• The Journal of the Acoustical Society of Korea
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• v.12 no.1
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• pp.47-54
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• 1993

Performance analysis is very important to transmit the high quality information and to construct the optimal system for the minimze the noise from the channel of spread spectrum system. In this paper the error rate performance is analyzed with computer simulation in noncoherent frequency hopping M-qry frequency shift keying(FH/MFSk) systems with regard to thermal noise under the partial band jamming environments. AS a result, in case the thermal noise is disregarded, bit error probability of system in jamming fraction ρ and Eb/Nj(bit energy to jamming power density) is reduced with the increase of K and in worst case 32FSK system is better than 2FSK system by 3.23dB with the variatio of Eb/Nj. In case thermal noise is considered, bit error probability of system by 3.23dB with the variation of Eb/Nj. In case thermal noise is considered, bit error probability of system are reduced with the increase of K and Eb/No(bit energy to thermal noise density). Bit error probability in connection with worst case ρ is not largely influenced form over the 14dB to K=1 and 8dB to K=5 accordingly thermal noise disregarding. These results may be useful for avoiding the common vulnerabilities when the spread spectrum system is designed.

• Journal of Navigation and Port Research
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• v.34 no.6
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• pp.429-434
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• 2010

The experimental study of the hull surface roughness on a developing turbulent boundary layer which exposed to a variety of operating environments were investigated by performing particle image velocimetry(PIV) in a circulating water channel. The Reynolds number based on the width of roughness was about Re=1000. the roughness elements used were periodically arranged two-dimensionally. the flow visualization, time-mean velocity fields and vorticity fields to measure the flow characteristics were obtained. The investigation shows that the vortex generation and its progress inside the walls. And the center of the vortex was located at the middle of the height of the surface roughness.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.840-866
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• 2014

Visibility in underwater images is usually poor because of the attenuation of light in the water that causes low contrast and color variation. In this paper, a new approach for underwater image quality improvement is presented. The proposed method aims to improve underwater image contrast, increase image details, and reduce noise by applying a new method of using contrast stretching to produce two different images with different contrasts. The proposed method integrates the modification of the image histogram in two main color models, RGB and HSV. The histograms of the color channel in the RGB color model are modified and remapped to follow the Rayleigh distribution within certain ranges. The image is then converted to the HSV color model, and the S and V components are modified within a certain limit. Qualitative and quantitative analyses indicate that the proposed method outperforms other state-of-the-art methods in terms of contrast, details, and noise reduction. The image color also shows much improvement.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1618-1622
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• 2004

In this paper, the linearly interpolated PRC(Pseudo Range Correction) regenerating algorithm was applied to improve the DGPS(Differential Global Positioning System) positioning accuracy at user's spot by using the various PRC information obtained from multi-DGPS reference stations. The PRC information of each GPS satellite is not varying rapidly; it is possible to assume that the variation of PRC information of each GPS satellite is linear. So the linearly interpolated PRC regenerating algorithm can be applied to improve the DGPS positioning accuracy at user's spot by using the various PRC information obtained from multi-DGPS reference stations. To test the performance of the linearly interpolated PRC regenerating algorithm, maritime DGPS reference stations' PRC data was used in RTCM format. 11 maritime DGPS reference stations are in service providing DGPS information to public since 1999. Two set of 3 DGPS reference stations are selected to compare the performance of the linearly interpolated PRC regenerating algorithm. The DGPS positioning accuracy was dramatically improved about 40%. Linearly interpolated PRC regenerating algorithm adopted multi-channel DGPS receiver will be developed in near future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.223-227
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• 2002

As the channel length of device shrinks below $0.13{\mu}m$, CMP(chemical mechanical polishing) process got into key process for global planarization in the chip manufacturing process. The removal rate and non-uniformity of the CMP characteristics occupy an important position to CMP process control. Especially, the post-CMP thickness variation depends on the device yield as well as the stability of subsequent process. In this paper, every wafer polished two times for the improvement of oxide CMP process characteristics. Then, we discussed the removal rate and non-uniformity characteristics of post-CMP process. As a result of CMP experiment, we have obtained within-wafer non-uniformity (WIWNU) below 4 [%], and wafer-to-wafer non-uniformity (WTWNU) within 3.5 [%]. It is very good result, because the reliable non-uniformity of CMP process is within 5 [%].

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.160-163
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• 1995

An optimal EEG and artifact classifier is proposed using neural network operating characteristics. The neural network operating characteristics are two dimensional parametric representations of the right and false identification probabilities of the network classifier. Since the EEG and EP signals acquired from multi -channel electrodes placed on the head surface are often interfered by other relatively large physiological signals such as electromyogram (EMG) or electroculogram (EOG), the removal of the artifact-affected EEGs is one of the key elements in neuro-functional mapping. Conventionally this task has been carried out by human experts spending lots of examination time. Using the neural-network based classification, human expert's efforts and time can be substantially reduced. From experiments, the neural-network based classification performs as good as human experts: variation of decisions between the neural network and human expert appears even smaller than that between human experts.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.69-72
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• 2001

In this paper, we study about a acupuncture point and a non-acupuncture point resistance characteristics for acupuncture research. For this study, we devised resistance variation measurement system. This system is consist of 4-channel skin resistance measuring parts, filters, 12bit A/D convertor, 8051 micro-controller, and personal computer The developed system insert a low current to skin and obtains voltages from standard resistor that is convected to measurement circuit in series. The obtained voltage is converted to 12bit digital signal. Therefore the converted signal is changed to skin resistance by calculation in the personal computer. As the results of experiment, the resistance of acupuncture point and non-acupuncture point are different from each other. The acupuncture point has very fast current flows than the other non- acupuncture point.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.369-372
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• 2004

The characteristics of antimony implants are relatively well-known. Antimony has lower diffusion coefficient, shorter implantation range, and smaller scattering as compared with conventional dopants such as phosphorous and arsenic. It has been commonly used in the doping of buried layer in Bi-CMOS process. In this paper, characteristics and appropriate condition of monitoring in antimony implant beam tuning using $Sb_2O_3$ were investigated to get a reliable process. TW(Thema Wave) and Rs(Sheet Resistance) test were carried out to set up condition of monitoring for stable operation through the periodic inspection of instruction condition. The monitoring was progressed at the point that the slant of Rs varied significantly to investigate the variation of instruction accurately.

• IE interfaces
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• v.20 no.2
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• pp.216-226
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• 2007

In code-division multiple-access (CDMA) systems with soft handoff, mobile station (MS) within soft handoff region can use multiple radio channels and receive their signals from multiple base stations (BSs) simultaneously. In this paper, the effects of soft handoff region ratio (SHRR) on reverse link of a CDMA cellular system are analytically investigated. In order to analyze the network performance and quality of service (QoS) perceived by users more realistically, both the soft capacity increasing factor and the traffic load variation affected by SHRR are jointly considered and a two-dimensional continuous time Markov chain (CTMC) model is built. In the numerical example, it is observed that the optimal guard channel exists according the variations of the traffic load and propagation conditions when the proper value of SHRR is determined.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.472-483
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• 1999

The evaporation heat transfer and pressure drop characteristics for HFC-l34a in flat plate type heat exchangers with enhanced beads were experimentally investigated. Three plate type evaporators with different geometric condition of U-turn area were tested. Mass fluxes were tested over the range of 83kg/$m^2$s to 166kg/$m^2$s, and heat fluxes were varied from 4㎾/$m^2$ to 12㎾/$m^2$. Evaporation temperature was 5$^{\circ}C$ with inlet qualities of 0.1 to 1.0. There was no notable difference in the heat transfer coefficient by geometric variation of U-turn area, but the third plate with cross-ribbed channel at U-turn area was better than others in the evaluation using volume goodness factor comparison. Also, the mixtures of HFC-l34a and PAG oil was tested to determine oil effects on heat transfer and pressure drop. As oil concentration was increased, heat transfer coefficient was increased by 22~48% up to the 3wt.%, but decreased by 14~22% at the 4wt.%. The pressure drop was increased by the maximum of 100% as oil concentration was increased.