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51.
Câtâlina Ioan Maria Bercea Jean-Louis Vernet Bogdan C. Simionescu 《Polymer-Plastics Technology and Engineering》2013,52(2):255-266
The article presents some Theological results obtained on a large domain of shear rates for semidilute solutions of ultrahigh-molecular-weight poly(methyl methacrylate) at different concentrations. The observed unusual behavior was explained as being due to the flow instabilities of long-chain polymers in an entangled state. 相似文献
52.
Cleopatra Vasiliu-Oprea Ioan Marcu Sorin Ciovica Florin Dan 《Polymer-Plastics Technology and Engineering》2013,52(4):609-620
Poly(acrylonim1e) fibers were preoxidated under stress, in the presence of air, then saponified by boiling in alkaline solutions. The chemomechani-cal behavior of these fibers, expressed as contraction and mechanical work, under different loads and in different solvent-nonsolvent and/or base-acid systems were investigated. Total nitrogen content, carboxyl groups content, tensile strength, and cross-link density were determined. Both contraction and mechanical work were expressed as functions of applied load in every studied system. The results of chemomechanical measurements were connected to those of chemical and physical investigations. Significant differences in chemomechanical behavior were found to be the result of different stress conditions during the preoxidation stage. 相似文献
53.
Teodora Larisa Timis Ioan Alexandru Florian Sergiu Susman Ioan Stefan Florian 《International journal of molecular sciences》2021,22(11)
Aneurysms and vascular malformations of the brain represent an important source of intracranial hemorrhage and subsequent mortality and morbidity. We are only beginning to discern the involvement of microglia, the resident immune cell of the central nervous system, in these pathologies and their outcomes. Recent evidence suggests that activated proinflammatory microglia are implicated in the expansion of brain injury following subarachnoid hemorrhage (SAH) in both the acute and chronic phases, being also a main actor in vasospasm, considerably the most severe complication of SAH. On the other hand, anti-inflammatory microglia may be involved in the resolution of cerebral injury and hemorrhage. These immune cells have also been observed in high numbers in brain arteriovenous malformations (bAVM) and cerebral cavernomas (CCM), although their roles in these lesions are currently incompletely ascertained. The following review aims to shed a light on the most significant findings related to microglia and their roles in intracranial aneurysms and vascular malformations, as well as possibly establish the course for future research. 相似文献
54.
55.
The conventional pulsed gradient Hahn or stimulated echo methods for diffusion measurements are briefly reviewed. Compared to these techniques, unconventional NMR diffusometry variants based on gradients of the amplitude of the radio frequency field, on nonlinear (or multiple) echoes, and on imaging techniques open promising aspects depending on the application envisaged. A series of typical pulse sequences representing the diversity of NMR diffusometry methods is described and discussed with respect to advantages and disadvantages. 相似文献
56.
57.
Razvan Iordache Ioan Tabus Jaakko Astola 《Circuits, Systems, and Signal Processing》2002,21(5):485-509
This paper presents a new index assignment (IA) method when
vector quantization indices are transmitted over a particular
class of Markov binary channels, namely the finite-memory
contagion channels. (See F. Alajaji and T. Fuja, IEEE
Trans. Inform. Theory, 40:2035-2041, 1994.) For this class of
binary channels, the Hadamard transform of the vector formed
with noise pattern probabilities obeys well-structured
recursions, allowing an efficient evaluation of the channel
distortion and also revealing a useful approximation based on
the dominant terms in the channel distortion expression. The
proposed IA method minimizes the distortion approximation and is
very robust to changes in the parameters of the channel model.
The same technique applies for both maximum likelihood and
mean-squared error decoding methods. The IA algorithm is applied
to the transmission of line spectral frequency parameters
quantized as in the G.729 standard to show the usefulness of the
proposed method. 相似文献
58.
Liliana Olenic Gheorghe Mihailescu Stela Pruneanu Ioan Bratu Alexandru R. Biris Dan Lupu Grigore Sigartau Lucian B. Tudoran 《Particulate Science and Technology》2005,23(1):79-83
Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au+. Na3Au(SO3)2 with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM). 相似文献
59.
Cationic polyurethanes were synthesized by a two step Menschutkin reaction. A prepolymer with tertiary dimethylamino end groups and a dihalide (1,3-dimethyl-4,6-di(chloromethyl) benzene) were used in the first step, and 1,8-diaza bicyclooctane in the second step. The polymers from flexible and transparent films and their solutions give ionomer dispersions by adding of acetone. The viscometric behaviour of diluted solutions was studied in solvents with different dielectrical constants. 相似文献
60.
This paper reports on the design and implementation of an expert system for computer process control (HESCPC). The complexity of the expertise necessary for computer process control applications requires that the expert system architecture be structured into a hierarchy of classes of specialized experts. The architecture of HESCPC integrates four classes of expert systems: operator/manager companion expert class, control system algorithm design expert class, hardware expert class, and software expert class. The paper is concerned with the design and implementation of the general system architecture, an operator adviser expert for a nuclear power plant and a control system designer expert using a state space feedback approach. Although the design and implementation aspects of all experts are discussed, the emphasis is on the latter.
At this stage of the HESCPC development, the declarative knowledge represented by 423 metarules and 1261 rules is distributed on a hierarchical structure among 20 experts on different levels of the hierarchy which are able to communicate among themselves to solve difficult control problems.
Examples of control system design sessions of linear mono and multivariable systems using feedback state space approach are given. A run time of an operator-adviser data-driven expert system for a nuclear plant is also presented. 相似文献