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1.
Selective enhancement (>10(3)) of harmonics extending to the water window (approximately 4 nm) generated in an argon gas filled straight bore capillary waveguide is demonstrated. This enhancement is in good agreement with modeling which indicates that multimode quasi-phase-matching is achieved by rapid axial intensity modulations caused by beating between the fundamental and higher-order capillary modes. Substantial pulse energies (>10 nJ per pulse per harmonic order) at wavelengths beyond the carbon K edge (approximately 4.37 nm, approximately 284 eV) up to approximately 360 eV are observed from argon ions for the first time. 相似文献
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Ohne Zusammenfassung
Uebersetzt von J. Matula (Wien). Eine vorl?ufige Mitteilung der in dieser und einer vorhergehenden in dieser Zeitschrift erschienenen
Abhandlung niedergelegten Ergebnisse erschien in Science43 (1916). 相似文献
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Samuel C. Hooker 《Fresenius' Journal of Analytical Chemistry》1889,28(1):711
Ohne Zusammenfassung 相似文献
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We take a regression-based approach to the problem of induction, which is the problem of inferring general rules from specific instances. Whereas traditional regression analysis fits a numerical formula to data, we fit a logical formula to boolean data. We can, for instance, construct an expert system for fitting rules to an expert's observed behavior. A regression-based approach has the advantage of providing tests of statistical significance as well as other tools of regression analysis. Our approach can be extended to nonboolean discrete data, and we argue that it is better suited to rule construction than logit and other types of categorical data analysis. We find maximum likelihood and bayesian estimates of a best-fitting boolean function or formula and show that bayesian estimates are more appropriate. We also derive confidence and significance levels. We show that finding the best-fitting logical formula is a pseudo-boolean optimization problem, and finding the best-fitting monotone function is a network flow problem.The first and second authors gratefully acknowledge the partial support of NSF (Grant DMS 89-06870) and AFOSR (Grants 89-0512 and 90-0008), and the third author that of AFOSR (Grant 91-0287) and ONR (Grant N00014-92-J-1028). 相似文献
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K. Osvay I. N. Ross C. J. Hooker J. M. D. Lister 《Applied physics. B, Lasers and optics》1994,59(3):361-365
A detailed investigation of laser-generated nonlinear processes of undoped barium fluoride is presented including two-photon-excited exciton fluorescence, color-center formation and damage-threshold measurements. A single-shot autocorrelator based on two-photon fluorescence of BaF2 was constructed to measure the phase and amplitude of pulses provided by large apeture excimer lasers. The capabilities of the autocorrelator are demonstrated at 248 nm and 268 nm with pulses in the regime of 100 fs to 10 ps. 相似文献
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Gonsalves AJ Rowlands-Rees TP Broks BH van der Mullen JJ Hooker SM 《Physical review letters》2007,98(2):025002
Transverse interferometric measurements are presented of the plasma channel formed in a hydrogen-filled capillary discharge waveguide recently used to generate 1 GeV electrons in a laser-driven plasma accelerator for the first time. The measurements were found to be in good agreement with nonlocal thermal equilibrium simulations, but showed significant differences with the results of a quasistatic model developed by Bobrova et al. [Phys. Rev. E. 65, 016407 (2001)]. The measurements are used to determine scaling laws for the axial electron density and matched spot size of the plasma channel, enabling optimization of the channel to specific applications. 相似文献
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Cover inequalities are commonly used cutting planes for the 0–1 knapsack problem. This paper describes a linear-time algorithm (assuming the knapsack is sorted) to simultaneously lift a set of variables into a cover inequality. Conditions for this process to result in valid and facet-defining inequalities are presented. In many instances, the resulting simultaneously lifted cover inequality cannot be obtained by sequentially lifting over any cover inequality. Some computational results demonstrate that simultaneously lifted cover inequalities are plentiful, easy to find and can be computationally beneficial. 相似文献
10.
Using optical probing techniques plasma jets have been observed in the underdense plasma corona of targets irradiated with green laser beams. Various experimental observations have produced evidence that the jets are generated by an instability rather than by non-uniformities in the incident laser beams. 相似文献