Korea. We also collected MSDS which has to be supplied by manufacturer and/or supplier and posted in the workplace according to the Hazard Communication Standards, and compared the number of metals listed in each MSDS with the number of metals determined by ICP-AES. Results were as followed; 1. Among seventeen yellowish-colored samples, chromium(2~19%) and lead(0.1~61%) were the two major metals. In thirteen reddish-colored samples, iron was the major component with 37~81%. Cobalt and manganese were detected in blue-colored samples with less than 1%, while antimony and titanium were the major two metals in white-colored pigments with 178~300 ppm and with 36~65%, respectively. 2. In area samples collected in workplace air(one pigments producing factory and five retailer stores), iron and manganese were detected but the concentrations not exceeded the TLVs(1 and $5mg/m^3$, respectively). In three of fifteen samples, the concentrations of lead exceeded the TLV ($0.05mg/m^3$). 3. Two out of seven companies provided MSDS, and the average provision rate was 22.4%. And the coincidence rate of the number of metals referenced in MSDS and determined by ICP-AES mostly accorded, but in one sample, different metal was detected from MSDS. In summary, metals have to be concerned in evaluation of the workplace air dealing with compounds of inorganic pigments dust are cobalt, chromium, iron, manganese, lead and antimony, and these are simultaneously determined by ICP-AES. Taking this opportunity, it is needed to reinforce that the personnel is to be concerned about prevention of workers' ill health regarding to provision of MSDS.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.4
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• pp.69-76
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• 2016

To produce the primary data for best management of soil nutrient in organically practiced soils, 75 leading organic farms whose paddy fields were certified as organic were selected. Soil samples were collected from the paddy fields before plowing, and then analyzed for the determination of physico-chemical properties. Soil pH, organic matter and available phosphate were analyzed and averaged 6.2, $25.6mg\;kg^{-1}$ and $88.4mg\;kg^{-1}$, respectively. Contrary to the national-scale-surveyed paddy soils including organic and conventional farming, pH was higher, available phosphate was lower in the organically practiced soils, but organic matter was similar. With the increasing cultivation period in organic, soil pH and porosity were also increased, EC, available phosphate, bulk density and soil hardness were lower than those from the national survey. Organic matter, however, was not significantly changed. The bulk density was negatively correlated with the organic matter content for both surface topsoil ($R^2=-0.5424$) and subsoil ($R^2=-0.6429$) (p<0.05). Soil quality is improved in most of soil chemical and physical composition factors excluding organic matter and available phosphate. However, it is necessary to establish the counter measure plan for organic matter management and to develop phosphate-containing materials which can be used as organic agricultural material in the future.

• Journal of Radiation Protection and Research
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• v.20 no.4
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• pp.265-274
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• 1995

Diffusivity of ions of radioactive species is an important factor for designing radwaste repositories. Clay minerals are used as a backfill material. In this study, diffusion of Co-60 ions through the bentonite having various densities has been studied, using a diffusion cell. The measured diffusivities of Co-60 ions decreased as the density of bentonite increased. The diffusivity of Co-60 ion decreased from $8.79{\times}10^{11}m^2/s$ to $6.82{\times}10-13m^2/s$ as the clay dry bulk density increased from 0.41 to 2.03g/cm3. The diffusivity of Co ion was larger than that of Sr ion at low density, but the diffusivity of Co ion decreased rapidly as the density of clay increased and became smaller than that of Cs ion at high density. This phenomenon is thought to be caused by the rapid decrease of the fraction of mobile cation since the chemical combination of Co ions with oxygen or oxide on clay surface and the entrance of Co ions into the crystal structure of clay increase as the clay density increases. This change should be considered especially in designing the clay back fill for low and intermediate radwaste disposal facilities.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.227-234
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• 2012

In this study, we make simulation of density log using a Monte Carlo N-Particle (MCNP) algorithm to make an analysis on density logging under different borehole environments, since density logging is affected by various borehole conditions like borehole size, density of borehole fluid, thickness and type of casing, and so on. MCNP algorithm has been widely used for simulation of problems of nuclear particle transportation. In the simulation, we consider the specific configuration of a tool (Robertson Geologging Co. Ltd) that Korea institute of geoscience and mineral resources (KIGAM) has used. In order to measure accurate bulk density of a formation, it is essential to make a calibration and correction chart for the tool under considerations. Through numerical simulation, this study makes calibration plot of the density tool in material with several known bulk densities and with boreholes of several different diameters. In order to make correction charts for the density logging, we simulate and analyze measurements of density logging under different borehole conditions by considering borehole size, density of borehole fluid, and presence of casing.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.45-50
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• 2008

Purpose: A soft contact lens was manufactured by adding naringin known as natural anti-bacterial material to resin solution. With solution eluted from manufactured contact lens, we examined its optical properties, physical and chemical states of naringin in the polymer, and elution properties. Methods: The soft contact lens with naringin was synthesized by bulk polymerization method. IR spectrum and HPLC were used to define the bonding type of naringin itself in the soft contact lens contained naringin, elution process of naringin to the saline solution, and the amount of naringin solution eluted from the lens with elapsed time. Results: Naringin was continuously eluted with constant concentration from the soft contact lens for about a month and the structure ofnaringin which is eluted was as same as before it was added to resin solution. Any change in optical properties such as transmittance couldn't be found. Bonding state and the structure of naringin in contact lens were explained with IR spectrum and HPLC results. Conclusions: In the contact lens with naringin, naringin remained in the contact lens bonding with weak hydrogen bonding and/or van der Waals force between naringin and polymer. Naringin was continuously eluted from the contact lens contained naringin during about 1 month. Even after 1 month, it showed that the concentration of the naringin eluted was approximately 10 ppm in a day. From the results, adding naringin to the soft contact lens resin is very effective method for manufacturing the soft contact lens which has anti-bacterial function for a period of time.

• Journal of the Korean GEO-environmental Society
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• v.17 no.5
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• pp.37-46
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• 2016

In order to determine the variability of environmental characteristics of lightweight air-foamed soil using marine clay according to freezing-thawing and soaking conditions, unconfined compressive strength of the lightweight air-foamed soil samples made by changing the amount of cement under curing conditions of outdoor low temperature, underground or indoor wetting were observed. Compressive strength was not increased under freezing-thawing (temperature range of $-9.1^{\circ}C{\sim}17.2^{\circ}C$) regardless of the amount of cement but the more cement using, it was increased rapidly by underground curing conditions within 30 cm beneath ground level. Therefore, it is necessary to install insulation layer cutting off exterior cold air after construction of lightweight air-foamed soil in condition of freezing-thawing. Bulk density was increased too small under the long-time soaking condition, it tended to decrease rapidly when samples were dried up and had below 6% of water contents. But variability of compressive strength and bulk density was very small for preventing drying and keeping its wet state. The lightweight air-foamed soil that installed beneath ground water level or covered by soil can be evaluated as a long-term reliable construction material.