• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.70-74
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• 1998

This paper describes a method for recognition of two-dimensional position of an object by use of aerial ultra-sonic sensor and signal processing technique, which would become a help for blind person or self-mobile robot. First, we have developed a method for measuring the time difference between the transmitted and the received burst wave by use of one ultrasonic transmitter and three receivers. Secondly, a new method is developed for measuring the distance to an object by use of M-sequence correlation method. Thirdly, a measurement method to obtain the position of an object is described by use of phase-arrayed ultrasonic sensor, which gives us a wide-range position determination in a short time.

• Proceedings of the KSPS conference
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• 1996.10a
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• pp.390-398
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• 1996

Acoustic analysis study was performed on 20 normal subjects by speaking nonsense syllables composed of Korean bilabial stops(/p, $p^{*}$/, ph/) and their Preceding and/or following vowel /a/(that is, [pa, $p^{*}a$, pha, apa, $ap^{*}a$, apha]) with an ultraminiature pressure sensor in their mouths. Speech materials were phonated twice, once with a moderate voice, another time with a loud voice. The acoustic signal and intraoral pressure were recorded simultaneously on computer. By these procedures, we were to measure the intraoral pressure, closure duration and VOT of Korean bilabial stops, and to compare the values one another according to the intensity of phonation and the position of the target consonants. Intraoral pressure was measured by the peak intraoral pressure value of its wave; closure duration by the time interval between the onset of intraoral pressure build-up and the burst meaning the release of closure; Voice onset time(VOT) by the time interval between the burst and the onset of glottal vibration. Heavily aspirated bilabial stop consonant /ph/ showed the highest intraoral pressure value, unaspirated /p$^{*}$/, the second, slightly aspirated /p/, the lowest. The syllable initial bilabial stops showed higher intraoral pressure than word initial stops, and the value of loudly phonated consonants were higher than moderate consonants. The longest closure duration period was that of /$p^{*}$/ and the shortest, /p/, and the duration was longer in word initial position and in the moderate voice. In VOT, the order of the longest to shortest was /ph/, /p/, /$p^{*}$/, and the value was shorter when the consonant was in intervocalic position and when it was phonated with a loud voice.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.7 no.1
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• pp.50-55
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• 1996

Acoustic analysis study was performed on 20 normal subjects by speaking nonsense syllables composed of Korean bilabial stops$(/P, P^{\star}, P^{h}/)$ and their preceding and/or following vowel /a/ (that is, $[pa, p^{\star}a, p^{h}a, apa, ap^{\star}a, ap^{h}a]$) with an ultraminiature pressure, sensor. in their mouths. Speech materials were phonated twice, once with a moderate voice, another time with a loud voice. The acoustic signal and intraoral pressure were recorded simultaneously on computer. By these procedures, we were to measure the intraoral pressure, closure duration and VOT of Korean bilabial stops, and to compare the values one another according to the intensity of phonation and the position of the target consonants. Intraoral pressure was measured by the peak intraoral pressure value of Its wave closure duration by the time interval between the onset of intraoral pressure build-up and the burst meaning the release of closure ; Voice onset time(VOT) on by the time interval between the burst and the onset or glottal vibration. Heavily aspirated bilabial stop consonant /$p^h$/ showed the highest intraoral pressure value, unaspirated /$p^{\star}$/, the second, slightly aspirated /P/, the lowest. The syllable initial bilabial stops showed higher intraoral pressure than word initial stops, and the value of loudly phonated consonants were higher than moderate consonants. The longest closure duration period was that of /$p^{\star}$/ and the shortest, /P/, and the duration was longer in word initial position and in the moderate voice. In VOT, the order of the longest to shortest was $/{p^h}/, /p/, /{p^\star}/$, and the value was shorer when the consonant was in intervocalic position and when it was phonated with a loud voice.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.285-290
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• 2006

The evaluation of clamping condition has been regarded as the main issue in the safety-maintenance of the clamped high-tension bolts. For this, this paper proposes a method to estimate the axial stress by measuring the TOF (Time-Of-Flight) of ultrasonic wave, which is based on the acoustoelasticity or the dependency of sound speed on the stress. In this method, however, the variation of sound speed within the range of stress induced under the field condition is very small, and thus the accuracy of the TOF measurement is important. We adopted the phase detection method using tone-burst ultrasonic wave to measure the precise TOF. In order to verify the usefulness of the proposed method experiments are carried out and the results were compared with the stress measured by the strain gage. The results show good agreement with each other, and from these we can conclude that the proposed method is highly useful fnr the evaluation of clamping condition in the clamped high-tension bolts.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.214-214
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• 2003

During a model test of Hutton TLP, a "ringing" response was first observed about 20 years ago. This phenomenon is a resonant build up over the time of wave period and this burst-like motion can cause the extreme load on the TLP tether. It is often detected in the large and steep irregular waves but the generation mechanism leading to the "ringing" is not yet well understood. According to the research since then, the higher order harmonic components may account for the "ringing" on the floating offshore structures. The main purpose of the present research is, thus, to measure the higher harmonic forces exerted on a vertical truncated circular column and to compare them with available data. A vertical truncated cylinder with a diameter of 3.5inch and a draft of 10.5inch is used as a test structure, which is a scaled model of ISSC TLP column. The cylinder is installed at a distance of 45ft from the wave maker in order to avoid parasitic waves created in the wave flap. Attached to the upper part of the cylinder are two force gages to measure the horizontal (surge) and vertical (heave) forces on the cylinder. The incoming waves are Stokes waves with a slope ranging from 0.06 to 0.24. The forces and waves are measured for 60 seconds with a sampling rate of 50 Hz. Among the recorded data, the first 10 waves are excluded because of transient behavior of the waves and the next The horizontal and vertical forces are analyzed up to 5th order harmonics. The horizontal forces are then compared to the values from the theoretical model called "FNV model". In addition, force transfer functions are also investigated. Major findings in this research are below. 1) The first order forces measured are slightly larger than the theoretical values of "FNV model" 2) The "FNV model" considerably overpredicts the second order forces. 3) The larger the amplitude and more extreme the wave slope, the smaller the predictions are compared to the experimental. 4) The higher harmonic forces are significantly smaller than the first harmonic force for all wave parameters. 5) The normalized forces vs. waves slopes are almost constant in the lower harmonics but vary a lot in the higher harmonics. 6) The trend of forces is more nonlinear in the horizontal forces than in the vertical forces as the wave slope increases. 7) The part of the results above is also observed by other researchers and confirmed again through the present work.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.3
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• pp.294-299
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• 2017

The aim of this study was to detect the status of epilepticus and seizure based on the initial patterns observed in the first 30 minutes of continuous electroencephalogram (cEEG) monitoring. An cEEG was recorded digitally using electrodes applied according to the International 10~20 System. The EEG data were reviewed from January 2014 to December 2015. The baselines of the EEG patterns were characterized by lateralized periodic discharges, generalized periodic discharges, burst suppression, focal epileptiform, asymmetric background, generalized slowing, and generalized periodic discharges with a triphagic wave. The etiology was classified into five categories. The subjects of this study were 128 patients (age: $56.9{\pm}17.5years$, male:female, 74:54). The mean cEEG monitoring duration was $5.5{\pm}5.1$ (min:max, 1:33) days. The EEG pattern categories included lateralized periodic discharges (N=7), generalized periodic discharges (N=10), burst suppression (N=6), focal epileptiform (N=19), asymmetric background (N=24), generalized slowing (N=51), and generalized periodic discharges with a triphagic wave (N=11). The etiological classifications of the patients with status epilepticus were remote symptomatic (N=4), remote symptomatic with acute precipitant (N=9), acute symptomatic (N=6), progressive encephalopathy (N=2), and febrile seizure (N=1). cEEG monitoring was found to be useful for the diagnosis of non-convulsive epileptic seizures or status epilepticus. The seizure was confirmed by the EEG pattern.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.6
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• pp.51-60
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• 2004

In this paper, we optimized the PDT laser system to improve the therapy effects of malignancies. In order to optimize, the variation of laser output and specific wavelength shift have to reduced. To improve the PDT therapy clinician require the diverse radiation mode which irradiate the tumor surface. Continuous wave mode that general application may causes tissue thermal damage not only to tumor tissue, but also to normal tissue. In this paper, therefore, we suggested new technique for radiation method to improved PDT effects and prevented to the thermal effects for the tissue. In the experimental we verified the stability of wavelength, laser output stability and proved the reduced thermal effects to the tissue using the pulse & burst radiation modes in vitro.

• Smart Structures and Systems
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• v.26 no.6
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• pp.735-751
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• 2020

Identification of structure parameters is crucial in Structural Health Monitoring (SHM) context for activities such as model validation, damage assessment and signal processing of structure response. In this paper, guided waves generated by piezoelectric transducers are used for in-situ and non-destructive structural parameter estimation based on Bayesian approach. As Bayesian approach needs iterative process, which is computationally expensive, this paper proposes a method in which an analytical model is selected and developed in order to decrease computational time and complexity of modeling. An experimental set-up is implemented to estimate three target elastic and geometrical parameters: Young's modulus, Poisson ratio and thickness of aluminum and steel plates. Experimental and simulated data are combined in a Bayesian framework for parameter identification. A significant accuracy is achieved regarding estimation of target parameters with maximum error of 8, 11 and 17 percent respectively. Moreover, the limitation of analytical model concerning boundary reflections is addressed and managed experimentally. Pulse excitation is selected as it can excite the structure in a wide frequency range contrary to conventional tone burst excitation. The results show that the proposed non-destructive method can be used in service for estimation of material and geometrical properties of structure in industrial applications.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.32-40
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• 1994

In this study by using EMAT(electro magnetic acoustic transducer)the artificial slit is installed on 12B-SUS pipe test piece. By making 4 cycle SH-burst (EMA) incidence to 45 .deg. angle, the signal data of pulse, received from EMAT are translated into digital-signal-processing- method SSP(Split Spectrum Processing) and Deconvolution method. The main conclusions obtained are as follows; (1) the signal data received from EMAT are translated with digital signal proc- essing of SSP-method and Deconvolution-method and this method shows exellent results more than Ultrasonic testing method does; (2) noise can well be removed by SSP with signal data, and resolution and S/N ratio are advanced; (3) when used with Ultrasonic wave general stainless steel has proporties of multiscattering and reflection phenomena, but resolution is progressed by using Deconvolution method;and (4) as addition-averaging-processing mumber is increasing, the resolution and S/N ratio are improved and the satisfactory signal is obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.78-89
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• 1999

In this paper, to improve bandwidth amplitude fluctuation for the broadband signal in indoor propagation environment, we measured and analyzed broadband signal using a vertically polarized, horizontally polarized and circularly polarized antenna, conducting by frequency sweeping method in NLOS (Non-Line-of-Sight) environment. And, to investigate the optimum condition for the improvement of broadband propagation characteristics we also examined the effects of both human motions and transmission antenna height in the NLOS environment. As a result, in the case of NLOS environment, it was found that the amplitude deviation characteristics in frequency bandwidth can be improved by polarization diversity reception. Especially, we found that it is the best effective one to make polarization diversity reception branches, which install the circularly polarized antenna at transmitting end and install the polarized diversity branches received vertical or/and horizontal polarized wave at receiving end. The affection of a human motions is not so much in LOS and NLOS environment, but it can lead to the cause of burst error in indoor digital radio communications as the fade of signal strength become more deeper. And also, when raise the transmitting antenna up to the ceiling, the LOS and NLOS environment could be coexisted. In this case, it can be also inferred that frequency bandwidth amplitude deviation must be fundamentally improved by using polarization diversity reception technique to make the possibility of high transmission rate.