• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.3049-3051
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• 2005

본 논문은 UWB(Ultra Wide Band) 펄스 기반의 단일 송수신을 통한 근거리 무선측위 시스템 및 방법에 관한 것으로서, UWB 펄스의 높은 시간 분해능을 이용하여 근거리에서 높은 정밀도를 가지고 태그의 위치를 획득할 수 있다. 특히, 마스터-슬레이브 형태로 구성된 비콘(beacon)들 간의 사전 설정을 통해 마스터 비콘과 무선측위 대상인 태그 사이의 단일 송수신만으로 ToA(Time of Arrival) 및 TDoA(Time Difference of Arrival) 기법을 적용할 수 있도록 하며, 이로써 태그의 신호 송신을 최소화하여 태그의 저전력 동작을 가능케하는 UWB기반 단일송수신을 통한 근거리 무선측위 시스템이다.

• Journal of Convergence for Information Technology
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• v.11 no.11
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• pp.17-22
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• 2021

Radar signal analysis of electronic warfare is a technique for identifying a radar type by signal parameters(direction, radion frequency, pulse repetition interval, pulse width, scan period..) extracted from a received radar pulse. However as the modern radar and new threat environments is advanced, radar identification ambiguity arises in the process of identifying the types of radars. In this paper, we analyze the problems of the existing method and propose a new method. This technique determines the validity of the scan period by the difference in the arrival time of the radar pulse and the minimum number of scan period discrimination. Experiments proved that the scan cycle results are derived regardless of the RMS((Root Mean Square) of the input amplitude.

• Communications of the Korean Mathematical Society
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• v.10 no.2
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• pp.443-460
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• 1995

We consider a G/M/1 vacation model where the vacation time has k-stages generalized Erlang distribution. By using the methods of the shift operator and supplementary variable, we explicitly obtain the limiting probabilities of the queue length at arrival time points and arbitrary time points simultaneously. Operational calculus technique is used for solving non-homogeneous difference equations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.28-32
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• 2007

While various methods for sound source localization have been developed, most of them utilize on the time difference of arrival (TDOA) between microphones or the measured head related transfer functions (HRTF). In case of a real robot implementation, the former has a merit of light computation load to estimate the sound direction but can not consider the effect of platform on TDOAs, while the latter can, because characteristics of robot platform are included in HRTF. However, the latter needs large resources for the HRTF database of a specific robot platform. We propose the compensation method which has the light computation load while the effect of platform on TDOA can be taken into account. The proposed method is used with spherical head related transfer function (SHRTF) on the assumption that robot platform, for example a robot head, installed microphones can be modeled to a sphere. We verify that the proposed method decreases the estimation error caused by the robot platform through the simulation and experiment in real environment.

• Ocean and Polar Research
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• v.36 no.3
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• pp.225-234
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• 2014

The 2011 Tohoku earthquake triggered extremely destructive tsunami waves which propagated over the Pacific Ocean, Atlantic Ocean through Drake Passage and Indian Ocean respectively. A total of 10 tide-gauge records collected from the UNESCO/IOC site were analyzed through a band-pass digital filtering device to examine the observed tsunami characteristics. The ray tracing method and finite-difference model with GEBCO 30 arc second bathymetry were also applied to compare the travel times of the Tohoku-originated tsunami, particularly at Rodrigues in the Indian Ocean and King Edward Point in the Atlantic Ocean with observation-based estimates. At both locations the finite-difference model produced the shortest arrival times, while the ray method produced the longest arrival times. Values of the travel time difference however appear to be within tolerable ranges, considering the propagation distance of the tsunami waves. The observed tsunami at Rodrigues, Mauritius in the west of the Madagascar was found to take a clockwise travel path around Australia and New Zealand, while the observed tsunami at King Edward Point in the southern Atlantic Ocean was found to traverse the Pacific Ocean and then passed into the Atlantic Ocean through the Drake Strait. The formation of icebergs captured by satellite images in Sulzberger in the Antarctica also supports the long-range propagation of the Tohoku-originated tsunami.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11C
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• pp.957-964
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• 2010

In this paper, we propose an indoor positioning algorithm based on 3 points near field angle-of-arrival estimation without side information. The conventional angle-of-arrival based positioning scheme requires the distance between the listener and the center of two points which is obtained by a received signal strength based range estimation. However, a received signal strength is affected by structure of room, placement of furniture, and characteristic of signal, these effects cause a large error to estimation of angle. In this paper, the proposed positioning scheme based on near field angle-of-arrival estimation can be used to estimate the position of listener without a prior distance information, just using time-difference-of-arrival information given from 3 points microphones. The performance of the proposed scheme is shown by cumulative distribution function of root mean squared error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1069-1080
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• 2016

TDOA(Time Difference Of Arrival)-based localization system such as the passive surveillance system performs the time synchronization between the receivers after separated installing multiple receivers to set the same clock for all receivers. And it estimates 2D(or 3D) location of the target by solving intersection of the multiple hyperbola(or hyperboloid) using TDOA. To perform time synchronization, one receiver must be set to the master, and it provide the reference data to compensate the clock of the rest of the slaves. The positioning accuracy of TDOA-based localization system is changed in accordance with the master that is selected among multiple receivers. So, the optimum receiver which is selected among multiple receivers must be set to master to get best performance in the considered deployment of receivers. In this paper, we propose a selection scheme of master receiver for time synchronization using DOP(Dilution Of Precision) which is based on location of the target and the multiple receivers. The proposed scheme has low complexity and short processing time, and it is easy to automate in the TDOA-based localization systems.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.383-390
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• 2024

When measuring the radiated noise of an underwater vehicle, the range information between the vehicle and the receiver is an important factor, but since Global Positioning System (GPS) is not available in underwater, an alternative method is needed. As an alternative, the range is measured by estimating the arrival time, arrival time difference, and arrival frequency difference using a separate acoustic signal. However, errors occur due to the channel environment, and these outliers become obstacles in continuously measuring range. In this paper, we propose a method to reduce errors by curve fitting with a function in the form of a V-curve as a post-processing to remove outliers that occurred in the process of measuring range information. Simulation, lake and sea trials were conducted to verify the performance of the proposed method. In the results of the lake trial, the range estimation error was reduced by about 85 % from the Root Mean Square Error (RMSE) point of view.

• Journal of Chest Surgery
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• v.57 no.3
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• pp.272-280
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• 2024

Background: The phenomenon known as the "weekend effect" impacts various medical disciplines. We compared outcomes between regular hours and off hours to investigate the presence of the weekend effect in extracorporeal cardiopulmonary resuscitation (ECPR). Methods: Between January 2018 and December 2020, 159 patients at our center were treated with veno-arterial extracorporeal membrane oxygenation (ECMO) for cardiac arrest. We assessed the time required for ECMO preparation, the rate of successful weaning, and the rate of in-hospital mortality. These factors were compared among regular hours ("daytime": weekdays from 7:00 AM-7:00 PM), off hours on weekdays ("nighttime": weekdays from 7:00 PM-7:00 AM), and off hours on weekends and holidays ("weekend": Fridays at 7:00 PM to Mondays at 7:00 AM). Results: The time from the recognition of cardiac arrest to the arrival of the ECMO team was shortest for the daytime group and longest for those treated over the weekend (daytime, 10.0 minutes; nighttime, 12.5 minutes; weekend, 15.0 minutes; p=0.064). The time from the ECMO team's arrival to ECMO initiation was shortest for the daytime and longest for the nighttime group (daytime, 13.0 minutes; nighttime, 18.5 minutes; weekend, 14.0 minutes; p=0.028). No significant difference was observed in the rate of successful ECMO weaning (daytime, 48.3%; nighttime, 39.5%; weekend, 36.1%; p=0.375). Conclusion: In situations involving CPR, the time to arrival of the ECMO team was longer during off hours. Furthermore, ECMO insertion required more time at night than during the other periods. These findings warrant specific training in decision-making and emergent ECMO insertion.

• Journal of Trauma and Injury
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• v.37 no.2
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• pp.106-113
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• 2024

Purpose: Helicopter transport with medical teams has been proven to be effective, with improvements in patient survival rates. This study compared and analyzed the clinical characteristics and treatment outcomes of trauma patients transported by doctor helicopters according to whether patients were transferred after a clinical evaluation or without a clinical evaluation. Methods: This study retrospectively reviewed data from the Korean Trauma Data Bank of trauma patients who arrived at a regional trauma center through doctor helicopters from January 1, 2014, to December 31, 2022. The patients were divided into two groups: doctor helicopter transport before evaluation (DHTBE) and doctor helicopter transport after evaluation (DHTAE). These groups were compared. Results: The study population included 351 cases. At the time of arrival at the trauma center, the systolic blood pressure was significantly lower in the DHTAE group than in the DHTBE group (P=0.018). The Injury Severity Score was significantly higher in the DHTAE group (P<0.001), and the accident to trauma center arrival time was significantly shorter in the DHTBE group (P<0.001). Mortality did not show a statistically significant between-group difference (P=0.094). Surgical cases in the DHTAE group had a longer time from the accident scene to trauma center arrival (P=0.002). The time from the accident to the operation room or from the accident to angioembolization showed no statistically significant differences. Conclusions: DHTAE was associated with significantly longer transport times to the trauma center, as well as nonstatistically significant trends for delays in receiving surgery and procedures, as well as higher mortality. If severe trauma is suspected, air transport to a trauma center should be requested immediately after a simple screening test (e.g., mechanism of injury, Glasgow Coma Scale, or Focused Assessment with Sonography in Trauma), which may help reduce the time to definitive treatment.