• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.222-227
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• 2001

Full scale construction tests of CFT(concrete filled steel tube) column to solve construction problem and to confirm quality were performed in apartment site. To improve construction efficiency, the tests has been accomplished two stages after the tests for material mixing design had been completed. In the first stage, the experimental variables were the placing methods, existence of guiding pipe, placing velocity and drop height and the height of specimen were $3.6{\cal}m$. In the second stage, Filling steel tube of 9.6m height with concrete was performed by two ways, that is, the pump-up method and the dropping method. The filled condition of the concrete and concrete strength distribution according to the column height were checked and the quality of the CFT column was confirmed.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.934-939
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• 1998

This study discusses the results of adiabatic temperature rise tests which were performed considering various parameters, such as cement type, water-cement ratio, unit cement weigh, admixtures and placing temperature, which influence the temperature rise(K) and reaction velocity ($\alpha$). Theadiabatic temperature rise models obtained from this study are similar to those of Japan Concrete Institute. The models to calculate temperature rise and reaction velocity could be used the analysis f concrete thermal stress.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.4
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• pp.295-302
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• 1990

The purpose of this study is augmentation of heat transfer without additional power in two-dimensional impinging air jet. The technique of heat transfer augmentation used in this experiment is to place rod bundles in front of the flat heated surface. The effects of rod diameter, nozzle-to-target plate distance and the nozzle exit velocity on heat transfer have been investigated. The main conclusions obtained from this experiment are as follows. High heat transfer augmentation is achieved by means of flow acceleration and thinning of boundary layer by placing rod bundles in front of the flat plate. Average heat transfer coefficient becomes maximum in the case of H/B=10,D=4mm. For H/B=2,D=4mm, maximum heat transfer augmentation has been determined to be about 1.5 times larger than that of the flat plate. Heat transfer augmentation by placing the rod bundles at 12m/s is to be about 2 times more than increasing nozzle exit velocity from 12m/s to 18m/s.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.61-62
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• 2021

Because of the problem of increasing self-weight due to the enlargement and high-rise of buildings using normal aggregate concrete, the need for structural lightweight aggregate concrete increases. However, early strength prediction is required when placing structural lightweight aggregate concrete, but research is insufficient. In this study, the ultrasonic pulse velocity of normal aggregate concrete and lightweight aggregate concrete was measured at early age. As a result, the ultrasonic pulse velocity of lightweight aggregate concrete was lower than normal aggregate concrete according to elapsed time at early age.

• Biomedical Science Letters
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• v.11 no.4
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• pp.435-439
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• 2005

To determine the appropriate concentration of papaverine hydrochloride(PPV) for therapeutic intraarterial infusion against cerebral vasospasm and to measure the mean blood flow velocity of the middle cerebral artery in rabbits. Vasospasm was induced in the experimental groups (3 days after infusion; group 1, n=3, 7 days after infusion; group 2, n=3) and a control group (n=l) by placing a blood clot in the subarachnoid space around the top of the internal carotid siphon. PPV (5 mg/kg) was infused into the internal carotid artery. The vascular diameters of the internal carotid artery (ICA) and middle cerebral artery (MCA) were measured on angiograms before and after infusion. The mean blood flow velocity in the MCA was measured on transcranial doppler sonograms before and 24 hours after infusion. After fixation, the MCA was dissected out, stained, and examined microscopically. After PPV infusion in both groups, vascular dilatation of about $20\%$ was seen. The mean increase in blood flow velocity in the group $1(30\%)$ was smaller than in the group $2(70\%)$. The mean blood flow velocity in the MCA decreased by about $30\%$ in both groups, but increased again after 24 hours nearly to the level before PPV infusion. PPV infusion may be more effective in early stages of vasospasm when vascular walls have fewer histologic changes.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.173-181
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• 1999

Eye movements serve vision by placing the image of an object on the fovea of each retina, and by preventing slippage of images on the retina. The brain employs two modes of ocular motor control, fast eye movements (saccades) and smooth eye movements. Saccades bring the fovea to a target, and smooth eye movements prevent retinal image slip. Smooth eye movements comprise smooth pursuit, the optokinetic reflex, the vestibulo-ocular reflex (VOR), vergence, and fixation. Saccades achieve rapid refixation of targets that fall on the extrafoveal retina by moving the eyes at peak velocities that can exceed $700^{\circ}/s$. Various brain lesions can affect saccadic latency, velocity, or accuracy. Smooth pursuit maintains fixation of a slowly moving target. The pursuit system responds to slippage of an image near the fovea in order to accelerate the eyes to a velocity that matches that of the target. When smooth eye movements velocity fails to match target velocity, catch-up saccades are used to compensate for limited smooth pursuit velocities. The VOR subserves vision by generating conjugate eye movements that are equal and opposite to head movements. If the VOR gain (the ratio of eye velocity to head velocity) is too high or too low, the target image is off the fovea, and head motion causes oscillopsia, an illusory to-and-fro movement of the environment.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.990-997
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• 2005

In this paper, the measured results obtained from the ground improved by SCP method at quay-wall caisson foundation in Pusan New Port 1-1 phase are analyzed and then compared with the values predicted by a consolidation theory. The measured settlement is generally smaller than the predicted settlement. For consolidation velocity, the measured velocity is later than the predicted value. According to the execution of caisson placing phases, the predicted value shows higher settlement than the measured one with time being.

• Journal of the Korea Concrete Institute
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• v.13 no.5
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• pp.423-429
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• 2001

In this study, strength characteristics of concrete specimens subjected to horizontal continuous vibration during initial curing were investigated. As experimental variables, vibration velocity(0.25, 0.5, 1.0, 2.0, 4.0 kine) and vibration time(3, 6, 12, 24 hrs) were used. Density and segregation of the specimens were also investigated. Vibrating was started soon after placing, and strengths investigated consist of compressive strength, splitting tensile strength, and bond strength. Strengths decrease were hardly occurred at 0.25 kine vibration velocity regardless of vibration times and all strengths were increased for 3 hrs vibration at 0.5 kine vibration velocity. Density was increased for all specimens due to the vibration and there was no serious segregation under even 4 kine vibration velocity.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.73-81
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• 2013

PURPOSES : In this study, various laboratory tests were performed to investigate basic physical properties of the asphalt concrete which uses wasted vinyl aggregates. METHODS : The thermal conductivity, ultrasonic velocity, Marshall stability, flow, indirect tensile strength were measured according to binder content and wasted vinyl aggregate content. An experimental construction was performed to verify construct ability of the asphalt pavement using the wasted vinyl aggregates. RESULTS : The thermal conductivity and ultrasonic velocity decreased showing insulation effect by mixing more wasted vinyl aggregate, whereas stability and flow increased. The void ratio shows similar value regardless of the mixing ratio. The highest indirect tensile strength was measured at 2.5% of wasted vinyl aggregate content. The construct ability was verified by observing the process of mixing, placing, and compaction and the state of the pavement surface. CONCLUSIONS : The basic properties and construct ability of the asphalt concrete using the wasted vinyl aggregates were verified. The temperature according to pavement depth will be measured to verify the insulation effect of the wasted vinyl aggregates. In addition, amount of snowfall, snowmelt area, and ice adhesion strength will be analyzed quantitively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1102-1108
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• 2014

This study was to compare the protection abilities of an SPF through ground or underwater casting. A mat of 1/10 scale was made and then mortar was placed on the ground and submerged conditions. A limit velocity of each mat was estimated with this experiment. As a result of the test, the mat failed because of the decrease of bearing power in the center of the waterway. On the one hand, the edge of the mat, where the velocity is slow, secures stability. The result of the limit velocity analysis suggests that a velocity of ground placement with 6.51m/s and underwater casting with 9.80m/s is the minimum to ensure stability. When SPF mat with a thickness of 0.50m is replaced with a concrete block, it is calculated to need a maximum thickness of 2.21m.