Semiparametric Cross Entropy for rare-event simulation

The Cross Entropy method is a well-known adaptive importance sampling method for rare-event probability estimation, which requires estimating an optimal importance sampling density within a parametric class. In this article we estimate an optimal importance sampling density within a wider semiparametric class of distributions. We show that this semiparametric version of the Cross Entropy method frequently yields efficient estimators. We illustrate the excellent practical performance of the method with numerical experiments and show that for the problems we consider it typically outperforms alternative schemes by orders of magnitude

Narrow-Linewidth Distributed Feedback Channel Waveguide Laser in Al2_2O3_3:Er3+^{3+}

We report on the fabrication and characterization of a distributed feedback channel waveguide laser in erbium-doped aluminium oxide on a standard thermally oxidized silicon substrate. Holographically-written surface-relief Bragg gratings have been integrated with the aluminium oxide waveguides via reactive ion etching of a silicon dioxide overlay film. The laser operates at a wavelength of 1545.2 nm and exhibits a threshold of 2.2 mW absorbed pump power, while it produces a maximum output power of 3 mW. The emission is TE polarized and has a Lorentzian linewidth of 1.70±0.58 kHz, which corresponds to a Q-factor of 1.14×E11

Far-field scattering microscopy applied to analysis of slow light, power enhancement, and delay times in uniform Bragg waveguide gratings

A novel method is presented for determining the group index, intensity enhancement and delay times for waveguide gratings, based on (Rayleigh) scattering observations. This far-field scattering microscopy (FScM) method is compared with the phase shift method and a method that uses the transmission spectrum to quantify the slow wave properties. We find a minimum group velocity of 0.04c and a maximum intensity enhancement of ~14.5 for a 1000-period grating and a maximum group delay of ~80 ps for a 2000-period grating. Furthermore, we show that the FScM method can be used for both displaying the intensity distribution of the Bloch resonances and for investigating out of plane losses. Finally, an application is discussed for the slow-wave grating as index sensor able to detect a minimum cladding index change of $10^{-8}$, assuming a transmission detection limit of $10^{-4}$

Line-Defect Waveguides in Hexagon-Hole type Photonic Crystal Slabs: Design and Fabrication using Focused Ion Beam Technology

Photonic-crystal slabs (PCS) patterned with a 2D triangular-lattice having hexagonal holes rotated with respect to their symmetry axis can provide a larger bandgap than similar slabs with circular holes. A step forward towards integrated optical devices is introducing line ‘defects’ in PCS, the goal being the achievement of single-mode waveguiding over a frequency range as large as possible, inside the gap. We present the design for defect waveguides with reduced width and a novel fabrication technique, which is an integration of optical lithography with focused ion beam (FIB) high-resolution etching. This technique allows a good alignment between a line ‘defect’ and conventional ridge waveguides

NNLO QCD corrections to event shape variables in electron positron annihilation

Precision studies of QCD at electron-positron colliders are based on measurements of event shapes and jet rates. To match the high experimental accuracy, theoretical predictions to next-to-next-to-leading order (NNLO) in QCD are needed for a reliable interpretation of the data. We report the first calculation of NNLO corrections O(alpha_s^3) to three-jet production and related event shapes, and discuss their phenomenological impact.Comment: Contributed to 2007 Europhysics Conference on High Energy Physics, Manchester, England 19-25 July 200

Dose- and Time-Dependent Increase of Lysosomal Enzymes in Embryonic Cartilage in Vitro after Ionizing Radiation

Radiation doses of 20, 50 or 100 Gy caused the same time related decrease for RNA and proteoglycan (PG) synthesis in embryonic cartilage in vitro (4 days culture). In this paper, participation of lysosomes in this radiation response is investigated. Therefore, we employ a cytochemical method using -glycerophosphate as substrate for acid phosphatase (AP) detection. Increase of AP was found 2 days after irradiation and increased during the whole culture period. The increase was more pronounced with a higher radiation dose. Stimulation of AP activity explains the observed radiation response of RNA and PG synthesis

The infrared structure of e+ e- --> 3 jets at NNLO reloaded

This paper gives detailed information on the structure of the infrared singularities for the process e+ e- --> 3 jets at next-to-next-to-leading order in perturbation theory. Particular emphasis is put on singularities associated to soft gluons. The knowledge of the singularity structure allows the construction of appropriate subtraction terms, which in turn can be implemented into a numerical Monte Carlo program.Comment: 59 pages, additional comments added, version to be publishe

The NBS: Processing/Microstructure/Property Relationships in 2024 Aluminum Alloy Plates

As received plates of 2024 aluminum alloy were examined. Topics covered include: solidification segregation studies; microsegregation and macrosegregation in laboratory and commercially cast ingots; C-curves and nondestructive evaluation; time-temperature precipitation diagrams and the relationships between mechanical properties and NDE measurements; transmission electron microscopy studies; the relationship between microstructure and properties; ultrasonic characterization; eddy-current conductivity characterization; the study of aging process by means of dynamic eddy current measurements; and Heat flow-property predictions, property degradations due to improve quench from the solution heat treatment temperature

Single-Frequency, Narrow-Linewidth Distributed Feedback Waveguide Laser in Al2O3:Er3+ on Silicon

A distributed feedback channel waveguide laser in erbium-doped aluminum oxide on a silicon substrate is reported. The optically pumped laser has a threshold pump power of 15 mW and emits 3 mW in single-frequency operation at 1545.2 nm wavelength with a slope efficiency of 6.2% and linewidth of 15 kHz