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61.
The interactional shape of XeF2 with respect to energy and distance was observed by He atom scattering in molecular beam experiments. The heterogeneous second virial coefficient and the binary coefficient of diffusion were calculated from the resulting interaction potential. 相似文献
62.
We study in this article the polynomial approximation properties of the Quadratic Set Covering problem. This problem, which arises in many applications, is a natural generalization of the usual Set Covering problem. We show that this problem is very hard to approximate in the general case, and even in classical subcases (when the size of each set or when the frequency of each element is bounded by a constant). Then we focus on the convex case and give both positive and negative approximation results. Finally, we tackle the unweighted version of this problem. 相似文献
63.
Amantea R. Carlson N.W. Palfrey S.L. Evans G.A. Hammer J.M. Lurie M. 《Quantum Electronics, IEEE Journal of》1990,26(6):1023-1038
The modes and threshold gain characteristics of two-dimensional grating-surface-emitting diode laser arrays that are evanescently coupled in the lateral direction and mutually injection coupled in the longitudinal direction are analyzed. The ratio of the grating transmissivity to reflectivity is found to be a critical parameter in obtaining uniform power distribution inside the array. Good qualitative agreement between the theory and experimentally measured near-field patterns and threshold currents is obtained 相似文献
64.
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
65.
66.
The glassy carbon electrode was modified with a nickel pentacyanonitrosylferrate film by electrodeposition of Ni and subsequent derivatization with NaPCNF. The film was characterized by XPS and electrochemical methods. Cyclic voltammetry of the NiPCNF onto the GC shows a redox couple (FeIII/FeII) with E°′ of 538 mV (Ipa/Ipc around 1) and ΔEp of 93 mV in 0.5 mol L?1 KNO3, with a diffusion‐controlled process. There was a decrease of anodic peak currents of the film in the presence of sulfide and 2‐propanethiol due to a precipitation reaction on the film surface by nucleophilic attack. 相似文献
67.
Reinemann DN Wright AM Wolfe JD Tschumper GS Hammer NI 《The journal of physical chemistry. A》2011,115(24):6426-6431
N-methyliminodiacetic acid (MIDA)-protected boronate esters are a new class of reagents that offer great promise in iterative Suzuki-Miyaura cross-coupling reactions. Compared to earlier reagents, MIDA esters are easily handled and are benchtop stable under air indefinitely. The success of this new species is tied to its unique molecular architecture. Compared to the simpler B-N containing molecules ammonia borane and trimethylamine borane, MIDA esters are much larger, and the sp(3) hybridized boron atom is secured by two five membered rings, making this molecular class stable for spectroscopic study. Here, we present infrared, Raman, and surface enhanced Raman (SERS) spectra of methylboronic acid MIDA ester. Comparisons of the spectroscopic results to those from electronic structure calculations suggest that the B-N stretching mode in this molecule lies in the range 560-650 cm(-1), making it among the lowest energy vibrations observed to date that can be primarily attributed to B-N stretching. 相似文献
68.
69.
S. A. Pikuz T. A. Shelkovenko V. M. Ramanova J. Abdallah Jr. G. Csanak R. E. H. Clark A. Ya. Faenov I. Yu. Skobelev D. A. Hammer 《Journal of Experimental and Theoretical Physics》1997,85(3):484-491
The first experimental studies of an electron beam generated in an X pinch on the XP machine (Cornell University, USA) and the BIN machine (P. N. Lebedev Physical Institute, Russian Academy
of Sciences) are reported. It is shown that it is possible in an X pinch to isolate the effect of a plasma-generated electron beam on the multiply charged ion radiation. The intensities of
the satellite lines corresponding to Li-, Be-, B-, and C-like ions are calculated for the Al spectrum on the basis of a collisional-radiative
model with a non-Maxwellian electron distribution in the plasma. The effect of an electron beam on the multiply charged light
ion radiation in an X-pinch plasma is demonstrated. Comparing our calculations with the experimental spectra, we conclude that the present model
can be used to estimate the electron beam intensity.
Zh. éksp. Teor. Fiz. 112, 894–909 (September 1997) 相似文献
70.
Microresonator filters, which are realized by evanescent coupling of circular cavities with two parallel bus waveguides, are promising candidates for applications in dense wavelength-division multiplexing. Tunability of these filters is an essential feature for their successful deployment. In this paper, we present a framework for modeling of tuning of the microresonators by changes in their cavity core refractive index. Using a reciprocity theorem, a perturbational expression for changes in the cavity propagation constants due to slight modifications of the cavity core refractive index is derived. This expression permits us to analytically calculate shifts in the spectral response of the 2-D resonators. Comparisons of the resultant shifts and spectra with direct simulations based on a coupled mode theory show satisfactory agreement. 相似文献