• 천문학회지
• /
• 제22권2호
• /
• pp.141-160
• /
• 1989

In order to derive time dependence of the atmospheric diffuse light, which consists of the airglow continuum emission and diffusely scattered radiations of the intergrated starlight, the diffuse Galactic light, and the zodiacal light, we have analyzed the meridian scan observations of the sky brightness at $5,080\;{\AA}$ and $5,300\;{\AA}$. Amplitude of the time-variation becomes larger for lower elevation, and maximum amplitude is found to be about $50\;S_{10}(V)_{G2V}$ at elevation $10^{\circ}$. The atmospheric diffuse radiation attains maximum brightness at around midnight, and afterward it decreases slowly with time. The time-variations for the two wavelengths are similar to each other. The observed brightness distribution of the diffuse light along the zenith distance is fitted to an empirical relation of two parameters. By making the two parameters time-dependent, we describe the spatial and time variations of the atmospheric diffuse light. This enables us to make time dependent correction for the atmospheric diffuse component in the reduction of zodiacal light brightness.

• 대한공간정보학회지
• /
• 제17권2호
• /
• pp.71-79
• /
• 2009

본 연구에서는 격자강우량과 격자기반의 GIS수문 매개변수와 연계하여 홍수기 유출량의 시공간적 분포를 파악할 수 있도록 물리적인 운동파 이론에 근거한 분포형 강우-유출모형인 K-DRUM을 자체 개발하였다. 이 모형은 홍수 기동안의 지표흐름과 지표하 흐름의 시간적 변화와 공간적 분포를 모의할 수 있으며, 전처리과정으로서 ArcView 를 이용하여 모형에 필요한 ASCII형태의 입력 매개변수 자료들을 가공하였다. 또한 후처리과정으로서 모형의 수행결과인 유역내의 유출량 분포 등을 GIS상에서 나타낼 수 있도록 ASCII형태로 출력하도록 구성하였으며 TecPlot 을 이용하여 유출량을 에니메이션으로 표현하였다. 또한, 유출량에 가장 큰 영향을 미치는 초기토양함수 상태에 대한 자동보정기법을 추가 개발하였으며, 남강댐유역을 대상으로 기저유출해석을 수행하여 개발된 자동보정기법의 활용가능성을 검토하였다. K-DRUM모형의 초기토양함수조건을 설정하는데 있어서 자동보정기법을 적용함으로써 기존의 시행착오법으로 인해 소요되는 시간과 부정확한 설정으로 발생될 수 있는 문제점을 해결할 수 있었다.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2018년도 학술발표회
• /
• pp.154-154
• /
• 2018

To interpret the climate projections for the future as well as present, recognition of the consequences of the climate internal variability and quantification its uncertainty play a vital role. The Korean Peninsula belongs to the Far East Asian Monsoon region and its rainfall characteristics are very complex from time and space perspective. Its internal variability is expected to be large, but this variability has not been completely investigated to date especially using models of high temporal resolutions. Due to coarse spatial and temporal resolutions of General Circulation Models (GCM) projections, several studies adopted dynamic and statistical downscaling approaches to infer meterological forcing from climate change projections at local spatial scales and fine temporal resolutions. In this study, stochastic downscaling methodology was adopted to downscale daily GCM resolutions to hourly time scale using an hourly weather generator, the Advanced WEather GENerator (AWE-GEN). After extracting factors of change from the GCM realizations, these were applied to the climatic statistics inferred from historical observations to re-evaluate parameters of the weather generator. The re-parameterized generator yields hourly time series which can be considered to be representative of future climate conditions. Further, 30 ensemble members of hourly precipitation were generated for each selected station to quantify uncertainty. Spatial map was generated to visualize as separated zones formed through K-means cluster algorithm which region is more inconsistent as compared to the climatological norm or in which region the probability of occurrence of the extremes event is high. The results showed that the stations located near the coastal regions are more uncertain as compared to inland regions. Such information will be ultimately helpful for planning future adaptation and mitigation measures against extreme events.

• Journal of Ecology and Environment
• /
• 제32권2호
• /
• pp.67-73
• /
• 2009

Soil $CO_2$ efflux can vary markedly in magnitude over both time and space, and understanding this variation is crucial for the correct measurement of $CO_2$ efflux in ecological studies. Although considerable research has quantified temporal variability in this flux, comparatively little effort has focused on its spatial variability. To account for spatial heterogeneity, we must be able to determine the number of sampling points required to adequately estimate soil $CO_2$ efflux in a target ecosystem. In this paper, we report the results of a study of the number of sampling points required for estimating soil $CO_2$ efflux using a closed-dynamic chamber in young and old Japanese cedar plantations in central Japan. The spatial heterogeneity in soil $CO_2$ efflux was significantly higher in the mature plantation than in the young stand. In the young plantation, 95% of samples of 9 randomly-chosen flux measurements from a population of 16 measurements made using 72-$cm^2$ chambers produced flux estimates within 20% of the full-population mean. In the mature plantation, 20 sampling points are required to achieve means within $\pm$ 20% of the full-population mean (15 measurements) for 95% of the sample dates. Variation in soil temperature and moisture could not explain the observed spatial variation in soil $CO_2$ efflux, even though both parameters are a good predictor of temporal variation in $CO_2$ efflux. Our results and those of previous studies suggest that, on average, approximately 46 sampling points are required to estimate the mean and variance of soil $CO_2$ flux in temperate and boreal forests to a precision of $\pm$ 10% at the 95% confidence level, and 12 points are required to achieve a precision of $\pm$ 20%.

• 한국멀티미디어학회논문지
• /
• 제13권1호
• /
• pp.102-110
• /
• 2010

H.264 SVC(Scalable Video Coding)는 디스크 저장 공간 효율성과 높은 확장성을 제공할 수 있는 장점이 있다. 그러나 스트리밍 서버나 단말기는 비트 스트림을 효율적으로 추출해야 한다. 본 논문에서는 네트워크 가용 대역폭을 넘지 않으면서 최대의 PSNR을 얻기 위한 SVC 비트 스트림 추출 기법을 제공한다. 이를 위하여 오프라인시에 최대의 PSNR을 얻기 위한 추출 지점에 대한 정보를 획득한 후, 온라인시에 네트워크 가용 대역폭을 만족하는 비트 스트림의 공간/시간 해상도를 결정한다. 이러한 공간/시간 해상도 정보는 네트워크 가용 대역폭과 함께 비트 스트림 추출기의 입력 파라미터로 사용된다. JSVM 참조 소프트웨어를 활용한 실험을 통하여 본 논문에서 제시한 추출 기법이 높은 PSNR을 제공함을 증명하였다.

• Geomechanics and Engineering
• /
• 제25권2호
• /
• pp.135-142
• /
• 2021

This study provided a new research perspective for processing and analyzing AE data to evaluate rock failure. Cluster method and information entropy theory were introduced to investigate temporal and spatial correlation of acoustic emission (AE) events during the rock failure process. Laboratory experiments of granite subjected to compression were carried out, accompanied by real-time acoustic emission monitoring. The cumulative length and dip angle curves of single links were fitted by different distribution models and distribution functions of link length and directionality were determined. Spatial scale and directionality of AE event distribution, which are characterized by two parameters, i.e., spatial correlation length and spatial correlation directionality, were studied with the normalized applied stress. The entropies of link length and link directionality were also discussed. The results show that the distribution of accumulative link length and directionality obeys Weibull distribution. Spatial correlation length shows an upward trend preceding rock failure, while there are no remarkable upward or downward trends in spatial correlation directionality. There are obvious downward trends in entropies of link length and directionality. This research could enrich mathematical methods for processing AE data and facilitate the early-warning of rock failure-related geological disasters.

• 한국정보통신학회논문지
• /
• 제7권8호
• /
• pp.1684-1690
• /
• 2003

본 논문에서는 H.263 부호기에서 적정 화질과 일정한 전송율을 유지하는 양자화 변수 추정을 위한 퍼지 제어기를 제안하였다. 퍼지화 방법으로는 Mamdani 방법을 이용하며, 역퍼지화는 무게중심법을 이용하였다. 움직임 벡터에 따른 시간적 특성을 추정할 때 공간영역에서 분산과 엔트로피는 시각적 특성과 상관관계가 있다. 따라서 퍼지 입력변수로 영상의 분산값, 엔트로피 및 움직임 벡터를 이용하였다. 퍼지 소속함수를 유도하고, 시각적 특성에 적합한 퍼지감도를 결정하였으며, FAM 뱅크를 설계하였다. 실제 동영상 압축에 퍼지 규칙을 적용하였으며, 퍼지 양자화를 이용하여 효율적인 율제어와 최적의 비트할당 및 주관적 화질 특성이 유지되는 결과를 얻었다.

• The Journal of the Acoustical Society of Korea
• /
• 제22권2E호
• /
• pp.78-86
• /
• 2003

We analyzed the measured acoustic field to explore the characteristics of a horizontal coherence in shallow water. Signal spatial coherence data were obtained in the continental shelf off the east coast of Korea using a horizontal line array. The array was deployed on the bottom of 130 m water depth and a sound source was towed at 26 m depth in the source-receiver ranges of 1-13 ㎞. The source transmitted 200 ㎐ pure tone. Topography and temperature profiles along the source track were measured to investigate the relationship between the horizontal coherence and environment variations. The beam bearing disturbance and array signal gain degradation is examined as parameters of horizontal coherence. The results show that the bearing disturbance is about ± 8° and seems to be affected by temporal variations of temperature caused by internal waves. The array signal gains show degradation more than 5㏈ by the temporal and spatial variations of temperature and by the down-sloped topography.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.717-720
• /
• 2002

The present study is to evaluate the performances of flow velocity and wall shear stress in the stenosed coronary artery using human in vivo hemodynamic Parameters and computer simulation. Initial and follow-up coronary angiographics in the patients with angulated coronary stenosis are performed. Follow-up coronary angiogram demonstrated significant difference in the percent of diameter in the stenosed coronary between two groups ($Group\;1:\;40.3{\%},\;Group\;2:\;25.5{\%}$). Flow-velocity wave obtained from in vivo intracoronary Doppler ultrasound data is used for the boundary condition for the computer simulation. Spatial and temporal variations of flow velocity vector and recirculation area are drawn throughout the selected segment of coronary models. The WSS of pre- and post-intracoronary stenting are calculated from three-dimensional computer simulation. Then negative shear stresses area on 3D simulation we noted on the inner wall of the post-stenotic area before stenting. The negative WSS is disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2. The present study suggest that hemodynamic forces exerted by pulsatile coronary circulation termed WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. The local recirculation area which has low or negative WSS, might lead to progression of atherosclerosis.

• 대한물리의학회지
• /
• 제7권2호
• /
• pp.205-212
• /
• 2012

Purpose : The aim of this study was to investigate the relationship between weight-supporting asymmetry and gait symmetry in patients with stroke. Methods : Sixty two stroke patients with hemiplegia stood quietly with eye opens on a force platform to calculate weight-supporting asymmetry from vertical reaction force. The GAITRite was used to evaluate their gait parameters. The data were analyzed using Pearson correlation. Results : The results of this study was showed that the medio-lateral index (ML) was correlated with symmetry rate (SR), symmetry index (SI), and Gait asymmetry (GA) of step time and length but stronger correlation with spatial gait symmetry than temporal symmetry. In gait symmetry, step length has stronger correlation with weight-supporting asymmetry than step time. Conclusions : The results of this study shows weight-supporting asymmetry was correlated with more spatial gait symmetry than temporal symmetry.