• Atmosphere
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• v.17 no.3
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• pp.231-240
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• 2007

The flow regimes of continuously stratified flow over a double mountain and the effects of a double mountain on wave breaking, upstream blocking, and severe downslope windstorms are investigated using a mesoscale numerical model (ARPS). According to the occurrence or non-occurrence of wave breaking and upstream blocking, three different flow regimes are identified over a double mountain. Higher critical Froude numbers are required for wave breaking and upstream blocking initiation for a double mountain than for an isolated mountain. This means that the nonlinearity and blocking effect for a double mountain is larger than that for an isolated mountain. As the separation distance between two mountains decreases, the degree of flow nonlinearity increases, while the blocking effect decreases. A rapid increase of the surface horizontal velocity downwind of each mountain near the critical mountain height for wave breaking initiation indicates that severe downslope windstorms are enhanced by wave breaking. For the flow with wave breaking, the numerically calculated surface drag is much larger than theoretically calculated one because the region with the maximum negative perturbation pressure moves from the top to the downwind slope of each mountain as the internal jump propagating downwind occurs.

• Journal of the Korean Society of Costume
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• v.28
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• pp.205-212
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• 1996

This paper is to study the characteristics of fabrics dyed with astringent unripe persimmon juice. The cotton silk rayon and nylon fabrics were dyed with astringet unripe persimmon juice. The structures of natural fabrics dyed fabrics and dyed fabrics followed by washing were examined by scanning electron mi-croscopy. Surface reflexibility of VIS trans-mittance of UV VIS and NIR were analyzed. The study conclues as follows: 1. Colour of cotton fabrics dyed with persim-mon juice became darkended as a function of exposing time to sunlight. That colour was chaged after washing. 2. Blocking effect of ultraciolet light and visible ray was increased in all dyed fabrics. Especially dyed cotton fabric blocked UV light perfectly and the blocking effect was still remained after 9 washings. 3. Persimmon juice dyeing produced coating effect to fabrics besides dyeing effect accord-ing to the scanning electron micrographs. In a word the cotton fabric dyed with per-simmon juice has blocking effect of UV light stiffness. Therefore I think persimmon juice dyeing is a very useful textile finishing and ex-pect a wide application of the technique in fu-ture.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.243-246
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• 2001

In this paper, we have proposed a novel trench electrode Base Resistance Thyristor(BRT) and trench electrode BRT with a intrinsic region. A new power BRTs have shown superior electrical characteristics including snab-back effect and forward blocking voltage more than the conventional BRT. Especially, the trench electrode BRT with intrinsic region has obtained high blocking voltage of 1600V. The blocking voltage of conventional BRT is about 400V at the same size. Because the breakdown mechanism of BRT is avalanch breakdown by impact ionization, the trench electrode BRT with intrinsic region has suppressed impact ionization, effectively. If we use this principle, we can develope super high voltage power devices and applicate to another power devices including IGBT, EST and etc.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.259-266
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• 2004

In this paper. a new two types of EST(Emitter Switched Thyristor) structures are proposed to improve the electrical characteristics including the current saturation capability. Besides, the two dimensional numerical simulations were carried out using MEDICI to verify the validity of the device and examine the electrical characteristics. First, a vortical trench electrode EST device is proposed to improve snap-back effect and its blocking voltage. Second, a dual trench gate EST device is proposed to obtain high voltage current saturation characteristics and high blocking voltage and to eliminate snap-back effect. The two proposed devices have superior electrical characteristics when compared to conventional devices. In the vertical trench electrode EST, the snap-back effect is considerably improved by using the vertical trench gate and cathode electrode and the blocking voltage is one times better than that of the conventional EST. And in the dual trench gate EST, the snap-back effect is completely removed by using the series turn-on and turn-off MOSFET and the blocking voltage is one times better than that of the conventional EST. Especially current saturation capability is three times better than that of the other EST.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.6
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• pp.663-671
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• 1988

In this paper, in order to reduce the blocking effect of block coded images, we propose the method considering the lowpass and bandpass components of Granrath's human visual model. This method consists of two-stage enhancement procedure. The first step is lowpass filtering which smooths out the blocking effect, and the second step is a high frequency enhancement procedure to increase the contrast decreased by the lowpass filtering in the first step. In the first step, the one-dimensional Gaussian filter which aligthns parallel to the edge direction is considered to preserve the edge in the block and the two-dimensional Gaussian filter is used to smooth out the blocking effect near the block boundaries. In the second step, the lowpass and bandpass components of the Granrath's model are considered to increase contrast in a restored image. The performance comparison of the proposed method and the existing mehtods is made by a computer simulation with several block coded images. We can see that the enhancement in the subjective quality of images of the proposed method is more significant than the enhancement in the subjective quality of images of the proposed method is more significant than the existing methods, though the proposed method does not show better performance on the PSNR gain, the poor measure of picture quality for block coded images.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.386-392
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• 2002

In this paper, we propose a novel blocking effect reduction method based on a rational B-spline. The blocking effect results from independent coding of each image block and becomes highly visible especially coded at very low bit rates. The proposed approach adopts a rational open uniform B-spline curve that used to produce a smooth curve through a set of control points. The pixels on the block boundary are treated as control points, and the weight values, which decide the shape of curve, are determined differentially by considering the distance the position of the pixels and that of the block boundary. The simulation results show that the proposed method has excellent performance for all pattern of the blocking effect with less computational complexity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.119-119
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• 2008

The electrical characteristics of Metal-Ferroelectric-Nitride-Oxide-Silicon (MFNOS) structure is studied and compared to the conventional Silicon-Oixde-Nitride-Oxide-Silicon (SONOS) capacitor. The ferroelectric blocking layer is SrBiNbO (SBN with Sr/Bi ratio 1-x/2+x) with the thickness of 200 nm and is fabricated by the RF sputter. The memory windows of MFNOS and SONOS capacitors with sweep voltage from +10 V to -10 V are 6.9 V and 5.9 V, respectively. The effect of ferroelectric blocking layer and charge trapping on the memory window was discussed. The retention of MFNOS capacitor also shows the 10-years and longer retention time than that of the SONOS capacitor. The better retention properties of the MFNOS capacitor may be attributed to the charge holding effect by the polarization of ferroelectric layer.

• Journal of Communications and Networks
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• v.11 no.1
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• pp.72-83
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• 2009

We have studied the effect of head of the line blocking (HOLB) on session initiation protocol (SIP) session establishment delays. Our results are based on experiments performed in a test bed and on the public Internet. We used the stream control transmission protocol (SCTP) as a transport for SIP because SCTP can be configured to suffer or to avoid HOLB. Our experiments show that the effect of HOLB on session establishment delays generally starts to be significant starting at fairly low packet loss rates. However, there are scenarios where network conditions are good enough to make the effect of HOLB insignificant.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.445-448
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• 2006

Bias stress effect in pentacene organic thin-flim transistors with cross-linked PVA gate dielectric is analyzed. For negative gate bias stress, positive threshold voltage shift is observed. The injected charges from the gate electrode to the defect states of gate dielectric are regarded as the main origin of $V_T$ shift. The reduced bias stress effect using $SiO_2$ blocking layer confirms the assumed mechanism. It is also demonstrated that the inverter with $SiO_2$ blocking layer shows the negligible hysteresis owing to the reduced bias stress effect.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.347-354
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• 1996

This paper presents digital hearing aids signal processing system in WT(wavelet transform) domain. For implementation of hearing aids in WT domain, the gain in frequency domain is approximated in WT domain. We also present the gain selection algorithm to deal with the change of input signal power. Most transform methods produce blocking effect, and this effect degrades the convergence rate of feedback canceller. As a solution, we proposed wavelet transform bascd feedback canceller. To evaluate the performance, we compared it with LOT (lapped orthogonal transform) method in the frequency domain. This system has not shown the blocking effect, and improves convergence rate as compared with the LOT based feedback canceller.