This paper shows a theoretical and experimental study of the CO2 laser remelting of plasma sprayed coatings. The aim of the process is the decrease of the porosity to improve the layer properties. In ...a first approach simulation helps in finding the right process parameters, those parameters allow the melting of the sprayed layer and a minimal amount of substrate material to minimize dilution. The presented modelling includes several features allowing the description of phase transition in the remelting process, the main point is the use of different absorption coefficient in the two phases. Monitoring results gave additional information about the process and another way of doing process validation. The main result are is the prediction size and shape of the remelted layers and due to that the simulation code can be used in the parameter finding and plays an important role in the complete understanding of the process. (Ni-Cr-B-Si deposited on AISI 304.)
Room temperature dual-mode oscillator - first results Torrealba, J.A.; Tobar, M.E.; Ivanov, E.N. ...
Proceedings of the 2005 IEEE International Frequency Control Symposium and Exposition, 2005,
2005
Conference Proceeding
A frequency stability analysis of a room temperature frequency-temperature compensated dual-mode resonator oscillator (patent pending) is presented. Using a single crystal cylindrical sapphire ...resonator, 40 mm in diameter and 20 mm high, two orthogonally polarized whispering gallery modes were simultaneously excited, with the difference frequency temperature dependence annulled near 304 K. The standard Allan deviation of the 3.39 GHz beat between the two modes was measured to be approximately 8 /spl times/ 10/sup -12/ between 1 and 4s.
Class.Quant.Grav.19:1877-1888,2002 To measure the standard quantum limit (SQL) a high quality transducer must be
coupled to a high quality mechanical system. Due to its monolithic nature, the
...monolithic sapphire transducer (MST) has high quality factors for both types of
resonances. Single loop suspension is shown to yield a mechanical quality
factor of 6.10^8 at 4 K. From standard analysis we show the MST has the
potential to measure noise fluctuations of the mechanical oscillator at the
SQL. also, we point out a new way to determine if the transducer back action is
quantum limited. We show that if the fluctuations are at the quantum limit,
then the amplitude of the oscillation will be amplified by the ratio of the
ringdown time to the measurement time, which is an inherently easier
measurement.
Resumen Objetivo Describir el uso de sedantes, analgésicos y bloqueantes neuromusculares (BNM) en los pacientes con ventilación mecánica (VM) prolongada y evaluar los factores asociados a su empleo y ...asociación con la mortalidad a los 28 días. Diseño Estudio multicéntrico, prospectivo y observacional de cohorte. Ámbito Trece unidades de cuidados intensivos (UCI) en Chile. Pacientes Pacientes con VM superior a 48 h. Excluimos los pacientes con enfermedad neurológica, cirrosis hepática, insuficiencia renal crónica, sospecha de adicción a drogas y limitación precoz del esfuerzo terapéutico. Intervención Ninguna Variables de interés principales Proporción de uso y dosis de sedantes, analgésicos y BNM. Nivel de sedación observado (SAS sedation-agitation scale ‘escala de sedación-agitación’). Variables asociadas al nivel de la SAS, y el uso de sedantes, analgésicos y BNM. Regresión logística multivariada de variables asociadas a la mortalidad a los 28 días. Resultados Participaron 155 pacientes (60±18 años, el 57% eran varones, SOFA 7 6–10, APACHE II 18 15–22, el 63% con sepsis y el 47% con lesión pulmonar aguda/síndrome de distrés respiratorio agudo. Los fármacos empleados fueron midazolam (85%; 4 mg/h 1,9–6,8) y fentanilo (81%; 76 μg/h 39–140). Un 30% de los pacientes usó BNM al menos un día. El 55% de la SAS fue 1-2. Existe una asociación entre el uso de BNM y la mortalidad a los 28 días, pero ésta no fue consistente en todos los modelos de uso de BNM evaluados. Conclusiones En el grupo estudiado fue frecuente el uso de sedantes y la presencia de sedación profunda, el midazolam y el fentanilo fueron los fármacos más usados. El uso de BNM podría asociarse de forma independiente a una mayor mortalidad.
We report the first observation of above-threshold maser oscillation in a
whispering-gallery(WG)-mode resonator, whose quasi-transverse-magnetic, 17th
azimuthal-order WG mode, at a frequency of ...approx. 12.038 GHz, with a loaded Q
of several hundred million, is supported on a cylinder of mono-crystalline
sapphire. An electron spin resonance (ESR) associated with Fe3+ ions, that are
substitutively included within the sapphire at a concentration of a few parts
per billion, coincides in frequency with that of the (considerably narrower) WG
mode. By applying a c.w. `pump' to the resonator at a frequency of approx.
31.34 GHz, with no applied d.c. magnetic field, the WG (`signal') mode is
energized through a three-level maser scheme. Preliminary measurements
demonstrate a frequency stability (Allan deviation) of a few times 1e-14 for
sampling intervals up to 100 s.
We report on measurements to characterize phase gradients inside the Cs microwave cavity in the SYRTE double fountain FO2. The clock frequency is measured as a function of the tilt of launch velocity ...with respect to gravity, as a function of the microwave power and when feeding the Ramsey cavity from either sides or symmetrically using the two microwave feedthroughs. These measurements are made with typical uncertainty below 3×10 -16 per point. They show clear non-vanishing results which can be compared to recent theoretical models of the phase distribution.
A dual-mode single crystal sapphire resonator with a frequency-temperature turning point at approximately 50.6 K has been designed (patent pending). It utilizes the inherent anisotropy of the ...temperature coefficient of frequency of two orthogonally polarized quasi-TE/TM modes separated by approximately 3.5 GHz as the oscillator output. The Q-factors of both modes have been measured to be both around 10/sup 8/. The dual mode oscillator was constructed as two individual loop oscillators, each connected to the cryogenic resonator via separate coaxial cables and coupling probes in transmission. The probes were oriented to maximize coupling to the design mode and minimize coupling to the other orthogonally polarized mode. The loop oscillators were operated with Pound locked servos. The beat frequency between the oscillators was measured against a HP8673 synthesizer referenced to an oscilloquartz 8600 OCXO stable reference. A fractional frequency Allan deviation of about 7/spl times/10/sup -13///spl tau//sup 1/2 / was obtained from 1 s to 26 s. Above 26 s the measurement was limited by the noise floor of the measurement system.
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