• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.746-752
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• 2009

In this paper, we deal with the development of an optimal design program for a triple-band PTFA(Planar Inverted-F Antenna) of 433 MHz, 912 MHz and 2.45 GHz by using evolution strategy. Generally, the resonance frequency of the PIFA is determined by the width and length of a U-type slot used. However the resonance frequencies of the multiple U slots are varied by the mutual effect of the slots. Thus the optimal width and length of U-type slots are determined by using an optimal design program based on the evolution strategy. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is constructed for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The resonance frequencies of the triple-band PIFA yielded by the optimal design program are 430 MHz, 910.5 MHz and 2.458 GHz that show a good agreement to the design target values.

• Explosives and Blasting
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• v.34 no.1
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• pp.11-18
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• 2016

It is necessary to minimize ground vibration and noise due to blasting work in urban environment. The blast induced ground vibration and noise are generally generated by a portion of detonation energy, where most of the energy is utilized for rock breakage and movement of rock mass. Recently a blast method utilizing U-shaped steel charge holder was suggested to reduce the ground vibration without decreasing destructive power toward the free surface. In this study, single hole blasting utilizing U-shaped steel charge holder were simulated and the stress waves caused by the detonation of explosives were monitored using AUTODYN software. In order to examine the fragmentation efficiency of the U-shaped steel charge holder, one free face blasting models which adapt the blast induced stress waves were simulated by dynamic fracture process analysis (DFPA) code. In addition, the general blasting models were also simulated to investigate the fragmentation effectiveness of the U-shaped steel charge holder in rock blasting.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.43-53
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• 2010

Seismic isolation is one of the most widely implemented and accepted seismic protection systems to limit or avoid damages from unforeseeable earthquakes. As an energy absorption device, however, the supplemental lead itself tends to pollute the environment. Consequently, it is predicted that the use of lead would be controlled. Considering the pollution caused by lead, several researchers are interested in the viability of using steel in place of lead. In this study, first, based on the results of a non-linear finite element analysis, the excellent deformation capacity of a very tough steel damper was demonstrated by comparing it with that of the SS400 damper and determining the effects of main parameters (the aspect ratio, thickness, and width) on the deformation capacity. Second, an optimum shape and design equation for a U-shaped damper with an opening based on stress distribution was suggested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.68-76
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• 2007

In the present study, tests for U-type steel box girder are performed to observe the effects of W-type and X-type of top lateral bracings on the bending behavior of the U-type steel box girder system. Another objective of the present study is to investigate the adequacy of the currently available design formula. For the structural tests, the test specimen with two third scale of the system constructed in the field was used. In this test, several different spacings are used for the top lateral bracings. The stresses measured from the bending tests are compared with those by the formula proposed by Helwig. An adequate type and the required number of panel for diagonal bracing was obtained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.205-212
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• 2006

In recent investigations, reinforced concrete beams strengthened with Carbon Fiber Sheets (CFS) subjected to fatigue loading were reported to be failed at the ends of CFS by its debonding. U-shaped CFS were attached to both ends of the CFS when fatigue tests on strengthened beams were conducted to delay and/or prevent fatigue failures of adhesive interface. The experimental parameters of this study were the usage of anchorage at the ends of CFS, the number of CFS layers, and the applied load levels of 60%~90% of the static ultimate load obtained from the static tests. The failure modes and the load cycle-deflection relations were observed and discussed from the experimental results. Those results also showed that the U-shaped anchoring system changes the fatigue failure modes and influences greatly on the fatigue capacity of the strengthened beams.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.937-942
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• 2018

This paper maximizes the research on broadband characteristics by using air layer instead of using microstrip structure of radiation part with U-shaped slot patched inside and microstrip antenna in order to make the microstrip antenna to have broadband characteristics. Experimental results show that the VSWR is 1.4 or less than the mobile communication frequency band(820~950MHz) and the gain of the antenna is 8.2dBd. This means that the antenna can be miniaturized, and it can be used in the wireless communication fields, and the mobile communication fields for other frequency bands in the future.

• Journal of Korean Society of Disaster and Security
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• v.16 no.3
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• pp.17-26
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• 2023

Prestressed Concrete (PSC) girders are divided into pre- and post-tension types as prestressing method, and I- and U-type as cross-sectional shape. There are both advantages and disadvantages depending on each prestressing method and cross-sectional shape, and each method is applied to bridge construction sites. In this study, a new girder design was attempted to develop that overcomes its shortcomings by using the pretension method and U-type cross sectional shape. Its structural performance was verified in this study. Pretension type girders are mainly manufactured in factories because they require a reaction arm and related facilities, and have the disadvantage of being limited in weight and span length for road transportation. In addition, in the case of the U-type cross-section, structural stability is very reliable during construction against overturning, but its own weight is relatively large comparing to I-type, and the post-tension method is mainly applied after on-site production. In this study, a PSC girder manufacturing method using the field pretension was proposed and a span length of 40 m real-scale test specimen was manufactured and verified its structural performance.

• 도로교통
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• s.92
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• pp.66-74
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• 2003

• Computational Structural Engineering
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• v.24 no.2
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• pp.37-42
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• 2011

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.516-521
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• 2001

Present study deals with combustion characteristics and performance of U type radiation tube burner with fin which combustion capacity is 30,000kcal/hr and the maximum capacity of supply fuel is $30Nm^{3}/hr$. Temperature difference of radiation tube is about $173^{\circ}C$ at 25% capacity and this show relatively small temperature difference for convenient type. Thermal efficiency is satisfactory as $72{\sim}81%$. Also, radiative efficiency of radiation tube is $52{\sim}73%$. The efficiency of heat exchanger is $27{\sim}37%$. Therefore, radiative efficiency is improved to $1{\sim}10%$ after installing fin.