• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.323-327
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• 2003

Microwave dielectric properties of (P $b_{0.4}$C $a_{0.6}$)[($Fe_{\frac{1}{2}}$N $b_{\frac{1}{2}}$)$_{1-x}$ (M $g_{1}$ 3/N $b_{2}$ 3/)x] $O_3$ (PCFMN) ceramics were investigated as a function of (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ content (0.1$\leq$x$\leq$0.8). A single perovskite phase with the cubic structure was obtained through the given composition range. The unit cell volume was increased with (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$, due to the larger average ionic size of (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ than that of ($Fe_{\frac{1}{2}}$N $b_{\frac{1}{2}}$)$^{4+}$ for B-site ion. Dielectric constant (K) and Temperature Coefficient of Resonant Frequency(TCF) of PCFMN ceramics were dependent on (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ content due to the decrease of ionic polarizability and B-site bond valence, respectively. Qf value was decreased with (M $g_{1}$ 3/N $b_{2}$ 3/)$^{4+}$ content due to the decrease of grain size. Typically, K of 73.56, Qf of 5,074 GHz and TCF of -6.45 ppm/$^{\circ}C$ were obtained for the specimens with x=0.4 sintered at 125$0^{\circ}C$ for 3 h.125$0^{\circ}C$ for 3 h.

• Journal of the Korean GEO-environmental Society
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• v.18 no.10
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• pp.23-34
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• 2017

As the electrical property of fully saturated soils is dependent on the pore water, it has been commonly used for the detection of the contamination into the ground. The objective of this study is to investigate the electrical characteristics according to the salinity and the lead concentration in fully saturated soils. Fresh water and saline water with the salinity of 1%, 2% and 3%, which are mixed with 6 different lead solutions with the range of 0~10 mg/L, are prepared in the cylindrical cell incorporated with sensors for measuring electrical resistance and time domain reflectometry signal. Then, the dried sands are water-pluviated into the cell. The electrical resistance and the time domain reflectometry signal are used to estimate the electrical conductivity. Test results show that electrical conductivity determined from electrical resistance at the frequency of 1 kHz continuously increases with an increase in the lead concentration, thus it may be used for the estimation of the contaminant level. In addition, the electrical conductivity estimated by the time domain reflectometry changes even at very low concentration of lead, the variation rate decreases as the lead concentration increases. Thus, the time domain reflectometry can be used for the investigation of the heavy metal leakage. This study demonstrates that complementary characteristics of electrical resistance and time domain reflectometry may be used for the detection of the leakage and contamination of heavy metal in coastal and marine environments.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.823-828
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• 2008

This study set out investigate what kind of changes would be caused to the craving of alcohol dependent patients by stimuli through virtual reality in the preparation stage for drinking refusal training. With regard to stimulation, it included alcohol exposure, a positive situation, and a negative situation on the basis of drinking encouraging situations(social pressure) known as drinking stimulating situations for alcoholics. The purpose of the study is to provide fundamental materials for the development of new training programs to refuse alcohol and for the examination of the possibility of utilizing virtual reality technology as a new treatment and training tool for alcoholics. To this end, a virtual reality program was conducted involving 12 alcoholics admitted to Severance Mental Health Hospital in Gyeonggi province from December 2006 to September 2007. The data was dealt with various statistic analyses such as frequency analysis, Wilcoxon Matched-pairs Signed-Ranks Test using SPSS/WIN 11.5 The analysis results indicate that avatars encouraging drinking caused more craving than just the background, that the scenes with alcohol exposed caused more craving than the scenes with no alcohol exposed, and that there were no significant changes to craving according to a positive or negative situation. The results confirmed that training sessions using virtual reality presented a situation and environment of drinking pressure that's similar to the actual social pressure and that the virtual reality approach had enormous potential as an effective treatment tool when combined with the existing treatment techniques.

• Journal of Korean Society of Forest Science
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• v.81 no.3
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• pp.263-272
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• 1992

In a torrential river, the flow of debris forms deposits in the river bed, which show the characteristics of the channel bed movement in the watershed. The annual rings of the trees, in the natural evenaged forests on the deposits, indicate when each deposit occurred. Based on the topographical and vegetational indicators on the sediment of Yongcheon and Yeounae rivers, the movement occurrence years were estimated. 1. The cross sectional shapes of deposits in torrential river are in tiers and even-aged forests tend to establish on each tier. 2. Generally the older the forest age is, the higher the height of step from the lowest base tend to become, which indicates discrete movement in magnitude and frequency. 3. The ages of trees indicate the year when deposition occurred, and so may be useful as plant indicator to get spatial-temporal information of deposits. 4. The deposits volumes(F. V.) were dependent on the age distribution of deposits in length, average width and average height. And the average width and the average height of deposits were increasing with the age.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.436-441
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• 2009

A fiber optic sensor is prospective to be applied to structural health monitoring. Especially, a fiber Bragg grating(FBG) sensor is one of the most popular sensors for the structural health monitoring. The FBG sensor has several demodulation systems for tracking the shift of the Bragg wavelength. The dynamic bandwidth is dependent on the demodulation system. In this paper, the sensing mechanism is that the slope of the optical spectrum of FBG could be used as its sensitivity when the tunable laser shot the monochromatic laser wavelength at the highest slope point. In this technique, the high sensitivity is guaranteed even though the sensing range is limited. In an example of the application, the composite plate embedding a FBG sensor was manufactured by using an autoclave method and the above sensing mechanism was applied to the composite plate. Firstly, the natural frequencies of the plate were successfully measured by the FBG sensor during the impact hammer test. Secondly, a high-power speaker was used to force the plate to be vibrated at the specific frequency that was one of the natural frequencies. During the shaking, the FBG sensor measures the dynamic characteristics and ESPI was also used to measure the mode shape. From the two dynamic tests, the availability of the FBG sensor system and the ESPI was proven as a technique for measuring the dynamic characteristics of composite structure.

• Korean Journal of Veterinary Research
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• v.41 no.4
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• pp.485-495
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• 2001

It was investigated whether $Ca^{2+}$ and $K^+$ channels were involved in the inhibitory action of nitric oxide (NO) on the contractile and slow wave activity of guinea pig gastric antral circular muscle. The gastric antral circular muscle showed spontaneous phasic contraction and slow wave. NO donors, 3-morpholinosydnonimine hydrochloride (SIN-1, $0.01{\sim}100{\mu}M$) and S-nitroso-L-cysteine (CysNO, $0.001{\sim}10{\mu}M$), reduced not only the amplitude of phasic contraction but also that of slow wave in a concentration-dependent manner. Both the perfusion of $Ca^{2+}$-free solution and the administration of $Ni^{2+}$, a nonselective $Ca^{2+}$ channel blocker, reduced the phasic contraction as well as the amplitude and frequency of the slow wave. The effects of these treatments were similar to those of NO donors. Nifedipine ($10{\mu}M$), a specific L-type $Ca^{2+}$ channel blocker, abolished the phasic contraction and remarkably reduced the plateau of slow wave but had no profound effect on the upstroke of slow wave. In the whole-cell patch clamp mode, CysNO shifted the steady-state activation curve for L-type $Ca^{2+}$ current to the right and the steady-state inactivation curve to the left. Pretreatment of various $K^+$ channel blockers such as tetraethylammonium (1 mM), 4-aminopyridine (0.5 mM), glibenclamide (10 mM), apamin ($0.1{\mu}M$), and iberiotoxin ($0.1{\mu}M$) did not affect the inhibitory action of SIN-1. These results suggest that NO donors suppress mechanical and electrical activity of guinea pig gastric antral circular muscle by inhibition of L-type $Ca^{2+}$ channel rather than by activation of $K^+$ channels.

• Korean Journal of Veterinary Research
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• v.43 no.3
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• pp.405-414
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• 2003

The purpose of this study was to assess the role of tachykinins (TK) in mediating nonadrenergic noncholinergic (NANC) contractions produced by electrical field stimulation (EFS) in the longitudinal muscle of the rat ileum. In the presence of atropine ($1{\mu}M$), guanethidine ($5{\mu}M$), and L-nitroarginine (L-NNA, $200{\mu}M$), EFS (0.5ms pulse duration, 120 V, 1-20 Hz for 2 min) produced a frequency-dependent slowly-developing tonic contraction with superimposed phasic contractions ('on'-contraction) followed by off slowly-decreasing tonic and superimposed phasic contractions ('off'-contraction) of mucosa-free longitudinal oriented muscle strip. These EFS induced responses were blocked by tetrotoxin. $NK_1$ receptor selective antagonist L-732,138 strongly inhibited the EFS-induced excitatory responses. However $NK_2$ receptor selective antagonist, GR 159897 and $NK_3$ receptor selective antagonist SB 222200 did not significantly inhibited the responses. $NK_1$ receptor selective agonist [$Sar^9$,$Met(O_2)^{11}$] Substance P and $NK_2$ receptor selective agonist [${\beta}-Ala^8$]-neurokinin A (4-10) induced tonic contraction with superimposed phasic contractions of longitudinal oriented muscle strip and almost blocked by selective antagonist L-732,138 and GR 159897, respectively. But $NK_3$ receptor selective agonist senktide did not showed any effect. Nifedipine ($1{\mu}M$) abolished the contraction produced either by EFS or by the TK receptor agonists [$Sar^9$,$Met(O_2)^{11}$] Substance P or [${\beta}-Ala^8$]-neurokinin A (4-10). It is concluded that, in the longitudinal muscle of rat ileum, both $NK_1$ and $NK_2$ receptors modulated the responses to exogenous tachykinins, whereas $NK_1$ is mainly involved in NANC neuromuscular contraction.

• Progress in Medical Physics
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• v.21 no.3
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• pp.261-273
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• 2010

For the use of Indirect-conversion CMOS (complementary metal-oxide-semiconductor) detectors for digital x-ray radiography and their better designs, we have theoretically evaluated the spatial-frequency-dependent detective quantum efficiency (DQE) using the cascaded linear-systems transfer theory. In order to validate the developed model, the DQE was experimentally determined by the measured modulation-transfer function (MTF) and noise-power spectrum, and the estimated incident x-ray fluence under the mammography beam quality of W/Al. From the comparison between the theoretical and experimental DQEs, the overall tendencies were well agreed. Based on the developed model, we have investigated the DQEs values with respect to various design parameters of the CMOS x-ray detector such as phosphor quantum efficiency, Swank noise, photodiode quantum efficiency and the MTF of various scintillator screens. This theoretical approach is very useful tool for the understanding of the developed imaging systems as well as helpful for the better design or optimization for new development.

• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.56-62
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• 2011

In the present study, the phase velocities of guided ultrasonic waves such as the first arriving signal (FAS) and the slow guided wave (SGW) propagating along the long axis on the 12 tubular cortical bone samples in vitro were measured and their correlations with the cortical thickness were investigated. The phase velocities of the FAS and the SGW were measured by using the axial transmission method in air with a pair of unfocused ultrasonic transducers with a diameter of 12.7 mm and a center frequency of 200 kHz. The phase velocity of the FAS measured at 200 kHz exhibited a very high negative correlation with the cortical thickness and that of the SGW arriving after the FAS showed a high positive correlation with the cortical thickness. The simple and multiple linear regression models with the phase velocities of the FAS and the SGW as independent variables and the cortical thickness as a dependent variable revealed that the coefficient of determination of the multiple linear regression model was higher than those of the simple linear regression models. The phase velocities of the FAS and the SGW measured at 200 kHz on the 12 tubular cortical bone samples were, respectively, consistent with those of the S0 and the A0 Lamb modes calculated at 200 kHz on the cortical bone plate.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 1999.03a
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• pp.175-186
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• 1999

Detecting the features of significant patterns from their own historical data is so much crucial to good performance specially in time-series forecasting. Recently, a new data filtering method (or multi-scale decomposition) such as wavelet analysis is considered more useful for handling the time-series that contain strong quasi-cyclical components than other methods. The reason is that wavelet analysis theoretically makes much better local information according to different time intervals from the filtered data. Wavelets can process information effectively at different scales. This implies inherent support for multiresolution analysis, which correlates with time series that exhibit self-similar behavior across different time scales. The specific local properties of wavelets can for example be particularly useful to describe signals with sharp spiky, discontinuous or fractal structure in financial markets based on chaos theory and also allows the removal of noise-dependent high frequencies, while conserving the signal bearing high frequency terms of the signal. To data, the existing studies related to wavelet analysis are increasingly being applied to many different fields. In this study, we focus on several wavelet thresholding criteria or techniques to support multi-signal decomposition methods for financial time series forecasting and apply to forecast Korean Won / U.S. Dollar currency market as a case study. One of the most important problems that has to be solved with the application of the filtering is the correct choice of the filter types and the filter parameters. If the threshold is too small or too large then the wavelet shrinkage estimator will tend to overfit or underfit the data. It is often selected arbitrarily or by adopting a certain theoretical or statistical criteria. Recently, new and versatile techniques have been introduced related to that problem. Our study is to analyze thresholding or filtering methods based on wavelet analysis that use multi-signal decomposition algorithms within the neural network architectures specially in complex financial markets. Secondly, through the comparison with different filtering techniques results we introduce the present different filtering criteria of wavelet analysis to support the neural network learning optimization and analyze the critical issues related to the optimal filter design problems in wavelet analysis. That is, those issues include finding the optimal filter parameter to extract significant input features for the forecasting model. Finally, from existing theory or experimental viewpoint concerning the criteria of wavelets thresholding parameters we propose the design of the optimal wavelet for representing a given signal useful in forecasting models, specially a well known neural network models.