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1.
Salah-Eddine Chorfi Ghita El Guermai Lahcen Maniar Walid Zouhair 《Mathematical Methods in the Applied Sciences》2023,46(1):911-929
This paper studies an inverse hyperbolic problem for the wave equation with dynamic boundary conditions. It consists of determining some forcing terms from the final overdetermination of the displacement. First, the Fréchet differentiability of the Tikhonov functional is studied, and a gradient formula is obtained via the solution of an associated adjoint problem. Then, the Lipschitz continuity of the gradient is proved. Furthermore, the existence and the uniqueness for the minimization problem are discussed. Finally, some numerical experiments for the reconstruction of an internal wave force are implemented via a conjugate gradient algorithm. 相似文献
2.
M. F. Lazarescu D. Pantelica A. S. Manea R. V. Ghita F. Negoita 《Journal of Crystal Growth》2002,240(3-4):401-406
We found Oxygen-doped GaAs crystals to be suitable materials for CO2 laser optical component preparation, with application at 10.6 μm. An optical transmission of 55% in the IR spectrum range, between 2 and 15 μm has been reached for such a GaAs type material. The GaAs crystals that we have analysed were grown by two procedures: Horizontal Bridgman (HB) and Liquid Encapsulated Czochralski (LEC). The HB method has been used for obtaining pure (undoped) crystals, while the oxygen-doped GaAs ingots were grown by LEC technique. The two types of samples processed in the same manner as regards mechanical polishing and chemical etching, which were investigated by Hall measurements, optical transmission spectrometry and elastic recoil detection analysis (ERDA) technique. The GaAs:O (LEC) has near semi-insulating properties as can be observed from the results of the electrical resistivity and Hall effect measurements. The ERDA spectrum shows an intense signal of oxygen in the bulk of GaAs:O (LEC) crystals, while the oxygen signal is not present in the ERDA spectrum of the undoped GaAs (HB). We consider that these results could recommend the ERDA technique as a possible qualitative and quantitative analysis in an ion-beam accelerator for oxygen content in oxygen-doped GaAs crystals. The analysis is not sensitive to the native oxide, as could be seen by measuring GaAs (HB) undoped crystals. 相似文献
3.
Journal of Fluorescence - 相似文献
4.
Recovering the depth information derived from dynamic scenes implies real-time range estimation. This paper addresses the implementation of a bifocal range sensor which estimates the depth by measuring the relative blurring between two images captured with different focal settings. To recover the depth accurately even in cases when the scene is textureless, one possible solution is to project a structured light on the scene. As a consequence, in the scene's spectrum a spatial frequency derived from illumination pattern is evident. The resulting algorithm involves only simple local operations, this assures the possibility of computing the depth at a rate of 10 frames per second. The experimental results indicate that the accuracy of this proposed sensor compares well with that offered by other methods such as stereo and motion parallax, while avoiding the problems caused by occlusion and missing parts. 相似文献
5.
G. Schettino M. Ghita K. M. Prise 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(1):157-161
Cellular response to radiation damage is made by a complex network of
pathways and feedback loops whose spatiotemporal organization is still
unclear despite its decisive role in determining the fate of the damaged
cell. The single-cell approach and the high spatial resolution offered by
microbeams provide the perfect tool to study and quantify the dynamic
processes associated with the induction and repair of DNA damage. The soft
X-ray microbeam has been used to follow the development of radiation induced
foci in live cells by monitoring their size and intensity as a function of
dose and time using yellow fluorescent protein (YFP) tagging techniques.
Preliminary data indicate a delayed and linear rising of the intensity
signal indicating a slow kinetic for the accumulation of DNA repair protein
53BP1. A slow and limited foci diffusion has also been observed. Further
investigations are required to assess whatever such diffusion is consistent
with a random walk pattern or if it is the result of a more structured
lesion processing phenomenon. In conclusion, our data indicates that the use
of microbeams coupled to live cell microscopy represent a sophisticated
approach for visualizing and quantifying the dynamics changes of DNA
proteins at the damaged sites. 相似文献
6.
Mark A. Beard Oana R. Ghita James McCabe Kenneth E. Evans 《Journal of Raman spectroscopy : JRS》2010,41(10):1283-1288
The dehydration kinetics of theophylline monohydrate is a two‐stage process. The first stage involves loosening of the crystal water followed by a second stage in which the water evaporates from the sample. During differential scanning calorimetry (DSC) measurements, the kinetics of the two stages can be dramatically altered because of the sample environment and DSC pan type. In‐depth understanding of how the sample environment alters the dehydration process and the kinetics involved requires more than DSC experiments alone. This paper describes the use of a novel, simultaneous thermal and spectral technique to monitor the dehydration kinetics of theophylline monohydrate. The analysis of the results obtained on the combined DSC‐near‐infrared and DSC‐Raman equipment clearly detects the two stages of the dehydration process and the polymorphic structural changes that take place. The combined technique provides a powerful method to monitor the dehydration of hydrous systems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
7.
C. Cotirlan-Simioniuc R. V. Ghita C. C. Negrila C. Logofatu 《Applied Physics A: Materials Science & Processing》2014,117(3):1359-1365
We report about the contribution of thermally grown SiOx overlayer on the SiOx/Si interface (with oxidation states Sin+, where n = 1, 2, 3, 4) to the optical losses of a resonant spectroscopic cavity. The experiments on Si oxide thin films were performed in evanescent wave for Si samples in contact with a total internal reflection surface of a BK7 prism. The evanescent field can be exploited to investigate properties and processes such as the absorption of thin film or solid/air interface reactions. The results show that the oxide overlayer thickness grows with the thermal exposure time and is limited after more than 7 h of treatment. Transmission electron microscopy has been used for the native oxide thickness measurement and angle-resolved X-ray photoelectron spectroscopy used to determine the thermal oxide thickness. A change of absorption coefficient Δα in the range 100–200 cm?1 is obtained by evanescent-wave cavity ring-down spectroscopy (EW-CRDS) for thermal silicon oxide overlayer, in agreement with the general trend from literature. The evaluation from the EW-CRDS experiments presents the used setup as a competitive method for measuring the absorption properties of thin overlayer. 相似文献
8.
Antti J. Koivisto Maija M?kinen Elina M. Rossi Hanna K. Lindberg Mirella Miettinen Ghita C.- M. Falck Hannu Norppa Harri Alenius Anne Korpi Joakim Riikonen Esa Vanhala Minnamari Vippola Pertti Pasanen Vesa-Pekka Lehto Kai Savolainen Jorma Jokiniemi Kaarle H?meri 《Journal of nanoparticle research》2011,13(7):2949-2961
This study presents a novel exposure protocol for synthesized nanoparticles (NPs). NPs were synthesized in gas phase by thermal decomposition of metal alkoxide vapors in a laminar flow reactor. The exposure protocol was used to estimate the deposition fraction of titanium dioxide (TiO2) NPs to mice lung. The experiments were conducted at aerosol mass concentrations of 0.8, 7.2, 10.0, and 28.5 mg m?3. The means of aerosol geometric mobility diameter and aerodynamic diameter were 80 and 124 nm, and the geometric standard deviations were 1.8 and 1.7, respectively. The effective density of the particles was approximately from 1.5 to 1.7 g cm?3. Particle concentration varied from 4 × 105 cm?3 at mass concentrations of 0.8 mg m?3 to 12 × 106 cm?3 at 28.5 mg m?3. Particle phase structures were 74% of anatase and 26% of brookite with respective crystallite sized of 41 and 6 nm. The brookite crystallites were approximately 100 times the size of the anatase crystallites. The TiO2 particles were porous and highly agglomerated, with a mean primary particle size of 21 nm. The specific surface area of TiO2 powder was 61 m2 g?1. We defined mice respiratory minute volume (RMV) value during exposure to TiO2 aerosol. Both TiO2 particulate matter and gaseous by-products affected respiratory parameters. The RMV values were used to quantify the deposition fraction of TiO2 matter by using two different methods. According to individual samples, the deposition fraction was 8% on an average, and when defined from aerosol mass concentration series, it was 7%. These results show that the exposure protocol can be used to study toxicological effects of synthesized NPs. 相似文献
9.
C.B. Collins B.W. Johnson C. Ghita I. Baltog M. Constantinescu L. Ghita 《Solid State Communications》1973,13(9):1351-1354
Strong excitonic emission from PbI2 has been observed to result from high intensity illumination with a nitrogen laser. Spectroscopic examination has shown both a shift and broadening of the excitonic band suggestive of excitonic interactions. 相似文献
10.