Initial data truncation for multivariate output of discrete-event simulations using the Kalman filter

Data truncation is a commonly accepted method of dealing with initialization bias in discrete-event simulation. An algorithm for determining the appropriate initial-data truncation point for multivariate output is proposed. The technique entails averaging across independent replications and estimating a steady-state output model in a state-space framework. A Bayesian technique called Multiple Model Adaptive Estimation (MMAE) is applied to compute a time varying estimate of the output's steady-state mean vector. This MMAE implementation features the use, in paralle, of a bank of Kalman filters. Each filter is constructed under a different assumption concerning the output's steady-state mean vector. One of the filters assumes that the steady-state mean vector is accurately reflected by an estimate, called the assumed steady-state mean vector, taken from the last half of the simulation data. As the filters process the output through the effective transient, this particular filter becomes more likely (in a Bayesian sense) to be the best filter to represent the data and the MMAE mean estimator is influenced increasingly towards the assumed steady-state mean vector. The estimated truncation point is selected when a norm of the MMAE mean vector estimate is within a small tolerance of the assumed steady-state mean vector. A Monte Carlo analysis using data from simulations of open and closed queueing models is used to evaluate the technique. The evaluation criteria include the ability to construct accurate and reliable confidence regions for the mean response vector based on the truncated sequences.     

Spherically symmetric fields in Rosen's bimetric theories of gravitation

By means of bimetric Killing vectors two spherically symmetric fields are investigated: (i) the time-dependent one in Rosen's flat-background bimetric theory; and (ii) the energy-preserving in Rosen's cosmological-background bimetric theory withk = 1. In the first case a wave behavior of the field is present. In the second case a time evolution is obtained for fields, created by insular systems of constant energy. These phenomena are typical for bimetric theories of gravitation.     

The beta decay of90g Tc and90m Tc

The level structure of⁹⁰Mo is investigated via the beta decay of^90g Tc and^90m Tc whose half-lives are measured to be 8.7±0.2 and 49.2±0.4 s, respectively. The decay properties are studied by means of beta and gamma spectroscopy techniques. The level structure of⁹⁰Mo populated in the decays of both isomers is proposed with deducedJ ^π values. Theβ-decay energies for^90g Tc and^90m Tc are 8.8±0.3 and 9.3±0.3 MeV, respectively. The structure is discussed in terms of the shell model.     

Does a generic connection depend continuously on its curvature?

For a principal bundle with semi-simple structure group over a smooth four-dimensional base manifold, the set of connections (gauge potentials)A which are uniquely determined by their curvature (field or field strength)F is generic in the set of all potentials, endowed with the WhitneyC ^∞ topology. However, the operator taking each such fieldF to its potentialA is not continuous. Partial negative results are given concerning the existence of a smaller generic set on which this operator is continuous.     

A re-evaluation of isotope shift constants

The field isotope shift constantC _unif for a uniform nuclear charge distribution has been re-evaluated fors-electrons for elements with 10≦Z≦ 95. A table is given which permitsC _unif to be found for any isotope pair.     

Identification of pyrrolo-pyridine derivatives as novel class of antibacterials

Molecular Diversity - A series of 5-oxo-4H-pyrrolo[3,2-b]pyridine derivatives was identified as novel class of highly potent antibacterial agents during an extensive large-scale high-throughput...     

Terahertz bandpass filters using double-stacked metamaterial layers

Bandpass filters are reported based on double-stacked metamaterial layers separated by an air gap for operation at terahertz frequencies. Several stacking configurations were investigated designed for a ~0.5 THz center frequency. The filters exhibited improved spectral transmission properties when compared with conventional ones based on single metamaterial layers. 3 dB bandwidth of ~78 GHz and sidelobe suppression ratio >16 dB were determined when symmetric or asymmetric double layers were stacked. We demonstrate that superior frequency selectivity can be achieved when metamaterial layers with different unit cells are used. Good agreement was found between measured and simulated transmission response.     

Spatial beam properties of combined lasers' delivery fibers

The superiority of parabolic-index fibers over step-index fibers in delivering high-beam-quality light out of incoherently combined lasers is demonstrated numerically and experimentally. By utilizing the tapered fused bundle-combining approach and connecting it with delivery fiber, we point to an efficient, rugged, all-glass, integrated, and nearly brightness-preserving device that is capable of transmitting high-quality output beams.