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131.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 相似文献
132.
133.
This paper deals with the application of smooth Karhunen-Loève decomposition (SKLD) procedure applied to random fields. The SKLD is obtained by solving a generalized eigenproblem defined by combining the covariance matrix of the random field with that of the associated time-derivative random field. The main properties of the SKLD procedure thus obtained are described and compared with the classical Karhunen-Loève decomposition. The SKLD is then applied to the responses of randomly excited vibrating systems in order to perform modal analysis. The resulting SKLD characteristics are discussed, in the case of linear vibrating systems subjected to white noise excitation, in terms of normal modes. 相似文献
134.
P.?S.?C.?Farias F.?J.?W.?A.?Martins L.?E.?B.?Sampaio R.?Serfaty L.?F.?A.?AzevedoEmail author 《Experiments in fluids》2012,52(3):633-645
A non-intrusive optical technique was developed to provide time-resolved longitudinal and cross-sectional images of the liquid
film in horizontal annular pipe flow of air and water, revealing the interfacial wave behavior. Quantitative information on
the liquid film dynamics was extracted from the time-resolved images. The planar laser-induced fluorescence technique was
utilized to allow for optical separation of the light emitted by the film from that scattered by the air–water interface.
The visualization test section was fabricated from a tube presenting nearly the same refractive index as water, which allowed
the visualization of the liquid film at regions very close to the pipe wall. Longitudinal images of the liquid film were captured
using a high-frame-rate digital video camera synchronized with a high-repetition-rate laser. An image processing algorithm
was developed to automatically detect the position of the air–water interface in each image frame. The thickness of the liquid
film was measured at two axial stations in each processed image frame, providing time history records of the film thickness
at two different positions. Wave frequency information was obtained by analyzing the time-dependent signals of film thickness
for each of the two axial positions recorded. Wave velocities were measured by cross-correlating the amplitude signals from
the two axial positions. For the film cross-section observations, two high-speed digital video cameras were used in a stereoscopic
arrangement. Comparisons with results from different techniques available in literature indicate that the technique developed
presents equivalent accuracy in measuring the liquid film properties. Time-resolved images of longitudinal and cross-section
views of the film were recorded, which constitute valuable information provided by the technique implemented. 相似文献
135.
A. P. Baêta Scarpelli Marcos Sampaio M. C. Nemes B. Hiller 《The European Physical Journal C - Particles and Fields》2008,56(4):571-578
The radiative induction of the CPT and Lorentz violating Chern–Simons (CS) term is reassessed. The massless and massive models
are studied. Special attention is given to the preservation of gauge symmetry at higher orders in the background vector b
μ
when radiative corrections are considered. Both the study of the odd and even parity sectors of the complete vacuum polarization
tensor at one-loop order and a non-perturbative analysis show that this symmetry must be preserved by quantum corrections.
As a complement we obtain the result that transversality of the polarization tensor does not fix the value of the coefficient
of the induced CS term. 相似文献
136.
C.J.M. Olguin S.C. Sampaio R.R. dos Reis M.B. Remor C.F.A. Olguin 《SAR and QSAR in environmental research》2019,30(5):299-311
Quantitative structure–property relationship (QSPR) modelling has been used in many scientific fields. This approach has been extensively applied in environmental research to predict physicochemical properties of compounds with potential environmental impact. The soil sorption coefficient is an important parameter for the evaluation of environmental risks, and it helps to determine the final fate of substances in the environment. In the last few years, different QSPR models have been developed for the determination of the sorption coefficient. In this study, several QSPR models were generated and evaluated for the prediction of log Koc from the relationship with log P. These models were obtained from an extensive and diverse training set (n = 639) and from subsets of this initial set (i.e. halves, fourths and eighths). The aim of this study was to investigate whether the size of the training set affects the statistical quality of the obtained models. Furthermore, statistical equivalence was verified between the models obtained from smaller sets and the model obtained from the total training set. The results confirmed the equivalence between the models, thus indicating the possibility of using smaller training sets without compromising the statistical quality and predictive capability, as long as most chemical classes in the test set are represented in the training set. 相似文献
137.
138.
E.W. Dias A.P. Baêta Scarpelli L.C.T. Brito M. Sampaio M.C. Nemes 《The European Physical Journal C - Particles and Fields》2008,55(4):667-681
We extend a constrained version of implicit regularization (CIR) beyond one-loop order for gauge field theories. In this framework,
the ultraviolet content of the model is displayed in terms of momentum loop integrals order by order in perturbation theory
for any Feynman diagram, while the Ward–Slavnov–Taylor identities are controlled by finite surface terms. To illustrate, we
apply CIR to massless abelian gauge field theories (scalar and spinorial QED) to two-loop order and calculate the two-loop
beta-function of spinorial QED.
PACS 11.10.Gh; 11.15.Bt; 11.15.-q 相似文献
139.
Bitencourt VL de Paula TA da Matta SL Fonseca CC dos Anjos Benjamin L Costa DS 《Micron (Oxford, England : 1993)》2007,38(6):584-589
The duration of the seminiferous epithelium cycle was estimated in adult maned wolves (Chrysocyon brachyurus, Illiger, 1811), by applying intratesticular injections with tritiated thymidine. The total duration of the seminiferous epithelium cycle in this species was calculated in 8.99 days. So, taking into account that approximately 4.5 cycles of the seminiferous epithelium are necessary for the whole spermatogenesis process to complete, the production of spermatozoa from one spermatogonia will take about 40.45 days. The duration of the spermiogenesis was calculated to be 12.3 days. The eight stages of the seminiferous epithelium cycle were described by the tubular morphology method, which is based either on the form and position of the spermatid nuclei and the occurrence of meiotic divisions. The values of the relative frequency for the pre-meiotic, meiotic and post-meiotic phases in this species were 3.5, 0.78 and 4.8 days, respectively. The maned wolf produces about 29 million spermatozoa a day for each testis gram, therefore being classified among the species provided with a high spermatogenetic efficiency. 相似文献
140.
Cliciane Guadalupe de Jesus Cristiane Maria Sampaio Forte Karen Wohnrath Christiana Andrade Pessôa Janete Elisa de Sá Soares Sérgio Toshio Fujiwara Pedro de Lima‐Neto Adriana Nunes Correia 《Electroanalysis》2011,23(8):1814-1820
A (SiPy+Cl?/CuTsPc)5 layer‐by‐layer film was employed for the electroanalytical determination of promethazine hydrochloride in BR buffer pH 5.0 with peaks at 0.48 and 0.79 V. After optimisation of the square‐wave parameters (f=100 s?1, a=40 mV and ΔEs=2 mV), the peak at 0.79 V was used for quantification and a detection limit of 8.71×10?9 mol L?1 and a quantification limit of 9.31×10?8 were calculated. The applicability of this procedure was tested on commercial formulations of promethazine hydrochloride by observing the stability, specificity, recovery and precision of the procedure in complex samples, without any preliminary treatment. 相似文献