排序方式: 共有87条查询结果,搜索用时 15 毫秒
1.
Suellen Christtine da Costa Sanches Flávio de Vasconcelos Carlos Emmerson Ferreira da Costa Patrícia Santana Barbosa Marinho Marcos R. Guilherme Eraldo José Madureira Tavares José Antônio Picanço Diniz Júnior José Otávio Carréra Silva Júnior Roseane Maria Ribeiro-Costa 《Journal of Thermal Analysis and Calorimetry》2015,120(1):991-999
2.
C. Carrasco-Vela X. Quintana E. Otón M. A. Geday J. M. Otón 《Opto-Electronics Review》2011,19(4):496-500
Liquid crystal properties make them useful for the development of security devices in applications of authentication and detection
of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices. 相似文献
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Taís Vanessa Gabbay Alves Eraldo José Madureira Tavares Fauze Ahmad Aouada Charles Alberto Brito Negrão Marcos Enê Chaves Oliveira Anivaldo Pereira Duarte Júnior Carlos Emmerson Ferreira da Costa José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2011,106(3):717-724
This paper reports the thermal characterization of polyacrylamide-co-methylcellulose hydrogels and the constituent monomers (acrylamide and methylcellulose). Polymeric materials can be used
to produce hydrogels, which can be natural, synthetic, or a mixture. The hydrogels described here were obtained by free radical
polymerization, in the presence of N,N′-methylene-bis-acrylamide as a cross-linker agent. Four acrylamide concentrations were used for the synthesis of hydrogels:
3.6, 7.2, 14.7, and 21.7% (w/v). The materials so obtained were analyzed by TG, DTG, DSC, and FT-IR. The TG curves of acrylamide
and methylcellulose showed three mass loss events. In DSC curves, the acrylamide exhibited one melting peak at 84.5 °C, and
methylcellulose indicated one exothermic event. Nevertheless, acrylamide was considered more stable than methylcellulose.
The TG curves of the hydrogels exhibited three mass loss events, and on the DSC curves, three endothermic events were observed.
It was verified that the different acrylamide proportions influenced the thermic behavior of hydrogels, and that the authors
considered the 7.2% hydrogel a promising drug carrier system. The absorption bands were well defined, confirming the presence
of the functional groups in the samples. 相似文献
4.
A.?Spad?o E.?Otón R.?D?browski M.??urowska J.?M.?Otón N.?Bennis 《Opto-Electronics Review》2010,18(2):219-222
Electrooptical properties of several new orthoconic antiferroelectric liquid crystal mixtures with partially fluorinated alkoxyalkoxy
terminal chains have been investigated in order to select the best mixture for display applications. Electrooptical studies
have been performed on these orthoconic materials aiming at evaluating their static and dynamic performance under passive
multiplexing conditions. A number of parameters have been evaluated, static and dynamic contrast, driving scheme for passive
multiplexing, rise and fall response times, dynamic range, and dynamic greyscale. 相似文献
5.
An approach formulated in terms of conserved variables for the characterisation of propellant combustion in internal ballistics 下载免费PDF全文
R. A. Otón‐Martínez G. Monreal‐González J. R. García‐Cascales F. Vera‐García F. J. S. Velasco F. J. Ramírez‐Fernández 《国际流体数值方法杂志》2015,79(8):394-415
A model formulated in terms of conserved variables is proposed for its use in the study of internal ballistic problems of pyrotechnical mixtures and propellants. It is a transient two‐phase flow model adapted from the non‐conservative Gough model. This conversion is mathematically attractive because of the wide range of numerical methods for this kind of systems that may be applied. We propose the use of the AUSM+, AUSM + up and Rusanov schemes as an efficient alternative for this type of two‐phase problem. A splitting technique is applied, which solves the system of equations in several steps. A second‐order approach based on Monotonic Upstream‐Centred Scheme for Conservation Laws (MUSCL) is also used. Some tests are used to validate the code, namely a shock wave test, a contact discontinuity problem and an internal ballistics problem. In this last case, one‐dimensional numerical results are compared with experimental data of 155‐mm gunshots. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Marina Nídia Ferreira dos Santos Costa Marcos Antônio Pena Muniz Charles Alberto Brito Negrão Carlos Emmerson Ferreira da Costa Maria Louze Nobre Lamarão Luiz Morais José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2269-2275
The Pracaxi oil—(Pentaclethra macroloba) contains high concentrations of fatty acids with emollient action that contribute to skin hydration. The use of this oil is supported by the utilization of natural resources thus enabling regional development and social contribution. The objective of this study was to characterize the P. macroloba oil by thermogravimetry (TG, DTG, and DTA), gas chromatography, Fourier transform infrared spectroscopy (FT-IR), and oxidation stability—Rancimat, aiming at the quality control of plant raw material. Three samples of crude oil sold by Amazon Oil Industry (Ananindeua, Pará, Brazil) were studied. The analysis of these oil samples showed different fatty acids, especially the behenic, oleic, linoleic, and lignoceric acids totalizing approximately 96 % of the grease composition and in smaller percentage arachidic, lauric, myristic, palmitic, and linolenic acids were found. The major acids have wide medicinal use. According to the TG/DTG curve, thermal stability was observed up to 220 °C, indicating a greater mass loss related to the dehydration and elimination of volatile substances. The thermal decomposition process occurred in the range of 430–450° C according to the DTG curve. The absorption spectrum in the infrared region (FT-IR) showed well-defined bands confirming the presence of functional groups present in the oil. Tests in a Rancimat have shown an induction period between 8 and 10 h demonstrating that the samples are in agreement with the standards required by ANP No. 14/2012 which requires at least 6 h of testing. 相似文献
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9.
Erwin Hernández Dante Kalise Enrique Otárola 《Computational Optimization and Applications》2010,47(1):161-178
The aim of this work is to obtain optimal-order error estimates for the LQR (Linear-quadratic regulator) problem in a strongly
damped 1-D wave equation. We consider a finite element discretization of the system dynamics and a control law constant in
the spatial dimension, which is studied in both point and distributed case. To solve the LQR problem, we seek a feedback control
which depends on the solution of an algebraic Riccati equation. Optimal error estimates are proved in the framework of the
approximation theory for control of infinite-dimensional systems. Finally, numerical results are presented to illustrate that
the optimal rates of convergence are achieved. 相似文献
10.
M. A. Geday D. P. Medialdea B. Cerrolaza N. Bennis X. Quintana J. M. Otón 《Opto-Electronics Review》2009,17(2):140-143
The ferroelectric-antiferroelectric transition in greyscale generation of antiferroelectric liquid crystal displays (AFLC)
is a heterogeneous process. The process has been described as the growth of finger-like domains [1]. We have previously studied
the ferroelectric-antiferroelectric phase transition, relaxation that follows the data pulse in surface stabilized asymmetric
antiferroelectric liquid crystal displays using biasless video frequency waveforms [2]. This relaxation involves an intensity
decay of the light transmitted by a pixel and depends on several parameters such as surface stabilization, rotational viscosity
of the AFLC, magnitude of the data pulse, and bias voltage.
The usual multiplexed driving of AFLC displays leads to long-term stabilisation of the grey levels induced by the data pulses
within the selection time. However, depending on the bias level, alternative greyscale mechanisms may be obtained by allowing
the grey levels to decay during the frametime. These greyscales may be advantageous in some instances since they improve the
dynamic response of the AFLC device and reduce the reset time of the waveform.
In this study we extend the previous work to include the effect of bias. We present the measured data, in terms of growth
pattern and speed and present an extension of the previously model on order to explain the results. 相似文献