• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.877-882
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• 2005

In order to fabricate a high breakdown SiC-SBD (Schottky barrier diode), we investigate an effect on metal guard ring (MGR) in breakdown characteristics of the SiC-SBD. The breakdown characteristics of MGR-type SiC-SBD is significantly dependent on both the guard ring metal and the alloying time of guard ring metal. The breakdown characteristics of MGR-type SiC-SBDs are essentially improved as the alloying time of guard ring metal is increased. The SiC-SBD without MGR shows less than 200 V breakdown voltage, while the SiC-SBD with Al MGR shows approximately 700 V breakdown voltage. The improvement in breakdown characteristics is attributed to the field edge termination effect by the MGR, which is similar to an implanted guard ring-type SiC-SBD. There are two breakdown origins in the MGR-type SiC-SBD. One is due to a crystal defects, such as micropipes and stacking faults, in the Epi-layers and the SiC substrate, and occurs at a lower electric field. The other is due to the destruction of guard ring metal, which occurs at a higher electric field. The demolition of guard ring metal is due to the electric field concentration at an edge of Schottky contact metal.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.69-78
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• 2004

This paper proposes architecture and characteristics of a multi-ring based optical network with single-hop between edge nodes using the concept of circuit switching and multi-wavelength label switching to solve delay problem caused by applying crossconnectors as transit nodes in the wavelength division multiplexing(WDM) network. We suggest multi-ring based architecture composed single and multiple wavelength-bands with multi-wavelength labels, and analyze characteristics of two models. To avoid the packet collision in output ports of edge nodes due to output contention, the static and dynamic allocation scheme, which packets are allocated in time slots, is provided. Based on our analysis, it shows that delay only occur in not core nodes but edge nodes in the proposed architecture. In addition, we evaluate the probabilities of delay, packet loss, and call blocking in the proposed optical packet network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.422-434
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• 2002

We propose 3-layered hierarchical fiber-optic backbone transmission network composed of B-DCS, Backbone ring, Edge ring for efficient transmission of high capacity traffic and consider design method to ensure network survivability of each layer at affordable cost. Mathematical ring-construction cost minimization using MIP(Mixed Integer Programming) models results in NP-complete problem. So, it is hard to solve it within reasonable computing time. on a large-scale network. Therefore we develop heuristic algorithms solving WSCAP(Working and Spared Channel Assignment Problem) for B-DCS, MRLB(Multi-Ring Load Balancing) problem for Backbone ring, and ORLB(Overlayed Ring Load Balancing) problem for Edge ring and show their usefulness through case study.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.252-257
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• 2011

The ring formation and electronic properties of furan adsorbed on graphene layers grown on 6H-SiC (0001) has been investigated using atomic force microscopy (AFM), near edge X-ray absorption fine structure (NEXAFS) spectra for the C K-edge, and core level photoemission spectroscopy (CLPES). Moreover, we observed that furan molecules adsorbed on graphene could be used for chemical functionalization via the lone pair electrons of the oxygen group, allowing chemical doping. We also found that furan spontaneously form rings with one of three different bonding configurations and the electronic properties of the ring formed by furan on graphene can be described using by AFM, NEXAFS and CLPES, respectively.

• Journal of the Korean Society of Safety
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• v.22 no.3 s.81
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• pp.45-50
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• 2007

In this study, reinforcing effects of umbrella-type shell roofs structures such as stadium, exhibition, auditorium and museum are analyzed. Umbrella-type shell roofs treated in this study are practical shapes of conical shells. The objective of this study is to analyze reinforcing effects of umbrella-type shell roofs with stiffeners. Various locations of stiffeners, that is, edge ring A, B, center ring, junction stringer and center stringer are presented and the effects of reinforcement is examined. Also, the reduction effects of roofs thickness by stiffeners are examined. It is shown that the thickness of roofs can be reduced about $20{\sim}30%$ by junction stringer and more than 60% by edge ring A.

• Journal of the Korean Wood Science and Technology
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• v.15 no.2
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• pp.67-78
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• 1987

This study was designed to investigate the effect of board thickness and ring angle on the characteristics including internal check. ring failure, surface check, end check, collapse, thickness shrinkage and width shrinkage of press-drying. The exprimental materials of 6mm-. 9mm- and 12mm-thick board were taken from heartwood and sapwood of oak (Quercus acutissima Carr.) respectively. And boards were numbered according to position in the log(No. 1 to No. 4 for heartwood :md No. 9 for sapwood). Press-drying was at $145^{\circ}C$ platen temperature and 3.5kg/$Cm^2$ platen pressure. The results of this study were summarized as follows. 1. Drying rates for sapwood materials were greater than those for heartwood materials. And drying rates for thinner materials were greater than those for thicker materials. 2. The thinner boards were. the severer surface checking developed in the heartwood materials, and surface checking for heartwood materials had no tendency in board position for the same thickness. Sapwood materials were completely free from surface checking. 3. End checking for heartwood materials had no tendency in board position. The greater deviation of ring angle from perfectly edge-grained was, the severer and checking developed in the sapwood materials. But end checking did not occur in 6mm-thick sapwood materials. 4. The greater deviation of ring angle from perfectly edge-grained was, the severer end checking developed for heartwood and sapwood materials. As board thickness increased, maternal checking developed more severely for heartwood and sapweed materials. 5. For heartwood materials, ring failure, reduced with increasing deviation of ring angle from perfectly edge-grained except 12mm-thick material and showed no significant difference attributable to board thickness. Sapwood materials were completely free from ring failure. 6. For heartwood and sapwood materials, collapse was slight and showed no significant differences attributable to both board thickness and board position. 7. As deviation of ring angle from perfectly edge-grained increased, shrinkage of board thickness decreased for heartwood and sapwood materials. 8. Shrinkage of board width showed no significant differences attributable to both board thickness and board position for heartwood and sapweed materials.

• Management Science and Financial Engineering
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• v.16 no.3
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• pp.85-93
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• 2010

Given an undirected network with a set of source-sink pairs, we are assumed to get a benefit if a pair of source and sink nodes are connected. The k-edge survivability of a network is defined as the total benefit secured after arbitrarily selected k edges are destroyed. The problem of computing k-edge survivability is known to be NP-hard and has applications of evaluating the survivability or vulnerability of a network. In this paper, we consider the k-edge survivability problem restricted to ring networks and develop an algorithm to solve it in O($n^3$|K|) time where n is the number of nodes and K is the set of source-sink pairs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.5
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• pp.364-367
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• 2010

The dual ion-implantation trench edge termination techniques were investigated and optimized using a two-dimensional device simulator. By trenching the field ring site which would be dual implanted, a better blocking capability can be obtained. The results show that the p-n junction with dual implanted junction field-ring can accomplish nearly 20% increase of breakdown voltage in comparison with the conventional trench field-rings. The fabrication is relatively difficult. But the trench etched field ring with dual ion-implantation is surpassed for breakdown voltage and consume same area and extensive device simulations as well as qualitative analysis confirm these conclusions.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.439-443
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• 2018

The outstanding characteristics of high quality GaN single crystal substrates make it possible to apply the manufacture of high brightness light emitting diodes and power devices. However, it is very difficult to obtain high quality GaN substrate because the process conditions are hard to control. In order to effectively control the formation of GaN polycrystals during the bulk GaN single crystal growth by the HVPE (hydride vapor phase epitaxy) method, a quartz ring was introduced in the edge of substrate. A variety of evaluating method such as high resolution X-ray diffraction, Raman spectroscopy and photoluminescence was used in order to measure the effectiveness of the quartz ring. A secondary ion mass spectroscopy was also used for evaluating the variations of impurity concentration in the resulting GaN single crystal. Through the detailed investigations, we could confirm that the introduction of a quartz ring during the GaN single crystal growth process using HVPE is a very effective strategy to obtain a high quality GaN single crystal.

• Tribology and Lubricants
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• v.11 no.4
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• pp.53-57
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• 1995

The contact pressure behavior is examined by means of a finite element analysis. The oil film between the piston ring and cylinder liner is analyzed on the basis that it behaves like a polymer material. The calculated results indicate that a shape of sloping edge with a straight line, which is designated as a Model III, shows a good performance on the contact pressure behavior for the increased speed. Obviously, the ring face profiles play an important role on the contact pressure between compression ring and oil film.