• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.97-101
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• 2014

With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.

• Asian Journal of Turfgrass Science
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• v.6 no.1
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• pp.39-45
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• 1992

This experiment was undertaken to study effect of fall Fertitizarion on spring regrowth of Korean lawngrass( Zoysia japonica Steud ) Results obtained are summarized as follows : 1. late fall fertilization stimulated the spring regrowth of Korean lawngrass. hut early spring application showed little effect on that 2. The yield of clippings on May 21 was obviously greater in late fertilization plots(treatment C, D and E) than other plots(treatment A, B and control, but there was no significant difference in clipping yields of C, D and F treatment. 3. Both nitrogen and reducing sugar contents of runner fell down in spring. It was suggested thatthese constituents be translocated from runner to other parts during the budding period. 4. The nitrogen content of runner was obviously mote in the plot of late fall fertilization. In contrast to nitrogen, no obvious difference was found in reducing sugar content of runner of seven application date. It was suggested that the roots of plant be still able to absorb to absorb nitrogen under dormancy. .5.From these results. late fall fertilization enhances the development of Korean lawngrass in the following spring. But early spring application shows little effect on spring regrowth.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.83-86
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• 2005

The front-end side members of automobiles, such as the hat-shaped section member, absorb most of the energy during the front-end collision. The side members absorb more energy in collision if they have higher strength and stiffness, and stable folding capacity (local buckling). Using the above characteristics on energy absorption, vehicle should be designed light-weight to improve fuel combustion ratio and reduce exhaust gas. Because of their specific strength and stiffness, CFRP are currently being considered for many structural (aerospace vehicle, automobiles, trains and ships) applications due to their potential for reducing structural weight. Although CFRP members exhibit collapse modes that are significantly different from the collapse modes of metallic materials, numerous studies have shown that CFRP members can be efficient energy absorbing materials. In this study, the CFRP side members were manufactured using a uni-directional prepreg sheet of carbon/Epoxy and axial static collapse tests were performed for the members. The collapse mode and the energy absorption capability of the members were analyzed under the static load.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1549-1552
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• 2003

The front-end side members of automobiles absorb most of the energy in a front-end collision. The front-end side members are required to have a high stiffness together with easiness to collapse sequentially to absorb more impact energy. The axial static collapse test (5mm/mim) was conducted by using UTM with respect to the single hat shaped section members which are the standard section shape of the spot welded section members, to the single cap shaped section members, to the double cap shaped section members and to the double hat shaped section members whose section shape are changed in order to give more stiffness. As a result of test, the energy absorbing characteristic was analyzed for different section shapes. That is, it was analyzed that the change of section shape influenced the absorbing energy, the mean collapse load and the maximum collapse load, and that the relation between the change of section shape and the collapse mode.

• Korean Journal of Applied Biomechanics
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• v.20 no.3
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• pp.345-353
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• 2010

The purpose of this study was to compare and biomechanical evaluate the effects of three varying functional insoles on the kinematics of the lower extremities and foot pressure distribution during gait. For this 12 subjects participated in this study and each worn the 3 functional insoles during gait which kinematics, kinetics, electromyography and foot pressures were recorded. The function on the first insole was to absorb shock and increase the dynamic stability, the second was a gel type to absorb shock, and the third was to massage the center regions of the foot sole. the results were as follows; the first insole reduced the joints range of motion and reduced muscular fatigue, the second insole reduce the maximum, total and average foot pressures. Finally, the third insole produced larger values for the contact times and contact area.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.149-152
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• 2007

The detection of yellow sand dust using satellite has been utilized from various bands from ultraviolet to infrared channels. Among them, Infrared channels have an advantage of detecting aerosols over high reflecting surface as well as during nighttime. Especially, brightness temperature difference between 11 and 12{\mu}m(BTD) was often used to distinguish between water cloud and yellow sand, because Ice and liquid water particles preferentially absorb longer wavelengths while aerosol particles preferentially absorb shorter wavelengths. We have found that the BTD significantly depends on surface temperature, emissivity, and zenith angle and thereby the threshold of BTD. In order to overcome these problems, we have constructed the background brightness temperature threshold of BTD and then subtracted it from BTD. Along with this, we utilized high temporal coverage of geostationary satellite, MTSAT-1R, to verify the reliability of the retrieved signal in conjunction with forecasted wind information. The statistical score test illustrated that this newly developed algorithm showed a promising result for detecting mineral dust by reducing the errors in the current BTD method.

• Journal of the Semiconductor & Display Technology
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• v.12 no.2
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• pp.7-11
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• 2013

This paper presents a study on the design for contamination preventation system of solar battery. The system of contamination preventation has an wind amplifier. Wind amplifier is conceptually designed by using TRIZ. The surface of solar battery is covered with dust during accumulate the energy. The dust cause reduce power of photovoltaic module and efficiency drop of photovoltaic system. Reflect and absorb of incident ray are caused by the dust on surface of solar battery. The solution of this problem has been derived using 6SC(6 steps creativity)TRIZ. The wind amplifier which has structure such as funnel shape. The incident wind in the wide hole is amplified by the gate become narrow. The system of contamination preventation with wind amplifier which mounted on the side of the solar battery surface reduces the reflect and absorb and improve the efficiency of photovoltaic system.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.3
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• pp.42-48
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• 2009

The various kinds of Hanji were manufactured by a few craftsmen at several provinces in Korea. It is very difficult to distinguish each others by its name so-called, Hanji, traditional Hanji, improved Hanji, mechanical Hanji and so on because the manufacturing process, raw materials and characteristics of Hanji are very different from each others. In this research, the functional properties of Hanji depending on the manufacturing process were evaluated and compared each others. The properties of Hanji was greatly changed according to grammage, lye and dochim. The higher the grammage resulted in the lower the pore size and the air permeability. Hanji made by NaOH and CaO showed relatively high brightness than that made by traditional lye(Yuokgae). Hanji treated with dochim can absorb high frequency(2,000 Hz) sound more effectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.70-70
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• 2013

As the costs of carbon-footprinetd fuels grow continuously and simultaneously atmospheric carbon dioxide concentration increases, solar fuels are receiving growing attention as alternative clean energy carriers. These fuels include molecular hydrogen and hydrogen peroxide produced from water, and hydrocarbons converted from carbon dioxide. For high efficiency solar fuel production, not only light absorbers (oxide semiconductors, Si, inorganic complexes, etc) should absorb most sunlight, but also charge separation and interfacial charge transfers need to occur efficiently. With this in mind, this talk will introduce the fundamentals of solar fuel production and artificial photosynthesis, and then discuss in detail on photoelectrochemical (PEC) water splitting and CO2 conversion. This talk largely divides into two section: PEC water oxidation and PEC CO2 reduction. The former is very important for proton-coupled electron transfer to CO2. For this oxidation, a variety of oxide semiconductors have been tested including TiO2, ZnO, WO3, BiVO4, and Fe2O3. Although they are essentially capable of oxidizing water into molecular oxygen, the efficiency is very low primarily because of high overpotentials and slow kinetics. This challenge has been overcome by coupling with oxygen evolving catalysts (OECs) and/or doping donor elements. In the latter, surface-modified p-Si electrodes are fabricated to absorb visible light and catalyze the CO2 reduction. For modification, metal nanoparticles are electrodeposited on the p-Si and their PEC performance is compared.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.1
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• pp.140-144
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• 2023

In recent years, there are so many serious crashes involving coaches, especially the frontal collision occupies 40% of the front of the vehicle, Frontal collisions account for 100% of the front of the vehicle affecting the driver and side-impact collisions that injure the person in the vehicle. Therefore, the research into improving and optimizing the structure is necessary for risk of injury for passengers in frontal accidents. In this paper, we have designed a Shock absorber that can absorb collision energy. Research using HYPERMESH software. to build the finite element model and calculate the meshing to suit the mesh size of 5mm. apply LS-DYNA software to calculate structural strength. In the study, for a vehicle to collide with a hard obstacle occupying 100% of the head of the vehicle. Then, the experimental design method, Minitab is used for find the structural parameters in the design. Improvement results showed that the acceleration of the impact on passengers and the driver is decreased by 55,17%. The mass of texture improvements is reduced by 11%, according to the requirements of European Standards ECE R94.