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11.
本文讨论了实时系统的特征、开发方法、设计工具、实现手段工具等开发过程中的主要问题,论述了实时系统开发语言PEARL及该语言的对实时系统的主要支持. 相似文献
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Jonathan M. Levin Lawrence L. Wald Marc J. Kaufman Marjorie H. Ross Luis C. Maas Perry F. Renshaw 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):292-295
Residual effects of an initial bolus of gadolinium contrast agent have been previously demonstrated in sequential dynamic susceptibility contrast MR experiments. While these residual effects quickly reach a saturation steady state, their etiology is uncertain, and they can lead to spurious estimates of hemodynamic parameters in activation experiments. The possible influence ofT1effects is now investigated with experiments in whichT1weighting is varied as well as with serial regionalT1measurements. Little evidence for significant residualT1effects is found, suggesting instead that susceptibility effects underlie these observations. An initial saturation dose of contrast agent minimizes this effect. 相似文献
14.
离散边界条件系统的最优控制 总被引:1,自引:0,他引:1
研究离散边界条件系统的最优控制问题,给出了最优控制存在的必要条件,证明了此类系统最优控制仍有最大值原理成立。 相似文献
15.
Wei Gengping~ Shen Jianhua~ 《高校应用数学学报(英文版)》2006,21(3):320-326
This paper studies the nonautonomous nonlinear system of difference equationsΔx(n)=A(n)x(n)+f(n,x(n)),n∈Z,(*) where x(n)∈R~N,A(n)=(a_(ij)(n))N×N is an N×N matrix,with a-(ij)∈C(R,R) for i,j= 1,2,3,...,N,and f=(f_1,f_2,...,f_N)~T∈C(R×R~N,R~N),satisfying A(t+ω)=A(t),f(t+ω,z)=f(t,z) for any t∈R,(t,z)∈R×R~N andωis a positive integer.Sufficient conditions for the existence ofω-periodic solutions to equations (*) are obtained. 相似文献
16.
This paper considers the problem of building a set of hybrid abstractions for affine systems in order to compute over approximations of the reachable space. Each abstraction is based on a decomposition of the continuous state space that is defined by hyperplanes generated by linear combinations of two vectors. The choice of these vectors is based on consideration of the dynamics of the system and uses, for example, the left eigenvectors of the matrix that defines these dynamics. We show that the reachability calculus can then be performed on a combination of such abstractions and how its accuracy depends on the choice of hyperplanes that define the decomposition. 相似文献
17.
Most of the novel highly potent drugs, developed on the basis of modern molecular medicine, taking into account cell surface recognition techniques, show poor water solubility. A chemical modification of the drug substance enhancing the solubility often decreases the pharmacological activity. Thus, as an alternative an increase of the solubility can be obtained by the reduction of the size of the drug particles. Unfortunately, it is often difficult to obtain micro or nanosized drug particles by classical or more advanced crystallization using supercritical gases or by milling techniques. In addition, nanosized particles are often not physically stable and need to be stabilized in an appropriate matrix. Thus, it may be of interest to manufacture directly nanosized drug particles stabilized in an inert hydrophilic matrix, i.e. nanostructured and nanocomposite systems. Solid solutions and solid dispersions represent nanostructured and nanocomposite systems. In this context, the use of the vacuum-fluidized-bed technique for the spray-drying of a low water soluble drug cosolubilized with a hydrophilic excipient in a polar organic solvent is discussed. In order to avoid the use of organic solvents, a special spray-freeze-drying technique working at atmospheric pressure is presented. This process is very suitable for temperature and otherwise sensitive drugs such as pharmaproteins. 相似文献
18.
We describe a new algorithm which uses the trajectories of a discrete dynamical system to sample the domain of an unconstrained objective function in search of global minima. The algorithm is unusually adept at avoiding nonoptimal local minima and successfully converging to a global minimum. Trajectories generated by the algorithm for objective functions with many local minima exhibit chaotic behavior, in the sense that they are extremely sensitive to changes in initial conditions and system parameters. In this context, chaos seems to have a beneficial effect: failure to converge to a global minimum from a given initial point can often be rectified by making arbitrarily small changes in the system parameters. 相似文献
19.
李必文 《湖北师范学院学报(自然科学版)》2002,22(4):14-19
考虑一个具有时滞的非自治的捕食——食饵生态系统。该系统是由一个捕食,二个食饵种群所构成我们给出了系统的周期解是全局稳定的充分条件。 相似文献
20.
Claudio Simeone 《General Relativity and Gravitation》2002,34(11):1887-1893
A consistent quantization with a clear notion of time and evolution is given for the anisotropic Kantowski–Sachs cosmological model. It is shown that a suitable coordinate choice allows to obtain a solution of the Wheeler–DeWitt equation in the form of definite energy states, and that the results can be associated to two disjoint equivalent theories, one for each sheet of the constraint surface. 相似文献