Alternative proof and interpretations for a recent state-dependent importance sampling scheme

Recently, a state-dependent change of measure for simulating overflows in the two-node tandem queue was proposed by Dupuis et al. (Ann. Appl. Probab. 17(4):1306–1346, 2007), together with a proof of its asymptotic optimality. In the present paper, we present an alternative, shorter and simpler proof. As a side result, we obtain interpretations for several of the quantities involved in the change of measure in terms of likelihood ratios. Part of this research has been funded by the Dutch BSIK/BRICKS project; part of this research was done while the first author was visiting INRIA/IRISA, Rennes, France.     

Importance sampling for non-Markovian tandem queues using subsolutions

Queueing Systems - In this paper, we use importance sampling simulation to estimate the probability that the number of customers in a d-node GI|GI|1 tandem queue reaches some high level N in a busy...     

Paramagnetic silver species in irradiated Ag−NaA zeolites. An EPR and ESEEM study

Several polymeric silver clusters have been observed in Ag_x?NaA zeolite (x=1,6) of varying water content, which was exposed to x-rays at 77 K and annealed at higher temperatures.¹⁰⁹Ag₁?NaA zeolite dehydrated at 130°C yields the dimer¹⁰⁹Ag₂ ⁺ and the trimer¹⁰⁹Ag₃ ²⁺ after irradiation at 77 K and annealing at 240 K. Owing to the use of one Ag isotope the EPR spectra of these species are highly resolved exhibitingg and hyperfine anisotropy. By irradiation of¹⁰⁹Ag_x?NaA zeolite (x=1,6) in hydrated form two new trimeric silver clusters I and II are produced. The ratio between I and II depends on the initial Ag content. ESEEM spectra of these species show interaction with aluminum nuclei of the framework and with distant water molecules. If Ag₆?NaA zeolite dehydrated at 130°C is irradiated the hexameric cluster Ag₆ ⁿ⁺ is formed. The ESEEM spectrum shows interaction only to aluminum nuclei. From ESEEM experiments on Ag₆ ⁿ⁺ with added adsorbates (D₂O, CD₃OD) it could be inferred that Ag₆ ⁿ⁺ is only stable if the neighbouring cages do not contain adsorbate molecules.