Beam amplitudes of successive orders diffracted on holographic gratings are calculated and thus nonlinear effects in amplitude, bleached phase and reversal bleached phase holograms are compared. Then values of intermodulation noise are compared for the above three types of Fourier hologram of two circular holes. 相似文献
Two-channel lidar signals that are composed of total rotational scattering and elastic signals provide good information about aerosol scattering coefficients. We can calculate the aerosol backscattering coefficient and extinction coefficient directly, without making any assumption or calibration. Generally, a high-spectral-resolution lidar is used for aerosol monitoring, but we have designed a new low-spectral-resolution lidar system that contains both kinds of scattering information simultaneously, and we have retrieved the aerosol scattering coefficient. The results show that there is no need to assume any relation between aerosol backscattering and extinction or to consider any wavelength calibration to determine the aerosol scattering coefficient. 相似文献
A Seifert matrix is a square integral matrix satisfying
To such a matrix and unit complex number there corresponds a signature,
Let denote the set of unit complex numbers with positive imaginary part. We show that is linearly independent, viewed as a set of functions on the set of all Seifert matrices.
If is metabolic, then unless is a root of the Alexander polynomial, . Let denote the set of all unit roots of all Alexander polynomials with positive imaginary part. We show that is linearly independent when viewed as a set of functions on the set of all metabolic Seifert matrices.
To each knot one can associate a Seifert matrix , and induces a knot invariant. Topological applications of our results include a proof that the set of functions is linearly independent on the set of all knots and that the set of two-sided averaged signature functions, , forms a linearly independent set of homomorphisms on the knot concordance group. Also, if is the root of some Alexander polynomial, then there is a slice knot whose signature function is nontrivial only at and . We demonstrate that the results extend to the higher-dimensional setting.
Large nonlinear phase shifts were generated with femtosecond pulses at 1560 nm through cascaded quadratic interactions in periodically poled MgO-doped LiNbO3. The off-diagonal component of the nonlinear coefficient was utilized for simultaneous quasi phase matching and group-velocity matching. The effective nonlinear refractive index was varied from -2.9 x 10(-14) to +3.3 x 10(-14) cm2/W by tuning the phase-mismatch conditions. 相似文献
Synthesis of novel substituted tetrahydropyrans with adjacent exo-methylene groups at the C3 and C4 positions via Prins-type cyclization has been described. 相似文献
Nanoparticle vesicles were spontaneously assembled from homopolymer polyamine polyelectrolytes and water-soluble, citrate-stabilized quantum dots. The further addition of silica nanoparticles to a solution of quantum dot vesicles generated stable micrometer-sized hollow spheres whose walls were formed of a thick, inner layer of close-packed quantum dots followed by an outer layer of silica. The method employed here to assemble both the nanoparticle vesicles and the hollow spheres is in direct contrast to previous syntheses that use either tailored block copolymers or oil-in-water emulsion templating. We propose that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system. The ease and processibility of the present approach gives promise for the production of a diverse array of materials ranging in applications from drug delivery to catalysis to micrometer-scale optical devices. 相似文献
We report a tunable stimulated-Brillouin-scattering resonator that does not require a starting mirror or a wavelength selector. The resonator is based on the Bragg scattering from the dynamic grating within the active medium itself. The laser dye (Rhodamine 6G dissolved in ethanol) was utilized as the active medium and was pumped by a frequency-doubled Nd:YAG laser. The quality factor (M(2)) of the output beam was 2.2. A single short pulse (<1 ns) with a pumping efficiency of ~4% was observed. 相似文献
The detection of radiocesium in microparticles was performed by using an ion trap mass spectrometer coupled with laser desorption
and ionization. Pulsed laser desorbed particle and the resulted ions were analyzed by an ion trap mass analyzer. The presence
of radiocesium, especially about137Cs, in microparticles was verified by single as well as successive particle analysis. The detection limit was reached to ≈ag/particle
level with a signal-to-background ratio of 4. The inhomogeneous distribution of particle size and the irregular shapes of
particle limit the quantitative evaluation of137Cs concentration in the microparticle. But this high sensitivity allows to monitor directly the radiocesium from small amounts
of a microparticle sample. 相似文献
A novel thin layer cell equipped with thin layer gas electrode (TLGE) was studied as electrochemical gas sensor for the measurement of dissolved oxygen in water or aqueous solutions. The working electrode (TLGE) is a hydrophobic gas diffusing electrode placed between the cell electrolyte and the solution to be tested. The hydrophobic pores in TLGE serve as a gas chamber. After the sampling period, in which the partial pressure of dissolved oxygen in test solution becomes in equilibrium with that in the gas chamber, the TLGE is polarized with square wave or linear potential signal. Then the Faradaic charge (Q) consumed in depletion of the oxygen contained in pores of TLGE is measured. The main merits of this system are good linearity between the partial pressure of dissolved oxygen in test solution and Q, low zero-reading, negligible liquid-gas difference, convenient calibration and very low temperature coefficient (ca. 0.5%/°C). This technique can also be applied to the measurement of oxygen partial pressure in gas phases. 相似文献