• Journal of Wetlands Research
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• v.21 no.4
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• pp.298-304
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• 2019

In this paper, the analytical method to derive wind fragility for urban street tree in Korea was shown. Monte Carlo Simulation method was used to determine the probability of failure for urban street tree. This probability result was used to determine wind fragility parameters for four types of tree based on the study of street tree species in urban area in Daegu, Korea. Wind fragility for street tree was presented in terms of median capacity and standard deviation of the natural logarithm of the capacity. Results showed that the dominant factor affecting the probability of failure of tree under wind load was their diameter. Moreover, amongst the four types of tree chosen, the tree with height 7m and diameter 35cm had the lowest probability of failure under wind loading, whereas the tree with height 8m and diameter 30cm could resist the least wind loading. The median failure wind speed for urban street tree with height 7m were 43.8m/s and 50.6m/s for diameter 30cm and 35cm, respectively. Also, for tree with height 8m, their median failure wind speeds were 38.7m/s and 45.4m/s for tree with diameter 30cm and 35cm, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.8
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• pp.1976-1995
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• 2023

The anchor-free object detector CenterNet regards the object as a center point and predicts it based on the Gaussian circle region. For each object's center point, CenterNet directly regresses the width and height of the objects and finally gets the boundary range of the objects. However, the critical range of the object's center point can not be accurately limited by using the Gaussian circle region to constrain the prediction region, resulting in many low-quality centers' predicted values. In addition, because of the large difference between the width and height of different objects, directly regressing the width and height will make the model difficult to converge and lose the intrinsic relationship between them, thereby reducing the stability and consistency of accuracy. For these problems, we proposed a center point prediction method based on the Gaussian elliptic region and a size component regression method based on the small solution space. First, we constructed a Gaussian ellipse region that can accurately predict the object's center point. Second, we recode the width and height of the objects, which significantly reduces the regression solution space and improves the convergence speed of the model. Finally, we jointly decode the predicted components, enhancing the internal relationship between the size components and improving the accuracy consistency. Experiments show that when using CenterNet as the improved baseline and Hourglass-104 as the backbone, on the MS COCO dataset, our improved model achieved 44.7%, which is 2.6% higher than the baseline.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.417-422
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• 2008

With standard orthorectification algorithms, one can produce unacceptable structure duplication in the orthophoto due to the double projection. Because of the abrupt height differences, such structure duplication is a frequently occurred phenomenon in the dense urban area which includes multi-history buildings. Therefore, occlusion area detection especially for the urban area is a critical issue in generation of true orthophoto. This paper deals with occlusion area detection with visible height based approach from aerial imagery and LiDAR. In order to accomplish this, a grid format DSM is produced from the point clouds of LiDAR. Next, visible height based algorithm is proposed to detect the occlusion area for each camera exposure station with DSM. Finally, generation of true orthophoto is presented with DSM and previously produced occlusion maps. The proposed algorithms are applied in the Purdue campus, Indiana, USA.

• Journal of the Korea Institute of Building Construction
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• v.11 no.1
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• pp.29-34
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• 2011

Since the study of building performance design was first undertaken by Building Research Station in 1930s, the results of such study has been reported from many parts of the world, building construction codes and standards have been revised based on performance in advanced nations as well in Korea, and various performance certification systems are in operation. The purpose of this study is to build a database of performance certification systems to investigate the co-relationship of various test methods related to the same test items. As test methods for case study, we selected test methods involving collision of the human body. Through analysis of Critical fall height test of EN 1177 and Head Model test of JIS A 6519 about 8 species of floor test-bodies, it was found that there are limits of application in terms of the depth and strength of cushion. Furthermore, although the measured physical parameters are the same, when the co-relationship between test methods is uncertain, the various physical parameters may not be compatible with the results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.4
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• pp.71-80
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• 1990

Model tests for the ultimate pullout resistance of anchorages and investigation of failure behaviors in cohesionless soil have been conducted. The factors affecting the anchorage are mostly the geometry of the system, and soil properties of sands. The main conclusions of the experimental work were as follows. 1. The load - displacement relationship can be a form of parabolic curve for all plates. 2. The change in ultimate pullout resistance of anchor is mostly affected by embedment ratio and size of anchor, and influenced to a lesser degree by its shape. 3. Critical embedment ratio which is defined as the failure mode changes from shallow to deep mode is increased with increasing height of anchor. 4. For a constant anchor height, as the width of anchor increases the ultimate pullout resistance also increases. However, considering the efficiency of anchor for unit area, width of anchor does not appear to have any sigrnificant contribution on increasing anchor city. 5. Anchor capacity has a linear relation to sand density for any given section and the rate of change increases as the section increases. Critical depth determining the failure patterns of anchor is decreased with a decrease of sand density. 6. With increasing inclination angle, size of anchor, and decreasing embedment ratio, the ultimate pullout resistance of anchor under inclined loading is significantly decreased. 7. The ultimate pullout resistance of double anchor, a method of improving single of anchor capacity, is influenced by the center - to - center spacing adjacent anchors. It is also found that tandem and parallel anchor rigging arrangements decrease the anchor system capacity to less than twice the single anchor capacity due to anchor interference.

• Tunnel and Underground Space
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• v.17 no.6
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• pp.503-510
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• 2007

Rock classification schemes such as RMR, Q-system were applied to investigate the stability of large-scale gangways mined in a limestone mine. 22 areas for engineering geological surveys were selected and rock classifications at each survey point had been carried out. Considering the fact that the observed gangways have not experienced some severe failure and have been stably maintained till now, it is found that Q-system is more reasonable than RMR in evaluating the stability of unsupported span. Also, extended Mathews stability graph method which is a kind of revised Q-system was used to assess the stability of gangways and the results represent that all gangways except for one area are under stable condition. Based on above the mentioned results, the empirical equations to design the maximum unsupported span and critical height of a large-scale gangway are suggested.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.451-461
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• 2016

The objective of this study is to illustrate the methods and procedures for estimating the failure probability of small fill dams subjected to earthquake events and to estimate the seismic failure probability of the Korean disaster risk fill dams where geotechnical information is not available. In this study, first of all, seismic failure probabilities of 7 disaster risk small fill dams, where geotechnical information is available, were evaluated using event tree analysis. Also, the methods and procedures for evaluating probabilities are illustrated. The relationship between dam height and freeboard for 84 disaster risk small dams, for which the safety diagnosis reports are available, was examined. This relationship was associated with the failure computation equation contained in the toolbox of US Army corps of engineers. From this association, the dam height-freeborard critical curve, which represents 'zero' failure probability, was derived. The seismic failure probability of the Korean disaster risk fill dams was estimated using the critical curve and the failure probabilities computed for 7 small dams.

• Journal of Sensor Science and Technology
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• v.7 no.1
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• pp.61-66
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• 1998

High quality c-axis oriented $YBa_{2}Cu_{3}O_{7}$ films were prepared using the pulsed laser deposition on $SrTiO_{3}$(100) substrate. The atomically smooth $SrTiO_{3}$surface with terraces one unit cell in height could be obtained by a high temperature annealing. $YBa_{2}Cu_{3}O_{7}$ thin films deposited on the substrates exhibited layer-by-layer growth with a c-axis unit cell height. $YBa_{2}Cu_{3}O_{7}$ thin films thus prepared showed critical temperature ${\ge}90$ K with transition width ${\le}0.6$ K, room temperature resistivity of ${\sim}300{\mu}{\Omega}cm$, and critical current density ${\sim}4.6{\times}10^{6}A/cm^{2}$ at 77 K.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.241-246
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• 2019

In this paper, reactive surfactants were synthesized by using acrylic acid or 3-butenoic acid as nonionic surfactants, polyoxyethylene(23) lauryl ether (Brij 35) and polyoxyethylene(20) stearyl ether (Brij S20). The synthesis of surfactants was confirmed by FT-IR and $^1H$-NMR. The surface tension, emulsifying property, and foam power and stability were also measured. The surface tension value was 35~41 dyne/cm at an critical micelle concentration (cmc) which was measured as $1.0{\times}10^{-4}{\sim}9.7{\times}10^{-5}mol/L$ using a surface tension method. The emulsifying power of synthesized surfactant was measured with benzene, soybean oil and monomer. Also, the initial height of the bubbles and the height after 5 minutes were measured and the values were compared with each other.

• Steel and Composite Structures
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• v.43 no.2
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• pp.271-278
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• 2022

Buckling is one of the most critical phoneme in the design of steel structures. Lateral torsional buckling (LTB) is particularly significant for slender beams generally subjected to loading in plane. The web distortion effects on LTB are not addressed explicitly in standards for flexural design of steel I-section members. Hence, the present study is focused to predict the influence of the web distortion on the elastic (L_r) limiting lengths given in American Institute of Steel Construction (AISC) code for the lateral torsional buckling (LTB) behavior of steel beams due to no provision in the code for consideration of web distortion. For this aim, the W44x335 beam is adopted in the buckling analysis carried out by the ABAQUS finite element (FE) program since it is one of the most critical sections in terms of lateral torsional buckling (LTB). The strain results at mid-height of the web at mid-span of the beam are taken into account as the monitoring parameters. The web strain results are found to be relatively greater than the yield strain value when L/L_r is equal to 1.0. In other words, the ratio of L/L_r is estimated from the numerical analysis to be about 1.5 when the beam reaches its first yielding at mid-span of the beam at mid-height of the section. Due to the effect of web distortion, the elastic limiting length (L_r) from the numerical analysis is obtained to be considered as greater than the calculated length from the code formulation. It is suggested that the formulations of the limiting length proposed in the code can be corrected considering the influence of the web distortion. This correction can be a modification factor or a shape factor that reduces sectional slenderness for the LTB formulation in the code.