• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.989-996
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• 2009

In this study, the effects of biofilter media type (three different activated carbons and anthracite), empty bed contact time (EBCT) and temperature on the removal of four aldehyde species (formaldehyde, acetaldehyde, glyoxal and methylglyoxal) in BAC filters were investigated. Experiments were conducted at three water temperature (5, 15 and $25^{\circ}C$) and four EBCTs (5, 10, 15, and 20 min). The experimental results indicated that the coal based BAC retained more bacterial biomass on the surface of the activated carbon than the other BACs, and increasing EBCT or increasing water temperature also increased the four aldehyde species removal in BAC filters. To achieve above 80% of removal efficiency for four aldehyde species in a BAC filter, above 15 min EBCT at $5^{\circ}C$ and 10 min EBCT at above $15^{\circ}C$ were required. The kinetic analysis indicated a first-order reaction rate for the biodegradation of four aldehyde species at various water temperatures. Data obtained from the BAC filters at various temperatures were also used to evaluate pseudo first-order rate constants for four aldehyde species. The half-lives evaluated for formaldehyde, acetaldehyde, glyoxal and methylglyoxal in the coal-based BAC ranging from 0.89 to 3.19 min, from 0.75 to 3.35 min, from 2.16 to 4.72 min and from 1.49 to 3.86 min, respectively, could be used to assist water utilities in designing and operating BAC filters.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.50-61
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• 1995

A time scale modification method yielding rate-modified speech while conserving the characteristic of speech was implemented in real-time using a goneral purpose digital signal processor. Time scale modification changed pronunciation speed only, producing a time difference between the input signal and the modified signal, making it impossible to implement it in real-time. In this thesis, a system was implemented to remove the time difference between the input and modified signals. Speech signals slowed down or speeded up by a physical time scale modification method, such as adjusting the motor speed of the cassett tape recorder, was used as the input signal. Physical modification that controled only the inter speed of the cassette tape player distorted the pitch period of the original speech. In this study, a real-time system was implemented so that the pitch-distorted speech was reconstructed back to the original by fractional sampling pitch shifting using an FIR filter, and this signal was time scale modified to match the cassette tape recorder motor speed using SOLA time-scale medification. In experiments using speech signals medifiedby the proposed method, results obtained using a 16-bit resolution ADSP2101 processor and using computer simulations employing floating point operations showed about the same average frame signal-to-noise ratio of about 20 dB.

• Journal of Broadcast Engineering
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• v.17 no.4
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• pp.625-633
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• 2012

Extended Depth of Focus (EDF) algorithms for extracting three-dimensional (3D) information from a set of optical image slices are studied by many researches recently. Due to the limited depth of focus of the microscope, only a small portion of the image slices are in focus. Most of the EDF algorithms try to find the in-focus area to generate a single focused image and a 3D depth image. Inherent to most image processing algorithms, the EDF algorithms need parameters to be properly initialized to perform successfully. In this paper, we select three popular transform-based EDF algorithms which are each based on pyramid, wavelet transform, and complex wavelet transform, and study the performance of the algorithms according to the initialization of its parameters. The parameters we considered consist of the number of levels used in the transform, the selection of the lowest level image, the window size used in high frequency filter, the noise reduction method, etc. Through extended simulation, we find a good relationship between the initialization of the parameters and the properties of both the texture and 3D ground truth images. Typically, we find that a proper initialization of the parameters improve the algorithm performance 3dB ~ 19dB over a default initialization in recovering the 3D information.

• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.103-118
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• 1999

This paper analyzes the performance of symbol timing recovery and equalizer in 8VSB digital terrestrial TV receiver under various multipath signals and proposes equalization techniques which improve indoor reception performance. Data segment sync is used for symbol timing recovery and timing offset is measured for echoes of various delays and amplitudes by using symbol timing detection filter whose pattern is +1. +1. -1. and -1. Measured timing offsets were below 10% for long echoes with more than 5 symbol delay and above 30% for short echoes with around 1 symbol delay. Indoor reception is always more challenging than outdoor reception due to lower signal strength. large and short multipaths. and moving interfering objects. So it is considered to use FSE (Fractionally Spaced Equalizer) which is very robust to timing offset and blind equalizer which can update equalizer tap coefficients even by information data. We compare the performance of conventional DFE (Decision Feedback Equalizer) and FSE-DFE using LMS algorithm and Stop and Go algorithm for the indoor reception. Experiments reveals FSE has excellent performance for large timing offset and Stop and Go algorithm shows good performance for Doppler shift. so we propose to use FSE-DFE structure with Stop and Go algorithm for the reliable indoor reception.

• Journal of Korean Society on Water Environment
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• v.33 no.1
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• pp.1-7
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• 2017

Bioretention systems, an advance low impact development and green infrastructure approach were currently utilized in different parts of the world because it promotes biodiversity thereby mimicking and preserving the pre-developed state of an area. This study investigated and compared the capability of four bioretention systems to identify factors affecting the hydraulic capabilities and pollutant removal efficiencies of each system. The two bioretention type A referred as Type A-C and Type A-FC were planted with perennials such as Chrysanthemum and Fan columbine, respectively. On the other hand, the two type B bioretention systems referred as Type B-A and Type B-JM were planted with shrub plant species such as Azalea and Japanese Meadowsweet, respectively. Based on the results, TV, infiltration mechanism, filter media depth and plant species were identified as the factors affecting the difference in flow attenuation, retained volume and pollutant removal efficiency of Type A-C, Type A-FC, Type B-A and Type B-JM bioretention systems. The design of bioretention Type B-A and Type B-JM were advantageous considering greater volume retention, groundwater recharge, longer HRT and peak flow attenuation and greater pollutant removal efficiency. On the other hand, the design of bioretention Type A-C and Type A-FC was more appropriate for design considering reduced groundwater contamination.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.231-242
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• 2011

Recently, the green spaces in the urban areas were greatly reduced due to urbanization and industrialization. As urban structures such as roads and buildings are built, the amount of impervious area within a watershed increases. High impervious surfaces are the common causes of high runoff volumes as the soil infiltration capacity decreases and the volume and rate of runoff increase thereby decreasing the groundwater recharge. These effects are causing many environmental problems, such as floods and droughts, climate change, heat island phenomenon, drying streams, etc. Most cities attempted to reduce sewer overflows by separating combined sewers, expanding treatment capacity or storage within the sewer system, or by replacing broken or decaying pipes. However, these practices can be enormously expensive than combined sewer overflows. Therefore, in order to improve these practices, alternative methods should be undertaken. A new approach termed as "Low Impact Development (LID)" technology is currently applied in developed countries around the world. The purpose of this study was to effectively manage runoff by adopting the LID techniques. Small Constructed Wetland(Horizontal Subsurface Flow, HSSF) Pilot-scale reactors were made in which monitoring and experiments were performed to investigate the efficiency of the system in removing pollutants from runoff. Based on the results of the Pilot-plant experiments, TSS, $COD_{Cr}$, TN, TP, Total Pb removal efficiency were 95, 82, 35, 91 and 57%, respectively. Most of the pollutants were reduced after passing the settling tank and the vertical filter media. The results of this study can contribute to the conservation of aquatic ecosystems and restoration of natural water cycle in the urban areas.

• Korean Journal of Ecology and Environment
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• v.46 no.1
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• pp.116-127
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• 2013

At weekly intervals, we monitored continuous changes in water quality by constructed floating wetland equipped with the four different filter media (sponge, volcanic stone, activated carbon and magnesium hydroxide) in a eutrophic lake from March 2011 to May 2012. We also investigated phyto- and zooplankton communities both in the influent and the effluent water through the floating wetland. Over a 10-month time period, average turbidity (66%), suspended solids (79%) and chlorophyll-a (80%) concentrations were remarkably reduced in the effluent water compared to the influent (P<0.001). The average removal rates of $NO_2-N$ and $NH_3-N$ were 24% and 20%, respectively (P<0.05). The average removal rates of $NO_3-N$ and TN were less than 10% (P>0.05). On the other hand, the average removal rates of $PO_4-P$ and TP were more than 65% (P<0.01). Interestingly, the abundance of phytoplankton in the effluent was decreased about 2.6 times compared to that of the influent, whereas the abundance of zooplankton in the effluent was increased about 3.5 times compared to that of the influent. Overall, particulate matters (SS, Chl-a and TP) and dissolved nutrients ($NO_2-N$, $NH_3-N$ and $PO_4-P$) were particularly reduced at high rates. Therefore, application of our constructed floating wetland in a eutrophic lake improved the water quality and demonstrated a potential for algal bloom mitigation.

• Korean Journal of Ecology and Environment
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• v.39 no.4 s.118
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• pp.489-497
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• 2006

The feasibility of the Natural and Ecological Wastewater treatment System (NEWS) was examined for rural wastewater treatment in Korea. The intermittent trickling biofilter with high hydrophilic filter media was used for pretreatment for suspended solids and organic pollutants. The subsequent constructed wetland with porous granule materials was used for promoting nutrient removal. The results show that the removal efficiencies of the system were high with respect to the water quality parameters except COD. Even if the effluent from the biofilter did not meet the guidelines for wastewater treatment plant effluent in Korea in terms of $BOD_5$ and TN, the final effluent of the system meets the guidelines us to good performance of the constructed wetland. The regression analysis between pollutant loading rate and removal rate indicated that the system could have stable removal for SS, $BOD_5$, TN, and TP in the given influent ranges. The analysis in the winter period indicated that the wetland covered with transparent polycarbonate glass had the statble performance during the winter period dus to increase of temperature inside the wetland without any heating system. With the stable performance, effective poilutant removal, low maintenance, and cost-effectiveness, the NEWS could be considered as an alternative treatment system for decentralized regions and rural communities in Korea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.10 no.1 s.20
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• pp.69-73
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• 2004

Control if Sediment is very important in prawn farm due to the eruption of toxic materials such as unionized $H_{2}S,\;NH_{3}\;and\;NO_3$. In this study, column test was conducted with filter media such as activated carbon, zeolite, oyster shell and iron chloride to evaluate the reduction of toxicity from sediment. ammonia-N($NH_3$) was effectively removed by Zeolite and oyster shell. It was indicated that ammonium ion($NH_4^+$) was removed by ion exchange of zeolite. And the ammonia in the column of oyster shell was existed as the form of $NH_4^+$, which is not toxic for prawn because oyster shell was stably kept at $8{\sim}9g$ of pH. Therefore, some of ammonia($NH_4^+$) was removed by oyster shell. Hydrogen sulfide and COD were effectively removed by adsorption of activated carbon and a partial removal of hydrogen sulfide was accomplished by Oyster shell. Phosphorous was removed by activated carbon, oyster shell and iron chloride. In prawn farm, the concentration of ammonia was increased with increase of pH by algae photosynthesis in the column of activated carbon, zeolite and iron chloride, but it was revealed that pH was stably kept in the column of oyster shell.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.06a
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• pp.91-120
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• 1996

경제발전과 더불어 산업의 많은 분야에서 순수 및 초순순의 사용이 증가하고 있으나, 환경오염에 의한 원수의 오염에 따라 순수 및 초순순제조의 장치비와 처리비용의 증가가 야기되고 있다. 현재 국내에는 화력, 원자력발전소를 비롯하여 열병합발전소, 석유화학공장, 제약회사, 전기 전자부품회사, 반도체회사 및 철강회사 등 많은 분야에서 순수 및 초순수 제조장치의 구성과 성능이 많은 차이를 나타내고 있다. 국내의 초순수 제조장치는 90% 이상이 이온교환수지를 사용하는 이온교환법과 UF, R/O System과 같은 Membrane을 사용하는 Membrane System을 병행하여 적용하고 있다. 국내 초순수처리 Plant에서는 통상 전처리 System과 1차 순수제조 System 및 초순수 System이 상호 연결되어 Plant가 구성 운영되고 있다. 전처리 System에는 응집침전, 여과 흡착, 살균 등이 적용되고 있으며 여과 System에 Membrane을 적용할 수 있으나 국내에서는 특별한 경우를 제외하고 대부분 전처리 여과 System에 Media Filter를 사용한다. 전처리 System도 순수처리 장치의 전처리로는 없어서는 안되는 System이지만 여기에는 전처리 System을 제외하고 국내에서 적용하고 있는 초순수처리 System의 공정현황과 각 System별 특징을 설명하고 있다. 초순순 System에는 요구 수질에 따라 다소 차이가 있지만 반도체 공업에서 사용되는 초순수 System이 이중 최고의 Grade로 반도체공업에서 적용되고 있는 System을 기준하였다. 특히 Membrane을 적용한 초순수제조 System이 증가하고 있어 R/O, ED, EDR, CDI, (EDI)와 같은 Membrane System의 특성과 원리를 검토하였다.대적으로 높은 산소확산계수와 물에 대해서는 낮은 투과도를 가져야 한다. 높은 산소확산계수는 반응을 빠르게 하는 잇점이 있으며 물에 대한 낮은 투과도는 센서내의 전해질 물질을 유지보호하는 역할을 한다. 분리막이 산소전극에 이용될 경우 높은 산소 확산계수 이외에도 적절한 기계적 강도, 열적 안정성 등이 요구된다. 몰입이 가능하여 임계치가 저하된 것으로 여겨진다. 또한 광학적 이득의 존재는 이 구조에 의한 극단파장 반도체 레이저다이오드의 실현 가능성을 나타내는 것이다.548 mL에 비해 통계학적으로 의의 있게 적었다(p<0.05). 결론: 관상동맥우회로 조성수술에서 전방온혈심정지액을 사용할 때 희석되지 많은 고농도 포타슘은 fliud overload와 수혈을 피하고 delivery kit를 사용하지 않음으로써 효과적이고 만족할 만한 심근보호 효과를 보였다.를 보였다.4주까지에서는 비교적 폐포는 정상적 구조를 유지하면서 부분적으로 소폐동맥 중막의 비후와 간질에 호산구 침윤의 소견이 특징적으로 관찰되었다. 결론: 분리 폐 관류는 정맥주입 방법에 비해 고농도의 cisplatin 투여로 인한 다른 장기에서의 농도 증가 없이 폐 조직에 약 50배 정도의 고농도 cisplatin을 투여할 수 있었으며, 또한 분리 폐 관류 시 cisplatin에 의한 직접적 폐 독성은 발견되지 않았다이 낮았으나 통계학적 의의는 없었다[10.0%(4/40) : 8.2%(20/244), p>0.05]. 결론: 비디오흉강경술에서 재발을 낮추기 위해 수술시 폐야 전체를 관찰하여 존재하는 폐기포를 놓치지 않는 것이 중요하며, 폐기포를 확인하지 못한 경우와 이차성 자연기흉에 대해서는 흉막유착술에 더 세심한 주의가 필요하다는 것을 확인하였다. 비디오흉강경수술은 통증이 적고, 입원기간이 짧고, 사회