• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.392-403
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• 2010

In this study, a new methodology by using the X-ray CT scan is proposed for estimating void ratio of very fine clayey soil. Since the particle size of the clay is too fine to calculate the volume of void inside the clays, CT scanning tests with a number of clay specimens that were artificially set to have various designated void ratios have been carried out. From the tests, a relationship between the CT values and void ratios is given to be used for estimating the invisible void ratio of very fine clay from a representative CT value scanned. The linear relationship was able to be acquired finally. It is expected that micro X-ray CT scanning can be capable of capturing the void ratio of very fine soils without any errors inherent in the conventional specific gravity tests.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1612-1617
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• 2003

Synchrotron X-ray micro imaging technique was employed to non-invasively monitor the water flow inside xylem vessels in a bamboo leaf. The phase contrast X-ray images clearly visualized plant anatomy and the rise of a water front inside the vessels. Consecutive X-ray images taken for 60 seconds revealed water rise kinetics against gravity in the xylem of a cut dry leaf taken from a bamboo tree. For the first time, traces of water rise, variation of contact angle between water and xylem wall as well as the internal structure of xylem were obtained. In xylem vessels, a repeating flow pattern has a typical flow velocity of 30.7$\mu\textrm{m}$/s and faster flow is established intermittently. It is concluded that the transmission type of X-ray micro imaging can be used as a powerful tool to investigate the ascent of sap in the xylem vessels at a resolution higher than that of MRI.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.6
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• pp.281-287
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• 2014

Microstructural and mechanical characteristics of Al-6Si-2Cu alloy for engine mount bracket prepared by gravity casting (as-cast) and die-casting (as-diecast) process have been investigated. For the microstructural characterization, the inductively coupled plasma mass spectrometry (ICP-MS), optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA) analyses are conducted. For the intermetallic phases, the X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) are also conducted with quantitative and qualitative analysis. Micro Vickers hardness and static tensile test are achieved in order to measure mechanical properties of alloys. Secondary dendrite arm spacing (SDAS) of as-cast and as-diecast show 37um and 18um, respectively. A large amount of coarsen eutectic Si, $Al_2Cu$ intermetallic phase and Fe-rich phases are identified in the Al-6Si-2Cu alloy. Mechanical properties of gravity casting alloy are much higher than those of die-casting alloy. Especially, yield strength and elongation of gravity casting alloy show 2 times higher than die-casting alloy. After shot peening, shot peening refined the surface grains and Si particles of the alloys by plastic deformation. The surface hardness value shows that shot peening alloy has higher value than unpeening alloy.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.103-106
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• 1999

In this study, the properties of mortar using ceramic wastes as admixtures and fine aggregates are considered experimentally. The main chemical of ceramic wastes is SiO2 and micro structure of ceramic wastes is porous. Absorption of ceramic wastes is higher than that of river sand and specific gravity is lower than that of river sand. Flow value of mortar using ceramic waste admixture and fine aggregates is increased more or less and the strength of mortar using ceramic wastes as fine aggregates is increased.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.56-56
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• 2004

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.265-273
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• 2003

Numerical analysis of bubble motion during nucleate boiling is performed by imposing a constant heat flux condition at the base of a heater which occurs in most of boiling experiments. The temporal and spatial variation of a solid surface temperature associated with the bubble growth and departure is investigated by solving a conjugate problem involving conduction in the solid. The vapor-liquid interface is tracked by a level set method which is modified to include the effects of phase change at the interface, contact angle at the wall and evaporative heat flux in a thin liquid micro-layer. Based on the numerical results, the bubble growth pattern and its interaction with the heating solid are discussed. Also, the effect of heating condition on the bubble growth under a micro-gravity condition is investigated.

• The Journal of Korean Medicine
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• v.19 no.1
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• pp.410-418
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• 1998

From the ancient times, herbs, animals and minerals were used as natural medicine to cure human disease in diverse ways. One of the representative forms in oral intake is decoction. But medicinal decoction degenerates as time passes just as all foods do by the environmental factors, such as micro-organism, enzyme, light and the air. Nowadays, as medicinal decoctions are kept in bottles and retort pouch for longtime, some standard data for preservation is necessary. In order to measure the standard statistics for safe preservation, Youngsunjetongeum used to treat rheumatism, and gout 'were used. According to this experiment which measured pH, specific gravity, analgesic effect and anti-inflammatory effect, the results were as follows: 1. No remarkable change was found in pH and in the specific gravity of decoction. 2. As for the analgesic effect induced by acetic acid in mice, no remarkable decrease in its medicinal efficacy was found, until the 9th day, but it showed in its medicinal efficacy from the 11th day. 3. As for the resultant anti-inflammatory effect caused by vascular permeability, induced by carrageenin and acetic acid, no remarkable decrease in its medicinal efficacy was found until the 9th day, but showed decrease in its medicinal efficacy from 11th day. In conclusion, keeping the natural medicinal decoction more than 9 days should be avoided.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.445-449
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• 2010

The purpose of this study is to improve recycling rate of the waste glasses by investigating bloating mechanism. In this study, we use waste glass(W/G) and hard clay(H/C) as raw materials. The artificial lightweight aggregates were formed by plastic forming($\phi$=10 mm) and sintered by fast firing method at different temperatures(between 700 and $1250^{\circ}C$). The physical properties of the aggregates such as bulk specific gravity, adsorption and microstructure of surface and cross-section are investigated with the sintering temperature and rate of W/G-H/C contents. As the result of the bulk specific gravity graphs, we can found out the inflection point at content of W/G 60 wt%. From the microstructure images, we considered the artificial lightweight aggregates content of W/ G over 60wt% are distributed numerous micro-pores by organic oxidation without Black Core and the artificial lightweight aggregates of W/G below 60 wt% are distributed macro-pores with Black Core.

• Journal of Adhesion and Interface
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• v.17 no.4
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• pp.131-135
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• 2016

We investigated the specific gravity and mechanical property changes of solid-state extruded polypropylene (PP)/talc composites before and after orientation. The specific gravity of the composites increases with increasing the filler contents. The specific gravity of the oriented specimen containing filler in PP matrix is found to be much smaller than that of pre-specimen due to the formation of more micro-voids. It was found that the tensile properties of the composites are increased up to the talc content of 10 wt%, but after the contents exceeding 10 wt%, the tensile properties are decreased. For oriented specimens, the tensile strength of the composites showed monotonously decrease with increasing talc contents. When the contents of talc is 10 wt%, the theoretical values according to Halpin-Tsai equation are close to the experimental values but over 20 wt% of talc contents, the deviation of the experimental values from the theoretical prediction becomes higher. The maximum flexural strength and modulus were observed for PP/talc composites when the talc contents was 10 wt% for both pre-specimen and oriented specimen.

• Journal of the Korea Society of Computer and Information
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• v.19 no.5
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• pp.43-52
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• 2014

In this paper, we propose Gravity Removal and Vector Rotation algorithm for counting steps of wearable device, and we evaluated the proposed GRVR algorithm with Micro-Electro-Mechanical (MEMS) 3-axis accelerometer equipped in low-power wearable device while the device is mounted on various positions of a walking or running person. By applying low-pass filter, the gravity elements are canceled from acceleration on each axis of yaw, pitch and roll. In addition to DC-bias removal and the low-pass filtering, the proposed GRVR calculates acceleration only on the yaw-axis while a person is walking or running thus we count the step even if the wearable device's axis are rotated during walking or running. The experimental result shows 99.4% accuracies for the cases where the wearable device is mounted in the middle and on the right of the belt, and 91.1% accuracy which is more accurate than 83% of commercial 3-axis pedometer when worn on wrist for the case of axis-rotation.