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1.
In a twisted nematic liquid crystal cell we report and study the self-transparency effect induced by the creation of an isotropic droplet. A simple theoretical model is presented and good agreement with experimental data is found. In a two beams configuration transistor-like behavior is observed and theoretically discussed. 相似文献
2.
F. Bloisi A. Pezzella M. Barra M. Alfè F. Chiarella A. Cassinese L. Vicari 《Applied Physics A: Materials Science & Processing》2011,105(3):619-627
Eumelanin is an important pigment almost ubiquitous in animals and plants exhibiting interesting charge transport capabilities.
Its poor solubility in common solvents represents a severe limitation for preparing thin films. It was recently demonstrated
that eumelanin films can be successfully deposited with the MAPLE (Matrix Assisted Pulsed Laser Evaporation) technique starting
from a frozen water suspension, using infrared laser radiation. The low laser absorption of ice together with the high absorption
of eumelanin suggests that the target ablation is due to laser energy absorbed by the eumelanin molecules, followed by thermal
energy transfer, and ejection of ice/water/vapor containing undamaged eumelanin molecules and supramolecular structures. 相似文献
3.
Valeria Califano Francesco Bloisi Luciano R.M. Vicari Paolo Colombi Laura E. Depero 《Applied Surface Science》2008,254(22):7143-7148
Double layers of polyethylene glycol (PEG) and 3-(3,4-dihydroxyphenyl)-2-methyl-l-alanine (m-DOPA) thin films were obtained by matrix assisted pulsed laser evaporation (MAPLE) technique, by depositing a first layer of m-DOPA on Si substrate and a second layer of PEG on top of it. The films were characterized by low angle X-ray diffraction (LAXRD), X-ray reflectivity (XRR), atomic force microscopy (AFM), and micro-Raman spectroscopy. From these analyses it resulted that PEG was deposited without any relevant damage both in terms of chemical structure and molecular weight. Furthermore, PEG chains were mostly in the extended conformation, although PEG micelles appeared. 相似文献
4.
Summary A mathematical model able to describe the temperature profiles generated in a thin film by the steady-state illumination by
a Gaussian laser beam is presented. The film is supposed to be made by a weakly absorbing liquid sample bounded by two parallel
transparent plates, the cell walls, whose thermal exchange to the surrounding ambient may be assumed to be linear with the
temperature difference. An analytical solution of the problem is presented in form of Hankel transform and a matrix numerical
approach to the computation of the temperature profiles is reported. It is particularly well suited to a computer implementation
and allows one to get very accurate results in very short computing times. The influence of the heat exchange coefficient
to the ambient is shown in an example. A check of the method accuracy is performed by comparison with literature results in
the particular case of infinite heat exchange coefficient.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
5.
F. Bloisi L. Vicari P. Cavaliere S. Martellucci J. Quartieri P. Mormile G. Pierattini 《Applied physics. B, Lasers and optics》1988,47(1):67-69
The temperature field generated by the weak absorption of a gaussian laser beam in an optically and thermally thin film bounded by two transparent plates is discussed. An analytical solution of the problem is presented together with an algorithm for the numerical integration. The influence of the finite thermal conductivity of the plates is shown in an example. 相似文献
6.
F.?Bloisi C.?Ebanista L.?Falcone L.?Vicari 《Applied physics. B, Lasers and optics》2010,101(1-2):471-479
Infrared reflectography, i.e. the use of images taken with infrared light, is currently applied in the field of cultural heritage mainly for paintings analysis to reveal the presence of underdrawings or alterations. Its use in archaeology for deciphering faded signs (texts, images, tattoos, etc.) is a lot more limited and in most cases no or simple data analysis and elaboration is performed. Here we show that infrared reflectography taken by using a wide spectral response (wavelength range from 400 to 2200 nm) VIDICON image acquisition system together with adequate post-elaboration, taking advantage from advanced techniques for data analysis (wavelet decomposition) and image registration and fusion, is able to produce high-quality ‘C&IR’ images. Such images can be obtained in a relatively easy way using the same hardware configuration generally used for infrared reflectographic analysis of paintings. The application to a medieval capsella (a small wooden relics container) from Cimitile, Italy, has shown that these results are of great interest for archaeologists. 相似文献
7.
Summary A mathematical model of the far-field diffraction pattern of a laser beam with laser heating self-phase modulation through
an optically thin film is presented. We deal with the steady-state temperature field generated by the weak absorption of a
laser beam in an optically and thermally thin film bounded by two transparent plates, the cell walls, whose thermal exchange
to the surrounding ambient has been assumed to be linear in the temperature difference to the ambient. These hypotheses describe
the application of the steady-state ?thermal lens? spectroscopy to the detection of the optical or thermal properties of liquid
samples. We give a very simple expression for the diffracted intensity that appears suitable for fast computer calculations.
The good accuracy of the technique is shown by comparison with the results given by more intricate approaches.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
8.
D. Benedetti E. Bontempi L.E. Depero M. Zoncheddu G. Di Blasio F. Bloisi L. Vicari C. Piccioli 《Applied Physics A: Materials Science & Processing》2006,83(4):657-661
The laser-cleaning technique has been effectively employed in many areas. Recently it has led to a huge development in art restoration. However, this technique must be optimised to remove contaminations and encrustations from surfaces without generating any physical or chemical changes of the original material.Its use has been considered to clean a 4th century B.C. chamber gravesite in Torricelle, near Nola (Naples). The wall painting could not be seen owing to bioorganic surface layer and resinous material originated from surrounding pinewood. In order to evaluate the technique effectiveness we studied the interaction of the light from a Q-switched Nd: YAG equipped with SHG to work at wavelength of 532 nm.Several characterization techniques have been employed to verify the laser effect on the cleaning of the surface versus the operating parameter configuration and to evaluate the possible damages induced by the beam. In particular, micro X-Ray fluorescence (μXRF) provided information on the chemical composition of the clean surface; X-ray microdiffraction (μXRD) was used to identify the phases and their microstructures. These techniques were effective in assessing the quality of the cleaning process and for following the changes in the microstructure of the sample.Preliminary results suggest a possible influence of the laser on the aragonite–calcite transformation. PACS 61.10.Nz; 33.20.Rm; 42.62.-b; 61.66.Fn; 81.65.Cf 相似文献
9.
M. Marinelli U. Zammit F. Scudieri S. Martellucci F. Bloisi L. Vicari 《Il Nuovo Cimento D》1987,9(7):855-862
Summary The photoacoustic-technique application to the simultaneous characterization of the thermal diffusivity, specific-heat capacity
and thermal conductivity of a liquid crystal at a phase transition is presented for the first time. The first two parameters
show a critical decrease and increase, respectively, while the third one does not exhibit any critical behaviour.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
10.
Summary We present a new computational method which allows to work out the director orientation in each location of a nematic liquid-crystal
cell from a measurement of its reflectivity. We show how it is possible to extract this information from the fringe pattern
due to the onset of total internal reflection inside the sample. The very good agreement with the expected results makes the
method suitable to study several kinds of deformations occurring in liquid crystals.
Work presented at the second USSR-Italy Bilateral Meeting on Liquid Crystals held in Moscow, September 15–21, 1988. 相似文献