• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.105-111
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• 1999

When the preparation method of iron silicide films possess the annealing process, the interfacial state of the films is not fine. The good quality films were obtained as the plasma was used without annealing processing. Since the injected precursors were various active species in the plasma state, the organic compound was contained in the prepared films. We confirmed the formation of Fe-Si bonds as well as the organic compound by Fe and Si vibration mode in Raman scattering spectrum at $250cm^{-1}$ and Ft-IR. Because of epitaxy growth being progressed by the high energy of plasma at the low temperature of substrate, iron silicide was epitaxially grown to ${\beta}$-phase that had lattice structure such as [220]/[202] and [115]. Band gap of the prepared films had value of 1.182~1.174 eV and optical gap energy was shown value of 3.4~3.7 eV. The Urbach tail and the sub-band-gap absorptions were appeared by organic compound in films. We knew that the prepared films by plasma were obtained a good quality films because of being grown single crystal.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.15 no.2
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• pp.133-140
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• 2004

Background and Objectives : Vowels and resonant including nasals and liquid are produced with vocal folds vibration have been used for voice therapy of hyperadduction patients. This study was conducted to investigate phonatory characteristics of vowels and resonant consonants through the EGG measures from Lx. Speech studio (Laryngograph Ltd, UK). Materials and Method : 7 male adults produced sustained vowel /a/, /i/, /u/, nasals /m/, /n/, /${\eta}$/and liquid /I/ and read the sentences (1nasals-liquid sentence, 1 non-nasals-liquid sentence) and tongue-tip trill and humming. Fx(Hz), Ox(%) were obtained of vowels, nasals, liquid and each of the posterior vowel /a/ of /ma/, /na/, /la/, /ha/ with same F0(around F#165Hz) and amplitude (75${\pm}$5db). And also DFx(Hz), DQx(%), CFx(%) and CAx(%) were obtained from reading two kinds of sentences. Results : Qx(%) was the highest in /u/ of vowels, and nasal/n/ of the resonant consonants and nasals-liquid sentence was higher Qx than non-nasals-liquid sentence but significant differences were not found. Qx(%) of the posterior vowel /a/ of nasal consonants/n/ was higher than in the isolated vowel/a/ and other posterior vowel of resonant consonants and fricatives /h/. Regularity or periodicity and higher Qx were observed in the nasals-liquid sentence than non-nasals-liquid sentence in graphs of QxFx & CFx produced by Quantiative analysis. In the nasalance score, /u/vowel was significant higher among the vowels and /I/ liquid was significant lower among the resonant consonants and nasals-liquid sentence is higher than non-nasals -liquid sentence. CQ(%) was not significantly correlated with nasalance(%). Conclusion : These findings might signify resonant phonation was not correlated with nasalance.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.436-441
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• 2009

A fiber optic sensor is prospective to be applied to structural health monitoring. Especially, a fiber Bragg grating(FBG) sensor is one of the most popular sensors for the structural health monitoring. The FBG sensor has several demodulation systems for tracking the shift of the Bragg wavelength. The dynamic bandwidth is dependent on the demodulation system. In this paper, the sensing mechanism is that the slope of the optical spectrum of FBG could be used as its sensitivity when the tunable laser shot the monochromatic laser wavelength at the highest slope point. In this technique, the high sensitivity is guaranteed even though the sensing range is limited. In an example of the application, the composite plate embedding a FBG sensor was manufactured by using an autoclave method and the above sensing mechanism was applied to the composite plate. Firstly, the natural frequencies of the plate were successfully measured by the FBG sensor during the impact hammer test. Secondly, a high-power speaker was used to force the plate to be vibrated at the specific frequency that was one of the natural frequencies. During the shaking, the FBG sensor measures the dynamic characteristics and ESPI was also used to measure the mode shape. From the two dynamic tests, the availability of the FBG sensor system and the ESPI was proven as a technique for measuring the dynamic characteristics of composite structure.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.283-287
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• 2008

The imogolite synthesis wore performed by using tetraethoxysilane (TEOS) and aluminium-sec-butoxide (ASB) at < $100^{\circ}C$. A mixure of TEOS and ASB in a molar ratio of 1:2 was prepared under vigorous stirring and the experiments were performed under the hydrothemal refluxing condition. When the concentration of TEOS and ASB in solution was 0.5 M, a well-crystallized imogolite was synthesized, and the reflections wore shown at d = 22.4, $9.5\;\AA$ etc., after XRD analysis. DTA analysis shows 2 exothemal peaks at 68 and $249^{\circ}C$, suggesting the dehydration and the dehyroxylation reaction, respectively. The result of TG indicates 41% weight loss. And the weak and unsymmetrical peaks by the Si-O-Al stretching vibrations at 953 and $993cm^{-1}$ and by O-Si-O bending vibration at $562cm^{-1}$ were observed after IR analysis. The synthetic imogolite was fibrous and shows a spiders web like network structure.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.101-112
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• 2002

In this study, a new methodology fur the assessment of liquefaction potential is proposed and characteristics of the proposed methodology are verified. The experimental parameter of this methodology, that is, the plastic shear strain trajectory, is compared with the dissipated energy. It is shown that this parameter can express the liquefaction behavior which is generated by excess pore water pressure. This methodology takes advantage of the shear strain time history determined from the site response analysis based on the real time history of earthquake. In this site response analysis, shock type and vibration type records of similar predominant frequency are inputted. The liquefaction safely factors based on the proposed methodology and Korean detailed assessment related to the classical method are calculated from the results of the site response analysis and laboratory dynamic tests. Through this study, it is found that the proposed methodology can not only simulate the liquefaction behavior of saturated soils hut also express the seismic characteristics reasonably : leading type, predominant frequency, maximum acceleration, duration time.

• 대한공업교육학회지
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• v.34 no.2
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• pp.331-345
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• 2009

In this research Sagnac interferometer three different types of mandrel are suggested and this fiber optic sensor is using in monitoring of electric transformer. Vibration characteristics of those mandrels were analyzed and finally more sensitivity mandrel are suggested. Three different mandrels using in fiber optic sensor are hollow cylinder with outer bump, pure hollow cylinder, hollow cylinder with inner bump. Natural frequencies and mode shapes are investigated using finite element method. Mode shape are considered at the frequency range from 2 kHz to 20 kHz. Fundamental dimensions of the hollow cylinder type's mandrel are 30 mm in outer diameter, 50 mm in length, 1 mm in cylinder thickness, $2mm{\times}2mm$ in bump size. Based on the finite element results, when the outer acoustic frequency is near 11 kHz outer bump type and hollow cylinder can get higher sensitivity. Near 17 kHz outer bump and inner bump mandrel can get higher sensitivity. Near 20 kHz hollow cylinder and inner bump mandrel is useful. This results can be applied to design of fiber optic sensor using in monitoring the electrical transformer. Several MHz of outer acoustic frequency can be easily detected using more sensitive mandrel in pursuing expand this technique.

• Science of Emotion and Sensibility
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• v.14 no.4
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• pp.545-554
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• 2011

In this study, the parameters of Polysomnography (PSG) test, such as total sleep time, snoring time, had been analyzed to evaluate the effectiveness of a developed anti-snore pillow. The developed anti-snore pillow is made up of two polyvinylidene fluoride (PVDF) vibration sensors, pumps, valves, and air bladders. The two PVDF sensors inside the pillow can acquire the sound signals and the algorithm was perfectly designed to extract snoring by removing unwanted noise accurately and automatically. Once the pillow recognizes snore, a pump inside the hardware activates, and a bladder under the neck area inside the pillow will be inflated. The PSG test was used and two volunteers were participated for the study. The parameters of the PSG results were analyzed to evaluate the effectiveness of the anti-snore pillow. The total sleep time of each volunteer was similar on each phase of test, but the snoring time and the longest snoring episode were significantly decreased with the use of anti-snore pillow. The overall results showed excellent possibilities for reducing snoring for the person who snores during sleep by using the anti-snore pillow. The effectiveness of the anti-snore pillow can be evaluated by the PSG test. Moreover, the relationship between each parameter of PSG test and the quality of sleep will be used for further researches.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.319-332
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• 2015

The pressure wave formed by the piston effects of the train proceeds within the tunnel when a train enters the tunnel with a high speed. Depending on the condition of tunnel exit, the compression waves reflect at a open end, change to the expansion waves, transfer to tunnel entrance back. Due to interference in the pressure waves and running train, passengers experience severe pressure fluctuations. And these pressure waves result in energy loss, noise, vibration, as well as in the passengers' ears. In this study, we performed comparison between numerical analysis and field experiments about the characteristics of the pressure waves transport in tunnel that appears when the train enter a tunnel and the variation of pressure penetrating into the train staterooms according to blockage ratio of train. In addition, a comparative study was carried out with the ThermoTun program to examine the applicability of the compressible 1-D model(based on the Method of Characteristics). Furthermore examination for the adequacy of the governing equations analysis based on compressible 1-D numerical model by Baron was examined.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.249-260
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• 2014

When a train enters the tunnel at high speed, the pressure wave occurs. When this pressure wave reaches at the exit of tunnel, some are either emitted to the outside or reflected in tunnel by the form of expansion wave. The wave emitted to the outside forms the impulsive pressure wave. This wave is called 'Micro Pressure Wave'. The micro pressure wave generates noise and vibration around a exit portal of tunnel. When it becomes worse, it causes anxiety for residents and damage to windows. Thus, it requires a counterplan and prediction about the micro pressure wave for high speed railway construction. In this paper, the effects of train head nose and tunnel portal shape were investigated by model test, measurement for the micro pressure wave at the operating tunnel as well as numerical analysis for the gradient of pressure wave in the tunnel. As results, a method for predicting the intensity of the micro pressure wave is suggested and then the intensity of the micro pressure wave is analyzed by the tunnel length and the cross-sectional area.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.213-224
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• 2014

Recently, tunnelling with TBM is getting popular for the construction of cable tunnel in urban area. Mechanized tunnelling method using shield TBM has various advantages such as minimization of ground settlement and prevention of vibration induced by blasting that should be accompanied by conventional tunnelling. In Korea, earth pressure balance (EPB) type shield TBM has been mainly used. Despite the popularity of EPB shield TBM for cable tunnel construction, study on the mechanical behavior of cable tunnel driven by shield TBM is insufficient. Especially, the effect of backfill grout injection on the behavior of cable tunnel driven by shield TBM is investigated in this study. Tunnelling with shield TBM is simulated using 3D FEM. The distance of backfill grout injection from the end of shield skin varies. Sectional forces such as axial force, shear force and bending moment are monitored. Vertical displacement at the ground surface is measured. Futhermore, the relation between volume loss and the distance of backfill grout injection from the end of skin plate is derived. Based on the stability analysis with the results obtained from the numerical analysis, the most appropriate injection distance can be obtained.