Single beta decay transitions in 114–120</sup>Pd are calculated. Theoreticalβ+</sup> and β−</sup> strength distributions, for transitions to 1+</sup> states in the nuclei 114–120</sup>Ag and 114–120</sup>Rh, are obtained in the framework of the quasiparticle random phase approximation (QRPA). The effective two-body interaction which is used in the calculations is constructed from the Bonn one-boson-exchange potential (OBEP). Particle-hole and particle-particle like channels of the two-body force are included in the definition of the QRPA matrix equations. Effects associated with the particle number violation of the quasiparticle mean field are accounted for by using a particle-number-projected version of the QRPA formalism. Theoretical strength distributions for the β−</sup> and β+</sup> braches are shown and compared with data. 相似文献
We define a simple form of homogeneous neural network model whose characteristics are expressed in terms of probabilistic assumptions. The networks considered operate in an asynchronous manner and receive the influence of the environment in the form of external stimulations. The operation of the network is described by means of a Markovian process whose steady-statesolution yields several global measures of the network's activity. Three different types of external stimulations are investigated, which represent possible input mechanisms. The analytical results obtained concern the macroscopic viewpoint and provide a quick insight into the structure of the network's behavior. 相似文献
The velocity-vorticity formulation of the Navier-Stokes equations is turned into an optimal control problem subject to linear constraints which consist of Laplacian equations for the velocity and for the vorticity. Various optimization algorithms can be used for the numerical resolution of the optimal control problem in question; in particular, the use of a conjugate-gradient method is discussed. 相似文献
Structural optimization is almost as old as the finite element method (FEM). Whereas FEM found its way to real-life applications very quickly, structural optimization remained a topic of interest in the research community for many years. However, there have been a number of attemps recently to develop general purpose program systems for property optimization. For shape optimization, there is no general purpose code currently available that can solve realistic problems. This paper will describe a method of calculating shape sensitivities within
, in a simple manner, without resort to external programs. Once the shape sensitivities are obtained, the shape optimization process can proceed in a manner similar to property optimization. The key concept is the use of natural design variables to define the shape changes in a given structure. The design variables are the magnitudes of enforced displacements applied to the structure. The displacements produced by these variables are added to the initial shape to obtain a new shape. This approach can be computationally intensive and since one shape variable is dependent of another, multiple CPU's can be used to significantly reduce the solution time.
Two examples are solved to demonstrate the capability of these techniques. The first is a cantilever beam with holes loaded by a point load at the free end. The shape of the holes as well as the thickness of the beam are selected as the design variables. The second example is the shape optimization of a connecting rod subjected to several different loading and boundary conditions. 相似文献
Based on a bang-bang control scheme acting on so called “electrorheological” fluids (ER-fluids), a vibration suppression method is proposed for a class of n-dimensional systems subjected to unknown perturbations. The proposed controller relates to robustness vis-a-vis unknown but bounded disturbances. Two approaches for designing the control scheme are presented and compared. On the one hand we employ Lyapunov stability theory; on the other hand there is an obvious reason for minimizing rate of energy change due to the spring/damper elements by varying the ER-fluid properties appropriately. The system under investigation is an n-degree of freedom one consisting of masses and spring/damper elements. The spring/damper elements contain an ER-fluid; their stiffness and damping properties are changed by varying an imposed electrical field. The changes in spring and damping properties can be effected in microseconds since the control does not involve the separate dynamics (inertia) of usual actuators. Detailed derivations are presented for a two-dimensional case and simulations are carried out for examples of smooth periodic and discontinuous periodic excitation forces. 相似文献
We have established experimentally that when biological cells, for example, blood, are suspended in concentrated solutions of inorganic electrolytes (for instance, in a 15% solution of sodium chloride) then around some cells (leucocytes, especially tumour cells) there form haloes, i.e., circular spaces free from background cells (erythrocytes, yeast cells, colloidal particles of Indian ink). In the medium made up of erythrocytes the haloes form during 5–10 min as a result of the background cells drawing apart from the central halo-forming cell (HFC) at a distance of 10–100 μm and more.
In the medium made of the Indian ink particles, the haloes form during 2–4 s and attain a thickness of about 10–20 μm. The erythrocytes and the haloes forming in their medium can be preserved for about three to five days at room temperature.
It has been established that, when tumour HFCs are present at sufficient concentrations, they form hexagonal periodic structures having a mean spacing between cells of up to 60 μm.
The authors put forward as one probable suggestion that the formation of haloes is largely determined by long-range repulsive forces arising from the phenomenon of diffusiophoresis generated by the diffusion currents that emerge from the surface of halo-forming cells. 相似文献