• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.763-768
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• 2002

This study was performed in the airlift bioreactor using the nitrifier consortium entrapped in polyvinyl alcohol(PVA) for removing low concentration total ammonia nitrogen(TAN). At the superficial air velocity of 0.83 cm/sec, TAN removal rate and removal efficiency was $316.6{\pm}7.2g/m^3{\cdot}day$ and $92.8{\pm}2.2%$ respectively. Removal rate was continuously increased with decreasing hydraulic residence time(HRT) from 0.5 hr to 0.05 hr, whereas removal efficiency decreased with decreasing HRT. The optimum temperature for nitrification was $30^{\circ}C$ at which removal efficiency was $95.5{\pm}1.5%$. Nitrification was effectively performed at low temperature, $10^{\circ}C$. In the pH range from 7 to 9 in the bioreactor, removal rate and removal efficiency was $310{\pm}10g/m^3{\cdot}day$ and $94{\pm}3%$ respectively.

• Journal of Environmental Impact Assessment
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• v.28 no.3
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• pp.332-345
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• 2019

The purpose of the study is to evaluate the treatability of contaminated groundwater with TPH and (or) $Cr^{6+}$. Laboratory scale tests were performed for oil/water separation, dissolved air flotation (DAF), coagulation and precipitation, and filtration with sand and activated carbon respectively. Two times of oil/water separation tests for total 40 minutes of separation or separating time shows 90.2 % of TPH removal rate. In case of DAF test for high TPH sample, the TPH removal rates were not varied significantly by the variation of microbubble size. However, tests for low TPH samples show that TPH removal rate increases as microbubbles are smaller. When coagulant was added to sample for DAF test, TPH removal rate was increased 12.3 %. SS removal rate by DAF was 97.9 % at $16-40{\mu}m$ and it was increased as the size of microbubble is reduced. Tests for coagulation and precipitation were performed to evaluate the removal of $Cr^{6+}$ in groundwater. The increase of $FeSO_4$ dosage increased $Cr^{6+}$ removal rate in the coagulation and precipitation process. As the amount of activated carbon in the filter media increased TPH removal rate in the filtration process. SS removal rate by the filtration was 96.7 % similar to the results of DAF process tests. The filtration process treats TPH and SS. Best design parameters are determined as the size of sand is $425-850{\mu}m$ and the ratio of activated carbon and sand is 50:50.

• Korean Journal of Crystallography
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• v.16 no.2
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• pp.128-137
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• 2005

We report on the phase transitions of the perovskite nanostructures made by sol-gel template synthesis. The lead titanate ($PbTiO_{3}$) nanostructures were prepared with a chelate sol-gel of titanium tetrabutoxide ($Ti(O^{i}Pr){4}$) and lead acetate ($Pb(OAc)_{2}-3H_{2}O$). $Whatman^{\circledr}$ anodisc membranes (with about 200 nm pore size) served as the template. The template was dipped into the sol, allowed to air dry, and then calcined at $650^{\circ}C$. We have characterized the temperatures of the phase transitions in the $PbTiO_{3}$ nano-structures using DSC, DTA, and second harmonic generation (SHG).

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.1
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• pp.38-44
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• 2015

We have investigated the productivity of microalgae, Nannochloropsis sp., using highly efficient vertical photobioreactor which has been developed by the company IMBiz. This experiment was performed in the field for one month with 2 sets of 2 tons of media under autotrophic cultural mode. In the culture with 0.1% of $CO_2$, the average daily productivity was shown to be up to 0.953g per liter, and 0.574g per liter in the culture with only ambient air. The temperature ranged from $20^{\circ}C$ to $31^{\circ}C$, and it didn't make any differences on the productivity. The light intensity ranged from 5,000 Lux to 40,000 Lux. The light has been appeared to have a very close relationship with the productivity of microalgae. Meanwhile, the harvesting method of pressurefloating attempted in this photobioreactor was found to be very effective.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.635-642
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• 2013

We have prepared a DEMO conveyor device for conveying a large 8G class glass sheet using ahorizontal air-cushion system. This device consists of the body frame and the driving frame that are combined to realize a frame for conveying glass without any contact.The driving frame comprises an air flotation table (bed), drive roller supported at both ends, and ASU. Part of the ASU serves to control the airflow as the chamber consists of a porous pad and fan. Fiber filters replace the porous pad and axial fans serve as an air compressor. In addition, to determine the appropriate glass levitation from the air table, this study examined the design specifications of the applied filter (discharge speed of HEPA and ULPA filters, and flow rate) as well as the height of the and the proper supporting roller height (14mm). Then, after adjusting the position of the ASU and the number of ASUs required to configure the UNIT air floating C/V, we analyzed the height and flatness of the glass and derived the appropriate layout (1140-mm distance between ASUs).

• Tribology and Lubricants
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• v.25 no.2
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• pp.108-113
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• 2009

This paper presents a experimental results for the performance evaluation of a double-bumped air foil bearing. The test results of a double-bumped AFB is compared with a single-bumped AFB at a heavily-loaded condition. The diameter of the test bearing is 50 mm, and the axial length is 50 mm. Nominal clearance of the single-bumped AFB is evaluated as $105{\mu}m$, and that of the double-bumped AFB is as $95{\mu}m$. The test of the AFBs are demonstrated at 3 test mode; the load variation mode, the speed variation mode, and start-stop mode. The single-bumped AFB demonstrated a upward load-carrying capacity of 95 N and a downward load-carrying capacity of 130 N at 20,000 rpm. The double-bumped AFB demonstrated a upward load-carrying capacity of 170 N and a downward load-carrying capacity of 170 N at 20,000 rpm. The single-bumped AFB demonstrated a downward lift-off speed of 16,300 rpm at 105 N. The double-bumped AFB demonstrated a downward lift-off speed of 15,400 rpm at 105 N. The start-stop test of the AFBs assure 5,000 cycle endurance life. The test results are compared with the theoretical calculation results. The test and theorectical results show thata double-bump air foil bearing provides a higher load-carrying capacity, stiffness and damping than a single-bump air foil bearing in a heavily-loaded condition.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.261-272
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• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.415-419
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• 2017

In recent years there have been large increases in the hydraulic loading rates used to design dissolved air flotation (DAF) facilities for drinking water applications. High rate DAF processes are now available at loading rates of 20 to $40m^3/m^2{\cdot}h$. This research evaluated dissolved air flotation as a separation method for algae and organic compounds from water treatment plants. During the service period of 2016. 5. to 2017. 6., DAF pilot plants ($500m^3/day$) process has shown a constantly sound performance for the treatment of raw water, yielding a significantly low level of turbidity (DAF treated water, 0.21~1.56 NTU). As a result of analyzing the algae cell counts in the influent source, it was expressed at 100-120 cells/mL. In DAF treated water, the removal efficient of alge cell counts was found to be upto 90%. The stable turbidity and algae removal were confirmed by operating the high rate DAF process under the condition of the surface loading rate of $30m^3/m^2{\cdot}hr$.

• Journal of Internet Computing and Services
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• v.21 no.5
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• pp.109-118
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• 2020

Recently, people are spending a lot of time inside their homes because of various diseases. It is difficult to ask others for help in the case of a single-person household that is injured in the house or infected with a disease and needs help from others. In this study, an algorithm is proposed to detect emergency event, which are situations in which single-person households need help from others, such as injuries or disease infections, in their homes. It proposes vision pattern detection algorithms using home CCTVs, audio pattern detection algorithms using artificial intelligence speakers, activity pattern detection algorithms using acceleration sensors in smartphones, and dust pattern detection algorithms using air purifiers. However, if it is difficult to use due to security issues of home CCTVs, it proposes a fusion method combining audio, activity and dust pattern sensors. Each algorithm collected data through YouTube and experiments to measure accuracy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.263-270
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• 2018

Recently, porous ceramic materials with anti-static performance are urgently needed for semiconductor and OLED/LCD display manufacturing industry. In this work, we fabricated porous titanium manganese oxide ceramics having the surface resistivity of $10^8-10^{10}$ ohm and enhanced mechanical strength by partial sintering method using nanosized titanium oxide. By addition of nano-sized titanium oxide in the matrix, neck formation between grains was strengthened, which remarkably increased flexural strength up to 170 MPa (@porosity: 15 %), 110 MPa (@porosity: 31 %), compared to 80 MPa (@porosity: 26 %) for pristine titanium manganese oxide ceramics. We evaluated the performances of our ceramics as air-floating module for OLED flexible display manufacturing devices.