• Archives of Pharmacal Research
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• v.18 no.6
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• pp.415-422
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• 1995

Twenty-four flavones were synthesized with various hydroxyl and/or methoxyl groups on A and B rings. Their antimutagenic properties were evaluated against ben:w(a)pyrene (BaP) and a pool of mutagenic urine concentrate (U) using a modified liquid incubation method of Ames test. The tester strain was Salmonella typhimurium TA98+S9 Mix. The antimutagenic activities were calculated by non linear regression analysis and the doses of flavones (in nmoles) required for a 50% reduction of induced revertants with BaP and U were defined as the inhibition doses (TEX>$ID_{508}{\;}and{\;}ID_{508}$ respectively). Seventeen flavones possessed significant antimutagenic activity against BaP. $ID_{508}$ ranged from 15.1 nmoles (F22) to 1000.6 nmoles (F13). Eighteen f1avones showed significant antimutagenic activity against U. $ID_{50U}$ ranged from 23.5 nmoles (F22) to 354.6 nmoles (F3). The 2',3',4'-trihydroxyflavone (F22, $ID_{508}=15.1$ nmoles, $ID_{50U}=23.5$ nmoles) and the 2',3',4',7-tetrahydroxyflavone (F20, $ID_{508}=37.8$ nmoles; $ID_{50U}=62.3$ nmoles) had antimutagenic activities similar to those of chlorophyllin ($ID_{508}=19.6$ nmoles and $ID_{50U}=44.2$ nmoles) and were evaluated against B(alP 7,8-dihydrodiol-9,10-epoxide. Against this last mutagen, the flavones which included three OH in B ring showed the highest activity and this property seemed independent of the substituent groups on A ring.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.149-156
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• 2022

In order to study the open-water test and analysis techniques for pumpjet propulsors in the Large Cavitation Tunnel (LCT), at the Korea Research Institute of Ships and Ocean Engineering, a set of test equipment was designed and manufactured. The pumpjet propulsor is composed of rotor, stator and duct resulting in the strong interaction between the components. A ring-shaped sensor was developed to measure the thrust and torque for duct and stator. The test equipment including the pumpjet is installed on an existing POW dynamometer in the reverse direction. The results from the reverse POW test setup were validated against those from the conventional POW test setup in the Towing Tank (TT) as well as in the LCT. The pumpjet open-water test was conducted at the Reynolds number of around 1.0×106, at which the obtained experimental data became stable in the Reynolds number effect test. The open-water test for the rotor (rotor-only) was conducted to study whether the duct and stator should be considered as a part of the hull or the propulsor. On the basis of the test results, it was shown that the duct and stator could be included in the propulsor. The total thrust, combined thrust of rotor, duct, and stator was used for the pumpjet open-water test analysis. As the whole pumpjet is defined as a propulsor, it is thought that the self-propulsion test and analysis could be conducted in the same way as that of the conventional propeller.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.267-272
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• 2011

We analyzed the wear characterization of $Si_3N_4$ ceramics according to the amount of added $SiO_2$ nanocolloid. The test specimen was prepared by hot-press sintering at 35 MPa and 2123 K in an $N_2$ gas atmosphere for 1 h. A wear test was performed with a block-on-ring tester, and the test conditions were as follows: (1) the ring with a diameter of 35 mm had a rotational speed of 50 rpm; (2) the load was 9.8 N; and (3) the temperature was $25^{\circ}C$. The test results show that $Si_3N_4$ ceramics have a friction coefficient of about 1.0 and a wear loss of about 0.02 mm. Of the specimens used this study, the test specimen with 1.3 wt% of added $SiO_2$ nanocolloid has the best wear resistance because it has the lowest friction coefficient and the smallest wear loss. This specimen also has the highest Vickers hardness and bending strength. In this study, the friction coefficient is inversely proportional to the hardness and bending strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.655-662
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• 2014

This study conducted tensile tests on an Alloy 690TT tube at room temperature (RT) and at $343^{\circ}C$ using tube- and ring-type specimens to investigate the stress-strain behavior and tensile properties of a steam generator (SG) tube in the axial and circumferential directions at RT and at the design temperature of a nuclear power plant (NPP). The results of the axial tensile test showed that yield point phenomena appeared at both RT and $343^{\circ}C$, and serrated flow in the stress-strain curve appeared at $343^{\circ}C$. Yield and tensile strengths for both directions were clearly lower at $343^{\circ}C$ compared to RT; however, the elongations were approximately the same at both test temperatures. Regardless of the test temperature, the strengths in the circumferential direction were lower by approximately 5~10 % than those in the axial direction. In addition, the test data revealed that the reduction in the yield and tensile strengths of the Alloy 690TT SG tube with the test temperature was more significant than that estimated by the temperature correction factor of ASME Sec.II.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.4
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• pp.16-23
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• 2015

The industrialization and urbanization forced to increase the density of pipelines such as water supply, sewers, and gas pipelines. The materials used for the existing pipe lines are mostly composed of concretes and steels, but it is true that the development for more durable and efficient materials has been continued performed to produce long lasting pipe lines. Recently, underground pipes serve in diverse applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. In this paper, we present the result of investigation pertaining to the structural behavior of unplasticized polyvinyl chloride (PVC-U) flexible pipes buried underground. In the investigation of structural behavior such as a ring deflection, pipe stiffness, 4-point bending test, experimental and analytical studies are conducted. In addition, pipe stiffness is determined by the parallel plate loading tests and the finite element analysis. The difference between test and analysis is about 8% although there are significant variations in the mechanical properties of the pipe material. In addition, it was found by the 4-point bending test there is no problem in the connection between the pipes by coupler.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.170-173
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• 2007

Cooling characteristics of a liner were investigated by a film cooling method using a gas nitrogen in a rocket engine. High temperature gas of this test was made by mixing liquid nitrogen with combustion gas of a liquid rocket. A supply system of gas nitrogen was additionally constructed to the existing test facility of liquid rocket engine, and a new test section consisted of a liner and a gas injection ring was manufactured. A 10 second firing test for finding cooling characteristics of the liner was successfully conducted and liner surface temperatures and hot gas temperature was obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.31-34
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• 2007

Performance tests of supersonic exhaust diffuser were conducted by using hot combustion gas for simulating high-altitude environment. The test rig consists of a combustion chamber, a vacuum chamber, water cooling ring and diffuser. Before combustion experiments, the preliminary leak tests were carried out on the liquid rocket engine and diffuser by using high pressure nitrogen(30barg) and a vacuum pump. The leak test results showed that there was no leaks at high pressure and vacuum pressure conditions.

• 보존과학연구
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• s.20
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• pp.139-154
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• 1999

We tested to obtain the excellent Epoxy resins on the property of matter. Existing Epoxy resins is tested to regulate the viscosity, color and hardening time etc. Benzen-ring structure of Bisphenol A type (AY 103) is replaced by Hydrogenated B.P.A type. And hardener is replaced by Polyoxyalkylene Amine. So we are developed into the two resins(L-30, L-40).To know if this Epoxy resins was fitted to repairing and restoration of stone cultural properties. Three kinds of Epoxy resins (AY 103, L-30, L-40) are tested on the artificial weathering test, freezing-melting test, exposure test etc. As a result of test, L-30 is less the discoloration than that of other Epoxy resins and was superior to the excellent property of matter.

• Journal of the Korean GEO-environmental Society
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• v.23 no.1
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• pp.31-37
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• 2022

This study is focused on developing a technology to prevent high-strength wire net from expanding damage due to insufficient performance of the existing PVC coating net. For the test method, reference was made to ISO 17746, an international standard. In addition, as a result of referring to the test criteria, a wire net was fabricated with a width of 1,000 mm or more a size of 1 m² sample. load-displacement curve of the test results was compared to analyze how much performance was improved compared to the existing PVC coating net.

• Journal of Korean Association for Spatial Structures
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• v.23 no.1
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• pp.61-68
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• 2023

Buckling Restrained Braces can not only express the strength considered at the time of design, but also reduce the seismic load by energy dissipation according to the plastic behavior after yield deformation of the steel core. The physical characteristics and damping effect may be different according to the buckling prevention method of the steel core by the lateral restraint element. Accordingly, in this study, To compare hysteresis characteristics, Specimen(BRB-C) filled with mortar, specimen(BRB-R) combined with a buckling restraint ring and Specimen(BRB-EP) filled with engineering plastics was fabricated, and a cyclic loading test was performed. As a result of the cyclic loading test, the maximum compressive strength, cumulative energy dissipation and ductility of each test specimen was similar. But in case of the cumulative energy dissipation and ductility, BRB-C filled with the mortar specimen showed the lowest. This is considered to be because the gap between the steel core and the reinforcing material for plastic deformation was not uniformly formed by pouring mortar around the core part.