• Proceedings of the KSME Conference
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• 2008.11a
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• pp.497-501
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• 2008

To improve occupants' safety in an emergency, crashworthy design is necessary to rotorcraft design and development. To improve crashworthiness capability, most of the crash energy should be absorbed by rotorcraft and the energy transmitted to the occupants should be minimized. To absorb the crash energy efficiently, the individual energy attenuation provided by landing gear, structure, fuel tank and seats should be considered totally. Especially, landing gear has the important role for crashworthy design because landing gear absorbs relatively large energy for the crash landing. In addition, military specifications require failure of landing gear shall not increase danger to any occupants by penetration of the airframe. To meet the specification requirements, failure mechanism should be prepared so that landing gear is collapsed safely and doesn't penetrate the airframe. In this study, design of failure mechanism which is necessary for the rotorcraft landing gear was performed and the results were presented.

• Tuberculosis and Respiratory Diseases
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• v.38 no.1
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• pp.25-33
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• 1991

The immune staus is known to be decreased in malignant disease and radiation therapy (RT), used as a therapeutic tool, further decrease this-attenuated immune status. We measured the number of peripheral lymphocytes, its subsets and lymphoblast transformation for PPD, PHA, monoclonal antibodies including anti-CD3 and anti-CD2 before and after RT in 19 patients with squamous cell lung cancer to search the fine mechanism behind the RT-induced attenuation of lymphoblast transformtion for mitogens and antigen. The results were as follows; 1) The number of lymphocytes and its subsets decreased significantly after RT, but the percentages of lymhocyte subsets did not change aftr RT except interleukin-2 receptor positive T lymphocytes. 2) The function of lymphoctes, measured by lymphoblast tranformation for PHA and PPD, decrased after RT and the compositions of PBMC used for lymphoblast transformtion were not different before and after RT. 3) The mitosis of lymphocytes to anti-CD2 or anti-CD3 decreased significantly after RT. And IL-2 plus anti-CD3 increased the mitosis than that of anti-CD3 only after RT, but before RT there was no difference. In conclusion, we suggested the fine mechanism behind the RT-induced attenuation of immune response might be the dysfunction of lymphocytes in terms of impaired synthesis of IL-2 rather than the decrease of circulating lymphocyte numbers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.9
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• pp.838-844
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• 2015

This paper includes summarization and analysis of previous research results on acoustic attenuation due to particles and flow turning in rocket motors among various damping parameters. Particle damping is the most effective mechanism in suppressing high-frequency combustion instabilities occurring in rocket combustion chambers, which is dependent on the size and the mass fraction of particles. Relatively weak attenuation by flow turning compared to particle damping depends on the geometry of propellant and a combustion chamber. Pumping driving effects need to be taken into account when realizing vorticity generation on the propellant surface. However, its driving effects become cancelled out by flow turning loss when the propellant geometry is cylindrical.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1476-1484
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• 2023

Laboratory experiments and point monitoring of reservoir sediments have proven that stable sulfate reduction (SSR) can lower the concentrations of toxic metals and sulfate in acidic groundwater for a long time. Here, we hypothesize that SSR occurred during in situ leaching after uranium mining, which can impact the fate of acid groundwater in an entire region. To test this, we applied a sulfur isotope fractionation method to analyze the mechanism for natural attenuation of contaminated groundwater produced by acid in situ leaching of uranium (Xinjiang, China). The results showed that δ³⁴S increased over time after the cessation of uranium mining, and natural attenuation caused considerable, area-scale immobilization of sulfur corresponding to retention levels of 5.3%-48.3% while simultaneously decreasing the concentration of uranium. Isotopic evidence for SSR in the area, together with evidence for changes of pollutant concentrations, suggest that area-scale SSR is most likely also important at other acid mining sites for uranium, where retention of acid groundwater may be strengthened through natural attenuation. To recapitulate, the sulfur isotope fractionation method constitutes a relatively accurate tool for quantification of spatiotemporal trends for groundwater during migration and transformation resulting from acid in situ leaching of uranium in northern China.

• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.121-129
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• 2017

The present study numerically investigated the influence of the waveform distribution on the tsunami-vegetation interaction using a non-reflected wave generation system for various tsunami waveforms in a two-dimensional numerical wave tank. First, it was possible to determine the wave attenuation mechanism due to the tsunami-vegetation interaction from the spatial waveform, flow field, vorticity field, and wave height distribution. The combination of fluid resistance in the vegetation and a large gap and creates a vortex according to the flow velocity difference in and out of the vegetation zone. Thus, the energy of a tsunami was increasingly reduced, resulting in a gradual reduction in wave height. Compared to existing approximation theories, the double volumetric ratio of the waveform increased the reflection coefficient of the tsunami-vegetation interaction by 34%, while decreasing the transfer coefficient and energy attenuation coefficient by 25% and 13%, respectively. Therefore, the hydraulic characteristics of a tsunami is highly likely to be underestimated if the solitary wave of the approximation theory is applied for the tsunami.

• Korean Journal of Plant Resources
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• v.37 no.3
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• pp.256-262
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• 2024

Blueberry (BB), fruit of Vacciniumi, has been hailed as an antioxidant superfood. BB is a rich source of vitamins, minerals, flavonoids, phenolic acids and known to have a variety of pharmacological actions. The purpose of this work is to clarify the anti-inflammatory mechanism of BB in lipopolysaccharide (LPS)-activated RAW264.7 macrophage. We explored the effects of BB on the production of inflammatory cytokines, prostaglandin E₂ (PGE₂) and expression of cyclooxygenase (COX)-2 in LPS-activated RAW264.7 macrophage. Moreover, to investigate the molecular mechanisms by BB, we evaluated whether BB modulate nuclear factor-kappa B (NF)-kB pathway and caspase- 1 activation. The findings of this work demonstrated that BB alleviated the LPS-enhanced inflammatory cytokines and PGE₂, as well as COX-2 levels. Additionally, we demonstrated that the anti-inflammatory mechanism of BB occurs due to the attenuation of IκB-α degradation, NF-kB translocation and caspase-1 activation. Conclusively, these findings provide evidence that BB may be useful agents in the treatment of inflammation.

• Journal of the Korean Society of Groundwater Environment
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• v.3 no.1
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• pp.37-49
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• 1996

The objectives of this study are to investigate the groundwater and surface water contamination, to interpret the attenuation mechanism of contaminant transport, and to find the appropriate contamination indicator. at the two big landfill sites : Nanjido Landfill and Hwasung Landfill. Leachate from the Nanjido, th, Hwasung and the Kimpo waste disposal sites is characterized by high temperature (31.7-40.1$^{\circ}C$), high electric conductivity (14,650-32,800 ${\mu}$S/cm), somewhat higher pH(7.58-8.45) and low Eh (-119.4-20.4 mV), and is enriched in both major (Na$^{＋}$, K$^{＋}$, Ca$^{2＋}$, Mg$^{2＋}$, HC $O_3$$^{－}$, Cl$^{－}$) and minor (Mn, Sr$^{2＋}$, Ba$^{2＋}$, Li$^{＋}$, F$^{－}$, Br$^{－}$) ions. Municipal solid waste leachate and industrial waste leachate are effectively discriminated by the content of S $O_4$$^{2－}$, Fe, and heavy metals. The attenuation mechanism of each component was assessed using the chemical analysis. Cl-normalizing process, WATEQ4F simulation, and preceding flownet analysis. Based on the calculation of Contamination Factor, K, Na, Ca, Mg, B, Zn, HC $O_3$, Cl, F, Br and TOC are effective contamination indicators in the Nanjido landfill site, and K, Na, Ca, Mg, B, S $O_4$, HC $O_3$, Cl, F, Br and TOC in the Habsburg landfill site Particularly, TOC is the best contamination indicator in landfill sites influenced by sea water.

• Geophysics and Geophysical Exploration
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• v.15 no.2
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• pp.85-91
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• 2012

Multiple Lapse Time Window (MLTW) analysis for obtaining intrinsic attenuation value require numerous data without directional bias to compensate focal mechanism. The first window of MLTW, therefore, shows large deviation in fitting smoothed theoretical curve. The information on the focal mechanism may reduce burdens of number and distribution. This study combined algorithm of computing focal mechanism to DSMC method by Yoshimoto (2000). However, the MLTW method based on the numerous data was not applicable to this study, because of the limited data to the almost same fault plane solution. This study showed that the available data was too insufficient to construct smoothed theoretical curve, although the deviation of the first window was improved. Instead of conventional solution by more data, the study seems to be needed for new constraints to obtain smoothed curve.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.332-337
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• 2004

The use of gas absorption refrigeration machine has considerably increased because of the shortage of the electric power in the summer and the regulation of freon refrigerant. Gas absorption refrigeration machine consists of a condenser, a heat exchanger. supplying pipes, a radiator etc, This system is likely to be corroded by acid. dissolved oxygen and gases, Cavitation erosion-corrosion by flow velocity of cooling water may happen in absorption refrigeration machine. In these cases. erosion and corrosion occur simultaneously. Then, it makes a serious damage with synergy effect. Therefore, this paper was studied on the cavitation damage of cupronickel(70/30) tube for gas absorption refrigeration machine, In the $30^{\circ}C$ tap water, linear polarization test and anodic polarization test were carried out for copper(C1220T-OL) and cupronickel(70/30) tube. Also, cavitation erosion-corrosion behavior of cupronickel (70/30) tube was considered, The main results are as following: (1) In the linear test, the corrosion current density of cupronickel(70/30) is higher than that of copper. (2) The erosion-corrosion rate of cupronickel(70/30) displayed later tendency than that of copper by vibratory cavitation in cooling water. (3) In cooling water, the progress mechanism of erosion-corrosion rate of copper and cupronickel(70/30) follows a pattern of incubation, acceleration, attenuation and a steady state period.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.7
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• pp.517-524
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• 2014

Micro-vibration induced by on-board equipments such as fly-wheel and cryogenic cooler with mechanical moving parts affects the image quality of high-resolution observation satellite. Micro-vibration isolation system has been widely used for enhancing the pointing performance of observation satellites. In general, the micro-vibration isolation system requires a launch locking mechanism additionally to guarantee the structural safety of mission payloads supported by the isolation system with low stiffness under launch environment. In this study, we propose a passive launch and on-orbit vibration isolation system using shape memory alloy mesh washers for the micro-vibration isolation of spaceborne compressor, which does not require the additional launch locking mechanism. The basic characteristics of the isolator were measured in static and free vibration tests of the isolator, and a simple equivalent model of the isolator was proposed. The effectiveness of the isolator design in a launch environment was demonstrated through sine vibration, random vibration and shock tests.