• 한국인터넷방송통신학회논문지
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• 제13권5호
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• pp.85-91
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• 2013

실내에서의 위치기반 서비스 및 상황인식 서비스를 위해서는 실내에서의 정밀한 위치인식 기술이 필수적이다. 신호원과 여러 개의 신호 수신기와의 거리 차이를 이용하여 신호원의 상대위치를 추정하는 TDOA(Time Difference of Arrival) 기술이 사용되고 있는데, 거리 차이 측정의 오차에 따른 위치 추정 오차가 발생하므로 이를 최소화하기 위한 연구가 많이 진행되어 왔다. 본 논문에서는 신호원과의 거리 차이값을 이용하여 계산된 여러 근중에서 실제의 근을 선별하고 이를 평균내어 신호원의 위치를 추정하는 알고리즘이 제안되었으며, 기존의 방법에 비해 오차가 개선되었다.

• 한국환경과학회지
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• 제17권11호
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• pp.1295-1305
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• 2008

This study aims at the analyze of unsteady downstream flow due to dam failure along dam failure scenario and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-RAS simulation model. The boundary conditions of this unsteady flow simulation are that dam failure arrival time could be at 02:45 a.m. August 1st 1999 and failure duration time could be also 30 minutes. Downstream 19.5 km from dam site was simulated for unsteady flow analysis in terms of dam failure and non-failure cases. For the parameter calibration, observed data of Jeonkok station were used and roughness coefficient was applied to simulation model. The result of the peak discharge difference was 2,696 to $1,745\;m^3/sec$ along the downstream between dam failure and non-failure and also peak elevation of water level showed meanly 0.6m difference. Those results of these studies show that dam failure scenarios for the unknown failure time and duration were rational because most results were coincident with observed records. And also those results and procedure could suggest how and when dam failure occurs and downstream unsteady flow analyzes.

• 한국통신학회논문지
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• 제28권6B호
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• pp.544-552
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• 2003

본 논문에서는 단일 채널에서 동작하는 무선인식 시스템에서 다수의 트랜스폰더가 접근할 때 데이터 충돌을 방지 할 수 있는 명령 코드 충족 알고리즘을 제안하였다. 기존에 사용되고 있는 시간 영역 방법에서는 무조건 충돌을 발생시키지만, 명령 코드 충족 알고리즘은 명령 코드를 충족해야만 데이터를 송신할 수 있게 구현함으로써 데이터 충돌을 방지하였다. 만약 트랜스폰더에서 데이터를 송신하는 중 또 다른 트랜스폰더가 데이터를 송신한다 면 인식거리의 차이에 의해서 데이터 도착속도가 틀려짐을 이용하여 원하는 데이터만 수신할 수 있게 하였다. 제안된 명령 코드 충족 알고리즘을 적용하기 위하여 13.56MHz대역의 무선인식 시스템을 제작하여 1비트 데이터 전송 시간인 14$\mu\textrm{s}$ 차이를 확보함으로써 데이터 충돌 방지하고 그로인한 데이터 손실이 방지됨을 실험을 통하여 입증하였다.

• Journal of Korean Neurosurgical Society
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• 제62권2호
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• pp.232-242
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• 2019

Objective : To investigate the effects of trauma center establishment on the clinical characteristics and outcomes of trauma patients with traumatic brain injury (TBI). Methods : We enrolled 322 patients with severe trauma and TBI from January 2015 to December 2016. Clinical factors, indexes, and outcomes were compared before and after trauma center establishment (September 2015). The outcome was the Glasgow outcome scale classification at 3 months post-trauma. Results : Of the 322 patients, 120 (37.3%) and 202 (62.7%) were admitted before and after trauma center establishment, respectively. The two groups were significantly different in age (p=0.038), the trauma location within the city (p=0.010), the proportion of intensive care unit (ICU) admissions (p=0.001), and the emergency room stay time (p<0.001). Mortality occurred in 37 patients (11.5%). Although the preventable death rate decreased from before to after center establishment (23.1% vs. 12.5%), the difference was not significant. None of the clinical factors, indexes, or outcomes were different from before to after center establishment for patients with severe TBI (Glasgow coma scale score ${\leq}8$). However, the proportion of inter-hospital transfers increased and the time to emergency room arrival was longer in both the entire cohort and patients with severe TBI after versus before trauma center establishment. Conclusion : We confirmed that for patients with severe trauma and TBI, establishing a trauma center increased the proportion of ICU admissions and decreased the emergency room stay time and preventable death rate. However, management strategies for handling the high proportion of inter-hospital transfers and long times to emergency room arrival will be necessary.

• 중환자간호학회지
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• 제13권2호
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• pp.12-23
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• 2020

Purpose : This study aimed to evaluate the clinical outcomes of direct interhospital transfers (IHTs) of patients with acute aortic syndrome (AAS) led by advanced practice nurses (APNs). Methods : From September 2014 to June 2017, the study retrospectively investigated 183 patients with AAS who were transferred to a high-volume tertiary hospital. Results : One hundred forty-eight (81%) patients were admitted through direct IHTs, and 35 (19%) patients were admitted through non-direct IHTs. The direct IHT group had a significantly shorter time from symptom onset to hospital arrival than the non-direct IHT group (11.4 vs. 32.1 h, p=.043). There were no significant differences in other clinical outcomes, such as peri-transfer status, mortality, hospital length of stay, and readmission, between the two groups. In the direct IHT group, 55% of transfers were led by APNs. There was no significant difference in outcomes between APN- and physician-led transfers. Conclusions : Implementation of direct IHTs markedly shortened the time from symptom onset to hospital arrival in patients with AAS. Finally, direct IHTs can potentially improve the outcomes of patients with AAS, a condition with time-dependent mortality and morbidity. In addition, APNs can effectively lead the direct IHT of patients with AAS.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.89-96
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• 2016

TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.

• 한국경영과학회지
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• 제37권4호
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• pp.73-93
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• 2012

In recent years, service delivery systems employing a self-service approach have been rapidly spreading. Since a self-service system provides a lower product price, it attracts more customers. However, some system managers are still hesitant to accept a self-service system, because there is no systematic model to predict its performance. Therefore, this research attempts to provide a systematic and quantitative model to predict the performance of a self-service system, focused specifically on a self-service gas station. Under this model, the traditional queuing theory was adopted to describe the general self-service process, but it is also assumed that some changes occur in both the customer arrival rate and the service performance rate. In particular, the price elasticity was introduced to capture the change in the customer arrival rate, and the existence of learning effect and helpers were assumed to design the changed service performance rate. Under these assumptions, a simulation model for a self-service gas station is established, and three performance measurements, such as average number of customers, average waiting time, and Utilization are observed, depending on the changes in price difference and helper-operating time. In this research, the optimal operation strategy for price differentiation and helper-operating time is proposed in accordance with the level of the customer learning rate. Although this research confines the scope of the study to the self-service gas station model, the results of this research can be applied to any type of self-service system.

• 한국군사과학기술학회지
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• 제19권1호
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• pp.9-15
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• 2016

Source localization has developed in various fields of signal processing including radar, sonar, and wireless communication, etc. Source localization can be found by estimating the time difference of arrival between the each of sensors. Several methods like the NLS(Nonlinear Least Square) cost function have been proposed in order to improve the performance of time delay estimation. In this paper, we propose a clustering method using the four sensors with the same aperture as previous methods of using the three sensors. Clustering method can be improved the source localization performance by grouping similar estimated values. The performance of source localization using clustering method is evaluated by Monte Carlo simulation.

• Journal of Information Technology Applications and Management
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• 제23권3호
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• pp.87-97
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• 2016

This paper proposes a fast sound source localization method using a TDOA sign-based algorithm. We present an L-shaped microphone set-up which creates four major regions in the range of $0^{\circ}{\sim}360^{\circ}$ by the intersection of the positive and negative regions of the individual microphone pairs. Then, we make an initial source region prediction based on the signs of two TDOA estimates before computing the azimuth value. Also, we apply a threshold and angle comparison to tackle the existing front-back confusion problem. Our experimental results show that the proposed method is comparable in accuracy to previous three microphone array methods; however, it takes a shorter computation time because we compute only two TDOA values.

• 제어로봇시스템학회논문지
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• 제18권10호
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• pp.947-954
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• 2012

Sand scorpions are nocturnal animals to mostly use tactile senses to detect their prey. It has been reported that sand scorpions have high vibration sensitivity for their prey-localizing behavior. We tested vibration experiments in the sand with microphone sensors to model the sand scorpion's behavior and a time-difference model was applied to find the direction of a vibration source. Using the information of the arrival time of the vibration signal to reach each leg position, we can find the location of the vibration source.