• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.137-140
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• 2007

The ordering of nanopores in AAO has been improved by using laser interference lithography. After growing Fe and Cu on this substrate in vacuum and removing AAO, Fe nanodots are fabricated. The nanopores in AAO and nanodots are ordered in one dimension following the prepatterning. It has been confirmed from the magnetic hysteresis loop that the Fe nanodots have vortex structure and the dipolar interaction is dominant among them.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.159-164
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• 2005

When an optical pulse propagates through the atmospheric channel, the atmospheric turbulence attenuates and spreads this pulse. This attenuation and broadening of pulse are occurred by the fluctuation in the arrival time of pulse at the optical receiver. This pulse broadening induces the intersymbol interference (ISI) between the adjacent pulses. finally, the adjacent pulses are overlapped and the bit rate and the repeaterless transmission length are limited by the ISI. In digital communication system, therefore, the pulse broadening is more important factor than the attenuation. In this paper, thus, we find the ISI in the atmospheric turbulence as the function of the structure constant for the refractive index fluctuation that presents the strength of turbulence using the temporal momentum function and present it by numerical analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2397-2408
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• 1994

In this paper, a structure for a nonlinear adaptive equalizer is discussed to reduce nonlinearity in digital high-density recording systems. We propose a nonlinear adaptive decision feedback equalizer which can reduce the nonlinear intersymbol interference increasing with high-density recording systems, and compare its performance with the RAM-DFE which is designed to remove nonlinear intersymbol interference existing in postcursor part. By observing the output SNR of each equalizer applied to recording channels with three different densities. we confirm that the nonlinear adaptive decision feedback equalizer performs the best in the general case where nonlinear intersymbol interference exists in both precursor and postcursor parts.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.803-814
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• 2010

In this paper, we propose a frame structure for modified ATSC transmission systems which is used for a terrestrial 3D HDTV broadcasting. The modified ATSC transmission systems [2] see the potential of increasing a transmission capacity at reasonable TOV (Threshold of Visibility) by modifying channel codes of conventional ATSC systems and varying modulations. We use PN symbols (Pseudorandom Noise) in a guard interval which is used for avoiding the ISI (Inter Symbol Interference) to estimate and compensate the time-varying multi path channel effectively with a maximum transmission payload. With PN symbols in the guard interval, a CIR (Channel Impulse Response) in a time domain can be estimated and a compensation in a frequency domain can be achieved for the accurate channel estimation and compensation. The prosed frame structure is applied to the modified ATSC systems and computer simulations are performed for SER (Symbol Error Rate) performances in TU (Typical Urban)-6 Channel.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.107-114
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• 2012

In this paper, the concerned existing blind equalizer convergence rate and residual inter-symbol interference using constellation reduced and cost function by separation the real part and an imaginary part, the dual structure CR-CMA(constellation Reduction CMA). The CMA methed compensates amplitude but does no compensate phase, On the other hand, The CMA method compensates both the amplitude and the phase but it has the convergence rate problem, and the MCMA method is a way to solve the phase problem of CMA method compensates both the amplitude and the phase after respectively calculating the real part and imaginary part components. Proposal a new method that the dual structure of CR-CMA, the cost function and error function and respectively calculating the real part and imaginary part components can advantages by improving the CMA and the MCMA algorithms so that the amplitude and phase retrieval and constellation reduce the residual ISI and faster convergence rate and performance is good SER (Symbol Error Ratio) was confirmed by computer simulations.

• The Korean Journal of Ecology
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• v.21 no.6
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• pp.791-797
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• 1998

An attempt to clarify the landscape structure of urban areas was carried out on Mt. Hwangryung located in the center of Pusan, southern Korea. By means of aerial photographs and field survey, a vegetation map including land-use pattern was made. Landscape structure was described by analyzing the vegetation map. Landscape element types were classified into secondary forest, introduced plantation, and other elements including urbanized area. almus firma and Pinus thunbergii communities, introduced plantation elements, formed matrix and some secondary forest elements and the other artificial plantations of small scale tended to distribute as small patches in such matrix. The number of patches per unit area in secondary forest elements was more than that in introduced plantation element. The result on patech size was vice versa. As the results of landscape ecological analyses, it was estimated that differentiation of patches recognized in community level would be related to artificial interference and those in sub-communities levels to natural process such as progression of succession. On the other hand, restoration plans in viewpoints of restoration and landscape ecology were suggested to improve ecological quality of Mt. hwangryung.

• Journal of Integrative Natural Science
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• v.3 no.3
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• pp.138-142
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• 2010

Polystyrene thin films containing Bragg structures have been successfully obtained by the removal of DBR porous silicon films from the DBR structured porous silicon/polystyrene composite film in HF/$H_2O$ mixture solution and by replicating the nano-structures of porous silicon containing Bragg structure. Polystyrene thin films containing Bragg structures displayed unique optical reflection resonances in optical reflection spectrum. This optical reflection band was resulted from the interference of reflection wavelength at Bragg structure of polystyrene thin films. The wavelength of reflection resonances could be modified by the change of Bragg structure of the master. Polystyrene thin films containing Bragg structures were flexible and maintained their optical characteristics upon bending. The Polystyrene thin films replicate the photonic features and the nanostructure of the master.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.398-402
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• 2009

We present a method of using one-dimensional dielectric multilayer structures for designing terahertz frequency spreading filters. The interference of terahertz pulses in these structures composed of alternating weak and strong refractive materials allows design of well-separated THz frequency components within a modulation-limited THz spectral envelope. The design characteristics of these coarse THz combs are limited by the saturation effect and also by the deformation of the THz pulse time-traveling within the structure. The details of the designed THz waveform synthesis from these THz multilayer spectral filters are verified by experiments using time-domain terahertz pulsed spectroscopy.

• Journal of Power Electronics
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• v.15 no.3
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• pp.830-840
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• 2015

The H-bridge inverter is the fundamental power cell of the cascaded distribution static synchronous compensator (DSTATCOM). Thus, cell reliability is important to the compensation performance and stability of the overall system. The concept of the power electronics building block (PEBB) is an ideal solution for the power cell design. In this paper, an H-bridge inverter-based “plug and play” HPEBB is introduced into the main circuit and the controller to improve the compensation performance and reliability of the device. The section that discusses the main circuit primarily emphasizes the design of electrical parameters, physical structure, and thermal dissipation. The section that presents the controller part focuses on the principle of complex programmable logic device -based universal controller This section also analyzes typical reliability and anti-interference issues. The function and reliability of HPEBB are verified by experiments that are conducted on an HPEBB test-bed and on a 10 kV/± 10 Mvar DSTATCOM industrial prototype.

• Current Optics and Photonics
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• v.1 no.3
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• pp.228-232
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• 2017

We propose a reflector-type perfect absorber with double absorption lines using electric and magnetic dipoles of Mie resonances in an array of silicon nanospheres on a silver substrate. In the visible range, hundreds of nanometer-sized nanospheres show strong absorption lines up to 99%, which are enhanced by the interference between Mie scattering and reflections from the silver substrate. The air gap distance between the silicon particles and silver substrate controls this interference, and the absorption wavelengths can be controlled by adjusting the diameter of the silicon particles over the entire range of visible wavelengths. Additionally, our structure has a filling factor of 0.322 when the absorbance is nearly 100%.