• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.453-458
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• 2002

The feasibility study on supporting a turbocharger rotor on air foil bearing is investigated. Based on finite difference method and Newton-Raphson method, the static equilibrium position of a turbocharger rotor is predicted. And using finite difference method and perturbation method, dynamic characteristics of air foil bearings are calculated. Rotordynamic analysis is performed by finite element method, with collaboration of calculated stiffness and damping of foil bearing. The effect of compliance and clearance of bump foil bearing on the oil-free turbocharger is investigated in terms of rotordynamics. And the critical speeds, eccentricity ratio, vibration amplitude, and stability are considered. It is demonstrated that foil bearings offer a rlausible replacement for oil-lubricated bearings in turbocharger.

• Phonetics and Speech Sciences
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• v.2 no.3
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• pp.3-10
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• 2010

The proposal that a sound change is occurring in Korean stops was evidenced in this study through identification experiments on Korean stops. Perceptual weight of acoustic correlates to Korean stop manner contrast [VOT (Voice Onset Time), H1-H2 (amplitude difference between the first and second harmonics), and F0 (Fundamental frequency)] was examined with re-synthesized /$t^ha$/, /ta/, and /$t^*a$/ syllables for younger and older Seoul speakers of Korean. For the identification of the aspirated and lenis stops, F0 cue weight relative to VOT was greater for the younger listeners than the older listeners. For H1-H2 cue weight, the two listener groups were more or less the same. These findings were parallel to the production differences found in the earlier work of the author. Combined with production differences, these perception differences between younger and older generations of Seoul speakers suggested that there are generational differences in the phonetic targets of Korean aspirated and lenis stops and such differences are realized in the perception of the stops.

• Journal of Chest Surgery
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• v.17 no.2
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• pp.280-285
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• 1984

Although it is suspected that the foreign body sensation on the pharyngoesophageal region is caused by motility disturbance of upper esophageal sphincter, its pathophysiology is not yet clear. Esophageal manometry has become an important diagnostic tool in the evaluation of esophageal motor disorders such as dysfunction of upper esophageal sphincter. Intraluminal esophageal pressures were measured by perfusion manometry in fifteen patients with foreign body sensation on the pharyngoesophageal region and in twenty six controls. In upper esophageal sphincter, mean value of resting pressure of the patients by rapid pull-through technique was 45,9\ulcorner 15.6mmHg and 80.9\ulcorner9.7mmHg in the controls. The difference between the two groups was statistically significant. The distance from nostril to sphincter, length of sphincter, and resting pressure by station pull-through technique were not significantly different. The amplitude of esophageal peristalsis in the patients was reduced significantly at the level of the upper, mid and lower esophagus. The wave duration of the patients was reduced significantly at the level the upper and mid esophagus. The speed showed no difference between two groups. Length and resting pressure of lower esophageal sphincter revealed almost same values in two groups.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.377-380
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• 2008

In this work, we measured the spatiotemporal surface charge distribution by the longitudinal electro-optic amplitude modulation method with BSO single crystal to investigate the decay and diffusion characteristics of surface charges in three types of MgO. The speed of decay and diffusion of two different kinds doped MgO is compared with those of pure MgO. The difference in the characteristics of the decay and diffusion between the electron and ion surface charges is investigated separately. We found that the rate of ion decay is the major factor that makes the difference of the temporal variation of wall voltage among different types doped MgO.

• Speech Sciences
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• v.7 no.2
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• pp.85-95
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• 2000

In this paper, the H1*-H2* measure is introduced and exact procedures for obtaining the H1*-H2* value are fully specified, The H1*-H2* measure (a corrected difference in dB between the first and second harmonics) has been devised to provide an acoustic correlate of the phonation mode of a vowel following a consonant. With this measure, we can investigate the phonation mode of a vowel that is free from the F1 amplitude perturbation effect caused by the preceding consonant, which is especially salient at the voicing onset position of the vowel. For identical research purposes, on the other hand, the H1-H2 measure (the observed difference in dB between the first and second harmonic) has been employed in many previous studies. This paper compares these two measures by illustrating experimental results of exploring post-release phonation modes of vowels following the different manner classes of stop consonants in Korean $\square$i.e., the tense, lenis, and aspirated stops.

• Journal of Korean Society of Steel Construction
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• v.8 no.3 s.28
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• pp.151-160
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• 1996

The fatigue test under the constant amplitude repeated loading is performed to investigate the fatigue behavior of the Torque Shear type high tension bolted joint which is able to manage the axial force uniformly. From the test results, it's known that the reduction of the axial force of T/S bolt followed by the elasped time is similar to that of the high tension bolts. The difference of relaxation is not occurred according to the position of bolts, the size of the introduced axial force but the effect of the variation of temperature is large. In the reduction of the axial force followed by the cumulation of the fatigue load, the outer bolt is larger than the inner bolt. This result depends on the difference in the distribution of the non-slip zone. The variation of the surface roughness affects the slip and the reduction of the anal force.

• Phonetics and Speech Sciences
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• v.2 no.4
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• pp.59-65
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• 2010

In this paper, we investigate acoustic characteristics of Korean /s/ when it is followed by both a high front and a round segment regardless of their order to one another. We show that Korean /s/ in this environment has characteristics of a labio-palatalized segment, being affected by both a high front and a round segment if they occur within the domain of a syllable. In the experiment, we show that Korean /s/ before a high front and a round segment shows a spectral shape different from that in other environments. Specifically, it is different from /s/ before a high front segment only, showing peaks around 2.5 kHz. Furthermore, it shows a rapid decrease of amplitude in 4-5 kHz, and sometimes another plateau of high peaks in 5-6 kHz. We also examined center of gravity frequency and band energy difference. Based on the results of this experiment, we argue that Korean /s/ is affected by the following segments within the domain of coarticulation, a syllable and that the degree of coarticulation is different from language to language.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.3
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• pp.323-330
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• 2011

Purpose : The purpose of this study was to examine the effects of using a pressure bio-feedback unit (PBFU) and a pelvic belt (PB) on the electromyographic (EMG) signal amplitude of the gluteus medius (Gmed) and the quadratus lumborum (QL) during hip abduction exercise when lying on the side. Methods : Twenty able-bodied volunteers (10 male, 10 female) were recruited for this study. The EMG signal amplitude was randomly measured during hip abduction with preferred hip abduction (PHA), with PBFU, and with PB. The surface EMG signal was recorded from the Gmed and the QL. Data were analyzed using a one-way repeated ANOVA. Results : Muscle activity of Gmed was significantly higher in PBFU and in PB than in PHA (p<.05). There were no significant difference between PBFU and PB(p>.05). Muscle activity of the QL was significantly lower in PB than in PHA(p<.05). The Gmed/QL muscle activity ratio was also significantly higher in PBFU and in PB than in PHA(p<.05), with no significant difference between PBFU and PB (p>.05). Conclusion : Based on these findings, using a PBFU and a PB is an effective method to disassociate QL use from Gmed use during hip abduction exercises when lying on the side.

• International Journal of Fluid Machinery and Systems
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• v.10 no.2
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• pp.138-145
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• 2017

The problem of non-uniform inflow exists in many practical engineering applications, such as the elbow suction pipe of waterjet pump and, the channel head of steam generator which is directly connect with reactor coolant pump. Generally, pumps are identical designs and are selected based on performance under uniform inflow with the straight pipe, but actually non-uniform suction flow is induced by upstream equipment. In this paper, CFD approach was employed to analyze unsteady hydrodynamic characteristics of reactor coolant pumps with different inflows. The Reynolds-averaged Naiver-Stokes equations with the $k-{\varepsilon}$ turbulence model were solved by the computational fluid dynamics software CFX to conduct the steady and unsteady numerical simulation. The numerical results of the straight pipe and channel head were validated with experimental data for the heads at different flow coefficients. In the nominal flow rate, the head of the pump with the channel head decreases by 1.19% when compared to the straight pipe. The complicated structure of channel head induces the inlet flow non-uniform. The non-uniformity of the inflow induces the difference of vorticity distribution at the outlet of the pump. The variation law of blade to blade velocity at different flow rate and the difference of blade to blade velocity with different inflow are researched. The effects of non-uniform inflow on radial forces are absolutely different from the uniform inflow. For the radial forces at the frequency $f_R$, the corresponding amplitude of channel head are higher than the straight pipe at $1.0{\Phi}_d$ and $1.2{\Phi}_d$ flow rates, and the corresponding amplitude of channel head are lower than the straight pipe at $0.8{\Phi}_d$ flow rates.

• Physical Therapy Korea
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• v.19 no.1
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• pp.46-55
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• 2012

The purpose of this study was to investigate the effect of the two different types of chairs on trapezius muscle activation during dictation tasks. Seventeen university students, each of whom were within ${\pm}1$ standard deviation of the mean Korean standard body size, voluntarily participated in this study. Surface electromyography was used to collect electrical signals from both the upper and lower trapezius muscles. Amplitude Probability Distribution Function (APDF) was performed to analyze the muscle activity. The findings of this study were 1) The backrest-point height of the auditorium chair and the height, length and width of the connected desk were shorter than what was suggested by the KS. Another difference was that the auditorium chair had a bigger angle of the backrest compared to the classroom chair. 2) Regarding within-subject effect the sole statistically significant difference was found between activation of the upper trapezius muscle. The upper trapezius muscle's %RVC in the APDF 10th-50th-90th percentile was statistically higher for participants sitting in the auditorium chair than for participants sitting in the classroom chair (p<.05). 3) There was an interaction effect between the 'two chair-types' and the 'two muscle-sides' in the APDF 10th-50th percentile (p<.05). 4) There was an interaction effect between the 'two chair-types' and the 'three gaze-direction' in the APDF 90th percentile (p<.05). The findings of this study indicated that maintaining a writing posture for a prolonged period of time in an auditorium chair significantly increased the left upper trapezius muscle activation compared to a classroom chair.