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991.
K Sheibani 《The Journal of the Operational Research Society》2010,61(5):813-818
This paper describes a polynomial-time heuristic for the permutation flow-shop scheduling problem with the makespan criterion. The proposed method consists of two phases: arranging the jobs in priority order and then constructing a sequence. A fuzzy greedy evaluation function is employed to prioritize the jobs for incorporating into the construction phase of the heuristic. Computational experiments using standard benchmark problems indicate an improvement of the new heuristic over the well-known Nawaz, Enscore and Ham (NEH) heuristic. It will be seen that the NEH heuristic is a special case of our more general heuristic. 相似文献
992.
Continuous demand is generated in a convex polygon. A facility located in the area covers demand within a given radius. The objective is to find the locations for p facilities that cover the maximum demand in the area. A procedure that calculates the total area covered by a set of facilities is developed. A multi start heuristic approach for solving this problem is proposed by applying a gradient search from a randomly generated set of p locations for the facilities. Computational experiments for covering a square area illustrate the effectiveness of the proposed algorithm. 相似文献
993.
A heuristic algorithm is described for vehicle routing and scheduling problems to minimise the total travel time, where the time required for a vehicle to travel along any road in the network varies according to the time of travel. The variation is caused by congestion that is typically greatest during morning and evening rush hours. The algorithm is used to schedule a fleet of delivery vehicles operating in the South West of the United Kingdom for a sample of days. The results demonstrate how conventional methods that do not take time-varying speeds into account when planning, except for an overall contingency allowance, may still lead to some routes taking too long. The results are analysed to show that in the case study using the proposed approach can lead to savings in CO2 emissions of about 7%. 相似文献
994.
One of the issues that the Basel Accord highlighted was that, though techniques for estimating the probability of default and hence the credit risk of loans to individual consumers are well established, there were no models for the credit risk of portfolios of such loans. Motivated by the reduced form models for credit risk in corporate lending, we seek to exploit the obvious parallels between behavioural scores and the ratings ascribed to corporate bonds to build consumer-lending equivalents. We incorporate both consumer-specific ratings and macroeconomic factors in the framework of Cox Proportional Hazard models. Our results show that default intensities of consumers are significantly influenced by macro factors. Such models then can be used as the basis for simulation approaches to estimate the credit risk of portfolios of consumer loans. 相似文献
995.
Lawrence W. Jones 《Czechoslovak Journal of Physics》2006,56(1):A201-A210
The L3 detector at the CERN electron-positron collider had a muon spectrometer which was employed during the last years of LEP operation for cosmic ray studies. The results of this program include a precise muon spectrum and charge ratio between 20 GeV and 3 TeV, a limit on TeV primary antiprotons from a study of the Moon’s shadow, the (possible) observation of a are signal from a fixed position in the northern hemisphere through muons, a solar anisotropy of 200 GeV protons, and other results. Negative limits on muons associated with known H.E. gamma sources or gamma bursts, the search for anomalous H.E. interaction or decay events such as reported from the Kolar Gold Fields, and a search for muons correlated with a solar are are also noted. 相似文献
996.
Tom Kennedy 《Journal of statistical physics》2008,131(5):803-819
We simulate several models of random curves in the half plane and numerically compute the stochastic driving processes that
produce the curves through the Loewner equation. Our models include models whose scaling limit is the Schramm-Loewner evolution
(SLE) and models for which it is not. We study several tests of whether the driving process is Brownian motion, as it is for
SLE. We find that testing only the normality of the process at a fixed time is not effective at determining if the random
curves are an SLE. Tests that involve the independence of the increments of Brownian motion are much more effective. We also
study the zipper algorithm for numerically computing the driving function of a simple curve. We give an implementation of
this algorithm which runs in a time O(N
1.35) rather than the usual O(N
2), where N is the number of points on the curve. 相似文献
997.
Aditya M. Vora 《Central European Journal of Physics》2008,6(2):238-252
Ashcroft’s empty core (EMC) model potential is used to study the superconducting state parameters (SSPs) viz. electron-phonon
coupling strength λ, Coulomb pseudopotential μ*, transition temperature T
C
, isotope effect exponent αand effective interaction strength N
O
V of some binary metallic glasses based on the superconducting (S), conditional superconducting (S’) and non-superconducting
(NS) elements of the periodic table. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi
(IU), Farid et al. (F) and Sarkar et al. (S) are used for the first time with EMC potential in the present investigation to study the screening influence on the aforesaid
properties. The T
C
obtained from the H-local field correction function are in excellent agreement with available theoretical or experimental
data. In the present computation, the use of the pseudo-alloy-atom model (PAA) was proposed and found successful. Present
work results are in qualitative agreement with such earlier reported experimental values which confirm the superconducting
phase in all metallic glasses. A strong dependency of the SSPs of the metallic glasses on the valence ‘Z’ is identified.
相似文献
998.
We present the number of dimer coverings N
d
(n) on the Sierpinski gasket SG
d
(n) at stage n with dimension d equal to two, three, four or five. When the number of vertices, denoted as v(n), of the Sierpinski gasket is an even number, N
d
(n) is the number of close-packed dimers. When the number of vertices is an odd number, no close-packed configurations are possible
and we allow one of the outmost vertices uncovered. The entropy of absorption of diatomic molecules per site, defined as
, is calculated to be ln (2)/3 exactly for SG
2. The numbers of dimers on the generalized Sierpinski gasket SG
d,b
(n) with d=2 and b=3,4,5 are also obtained exactly with entropies equal to ln (6)/7, ln (28)/12, ln (200)/18, respectively. The number of dimer
coverings for SG
3 is given by an exact product expression, such that its entropy is given by an exact summation expression. The upper and lower
bounds for the entropy are derived in terms of the results at a certain stage for SG
d
(n) with d=3,4,5. As the difference between these bounds converges quickly to zero as the calculated stage increases, the numerical
value of
with d=3,4,5 can be evaluated with more than a hundred significant figures accurate.
This paper is written during the Lung-Chi Chen visit to PIMS, University of British Columbia. The author thanks the institute
for the hospitality. 相似文献
999.
G. S. Khadekar B. Sarada Cenap Ozel 《International Journal of Theoretical Physics》2008,47(6):1542-1551
A homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model with varying gravitational and cosmological constant is
studied in the context of higher dimensional space time. Exact solution of the field equations are obtained by using the “gamma
law” equation of state p=(γ−1)ρ, where γ is adiabatic parameter varies continuously as the universe expands. The functional form γ which is assumed to be the function of scale factor R as proposed by Carvalho (1996) is used to analyse the behavior of scale factor R, cosmological constant Λ and the gravitational constant G for two different phases: inflation and radiation. The various physical aspects of the early cosmological models has also
been discussed in the framework of higher dimensional space time. 相似文献
1000.
Joseph Akeyo Omolo 《Pramana》2008,71(6):1311-1320
The quantum dynamics of a two-mode non-resonant parametric down-conversion process is studied by recasting the time evolution
equations for the basic operators in an equivalent spin equation form with simpler exact solutions for a pump field with harmonic
time dependence. Expectation values of suitable operators for studying important features such as squeezing and quantum revivals
are presented in simple forms.
相似文献