• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.5 no.3
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• pp.27-45
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• 2010

It is strongly believed that multicast will become one of the most promising services on internet for the next generation. Multicast service can be deployed either on network-layer or application-layer. IP multicast (network-layer multicast) is implemented by network nodes (i.e., routers) and avoids multiple copies of the same datagram on the same link. Despite the conceptual simplicity of IP multicast and its obvious benefits, it has not been widely deployed since there remain many unresolved issues. As an alternative to IP multicast, overlay multicast (application-layer multicast) implements the multicast functionality at end hosts rather than routers. This may require more overall bandwidth than IP multicast because duplicate packets travel the same physical links multiple times, but it provides an inexpensive, deployable method of providing point-to-multipoint group communication. In this paper we develop an efficient method applied greedy algorithm for solving two models of overlay multicast routing protocol that is aimed to construct MDST (Minimum Diameter Spanning Tree : minimum cost path from a source node to all its receivers) and MST (Minimum Spanning Tree : minimum total cost spanning all the members). We also simulate and analyze MDST and MST.

• 한국해양학회지
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• v.30 no.4
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• pp.355-364
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• 1995

A heavy fluid is injected to a rotating cylindrical container of flat or inclined bottom filled with homogeneous lighter fluid. Continuous flow-in and spreading patterns over the bottom of the container are observed and at the same time upper-layer motions induced by the movement of the heavy fluid are traced by thymol blue solution. Regardless of bottom geometry, the injected denser fluid is deflected toward "western wall" and continuous its path along the boundary with radial spreading which occurs in the bottom boundary layer to make a quite asymmetric flow. When the bottom contains a slope(${\beta}$-plane), increased pressure gradient causes the fluid move faster to produce a stronger Coriolis force. This makes the width of the flow narrower than that of f-plane. But, when the denser flow reaches the southern part of the container, a local-depth of denser fluid increases (much greater than the Ekman-layer depth) such that the spreading velocity along the wall is reduced and the interfacial slope increases to make the upper-layer adjust geographically to have oppositely directed upper-layer motion along the interfacial boundary. The role of the denser fluid in terms of vorticity generation in the upper-layer is such that it produces local topographic effect over the western half of the container and also induces vortex-tube stretching which is especially dominant in the f-plane.

• Journal of Korean Society of Transportation
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• v.23 no.3 s.81
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• pp.35-47
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• 2005

This paper is to review a literature concerning Bus Transit Route Network Design(BTRNDP), to describe a future study direction for a systematic application for the BTRNDP. Since a bus transit uses a fixed route, schedule, stop, therefore an approach methodology is different from that of auto network design problem. An approach methodology for BTRNDP is classified by 8 categories: manual & guideline, market analysis, system analytic model. heuristic model. hybrid model. experienced-based model. simulation-based model. mathematical optimization model. In most previous BTRNDP, objective function is to minimize user and operator costs, and constraints on the total operator cost, fleet size and service frequency are common to several previous approach. Transit trip assignment mostly use multi-path trip assignment. Since the search for optimal solution from a large search space of BTRNDP made up by all possible solutions, the mixed combinatorial problem are usually NP-hard. Therefore, previous researches for the BTRNDP use a sequential design process, which is composed of several design steps as follows: the generation of a candidate route set, the route analysis and evaluation process, the selection process of a optimal route set Future study will focus on a development of detailed OD trip table based on bus stop, systematic transit route network evaluation model. updated transit trip assignment technique and advanced solution search algorithm for BTRNDP.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.535-541
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• 2005

We report on the development of a passively mode-locked near-infrared femtosecond laser with Cr:YAG crystal that operates near room temperature. The laser wavelength could easily be tuned by using only the internal prism pair over 110 nm from 1400 nm to 1510 nm in cw and over about 30 nm in mode-locked operation, respectively Maximum cw output powers of 810 mW were obtained with $1.5 \%$ output coupler for absorbed pump powers of 7.6 W. For compensation of the internal group velocity dispersion, an IR graded prism pair was used. The Cr:YAG laser delivered nearly Fourier-transform limited pulses with a pulse duration as short as 64 fs at 100 MHz repetition rate. In the mode-locked regime, the laser was operating at 1510 nm with a spectral bandwidth of 44 nm. In order to avoid unstable mode-locking and power instabilities, self-built tubes were inserted into the beam path in the resonator and purged with N2 gas. Finally, output powers of the Cr:YAG laser were optimized to 250 mW fer long time stable mode-locked operation.

• Journal of the Korean Chemical Society
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• v.19 no.3
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• pp.186-192
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• 1975

In the course of anthracite briquet combustion, air draft is usually controlled to continue burning of definite amount of briquet in the conventional hollow clay cylinder with air inlet hole open for given time, so that a large amount of CO tends to be produced. Therefore, it is necessary to establish an improved combustion process to depress the yielding rate of CO and for this purpose, we performed a basic experiment in which combustion rate of CO was measured in the mixture of $N_2, O_2 $and CO gas with or without the presence charcoal at the various temperature. The observed results showed that the burning temperature of CO is about 680${\sim}700^{\circ}C$, further burning rate of it was increased with increasing the amount of draft. From these facts, longer combustion time and low CO generation are thus contradictory to each other and it has been long desired to make those two compatible somehow. The purpose of the present investigation lies in designing an effective new briquet stove to meet the above requirements. The essential feature of the new briquet stove consisted in the use of two hollow iron cylinders with different inside diameter. A cylindrical air jacket thus formed served as a path through which small amount of secondary air run from the bottom of the stove to the upper vent holes. Heat exchange occurred between the upgoing secondary air and the burning briquet, which lowered the combustion temperature of the briquet. The results observed were selfevident as anticipated. It was confirmed that the combustion time was increased tolerably due to the heat loss from the combustion zone and that CO in the flue gas was reoxidized at the upper portion of the stove by the upgoing hot secondary air. By this reoxidation reaction the concentration of CO in the flue gas was found to be about 1/20 of that in case the conventional clay cylinder was used as briquet jacket.

• 한국벤처창업학회:학술대회논문집
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• 2010.08a
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• pp.71-89
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• 2010

It is strongly believed that multicast will become one of the most promising services on internet for the next generation. Multicast service can be deployed either on network-layer or application-layer. IP multicast (network-layer multicast) is implemented by network nodes (i.e., routers) and avoids multiple copies of the same datagram on the same link. Despite the conceptual simplicity of IP multicast and its obvious benefits, it has not been widely deployed since there remain many unresolved issues. As an alternative to IP multicast, overlay multicast (application-layer multicast) implements the multicast functionality at end hosts rather than routers. This may require more overall bandwidth than IP multicast because duplicate packets travel the same physical links multiple times, but it provides an inexpensive, deployable method of providing point-to-multipoint group communication. In this paper we develop an efficient method applied greedy algorithm for solving two models of overlay multicast tree building problem that is aimed to construct MDST (Minimum Diameter Spanning Tree : minimum cost path from a source node to all its receivers) and MST (Minimum Spanning Tree : minimum total cost spanning all the members). We also simulate and analyze MDST and MST.

• Journal of Navigation and Port Research
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• v.37 no.4
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• pp.375-381
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• 2013

In order to establish eLoran system it needs the betterment of a receiver and a transmitter, the add of data channel to loran pulse for loran system information and the differential Loran for compensating Loran-c signal. Precise ASF database map is essential if the Loran delivers the high absolute accuracy of navigation demanded at maritime harbor entrance. In this study we developed the ASF mapping method using predicted ASFs compensated by the measured ASFs for maritime in the harbor. Actual ASF is measured by the legacy Loran signal transmitted from Pohang station in the GRI 9930 chain. We measured absolute propagation delay between the Pohang transmitting station and the measurement points by comparing with the cesium clock for the calculation of the ASFs. Monteath model was used for the irregular terrain along the propagation path in the Yeongil Bay. We measured the actual ASFs at the 12 measurement points over the Yeongil Bay. In our ASF-mapping method we estimated that the each offsets between the predicted and the measured ASFs at the 12 spaced points in the Yeongil. We obtained the ASF map by adjusting the predicted ASF results to fit the measured ASFs over Yeungil bay.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.1 s.28
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• pp.69-77
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• 2004

Since there are a lot of changes in climate on domestic and natural disasters owing to the disturbance-development of the land, damages of properties and human life frequently occur due to the coastal floodings. Accordingly, it is necessary to find the area where the danger of flooding coasts is relatively high and to inform resident the characteristics of the area As a part of preventive land management to minimize the flooding damages of the coastal area, this study suggested the generation of the coastal flood hazard map that provides detailed information such as refuge path, a place of refuge, and the location of medical supplies, food, and main rescue equipment, etc. This study selected the southern region of Daebu-do as an exemplary area, conducted a document study to establish GIS data, secured pre-structured data, and suggested the method of establishing GIS data fit to the study area. In particular, it emphasized the efficient construction of the geographical spatial data that were accurate, economic, objective, and realistic in supporting the modeling to predict the flooding zone. The specific type of established database was divided into flooding risk area, flooding warning area, and flooding-volume area. The prototype of coastal flood hazard map can be widely used for efficient disaster management. Furthermore, it is considered that the map could be applied for arousing residents' attentions to the flooding, prior education, and local governments' management actions against the danger of flooding.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.447-454
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• 2003

Optical burst switching (OBS) has been proposed to reduce the use of fiber delay lines (FDLs) and to realize the optical switching paradigm of the next-generation ail optical networks. The OBS can provide improvements over wavelength routing in terms of bandwidth efficiency and core network scalability via statistical multiplexing of bursts. Recently, another challenging issue is how to upport quality of service (QoS) in the optical burst switching networks. In this paper, we propose a deflection routing scheme to guarantee the QoS for the OBS networks to detour lower priority burst forward to the deflection routing path when congested. A big advantage of the proposed scheme is the simplicity of QoS provision, that comes from the simple QoS provisioning algorithm. Also, the QoS provisioning scheme be able to make efficient networks by fairly traffic distributing with the reduce of the use of FDLs at core routers. The QoS provisioning scheme has been verified to reliably guarantee the QoS of priority 0, 1, 2 burst and to efficiently utilize network resources by computer simulations using OPNET As results, the end-to-end delay of high priority burst is improved, and the network efficiency is also improved.

• Economic and Environmental Geology
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• v.52 no.2
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• pp.189-197
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• 2019

HLW (High Level Radioactive Waste) is one of the problems that must be solved in the countries that implement nuclear power generation. Most countries that are concerned about HLW treatment are considering complete isolation from human society by disposing them deep underground. For perfect isolation, understanding the characteristics of underground rocks is very important. In particular, understanding the characteristics of discontinuity as a path way is one of the first things in order to predict the movement of exposed nuclear species to the surface. In this study, we used 500m underground core samples obtained from granite and gneiss area. The purpose of this study is to understand the characteristics of the discontinuities in each rock type and to analyze the properties of the joints in the underground relative to the surrounding environment. For this purpose, the types of discontinuities were classified and the distribution of each discontinuity were analyzed through visual analysis of the each sample obtained at 500m underground. This study can be used as a basic data for understanding the properties of discontinuities in the rock of the survey area and it can be also used as an important data for understanding the distribution characteristics of discontinuities according to the rock types.