Spectral beam combining of 2 μm Tm fiber laser systems

Output beams from three independently frequency-stabilized thulium master-oscillator power-amplifier fiber laser systems were spectrally combined using a plane-ruled metal diffraction grating. Two laser channels were frequency-stabilized with guided mode resonance filters and the third was stabilized using a plane-ruled metal diffraction grating. The systems had output wavelengths between 1984 and 2015 nm, each with a spectral width of 100-450 pm and output powers between 40-120 W. The combined beam had powers up to 49 W and was 32% efficient with respect to the launched pump power.     

Amorphous BeN as a new solid host for rare‐earth‐related luminescent materials

Beryllium‐nitride (BeN) thin films were prepared by sputtering a Be target in an atmosphere of pure nitrogen. The films were doped with samarium simply by placing a piece of Sm metal on the surface of the Be target. Under these deposition conditions the films present an amorphous structure and an optical bandgap of approx. 4 eV. They also exhibit visible light emission due to Sm³⁺ ions as a result of either photon or electron excitation. The present experimental results show that amorphous BeN films are suitable, and efficient, III‐nitride hosts for rare‐earth doping purposes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Speaking rate of adventitiously deaf male cochlear implant candidates

No objective group data on speaking rate or speaking duration have been reported on the speech of adventitiously profoundly hearing-impaired adults. Results of the present study showed that speaking rate, i.e., number of syllables per second, was significantly slower and speaking duration was significantly longer for 25 adventitiously profoundly hearing-impaired adult male cochlear implant candidates than for 10 normal-hearing control subjects. The factors of length of time since onset of profound hearing loss and hearing aid use did not significantly affect speaking rate. Based on these objective data, a rationale and method are presented for aural rehabilitation of the profoundly hearing-impaired who exhibit speaking rate abnormalities.     

Effects of bleaching on the sensitivity to dose of the infrared-stimulated luminescence of potassium-rich feldspars from Ynyslas, Wales

Reduction of the luminescence signal to a residual level before irradiation is an inherent part of the regeneration method of equivalent dose (ED) determination, but is likely to lead to changes in the sensitivity of the dosimeter. Sensitivity changes caused by different methods of reduction of the infrared- stimulated luminescence (IRSL) signal have been investigated by subjecting potassium-rich feldspars extracted from modern dune sand from Ynyslas, on the Dyfi Estuary in Wales, to repeated cycles of removal of the luminescence signal and beta irradiation. The methods used to remove the signal were exposure to natural sunlight, a solar simulator and infrared-emitting diodes with a wavelength of 880Δ 80 nm and heating to 450°C.     

Comparative extreme ultraviolet emission measurements for lithium and tin laser plasmas

Detailed spectroscopic studies on extreme UV emission from laser plasmas using tin and lithium planar solid targets were completed. At 13.5 nm, the best conversion efficiency (CE) for lithium was found to be 2.2% at intensities near 7 x 10(10) W/cm(2). The highest CE measured for tin was near 5.0% at an intensity close to 1 x 10(11) W/cm(2).     

Freezing-off in disc cavities

A semi-quantitative analysis is presented of freezing-off in a disc cavity during the injection moulding of thermoplastics. A criterion is obtained which enables the occurrence of freezing-off to be predicted, at least crudely. The form of the criterion is found to depend on the direction of flow (radially outward or inward) in the disc.     

Injection moulding of thermoplastics. I. Freezing-off at gates

The injection moulding of thermoplastics involves, during mould filling, flow of a hot molten polymer into a mould network, the walls of which are so cold that the polymer freezes on them. During the constant pressure drop part of the filling stage, but not during the preceding constant flow-rate part, freezing-off, that is premature blockage of the mould network by frozen polymer, is possible. A semi-quantitative analysis of such freezing-off at a gate is presented here. The length-scales and time-scales of all the relevant physical processes occurring during freezing-off are identified and a criterion is obtained which enables the occurrence of freezing-off to be predicted, at least crudely. a _j constant - b _jk constant - Br Brinkman number - Br ₀ initial Brinkman number - Gz Graetz number - Gz ₀ initial Graetz number - h _c half-height of flat cavity - h _g half-height of flat gate - h _g ^* half-height of polymer melt region in flat gate - L _c length of cavity - L _f filled length - L _g length of gate - m viscosity shear-rate exponent - P pressure drop - Q volumetric flow-rate - r radial coordinate in round gate and cavity - R _c radius of round cavity - R _g radius of round gate - R _g ^* radius of polymer melt region in round gate - Sf Stefan number - t time - t _f freeze-off time - T temperature - T _i inlet polymer melt temperature - T _m melting temperature of polymer - T _w gate wall temperature - u _r radial velocity in round gate - u _x axial velocity in flat gate - u _y transverse velocity in flat gate - u _z axial velocity in round gate - w _c width of flat channel - w _g width of flat gate - x axial coordinate in flat gate and cavity - y transverse coordinate in flat gate and cavity - z axial coordinate in round gate and cavity - thermal conductivity of molten polymer - thermal conductivity of frozen polymer - heat capacity of molten polymer - heat capacity of frozen polymer - _h ratio of half-height of flat gate to that of flat cavity - _R ratio of radius of round gate to that of round cavity - _w ratio of width of flat gate to that of flat cavity - dimensionless axial coordinate in round gate and cavity - dimensionless transverse coordinate in flat gate and cavity - ^* dimensionless half-height of polymer melt region in flat gate - dimensionless temperature - _i dimensionless inlet temperature - _j j-th term in power series expansion of dimensionless temperature - thermal diffusivity ratio - dimensionless filled length - latent heat of fusion of polymer - µ viscosity - µ ₀ unit shear-rate viscosity - v _j j-th eigenvalue - j-th zero of zeroth-order Bessel function of first kind - dimensionless axial coordinate in flat gate and cavity - _c dimensionless pressure drop in cavity - _g dimensionless pressure drop in gate - density of molten polymer - density of frozen polymer - dimensionless radial coordinate in round gate and cavity - ^* dimensionless radius of polymer melt region in round gate - dimensionless time - _f dimensionless freeze-off time - ₀ dimensionless time at start of final phase of freezing-off - rescaled dimensionless time - rescaled dimensionless freeze-off time - rescaled dimensionless time at start of final phase of freezing-off - dimensionless similarity variable - dummy variable - scaled dimensionless axial coordinate in gate     

A Districtwide Study of Automaticity When Included in Concept‐Based Elementary School Mathematics Instruction

While conceptual understanding of properties, operations, and the base‐ten number system is certainly associated with the ability to access math facts fluently, the role of math fact memorization to promote conceptual understanding remains contested. In order to gain insight into this question, this study looks at the results when one of three elementary schools in a school district implements mandatory automaticity drills for 10 minutes each day while the remaining two elementary schools, with the same curriculum and very similar demographics, do not. This study looks at (a) the impact that schoolwide implementation of automaticity drills has on schoolwide computational math skills as measured by the ITBS and (b) the relationship between automaticity and conceptual understanding as measured by statewide standardized testing. The results suggest that while there may be an association between automaticity and higher performance on standardized tests, caution should be taken before assuming there are benefits to promoting automaticity drills. These results are consistent with those that support a process‐driven approach to automaticity based on familiarity with properties and strategies associated with the base‐ten number system; they are not consistent with those that support an answer‐driven approach to automaticity based on memorization of answers.