• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1307-1316
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• 1998

Engine turbulences obtained by LDV measurement near the compression TDC was analyzed by the classic turbulence theory. Turbulences were quantified by a cycle resolved analysis and processed to reveal integral time scale and length scale. Three different definitions were applied to obtain the turbulence time scales and then compared each others. The classic turbulence theory with the several assumptions for engine application proven to be very efficient for understanding engine turbulence in this study. It was found that the integral length scale is strongly affected and increased by tumble flow.

• Journal of Biosystems Engineering
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• v.30 no.1 s.108
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• pp.38-44
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• 2005

In this study, the acoustic response technique was applied to evaluate the maturity of melon nondestructively. The acoustic response signals through melon were obtained by microphone and signal conditioner with the lapse of days after fruit set. The acoustic parameters such as resonant frequencies and the spectrum energy ratio were analyzed. To investigate the relation between acoustic parameters and firmness of melon, the compression test was performed. Three resonant frequencies representing f1, f2 and f3 were 150 to 250 Hz, 300 to 400 Hz, and 450 to 550 Hz, respectively. The resonant frequencies were shifted to the lower frequencies and the magnitude of spectrum decreased as the maturity of melon increased. Some significant correlations were found between melon firmness and the spectrum energy ratio in some frequency ranges. It is possible to estimate the maturity of melon by acoustic response technique.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.716-719
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• 1999

In this Paper, we Present a method for embedding digital watermarks into digital audio signals. The watermarking must be imperceptible and should be robust to attacks, such as filtering and compression etc. In our method, we adaptively embedded the watermarks changing the scale factor using the spread spectrum and MPEG-2 AAC psychoacoustic model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.824-833
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• 2004

Due to the bandwidth and storage limitations, medical images are needed to be compressed before transmission and storage. DICOM (Digital Imaging and Communications in Medicine) specification, which is the medical images standard, provides a mechanism for supporting the use of JPEG still image compression standard. In this paper, we explain a method for compressing medical images by JPEG standard and propose two methods for JPEG compression. First, because medical images differ from natural images in optical feature, we propose a method to design adaptively the quantization table using spectrum analysis. Second, because medical images have higher pixel depth than natural images do, we propose a method to design Huffman table which considers the probability distribution feature of symbols. Therefore, we propose methods to design a quantization table and Huffman table suitable for medical images. Simulation results show the improved performance compared to the quantization table and the adjusted Huffman table of JPEG standard. Proposed methods which are satisfied JPEG Standard, can be applied to PACS (Picture Archiving and Communications System).

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.443-446
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• 2005

This paper presents the results of the design and implementation of the airborne pulse doppler radar signal processor using high multi-DSP for the multi-function radar capability such as short-range, midium-range, and long-range depending on the mission of the vehicle. Particularly, the radar signal processor is developed using two DSP boards in parallel for the various radar signal processing algorithm. The key algorithms include LFM chirp waveform-based pulse compression, MTI clutter filter, MTD processor, adaptive CFAR, and clutter map. Especially airborne moving clutter Doppler spectrum compensation algorithm such as TACCAR is implemented for the multi-mode airborne radar system. The test results shows the good Doppler spectral separation for the clutter and the moving target in the flight test environment using helicopter

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.23-28
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• 2005

An airborne radar is an essential aviation electronic system of the helicopter to perform various missions in all-weather environments. This paper presents the results of the design and implementation of the airborne pulse doppler radar signal processor using high multi-DSP for the multi-function radar capability such as short-range, midium-range, and long-range depending on the mission of the vehicle. Particularly, the radar signal processor is developed using two DSP boards in parallel for the various radar signal processing algorithm. The key algorithms include LFM chirp waveform-based pulse compression, MTI clutter filter, MTD processor, adaptive CFAR, and clutter map. Especially airborne moving clutter Doppler spectrum compensation algorithm such as TACCAR is implemented for the multi-mode airborne radar system. The test results shows the good Doppler spectral separation for the clutter and the moving target in the flight test environment using helicopter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.703-719
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• 2011

In multi-user wireless communication systems, adaptive modulation and scheduling are promising techniques for increasing the system throughput. However, a mass of wireless recourse will be occupied and spectrum efficiency will be decreased to feedback channel quality indication (CQI) of all users in every subcarrier or chunk for adaptive orthogonal frequency division multiplexing (OFDM) systems. Thus numerous limited feedback schemes are proposed to reduce the system overhead. The recently proposed compressive sensing (CS) theory provides a new framework to jointly measure and compress signals that allows less sampling and storage resources than traditional approaches based on Nyquist sampling. In this paper, we proposed two novel CQI feedback schemes based on general CS and subspace CS, respectively, both of which could be used in a wireless OFDM system. The feedback rate with subspace CS is greatly decreased by exploiting the subspace information of the underlying signal. Simulation results show the effectiveness of the proposed methods, with the same feedback rate, the throughputs with subspace CS outperform the discrete cosine transform (DCT) based method which is usually employed, and the throughputs with general CS outperform DCT when the feedback rate is larger than 0.13 bits/subcarrier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.11
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• pp.1645-1654
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• 1993

Unlike a noise removal recursive temporal filter, this paper presents a temporal filter which improves visual quality and data compression efficiency. In general, for the temporal band-limitation, temporal aliasing should be considered. Since most of a video signal has temporally aliased components, it is desirable to consider them. From a signal processing point of view, it is impossible to realize the filtering not afeced by the aliasings. However, in this paper, efficient filtering with de-aliasing characteristics is proposed. Considering the location of a video signal, temporal filtering can be accomplished by the spatial filtering along the motion vector trajectory (Motion Adaptive Spatial Filter). This filtered result dose not include the aliasings. Besides the efficient band-limitation, temporal noise is also reduced. For the evaluation of the MASF, its realization and filtering characteristics will be discussed in ditail.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.430-436
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• 2009

In this paper, we propose and describe our implementation of an automatic control system for the center wavelength of a fiber Bragg grating. The proposed system consists of a Fabry-Perot filter and cantilever structure controlled by a step motor interfacing computer. We consider the change of the center wavelength and the reflective spectrum shape for a given FBG according to the translation distance of the push stick and the cantilever thickness variation. The proposed system can control the center wavelength of a FBG with a resolution of 0.01 nm by applying compression or extension to the FBG. The proposed system has characteristics that keep the desired wavelength of the FBG with a variation of environmental conditions.

• The KIPS Transactions:PartB
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• v.14B no.5
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• pp.337-342
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• 2007

Multi-level has advantage to express image in all levels with different images. This paper proposes digital watermarking built-in technique to transform color image to YCbCr color space to guarantee robustness and imperceptibility of the watermark in the various expression of color images, and to hide multi-level data which shows spread spectrum from low resolution to whole resolution for the Y-signal of multi-level. In color signal, Y-signal and low resolution built-in watermark has risk to be visible, but it can guarantee the robustness of watermark in various colors and transformed images. As a result of the experiment, wavelet compression image with built-in watermark showed robustness and imperceptibility of watermark.