• Journal of electromagnetic engineering and science
• /
• 제18권1호
• /
• pp.20-28
• /
• 2018

The time synchronization of each sub-unit of a pulsed generator is important to generate an output high-power radio frequency (RF) signal. To obtain the time synchronization between an input RF signal fed by an external source and an electron beam produced by an electric pulse generator, the influence of different charging voltages on a delay and a rise time of the output pulse waveform in the electric pulse generator should be carefully considered. This paper aims to study the timing characteristics of the delay and the rise time as a function of different charging voltages with a peak value of less than -35 kV in the high-voltage pulse generator, including a trigger generator (TG) and a pulse-forming line (PFL). The simulation has been carried out to estimate characteristics in the time domain, in addition to their output high-voltage amplitude. Experimental results compared with those obtained by simulation indicate that the delay of the output pulses of the TG and PFL, which are made by controlling the external triggering signal with respect to different charging voltages, is getting longer as the charging voltage is increasing, and their rise times are inversely proportional to the amplitude of the charging voltage.

• 한국통신학회논문지
• /
• 제22권12호
• /
• pp.2635-2643
• /
• 1997

본 논문에서는 다중경로가 가능한 고속망에서 병목을 감소시키며 또한 평균지연을 감소시키는 새로운 경로설정 방법을 제안한다. 기존의 적응균등부하조절 경로설정기법과 경로의 거리에 비례하는 전송지연을 비용을 개념으로 고려하는 경로설정기법이 결합된 이 알고리듬은 계산에 드는 시간이 적고 효율적인 동적 트래픽 할당을 하는 알고리듬이다. 사용자의 트래픽 형태가 바뀜에 따라 각 링크의 전송용량에 비례하면서, 전송지연이 적은 경로로 적절하게 트래픽을 할당하도록 적응성 있게 경로를 설정한다. 그렇게 함으로써 병목을 줄이고 최단 링크의 사용도를 높여 망의 평균지연을 감소시키게된다. 이는 다른 경로설정기법보다 고 품질의 서비스를 사용자에게 제공하는 기반이 된다. 그리고 제안된 알고리듬을 시뮬레이션을 통해서 저부하에서 고부하상태까지 기존의 적응균등부하조절 경로설정기법보다 평균지연이 감소됨을 보인다.

• 한국정보과학회논문지:시스템및이론
• /
• 제36권4호
• /
• pp.291-303
• /
• 2009

라운드 로빈 기반 비례지분 스케줄링(Round Robin based Proportional Share scheduling, RRPS)은 각 태스크에게 지분(share)을 결정하는 비중(weight)이라는 속성을 정의하고 각 태스크의 비중에 비례하여 CPU 자원을 할당한다. 라운드 로빈 기반 비례지분 스케줄링은 공평성(fairness)을 성능의 척도로 사용하며 스케줄링의 높은 공평성을 목표로 한다. 그러나 태스크를 간의 동기화로 인한 스케줄링의 공평성 문제에 대한 연구는 부족하다. 본 논문에서는 라운드 로빈 기반 비례지분 스케줄링에서 동기화로 인한 스케줄링의 지연이 높은 불공평성을 발생시킴을 보인다. 이를 비중역전(weight inversion)이라는 현상으로 설명한다. 다음, 비중역전을 방지하는 동기화 기법인 비중상속 프로토콜(weight inheritance protocol, WIP)을 제안한다. 또한, 공평성분석과 시뮬레이션을 통해 비중상속 프로토콜이 불공평성을 감소시킴을 보인다.

• 대한기계학회논문집A
• /
• 제21권8호
• /
• pp.1229-1240
• /
• 1997

The purpose of this study is to build up control scheme that promptly control pressure in a hydraulic cylinder having comparatively small control volume, using a PCV (proportional control valve) and a digital computer. Object pressure control system has the character to be unstable easily, because the displacement-flow gain of the PCV is too large considering the small volume of the hydraulic cylinder and the time delay of response of the PCV is comparatively long. Considering the above-mentioned characteristics of the object pressure control system, in this study, control system is designed with two degree of freedom control scheme that is composed by adding a feed-forward control path to I-PDD$^{2}$ control system, and a reference model is used on the decision of control parameters. And through some experiments on the control system with FF-I-PDD$^{2}$ controller, the validity of this control method has been confirmed.

• Nuclear Engineering and Technology
• /
• 제55권11호
• /
• pp.4266-4273
• /
• 2023

In a severe reactor accident, a crust will form on the surface of the molten material during the core melting process. The crust will have a contact melting with the internal components of the reactor. In this paper, the contact melting process of the molten material on the austenitic stainless steel plate bundles is studied. The contact melting model of parabolic molten material on the plate bundles is proposed, and the rule and main effect factors of the contact melting are analyzed. The results show that the melting velocity is proportional to the slope of the paraboloid, the heat flux and the distance between two plates D. The influence of melt gravity and the plate width on melting velocity is negligible. The thickness of the molten liquid film is proportional to the heat flux and plate width, and it is inversely proportional to the gravity. With the increase of D, the liquid film thickness decreases at first and then increases gradually. The liquid film thickness has a minimum against D. When the width of the plate is small, the width of the plate is the main factor affecting the thickness of the liquid film. The parameters are coupled with each other. In a severe reactor accident, the wider internal components of reactor, which can increase the thickness of the melting liquid film and reduce the net input heat flux from the molten material to the components, are the effective measures to delay the melting process.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제5권11호
• /
• pp.1946-1958
• /
• 2011

Wireless Sensor Network (WSN) is made up of a number of sensor nodes and base stations. Traffic flow in WSN appears self-similar due to its data delivery process, and this impacts queue length greatly and makes queuing delay worse. Active queue management can be designed to improve QoS performance for WSN. In this paper, we propose self-similar traffic rate estimating algorithm named Power-Law Moving Averaging (PLMA) to regulate packet marking probability. This algorithm improves the availability of the rate estimation algorithm under the self-similar traffic condition. Then, we propose an adaptive Proportional Integral algorithm (SSPI) based on the estimation of the Self-Similar traffic rate by PLMA. Simulation results show that SSPI can achieve lower queue length jitter and smaller setting time than PI.

• Earthquakes and Structures
• /
• 제6권2호
• /
• pp.217-235
• /
• 2014

In this paper, different feedback control strategies are presented for active seismic control using proportional-integral-derivative (PID) type controllers. The parameters of PID controller are found by using an numerical algorithm considering time delay, maximum allowed control force and time domain analyses of shear buildings under different earthquake excitations. The numerical algorithm scans combinations of different controller parameters such as proportional gain ($K_p$), integral time ($T_i$) and derivative time ($T_d$) in order to minimize a defined response of the structure. The controllers for displacement, velocity and acceleration feedback control strategies are tuned for structures with active control at the first story and all stories. The performance and robustness of different feedback controls on time and frequency responses of structures are evaluated. All feedback controls are generally robust for the changing properties of the structure, but acceleration feedback control is the best one for efficiency and stability of control system.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2012년도 추계학술대회 논문집
• /
• pp.636-642
• /
• 2012

Delay-and-sum (DAS) Planar Beamforming has been a widely used Noise Source Identification Technique for the last decade. It is a quick one shot measurement technique being able to map sources that are larger than the array itself. The spatial resolution is proportional to distance between array and source, and inversely proportional to wavelength, thus the resolution is only good at medium to high frequencies. Improved algorithms using iterative de-convolution techniques offers up to ten times better resolution. The principle behind these techniques is described in this paper, as well as measurement examples from the automotive industry are presented.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권3호
• /
• pp.110-120
• /
• 1996

The purpose of this study is to build up the control scheme that promptly controls the pressure in a hydraulic cylinder having small control volume, using a PCV(proportional control valve) and a digital computer. Object pressure control system has the character to be unstable easily, because the displacement-flow gain of the PCV is so large considering comparatively small volume of the hydraulic cylinder and the time delay of response of PCV is long. Considering the above-mentioned characteristics of the object pressure control system, in this study, a control system is designed with two degree of freedom scheme that is composed by adding a feed-forward control path to I-PD control system, and the reference model is used to decide control parameters. And through some experiments on FF-I-PD, the validity of this control method is confirmed.

• 한국산학기술학회논문지
• /
• 제18권1호
• /
• pp.572-578
• /
• 2017

사용자가 원격으로 가상환경에 접속하여 가상물체를 조작할 때 현실감을 증강시키기 위해서 햅틱 시스템이 사용된다. 그러나 원격 시스템 환경에는 통신시간지연이 발생하며, 발생된 통신시간지연은 햅틱 시스템을 불안정하게 만들 수 있다. 본 논문에서는 종래의 샘플-홀드 방식인 영차홀드 (ZOH; Zero-Order-Hold)가 아닌 일차홀드 (FOH; First-Order-Hold)를 포함하는 햅틱 시스템에서 시뮬레이션을 통해 통신시간지연과 햅틱 장치의 물성치 변화에 따른 가상 스프링상수의 안정성 영역을 분석하고 이를 통해 안정적인 햅틱 시스템을 구현하고자 한다. 통신시간지연이 없으면 일차홀드 (FOH) 방식이 영차홀드(ZOH) 방식보다 가상 스프링상수의 안정성 영역을 증가시킬 수 있었다. 그러나 통신시간지연이 증가하면, 샘플-홀드 방식보다 통신시간지연이 시스템 안정성에 더 큰 영향을 끼치므로, 샘플-홀드 방식에 따른 가상 스프링상수의 안정성 영역 크기에는 차이가 없어진다. 또한 통신시간지연과 일차홀드 방식이 포함되면 가상 스프링상수의 안정성 영역은 통신시간지연 크기에 반비례하고, 햅틱 장치의 댐핑상수 ($B_d$)에 정비례하여 증가하지만, 햅틱 장치의 질량 ($M_d$)에는 영향받지 않음을 알 수 있었다.