• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.1917-1922
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• 2000

The split Hokinson pressure bar(SHPB) test has been used to find the mechanical property of materials at high strain rate. A tensile split Hopkinson pressure bar test system is developed and the threaded tensile specimen and the split collar are placed between elastic bars. When the compressive elastic wave generated by a striker is transferred from the transmit bar to the incident bar, some elastic wave is reflected at the threaded parts of the specimen and the transmit bar. This reflected wave can interfere with the transmitted wave. A proper length of elastic bars and the location of strain gage in these elastic bars are determined to avoid this interference. In order to avoid the interference of elastic wave reflected at the threaded parts of specimen and elastic bar, the length of transmit bar must be longer than that of incident bar. Strain gage in transmit bar must be located as close as possible from the interface of a transmit bar and specimen. In the developed tensile SHPB test system, A12011-T3 and A17075-T6 are tested to get the true stress-strain relation in the range of strain rate at $10^3/sec$

• Architectural research
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• v.20 no.4
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• pp.129-135
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• 2018

In order to compare the development performance of headed reinforcing bar and straight reinforcing bar in tension for steel fiber reinforced concrete (SFRC), pullout test of specimens with reinforcing bar which was anchored on simple beam perpendicularly was conducted. The experimental variables were steel fiber volume ratio ($V_{Rsf}$), concrete compressive strength, and existence of head. As the result of test, splitting failure of concrete in the development direction of reinforcing bar in most specimens was observed. For development detail of headed reinforcing deformation bar, specimens with 1% $V_{Rsf}$ showed approximately 63%~119% increase in pullout strength compare to specimens with 0% $V_{Rsf}$. Test result shows that SFRC is more effective in increasing pullout strength for headed reinforcing bars than increasing pullout strength of straight bars.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.408-415
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• 1997

Bond strength of reinforcing bar to high-performance concrete using Belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that for the group with portland cement I using superplasticizer additional slump does not decrease the bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfy the modification factor for top reinforcement. The result also show that bond strength is function of square root of concrete compressive strength and cover thickness. More detailed evaluation will be conducted from the test specimen with high strength concrete using the belite cement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.511-518
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• 2010

The split Hopkinson pressure bar (SHPB) has been widely used to determine the mechanical properties of materials at high loading rates. However, to ensure test reliability, the source of measurement error must be identified and eliminated. During the experiment, specimens were placed between the incident and the transmit bar. Contact friction between the test bars and specimen may cause errors. In this study, numerical experiments were carried out to investigate the effect of friction on the test results. In the SHPB test, the stress measured by the transmitted bar is assumed to be the flow stress of the test specimen. However, performing numerical experiments, it was shown that the stress measured by the transmit bar is axial stress components. When the contact surface is frictionless, the flow stress and axial stress of the specimen are approximately equal. On the other hand, when the contact surface is not frictionless, the flow stress and axial stress are no longer equal. The effect of friction on the difference between the flow stress and axial stress was investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.175-181
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• 2004

This study is about a section where underground water level occurs at the underground 5m depth by the excavation of the ground, as a stream is adjacent to a excavation section of High Speed Railway ${\bigcirc}{\bigcirc}$ Station construction sections and a reservoir being always full of water is located at the left side of the construction section. Therefore this test is executed for the design and construction of buoyance anchors able to permanently prevent buoyance by the underground water level at working and for the stable construction and permanent smooth maintenance of structures. In this test, bar type anchors are divided according to their length and standard to execute test-anchor test, and In spot test, 9 test-anchors test, proof test to construction process, suitability test and acceptance test are executed 4 times to 9 test-anchors by dividing anchors according to the length of permanent anchor, the outer diameter of bar and boring diameter. Standard motion characteristic centering on load transmission and break mechanism of bar-type anchors for the prevention of buoyance will be showed in the thesis.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.23-36
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• 2013

PURPOSES: The problem under this circumstance is that the erosion not only drops strength of the steel dowel bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem, alternative dowers bars are developed. METHODS: In this study, the bearing stresses between the FRP tube dowel bar and concrete slab are calculated and compared with its allowable bearing stress to check its structural stability in the concrete pavement. These comparisons are conducted with several cross-sections of FRP tube dowel bars. Comprehensive laboratory tests including the shear load-deflection test on a full-scale specimen and the full-scale accelerated joint concrete pavement test are conducted and the results were compared with those from the steel dowel bar. RESULTS: In all cross-sections of FRP tube dowel bars, computed bearing stresses between the FRP tube dowel bar and concrete slab are less than their allowable stress levels. The pultrusion FRP-tube dowel bar show better performance on direct shear tests on full-scale specimen and static compression tests at full-scale concrete pavement joints than prepreg and filament-winding FRP-tube dowel bar. CONCLUSIONS: The FRP tube dowel bars as alternative dowel bar are invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Also, the pultrusion FRP-tube dowel bar performed very well on the laboratory evaluation.

• The Journal of Dong Guk Oriental Medicine
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• v.2 no.1
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• pp.19-54
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• 1993

To see both $Sh{\grave{u}}nq{\grave{i}}daot{\acute{a}}nt{\bar{a}}ng$(dissipate phlegm and promote vital energy circulation) and $Hu{\grave{a}}y{\bar{u}}t{\bar{a}}ng$(blood circulation and disperse blood stasis) influencing on thrombosis, contusion-hyperemia, and hyperlipidemia, at first we measured the density of FDP, the quantity of fibrinogen, prothrombin time, and the number of platelet of rat taken thrombosis by endotoxin. Secondly we measured the increase-rate of "paw swelling", the number of platelet, the quantity of fibrinogen, and prothrombin time of rat taken contusion-hyperemia. And then we measured the quantity of total cholesterol in serum and of H.D.L-cholesterol and of triglyceride and of phospholipid and of ${\beta}-lipoprotein$, its weight, and the variation of the quantity of electrolyte of rat taken hyperlipidemia by the oral-injection of choleserol. As a result, we can conclude as follows : 1. Out of the test of thrombosis, we can recognize not only the noticeable increae of the number of platelet and the quantity of fibrinogen, but also the noticeable decrease of prothrombin time and the density of FDP in case of $Sh{\grave{u}}nq{\grave{i}}daot{\acute{a}}nt{\bar{a}}ng$-injected rat and $Hu{\grave{a}}y{\bar{u}}t{\bar{a}}ng$-injected rat. 2. Out of the test of contusion-hyperemia, we can recognize not only the noticeable increase of the number of platelet and the quantity of fibrinogen, but also the noticeable decrease of prothrombin time and "increase-rate of paw swelling" in case of $Sh{\grave{u}}nq{\grave{i}}daot{\acute{a}}nt{\bar{a}}ng$-injected rat and $Hu{\grave{a}}y{\bar{u}}t{\bar{a}}ng$-injected rat. 3. Out of the test of hyperlipidemia, at first we can recognize that test rat's weight increased as close as that of normal rat. And we can recognize the noticeable decrease of the triglyceride and phospholipid and ${\beta}-lipoprotein$." Also, in case of the variation of electrolyte we can recognize the decrease of calcium and potassium in $Sh{\grave{u}}nq{\grave{i}}daot{\acute{a}}nt{\bar{a}}ng$-injected rat, and of sodium and magnesium in $Hu{\grave{a}}y{\bar{u}}t{\bar{a}}ng$-injected rat. Thus, as the above-mentioned, in covering thrombosis, contusion-hypermia, and hyperlipidemia, the effect of $Sh{\grave{u}}nq{\grave{i}}daot{\acute{a}}nt{\bar{a}}ng$ and $Hu{\grave{a}}y{\bar{u}}t{\bar{a}}ng$ can be recognized. Granting that $Hu{\grave{a}}y{\bar{u}}t{\bar{a}}ng$ reveals its effectiveness in thrombosis and contusion-hyperemia, and $Sh{\grave{u}}nq{\grave{i}}daot{\acute{a}}nt{\bar{a}}ng$ in hyperlipidemia, it can be inferred that contusion-hyperemia is like "model of blood stasis form" as thrombosis and hyperlipidemia "phlegm-retention diseases form", and both phlegm-retention and blood stasis have correlation each other.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.770-775
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• 2001

Steel bar breaking system is a component of a sled test system for automobile crashworthiness. It is a recent idea for the sled test. In a sled test, a crash pulse is given as a input made from a real test. The steel bar breaking system is designed to generate a certain crash pulse. Orthogonal arrays from design of experiments (DOE) are employed. The factors of the array are panel thickness and the number of steel bars, and the levels are candidate values of them. A simulation is utilized for the crash analysis. A commercial system called LS/DYNA3D is adopted. A test system is designed based on the results.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.653-660
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• 1998

Bond strength of reinforcing bar to high-performance concrete using belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that the specimens with belire cement concrete show higher bond strength than those with portland cement concrete. Bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfies the modification factor for top reinforcement. The results also show that the bond strength is function of the square root of concrete compressive strength and cover thickness. The recently developed high-strength and high-slump concrete with belite cement performs well in terms of bond strength to reinforcing steel.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1657-1662
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• 2017

Rotor bar faults in induction machines, which are a part of main distribution of power system, can even stop the entire system by causing contact between a stator and a rotor. There are two methods of diagnosing rotor bar faults in induction motors, online and offline tests, and existing diagnosis methods have many limitations which can lead to misdiagnosis. This paper proposes a potable rotor bar faults diagnosis system based on single phase rotation test, one of offline test methods, which detects rotor bar faults through impedance interpretation by exciting AC current in a stator winding. The test was conducted on a motor of 0.4kW in the laboratory and a motor of 1500kW in industry field.