• Journal of Energy Engineering
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• v.20 no.4
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• pp.346-352
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• 2011

The experiment was designed to study the char oxidation kinetics of pulverized coals commonly utilized in Korean power plants. The kinetics has been estimated using the Semenov's thermal spontaneous ignition theory adapted to coal char particle ignition temperature. The ignition temperature of coal char particle is obtained by a direct measurement of the particle temperature with photo detector as well as by means of a solid thermocouple which is used as both a heating and a measuring element. The ignition temperatures for subbituminous coal, Wira, and bituminous coal, Yakutugol, have been measured for 4 sizes in the range of 0.52-1.09 mm. The ignition temperature of the particle increases with the increasing diameter. The results were used to calculate the activation energy and the pre-exponential factor. As a result, the kinetic parameters are in an agreement with ones reported from other investigations.

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.115-120
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• 2005

As a popularity of a portable digital device such as a cellular phone, a digital camera and a MP3 player is spreading, the demand of the mobile storage device increases rapidly. A bluray technology using 405nm laser diode and objective lens having high NA(Numerical Aperture), 0.85, satisfies a miniaturization and a high capacity which are the requirements of the portable device. To develop SFFOP(small form factor optical pickup), it is prerequisite to minimize the number of optical components and establish evaluation and assembly method of micro optical pickup system as well as mass production method of micro optical component. To minimize optical elements of optical pickup, there have been many researches to use P-HOE(Polarized Holographic Optical Element) due to its extremely small size and versatile function. However, P-HOE is handled and assembled very accurately in SFFOP. In this paper, static error signal detection method is developed for an alignment of P-HOE in SFFOP. Using developed static error signal detection method, P-HOE can be aligned very accurately with real time result of static error signals of pickup such as FES(focusing error signal) and TES(Tracking Error Signal). The developed static error signal detection method is verified by the evaluation of commercialized DVD Pickup. And finally. developed static error signal detection method is applied for the assembly of P-HOE in SFFOP system satisfies specification of BD(Blu-ray Disk).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.416-419
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• 2002

There are being two prominent studying for Digital Radiography. Direct and Indirect method of Digital Radiography are announced for producing high quality digital image. The one is using amorphous selenium as photoconductor and the other is using phosphor layer as a light conversion. But each two systems have strength and weakness such as high voltage and blurring effect. In this study, we investigated the electrical characteristic of $multi-layer\left(CaWO_{4}+a-Se \right)$ as a photoconductor according to the changing arsenic composition ratio. This is a basic research for developing of Hybrid digital radiography which is a new type X-ray detector. The arsenic composition ratio of a-Se compound is classified into 7 different kinds which have 0.1%, 0.3%, 0.5%, 1%, 1.5%, 5%, 10% and were made test sample throught thermo-evaporation. The phosphor layer of $CaWO_4$ was overlapped on a-Se using EFIRON optical adhesives. We measured the dark and photo current about the test sample and compared the electrical characteristic of the net charge and signal-to-noise ratio. Among other things, test sample of compound material of 0.3% arsenic showed good characteristic of $2.45nA/cm^2$ dark current and $357.19pC/cm^2/mR$ net charge at $3V/{\mu}m$.

• Journal of Ginseng Research
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• v.36 no.2
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• pp.205-210
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• 2012

For quality control of components in Korean red ginseng powder and extract, a new method for simultaneous quantification of 12 ginsenosides ($Rg_1$, Re, Rf, $Rh_1$, $Rg_2$[S], $Rg_2$[R], $Rb_1$, Rc, $Rb_2$, Rd, $Rg_3$[S], and $Rg_3$[R]) was studied. Compared to the official method for quantification of marker substances (ginsenosides $Rg_1$ and $Rb_1$), the proposed methods were guaranteed by in-house method validation. Several criteria such as linearity, specificity, precision and accuracy were evaluated. For red ginseng powder, recovery (averaging 95% to 105%) was calculated, and analysis of variance was carried out to estimate the relative standard deviation (0.20% to 2.12%). For red ginseng extract, the average recovery rate was 90% to 99% and the relative standard deviation was 0.39% to 2.40%. These results indicate that the proposed method could be used in the laboratory for determination of 12 ginsenosides in red ginseng powder and extract. In addition, this method was found to be suitable for quality control of ginseng products and potentially offer time and cost benefits.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.2
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• pp.89-98
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• 2004

In this paper, we implement a digital holographic security card system that combines digital holographic memory using random phase encoded reference beams with electrical biometrics. Digitally encoded data including a document, a picture of face, and a fingerprint are recorded by multiplexing of holographic memory. A random phase mask encoding reference beams are used as a decoded key to protect illegal counterfeit. As a result, we can achieve a raw BER of 3.6${\times}$10-4 and shift selectivity of 4${\mu}{\textrm}{m}$ using the 2D random phase mask. Also, we develop a recording pattern and image processing which are suitable for a low cost reader without a position sensing photo-detector for real time data extraction and remove danger of fraud from unauthorized person by comparing the reconstructed holographic data with the live fingerprint data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.605-611
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• 2015

The measurement and analysis of angular change have been studied in many fields. This study developed an angle measurement technique with optical fiber and photodiode. The position and attached angle of photodiode were investigated to find the proper combination of parameter. The results showed that the increased measuring range was achieved when the position of detector was away from the center of rotation. Inverse mathematical model was used to obtain angular changes with an optical fiber. The applications of this study include in optical sensor, joint angle measurement, and sport science.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.90-95
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• 2014

The system design and the system performance analysis of 3D imaging laser radar system for the mapping purpose is addressed in this article. For the mapping, a push-bloom scanning method is utilized. The pulsed fiber laser with high pulse energy and high pulse repetition rate is used for the light source of laser radar system. The high sensitive linear mode InGaAs avalanche photo-diode is used for the laser receiver module. The time-of-flight of laser pulse from the laser to the receiver is calculated by using high speed FPGA based signal processing board. To reduce the walk error of laser pulse regardless of the intensity differences between pulses, the time of flight is measured from peak to peak of laser pulses. To get 3D image with a single pixel detector, Risley scanner which stirs the laser beam in an ellipsoidal pattern is used. The system laser energy budget characteristics is modeled using LADAR equation, from which the system performances such as the pulse detection probability, false alarm and etc. are analyzed and predicted. The test results of the system performances are acquired and compared with the predicted system performance. According to test results, all the system requirements are satisfied. The 3D image which was acquired by using the laser radar system is also presented in this article.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.174-174
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• 2010

Gallium Nitride(GaN) attracts great attention due to their wide band gap energy (3.4eV), high thermal stability to the solid state lighting devices like LED, Laser diode, UV photo detector, spintronic devices, solar cells, sensors etc. Recently, researchers are interested in synthesis of polycrystalline and amorphous GaN which has also attracted towards optoelectronic device applications significantly. One of the alternatives to deposit GaN at low temperature is to use Single Source Molecular Percursor (SSP) which provides preformed Ga-N bonding. Moreover, our group succeeds in hybridization of SSP synthesized GaN with Single wall carbon nanotube which could be applicable in field emitting devices, hybrid LEDs and sensors. In this work, the GaN thin films were deposited on c-axis oriented sapphire substrate by MBE (Molecular Beam Epitaxy) using novel single source precursor of dimethyl gallium azido-tert-butylamine($Me_2Ga(N_3)NH_2C(CH_3)_3$) with additional source of ammonia. The surface morphology, structural and optical properties of GaN thin films were analyzed for the deposition in the temperature range of $600^{\circ}C$ to $750^{\circ}C$. Electrical properties of deposited thin films were carried out by four point probe technique and home made Hall effect measurement. The effect of ammonia on the crystallinity, microstructure and optical properties of as-deposited thin films are discussed briefly. The crystalline quality of GaN thin film was improved with substrate temperature as indicated by XRD rocking curve measurement. Photoluminescence measurement shows broad emission around 350nm-650nm which could be related to impurities or defects.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.475-475
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• 2010

We have generated Ar plasma in dense plasma focus device with coaxial electrodes for extreme ultraviolet (EUV) lithography and investigated an emitted visible light for electro-optical plasma diagnostics. We have applied an input voltage 4.5 kV to the capacitor bank of 1.53 uF and the diode chamber has been filled with Ar gas of pressure 8 mTorr. The inner surface of the cylindrical cathode has been attatched by an acetal insulator. Also, the anode made of tin metal. If we assumed that the focused plasma regions satisfy the local thermodynamic equilibrium (LTE) conditions, the electron temperature and density of the coaxial plasma focus could be obtained by Stark broadening of optical emission spectroscopy (OES). The Lorentzian profile for emission lines of Ar I of 426.629 nm and Ar II of 487.99 nm were measured with a visible monochromator. And the electron density has been estimated by FWHM (Full Width Half Maximum) of its profile. To find the exact value of FWHM, we observed the instrument line broadening of the monochromator with a Hg-Ar reference lamp. The electron temperature has been calculated using the two relative electron density ratios of the Stark profiles. In case of electron density, it has been observed by the Stark broadening method. This experiment result shows the temporal behavior of the electron temperature and density characteristics for the focused plasma. The EUV emission signal whose wavelength is about 6 ~ 16 nm has been detected by using a photo-detector (AXUV-100 Zr/C, IRD). The result compared the electron temperature and density with the temporal EUV signal. The electron density and temperature were observed to be $10^{16}\;cm^{-3}$ and 20 ~ 30 eV, respectively.

• Journal of Ginseng Research
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• v.37 no.4
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• pp.457-467
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• 2013

A quick and simple method for simultaneous determination of the 30 ginsenosides (ginsenoside Ro, Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, 20(S)-Rg2, 20(R)-Rg2, 20(S)-Rg3, 20(R)-Rg3, 20(S)-Rh1, 20(S)-Rh2, 20(R)-Rh2, F1, F2, F4, Ra1, Rg6, Rh4, Rk3, Rg5, Rk1, Rb3, Rk2, Rh3, compound Y, compound K, and notoginsenoside R1) in Panax ginseng preparations was developed and validated by an ultra performance liquid chromatography photo diode array detector. The separation of the 30 ginsenosides was efficiently undertaken on the Acquity BEH C-18 column with gradient elution with phosphoric acids. Especially the chromatogram of the ginsenoside Ro was dramatically enhanced by adding phosphoric acid. Under optimized conditions, the detection limits were 0.4 to 1.7 mg/L and the calibration curves of the peak areas for the 30 ginsenosides were linear over three orders of magnitude with a correlation coefficients greater than 0.999. The accuracy of the method was tested by a recovery measurement of the spiked samples which yielded good results of 89% to 118%. From these overall results, the proposed method may be helpful in the development and quality of P. ginseng preparations because of its wide range of applications due to the simultaneous analysis of many kinds of ginsenosides.