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71.
72.
P.K.?MukhopadhyayEmail author M.B.?Alsous K.?Ranganathan S.K.?Sharma P.K.?Gupta J.?George T.P.S.?Nathan 《Applied physics. B, Lasers and optics》2004,79(6):713-720
Simultaneous Q-switching and mode locking in a laser-diode end-pumped intracavity frequency-doubled Nd:YVO4/KTP green laser using a Cr4+:YAG saturable absorber with 81% initial transmission is experimentally demonstrated. At an incident pump power of 6 W, 300 mW of average green power was obtained, which is around four times higher than the cw green power obtained without the Cr4+:YAG crystal. The repetition rate of the mode-locked green pulses was 400 MHz and the individual mode-locked pulse width was measured to be 500 ps. The repetition rate of the Q-sw itched envelope of the mode-locked pulses was 15 kHz at 6 W of incident pump power. The energy of the mode-locked pulse at the peak of the Q-sw itched envelope was estimated to be 1 J and the peak power was estimated to be 2.4 kW. The measured width and the total energy of the Q-sw itched envelope of the mode-locked pulses was 47 ns and 21 J, respectively, at the maximum incident pump power. An analysis of the system by incorporating a nonlinear loss term due to the intracavity second-harmonic generation to the general recurrence relation for the mode-locked pulses under the Q-sw itched envelope at the fundamental wavelength has been presented. Using a hyperbolic secant square function to model the mode-locked pulse, the temporal shape of a single Q-sw itched pulse at the second-harmonic wavelength has been reconstructed. The theoretical calculations of the pulse parameters like pulse energy, peak power, pulse width and pulse-symmetry factor have shown fairly good agreement with the experimental results. PACS 42.55.Rz; 42.55.Xi; 42.60.By 相似文献
73.
Hemalatha Ranganathan T. Ramasami C. K. Ranganathan D. Ramaswamy M. Santappa 《国际化学动力学杂志》1982,14(2):161-172
The kinetics and product analyses of the amine exchange reactions of two 2-aminopyridine derived Schiff-base ligands and their monomeric bischelate and dimeric copper(II) complexes have been studied. The Schiff-base ligands investigated underwent amine exchange reactions with n-butyl, cyclohexyl, t-butyl amines. The coordination of the Schiff-base ligands to copper(II) rendered the amine exchange reactions slower. With n-butyl and cyclohexyl amines, parallel first- and second-order terms on their concentrations are observed for the amine exchange reactions of copper(II) bischelates and dimer. The kinetic data favor a mechanism involving a rate-limiting elimination of 2-aminopyridine from a diaminoacetal intermediate in preference to a scheme in which a dissociation of the complexes into free ligands and Cu(II) may precede the amine exchange. The steric factors influence the amine exchange reactions of Cu(II) bischelates with the bulkier amines reacting slower as given by the order t-butylamine (3.3 ± 0.3 × 10?3 dm3/mol·s) < cyclohexylamine (0.2 ± 0.03 dm3/mol·s) < n-butylamine (2.2 ± 0.2 dm3/mol·s). The bulkiness of the t-butyl group and the constraints imposed by the changes in the coordination geometry of Cu(II) on amine exchange not only render the reactions of Cu(II) bischelates slower but also make the formation of the mixed adduct ([N-(5-methyl)-2-pyridyl salicylaldimine][N-t-butyl salicylaldimine] Cu(II)) more favored. 相似文献
74.
A series of 4,4'-disubstituted biphenyls, designated as series HBC, in which, one substituent is an ester group linked directly to the ring and the other is the hydroxy-containing group O(CH2)nOH, have been prepared and analysed by differential scanning Calorimetry, polarizing optical microscopy and X-ray diffraction. The introduction of a trimethylene unit between the ester functional group and the biphenyl moiety of the HBC series gives rise to the HBB series, which did not exhibit liquid crystalline behaviour. Interestingly, mesophase behaviour could be restored by replacing the methylene group (of the trimethylene unit) that was directly attached to the biphenyl ring by a keto group (HBOB series). When the terminal hydroxy group of these three series was substituted by a group such as acetoxy or hydrogen, the transition temperatures were reduced, and the disappearance of mesophase behaviour was observed in some cases. However, this could be recovered by the replacement of the ester group by a carboxylic acid group. 相似文献
75.
In the new approach to the cascade theory suggested by Alladi Ramakrishnan and one of us (S. K. S.), we deal with the number of electrons produced between 0 andt in a soft cascade, each of these electrons having an energy greater than E at the point of its production as contrasted with the usual approach where we are interested in the number of electrons with energy greater than E att. We present here numerical calculations of the mean numbers on the basis of the new approach. 相似文献
76.
Cover Feature: Laccase‐Catalyzed Synthesis of Low‐Molecular‐Weight Lignin‐Like Oligomers and their Application as UV‐Blocking Materials (Chem. Asian J. 3/2018)
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The present paper considers the formation of crystalline phases during solidification and crystallisation of the Zr53Cu21Al10Ni8Ti8 alloy. Solidification was carried out by a copper mould casting technique, which yielded a partially crystalline microstructure comprising a ‘big cube phase’ in a dendritic morphology and a bct Zr2Ni phase. Detailed high-resolution microscopy was carried out to determine possible mechanisms for the formation of the crystalline phases. Based on microstructural examinations, it was established that the dendrites grew by the attachment of atomistic ledges. The bct Zr2Ni phase, formed during solidification and crystallisation, showed various types of faults depending on the crystallite size, and its crystallography was examined in detail. It has been shown that the presence of these faults could be explained by anti-site occupancy in the bct lattice of the Zr2Ni phase. 相似文献
80.
We report the design and construction of a thermoelectric power apparatus using home-made electro-optic relays with Z-80A
microprocessor for automatic data acquisition and control. The advantages of such relays made out of LED-LDR combinations
for the measurement of ΔE and ΔT are discussed in detail. 相似文献