• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.917-921
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• 1991

Hydraulic fitting impulse tester is equipment which produce impulse pressure waveform that specified foreign standard of SAE, JIS etc. Test conditions of SAE J1453 about waveform standard indicates frequency of 35-70 cycle/min, pressure of 560 bar, oil temperature of 93 .+-.3.deg. C etc. and required cycle is a million over. In additions, Test condition operated continuously equipment. This development item adopted new pattern method such as intensifier and rotary distributor is different from already established fitting impulse tester applied servo valve and high pressure direct directional control valve. Therefore, this development item which compares already established item is good reliability, low cost of manufacture and save of electric energy. especially, Domestic small and medium enterprise uses this tester because of economical cause. We develope appropriateness tester which conforms to demand of user.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.852-856
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• 1997

This paper describes a ultrasonic method for direct measurement of tool wear in turning operations. An integrated single ultrasonic transducer operating at a frequency of 10MHz is placed in contact with the insert tip. The change in amount of the reflected energy form the nose and flanks of the tool can be related to the level of tool wear and thr mechanical integrity of the tool. As a results, a correlation exists between the untrasonic measurement and tool wear and that it is tool dependent.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1922-1927
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• 2003

Nonlinear normal mode (NNM) vibration, in a nonlinear dual mass Hamiltonian system, which has 6$\^$th/ order homogeneous polynomial as a nonlinear term, is studied in this paper. The existence, bifurcation, and the orbital stability of periodic motions are to be studied in the phase space. In order to find the analytic expression of the invariant curves in the Poincare Map, which is a mapping of a phase trajectory onto 2 dimensional surface in 4 dimensional phase space, Whittaker's Adelphic Integral, instead of the direct integration of the equations of motion or the Birkhoff-Gustavson (B-G) canonical transformation, is derived for small value of energy. It is revealed that the integral of motion by Adelphic Integral is essentially consistent with the one obtained from the B-G transformation method. The resulting expression of the invariant curves can be used for analyzing the behavior of NNM vibration in the Poincare Map.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.43-46
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• 2007

To find out the optimum design of hydrogen storage and supply tank using Metal Hydride (briefly MH) and to make clear the performance characteristics under various conditions are our research purpose. In order to use the low-temperature exhaust heat, $LaNi_{4.7}Al_{0.3}$ which operates under the low pressure of 1MPa is chosen, and we measure the basic properties, namely density, specific heat, PCT(Pressure-Concentration-Temperature) characteristic, and effective thermal conductivity. Then, a numerical calculation model of hydrogen storage using MH alloy is suggested and this thermal diffusion equation of model is solved by the backward difference method. This calculation results rate compared with the experimental results of the systems which installed 1kg MH alloy and, it is found out that our calculation model can well predict the experimental results. By the experimental using MH alloy, it is recognized that the hydrogen flow rate can control by the step adjustment of brine temperature.

• Journal of Drive and Control
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• v.12 no.2
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• pp.1-6
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• 2015

Recently, the Electro-Hydrostatic Actuator(EHA) has been developed as a result of research on energy saving. EHA is usually composed of a direct driven pump from an electric motor and is available to control cylinder displacement or velocity with high efficiency. In addition, it has the advantage of compactness, minimum leakage and availability of decentralized control. In this study, an EHA system was designed to decrease the path tracking error and manufactured for test. The linearization method provided in AMESim software was used to derive the model of EHA system. The derived model was applied to design the PI-D controller to effectively overcome the disturbance. The effectiveness of this controller was verified by further testing.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.81-88
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• 2002

It's well known that with the increase of preheated air temperature NOx is increasing ,while the energy consumption is decreasing. In this study the experimental study was carried out to find out a new method breaking the above-mentioned old concept. From the variation of configuration of gas nozzle and hot test on the temperature distribution and NOx, it was found out that the reduction of NOx was due to the effect of internal gas recirculation, which will be caused by air emitting velocity from burner nozzle.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.159-159
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• 2009

In this work, nitrogen and oxygen functionalities was introduced to the graphite nanofibers (GNFs) and their effect on electrocatalytic performance of the GNF supports for direct methanol fuel cells (DMFCs) was invesigated. The nitrogen and oxygen groups were introduced through the urea treatments and acid treatment, respectively. And, PtRu catalysts deposited on modified GNFs were prepared by a chemical reduction method. The catalysts were characterized by means of elemental analysis, nitrogen adsorption, and X-ray photoelectron spetroscopy (XPS). The structure and morphological characteristics of the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). As a result, the Pt-Ru nanoparticles were impregnated on GNFs with good formation in 3-5 nm. And, the cyclic voltammograms for methanol oxidation revealed that the methanol oxidation peak varied depending on changes of surface functional groups. It was thus considered that the PtRu deposition was related to the reduction of PtRu and surface characteristics of the carbon supports. The changes of surface functional groups were related to PtRu reduction, significantly affect the methanol oxidation activity of anode electrocatalysts in DMFCs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.339-345
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• 2006

In this paper, a physically meaningful methodology which can assess the contribution of each vibration mode to various vibration response signals (displacement, velocity, acceleration) is developed. Based on these results, the problem of quantitative assessment of the relative importance of a structural system's vibrational modes is discussed. In addition, a direct method which ran assess the relative importance of each mode from uniformly sampled experimental data is also proposed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.618-621
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• 2001

Plate-type $\beta$-FeSi$_2$single crystals were grown using FeSi$_2$, Fe, and Si as starting materials by the chemical transport reaction method. The $\beta$-FeSi$_2$single crystal was an orthorhombic structure. The direct optical energy gap was found to be 0.87eV at 300K. Hall effect shows a n-type conductivity in the $\beta$-FeSi$_2$ single crystal. The electrical resistivity values was 1.608Ωcm and electron mobility was 3x10$^{-1}$ $\textrm{cm}^2$/V.sec at room temperature.

• Nuclear Engineering and Technology
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• v.44 no.6
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• pp.587-596
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• 2012

The present paper deals with the participation of the University of Pisa in the last International Standard Problem (ISP) focused on system thermal hydraulic, which was led by the Korean Atomic Energy Research Institution (KAERI). The selected test was a Direct Vessel Injection (DVI) line break carried out at the ATLAS facility. University of Pisa participated, together with other eighteen institutions, in both blind and open phase of the analytical exercise pursuing its methodology for developing and qualifying a nodalization. Qualitative and quantitative analysis of the code results have been performed for both ISP-50 phases, the latter adopting the Fast Fourier Transfer Based Method (FFTBM). The experiment has been characterized by three-dimensional behavior in downcomer and core region. Even though an attempt to reproduce these phenomena, by developing a fictitious three-dimensional nodalization has been realized, the obtained results were generally acceptable but not fully satisfactory in replicating 3D behavior.