• The Journal of the Acoustical Society of Korea
• /
• v.28 no.1
• /
• pp.10-18
• /
• 2009

A moving surface vessel generates a ship wake which contains a cloud of micro-bubbles with radii ranging between $8{\sim}200{\mu}m$. Such micro-bubbles can be detected by active sonar system for more than ten minutes depending on the size and speed of the surface vessel. In this paper, a reverberation model for the ship wake is presented. The developed model consists of the acoustic scattering model due to the distribution of the micro-bubbles and the kinematic model for the moving active sonar. The acoustic scattering model is based on the volume integration, where the volume scattering strengths are obtained from the spatial distribution of micro-bubbles. Since the directivity and look-direction of active sonar are important factors for moving active sonar, the kinematic model utilizes the Euler transformation to obtain the relative motion between the global and local coordinates. In order to verify the developed model, a series of sea experiment was executed in September 2007 to obtain the spatial-temporal distribution of a bubble cloud, and analyzed to be compared with the simulation results.

• Information Systems Review
• /
• v.22 no.2
• /
• pp.43-52
• /
• 2020

The mobile game industry has become the one of the fastest growing industries with its astonishing market size. Despite its industrial importance, a few studies empirically considered actual purchasing behavior in mobile games rather than the intention to purchase. Therefore, this paper investigates the key drivers of in-app purchase by analyzing the game-log dataset provided from a mobile game company in Korea. Specifically, the effects of goal-directed, habitual and social-interacted playing behavior are analyzed on in-app purchase. Furthermore, the recursive relationship with playing and purchasing behaviorsis also considered. The result shows that all suggested factors have positive impacts on in-app purchase in the current period. In addition, the effect of previous habitual playing has a positive impact, but the effect of social-interacted playing and in-app purchase in the previous period have negative impacts on in-app purchase of the current period. These findings can improve our understanding of the impact of game playing on in-app purchase in mobile games, and provide meaningful insights for researchers and practitioners.

• Journal of Korea Water Resources Association
• /
• v.57 no.2
• /
• pp.111-125
• /
• 2024

The study has examined alterations in groundwater quality by investigating the influence of rainfall on electrical conductivity (EC) and nitrate concentration in the groundwater of the Geum River Basin in South Korea. Mann Kendall and Sen's Slope estimator were employed to analyze the trends and estimate the trend's magnitude. The administrative map of the study area was utilized to assess the trends of these parameters within each administrative region. Seventeen years (from 2005 to 2021) of data on EC, groundwater levels (GWL), precipitation, and six years (from 2015 to 2020) of nitrate concentration data were utilized for this analysis. The results indicate that, in most administrative regions, there has been an increase in nitrate concentration, and EC, whereas precipitation has seen a slight decrease in a downstream and an increasing trend in upstream. The correlation coefficients calculated between these parameters reveal that there is no direct impact of precipitation on nitrate and EC, but a negative correlation was observed between GWL and EC. The most significant increasing trend in nitrate concentration was observed in two districts (Iksan and Gunsan ), which correspond to regions with significant agricultural activity; about 50% of these districts area are used for agricultural activities.

• Journal of Chest Surgery
• /
• v.29 no.10
• /
• pp.1081-1089
• /
• 1996

Pulmonary atresia with intact ventricular septum has continued to have a high surgical mortality and morbidity. This mAy attribute to the non-uniformity of the anomaly. We reviewed a total of 34 infants with pulmonary atresla and intact ventricular septum managed in this hospital between 1987 and 1995. Mean age and body weight were 57.2 (range, 3-208) days and 4.1 (range, B.3∼6.8) kg. The preoperative Z-value of the diameter of the tricuspid valve was less than -2 in 85.2% of patients and less than -4 in 33. 3% . It is well correlated w th right ventricular cavity size (n=27. r10.68, p< 0.05). Coronary artery-right ventricular fistulas were identified in 3 patients, and right ventricular dependency was suspected in 1 Over All hospital mortality was 23.5%(8/34), although it decreased to 16.6%(4124) in 1990s. Subsequent procedures were performed in 6 patients between 3 days and 58 months after Initial palliation : one bidirectional cavopulmonary shunt and 1 Fontan operation after systemic-pulmonary shunt, 3 transannular patch + atrial septal defect closure and 1 additional systemic-pulmonary shunt after polmonary valvectomy or valvotomy. Changes of Z-values of the diameter of tricuspid valve have been followed up in 11 patients between 1 and 66 months postoperatively. Z-values were increased In 5 out of 8 transannular right ventriculAr outflow tract enlargement group and in 1 out of 3 pulmonary valvectomy or valvotomy group. Our data suggest that tailoring a treatment to right ventricular cavity size and coronary anom lies may improve the surgical outcome. A Z-value of the tricuspid valve diameter could be used.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.11
• /
• pp.82-88
• /
• 2016

In this paper, we propose an intelligibility enhancement algorithm for multimedia contents using spectral shaping. The dialogue signals is essential to understand the plot of audio-visual media contents such as movie and TV. However, the non-dialogue components as like sound effects and background music often degrade the dialogue clarity. To overcome this problem, this paper tries to improves the dialogue clarity of audio soundtracks which contain important cues for the visual scenes. In the proposed method, the dialogue components are first detected by soft masker based on speech presence probability (SPP) which is widely used in speech enhancement field. Then, extracted dialogue signals are applied to the spectral shaping method. It reallocate the spectral-temporal energy of speech to enhanced the intelligibility. The total energy is maintained as unchanged via a loudness normalization process to prevent saturation. The algorithm was evaluated using the modeled and real movie soundtracks and it was shown that the proposed algorithm enhances the dialogue clarity while preserving the total audio power.

• Journal of the HCI Society of Korea
• /
• v.12 no.4
• /
• pp.37-44
• /
• 2017

Eye-typing is one kind of human-computer interactive input system which is implemented by location data of gaze. It is widely used as an input system for paralytics because it does not require physical motions other than the eye movement. However, eye-typing interface based on Korean character has not been suggested yet. Thus, this research aims to implement the eye-typing interface optimized for Korean. To begin with, design objectives were established based on the features of eye-typing: significant noise and Midas touch problem. Multilevel input system was introduced to deal with noise, and an area free from input button was applied to solve Midas touch problem. Then, two types of eye-typing interfaces were suggested on phonological consideration of Korean where each syllable is generated from combination of several phonemes. Named as consonant-vowel integrated interface and separated interface, the two interfaces are designed to input Korean in phases through grouped phonemes. Finally, evaluation procedures composed of comparative experiments against the conventional Double-Korean keyboard interface, and analysis on flow of gaze were conducted. As a result, newly designed interfaces showed potential to be applied as practical tools for eye-typing.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.7
• /
• pp.796-808
• /
• 2007

In this paper, two novel compact microstrip bandstop filters using complimentary split ring resonators(CSRRs) and spiral resonators is proposed. The first one is the bandstop filter using an array of CSRRs etched on the center line of a microstrip. The bandstop is due to the presence of negative effective permittivity and positive permeability near resonant frequency which prevent the wave propagation. The second on is the bandstop filter using an array of spiral resonators etched on the center line of a microstrip. The bandstop is due to the self-resonance of spiral circuit. We have achieved controllable resonance frequency and bandwidth, super compact dimension, low insertion losses in the passband and high level of rejection in the stopband with sharp cutoff. The electrical sizes of two proposed filter are very small. Additionally, they can be easily fabricated and compatible with MMIC or PCB technology.

• Korean Journal of Microbiology
• /
• v.22 no.1
• /
• pp.1-18
• /
• 1984

With 156 water samples collected from 39 locations in the Yeong San River estuary during the 12month period from March 1976 to February 1977, the seasonal distribution of yeast and the distributional pattern of yeast on salinity gradient have been investigated. An overall average number of yeast ranged from 52 to 487 viable cells (c.f.u.) per 100ml water sample. The highest count of yeast was obtained in spring while the lowest value came in summer. 933 yeast and one yeast-like fungus pertaining to 14 genera and 83 species were recovered, of which Candida were 29%, Debaryomyces 17.3%, Rhodotorula Glutinis were dominant forms in all locations as well as throughout the year. The population size of total aerobic bacteria, the amount of terrestrial imputs, and some of geographical and/or climatic factor appear to reflect the seasonal distribution of yeast as well as the composition of yeast species in an estuarine environ. Average number of yeast, species diversity, and particularly the number of fermentative and pseudomycelium-producing yeasts increased with decreasing salinity whereas nitrate-utilizing yeasts showed opposite trend, suggesting that salinity gradient can be used as a feasible detector for the distributional pattern of yeast in estuarine habitat.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.1
• /
• pp.19-26
• /
• 2002

This paper defines the visual basic speech units, visemes and investigates various visual features of a lip for the effective Korean lipreading. First, we analyzed the visual characteristics of the Korean vowels from the database of the lip image sequences obtained from the multi-speakers, thereby giving a definition of seven Korean vowel visemes. Various spatio-temporal features of a lip are extracted from the feature points located on both inner and outer lip contours of image sequences and their classification performances are evaluated by using a hidden Markov model based classifier for effective lipreading. The experimental results for recognizing the Korean visemes have demonstrated that the feature victor containing the information of inner and outer lip contours can be effectively applied to lipreading and also the direction and magnitude of the movement of a lip feature point over time is quite useful for Korean lipreading.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.14 no.2
• /
• pp.101-111
• /
• 2006

In the present work, life cycle assessments (LCA) of various waste-plastic recycling methods (material recycling, refused derived fuel (RDF), recycling on furnace, and pyrolytic oil production) were carried out to investigate their impacts on the environment. Six types of impacts were considered. While the impact on global warming was found to be significant, the impact on others were negligible. The impact values on the global warming caused by the material recycling, RDF, and the recycling on furnace were negative, which implied that their impacts could be noticeably reduced when waste-plastic are used as an alternative to newly drawn plastics. The pyrolytic oil production, however, showed positive value, which may be due to the carbon dioxide produced during electric power generation. The pyrolytic oil production had the largest impact on the ozone layer destruction, which was due to ozone depleting substances produced from the process itself. These results can be used as a useful data for the enhancement of waste-plastic recycling.