Results 1 - 10 of 9090
Results 1 - 10 of 9090. Search took: 0.03 seconds
|Sort by: date | relevance|
[en] In this paper, we investigate the features of the Fourier-IR reflection spectra of γ-irradiated GaS crystals in the region of absorbed doses of Φγ = 30-200 krad at room temperature. Dispersion dependences of the real ε1(ν) = n2-k2 and imaginary ε2(ν=2nk of the parts of the dielectric constant, the function Ιmε-1(ν)=ε2/(ε12+ε22), as well as the absorption n(ν) and refraction k(ν) coefficients for the initial and γ irradiated GaS samples were obtained and studied.The effect of γ quanta on the optical parameters of these crystals was considered. It has been established that at relatively low doses of 30 ≤Φγ≥100 krad are not radiation-resistant.
[en] In this paper, polyacrylamide (PAAm) hydrogels grafted via photo polymerization onto various types of polyethylene terephthalate (PET) as matrix were designed and synthesized. The investigation was carried out based on thickness (0.02 -0.07 mm) of nonwoven PET textiles from various resources as well as commercial PET membrane. In this study, PET matrices with a disk shape of 4.5 cm in diameter were coated with thin hydrogel using UVA photo polymerization system. The resulting grafted PAAm-g-PET was examined through degree of grafting (DG) and characterized by using Fourier Transformed Infrared Spectroscopy (FTIR). The DG above 50 % results showed the ability of PAAm hydrogel to be grafted onto PET. The various range of thickness and surface of PET also gave an impact onto the performance of grafting of PAAm onto PET. FTIR results also confirmed the addition of amide group after grafting process (1720 cm-1, 1100 cm-1, 850 cm-1). The hydrophilicity of hydrogels was reported to impart oil fouling resistance. We expect that grafted hydrogel layer has fascinating future for oil/ water separation. (author)
[en] We have acquired spatial-spectral datacubes of astronomical objects using the Livermore visible-band imaging Fourier transform spectrometer at Apache Point Observatory. Each raw datacube contains hundreds of thousands of spectral interferograms. We present in-progress demonstrations of these observations
[en] The possibility of performing a spectral analysis of radiation by means of Fourier spectrometers with the photoreceiving channel operating in a nonlinear mode is considered. It is shown that a special processing of the results obtained from observations by means of an a priori known coefficient of nonlinearity allows one to achieve a significant compensation for the effect of the photoreceiving system on the spectrum under study. The technique proposed is illustrated with calculations
[en] Signal phase values are crucial in seismic data interpretation to enhance the analysis of amplitudes, bright spots, dim spots etc. Phase values can be zeroed in a section to enhance signal comparison which can be related to velocities and other petro-physical properties. Homomorphic signal processing and deconvolution both require exact phase value estimates. Consequently, in-depth investigations are necessary to solve problems of phase estimation in various wave propagation situations. Meanwhile, phase values are often measured modulo-2 called principal values and the amount of phase estimation in various wave propagation situations. Meanwhile, values are often measured modulo-2 called principal values and the amount of phase information is independent of any integer multiple of 2 added to the principal value phase. However, to be useful for linear processing, this principal value phase has to be unwrapped. This will result in a continuous function, the 2 discontinuities being eliminated, or at least reduced. Operations like deconvolution and homomorphic signal processing require unwrapped phase values. Phase unwrapping is applied to pre-stack data for the computation of PVA phase variation with angle of incidence attribute used to improve processing and interpretation.Conventional 1D phase unwrapping algorithms integrate the wrapped phase difference between two contiguous points. This was later improved to use adaptive integration of phase differences. Alternatively, phase difference ambiguity due to sparse sampling can be overcome by taking samples at progressively closer intervals. These methods are often inadequate due to problems of aliasing caused by rapid phase value variations. We develop a 1D phase unwrapping technique using the amplitude of a complex trace and discrete Fourier transforms. This technique is simple, very reliable and less sensitive to aliasing. It exploits the periodicity of Fourier transform to unwind wrapped phase values. We demonstrate this technique using synthetic and real data
[en] This research focuses on microstructure characterization and exploring mechanical properties of sisal fabric reinforced Polyvinyl Alcohol composites using conventional vacuum-assisted pressure compression method. Naturally available sisal fiber is used as reinforcement material in this composite because of its abundant availability in Southern India. The sisal fiber, PVA and its composites were characterized using Fourier Transform Infrared Spectroscopy. Initially, Polyvinyl Alcohol polymer was cross-linked with Glutaraldehyde, and mechanical properties were evaluated. It was observed that 20% Glutaraldehyde and 80% Polyvinyl Alcohol polymer combination yielded best mechanical properties. Further, two plain and one weft rib were considered and their textile properties were characterized. The results revealed that fabric crimp and yarn linear density had significant influence on tensile properties of the fabric. Influence of different fabric properties such as weaving pattern, grams per unit area, and loading direction on mechanical properties of composites were analyzed. The woven fabric having least gram per unit area of sisal resulted in best mechanical properties like tensile, bending, and impact. The weft rib fabric composites in weft direction exhibited best mechanical properties. (paper)
[en] Complete text of publication follows. We used some methods for spectral analyses and wavelet of geomagnetic data acquisitioned at Surlari National Geomagnetic Observatory (SNGO) and data from different observatories in the world. These methods can be used for determining a spectrum of geomagnetic phenomena at the different time. Disadvantages of applying only the spectral analysis of geomagnetic data are related to lack of capacity of locating frequencies, amplitudes and phases in time. Other limitations of harmonic analysis occur when processing analog or digital signals, particularly when they are non-stationary phenomena, such as the great majority of real signals. In the harmonic spectrum, calculated using Fourier transformers, is variable in time, however, for time intervals of convenient length (depending on the frequencies that fall within the signal and speed of change of the spectrum), it can be considered invariant. Modeling of these signals can be simultaneously both but considering their properties in time, and those of frequency. The time - frequency allows us to identify the frequency characteristics of signal at a time. For this is considered a window which moves on the signal, starting from t0 to any position on the temporal axis ti , the content is analyzed, there by achieving the desired frequency information: a spectrum of frequencies located. The complex methodology for analyzing spectral and wavelet fills easily visible results of morphological analysis. We used the Morlet, Paul and Gauss windows, for different adjustable parameters. For examples of this we have used geomagnetic data recorded in SNGO, and in other planetary geomagnetic observatories at different latitude and longitude.