• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.13-16
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• 2001

In this paper, the emission and aging properties of ZnS:Cu electroluminescent device were experiment respectively at room temperature and 7$0^{\circ}C$ relative humidity 100%. ZnS:Cu and BaTiO$_3$were respectively used for phosphor and dielectric. While AC 100V on 400Hz frequency were applied to the devices at room temperature and 70$_3$relative humidity 100%, the change of brightness were measured and compared. The surface of aged devices were investigated by scanning electron microscope. With the continuously operated environment of room temperature and 7$0^{\circ}C$ relative humidity 100%, the decay time were measured and the dark spot and aging status on the surface of the device were investigated. ZnS:Cu electroluminescent properties were deteriorated by the Increased temperature and humidity. Also the deteriorated properties were confirmed by the brightness and surface chanties of device, and the aging mechanism from the simulation on sulfur vacancy and deep tracts density.

• Nuclear Engineering and Technology
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• v.7 no.3
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• pp.223-226
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• 1975

The relative detection efficiency of ${\gamma}$-ray full-energy Peaks was obtained by a pair-point method using the $^{56}$ Co source whose ${\gamma}$-ray relative emission rates were well measured. Three Ge(Li) detectors with active volumes of 43.8cc, 32.6cc, and 6cc were calibrated over the ${\gamma}$-ray energy energy range 800-5, 500keV.

• Journal of the Optical Society of Korea
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• v.10 no.2
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• pp.86-90
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• 2006

The external feedback effect on the relative intensity noise (RIN) characteristics of blue InAlGaN laser diode has been analyzed taking into account the spontaneous emission noise and the injection current for the high frequency modulation. A Langevin diffusion model was exploited to characterize its relative intensity noise. The simulation parameters were quantitatively evaluated from the optical gain properties of the InAlGaN multiple quantum well active regions by using the multiband Hamiltonian for the strained wurtzite crystals. The extracted parameters were then applied to the rate equations taking into account the external feedback and the high frequency modulation current. The RIN characteristics were investigated to optimize the low frequency laser diode noise characteristics.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.189-196
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• 2014

Water dispersible ZnS based nanocrystals: ZnS (blue), ZnS:Cu (green) and ZnS:Mn (yellow-orange) were synthesized by capping the surface of the nanocrystals with a mercaptopropionic acid (MPA) molecule. The MPA capped ZnS based nanocrystal powders were characterized by using XRD, HR-TEM, EDXS, FT-IR, and FT-Raman spectroscopy. The optical properties of the colloidal nanocrystals were also measured by UV/Vis and photoluminescence (PL) spectroscopies in aqueous solvents. The PL spectra showed broad emission peaks at 440 nm (ZnS), 510 nm (ZnS:Cu) and 600 nm (ZnS:Mn), with relative PL efficiencies in the range of 4.38% to 7.20% compared to a reference organic dye. The measured average particle sizes from the HR-TEM images were in the range of 4.5 to 5.0 nm. White light emission was obtained by mixing these three nanocrystals at a molar ratio of 20 (ZnS):1 (ZnS:Cu):2 (ZnS:Mn) in water. The measured color coordinate of the white light was (0.31, 0.34) in the CIE chromaticity diagram, and the color temperature was 5527 K.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.21-26
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• 2002

In order to search new phosphors for plasma display panel(PDP), phosphate hosts which has a host excitation band at around 150nm were prepared and their luminescent properties were investigated. In the preparation of $YPO_4: Eu\; and\; (Y,Gd)PO_4: Eu$ phosphors, the effect of oxide and oxalate starting materials on prepared phosphors were compared in terms of relative emission intensities and particle characteristics. The results showed that oxalate starting materials gave better performance in emission intensities and smaller size and more round shape phosphors which would be more applicable for high resolution display. Additionally, Gd, V, Nb and Ta ions were doped to $YPO_4:Eu$ and the luminescent properties of the resulant solid solutions were investigated to find efficient sensitizer. Among these ions, Gd, V and Nb ions increased the emission intensities of parent phosphor to around 10%. While Nb ion gave the best result in emission intensities, CIE color coordinate were improved by doping V ion into $YPO_4:Eu$ phosphor to give x=0.6523, y=0.3406 compared to commercial sample.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.169-176
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• 2001

The purpose of study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The test engine was named heavy-duty variable compression ratio single cylinder engine (VCSCE). The fuel supply system provides LPG/hydrogen mixtures based on same heating value. Various sensors such as crank shaft position sensor (CPS) and hall sensor supply spark timing data to ignition controller. Displacement of VCSCE is $1858.2cm^3$. VCSCE was runned 1400rpm with compression ratio 8. Spark timing was set MBT without knocking. Relative air-fuel ratio(${\lambda}$) of this work was varied between 0.76 and 1.5. As a result, i) Maximum thermal efficiency occurred at ${\lambda}$ value 1.0. It was shown that thermal efficiency was increased approximately 5% with hydrogen enrichment at same ${\lambda}$ value. ii) Engine-out carbon monoxide (CO) emissions were decreased at a great rate under LPG/hydrogen mixture fuelling. iii) Total hydrocarbon (THC) emission was much exhausted in rich zone, same as CO. But THC was exhausted a little bit more in lean zone. iv) Finally, engine-out oxides of nitrogen (NOx) was increased with ${\lambda}$ value 1.0 zone at a greater rate with hydrogen enrichment due to high adiabatic flame temperature.

• Journal of Environmental Health Sciences
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• v.44 no.2
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• pp.169-177
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• 2018

Objectives: The emission characteristics of aldehydes were investigated in five industries for the efficient management of aldehydes. Methods: Aldehydes and THC were measured from the stack and boundary of facilities. The relative concentrations and odor contribution of aldehydes were evaluated. Results: The concentrations of aldehydes in the asphalt manufacturing and printing industries were relatively high. Formaldehyde met emission limits for all facilities. According to the odor contribution analysis of aldehydes, i-valeraldehyde and butyraldehyde, which have a relatively low odor threshold value, were found to be the major odor-causing substances in the painting and textile processing industries. Conclusions: Among the aldehydes, the major emission compounds were formaldehyde in asphalt manufacturing, acetaldehyde in the paper manufacturing and textile processing industries, and butyraldehyde in the printing and painting industries. Therefore, to increase the effectiveness of aldehyde reduction, proper control devices need to be installed and operated according to the emission characteristics of aldehydes.

• Korean Journal of Environmental Agriculture
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• v.18 no.1
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• pp.1-5
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• 1999

This study was conducted to investigate methane emission among rice ecotypes in paddy soil (Jeonbug series). The varieties of rice involved early maturing short-grain variety, Samcheonbyeo, middle maturing variety, Hawsungbyeo and late maturing variety, Dongjinbyeo. The seasonal change of methane flux was high from ear formation stage to heading stage. It was found that the methane flux was tended to be lower in early maturing variety than in the mid-to-late maturing variety. The plots without rice straw reduced methane emission as much as 46% relative to rice straw application. The methane emission rate through rice stem was highly correlated with temperature fluctuation. Methane emission on ecotypes by rice straw application was 0.394 g $m^{-2}day^{-1}$ in early maturing variety (Samcheonbyeo), 0.407 g $m^{-2}day^{-1}$ in mid maturing variety(Hawsungbyeo), 0.411 g $m^{-2}day^{-1}$ in late maturing variety(Dongjinbyeo).

• Smart Structures and Systems
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• v.6 no.3
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• pp.197-209
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• 2010

The structural state of a bridge is currently examined by visual inspection or by wired sensor techniques, which are relatively expensive, vulnerable to inclement conditions, and time consuming to undertake. In contrast, wireless sensor networks are easy to deploy and flexible in application so that the network can adjust to the individual structure. Different sensing techniques have been used with such networks, but the acoustic emission technique has rarely been utilized. With the use of acoustic emission (AE) techniques it is possible to detect internal structural damage, from cracks propagating during the routine use of a structure, e.g. breakage of prestressing wires. To date, AE data analysis techniques are not appropriate for the requirements of a wireless network due to the very exact time synchronization needed between multiple sensors, and power consumption issues. To unleash the power of the acoustic emission technique on large, extended structures, recording and local analysis techniques need better algorithms to handle and reduce the immense amount of data generated. Preliminary results from utilizing a new concept called Acoustic Emission Array Processing to locally reduce data to information are presented. Results show that the azimuthal location of a seismic source can be successfully identified, using an array of six to eight poor-quality AE sensors arranged in a circular array approximately 200 mm in diameter. AE beamforming only requires very fine time synchronization of the sensors within a single array, relative timing between sensors of $1{\mu}s$ can easily be performed by a single Mote servicing the array. The method concentrates the essence of six to eight extended waveforms into a single value to be sent through the wireless network, resulting in power savings by avoiding extended radio transmission.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.261-265
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• 1995

Methane flux from a rice paddy in Korea was measured to study the effects of water management and rice straw application on methane emission under different water managements ; flooding and intermittent irrigation, and with or without rice straw application. Methane emission ranged from 0.066 to $0.455g\;CH_4m^{-2}d^{-1}$. Intermittent irrigation has shown a mitigation effect of methane emission, 70% in NPK plot and 47% in NPK plus rice straw plot, relative to that of flooding. Methane emission from Korean paddy was estimated as 399,590tons per year assuming that paddy fields were managed under intermittent irrigation and rice straw application. This estimation was lower than that of OECD's by 56%, Neue's by 51%, and Matthew's by 62%, while higher than that of Taylor's by 118%.