• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.500-506
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• 1999

We designed and fabricated a bidirectional optical transceiver module for low cost access network. An integrated chip forming a pin-PD on an 1.3 urn FP-LD was assembled by flip-chip bonding on a Si optical bench, a single mode fiber with an angled end facet was aligned passively with the integrated chip on V-groove of Si-optical bench. Gaussian beam theory was applied to evaluate the coupling coefficients as a function of some parameters such as alignment distance, angle of fiber end facet, vertical alignment error. The theory is also used to search the bottle-neck between transmittance and receiving coupling efficiency in the bi-directional optical system. Tn this paper, we confirmed that reduction of coupling efficiency by the vertical alignment error between laser beam and fiber core axis can be compensated by controlling the fiber facet angle. In the fabrication of sub-module, a'||'&'||' we made such that the fiber facet have a corn shape with an angled facet only core part, the reflection of transmitted laser beam from the fiber facet could be minimized below -35 dE in alignment distance of 2: 30 /J.m. In the same condition, transmitted output power of -12.1 dEm and responsivity of 0.2. AIW were obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1113-1120
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• 2013

A numerical analysis of the effect of the position of a circular cylinder in a $45^{\circ}$ tilted enclosure on natural convection in the enclosure is presented. The location of the cylinder is changed between -0.4 and 0.4. The Rayleigh number is varied between $10^3$ and $10^5$. The effect of the location of the cylinder on natural convection in the enclosure is analyzed by the isothermal line, stream line, and surface-averaged Nusselt number. The flow and heat transfer characteristics are independent of time in the range of the Rayleigh number and cylinder location that is considered in this study. The surface-averaged Nusselt number of the cylinder and enclosure increases as the cylinder gets closer to the wall of the enclosure.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.4
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• pp.196-203
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• 2005

To describe dinoflagellate cyst distribution from Busan Harbor, eleven surface sediment samples and a vertical sediment sample were collected in 2003. Dinoflagellate cysts were identified 12 genera 22 species, and the total cyst concentrations varied from $210\~869\;cysts/g$. The proportion of heterotrophic dinoflagellate cysts was higher in inner parts than in outer parts of the harbor, which reflects that water quality is worse in inner harborthan that in outer harbor. On the basis of the sedimentation rate of 2.0 mm/yr, total depth of the vertical core reflects marine environment far the past 260 years, where dinoflagellate cysts were identified 9 genera 18 species and the total cyst concentrations were $79\~446\;cysts/g$. The cyst concentrations were low and the proportion of heterotrophic dinoflagellate cysts were incerased in the upper part from $14\~15cm$ depth$(1928\~1933)$, which shows industrialization and urbanization in this study area.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.31-40
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• 2002

We propose a novel ultra-short asymmetric vertical directional coupler switch (VDCS) with high extinction ratios larger than 30㏈ composed of switching operation induced section (SOIS), extinction ratio adjusted section (ERAS), and extinction ratio enhanced section (ERES). In this VDCSs, switching operation is achieved by changing the refractive index of one core in SOIS. The improvement of extinction ratios larger than 30㏈ for both cross and bar states is achieved by controlling the asymmetry of refractive indices between both cores in ERES. After propagating through ERAS with symmetry in the structure, different extinction ratios between cross and bar states at the end of SOIS are changed to the same value. For this reason, the optimum asymmetry of the refractive indices of cores to have the maximum extinction ratios and the lengths of ERES are the same for cross and bar states. Design guidelines to achieve high extinction ratios with large tolerances are presented.

• Fire Science and Engineering
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• v.26 no.2
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• pp.90-96
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• 2012

Since vertical flame spread speed on exterior materials is much faster than horizontal fire, analysis of its fire characteristic is required. For the study of vertical fire pattern created by penetrating windows or openings from the exterior wall of buildings, the research is based on the fire simulation for an aluminum-complex-panel with which is commonly used as exterior materials and consists of polyethylene core material. As a result, the flame reaches the 2nd floor after 135 seconds in the early stage of fire, the 10the floor after 470 seconds and the 30th floor, the highest floor, after 711 seconds. The result shows that fire spread abruptly expands on upper floor due to stack effect of a turbulent flow or exterior materials. In consequence, we can confirm a serious problem that a conflagration of a building through an opening that is equipped with the exterior-materials spreads into interior of building at that same time.

• The Journal of the Korea Contents Association
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• v.11 no.11
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• pp.137-144
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• 2011

This study explored the risk sharing mechanism in the US TV drama industry. The hollywood system of TV production and distribution can be understood to be the result of the efforts to reduce the uncertainty and the risk of investment. Since the 1990s, the vertical integration of major studios and networks has been one of the core strategies for risk sharing. In the strategy, the most important role of networks is to schedule new series that the affiliated studios produce. Networks also provide the new series their brand value. On the other hand, the most important role of studios in the vertical integrated environment is to provide the affiliated networks the infrastructures for production and distribution, financial management, and product management. In addition, networks keep the right on the series in the secondary markets, and attempt to increase the aggressive investment on new series on the base of the rights. However, such a risky investment can be the potential burden and risk for the networks in the future. This paper shows the importance of the reasonable risk sharing in the television drama industry to the Korean TV drama industry that has experienced the conflict between networks and independent production companies.

• Journal of Internet Computing and Services
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• v.7 no.5
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• pp.43-57
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• 2006

Next-generation mobile communication systems evolve in the form of high speed data transmission along with integration of wired-wireless network. Therefore, it needs researches on integrating service to heterogeneous networks to offer high speed data transmission and various services while supporting user mobility. In existing studies, heterogeneous networks are linked to single core network separatively, Since vertical handoff between heterogeneous networks leads to some delay, packets may be lost during vertical handoff. To solve this problem, this paper proposes an hierarchically integrated network architecture considering the characteristics of CDMA2000, WiBro, and WLAN. The hierarchically integrated networks are overlaid according to coverage of each network. Therefore, the proposed architecture can minimize handoff delay and packet loss. In addition, this paper proposes an integrated framework for next generation mobile communication networks.

• Land and Housing Review
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• v.4 no.3
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• pp.295-301
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• 2013

In this study, cases of domestic tall residential buildings were investigated for the structural types, numbers of stories, total heights, type of lateral load resisting systems, and zoning of concrete strength. Based on these investigation data, the structural planning pattern of tall residential building was analyzed. SRC structure is main structural types of tall residential building at the initial stage of domestic tall residential building, but RC structure is substituted for main structural types since 2005. Retaining wall system is positioned at the core part of structural plan as a lateral load resisting system. Concrete strength zoning of vertical members like columns are divided by vertical heights of lower parts, middle parts, and upper parts. Basic data of structural planning of 40stories and 60 stories residential buildings was proposed based on case investigation.

• Steel and Composite Structures
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• v.29 no.5
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• pp.603-622
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• 2018

Precast concrete structures are erected from individual prefabricated components, which are assembled on-site using different types of connections. In the present design of these structures, beam-to-column connections are assumed pin jointed. Bolted billet beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is currently limited information concerning their detailed structural behaviour under vertical loadings. The experimental work has involved the determination of moment-relative rotation relationships for semi-rigid precast concrete connections in full-scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and bolt arrangements conformed to successful commercial practice. Proprietary hollow core floor slabs were tied to the beams by 2T25 tensile reinforcing bars, which also provide the in-plane continuity across the connections. The contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. The flexural strength of the connections in the double-sided tests was at least 0.93 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.94 to 1.94 times the flexural stiffness of the attached beam. In general, the double-sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided bolted billet connection test results are presented in this paper. The behaviour of single sided bolted billet connection test results is the subject of another paper.

• Steel and Composite Structures
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• v.31 no.1
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• pp.1-12
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• 2019

Steel-concrete composite walls have been proposed and developed for applications in various types of structures. The double-skin profiled composite walls, as a natural development of composite flooring, provide structural and architectural merits. However, adequate intermediate fasteners between profiled steel plates and concrete core are required to fully mobilize the composite action and to improve the structural behavior of the wall. In this research, two new types of fasteners (i.e., threaded rods and vertical plates) were proposed and three specimens with different fastener types or fastener arrangements were tested under axial compression. The experimental results were evaluated in terms of failure modes, axial load versus axial displacement response, strength index, ductility index, and load-strain relationship. It was found that specimen with symmetrically arranged thread rods sustained more stable axial strain than that with staggered arranged threaded rods. Meanwhile, vertical plates are more suitable for practical use since they provide stronger confinement to profiled steel plate and effectively prevent the steel plate from early local buckling, which eventually enhance the composite action and increase the axial compressive capacity of the wall. The calculation methods were then proposed and good agreement was observed between the test results and the predicted results.