排序方式: 共有11条查询结果,搜索用时 15 毫秒
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An indirect laser-induced method for selective removal of large copper areas from a printed circuit board is theoretically and experimentally investigated. The results show that the threshold condition for the process involves phase transition of the epoxy-based substrate resin. Optimal parameters for maximizing process speed are found and discussed. 相似文献
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Diode-pumped passively mode-locked Nd:YAG laser with 10-W average power in a diffraction-limited beam 总被引:2,自引:0,他引:2
Spühler GJ Paschotta R Keller U Moser M Dymott MJ Kopf D Meyer J Weingarten KJ Kmetec JD Alexander J Truong G 《Optics letters》1999,24(8):528-530
We present a passively mode-locked Nd:YAG laser with 10.7-W average output power in a diffraction-limited beam. Stable self-starting mode locking with a pulse duration of 16 ps and a pulse energy of 120 nJ is obtained with a semiconductor saturable-absorber mirror. The laser is directly side pumped with two 20-W diode bars. Single-pass frequency doubling in an external 5-mm-thick KTP crystal yields 3.2-W average power at 532 nm. 相似文献
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Moisture content of solid-state pharmaceutical products is one of the main factors that affect drug stability, therefore suitable sorption studies need to be performed to assure drug quality throughout their shelf life. The Brunauer-Emmett-Teller (BET) and the Guggenheim-Anderson-de Boer (GAB) models are usually used for this purpose. Using gravimetrically obtained data, both methods were applied in the present work to evaluate the sorption characteristics of several excipients. Microcalorimetric analysis was also performed in order to evaluate the interaction between water and the substances. The results of these experiments show excellent agreement between data and the BET model up to 55% RH and the GAB model over the entire humidity range, confirmed by high values of the statistical determination coefficients. Furthermore, microcalorimetric measurements suggested that the hygroscopicity of solid materials could be estimated approximately using this approach. 相似文献
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A model-based optimisation of the process of printed circuit board laser structuring is presented. For this purpose, a comprehensive theoretical model of the interaction between the travelling pulsed laser beam and conductive layer, as well as between the laser beam and the induced plasma plume is employed. The model is used to calculate process speed. Based on the process speed determined, the influence of pulse power, duration, and frequency on process speed is analysed. In addition, an optimal range of process parameters with respect to process speed and quality is defined. 相似文献
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We present a pump-and-signal-resonant optical parametric oscillator that provides 25 dB of amplitude noise suppression of the transmitted pump beam from dc to 20 kHz. The upper frequency range of the optical limiter increases as the pump power is increased, up to 1 MHz with 580 mW of input power. The amount of noise suppression is limited by pump-depletion effects. The upper frequency range is limited by the temporal response of the device. We present a numerical analysis that predicts this behavior. 相似文献
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Miha Vivoda Robert Roškar Vojko Kmetec 《Journal of Thermal Analysis and Calorimetry》2011,105(3):1023-1030
This study presents a contribution in the development of a quick and accurate testing method for the determination of amorphous
content using isothermal microcalorimetry. Examples demonstrated how the choice of the experimental conditions, especially
sample load, temperature and humidity, influences the crystallization of the amorphous material. The suitability of this systematic
approach was first tested on well-known lactose and afterwards on nifedipine as model compounds. It was shown that by proper
method design and careful selection of experimental conditions, it is possible to achieve quick determination of the amorphous
content in samples with a quantification limit of less than 1%, what is considerably better than by classical analytical methods
such as DSC and XRPD. Our optimized microcalorimetry method gave also better results compared to previously reported literature
data for nifedipine. 相似文献
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Isothermal microcalorimetry has been applied as a method for predicting (in)stability of ascorbic acid and several amino acids
that undergo oxidative degradation in aqueous media. The fast and simple method involved the addition of different amounts
of hydrogen peroxide. The appearance of the heat flow curves gave a clear general indication of how stability was influenced.
The accuracy of the microcalorimetric result was investigated by comparing it with an HPLC assay and a good agreement between
the results of both methods was demonstrated. It was also established that susceptibility to oxidative degradation decreases
in the following order: cysteine, methionine, ascorbic acid, tyrosine and tryptophan. 相似文献
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