• Wind and Structures
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• v.31 no.6
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• pp.549-560
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• 2020

Methods for stochastic simulation of non-Gaussian wind pressure have increasingly addressed the efficiency and accuracy contents to offer an accurate description of the extreme value estimation of the long-span and high-rise structures. This paper presents a linear prediction and z-transform (LPZ) based Cumulative distribution function (CDF) mapping algorithm for the simulation of multivariate non-Gaussian fluctuating wind pressure. The new algorithm generates realizations of non-Gaussian with prescribed marginal probability distribution function (PDF) and prescribed spectral density function (PSD). The inverse linear prediction and z-transform function (ILPZ) is deduced. LPZ is improved and applied to non-Gaussian wind pressure simulation for the first time. The new algorithm is demonstrated to be efficient, flexible, and more accurate in comparison with the FFT-based method and Hermite polynomial model method in two examples for transverse softening and longitudinal hardening non-Gaussian wind pressures.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.813-814
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• 2005

• Journal of the Korean earth science society
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• v.28 no.5
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• pp.585-597
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• 2007

The characteristics of the rainfall events on the Korean peninsula have been investigated by means of regional and global observational data collected from 1954 to 2004 with an emphasis on extreme cases $80\;mm\;day^{-1}$. According to our analysis, long-term annual rainfall anomalies show an increasing trend. This trend is pronounced in the month of August, when both the amount of monthly rainfall and the frequency of extreme events increase significantly. Composite maps on August during the 8 wet years reveal warm SST anomalies over the eastern Philippine Sea which are associated with enhanced convection and vertical motion and intensified positive SLP over central Eurasia during August. The rainfall pattern suggests that the most significant increase in moisture supply over the southern parts of China and Korea in August is associated with positive SLP changes over Eurasia and negative SLP changes over the subtropical western Pacific off the east coast of south China. The frequent generation of typhoons over the warm eastern Philippine Sea and their tracks appear to influence the extreme rainfall events in Korea during the month of August. The typhoons in August mainly passed the western coast of Korea, resulting in the frequent occurrence of extreme rainfall events in this region. Furthermore, anomalous cyclonic circulations over the eastern Philippine Sea also promoted the generation of tropical cyclones. The position of pressure systems - positive SLP over Eurasia and negative SLP over the subtropical Pacific - in turn provided a pathway for typhoons. The moisture is then effectively transported further north toward Korea and east toward the southern parts of China during the extreme rainfall period.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.459-473
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• 2008

This study investigated typhoon characteristics that provoke precipitation which is much attacking periodically in our country, and calculated probability precipitation of extreme rainfalls using Empirical Simulation Technique. The typhoon influenced in Korea was happened 3.18 times per, and year exposed to affect Korea during 107 hours. The depth of precipitation with the typhoon was different according to observation points. The extreme precipitation of typhoon events has analyzed by change and trend analyses. In the results, mean and standard deviation of extreme rainfall has been increasing than the past events in some areas. Also, About 143 typhoons influenced Korea was applied in EST techniques using center position, central pressure, time precipitation data using rainfall observatory in Korea. Therefore, we applied EST techniques and calculated probability precipitation. In the results, Jeonla-do, Gyeongsang-do and Gangwon-do will have heavy rain with typhoon events in high probability.

• Journal of the Korean Geographical Society
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• v.49 no.1
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• pp.32-44
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• 2014

This study aimed to analyze the characteristic of the distribution of minimum temperature during January in the central region of South Korea and to investigate causes for the occurrence of extreme minimum temperature in Cheorwon. January temperature distribution data which were collected from 25 weather stations in central area from 1991 to 2010 were investigated, and the difference of temperature between Cheorwon and the other stations in central region, such as Chuncheon, Hongcheon, Bonghwa, Daegwallyoung, Wonju and Jecheon were analyzed by the type of atmospheric pressure system. Daily mean temperature and mean of daily minimum temperature appear to be low at Cheorwon and at the sites in high altitudes, but the frequency of extreme cold wave such as below $-15^{\circ}C$ is also noticeable in Cheorwon. When the Siberian High has expanded and migratory anticyclone has moved onto the north of the Korean Peninsula, the temperature at Cheorwon is relatively low. Furthermore it shows a lesser difference between Cheorwon and the compared stations when the migratory anticyclone affected the area, even at basin like Bonghwa, Jecheon more lower than Cheorwon.

• Tribology and Lubricants
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• v.14 no.2
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• pp.57-62
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• 1998

When lubricants is used under severe running conditions, their tribological characteristics are very important. We have studied the lubricating oil viscosity, kinds of additives and their amounts, and lubricating oil temperatures were changed. In order to study the effect of oil temperature on the wear of the surface, the temperature of the oil was changed for the same sample. Moreover, the temperatures of three kinds of oils which have very different viscosities at room temperature, were varied between 6$0^{\circ}C$ and 115$^{\circ}C$ while the oil viscosity was unchanged. It was shown from the test results that surface wear is not greatly affected by the amount of ZnDTP (Zinc dialkyl dithio phosphate) antiwear agent, but EP (Extreme pressure) additives are less effective against wear than ZnDTP additives. The viscosity of lubricating oil and its temperature greatly affect the wear of the surface. Combining all the wear data with those of the surface strength, it was observed that the higher the load, the wider the scratching of wear, and also in the case of the same running load, the lower the wear, the longer the life of the surface strength.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.2
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• pp.57-62
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• 2007

The lubricational characteristics about friction wear has an effect on the material quality of surface. In this paper, we studied the lubricational characteristics through the surface modification experiment by spray coating the surface with $MoS_{2}$ and PTFE solid lubricants. In the case of $MoS_{2}$ and PTFE coating, the friction coefficient of Journal is lower than that for noncoating so the friction characteristics is excellent. In particular, the beginning characteristics of $MoS_{2}$ coating is excellent, and in the case of PTFE coating, seizure dose not appear seizure. $MoS_{2}$ and PTFE coating are excellent in the extreme pressure at high load. The wear characteristics is excellent in the following order; PTFE < $MoS_{2}$ < Non Coating. For Non coating, seizure appears at the beginning due to the heat, but in the case of $MoS_{2}$ and PTFE coating, it will have the excellent heat stability even at high temperature.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.807-811
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• 2002

In this work, we investigated the deposition behavior of Mo/Si multilayer thin film structures simulated by a PVD process simulator based on Monte Carlo method to assist the optimized fabrication of the high quality mask in EUVL(Extreme Ultra-Violet Lithography) process. The shape of simulated thin film structures turned out to be largely dependent on the gas pressure(1∼30 mTorr), the target-substrate distance(1∼30 cm) and the diffusion length(1∼10 nm). From the simulation studies, it was predicted that relatively uniform thin film structures can be fabricated by decreasing gas pressure and increasing the target-substrate distance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.432-436
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• 2007

We have studied on the tribological characteristics of Plasma Vapour Deposition(PVD) coating method in Automotive Structural Materials. Coating materials were deposited by the Titanium carbide(TiC) and Titanium nitride(TiN). An experimental process was established to determine the tribological characteristics of friction and wear behaviour with the variation of applied load, temperature and the time with the Falex friction and wear test machine. It was improved that when the surface modification of hard coatings(TiC, TiN) was deposited steel, the tribological characteristics become better. It is argued that it is improved because of excellence of the anti-wear, the extreme pressure properties and tile heat stability.

• Wind and Structures
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• v.8 no.5
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• pp.357-372
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• 2005

Mean and extreme pressure distributions on a large cantilevered flat roof model are measured in a boundary layer wind tunnel. The largest peak suction values are observed from pressure taps beneath conical "delta-wing type" corner vortices that occur for oblique winds, then the characteristics and causes of the local peak suctions are discussed in detail. Power spectra of fluctuating wind pressures measured from some typical taps located at the roof edges under different wind directions are presented, and coherence functions of fluctuating pressures are also obtained. Based on these results, it is verified that the peak suctions are highly correlated with the conical vortices. Furthermore, according to the characteristics of wind loads on the roof, an aerodynamic solution to minimize the peak suctions by venting the leading edges and the corners of the roof is recommended. The experimental results show that the suggested strategy can effectively control the generation of the conical vortices and make a reduction of 50% in mean pressures and 25% in extreme local pressures at wind sensitive locations on the roof.