• International Journal of Highway Engineering
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• v.20 no.3
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• pp.19-26
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• 2018

PURPOSES : The main purpose of this study is suggest of field bond strength evaluation method for more objective evaluation method through Evaluation of Bond Strength Properties with changing aspect ratio and temperature. METHODS : The evaluation is laboratory bond strength test. Using the core machine, the pull-off test method ; the bond strength test of interface layer the universal testing machine. RESULTS : As a result of the laboratory bond strength evaluation, it was verified that the bond strength by aspect ratio decreases linearly with increasing aspect ratio and the bond strength properties by temperature change existed at high and low temperature condition relative to odinary temperature condition. CONCLUSIONS : According to the results of laboratory bond strength evaluation, the field bond strength evaluation results suggest applying the proposed correction factor (0.8, 1.0, 1.4, 1.9) according to aspect ratio(0.5, 0.1, 1.5, 2.0), For more objective evaluation of the bond strength, it is analyzed that the evaluation value is within $6{\sim}32^{\circ}C$ and the result can be obtained within 5% of the coefficient of variation.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1277-1297
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• 2015

Post-tensioned precast segmental bridge columns have shown high level of strength and ductility, and low residual displacement, which makes them suffer minor damage after earthquake loading; however, there is still lack of confidence on their lateral response against severe seismic loading due in part to their low energy dissipation capacity. This study investigates the influence of major design factors such as post-tensioning force level, strands position, columns aspect ratio, steel jacket and mild steel ratio on seismic performance of self-centring segmental bridge columns in terms of lateral strength, residual displacement and lateral peak displacement. Seismic analyses show that increasing the continuous mild steel ratio improves the lateral peak displacement of the self-centring columns at different levels of post-tensioning (PT) forces. Such an increase in steel ratio reduces the residual drift in segmental columns with higher aspect ratio more considerably. Suggestions are proposed for the design of self-centring segmental columns with various aspect ratios at different target drifts.

• Journal of Welding and Joining
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• v.26 no.6
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• pp.42-47
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• 2008

TIG welding enables to produce high quality weldment. However it has some problems such as shallow penetration and large distortion due to low penetration aspect ratio after welding. In order to overcome those problems, there are many ongoing studies on A-TIG welding, which use active flux. In this study, the effect of arc length and shield gas on penetration aspect ratio with melt-run welding on STS 304 6t, on which active flux was spreaded, was investigated. Arc length was changed from 1mm to 3mm, and aspect ratio became higher as arc length was decreased in this range. 100% Ar gas, Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were used as shield gas in this study. When Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were applied, penetration and melting efficiency were both increased as compared with 100% Ar gas. Aspect ratio was the highest with Ar-2.5% $H_2$ mixed gas.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.317-322
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• 2013

We have proposed and demonstrated a low numerical aperture technique to measure the depth of through silicon vias (TSVs) using white-light scanning interferometry. The high aspect ratio hole like TSV's was considered to be impossible to measure using conventional optical methods due to low visibility at the bottom of the hole. We assumed that the limitation of the measurement was caused by reflection attenuation in TSVs. A novel interference theory which takes the structural reflection attenuation into consideration was proposed and simulated. As a result, we figured out that the low visibility in the interference signal was caused by the unbalanced light intensity between the object and the reference mirror. Unbalanced light can be balanced using an aperture at the illumination optics. As a result of simulation and experiment, we figured out that the interference signal can be enhanced using the proposed technique. With the proposed optics, the depth of TSVs having an aspect ratio of 11.2 was measured in 5 seconds. The proposed method is expected to be an alternative method for 3-D inspection of TSVs.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.387-394
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• 2006

In this study, the effect of using a neutral beam formed by low-angle forward reflection of a reactive ion beam on aspect-ratio-dependent etching (ARDE) has been investigated. When a SF6 Inductively Coupled Plasma and $SF_6$ ion beam etching are used to etch poly-Si, ARDE is observed and the etching of poly-Si on $SiO_2$ shows a higher ARDE effect than the etching of poly-Si on Si. However, by using neutral beam etching with neutral beam directionality higher than 70 %, ARDE during poly-Si etching by $SF_6$ can be effectively removed, regardless of the sample conditions. The mechanism for the removal of ARDE via a directional neutral beam has been demonstrated through a computer simulation of different nanoscale features by using the two-dimensional XOOPIC code and the TRIM code.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.456.1-456.1
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• 2014

Transmutation characteristics of transuranics (TRU) in a transmutation reactor based on LAR (Low Aspect Ratio) tokamak as a neutron source are investigated. Optimum radial build of a transmutation reactor is found by coupled analysis of the tokamak systems and the neutron transport. The dependence of the transmutation characteristics on an aspect ratio, A in the range of 1.5 to 2.5, and on a fusion power in the range of 150 MW to 500 MW are investigated. Equilibrium fuel cycle is developed for effective transmutation and it is shown that with one unit of the transmutation reactor based on the LAR tokamak producing fusion power in the range of a few hundred MW, up to 3 PWRs (1.0 GWe capacity) can be supported with the burn-up fraction bigger than 50%.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.311.2-311.2
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• 2013

Transmutation characteristics of minor actinides in a transmutation reactor based on a Low Aspect Ratio (LAR) tokamak are investigated. One-dimensional neutron transport and burn-up calculation coupled with the tokamak systems analysis were performed to find the optimal system parameters. The dependence of the transmutation characteristics such as neutron multiplication factor, produced power and transmutation rate on an aspect ratio A in the range of 1.5 to 2.0 was investigated. By adding Pu239 in the transmutation blanket as a neutron multiplication material, it was shown that the one unit of the transmutation reactor based on the LAR tokamak producing fusion power of 150 MWth can destroy the minor actinides contained in the spent fuels produced from more than 19 units of l GWe PWRs with production of the power being in the range of 0.9 - 3.4 GWth.

• Steel and Composite Structures
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• v.42 no.1
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• pp.107-121
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• 2022

Past studies have shown that the aspect ratio (width-to-height) of a steel plate shear wall (SPSW) can significantly affect its seismic response. SPSWs with lower aspect ratio (narrow SPSW) may experience low lateral stiffness and flexure dominated drift response. As the height of the frame increases, the narrow SPSWs prove to be uneconomical and demonstrate inferior seismic response than their wider counterparts. Moreover, the thicker web plates required for narrow SPSWs exerts high inward pull on the VBEs. The present study suggests the limiting values of the aspect ratio for an SPSW system by evaluating the seismic collapse performance of 3-, 6- and 9-story SPSW systems using FEMA P695 methodology. For this purpose, nonlinear models are developed. These models are validated with the past quasi-static experimental results. Non-linear static analyses and Incremental dynamic analyses are then carried. The results are then utilized to conservatively suggest the limiting values of aspect ratios for SPSW system. In addition to the conventional-SPSW (Conv-SPSW), the collapse performance of staggered-SPSW (S-SPSW) is also explored. Its performance is compared with the Conv-SPSW and the use of S-SPSW is suggested in the cases where SPSW with lower than recommended aspect ratio is desired.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.349-356
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• 2020

This paper introduces the implementation of a driver's condition warning system using eye aspect ratio to prevent a car accident. The proposed driver's condition warning system using eye aspect ratio consists of a camera, that is required to detect eyes, the Raspberrypie that processes information on eyes from the camera, buzzer and vibrator, that are required to warn the driver. In order to detect and recognize driver's eyes, the histogram of oriented gradients and face landmark estimation based on deep-learning are used. Initially the system calculates the eye aspect ratio of the driver from 6 coordinates around the eye and then gets each eye aspect ratio values when the eyes are opened and closed. These two different eye aspect ratio values are used to calculate the threshold value that is necessary to determine the eye state. Because the threshold value is adaptively determined according to the driver's eye aspect ratio, the system can use the optimal threshold value to determine the driver's condition. In addition, the system synthesizes an input image from the gray-scaled and LAB model images to operate in low lighting conditions.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.158-167
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• 1998

Natural convection heat transfer in a rectangular enclosure is investigated numerically for low aspect ratio(height/width) cavities. Numerical results are obtained for aspect ratios between ${10}^{-2}$ and ${10}^0$, Rayleight numbers from ${10}^3$ to ${10}^7$ and Prandtl numbers from 10$^{-2}$ to 10$^3$. Results are compared with existing analytical and experimental results. A heat transfer correlation is developed to predict the mean Nusselt number as a function of the three governing dimensionless parameters: Rayleigh number, aspect ratio and Prandtl number.