• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.842-845
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• 2005

A method for the numerical simulation of two-dimensional free-surface flow resulting from the propagation of regular gravity waves over topography with arbitrary bottom shape is presented. The method is based on the numerical solution of the Euler equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow conditions using a hybrid finite-differences and spectral-method scheme. The formulation includes a boundary-fitted transformation, and is suitable for extension to incorporate large-eddy simulation (LES) and large-wave simulation (LWS) terms for turbulence and breaking wave modeling, respectively. Results are presented for the simulation of the free-surface flow over two different bottom topographies, with constant slope values of 1:10 and 1:20, two different inflow wave lengths and two different inflow wave heights. An absorption outflow zone is utilized and the results indicate minimum wave reflection from the outflow boundary. Over the bottom slope, lengths of waves in the linear regime are modified according to linear theory dispersion, while wave heights remain more or less unchanged. For waves in the nonlinear regime, wave lengths are becoming shorter, while the free surface elevation deviates from its initial sinusoidal shape.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.80.1-80.1
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• 2012

NGC 6803 is an elliptical ring shape planetary nebula. We analyzed the high dispersion spectra which had been observed with the Hamilton Echelle Spectrograph attached to the 3-m Shane telescope of Lick Observatory. We also investigated the low dispersion UV spectral data obtained with the 60-cm interstellar ultraviolet explorer. Diverse excitation lines were found from neutral to quadruply ionized ions. The temperature diagnostic lines indicate relatively low electron temperatures, i.e., $T_{\epsilon}{\leq}9500$ K for most lines except for [ClIV] - 11,500 K. In spite of its simplistic bi-laterally symmetrical elliptical shape, the nebula appears to be very complex of a hugh density range from 1300 to 80,000 $cm^3$. A comparison of the two epoch data suggests that the density increase occurred in the high excitation line zone near the inner boundary. We derived the chemical abundances of He, C, N, O, Ne, S, Ar, Cl, and K. The chemical abundances of NGC 6803 are enhanced compared with the average Galactic planetary nebula. Our self-consistent photo-ionization model study implies that the effective temperature of the central star is 90,000 K and its luminosity is 2400 $L_{\odot}$. The evolutionary track suggests that the progenitor of NGC 6803 was about 0.9 -- 1.0 $M_{\odot}$ star, which might be born from a metal-rich zone near the galactic disk, but now relocated into the present high Galactic latitude.

• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.499-508
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• 2013

This article presents a new method for semi-automatic extraction of building information (height, shape, and footprint location) from monoscopic urban scenes. The proposed method is to expand Semi-automatic Volumetric Shadow Analysis (SVSA), which can handle occluded building footprints or shadows semi-automatically. SVSA can extract wrong building information from a single high resolution satellite image because SVSA is influenced by extracted shadow area, image noise and objects around a building. The proposed method can reduce the disadvantage of SVSA by using multi-spectral images. The proposed method applies SVSA to panchromatic and multi-spectral images. Results of SVSA are used as parameters of a cost function. A building height with maximum value of the cost function is determined as actual building height. For performance evaluation, building heights extracted by SVSA and the proposed method from Kompsat-2 images were compared with reference heights extracted from stereo IKONOS. The result of performance evaluation shows the proposed method is a more accurate and stable method than SVSA.

• Journal of the Korea Society of Computer and Information
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• v.18 no.7
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• pp.23-35
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• 2013

This paper proposes an effective technique that is used to automatically extract feature vectors from vibration signals for fault classification systems. Conventional mel-frequency cepstral coefficients (MFCCs) are sensitive to noise of vibration signals, degrading classification accuracy. To solve this problem, this paper proposes spectral envelope cepstral coefficients (SECC) analysis, where a 4-step filter bank based on spectral envelopes of vibration signals is used: (1) a linear predictive coding (LPC) algorithm is used to specify spectral envelopes of all faulty vibration signals, (2) all envelopes are averaged to get general spectral shape, (3) a gradient descent method is used to find extremes of the average envelope and its frequencies, (4) a non-overlapped filter is used to have centers calculated from distances between valley frequencies of the envelope. This 4-step filter bank is then used in cepstral coefficients computation to extract feature vectors. Finally, a multi-layer support vector machine (MLSVM) with various sigma values uses these special parameters to identify faulty types of induction motors. Experimental results indicate that the proposed extraction method outperforms other feature extraction algorithms, yielding more than about 99.65% of classification accuracy.

• Korean Journal of Ophthalmology
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• v.32 no.6
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• pp.506-516
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• 2018

Purpose: We measured the thicknesses of the ganglion cell and inner plexiform layer (GCIPL), the macula, and the retinal nerve fiber layer (RNFL) using spectral-domain optical coherence tomography in patients with idiopathic macula holes to analyze the repeatability of these measurements and compare them with those of the fellow eye. Methods: We evaluated 85 patients who visited our retinal clinic. The patients were divided into two groups according to their macular hole size: group A had a size of $<400{\mu}m$, while group B had a size of ${\geq}400{\mu}m$. Repeatability was determined by comparing the thicknesses of the GCIPL, macula, and RNFL with those of the normal fellow eye. Results: The average central macular thickness in patients with macular holes was significantly thicker than that in the normal fellow eye ($343.8{\pm}78.6$ vs. $252.6{\pm}62.3{\mu}m$, p < 0.001). The average thickness of the GCIPL in patients with macular holes was significantly thinner than that in the normal fellow eye ($56.1{\pm}23.4$ vs. $77.1{\pm}12.8{\mu}m$, p < 0.001). There was no significant difference in the average RNFL thickness between eyes with macular holes and fellow eyes ($92.4{\pm}10.0$ vs. $95.5{\pm}10.7{\mu}m$, p = 0.070). There were also no significant differences in the thicknesses of the GCIPL and RNFL among the two groups (p = 0.786 and p = 0.516). The intraclass correlation coefficients for the macula and RNFL were 0.994 and 0.974, respectively, in patients with macular holes, while that for the GCIPL was 0.700. Conclusions: Macular contour change with macular hole results in low repeatability and a tendency of thinner measurement regarding GCIPL thickness determined via spectral-domain optical coherence tomography. The impact of changes in the macular shape caused by macular holes should be taken into consideration when measuring the GCIPL thickness in patients with various eye diseases such as glaucoma and in those with neuro-ophthalmic disorders.

• Korean Journal of Remote Sensing
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• v.37 no.4
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• pp.699-717
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• 2021

South Korea is pushing for the advancement of crop production technology to achieve food self-sufficiency and meet the demand for safe food. A medium-sized satellite for agriculture is being launched in 2023 with the aim of collecting and providing information on agriculture, not only in Korea but also in neighboring countries. The satellite is to be equipped with various sensors, though reference data for ground information are lacking. Hyperspectral remote sensing combined with 1st derivative is an efficient tool for the identification of agricultural crops. In our study, we develop a system for hyperspectral analysis of the ground-based reflectance spectrum, which is monitored seven times during the cultivation period of three soybean crops using a PSR-2500 hyperspectral sensor. In the reflection spectrum of soybean canopy, wavelength variations correspond with stages of soybean growths. The spectral reflection characteristics of soybeans can be divided according to growth into the vegetative (V)stage and the reproductive (R)stage. As a result of the first derivative analysis of the spectral reflection characteristics, it is possible to identify the characteristics of each wavelength band. Using our developed monitoring system, we observed that the near-infrared (NIR) variation was largest during the vegetative (V1-V3) stage, followed by a similar variation pattern in the order of red-edge and visible. In the reproductive stage (R1-R8), the effect of the shape and color of the soybean leaf was reflected, and the pattern is different from that in the vegetative (V) stage. At the R1 to R6 stages, the variation in NIR was the largest, and red-edge and green showed similar variation patterns, but red showed little change. In particular, the reflectance characteristics of the R1 stage provides information that could help us distinguish between the three varieties of soybean that were studied. In the R7-R8 stage, close to the harvest period, the red-edge and NIR variation patterns and the visible variation patterns changed. These results are interpreted as a result of the large effects of pigments such as chlorophyll for each of the three soybean varieties, as well as from the formation and color of the leaf and stem. The results obtained in this study provide useful information that helps us to determine the wavelength width and range of the optimal band for monitoring and acquiring vegetation information on crops using satellites and unmanned aerial vehicles (UAVs)

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.87.2-87.2
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• 2016

As an era of nano science approaches, the understanding on the shape and optical properties of various materials in a nanoscale range is getting important more seriously than ever. Accordingly the development of high spatial-temporal-spectral resolution measurement tools for characterization of nanomaterials/structures is highly required. Generally, the various properties of sample can be measured independently, e.g. to observe the structural property of sample, we use the scanning electron microscopy or atomic force microscopy, and to observe optical property, we have to use another independent measurement tool such as photoluminescence spectroscopy or Raman spectroscopy. In the case of nano-materials, however, it is very difficult to find out the same position of sample at every different measurement processes, and the condition of sample can be changed by the influence of first measurement. The tip enhanced Raman scattering(TERS), which can simultaneously measure the two or more information of sample with nanoscale spatial resolution, is one of solutions of this problem. In this talk, I will present our recent nano Raman scattering data of graphene that measured by TERS and optimized tip fabrication method for efficient experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.281-286
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• 2007

Needs of fuel's performance evaluation for the dual-cooled fuel pellet (annular shape) necessitate the irradiation test in the test reactor. Irradiation test rig for the HARARO reactor, which is a special-purposed equipment used for material, irradiation and creep test, must satisfy the operational requirement on the hydraulic characteristics and structural integrity. In this paper, pressure drop and flow-induced vibration test for the newly developed non-instrumented test rig were carried out using FIVPET as a out-pile evaluation test. The test results show that the new test rig satisfy the HANARO operational requirement with sufficient margin. The spectral response characteristics of the flow-induced vibration of the test rid were also discussed.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.37-46
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• 2007

The vibration environment essentially companied by vehicle operation on the ground is determined by the shape of road surface, which is called profile. This paper focuses on development of a profile and severity measurement system for unpaved test courses. In general, the profile and severity of unpaved road is an important issue in the reliability of endurance test. In order to measure unpaved road profile and severity, it is necessary to develop a profilometer system. The developed profilometer system is composed of data processing computer, power unit, air compressor and sensors(encoder, vertical gyro and laser displacement) This paper presents the measuring system configuration, measurement principle of road profile and analysis method of road characteristics used at CPG(Changwon Proving Ground) for this purpose.

• Journal of the Ergonomics Society of Korea
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• v.16 no.3
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• pp.37-48
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• 1997

It is very common for women wear shoes with a high heel. It has been known that the high heel could disfigure the foot shape and cause various joint problems including back pain. However, few quantitative studies have been conducted. Therefore, in this study, the low back muscle has been investigated in order to find fatifue effect due to different heights of the heel. In particular, 0, 4, 6 and 8cm heel and two different shapes of heel have been used for an experiment. Ten healthy female subjects volunteered for the study. Isometric Trunk Exertion Frame(ITEF) and Electromyography were used to measure tha Median Frequency via Spectral analysis. The results indicated that the heel height significantly affected the local muscle fatigue of the back. After post hoc analysis, it was found that a proper heel height ougth to be lower than 5cm not to have severely fatigued back muscle after a casual walk for an hour. Such results could be applies to female industrial workers in order to prevent a cumulative trauma disorder of the back, and also to design a female dress shoes minimizing low back fatigue.