• Title/Summary/Keyword: active state

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A study on the effects of active suspension upon vehicle handling (능동 현가장치가 차량의 핸들링에 미치는 영향에 관한 연구)

  • Lee, Jung-Sup;Kwon, Hyok-Jo;Oh, Chae-Youn
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.3
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    • pp.603-610
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    • 1998
  • This paper develops a 7 DOF vehicle model to study the effects of the active suspension on ride. The model is used to derive a control law for the active suspension using a full state linear optimal control technique. A wheelbase preview type active suspension is also considered in the control law derivation. The time delay between wheelbases is approximated using Pade approximation technique. The ride model is extended to a 14 DOF handling model. The 14 DOF handling model includes lateral, longitudinal, yaw and four wheel spin motions in addition to the 7 DOF ride model. A control law which is derived considering only ride related parameters is used to study the effects of the active suspension on a vehicle handling. J-turn maneuver simulation results show that the active suspension has a slower response in lateral acceleration and yaw rate, a bigger steady state lateral acceleration and an oversteer tendency. Lane changing maneuver simulation results show that the active suspension has a little bigger lateral acceleration but a much smaller roll angle and roll motion. Braking maneuver simulation results show that the active suspension has a much smaller pitch angle and pitch motion.

Reorganization of Chromatin Conformation from an Active to an Inactive State After Cessation of Transcription

  • Lee, Myeong-Sok
    • Journal of Microbiology
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    • v.34 no.1
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    • pp.54-60
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    • 1996
  • Taking advantage of the heat inducible HSP82 gene in yeast, chromatin structure after transcription cessation was investigated. Alteration of chromating conformation within the HSP82 gene transcription unit into an active state has been shown to correlate with its transcriptional induction. It was thus of interest to examine whether the active chromatin state within the HSP82 mRNA analysis, the gene ceased its transcription within a few hours of cultivation at a normal condition after heat induction. In this condition, an active chromatin conformation in the HSP82 gene body was changed into an inactie state which was revealed by DNase I resistance and by typical nucleosomal cutting periodicity in the corresponding chromatin. These results thus ruled out the possibility of a long-term maintenance of the DNase I sensitive chromatin after transcription cessation. DNA replication may be a critical event for the chromatin reprogramming.

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Technique for Estimating the Number of Active Flows in High-Speed Networks

  • Yi, Sung-Won;Deng, Xidong;Kesidis, George;Das, Chita R.
    • ETRI Journal
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    • v.30 no.2
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    • pp.194-204
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    • 2008
  • The online collection of coarse-grained traffic information, such as the total number of flows, is gaining in importance due to a wide range of applications, such as congestion control and network security. In this paper, we focus on an active queue management scheme called SRED since it estimates the number of active flows and uses the quantity to indicate the level of congestion. However, SRED has several limitations, such as instability in estimating the number of active flows and underestimation of active flows in the presence of non-responsive traffic. We present a Markov model to examine the capability of SRED in estimating the number of flows. We show how the SRED cache hit rate can be used to quantify the number of active flows. We then propose a modified SRED scheme, called hash-based two-level caching (HaTCh), which uses hashing and a two-level caching mechanism to accurately estimate the number of active flows under various workloads. Simulation results indicate that the proposed scheme provides a more accurate estimation of the number of active flows than SRED, stabilizes the estimation with respect to workload fluctuations, and prevents performance degradation by efficiently isolating non-responsive flows.

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A Study on Quasi Resonant Converter with Low Switching Surge Voltage Characteristics by Applying Auxiliary Winding Type Active Snubber (보조 권선형 능동 스너버를 적용하여 낮은 스위치 서지 전압 특성을 갖는 유사 공진형 컨버터에 관한 연구)

  • Ahn, Tae Young
    • Journal of the Semiconductor & Display Technology
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    • v.17 no.4
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    • pp.56-61
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    • 2018
  • In this paper, a new type of active snubber was proposed to lower the excessive rated voltage of the clamp capacitor which was a problem in the conventional circuit by applying auxiliary winding into the active snubber. A simplified equivalent circuit of the proposed snubber was derived by applying it to QR flyback converter, and the equivalent circuits for each switch state was shown under the steady-state condition. In addition, the maximum voltage of the clamp capacitor as well as the main switch was found by using the steady-state equations. In particular, it was found that the clamp capacitor voltage could be controlled by the auxiliary winding ratio. In order to verify the utility and practicality of the proposed converter with auxiliary winding type active snubber circuit, a prototype with an output voltage of 19V and a maximum load current of 6A was produced and the results were reported.

Investigation of the Protonated State of HIV-1 Protease Active Site

  • Nam, Ky-Youb;Chang, Byung-Ha;Han, Cheol-Kyu;Ahn, Soon-Kil;No, Kyoung-Tai
    • Bulletin of the Korean Chemical Society
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    • v.24 no.6
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    • pp.817-823
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    • 2003
  • We have performed ab initio calculation on the active site of HIV-1 protease. The FEP method was used to determine the binding free energy of four different of protonated states of HIV-1 protease with inhibitor. The structure of the active site and hole structure was taken from the X-ray crystallographic coordinates of the C₂ symmetric inhibitor A74704 protease bound. The active site was modeled with the fragment molecules of binding pocket, acetic acid/ acetate anion (Asp25, Asp125), formamide (amide bond of Thr26/Gly27, Thr126/ Gly127), and methanol as inhibitor fragment. All possibly protonated states of the active site were considered, which were diprotonated state (0, 0), monoprotonated (-1, 0),(0, -1) and diunprotonated state (-1, -1). Once the binding energy Debind, of each model was calculated, more probabilistic protonated states can be proposed from binding energy. From ab-initio results, the FEP simulations were performed for the three following mutations: Ⅰ) Asp25 … Asp125 → AspH25 … Asp125, ⅱ) Asp25 … Asp125 → Asp25 … AspH125, ⅲ) AspH25 … Asp125 → AspH25 … AspH125. The free energy difference between the four states gives the information of the more realistic protonated state of active site aspartic acid. These results provide a theoretical prediction of the protonation state of the catalytic aspartic residues for A74707 complex, and may be useful for the evaluation of potential therapeutic targets.

A New Active Zero State PWM Algorithm for Reducing the Number of Switchings

  • Yun, Sang-Won;Baik, Jae-Hyuk;Kim, Dong-Sik;Yoo, Ji-Yoon
    • Journal of Power Electronics
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    • v.17 no.1
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    • pp.88-95
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    • 2017
  • To reduce common-mode voltage (CMV), various reduced CMV pulse width modulation (RCMV-PWM) algorithms have been proposed, including active zero state PWM (AZSPWM) algorithms, remote state PWM (RSPWM) algorithms, and near state PWM (NSPWM) algorithms. Among these algorithms, AZSPWM algorithms can reduce CMV, but they increase the number of switchings compared to the conventional space vector PWM (CSVPWM). This paper presents a new AZSPWM algorithm for reductions in both the CMV and total number of switchings in BLAC motor drives. Since the proposed AZSPWM algorithm uses only active voltage vectors for motor control, it reduces CMV by 1/3 compared to CSVPWM. The proposed AZSPWM algorithm also reduces the total number of switchings compared to existing AZSPWM algorithms by eliminating the switchings required from one sector to the next. The performance of the proposed algorithm is verified by analyses, simulations, and experimental results.

Practical Design Methodology of Dual Active Bridge Converter as Isolated Bi-directional DC-DC Converter for Solid State Transformer (Solid State Transformer를 위한 양방향 Dual Active Bridge DC-DC 컨버터의 설계 기법)

  • Choi, Hyun-Jun;Lee, Won-Bin;Jung, Jee-Hoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.22 no.2
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    • pp.102-108
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    • 2017
  • Proper design guides are proposed for a practical dual-active bridge (DAB) converter based on the mathematical model on the steady state. The DAB converter is popular in bidirectional application due to its zero-voltage capability and easy bidirectional operation for seamless control, high efficiency, and performance. Some design considerations are taken to overcome the limitation of the DAB converter. The practical design methodology of power stage is discussed to minimize the conduction and switching losses of the DAB converter. Small-signal model and frequency response are derived and analyzed based on the generalized average method, which considers equivalent series resistance, to improve the dynamics, stability, and reliability with voltage regulation of the practical DAB converter. The design of closed-loop control is discussed by the derived small-signal model to obtain the pertinent gain and phase margin in steady-state operation. Experimental results of a 3.3 kW prototype of DAB converter demonstrate the validity and effectiveness of the proposed methods.

Stabilized Adaptive Fuzzy LMS Algorithms for Active Noise Control (능동소음제어를 위한 안정화된 퍼지 LMS 알고리즘)

  • Ahn, Dong-Jun;Baek, Kwang-Hyun;Nam, Hyun-Do
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.1
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    • pp.150-155
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    • 2011
  • In an active noise control systems, an IIR filter may cause a problem in stability beacause of its poles. For IIR filter, its poles goes sometimes out of a unit circle in a z-plane in the transition state, where the adaptive algorithm converges to the optimum value, which causes the system to diverge. Fuzzy LMS algorithm has a better convergence property than conventional LMS algorithms, but is not applicable to IIR filter because of the reasons. Stabilized adaptive algorithm could be improves stability by moving the pole of IIR filer toward the origin forcibly in the transient state, and by introducing forgetting factor to maintain the optimum convergence when it reaches to the steady state. In this paper, We proposed stabilized adaptive fuzzy LMS algorithms with IIR filter structures, for single channel active noise control with ill conditioned signal case. Computer simulations were performed to show the effectiveness of a proposed algorithm.

Tracking Control of IPMSM using the Active Disturbance Rejection Control (매입형 영구자석 동기전동기의 능동외란제거제어를 이용한 추종제어)

  • Jeon, Yong-Ho;Chae, Seong-Byeong
    • The Journal of the Korea institute of electronic communication sciences
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    • v.17 no.5
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    • pp.859-866
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    • 2022
  • Active disturbance rejection control is a method in which the disturbance is removed from the controller by estimating the state variable using the Luenberger observer. The Luenberger observer is estimated by defining a nonlinear term including disturbance with constant characteristics in a steady state as a state variable. It can be shown that the speed tracking performance is improved by compensating the estimated state variable to the PI controller and the IP controller. The disturbance removal performance of the tracking control can be confirmed by observing that the estimated state error is within 1.9 [%] in the case of load fluctuation and the steady-state state tracking error converges to zero.

PERFORMANCE ANALYSIS OF A STATISTICAL MULTIPLEXER WITH THREE-STATE BURSTY SOURCES

  • Choi, Bong-Dae;Jung, Yong-Wook
    • Communications of the Korean Mathematical Society
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    • v.14 no.2
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    • pp.405-423
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    • 1999
  • We consider a statistical multiplexer model with finite buffer capacity and finite number of independent identical 3-state bursty voice sources. The burstiness of the sources is modeled by describing both two different active periods (at the rate of one packet perslot) and the passive periods during which no packets are generated. Assuming a mixture of two geometric distributions for active period and a geometric distribution for passive period and geometric distribution for passive period, we derive the recursive algorithm for the probability mass function of the buffer contents (in packets). We also obtain loss probability and the distribution of packet delay. Numerical results show that the system performance deteriorates considerably as the variance of the active period increases. Also, we see that the loss probability of 2-state Markov models is less than that of 3-state Markov models.

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