• Journal of Korea Water Resources Association
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• v.32 no.3
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• pp.247-254
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• 1999

The frequency analyses of annual maximum rainfall data for 22 rainfall gauging stations is Korea were performed. The method of moments (MOM), maximum likelihood (ML), and probability weighted moments (PWM) were used in parameter estimation. The GEV distribution was selected as an appropriate model for annual maximum rainfall data based on parameter validity condition, graphical analysis, separation effect, and goodness of fit tests. For the selected GEV model, spatial analysis was performed and rainfall intensity-duration-frequency equation was derived by using linearization technique. The derived rainfall intensity-duration-frequency equation can be used for estimating rainfall quantiles of the selected stations with convenience and reliability in practice.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2125-2129
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• 2007

본 연구에서는 영산강 하구언 배수갑문의 개방으로 대량의 담수가 방류될 경우 목포항 인근해역의 해수유동 변화와 이에 수반되는 부유물질/염분 농도의 시공간적인 변화를 파악하기 위해 방류조건과 확산성분별로 12가지의 계산 시나리오를 구성하고 MIKE21의 해수유동(HD)모듈과 오염 확산(AD)모듈을 이용하여 하구언 방류의 영향을 살펴보았다. 해수유동 모의결과, 배수갑문과의 거리에 따라 방류조건별로 수위와 유속이 최대 144.5cm, 175.6cm/sec까지 상승하였다. 특히 청계만 수역에서는 방류시기에 낙조시 유속이 최대 68.8cm/sec까지 감소해 방류에 따른 수위상승으로 낙조시 해수유출이 지체되는 것으로 판단된다. 부유물질 확산모의 결과, 목포 기준검조소를 기준으로 목포항 내부수역은 원활한 해수순환이 이루어지지 않아 각종 오염원 유입시 외해로 쉽게 확산되거나 희석되지 못하고 계속 정체되는 것으로 나타나 항내 오염이 심각하게 우려되며, 특히 연속적인 담수 방류와 방류량의 크기가 내부수역의 부유물질 농도 감소에 큰 영향을 미치는 것으로 판단됨에 따라 방류량이 작고 연속 방류가 행해지지 않는 비우기시의 오염은 더욱 심해질 것으로 판단된다. 방류조건별 염분농도 역시 방류량이 크고, 연속적인 담수 방류가 행해질 경우 농도가도 크게 감소하며 확산면적도 증가하였다.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.75-84
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• 2017

This study is concerned with the estimation of daily instantaneous maximum wind velocity in the meteorological major cities (selected each 17 points) during the yearly 1973-2016. The purpose of this paper is to present the turbulence statistic characteristics (probability distribution, correlation coefficient, turbulency intensity, shear velocity, roughness length, turbulence integral length, skewness, and kurtosis) of the daily instantaneous maximum wind velocity. In the processes of analysis, used observations data obtained at Korea Meteorological Adminstration (KMA). The estimation of non-Gaussian load effects for design applications has often been treated tacitly by invoking a conventional wind design load on the basis of Gaussian processes. This assumption breaks down when the instantaneous wind velocity processes exhibits non-Gaussianity. From the analysis results, the probability distribution of the daily instantaneous maximum wind velocity shows a very closed with non-Gaussian in the ensemble population 748, the correlation coefficient shows larger at inland area more than coastal area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3251-3259
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• 2014

This paper presents experimental and analytical research results to predict nonlinear flexural behavior of corroded reinforced concrete beams. For this purpose, a series of test and an analytical simulation using the Maaddawy's model were carried. Test specimens of total 12 RC beams were placed in accelerated corrosion status using salt water spray test chamber for 5 months and 10 months, after they were preloaded up to 30% and 60% of the maximum load corresponding to nominal flexural strength. The test results showed that flexural strength and ductility decreased to 5.4% and 43% at the most respectively due to breakdown of bond at the steel-concrete interface. Comparative study between the analytical predictions and the experimental results showed that the Maaddawy's model can be applied to predict a real corroded RC flexural members.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1631-1637
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• 2019

In this paper, we propose a low-complexity robust maximum likelihood (ML) receiver for generalized spatial modulation. The proposed receiver performs the transmit antenna partition to lower the computational loads. After we divide the transmit antenna combinations into two parts, one of which is "the likely TAC part," and the other of which is "the unlikely TAC part", based on the minimum mean square error (MMSE) filtering output. We first perform the maximum likelihood detection only in the likely TAC part. Then we evaluate the reliability of the solution found in the first search, and based its reliability we decide whether we continue the search in the unlikely TAC part. This partitioned search strategy maintains the performance of the conventional robust maximum likelihood receiver and simultaneously lowers computational loads. Through simulation, we found that our newly-proposed receiver achieves considerable gains over the conventional robust ML detector in terms of the computational loads while providing almost the same performance.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.47-55
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• 2008

This study was carried out to investigate and analyse the influence of maximum size of coarse aggregate and quality control of aggregate on the properties of shotcrete through the laboratory and field test. From the results of the test, as the maximum size of coarse aggregate decreased from 13 mm to 8 mm, plasticity property declined and compressive strength and dynamic modulus of elasticity of hardened concrete increased remarkably, so it was found that the aggregate size 8 mm was superior to 13, 10 mm in fluidity, constructability and durability. Therefore, it was advisable for well maximum size of coarse aggregate to apply to the 8mm aggregates through the Ready-mixed Method for quality control and minimum segregation.

• Journal of Korea Technology Innovation Society
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• v.20 no.1
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• pp.239-270
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• 2017

This paper examines the relationship between ownership structure and the intensity of R&D expenditures of a firm by analyzing the panel data composed of 553 manufacturing firms in KSE(Korea Stock Exchange) and KOSDAQ listed firms for the period of 2007-2014. The major findings are as follows; (1) Regarding the relationship between CEO stockholding and R&D intensity, we find the inverted-U shape relationship in KOSDAQ firms, consistent with the theoretical discussion and empirical studies on U.S. firms. The result suggests that management stockholding reduces agency problem at the R&D margin. On the contrary, the insignificant result in KSE firms seems to be due to the scant stockholding of most 'non-owner' CEOs. (2) Regarding the relationship between the largest shareholder's portion and R&D intensity, KSE firms exhibit negatively significant relationship, suggesting the existence of serious agency problem between the largest shareholder and the minor shareholders. This agency problem seems to be alleviated in KOSDAQ firms mainly because the founders with technology expertise are still in charge of the business. (3) Foreign investors seem to fail in effectively encouraging R&D expenditures in either KSE or KOSDAQ listed firms. This study contributes to the existing literature by showing for the first time that ownership structure affects R&D activities in different ways between KSE and KOSDAQ firms.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.39-49
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• 2017

The factor of safety (FOS) is commonly used as an index to quantitatively state the degree of safety of various rock structures. Therefore it is important to understand the definition and characteristics of the adopted FOS because the calculated FOS may be different according to the definition of FOS even if it is estimated under the same stress condition. In this study, four local factors of safety based on maximum shear stress, maximum shear strength, stress invariants, and maximum principal stress were defined using the Mohr-Coulomb and Hoek-Brown failure criteria. Then, the variation characteristics of each FOS along five stress paths were investigated. It is shown that the local FOS based on the shear strength, which is widely used in the stability analysis of rock structures, results in a higher FOS value than those based on the maximum principal stress and the stress invariants. This result implies that the local FOS based on the maximum shear stress or the stress invariants is more necessary than the local FOS based on the shear strength when the conservative rock mechanics design is required. In addition, it is shown that the maximum principal stresses at failure may reveal a large difference depending on the stress path.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.611-619
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• 2021

Porous asphalt pavement (PAP) has many functions, such as reducing accidents and decreasing noise. On the other hand, vulnerability is inevitable because PAP contains approximately 20% porosity. This study evaluated the effects of the maximum aggregate size (MAS), temperature, and porosity on the PAP durability. The indirect tensile strength measures durability. This study tested the samples that stayed dry and were moisturized by freezing and thawing for mixtures having the same porosity of 20% and MAS of 13mm, 10mm, and 8mm. The same test was performed on a mixture of 20% and 22% voids made of the same material with a MAS of 10mm. As a result, for 20% porosity, significant differences in the changes in MAS and temperature were found. A clear difference was observed between 8mm and 13mm under dry conditions, but there were no other significant differences in the MAS change. Furthermore, there was a clear difference in temperature for the change in porosity and temperature, but the gap in 2% porosity at 20% did not show a clear difference. Therefore, it is necessary to develop a more durable PAP through quantitative evaluations of the factors affecting the PAP durability.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.257-267
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• 2008

Results of seventy-seven specimens tested by this study and previous research were collected and evaluated to propose the flexural strength and shear strength for flexural members with steel fiber concrete. For strength evaluation, structural parameters such as compressive strength, steel fiber content, tensile reinforcement ratio, and shear span to effective depth ratio are involved. The proposed equations for flexural and shear strength are regarded to give a good prediction for the strength of steel fiber reinforced composite and/or RC beams to compare with equations by previous researchers. Especially, the proposed shear strength equation in this study shows the lowest the mean value, the coefficient of variation and the error ratio among predictions by several equations. Therefore, equations for shear strength and flexure strength, which are proposed in this study are to be useful measure to predict the actual behavior and failure mode of steel fiber reinforced composite beams.