• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.587-592
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• 2021

Change in the cortical thickness of long bones occurring with aging and osteoporosis is known to be a risk factor for fracture. The present study aims to investigate the dependencies of phase velocities of ultrasonic guided waves on the cortical thickness in 7 soft tissue-bone mimicking phantoms consisting of acrylic plates covered by a 2 mm-thick silicone rubber layer by using the axial transmission technique with a pair of transducers with a center frequency of 200 kHz and a diameter of 12.7 mm. Two distinct propagating waves with different velocities, the First Arriving Signal (FAS) and the Slow Guided Waved (SGW), were consistently observed for all the soft tissue-bone mimicking phantoms. The FAS velocity decreased slightly with increasing thickness, whereas the SGW velocity increased strongly with increasing thickness. The FAS and the SGW velocities were found to be closely consistent with the S0 and the A0 Lamb mode velocities for a free acrylic plate, respectively, suggesting that the presence of the soft tissue mimicking material (2 mm-thick silicone rubber layer) covering the acrylic plates does not influence significantly the velocity measurements.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.25-31
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• 2023

In order to estimate the radial speed of an underwater object so-called target with active sonar, Continuous Wave (CW) pulse is generally used, but if a target is slow and at near distance, it is not easy to estimate the radial velocity of the target due to acoustic reverberation in the ocean. In 2017, Wang et al. utilized broadband signal of two Hyperbolic Frequency Modulation (HFM) pulses, which is known as a doppler-invariant pulse, with equal frequency band and in opposite sweep directions to overcome this problem and successfully estimate the radial speed of slow-moving nearby target. They demonstrated the estimation of the radial velocity with computer simulation using the parameters of two HFM starting time differences and receiving times. However, for it uses two HFM pulses with equal frequency, cross-correlation between the two pulses negatively affect the detection performance. To mitigate this cross-correlation effect, we suggest using two different band HFM with the opposite sweep directions. In this paper, a method of radial velocity estimation is derived and simulated using two HFM pulses with the pulse length of 1 second and bandwidth of 400 Hz. Applying the suggested method, the radial velocity was estimated with approximately 6 % of relative error in the simulation.

• Dementia and Neurocognitive Disorders
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• v.23 no.1
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• pp.22-29
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• 2024

Background and Purpose: Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive decline in cognition and performance of daily activities. Recent studies have attempted to establish the relationship between AD and sleep. It is believed that patients with AD pathology show altered sleep characteristics years before clinical symptoms appear. This study evaluated the differences in sleep characteristics between cognitively asymptomatic patients with and without some amyloid burden. Methods: Sleep characteristics of 76 subjects aged 60 years or older who were diagnosed with subjective cognitive decline (SCD) but not mild cognitive impairment (MCI) or AD were measured using Fitbit^® Alta HR, a wristwatch-shaped wearable device. Amyloid deposition was evaluated using brain amyloid plaque load (BAPL) and global standardized uptake value ratio (SUVR) from fluorine-18 florbetaben positron emission tomography. Each component of measured sleep characteristics was analyzed for statistically significant differences between the amyloid-positive group and the amyloid-negative group. Results: Of the 76 subjects included in this study, 49 (64.5%) were female. The average age of the subjects was 70.72±6.09 years when the study started. 15 subjects were classified as amyloid-positive based on BAPL. The average global SUVR was 1.598±0.263 in the amyloid-positive group and 1.187±0.100 in the amyloid-negative group. Time spent in slow-wave sleep (SWS) was significantly lower in the amyloid-positive group (39.4±13.1 minutes) than in the amyloid-negative group (49.5±13.1 minutes) (p=0.009). Conclusions: This study showed that SWS is different between the elderly SCD population with and without amyloid positivity. How SWS affects AD pathology requires further research.

• The Korean Journal of Physiology
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• v.28 no.1
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• pp.37-50
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• 1994

Synthetic potassium channel openers (KCOs) are agents capable of opening K-channels in excitable cells. These agents are known to have their maximal potency in the smooth muscle tissue, especially in the vascular smooth muscle. Much attention has been focused on the type of K-channel that is responsible for mediating the effects of KCOs. As the KCO-induced changes are antagonized by glibenclamide, an $K_{ATP}$ (ATP-sensitive K-channel) blocker in the pancreatic ${\beta}-cell,\;K_{ATP}$ was suggested to be the channel responsible. However, there also are many results in favor of other types of K-channel $$(maxi-K,\;small\;conductance\;K_{Ca,}\; SK_{ATP}) mediating the effects of KCOs. Effects of lemakalim, (-)enantiomer of cromakalim (BRL 34915), on the spontaneous contractions and slow waves, were investigated in the antral circular muscle of the guinea-pig stomach. Membrane currents and the effects on membrane currents and single channel activities were also measured in single smooth muscle cells and excised membrane patches by using the patch clamp method. Lemakalim induced hyperpolarization and inhibited spontaneous contractions in a dose-dependent manner. These effects were blocked by glibenclamide and low concentrations of tetraethyl ammonium (< mM). Glibenclamide blocked the effect of lemakalim on the membrane potential and slow waves. The mechanoinhibitory effect of lemakalim was blocked by pretreatment with glibenclamide. In a whole ceIl patch clamp condition, lemakalim largely increased outward K currents. These outward K currents were blocked by TEA, glibenclamide and a high concentration of intracelIular EGTA (10 mM). Volatage-gated Ca currents were not affected by lemakalim. In inside-out patch clamp experiments, lemakalim increased the opening frequency of the large conductance $Ca^{2+}-activated$ K channels $(BK_{Ca},\;Maxi-K).$ From these results, it is suggested that lemakalim induces hyperpolarization by opening K-channels which are sensitive to internal Ca and such a hyperpolarization leads to the inhibition of the spontaneous contraction.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.6
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• pp.1378-1382
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• 2008

This study is aim to evaluate pulse diagnosis as indicators for classification of the pattern identifications in stroke patients. To get the clinical information, we recruited the onset 1 month stroke patients through the multicenter network which consists of 13 oriental hospitals. The clinical informations about three pairs of pulse wave form and levels of their significancy based on the case report form (CRF) were collected and their distribution in each pattern identification were analyzed. The results are as follows Fire-Heat group shows high portions of floating pulse, rapid pulse and solid pulse. Qi Defficiency group has a greater portion of deep pulse, slow pulse, deficient pulse. The well-defined character of Phlegm-Retained Fluid, Yin Defficiency, Static Blood groups cannot be explained by pulse wave form. These results show a rough relationship between the pulse diagnosis and pattern identifications of stroke therefore, further studies are required to determine the pulse diagnosis as significant indicators of stroke pattern identification.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.98-98
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• 2014

Due to the simple vertical structure of magnetic field, pores can be exploited to study the transport of mechanical energy by waves along the magnetic field to the chromosphere and corona. For a better understanding of physics of pores, we have investigated chromospheric traveling features running across two merged pores from their centers at the speed about 55 km s-1, in the active region AR 11828. The pores were observed on 2013 August 24 by using high time, spatial, and spectral resolution data from the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer a LOS velocity by applying the bisector method to the Ca II $8542{\AA}$ band and $H{\alpha}$ band, and investigate intensity and the line-of-sight velocity changes at different wavelengths and different positions at the pores. We find that they have 3 minutes oscillations, and the intensity oscillation from the line center is preceded by that from the core ($-0.3{\AA}$) of the bands. There is no phase difference between the intensity and the LOS velocity oscillations at a given wavelength. The amplitude of LOS velocity from near the core spectra is greater than that from the far core spectra. These results support the interpretation of the observed wave as a slow magnetoacoustic wave propagating along the magnetic field lines in the pores. The apparent horizontal motion and a sudden decrease of its speed beyond the pores can be explained by the projection effect caused by inclination of the magnetic field with a canopy.

• Korean Journal of Oriental Medicine
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• v.12 no.2 s.17
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• pp.93-101
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• 2006

Pulse feeling is one of the most important diagnosis method in Oriental medicine. But it is not easy to make an objective and standardized diagnosis. In this study, we found how to quantify diagnosis. Specially dally the high practicality in clinic, we search some parameters especially well-related to floating and sinking pulse by statistic analysis. By extension, we find the pulse patterns of the floating and sinking pulse. We choose 15 subjects diagnosed as floating pulse and 15 subjects diagnosed as sinking pulse by oriental doctors. And their pulse signals were acquired by Pulse analyzer which has piezoresistive pressure sensor. For the quantification of the floating and sinking pulse, at first, we examined the parameters which were highly correlated with oriental doctor's diagnosis. And then we derived pulse patterns of the floating-sinking pulse from preprocessed signal and its ensemble average. We also looked trend variation (PH-Curve) between contact and pulse pressure. As a result, statistically there is the biggest difference between contact pressure, the maximum pulse pressure, diastolic area (Ad) and floating and sinking data. Through the PH-Curve, which represented the relationship between contact and pulse pressure, we could divide the floating and sinking pulse clearly. As a basic research of pulse diagnosis algorithm, we can contribute to select essential parameters in diagnosis algorithm And using these diagnosis method, we expect to find typical pulse patterns and some useful parameters about other pulses like slow/rapid, large/fine pulse and so on. We hope that this study will contribute pulse objectification.

• Journal of the Korean Geophysical Society
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• v.5 no.2
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• pp.87-97
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• 2002

P wave travel-time delays have been analyzed and average travel-time anomalies due to lateral variation of the crustal structure have been calculated at the broad-band earthquake observatories of Korea Meteorology Administration (KMA) using the teleseismic deata collected during the period from 2000 to 2001. Maximum variation in the relative travel-time residuals is almost 1.5 seconds Azimuthal variation in the travel-time residuals is observed to indicate the existence of lateral P velocity heterogeneity beneath the stations with velocity contrasts of -4~4%. The estimated average travel-time delays are ranging from 0.05 to 0.3 seconds at the stations including Seoul, Chuncheon, Kanneung, Uljin, and Ulleung Island showing slow velocity contrasts of 0~4% P through the crust. Faster velocity contrasts of 0~4% have been observed at the stations including Seosan, Taejeon, Daegu, Seoguipo, and Busan showing average travel-time delays ranging from -0.05 to -0.3 seconds.

• Journal of Korea Society of Digital Industry and Information Management
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• v.4 no.2
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• pp.67-74
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• 2008

Entering the 21st century, the primary influence leading world economy have been shifting. U.S. economy has seemed to slow down, Japan and EU are also in same situation. But China have started to lead Asia economy and expended to the World. According to Goldman Sachs Group, "The 21st century will be a era of Brics because of their enormous territory, a large population and abundant natural resources." We have to more focus on China because China have directly effect on Korean market and have a great potential market opportunity for our industries. However, this report mentioned above didn't carefully deal with a field of information and technology(from here IT), Digital contents consumption wasn't mentioned at all. Now Digital Contents (from here 'DC') emerge as new value creator and actually Korea has been a dominant in IT industries and is leading Digital contents market in China. This phenomenon is called as 'Korean wave (Han-Ryu)'. Many researchers have studied about 'Korean wave(Han-Ryu)' focusing on the economic effect but Korean DC industries need to build specifical strategies for exporting Korean DC to China market. Therefore, purpose of this study is following : Firstly, to analyze environment of DC in China and competitive advantages of it. Secondly, to compare ICAI (Industrial Comparative Advantage Index) according to a kind of DC. Finally, to make an analysis of China consumer's attitude to DC. This study will give much implication for Korean DC industries to enter China market.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.97-104
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• 2009

Ever increasing fuel prices, almost doubled in the last three years, and global pressure to reduce their environmental impact have been enforcing commercial vessel operators and designers to re-assess current vessel designs with emphasis on their propulsion systems and operational practices. In this paper the "Inclined Keel Hull (IKH)" concept, which facilitates to use larger propeller diameter in combination with lower shaft speed rates and hence better transport efficiency, is explored for a modern 3600 TEU container vessel with the aim of fitting an 13 % larger diameter propeller (and hence resulting 20% lower rpm) to gain further power saving over the similar size basis container ship with conventional "level keel" configuration. It appears that successful application of the "inclined keel Hull" concept is a fine balance amongst the maximum gain in propulsive efficiency, minimum increase in hull resistance and satisfaction of other naval architectural and operational requirements. In order to make the concept economically more viable, this paper concentrates on the fore body design with the possible combination of increase of volume in its fore body to recover the expected volume loss in the aft body due to the space for larger propeller and its low wave-making resistance to minimize the efficiency loss using a well-established optimization software.