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121.
We report a method of scaling the spatial brightness from commercial off-the-shelf diode laser stacks through wavelength beam combining, by use of a linearly wavelength-chirped volume Bragg grating (VBG). Using a three-bar commercial stack of broad-area lasers and a VBG, we demonstrate 89.5 W cw of beam-combined output with a beam-combining efficiency of 75%. The output beam has a propagation factor M2 approximately 26 on the slow axis and M2 approximately 21 on the fast axis. This corresponds to a brightness of approximately 20 MW/cm2 sr. To our knowledge, this is the highest brightness broad-area diode laser system. We achieve 81% coupling efficiency into a 100 microm, 0.22 N.A. fiber. 相似文献
122.
In this paper, we address the following probabilistic version (PSC) of the set covering problem: where A is a 0-1 matrix, is a random 0-1 vector and is the threshold probability level. We introduce the concepts of p-inefficiency and polarity cuts. While the former is aimed at deriving an equivalent MIP reformulation of (PSC), the latter is used as
a strengthening device to obtain a stronger formulation. Simplifications of the MIP model which result when one of the following
conditions hold are briefly discussed: A is a balanced matrix, A has the circular ones property, the components of are pairwise independent, the distribution function of is a stationary distribution or has the disjunctive shattering property. We corroborate our theoretical findings by an extensive computational experiment on a test-bed consisting of almost
10,000 probabilistic instances. This test-bed was created using deterministic instances from the literature and consists of
probabilistic variants of the set covering model and capacitated versions of facility location, warehouse location and k-median models. Our computational results show that our procedure is orders of magnitude faster than any of the existing approaches
to solve (PSC), and in many cases can reduce hours of computing time to a fraction of a second.
Anureet Saxena’s research was supported by the National Science Foundation through grant
#DMI-0352885 and by the Office of Naval Research through contract N00014-03-1-0133. Vineet Goyal’s research was supported
in part by NSF grant CCF-0430751 and ITR grant CCR-0122581. 相似文献
123.
124.
125.
Electrochemical sensor employing edge-plane pyrolytic graphite electrode (EPPGE) for the sensitive detection of hydrocortisone (HC) is delineated for the first time. The electrochemical properties are investigated exercising the cyclic voltammetry and square-wave voltammetry (SWV). When equating with the bare basal-plane pyrolytic graphite electrode (BPPGE), the EPPGE gave better response towards the detection of HC both in terms of sensitivity and detection limit. The voltammetric results indicated that EPPGE remarkably enhances the reduction of HC which leads to considerable amelioration of peak current with shift of peak potential to less negative values. The difference in the surface morphology of two electrodes has been studied. Also, the EPPGE delivered an analytical performance for HC with a sensitivity of 45 nA nM−1 and limit of detection of 88 nM in the concentration range 100-2000 nM. The method has been utilized for the determination of HC in pharmaceuticals and real samples. The electroanalytical method using EPPGE is the most sensitive method for determination of HC with lowest limit of detection to date. The major metabolites present in blood plasma did not intervene with the present investigation as they did not exhibit reduction peak in the experimental range used. A comparison of results with high performance liquid chromatography (HPLC) signalizes a good agreement. 相似文献
126.
Mazaahir Kidwai Poonam Mothsra Vikas Bansal Ritu Goyal 《Monatshefte für Chemie / Chemical Monthly》2006,120(5):1189-1194
Elemental iodine is used as an efficient catalyst for the synthesis of 2,4,5-triarylimidazoles in excellent yields via condensation of benzoin, ammonium acetate, and aromatic aldehydes. This is a simple, one-pot, high yielding technique using
cheap, non-toxic iodine in catalytic amounts. 相似文献
127.
Recentcern
collider data on anomalousZ° events suggest, among other possibilities, a composite structure for the weak intermediate vector bosons. We present a short
review of these developments and examine how far the scenario for weak interactions with such composite models of the weak
vector bosons presents a viable alternative to the standard electroweak theory. In particular, we show how the scale of the
dynamics underlying the composite structure is set by the magnitude of the weak mixing angle sin2
θ
w and point out the possibility of accommodating the anomalous
decay events presently observed within this picture. 相似文献
128.
Bragg cut-off for
plane of polycrystalline beryllium of various lengths of 300 and 116 K has been measured with an energy resolution of 5 μeV.
The natural width of the cut-off is 12.5±1.5 μeV, independent of temperature and length of beryllium and also of physical
characteristics and certain metallurgical treatments of the powder. Such blocks of beryllium would be suitable for designing
a ΔT-window spectrometer with resolution ⩾20 μeV. Bragg cut-offs corresponding to (0002) and
planes of beryllium have been separated for the first time. These can also be used for producing additional energy windows
in a ΔT-window spectrometer, thus increasing its efficiency.
Paper entitled ‘ΔT-window spectrometer’ will appear in the November issue of Pramana. 相似文献
129.
Maiti S Chatterji PR Nisha CK Manorama SV Aswal VK Goyal PS 《Journal of colloid and interface science》2001,240(2):630-635
Aggregation behavior in aqueous solution of a series of poly (ethylene glycol) (PEG)-based macromonomers with methacryloyl group as the only hydrophobic segment has been investigated using surface tension, steady-state and time-resolved fluorescence spectroscopy using pyrene as a probe, and small-angle neutron scattering techniques. The general formula of these macromonomers is CH2=C(CH3)–CO–O–Em–CH3, where E is the ethylene glycol unit and m=8 (ME8), 18 (ME18), 49 (ME49), and 120 (ME120). The results indicate that a macromonomer with 8 ethylene glycol units forms as an aggregate above a certain critical concentration, which can be defined as critical aggregation concentration. The observed high value of I1/I3 in pyrene emission spectra at the interface of these aggregates and the inability to scatter a neutron beam by these aggregates indicate that the hydrophobic cluster formed by this macromonomer is remarkably solvated. ME18 has a tendency to aggregate but others do not form any hydrophobic cluster. The homopolymerization behaviors of these macromonomers in an aqueous medium at 70°C are consistent with these possibi- lities. 相似文献
130.
D. J. Goyal Chitra Agashe M. G. Takwale V. G. Bhide 《Journal of Crystal Growth》1993,130(3-4):567-570
Antimony-doped tin oxide films were deposited by spray pyrolysis on Corning 7059 substrates. The structural and electrical properties of the films deposited with different doping levels were studied. Relative variations in the structural properties were explained on the basis of structure factor calculations. The results show that the incorporation of antimony atoms takes place only at substitutional sites. As expected, the substitutional replacement of tin by antimony atoms increased appreciably the free carrier density of the film. 相似文献