• 대한원격탐사학회지
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• 제33권1호
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• pp.47-60
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• 2017

The permafrost active layer plays an important role in permafrost dynamics. Ecological patterns, processes, and water and ice contents in the active layer are spatially and temporally complex depending on landscape heterogeneity and local-scale variations in hydrological processes. Although there has been emerging interest in the application of optical remote sensing techniques to permafrost environments, optical sensors are significantly limited in accessing information on near surface geo-cryological conditions. The primary objective of this study was to investigate capability of L-band SAR data for monitoring spatio-temporal variability of permafrost ecosystems and underlying soil conditions. This study exploits information from different polarimetric SAR observables in relation to permafrost environmental conditions. Experimental results show that each polarimetric radar observable conveys different information on permafrost environments. In the case of the dual-pol mode, the radar observables consist of two backscattering powers and one correlation coefficient between polarimetric channels. Among them, the dual-pol scattering powers are highly sensitive to freeze/thaw transition and can discriminate grasslands or ponds in thermokarst area from other permafrost ecosystems. However, it is difficult to identify the ground conditions with dual-pol observables. Additional backscattering powers and correlation coefficients obtained from quad-pol mode help understanding seasonal variations ofradar scattering and assessing geo-cryological information on soil layers. In particular, co-pol coherences atHV-basis and circular-basis were found to be very usefultools for mapping and monitoring near surface soil properties.

• 한국전문물리치료학회지
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• 제10권1호
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• pp.1-13
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• 2003

The purpose of the study was to determine if there was a difference in the Functional Ambulation Performance score of senior adults with or without a history of falls during walking at a preferred velocity. Twelve subjects with a history of falling (mean age=73.8) and eight subjects with no history of falling (mean age=70.4) participated in the study. Temporal and spatial parameters of gait were analyzed using the computerized GAITRite system. The GAITRite system integrates specific components of locomotion to provide a single, numerical representation of gait, the Functional Ambulation Performance score. The Functional Ambulation Performance score is a Quantitative means of assessing gait based on specific temporal and spatial parameters. Statistical analysis of the two groups demonstrated a significant decrease in Functional Ambulation Performance score for those with a history of falls. They had lower values for step/extremity ratios, mean normalized velocity, and greater values for step times, percent in double support. These results indicate that the GAITRite system can be useful in detecting footfall patterns and selected time and distance measurements of persons with a history of falls and the Functional Ambulation Performance score can be used as indicators of gait performance for senior adults with a history of falls.

• 수산해양교육연구
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• 제25권5호
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• pp.1046-1054
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• 2013

Spatial and temporal variations of sea surface temperature (SST), abundances of copepods, euphausiids, amphipods, and chaetognaths were investigated in the western waters of the Korean Peninsula. Zooplankton and SST were monitored at 63 stations arrayed in six transects ($124^{\circ}00^{\prime}-126^{\circ}30^{\prime}E$, $34^{\circ}00^{\prime}-37^{\circ}00^{\prime}N$) in February, April, June, August, October, and December during 1978-2010. In general, SST increased $0.7-3.8^{\circ}C$ during the last three decades with spatio-temporal variations. SST was lowest in February and highest in August. SST was highest in the northernmost transect and declined gradually along transects to the south. The general pattern of interannual variations of SST was similar to the global pattern, which has been increasing. Trends of abundances of all zooplankton groups slightly increased interannually and peaked seasonally in June and August, except chaetognaths, which fluctuated around the long-term mean value with a seasonal peak in August and October. Abundances of zooplankton groups were highest in the northernmost transect while those of euphausiids were highest in the southern transect. We discuss the distribution patterns of SST and zooplankton groups in relation to oceanographic characteristics in the study area.

• Spatial Information Research
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• 제15권3호
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• pp.311-322
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• 2007

시각적 공간분석학은 인간의 공간인지 및 분석 능력을 최대한 발휘할 수 있는 다양한 시각화 도구를 개발함으로써 복잡한 시공간 데이터를 효율적으로 분석하는 학문으로, 궁극적으로는 인간의 추론능력과 시각적 분석도구의 효과적인 융합을 목적으로 한다. 시각적 공간분석학은 최적의 의사결정지원 도구를 개발하는 방법론으로 그 활용 범위가 매우 넓은데, 최근에는 지리적 시각화의 연구 전통을 계승하여 새로운 시각화 도구를 개발하고 다양한 분석을 통해 그 유용성을 확인하는 연구들이 시작되고 있다. 본 연구는 최근에 제안된 시각화 도구인 T 산포도와 전산분석법을 통합하여 우리나라 지역별 수출화물 발생패턴을 7개 유형으로 분석함으로써, 향후 공간의사결정 지원과정에서 시각적 공간분석학의 다양한 활용 가능성을 제시해주고 있다.

• 한국농공학회논문집
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• 제63권6호
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• pp.49-60
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• 2021

BCSA (Bias-Correction and Stochastic Analog) is a statistical downscaling technique designed to effectively correct the systematic errors of GCM (General Circulation Model) output and reproduce basic statistics and spatial variability of the observed precipitation filed. In this study, the applicability of BCSA was evaluated using the ASOS observation data over South Korea, which belongs to the monsoon climatic zone with large spatial variability of rainfall and different rainfall characteristics. The results presented the reproducibility of temporal and spatial variability of daily precipitation in various manners. As a result of comparing the spatial correlation with the observation data, it was found that the reproducibility of various climate indices including the average spatial correlation (variability) of rainfall events in South Korea was superior to the raw GCM output. In addition, the needs of future related studies to improve BCSA, such as supplementing algorithms to reduce calculation time, enhancing reproducibility of temporal rainfall patterns, and evaluating applicability to other meteorological factors, were pointed out. The results of this study can be used as the logical background for applying BCSA for reproducing spatial details of the rainfall characteristic over the Korean Peninsula.

• Journal of Information Science Theory and Practice
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• 제9권1호
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• pp.35-53
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• 2021

The study reported in this paper aimed to evaluate the topics and opinions of COVID-19 discussion found on Twitter. It performed topic modeling and sentiment analysis of tweets posted during the COVID-19 outbreak, and compared these results over space and time. In addition, by covering a more recent and a longer period of the pandemic timeline, several patterns not previously reported in the literature were revealed. Author-pooled Latent Dirichlet Allocation (LDA) was used to generate twenty topics that discuss different aspects related to the pandemic. Time-series analysis of the distribution of tweets over topics was performed to explore how the discussion on each topic changed over time, and the potential reasons behind the change. In addition, spatial analysis of topics was performed by comparing the percentage of tweets in each topic among top tweeting countries. Afterward, sentiment analysis of tweets was performed at both temporal and spatial levels. Our intention was to analyze how the sentiment differs between countries and in response to certain events. The performance of the topic model was assessed by being compared with other alternative topic modeling techniques. The topic coherence was measured for the different techniques while changing the number of topics. Results showed that the pooling by author before performing LDA significantly improved the produced topic models.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1996년도 추계학술대회논문집
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• pp.21-25
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• 1996

The Electomyographic (EMG) signals of flexor-extensor muscle pairs were investigated to identify the neural excitation pattern of low-back pain (LBP) patients during a repetitive bending motion. New parameters and EMG normalization technique were developed to quantitatively represent the difference of temporal EMG patterns between ten healthy subjects and ten LBP patients. Flexor-extensor muscle pairs such as rectus abdominis(RA)-erector spinae (ES at LS), external oblique(EO)-internal oblique(IO), rectus femois (quadriceps: QUD)-biceps femoris(hamstrings:HAM), and tibialis anterior(TA)-gastrocnemius(GAS) pairs of muscles were selected in this study. Results indicated that the temporal EMG pattern such as the peak timing difference of QUD-HAM muscle pair and the duration of coexcitation of ES-RA muscle pair showed a statistically isgnificant difference between healthy subjects and LBP patients. These results indicated that the new technique and parameters could be used as a diagnostic tool especially for LBP patients with soft tissue injuries that are rarely dentified by traditional imaging techniques such as X-ray, CT scan or MRI. Improtantly, the new EMG technique did not require the maximal volutary contraction(MVC) measure for normalization that helped patients minimize the pain experience during and after the session. Further study needs to be made to validate and refine this method for clinical application.

• 한국해양학회지:바다
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• 제12권3호
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• pp.186-190
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• 2007

The species composition and the biomass of intertidal microphytobenthos (MPB) were investigated at four sites in the Nakdong Estuary from Feb. to Dec. 2006. The chlorophyll (chl) ${\alpha}$ concentration showed a positive correlation with MPB abundance, and depth profiles showed similar patterns: high at the surface, rapidly decreasing within 4 cm from the surface, and slowly decreasing thereafter. A MANOVA analysis revealed that the chl ${\alpha}$ concentration varied significantly not only with depth, month, and site, but also with combinations of these factors. Among the four investigated sites, site D (Baekhabdeung) showed a seasonal biomass variation trend distinct from those of the other sites: higher in summer, decreased in autumn and with sustained low values until winter. As indicated, the other sites contrastingly showed low biomasses in summer, after which the biomasses continuously increased, with some variation among the sites. A cluster analysis of species composition indicated that sites near to each other and with similar sediment structures had closer similarities in the same seasons. The species of genus Amphora and Navicula were dominant at the four sites throughout the study period.

• 한국광학회지
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• 제25권6호
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• pp.326-333
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• 2014

액체 속에 담긴 시료를 투과형 편향법을 이용하여 3차원 형상을 측정하고 시료의 굴절률 분포를 측정하였다. 편향법은 면적이 비교적 크고 거울과 같이 산란이 거의 없는 물체의 3차원 측정을 하는데 유용하다. 편향법을 통해 얻은 왜곡 무늬로부터 위상과 기울기를 구하기 위해 위상이동법과 시간추적 위상펼침 (TPU:Temporal Phase Unwrapping) 방법을 이용하였고, 구한 기울기로부터 높이를 구하기 위해 최소자승법을 이용하였다. 굴절률 분포 측정을 위해 2개의 유체를 이용하였다. 전산기 시늉과 실험결과 액체를 이용한 투과형 편향법을 이용하여 시료내의 굴절률 분포를 측정 할 수 있음을 확인하였다.

• 한국측량학회지
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• 제37권6호
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• pp.417-426
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• 2019

이 연구에서는 미세먼지 시공간 변화 표현의 단점을 개선하고자 미세먼지를 흐름으로 시각화하였다. 일반적으로 미세먼지 흐름 시각화는 농도 분포와 바람장을 중첩해 표현하지만 도시 단위 이하 국지적 이동의 경우 바람과 미세먼지 이동이 다를 수 있으므로 바람장을 사용하는 것이 적합하지 않을 수 있다. 제시하는 시각화 방법론은 미세먼지 자료에서 직접 흐름 정보를 추출한다는 점에서 기존 연구와 차별성을 갖는다. 공간 상호작용을 설명하는 중력모델을 확장한 흐름 추출 방법을 미세먼지 자료에 적용하여 미세먼지 분포 변화에서 흐름 정보를 추출하였다. 이를 위해 공간보간법을 이용하여 미세먼지 분포도를 작성하였으며 추출된 미세먼지 흐름 정보를 물방울 모양의 움직이는 입자를 이용해 동적으로 시각화하였다. 산업 및 교통 활동이 시작하는 오전 5~7시 시간대를 대상으로 서울시 미세먼지 평균 흐름을 시각화하였으며 미세먼지 요인 중 하나인 교통정보와 연계하여 시각적으로 관련성을 분석하였다.