• 정보처리학회논문지C
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• 제11C권6호
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• pp.799-806
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• 2004

근래에 인터넷 등의 네트워크를 통해 어떤 정보에 접근할 수 있는 다양한 클라이언트 장치들이 널리 보급되고 있다. 하지만 통신능력이나 처리 및 저장능력, 화면표시 능력 등 여러 가지 제약을 가진 클라이언트 장치들로서는 방대한 양의 멀티미디어 콘텐츠를 쉽게 처리할 수 없는 문제가 있다. 또한 네트워크 측면에서도 음성, 데이터 및 비디오의 통합 서비스는 네트워크 기술의 목표를 수정하게 되어 네트워크가 다양한 서비스의 종합 제공 능력과 각 서비스에 필요한 QoS를 제공할 수 있는 능력을 가져야 하게 되었다. 이러한 이유로 ATM망과 인터넷 사이에 중단없는 멀티미디어 서비스를 제공할 수 있는 EAGIS(Efficient ATM Gateway for real time Internet Service)를 개발하게 되었다. EAGIS는 연동장치, 콘텐츠 서버, 트랜스코딩 서버, 서비스 브로커로 구성된다. 본 논문에서는 EAGIS의 구조 설계와 트랜스코딩 서비스 제공 방식을 설계하였다. RTP(Real Time Protocol)를 이용한 양방향 통신은 RTCP(Real Time Control Protocol)의 시각-소인(time-stamp)에 의하여 트랜스코딩 시간을 설정하며, HTTP를 이용한 단방향 통신은 셀프타이며(self-timer)를 이용한다. 이러한 기준 시간을 이용함으로써 네트워크 트래픽 부하와 프레임 전송률에 의한 표준화된 트랜스코딩 방법을 적용할 수 있었다. 또한 다중 사용자 유효 대역폭 확보 알고리즘을 통한 서비스의 품질을 보장할 수 있었다.

• 대한기계학회논문집 C: 기술과 교육
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• 제4권1호
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• pp.3-10
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• 2016

국내 히트펌프 유닛에 대한 성능 기준은 KS C 9306에서 제시하는 표준조건에서의 COP로 표현된다. 그러나 히트펌프 시스템이 실제 건물에 적용될 경우에는 표준조건에서 운전되는 것이 아니기 때문에 현장의 기후 조건, 건물의 특성에 따라 히트펌프 시스템의 성능은 다르게 나타난다. 본 논문에서는 주거건물을 대상으로 국내 주요 도시의 기후 조건에 따른 공기 대 공기 히트펌프 시스템의 연성능을 평가하여 기존의 BIN 데이터를 활용한 연성능 평가 결과와 정량적으로 비교 분석하였다. 연성능 평가도구로는 IPMVP 4.4.2에서 제시한 국제호환형 프로그램인 TRNSYS를 사용하였다. 공기 대 공기 히트펌프 유닛의 멀티 성능 데이터를 적용한 경우, 연성능 평가 기준인 APF는 BIN 데이터를 적용했을 때보다 전체적으로 높았으며, 부산이 2.36으로 가장 높았고, 대전이 2.29로 가장 낮았다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1705-1711
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• 1991

On-line fault detection and diagnosis has an increasing interest in a chemical process industry, especially for a process control and automation. The chemical process needs an intelligent operation-aided workstation which can do such tasks as process monitoring, fault detection, fault diagnosis and action guidance in semiautomatic mode. These tasks can increase the performance of a process operation and give merits in economics, safety and reliability. Aiming these tasks, series of researches have been done in our lab. Main results from these researches are building appropriate knowledge representation models and a diagnosis mechanism for fault detection and diagnosis in a chemical process. The knowledge representation schemes developed in our previous research, the symptom tree model and the fault-consequence digraph, showed the effectiveness and the usefulness in a real-time application, of the process diagnosis, especially in large and complex plants. However in our previous approach, the diagnosis speed is its demerit in spite of its merits of high resolution, mainly due to using two knowledge models complementarily. In our current study, new knowledge representation scheme is developed which integrates the previous two knowledge models, the symptom tree and the fault-consequence digraph, into one. This new model is constructed using a material balance, energy balance, momentum balance and equipment constraints. Controller related constraints are included in this new model, which possesses merits of the two previous models. This new integrated model will be tested and verified by the real-time application in a BTX process or a crude unit process. The reliability and flexibility will be greatly enhanced compared to the previous model in spite of the low diagnosis speed. Nexpert Object for the expert system shell and SUN4 workstation for the hardware platform are used. TCP/IP for a communication protocol and interfacing to a dynamic simulator, SPEEDUP, for a dynamic data generation are being studied.

• Child Health Nursing Research
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• 제26권2호
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• pp.212-221
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• 2020

Purpose: Nursing protocols for glucose management are well known for both healthy term newborns and high-risk newborns. However, for less risky newborns who are under only observation surveillance, hypoglycemia could be overlooked unless clinical symptoms develop. Methods: A retrospective study was performed to explore factors influencing variations in glucose levels in 91 newborns who did not require any interventions, but were under nursing surveillance, at a level II neonatal intensive care unit. Data were retrieved from electrical medical records on glucose levels, demographic characteristics, and other clinical characteristics of newborns in their first day of life from January 2016 to May 2019. Results: Glucose levels tended to stabilize within the normal range (60~80 mg/dL) as time passed during the first day of life. Cesarean section, multiple gestation, abnormal growth, and later preterm birth were associated with low glucose levels in the first 2 hours of life. Thirty-one newborns experienced a hypoglycemic episode (< 45 mg/dL) during the first 24 hours of life. Conclusion: The findings of this study support the active encouragement of early feeding within 2 hours of birth and urgent adoption of a structural protocol for glucose surveillance in newborns with potential health problems immediately after birth.

• Journal of Korean Neurosurgical Society
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• 제54권3호
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• pp.159-163
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• 2013

Objective : Cerebral hyperperfusion syndrome (CHS) is a serious complication after carotid endarterectomy (CEA). However, the prevalence of CHS has decreased as techniques have improved. This study evaluates the role of strict blood pressure (BP) control for the prevention of CHS. Methods : All 18 patients who received CEA from February 2009 through November 2012 were retrospectively reviewed. All patients were routinely managed in an intensive care unit by a same protocol. The cerebral perfusion state was evaluated on the basis of the regional cerebral blood flow (rCBF) study by perfusion computed tomography (pCT) and mean velocity by transcranial doppler (TCD). BP was strictly controlled (<140/90 mm Hg) for 7 days. When either post-CEA hyperperfusion (>100% increase in the rCBF by pCT or in the mean velocity by TCD compared with preoperative values) or CHS was detected, BP was maintained below 120/80 mm Hg. Results : TCD and pCT data on the patients were analyzed. Ipsilateral rCBF was significantly increased after CEA in the pCT (p=0.049). Post-CEA hyperperfusion was observed in 3 patients (18.7%) in the pCT and 2 patients (12.5%) in the TCD study. No patients developed clinical CHS for one month after CEA. Furthermore, no patients developed additional neurological deficits related to postoperative cerebrovascular complications. Conclusion : Intensive care with strict BP control (<140/90 mm Hg) achieved a low prevalence of post-CEA hyperperfusion and prevented CHS. This study suggests that intensive care with strict BP control can prevent the prevalence of post-CEA CHS.

• Child Health Nursing Research
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• 제10권1호
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• pp.5-13
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• 2004

Purpose: The aim of this study was to analyze the correlation of gestational age and birth weight with weight gain of very low birth weight infants(VLBWI) during their hospital stay. Method: This is a 5 year retrospective study of which data were collected through review of medical records. Subjects were 124 VLBW infants with a birth weight more than 1000g and less than 1500g who received neonatal intensive care at the university hospital between January 1, 1997 to December 31, 2001. Result: After calculating the z scores of birth weights and discharge weights, z scores of discharge weight and birth weight were compared with the median weight of a fetus of comparable gestational age based on an intrauterine growth reference. There was a significant difference between z scores of birth weight and discharge weight(t=11.60, df=122, p=0.000). Regardless of intensive care during the prolonged hospital stay, VLBW infants showed slow growth rate compared with the median weight of a fetus of comparable gestational age. Conclusion: VLBW infants developed a poor velocity of weight gain during the prolonged hospital stay after birth. The development worsened during the period of physiological weight loss and regain, and they did not reach to comparable growth rate of normal fetus even at the time of discharge. This poor growth velocity of VLBW infants influence negatively for their future growth. Therefore nureses who work at the neonatal intensive care unit must develop an effective nursing intervention protocol to promote the velocity of weight gain and to conduct the parental educational sessions to emphasize the importance of weight gain for VLBW infants at home.

• 한국기후변화학회지
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• 제4권4호
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• pp.385-395
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• 2013

본 논문에서는 이동성이 용이한 스마트기기에서 웨비게이션(Weavigation) 서비스를 이용할 수 있도록 기상플랫폼 및 서비스 구현을 목표로 한다. 기존에 개발된 TPEG(Transport Protocol Expert Group) 기반의 웨비게이션 서비스는 전용 단말의 필요, DMB 통신방식 및 서비스 확장성 등에서 한계가 존재한다. 본 논문에서는 일반 사용자의 스마트기기 내비게이션에 적합한 실시간 기상정보를 분석, 가공, 저장, 제공할 수 있는 표준화된 "웨비게이션용 기상정보 제공 플랫폼"을 개발하였으며, 또한 범용 스마트기기에서 Open API를 사용하여 쉽게 다양한 서비스 개발이 가능하도록 웨비게이션용 Open API 개발과 이를 활용한 웨비게이션 서비스를 구현하여 자연재해 위험지구 정보를 이용한 위험구간 예측정보 안내서비스 연구 결과를 소개한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권4호
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• pp.1293-1316
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• 2021

Using directional antennas in wireless Ad hoc networks has many superiorities, including reducing interference, extending transmission range, and increasing space division multiplexing. However, directional transmission introduces two problems: deafness and directional hidden terminals problems. We observe that these problems result in saturation throughput disparity among the competing flows in directional CSMA/CA based Ad hoc networks and bring challenges for modeling the saturation throughput of the flows. In this article, we concentrate on how to model and analyze the saturation throughput disparity of different flows in directional CSMA/CA based Ad hoc networks. We first divide the collisions occurring in the transmission process into directional instantaneous collisions and directional persistent collisions. Then we propose a four-dimensional Markov chain to analyze the transmission state for a specific node. Our model has three different kinds of processes, namely back-off process, transmission process and freezing process. Each process contains a certain amount of continuous time slots which is defined as the basic time unit of the directional CSMA/CA protocols and the time length of each slot is fixed. We characterize the collision probabilities of the node by the one-step transition probability matrix in our Markov chain model. Accordingly, we can finally deduce the saturation throughput for each directional data stream and evaluate saturation throughput disparity for a given network topology. Finally, we verify the accuracy of our model by comparing the deviation of analytical results and simulation results.

• 한국의학물리학회지:의학물리
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• 제29권3호
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• pp.92-100
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• 2018

The manufacturer of a linear accelerator (LINAC) has reported that the target melting phenomenon could be caused by a non-recommended output setting and the excessive use of monitor unit (MU) with intensity-modulated radiation therapy (IMRT). Due to these reasons, we observed an unexpected beam interruption during the treatment of a patient in our institution. The target status was inspected and a replacement of the target was determined. After the target replacement, the beam profile was adjusted to the machine commissioning beam data, and the absolute doses-to-water for 6 MV and 10 MV photon beams were calibrated according to American Association of Physicists in Medicine (AAPM) Task Group (TG)-51 protocol. To verify the beam data after target replacement, the beam flatness, symmetry, output factor, and percent depth dose (PDD) were measured and compared with the commissioning data. The difference between the referenced and measured data for flatness and symmetry exhibited a coincidence within 0.3% for both 6 MV and 10 MV, and the difference of the PDD at 10 cm depth ($PDD_{10}$) was also within 0.3% for both photon energies. Also, patient-specific quality assurances (QAs) were performed with gamma analysis using a 2-D diode and ion chamber array detector for eight patients. The average gamma passing rates for all patients for the relative dose distribution was $99.1%{\pm}1.0%$, and those for absolute dose distribution was $97.2%{\pm}2.7%$, which means the gamma analysis results were all clinically acceptable. In this study, we recommend that the beam characteristics, such as beam profile, depth dose, and output factors, should be examined. Further, patient-specific QAs should be performed to verify the changes in the overall beam delivery system when a target replacement is inevitable; although it is more important to check the beam output in a daily routine.

• 한국멀티미디어학회논문지
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• 제12권8호
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• pp.1109-1119
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• 2009

최근 무선 인터넷 수요의 증가와 더불어 WLAN의 표준화 작업도 활발히 진행 중이다. IEEE 802.11e에서 통신 품질 보장과 함께 데이터 전송속도가 54Mbps 이상의 성능을 보이고 있지만 아직까지 사용자들의 요구에 부응하지 못하고 있는 것이 현실이다. IEEE802.11e다음 버전인 IEEE 802.11n의 연구 동향은 크게 두 가지로 MAC 계층에서 패킷 간의 Aggregation을 통하여 시스템 처리량을 높인 결과와 PHY 계층에서 MIMO 시스템을 적용하여 데이터 전송속도를 높인 결과로 정리될 수 있다. 그러나 아직까지 MAC 계층과 PHY 계층의 연동을 고려하여 IEEE 802.11n의 성능 분석을 보인 결과는 발표되지 않았다. 그래서 본 논문에서는 IEEE 802.11n 시스템에서 MAC계층과 PHY 계층의 연동을 고려하여 성능을 분석한다. MAC 계층에서의 A-MPDU 기반 하에 PHY 계층에서 MIMO 방식을 적용한다. MIMO 방식은 실내용 WLAN MIMO TGn 채널 모델의 사용과 함께 SVD 기법을 적용하여 분석하였고, 결과적으로 기존의 방식에 비해 데이터 전송속도의 증가와 처리량이 향상되었음을 보인다. 또한, MAC과 PHY의 연동을 고려하여 현실성 있는 시뮬레이터인 Ns-2를 사용하기로 한다.