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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
Electronics and Telecommunications Research Institute
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Volume & Issues
Volume 18, Issue 3 - Oct 1996
Volume 18, Issue 2 - Jul 1996
Volume 18, Issue 1 - Apr 1996
Volume 17, Issue 4 - Jan 1996
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An Architecture of Scalable ATM Switching System and Its Call Processing Capacity Estimation
Kim, Young-Boo ; Lee, Soon-Seok ; Oh, Chang-Hwan ; Kim, Young-Sun ; Han, Chi-Moon ; Yim, Chu-Hwan ;
ETRI Journal, volume 18, issue 3, 1996, Pages 107~107
In this paper, we define the general requirements of ATM switching systems such as scalability, distributed fashion, and modularity. Also we propose a practical implementation of a scalable ATM switching system whose capacity can be easily expanded. Firstly, the architecture of the system is discussed with an emphasis on system scalability, modularity of subsystems and the simple control network of the design requirements. Secondly, we suggest the three types of distributed call/connection control schemes that are suitable for our switching system. We also estimate their call processing capacity on the average and make a comparison of them under the various system architectures. Since our scalable switching system can be constructed to perform the call processing functions on the various levels of the system capacity, it has much adaptability at the various evolution phases or regions of the network environment.
A Novel Algebraic Framework for Analyzing Finite Population DS/SS Slotted ALOHA Wireless Network Systems with Delay Capture
Kyeong, Mun-Geon ;
ETRI Journal, volume 18, issue 3, 1996, Pages 127~127
A new analytic framework based on a linear algebra approach is proposed for examining the performance of a direct sequence spread spectrum (DS/SS) slotted ALOHA wireless communication network systems with delay capture. The discrete-time Markov chain model has been introduced to account for the effect of randomized time of arrival (TOA) at the central receiver and determine the evolution of the finite population network performance in a single-hop environment. The proposed linear algebra approach applied to the given Markov problem requires only computing the eigenvector
of the state transition matrix and then normalizing it to have the sum of its entries equal to 1. MATLAB computation results show that systems employing discrete TOA randomization and delay capture significantly improves throughput-delay performance and the employed analysis approach is quite easily and staightforwardly applicable to the current analysis problem.
Nonequilibrium Phenomena in Globally Coupled Active Rotators with Multiplicative and Additive Noises
Kim, Seung-Hwan ; Park, Seon-Hee ; Ryu, Chang-Su ;
ETRI Journal, volume 18, issue 3, 1996, Pages 147~147
We investigate noise-induced phase transitions in globally coupled active rotators with multiplicative and additive noises. In the system there are four phases, stationary one-cluster, stationary two-cluster, moving one-cluster, and moving two-cluster phases. It is shown that multiplicative noise induces a bifurcation from one-cluster phase to two-cluster phase. Pinning force also induces a bifurcation from moving phase to stationary phase suppressing the multiplicative noise effect. Additive noise reduces both effects of multiplicative noise and pinning force urging the system to the stationary one-cluster phase. The frustrated effects of pinning force and additive and multiplicative noises lead to a reentrant transition at intermediate additive noise intensity. Nature of the transition is also discussed.
Switching among Alternate Synchronization Patterns in an Electrically Coupled Neuronal Model
Park, Seon-Hee ; Han, Seung-Kee ; Kim, Seung-Hwan ; Ryu, Chang-Su ; Kim, Sang-Wook ; Yim, Tae-Gyu ;
ETRI Journal, volume 18, issue 3, 1996, Pages 161~161
We show that the electrically coupled Hindmarsh-Rose neuronal model exhibits various patterns of phase locking at fixed parameter value. Through the analysis of the effective coupling, the system is shown to be stabilized in one of these patterns according to the initial conditions. This corresponds to the parameter-tuning independent mode-switching mechanism that changes the electrical output of neuronal systems. It is also presented how the stable fixed points of the effective coupling which characterize the phase locking patterns depend on the external current.
Pseudomorphic AlGaAs/InGaAs/GaAs High Electron Mobility Transistors with Super Low Noise Performances of 0.41 dB at 18 GHz
Lee, Jin-Hee ; Yoon, Hyung-Sup ; Park, Byung-Sun ; Park, Chul-Soon ; Choi, Sang-Soo ; Pyun, Kwang-Eui ;
ETRI Journal, volume 18, issue 3, 1996, Pages 171~171
Fully passivated low noise AlGaAs/InGaAs/GaAs pseudomorphic (PM) HEMT with wide head T-shaped gates were fabricated by dose split electron beam lithography (DSL). The dimensions of gate head and footprint were optimized by controlling the splitted pattern size, dose, and spaces of each pattern. We obtained stable T-shaped gate of
gate length with
head. The maximum extrinsic transconductance was 560 mS/mm. The minimum noise figure measured at 18 GHz at
was 0.41 dB with associated gain of 8.19 dB. At 12 GHz, the minimum noise figure and an associated gain were 0.26 and 10.25 dB, respectively. These noise figures are the lowest values ever reported for GaAs-based HEMTs. These results are attributed to the extremely low gate resistance of wide head T-shaped gate having a ratio of the head to footprint dimensions larger than 9.
Electroluminescent Devices Using a Polymer of Regulated Conjugation Length and a Polymer Blend
Zyung, Tae-Hyoung ; Jung, Sang-Don ;
ETRI Journal, volume 18, issue 3, 1996, Pages 181~181
A blue light emitting device has been successfully fabricated using a polymer with regulated conjugation length containing trimethylsilyl substituted phenylenevinylene units. Electroluminescence from the device has an emission maximum at 470 nm. The device shows typical diode characteristics with operating voltage of 20 V and the light becomes visible at a current density of less than
. The electroluminescence spectrum is virtually identical with the photoluminescence spectrum, indicating that the radiation mechanisms are the same for both. A light emitting device using the blend of a large band gap polymer and a small band gap polymer was also fabricated. Light emission from the small band gap polymer shows much improved quantum efficiency, but there is no light emission from the large band gap polymer. Quantum efficiency of the blend increases up to about two orders of magnitude greater than that of the small band gap polymer with increasing proportion of the large band gap polymer. The improvement in quantum efficiency is interpreted in terms of exciton transfer and the hole blocking behaviour of the large band gap polymer. Finally, we have fabricated a patterned flexible light emitting device using the high quantum efficiency polymer blend system.
Molecular Conformation and Application of Stereoregular PMMA Langmuir-Blodgett Films
Kim, Jang-Joo ; Jung, Sang-Don ; Hwang, Wol-Yon ;
ETRI Journal, volume 18, issue 3, 1996, Pages 195~195
Molecular conformations of stereoregular poly(methyl methacrylate) (PMMA) monolayers have been investigated by scanning probe microscopes. Isotactic and syndiotactic PMMAs were found to have right and left hand helical structures, respectively. On the contrary atactic PMMA showed rather random arrangement of the chains. It has been demonstrated that the PMMA Langmuir-Blodgett (LB) films can be utilized to form nanoscale patterns down to 50 nm and to forma geodesic lens. It has also been manifested that the quantum efficiency of a polymer electroluminescent device can be significantly enhanced by inserting the PMMA LB films between the emitting layer and the cathode. All the applications utilize the unique characteristics of the LB films to form thin and uniform films in the molecular level.
On Testing Monotonicity of Mean Residual Life from Randomly Censored Data
Lim, Jae-Hak ; Koh, Jai-Sang ;
ETRI Journal, volume 18, issue 3, 1996, Pages 207~207
This paper proposes a new nonparametric test for testing the null hypothesis that the MRL is constant against the alternative hypothesis that the MRL is decreasing (increasing) for ramdomly censored data. The proposed test statistic is a L-statistic, and we use L-statistic theory to establish its asymptotic normality of the test statistic. We discuss the efficiency loss due to censoring and also calculate the asymptotic relative efficiencies of our test statistic with respect to the Chen, Hollander and Langberg's test for several alternatives.