• 한국물환경학회지
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• 제25권5호
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• pp.764-767
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• 2009

For a more effectively designed gravity thickener, thickening experiments were conducted for residuals produced by a ceramic membrane water treatment plant (WTP). Two kinds of residuals, one from backwashing (BW) and the other from chemically enhanced backwashing (CEB) procedure, were separately collected during a pilot plant experiment and their limiting solid flux ($SF_L$) measured. Batch thickening experiments showed that the BW and CEB residual had $SF_L$ of 10 and $25kg/m^2{\cdot}d$, respectively. Continuous operation of a pilot-scale gravity thickener proved that a mixed BW and CEB residual could be successfully thickened at the solid loading rate (SLR) of $12kg/m^2{\cdot}d$, allowing the concentration of the thickened residual to be about $15kg/m^2{\cdot}d$. From the experimental results and consideration of the seasonal thickening characteristics of the residual, SLR of $15kg/m^2{\cdot}d$ was proposed as a design parameter for full-scale gravity thickeners.

• 약학회지
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• 제39권5호
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• pp.487-494
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• 1995

Solid lipid microspheres (SLMs) were prepared using various lipids and solidifying agents, in order to enhance the gastrointestinal absorption of Cyclosporine A (Cs A) which is a practically water-insoluble drug with low systemic bioavailability. Egg lecithin and HCO-60 (polyoxyethylated 60 mol, hydrogenated castor oil) were used as lipids. Stearic acid and stearyl alcohol were used as solidifying agents. Emulsion concentrates containing Cs A were prepared by mixing the melted lipid and solidifying agent with water, employing bile salts as a cosurfactant. SLMs were obtained by dispersing the warm emulsion concentrate in cold distilled water under mechanical stirring, followed by freeze drying. Physical characteristics of each SLM were investigated by particle size analysis, optical microscopy and scanning electron microscopy. Mean particle size of SLMs was in the range of 30 to 40.mu.m. The SLMs were in good appearance with spherical shape before freeze drying, but were deformed partially after freeze drying. Drug loading efficiencies of SLMs were observed as high as 80 to 90% in average. The systemic bioavailability of Cs A from different SLM formula was investigated in rats following oral administration. Cs A in whole blood was extracted and assayed by HPLC. SLMs revealed the higher bioavailabilities than the standard formula based on the marketed product. SLMs might have several advantages over standard formula for enhanced gastrointestinal absorption, controlled release properties, high loading capacity of the water-insoluble drug, and feasibility of solid dosage forms with better stability in storage.

• 환경위생공학
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• 제14권2호
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• pp.25-31
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• 1999

Energy recovery technology from municipal solid waste has been increasingly established in many countries. Anaerobic treatment of municipal sewage sludge has low digestion efficiency because of low organic loading rate of sewage sludge. The purpose of this study was to evaluate anaerobic biodegradability of food waste which was based on organic loading rate and seeding rate. From the results of anaerbic biodegration, the optimum condition for seeding rate was turn out over 40%, which did not inhibition of methane production.

• Journal of Electrochemical Science and Technology
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• 제10권1호
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• pp.22-28
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• 2019

To maximize the oxygen evolution reaction (OER) in the electrolysis of water, nano-grade $IrO_2$ powder with a low specific surface was prepared as a catalyst for a solid polymer electrolyte (SPE) system, and a membrane electrode assembly (MEA) was prepared with a catalyst loading as low as $2mg\;cm^{-2}$ or less. The $IrO_2$ catalyst was composed of heterogeneous particles with particle sizes ranging from 20 to 70 nm, having a specific surface area of $3.8m^2g^{-1}$. The anode catalyst layer of about $5{\mu}m$ thickness was coated on the membrane (Nafion 117) for the MEA by the decal method. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) confirmed strong adhesion at the interface between the membrane and the catalyst electrode. Although the loading of the $IrO_2$ catalyst was as low as $1.1-1.7mg\;cm^{-2}$, the SPE cell delivered a voltage of 1.88-1.93 V at a current density of $1A\;cm^{-2}$ and operating temperature of $80^{\circ}C$. That is, it was observed that the over-potential of the cell for the oxygen evolution reaction (OER) decreased with increasing $IrO_2$ catalyst loading. The electrochemical stability of the MEA was investigated in the electrolysis of water at a current density of $1A\;cm^{-2}$ for a short time. A voltage of ~2.0 V was maintained without any remarkable deterioration of the MEA characteristics.

• 한국응용과학기술학회지
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• 제38권3호
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• pp.662-668
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• 2021

본 연구에서는 피부 미백 개선 기능성 화장품 소재이자 친수성 소재인 ascorbyl glucoside(AG)의 피부 투과율을 개선시키기 위해 고형지질나노입자(SLN)을 설계하였다. AG는 이중 에멀젼 가온 용융유화법으로 SLN 내에 봉입하였다. 제조 된 AG 봉입 SLN의 입자크기, 다분산 지수, 제타전위, 봉입율등의 입자의 물리화학적 특성을 평가하였다. 피부 투과시험의 경우 인체 유래 인조 피부 조직 모델 중 SkinEthic RHE를 사용하였다. 제조 된 AG 봉입 SLN의 평균 입자크기는 172.65 - 347.19 nm 이었고, 평균 제타전위는 -22.90 - -41.20 mV이었다. SLN 내 AG의 평균 봉입효율은 44.18 - 57.77%이었고, 평균 봉입율은 12.83 - 16.15%이었다. AG 봉입 SLN의 피부 투과 결과는 SLN을 적용하였을 때가 적용하지 않을 때 보다 약 3.7 - 7.4 배 피부 투과율이 개선되었다. 따라서, 본 연구에서 제조 된 SLN은 AG의 국소약물전달시스템으로 사용하는데 유용할 것이다.

• KSTLE International Journal
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• 제2권1호
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• pp.29-34
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• 2001

The stress field in a body caused by the tangential loading of a rectangular patch on a semi-infinite solid has been solved analytically using a potential function. The validity of the results of this study was preyed by Saint-Venant's principle in the remote region and by the superposition of point loads in the vicinity of the surface.

• Steel and Composite Structures
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• 제46권6호
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• pp.793-804
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• 2023

In this study, cyclic loading tests were conducted to assess the seismic performance of cast-in-place (CIP) concrete-filled hollow core precast concrete columns (HPCC) constructed using steel ducts and rubber tubes. The outer shells of HPCC, with a hollow ratio of 47%, were fabricated using steel ducts and rubber tubes, respectively. Two combinations of shear studs & long threaded bars or cross-deformed bars & V-ties were employed to ensure the structural integrity of the old concrete (outer shell) and new CIP concrete. Up to a drift ratio of 3.8%, the hysteresis loop, yielding stiffness, dissipated energy, and equivalent damping ratio of the HPCC specimens were largely comparable to those of the solid columns. Besides the similarities in cyclic load-displacement responses, the strain history of the longitudinal bars and the transverse confinement of the three specimens also exhibited similar patterns. The measured maximum moment exceeded the predicted moment according to ACI 318 by more than 1.03 times. However, the load reduction of the HPCC specimen after reaching peak strength was marginally greater than that of the solid specimen. The energy dissipation and equivalent damping ratios of the HPCC specimens were 20% and 25% lower than those of the solid specimen, respectively. Taking into account the overall results, the structural behavior of HPCC specimens fabricated using steel ducts and rubber tubes is deemed comparable to that of solid columns. Furthermore, it was confirmed that the two combinations for securing structural integrity functioned as expected, and that rubber air-tubes can be effectively used to create well-shaped hollow sections.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.71.1-71.1
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• 2007

• 구강회복응용과학지
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• 제21권1호
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• 멤브레인
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• 제14권4호
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• pp.289-297
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• 2004

유기물과 질소를 동시에 제거하기 위하여 연속회분식으로 운전한 MBR (membrane bioreactor)시스템에서 미생물농도와 슬러지 부하량이 막오염과 미생물 활성에 미치는 영향을 살펴보았다. 막오염은 MLSS (mixed liquor suspended solid) 농도 증가에 따라 조금씩 증가하는 경향을 보였고, 그 효과는 비포기 조건보다 포기 조건에는 좀더 두드러지게 나타났다. MLSS 농도는 막오염에 직접적인 커다란 영향을 주지는 않으나, 지나치게 높은 MLSS에서 유도되는 낮은 슬러지 부하에서는 막오염이 크게 증가하는 현상이 발견되었고, 이러한 조건에서는 포기에 의한 막 세척 효과도 크게 줄어들었다. 미생물의 개별 활성도는 슬러지 부하가 감소할수록 지속적으로 감소하는 경향을 나타내었다 반응조 전체 활성도 또한 17,000 mg/L 이상의 높은 MLSS로부터 유도되는 낮은 슬러지 부하율에서는 높은 미생물 농도에도 불구하고 오히려 감소했는데 이는 기질 부족으로 인한 경쟁으로 활성도가 떨어지고, 용액의 점성 증가로 인해 산소 전달율이 저하되었기 때문이다.