• 유기물자원화
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• 제32권2호
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• pp.15-25
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• 2024

본 연구에서는 하수슬러지 필터프레스 공정에서 발생하는 오염 여과포에 대하여 가압수 및 초음파 세척에 대한 재생효율을 평가하였다. 이를 위하여 3톤 규모 하수슬러지 수열탄화물 처리 필터프레스로부터 오염된 여과포를 채취하였다. 먼저, 필터프레스 여과포의 오염 특성을 평가하였다. 오염 여과포의 위치에 따른 공기투과도와 단위질량을 측정하였으며, 새 여과포 측정값과 비교하였다. 다음으로 오염 여과포 전체 면적에 대하여 공기투과도 및 단위질량 분포를 지도화하여 오염 특성을 평가하였다. 마지막으로 오염 여과포를 대상으로 3 bar의 압력 세정 및 34, 76, 120, 168 kHz 주파수의 초음파 세척을 수행하였다. 이때, 여과포의 기공 오염 정도를 3단계로 나누어 세척효율을 평가하였다. 여과포 오염 비교 결과, 기공 오염은 여과물질이 지속적으로 투입, 압착되는 여과포 하부와 양측면 위주로 발생하였으며, 표면 오염은 전체면적에 걸쳐 고르게 나타났다. 가압 세척 결과, 공기투과도는 1.3-3.1%p 증가하였으며, 오염물질은 2.7-4.4% 제거되었다. 초음파 세척결과, 공기투과도는 12.5-61.5%p 증가하였으며 오염물질은 2.7-29.2% 제거되었다. 초음파 세척에서 주파수가 낮을수록 공기투과도 재생율과 오염물질 제거율이 우수하였다. 여과포의 기공 오염 정도가 클수록 초음파 세척 후 공기투과도 향상 및 오염물질 제거 효과가 우수하였다.

• Tribology and Lubricants
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• 제20권6호
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• pp.343-349
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• 2004

The adsorption of soot particles onto a sensor surface of the engine soot detector posses a critical problem in the measurement. In order to prevent the optical rod surface from soot contamination, various functional coatings and flow-induced cleaning were applied to the surface in this work. For surface coatings, various materials of self-assembled monolayers (SAM) such as OTS (octadecyltrichlorosilane), PFDTES (perfluorodecyl-triethoxysilane) and PFDTMS (perfluorodecyltrimethoxysilane) were coated on the optical rod surface ,which have different characteristics in both hydrophobicity and oleophobicity. These coatings were tested with soot content varying from $0\%\;to\;3wt\%$ and oil temperature from 20 to $70^{\circ}C$. Test results showed that surface coatings were not effective for preventing the adsorption of soot panicles on the surface of optical rod. It was thought that these coatings provided the surface with additional attractive surface forces. However, it was found that adsorption of soot particles onto a sensor surface was minimized by flow-induced cleaning. This effect was tested with varying the flow velocity.

• Restorative Dentistry and Endodontics
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• 제27권2호
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• pp.150-157
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• 2002

One of the latest concepts in bonding are "total etch", in which both enamel and dentin are etched with an acid to remove the smear layers, and "wet dentin" in which the dentin is not dry but left moist before application of the bonding primer Ideally the application of a bonding agent to tooth structure should be insensitive to minor contamination from oral fluids. Clinically, contaminations such as saliva, gingival fluid, blood and handpiece lubricant are often encountered by dentists during cavity preparation. The aim of this study was to evaluate the effect of contamination by hemostatic agents on shear bond strength of compomer restorations. One hundred and ten extracted human maxillary and mandibular molar teeth were collected. The teeth were removed soft tissue remnant and debris and stored in physiologic solution until they were used. Small flat area on dentin of the buccal surface were wet ground serially with 400, 800 and 1200 abrasive papers on automatic polishing machine. The teeth were randomly divided into 11 groups. Each group was conditioned as follows : Group 1: Dentin surface was not etched and not contaminated by hemostatic agents. Group 2: Dentin surface was not etched but was contaminated by Astringedent$^{\circledR}$(Ultradent product Inc., Utah, U.S.A.) Group 3: Dentin surface was not etched but was contaminated by Bosmin$^{\circledR}$(Jeil Pharm, Korea.). Group 4: Dentin surface was not etched but was contaminated by Epri-dent$^{\circledR}$(Epr Industries, NJ, U.S.A.). Group 5: Dentin surface was etched and not contaminated by hemostatic agents. Group 6: Dentin sorface was etched and contaminated by Astringedent$^{\circledR}$. Group 7 : Dentin surface was etched and contaminated by Bosmin$^{\circledR}$. Group 8: Dentin surface was etched and contaminated by Epri-dent$^{\circledR}$. Group 9: Dentin surface was contaminated by Astringedent$^{\circledR}$. The contaminated surface was rinsed by water and dried by compressed air. Group 10: Dentin surface was contaminated by Bosmin$^{\circledR}$. The contaminated surface was rinsed by water and dried by compressed air. Group 11 : Dentin surface was contaminated by Epri-dent$^{\circledR}$. The contaminated surface was rinsed by water and dried by compressed air. After surface conditioning, F2000$^{\circledR}$ was applicated on the conditoned dentin surface The teeth were thermocycled in distilled water at 5$^{\circ}C$ and 55$^{\circ}C$ for 1,000 cycles. The samples were placed on the binder with the bonded compomer-dentin interface parallel to the knife-edge shearing rod of the Universal Testing Machine(Zwick Z020, Zwick Co., Germany) running at a cross head speed or 1.0 mm/min. Group 2 showed significant decrease in shear bond strength compared with group 1 and group 6 showed significant decrease in shear bond strength compared with group 5. There were no significant differences in shear bond strength between group 5 and group 9, 10 and 11.

• 반도체디스플레이기술학회지
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• 제20권3호
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• pp.77-82
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• 2021

This numerical study focuses on the analysis of fume particle dispersion characteristics over the surface of target workpiece in laser micro-hole machining process. The effects of oblique stagnation flow over fume generating machining point are examined by carrying out a series of three-dimensional random particle simulations along with probabilistic particle generation model and particle drag correlation of low Reynolds number. Present computational model of fume particle dispersion is found to be capable of assessing and quantifying the fume particle contamination in precision hole machining which may influenced by different types of air flow patterns and their flow intensity. The particle size dependence on dispersion distance of fume particles from laser machining point is significant and the effects of increasing flow oblique angle are shown quite differently when slot blowing or slot suction flows are applied in micro-hole machining.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1845-1852
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• 2001

This paper deals with the experiment to obtain quantitative information about conditions of the interface between a water drop and surrounding oil. Velocity distributions in very close region of the interface are measured by introducing a new illumination technique and a telecentric lens. It enables precise measurements of velocity distributions in the close region to the interface. Although the measured velocity distributions exhibit strong influence from the solid wall of an experimental tube, the coincidence of inner and outside velocities on the interface is clearly confirmed for the clean interface. The shearing stresses on the interface, which are proportional to the velocity gradient normal to the interface, clearly show conditions of contaminated interface, which can be divided into two parts. From front stagnation point to somewhere near a separation point, the distribution of shearing stresses is well coincide with that of the Hadamard's analytical solution, while the distribution on the latter part of the interface sows quite different feature, which is supposed to be strongly influenced by contamination of the surface.

• 한국식품위생안전성학회지
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• 제12권1호
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• pp.78-82
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• 1997

Surface swab samples from beef (188), pork (240) and chicken (95) carcasses were collected from slaughterhouse in Kangwon and Kyunggi areas from March through July 1996. The samples were examined on the level of E. coli biotype I relevant to fecal contamination due to unsanitary processing control and the existence of verocytotoxin-producing E. coli (VTEC). E. coli biotype I were confirmed from 38.8% of beef, 40.0% of pork, and 69.5% of chicken carcasses. Little variation was noted among three sampling points; rump, flank and neck of beef, ham, belly and jowls of pork. coli O157:H7 was only confirmed from 2 of 188 beef carcasses. E. coli biotype I. All the isolated E. coli O157 showed positive for vero cell cytotoxicity test. Isolation rate of E. coli O157 in summer was higher than in spring. In case of pork and chicken carcasses, E. coli O157 was isolated in summer only.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
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• pp.115-119
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• 2003

Pollutants from industry, mining, agriculture, and other sources have contaminated sediments in many surface water bodies. Sediment contamination poses a severe threat to human health and environment because many toxic contaminants that are barely detectable in the water body can accumulate in sediment at much higher levels, the purpose of this study was to make convenient sampling method and optimal treatment of sediment for water quality improvement in reservoir or stream based on an evaluation of degree of contamination. Results for analysis of S-reservoir sediments were observed that copper concentration of almost areas were higher than the regulation of soil pollution (50 mg/1) for the riverbed. S-stream sediments were observed that copper, arsenic and TPH concentration of almost areas were exceeded soil pollution concerning levels for factorial areas. We used Remscreen(version. 1.0) program which is contaminated soil recovery program to select optimal treatment method of contaminant sediments. The result was shown in the order of Thermal Calcination > Excavation, Retrieval and Off-site Disposal(comparative less then contaminant) > Low Temperature Thermal Desorption + Solidification/Stabilization.

• 정보학연구
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• 제8권2호
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• pp.85-91
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• 2005

We studied a pollution mechanism for simulation of contamination environment in industrial concentrated area of around a metropolitan that made to circulated flow in the chamber. In case of the virgin both side of EPDM or Silicon insulator, we confirmed that the pollution to much more than service insulator in the field. Also contamination of initial state of the virgin didn't falling in spite of physical outside factor easily. This study confirmed to that the silicon was too much accumulated pollution contrast to EPDM insulator from scatter(spray) point to regular interval position use the Kaolin contaminant in the chamber. There are effected to the hydrophobicity of polymer insulator due to the pollution. In ceramic insulator, we get to know that pollution is much more at the Post insulator with vertical than with horizontal setup insulator.

• 한국산업보건학회지
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• 제23권2호
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• pp.57-64
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• 2013

Objectives: Skin exposure to diisocyanates may be an important risk factor for respiratory sensitization to leading asthma. However little is known about the extent of worker's diisocyanates skin exposure and the effectiveness of personal protective equipments in polyurethane foam manufacturing companies. This study provides data on diisocyanates skin exposure, surface diisiocyantes contamination of foams and the effectiveness of personal protective gloves in five polyurethane foam manufacturing companies. Materials and methods Colorimetric SWYPE pads are used for the determination of diisocyanates on surfaces of workers skin and polyurethanes foams. Results: The forearms, necks and faces of workers in polyurethane foam manufacturing companies were found to be contaminated with diisocyanates. Heavy contamination with uncured diisocyanates at large block foams surfaces were found. Personal gloves of workers for skin protection showed significant penetrations by diisocyanates. Conclusions: We found that all workers in polyurethane foam manufacturing companies could be exposed to diisocyanates by skin exposure. Also further researches which would better quantify skin exposure are needed.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2006년도 총회 및 춘계학술발표회
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• pp.209-212
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• 2006

Using sulfur sotope analysis of dissolved sulfate in surface water, we have investigated the source of sulfate in order to identify the abandoned metallic mines, which have the potential of heavy metal contamination within watershed. The range of the sulfur isotope values for dissolved sulfate in stream waters (DD-1 and 2) are similar to those of sulfides from the Dunjun mine, which suggests that oxidation of sulfides is the principal source of $SO_4^{2-}$ in these stream waters. Also, heavier sulfur isotopes in waters near Baekjun and Hamchang mines imply the possibility of contamination in waters by these metallic mines.