• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1752-1758
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• 2010

A FM-CW radar is used for the various purposes as a remote sensing device since it has the advantages of the relatively simple implementation and the low probability of signal interception. A FM-CW radar uses the same frequency modulated continuous wave for both transmission and demodulation. Therefore, the received beat frequency represents the range and Doppler information of targets. However, using the conventional FFT method, the degree of accuracy and resolution in the spectrum estimation can be seriously degraded in the detection and tracking of fast moving targets because of the short dwell time. Therefore, in this paper, the model parameter estimation methods called as an autoregressive method is applied to overcome these problems and showed that the improved accuracy and resolution can be obtained for the target range and velocity estimation.

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.214-220
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• 1997

A thin film optical waveguide sensor has been developed to measure and analyze quantitatively some inherent optical properties of biochemical substances. In this paper, two different kinds of thickness of thin film waveguide were prepared by RF sputtering of Corning-7059 glass(n = 1.588 at ${\lambda}=\;514nm$, Ar laser) on Pyrex glass substrates. We made a sensing membrane coated on the thin film waveguide with the poly(vinyl chloride-co-vinyl acetate-co-vinyl alcohol) (91 : 3 : 6) copolymer membrane based on $H^{+}$-selective chromoionophore and $K^{+}$-selective neutral ionophore and then proposed the thin film opptical waveguide ion sensor which can select a potassium ion. This sensor based ell the absorbance change by utilizing chromoionophore and neutral ionophore, which changes their absorption spectrum in the UV-vis region upon complexation of the corresponding ionic species, have been reported. The sensitivity dependence of the proposed sensor on interaction length, waveguide thickness, and content of a chromoionophore was investigated. This sensor has the measurement range of $10^{-6}M{\sim}1M$ for $K^{+}$ concentration and 90% response time of duration within 1 min. Also, our thin film optical waveguide sensor using the evanescent field was investigated as compared with conventional transmission sensor or optode sensor by the optical fiber. The sensitivity of thin-film waveguide $K^{+}$ sensor is higher than that of the conventional transmission sensor. The proposed sensor is expected to be useful to biochemical, medical, environmental inspection and so on.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.500-506
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• 2019

In this study, we present a decision function of optimal smoothing parameter for baseline correction using Asymmetrically reweighted penalized least squares (arPLS). Baseline correction is very important due to influence on performance of spectral analysis in application of spectroscopy. Baseline is often estimated by parameter selection using visual inspection on analyte spectrum. It is a highly subjective procedure and can be tedious work especially with a large number of data. For these reasons, an objective procedure is necessary to determine optimal parameter value for baseline correction. The proposed function is defined by modeling the median value of possible parameter range as the length and order of the background signal. The median value increases as the length of the signal increases and decreases as the degree of the signal increases. The simulated data produced a total of 112 signals combined for the 7 lengths of the signal, adding analytic signals and linear and quadratic, cubic and 4th order curve baseline respectively. According to the experimental results using simulated data with linear, quadratic, cubic and 4th order curved baseline, and real Raman spectra, we confirmed that the proposed function can be effectively applied to optimal parameter selection for baseline correction using arPLS.

• Journal of Korean Library and Information Science Society
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• v.39 no.3
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• pp.479-500
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• 2008

This study investigates Kim Inhue's view of reading through the analysis of reference books in Haseo-Chunjib(하서전집). As the result, he had read 123 different books ar least. He had quoted frequently $Sish{\bar{u}}$ $S{\bar{a}}nj{\bar{i}}ng$(사서삼경), $Sh{\check{i}}ji$(사기), $H{\grave{a}}nsh{\bar{u}}$(한서), $Zhu{\bar{a}}ngz{\check{i}}$(장자), $G{\check{u}}wenzh{\bar{e}}nb{\check{a}}o$(고문진보), $Ch{\check{u}}c{\acute{i}}$(초사), $W{\acute{e}}nxu{\check{a}}n$(문선). He had read books beyond the contemporary(sixteen centurtry) scholar's common list, and had enjoyed reading over the boundaries of stereotyped idea. While he had emphasized on the scripture of Confucian, had earned more knowledges for usefulness and the bases of scholarly writings by reading a wide spectrum of books.

• Transactions on Electrical and Electronic Materials
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• v.17 no.3
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• pp.146-149
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• 2016

The CrN/TiN/Al thin films for solar selective absorber were prepared by dc reactive magnetron sputtering with multi targets. The binary nitride CrN layer deposited with change in N₂ gas flow rates. The gas mixture of Ar and N2 was an important parameter during sputtering deposition because the metal volume fraction (MVF) was controlled by the N2 gas flow rate. In this study, the crystallinity and surface properties of the CrN/TiN/Al thin films were estimated by X-ray diffraction (XRD), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The composition and depth profile of thin films were investigated using Auger electron spectroscopy (AES). The absorptance and reflectance with wavelength spectrum were recorded by UV-Vis-NIR spectrophotometry at a range of 300~1,100 nm.

• ETRI Journal
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• v.40 no.3
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• pp.366-375
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• 2018

Recently, techniques involving head-mounted displays (HMDs) have attracted much attention from academia and industry owing to the increased demand for virtual reality and augmented reality applications. Because HMDs are positioned near to users' eyes, it is important to solve the accommodation-vergence conflict problem to prevent dizziness. Therefore, holography is considered ideal for implementing HMDs. However, within the Nyquist region, the accommodation effect is limited by the space-bandwidth-product of the signal, which is determined by the sampling number of spatial light modulators. In addition, information about the angular spectrum is duplicated over the Fourier domain, and it is necessary to filter out the redundancy. The size of the exit-pupil of the HMD is limited by the Nyquist sampling theory. We newly propose a holographic HMD with an expanded exit-pupil over the Nyquist region by using the time-multiplexing method, and the accommodation effect is enhanced. We realize time-multiplexing by synchronizing a high-speed digital micromirror device and a liquid-crystal shutter array. We also demonstrate the accommodation effect experimentally.

• Korean Journal of Materials Research
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• v.15 no.5
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• pp.293-300
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• 2005

ZnO:Li epilayers were synthesized on sapphire substrates by the pulesd laser deposition (PLD) after the surface of the ZnO:Li sintered pellet was irradiated by the ArF (193 nm) excimer laser. The growth temperature was fixed at $400^{\circ}C$. The crystalline structure of epilayers was investigated by the photoluminescence (PL) and double crystal X-ray diffraction (DCXD). The carrier density and mobility of epilayers measured by van der Pauw-Hall method are $2.69\times10cm^{-3}$ and $52.137cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of epilayers obtained from the absorption spectra is well described by the Varshni's relation, $E_g(T)=3.5128eV{\cdot}(9.51\times10^{-4}eV/K)T^2/(T+280K)$. After the as-grown ZnO:Li epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO:Li has been investigated by PL at 10 K. The Peaks of native defects of $V_{zn},\;V_o,\;Zn_{int},\;and\;O_{int}$ showned on PL spectrum are classified as a donors or accepters type. We confirm that $ZnO:Li/Al_2O_3$ in vacuum do not form the native defects because ZnO:Li epilayers in vacuum existe in the form of stable bonds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.58-61
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• 2008

$TiO_2$ is a wide band-gap semiconductor (3.4 eV) and can only absorb about 5% of sun light in the ultraviolet light region, which largely limits its practical applications because of the lower utility of sun light and quantum yield. In order to move the absorption edge of $TiO_2$ fims to visible spectrum range, we have made the impurity level within a band-gap of $TiO_2$ thin film by introduction of oxygen vacancy. Oxygen-defected $TiO_2$ thin film have prepared by reactive sputtering with the partial pressure of $Ar:O_2=10:90{\sim}99.33:0.66$ ratio. As a result, we could have the impurity level of about 2.75 eV on condition that oxygen partial pressure is below 7%.

• Journal of Powder Materials
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• v.11 no.1
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• pp.50-54
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• 2004

Nanoparticles of iron oxides have been prepared by the levitational gas condensation (LGC) method, and their structural and magnetic properties were studied by XRD, TEM and Mossbauer spectroscopy. Fe clusters were evaporated from a surface of the levitated liquid Fe droplet and then condensed into nanoparticles of iron oxide with particle size of 14 to 30 nm in a chamber filled with mixtures of Ar and $O_2$ gases. It was found that the phase transition from both $\gamma$-$Fe_2O_3$ and $\alpha$-Fe to $Fe_3O_4$, which was evaluated from the results of Mossbauer spectra, strongly depended on the $O_2$ flow rate. As a result, $\gamma$-$Fe_2O_3$ was synthesized under the $O_2$ flow rate of 0.1$\leq$$Vo_2$(Vmin)$\leq$0.15, whereas $Fe_3O_4$ was synthesized under the $O_2$, flow rate of 0.15$\leq$$Vo_2$(Vmin)$\leq$0.2.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.18-25
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• 1997

This study describes a modified preemphasis formula, what we call energy-dependent preemphasis(EDP). This uses the normalized short-term energy of speech signal, with the assumption that the source characteristics of the glottal pulses and the radiation characteristics of the lips are approximately proportional to the energy of speech signal. Using this method, speech analyses, such as AR spectrum estimation, formant detection, are performed for nonstationary starting parts of 5 Korean single vowels. The results are compared with the conventional two preemphasis methods. We found that the proposed preemphasis gave enhanced spectral shapes and more accurate formant frequencies and avoided overlapping phenomenon of adjacent two formants.