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RISS 인기검색어
- 검색키워드
- 저자 : Choi Bo-Hun (검색결과 240 건)
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UV 광산화 공정 및 광촉매 공정을 이용한 벤젠 및 톨루엔 가스의 처리
황철원,전보경,김찬훈,서정민,최금찬 동아대학교 환경문제연구소 2003 硏究報告 Vol.25 No.2
Volatile organic compounds (VOCs) are widely used in both industrial and domestic activities. This extensive use results in adverse effect in aquatic, soil and atmospheric environments. Conventional methods for treating VOCs from gas streams, such as absorption, adsorption, condensation and thermal /catalytic incineration all have their inherent limitations and none are definitely cost-effective to treat emissions from the small workplace such as architectural coating, printing, and dry cleaning. In this study, photooxidation-photocatalytic oxidation process was applied in the decomposition of VOCs and benzene and toluene, typical VOCs in industrial area, which were adapted as experimental gases. In photooxidation process, the decomposition efficiency of benzene and toluene was evaluated by varying different conditions, such as UV output, flowrate and background gas. The results showed that the decomposition efficiency of benzene and toluene increased considerably with increasing UV output and retention time. In case of background gas, the decomposition efficiency in standard air was higher than that in nitrogen. In photooxidation-photocatalytic oxidation process, the decomposition efficiency was higher than that in photooxidation process and the concentration of ozone generated from photooxidation reactor was drastically decreased after photocatalytic oxidation process. From this study, the results indicate that photooxidation-photocatalytic oxidation process is ideal for treatment of benzene and toluene from the small workplace. But further process optimization must be achieved to apply this process in workplace.
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황성욱,전보경,김찬훈,서정민,최금찬 동아대학교 환경문제연구소 2001 硏究報告 Vol.24 No.1
It is important to know the impacts of acid rain because of soil acidification, reduced biological productivity. Many researchers were interested in regional acid problems, and former research were focued in short-term trends of acid rain. It is not easy to evaluate acid rain problems because of many parameters relating to meteorological factors, which are wind, temperature, humidity and other factors. Rainfall sampling for this study was done from September 1933 to December 2000 in Dong-A University, Busan. All Samples were collected in separately to early fraction and succeeding fraction. Also, the samples were measured for pH, and EC, cations and anions were analysed by ion Chromatography.
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Choi, Bo-Hun,Kwon, Il-Bum Elsevier Science Ltd 2019 Composites Part B, Engineering Vol.173 No.-
<P><B>Abstract</B></P> <P>Impact damage was mapped using the strain distributed in an optical fiber that was embedded in a composite cylinder after low-velocity impact. Three-dimensional strain images were obtained to allow damage inspection using the optical fiber as a distributed sensor for the first time. An acrylate-coated standard optical fiber was embedded in the hoop layer of the composite cylinder, [90<SUB>1</SUB>/OF/90<SUB>1</SUB>/+-20<SUB>1</SUB>/90<SUB>3</SUB>/+-20<SUB>1</SUB>/90<SUB>3</SUB>/+-20<SUB>2</SUB>/EPDM]<SUB>T</SUB>, as a sensor. This sensing fiber was wound around the cylinder at intervals of 12 mm in the longitudinal direction. Impacts of varied energies that yield barely visible impact damage (BVID) were applied to the cylinder by a drop-weight impact machine with a hemispherical tip. The residual strain caused by external impact of the composite cylinder was measured by the sensing fiber with a Brillouin optical correlation domain analysis (BOCDA) sensor system using phase code modulation. To determine the impact damage location and severity, the strains of the sensing fiber were mapped to positions on the cylinder surface. In the first impact test, eight impacts were applied to the cylinder at energy levels of 10 and 20 J. After impact, the strain measurement using the BOCDA system gave well damage information via cylinder surface strain mapping. In the second impact test, five impacts were applied at four points with the energy of 40 J and at one point with that of 30 J. The strain mapping clearly identified the additional impact locations and severities. These results verified that impact damage to the composite cylinder could be accurately analyzed as mapping images by the buried sensing fiber and the BOCDA sensing system.</P>
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Choi, Bo-Hun,Kwon, Il-Bum Optical Society of America 2015 Optics express Vol.23 No.5
<P>We propose a distributed residual strain sensor that uses an Al-packaged optical fiber for the first time. The residual strain which causes Brillouin frequency shifts in the optical fiber was measured using Brillouin optical correlation domain analysis with 2 cm spatial resolution. We quantified the Brillouin frequency shifts in the Al-packaged optical fiber by the tensile stress and compared them for a varying number of Al layers in the optical fiber. The Brillouin frequency shift of an optical fiber with one Al layer had a slope of 0.038 MHz/με with respect to tensile stress, which corresponds to 78% of that for an optical fiber without Al layers. After removal of the stress, 87% of the strain remained as residual strain. When different tensile stresses were randomly applied, the strain caused by the highest stress was the only one detected as residual strain. The residual strain was repeatedly measured for a time span of nine months for the purpose of reliability testing, and there was no change in the strain except for a 4% reduction, which is within the error tolerance of the experiment. A composite material plate equipped with our proposed Al-packaged optical fiber sensor was hammered for impact experiment and the residual strain in the plate was successfully detected. We suggest that the Al-packaged optical fiber can be adapted as a distributed strain sensor for smart structures, including aerospace structures.</P>
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Choi, Bo-Hun,Chu, Moo-Jung,Park, Hyo-Hoon,Lee, Jong-Hyun Electronics and Telecommunications Research Instit 2001 ETRI Journal Vol.23 No.1
The performance of a long wavelength-band erbium-doped fiber amplifier (L-band EDFA) using 1530nm-band pumping has been studied. A 1530nm-band pump source is built using a tunable light source and two C-band EDFAs in cascaded configuration, which is able to deliver a maximum output power of 23dBm. Gain coefficient and noise figure (NF) of the L-band EDFA are measured for pump wavelengths between 1530nm and 1560nm. The gain coefficient with a 1545nm pump is more than twice as large as with a 1480nm pump. It indicates that the L-band EDFA consumes low power. The noise figure of 1530nm pump is 6.36dB at worst, which is 0.75dB higher than that of 1480nm pumped EDFA. The optimum pump wavelength range to obtain high gain and low NF in the 1530nm band appears to be between 1530nm and 1540nm. Gain spectra as a function of a pump wavelength have bandwidth of more than 10nm so that a broadband pump source can be used as 1530nm-band pump. The L-band EDFA is also tested for WDM signals. Flat Gain bandwidth is 32nm from 1571.5 to 1603.5nm within 1dB excursion at input signal of -10dBm/ch. These results demonstrate that 1530nm-band pump can be used as a new efficient pump source for L-band EDFAs.
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An All-Optically Gain-Controlled Two-Stage Amplifier Using Two Independent Feedback Loops
Choi, Bo-Hun,Kim, Chang-Bong,Ko, Jesoo IEEE 2007 IEEE photonics technology letters Vol.19 No.18
<P> We propose and demonstrate the scheme to combine a two-staged amplifier with a fixed gain flattening filter and two parallel optical feedback loops. This amplifier all-optically controls constant signal gain and gain level through all <TEX>$C$</TEX>-band with a dynamic input power range of up to <TEX>$-$</TEX> 1 dBm while input signals are dynamically changed between one channel and 40 wavelength- division- multiplexing channels. The transient effects of each channel and their wavelength dependency are investigated. It is shown that the amplifier can be used in real field applications through transmission experiments, in which the amplifier performance is kept unchanged under wide dynamic traffic variance. </P>
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Strain pattern detection of composite cylinders using optical fibers after low velocity impacts
Choi, Bo-Hun,Kwon, Il-Bum Elsevier 2018 Composites science and technology Vol.154 No.-
<P><B>Abstract</B></P> <P>The strain pattern distributed on composite cylinders after impacts was detected using optical fibers for the first time. The sensing optical fiber was implemented on the composite cylinders using aluminum (Al)-coated optical fiber, polyimide-coated optical fiber, or standard single mode fiber (SSMF) of polymer-coating. The residual strain of this sensing fiber was measured by a Brillouin optical correlation domain analysis (BOCDA) sensor system, using phase modulation and single side band modulation methods. Impact events of 10, 20, and 40 J energies as barely visible impact damages (BVID) were applied on the cylinders, and these fibers were deployed on the cylinder surface, or were embedded in the cylinders. For the surface deployment, Al-coated fiber exhibited the highest residual strain due to Al plastic deformation, and the strain was three times higher than the lowest SSMF value. For the embedment deployment, these fibers were individually embedded in the cylinder, which was composed of sixteen carbon fiber reinforced polymer layers using a filament winding process. In contrast to the surface deployment, the embedded SSMF gave as high residual strain as that of the Al-coated fiber. These similar residual strains of the three embedded optical fibers suggested that they came from permanent material damage inside the material. Impact events with fiber embedment caused the optical signal in the Al-coated fiber to suffer serious additional insertion loss, but the SSMF did not show loss. So the general fiber for optics communications was successfully demonstrated as a distributed residual strain sensor to detect BVID impacts of composite materials. The strain values were maintained for at least 15 months after impact events. This residual strain sensor is economical, because special fibers like Al-coated fiber were not needed, and the sensor is efficient, because it could sense the strain for long distance, without additional impact-driven insertion loss.</P>
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