• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.569-572
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• 2008

This study carried out to evaluate the quality deviation according to Premixed and Non-Premixed cement for normal and high strength concrete using blast furnace slag and fly ash. The results of experiment are founded that concrete using premixed cement have more performance than non-premixed cement at a point of view for the quality deviations both strength and Chloride ion diffusion. Therefore, it is desirable that premixed cement should be used to decrease strength deviation in high strength concrete and durability deviation in normal strength concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2A
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• pp.115-120
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• 2011

The strength of reinforced concrete members has uncertainty from material properties of, concrete and reinforcements, section dimensions, and construction errors and so on. The accurate evaluation of these uncertainties is necessary to assure the reasonable safety. The uncertainties should be taken into account in design using structural reliability theory which requires probabilistic models for such uncertainties. In current Korean design code, most reliability evaluations were performed based on foreign data because of lack of local data. In this paper, the probabilistic models for yield strength of reinforcements were developed based on local data. The effects of various factors, nominal yield strength, diameter of reinforcements, and companies, on the models are also examined. According to data analysed, the effects of those factors are not significant. The probability model for yield strength of reinforcements in Korea can be expressed with Beta distribution based on collected data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.223-230
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• 2012

The strength of brittle material has commonly been characterized by a normal distribution or Weibull distribution, but it may fit the gamma distribution for some material. The use of an extreme value distribution is proper when the largest values of a set of stresses dominate the failure of the material. This paper presents a formula for reliability estimation based on stress-strength interference theory that is applicable when the strength of material is distributed like a gamma distribution and the stress is distributed like an extreme value distribution. We verified the validity of the equation for the reliability estimation by examining the relationships among the factor of safety, the coefficient of variation, and the reliability. The required minimum factor of safety and the highest allowable coefficient of variation of stress can be estimated by choosing an objective reliability and estimating the reliabilities obtained for various factors of safety and coefficients of variation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.4
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• pp.61-71
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• 1987

Accelerated strength testing is a available method for quality control of concrete. This paper presents the improved hot water ($70^{\circ}C$) methods and discusses how these methods can be adapted for predicting 28 day strength. The strength results have been analyzed by statistical techniques and correlation between early and 28 day strength are showed by prediction line. The test results show that the methods proposed in this paper are usable to predict the potential quality of concrete with low variation and good relationship between two strengths.

• Journal of the Korean GEO-environmental Society
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• v.7 no.2
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• pp.33-42
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• 2006

Eighteen biotite granites on Andong area and twenty seven igneous rocks(diorite, granite, andesite, rhyolite) on Yeosu area were tested to evaluate the correlations between the uniaxial compressive strength values, as determined by the standard uniaxial compression test, and the corresponding results of the ultrasonic velocity. The variability of test results for each test was evaluated by calculating the coefficient of determination or variation. Results indicate that strong correlations exist between the results of uniaxial compression vs the point load, Schmidt hammer and ultrasonic velocity test. The correlation equations for predicting compressive strength using different methods are presented along with their confidence limits. Ultrasonic velocity test used provide reliable estimates of compressive strength.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.164-164
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• 2018

강우침식인자는 토양침식에 영향을 주는 한 인자이다. 강우침식인자는 강우강도, 강우량, 강우빈도 등과 같은 강우패턴으로 산정되는 값으로 기후변화로 인해 많은 지역에서 강우패턴의 변화가 관측되었기에 강우침식인자 또한 기후변화로 인한 변화가 예상된다. 한국의 강우의 시공간적인 변동성에 대한 연구는 많이 진행되었으나, 강우침식인자에 대한 연구는 아직까지 미흡한 상태이기 때문에 본 연구에서는 한국의 강우침식인자의 시공간적 변동성을 분석하였다. 강우강도, 강우량, 강우빈도, 강우지속기간 등 강우패턴을 결정하는 인자들 중 어떤 인자가 강우침식인자의 시간적인 변동성에 영향을 주는지 조사하였다. 시간적인 변동성을 조사하기 위해서 경향성 검사를 진행하였다. 적용된 경향성 검사는 Mann-Kendall test, 수정된 Mann-Kendall test, Block Bootstrapping Mann-Kendall test, T-test를 적용하였다. 검사결과 대부분의 지점에서는 강우침식인자에서는 경향성이 발견되지 않았다. 경향성이 발견된 지점에 대하여 경향성의 원인을 검토해본 결과, 복합적인 강우패턴 인자의 영향으로 인하여 강우침식인자의 경향성이 발생하는 것을 확인하였다. 강우패턴 인자 중에서는 유효강우사상의 강우량이 가장 큰 영향인자인 것을 확인 할 수 있었다.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.127-134
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• 2009

This study was performed to establish the process mean which is statistically satisfying the critical limit of deformation strength $(S_D)$, which is found to reflect rutting characteristics of asphalt mixture relatively well. The process means were determined using the critical $S_D$ values (3MPa for local highway and 4MPa for arterial highways), which were obtained from correlation analysis of APA and $S_D$ test data of actual highway projects, and coefficient of variation of 32 combinations of domestic mixtures. The process means of 3.2 MPa for local highway and 4.25 MPa for arterial highways were suggested when using 3 specimens (diameter of 100mm). However, since these values are based on the loading speed of 30mm/min, the higher values, 3.5 MPa for local highway and 4.5 MPa for arterial highways, were suggested, respectively, if the loading speed of 50mm/min is applied using the old Marshall machine, which should give higher test values.

• Digital Contents
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• no.7 s.146
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• pp.22-27
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• 2005

게임의 패러다임이 2D에서 3D로 변화하면서 모바일게임 시장도 대규모 지각변동 조짐이 뚜렷해지고 있다. 그동안 모바일게임 업계와 유선 게임업계간의 분명한 구분이 있었는데 최근 이러한 영토구분이 허물어지고 있다. 모바일게임 업계와 유선 게임업계간의 제휴 및 독자적인 3D게임 개발 등 3D 모바일게임 시장을 차기 수익원으로 판단, 업체마다 고강도의 시장 대응전략을 마련 중이다.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.80-85
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• 2013

This paper describes a probabilistic structural design method of composite propulsion system by comparing safety factor based on average value and allowable value with structural reliability. Generally, the required structural safety factor and reliability of composite pressure vessel are 1.5 and 0.999, respectively. In the case of structural design using average strength, the safety factor which satisfies the required structural reliability depends on the variation of fiber strength. However, the structural design using allowable value shows constant safety factor for the variation of fiber strength, because the allowable value of fiber strength is calculated by considering the variation of fiber strength. Through the analysis results, it was known that the fiber strength is the most important design random variable for the structural design of composite pressure vessel and the variation of fiber strength must be minimized to develop the high performance composite propulsion system.

• Journal of Korean Society of Disaster and Security
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• v.6 no.2
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• pp.49-56
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• 2013

In this paper, used by the boundary layer wind tunnel test, have conducted a series of wind tunnel experiments, i.e. test the mean velocity profile regarding the surface roughness, turbulence intensity and power spectrum measured by augmentation device. After that, to provide data relevant for the preliminary design step of tall building hazard fluctuating wind loads may be obtained fluctuating pressure coefficients, fluctuating pressure spectrum, autocorrelation coefficients by the boundary layer wind tunnel test. From the results of experiments, this study can be obtained conclusions as follows. 1. We know the fact that the mean velocity profile and the turbulence intensity are well fitted natural wind flow in the boundary layer wind tunnel. 2. The satisfactory agreement of velocity spectrum can be obtained from the compare of fluctuating power spectrum and Von Karman spectrum. 3. We know the fact that the fluctuating pressure spectrums distributed peak at 0.01 Hz-0.1 Hz in the windward surfaces and at 0.1 Hz in the leeward surfaces. 4. We know the fact that the autocorrelation coefficients distributed stationary random processes with application time of hazard fluctuating wind loads.