• Korean Journal of Environment and Ecology
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• v.27 no.5
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• pp.571-578
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• 2013

This study generated regression models through a direct harvesting method to estimate carbon storage and uptake by Pinus densiflora and Pinus koraiensis, the major evergreen tree species in urban landscape, and established essential information to quantify carbon reduction by urban trees. Open-grown landscape tree individuals for each species were sampled reflecting various diameter sizes at a given interval. The study measured biomass for each part including the roots of sample trees to compute the total carbon storage per tree. Annual carbon uptake per tree was quantified by analyzing radial growth rates of stem samples at breast height. The study then derived a regression model easily applicable in estimating carbon storage and uptake per tree for the two species by using diameter at breast height (DBH) as an independent variable. All the regression models showed high fitness with $r^2$ values of higher than 0.98. While carbon storage and uptake by young trees tended to be greater for P. densiflora than for P. koraiensis in the same diameter sizes, those by mature trees with DBH sizes of larger than 20 cm showed results to the contrary due to a difference in growth rates. A tree of P. densiflora and P. koraiensis with DBH of 25 cm stored 115.6 kg and 130.0 kg of carbon, respectively, and annually sequestered 9.4 kg and 14.6 kg. The study has broken new grounds to overcome limitations of the past studies which quantified carbon reduction of the study species by substituting, due to a difficulty in direct cutting and root digging of landscape trees, coefficients from forest trees such as biomass expansion factors, ratios of below ground/above ground biomass, and diameter growth rates.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.19-27
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• 2018

Terzaghi proposed a 2D formula for arching based on the assumption of a vertical sliding surface induced in the upper part due to the downward movement of a trapdoor. The formula was later expanded to consider 3D tunnel excavation conditions under inclined sliding surfaces. This study further extends the expanded formula to consider the effects of different ground properties and inclined sliding conditions in the transverse and longitudinal directions considering anisotropic ground conditions, as well as 3D tunnel excavation conditions. The 3D formula proposed in this study was examined of the induced vertical stress under various conditions (ground property, inclined sliding surface, excavation condition, surcharge pressure, earth pressure coefficient) and compared with the 2D Terzaghi formula. The examination indicated that the induced vertical stress increased as the excavation width and length increased, the inclination angle increased, the cohesion and friction angle decreased, the earth pressure coefficient decreased, and the surcharge pressure increased. Under the conditions examined, the stress was more affected at low excavation lengths and by the ground properties in the transverse direction. In addition, The comparison with the 2D Terzaghi formula showed that the induced vertical stress was lower and the difference was highly affected by the ground properties, inclined sliding conditions, and 3D tunnel excavation conditions. The proposed 3D arching formula could help to provide better understanding of complex arching phenomena in tunnel construction.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.4
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• pp.196-203
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• 2022

Purpose: This study aimed to evaluate the accuracy and clinical usability of an identification model using deep learning for 79 dental implant types. Materials and Methods: A total of 45396 implant fixture images were collected through panoramic radiographs of patients who received implant treatment from 2001 to 2020 at 30 dental clinics. The collected implant images were 79 types from 18 manufacturers. EfficientNet and Meta Pseudo Labels algorithms were used. For EfficientNet, EfficientNet-B0 and EfficientNet-B4 were used as submodels. For Meta Pseudo Labels, two models were applied according to the widen factor. Top 1 accuracy was measured for EfficientNet and top 1 and top 5 accuracy for Meta Pseudo Labels were measured. Results: EfficientNet-B0 and EfficientNet-B4 showed top 1 accuracy of 89.4. Meta Pseudo Labels 1 showed top 1 accuracy of 87.96, and Meta pseudo labels 2 with increased widen factor showed 88.35. In Top5 Accuracy, the score of Meta Pseudo Labels 1 was 97.90, which was 0.11% higher than 97.79 of Meta Pseudo Labels 2. Conclusion: All four deep learning algorithms used for implant identification in this study showed close to 90% accuracy. In order to increase the clinical applicability of deep learning for implant identification, it will be necessary to collect a wider amount of data and develop a fine-tuned algorithm for implant identification.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.133-144
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• 2003

Horizontal consolidation characteristics of Busan marine clay were investigated by computing coefficient of horizontal consolidation from Piezocone data and comparing their results with those of standard consolidation test. It is well known that current prediction models of $c_h$ for high plastic soils have large uncertainties, and show a great difference between the predicted and the measured values. However, the spherical models and expanding cavity theory of Torstensson(1977), and Burns & Mayne(1998) based on modified Cam-Clay model with critical limit state concepts have relative reliability in estimating $c_h$ and good applicability in highly plasticity soils. In this paper, a normalization technique was used to evaluate $c_h$ using the Burns and Mayne's method based on the dissipation test, and their normalized consolidation curves give 0.015 of time factor($T_{50}$) when 50% degree of consolidation is completed. Comparison study using Piezocone data obtained at other similar ground site shows 1.5 times less systematicality than that of standard consolidation test, which indicates considerable approximation with the measured values because standard consolidation test gives the difference of three to few times compared with the measured values. In addition, design chart for estimating $c_h$ based on the chart from Robertson et al.(1992) and using the other method of the direct prediction from the of dissipation test was newly proposed. It is judged that new proposed chart is very applicable to Korean marine soils, especially in very high plastic soils.

• Environmental and Resource Economics Review
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• v.15 no.1
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• pp.27-50
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• 2006

We estimate $CO_2$ emissions in Korea industry, 1990 and 2000 using a commodity- by-industry IO model ($CO_2$ hybrid IO mode]). Estimated $CO_2$ emissions in industries include both $CO_2$ emissions from direct and indirect consumption. The results show that total $CO_2$ emissions has increased by 51.6 million TC (Tonne of Carbon) from 64.4 million TC in 1990 to 115.5 million TC in 2000. By applying the structural decomposition analysis technique, we decompose change of $CO_2$ emissions in Korea industry between the period 1990~2000. In the decomposition, we figure out two contributing factors, changes in $CO_2$ coefficient and changes in final demand. The latter is further decomposed as growth effects and structural effects. We also estimated each factor's contribution to the changes in $CO_2$ emissions in industries between 1990~2000. The analysis can be used as a useful resource for policy makers in improving the effectiveness of $CO_2$ emissions mitigation policy.

• The Transactions of the Korea Information Processing Society
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• v.4 no.3
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• pp.880-894
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• 1997

In this paper,we propose a new algorithm to perform DCT(Discrete Cosine Transform) withn the area reduced by prdeicting position of quantization coefficients to be zero.This proposed algorithm not only decreases the enoding time and the decoding time by reducing computation amount of FDCT(Forward DCT)and IDCT(Inverse DCT) but also increases comprossion ratio by performing each diffirent horizontal- vereical zig-zag scan assording to the calssified block size for each block on the huffiman coeing.Traditional image coding method performs the samd DCT computation and zig-zag scan over all blocks,however this proposed algorthm reduces FDCT computation time by setting to zero insted of computing DCT for quantization codfficients outside classfified block size on the encoding.Also,the algorithm reduces IDCT computation the by performing IDCT for only dequantization coefficients within calssified block size on the decoding.In addition, the algorithm reduces Run-Length by carrying out horizontal-vertical zig-zag scan approriate to the slassified block chraateristics,thus providing the improverment of the compression ratio,On the on ther hand,this proposed algorithm can be applied to 16*16 block processing in which the compression ratio and the image resolution are optimal but the encoding time and the decoding time take long.Also,the algorithm can be extended to motion image coding requirng real time processing.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.596-608
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• 2018

As urban infrastructure is aging, the possibility of accidents due to the failures or breakdowns of infrastructure increases. Especially, aging underground infrastructures like sewer pipes, waterworks, and subway have a potential to cause an urban ground sink. Urban ground sink is defined just as a local and erratic collapse occurred by underground cavity due to soil erosion or soil loss, which is separated from a sinkhole in soluble bedrock such as limestone. The conventional measurements such as differential settlement gauge, inclinometer or earth pressure gauge have a shortcoming just to provide point measurements with short coverage. Therefore, these methods are not adequate for monitoring of an erratic subsidence caused by underground cavity due to soil erosion or soil loss which occurring at unspecified time and location. Therefore, an alternative technology is required to detect a change of underground physical condition in real time. In this study, the feasibility of a novel magnetic resonance based monitoring method is investigated through laboratory tests, where the changes of path loss (S21) were measured under various testing conditions: media including air, water, and soil, resonant frequency, impedance, and distances between transmitter (TX) and receiver (RX). Theoretically, the transfer characteristic of magnetic field is known to be independent of the density of the medium. However, the results of the test showed the meaningful differences in the path loss (S21) under the different conditions of medium. And it is found that the reflection coefficient showed the more distinct differences over the testing conditions than the path loss. In particular, input reflection coefficient (S11) is more distinguishable than output reflection coefficient (S22).

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.64-70
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• 2023

In this study, reliability tests of torsion control expansion anchors according to drill bit diameters were performed. The standard deviation and coefficient of variation of the anchor were reviewed through the tests for each variable, and the results were compared and evaluated with the standard test results. As a result of the reliability test of the M12 and M16 anchors with 1.04 times the drill bit diameter, they were within 20% of the ultimate tensile load permissible standard coefficient of variation. It was found that the pulling-out performance of the anchor installed in the large hole was sufficiently secured. However, it was found to be about 253% and 210% of the design strength, indicating that the pulling performance of the anchor installed in 1.04 times the drill bit diameter was sufficiently secured. As a result of the reliability test of the M12 and M16 anchors with 1.02 times the drill bit diameter, the value of the coefficient of variation of the ultimate tensile load limit was within 20%, which satisfies the test standard. It was shown to be about 136% and 168% of the design strength, indicating that the pulling-out performance of the anchor installed in 1.02 times the drill bit diameter is sufficiently secured.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.2
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• pp.79-89
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• 1997

The objective of this paper is to investigate the mechanical characteristics of the laminated rubber bearings (LRBs) for the seismic isolation. The evaluations of the proposed equations of the LRB horizontal stiffness are carried out and these equations are extended to the visco-elastic problems to investigate the damping amplifications of LRBs. The stability evaluation of LRBs is also performed. For investigation of the dynamic characteristics of LRBs, the horizontal stiffness equations of the LRBs considering the P-delta effects are applied to the modeling of a seismically isolated structure and the earthquake response time history analyses are carried out. From this research, the proposed simple equation of the horizontal stiffness of LRB is so useful for the design loads and easily extended to the visco-elastic problems. Through the stability evaluation of LRB, the increasing ratio of the total rubber thickness of the LRB severely decrecises the bucking load than the increasing ratio of unit rubber thickness. From the comparison of the dynamic shear deflection of LRB, the analysis results are in good agreement with those of the experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.628-636
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• 2010

In this paper, we present a new type high speed parallel multiplier for performing the multiplication of two polynomials using standard basis in the finite fields GF($2^m$). Prior to construct the multiplier circuits, we design the basic cell of vector code generator(VCG) to perform the parallel multiplication of a multiplicand polynomial with a irreducible polynomial and design the partial product result cell(PPC) to generate the result of bit-parallel multiplication with one coefficient of a multiplicative polynomial with VCG circuits. The presented multiplier performs high speed parallel multiplication to connect PPC with VCG. The basic cell of VCG and PPC consists of one AND gate and one XOR gate respectively. Extending this process, we show the design of the generalized circuits for degree m and a simple example of constructing the multiplier circuit over finite fields GF($2^4$). Also, the presented multiplier is simulated by PSpice. The multiplier presented in this paper uses the VCGs and PPCS repeatedly, and is easy to extend the multiplication of two polynomials in the finite fields with very large degree m, and is suitable to VLSL.