• Tunnel and Underground Space
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• v.33 no.6
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• pp.495-507
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• 2023

The roughness of discontinuity significantly influences the mechanical characteristics of rock masses and extensively affects thermal and hydraulic behaviors. In this study, we utilized photogrammetry to generate 3D point cloud data for discontinuity and applied this data to characterize the roughness of discontinuity. The discontinuity profiles, reconstructed from the 3D point cloud data, were compared with those manually measured using a profile gauge. This comparison served to validate the accuracy and reliability of the acquired point cloud data in replicating the actual configurations of rock surfaces. Subsequent to this validation, influence of the number of profiles for representative JRC assessment was further investigated followed by suggestion of roughness anisotropy evaluation method with application of it to actual rock discontinuity surfaces.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.2
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• pp.27-33
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• 2014

There are several methods to improve the flight efficiency of HALE(High Altitude Long Endurance) UAV(Unmaned Aerial Vehicle). Airframe structural point of view, weight reduction of the airframe structure is the most important method to improve the flight efficiency. In order to reduce the weight of airframe structures, new concepts which are different from traditional airframe structure design such as the mylar wing skin should be introduced. The spar is the most important component in a mylar skin wing structure, so the spar weight reduction is the key point for reduction of the wing structural weight. In this study, design trade-off study for the front spar of the HALE UAV wing is conducted in order to reduce the weight. Design and analysis procedure of high aspect ratio wing spar are introduced. Several front spar structures are designed and trade-off study regarding the weight and strength for the each spar are performed. Spar design configurations are verified by the static strength test. Finally, optimal front spar design is decided and applied to the HALE UAV wing design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1110-1116
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• 2004

Experimental measurements of laser-induced ion mobility(LIIM) were performed for ethene/air premixed flames operated near the soot inception point. Soot was ionized using a pulsed laser operated at 532 nm. The ionization signal was collected with a tungsten electrode located in the post-flame region. ionization signals were collected using both a single electrode and dual electrode configuration. Prior LIIM studies have focused on the use of a single biased electrode to generate the electric field, with the burner head serving as the path to ground. In many practical combustion systems, a path to ground is not readily available. To apply the LIIM diagnostic to these geometries, a dual electrode geometry must be employed. The influence of electrode configuration, flame equivalence ratio, and flame height on ionization signal detection was determined. The efficacy of the LIIM diagnostic to detect soot inception in the post-flame region of a premixed flame using a dual electrode configuration was investigated. For the different dual electrode configurations tested, the dual parallel electrode geometry was observed to be most sensitive to detect the soot inception point in a premixed flame.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.72-76
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• 1996

The magnetostrictive characteristics of three different forms of magnetostrictive transducers made of 2605SC and 2826MB metallic glasses were measured. In both cases, the two-end-point bonding configuration exhibited the best characteristics. With the two-end-point bonding we measured the effective magnetostrictive coefficient $C_{eff}$ of $1.2{\times}^{-5}Oe^{-2}$, the saturation magnetostriction ${\lambda}_s$ of $7.4{\times}10^{-4}$ and the minimum detectable magnetic field $H_{min}$ of $1.6{\times}10^{-7}Oe$/ √Hz for the 2605SC metallic glass ribbon. Also for the 2826MB metallic glass ribbon, Ceff and ${\lambda}_s$ were $7.6{\times}10^{-6}Oe^{-2}$ and $3.4{\times}10^{-4}$ respectively.

• Advances in concrete construction
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• v.9 no.6
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• pp.557-568
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• 2020

In this study, the impact of ring supports around the shell circumferential has been examined for their various positions along the shell axial length using Rayleigh-Ritz formulation. These shells are stiffened by rings in the tangential direction. For isotropic materials, the physical properties are same everywhere where the laminated and functionally graded materials, they vary from point to point. Here the shell material has been taken as functionally graded material. The influence of the ring supports is investigated at various positions. These variations have been plotted against the locations of ring supports for three values of length-to-diameter ratios. Effect of ring supports with middle layer thickness is presented using the Rayleigh-Ritz procedure with three different conditions. The influence of the positions of ring supports for clamped-clamped is more visible than simply supported and clamped-free end conditions. The frequency first increases and gain maximum value in the midway of the shell length and then lowers down. The Lagrangian functional is created by adding the energy expressions for the shell and rings. The axial modal deformations are approximated by making use of the beam functions. The comparisons of frequencies have been made for efficiency and robustness for the present numerical procedure. Throughout the computation, it is observed that the frequency behavior for the boundary conditions follow as; clamped-clamped, simply supported-simply supported frequency curves are higher than that of clamped-simply curves. To generate the fundamental natural frequencies and for better accuracy and effectiveness, the computer software MATLAB is used.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.242-246
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• 2004

Effects of circumferentially local wall thinning on the fracture behavior of pipes were investigated by monotonic four-point bending. Local wall thinning was machined on the pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area included an eroded ratio of d/t= 0.2, 0.5, 0.6, and 0.8, and an eroded length of I = 10 mm, 25 mm, and 120 mm. Fracture type could be classified into ovalization, local buckling, and crack initiation depending on the eroded length and eroded ratio. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors excepting failure due to cracking. It was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the eroded area.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.4
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• pp.83-93
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• 2004

Due to the pressures from surrounding conditions, the current Gyeong-Po Lake has been loosing its original appearance. Historically, the value of Gyeong-Po Lake has been highlighted at the Ru-Jeongs, which were once used to enjoy the various lakeside landscapes. However, the changes in physical appearance of the lake surroundings have ruined the value of the Ru-Jeongs, and even more changed the view point. As an initiating effort to reestablish and to manage the traditional visual landscapes of the lake, this study puts its emphasis on the traditional point of view. Also, this study tries to find the traditional visual values that are not visible at the current time, based on historic literature such as historic documents, paintings and poems. One of the important findings of this study is that viewing the different landscapes was more highly valued than their physical configurations in historic literatures, and that the focal points in viewing landscape were the Ru-Jeongs(누정). Hence, this study suggests that it is necessary to set the Ru-Jeongs, including Gyeong-Po(경포), Bang-Hye(방해), Hwan-Sun(환선), and Ho-Hae(호해), as the focal points for viewing the landscapes in order to reestablish and manage the traditional landscapes of Gyeong-Po Lake.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.10
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• pp.494-501
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• 2001

In this study, the effects of vascular parameter changes and electrodes on VOP measurement based on IPG were simulated mathematically. For the evaluation of the effects of hemodynamic changes on VOP, a mathematical model, which consists of cardiovascular system model and venous occlusion model, was developed and the model solution representing the blood flow and pressure in measuring point was found by 2nd order Runge-Kutta method. And, with sensitivity coefficients obtained from finite element solution of electric field in measuring point, the effects of electrode system on measurement were evaluated. As increasing the resistance, the venous capacitance was not changed but the venous outflows were decreased and the decreased compliance reduced the venous capacitance. And, for several configurations of round electrodes and band electrodes, the sensitivity coefficients were computed using the electric field distribution along deep vein. In conclusion, the proposed mathematical cardiovascular model could be applied to the simulation study on the effects of hemodynamic parameters on DVT diagnosis with IPG. And, also the sensitivity coefficients could provide effective electrode configuration for exact measurement of VOP.

• Computers and Concrete
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• v.32 no.2
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• pp.173-184
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• 2023

In this study, mechanical, flexural post-cracking, and torsional behaviors of recycled steel fiber-reinforced concrete (RSFRC) incorporating steel fibers obtained from recycling of waste tires were investigated. Initially, three concrete mixes with different fiber contents (0, 40, and 80 kg/m³) were designed and tested in fresh and hardened states. Subsequently, the flexural post-cracking behaviors of RSFRCs were assessed by conducting three-point bending tests on notched beams. It was observed that recycled steel fibers improve the post-cracking flexural behavior in terms of energy absorption, ductility, and residual flexural strength. What's more, torsional behaviors of four RSFRC concrete beams with varying reinforcement configurations were investigated. The results indicated that RSFRCs exhibited an improved post-elastic torsional behaviors, both in terms of the torsional capacity and ductility of the beams. Additionally, numerical analyses were performed to capture the behaviors of RSFRCs in flexure and torsion. At first, inverse analyses were carried out on the results of the three-point bending tests to determine the tensile functions of RSFRC specimens. Additionally, the applicability of the obtained RSFRC tensile functions was verified by comparing the results of the conducted experiments to their numerical counterparts. Finally, it is noteworthy that, despite the scatter (i.e., non-uniqueness) in the aspect ratio of recycled steel fiber (as opposed to industrial steel fiber), their inclusion contributed to the improvement of post-cracking flexural and torsional capacities.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.527-535
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• 2016

Statistical optimization algorithms have been variously developed to estimate the 3D shape and motion. However, statistical approaches are limited to analyze the sensitive effects of SfM(Shape from Motion) according to the camera's geometrical position or viewing angles and so on. This paper propose the quantitative estimation method about the uncertainties of an observation matrix by using camera imaging configuration factors predict the reconstruction ambiguities in SfM. This is a very efficient method to predict the final reconstruction performance of SfM algorithm. Moreover, the important point is that our method show how to derive the active guidelines in order to set the camera imaging configurations which can be expected to lead the reasonable reconstruction results. The experimental results verify the quantitative estimates of an observation matrix by using camera imaging configurations and confirm the effectiveness of our algorithm.