排序方式: 共有105条查询结果,搜索用时 15 毫秒
51.
G. Ungureanu 《Isotopes in environmental and health studies》2013,49(7):237-242
The paper describes different methods of isotopic analysis for hydrogen, nitrogen, and oxygen. In the cases of the hydrogen and the oxygen, a light source with high frequency excitation and a Fabry-Perot spectrometer with photoelectric recording were employed. For the nitrogen we used a Zeiss Q-24-spectrograph, or a Zeiss SPM-2 monochromator, converted by us to photoelectric automatic recording instruments. In the last case the method teas extended for determining the nitrogen isotopic concentration in nitric oxide gas. 相似文献
52.
The challenge of maximizing the diversity of a collection of points arises in a variety of settings, including the setting
of search methods for hard optimization problems. One version of this problem, called the Maximum Diversity Problem (MDP),
produces a quadratic binary optimization problem subject to a cardinality constraint, and has been the subject of numerous
studies. This study is focused on the Maximum Minimum Diversity Problem (MMDP) but we also introduce a new formulation using
MDP as a secondary objective. We propose a fast local search based on separate add and drop operations and on simple tabu
mechanisms. Compared to previous local search approaches, the complexity of searching for the best move at each iteration
is reduced from quadratic to linear; only certain streamlining calculations might (rarely) require quadratic time per iteration.
Furthermore, the strong tabu rules of the drop strategy ensure a powerful diversification capacity. Despite its simplicity,
the approach proves superior to most of the more advanced methods from the literature, yielding optimally-proved solutions
for many problems in a matter of seconds and even attaining a new lower bound. 相似文献
53.
Raluca Ianchiş Dan Donescu Mihai Cosmin Corobea Cristian Petcu Marius Ghiurea Sever Serban Constantin Radovici 《Colloid and polymer science》2010,288(12-13):1215-1224
Synthesis of nanocomposites based on polystyrene/polybutylacrylate with layered silicates using emulsion polymerization procedure in aqueous medium allowed obtaining stable nanolatexes with sodium dodecyl sulfate as surfactant. Monomer and layered silicate nature influences the average diameter of the particles and the zeta potential appeared on the particle-disperse medium interface, as it was shown by dynamic light scattering analyses. In order to evidence the layered silicate structure, two structural evaluation methods were used. A new approach was used based on Fourier transform infrared analyses as a method to asses the clay delamination. The method was followed in conjunction with X-ray diffraction patterns and showed the pronounced delamination of the clay in the polymer matrix. The thermal stability was investigated by thermogravimetric analyses and the morphologies in solid state observed by environmental scanning electron microscope measurements. 相似文献
54.
Vlad Constantin Ursachi Gianina Dodi Alina Gabriela Rusu Cosmin Teodor Mihai Liliana Verestiuc Vera Balan 《Molecules (Basel, Switzerland)》2021,26(11)
A considerable interest in cancer research is represented by the development of magnetic nanoparticles based on biofunctionalized polymers for controlled-release systems of hydrophobic chemotherapeutic drugs targeted only to the tumor sites, without affecting normal cells. The objective of the paper is to present the synthesis and in vitro evaluation of the nanocomposites that include a magnetic core able to direct the systems to the target, a polymeric surface shell that provides stabilization and multi-functionality, a chemotherapeutic agent, Paclitaxel (PTX), and a biotin tumor recognition layer. To our best knowledge, there are no studies concerning development of magnetic nanoparticles obtained by partial oxidation, based on biotinylated N-palmitoyl chitosan loaded with PTX. The structure, external morphology, size distribution, colloidal and magnetic properties analyses confirmed the formation of well-defined crystalline magnetite conjugates, with broad distribution, relatively high saturation magnetization and irregular shape. Even if the ability of the nanoparticles to release the drug in 72 h was demonstrated, further complex in vitro and in vivo studies will be performed in order to validate the magnetic nanoparticles as PTX delivery system. 相似文献
55.
Dan Donescu Mihai Cosmin Corobea Ignac Capek Constantin Radovici Sever Serban Cristian Petcu 《Journal of Dispersion Science and Technology》2013,34(2):166-173
Styrene (St) and butyl acrylate (BuA) microemulsion polymerizations were investigated in presence of layered silicates (LS) and sodium dodecyl sulfate (SDS) as surfactant. Two main LS categories were used: one in the sodium form as Na montmorillonite (MMT) and the other in organomodified form LS (OLS) with quaternary ammonium salts having different hydrophobic modifiers. The swelling capacity of OLS in presence of monomers with different polarity is more pronounced for partners with closer hydrophobicity to St. The latexes obtained by microemulsion polymerization showed larger particles size for BuA polymer and BuA copolymer with sulfonated styrene than for St. Analyzing the dried hybrid polymers by XRD, we found structures which corresponds to exfoliated LS. The thermal behavior of hybrids, examined by TGA, showed higher rates of decomposing temperatures in the case of OLS, in comparison with the NaMMT hybrids. The obtained hybrids were evaluated by DLS, FTIR, DSC, and SEM. 相似文献
56.
Filiz Gurtuna Cosmin Petra Florian A. Potra Olena Shevchenko Adrian Vancea 《Computational Optimization and Applications》2011,48(3):453-485
We present a new corrector-predictor method for solving sufficient linear complementarity problems for which a sufficiently centered feasible starting point is available. In contrast with its predictor-corrector counterpart proposed by Miao, the method does not depend on the handicap κ of the problem. The method has \(O((1+\kappa)\sqrt{n}L)\)-iteration complexity, the same as Miao’s method, but our error estimates are sightly better. The algorithm is quadratically convergent for problems having a strictly complementary solution. We also present a family of infeasible higher order corrector-predictor methods that are superlinearly convergent even in the absence of strict complementarity. The algorithms of this class are globally convergent for general positive starting points. They have \(O((1+\kappa)\sqrt{n}L)\)-iteration complexity for feasible, or “almost feasible”, starting points and O((1+κ)2 nL)-iteration complexity for “sufficiently large” infeasible starting points. 相似文献
57.
Highly internal phase emulsion (polyHIPE) materials are promising macrocellular foams bearing versatile applications ranging from catalysis, optics, filtration, insulator and so forth. In this critical review water-in-oil HIPE, oil-in-water HIPE and Pickering-based HIPE are discussed. Also in each above-mentioned HIPE family, declination between the organic, inorganic or hybrid-organic foams chemical nature is proposed. The polyHIPE audience is thereby strongly interdisciplinary in nature crossing boundaries of physical chemistry, colloids, polymer science, sol-gel chemistry, hybrid materials, biology and beyond (114 references). 相似文献
58.
The well-known Schur's Lemma states that the endomorphism ring of a simple module is a division ring. But the converse is not true in general. In this paper we study modules whose endomorphism rings are division rings. We first reduce our consideration to the case of faithful modules with this property. Using the existence of such modules, we obtain results on a new notion which generalizes that of primitive rings. When R is a full or triangular matrix ring over a commutative ring, a structure theorem is proved for an R-module M such that End R (M) is a division ring. A number of examples are given to illustrate our results and to motivate further study on this topic. 相似文献
59.
We introduce the notion of 𝒦-nonsingularity of a module and show that the class of 𝒦-nonsingular modules properly contains the classes of nonsingular modules and of polyform modules. A necessary and sufficient condition is provided to ensure that this property is preserved under direct sums. Connections of 𝒦-nonsingular modules to their endomorphism rings are investigated. Rings for which all modules are 𝒦-nonsingular are precisely determined. Applications include a type theory decomposition for 𝒦-nonsingular extending modules and internal characterizations for 𝒦-nonsingular continuous modules which are of type I, type II, and type III, respectively. 相似文献
60.
Č. Ungureanu 《Isotopes in environmental and health studies》2013,49(6):237-239
The isotopic analysis of oxygen (range of concentration: 1 to 31 at. %O18) by emission spectroscopy (O 1 8446 Å line) by using a Fabry-Pérpt spectrometer with photoelectric recording of the spectral lines is described. The measuring error is within ± 8% (for 1 at. %O18). The results are compared with those obtained by mass spectrometry. 相似文献