Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
We consider the problem of maximizing a linear fractional function on the Pareto efficient frontier of two other linear fractional functions. We present a finite pivoting-type algorithm that solves the maximization problem while computing simultaneously the efficient frontier. Application to multistage efficiency analysis is discussed. An example demonstrating the computational procedure is included. 相似文献
The ESTU began operation in 1988 and achieved the design voltage of 20 MV in 1990. Since that time, improvements to the gas
handling system, negative ion injector, accelerator terminal and control system have greatly increased its capability and
reliability. Today, the ESTU can efficiently produce an extensive assortment of stable ions at wide-ranging energies in support
of low-energy nuclear physics. 相似文献
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
Nonlinear optical parameters (nonlinear refractive indices and nonlinear absorption coefficients) of solutions of polyvinylpyrrolidone doped by cobalt to various concentrations are measured at the lasing and second-harmonic wavelengths of a picosecond Nd:YAG laser (λ=1064 and 532 nm, respectively, and τ=35 ps). Data on optical limitation in these solutions are presented. The absence of nonlinear absorption in the IR spectral range and its significant effect in the visible range are demonstrated. Optical limitation at a wavelength of 1064 nm is related to defocusing, whereas at 532 nm, this effect is caused by two-photon absorption and partially by inverse saturated absorption and defocusing. Nonlinear optical parameters of metal-polymer complexes are reported. 相似文献
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4R3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献
RSMR experiments with57Fe radiation were performed on myoglobin. An areasensitive detector was employed for simultaneous angular dependent collection of the scattered quanta up to a maximum angle 2θ of 17‡. Experimental data of polycrystalline and lyophilized myoglobin are compared with computer calculations of the scattering which are based on the atomic coordinates determined by X-ray structure analysis. Special attention has been paid to the influence of coherence effects from collectively moving parts of the protein. A simple model is introduced in order to take into account these segmental motions. Our first results indicate that the sizes of collectively moving segments are comparable with spheres of about 6 å in diameter in dry myoglobin. In myoglobin crystals, where the molecules are surrounded by large hydration shells, the movements appear to be correlated in segments with sizes comparable to helices.
Consider an organization with several categories of staff, each having a specified number of members. The age of entry into service and the age of retirement are both specified. Withdrawals occur at time-independent rates. Under this set-up, the authors have computed the maximum ages at which promotions should take place, assuming that the staff members continuing at various ages are random. Some illustrative calculations have been carried out. 相似文献
In agreement with the Kohn theorem the relative motion (rel) of three electrons in a two-dimensional parabolic trap separates
from the centre-of-mass (CM) motion. By introducing new coordinates the Hamiltonian for relative motion in the approximation
of non-interacting electrons can be taken to the normal form. The eigenstates of the normalized Hamiltonian are products of
the Fock-Darwin states for normal modes. The energy levels for relative motion are obtained by diagonalizing the exact Hamiltonian
in the eigenbasis for the non-interacting case. In this basis the interaction matrix elements can be obtained in the analytical
form. Since the rank of the Hamiltonian matrix is significantly reduced, the calculations are faster and more accurate than
those for the full (CM + rel) motion. This advantage is especially important for the calculations of excited states and the
analysis of energy spectra. 相似文献