• 한국측량학회지
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• 제33권6호
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• pp.605-614
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• 2015

Drone imaging, which is more cost-effective and controllable compared to airborne LiDAR, requires a low-cost camera and is used for capturing color images. From the overlapped color images, we produced two high-resolution digital surface models over different test areas. After segmentation, we performed tree identification according to the method proposed by , and computed the tree height and the canopy crown size. Compared with the field measurements, the computed results for the tree height in test area 1 (coniferous trees) were found to be accurate, while the results in test area 2 (deciduous coniferous trees) were found to be underestimated. The RMSE of the tree height was 0.84 m, and the width of the canopy crown was 1.51 m in test area 1. Further, the RMSE of the tree height was 2.45 m, and the width of the canopy crown was 1.53 m in test area 2. The experiment results validated the use of drone images for the extraction of a tree structure.

• Journal of Ecology and Environment
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• 제42권4호
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• pp.155-162
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• 2018

Background: In ecosystem carbon cycle studies, distinguishing between $CO_2$ emitted by roots and by microbes remains very difficult because it is mixed before being released into the atmosphere. Currently, no method for quantifying root and microbial respiration is effective. Therefore, this study investigated the relationship between soil respiration and underground root biomass at varying distances from the tree and tested possibilities for measuring root and microbial respiration. Methods: Soil respiration was measured by the closed chamber method, in which acrylic collars were placed at regular intervals from the tree base. Measurements were made irregularly during one season, including high temperatures in summer and low temperatures in autumn; the soil's temperature and moisture content were also collected. After measurements, roots of each plot were collected, and their dry matter biomass measured to analyze relationships between root biomass and soil respiration. Results: Apart from root biomass, which affects soil's temperature and moisture, no other factors affecting soil respiration showed significant differences between measuring points. At each point, soil respiration showed clear seasonal variations and high exponential correlation with increasing soil temperatures. The root biomass decreased exponentially with increasing distance from the tree. The rate of soil respiration was also highly correlated exponentially with root biomass. Based on these results, the average rate of root respiration in the soil was estimated to be 34.4% (26.6~43.1%). Conclusions: In this study, attempts were made to differentiate the root respiration rate by analyzing the distribution of root biomass and resulting changes in soil respiration. As distance from the tree increased, root biomass and soil respiration values were shown to strongly decrease exponentially. Root biomass increased logarithmically with increases in soil respiration. In addition, soil respiration and underground root biomass were logarithmically related; the calculated root-breathing rate was around 44%. This study method is applicable for determining root and microbial respiration in forest ecosystem carbon cycle research. However, more data should be collected on the distribution of root biomass and the correlated soil respiration.

• Journal of Communications and Networks
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• 제18권5호
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• pp.699-712
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• 2016

Recently, greedy algorithm has received much attention as a cost-effective means to reconstruct the sparse signals from compressed measurements. Much of previous work has focused on the investigation of a single candidate to identify the support (index set of nonzero elements) of the sparse signals. Well-known drawback of the greedy approach is that the chosen candidate is often not the optimal solution due to the myopic decision in each iteration. In this paper, we propose a tree search based sparse signal recovery algorithm referred to as the tree search matching pursuit (TSMP). Two key ingredients of the proposed TSMP algorithm to control the computational complexity are the pre-selection to put a restriction on columns of the sensing matrix to be investigated and the tree pruning to eliminate unpromising paths from the search tree. In numerical simulations of Internet of Things (IoT) environments, it is shown that TSMP outperforms conventional schemes by a large margin.

• 한국전문물리치료학회지
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• 제30권2호
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• pp.102-109
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• 2023

Background: While efforts have been made to differentiate fall risk in older adults using wearable devices and clinical methodologies, technologies are still infancy. We applied a decision tree (DT) algorithm using inertial measurement unit (IMU) sensor data and clinical measurements to generate high performance classification models of fall risk of older adults. Objects: This study aims to develop a classification model of fall risk using IMU data and clinical measurements in older adults. Methods: Twenty-six older adults were assessed and categorized into high and low fall risk groups. IMU sensor data were obtained while walking from each group, and features were extracted to be used for a DT algorithm with the Gini index (DT1) and the Entropy index (DT2), which generated classification models to differentiate high and low fall risk groups. Model's performance was compared and presented with accuracy, sensitivity, and specificity. Results: Accuracy, sensitivity and specificity were 77.8%, 80.0%, and 66.7%, respectively, for DT1; and 72.2%, 91.7%, and 33.3%, respectively, for DT2. Conclusion: Our results suggest that the fall risk classification using IMU sensor data obtained during gait has potentials to be developed for practical use. Different machine learning techniques involving larger data set should be warranted for future research and development.

• Journal of Communications and Networks
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• 제18권3호
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• pp.446-459
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• 2016

In this paper, we propose virtual direction multicast (VDM) for video multicast applications on peer-to-peer overlay networks. It locates the end hosts relative to each other based on a virtualized orientation scheme using real-time measurements. It builds multicast tree by connecting the nodes, which are estimated to be in the same virtual direction. By using the concept of directionality, we target to use minimal resources in the underlying network while satisfying users' quality expectations. We compare VDM against host multicast tree protocol.We simulated the protocol in a network simulator and implemented in PlanetLab. Results both from simulation and PlanetLab implementation show that our proposed technique exhibits good performance in terms of defined metrics.

• Journal of Forest and Environmental Science
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• 제27권1호
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• pp.47-54
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• 2011

Allometry and basal area equations were developed with various tree measurement variables for the major species; Quercus variabilis, Quercus mongolica, Pinus koraiensis and Larix leptolepis in Korea. For allometry models, the relationships between total height-DBH, crown width-DBH, height to the widest portion of the crown-total height, and height to base of crown-total height were investigated. Multiple regression methods were used to relate annual basal area growth to tree variables of initial size (DBH, total height, and crown width), relative size (relative diameter and relative height) as well as competition measures (competition index, crown class, and live crown ratio).

• 대한전기학회논문지
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• 제35권12호
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• pp.555-559
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• 1986

It is shown that water tree grown using the water needle method in polyethylen do not behave as conductor but as dielectrics. It is decuded that water trees are not non-interconnected cavities. This result is confirmed by gas flow measurements through freeze-fractured water trees.

• International Journal of Ocean System Engineering
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• 제3권3호
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• pp.116-130
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• 2013

The prediction of ocean currents in real time over the warning times of a few hours or days is required in planning many operation-related activities in the ocean. Traditionally this is done through numerical models which are targeted toward producing spatially distributed information. This paper discusses a complementary method to do so when site-specific predictions are desired. It is based on the use of a recurrent type of neural network as well as the statistical tool of model tree. The measurements made at a site in Indian Ocean over a period of 4 years were used. The predictions were made over 72 time steps in advance. The models developed were found to be fairly accurate in terms of the selected error statistics. Among the two modeling techniques the model tree performed better showing the necessity of using distributed models for different sub-domains of data rather than a unique one over the entire input domain. Typically such predictions were associated with average errors of less than 2.0 cm/s. Although the prediction accuracy declined over longer intervals, it was still very satisfactory in terms of theselected error criteria. Similarly prediction of extreme values matched with that of the rest of predictions. Unlike past studies both east-west and north-south current components were predicted fairly well.

• 한국산림과학회지
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• 제111권3호
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• pp.394-404
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• 2022

본 연구는 우리나라의 가로경관 및 관상 목적으로 활용되는 주요 중형 조경수인 왕벚나무를 대상으로 컨테이너 재배 점적 관수 시 관수량에 따른 4년생, 8년생 묘목의 생장 및 생리 특성을 평가하여, 왕벚나무 컨테이너 재배를 위한 적정관수 기준을 제시하고자 수행되었다. 연구 결과 관수량 처리에 따른 묘고와 근원직경의 상대생장률의 경우 왕벚나무 4년생은 288 L/year/tree 처리에서 8년생은 416 L/year/tree 처리에서 가장 높은 값을 나타내었다. 물질생산량과 묘목품질지수 또한 두 연생 모두 관수처리에 따른 유의적인 차이를 보이면서 4년생은 288 L/year/tree 처리에서 8년생은 416 L/year/tree 처리에서 양호한 생장을 보였다. 뿌리발달 특성 중 총뿌리길이, 평균뿌리직경, 뿌리부피는 두 연생 모두 관수량 처리에 대해 차이를 보였다. 엽록소함량의 경우 왕벚나무 4년생은 288 L/year/tree 처리에서 8년생은 416 L/year/tree처리에서 가장 높은 활성을 보였다. 본 연구결과를 종합적으로 고려해 볼 때 컨테이너 재배 시 관수량의 차이는 묘목의 형태적 상대생장률, 물질생장량, 묘목품질, 생리적 반응에 영향을 미치며, 왕벚나무를 컨테이너로 재배 할 시 적절한 관수량은 4년생 묘목 (근원직경 3 cm급)은 288 L/year/tree, 8년생 묘목 (근원직경 7 cm급)은 416 L/year/tree가 적절한 것으로 판단된다.

• 헤리티지:역사와 과학
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• 제44권1호
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• pp.182-195
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• 2011

천연기념물 노거수는 오랫동안 우리 민족의 역사, 문화와 함께해 온 존재로서 단순한 나무 이상의 의미를 지니고 있다. 문화재청에서는 노거수 중에서도 크기뿐만 아니라 진귀성, 상징성, 고유성 등 문화적 자연적 요소가 뚜렷한 것들을 천연기념물로 지정하여 보호하고 있다. 본 연구는 천연기념물 노거수 중 강원도내 분포하는 14건의 생육현황과 제원 및 토양환경, 보호시설 현황을 파악하고자 수행하였다. 연구결과, 강원도의 천연기념물 노거수는 78.57% 이상이 보통이거나 보통 이상의 생육현황을 나타내었다. 수고는 평균 18.80m, 근원둘레는 평균 7.34m인것으로 나타났다. 토양환경 분석결과 대부분 전국 산림토양 대비 평균치를 나타내었으나 유효인산은 과영양 상태인 것으로 분석되었다. 보호시설은 대부분 양호한 상태이나 지주대와 쇠당김 시설 일부는 수목에 피해를 주고 있는 것으로 나타났다. 본 연구는 강원도 내 천연기념물 노거수의 생육환경과 관리현황 분석을 통한 관리 기초자료 제공에 의의를 두며, 생육에 영향을 주는 환경인자와의 관련성 등은 추후 과제로 남겨둔다.