• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.617-627
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• 2021

Underwater Acoustic Channels (UAC) have inherent sparse characteristics. The traditional adaptive equalization techniques do not utilize this feature to improve the performance. In this paper we consider the Variable Adaptive Subgradient Projection (V-ASPM) method to derive a new sparse equalization algorithm based on the Minimum Symbol Error Rate (MSER) criterion. Compared with the original MSER algorithm, our proposed scheme adds sparse matrix to the iterative formula, which can assign independent step-sizes to the equalizer taps. How to obtain such proper sparse matrix is also analyzed. On this basis, the selection scheme of the sparse matrix is obtained by combining the variable step-sizes and equalizer sparsity measure. We call the new algorithm Sparse-Control Proportional-MSER (SC-PMSER) equalizer. Finally, the proposed SC-PMSER equalizer is embedded into a turbo receiver, which perform turbo decoding, Digital Phase-Locked Loop (DPLL), time-reversal receiving and multi-reception diversity. Simulation and real-field experimental results show that the proposed algorithm has better performance in convergence speed and Bit Error Rate (BER).

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.1-11
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• 2005

This study applied EK method to remediate contaminated soil by lead (Pb), tried increasing efficiency of remediation using adsorbent (apatite and zeolite) as enhanced EK remediation method to overcome the limit of traditional EK remediation method. Adsorption tests on Pb were practiced to extract EK, making different concentration of contaminated soil, voltage condition, operating time etc., transferring Pb-ion into the position of adsorbent, then tried immobilization. On this results, the efficiency of remediation is different on its test conditions. In addition, the efficiency of remediation was not only improved by adding electrode revεrsal and install position of adsorbent but also satisfied TCLP regulation of EPA in USA through the whole sample range. Finally, absorption and immobilization capacity of apatite and zeolite proved on its excellence and confirmed the possibility of application of apatite and zeolite as enhanced EK remediation method.

• Journal of the Ergonomics Society of Korea
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• v.31 no.2
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• pp.371-377
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• 2012

Objective: The aim of this study is to investigate effect of driver's cognitive distraction on driver's physiological state and driving performance, and then to determine parameters appropriate for detecting the cognitive distraction. Background: Driver distraction is a major cause of traffic accidents and poses a serious threat to traffic safety due to ever increasing use of in-vehicle information systems and mobile phones during driving. Cognitive distraction, among four different types of distractions, prevents a driver from processing traffic information correctly and adapting to change in surround vehicle behavior in time. However, the cognitive distraction is more difficult to detect because it normally does not involve significant change in driver behavior. Method: A full-scale driving simulator was used to create virtual driving environment and situations. Participants in the experiment drove the driving simulator in three different conditions: attentive driving with no secondary task, driving and conducting secondary task of adding numbers, and driving and conducting secondary task of conversing with an experimenter. Parameters related with driver's physiological state and driving performance were measured and analyzed for their change. Results: The experiment results show that driver's cognitive distraction, induced by secondary task of addition and conversation during driving, increased driver's cognitive workload, and indeed brought change in driver's physiological state and degraded driving performance. Conclusion: The galvanic skin response, pupil size, steering reversal rate, and driver reaction time are shown to be statistically significant for detecting cognitive distraction. The appropriate combination of these parameters will be used to detect the cognitive distraction and estimate risk of traffic accidents in real-time for a driver distraction warning system.

• Geophysics and Geophysical Exploration
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• v.2 no.4
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• pp.184-190
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• 1999

A study of gas hydrate is a worldwide popular interesting subject as a potential energy source. A seismic survey for gas hydrate have performed over the East sea by the KIGAM since 1997. General indicators of natural submarine gas hydrates in seismic data is commonly inferred from the BSR (Bottom Simulating Reflection) that occurred parallel to the see floor, amplitude decrease at the top of the BSR, amplitude Blanking at the bottom of the BSR, decrease of the interval velocity, and the reflection phase reversal at the BSR. So the seismic data processing for detecting gas hydrates indicators is required the true amplitude recovery processing, a accurate velocity analysis and the AVO (Amplitude Variation with Offset) analysis. In this paper, we had processed the field data to detect the gas hydrate indicators, which had been acquired over the East sea in 1998. Applied processing modules are spherical divergence, band pass filtering, CDP sorting and accurate velocity analysis. The AVO analysis was excluded, since this field data had too short offset to apply the AVO analysis. The accurate velocity analysis was performed by XVA (X-window based Velocity Analysis). This is the method which calculate the velocity spectrum by iterative and interactive. With XVA, we could determine accurate stacking velocity. Geobit 2.9.5 developed by the KIGAM was used for processing data. Processing results say that the BSR occurred parallel to the sea floor were shown at $367\~477m$ depths (two way travel time about 1800 ms) from the sea floor through shot point 1650-1900, the interval velocity decrease around BSR and the reflection phase reversal corresponding to the reflection at the sea floor.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.559-564
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• 2023

It is known that change in the bone strength of cortical bone constituting the outer shell of long bones such as the tibia or radius due to aging and osteoporosis is a risk factor for fracture. In this study, the group velocity of time-reversed Lamb waves generated in tibial cortical bone in vivo was measured using a time reversal method, and the correlations of the group velocity with the cortical bone thickness (cTh) and cortical bone mineral density (cBMD) closely related to the bone strength were investigated. It was found that the group velocity of time-reversed Lamb waves measured in the right tibia of 7 subjects showed a very high correlation, r = 0.90 (p < 0.0001), with the cTh and a relatively low correlation, r = 0.69 (p < 0.0001), with the cBMD. A limitation of this in vivo study is that the group velocity of time-reversed Lamb waves was measured for a normal group consisting of only 7 healthy adults. In the future, if the clinical usefulness of the time-reversed Lamb wave is demonstrated by follow-up studies on normal and osteoporotic groups consisting of a large number of healthy adults and osteoporotic patients, respectively, it is expected to improve the reliability of quantitative ultrasound technology for osteoporosis diagnosis. In addition, it is necessary to expand the skeletal site for measuring the group velocity of time-reversed Lamb waves not only to the tibia but also to the femur or radius.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.156-157
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• 2005

Gas hydrate is ice-like crystalline lattice, formed at appropriate temperature and pressure, in which gas molecules are trapped. It is worldwide popular interesting subject as a potential energy. In korea, a seismic survey for gas hydrate have performed over the East sea by the KIGAM since 1997. In this paper, we had conducted numerical and physical modeling experiments for seismic properties on gas hydrate with field data which had been acquired over the East sea in 1998. We used a finite difference seismic method with staggered grid for 2-D elastic wave equation to generate synthetic seismograms from multi-channel surface seismic survey, OBC(Ocean Bottom Cable) and VSP(Vertical Seismic Profiling). We developed the seismic physical modeling system which is simulated in the deep sea conditions and acquired the physical model data to the various source-receiver geometry. We carried out seismic complex analysis with the obtained data. In numerical and physical modeling data, we observed the phase reversal phenomenon of reflection wave at interface between the gas hydrate and free gas. In seismic physical modeling, seismic properties of the modeling material agree with the seismic velocity estimated from the travel time of reflection events. We could easily find out AVO(Amplitude Versus Offset) in the reflection strength profile through seismic complex analysis.

• Atmosphere
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• v.33 no.1
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• pp.49-59
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• 2023

Blocking refers to a class of weather phenomena appearing in the mid and high latitudes, whose characteristics are blocked airflow of persistence. Frequently found over the Pacific and Atlantic regions of the Northern Hemisphere, blocking affects severe weather in the surrounding areas with different mechanisms depending on the type of blocking patterns. Along with lots of studies about persistent weather extremes focusing on the specific types of blocking, a new categorization using Rossby wave breaking has emerged. This study aims to apply this concept to the classification of blockings over the Pacific and examine how different wave breakings specify the associated cold weather in the Korean peninsula. At the same time, we investigate a strongly developing ridge around the Pacific by designing a new detection algorithm, where a reversal method is modified to distinguish ridge-type blocking patterns. As result, Kamchatka blocking (KB) and strong ridge over the Central Pacific are observed the most frequently during 20 years (2001~2020) of the studied period, and anomalous low pressures with cold air over the Korean Peninsula are accompanied by blocking events. When it considers the Rossby wave breaking, cyclonic wave-breaking is dominant in KB, which generates low-pressure anomalies over the Korean Peninsula. However, KB with anticyclone wave breaking appears with the high-pressure anomalies over the Korean Peninsula and it generates the warm temperature anomaly. Lastly, the low-pressure anomalies are also generated by the strong ridge over the Central Pacific, which persists for approximately three days and give a significant impact on cold surge on the Korean Peninsula.

• The Journal of Korean Academy of Sensory Integration
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• v.12 no.2
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• pp.25-36
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• 2014

Objective : The purpose of this study is learning the characteristics of literature applying single subject researches in the field of sensory integration therapy of Korean occupational therapy and evaluating the quality level of them. Methods : Analyzed the characteristics of 17 single subject research papers (independent variable, study design, study subject, total number of session, study period, intervention time, intervention place, dependent variable, measuring tool and result) published between 2002 and 2013 using the document delivery service of Korean Society of Occupational Therapy, National Discovery for Science Leaders (NDSL), Nuri Media (DBpia), Research Information Sharing Service (RISS), Korean Studies Information Service System (KISS) and National Assembly Library and evaluated the literatures using quality evaluation scale. Results : According to the analysis result on the literature characteristics, reversal design was the most used study method. Total number of session was 10 sessions to 34 sessions. Study period was 4 weeks to 16 weeks. Intervention time was 8 minutes to 70 minutes and most interventions were done in occupational therapy room or sensory integration therapy room. According to the result of quality level evaluation, 4 papers out of 17 papers were on high level and remaining papers were on intermediate level. However, there was no study which included intervention blind. Conclusion : Suggested standards that need to be supplemented and discussions on qualitative improvement including repetitive research on the mediation effect during the application of the single subject research methodology, the securement of adequate data sections, and processing of a mediation blind. It is expected to be used as basic data for conducting a better qualitative research in the future.

• Physical Therapy Korea
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• v.12 no.2
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• pp.81-89
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• 2005

The purpose of this study was to investigate the effect of Modified Constraint-Induced Therapy (MCIT) on the effected upper extremity of children with hemiparesis. Four children with hemiparetic upper extremity caused by brain injuries were trained by MCIT for ten weeks. During the same period, all of the subjects were also involved in thirty-minute regular physical therapy and occupational therapy. During the treatment period, the unaffected upper extremities of the subjects were restrained by a specially designed hand splint or a mitten for five hours a day, five days per week. For two hours out of the five-hour restraint period, the affected upper extremities were intensively trained by performing various functional tasks, which were individually structured to emphasize use of the affected arm. A single-subject design with A-B-A reversal was employed in this study. The affected limb motor ability was evaluated by Melbourne Assessment, measuring the time to grasp and release nine pegs, and measuring grasping power. As a consequence of this study, the affected limb motor test scores of all four subjects in the baseline period were improved during the treatment period. Furthermore, the treatment effect was maintained during a one-month follow-up period. The results of this study support the assumption that MCIT is an effective therapeutic method to improve the sensory and motor abilities of hemiparetic children. It also increases the frequency of functional use of the hemiparetic hands of brain-injured children. Based on the results of this study, it can also be assumed that the modified CIT method is especially beneficial to these children by reducing the negative emotional effects of forceful restraint of the unaffected upper extremity. To optimize the functional recovery of the paretic upper extremity by CIT, the restriction period per day should be decided individually, according to the characteristics of the individual.

• Journal of Intelligence and Information Systems
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• v.19 no.1
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• pp.79-94
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• 2013

Recently, the high value added business is steadily growing in the culture and art area. To generated high value from a performance, the satisfaction of audience is necessary. The flow in a critical factor for satisfaction, and it should be induced from audience and measures. To evaluate interest and emotion of audience on contents, producers or investors need a kind of index for the measurement of the flow. But it is neither easy to define the flow quantitatively, nor to collect audience's reaction immediately. The previous studies of the group flow were evaluated by the sum of the average value of each person's reaction. The flow or "good feeling" from each audience was extracted from his face, especially, the change of his (or her) expression and body movement. But it was not easy to handle the large amount of real-time data from each sensor signals. And also it was difficult to set experimental devices, in terms of economic and environmental problems. Because, all participants should have their own personal sensor to check their physical signal. Also each camera should be located in front of their head to catch their looks. Therefore we need more simple system to analyze group flow. This study provides the method for measurement of audiences flow with group synchronization at same time and place. To measure the synchronization, we made real-time processing system using the Differential Image and Group Emotion Analysis (GEA) system. Differential Image was obtained from camera and by the previous frame was subtracted from present frame. So the movement variation on audience's reaction was obtained. And then we developed a program, GEX(Group Emotion Analysis), for flow judgment model. After the measurement of the audience's reaction, the synchronization is divided as Dynamic State Synchronization and Static State Synchronization. The Dynamic State Synchronization accompanies audience's active reaction, while the Static State Synchronization means to movement of audience. The Dynamic State Synchronization can be caused by the audience's surprise action such as scary, creepy or reversal scene. And the Static State Synchronization was triggered by impressed or sad scene. Therefore we showed them several short movies containing various scenes mentioned previously. And these kind of scenes made them sad, clap, and creepy, etc. To check the movement of audience, we defined the critical point, ${\alpha}$and ${\beta}$. Dynamic State Synchronization was meaningful when the movement value was over critical point ${\beta}$, while Static State Synchronization was effective under critical point ${\alpha}$. ${\beta}$ is made by audience' clapping movement of 10 teams in stead of using average number of movement. After checking the reactive movement of audience, the percentage(%) ratio was calculated from the division of "people having reaction" by "total people". Total 37 teams were made in "2012 Seoul DMC Culture Open" and they involved the experiments. First, they followed induction to clap by staff. Second, basic scene for neutralize emotion of audience. Third, flow scene was displayed to audience. Forth, the reversal scene was introduced. And then 24 teams of them were provided with amuse and creepy scenes. And the other 10 teams were exposed with the sad scene. There were clapping and laughing action of audience on the amuse scene with shaking their head or hid with closing eyes. And also the sad or touching scene made them silent. If the results were over about 80%, the group could be judged as the synchronization and the flow were achieved. As a result, the audience showed similar reactions about similar stimulation at same time and place. Once we get an additional normalization and experiment, we can obtain find the flow factor through the synchronization on a much bigger group and this should be useful for planning contents.