• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.209-216
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• 2023

This study aimed to use national forest inventory data to develop a forest productivity index and yield prediction model of a Tilia amurensis stand. The site index displaying the forest productivity of the Tilia amurensis stand was developed as a Schumacher model, and the site index classification curve was generated from the model results; its distribution growth in Korea ranged from 8-16. The growth model using age as an independent variable for breast height and height diameter estimation was derived from the Chapman-Richards and Weibull model. The Fitness Indices of the estimation models were 0.32 and 0.11, respectively, which were generally low values, but the estimation-equation residuals were evenly distributed around 0, so we judged that there would be no issue in applying the equation. The stand basal area and site index of the Tilia amurensis stand had the greatest effect on the stand-volume change. These two factors were used to derive the Tilia amurensis stand yield model, and the model's determination coefficient was approximately 94%. After verifying the residual normality of the equation and autocorrelation of the growth factors in the yield model, no particular problems were observed. Finally, the growth and yield models of the Tilia amurensis stand were used to produce the makeshift stand yield table. According to this table, when the Tilia amurensis stand is 70 years old, the estimated stand-volume per hectare would be approximately 208 m³ . It is expected that these study results will be helpful for decision-making of Tilia amurensis stands management, which have high value as a forest resource for honey and timber.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.108-114
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• 2012

We propose a dispersive finite-difference time domain(FDTD) algorithm suitable for the electromagnetic analysis of the human body. In this work, the dispersion relation of the human body is modeled by a quadratic complex rational function(QCRF), which leads to an accurate and efficient FDTD algorithm. Coefficients(involved in QCRF) for various human tissues are extracted by applying a weighted least square method(WLSM), referred to as the complex-curve fitting technique. We also presents the FDTD formulation for the QCRF-based dispersive model in detail. The QCRFbased dispersive model is significantly accurate and its FDTD implementation is more efficient than the counterpart of the Cole-Cole model. Numerical examples are used to show the validity of the proposed FDTD algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.670-678
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• 2014

This paper presents a method to extract objects in radiographic images where all the allowable combinations of segmented regions are compared to a target object using Fourier descriptor. In the object extraction for usual images, a main problem is occlusion. In radiographic images, there is an advantage that the shape of an object is not occluded by other objects. It is because radiographic images represent the amount of radiation penetrated through objects. Considering the property of no occlusion in radiographic images, the shape based descriptors can be very effective to find objects. After all, the proposed object extraction method consists of three steps of segmenting regions, finding all the combinations of the segmented regions, and matching the combinations to the shape of the target object. In finding the combinations, we reduce a lot of computations to remove unnecessary combinations before matching. In matching, we employ Fourier descriptor so that the proposed method is rotation and shift invariant. Additionally, shape normalization is adopted to be scale invariant. By experiments, we verify that the proposed method works well in extracting objects.

• Education of Primary School Mathematics
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• v.1 no.1
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• pp.59-71
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• 1997

기하학적 사고력 개발이라는 우리의 목표는 궁극적으로 보다 낮은 수준의 학생들에게 보다 높은 수준으로 나아가게 하는 경험을 주는 것이다. 학생들이 보다 높은 수준에서 추론할 수 있도록 하기 위하여 그들이 보다 낮은 수준에서 충분하고 효율적인 학습 경험을 가져야 한다는 것이다. 예를 들면 분수에서 이루어지는 것처럼 기계적인 암기식으로 사물을 학습함으로써 수준(단계)을 뛰어 넘으려고 노력하면은 그들이 학습한 것에 관한 많은 것을 기억할 수 없을 것이다. 조작에 관한 보다 풍부한 경험과 시각적으로 입체감을 주는 설명을 들은 어린이들이 보다 훌륭한 공간 추론을 할 수 있을 것이라 믿는다. 본 고에서는 기하학적인 사고의 개발에 관한 van Hiele 모델이 초등학교에서 기하 수업의 토론을 위한 기초로서 사용되어졌다. 그 모델의 수준들이 묘사되었고 일반적으로 초등학교 아동들의 사고는 0수준과 1수준이라 는 것이 밝혀졌다. 단지 극소수의 아동들이 2수준의 사고에 도달해 있을 것이다. 그러나 만약 초등학교에서의 수업이 기하학적인 개념을 구성하는데 주안점을 둔다면 보다 많은 어린이들이 2 수준의 사고를 보여줄 수 있을 것으로 생각된다. 0 수준의 어린이들은 도형의 형태에 초점이 맞추어져있고 1 수준의 어린이들은 도형의 성질을 이해하는데 에 있다. 2 수준의 사고자는 도형의 포함관계를 이해하고 비공식적으로 추론 할 수 있다. 처음 세 수준에서의 활동들에 대한 지침이 주어져 있으며 0 수준과 1수준에 연관되는 다수의 활동들을 묘사했다. 0수준의 어린이들을 위해 묘사된 활동들은 그들이 2차원 및 3차원의 도형 둘 다를 시각화하는데 도움을 주는 것이다. 1 수준에서 사고하는 학습자들을 위해 묘사된 활동들은 2차원 및 3차원 도형의 성질들을 강조했다. 아울러 본 고에서 언급한 활동들은 상호교수에의 접근을 반영했다. 그러한 접근방식은 학습자들로 하여금 그들의 활동과 의견으로부터 개념을 구성하게 해주며 그들의 활동 결과에 대해 다른 사람들과 의사소통 함으로서 개념을 명확하게 다듬어지게 해줄 수 있을 것이다. 아울러 평가 활동들이 본고의 마지막 부분에 주어져있다. 그러한 활동들은 교사들에게 어린이들의 기하학적인 사고수준을 결정하게 해주며 학습자들로 하여금 수업시간 이외에 보다 높은 사고수준으로 나아가게 해줄 수 있을 것으로 기대된다.

• Education of Primary School Mathematics
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• v.20 no.3
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• pp.205-224
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• 2017

A model method has been known as the main characteristic of Singaporean elementary mathematics textbooks. However, little research has been conducted on how the model method is employed in the textbooks. In this study, we extracted contents related to the model method in the Singaporean elementary mathematics curriculum and then analyzed the characteristics of the model method applied to the textbooks. Specifically, this study investigated the units and lessons where the model method was employed, and explored how it was addressed for what purpose according to the numbers and operations. The results of this study showed that the model method was applied to the units and lessons related to operations and word problems, starting from whole numbers through fractions to decimals. The model method was systematically applied to addition, subtraction, multiplication, and division tailored by the grade levels. It was also explicitly applied to all stages of the problem solving process. Based on these results, this study described the implications of using a main model in the textbooks to demonstrate the structure of the given problem consistently and systematically.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.1
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• pp.53-60
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• 2012

To reduce the vibration in industrial settings, the viscous fluid dampers have been widely used. Since the damper shows a viscoelastic behavior, many methods to predict the behavior have been investigated. But the methods did not consider a change of damper size that is important factor for practical design engineer. In this study, to predict a change of damper ability with respect to a change of damper size, the dynamic experiment were conducted with fixed aspect ratio and gap. The damping coefficient at zero frequency was computed through theoretical and experiment approach in order to fit the experimental results using fractional derivative Maxwell model.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.146-151
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• 2017

This paper proposes a transmission algorithm that optimizes transmission power and sub-channel allocation to maximize energy efficiency considering characteristics of the channel impedance of power lines in power line communication systems. Since the received power at the receiver is influenced by the characteristics of the power line channel, it is necessary to consider channel characteristics when developing a transmission strategy in a power line communication systems. In addition, the energy efficiency should be optimized while meeting the practical constraints, such as the maximum transmission power limit of the transmitter and minimum quality of service for each user. In the computer simulation, we confirm that the energy efficiency of the proposed algorithm is improved compared to baseline schemes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.3
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• pp.223-237
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• 2010

The initial heating rate is well known as one of the most influencing factors on the occurrence of spalling and the loss of strength in concrete after fire initiation. In this study, a series of fire tests were carried out at different initial heating rates to find out its effects on the deterioration of tunnel structural members. Heat transfer analyses combined with an element elimination model were also carried out to verify its applicability in the same conditions as the fire tests. Moreover, the convection heat transfer coefficients compatible with fire test results were derived from parametric studies. In this course, their time-dependent variations were also analyzed at different initial heating rates. Finally, a numerical formula to estimate the heat transfer coefficients at the various initial heating rates was proposed by the interpolation of the results of numerical analyses.

• Journal of Korean Society of Forest Science
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• v.106 no.2
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• pp.267-273
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• 2017

This study was conducted to construct a empirical yield table for Pinus densiflora in real forest. Since existing normal yield tables have been derived by studying and analyzing communities in ideal environment for tree growth, those tables provide more over-estimated values than ones from real forest. Because of this, there are some difficulties to apply the tables to empirical forest except for normal forest. In this study, therefore, we estimated stand growth for real forest on P. densiflora as the representative species of conifers. We used 1,957 sample plot data of P. densiflora in central Korea from National Forest Inventory (NFI) system, and analyzed through estimation, recovery and prediction in order by using Weibull function as a diameter distribution model. Weilbull and Schumacher models were applied for estimating mean DBH and mean basel area and it was found that the site index for P. densiflora in central Korea ranges from 8 to 14 at reference age 30. According to site 12 in the stand yield table, the Mean Annual Increment (MAI) of P. densiflora was $4.42m^3/ha$ at 30 years of age. Compared to existing volume table constructed before, it is showed that MAI of this study were lower. According to the paired t-test that is conducted with the gap of volume values between normal forest and real forest by site index and age, the P-value was less than 0.001 which is recognized to have a statistically significant difference. Based on the results in this study, it is considered to be helpful for practical management and management policy on P. densiflora in central Korea.

• Journal of the Korean association of regional geographers
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• v.14 no.2
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• pp.114-125
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• 2008

Colored dissolved organic matter(CDOM) is an important component of ocean color that can be used as an invaluable tool in water quality and ocean color studies. With the largest source of coastal CDOM appearing to be from freshwater discharge into the ocean, coastal predictive models will do much to refine our knowledge about major processes that control CDOM distributions in coastal waters and provide a better insight into the global carbon cycle. This study aims at developing a GIS-based watershed-scale predictive model of CDOM distributions in Neponset river watersheds that can be used to appraise our understanding of CDOM sources and distributions in coastal waters and predict the response of CDOM concentration to changes in land use patterns. Weighting factors are developed for CDOM freshwater sources after extensive groundtruthing from various landuse types in the watershed. This model makes use of a publicly available DEM(Digital elevation model) as the base data for analysis. Stream networks, discharge, and land use data are used from public repositories while sub- watershed delineation, pour-points, and land use parcels are generated using Spatial Analysis of ArcGIS 9.2 to estimate the CDOM loading from various sources to the lower tributaries of rivers. The Neponset Watershed in eastern Massachusetts is selected as the site for development of the model.