• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.3
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• pp.211-218
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• 2015

The analysis of remote sensing data depends on sensor specifications that provide accurate and consistent measurements. However, it is not easy to establish confidence and consistency in data that are analyzed by different sensors using various radiometric scales. For this reason, the cross-calibration method is used to calibrate remote sensing data with reference image data. In this study, we used an airborne hyperspectral image in order to calibrate a multispectral image. We presented an automatic cross-calibration method to calibrate a multispectral image using hyperspectral data and spectral mixture analysis. The spectral characteristics of the multispectral image were adjusted by linear regression analysis. Optimal endmember sets between two images were estimated by spectral mixture analysis for the linear regression analysis, and bands of hyperspectral image were aggregated based on the spectral response function of the two images. The results were evaluated by comparing the Root Mean Square Error (RMSE), the Spectral Angle Mapper (SAM), and average percentage differences. The results of this study showed that the proposed method corrected the spectral information in the multispectral data by using hyperspectral data, and its performance was similar to the manual cross-calibration. The proposed method demonstrated the possibility of automatic cross-calibration based on spectral mixture analysis.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.181-184
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• 2006

High-speed flight vehicle have various cavities. The supersonic cavity flow is complicated due to vortices, flow separation and reattachment, shock and expansion waves. The general cavity flow phenomena include the formation and dissipation of vortices, which induce oscillation and noise. The oscillation and noise greatly affect flow control, chemical reaction, and heat transfer processes. The supersonic cavity' flow with high Reynolds number is characterized by the pressure oscillation due to turbulent shear layer, cavity geometry, and resonance phenomenon based on external flow conditions, The resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. In the present study, we performed numerical analysis of cavities by applying the unsteady, compressible three dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with the ${\kappa}-{\omega}$ turbulence model. The cavity model used for numerical calculation had a depth(D) of 15mm cavity aspect ratio(L/D) of 3, width to spanwise ratio(W/D) of 1.0 to 5.0. Based on the PSD(Power Spectral Density) and CSD(Cross Spectral Density) analysis of the pressure variation, the dominant frequency was analyized and compared with the results of Rossiter's Eq.

• Journal of computational fluids engineering
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• v.11 no.4 s.35
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• pp.62-66
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• 2006

High-speed flight vehicle have various cavities. The supersonic cavity flow is complicated due to vortices, flow separation, reattachment, shock waves and expansion waves. The general cavity flow phenomena includes the formation and dissipation of vortices, which induce oscillation and noise. The oscillation and noise greatly affect flow control, chemical reaction, and heat transfer processes. The supersonic cavity flow with high Reynolds number is characterized by the pressure oscillation due to turbulent shear layer, cavity geometry, and resonance phenomenon based on external flow conditions. The resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. In the present study, we performed numerical analysis of cavities by applying the unsteady, compressible three dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with the ${\kappa}-{\omega}$ turbulence model. The cavity model used for numerical calculation had a depth(D) of 15mm cavity aspect ratio (L/D) of 3, width to spanwise ratio(W/D) of 1.0 to 5.0. Based on the PSD(Power Spectral Density) and CSD(Cross Spectral Density) analysis of the pressure variation, the dominant frequency was analyzed and compared with the results of Rossiter's Eq.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.221-224
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• 2000

The purposes of this paper are to clarify the influences of artifacts on a cerebrovascular audiospectroscopy (CeVASS) and to improve the detecting precision of the CeVASS. First, we perform the CeVASS in 15 healthy adults with various measuring positions such as forehead eyes, cervical parts, temple parts, and occipitomastoid parts, and the influences of artifacts on each position is estimated. Next, we discuss about the removal of the artifacts using cross-spectral analysis. Finally, we propose an improved system of the CeVASS.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2810-2815
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• 2008

Flow pulsation in the gap connecting with two parallel channels is investigated by RANS and URANS approaches. The two parallel channels are connected by a small channel called for a gap. The parallel channels are designed to have different cross section area with its ratio of 0.5. Computations are conducted using a CFX 11.0 code. The bulk Reynolds number is 60,000. Predicted results are compared with the previous experimental result. Mean velocity profile at the center of gap region are compared with experiments for its validation. Spectral analysis on the lateral velocity in the center of the gap is presented. Auto and cross correlation for the axial-flow velocity pattern are presented. The unsteady structure of the flow pulsation was visualized in the region of the gap in the parallel channel.

• Earthquakes and Structures
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• v.5 no.4
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• pp.439-459
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• 2013

Main objective of the present study is to determine the statistical properties and suitable probability distribution functions of spectral displacements from nonlinear static and nonlinear dynamic analysis within the frame work of Monte Carlo simulation for typical low rise and high rise RC framed buildings located in zone III and zone V and designed as per Indian seismic codes. Probabilistic analysis of spectral displacement is useful for strength assessment and loss estimation. To the author's knowledge, no study is reported in literature on comparison of spectral displacement including the uncertainties in capacity and demand in Indian context. In the present study, uncertainties in capacity of the building is modeled by choosing cross sectional dimensions of beams and columns, density and compressive strength of concrete, yield strength and elastic modulus of steel and, live load as random variables. Uncertainty in demand is modeled by choosing peak ground acceleration (PGA) as a random variable. Nonlinear static analysis (NSA) and nonlinear dynamic analysis (NDA) are carried out for typical low rise and high rise reinforced concrete framed buildings using IDARC 2D computer program with the random sample input parameters. Statistical properties are obtained for spectral displacements corresponding to performance point from NSA and maximum absolute roof displacement from NDA and suitable probability distribution functions viz., normal, Weibull, lognormal are examined for goodness-of-fit. From the hypothesis test for goodness-of-fit, lognormal function is found to be suitable to represent the statistical variation of spectral displacement obtained from NSA and NDA.

• Journal of The Korean Astronomical Society
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• v.47 no.5
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• pp.195-199
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• 2014

We present a GUI-based interactive Python program, VIMAP, which generates radio spectral index maps of active galactic nuclei (AGN) from Very Long Baseline Interferometry (VLBI) maps obtained at different frequencies. VIMAP is a handy tool for the spectral analysis of synchrotron emission from AGN jets, specifically of spectral index distributions, turn-over frequencies, and core-shifts. In general, the required accurate image alignment is difficult to achieve because of a loss of absolute spatial coordinate information during VLBI data reduction (self-calibration) and/or intrinsic variations of source structure as function of frequency. These issues are overcome by VIMAP which in turn is based on the two-dimensional cross-correlation algorithm of Croke & Gabuzda (2008). In this paper, we briefly review the problem of aligning VLBI AGN maps, describe the workflow of VIMAP, and present an analysis of archival VLBI maps of the active nucleus 3C 120.

• Earthquakes and Structures
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• v.13 no.2
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• pp.193-200
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• 2017

To overcome the difficulty of performing multi-point response spectrum analysis for engineering structures under spatially varying ground motions (SVGM) using the general finite element code such as ANSYS, an approach has been developed by improving the modelling of the input ground motions in the spectral analysis. Based on the stochastic vibration analyses, the cross-power spectral density (c-PSD) matrix is adopted to model the stationary SVGM. The design response spectra are converted into the corresponding PSD model with appropriate coherency functions and apparent wave velocities. Then elements of c-PSD matrix are summarized in the row and the PSD matrix is transformed into the response spectra for a general spectral analysis. A long-span high-pier bridge under multiple support excitations is analyzed using the proposed approach considering the incoherence, wave-passage and site-response effects. The proposed approach is deemed to be an efficient numerical method that can be used for seismic analysis of large engineering structures under SVGM.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.7
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• pp.512-519
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• 2009

Flow pulsation in the gap connecting with two parallel channels is investigated by RANS and URANS approaches. The two parallel channels are connected by a small channel called for a gap. The parallel channels are designed to have different cross section area with its ratio of 0.5. Computations are conducted using a CFX 11.0 code. The bulk Reynolds number is 60,000. Predicted results are compared with the previous experimental data. Mean velocity profile at the center of gap region are compared with experiments for its validation. Spectral analysis on the lateral velocity in the center of the gap was performed. Auto correlation for the axial-flow velocity pattern was presented. The unsteady structure of the flow pulsation was visualized in the region of the gap in the parallel channel.

• Journal of Astronomy and Space Sciences
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• v.35 no.4
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• pp.211-218
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• 2018

Solar microwave bursts carry information about the magnetic field in the emitting region as well as about electrons accelerated during solar flares. While this sensitivity to the coronal magnetic field must be a unique advantage of solar microwave burst observations, it also adds a complexity to spectral analysis targeted to electron diagnostics. This paper introduces a new spectral analysis procedure in which the cross-section and thickness of a microwave source are expressed as power-law functions of the magnetic field so that the degree of magnetic inhomogeneity can systematically be derived. We applied this spectral analysis tool to two contrasting events observed by the Owens Valley Solar Array: the SOL2003-04-04T20:55 flare with a steep microwave spectrum and the SOL2003-10-19T16:50 flare with a broader spectrum. Our analysis shows that the strong flare with the broader microwave spectrum occurred in a region of highly inhomogeneous magnetic field and vice versa. We further demonstrate that such source properties are consistent with the magnetic field observations from the Michelson Doppler Imager instrument onboard the Solar and Heliospheric Observatory (SOHO) spacecraft and the extreme ultraviolet imaging observations from the SOHO extreme ultraviolet imaging telescope. This spectral inversion tool is particularly useful for analyzing microwave flux spectra of strong flares from magnetically complex systems.