A control system for automated multiscale measuring systems

Quality inspection of micro systems on wafer scale must cope with conflicting demands: nanometer accuracy and high velocity in a comparatively large workspace. An Automated Multiscale Measuring System (AMMS) combines multiple sensors that operate at specific scales by an intelligent measurement strategy in order to balance speed and accuracy. The AMMS demonstrator is based on a modified Mahr MFU 100 with a position and tilt deflection measurement resolution of 1 nm. In this paper multiscale models of a horizontal axis with an operating range of 200 mm and their application to state linearization and control parameterization of the residual dynamics according to multiscale sensor system characteristics are developed and discussed. Main modeling issues are sliding and submicron presliding friction for model-based compensation and control, reaching from submicron positioning to high-velocity trajectory tracking with desired performance. A new experimental design for the identification of presliding friction parameters and a higher-order friction calculator are presented. Experimental results show the effectiveness of this approach.     

A new method of dark resonance excitation on D<Subscript>2</Subscript> line in <Superscript>87</Superscript>Rb vapor

A new method based on optical pumping is proposed for increasing the parameters of dark resonance excitation on D ₂ line in ⁸⁷Rb vapor. The pumping is provided by linearly polarized two-frequency laser radiation propagating in the direction perpendicular to the probing field directed along the cell with atomic rubidium vapor. This method significantly improves the dark resonance parameters as compared to the case of pumping by a circularly polarized field. Qualitative considerations are confirmed by the results of numerical calculations.     

Influence of laser sources with different spectral properties on the performance of vapor cell atomic clocks based on lin‖lin CPT

We evaluate the influence of 2 types of laser sources with different spectral profiles on the performance of vapor cell atomic clocks based on lin‖lin coherent population trapping (CPT) resonances. We show that a short-term stability of 1 − 2 · 10⁻¹¹τ{−1/2} may be reached in a compact system using a modulated vertical cavity surface-emitting laser. Here the stability is limited by the detection noise level and can be improved up to a factor of 4 by increasing the lock-in detection frequency to several tens of kilohertz, which is not possible in standard double resonance atomic clocks. We compare these results with CPT prepared under the same experimental conditions, using 2 phase-locked extended cavity diode lasers, with which we predict a challenging short-term stability of 1 − 3 · 10⁻¹³τ^−1/2, comparable to the state-of-the-art laser-pumped Rb-clocks.     

Visual sensitivity in the black-bellied tree duck (Dendrocygna autumnalis), a crepuscular species.

Produced visual adaptation curves for 3 black-bellied tree ducks using D. S. Blough's (1955) psychophysical tracking procedure. 2 scotopic curves from different preexposure light intensities and 1 photopic curve were generated. Nonlinear regression curves were then fit to the raw data. The mean scotopic thresholds did not differ significantly, but as expected, they were significantly lower than the mean photopic threshold. Time to the curves' asymptotes correlated with preexposure light intensity. Although the adaptation curves showed no distinct rod-cone "break," retinal histology revealed a duplex retina with a preponderance of rods, which reflects this species' crepuscular habits. Results are discussed in relation to the ecology of the species. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimized scheme of a rubidium all-optical frequency standard

A new approach to the creation of a quantum frequency standard based on the phenomenon of coherent population trapping is proposed, which employs linearly polarized radiation and involves signal discrimination at the absorption maximum.     

Subhomogeneous spectroscopy of a Bose condensate of neutral atoms

A method is proposed for resolving experimentally the details of the resonant fluorescence spectrum of a Bose condensate within a homogeneous line whose width is greatly increased because of collective effects. A discussion is presented concerning the application of this method for determining the shifts of the resonant frequencies of the transitions in the condensate as compared to the usual case of nondegenerate atom ensembles. Pis’ma Zh. Tekh. Fiz. 23, 33–38 (January 26, 1997)     

Exchange-induced self-polarization of an electron beam

A mechanism leading to self-polarization of a beam of free electrons injected from a light-emitting cathode is considered. It is shows that the exchange interaction may lead to self-polarization of an electron beam in vacuum and maintain the polarization of a beam in a substance.     

Using Entropy Analysis to Find Encrypted and Packed Malware

In statically analyzing large sample collections, packed and encrypted malware pose a significant challenge to automating the identification of malware attributes and functionality. Entropy analysis examines the statistical variation in malware executables, enabling analysts to quickly and efficiently identify packed and encrypted samples.