• 한국산학기술학회논문지
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• 제11권7호
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• pp.2719-2726
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• 2010

본 연구는 포항지역 환경오염물질의 보건 환경 위해성 평가를 위한 기초연구의 일환이며, 이를 위하여 포항시에 소재한 지역대기자동측정 자료를 이용하여 연별, 계절별 $PM_10$ 농도분포에 대한 현황, 기상특성 및 오염물질 농도분포 분석을 수행하였고, 대기확산 모델(CALPUFF)을 이용하여 농도분포 특성에 대해 정성적, 정량적으로 확인하였다. 포항지역의 $PM_10$ 농도분포를 확인한 결과, 포항지역의 계절별 $PM_10$ 평균농도는 봄($75.7{\mu}g/m^3$)>여름($56.8{\mu}g/m^3$)>겨울($53.6{\mu}g/m^3$) >가을($52.7{\mu}g/m^3$) 순으로 봄에는 빈번히 발생하는 황사의 영향으로 높은 농도를 나타내었다. 포항지역 오염원별 $PM_10$ 배출량은 점오염원 62%>이동오염원 33%>면오염원 5% 순이며, 점오염원 중 전체 97%가 철강산업인 제철제강업에서 발생되었다. 포항지역은 $PM_10$의 영향을 많이 받고 있는 지역으로 포항철강공단지역에 대한 환경오염물질 원인배출원에 대한 감시체계의 보완 및 집중관리와 함께 포항지역 주민의 건강 보호를 위하여 보건 및 환경에 악영향을 미치는 위해인자 및 오염물질을 원천적으로 차단하는 작업이 지속적으로 수행되어야 할 시점이다.

• 대한기계학회논문집B
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• 제39권1호
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• pp.61-69
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• 2015

본 논문은 수직 오리피스 이젝터의 혼합유동 및 산소전달 특성에 대한 실험적 연구를 목적으로 한다. 실험장치는 전동 모터-펌프, 오리피스 이젝터, 순환 수조, 공기압축기, 고속 카메라 시스템 그리고 제어 및 측정기기로 구성하였다. 측정된 구동유체 및 유입공기의 유량을 이용하여 유량비를 도출하였다. 이적터에서 분출된 혼합유동의 가시화를 통해 정성적 거동을 고찰하였으며, 용존산소 농도를 측정하여 총괄 산소전달계수를 도출하였다. 구동유체의 유량이 일정하고 압축기의 공기압이 높아지면 유량비와 산소전달계수는 증가하며, 압축기의 공기압이 일정하고 구동유체의 유량이 증가하면 유량비는 감소하지만 산소전달계수는 증가하였다. 기포의 크기에 따른 체류시간 및 확산도와 수직 혼합유동의 도달거리는 2 상의 접촉면적과 시간에 크게 영향을 미치기 때문에 산소전달율의 중요한 변수임을 유추할 수 있다.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.145-152
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• 1999

This paper presents the principle and experimental results of a non-contact surface roughness measurement by means of screen projected pattern of lase beam reflected from a polished surface. In the reflected laser beam pattern especially from a fine surface like ground or polished one, light intensity varies from the center fo the image to its boundary as the Gaussian distribution. The standard deviation of a light intensity distribution is assumed to be a good non-contact estimator for measuring the surface roughnes, because the light reflectivity is known to be well related with the surface roughness. This method doesn't need to discriminate between the specularly reflected light and the diffusely reflected one, whereas the scattered laser intensity method must do. Nor it needs to adjust the change of light intensity caused by environmental lights or specimen materials. Reflected laser beam pattern narrowly spreads out in the vertical direction to tiny scratches on the polished surface due to abrasives. The deeper the scratch the more the dispersion, which means the rougher surface. The standard deviation of the pattern is nearly in proportion to the surface roughness. Measurement errors by this method are shown to be below 10 percent compared with those obtained by a common contact method. The inclination of measuring unit from the normal axis causes the measurement errors up to 10 percent for an angle of 4 degree. Therefore the proposed method can be used as an on-the-machine quick roughness estimator within 10 percent measurement error.

• 펄프종이기술
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• 제44권5호
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• pp.8-13
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• 2012

The flexography ink has disadvantage in a deinking process because it tends to form too fine particles in alkali condition to be removed in flotation deinking. The influence of pH conditions on the particle size of phthalocyanine cyan ink used for flexo-printing was investigated to see the effect of pH conditions on flexography ink dispersion. Flexography ink particles prepared by grinding dried ink films were used in this experiment. Greater reduction of the ink particle size was noticed under alkaline pH condition, which was attributed to dissolution of resin component of the ink. Adsorption behavior of flexography ink onto pigment particles was examined using clay and talc as substrate pigments. Pretreatment of inorganic pigments with a cationic poly-DADMAC increased the surface adsorption of flexography ink particles, which improved the removal of the inks by centrifugal sedimentation of inorganic pigments. Most efficient removal of the ink particles was achieved when an optimal addition level of the cationic polymer was used for pretreatment of inorganic pigments, and this optimal addition level corresponds to the surface saturation point of the polyelectrolyte. Adsorption of flexography ink particles onto inorganic pigments improved the ink removal in flotation deinking since the pigment particles has the optimal particle size for flotation deinking.

• 한국응용과학기술학회지
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• 제24권3호
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• pp.238-245
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• 2007

$Eu^{3+}$ doped $YGdO_3$ phosphors particles which have fine size and narrow size distribution with non aggregated uniform morphology were prepared by solvent evaporation method for the improvement of emission efficiency. Several parameters have been investigated in this study such as the influences of composition ratio of host materials, calcination temperature, amount of activator, surfactant, pH and flux on the photoluminescence intensity, particle size and dispersion. $Eu^{3+}$ doped $YGdO_3$ phosphor presented a strong narrow band emission peak at 612nm. The maximum emission intensity of$YGdO_3:Eu^{3+}$ occurred when $Eu^{3+}$ concentration is 3wt% under vacuum ultra violet excitation. Prepared phosphors were found to have small round-shaped particles about 150nm in size. The addition of PVA as a surfactant inhibits the grain growth and the agglomeration of particles efficiently by reducing the oxygen bridge bonds. As the pH reduces, PL intensity increase due to reducing the formation of oxygen bridge bonds. The particles prepared from solvent evaporation method with 5wt% LiCl were found to have 120% PL intensity compare to particles prepared without LiCl flux.

• Advances in concrete construction
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• 제9권4호
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• pp.387-395
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• 2020

This study has been carried out in two-phases to develop Fiber Reinforced Self-Compacting Concrete (FRSCC) performance. In the first phase, the composition of the quaternary composite binder compromised CEM I 42.5N (58-70%), Rice Husk Ash (25-37%), quartz sand (2.5-7.5%) and limestone crushing waste (2.5-7.5%) were optimized. And in the second phase, the effect of two fiber types (steel brass-plated and basalt) was investigated on the SCC optimized with the optimum CB as disperse reinforcement at 6 different ratios of 1, 1.2, 1.4, 1.6, 1.8, and 2.0% by weight of mix for each type. In this study, the theoretical principles of the synthesis of self-compacting dispersion-reinforced concrete have been developed which consists of optimizing structure-formation processes through the use of a mineral modifier, together with ground crushed cement in a vario-planetary mill to a specific surface area of 550 m2 / kg. The amorphous silica in the modifier composition intensifies the binding of calcium hydroxide formed during the hydration of C3S, helps reduce the basicity of the cement-composite, while reducing the growth of portlandite crystals. Limestone particles contribute to the formation of calcium hydrocarbonate and, together with fine ground quartz sand; act as microfiller, clogging the pores of the cement. Furthermore, the results revealed that the effect of fiber addition improves the mechanical properties of FRSCC. It was found that the steel fiber performed better than basalt fiber on tensile strength and modulus of elasticity; however, both fibers have the same performance on the first crack strength and sample destruction of FRSCC. It also illustrates that there will be an optimum percentage of fiber addition.

• Journal of Pharmaceutical Investigation
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• 제17권3호
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• pp.111-126
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• 1987

Methyl methacrylate-butyl methacrylate copolymer (MMBM)-dibutyl phthalate (DBP) films were investigated as a potential topical drug delivery system for the controlled release of nitrofurazone. The kinetic analysis of release data indicated that drug release followed a diffusion-controlled granular matrix model, where the quantity released per unit area is proportional to the square root of time. DBP of several hydrophobic plasticizers selected was found to give the highest release of nitrofurazone. However, hydrophilic plasticizers such as propylene glycol and polyethylene glycol 400 had no controlled release properties and acceptable film formation. The effects of changes in film composition, drug concentration, film thickness, pH of release medium, and temperature on the in vitro release of nitrofurazone were analyzed both theoretically and experimentally. The release rate constant (k') was found to be proportional to DBP content, pH, and the temperature of release medium, but independent of film thickness, and drug concentration in a range of 0.1-0.4% by weight. The linear relationship was found to exist between the log k' and DBP content. The release of nitrofurazone from MMBM-DBP (8:2) films was found to be an energy-linked process. Two energy terms were calculated ; the activation energy for matrix diffusion was 13.45 kcal/mole, and the heat of drug crystal solvation was 27.26-29.34 kcal/mole. Observation of scanning electron micrographs and microscopic photographs showed that the incorporation of DBP in films increased markedly the particle size of nitrofurazone dispersed in the film matrix, comparing with the fine dispersion of nitrofurazone in pure MMBM film alone.

• 열처리공학회지
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• 제22권3호
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• pp.155-161
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• 2009

An investigation of the deformation behavior of ${\gamma}'-Ni_3Al$ single crystals containing fine dispersion of disordered ${\gamma}$ particles was performed for several different crystal orientations. Deformation structures were observed by the weak-beam method of transmission electron microscopy (TEM). The critical resolved shear stress (CRSS) for (111) [$\bar{1}$01] slie. increases with increasing temperature in the temperature range where (111) slip operates. The CRSS for (111) [$\bar{1}$01] slip is dependent on crystal orientation in the corresponding temperature range. The temperature where the strenjlth reaches a maximum is dependent on crystal orientation; the higher the ratio of the Schmid factors of (010) [$\bar{1}$01] to that of (111) [$\bar{1}$01], the higher the peak temperature. The peak temperatures were increased by the precipitation of y particles for the samples of all orientations. Electron microscopy of deformation induced dislocation arrangements under peak temperature has revealed that most of dislocations are straight screw dislocations. The mobility of screw dislocations decreases with increasing temperature. Above the peak temperature, dislocations begin to cross slip from the (111) [$\bar{1}$01] slip system to the (010) [$\bar{1}$01] slip system, thus decreasing the strength.

• Elastomers and Composites
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• 제35권2호
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• pp.149-156
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• 2000

trans-octylene rubber(TOR)를 비상용성 블렌드인 NBR/EPDM(70/30)에 첨가하고, 이에 따른 혼합 특성 모폴로지 및 물성의 변화에 관하여 조사하였다. TOR이 첨가됨으로써 블렌드 시 혼합에너지가 감소하였고, 혼합 시 수반되는 온도상승도 저하됨을 볼 수 있었다. 블렌드의 모폴로지를 SEM으로 관찰한 결과, EPDM이 NBR 매트릭스에 분산된 형태인 것을 알았으며, TOR의 첨가에 의해 분산상인 EPDM상이 균일하고 미세해지는 것이 관찰되었다. TOR이 첨가됨으로써 NBR/EPDM의 인장강도, 파단신율 및 모듈러스 둥의 인장물성이 향상되었다. 오존저항성은 임계 응력-변형관계로부터 정량적으로 평가하였으며, TOR이 첨가된 블렌드에서 오존크랙을 일으키는 임계에너지값이 증가됨을 알 수 있었다. TOR의 첨가로 인한 NBR/EPDM 블렌드의 물성 향상은 모폴로지의 미세화와 사슬얽힘으로 인한 가교밀도의 변화 때문인 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3227-3232
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• 2013

A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state.