• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.11-14
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• 2001

We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 30[mN/m]. LB layers of Arac. acid deposited by LB method were deposited onto slide glass as Y-type film. The physicochemical properties of the LB films were examined by UV absorption spectrum, SEM and AFM. The structure of manufactured device is Au/arachidic acid/Al. the number of accumulated layers are 3~9. Also. we then examined of the MIM device by means of I-V. The I-V characteristic of the device is measured from -3 to +3[V]. The insulation property of a thin film is better as the distance between electrodes is larger.

• Journal of the Korean Applied Science and Technology
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• v.15 no.3
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• pp.85-90
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• 1998

In this study, organic electroluminescent devices(OELD) with a structure of a glass $substrate/ITO/TPD/Tb(ACAC)_3(Phen-Cl)/Alq_3/Al$ was fabricated by vacuum evaporation method, where Tb complex was known to have green light emitting property. Electroluminescent(EL) and I-V characteristics of this structure were investigated. This triple-layer structure shows the green EL spectrum at the wavelwngth of 546nm, which is almost the same as the PL spectrum of $Pb(ACAC)_3(Phen_Cl)$. It was found in current-voltage(I-V) characteristics of the devices that the operating voltage was about 12V.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.371-374
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• 2000

We propose an efficient method for content-based ultrasound image retrieval using magnitude frequency spectra and implement a retrieval system based on the proposed method. The target images are ultrasound images of adult organs. Trained users often acquire such images so that images of the same kind of organs are very similar, although their locations may not exactly coincide. Therefore, the magnitude frequency spectrum, which has a translation-invariant property, is used as a feature. All the object images in the image DB is pre-classified in the same kind organs. Experimental results show that the proposed method is superior to some well-known conventional methods.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.543-550
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• 2000

The objective of this research was to study the effect of contact force of ultrasonic probe on the ultrasonic attenuation measurement of radish. The relationship between ultrasonic attenuation (y) and contact force (x) for radish can be expressed as equation y=a+bLn(x), where a=8.7194+2.l68x(porosity) and b =-9.9188+0.0075 ${\times}$ (volume). The relationship between ultrasonic power spectrum (y) and contact force (x) for radish is also represented by equation y=a+bLn(x), where a= 60.l965-1.47l4${\times}$(porosity). The coefficient b has no significant relation with radish properties.

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

• Wind and Structures
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• v.25 no.1
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• pp.39-61
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• 2017

Buffeting induced resonance (BIR) of hangers on long-suspension bridges is briefly reviewed, including mechanism and experimental verification. Taken the Xihoumen suspension bridge as a numerical example, sensitivities of the BIR of hangers to wind properties are investigated, including types of wind spectrum, turbulence intensity, and spacial coherence of wind fluctuations. Numerical simulations indicate that the BIR of hangers occur to both cases of different wind spectra, showing that it is insensitive to types of wind spectrum. On the other hand, it is found that the turbulence intensity affects buffeting of main cables almost in a linear manner, and so it does to the BIR of the hangers; however, the resonance factors, namely the ratio of the response of the hanger to that of the main cable, are little affected by the turbulence intensity. The spacial coherence of the wind fluctuations, although plays an important role on the buffeting responses of the main structure, has no substantial effects on the BIR of the hangers. Finally, replacement of steel strand with CFRP material has been verified as a very effective countermeasure against the BIR of hangers.

• Journal of Korea Multimedia Society
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• v.7 no.12
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• pp.1639-1649
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• 2004

In this paper, a method for detection of forged signatures based on spectral analysis of directional gradient density function and a weighted fuzzy classifier is proposed. The well defined outline of an incoming signature image is extracted in a preprocessing stage which includes noise reduction, automatic thresholding, image restoration and erosion process. The directional gradient density function derived from extracted signature outline is highly related to the overall shape of signature image, and thus its frequency spectrum is used as a feature set. With this spectral feature set, having a property to be invariant in size, shift, and rotation, a weighted fuzzy classifier is evaluated for the verification of freehand and random forgeries. Experiments show that less than 5% averaged error rate can be achieved on a database of 500 signature samples.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.10-16
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• 2004

The detection and analysis of chatter behaviour in endmilling is very complex and difficult so it is necessary to detect and diagnose this chatter phenomenon clearly. This paper presents a new method for detecting the abnormal chatter in endmilling operation, based on the wavelet transform. Using AR spectrum the data that has chatter phenomenon was verified and the fundamental property of chatter and its characteristics in endmilling by using the wavelet transform is reviewed. This result obtained by wavelet transform proves the possibility and reliability of detecting the chatter in endmilling operation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.211-218
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• 2003

Most structures are expected to deform beyond the limit of linearly elastic behavior when subjected to strong ground motion. Seismic evaluation of structure requires an estimation of the structural performance in terms of displacement demand imposed by earthquakes on the structure. Nonlinear response history analysis(NRHA) is the most rigorous procedure to compute seismic performance among various inelastic analysis methods. But nonlinear analysis procedures necessitate more practical and reliable tools for predicting seismic behavior of structures. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) system. The purpose of this paper is to investigate the accuracy and reliability of this method from a point of view of various earthquakes and structure parameters.

• Proceedings of the KSPS conference
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• 1996.10a
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• pp.448-455
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• 1996

In this paper, we have proposed a VQ algorithm which uses a generating order to make quantize feature vector of speech signal. The proposed algorithm inspects what codeword follows a(ter present codeword and adds new index to established codebook, when mapping speech signal. We present a variable bit rate for new codebook, and propose an efficient compressed way of information. In this way, the number of computation and the number of codewords to be searched are reduced considerably. The performance of the proposed VQ algorithm is evaluated by spectrum distortion measure and bit rate. The obtained spectrum distortion is reduced about 0.22 [db], and the bit rate is saved over 0.21 bit/frame.