• The Korean Journal of Pain
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• 제26권3호
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• pp.270-276
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• 2013

Background: Ketamine, an N-methyl-D-aspartate receptor antagonist, might play a role in postoperative analgesia, but its effect on postoperative pain after caesarean section varies with study design. We investigated whether the preemptive administration of low-dose intravenous ketamine decreases postoperative opioid requirement and postoperative pain in parturients receiving intravenous fentanyl with patient-controlled analgesia (PCA) following caesarean section. Methods: Spinal anesthesia was performed in 40 parturients scheduled for elective caesarean section. Patients in the ketamine group received a 0.5 mg/kg ketamine bolus intravenously followed by 0.25 mg/kg/h continuous infusion during the operation. The control group received the same volume of normal saline. Immediately after surgery, the patients were connected to a PCA device set to deliver 25-${\mu}g$ fentanyl as an intravenous bolus with a 15-min lockout interval and no continuous dose. Postoperative pain was assessed using the cumulative dose of fentanyl and visual analog scale (VAS) scores at 2, 6, 24, and 48 h postoperatively. Results: Significantly less fentanyl was used in the ketamine group 2 h after surgery (P = 0.033), but the difference was not significant at 6, 12, and 24 h postoperatively. No significant differences were observed between the VAS scores of the two groups at 2, 6, 12, and 24 h postoperatively. Conclusions: Intraoperative low-dose ketamine did not have a preemptive analgesic effect and was not effective as an adjuvant to decrease opioid requirement or postoperative pain score in parturients receiving intravenous PCA with fentanyl after caesarean section.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2901-2907
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• 1996

Flatness of cold rolled strip is vital to the quality of the product and productivity of the mill. Therefore, in recent year requirement for flatness control in strip rolling have become increasingly severe. The necessity for more accurate automatic gauge control and automatic flatness control(AFC) has increased by customer's requirement for cold rolled steel sheets with thinner gauge and better flatness quality. In this paper, the performance and functions of AFC system installed on the 4 hi-reversing mill has been investigated under actual conditions. The test results are as follows : The more strip thickness is thick, the smaller the I-value. The I-value is a strain measured by stressometer. Complex distributions of strip tension are controlled to remove not only a quarter buckle but also a simple center wave and edge wave. The defects caused by poor flatness have been drastically decreased. And a proper coolant temperature for work roll cooling system on the AFC system is about $50~55^{\circ}C$.

• 대한임베디드공학회논문지
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• 제10권5호
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• pp.297-305
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• 2015

AFLS (Adaptive front lighting System) is being applied to improve safety in driving automotive at night. Safe embedded system for controlling head-lamp has to be tightly designed by considering safety requirement of hardware-dependent software, which is embedded in automotive ECU(Electronic Control Unit) hardware under severe environmental noise. In this paper, we propose an adaptive headlight controller with newly-designed symmetric angle sensor compensator, which is integrated with ECU-based adaptive front light system. The proposed system, on which additional backup hardware and emergency control algorithm are integrated, effectively detects abnormal situation and restore safe status of controlling the light-angle in AFLS operations by comparing result in symmetric angle sensor. The controlled angle value is traced into internal memory in runtime and will be continuously compared with the pre-defined lookup table (LUT) with symmetric angle value, which is used in normal operation. The watch-dog concept, which is based on using angle sensor and control-value tracer, enables quick response to restore safe light-controlling state by performing the backup sequence in emergency situation.

• 대한전자공학회논문지SD
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• 제48권12호
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• pp.73-81
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• 2011

초고속 디지털 통신시스템의 성능은 빠른 에지율(edge rate), 클럭속도 및 디지털 정보전송방법 등에 영향을 받는다. 특히 고주파 통신시스템의 잡음원은 다수 전송선에서의 신호 간 동시 스위칭, 전원 공급, 신호 반사와 왜곡 등에 의해 발생하며, 다층(multilayer) PCB를 설계할 경우 신호의 충실성이 더욱 훼손된다. 따라서 시스템 H/W의 신호충실성을 얻기 위해 최적 임피던스 정합을 갖는 PCB 설계가 필요하다. 본 논문에서는 시스템 신호의 충실성을 위하여 다층 PCB 선로의 패턴에 따른 트랙계산 이론, 설계에 필요한 임피던스 및 특성 자동 분석 시뮬레이터를 개발한다. 특히 다층으로 PCB를 설계할 때 신호선과 접지부분 배치를 사전에 컴퓨터 모의실험을 통하여 최적조건의 임피던스에 맞는 설계가 가능하도록 시뮬레이터를 개발함은 물론 이를 데이터베이스화한다. 그리하여 제안된 시뮬레이션 툴은 PCB 설계 시 소요되는 시간을 단축하고 경제적인 PCB 개발을 가능케 한다.

• Journal of Communications and Networks
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• 제5권1호
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• pp.73-81
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• 2003

The controlled load service defined within the IETF's Integrated Services architecture for quality-of-service (QoS) in the Internet requires source nodes to regulate their traffic while the network, in combination with an admission control strategy, provides a guarantee of performance equivalent to that achieved in a lightly loaded network. Packets sent in violation of the traffic contract are marked so that the network may assign them a lower priority in the use of bandwidth and buffer resources. In this paper, we define the requirements of a scheduler serving packets belonging to the controlled load service and present a novel scheduler that exactly achieves these requirements. In this set of requirements, besides efficiency and throughput, we include an additional important requirement to bound the additional delay of unmarked packets caused due to the transmission of marked packets while dropping as few marked packets as possible. Without such a bound, unmarked packets that are in compliance with the traffic contract are not likely to experience delays consistent with that in al lightly loaded network. For any given desired bound ${\alpha}$ on this additional delay, we present the CL(${\alpha}$) scheduler which achieves the bound while also achieving a per-packet work complexity of O(1) with respect to the number of flows. We provide an analytical proof of these properties of the CL(${\alpha}$) scheduler, and we also verify this with simulation using real traces of video traffic. The scheduler presented here may be readily adapted for use in scheduling flows with multi-level priorities such as in some real-time video streams, as well as in other emerging service models of the Internet that mark packets to identify drop precedences.

• 한국통신학회논문지
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• 제21권12호
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• pp.3215-3226
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• 1996

In this paper a K-band harmonic oscillator competitive to ordinary Push-Push type oscillators is introduced. This oscillator is composed of two-X-band dielectric resonance circuits. To favor its harmonic generation, the load effect and the bias effect are studied to allow the maximum harmonic distortion. As results, the dielectric resonated load and the class A bias are used for the 2nd harmonic generation. analytical study for modelling of voltage controlled dielectric resonator is carried out with theoretical background. The performance of the circuit is evaluated by simulation using harmonic balanced method. The novel structure has ont only a voltage tuning circuit but also an output port at fundamental frequency as the function of prescaler for phase lockede loop application on the just single oscillation structure. In experimentation, the output freqneyc of the 2nd harmonic signal is 20.5GHz and the maximum power level of output is +5.5dBm without additional post amplifiers. the harmonic oscillator exhibits -30dBc of high fundamental frequency rejection without added extra filters. The phase noise of -90dBc/Hz at 100kHz off-carrier has been achieved under free running condition, that satisfies phase noise requirement of IESS 308. The proposed oscillator may be utilized as the clean and stable fixed local oscillator in Transmit Block Upconvertor(TBU) or Low oise Block downconvertor(LNB) for K/Ka-band digital communications and satellite broadcastings.

• International Journal of Ocean System Engineering
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• 제1권4호
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• pp.205-210
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• 2011

High data-rate underwater communications is demanded. This demand imposes stringent requirements on underwater communication equipment of phase-locked-loop (PLL). Phase noise in PLL is unwanted and unavoidable. In this paper, we investigate the PLL phase noise effect on high order QAM for underwater communication systems. The phase noise model using power spectral density is adopted for performance evaluation. The phase noise components considered in PLL are reference oscillator, voltage controlled oscillator (VCO), filter and divider. The filters in PLL noise are assumed to be second order active and passive low pass filters. Through simulation, we analyze the phase noise characteristics of the four components and then investigate the performance improvement factor of each component. Consequently, we derive specifications of VCO, phase detector, divider to meet performance requirement of high data-rate communication using QAM under phase noise influence.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.867-872
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• 2002

A high intensity acoustic test facility is constructed at Korea Aerospace Research Institute (KARI) by 2003. The reverberant chamber of the facility has a volume of 1,228 cubic meters and shall provide an acoustic environment of 152 dB over the frequency range of 25 Hz to 10,000 Hz. The facility consists of a large scaled reverberant chamber, acoustic power generation systems, gases nitrogen supply systems, and acoustic control systems. This paper describes how the basic parameters of a chamber and power generation systems are controlled to meet the requirement of the test. The volume of a reverberant chamber is controlled by the size of test objects and the reverberant characteristics of a chamber. The capacity of acoustic power generation systems is determined by the energy absorption of a chamber and the efficiency of acoustic modulators. Simple math is employed to calculate the required power of acoustic modulators. Moreover, the paper explains how the distribution of sound pressure level at low frequency is checked by analytical and numerical methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.285-287
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• 2001

To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권2호
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• pp.69-76
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• 2002

To obtain a high performance in a vector controlled induction motor, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantage with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations and experimentals.