• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.257-265
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• 2017

In this work, the effect of field-degradation of automotive polymeric interior parts on the squeak characteristics was studied for a number of used vehicles with various mileages and years of service. The purpose of this study was to characterize the squeak noise related with long-term degradation in service life. The characteristics of field-degraded polymeric samples are analyzed using Fourier transform infrared(FT-IR) spectroscopy and scanning electron microscopy(SEM). Complicated carbonyl spectra from FT-IR were deconvoluted into various carbonyls to trace field-degradation phenomenon. In addition, various mechanical tests, i.e. tensile test, hardness test as well as coefficient of friction test, were performed to analyze the variation in mechanical properties due to field-degradation. Squeak noise was measured and analyzed by frequency analysis. It was shown that the changes in the chemical structures of polymer due to field-degradation influenced the variation in mechanical properties, and squeak noise may worsen by increasing the squeak noise level in the wide frequency range. The results indicated that customer complaints regarding the squeak noise coming from used vehicles might be one of the important reliability issues because the increase in sound pressure level especially in the high frequency range could annoy drivers and passengers.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.70-74
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• 2007

This paper describes the development of a nano-positioning system for nanoscale science and engineering. Conventional positioning systems, which can be expensive and complicated, require the use of laser interferometers or capacitive transducers to measure nanoscale displacements of the stage. In this study, a new self-displacement sensing (SDS) nano-stage was developed using mechanical magnification of its displacement signal. The SDS nano-stage measured the displacement of its movement using a position-sensitive photodiode (PSPD), a laser source, and a hinge-connected rotating mirror plate. A beam from a laser diode was focused onto the middle of the plate with the rotating mirror. The position variation of the reflected beam from the mirror rotation was then monitored by the PSPD. Finally, the PSPD measured the amplified displacement as opposed to the actual movement of the stage via an optical lever mechanism, providing the ability to more precisely control the nanoscale stage. The displacement amplification process was modeled by structural analysis. The simulation results of the amplification ratio showed that the distance variation between the PSPD and the mirror plate as well as the length L of the mirror plate could be used as the basic design parameters for a SDS nano-stage. The PSPD was originally designed for a total travel range of 30 to 60 mm, and the SDS nano-stage amplified that range by a factor of 15 to 25. Based on these results, a SDS nano-stage was fabricated using principle of displacement amplification.

• Fisheries and Aquatic Sciences
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• v.3 no.1
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• pp.26-32
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• 2000

Monospecific red tide by a toxic dinoflagellate belonging to the genus Alexandrium occurred at Chindong Bay in the southern coast of Korea and continued from April 6th to 15th in 1997. The ratio of its cell number to total phytoplankton cell number was much higher than $95\%$. This organism was identified as Alexandrium tamarense, although slight morphological differences were found comparing to the original and successive descriptions of the species. We found neither anterior nor posterior attachment pores in these cells of the bloom population. The occurrence of red tide caused by A. tamarense was first reported in Korea. Its plate formula is Po, Pc, 4', 6"c, 8s, 5"' and 2"". Thecal plates are thin with pore-like ornamentation. In those plates, the anterior part of the first apical plate (1') is narrower and its posterior end has sometimes a block-like accessory, but this variation was considered within the range of the morphological variability of this taxon. The cell density during the red tide exhibited a wide range of variation by the depth of water column, ranging from $2\times10^6$ cells$l^{-1}$ to $5\times10^6$ cells·$l^{-1}$. Water temperature varied from 11.8 to $12.3^{\circ}C$. Toxicity of A. tamarense during red tide was measured as $8.8\times10^5$. $MU\;\cdot\;cell^{-1}$ by mouse bioassay.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.4
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• pp.396-403
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• 2017

We measured the target strength according to the swimming tilt angle and size change for Pacific herring at the frequency of 70 kHz as the basic database in order to estimate its abundance as well as density in the survey area using the hydroacoustical method. The number of the sample used in this study was 14 individuals, and its size distribution by fork length ranged between 20.3 and 29.8 cm and wet weight was measured between 187.6 and 269.9 g. The variation of TS according to the swimming angle ($-30{\sim}30^{\circ}$) was measured between 10.3 and 18.8 dB in frequency range, the highest value was measured at head-down of Pacific herring in the tilt angle range between 5 and 9 deg. of its swimbladder. The relationship between TS-FL of herring was the same as $TS=20log_{10}$ (FL) - 66.79 when its swimming tilt angle in the daytime ($3.8{\pm}6.0^{\circ}$) and nighttime ($-3.2{\pm}13.6^{\circ}$), respectively.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.1
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• pp.39-45
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• 2005

As a basic research for the development of a non-invasive blood glucose sensor using millimeter waves, we have presented a method for measuring the dielectric properties of high loss dielectrics, based on the reflection method, and investigated the variation of the dielectric properties of glucose-water and glucose -0.9% NaCl solutions in the 10～90 GHz range. In the proposed method, a minimal reflection condition is formed by placing a specially-chosen low-loss plane-parallel plate in front of a high-loss medium under test at a given frequency range. Using the minimal power reflection coefficient and the corresponding frequency at this condition, tile dielectric properties of the medium can be determined. The measured results on pure water have shown the adequacy of the proposed method. The measured results on glucose-water and glucose -0.9% NaCl solutions in the 10～90 GHz range showed that the variations of the dielectric properties of glucose solutions according to the change of their glucose concentration were maximum in the 30～45 GHz range. From these facts we concluded that the variation of about 3 mole/L in the glucose solutions must be distinguished With the measurement accuracies of ±0.1 dB and ±0.01 GHz.

• Journal of Korean Society on Water Environment
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• v.29 no.2
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• pp.155-164
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• 2013

To confirm the relationship between climate change and Stephanodiscus in Mulgeum station of Nakdong River, Korea, this study was conducted. The temperature in crease by climate change was observed in the study site, where the temperature was gradually increased in most seasons, except for summer season. The mass proliferation of Stephanodiscus constantly appeared in every year, especially between November and March, and when Stephanodiscus abundance was above 90% in phytoplankton biomass. Among this period, phytoplankton biomass was high related with water temperature ($r^2$=0.249, P<0.01) than nutrient factors such as nitrogen and phosphorus in the study site. Finally, temperature by climate change can be regarded as the affecting factor for chl. a variation, because temperature was strongly related with water temperature ($r^2$=0.748, P<0.01). From 1997 to 2010, the annual maximum phytoplankton biomass was recorded in the range of temperature from $4.8^{\circ}C$ to $8.4^{\circ}C$, and the range was regarded as the temperature condition for the optimal growth of Stephanodiscus in the study site. On the optimal growth temperature, the trend of monthly average temperature corresponded to the trend of chl. a variation from November to March. In future, the increase of temperature by climate change can prolong Stephanodiscus blooming period in winter and spring seasons.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.3
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• pp.171-177
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• 2007

In this paper, we have designed and implemented an optical signal processor in order to use in a fiber-optic current CT for electric equipments where its properties were discussed. The fabricated optical signal processor is used to reduce a measurement current error that induced by the effects of intensity variation in the optical output signal due to losses coming from optical components or polarization variation in a PFOCS. Also, the optical signal processor was fabricated in compact/lightweight with unification of opto-electronic transducer part, analog signal process part, and real-time measurement part consisted of a level shift and ${\mu}-processor$. The experiment of optical signal processor has been performed in the range of $0{\sim}7,500A$ using the PFOCS made all fiber-optic components. As a result of experiment, the linearity error of measurement current is less than 1.7% and its average error is less than 0.3% in the range of $1,000A{\sim}7,000A$.

• Phonetics and Speech Sciences
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• v.10 no.4
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• pp.155-161
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• 2018

The purpose of this study was to evaluate the efficacy of a multiple voice therapy technique ($SKMVTT^{(R)}$) using laughter for the treatment of various benign vocal fold lesions. To achieve this, 23 female patients diagnosed with vocal nodules, vocal polyp, and muscle tension dysphonia through videostroboscopy were enrolled in vocal hygiene and $SKMVTT^{(R)}$. All of the patients were treated once a week for 4 to 12 sessions. The GRBAS scale was used to confirm the changes in voice quality before and after the treatment. Acoustic analysis was performed to evaluate jitter, shimmer, NHR, fundamental frequency variation, amplitude variation, PFR, and dB range. Videostroboscopy was performed to confirm the changes in the laryngeal features before and after the treatment. After the $SKMVTT^{(R)}$, the results of the perceptual evaluation demonstrated that the G, R, and B scales significantly improved. An acoustic evaluation also demonstrated that jitter, shimmer, NHR, vAm, vFo, PFR, and dB range also significantly improved after the $SKMVTT^{(R)}$. In comparison to the videostroboscopic findings, the size of the vocal nodules and vocal polyp decreased or disappeared after the treatment. In addition, the size of the cuneiform tubercles decreased, the length of the aryepiglottic folds became longer, and the laryngeal findings of the supraglottic compressions improved after the $SKMVTT^{(R)}$. These results suggest that the $SKMVTT^{(R)}$ is effective in improving the vocal quality of patients with benign vocal fold lesions. In conclusion, it seems that laughter and inspiratory phonation suppressed abnormal laryngeal elevation and lowered laryngeal height, which seems to have the effect of improving hyperfunctional phonation.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.2
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• pp.91-97
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• 2006

The intraocular pressure for Korean youth were measured by using tonometer (AT555-Reichert). The relative frequency distributions of intraocular pressures have been studied for samples of 1,027 persons(475 males, 552 females). The most commonly recorded IOP for both men and women was around 14.5mmHg and 17.5mmHg, respectively. They were in the range of 7 to 23mmHg(males) and 7 to 22mmHg(females). The median pressure(cumulative frequency=0.5%) is 13.0~16.5mmHg for males and 16.5~18.5mmHg for females, so the values for females are slightly higher than males. The mean pressure is 15.2mmHg for males and 15.8mmHg for females, respectively. The 98% of population was in the range of the normal IOP. There are long-term diurnal variation in mean intraocular pressure and the IOP was decreased as a function of time from morning to night. The measured IOP was affected by several factors: exercise made to decrease the IOP and tight collars, dark places and posture of decubitus position got to elevate the IOP.

• Geophysics and Geophysical Exploration
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• v.13 no.2
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• pp.144-152
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• 2010

To study the thickness variation of volcanic rocks of Jeju Island, microtremor data were recorded at eight and four sites using short-period and broadband seismometers, respectively, for 30 ~ 60 minutes with a 100 Hz sampling rate. During the daytime, these records show increased cultural noise at frequencies above 1.8 Hz. Natural noise occurs in the frequency range of 0.4 to 0.8 Hz in both daytime and nighttime data. Predominant frequencies determined by the H/V spectral-ratio method are in the range of 0.2 ~ 0.7 Hz. These frequencies decrease gradually as the central part of the Mt. Halla is approached. This may indicate that the basement is warped downward beneath the center of the island, which is consistent with previous gravimetric and magnetic models. Assuming an average shear-wave velocity of 1,800 m/s for the overburden basalts, the depths to basement are estimated to be between 640 and 2,140 m.