• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.539-548
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• 2007

This paper deals with flexural-torsional free vibrations of the circular strip foundation with the variable breadth on Pasternak soil. The cross-section of the strip foundation is chosen as the rectangular one with the constant thickness and variable breadth, which is symmetrical about the mid-arc. Also, the foundation that supports the circular strip is modeled as the Pasternak soil with the shear layer. Ordinary differential equations accompanying the boundary conditions are derived. In the governing equations, the transverse, rotatory and torsional inertias are included. These equations are solved numerically and four lowest frequencies are obtained. In the numerical results, the effects of foundation parameters on frequencies are extensively investigated. It is expected that the theories and numerical results of this study can be used in the dynamic design of strip foundations.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.2
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• pp.73-80
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• 2015

PURPOSE: The purpose of this study is to compare ultrasound images of trunk muscles according to gender in healthy subjects. METHODS: Twenty six subjects(13 males and 13 females) were enrolled in this study. The thickness of trunk muscles was measured for transverse abdominis (TrA), external oblique abdominis (EOA), internal oblique abdominis (IOA), and multifidus (MF) using ultrasound. The thickness of the muscles was measured for the length of cross-section except for fascia. The muscle thickness wasmeasured at the both side, then the mean value was calculated. Also, each of trunk muscle wasanalysed by echodensity, white area index. RESULTS: As a results, there was significant difference in muscle thickness of EOA, IOA according to gender (p<0.05). The male was significant increase than female of EOA, IOA in muscle thickness. There was significant difference in echo intensity of TrA, MF according to gender(p<0.05). The female was significant increase than male of TrA, MF in echo intensity. There was significant difference in white area index of EOA according to gender(p<0.05). The female was significant increase than male of EOA in white area index. CONCLUSION: The findings of this study suggest that healthy male have a greater EOA, IOA trunk muscle thickness than female. However, the difference of muscle quality between male and female was showed through thisexperiment. Therefore, the ultrasonography images will be useful tool for seeing quantitative and qualitative difference of trunk muscles according to gender.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.799-802
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• 2008

General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research must be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study based on 2-D advection-dispersion equation, flow and tracer experiments were performed in the S-curved meandering laboratory channel with a rectangular cross-section. The channel was equipped with instrument carriages which was equipped with an auto-traversing system to be used with velocity measuring sensors throughout the depth and breadth of the flow field. To measure concentration distribution of the salt solution was adjusted to that of the flume water by adding methanol and a red dye (KMnO4) was added to aid the visualization of the tracer cloud, the tracer was instantaneously injected into the flow as a full-depth vertical line source by the instantaneous injector and the initial concentration of the tracer was 100,000 mg/l. The secondary current as well as the primary flow pattern was analyzed to investigate the flow distribution in the meandering channels. The velocity distribution of the primary flow for all cases skewed toward the inner bank at the first bend, and was almost symmetric at the crossovers, and then shifted toward the inner bank again at the next alternating bend. Thus, one can clearly notice that the maximum velocity occurs taking the shortest course along the channel, irrespective of the flow conditions. The result of the tracer tests shows that pollutant clouds are spreading following the maximum velocity lines in each cases with various mixing patterns like superposition, separation, and stagnation of pollutant clouds. Flow characteristics in each cases performed in this study can be compared with tracer dispersion characteristics with using evaluation of longitudinal and transverse dispersion coefficients(LDC, TDC). As expected, LDC and TDC in meandering parts have been evaluated with increasing distribution and straight parts have effected to evaluate minimum of LDC and TDC due to symmetric flow patterns and attenuations of secondary flow.

• Journal of Korea Water Resources Association
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• v.52 no.2
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• pp.115-123
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• 2019

The effects of the Froude numbers on turbulent flow patterns downstream of a non-submerged spur dike were investigated in a laboratory flume. Three-dimensional velocities and water depths were measured using Acoustic Doppler Velocimetry and distance sensors under three Froude number conditions ($Fr_d=0.31$, 0.38, and 0.46). The results show that there are marginal differences in the velocity fields downstream of a spur dike due to the change of the Froude number. However, an increase of the Froude number was found to reduce cross-sectional area in the flow and to increase the strength of the jet-like flow. The jet-like flow was observed to displace the location of the maximum turbulence kinetic energy within a cross section toward the inner bank in the transverse direction.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.643-654
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• 2018

Tunnel excavation leads to a disturbance on the initial stress balance of surrounding soils, which causes convergences around the tunnel and settlements at the ground surface. Considering the effective impact of settlements on the structures at the surface, it is necessary to estimate them, especially in urban areas. In the present study, ground settlements due to the excavation of East-West Line 7 of the Tehran Metro (EWL7) and the Abuzar tunnels are evaluated and the effect of the lateral earth pressure coefficient ($K_0$) on their extension is investigated. The excavation of the tunnels was performed by TBMs (Tunnel Boring Machines). The coefficient of lateral earth pressure ($K_0$) is one of the most important geotechnical parameters for tunnel design and is greatly influenced by the geological characteristics of the surrounding soil mass along the tunnel route. The real (in-situ) settlements of the ground surface were measured experimentally using leveling methods along the studied tunnels and the results were compared with evaluated settlements obtained from both semi-empirical and numerical methods (using the finite difference software FLAC3D). The comparisons permitted to show that the adopted numerical models can effectively be used to predict settlements induced by a tunnel excavation. Then a numerical parametric study was conducted to show the influence of the $K_0$ values on the ground settlements. Numerical investigations also showed that the shapes of settlement trough of the studied tunnels, in a transverse section, are not similar because of their different diameters and depths of the tunnels.

• Advances in nano research
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• v.7 no.1
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• pp.39-49
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• 2019

This paper focuses on two main objectives. The first one is to exploit an energy equivalent model and finite element method to evaluate the equivalent Young's modulus of single walled carbon nanotubes (SWCNTs) at any orientation angle by using tensile test. The calculated Young's modulus is validated with published experimental results. The second target is to exploit the finite element simulation to investigate mechanical buckling and natural frequencies of SWCNTs. Energy equivalent model is presented to describe the atomic bonding interactions and their chemical energy with mechanical structural energies. A Program of Nanotube modeler is used to generate a geometry of SWCNTs structure by defining its chirality angle, overall length of nanotube and bond length between two adjacent nodes. SWCNTs are simulated as a frame like structure; the bonds between each two neighboring atoms are treated as isotropic beam members with a uniform circular cross section. Carbon bonds is simulated as a beam and the atoms as nodes. A finite element model using 3D beam elements is built under the environment of ANSYS MAPDL environment to simulate a tensile test and characterize equivalent Young's modulus of whole CNT structure. Numerical results are presented to show critical buckling loads, axial and transverse natural frequencies of SWCNTs with different orientation angles and lengths. The understanding of mechanical behaviors of CNTs are essential in developing such structures due to their great potential in wide range of engineering applications.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.4
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• pp.157-165
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• 2019

Recently, lean duplex stainless steel, STS329FLD with less nickel (reduced to 0.5~1.5%) has been developed as a substitute of austenitic stainless steel (8%~10.5% nickel in STS304) and included in Korean standards (KS). This paper investigates the block shear behavior of cold-formed duplex stainless steel (STS329FLD, nominal plate thickness of 1.5mm) fillet-welded connection with base metal fracture. Main variables are weld lengths in the longitudinal and the transverse directions of applied force ranged from 20mm to 50mm. As a result, specimens failed by typical block shear facture (the combination of gross section tensile fracture and shear fracture or shear yielding) and ultimate strength of the specimens got higher with the increase of weld length. Block shear fracture strengths predicted by current design specifications (KBC2016/AISC2016 and EC3) and existing proposed equations for welded connections by Topkaya, Oosterhof & Driver and Lee et al. were compared with test strengths. KBC2016/AISC2016 and EC3 design specifications underestimated block shear strength of STS329FLD welded connections by on average 24%, 29%, respectively and Oosterhof & Driver, Topkaya and Lee et al's equations overestimated the ultimate strength of the welded connection by the range of 3% to 44%.

• The Korea Journal of Herbology
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• v.34 no.6
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• pp.25-32
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• 2019

Objectives : Ephedra regeliana, although similar to the other E. sinica, E. intermedia, and E. equisetina, is not authorized by The Korean Pharmacopoeia and yet has also been imported under the name of 'Ma-Hwang'. The aim of this study was to perform a comparative anatomical evaluation of Ephedrae Sinicae Herba (ESH), Ephedrae Intermedicae Herba (EIH), Ephedrae Equisetinae Herba (EEH) and Ephedrae Regelianae Herba (ERH). Methods : Permanent paraffin-embedded specimens were produced using the paraffin-tertiary butyl alcohol (TBA) method, to visualize their anatomical features via light microscopy. Results : ESH and ERH transverse sections were in the shape of a long ellipse, while those of EIH and EEH were in the shape of a circle. These anatomical characteristics substantiated the results of external morphological examination. The sections revealed that each of the four samples showed significantly different cortexes. The cortex of ESH was wider than two thirds of the section, unlike that of the other samples which was relatively narrow. The xylems of ERH, EIH, and EEH demonstrated interconnectivity with other adjacent xylems, contrary to those in ESH. Therefore, the characteristic development of the xylems over time was used to distinguish ERH from the other. Furthermore, parenchymal morphology in the central cylinder was also a good criterion to differentiate between EIH and EEH, since EIH demonstrated parenchymal cells that were shaped like a rounded-triangle, whereas EEH parenchymal cells were chrysanthemum-shaped. Conclusions : The identification-keys established in this study would facilitate the accurate identification of microscopic features of the four varieties of 'Ma-Hwang'.

• Journal of the Korean Wood Science and Technology
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• v.30 no.2
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• pp.108-114
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• 2002

Red pine(Pinus densiflora) square timbers with 14.0 cm and 16.5 cm of face size and 24 m long were dried in a vacuum-press kiln and in a radio-frequency/vacuum(RF/V) kiln to compare drying rate, moisture content(MC) distribution and specific energy. RF/V drying rate was higher than vacuum-press drying rate. The effect of size of cross section on the RF/V drying rates were more pronounced than those of vacuum-press drying. The longitudinal- and the transverse MC distribution of dried square timber showed convex profile for the vacuum-press drying and concave profile for the RF/V drying. Moisture gradient of width direction was similar to the thickness direction in vacuum-press dried square timber and was more slight than that of the thickness direction in the RF/V dried large square timber. The specific energy consumption curve increased as MC decreased. Specific energy(kWh/kg of water evaporated) of the vacuum-press process required more than that of the RF/V process.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.154-162
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• 2022

In this study, a technique for estimating water surface velocity fields in the Universal Transverse Mercator coordinate system using the GPS information of a propagating drone but not ground control points is developed. First, we determine the image direction in which the upper side of an image is directed based on the navigation information of the drone. Subsequently, we assign the start and end frames of the video used and determine the analysis range. Using these two frames, we segment the measurement cross-section into a few subsections at regular intervals. At these subsections, we analyze 30 frame images to create spatio-temporal volumes for calculating the velocity fields. The results of the developed method (propagating drone surface image velocimetry) are compared with those of the existing method (hovering drone surface image velocimetry), and relatively good agreement is indicated between both in terms of the velocity fields.