• The Journal of the Acoustical Society of Korea
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• v.29 no.7
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• pp.422-430
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• 2010

The radiation property of a Tonpilz transducer is influenced by the structural variables of the transducer. In this study, with respect to a single mode Tonpilz transducer, the radiation patterns were calculated for different head mass geometries of the same effective radiation area. The shapes of the head mass analyzed were the most popular circular, regular triangular, square, regular hexagonal and regular octagonal types, and radiation pattern equations were derived for each of the head mass shapes. Based on the derived equations, radiation patterns in accordance with the shape and size of the head mass were calculated and the results were compared with each other. Validity of the calculation results were confirmed by means of finite element analysis.

• Journal of Biosystems Engineering
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• v.33 no.2
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• pp.101-105
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• 2008

Some physical properties of rapeseed such as geometric properties (linear dimensions, sphericity, seed volume, surface area) and gravimetric properties (the mass of one thousand seeds, bulk density) were analyzed at five levels of moisture content of 10.03, 14.91, 20.07, 25.06 and 30.12% (w.b.). The physical properties of rapeseed were evaluated as a function of seed moisture content. In the moisture range, when the moisture content increase, sphericity decreased from 0.946 to 0.927, and geometric mean diameter, seed volume and surface area increased from 2.17 to 2.31 mm, 5.58 to $6.88 \;mm^3$ and 14.76 to $16.77\;mm^2$ respectively. Mass of one thousand seeds increased from 5.04 to 6.46 g. Bulk density decreased from 579.3 to $549.2\;kg/m^3$ due to swelling of the seed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.15-26
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• 1999

The marine structures with sea water cooling system always expose to the oceanic atmosphere. Therefore, the protection of the equipments is very important. To investigate the effectiveness of advanced composite materials for the application in offshore environments, the tensile test, hardness test, undercutting property test, permeance test and the friction and wear test were carried out by using various applicable coating materials. The main results obtained can be summarized as follows; 1. The micro-hardness of the Archcoat 502B showed the highest value. 2. The coefficient of friction of the Rigspray coating at the speed of 2.21m/sec showed the lowest value, and that of the Archcoat 502B coating at 1.08m/sec and 0.18m/sec indicated the lowest values. 3. The wear mass at the speed of 0.18m/sec and 1.08m/sec in dry condition showed the smallest values. 4. The Archcoat 502B coating is fitted to the dynamic instruments in the range of low speed and middle speed. Rigspray coating is fitted to the dynamic instruments in the range of high speed. 5. The wear mass of five kinds of coating materials at the range of low speed was very small, and those of the Archcoat S02B, Archcoat 402B and Rigspray coating at high speed range were quitely smaller than those of the Modified Epoxy and Tar Epoxy.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.644-655
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• 2012

As soon as a new air filter is applied to an air purification process, the filter gets loaded with dust particles. Thus, the study on the particle loading characteristics of air filter is very essential in order to understand the real filtration phenomena during filter use. In this study, we investigated the effect of particle and filter charge on the particle loading property of air filter. Charged filter and uncharged filter prepared by discharging the charged filter by isopropyl alcohol were used as test samples, and three types of particle having different charge states were supplied to filters tested. For neutralized particles there was a big difference in areal mass loading rates between charged and uncharged filters due to the very small amount of particle charge, on the other hand the difference was diminished for atomized particle and finally almost vanished for corona charged particles. The pressure drop of filter loaded with corona charged particles was only half of those for neutralized and atomized particles at the same areal mass loading because of the porous structure of particle deposit formed on filter fibers, caused by the space charge effect between particles.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.984-986
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• 1999

In the case of immobilizing of glucose oxidase in organic polymer using electrosynthesis, the glucose oxidase obstructs charge transfer and mass transport during the film growth. This may lead to short chained polymer and make charge-coupling weak between the glucose oxidase and the backbone of the polymer. That is mainly due to insulating property and net chain of the glucose oxidase. Such being the case, it is useless to increase in amount of glucose oxidase more than reasonable in the synthetic solution. We establish by means of qualitative analysis that amount of immobilized glucose oxidase can be improved by adding a hole ethyl alcohol in the synthetic solution. As ethyl alcohol was added by 0.1mol $dm^{-3}$ in the synthetic solution, the faradic impedance of resultant electrode was increased about five times as much as the case of ethyl alcohol free in the solution, and mass transport was limited more than over. That is due to insulating property and net chain of the glucose oxidase. Moreover, in ultraviolet spectra of the synthetic solution, the adsorption peak at 285nm corresponding to glucose oxidase was decreased. It suggests increase in amount of immobilized glucose oxidase.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1872-1875
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• 1998

In the industrial motor drive system, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. Recently, there are new methods which estimate unknown state variables by using a reduced order observer and feedback these state variables by using a pole placement design method. But there is a trade-off between the fast command following property and the attenuation of disturbances and vibrations in these design methods. In this paper, the vibration suppression control of a two-mass system using a reference model is proposed. Because of using a reference model, the proposed control satisfy the fast command following property and the attenuation of disturbances and vibrations. Control parameter can be changed to maintain high system performance in control using a reference model. Experimental results show the validity of the proposed state feedback control using a reference model, and this controller is compared with the state feedback controller.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.975-980
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• 2003

The electrochemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH)₂ in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH)₂ was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in α phase, which had a lower Al content. In the anodic polarization test in 0.017 mol·$dm^{-3}$ NaCl and 0.1 mol·$dm^{-3}$ Na₂SO₄ at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the α phase is a non-compacted film. The anodic film on the α phase at 30 min was a compact film as compared with that at 10 min.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1305-1306
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• 2006

A monolayer assembly of anthracene-viologen linked thiol ($AMVC_{8}SH$) was fabricated on a gold electrode by self-assembly method. Structural property of the self-assembled monolayers (SAMs) was carried out by optical and electrochemical method. Firstly, we investigated PL spectrum and UV/visible absorption for the optical properties in solution state. Secondly, we determined the characteristics of charge transfer in different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the PL spectrum and UV/visible absorption were observed and the well-defined shape peaks were nearly equal charges during redox reactions and existed to an excellent linear relationship between the scan rates and existed to currents. The mass change was determined during redox reaction. The mass change behavior of SAMs was not only governed by the mobility of the ion in the viologen but the valence of the ion in the electrolyte solution.

• Journal of Hydrogen and New Energy
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• v.23 no.1
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• pp.19-25
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• 2012

The efficiency and life time of the Proton Exchange Membrane fuel cell (PEMFC) system is critically affected by incoming gas with humidity which should be maintained properly at normal operating conditions. Typically, incoming gas of automotive fuel cell is humidified by external humidifier but the characteristics of device is rarely reported. In this study, characteristics of water transfer in the membrane humidifiers have been experimentally investigated for flow rates of gas and for different flow arrangement under steady state condition. At first, capability of mass transfer through the membrane is examined at constant temperature. Then, the temperature distribution effect on the capability of mass transfer is tested over various inlet conditions. In summary, this research presents the mass transfer capability of hydrophilic membrane over various operating conditions.

• Journal of Power System Engineering
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• v.20 no.2
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• pp.85-90
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• 2016

Coefficient of performance (COP) for two-stage compression system is investigated in this paper to develop seawater ice machine. The system performance is analyzed with respect to degrees of superheating and subcooling, condensing and evaporating temperatures, compression and mechanical efficiencies and mass flow ratio in an inter-cooler. The main results are summarized as follows : The COP of the system grows when the mass flow ratio, subcooling degree and evaporating temperature edge up. Contrariwise, the system performance descends in case that superheating degree and condensing temperature increase. The most effective factor for the COP is the mass flow rate ratio. Each refrigerant has different limitation for a value of the mass flow ratio in the inter-cooler because of difference in material property.