• International Journal of Highway Engineering
• /
• v.10 no.4
• /
• pp.9-18
• /
• 2008

Curling is caused by the difference in the temperature and humidity by the depth of the slab in Jointed Plain Concrete Pavement. Slab curvature shape and size change due to curling exert a profound influence on the internal stress and roughness of the pavement, affecting structural and functional performance of the pavement. Direct measurement of the slab curvature entails many problems. Many measuring instruments have to be installed at the early-stage of the pavement construction, and the behavior of the slab curvature needs to be measured accurately from the early-stage. Moreover, the cost and technical difficulty are very formidable to measure the slab curvature. This study develops a measurement method for slab curvature in jointed concrete pavement at any given time by applying Power Spectrum Density Analysis and Inverse Fast Fourier Transformation to the profile data, that can be easily obtained at the construction field site. The effectiveness of this developed method is verified by measuring the profile data of the test road of jointed concrete pavement at an inland central expressway by the hour and by examining the result of extracting the slab curvature shape from this profile data. Additionally, the profile data of CRCP(Continuously Reinforced Concrete Pavement) sections on the same expressway were obtained and analyzed at the same time. The validity of the method developed for the slab curvature shape extraction is verified by comparing the result from the analysis of the profile data of CRCP sections with that from the analysis of the prof1Ie data of jointed concrete pavement sections.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.6
• /
• pp.5-20
• /
• 2010

One-dimensional equivalent linear site response analysis is widely used in practice due to its simplicity, requiring only few input parameters, and low computational cost. The main limitation of the procedure is that it is essentially a linear method, in which the time dependent change in the soil properties cannot be modeled and constant values of shear modulus and damping is used throughout the duration of the analysis. Various forms of modified equivalent linear analyses have been developed to enhance the accuracy of the equivalent linear method by incorporating the dependence of the shear strain with the loading frequency. The methods are identical in that it uses the shear strain Fourier spectrum as the backbone of the analysis, but differ in the method in which the strain Fourier spectrum is smoothed. This study used two domestically measured soil profiles to perform a series of nonlinear, equivalent linear, and modified equivalent linear site response analyses to verify the accuracy of two modified procedures. The results of the analyses indicate that the modified equivalent linear analysis can highly overestimate the amplification of the high frequency components of the ground motion. The degree of overestimation is dependent on the characteristics of the input ground motion. Use of a motion rich in high frequency contents can result in unrealistic response.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.2
• /
• pp.276-284
• /
• 2020

This paper proposes a new convolutional neural network (CNN) based spectrum sensing technique for cognitive radio communications. The proposed technique determines the existence of the primary user (PU) by using energy detection without any prior knowledge of the PU's signal. In the proposed method, the received signal is high-rate sampled to sense the entire spectrum bands of interest. After that, fast Fourier transform (FFT) of the signal converts the time domain signal to frequency domain spectrum and by stacking those consecutive spectrums, a 2 dimensional signal is made. The 2 dimensional signal is cut by the sensing channel bandwidth and inputted to the CNN. The CNN determines the existence of the primary user. Since there are only two states (existence or non-existence), binary classification CNN is used. The performance of the proposed method is examined through computer simulation and indoor experiment. According to the results, the proposed method outperforms the conventional threshold-based method by over 2 dB.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.6
• /
• pp.881-885
• /
• 2006

We have employed a technique of corona excited supersonic expansion to generate electronically excited but jet-cooled o-tolunitrile. The vibronically well-resolved emission spectrum of the jet-cooled o-tolunitrile in the $S_{1}\rightarrow S_{0}$ transition was recorded in the uv region using a Fourier transform spectrometer equipped with a Quartz-uv beam splitter. The electronic transition and vibrational mode frequencies in the ground electronic state were accurately determined from the analysis of the spectra observed.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.9
• /
• pp.1377-1380
• /
• 2006

The technique of corona-excited supersonic expansion was applied to produce electronically excited but rovibrationally cooled m-tolunitrile. The well-resolved vibronic emission spectrum of the jet-cooled m-tolunitrile in the $S_1\;\rightarrow \;S_0$ transition was recorded in the uv region using a Fourier transform spectrometer equipped with a Quartz-uv beam splitter. From an analysis of the spectrum observed, it was confirmed that the electronic transition and vibrational mode frequencies in the ground electronic state were accurately determined.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.474-477
• /
• 2002

Hearing loss caused by exposure to industrial machine noise results in devastating disability that is mostly preventable. And recent researches indicate that the noise may also induce hypertension and cardiovascular disease. In addition the sleep polygraph provides many indicators of sleep disturbance by the noise. In this paper we make an analysis on ball bearing machine noise, a kind of the industrial noise. The analysis of Its power spectrum is based on FFT(Fast Fourier Transform). And then the spectral results of the noise are compared with that of the spectrum for an auditory signal. The signal is measured from the pronunciation of two Koreans. Finally we suggest the most important stratagem to prevent the noise for worker's health and efficiency.

• Proceedings of the IEEK Conference
• /
• 2000.06d
• /
• pp.135-138
• /
• 2000

흉부 X선 CT 화상을 이용한 폐종류의 경계 형상을 정량적으로 평가하기 위하여 푸리에 변환된 폐종류 음영의 윤곽선 내 power spectrum 고주파 성분의 총합이 폐종류 음영의 경계 형상에 관한 유효한 평가 값이 되는지의 여부를 검토하였다. 이 평가 값은 폐종류 음영의 CT 화상 위의 특징을 명확히 반영한다고 판단된다. 다시 말해서, 윤곽선은 양성 혹은 악성 종류에 있어서 각각 명확하거나 불투명하다. 양성 IS명과 악성 16명인 환자 31명에 대해서 이 평가 값을 계산하여 통계적 처리를 행한 결과 양성과 악성 간에 뚜렷한 차이를 인식할 수 있었다. 이러한 제안된 평가 방법에 의해, power spectrum 고주파 성분의 총합이 폐종류 경계 형상의 평가치가 되어, 정량적인 폐종류의 양성과 악성 감별을 행할 때 유용한 값이 될 가능성을 시사한다고 볼 수 있다.

• ETRI Journal
• /
• v.37 no.1
• /
• pp.1-10
• /
• 2015

A blind hopping phase estimator is proposed for the demodulation of received signals in frequency-hopping spread spectrum systems. The received signals are assumed to be bandwidth limited with a shaping filter, modulated as frequency modulation (FM) or binary frequency shift keying (BFSK), and hopped by predetermined random frequency sequences. In the demodulation procedure in this paper, the hopping frequency tracking is accomplished by choosing a frequency component with maximum amplitude after taking a discrete Fourier transform, and the hopping phase estimator performs the conjugated product of two consecutive signals and moving-average filtering. The probability density function and Cramer-Rao low bound (CRLB) of the proposed estimator are evaluated. The proposed scheme not only is very simple to implement but also performs close to the CRLB in demodulating hopped FM/BFSK signals.

• Journal of Biosystems Engineering
• /
• v.23 no.1
• /
• pp.57-66
• /
• 1998

This study was conducted to investigate the relationships between parameters affecting internal quality of watermelon and its acoustic characteristics. The measuring and analyzing system was established to study the acoustic characteristics of watermelon. Algorithms for analyzing sound signals were developed. Sound signals which was detected with the microphone were filtered, and their spectrum was computed by means of the Fast Fourier Transform. As watermelon changed from the unripe stage to ripe, acoustic waves in time domain became complicated, and several components appeared in frequency domain. The correlationship was investigated between some parameters affecting internal quality of the watermelon and several peak frequencies. Results indicated that weight, density and sugar content had high correlations with several frequencies(the first peak frequency, the second peak frequency, and the third peak frequency). And the sugar content and the volume of the watermelon were highly correlated with the third peak frequency.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.41 no.5
• /
• pp.50-58
• /
• 2009

Periodic variation of local paper structure was evaluated using two-dimensional fast Fourier transform (FFT) and spectral analysis. Since the periodic variation could originate from various sources and have different magnitudes and patterns depending on the origins, a complete analysis of local paper structure properties such as local grammage, local thickness, local apparent density and surface topography was proposed in this study. For a commercial copy paper, the individual periodic patterns for each local structural property were identified by using inverse FFT spectrums of the filtered spectrum. The spectral analysis of newsprint sample provided the period of variation quantitatively, which was useful in comparing the origins of the individual periodic patterns of the local structural properties.