• Restorative Dentistry and Endodontics
• /
• 제10권1호
• /
• pp.85-92
• /
• 1984

The aim of this study was to examine the influence of the speed of grinding and coolants on mercury vaporization during amalgam removal. Forty amalgam filled stone dies were stored at $37^{\circ}C$ and 100% relative humidity for 7 days prior to the beginning of the mercury vapor experiment and were divided into 4 different groups; In Group I; Used by high speed without coolant & evacuator during amalgam removal. In Group II; Used by high speed with coolant & evacuator during amalgam removal. In Group III; Used by low speed without coolant & evacuator during amalgam removal. In Group IV; Used by low speed with coolant & evacuator during amalgam removal. The amalgam specimens were removed in a 30-second time period and mercury vapor was collected with membrane filter at 27mm from the site of removal and 45 degree above there. Samples in Group II, IV were removed with coolant spray at a flow rate of 30 ml/min with high-velocity evacuator. Mercury vapor collected membrane filter was analysed by Atomic Absorption Spectrophotometer using cold vapor method. The results were as follows; 1. The mercury vapor levels were obtained all of the Groups. 2. The mercury vapor levels of the Group II, IV (with coolant & evacuator) were less than that of the Group I, III (without coolant & evacuator). 3. The highest mercury vapor level recorded during amalgam removal procedure was Group I (used by high speed without coolant & evacuator) and its record was $0.78{\pm}0.09\;mg/m^3$, which exceed the T.L.V. by 15 times. 4. The mercury vapor level of the Group IV (used by low speed with coolant & evacuator) was more than that of the Group II (used by high speed with coolant & evacuator), but its difference was not significant, statistically. (p > 0.05)

• 한국환경농학회지
• /
• 제27권1호
• /
• pp.18-26
• /
• 2008

본 연구는 농촌전원독립가구 하수처리장에서 오염물질의 존재형태별 처리 경향을 파악하여 하수처리장의 설계 및 시공 시 부지면적 감소와 오염물질의 처리효율 극대화를 위한 기초자료로 활용하기 위하여 농촌전원독립가구 하수처리장에서 하수 중 오염물질의 거동 특성과 오염물질의 존재형태별 분해속도를 각각 조사하였다. 하수 중 오염물질의 존재형태별 거동을 조사한 결과 BOD 및 COD는 대부분 호기성조에서 처리되었으며, 처리된 BOD와 COD는 대부분 insoluble형태이었다. 그러나 무산소조와 혐기성조에서의 BOD와 COD는 존재형태별로 별 차이 없었다. SS는 대부분 호기성조에서 처리되었으며, 처리된 SS는 대부분 volatile 형태이었다. T-N은 BOD, COD 및 SS와 달리 호기성조에서 처리효율이 높지 않았고, 처리된 대부분의T-N은 dissolved 형태이었다. T-P는 모든 조에서 일정하게 처리효율이 증가되었으며, 처리된 T-P는 대부분 dissolved 형태이었다. 현장 하수처리장에서 존재형태별 오염물질의 분해속도를 조사한 결과 BOD, COD 및 SS의 분해속도는 호기성조에서 각각 30.79, 17.15 및 29.96 $day^{-1}$로 무산소조 및 혐기성조에 비해 매우 빨랐으며, 호기성조에서 존재형태별 분해속도는BOD 및 COD의 경우 insoluble 형태가 빨랐으며, SS의 경우 fixed 형태가 빨랐다. T-N 및 T-P의 분해속도는 호기성조에서 각각 4.78 및 13.09 $day^{-1}$로 다른 조에 비해 약간 빨랐으며, 호기성조에서 존재형태별 분해속도는 suspended 형태가 약간 빨랐고, 혐기성조와 무산소조에서는 별 차이 없이 비슷하였다. 이상의 결과는 하수처리장의 설계 및 시공 시 부지면적 감소와 오염물질의 처리효율 극대화를 위한 기초자료로 활용 할 수 있을 것으로 판단된다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
• /
• pp.125-128
• /
• 2004

Chemical Mechanical Polishing(CMP) in semiconductor production is characterized its output property by Removal Rate(RR) and Non-Uniformity(NU). Some Previous works shows that RR is determined by production of pressure and velocity and NC is also largely affected by velocity of flow-field during CMP. This study is about the direct measurement of velocity of slurry during CMP and reconstruction whole flow-field by Particle Image Velocimetry(PIV) Techniques. Typical PIV system is tuned adequately for inspecting CMP and Slurry Flow-field is measured by changing both Pad RPM and Carrier RPM. The results show that velocity is majorly determined not by Carrier RPM, but by Pad RPM.

• 상하수도학회지
• /
• 제20권2호
• /
• pp.245-255
• /
• 2006

Dissolved air flotation is a solid-liquid separation system that uses fine bubbles rising from bottom to remove particles in water. In order to enhance the flotation velocity and removal efficiency of flocs in the flotation process, we tried to obtain pretreatment conditions for the optimum DAF process operation by comparing and evaluating features of actual floc formation and flotation velocity etc, according to coagulant types and conditions for flocculation mixing intensity by using PIA, PDA, and FSA. Accordingly, generating big flocs that have low density at low flocculation mixing intensity may reduce treatment efficiency. In addition, generating small flocs at high flocculation mixing intensity makes floc-bubbles smaller, which reduces flotation velocity, In this study, it was found that high flocculation mixing intensity could not remove the remaining micro-particles after flocculation, which had negative effects on treated water quality, Therefore, in order to enhance treatment efficiency in a flotation process, flocculation mixing intensity around $50sec^{-1}$ is effective.

• 한국환경과학회지
• /
• 제3권4호
• /
• pp.367-372
• /
• 1994

A predictive model is demonstrated for gas removal rates from the aklosphere by dw deposition. Typical deposition velocities are complex functions of surface types, atmospheric stabilities, friction velocities, air pollutants, and so on. In this paper we simulated the calculation of dry deposition velocities near the earth surfaces, simultaneously we estimated real dry deposition velocities using the previous simulation. The measurement taken over a deciduous forest by Padro et d.(1988) were used to verify this model. In the comparison of the value of deposition velocity between numerical computation and observation, there are partially overestimations and underestimations between them, but we can speak that they are in a good accordance.

• 수산해양기술연구
• /
• 제40권2호
• /
• pp.155-160
• /
• 2004

Water jet trajectories and velocity deficits from a high pressurize nozzles were experimentally observed. In this article, several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA (Phase Doppler Particle Analyzer) system. The results indicated that trajectories along the centerline regardless of their momentum has its potential core region. However, the phenomena from the peripheral part need to be meticulosly considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
• /
• pp.25-28
• /
• 2004

The capillary number is used to represent the mobilization potential of organic phase trapped within porous media. The capillary number has been defined by three different forms, according to types of flow velocity and viscosity used in the definition of capillary number. This study evaluated the suitability of the capillary number definitions for representing TCE mobilization by constructing capillary number-TCE saturation relationships. The results implied that the capillary number should be correctly employed, according to interest of scale and fluid flow behavior. This study suggests that the pore-scale capillary number may be used only for investigating the organic-phase mobilization at the pore scale because it is defined by the pore-velocity and the dynamic viscosity. The Newtonian-fluid capillary number using Darcy velocity and the dynamic viscosity may be suitable to quantify flood systems representing Newtonian fluid behavior. For viscous-force modified flood systems such as surfactant-foam floods, the apparent capillary number definition employing macroscopic properties (permeability and potential gradient) may be used to appropriately represent the desaturation of organic-phases from porous media.

• 한국대기환경학회지
• /
• 제16권6호
• /
• pp.633-640
• /
• 2000

The effects of structure modification of the vortex finder on the collection efficiency and pressure drop have been investigated. The pressure drop in a cyclone having the two stage vortex finder is higher than that in a conventional cyclone and increases proportionally with the increase of square of gas inlet velocity in both cases. The pressure drop of both conventional cyclone of friction resistance at the boundary layer. The collection efficiency of fine dust has been enhanced by addition of vortex finder in a conventional cyclone and gas inlet velocity showing maximum dust removal efficiency increase to 17 m/s(1.7 times of saltation velocity). Optimum size of two stage vortex finder has been induced to 13 cm I.D$\times$2.6cm Length from the results of overall dust collection efficiency. Previous models were tested for the simulation of collection efficiency of cyclone having two stage vortex finder and the Dietz model predict the similar value with experimental results of the present study.

• 상하수도학회지
• /
• 제11권1호
• /
• pp.81-87
• /
• 1997

Coagulation is very important process in water works. The subsequent processes are directly affected by this process. Many factors such as turbidity, alkalinity, pH, hardness, total organic carbon(TOC), velocity gradient and flocculation time effect on coagulation process. Among these factors, specially TOC is being concerned target substance to be removed due to trihalomenthanes(THMs) precursor and alkalinity is being one of the major parameter for removing TOC. We have researched the consumption of coagulant with TOC alkalinity concentration of water and removal efficiency of residual TOC and turbidity with alkalinity. Furthermore we have investigated particle size distributions with velocity gradient and alkalinity. The consumption of coagulant was proportionally increased to TOC and alkalinity concentration and the removal of TOC in Nakdong river water was very difficult more than 150 mg/l in alkalinity but large morecular weight organic such as humic acid could be removed easily. Coagulation of low alkalinity water was more rapidly occured than of high alkalinity water by analyzing the particle size distributions. High alkalinity water needed higher mixing energy for a good coagulation within limited flocculation time.

• Journal of Microbiology and Biotechnology
• /
• 제15권6호
• /
• pp.1207-1213
• /
• 2005

In a search for bacteria capable of degrading styrene better than previously isolated strains, bacterium IS-3 was isolated from activated sludge and found to be most closely related to Pseudomonas sp. Styrene degradation by this strain was tested in liquid cultures and polyurethane-packed biofilters. In liquid cultures, the rate of styrene degradation by this bacterium increased from 24.93 to $76.53\;{\mu}mol\;g^{-1}\;DCW\;H^{-1}$ for an initial mass range from 8.7 to $34.8{\mu}mol$. The maximum styrene elimination capacity was 580-635 $g/m^{3}\cdot$h at a space velocity (SV) of 50-200/h. The critical elimination capacities guaranteeing $95\%$ removal of the input styrene were determined to be 635, 170, and 38 $g/m^{3}\cdot$h, respectively, at SVs of 50, 100, and 200/h. Kinetic analysis revealed that the maximum styrene elimination velocity ($V_{m}$) for this biofilter was 1,000 g/m$\cdot$h, and the saturation constant ($K_{m}$) was 454 ppmv. Together, these results suggest that a polyurethane biofilter containing Pseudomonas sp. IS-3 could have potential practical applications for the effective removal of styrene gas.