• 제목/요약/키워드: State-Space

검색결과 3,303건 처리시간 0.043초

Rovibrational Energy Transitions and Coupled Chemical Reaction Modeling of H+H2 and He+H2 in DSMC

  • Kim, Jae Gang
    • International Journal of Aeronautical and Space Sciences
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    • 제16권3호
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    • pp.347-359
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    • 2015
  • A method of describing the rovibrational energy transitions and coupled chemical reactions in the direct simulation Monte Carlo (DSMC) calculations is constructed for $H(^2S)+H_2(X^1{\Sigma}_g)$ and $He(^1S)+H_2(X^1{\Sigma}_g)$. First, the state-specific total cross sections for each rovibrational states are proposed to describe the state-resolved elastic collisions. The state-resolved method is constructed to describe the rotational-vibrational-translational (RVT) energy transitions and coupled chemical reactions by these state-specific total cross sections and the rovibrational state-to-state transition cross sections of bound-bound and bound-free transitions. The RVT energy transitions and coupled chemical reactions are calculated by the state-resolved method in various heat bath conditions without relying on a macroscopic properties and phenomenological models of the DSMC. In nonequilibrium heat bath calculations, the state-resolved method are validated with those of the master equation calculations and the existing shock-tube experimental data. In bound-free transitions, the parameters of the existing chemical reaction models of the DSMC are proposed through the calibrations in the thermochemical nonequilibrium conditions. When the bound-free transition component of the state-resolved method is replaced by the existing chemical reaction models, the same agreement can be obtained except total collision energy model.

실시간 시스템 검증을 위한 지역모형 검사 (Local Model Checking for Verification of Real-Time Systems)

  • 박재호;김성길;황선호;김성운
    • 한국멀티미디어학회논문지
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    • 제3권1호
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    • pp.77-90
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    • 2000
  • 실시간 검증은 명세와 요구사항과의 논리적 정확성 뿐만 아니라 시간적 정확성을 확인하는 일련의 과정이다. 하지만 시간의 무한성에 의해 시스템 상태가 무한히 증가할 수 있는 상태 폭발 문제가 검증과정에서 중요한 문제점이 되고 있다. 본 논문에서는 형식 검증에 기반을 두며, 시스템의 행위 측면을 시간 오토마타로 기술한 시스템 모델이 Timed mu-calculus로 표현된 시스템의 특성에 만족하는지의 여부를 통해 명세의 완전성을 확인하는 실시간 검증 비법을 기술한다. 이를 위해 초기상태의 논리값에 초점을 두어 검증과정에서 필요로 하는 노드로만 Product Graph를 구성하여 노드 값을 결정해나가는 지역모형검사 기법에 대해 제안한다. 이 방법은 모델의 모든 상태를 조사하지 않으므로 상태 폭발 문제를 최소화 시킬 수 있어 실시간 시스템 검증에 효과적으로 적용이 가능하다.

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Pretension process control based on cable force observation values for prestressed space grid structures

  • Zhou, Zhen;Meng, Shao-Ping;Wu, Jing
    • Structural Engineering and Mechanics
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    • 제34권6호
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    • pp.739-753
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    • 2010
  • Pointing to the design requirement of prestressed space grid structure being the target cable force, the pretension scheme decision analysis method is studied when there's great difference between structural actual state and the analytical model. Based on recursive formulation of cable forces, the simulative recursive system for pretension process is established from the systematic viewpoint, including four kinds of parameters, i.e., system initial value (structural initial state), system input value (tensioning control force scheme), system state parameters (influence matrix of cable forces), system output value (pretension accomplishment). The system controllability depends on the system state parameters. Based on cable force observation values, the influence matrix for system state parameters can be calculated, making the system controllable. Next, the pretension scheme decision method based on cable force observation values can be formed on the basis of iterative calculation for recursive system. In this way, the tensioning control force scheme that can meet the design requirement when next cyclic supplemental tension finished is obtained. Engineering example analysis results show that the proposed method in this paper can reduce a lot of cyclic tensioning work and meanwhile the design requirement can be met.

Guidance Law for Near Space Interceptor based on Block Backstepping Sliding Mode and Extended State Observer

  • Guo, Chao;Liang, Xiao-Geng
    • International Journal of Aeronautical and Space Sciences
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    • 제15권2호
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    • pp.163-172
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    • 2014
  • This paper proposes a novel guidance law based on the block backstepping sliding mode control and extended state observer (ESO), which also takes into account the autopilot dynamic characteristics of the near space interceptor (NSI), and the impact angle constraint of attacking the maneuvering target. Based on the backstepping control approach, the target maneuvers and the parameter uncertainties of the autopilot are regarded as disturbances of the outer loop and inner loop, respectively. Then, the ESO is constructed to estimate the target acceleration and the inner loop disturbance, and the block backstepping sliding model guidance law is employed, based on the estimated disturbance value. Furthermore, in order to avoid the "explosion of complexity" problem, first-order low-pass filters are also introduced, to obtain differentiations of the virtual control variables. The stability of the closed-loop guidance system is also proven, based on the Lyapunov theory. Finally, simulation results demonstrate that the proposed guidance law can not only overcome the influence of the autopilot dynamic delay and target maneuvers, but also obtain a small miss distance.

An amplify-and-forward relaying scheme based on network coding for Deep space communication

  • Guo, Wangmei;Zhang, Junhua;Feng, Guiguo;Zhu, Kaijian;Zhang, Jixiang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제10권2호
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    • pp.670-683
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    • 2016
  • Network coding, as a new technique to improve the throughput, is studied combined with multi-relay model in this paper to address the challenges of long distance and power limit in deep space communication. First, an amplify-and-forward relaying approach based on analog network coding (AFNC) is proposed in multi-relay network to improve the capacity for deep space communication system, where multiple relays are introduced to overcome the long distance link loss. The design of amplification coefficients is mathematically formulated as the optimization problem of maximizing SNR under sum-power constraint over relays. Then for a dual-hop relay network with a single source, the optimal amplification coefficients are derived when the multiple relays introduce non-coherent noise. Through theoretic analysis and simulation, it is shown that our approach can achieve the maximum transmission rate and perform better over single link transmission for deep space communication.

치아결손부(齒牙缺損部)에 인접(隣接)된 치아(齒牙)의 이동상태(移動狀態)에 관(關)한 연구(硏究) (A STUDY OH THE MOVEMENT STATE OF THE ADJACENT TOOTH INTO THE EDENTULOUS AREA)

  • 김준연
    • 대한치과보철학회지
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    • 제13권1호
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    • pp.11-22
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    • 1975
  • This study is to determine the severity and direction of the movement of the adjacent tooth into the created space by tooth or teeth loss. The random samples 387 cases (upper; 121 cases, lower; 266 cases) were selected with surveying record under some criteria. Edentulous area is grouped into the free end type and the tooth borne type. The following results were obtained. In the tooth borne type, slight distal movement of the adjacent tooth into the edentulous space was obtained. And the tooth distal to the edentulous space moved into the space in proportion to the duration of the edentulous state. Elongation of the opposing tooth of the free end type was more severe than that of the tooth borne type. And no inter-relationship between the severity of the elongation and the duration of the edentulous state In general, adjacent teeth had normal and mesial inclination. Lower teeth migrated mesially and lingually (especially in the distal tooth to the edentulous space in the tooth borne type). Upper adjacent teeth usually moved into the normal direction.

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