• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.513-520
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• 2016

It is well known that volatile compounds including disinfection by-products as well as emissive dissolved gas in water can be removed effectively by air stripping. The micro-bubbles of flotation unit are so tiny as microns while the diameter of fine bubbles applied to air stripping is ranged from hundreds to thousands of micrometer. Therefore, the micro-bubbles in flotation can supply very wide specific surface area to transfer volatile matters through gas-liquid boundary. In addition, long emission time also can be gained to emit the volatile compound owing to the slow rise velocity of micro-bubbles in the flotation tank. There was a significant difference of the THMs species removal efficiency between air stripping and flotation experiments in this study. Moreover, the results of comparative experiments on the removal characteristics of THMs between air stripping and flotation revealed that the mass transfer coefficient, $K_La$ showed obvious differences. To overcome the limit of low removal efficiency of dissolved volatile compounds such as THMs in flotation process, the operation range of bubble volume concentration is required to higher than the operation condition of conventional particle separation.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.781-784
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• 2013

Ocean dumping of sewage sludge is banned. Therefore, it is needed to develop alternative treatment method. Sewage sludge and waste glass are used to prepare lightweight brick. Large amount of energy is consumed to prepare building material, because of its high preparation temperature, or above $1,200^{\circ}C$. We study to prepare lightweight brick, using sewage sludge and waste glass as raw materials in this research. Lightweight brick was made at low temperature of below $800^{\circ}C$ to reduce $CO_2$ emission by geopolymer technique. Calcination temperature, mixing ratio of sewage sludge/waste glass and water glass/water were discussed to evaluate their effect on the brick prepared. In this study, the optimal conditions for preparing bricks was $750^{\circ}C$ of firing temperature, 1.5 of mixing ratio for water glass/water and 10 : 90 wt% of sewage sludge/waste glass. At this condition, compressive strength and specific gravity of brick prepared were 5.1 MPa and 0.46, respectively. These values satisfy the criteria on a lightweight brick.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.27-30
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• 2008

Purpose: This research is that $V_2O_5$ cathode's composition is possible in low temperature. Methods: Transparent in visible spectra range and crystallographically amorphous $V_2O_5$ thin films were prepared by simple vacuum thermal evaporation on soda-lime-silica slide glass substrate. After annealing at 100$^{\circ}C$, 150$^{\circ}C$ and 200$^{\circ}C$ for 10 minutes in air, the surface morphology and the fracture-cross section of the films were investigated by field emission - scanning electron microscope. Transmittance in visible spectra range and surface roughness of the films were analyzed by ultra violet - visible spectrophotometer and scanning probe microscope, respectively. Results: As the increase of annealing temperature from 100$^{\circ}C$ to 150$^{\circ}C$ and 200$^{\circ}C$, transmittance of the $V_2O_5$ films decreased. Optical properties will be fully discussed on the basis of the surface morphological results. Conclusions: Optical transmissivity was superior in case of 100$^{\circ}C$, and could make amorphous $V_2O_5$ thin film that surface quality of thin film did homogeneity.

• Korean Journal of Veterinary Service
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• v.31 no.3
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• pp.385-395
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• 2008

This study was carried out to investigate the residue level of fluoroquinolones in hen's general eggs and specific eggs by microbiological assay method and high performance liquid chromatography (HPLC) method. HPLC separation was carried out by reversed phase chromatography on a Symmetry $C_{18}$ (250${\times}$4.6 mm, $5{\mu}m$ particle size) with a phase composed of distilled water (containing 0.4% triethylamine and phosphoric acid) : Methanol (780 : 220, v/v), pumped isocratically at a flow rate of 1.0ml/min. A fluorescence detector was utilized with an excitation wavelength of 278nm and an emission wavelength of 456nm. The calibration curves were linear $({\gamma}^2{\geq}0.999)$ over a concentration range of $0.025{\sim}0.4{\mu}g/ml$. Average recoveries of the five fluoroquinolones in whole eggs at fortified levels of $0.05{\sim}0.2{\mu}g/g$ were ranged mean $78.1{\sim}91.7%$ and low coefficient of variation was less than 10% for all analysed samples. The limits of detection and limits of quantification for whole eggs were $1.2{\sim}6.0ng/g$ and $2.3{\sim}9.1ng/g$, respectively. Only one hen's general eggfrom chicken farm in Incheon was detected with the residual fluoroquinolones (Microbiological assay method; 1 of 47 general eggs) ; the range of residual concentration enrofloxacin was 0.12ppm. Those in food stores were detected with the residual fluoroquinolones (Microbiological assay method; 4 of 88 general eggs) ; the ranges of residual concentration enrofloxacin were $0.15{\sim}2.2 ppm$, ciprofloxacin $0.01{\sim}0.06ppm$, and hen's specific eggs (40) in food stores were not detected. For the microbiological assay method of fluoroquinolones in hen's eggs, as the results of comparative analysis, the disc diffusion method with E coli may be a little highly detected for the residual fluoroquinolones.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.146-150
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• 2002

1.55${\mu}{\textrm}{m}$ PnpN optical thyristor as a smart optical switch has potential applications in advanced optical communication systems. PnpP optical thyristors operating at 1.55${\mu}{\textrm}{m}$ are proposed and fabricated for the first time. In the optical thyristors, we employ InGaAs/InP multiple quantum well (MQW) for the active n- and p-layers. The thyristors show sufficiently nonlinear s-shape I-V characteristics and spontaneous emission. In the OFF-state, the device has a high-impedance up to switching voltage of 4.03(V). On the other hand, it has low-impedance and emits spontaneous light as a light-emitting diode in the ON-state voltage of 1.77(V), and switching voltage is changed under several light input conditions. It can be used as a header processor in optical asynchronous transfer mode (ATM), as a hard limiter in optical code division multiple access (CDMA) and as a wavelength converter in optical WDM systems.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.285-290
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• 2013

As well as the advanced development of modern society, and the environmental problems caused by the use of fossil fuels is emerging. So do not reap the performance level of the car to be able to replace existing fossil fuel and low-emission energy and technology development are continually strives. Therefore, this study aims to present the direction of the new interface 21st century Mobile Auto Electric Segway technology in the field of security and disadvantages based. The Segway is a problem because the control itself skewed by certain slope where the slope in the wrong adjustment tipping. In this study, the year saw the introduction of two pressure sensors(Load cell) used to solve these drawbacks, according to the ratio of the weight control methods. In addition, the ramps operate in a straightforward, using an acceleration sensor and a gyro sensor in order to compensate for the slope value in free control method to study looked. Measured by calculating the value of the occupant's weight and according to the inclination of the pressure sensor pressure sensing experiment results this year, we can see that the control variable for the change in body weight is greater than the inclination. Segway is also easy to control, and the stability of the ramps, etc. As a result, created using a pressure sensor.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.3
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• pp.254-263
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• 2006

Manganese has a role as both toxic and essential in humans. Manganese is also an essential component in the welding because it increases the hardness and strength, prevents steel from cracking of welding part and acts as a deoxidizing agent to form a stable weld. In this study, manganese generation rate and its content was determined in flux cored arc welding on stainless steel. Domestic two products and foreign four products of flux cored wires were tested in the well designed fume generation chamber as a function of input power. Welding fume was measured by gravimetric method and metal manganese was determined by inductively coupled plasma-atomic emission spectrophotometer. The outer shell of the flux cored wire tube and inner flux were analyzed by scanning electron microscopy to determine their metal compositions. Manganese generation rate($FGR_{mn}$) was increased as the input power increased. It was 16.3 mg/min at the low input power, 38.1 mg/min at the optimal input power, and up to 55.4 mg/min at the high input power. This means that $FGR_{mn}$ is increased at the work place if welder raise the current and/or voltage for the high productivity. The slope coefficient of $FGR_{mn}$ was smaller than that of the generation rate of total fume(FGR). Also, the correlation coefficient of $FGR_{mn}$ was 0.65 whereas that of FGR is 0.91. $FGR_{mn}$ was equal or higher in the domestic products than that of the foreign products although FGR was similar. From the electron microscopic analytical data, we concluded that outer shell of the wire was composed mainly of iron, chromium, nickel and less than 1.2 % of manganese. There are many metal ingredients such as iron, silica, manganese, zirconium, titanium, nickel, potassium, and aluminum in the inner flux but they were not homogeneous. It was found that both $FGR_{mn}$ and content of manganese was higher and more varied in domestic flux cored wires than those of foreign products. To reduce worker exposure to fumes and hazardous component at the source, further research is needed to develop new welding filler materials that improve the quality of flux cored wire in respect to these points. Welder should keep in mind that the FGR, $FGR_{mn}$ and probably the generation rate of other hazardous metals were increased as the input power increase for the high productivity.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.4
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• pp.13-16
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• 2013

A lot of various researches have been going on to use heat spreader for LED module. Nano porous aluminum anodic oxide (AAO) applied LED, which is produced from anodization, is easy and economically advantageous. Convensional LED module is consist of aluminum/adhesive/copper circuit. The polymer adhesive in this module is used as heat spreader. However the thermal emission of LED component is degraded because of low heat conductivity of polymer and also reliability of LED component is reduced. Therefore, AAO in this work was applied to heat spreader of LED module which has higher heat conductivity compare to polymer. Bonding strength between AAO and copper circuit was improved with Ti/Cu seed layer by copper sputtering process (DBC) before the bonding. And this copper circuit has been fabricated by electro plating method. Peel strength of AAO and copper circuit in this work showed range between 1.18~1.45 kgf/cm with anodizing process which is very suitable for high power LED application.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.111-117
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• 2011

In the wake of increased concerns on reduction of greenhouse emission which started with United Nation's Framework Convention on Climate Change (UNFCCC) and Kyoto protocol, Korean government is making various efforts under the represented slogan "Low Carbon, Green Growth". Therefore, it is inevitable that construction industry also follow the Korea government's slogan and the international trend in environmental problems. This study identified several main construction materials and equipments of civil construction projects and suggested a environmental cost estimation method and related estimation standards (Public and private owners are distinguished). A case analysis of a real road construction project is also performed and characteristics according to the owner type is compared. This study analyzed the environmental impact to total construction cost variations. In the result, public owner required 11~16% of extra budget and private owner required 19~22% of extra costs. This study is limited in consideration of environmental factors and carbon trading prices.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.577-583
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• 2011

To meet the requirements of the Tier 4 interim regulations for off-road vehicles, emissions of particulate matter (PM) and nitrogen oxides (NOx) must be reduced by 95% and 30%, respectively, compared to current regulations. In this research, both the DPF and HPL EGR systems were investigated, with the aim of decreasing the PM and NOx emissions of a 56-kW off-road vehicle. The results of the experiments show that the DOC-DPF system is very useful for reducing PM emissions. It is also found that the back pressure is acceptable, and the rate of power loss is less than 5%. By applying the HPL EGR system to the diesel engine, the NOx emissions under low- and middle-load conditions are reduced effectively because of the high differential pressure between the turbocharger inlet and the intake manifold. The NOx emissions can be decreased by increasing the EGR rate, but total hydrocarbon (THC) emission increases because of the increased fuel consumption needed to compensate for the power loss caused by EGR and DPF.