• Journal of Positioning, Navigation, and Timing
• /
• 제4권2호
• /
• pp.87-95
• /
• 2015

In this study, the temporal and spatial variation in precipitable water vapor (PWV) was analyzed for typhoon Ewiniar which had made landfall in the Korean peninsula in 2006. To make a contour map of PWV, zenith total delay (ZTD) was calculated using about 60 GPS permanent stations in Korea, and the pressure and temperature data of nearby AWS stations were interpolated and applied to the equation for calculating the PWV. While Typhoon Ewiniar was migrating north from the southern coast to the eastern coast of Korea, the PWV migrated showing a spatial distribution similar to that of rainfall. Also, the fluctuating pattern of the normalized PWV was analyzed, and the moving speed of the PWV was estimated using the delay time of the increase/decrease pattern in the eight-test stations. The result indicated that the moving speed of the PWV was about 35 km/h, which was similar to the average moving speed of the typhoon (38.9 km/h).

• 대기
• /
• 제20권3호
• /
• pp.343-353
• /
• 2010

A regional wind network with complex surface conditions must be designed with sufficient space and time resolution to resolve the local circulations. In this study, the spatial variations of the wind field observed in the Seoul and Jeju regional networks were evaluated in terms of annual, seasons, and months to assess the spatial homogeneity of wind fields within the regional networks. The coherency of the wind field as a function of separation distance between stations indicated that significant coherency was sometimes not captured by the network, as inferred by low correlations between adjacent stations. A meso-velocity scale was defined in terms of the spatial variability of the wind within the network. This problem is predictably most significant with weak winds, dull prevailing wind, clear skies and significant topography. The relatively small correlations between stations imply that the wind at a given point cannot be estimated by interpolating winds from the nearest stations. For the Seoul and Jeju regional network, the meso-velocity scale has typically a same order of magnitude as the speed of the network averaged wind, revealing the large spatial variability of the Jeju network station imply topography and weather. Significant scatter in the relationship between spatial variability of the wind field and the wind speed is thought to be related to thermally-generated flows. The magnitude of the mesovelocity scale was significantly different along separation distance between stations, wind speed, intensity of prevailing wind, clear and cloudy conditions, topography. Resultant wind vectors indicate much different flow patterns along condition of contributing factors. As a result, the careful considerations on contributing factors such as prevailing wind in season, weather, and complex surface conditions with topography and land/sea contrast are required to assess the spatial variations of wind field on a regional network. The results in the spatial variation from the mesovelocity scale are useful to represent the characteristics of regional wind speed including lower surface conditions over the grid scale of large scale atmospheric model.

• 한국환경과학회지
• /
• 제9권6호
• /
• pp.475-482
• /
• 2000

The purpose of this study is to find out the temporal and spatial characteristics of the diurnal wind variation between coastal and inland areas using the hourly wind data of 58 AWS-stations in the South Korea which are collected during the 10 years from 1980. Diurnal variation is investigated by using the Fast Fourier Transform(FFT), and the wind direction in investigated by comparing C(sub)r with C(sub)v represented the constancy of wind. For the scalar wind speed, the maximum wind speed occurs in the daytime 14h to 16h. The maximum diurnal amplitude at coastal areas occurs from 12h to 16h, and is about 2 hours faster than that at inland areas. Vector mean wind speed is strong at coastal areas and Chupungnyong, Kumi, Taegu of inland areas. The diurnal variation ellipses make a right angle with coastline show that the land and sea breezes are prevailing. The constancy of wind is strong at all observations in January. In the relationship between $C_r and C_v, C_v is higher than C_r$.

• 한국안전학회지
• /
• 제18권2호
• /
• pp.132-138
• /
• 2003

고속철도교량에서 장대레일의 사용은 연결부 근처에서 레일과 교량상판사이의 비선형 거동으로 인하여 부가적인 응력을 유발한다. 고속철도 교량의 지진응답해석에서, 구조물응답은 지반운동특성에 매우 영향을 많이 받으므로, 지반운동의 위치에 따른 변화가 구조물의 응답에 영향을 미치게 되고, 그 결과는 레일에 응력을 유발하게 된다. 또한 고속철도에서 사용지진 수준의 지진발생 시에 열차의 긴 제동거리가 필요하므로 열차의 안전한 정지를 확보하는 것이 요구된다. 이러한 관점에서 장대레일에 의해 부가적으로 발생하는 응력, 지반운동의 공간변화에 대한 구조물 응답의 영향, 그리고 안전하게 정지하기 위해 필요한 열차의 제동거리 등의 사항이 레일의 응력해석에 고려될 필요가 있다. 본 논문에서는 지진하중을 받는 고속철도교량의 장대레일 응력해석을 위하여 제동하중, 지반운동의 공간적 변화, 그리고 레일의 재료 비선형을 고려한 시간영역에서의 비선형 동적해석방법을 개발하고 적용하였다. 제시된 방법을 한국고속철도의 특정부지에 적용하여 지반운동의 공간변화에 따른 응답의 타당성을 보였다.

• 한국공간구조학회논문집
• /
• 제17권1호
• /
• pp.77-84
• /
• 2017

Vortex-induced vibration and instability vibration of tall buildings are very important fluid-structure interaction phenomenon, and many fundamental questions concerning the influence of body movement on the unsteady aerodynamic force remain unanswered. For tall buildings, there are two experimental methods to investigate the characteristics of unsteady aerodynamic forces, one is forced vibration method and the other is free vibration method. In the present paper, a free vibration method was used to investigate the unsteady aerodynamic force on tall building whose aspect ratio is 9 under boundary layer simulating city area. Wind pressures on surfaces and tip displacements were measured simultaneously, and the characteristics of tip displacements and generalized forces were discussed. It was found that variation of across-wind displacements showed different trend between the case when wind speed increases and wind speed decreases, and the fluctuating generalize forces in across-wind direction of vibrating model are larger than that of static model near the resonant wind speed and approach to the static value. And for higher wind speed range, there were two peaks in across-wind power spectra of generalize forces of vibrating model, which means that two frequency components are predominant in unsteady aerodynamic forces.

• 대기
• /
• 제18권4호
• /
• pp.493-506
• /
• 2008

In order to examine the variational features of Asian dust outbreak in recent years, observed WMO synop data were employed for the period from 1996 to 2007. We first divided Asian dust source regions into four subregions; 1) Taklamakan, 2) Gobi, 3) Inner Mongolia-Manchuria and 4) Loess, and the meteorogical variables such as wind speed, precipitation and threshold wind speed observed during the Asian dust outbreak period were compared with those during non-Asian dust period. The results showed that temporal variation of occurrence frequency of dust outbreak had a strong positive correlation with the frequency of strong wind speed and low precipitation in each of the 4 source regions. Spatial distributions of frequency of dust occurrence after 2002 showed increasing trend in Gobi and Inner Mongolia-Manchuria but decreasing trend in Loess region. This is showing a shift in main source region toward Northwest, especially since 2003.

• 한국실내디자인학회논문집
• /
• 제23권2호
• /
• pp.108-116
• /
• 2014

This study is based on the arguments of Sofia Sarah and concept of 'Sequence Narrative' of Nigel Coates, the founder of Nato. Specifically, this study was conducted under the premise that narrative exhibition space will affect the engagement of viewers. As a result of this study, a method of analyzing a science museum's exhibition space was presented using the narrative structure and the following attributes of visuals: sequence of viewing; spatial tension; spatial pace. The findings are as follows. In terms of 'spatial tension', the exhibiton space with the following progression was more likely to provide viewers with in-depth experience: 'raise of tension' - 'change of pace' - detente.' Although the limited sample doesn't lead to verification of the analysis method and conclusion of its significance, the following was clearly revealed: Exhibiton space that utilizes the structure and attributes of a narrative that provides progression and dramatic tension, as if the viewers were watching a film, is more likely to offer in-depth experience than other spaces. In terms of 'phase transition', the following was revealed: Pace variation around the space with the strongest spatial tension could affect the concentration and engagement of viewers. It suggests the following fact: Spatial rhythm and speed variation in the area with the strongest visual emphasis encourage viewers to feel the spatial changes, maintain their concentration, and continue their viewing.

• 한국환경과학회지
• /
• 제29권1호
• /
• pp.1-13
• /
• 2020

Recently, a heavy rainfall with high spatial variation occurred frequently in the Korean Peninsula. The meteorological event that occurred in Busan on 3 May 2016 is characterized by heavy rain in a limited area. In order to clarify the reason of large spatial variation associated with mountain height and location of low level jet, several numerical experiments were carried out using the dynamic meteorological Weather Research and Forecasting (WRF) model. In this case study, the raised topography of Mount Geumjeong increased a barrier effect and air uplifting due to topographic forcing on the windward side. As a result, wind speed reduced and precipitation increased. In contrast, on the downwind side, the wind speed was slightly faster and since the total amount of water vapor is limited, the precipitation on the downwind side reduced. Numerical experiments on shifting the location of the lower jet demonstrated that if the lower jet is close to the mountain, its core becomes higher due to the effect of friction. Additionally, the water vapor convergence around the mountain increased and eventually the precipitation also increased in the area near the mountain. Hence, the location information of the lower jet is an important factor for accurately predicting precipitation.

• 한국대기환경학회지
• /
• 제14권3호
• /
• pp.177-190
• /
• 1998

The concentrations of air pollutants In large cities such as Pusan area have been increased every year due to the increasing of fuels consumption at factories and by vehicles as well as the gravitation of the population. In addition to the pollution sources, time and spatial variation of air pollutants concentration and meteorological factors have a great influence on the air pollution problem. Especially , its concentration is governed by wind direction, wind speed, precipitation, solar radiation, temperature, humidity and cloud amounts, etc. In this study, we have analyzed various data of meteorological factors using typical patterns of the air pressure to investigate how the concentration of air pollutants is varied with meteorological condition. Using the relationship between meteorological factors (air temperature, relative humidity, wind speed and solar radiation) and the concentration of air pollutants (SO2, O3) , experimental prediction formulas for their concentration were obtained. Therefore, these prediction formulas at each meteorological factor in a pressure pattern may be roughly used to predict the air pollutants concentration and contributed to estimate the variation of its value according to the weather condition in Pusan city.

• 해양환경안전학회지
• /
• 제3권2호
• /
• pp.23-31
• /
• 1997

The results of high speed photography, acoustic emission detection and plasma UV radiation intensity measurement during CO2 laser welding of stainless steel 304 are presented. Video images with high spatial and temporal resolution allowed to observe the melt dynamics and keyhole evolution. The existence of a high speed melt flow which originated from the part of weld pool and flowed along the sides wall of keyhole was confirmed by the slag motion on the weld pool. the characteristic frequencies of flow instability and keyhole fluctuations at different welding speed were measured and compared with the results of Fourier analyses of temporal acoustic emission (AE) and light emission (LE) spectra. The experimental results were compared with the newly developed numerical model of keyhole dynamics. (The model is based on the assumption that the propagation of front part of keyhole into material is due to the melt ejection driven by laser induced surface evaporation.) The calculations predict that a high speed melt flow is induced at the front part of keyhole when the sample travel speed exceeds several 10mm/s. The numerical analysis also shows the hump formation on the front keyhole wall surface. Experimentally observed melt behavior and transformation of the AE and LE spectra with variation of welding speed are qualitatively in good agreement with the model predictions.