• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.399-399
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• 2021

최근 전세계적으로 발생하고 있는 기후변화로 인해 가뭄, 홍수, 태풍 등 자연재해의 빈도가 증가하고 있다. 특히, 강수량의 변동성이 커지면서 가뭄과 홍수가 단기간에 번갈아 가며 발생하는 경우가 자주 발생하고 있다. 가뭄과 홍수가 짧은 기간 동안에 교차해서 발생하는 급변사상은 예측하기 어려우며, 갑작스럽게 중첩되는 재난으로 인명과 재산피해 뿐 아니라 생태계에까지 심각한 영향을 미칠 것이다. 본 연구에서는 일 강수량 자료를 바탕으로 표준가중평균강수지수(Standard Weighted Average Precipitation, SWAP)를 산정하고 한강 유역의 가뭄-홍수 급변사상에 대한 특성을 분석하였다. 1966년부터 2018년까지의 한강유역 중권역별 면적평균강수량과 가중치, 이전 강수량의 영향을 받는 일수를 바탕으로 SWAP를 산정하였다. SWAP 지수가 10일 연속 -1 미만일 때를 가뭄이라 정의하고, 이후 SWAP 지수가 7일 연속 0.5 이상이면 가뭄사상이 종료된다고 판정하였다. 또한 SWAP 지수가 10일 연속 +1 초과일 때를 홍수라고 정의하고, SWAP 지수가 7일 연속 -0.5 이하가 되면 홍수사상이 종료된다고 판정하였다. 가뭄-홍수 급변사상이란 가뭄의 종료시점과 홍수의 시작시점의 차이가 5일 이내일 경우에 해당한다. 급변사상의 전·후로 강수량이 얼마나 급격하게 차이 나는지를 판단하기 위하여 급변 시점 전·후 5일의 누적 SWAP 지수인 심각도 K(Severity)를 분석지표로 활용하였다. K를 통해 한강유역 가뭄-홍수 급변사상의 시·공간적 분포를 분석하고 미래의 급변사상의 발생가능성을 예측할 수 있다. 본 연구 결과, 한강 유역의 24개 중권역 중에서 18개의 중권역이 가뭄-홍수 급변사상의 심각도가 점점 상승하는 추세이고, 가장 심각도 상승폭이 높은 중권역은 홍천강(1014)으로 첫 사상인 1967년부터부터 2015년의 마지막 사상까지 약 55% 정도 상승하였다.

• Journal of the Korean Society of Radiology
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• v.18 no.2
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• pp.153-159
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• 2024

In X-ray projection, Unskilled radiologists become skilled through fail exam. This causes the patient to be exposed to unnecessary radiation. In this study, pre-position unskilled radiologic technologist presented ways to improve clinical proficiency. presented a skull lateral x-ray projection practice method using visual, spatial, and assistive devices. In addition, the accuracy and usefulness of the use of assistive devices were evaluated. When X-ray images were taken based on learning, the rotational spacing, which indicates image distortion, was 7.85 ± 1.45 mm and the tiliting spacing was 4.84 ± 0.5 mm. When practicing using visual aids, the rotational spacing is 4.4 ± 0.76 mm and the inclination spacing is 3.01 ± 0.87 mm. using a spatial compensation device, the rotational spacing is 5.2 ± 0.69 mm and the tiliting spacing is 3.33 ± 0.61 mm. Skull lateral X-ray Image distortion caused by empirical photography practice decreased by 5.4%, but image distortion caused by tilting increased by 1.2%. When practicing using a visual assistive devices, the degree of rotational spacing by 40.1% and the tiliting spacing decreased by 30.7% compared to the empirical x-ray exposure practice. When using spatial assistive devices, the rotation interval was reduced by 41.7% and the tilting interval by 23.7% compared to conventional empirical x-ray exposure practice. Therefore, if an unskilled radiologist practices using visual and spatial aids,the accuracy will be improved in skull lateral x-ray projection.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.3
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• pp.220-235
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• 2020

Heat wave generation in cities is basically affected by global warming, but it is further exacerbated by the impact of artificial heat emission and heat accumulation in the city. In particular, the effects of urban heat waves directly affect the occurrence of tropical nights. Basically, however, the choice of countermeasures against tropical nights is very limited compared to the daytime heat wave response. The purpose of this study was to analyze the characteristics of cold air flow at night as a countermeasure against tropical nights in Daegu Metropolitan City and to suggest its spatial applicability. As a research method, the spatial characteristics (flow velocity, flow rate, flow direction and range) of cold air flow in Daegu were quantitatively analyzed using KLAM_21, a cold air flow analysis program. As a result of the analysis, it was found that cold air generation and flow in the surrounding mountains of Daegu Metropolitan City was very active, but the inflow was limited to the urban area, which has tropical nights. However, it has been shown that the flow of cold air flowing from the surrounding mountains is very active in some urban areas, so it has spatial conditions that are very effective in countering tropical nights. If these spatial conditions are used for the urban planning, it will be very useful to develop countermeasures for tropical nights.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.789-799
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• 2007

In this paper, we propose a stochastic finite element formulation which takes into account the randonmess in the material and geometrical parameters. The formulation is proposed for plate structures, and is based on the weighted integral approach. Contrary to the case of elastic modulus, plate thickness contributes to the stiffness as a third-order function. Furthermore, Poisson's ratio is even more complex since this parameter appears in the constitutive relations in the fraction form. Accordingly, we employ Taylor's expansion to derive decomposed stochastic field functions in ascending order. In order to verify the proposed formulation, the results obtained using the proposed scheme are compared with those in the literature and those of Monte Carlo analysis as well.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.3
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• pp.37-48
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• 2010

The purpose of this paper is to evaluate how the rainfall field effect on a runoff simulation using grid radar rainfall data and ground gauge rainfall. The Gwangdeoksan radar and ground-gauge rainfall data were used to estimate a spatial rainfall field, and a hydrologic model was used to evaluate whether the rainfall fields created by each method reproduced a realistically valid spatial and temporal distribution. Pilot basin in this paper was the Naerin stream located in Inje-gun, Gangwondo, 250m grid scale digital elevation data, land cover maps, and soil maps were used to estimate geological parameters for the hydrologic model. For the rainfall input data, quantitative precipitation estimation(QPE), adjusted radar rainfall, and gauge rainfall was used, and then compared with the observed runoff by inputting it into a $Vflo^{TM}$ model. As a result of the simulation, the quantitative precipitation estimation and the ground rainfall were underestimated when compared to the observed runoff, while the adjusted radar rainfall showed a similar runoff simulation with the actual observed runoff. From these results, we suggested that when weather radars and ground rainfall data are combined, they have a greater hydrological usability as input data for a hydrological model than when just radar rainfall or ground rainfall is used separately.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.2
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• pp.96-104
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• 2001

Usage of ecosystem models has been extended to landscape scales for understanding the effects of environmental factors on natural and agro-ecosystems and for serving as their management decision tools. Accurate prediction of spatial variation in daily temperature is required for most ecosystem models to be applied to landscape scales. There are relatively few empirical evaluations of landscape-scale temperature prediction techniques in mountainous terrain such as Korean Peninsula. We derived a periodic function of seasonal lapse rate fluctuation from analysis of elevation effects on daily temperatures. Observed daily maximum and minimum temperature data at 63 standard stations in 1999 were regressed to the latitude, longitude, distance from the nearest coastline and altitude of the stations, and the optimum models with $r^2$ of 0.65 and above were selected. Partial regression coefficients for the altitude variable were plotted against day of year, and a numerical formula was determined for simulating the seasonal trend of daily lapse rate, i.e., partial regression coefficients. The formula in conjunction with an inverse distance weighted interpolation scheme was applied to predict daily temperatures at 267 sites, where observation data are available, on randomly selected dates for winter, spring and summer in 2000. The estimation errors were smaller and more consistent than the inverse distance weighting plus mean annual lapse rate scheme. We conclude that this method is simple and accurate enough to be used as an operational temperature interpolation scheme at landscape scale in Korea and should be applicable to elsewhere.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.5
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• pp.725-731
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• 2013

In This paper, through simulation, proposes a system which makes it possible for freely moving multiple agents with ultrasonic receivers to estimate their own position by themselves using the ultrasonic signals sequentially emitted from multiple ultrasonic transmitters. This system possesses an advantage that there is no limit in the number of agents existing in the space covered by more than three transmitters fixed at proper locations. Hence, the proposed system can be utilized effectively in position tracking control of multiple robotic agents system and motion capturing system.

• Korea journal of population studies
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• v.21 no.2
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• pp.113-143
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• 1998

Married women who follow occupations have remarkably increased. Economic-activies married women[EAMW] have experienced a great degree of role confilcts as the results of that they should play the role of wage workers and do duty as household affairs as well as raise children. To understand problems of EAMW and to make alterniative plans for EAMW, the daily life actives of EAMW should be examined. This study attempts to understand the daily life activites of EAMW. To obtain the goal this research generalizes the daily life actives of EAMW. classifies the patterns the activites, and analyzes the activites in the micro-level. The acivites of EAMW mainly consist of formal business and household affairs. The spatial bounds of activities are influenced by weekdays and holidays. During the weekday their activities are mainly found around residences and/or work places; while, during the weekend, they are discovered around residences and/or around residences or relatives who take care of their children. EAMW move longer distance rather than a full-time housewife; however, the activites of EAMW are residential orientation like those of full-time housewives. The role conflicts of EAMW are mainly from social cultural structure, the distance between workplace and residence, and the location of public service institutes.

• Journal of the Korean GEO-environmental Society
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• v.15 no.3
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• pp.41-48
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• 2014

Experimental study of sedimentation and self-weight consolidation has been primary research area in dredged soil. However, good quality of the dredged soil and minimum water pollution caused by the pumping of reclaimed soil require intensive study of the flow characteristics of dredged material due to dumping. In this study, continuity and the equilibrium equations for mass flow assuming single phase was derived to simulate mass flow in dredged containment area. To optimize computation and modeling time for three dimensional geometry and boundary conditions, depth integration is applied to governing equations to consider three dimensional topography of the site. Petrov-Galerkin formulation is applied in spatial discretization of governing equations. Generalized trapezoidal rule is used for time integration, and Newton iteration process approximated the solution. DG and CDG technique were used for weighting matrix in discontinuous test function in dredged flow analysis, and numerical stability was evaluated by performed a square slump simulation. A comparative analysis for numerical methods showed that DG method applied to SU / PG formulation gives minimal pseudo oscillation and reliable numerical results.

• Journal of Korea Spatial Information System Society
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• v.12 no.1
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• pp.18-27
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• 2010

In u-GIS environment, GeoSensor environment requires that dynamic data captured from various sensors and static information in terms of features in 2D or 3D are fused together. GeoSensors, the core of this environment, are distributed over a wide area sporadically, and are collected in any size constantly. As a result, storage space could be exceeded because of restricted memory in DSMS. To solve this kind of problems, a lot of related studies are being researched actively. There are typically 3 different methods - Random Load Shedding, Semantic Load Shedding, and Sampling. Random Load Shedding chooses and deletes data in random. Semantic Load Shedding prioritizes data, then deletes it first which has lower priority. Sampling uses statistical operation, computes sampling rate, and sheds load. However, they are not high accuracy because traditional ones do not consider spatial characteristics. In this paper 'Pre-Filtering based Post Load Shedding' are suggested to improve the accuracy of spatial query and to restrict load shedding in DSMS. This method, at first, limits unnecessarily increased loads in stream queue with 'Pre-Filtering'. And then, it processes 'Post-Load Shedding', considering data and spatial status to guarantee the accuracy of result. The suggested method effectively reduces the number of the performance of load shedding, and improves the accuracy of spatial query.