Combined vehicle routing and scheduling with temporal precedence and synchronization constraints

We present a mathematical programming model for the combined vehicle routing and scheduling problem with time windows and additional temporal constraints. The temporal constraints allow for imposing pairwise synchronization and pairwise temporal precedence between customer visits, independently of the vehicles. We describe some real world problems where in the literature the temporal constraints are usually remarkably simplified in the solution process, even though these constraints may significantly improve the solution quality and/or usefulness. We also propose an optimization based heuristic to solve real size instances. The results of numerical experiments substantiate the importance of the temporal constraints in the solution approach. We also make a computational study by comparing a direct use of a commercial solver against the proposed heuristic, where the latter approach can find high quality solutions within specific time limits.     

On nonlinear spatio-temporal instability regime for electrically forced viscous jets [Errata Corrige]

The authors have found errors in the published paper, Nonlinear spatio-temporal instability regime for electrically forced viscous jets, Int. J. Nonlinear Mech. 67 (2014), 218–230. The errors and the corrections provided here do not affect the abstract, main findings and conclusions of the original paper.     

Temporally regularized direct numerical simulation

Experience with fluid-flow simulation suggests that, in some instances, under-resolved direct numerical simulation (DNS), without a residual-stress model per se but with artificial damping of small scales to account for energy lost in the cascade from resolved to unresolved scales, may be as reliable as simulations based on more complex models of turbulence. One efficient and versatile manner to selectively damp under-resolved spatial scales is by a relaxation regularization, e.g. Stolz and Adams [S. Stolz, N.A. Adams, An approximate deconvolution procedure for large eddy simulation, Phys. Fluids II (1999) 1699-1701]. We consider the analogous approach based on time scales, time filtering and damping of under-resolved temporal features. The paper explores theoretical and practical aspects of temporally damped fluid-flow simulations. We prove existence of solutions to the resulting continuum model. We also establish the effect of the damping of under-resolved temporal features as the energy balance and dissipation and prove that the time fluctuations → 0 in a precise sense. The method is then demonstrated to obtain both steady-state and time-dependent coarse-grid solutions of the Navier-Stokes equations.     

On the service performance of alternative shipment consolidation policies

In order to compare the performances of alternative shipment consolidation policies, we develop closed-form expressions of the distribution of the maximum waiting time and the average order delay. We examine the tradeoff between the expected delivery frequency, as measured by the expected shipment consolidation cycle length, and the average order delay. The previous analytical results regarding shipment consolidation are aimed at optimizing the performances of alternative policies using cost-based criteria whereas our results are useful under service-based criteria.     

Performance evaluation of the phase encoded optical CDMA system

Recently, there has been increasing interest in field of Optical CDMA due to its potential for offering unmatched features at ultra high data rates in field of local and metro area networks. In this paper, a very simple method of Optical CDMA encoding known as the Temporal Phase Encoding is discussed and the performance of the system with this encoding technique is evaluated on the basis of number of users, length of the spreading code for 4-phase and 8-phases. Simulation results for the system are presented for upto seven users. Bit error rate curves are plotted with data rate of 1 Gbps. This has been found that performance improves if normalized threshold higher than 0.5 is used.     

Origin of the broad-band noise in acoustic cavitation

The broad-band noise has been experimentally used to monitor the cavitation activity in a sonochemical reactor, an ultrasonic cleaning bath, a biological tissue, etc. However, the origin of the broad-band noise is still under debate. In the present review, two models for the mechanism of the broad-band noise are discussed. One is acoustic emissions from chaotically (non-periodically) pulsating bubbles. The other is acoustic emissions from bubbles with temporal fluctuation in the number of bubbles. It is suggested that the latter mechanism is sometimes dominant. Further studies are required on the role for bubble cluster dynamics as well as the bubble–bubble interaction in the broad-band noise especially at relatively low ultrasonic frequencies.     

Weighted o-minimal hybrid systems

We consider weighted o-minimal hybrid systems, which extend classical o-minimal hybrid systems with cost functions. These cost functions are “observer variables” which increase while the system evolves but do not constrain the behaviour of the system. In this paper, we prove two main results: (i) optimal o-minimal hybrid games are decidable; (ii) the model-checking of WCTL, an extension of CTL which can constrain the cost variables, is decidable over that model. This has to be compared with the same problems in the framework of timed automata where both problems are undecidable in general, while they are decidable for the restricted class of one-clock timed automata.     

Past–future separation and normal forms in temporal predicate logic specifications

Temporal specifications are often used when phenomena are modelled where dynamics play a main role. If simulation is one of the aims of modelling, usually a restricted, executable modelling language format is used, based on some form of past to future implications. In this paper a detailed transformation procedure is described that takes any temporal predicate logic specification and generates a specification in a past-implies-future normal format. The procedure works for temporal specifications in which the atoms either express time ordering relations or are state-related, i.e., include only one time variable.     

具不同分数阶扩散趋化模型的衰减估计

研究了生物学中具有分数阶扩散的Keller-Segel模型.该模型是由两个分数阶抛物方程和一个经典抛物方程组成.在小初值条件下,利用[李大潜,陈韵梅.非线性发展方程[M].北京:科学出版社,1999.]中的能量方法,作者建立了该模型古典解的全局存在性及最优的衰减估计,得到了u,v及▽Ψ高阶导数的衰减估计.