• Analytical Science and Technology
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• v.28 no.1
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• pp.33-39
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• 2015

CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.4
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• pp.467-472
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• 2012

In this paper, we present a finite element method (FEM) study on the space charge effects in organic light emitting diodes. The physical model covers all the key physical processes in OLEDs, namely charge injection, transport and recombination, exciton diffusion, transfer and decay as well as light coupling, and thin-film-optics. The exciton model includes generation, diffusion, and energy transfer as well as annihilation. We assumed that the light emission originates from oscillation which thus is embodied as exciton in a stack of multilayer. We discuss the accumulation of charges at internal interfaces and their signature in the transient response as well as the electric field distribution. We also report our investigation on the influence of the insertion of the emission layer (EML) in the bilayer structure.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.151-155
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• 2007

In this paper, we have analyzed EMI characteristics for the most widely used LED light source for general light purposes. The magnetic field induced current of LED light source and noise terminal voltage for each electric power line has been measured and analyzed. we conclude it is used as a reference when the standards related to LED light source are proposed.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.8
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• pp.767-773
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• 2008

This paper presents a localization system based on the use of electric compass and tracking IR light source. Digital RGB(Red, Green, Blue)signal of digital CMOS Camera is sent to CPLD which converts the color image to binary image at 30 frames per second. CMOS camera has IR filter and UV filter in front of CMOS cell. The filters cut off above 720nm light source. Binary output data of CPLD is sent to DSP that rapidly tracks the IR light source by moving Camera tilt DC motor. At a robot toward north, electric compass signals and IR light source angles which are used for calculating the data of the location system. Because geomagnetic field is linear in local position, this location system is possible. Finally, it is shown that position error is within ${\pm}1.3cm$ in this system.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.7-12
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• 2003

In scrapped material field, about ten millions ton of waste plastic materials are produced in korea. However recycling rate of waste plastic materials have above 25%. Therefore, it is urgently needed that they are used as recycled materials in order to prevent environment pollution and grain economic profits. In this paper, physical and mechanical properties of light weight concrete using waste plastic materials for aggregates are described in order to develop a light weight concrete with the aggregate made from waste plastic goods, it was carried out many experiments on mix proportion and strength. According to the experimental results, high-strength mortar was necessary to make light weight concrete using aggregate of waste plastic materials. Especially, considering the side of recycling of plastic wastes, it is recommended that recycled aggregates made from waste plastic materials is applied to light weight concrete.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.E2
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• pp.49-56
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• 2005

A long-path transmissometer is one of the optical instruments widely used to measure atmospheric light extinction coefficient without enclosing a light beam and perturbing aerosols. Over the past two decades, a number of measurements have been carried out using the long-path transmissometer manufactured by OPTEC, Inc. Calibration of the transmissometer should be performed when any component of the transmissometer system is interchanged or installation condition is changed. For a better calibration of the transmissometer, application of a modified calibration method for the existing neutral density (ND)-filter method was recommended for the computation of the atmospheric transmittance using model MODTRAN 4 in this study. It was revealed that the measured light extinction coefficient from the transmissometer which was calibrated using the existing ND-filter method could be overestimated due to the assumption of the atmospheric transmittance suggested by OPTEC, Inc. The uncertainty of the measured light extinction coefficient from the transmissometer calibrated based on the modified ND-filter method was calculated to be approximately $13Mm^{-1}$.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1131-1137
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• 2005

Methods for measuring surface roughness based on light reflectivity have advantages over methods based on light interference or diffraction, especially in in-situ, on-the-machine and in-process applications. However, measurement inconsistencies caused by changes in the specimen are still a drawback for field applications. In this study, we propose a new feedback-based algorithm to enhance the consistency against changes in the specimen. The algorithm is deduced from simulations based on light reflectance theory with typical modeled surfaces. The proposed method is similar to a digital controller and regulates the power of reflected light. Experiments varying heights and materials, verified the improvements in robustness of the method against measurement disturbances caused by specimen changes.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.9
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• pp.676-680
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• 1999

To do breath alcohol measurement, a sensor is necessary that it can detect low alcohol gas concentration of 0.01% at least. In this work, a capacitance-type alcohol gas sensor using porous silicon layer is developed to measure low alcohol gas concentration. The sensor using porous silicon layer has some sensitivity at room temperature by very large effective surface area, but there is still much room for improvement. In this experiment, we measured the capacitance of the sensor under 254 nm UV light on the porous silicon layer, in which alcohol solution was kept in a flask at 25, 35, and $45^{\circ}C$ by a heater. As the result, the improvement of sensitivity by illuminating UV light was observed. The increasing rate of the capacitance was shown to be double more than those measured under UV-off state. It is supposed that UV light activates response of the oriental and interfacial polarizations which have slow relaxation time for AC field.

• Journal of Plant Biology
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• v.37 no.3
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• pp.285-292
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• 1994

Ultrastructural changes in Panax ginseng C. A. Meyer mesophyll chloroplasts and variation of thylakoid membrane protein in responce to the light intensity were studied in leaves of two-y-old plants exposed to two different light intensities under field coditions. The leaves were allowed to function for three months after emergence under two contrasting light conditions. The ginseng chloroplasts of 5% light were filled with highly stacked grana of condensely arrayed thylakoids, so that the stroma space was hardly observed. In contrast, chloroplasts from leaves at 100% sunlight had fewer thylakoid membranes and smaller grana stacks. The number of osmiophilic globules increased. Total Chl content and Chl b content were lower at 100% sunlight than 5% sunlight. The thylakoid membrane proteins in the leaves grown at 100% sunlight showed lower CPIa, LHCII and CP29 than those with 5% sunlight. This effect was most obvious for LHCII. Polypeptides showed major bands at 90, 64, 29-30, 22 and 14 kD, and minor bands at 59, 58, 54, 52, 49, 46, 44, 35, 23, 21 and 18-19 kD. All these bands were lower in intensity in the leaves exposed to 100% sunlight. Moreover, the bands at 58-59, 46-47 and 23 kD disappeared.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.149-152
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• 2005

To make artificial light-weight aggregate with EAF-dust and estimate ability to apply to concrete, characteristics of the aggregate were considered in density, weight of unit volume, fineness modulus and so on. And then it was executed to experiments of the concrete mixed with the light-weight aggregate. As it was results that artificial light-weight aggregate with EAF-dust was heavier and more watertight than with only clay, concrete weight of unit volume was heavier than with expended clay aggregate. But it was regarded that concrete with EAF-dust artificial aggregate was able to field application as light-weight concrete because concrete of the weight of unit volume was lighter and compress strength and workability were similar to normal concrete.