• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.325-333
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• 1997

In addition to their function, there is growing interest in esthetics of restorations for teeth from fracture and loss. Because the perception of color depends on a lot of factors such as light source, object, observer and so on. It is difficult to make an objective expression. Therefore the using of mechanical equipment is recommended to exclude these variables and observer's vias. This study was carried out to evaluate the teeth color with a newly developed digital camera and to suggest a way to solve its flaws. After photo-taking and storaging the images of normal teeth into a computer, color spaces were examined with an image analysis system, Adobe Photoshop 3.04 and a statistical significance was determined between groups in term of teeth positions and ages. Results were as follow ; 1. Central incisor looked darker than lateral incisor(p<0.05), but lateral incisor and canine showed a similar lightness. 2. Central incisor showed more greenish color than lateral incisor and canine(p<0.05). 3. Canine showed higher yellowish value than central and lateral incisors(p<0.05). 4. Central incisor and canine showed no difference with aging. But in lateral incisor, teeth in fifth decade were lighter than those of third(p<0.05) and teeth in third decade were more reddish and yellowish than those of fourth decade(p<0.05).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.971-980
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• 1994

The need increased capacity in the cellular system has resulted in the adoption of digital technology with CDMA as the channel access method. It has been recognized that the distinction of the base station is important for its performance in CDMA, since the same spreading sequences are used by the all base stations. Time offset of the pseudo-random noise binary code are used to distinguish signals received at a mobile station from different base station. But the start of the zero offset PN sequence is chosen arbitrary without the background of the systematic and mathematical elaboration. This paper proposes a mothed that define the start of the zero offset PN sequence mathematically. This paper also discusses a method that can easily calculate the time offset of the received spreading sequence with respect to the zero offset PN sequence.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.1-7
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• 1998

The measurement of breakup length of viscous liquid jet in stagnant air was conducted by a 3CCD digital video camera. The nozzle diameters of 4, 6, 8mm with L/d=50 were selected and the dynamic viscosity of viscous liquid made of glycerine and water was in the range of $1.061\times10^{-6}m^2/s$ to $4.935\times10^{-5}m^2/s$. The critical velocity is decreased and the breakup length is increased with the increase of nozzle diameter at the same dynamic viscosity of liquid. At the same nozzle diameter, the breakup length and the critical velocity are both increased with the increase of dynamic viscosity of liquid. It is found in the theoretical analysis that the initial disturbance level is the main cause of occurrance of critical Reynolds number in the stability curve. The comparison of experimental critical Reynolds number and the empirical correlation by Tanasawa and Toyota reveals the relatively good agreement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.10
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• pp.1063-1073
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• 1992

This paper deals with a method for extracting picture signals from CD graphics with a conventional CD player, schemes for designing circuits for the effective extraction of control signals, and the implementation of such circuits using commercially available logic components, thereby achieving cost-effectiveness. This paper also presents an implementation and evaluation of the CD-G system, which requires extracting picture signals, deinterleaving the extracted signals and analyzing control commands and displaying them on a screen. The CD-G system implemented using the extraction circuit presented herein has been observed to operate well in real time.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.10
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• pp.771-782
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• 1991

In industrial multivariable plants, it is ofte the case that the plant outputs are measured in similar components not simultaneously but serially. In this paper, the problem of estimating the state vector of the plant based on the data obtained from such a measuring scheme is considered, and a special type of observer(referred to as a $'$multiple serial-sampling$'$ type observer) which renews its internal states whenever a new group of data is obtained is proposed. It is proved that such an observer can be constructed for almost every sampling period if the palnt is observable as a continuous-time multivariable system, and that the poles of the closed-loop system using the multiple serial-sampling type observer consist of the poles of the observer and those of the state feedback system. The behaviors of the observer and the closed-loop system are studied by simulation. The results of simulation indicate that a multiple serial-ampling type observer can estimate the state of the plant more accurately than the ordinary type observers and improve the closed-loop performance, especially, in the existence of measuring noise.ng noise.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.794-801
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• 2000

In this paper, the efficient new performance evaluation method for digital communication channels is suggested and verified its efficiency in terms of simulation run-tim for the digital satellite broadcasting satellite TV channel. In order to solve the difficulties of the existing Importance Sampling(IS) Technics, we adopted the discrete probability mass function(PMF) in the new method for estimating the statistical characteristics of received signals from the measured Nth order central moments. From the discrete probability mass function obtained with less number of the received signal than the one required in the IS technic, continuous cumulative probability function and its inverse function are exactly estimated by using interpolation and extrapolation technic. And the overall channel is simplified with encoding block, inner channel performance degra-dation modeing block which is modeled with the Uniform Random Number Generator (URNG) and concatenated Inverse Cummulative Pr bility Distribution function, and decoding block. With the simplified channel model, the overall performance evaluation can be done within a drastically reduced time. The simulation results applied to the nonlinear digital satellite broadcasting TV channel showed the great efficiency of the alogrithm in the sense of computer run time, and demonstrated that the existing problems of IS for the nonlinear satellite channels with coding and M-dimensional memory can be completely solved.