• Korean Journal of Computational Design and Engineering
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• v.18 no.1
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• pp.58-70
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• 2013

This study for establishing specific standards of atrium design aims to discuss design of atrium to consider energy performance atrium in office buildings. In order to evaluate a type and a scale of atrium at the early design stage, modeling details of mass design were set as standards of conceptual design. In the experiment, Project Vasari was used to analyze modeling and energy consumption, based on the LOD 100-step suggested by AIA, because there is no guideline to specify a level of modeling details at each design process. From this analysis, the correlation among a simple-typed atrium and scale and energy load was considered. The result of this research is as follows: First, the single-sided atrium reduced energy the most, and it was followed by three-sided, two-sided, four-sided and continuous-typed ones. On the whole, they could decrease energy by up to about 15%. Also, the atrium with a wide facade facing in the south was more favorable to reduce energy. Second, planning the atrium within 10~30% of the whole building area was more energy efficient. Third, rather than the depth, adjusting the length in designing an atrium could reduce cooling and heating loads by 1.5% per 1m. As explained above, energy performance evaluation considering types and planning elements of atrium helps to assess alternatives in a reasonable way. In particular, considering the use of building needs to be preceded to select a type of atrium, although it is also important to consider its planning elements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1221-1229
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• 2014

This paper proposes an approach for predicting the fatigue life of a propeller shaft of a forklift truck by an accelerated life test method. The accelerated life test method adopted in this study is the calibrated accelerated life test, which is highly effective in the prediction of the lifetime and enables significant reduction of the test time as well as a quantification of reliability in the case of small sample sizes. First, the fatigue test was performed under two high stress levels, and then, it was performed by setting low stress levels in consideration of the available test time and extrapolation. Major reliability parameters such as the lifetime, accelerated power index, and shape parameter were obtained experimentally, and the experimentally predicted lifetime of the propeller shaft was verified through comparison with results of an analysis of load spectrum data under actual operating conditions.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1320-1327
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• 2013

In this paper, two different electromagnetic energy harvesters using bulk micromachined silicon spiral springs and Polydimethylsiloxane (PDMS) packaging technique have been fabricated, characterized, and compared to generate electrical energy from ultra-low ambient vibrations under 0.3g. The proposed energy harvesters were comprised of a highly miniaturized Neodymium Iron Boron (NdFeB) magnet, silicon spiral spring, multi-turned copper coil, and PDMS housing in order to improve the electrical output powers and reduce their sizes/volumes. When an external vibration moves directly the magnet mounted as a seismic mass at the center of the spiral spring, the mechanical energy of the moving mass is transformed to electrical energy through the 183 turns of solenoid copper coils. The silicon spiral springs were applied to generate high electrical output power by maximizing the deflection of the movable mass at the low level vibrations. The fabricated energy harvesters using these two different spiral springs exhibited the resonant frequencies of 36Hz and 63Hz and the optimal load resistances of $99{\Omega}$ and $55{\Omega}$, respectively. In particular, the energy harvester using the spiral spring with two links exhibited much better linearity characteristics than the one with four links. It generated $29.02{\mu}W$ of output power and 107.3mV of load voltage at the vibration acceleration of 0.3g. It also exhibited power density and normalized power density of $48.37{\mu}W{\cdot}cm-3$ and $537.41{\mu}W{\cdot}cm-3{\cdot}g-2$, respectively. The total volume of the fabricated energy harvesters was $1cm{\times}1cm{\times}0.6cm$ (height).

• Steel and Composite Structures
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• v.26 no.4
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• pp.485-499
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• 2018

In this paper, a hollow steel tube (HST) shear connector is proposed for use in a slim-floor system. The HST welded to a perforated steel beam web and embedded in concrete slab. A total of 10 push-out tests were conducted under static loading to investigate the mechanical behavior of the proposed HST connector. The variables were the shapes (circular, square and rectangular) and sizes of hollow steel tubes, and the compressive strength of the concrete. The failure mode was recorded as: concrete slab compressive failure under the steel tube and concrete tensile splitting failure, where no failure occurred in the HST. Test results show that the square shape HST in filled via concrete strength 40 MPa carried the highest shear load value, showing three times more than the reference specimens. It also recorded less slip behavior, and less compressive failure mode in concrete underneath the square hollow connector in comparison with the circular and rectangular HST connectors in both concrete strengths. The rectangular HST shows a 20% higher shear resistance with a longer width in the load direction in comparison with that in the smaller dimension. The energy absorption capacity values showed 23% and 18% improvements with the square HST rather than a headed shear stud when embedded in concrete strengths of 25 MPa and 40 MPa, respectively. Moreover, an analytical method was proposed and predicts the shear resistance of the HST shear connectors with a standard deviation of 0.14 considering the shape and size of the connectors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.815-820
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• 2005

ZnO varistor ceramics were fabricated with variation of addition of glass-frit amount and the sintering temperature was $1100^{\circ}C$. The average grain sizes were showed increased from $8.6{\mu}m\;to\;10{\mu}m$, and varistor voltages were decreased from 506V to 460V by added amount of glass-frit. Nonlinear coefficient $\alpha$, of all were with increasing the amount of glass-frit more than 70, in case of added on $0.03wt\%$ glass-frit was 83. And leakage current were less than $1{\mu}A$ with applied at $82\%$ of varistor voltage. The clamping voltage ratio of the specimens added $0.03wt\%$ glass-frit was 1.41 at applied 25A $[8/20\;{\mu}s]$. In the specimen added $0.03wt\%$ glass-frit, endurance of surge current and deviation of varistor voltage were $6200A/cm^2,\;\Delta-1.67\%$, respectively and clamping voltage ratio was 2.33. In the Specimen added $0.03wt\%$ glass-frit were superior to any other compositions on High Temperature Load Test(HTLT) for 1000 hr at $85^{\circ}C$, and deviation of the varistor voltage were $\Delta-1.29\%$.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.6
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• pp.75-83
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• 2004

Ice rubble pieces broken by the bow impact load and side hull of an icebreaking vessel usually pass along the ship's bottom hull and may hit the propeller/rudder or other stern structures causing serious damage to ship's hull . Therefore it is important to estimate the size of broken ice pieces during the icebreaking process. The dynamic interaction process of icebreaker with infinite ice sheet is simplified as a wedge type beam of finite length supported by elastic foundation. The wedge type ice beam is leaded with vertical impact forces due to the inclined bow stem of icebreaking vessels. The numerical model provides locations of maximum dynamic bending moment where extreme tensile stress arises and also possible fracture occurs. The model can predict a failure length of broken ice sheet given design parameters. The results are compared to Nevel(1961)'s analytical solution for static load and observed pattern of ice sheet failure onboard an icebreaker. Also by comparing computed failure length with the characteristic length, the meaning of ice rubble sizes is discussed.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.375-384
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• 2009

The application of the diagrid structural system has increased of late, but cyclic loadings such as winds and earthquakes cannot be fully understood through only an analytical study due to the difficulty of considering its welding property. In this study, diagrid nodes that had been scaled down to 1/5 of their full sizes were tested to find out their structural behavior under seismic or wind loads. Four specimens were used with five parameters, including the welding method and the design details. Cyclic loading tests were carried out, where a tensile load was applied to one brace member and a compression load to the other. The major failure modes in the tests were only failure of bending with tensile stress and tension failure. The welding method and the design details had no effect on the initial stiffness and yielding stress but play a significant role in the failure mode and energy dissipation, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.137-144
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• 1983

Core walls for tall building is one of the structures to support lateral load. Since most structural elements used for resisting which ate relatively weak against torsion, it is important to investigate tosional effects in the analysis and design of tall buildings. Rutenberg proposed a more refined theory on the torsional analysis of core walls which can be used when the stiffness of lintel beams are small or large. In this paper a more refined method to analysis the torsion of core wall structures with variable cross sections and being subjected to arbitrarilly distributed load was suggested. To reduce complex and a great number of calculations and to enhance the generality and flexibility of application of this method, the discrete method using transfer matrix formulation was used. Then this method can be easily applied to irregular and variational sections, has no necessity to get particular solution for each of loading conditions, and the maximum size of matrix calculated is $4{\times}4$, which makes this approach more appropriate for design office calculations using comuters of any sizes or even desk calculators.

• Journal of Korea Multimedia Society
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• v.12 no.3
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• pp.345-353
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• 2009

It is for sure that a stable game managing system is absolutely needed to accept simultaneous interfacing of many users for P2P on-line game system. The proposed P2P on-line game system in this paper is able to get smart and stable game managing taking care of extensive players through reorganizing numerous RS(Region Server) and mutual communications among RS's which can be avoid congestion on one region. Moreover, it is possible to synchronize for game nodes in time stamp utilizing Global Zone Buffer of Monitoring Server which leads to breakup loads. The system manages middleware layers in the so-called sub area, and it is able to execute no matter how big the game sizes are. That means, in some ways, we got everything we try to ensure such as the problems of high cost server and stabilization of message transmission. This paper welcomes to prove efficiency of the suggested system through the simulation.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.5 no.2
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• pp.17-23
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• 1999

Top-to-bottom compression strength of corrugated fiberboard boxes is partly dependent on the load-carrying ability of the central panel areas. The ability of these central areas to resist bending under load will increase the stacking strength of the box. The difference of box compression strengths, among boxes which are made with identical dimensions and fabricated with same components but different flute sizes, is primarily due to difference of the flexural stiffness of the box panels. Top-to-bottom compression strength of a box is accurately predicted by flexural stiffness measurements and the edge crush test of the combined boards. This study was rallied out to analyze the flexural stiffness, maximum bending force and maximum deflection for various corrugated fiber-boards by experimental investigation. There were significant differences between the machine direction (MD) and the cross-machine direction (CD) of corrugated fiberboards tested. It was about 50% in SW and DW, and $62%{\sim}74%$ in dual-medium corrugated fiberboards(e.g. DM, DMA and DMB), respectively. There were no significant differences of maximum deflection in machine direction among the tested fiberboards but, in cross direction, DM showed the highest value and followed by SW, DMA, DMB and DW in order. For the corrugated fiberboards tested, flexural stiffness in machine direction is about $29%{\sim}48%$ larger than cross direction, and difference of flexural stiffness between the two direction is the lowest in DMA and DMB.