Laser-mode selection by a combination of biprism-like reflectors with narrow amplitude masks

In recent work the laser mode selectivity induced separately by a biprism-like reflector and by an absorbing strip was investigated by numerical analysis. It was shown that each of these elements in an otherwise conventional resonator was suitable to cause the laser to oscillate preferentially on the first odd mode that contains a line singularity, which is a useful dark beam (i.e., a laser beam with a dark central region) for high-resolution metrological applications. We study the combined effect of these two mode-selecting elements and show that the unified analysis leads to much better performance than could be expected from a simple superposition of the performance with each element alone. The results indicate that the mode selectivity can be enhanced by at least a factor of 3 compared with that of laser resonators with biprism-like reflectors alone. Thus a laser equipped with such a combined element will oscillate on a pure first-order mode with high power efficiency. Moreover, calculations show that the resultant dark beam, focused for metrological applications, has a significantly improved shape compared with the dark beam obtained by external modulation of a fundamental Gaussian beam.     

Design,analysis and testing of a smart fin

The paper presents a design concept for a control fin usually used in airborne vehicles such as UAV’s, Micro UAV’s and missiles. The research presents the design of a smart fin with integral piezoelectric actuators embedded in the airfoil skin. Electric field applied to the actuators would twist the airfoil leading to a change of the angle of attack. The study presents, analyze and demonstrates various lamination and actuation methods including a parametric performance investigation by finite elements models and closed form analytical model. The design and the theoretical results are verified by a manufactured smart wing demonstrator subjected to series of static and dynamic lab tests.     

Zonal flow energy ratio evolution during L-H and H-L transitions in EAST plasmas

The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized probe arrays are used to measure the zonal flow during L-H transition and H-L back transition.The energy ratio of the low frequency zonal flow to the total drift wave turbuletce is calculated.During ELM-free H mode,the energy ratio is higher than that in L mode,which reveals the important role of zonal flows in regulating turbulence amplitude in L-H transition.     

Preparative separation of mixtures by mass spectrometry

A specially designed mass spectrometer which allows for preparative separation of mixtures is described. This mass spectrometer allows for large ion currents, on the order of nanoamperes, to be produced by electrospray and transmitted into a high vacuum. Accumulation of nanomole quantities of collected and recovered material in several hours is demonstrated. The use of high-velocity ions reduces space charge effects at high ion currents. Separation of mass occurs simultaneously for all ions, providing a 100% duty cycle. The use of a linear dispersion magnet avoids compression at higher m/z ratios. A deceleration lens slows the ions to allow for soft landing at low kinetic energy. The ions are neutralized by ion pairing on an oxidized metal surface. Retractable landing plates allow for easy removal of the separated components.     

Incorporating reliability in optimal design of water distribution networks—review and new concepts

Much of the effort in optimal design of water distribution networks (WDNs) has focussed so far on minimizing cost alone, with little emphasis on reliability or on investigating the tradeoff between cost and reliability. This is a consequence of the difficulty in defining reliability measures which are meaningful and appropriate, while still of a form which can be incorporated directly into optimization models. This paper will deal with these issues. It contains three parts: (1) conceptual discussion of reliability definitions from different points of view (system versus consumers), (2) a literature survey of existing techniques to incorporate reliability in the optimal design of WDNs, and (3) a new concept for explicitly including reliability in the optimal design of WDNs.     

Matrix continued fractions are directly related to the maximal (A, B)-invariant subspace in KerC

The maximal(A, B)-invariant subspace in KerCis characterized in terms of polynomial models, by its properties pertaining to the Hankel map. This characterization is directly related to the first stage in a continued fraction representation of the transfer function. The atoms of the continued fraction are given explicitly in terms of Tocplitz operators. We also obtain a complete characterization and parametrization of eligible first-atoms, based on Weiner-Hopf indexes. We show how to construct a first atom which is column proper and determines a feedback equivalent, feedback irreducible transfer function.