• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.73-76
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• 2004

Tapping mode atomic force microscopy (TM-AFM) utilizes the dynamic response of a resonating probe tip as it approaches and retracts from a sample to measure the topography and material properties of a nanostructure. We present recent results based on numerical techniques that yield new perspectives and insight into AFM. It is compared that the dynamic models including van der Waals and Derjaguin-Muller-Toporov(DMT) or Johnson-Kendall-Roberts(JKR) contact forces demonstrates that periodic solutions can be represented with respect to the approach distance and excitation frequency.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.1121-1124
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• 2003

PZT(30/70) thick film was fabricated by using 1,3 propanediol-based sol-gel method. Prepared film of pyroelectric property was investigated by Dynamic method of modulation frequency dependence. Pyroelectric coefficient was obtained about 5.0$\times$10$^{-8}$ C/$\textrm{cm}^2$.K. The figure of merits for voltage responsivity and specific detectivity were 3.4$\times$10$^{-11}$ C.cm/J and 5.9$\times$10$^{-9}$ C.cm/J, respectively, because of relative high-dielectric constant and high-pyroelectric coefficient. Voltage responsivity was increased at low modulation frequency and it was decreased at high modulation frequency. Voltage responsivity was maximum 1.84 V/W at 10 Hz. As Johnson noise is dominant, Noise voltage was increased nearly proportional to f$^{-1}$ 2/. Noise equivalent power and specific detectivity were 2.83$\times$10$^{-7}$ W/Hz$^{1}$2/ and 3.13$\times$10$^{5}$ cm.Hz$^{1}$2//W the same frequency at 80 Hz, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.6
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• pp.9-15
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• 2004

PZT(30/70) thick film was fabricated by using 1,3 propanediol-based sol-gel method. Prepared film of pyroelectric property was investigated by Dynamic method of modulation frequency dependence. Pyroelectric coefficient was obtained about $5.0{\times}10^{-8}\;C/cm^2{\cdot}K$. The figure of merits for voltage responsively and specific detectivity were $3.4{\times}10^{-11}\;C{\cdot}cm/J$ and $5.9{\times}10^{-9}\;C{\cdot}cm/J$, respectively, because of relative high-dielectric constant and high-pyroelectric coefficient. Voltage responsively was increased at low modulation frequency and it was decreased at high modulation frequency. Voltage responsively was maximum 1.84 V/W at 10Hz. As Johnson noise is dominant, Noise voltage was increased nearly proportional to $f^{-1/2}$. Noise equivalent power and specific detectivity were $2.83{\times}10^{-7}\;W/Hz^{1/2}$ and 3.13{\times}10^5\;cm{\cdot}Hz^{1/2}/W$ the same frequency at 80Hz, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.51-59
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• 2017

In this paper, we propose a gray code order of antenna index permutations for differential spatial modulation (DSM). To facilitate the implementation, the well-known Trotter-Johnson ranking and unranking algorithms are adopted, which result in similar computational complexity to the existing DSM that uses the lexicographic order. The signal-to-noise ratio gain achieved by the proposed gray code order over the lexicographic order is also analyzed and verified via simulations. Based on the gray coding framework, we further propose a diversity-enhancing scheme named intersected gray (I-gray) code order, where the permutations of active antenna indices are selected directly from the odd (or even) positions of the full permutations in the gray code order. From analysis and simulations, it is shown that the I-gray code order can harvest an additional transmit diversity order with respect to the gray code order.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.70.5-71
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• 2015

We present a preliminary result from a high-resolution and high signal-to-noise spectroscopic survey, providing atmospheric parameters for about 170 nearby field dwarfs in the Hipparcos catalog. Our preliminary analysis shows that when Hipparcos parallaxes are adopted, a few stars in our sample are too faint compared to main-sequence fitting distances based on our accurately measured [Fe/H]. We discuss magnitude deficits of these field stars in connection with the short Hipparcos distance to the Pleiades.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.323-330
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• 2005

In order to increase reliability and reduce system cost, this paper studies particularly applicable method for sensorless PM BLDCM drive system. The waveform of the motor internal voltages(or back emf) contains a fundamental and higher order frequency harmonics. Therefore the third harmonic component is extracted from the stator phase voltage. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition, and is practically free of noise that can be introduced by the inverter switching, making this a robust sensing method. In addition, a simple starting method and a speed estimation approach are also proposed. Some experimental results are Provided to demonstrate the validity of the proposed control method.