• Journal of Astronomy and Space Sciences
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• v.38 no.2
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• pp.93-103
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• 2021

In this work, the problem of resonance caused by some gravitational potentials due to Mercury and a third body, namely the Sun, together with some non-gravitational perturbations, specifically coronal mass ejections and solar wind in addition to radiation pressure, are investigated. Some simplifying assumptions without loss of accuracy are employed. The considered force model is constructed. Then the Delaunay canonical set is introduced. The Hamiltonian of the problem is obtained then it is expressed in terms of the Deluanay canonical set. The Hamiltonian is re-ordered to adopt it to the perturbation technique used to solve the problem. The Lie transform method is surveyed. The Hamiltonian is doubly averaged. The resonance capture is investigated. Finally, some numerical simulations are illustrated and are analyzed. Many resonant inclinations are revealed.

• Journal of the Korean Statistical Society
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• v.23 no.2
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• pp.271-292
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• 1994

The comparison of statistical experiments with a common parameter and parameter space is discussed using the concept of the Blackwell's sufficiency and the Shannon's entropy. Binomial and censored experiments are considered as applications. The loss of information is studied under teh aggregated experiments and truncated experiments, and summerized in some tables which make it possible to indicate the choice of an appropriate experiment.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.51.4-51.4
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• 2018

Luminous blue variables (LBVs) are luminous evolved massive stars (thus with very large initial masses) typified by their irregular variabilities, which are sometimes associated with eruptive mass loss. G026.47+0.02 is one of the known Galactic LBV surrounded by large circumstellar shell (r~1') detected in far IR. In this presentation, we report the identification of another shell of smaller radii (r~20") indicating that the central star experienced multiple episodes of eruptions. We present detailed multi-wavelength study of the inner shell in near IR and sub-mm, with which we reconstruct its mass-loss history.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.84.2-84.2
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• 2015

There are probabilistic forecast models for solar flare occurrence, which can be evaluated by various skill scores (e.g. accuracy, critical success index, heidek skill score, true skill score). Since these skill scores assume that two types of forecast errors (i.e. false alarm and miss) are equal or constant, which does not take into account different situations of users, they may be unrealistic. In this study, we make an evaluation of a probabilistic flare forecast model (Lee et al. 2012) which use sunspot groups and its area changes as a proxy of flux emergence. We calculate daily solar flare probabilities from 1996 to 2014 using this model. Overall frequencies are 61.08% (C), 22.83% (M), and 5.44% (X). The maximum probabilities computed by the model are 99.9% (C), 89.39% (M), and 25.45% (X), respectively. The skill scores are computed through contingency tables as a function of forecast probability, which corresponds to the maximum skill score depending on flare class and type of a skill score. For the critical success index widely used, the probability threshold values for contingency tables are 25% (C), 20% (M), and 4% (X). We use a value score with cost/loss ratio, relative importance between the two types of forecast errors. We find that the forecast model has an effective range of cost/loss ratio for each class flare: 0.15-0.83(C), 0.11-0.51(M), and 0.04-0.17(X), also depending on a lifetime of satellite. We expect that this study would provide a guideline to determine the probability threshold for space weather forecast.

• Journal of Information Processing Systems
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• v.14 no.6
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• pp.1464-1479
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• 2018

In face recognition, sometimes the number of available training samples for single category is insufficient. Therefore, the performances of models trained by convolutional neural network are not ideal. The small sample face recognition algorithm based on novel Siamese network is proposed in this paper, which doesn't need rich samples for training. The algorithm designs and realizes a new Siamese network model, SiameseFacel, which uses pairs of face images as inputs and maps them to target space so that the $L_2$ norm distance in target space can represent the semantic distance in input space. The mapping is represented by the neural network in supervised learning. Moreover, a more lightweight Siamese network model, SiameseFace2, is designed to reduce the network parameters without losing accuracy. We also present a new method to generate training data and expand the number of training samples for single category in AR and labeled faces in the wild (LFW) datasets, which improves the recognition accuracy of the models. Four loss functions are adopted to carry out experiments on AR and LFW datasets. The results show that the contrastive loss function combined with new Siamese network model in this paper can effectively improve the accuracy of face recognition.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.894-903
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• 2014

Insertion loss prediction of large acoustical enclosures using Statistical Energy Analysis (SEA) method is presented. The SEA model consists of three elements: sound field inside the enclosure, vibration energy of the enclosure panel, and sound field outside the enclosure. It is assumed that the space surrounding the enclosure is sufficiently large so that there is no energy flow from the outside to the wall panel or to air cavity inside the enclosure. The comparison of the predicted insertion loss to the measured data for typical large acoustical enclosures shows good agreements. It is found that if the critical frequency of the wall panel falls above the frequency region of interest, insertion loss is dominated by the sound transmission loss of the wall panel and averaged sound absorption coefficient inside the enclosure. However, if the critical frequency of the wall panel falls into the frequency region of interest, acoustic power from the sound radiation by the wall panel must be added to the acoustic power from transmission through the panel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2328-2339
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• 1994

The PBS(Partial Buffer Sharing) space priority mechanism is one of priority control methods which may improve the performance of a single server queueing system when mixed traffic with different performance requirements is applied to the system. This paper analyzes the cell loss behavior of PBS assuming loss sensitive traffic and delay sensitive traffic are applied to the system. To derive the successive cell loss probabilities. which are an important performance measure of realtime traffic, we develop a recursive algorithm. Performance results show the successive cell loss probabilities obtained by our method are lager than the probabilities derived from an independent cell loss assumption. These results may indicate the limitation of PBS for realtime traffic and the increase of the admissible load with the criterion of quality of service.

• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.287-293
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• 2016

The equatorial region of the Earth's ionosphere exhibits large temporal variations in electron density that have significant implications on satellite signal transmissions. In this paper, the first observation results of the variations in the trough of the equatorial ionospheric anomaly at the permanent Global Navigation Satellite System (GNSS) site in Chuuk (Geographic: $7.5^{\circ}N$, $151.9^{\circ}E$; Geomagnetic: $0.4^{\circ}N$) are presented. It was found that the daytime Global Positioning System (GPS) total electron content (TEC) values vary according to the 27 day period of solar rotation, and that these trends show sharp contrast with those of summer. The amplitudes of the semi-annual anomaly were 12.4 TECU (33 %) on $19^{th}$ of March and 8.8 TECU (23 %) on $25^{th}$ of October respectively, with a yearly averaged value of 38.0 TECU. The equinoctial asymmetry at the March equinox was higher than that at the October equinox rather than the November equinox. Daily mean TEC values were higher in December than in June, which could be interpreted as annual or winter anomalies. The nighttime GPS TEC enhancements during 20:00-24:00 LT also exhibited the semi-annual variation. The pre-midnight TEC enhancement could be explained with the slow loss process of electron density that is largely produced during the daytime of equinox. However, the significant peaks around 22:00-23:00 LT at the spring equinox require other mechanisms other than the slow loss process of the electron density.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.446-452
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• 1999

Ectopic eruption of the first permanent molar means the first permanent molar assumes an atypical path of eruption resulting in premature atypical resorption of the second primary molar. If the reversible eruption does not occur, early loss of the second primary molars results in space loss, mesial tipping of the first permanent molar, impaction of the second premolar, buccal segment crowding and overeruption of opposing tooth. The main objectives of treatment are (1) to prevent loss of the second deciduous molars so it can continue to serve as a space maintainer and (2) to regain lost arch length, allowing the second premolar to erupt into normal position. The optimal treatment approach depends on a number of factors including the clinical eruption status of /6/, the change in position of /6/, the amount of enamel ledge of /E/ entrapping /6/, the mobility of /E/, and the presence of pain or infection. Unilateral appliance to correct the mesial angulation of ectopic permanent first molars, as in the majority of the appliance designs, would produce a resultant force that would further enhance the space loss. A bilateral support similar to the holding arch design is recommended to maximize the anchorage. These case reports present the successful result of preserving space for the second premolar in treatment of ectopic eruption of the first permanent molar using Halterman appliance with bilateral anchorage on patients visiting department of pediatric dentistry in Samsung Medical Center.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.369-377
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• 2018

This study investigated the effect of noise and reverberation on subjective measure of speech transmission performance for elderly person with hearing loss in residential space through listening test. Floor impact, road traffic, airborne, and drainage noise were employed as the residential noise, and several impulse responses were obtained through room acoustical computer simulation for an apartment building. Sound sources for the listening test consisted of residential noises and speech sounds for boh the young (the original sound) and the aged (the sound filtered out by filters with frequency responses of hearing loss of 65 years elderly person). In the listening test, subjects evaluated speech intelligibility and listening difficulty for the presented word ($L_{Aeq}$ 55 dB) at three noise levels ($L_{Aeq}$ 30, 40, 50 dB) and three reverberation times (0.5, 1.0, 1.5 s). Results showed that the residential space with noise level lower than equal to 50 dB ($L_{i,Fmax,AW}$) for jumping noise and 40 dB ($L_{Aeq}$) for road traffic, airborne, and drainage noise had speech intelligibility of 90 % and over and listening difficulty of 30 % and below. Speech intelligibility and listening difficulty for the aged sound source was shown to be 0 % ~ 5 % lower and 2 % ~ 20 % higher than those for the young sound source, respectively.