• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.7-14
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• 1998

In this paper, Fractal analysis applied to evaluate machined surface profile. The spectrum method was used to calculate fractal dimension of generated surface profiles by Weierstrass-Mandelbrot fractal function. To avoid estimation errors by low frequency characteristics of FFT, the Maximum Entropy Method (MEM) was examined. We suggest a new criterion to define the MEM order m. MEM power spectrum with our criterion is proved to be advantageous by the comparison with the experimental results.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.312-316
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• 2000

Vole lllvesnguted the surface roughness charactenstics of the super~polished mirror substrate made by bowl-feed technique. in comparison with the case of fresh-feed technique. Fresh-feed techmque and bowl-feed technique were tried lor substrate surface polishing, and the surface roughne~s was estimated by phase-measunng interferometry. l11e slilface roughness of the substrate after bowl-feed procedure was Improved approxImately three times as fine as that after fresh-feed procedure. and tbe nns roughness of less than $0.5\AA$ and up to $0.3\AA$ at its best was obtained for the bowl-feed procedure. The surface roughness changes by (he bowl-feed technique. compated with tbe fresh-feeclleclmique. were analyzed witb tbe help of both 1 -dimensional roughne,>s profde and rougbness amplItude spect1U1l1 of the polished substrate, whIch ascertained that the final polishing partIcle size of the bowl-feed ptocedure was much smaller than that of the fresh~feed procedure. edure.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.72-77
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• 1992

In this study, using in-process tool failure detecting system by AE method in turning machining, we measured AE signal from the tool, and the surface roughness of workpiece and then compared it with tool wear. As a result, we found that tool failure can be predicted by means of surface roughness of the workpiece and it can be predicted more precisely by the arithmetical average roughness (Ra) than by the maximum height of irregularities (Rmax) of the workpiece. Also, we found that we could judge whether it was sudden failure or the wear by means of the shape of AE signal and the range distri- bution of power spectrum frequency when tool danage was happened.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.326-331
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• 2000

This paper describes the statistical analysis techniques for the surface roughness assessment of polished surfaces. In experiments, the polishing process of the sample surfaces which are manufactured by ball end mill is consist of two steps; the cusp removal process and the surface finishing process. For the cusp removal process, the criterion of cusp removal was established from the power spectrum analysis to assess the change of the cusp removal rate. For the finishing process, the surface was polished by the rotational CBN tool and vibration wood tool. And the surface quality of polished surface was assessed using the functional parameters based on the statistical values of surface profiles. Consequently, the surface finish performance of the polished surface using the vibration wood tool was improved.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.125-125
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• 2020

European Space Agency's Sentinel-1 has an improved spatial and temporal resolution, as compared to previous satellite data such as Envisat Advanced SAR (ASAR) or Advanced Scatterometer (ASCAT). Thus, the assumption used for low-resolution retrieval algorithms used by ENVISAT ASAR or ASCAT is not applicable to Sentinel-1, because a higher degree of land surface heterogeneity should be considered for retrieval. The assumption of homogeneity over land surface is not valid any more. In this study, considering that soil roughness is one of the key parameters sensitive to soil moisture retrievals, various approaches are discussed. First, soil roughness is spatially inverted from Sentinel-1 backscattering over Yanco sites in Australia. Based upon this, Artificial Neural Networks data (feedforward multiplayer perception, MLP, Levenberg-Marquadt algorithm) are compared with Fractal approach (brownian fractal, Hurst exponent of 0.5). When using ANNs, training data are achieved from theoretical forward scattering models, Integral Equation Model (IEM). and Sentinel-1 measurements. The network is trained by 20 neurons and one hidden layer, and one input layer. On the other hand, fractal surface roughness is generated by fitting 1D power spectrum model with roughness spectra. Fractal roughness profile is produced by a stochastic process describing probability between two points, and Hurst exponent, as well as rms heights (a standard deviation of surface height). Main interest of this study is to estimate a spatial variability of roughness without the need of local measurements. This non-local approach is significant, because we operationally have to be independent from local stations, due to its few spatial coverage at the global level. More fundamentally, SAR roughness is much different from local measurements, Remote sensing data are influenced by incidence angle, large scale topography, or a mixing regime of sensors, although probe deployed in the field indicate point data. Finally, demerit and merit of these approaches will be discussed.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.3
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• pp.184-191
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• 1996

The purpose of this paper is to investigate components of surface roughness in turning with respect to the tool configuration and the changes of working conditions. Tool configurations of SNMG120404, SNMG120408 and DNMG150404, DNMG150408 are used, and working conditions such as cutting speed 3nd feed are varied. That is, the changes of cutting speed and feed were 150, 200, 250 m/min and 0.05, 0.1, 0.3 mm/rev, respectively. From the results obtained by the frequency analysis with spectrum, it is noted that the surface roughness was influenced most significantly by the feed. It is also observed that the vibration of bite had an effect on both the surface roughness and the surface waviness. Moreover, the influence of surface roughness increases as the feed decreases. Lastly, the vibration of the spindle was found to have little influence on the surface roughness in normal cases and the tool configuration was not the components of the surface roughness.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.1-9
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• 2021

High-frequency bistatic sea surface scattering channels according to sea state were measured at an experimental site of Geoje bay in April 2020, and compared with predictions based on scattering theory. A linear frequency-modulated signal with a center frequency of 128 kHz and a bandwidth of 32 kHz was used for the acoustic measurements. Sea surface wavenumber spectrum was calculated from surface roughness data measured by a wave buoy, and bistatic scattering cross-section of Small Slope Approximation (SSA) based on the wavenumber spectrum was estimated. In addition, scattering from near-surface bubbles using wind speed measured during experiments was considered. Surface scattering channel intensity impulse responses were simulated using the scattering cross-section and the simulation results were compared and analyzed with the field data.

• Journal of Korean Society of Disaster and Security
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• v.6 no.2
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• pp.49-56
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• 2013

In this paper, used by the boundary layer wind tunnel test, have conducted a series of wind tunnel experiments, i.e. test the mean velocity profile regarding the surface roughness, turbulence intensity and power spectrum measured by augmentation device. After that, to provide data relevant for the preliminary design step of tall building hazard fluctuating wind loads may be obtained fluctuating pressure coefficients, fluctuating pressure spectrum, autocorrelation coefficients by the boundary layer wind tunnel test. From the results of experiments, this study can be obtained conclusions as follows. 1. We know the fact that the mean velocity profile and the turbulence intensity are well fitted natural wind flow in the boundary layer wind tunnel. 2. The satisfactory agreement of velocity spectrum can be obtained from the compare of fluctuating power spectrum and Von Karman spectrum. 3. We know the fact that the fluctuating pressure spectrums distributed peak at 0.01 Hz-0.1 Hz in the windward surfaces and at 0.1 Hz in the leeward surfaces. 4. We know the fact that the autocorrelation coefficients distributed stationary random processes with application time of hazard fluctuating wind loads.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.263-263
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• 2010

High temperature annealing is required to synthesize graphene using CVD. When thin metal catalyst is used for the synthesis, the high temperature pre-annealing makes the thin catalyst highly agglomerated. We investigated the agglomeration effect on the shape of the synthesized graphene. It is found that high temperature annealing makes randomly distributed many hole or blister on metal catalyst, and the synthesized graphene features floral pattern around the hole. The floral patterns of graphene turned out to be multi-layers and higher D peaks in raman spectrum.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.274-274
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• 2013

We fabricate encapsulation-layer of OLED panel from organic-inorganic hybrid thin film by atomic layer deposition (ALD) molecular layer deposition (MLD) using Al2O3 as ALD process and Adipoyl Chloride (AC) and 1,4-Butanediamine as MLD process. Ellipsometry was employed to verify self-limiting reaction of MLD. Linear relationship between number of cycle and thickness was obtained. By such investigation, we found that desirable organic thin film fabrication is possible by MLD surface reaction in monolayer scale. Purging was carried out after dosing of each precursor to eliminate physically adsorbed precursor with surface. We also confirmed roughness of the organic thin film by atomic force microscopy (AFM). We deposit AC and 1,4-Butanediamine at $70^{\circ}C$ and investigated surface roughness as a function of increasing thickness of organic thin film. We confirmed precursor's functional group by IR spectrum. We calculated WVTR of organic-inorganic hybrid super-lattice epitaxial layer using Ca test. WVTR indicates super-lattice film can be possibly use as encapsulation in flexible devices.