• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.338-345
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• 2000

A model testing has been performed to investigate the flow characteristics of a vortex chamber, which plays a role of a flow switch and passively controls the discharge flow rate. This method of passive flow control is a matter of concern in the design of advanced nuclear reactor systems as an alternative to the active flow control to provide emergency water to the reactor core in case of postulated accidents like LOCA (Loss-Of-Coolant Accident). By changing the inflow direction in the vortex chamber and varying the flow resistance inside the chamber, the vortex chamber can control passively the injection flowrate. Fundamental characteristics such as discharge flow rate and pressure drop of the vortex chamber are measured, and its parametric effects on the performance of the vortex chamber are also systematically investigated.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.899-903
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• 2009

Recently, research and development of the linear compressor are being active. The reason is that the one has not only higher efficiency than reciprocating type, but also lower noise. But because the dicharge valve of linear compressor is operated in high pressure and temperature circumstance, it is important to prevent leakeage. In this paper three other plastic reinforced composite materials were used. Those are TPI, PEEK and PEK which were containing other volume and kind of carbon fibers. First, for assessing mechanical properties, we measured the hardness and the heating property of the trst sepecimen by the microvickers hardness tester and the differential scanning calorimeter respectively. Finally, through FALEX tester, we could know the characteristics of the wear proving the results of before-conducted experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.922-927
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• 2009

The transducers used in active sonar on surface ships are packed in a specific geometry in the array drum in order to meet the requirements such as the source level, directional beam pattern, etc. This paper describes the acoustic characteristics of the cylindrical array which is based on a 64 vertical staves arrangement, each stave composed 5 independent transducers. Firstly, the single transducer on the rigid baffle in the water is analyzed with the Finite Element Method. From the result of the FE analysis nodal velocities on the radiation surface is calculated and used with the boundary conditions of the transducers mounted on the array drum. Then the acoustic pressure is calculated in the field points using the Boundary Element Method and the other acoustic informations, the source level, beam pattern, near field and far-field distance, were acquired.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.4
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• pp.304-308
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• 2012

Transparent thin film transistors (TTFT) were fabricated using the rf magnetron sputtered ZnO-$SnO_2$ films as active layers. A ceramic target whose Zn atomic ratio to Sn is 2:1 was employed for the deposition of ZnO-$SnO_2$ films. To study the post-annealing effects on the properties of TTFT, ZnO-$SnO_2$ films were annealed at $200^{\circ}C$ or $400^{\circ}C$ for 5 min before In deposition for source and drain electrodes. Oxygen was added into chamber during sputtering to raise the resistivity of ZnO-$SnO_2$ films. The effects of oxygen addition on the properties of TTFT were also investigated. 100 nm $Si_3N_4$ film grown on 100 nm $SiO_2$ film was used as gate dielectrics. The mobility, $I_{on}/I_{off}$, interface state density etc. were obtained from the transfer characteristics of ZnO-$SnO_2$ TTFTs.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.70-73
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• 2005

The HANARO, multi-purpose research reactor, 30 MWth open-tank-in-pool type, is planning to produce a fission moly-99 of radio isotopes, a mother nuclide of Tc-99m, a medical isotope and is under developing a target handling tool for loading and unloading it in a circular flow tube (OR-5). A guide tube is extended from the reactor core to the top of the reactor chimney for easily loading the target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube. The jet flow was suppressed in the guide tube after reducing the inner diameter of a flow restriction orifice installed in the OR-5 flow tube for adding the pressure difference in the flow tube after unloading the target. This paper describes an analytical analysis to calculate the flow distribution in the core of the HANARO after suppressing the jet flow of the guide tube. As results, it was confirmed through the analysis results that the flow distribution in the core of the HANARO were not adversely affected.

• Microbiology and Biotechnology Letters
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• v.24 no.5
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• pp.624-629
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• 1996

The ethanol extracts from Angelica gigas Nakai and Angelica acutiloba Kitagawa were fractionated to diethyl ether and aqueous partitions. Both partitions had strong antimutagenic effect on the MNNG (N-methyl-N-nitro-N-nitrosoguanidine) by Ames mutagenicity test. Diethyl ether fractions exhibited the greatest antimutagenic effect suppressing the mutagenicity of MNNG with inhibition of 78-80%. The ethanol extracts from both species showed the inhibitory effect on the growth of several human cancer cell lines. Especially, the diethyl ether fraction from ethanol extracts was most effective on human hepatocellular carcinoma cells, inhibiting 90-95% of cell growth. However, the aqueous fractions had least inhibition activity on many cancer cells. There was little cytotoxicity on human normal liver cell by ethanol extracts. Diethyl ether fraction from Angelica gigas Nakai ethanol extract had cytotoxicity less than 20% on human normal liver cells, compared with that from Angelica acutiloba Kitagawa ethanol exract. The adding of 0.5 (g/l) of diethyl ether fractions of Angelica gigas Nakai or Angelica acutiloba Kitagawa increased immune activity by enhacing human B and T cells up to three to four times. It was proven that diethyl ether fraction (0.7 g/1) from Angelica gigas Nakai could control blood pressure by suppressing angiotensin converting enzyme activity up to 98%. From TLC, it was appeared that both of diethyl ether partitions had umbelliferon, known to one of active substances from Angelica gigas Nakai and Angelica acutiloba Kitagawa.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.479-491
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• 1994

Discrete vortex method was applied for simulating an active control of turbulent leading- edge separation bubble. The leading-edge separation zone was perturbed by a time-dependent sinusoidal perturbation of different frequencies and levels. In order to describe the local sinusoidal perturbation at the separation point, a source pulsation vortex technique was proposed. The present two-dimensional vortex simulations were qualitatively compared with the experimental results for a blunt circular cylinder, where perturbation was introduced along the square-cut leading edge of the cylinder $(Kiya et al.^{(6,7)}).$ It was found that the reattachment length attained a minimum point at low levels of perturbation and two minima at a moderate higher perturbation frequency. The effects of local perturbation on the evolution of leading-edge separation bubble were scrutinized by comparing the perturbed flow with the natural flow. These comparisons were made for the distributions of mean velocity and its velocity fluctuations, intermittency and wall velocity. The motions of instantaneous reattachment in the space-time domain were demonstrated, which were also compared with the experimental findings. In order to investigate the reduction mehanism of reattachment length in the separation bubble, various cross-correlations for velocity and pressure and the relevant convection velocities were evaluated. It was observed that the convection velocity was closely associated with its corresponding pulsationg frequency.

• Korean Journal of Medicinal Crop Science
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• v.21 no.3
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• pp.204-212
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• 2013

In general, stepwise hot steaming process is known to be effective in improving its biological activities; however, not much employed in processing Codonopsis lanceolata due to its hardness. The complex processed C. lanceolata showed highest free radical scavenging acitivity as 45.21%. Total phenol and flavonoid content were of complex processed C. lanceolata higher than conventional extract and alone steaming process. It was showed the lower melanogenesis rate on melanin production test by B16F10 cells as 27.46%. High inhibitory of tyrosinase was also measured as 28.61% by adding steamed Codonopsis lanceolata extracts by high pressure extraction of 1.0 $mg/m{\ell}$. And anti-wrinkle activity were 39.08%. In comparing phenolic acids profiles in the extract, in general higher amounts of polyphenol were obtained possibly by easy release of active components during thermal processing, which results in better antioxidant activities than that of general extract. This findings can also be supported by result that the extract by steaming process showed better activities than the general extraction extract.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.159-163
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• 2005

This paper gives characterization of ZnO thin film deposited by RF magnetron sputtering method, which is concerned in deposition process and device fabrication process, to fabricate solidly mounted resonator(SMR)-type film bulk acoustic resonator(FBAR). A piezoelectric layer of 1.1${\mu}{\textrm}{m}$ thick ZnO thin films were grown on thermally oxidized SiO$_2$(3000 $\AA$)/Si substrate layers by RF magnetron sputtering at the room temperature. The highly c-axis oriented ZnO thin film was obtained at the conditions of 265 W of RF power, 10 mtorr of working pressure, and 50/50 of Ar/O$_2$ gas ratio. The piezoelectric-active area was 50 ${\mu}{\textrm}{m}$${\times}$50${\mu}{\textrm}{m}$, and the thickness of ZnO film and Al-3 % Cu electrode were 1.4 ${\mu}{\textrm}{m}$ and 180${\mu}{\textrm}{m}$, respectively. Its series and parallel frequencies appeared at 2.128 and 2.151 GHz, respectively, and the qualify factor of the resonator was as high as 401.8$\pm$8.5.

• Journal of Pharmaceutical Investigation
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• v.13 no.4
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• pp.153-172
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• 1983

The use of carrier systems for the delivery of drugs to areas in the body in need of pharmacological intervention is now the subject of intense research in many laboratories. Because of its obvious advantages (e.g. protection of drugs from hostile environments, facilitated target penetration and avoidance of side effects), drug delivery is expected to ease the pressure and expense of new drug development by making better use of drugs in existence. Generally, carrier-mediated delivery has been envisaged either as direct transport of drugs to a biological target by a carrier that will associate with it selectively, or as release of drugs from a carrier circulating in the blood or immobilized in tissues, at rates compatible with optimal action. One system that has attracted considerable attention is the use of liposomes as carriers of pharmacologically active agents. 154 references were reviewed with special emphasis on the targeting of drugs by use of liposomes in this respect. Recent advances in the other carrier systems and in methods for the preparation of liposomes were also reviewed briefly.