• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.110-116
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• 2015

This study investigates the whirling stability of a rotating shaft-disk system under parametric excitation using periodically varying torque. The equations of motion were derived using a lumped-mass model, and the Floquet method was employed to find the effects of torque fluctuation, internal and external damping, and rotational speed on whirling stability. Results indicated that the effect of torque fluctuation was considerable on the instability around resonance, but minimal on supercritical instability. Stability diagrams were sensitive to the parametric excitation frequency; critical torque decreased upon increasing excitation frequency, with faster response convergence or divergence. In addition, internal and external damping had a considerable effect on unstable regions, and reduced the effects of the parametric excitation frequency on critical torque and speed. Results obtained from the Floquet approach were in good agreement with those obtained by numerical integration, except for some cases with Floquet multipliers very close to unity.

• International Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.79-82
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• 2015

The handicap for investigating the aero-optical effect focuses on the accurate prediction on the index refraction fluctuation or density fluctuation. In recent years, with the development of CFD techniques and optical experimental techniques, the comprehension have developed on the aero-optical transmitting effect in many kinds of complex flow. This study mainly introduces the optical aberration in compressible mixing layer. And then the debates about the mechanism of aero-optical effects and assessment of image blur also present.

• The Korean Journal of Zoology
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• v.39 no.2
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• pp.182-189
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• 1996

It has been known that spermatozoa should obtain their fertilizing ability through capacitation and acrosome reaction, and that in these processes of fertilization, Ca2+ platys an important role for their conjugation. Therefore the present study has been designed in order to clarify the effect of fluctuation of the media Ca2+ level and the intracellular concentration of the spermatozoa on the acrosomes. During the incubation of spermatozoa, a considerable fluctuation in the media Ca2+ level has been observed after the BSA administration and the media concentration of Ca2+. It is deduced that these fluctuation rates may have an effect on the acrosome reaction. The fluctuation of K+ flux has been observed in accordance with the incubation period over time, and it's concentration seems to be closely related with the acrosomal reaction. The respiratory exchange rate (RERI of the spermatozoa is kept more regular in the BSA and Cacl2 administration groups than the non-administration group. Based on the experimental findings, it is possible to deduce a hypothesis from these findings that physiological activities of the acrosome reaction are not functionally related to the media Ca2+ level and the intracellular influx of Ca2+ concentration, although Ca2+ platys an important role as a stimulating factor in the acrosome reaction.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.5-9
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• 2019

Optical emission spectroscopy is used to identify chemical species and monitor the changes of process results during the plasma process. However, plasma process monitoring or fault detection by using emission signal variation monitoring is vulnerable to background signal fluctuations. IR heaters are used in semiconductor manufacturing chambers where high temperature uniformity and fast response are required. During the process, the IR lamp output fluctuates to maintain a stable process temperature. This IR signal fluctuation reacts as a background signal fluctuation to the spectrometer. In this research, we evaluate the effect of infrared background signal fluctuation on plasma process monitoring and improve the plasma process monitoring accuracy by using simple infrared background signal subtraction method. The effect of infrared background signal fluctuation on plasma process monitoring was evaluated on $SiO_2$ PECVD process. Comparing the $SiO_2$ film thickness and the measured emission line intensity from the by-product molecules, the effect of infrared background signal on plasma process monitoring and the necessity of background signal subtraction method were confirmed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.891-897
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• 2006

The SRS method is applied to a turbulent flame with radiation/turbulence interaction to invert the temperature and concentration profile. The flame is conditioned as optically thin per each fluctuation length and the flame spectral intensity is measured for inversion. From inversion result, we find that SRS can successfully invert the coupled temperature/concentration fluctuation amplitudes. For two cases of experiments, inverted values are within approximately 1% over the full range of fluctuation amplitude. However, SRS cannot find the detailed local fluctuation parameters such as pattern and phase, etc. as far as they do not affect the resulting radiation intensity. Important available parameters are the mean temperature and the temperature fluctuation amplitude. The radiation/turbulence interaction effect is verified to play an important role in the radiation.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1454-1456
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• 2013

The fluctuations in concentrations of reactants dominate the long-time dynamics of the single (A + A ${\rightarrow}$ 0) and two species (A + B ${\rightarrow}$ 0) diffusion-influenced annihilation reactions. Although hierarchical Smoluchowski approaches can provide a systematic and flexible framework to deal with the fluctuation effects, their results are too complicated to be analytically solved. For the efficient numerical calculation of the complicated fluctuation effect terms, we show that the presented point particle approximation is not only practical but also quite accurate for most conditions in diffusion-influenced reaction systems.

• Journal of agriculture & life science
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• v.44 no.2
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• pp.85-96
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• 2010

In this paper, we tried to investigate the adjusting patterns of production fluctuation of major soybean production countries. In particular, we focus our attention on the trade transmission effect of major soybean production countries on world market. We found that the instability of world market for soybean is likely to be increased mainly due to the production fluctuation and trade transmission effect of major production countries, e.g. Brazil, Paraguay, and Canada. Most of the major production countries have adjusted the production fluctuation through consumption and trade rather than inventory management, and hence the instability of world market for soybean tends to be more instable. Therefore we need to develop the effective policy measures for making domestic soybean market more stable such as a plan for keeping domestic production, a valid inventory management strategy, a use of futures market, and a strategy to diversify import market as a large importing country.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.1
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• pp.45-49
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• 2013

High frequency system has been used for the purpose of skin care and obesity treatment, by high-frequency energy is applied to the human body generates deep heat. Conventional high frequency system could not selection control by depending on the body load fluctuations. Such as burns and side effects have been reported by system instability and then therapeutic effect is insufficient. During treatment, objective information about the status of the patient was no. Because of treatment methods are subjective, and so tailored treatments were impossible. In this paper, high frequency medical system with sinusoidal frequency characteristics without distortion of the Push pull switching scheme for pain relief therapy was designed. And control circuit that was designed by feedback using the output changes according to the body-load fluctuation. Last, power circuit for efficient control the heat generated from the hardware was proposed.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.219-226
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• 1996

The wave-particle duality of light plays important role in quantum optics and it often produces a result different from that of classical wave theory. In this paper, we study the intensity and phase fluctuation of light which show certain change after light goes through a beam splitter, and show the difference between the classical and quantum theory. We show quantitatively that the uncertainty of phase increases at the output of a beam splitter due to the contribution of vacuum fluctuation, even though classical theory predicts no such change in phase fluctuation. The expectation values of normally ordered operators are introduced where the vacuum effect is naturally eliminated, and it is shown that the classical informations are recovered in this way. Analysis on the expectation values produces a distinction between measured phase and inferred phase values and they are related through the contribution of vacuum field.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.1-8
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• 2011

In this paper, a water tank experiment using Binary Frequency Shift Keying (BFSK) method for text transmission performance by water surface fluctuation is conducted. Water surface fluctuation and delay spread which affect the channel coherence bandwidth is a limiting factor in underwater acoustic communication. The amplitude fluctuation and delay spread the smooth surface and fluctuation surface, were identified. The effective delay spread of both cases are 5ms, 4ms corresponding to the coherence bandwidth of 200Hz, 250Hz, respectively. The bit error rate of BFSK modulated text transmission is about $10^{-4}$ in less than 200bps in smooth surface but less than 250bps in fluctuation surface. Therefore, this experiment shows that the water surface fluctuation is important factor determining the performance of the underwater acoustic transmission.