• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.177-184
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• 2005

Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall building, the probable structural impact of the design basis earthquake or the maximum credible earthquake on the selected structural system should be considered at least in finalizing the design. In this study, by using response spectrum analysis and time history analysis method, seismic performance evaluation was conducted for wind-designed concentrically braced steel highrise buildings. Input ensemble was normalized to be compatible with expected peak ground acceleration. The analysis results showed that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seismic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. The time history analysis tended to significantly underestimated the seismic response as compared to response spectrum analysis. Further detailed studies regarding selection and scaling scheme of input ground motions is needed.

• Journal of Welding and Joining
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• v.18 no.4
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• pp.82-86
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• 2000

Gas metal arc welding(GMAW) is regarded as one of the best candidate for welding automation in industrial joining application. It is important to monitor the weld quality for the high performance weld automation. In GMAW, weld quality is closely related to arc stability especially. In this paper, arc light signal is measured and spectrum analyzed to the detect the variation of the weld quality. The FFT of the signal showed that the amplitude variance of FFT power spectrum was very large in poor weld process such as the decrease of weld bead width and height. The results show that it is possible to detect the weld defect position in weld process.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.9-15
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• 2007

As the development of nanotechnology, the use of composite resins which containing nanofillers becomes popular. The purpose of this study was to test the degree of polymerization of nanofillercontaining composite resins. For the study, three different nanofiller-containing composite resins and two different light-curing units were used. To evaluate the degree of polymerization, the maximum polymerization shrinkage taking place during the light curing, and the microhardness, after the light curing, were measured. As results, two light-curing units exhibited a similar emission spectrum to that of the included photoinitiator, camphorquinone. The only difference between the light-curing units were the width of the emission spectrum. Three different composite resins showed different microhardness values. Among them, Grandio showed the greatest microhardness value. However, there was less microhardness difference on the top and bottom surfaces due to the difference of the light-curing units. The maximum polymerization shrinkage values were also similar in the tested specimens regardless of the difference of the light-curing units. However, Grandio showed the least polymerization shrinkage. According to the manufacturers' data, Grandio showed the highest filler content(vol%).

• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.2
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• pp.1-9
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• 1977

The waveform, power spectrum and optimal receiver structure for fast FSK are analysed. It is shown and verified experimentally that for the observation interval of two bit periods, the bit error rate is as good as that of PSK. At the same time, it is shown to have the advantage of narrower band width than PSK. In experiment, the FFSK signal is generated by using a binary transversal filter and a low pass filter.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.4
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• pp.61-66
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• 1983

This paper is concerned with the design of a pseudonoise (PN) sequence used in direct-sequence spread spectrum multiple-access (DS/SSMA) communication systems. Here we propose a new waveform, a generalized version of rectangular waveform, which can reduce the multiple access interference to zero as the pulse width becomes narrower. It gives far better performance than either rectangular or sine waveform.

• Bulletin of the Korean Chemical Society
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• v.19 no.9
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• pp.942-947
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• 1998

The >$^13C$ NMR spectrum of >$^13CO$ adsorbed on Pd particles varies dramatically depending on dispersion. The spectrum of highly dispersed Pd particles supported on silica is a powder pattern ∼800 ppm wide with a first moment of 410 ppm. A low dispersion sample has a motionally narrowed line centered at 750±30 ppm and only ∼85 ppm full width at half height (FWHH). Over several years, high dispersion samples show an increase in the intensity near 750 ppm. These observations are interpreted as an increase of mobile bridging CO on high dispersion Pd surfaces of particles which resulted from smoothing of the metal particle surfaces in the presence of CO.

• Proceedings of the KIEE Conference
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• 2006.10b
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• pp.154-158
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• 2006

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. Random Pulse Width Modulation (RPWM) is peformed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300v/1kW with $5%{\sim}30%$ white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.908-912
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• 2014

Microgratings whose diffracted field at a fixed angle generate IR spectra of $SF_6$ or $NH_3$ were fabricated by MEMS techniques for the purpose of IR correlation spectroscopy. Each micrograting was composed of 1441 reflecting lines in the area of $19.2{\times}19.2mm^2$. The depth profile of the line elements was determined with a gradient searching method that was described in our previous publication (J. Mod. Opt. 2013, 60, 324-330), and was discretized into 16 levels between 0 and $6.90{\mu}m$. The diffraction field from a given depth profile was calculated with Fraunhofer equation. The fabricated microgratings showed errors in the depth and the width within acceptable ranges. As the result, the diffracted IR spectrum of each micrograting matched well with its target reference spectrum within spectral resolution of our optical setup.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.443-447
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• 2014

$^{134}Cs$ radioactive concentration among soil samples is difficult to classify due to the background impact on crust originated natural radioactive nuclide, and overlapping and interfering between peaks. The ways to identify true peaks in gamma-ray spectroscopy are as follows to reduce statistical fluctuation by smoothing based on the fact that the shapes of peak are mostly Gaussian, to inspect the levels of width and height of peaks, to add functions on low-energy trailing phenomena, or 4) to check the peaks after modifying Gaussian function itself. Therefore, it is considered that information and knowledge for spectrum analysis are necessary.

• Earthquakes and Structures
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• v.14 no.6
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• pp.493-503
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• 2018

With the further increase of span length, the cable-stayed bridge tends to be more slender, and becomes more susceptible to the seismic action. By taking a super long-span cable-stayed bridge with main span of 1400m as example, structural response of the bridge under the E1 horizontal and vertical seismic excitations is investigated numerically by the multimode seismic response spectrum and time-history analysis respectively, the seismic behavior and also the effect of structural nonlinearity on the seismic response of super long-span cable-stayed bridge are revealed. Furthermore, the effect of structural parameters including the girder depth and width, the tower structural style, the tower height-to-span ratio, the side-tomain span ratio, the auxiliary piers in side spans and the anchorage system of stay cables etc on the seismic performance of super long-span cable-stayed bridge is investigated numerically by the multimode seismic response spectrum analysis, and the favorable earthquake-resistant structural system of super long-span cable-stayed bridge is proposed.