• Structural Engineering and Mechanics
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• v.36 no.3
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• pp.247-278
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• 2010

The study of the seismic vulnerability of masonry buildings requires structural properties of walls such as stiffness, ultimate load capacity, etc. In this article, a method is suggested for modeling the masonry walls under in-plane loading. At the outset, a set of analytical equations was established for determining the elastic properties of an equivalent homogeneous material of masonry. The results for homogenized unreinforced brick walls through detailed modeling were compared in different manners such as solid and perforated walls, in-plane and out-of-plane loading, etc, and it was found that this method provides suitable accuracy in estimation of the wall linear properties. Furthermore, comparison of the results of proposed modeling with experimental out coming indicated that this model considers the non linear properties of the wall such as failure pattern, performance curve and ultimate strength, and would be appropriate to establish a parametric study on those prone factors. The proposed model is complicated; therefore, efforts need to be made in order to overcome the convergency problems which will be included in this study. The nonlinear model is basically semi-macro but through a series of actions, it can be simplified to a macro model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.633-640
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• 2007

In this paper, 3-D reciprocating compressor is taken into flow-structure interaction analysis. The full cycle process consisted of cylinder expansion and compression has been modeled without considering flow leakage through cylinder wall. Fully-coupled FSI analysis of this compressor model was iteratively solved and gives sufficient result with the experimental test. The study is emphasized to thoroughly investigate discharge valve motion, opening and closing, in order to determine discharge valve region which is prone to have high effective stress. The cylinder pressure is successfully validated before conducting impact analyses between discharge valve and other susceptible supported structure. Velocity profile has been obtained in FSI analysis is used as initial condition to carry out further impact analyses. Stress result of discharge valve and valve spring gives preliminary estimation of higher stress area due to its impact phenomena.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1721-1730
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• 1999

In this thesis, an error resilient video coding algorithm, under the error-prone environment such as wireless communication, is suggested. The suggested algorithm adapts the Classified VQ method for intra imagers that reduces some load by searching similar vectors. The Duplicate Vector Position Code is proposed for the higher compression efficiency and the robust decoding in error environment. As a result, the bitstream encoded by the proposed method is in a CBR(Constant Bit Rate) preventing from error propagation. The experiment that adds practical error to the encoded bitsrteam shows the error-robustness superior to H.263.

• Structural Engineering and Mechanics
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• v.36 no.4
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• pp.513-527
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• 2010

This paper presents a three-dimensional finite element method based structural analysis model for structural analysis of reinforced concrete high-rise buildings during construction. The model considered the time-dependency of the structural configuration and material properties as well as the effect of the construction rate and shoring stiffness. Uniaxial compression tests of young concrete within 28 days of age were conducted to establish the time-dependent compressive stress-strain relationship of concrete, which was then used as input parameters to the structural analysis model. In-situ tests of a RC high-rise building were conducted, the results of which were used for model verification. Good agreement between the test results and model predictions was achieved. At the end, a parametric study was conducted using the verified model. The results indicated that the floor position and construction rate had significant effect on the shore load, whereas the influence of the shore removal timing and shore stiffness have much smaller. It was also found that the floors are more prone to cracking during construction than is ultimate bending failure.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.133-139
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• 2019

The utilizations of ceramics in the modern industries are increasing due to the desirable combinations of electrical, mechanical and physical properties found in ceramics. Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension which is prone to affect the defects such as scratch, crack and breakage during the machining. Generally, the defects of the ceramic machining are generated from the structural vibrations of the machine. In this study, the dynamic characteristics of a machining center for ceramic machining were investigated to analyze the structural vibrations for the improved stability. Frequency response test and computer simulation have been conducted for the analysis and the design improvement. The improved design is suggested to suppress vibrations for the higher stability of the machine and further to reduce vibrations. And the result shows that simple design alterations without any change of major parts of the machine can reduce the vibration of the machine effectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.78-83
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• 2011

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its high thermal efficiency and lower harmful emissions, including $CO_2$. Although the high octane value of natural gas increases engine output and efficiency due to the high compression ratio, this fuel is prone to such difficulties as a narrow limit of inflammability and a slow combustion speed in the lean burn operation domain, leading to unstable combustion and higher emissions of harmful exhaust gases. Hydrogen blended with natural gas can extend the lean burn limit while maintaining stable, efficient combustion and achieving lower NOx, hydrocarbon and green house gas emissions. In this study, the effect of hydrogen addition on an engine performance and NOx emission characteristics was investigated in a heavy duty natural gas engine. The results showed that thermal efficiency was increased and NOx emissions were reduced due to the expansion of lean operation range under stable operation. NOx emission can be significantly reduced with the retard of spark advance timing.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.1
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• pp.21-28
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• 2012

In this paper, we present the analytical study results pertaining to the buckling of the orthotropic plates and local buckling of structural compression members composed of orthotropic plate components. Fiber reinforced polymeric plastic (FRP) materials, have many advantages over conventional structural materials such as steel and concrete. The advantages of the FRP materials are high specific strength and stiffness, high corrosion resistance, right weight, etc. Among the various manufacturing methods, pultrusion process is one of the best choices for the mass production of structural plastic members. Since the major reinforcing fibers are placed along the axial direction of the member, this material is usually considered as an orthotropic (tranversely isotropic, more specifically) material. However, pultruded fiber reinforced plastic structural members have low modulus of elasticity and are composed of orthotropic thin plate components the members are prone to buckle. Therefore, stability is an important issue in the design of the pultruded FRP structural members. In this paper, the buckling of orthotropic plates and the local buckling of pultruded FRP structural members are investigated by following the previous research results and the local buckling strength of the member produced in the domestic manufacturer is found.

• Radiation Oncology Journal
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• v.15 no.3
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• pp.263-268
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• 1997

Purpose : Authors designed a customized Small Bowel Displacement System (SBDS) to displace the small bowel from the Pelvic radiation fields and minimize treatment-related bowel morbidities. Materials and Methods : From August 1995 to Mar 1996. 55 consecutive patients who received pelvic radiation therapy with the SBDS were included in this study. The SBDS consists of a customized styrofoam compression device which can displace the small bowel from the radiation fields and an individualized immobilization abdominal board for easy daily setup in prone position After opacifying the small bowel with Barium3, the patients were laid Prone and posterior-anterior (PA) and lateral (LAT) simulation films were taken with and without the SBDS. The areas of the small bowel included in the radiation fields with and without the SBDS were compared. Results : Using the SBDS, the mean small bowel area was reduced by $59\%;on\;PA\;and\;51\%$ on LAT films (P=0.0001). In six Patients (6/55. $11\%$), it was Possible that no small bowel was included within the treatment fields. The mean upward displacement of the most caudal small bowel was 4.8 cm using the SBDS. Only $15\%$ (8/55) of patients treated with the SBDS manifested diarrhea requiring medication. Conclusion : The SBDS is a novel method that can be used to displace the small bowel away from the treatment portal effectively and reduce the radiation therapy morbidities. Compliance with setup is excellent when the SBDS is used.