• Journal of Information Technology Applications and Management
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• v.22 no.3
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• pp.105-114
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• 2015

This paper presents a fast Time Difference of Arrival (TDOA) estimation for sound source localization. TDOA is the time difference between the arrival times of a signal at two sensors. We propose a partial cross correlation method to increase the speed of TDOA estimation for sound source localization. We do this by predicting which part of the cross correlation function contains the required TDOA value with the help of the signal energies, and then we compute the cross correlation function in that direction only. Experiments show approximately 50% reduction in the cross correlation computation time thereby increasing the speed of TDOA computation. This makes it very relevant for real world surveillance.

• The Journal of the Acoustical Society of Korea
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• v.36 no.6
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• pp.378-386
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• 2017

Accurate distance measurement between maneuver target in underwater and measuring devices is required to perform quantitative test evaluation in marine weapons system R&D process. In general, the target distance is measured using a one-way ToA (Time of Arrival) method that calculates the time difference between transmitted and received signals from the two accurately synchronized devices. However, the distance estimation performance is degraded because of the multi-path environments. In this paper, the time-variant transfer function of complex underwater environment is estimated from each received data frame using RBD (Ray-based Blind Deconvolution), and the estimated time-variant transfer function is then used to get rid of the effect about complex underwater environment and to recover the data signal using PTRM (Passive Time Reversal Mirror). The result from the simulation and experimental data show that the suggested method improve the distance estimation performance when comparing with the conventional ToA method.

• Journal of Korean Academy of Nursing
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• v.33 no.8
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• pp.1153-1160
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• 2003

Purpose. 1) To identify the time taken from symptom onset to the arrival at the hospital (pre-hospital delay time) and time taken from the arrival at the hospital to the initiation of the major treatment (in-hospital delay time) 2) to examine whether rapid treatment results in lower mortality. 3) to examine whether the pre- and in-hospital delay time can independently predict in-hospital mortality. Methods. A retrospective study with 586 consecutive AMI patients was conducted. Results. Pre-hospital delay time was 5.25 (SD=10.36), and in-hospital delay time was 1.10 (SD=1.00) hours for the thrombolytic therapy and 50.24 (SD=121.18) hours for the percutaneous transluminal coronary angio-plasty (PTCA). In-hospital mortality was the highest when the patients were treated between 4 to 48 hours after symptom onset using PTCA (p=.02), and when treated between 30 minutes and one hour after hospital arrival using thrombolytics (p=.01). Using a hierarchical logistic regression model, the pre- and in-hospital delay times did not predict the in-hospital mortality. Conclusion. Pre- and in-hospital delay times need to be decreased to meet the desirable therapeutic time window. Thrombolytics should be given within 30 minutes after arrival at the hospital, and PTCA should be initiated within 4 hours after symptom onset to minimize in-hospital mortality of AMI patients.

• Journal of Communications and Networks
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• v.15 no.5
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• pp.514-526
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• 2013

With a long sensing period, the inter-frame spectrum sensing in IEEE 802.22 standard is vulnerable to the effect of the traffic of the primary user (PU). In this article, we address the two degrading factors that affect the inter-frame sensing performance with respect to the random arrival/leaving of the PU traffic. They are the noise-only samples under the random arrival traffic, and the PU-signal-contained samples under the random leaving traffic. We propose the model in which the intra-frame sensing cooperates with the inter-frame one, and the inter-frame sensing uses the time-of-arrival (ToA), and time-of-leave (ToL) detectors to reduce the two degrading factors in the inter-frame sensing time. These ToA and ToL detectors are used to search for the sample which contains either the ToA or ToL of the PU traffic, respectively, which allows the partial cancelation of the unnecessary samples. At the final stage, the remaining samples are input into a primary user detector, which is based on the energy detection scheme, to determine the status of PU traffic in the inter-frame sensing time. The analysis and the simulation results show that the proposed scheme enhances the spectrum-sensing performance compared to the conventional counter-part.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.10
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• pp.1-8
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• 2000

In this paper, positioning schemes based on AOA(Angle of Arrival), TOA(Time of Arrival), and TDOA(Time Difference of Arrival) measurements are reviewed and analyzed. In the case of using those schemes in microcell structure with severe multipath fading and shadowing conditions, the rapid and unpredictable variation of signal level makes it difficult to estimate the position and velocity of mobiles. Therefore, we propose a novel mobile tracking method based on the multicriteria decision making, in which uncertain parameters such as RSS(Received Signal Strength), the distance between mobile and base station, the moving direction, and the previous location are participated in the decision process using aggregation function in fuzzy set theory. Through a simulation, we analysis the impaction of the frequent change of direction and speed of mobiles.

• The Journal of the Korea Contents Association
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• v.6 no.5
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• pp.14-19
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• 2006

In this paper, we describe an arrival time guidance system of circular vehicles using GPS, CDMA and TCP/IP technology. The on-board equipment consists of a GPS receiver and a PDA phone. The on-board equipment sends the current position data of the vehicle to the positioning server via CDMA and Internet. The server predicts the arrival time to the next bus-stop. Any user can lookup the current position and the predicted arrival time of the vehicle utilizing his mobile phone, PDA phone, or Web.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.1-8
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• 2022

In this study, we propose trajectory-based arrival management using CDO (Continuos Descent Operations). The operational procedures with TBO (Trajectory-Based Operations) concept were established to allow aircraft and ground system to share the trajectories with each other in real time. The proposed operational concept was validated in the air traffic control simulation environment, which consists of controller working position, pseudo pilot system, air traffic generation system, and controllers' decision support system for arrival management using CDO. Simulation results compared with actual flight data indicate that proposed concept could improve the efficiency of traffic flow management in terms of total descending time and fuel consumption. And it was confirmed that if there is a system that can share and utilize the synchronized trajectory, it can be helpful to control arrival aircraft and apply CDO concept.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.3
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• pp.28-34
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• 2015

An analysis method of trajectory prediction has been suggested and the developed trajectory prediction module, which is an important functional component of the Arrival Manager (AMAN) of Jeju airport, has been tested by applying the suggested method. The objective of this method is to improve prediction performance of the trajectory prediction module. The trajectory prediction module predicts the trajectories based on the real-time track data and flight plans. Therefore, the suggested analysis method includes the simulation framework which is based on real-time playback, recording, and graphic display systems for testing. Besides, the definition of time error, which is a important index for the time based scheduling system, such as AMAN, is included in the suggested analysis method. An example of arrival time prediction accuracy improvement through the suggested analysis method has also been presented.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.6
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• pp.101-111
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• 2017

This study propose a method to predict the bus arrival time by considering the signal delay time which is an element which can not be considered in the current bus arrival prediction information generation algorithm. In order to consider the signal delay time, travel time is divided into three components: service time, cruising travel time, and signal delay time. Signal delay time was estimated using intersection arrival time and TOD. The results show that most of the errors that occurred in predicting the arrival time are within about 30 seconds. Some of the estimates have large errors due to the nature of this methodology that uses the estimated value of the intersection arrival time rather than the observation value. It is also difficult to predict the arrival time of the express buses using this method. Future studies such as improving this through real-time location information will greatly improve the accuracy of the methodology.

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.5 no.2
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• pp.49-60
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• 1987

To decide on the queuing system of the optimum-sized bank window, data by means of simulation was reckoned. That is, by linking the average arrival rate and the average service rate with the exponential random number, customers' arrival time and service time was reckoned and simulation size optionally decided. By so doing, this paper is aimed at predicting the conditions of a bank, average arrival time, average waiting time, aveerage service time, average queuing length, servers' idle time, etd, and at preparing for a simulation model of the queuing system that can apply not only to the bank window box but also to all system under which queuing phenomena may arise.