• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.11
• /
• pp.821-827
• /
• 2018

In devices used for re-forming osteoblasts to treat osteoporosis, a magnetic field is applied from the outside of the bone, and the minerals contained in the bone are aligned in a certain direction and undergo precessional motion. When a $90^{\circ}$ RF pulse is applied by using an RF coil, protons of minerals are brought to an excited state, and phosphorus activity promoting the deposition of osteoblasts in the bone is increased, thereby reshaping the bone. Miniaturizing the RF coil that generates a signal corresponding to the harmonic of the precessional motional frequency by means of the $90^{\circ}$ RF pulse can drastically reduce the overall size of the bone reshaping system. In this study, we propose a methodology for the miniaturization of the RF coil that can be used for osteoblast re-formation using a bone reshaping system. The capacitance of the designed RF coil is 25 pF, the inductance is approximately 100 nH, and the resonance frequency is 96 MHz. The radius of the end ring of the designed RF coil is 18 cm, and the total length of the leg is $2{\times}11.6cm$. The performance of the coil is verified through post-design measurement.

• Economic and Environmental Geology
• /
• v.54 no.1
• /
• pp.117-126
• /
• 2021

Satellite magnetic observations reflect the magnetic properties of deep crust about the depth of Curie isotherm that is a boundary where the magnetic nature of the rocks is disappeared, showing long wavelength anomalies that are not easily detected in near-surface data from airborne and shipborne surveys. For this reason, they are important not only in the analyses on such as plate reconstruction of tectonic boundaries and deep crustal structures, but in the studies of geothermal distribution in Antarctic and Greenland crust, related to global warming issue. It is a conventional method to compute the spherical harmonic coefficients from global coverage of satellite magnetic observations but it should be noted that inclusion of erroneous data from the equator and the poles where magnetic observations are highly disturbed might mislead the global model of the coefficients. Otherwise, the reduced anomaly model can be obtained with less corruption by choosing the area of interest with proper data processing to the area. In this study, I produced a satellite crustal magnetic anomaly map over East Asia (20° ~ 55°N, 108° ~ 150°E) centered on Korean Peninsula, from CHAMP satellite magnetic measurements about mean altitude of 280 km during the last year of the mission, and compared with the one from global crustal magnetic model (MF7). Also, a comparison was made with long wavelength anomalies from EMAG2 model compiled from all near-surface data over the globe.

• Phonetics and Speech Sciences
• /
• v.13 no.2
• /
• pp.57-66
• /
• 2021

This study focuses on the issue of automatic severity classification of dysarthric speakers based on speech intelligibility. Speech intelligibility is a complex measure that is affected by the features of multiple speech dimensions. However, most previous studies are restricted to using features from a single speech dimension. To effectively capture the characteristics of the speech disorder, we extracted features of multiple speech dimensions: voice quality, prosody, and pronunciation. Voice quality consists of jitter, shimmer, Harmonic to Noise Ratio (HNR), number of voice breaks, and degree of voice breaks. Prosody includes speech rate (total duration, speech duration, speaking rate, articulation rate), pitch (F0 mean/std/min/max/med/25quartile/75 quartile), and rhythm (%V, deltas, Varcos, rPVIs, nPVIs). Pronunciation contains Percentage of Correct Phonemes (Percentage of Correct Consonants/Vowels/Total phonemes) and degree of vowel distortion (Vowel Space Area, Formant Centralized Ratio, Vowel Articulatory Index, F2-Ratio). Experiments were conducted using various feature combinations. The experimental results indicate that using features from all three speech dimensions gives the best result, with a 80.15 F1-score, compared to using features from just one or two speech dimensions. The result implies voice quality, prosody, and pronunciation features should all be considered in automatic severity classification of dysarthria.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.1
• /
• pp.94-108
• /
• 1997

The temperature of the upper thermosphere is generally varied with the solar activity, and largely with geomagnetic activity in the high latitude. The data analyzed in this study are acquired at two ground stations, Thule Air Base($76,5{deg} N, 68.4{deg} W, A = 86{deg}$) and $S{psi}ndre Str{psi}mfjord (67.0{deg} N, 50.9{deg} W, A = 74{deg}$), Greenland. Both stations are located in the high latitude not only geographically but also geomagnetically. The terrestrial night glow at 6300 ${angs}$ from atomic oxygen has been observed from the two ground-based Fabry-Perot interferometers, during periods of 1986~1991 in Thule Air Base and 1986~1994 in $S{psi}ndre Str{psi}mfjord$. Some features noted in this study are as follows: (1) The correlation between the solar activity and the measured thermospheric temperature is highest in the case of $3{leq}Kp{leq}4$ in Thule, and increases with the geomagnetic activity in $S{psi}ndre Str{psi}mfjord$. (2) The measured temperatures at Thule is generally higher than those at $S{psi}ndre Str{psi}mfjord$, but the latter shows steeper slope with the solar activity. (3) The harmonic analysis shows that the diurnal variation(24hrs) is the main feature of the daily temperature variation with a temperature peak at about 13-14 LT (LT=UT-4). However, the semi-diurnal variation is evident during the period of weak solar activity. (4) Generally the predicted temperatures from both MSIS86 and VSH models are lower than the measured temperature, and this discrepancy grows as the solar activity increases. Therefore, we urge modelers to develope a new thermospheric model utilizing broader sets of measurements, especially for high solar activity.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.3
• /
• pp.207-217
• /
• 2008

The SSTop (Sea Surface Topography) provides an estimate of the large scale structure of the deviations between the geoid height and the mean sea surface in terms of a normalized surface spherical harmonic series. The SSTop is the key information which has been used to determine the shape of earth, geoid, current and tide etc. Also, the SSTop is a basic source for the unification of vertical datums at the different height systems which were established according to the their respective purposes. In order to unify the vertical datum around the East-Asian (E-A) region (covers the area: $20^{\circ}-45^{\circ}N$ and $110^{\circ}-140^{\circ}E$), we estimated the value of SSTop in the E-A region using the predicted values of mean sea surface (from KMSS04) and geoid height (from EGM96 and EIGEN-GL04C) and analyzed to aspect of SSTop at 5 tidal stations (InCheon, JeJu, QingDao, Aburatsubo, KeeLung) with the estimated values of each station previously. The result from this study indicates that the SSTop in the E-A region is relatively stable except for the area around the Japanese and Ryukyu deep, and also shows that the distribution of values of SSTop is ranged from 40 to 60 cm at tidal stations except InCheon station.

• Journal of Intelligence and Information Systems
• /
• v.20 no.2
• /
• pp.123-136
• /
• 2014

Recently, online shopping has further developed as the use of the Internet and a variety of smart mobile devices becomes more prevalent. The increase in the scale of such shopping has led to the creation of many Internet shopping malls. Consequently, there is a tendency for increasingly fierce competition among online retailers, and as a result, many Internet shopping malls are making significant attempts to attract online users to their sites. One such attempt is keyword marketing, whereby a retail site pays a fee to expose its link to potential customers when they insert a specific keyword on an Internet portal site. The price related to each keyword is generally estimated by the keyword's frequency of appearance. However, it is widely accepted that the price of keywords cannot be based solely on their frequency because many keywords may appear frequently but have little relationship to shopping. This implies that it is unreasonable for an online shopping mall to spend a great deal on some keywords simply because people frequently use them. Therefore, from the perspective of shopping malls, a specialized process is required to extract meaningful keywords. Further, the demand for automating this extraction process is increasing because of the drive to improve online sales performance. In this study, we propose a methodology that can automatically extract only shopping-related keywords from the entire set of search keywords used on portal sites. We define a shopping-related keyword as a keyword that is used directly before shopping behaviors. In other words, only search keywords that direct the search results page to shopping-related pages are extracted from among the entire set of search keywords. A comparison is then made between the extracted keywords' rankings and the rankings of the entire set of search keywords. Two types of data are used in our study's experiment: web browsing history from July 1, 2012 to June 30, 2013, and site information. The experimental dataset was from a web site ranking site, and the biggest portal site in Korea. The original sample dataset contains 150 million transaction logs. First, portal sites are selected, and search keywords in those sites are extracted. Search keywords can be easily extracted by simple parsing. The extracted keywords are ranked according to their frequency. The experiment uses approximately 3.9 million search results from Korea's largest search portal site. As a result, a total of 344,822 search keywords were extracted. Next, by using web browsing history and site information, the shopping-related keywords were taken from the entire set of search keywords. As a result, we obtained 4,709 shopping-related keywords. For performance evaluation, we compared the hit ratios of all the search keywords with the shopping-related keywords. To achieve this, we extracted 80,298 search keywords from several Internet shopping malls and then chose the top 1,000 keywords as a set of true shopping keywords. We measured precision, recall, and F-scores of the entire amount of keywords and the shopping-related keywords. The F-Score was formulated by calculating the harmonic mean of precision and recall. The precision, recall, and F-score of shopping-related keywords derived by the proposed methodology were revealed to be higher than those of the entire number of keywords. This study proposes a scheme that is able to obtain shopping-related keywords in a relatively simple manner. We could easily extract shopping-related keywords simply by examining transactions whose next visit is a shopping mall. The resultant shopping-related keyword set is expected to be a useful asset for many shopping malls that participate in keyword marketing. Moreover, the proposed methodology can be easily applied to the construction of special area-related keywords as well as shopping-related ones.