• Journal of Navigation and Port Research
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• v.28 no.2
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• pp.135-140
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• 2004

A purpose of developing a sound source tracking system in this paper is to reduce the noise efficiently from the received signal by microphone array and measure the signal's time delay between the microphones. I have applied the wavelet analysis algorithm to the system and calculated the sound source's relative position For the performance evaluation, I have compared with the results of utilizing the digital filtering methods based on the FIR LPF using Kaiser window function and the inverse Chebyshev IIR LPF. As a result, I have confirmed the fact that 'time-scale' filter using inverse discrete wavelet transform was suitable for this system.

• Atmosphere
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• v.18 no.2
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• pp.83-95
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• 2008

In this study we have investigated the preceding eighteen large-scale climate indices with a lead time from zero to twelve months that have an influence on the variability of temperature and precipitation in Korea in order to understand which climate indices are overall available as predictors for long-range forecasting. We also have studied the dynamic link between preceding large-scale climate indices and regional climate using singular value decomposition analysis (SVDA) and correlation analysis (CA). Based on the coupled mode between large-scale circulation and regional climate, and correlation pattern between the preceding large-scale climate indices and large-scale circulation, the level of significance on climate indices as a predictor for monthly mean temperature and precipitation was evaluated for 5 and 1% level.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.182-186
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• 2008

The microstructures of the oxide scale developed at high temperature on steels are very complex and their development depends on many factors including time, temperature, oxidation conditions and alloying elements. The classical model of an oxide scale on steel consisting of wüstite, magnetite and haematite layers, is more complicated in reality and its properties change with the factors that affect their development. An understanding of the oxide scale formation and its properties can only be achieved by careful examination of the scale microstructure. The oxide scale microstructure may be difficult to characterise by conventional techniques such as optical or standard scanning electron microscopy. An unambiguous characterisation of the scale and the correct identification of the phases within the scale are difficult unless the crystallographic structure for each phase in the scale is considered and a simultaneous microstructure-microtexture analysis is carried out. In the current study Electron Backscatter Diffraction (EBSD) has been used to investigate the microstructure of iron oxide layers grown on low carbon steels at different times and temperatures. EBSD has proved to be a powerful technique for identifying the individual phases in the oxide scale accurately. The results show that different grain shapes and sizes develop for each phase in the scale depending on time and temperature.

• Journal of the Korean Society of Visualization
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• v.6 no.1
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• pp.41-46
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• 2008

In this paper, the recirculation flow motion and mixing characteristics driven by air bubble stream in a rectangular water tank is studied. The time-resolved PIV technique is adopted for the quantitative visualization and analysis. 488 nm Ar-ion CW laser is used for illumination and orange fluorescent ($\lambda_{ex}=540nm,\;\lambda_{em}=560nm$) particle images are acquired by a PCO 10bit high-speed CCD camera (1280$\times$1024). To obtain clean particle images, 545 nm long pass optical filter and an image intensifier are employed and the flow rates of compressed air is 3 l/min at 0.5 MPa. The recirculation and mixing flow field is further investigated by time-resolved POD analysis technique. It is observed that the large scale recirculation resulting from the interaction between rising bubble stream and side wall is the most dominant flow structure and there are small scale vortex structures moving along with large scale recirculation flow. It is also verified that the sum of 20 modes of velocity field has about 67.4% of total turbulent energy.

• Journal of International Society for Simulation Surgery
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• v.2 no.2
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• pp.64-66
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• 2015

Purpose : In this paper we proposed cascade feature filter and projection method for rapid human face recognition for the large-scale high-dimensional face database. Materials and Methods : The relevant features are selected from the large feature set using Fast Correlation-Based Filter method. After feature selection, project them into discriminant using Principal Component Analysis or Linear Discriminant Analysis. Their cascade method reduces the time-complexity without significant degradation of the performance. Results : In our experiments, the ORL database and the extended Yale face database b were used for evaluation. On the ORL database, the processing time was approximately 30-times faster than typical approach with recognition rate 94.22% and on the extended Yale face database b, the processing time was approximately 300-times faster than typical approach with recognition rate 98.74 %. Conclusion : The recognition rate and time-complexity of the proposed method is suitable for real-time face recognition system on the large-scale high-dimensional face database.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.54-67
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• 2018

There have been recent efforts to establish methods for high-fidelity and multi-physics simulation with coupled thermal-hydraulic (T/H) and neutronics codes for the entire core of a light water reactor under accident conditions. Considering the computing power necessary for a pin-by-pin analysis of the entire core, subchannel-scale T/H analysis is considered appropriate to achieve acceptable accuracy in an optimal computational time. In the present study, the applicability of in-house code CUPID of the Korea Atomic Energy Research Institute was extended to the subchannel-scale T/H analysis. CUPID is a component-scale T/H analysis code, which uses three-dimensional two-fluid models with various closure models and incorporates a highly parallelized numerical solver. In this study, key models required for a subchannel-scale T/H analysis were implemented in CUPID. Afterward, the code was validated against four subchannel experiments under unheated and heated single-phase incompressible flow conditions. Thereafter, a subchannel-scale T/H analysis of the entire core for an Advanced Power Reactor 1400 reactor core was carried out. For the high-fidelity simulation, detailed geometrical features and individual rod power distributions were considered in this demonstration. In this study, CUPID shows its capability of reproducing key phenomena in a subchannel and dealing with the subchannel-scale whole core T/H analysis.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.77-85
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• 2001

This paper proposes a method of time-scale modification of polyphonic audio signals based on a sinusoidal model. The signals are modeled with sinusoidal component and noise component. A multiresolution filter bank is designed which splits the input signal into six octave-spaced subbands without aliasing and sinusoidal modeling is applied to each subband signal. To alleviate smearing of transients in time-scale modification a dynamic segmentation method is applied to subbands which determines the analysis-synthesis frame size adaptively to fit time-frequency characteristics of the subband signal. For extracting sinusoidal components and calculating their parameters matching pursuit algorithm is applied to each analysis frame of subband signal. In accordance with spectrum analysis a psychoacoustic model implementing the effect of frequency masking is incorporated with matching pursuit to provide a resonable stop condition of iteration and reduce the number of sinusoids. The noise component obtained by subtracting the synthesized signal with sinusoidal components from the original signal is modeled by line-segment model of short time spectrum envelope. For various polyphonic audio signals the result of simulation shows suggested sinusoidal modeling can synthesize original signal without loss of perceptual quality and do more robust and high quality time-scale modification for large scale factor because of representing transients without any perceptual loss.

• Interaction and multiscale mechanics
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• v.5 no.1
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• pp.27-40
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• 2012

The two-dimensional incompressible flow of a linear viscoelastic fluid we considered in this research has rapidly oscillating initial conditions which contain both the large scale and small scale information. In order to grasp this double-scale phenomenon of the complex flow, a multiscale analysis method is developed based on the mathematical homogenization theory. For the incompressible flow of a linear viscoelastic Maxwell fluid, a well-posed multiscale system, including averaged equations and cell problems, is derived by employing the appropriate multiple scale asymptotic expansions to approximate the velocity, pressure and stress fields. And then, this multiscale system is solved numerically using the pseudospectral algorithm based on a time-splitting semi-implicit influence matrix method. The comparisons between the multiscale solutions and the direct numerical simulations demonstrate that the multiscale model not only captures large scale features accurately, but also reflects kinetic interactions between the large and small scale of the incompressible flow of a linear viscoelastic fluid.

• Journal of Power Electronics
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• v.18 no.3
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• pp.944-953
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• 2018

This paper proposes an analysis method based on the magnitude-phase dynamic theory for isolated power systems with static synchronous compensators (STATCOMs). The stability margin of an isolated power system is greatly reduced when a load is connected, due to the disadvantageous features of the self-excited induction generators (SEIGs). To analyze the control process for system stability and to grasp the dynamic characteristics in different timescales, the relationships between the active/reactive components and the phase/magnitude of the STATCOM output voltage are derived in the natural reference frame based on the magnitude/phase dynamic theory. Then STATCOM equivalent mechanical models in both the voltage time scale and the current time scale are built. The proportional coefficients and the integral coefficients of the control process are converted into damping coefficients, inertia coefficients and stiffness coefficients so that analyzing its controls, dynamic response characteristics as well as impacts on the system operations are easier. The effectiveness of the proposed analysis method is verified by simulation and experimental results.

• Journal of the Korean Society of Clothing and Textiles
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• v.19 no.2
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• pp.216-229
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• 1995

The main purpose of this study was to develop and validate a scale for measuring situation\ulcornerspecific anxiety that consumers experience while shopping for ready\ulcornerto-wear clothes. A 92 five-point items, Likert type scale, entitled the RMCCAS(The Ready\ulcornerMade Clothes Consumer Anxiety Scale) was developed and administered to 354 female college students. Data collected were subjected to a series of statistical analysis: item analysis, factor analysis, estimation of validity and reliability and descriptive statistics. A second-order factor analysis conducted to 15 factors obtained from a first-order factor analysis yieled three factors; Fitness of Fashion and Design to indiviuality and time(scale 1), Reliance on Price and Quality including Suitableness of Material and Color(scale 2), and Practicality in Dressing and Maintaining(scale 3). Obtained concurrent validity of the RMCCAS subscales with the trait anxiety were .056(subscale I), .082(subscale 2), .033(subscale 3), and .050(total scale). that with state anxiety were .421(subscale I), .217(subscale 2), .198 (subscale 3), and .407(total scale); that with the CP AS were. 721(subscale 1), .789(subscale 2), .570(subscale 3), and .841(total scale). All of the obtained coefficients of Cronbach alpha, split\ulcornerhalf reliability, and test-retested reliability over an interval of. 8 weeks were above .80. Besides, descriptive data from the RMCCAS satisfactorily supported conditions required for the normal distribution of obtained scores. In conclusion, a close exa:nination of validity, reliability, and descriptive statistics of the RMCCAS indicates that three subscales including the scale have a resonable scaling-prop\ulcornererties. Further research is suggested for obtaining norms for more representative target samples and for tapping the possibility of using subsea Ie 2 as a unidimensional measure .