• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.248-251
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• 2004

This study was performed to propose the minimum thickness of RC slab that satisfies constructibility, fatigue safety, and serviceability requirements such as deflection control. Three different minimum thicknesses are calculated using concrete shear and rebar fatigue formulas, and deflection control, respectively, and checked by constructiblity. The maximum of these three minimum thicknesses is proposed as the minimum thickness of RC slab, which shows that the minimum thickness requirement of RC slab from Korean Bridge Design Code can be thinner than now.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.105-108
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• 2000

With exact analysis of cracks in RC beam, present or past stress states can be traced. For analysis of Flexural cracks, experiments are carried out focusing on variation of crack widths and crack spacing due to stress, beam properties. The crack width expectation formulas of each code are compared and initial crack spacing expectation formula is proposed.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.11-20
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• 1993

In this paper, the asymtotic performance of a multiple trellis coded differential MPSK modulation over a satellite land mobile communication channel characterized by additive white Gaussian noise (AWGN) and fading is presented. Simple formulas for the bit error probability are derived for systems using differential MTCM over Rician and Rayleigh fading channel. Also are given numerical results which are more indicative of the actual system performance. Finally, the comparisons with results previously obtained for the uncoded and conventional trellis coded modulation are provided.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.252-255
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• 2000

In this paper, a fast pseudo-noise (PN) code acquisition with novel adaptive architecture is presented in direct-sequence spread- spectrum (DS-SS) systems. Since an existing acquisition system has a fixed correlation tap size and threshold value, this system cannot adapt to various mobile communication environments and results in a low detection probability or a high false alarm rate and long acquisition time. Therefore, if a correlation tap size and a threshold value can be controlled adaptively according to received signals, problems of ail existing system will be solved. The system parameter varies adaptively by using constant false alarm rate (CFAR) algorithm well known in a field of detection and proposed signal-to-noise ratio (SNR) measurement system. By deriving formulas of the proposed system, the performance is analyzed.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.1
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• pp.1-7
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• 1991

Degradation of communication quality is due to transmission error rather than quantization noise when DPCM signal is transmitted over a heavily noise channel. The communication quality can be improved by employing an error correcting code to the DPCM signal transmission over such a channel. We considered both quantization noise and transmission error simultaneously in evaluating the signal to noise ratio. To efficiently improve the signal to noise ratio, we analyze the unequal symbol error probability of convolutional code, and encoded to more protect significant symbols from channel errors than least ones, so that the signal to noise ratio is improved. We derived related formulas and also made computer simulations.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.33-36
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• 2008

In Korean Building Code 2005(KBC-2005), the Seismic Zone Factor is regulated by separating the seismic zone into two part. This seismic zone factor is not matched to regional seismic characteristics of our country because the factor is based on International Building Code 2000 (IBC-2000) of USA. This study inquiry for having a sufficient grasp of the seismic characteristics of south Korea region and appling for the seismic cope plan. We have collected and analyzed earthquake record happened in domestic region. There are two kinds of earthquake record. One is Historical earthquake data, another is Instrumental earthquake data. I used Instrumental earthquake record data which reliance is higher than historical earthquake data for proposing attenuation formulas by analyzing a correlation the epicenter and the distance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.1
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• pp.93-100
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• 2000

The purpose of this study is to investigate the shear behavior of reinforced concrete beams according to small shear span-depth ratio between a/d=1.5, 2.8, 3.6. In general, shear strength of reinforced concrete beams is dependent on the compressive strength of concrete the longitudinal steel ratio, the shear span-depth ratio and shear reinforcement. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns, fracture modes. The load versus strain and load versus deflection relations were obtained from the static test. The test results on shear strength were compared with results obtained by the formulas of ACI code 318-95. The shear strength of reinforced concrete beams exceeded those predicted following present ACI code 318-95(11-6).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.768-778
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• 2019

The ability to calculate aerodynamic heating and surface temperature is essential to ensure proper design of aircraft components in high speed flight. In this study, various empirical formulas for efficiently calculating aerodynamic heating of aircraft were first analyzed. A simple computational code based on empirical formulas was developed and then compared with commercial codes; ANSYS FLUENT based on the Navier-Stokes-Fourier equation, and ThermoAnalytics MUSES based on an empirical formula. The code was found to agree well with the results of FLUENT in the wall and stagnation point temperatures. It also showed excellent agreement with MUSES, within 1% and 5% in temperature and heat flux, respectively.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.423-438
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• 2018

This pioneer study focuses on finite element modeling and numerical modeling of three types of Reinforced Concrete Haunched Beams (RCHBs). Firstly, twenty RCHBs, consisting of three types, and four prismatic beams which had been tested experimentally were modeled via a nonlinear finite element method (NFEM) based software named as, ATENA. The modeling results were compared with experimental results including load capacity, deflection, crack pattern and mode of failure. The comparison showed a good agreement between the results and thus the model used can be effectively used for further studies of RCHB with high accuracy. Afterwards, new mechanism modes and design code equations were proposed to improve the shear design equation of ACI-318 and to predict the critical effective depth. These equations are the first comprehensive formulas in the literature involving all types of RCHBs. The statistical analysis showed the superiority of the proposed equation to their predecessors where the correlation coefficient, $R^2$ was found to be 0.89 for the proposed equation. Moreover, the new equation was validated using parametric and reliability analyses. The parametric analysis of both experimental and predicted results shows that the inclination angle and the compressive strength were the most influential parameters on the shear strength. The reliability analysis indicates that the accuracy of the new formulation is significantly higher as compared to available design equations and its reliability index is within acceptable limits.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.4 s.56
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• pp.148-158
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• 2009

Firstly the problems of existing foreign code concerning wheel load distribution factor for skew box girder bridges have been examined, and the main parameters which have effects on wheel load distribution factors are evaluated in this study. Further finite element analyses on various skew steel box girder bridges are carried out. Based on the analysis results, formulas to determine wheel load distribution factors are proposed using multiple regression analysis. It is found when using the proposed formulas in this study weak points of existing specifications could be improved and also time spent at structural analysis should be saved a lot, so that the validity and practicality could be verified.