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101.
In this work, the surface treatment of poly(ethylene terephtalate) (PET) films in a low frequency (70 kHz) discharge in helium-oxygen mixtures is investigated. Optical emission spectroscopy and mass spectrometry are used to analyze the gas phase. Surface properties are analyzed via the X-ray photoelectron spectroscopy (XPS) technique and contact angle measurements. The treatment conditions are optimized in order to obtain a surface functionalization, which would show a reduced ageing effect. The stability of the treated surface via the crosslinking process seems to be closely correlated to the presence of the helium metastable species in the discharge. A very good stability with the ageing time is obtained for samples treated in gaseous mixtures that contain less than 5% O2, conditions for which the oxidized polymeric structure seems to be formed on a reinforced crosslinked layer. The very efficient loss of He excited species, for amounts of O2 higher than a few percent, affects the surface crosslinking. For high quantities of oxygen introduced in the reactor (more than about 50%), a balance is established between the introduction of oxygenated groups and the ablation of the surface. In this case, the surface degradation has, as a consequence, the ageing effect. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1367–1375, 1997 相似文献
102.
Clustering is an important problem in malware research, as the number of malicious samples that appear every day makes manual analysis impractical. Although these samples belong to a limited number of malware families, it is difficult to categorize them automatically as obfuscation is involved. By extracting relevant features we can apply clustering algorithms, then only analyze a couple of representatives from each cluster. However, classic clustering algorithms that compute the similarity between each pair of samples are slow when a large collection is involved. In this paper, the features will be strings of operation codes extracted from the binary code of each sample. With a modified suffix tree data structure we can find long enough substrings that correspond to portions of a program’s code. These substrings must be filtered against a database of known substrings so that common library code will be ignored. The items that have common substrings above a certain threshold will be grouped into the same cluster. Our algorithm was tested with data extracted from real-world malware and constructed quality clusters. 相似文献
103.
The curable formulations containing monomer‐diacrylate, photoinitiator‐p‐methoxybenzoyldiphenylphosphine oxide/benzyldimethylketal, additive reactive‐triethylamine, and inorganic thermoresistant pigments‐white, red, green, and blue were cured by UV exposure films. A series of experiments was carried out to investigate the relationship between the particle size distribution of the inorganic pigment and the colorimetric and mechanical properties of the UV acrylic curable coatings. Pendulum hardness and appearance of the films depend on the content and particle size distribution of the pigment. Optimal particle size distribution and pigment content were established to obtain the best films concerning their pendulum hardness and chromatic parameters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 247–252, 2007 相似文献
104.
Alexandru Gheorghe Ai Matsuno Oliver Reiser 《Advanced Synthesis \u0026amp; Catalysis》2006,348(9):1016-1020
TEMPO was readily grafted by copper(I)‐catalyzed azide‐alkyne cycloaddition onto polystyrene. Starting with commercially available Merrifield resin (4.3 mmol/ g) almost quantitative loading of TEMPO onto the polymer was achieved (≥ 4 mmol/ g). The so obtained PS‐CLICK‐TEMPO allowed the oxidation of alcohols to aldehydes with bleach or molecular oxygen as the terminal oxidant with high yields and selectivity in multiple cycles without loss of activity. 相似文献
105.
This work reports a method used to control Al doping of ZnO thin films deposited by high-power impulse magnetron sputtering of a pure Zn target in low-pressure Ar/O2 gas mixture. The method uses sputtering of an electrically negative biased aluminum electrode placed in the proximity of the negative glow of the magnetron discharge. Resonant laser absorption measurements of Al atom concentration in vapor phase and the X-ray Photoelectron Emission Spectroscopy measurements of Al concentration in the deposited ZnO:Al films confirm that the electrode biasing potential is the key parameter that controls the Al doping process. Optically transparent ZnO:Al films with resistivity as low as 3.6 × 10− 3 Ω × cm have been obtained at an optimum value of Al concentration of 1.5 at.%. It has been found that the film electrical conductivity is limited by the effect of decreasing of crystalline grain size in the films with the increased Al doping concentration. 相似文献
106.
M.?Burdusel G.?Aldica S.?Popa M.?Enculescu P.?BadicaEmail author 《Journal of Materials Science》2012,47(8):3828-3836
Superconducting bulks of MgB2 with addition of Sb2O3 and Sb with different stoichiometric compositions ((MgB2) + (Sb2O3)
x
, x = 0.0025, 0.005, 0.015, and (MgB2) + (Sb)y, y = 0.01) were obtained by the Spark Plasma Sintering (SPS) technique. All added samples have high density, above 95% and critical
temperature, T
c, of 38.1–38.6 K. This result and XRD data suggest that Sb does not enter the lattice of MgB2. Impurity phases are Mg3Sb2, MgO, and MgB4. The optimum addition is Sb2O3 for x = 0.005. This sample shows the critical current density, J
c(5 K, 0 T) = 4 × 105 A/cm2 and J
c(5 K, 7 T) = 6 × 102 A/cm2, while the irreversibility field, H
irr (5 K, 100 A/cm2) = 8.23 T. Indicated values of J
c and H
irr are higher than for the pristine sample. The mechanism of J
c and H
irr increase in the Sb2O3 added samples is complex and composed of opposite effects most probably involving morphology elements, the presence of nano
metric MgB4 and the indirect influence of oxygen or oxygen and Sb. Crystallite size of MgB2 is decreasing when Sb-based additions are introduced and the effect is stronger for the Sb-metal addition. The sample with
Sb-metal addition does not improve J
c and H
irr when compared with pristine sample. 相似文献
107.
Simona PotoracMarcel Popa Vasilica MaierGabriela Lisa Liliana Verestiuc 《Materials science & engineering. C, Materials for biological applications》2012,32(2):236-243
New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H1 NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices. 相似文献
108.
Florin Tudorache Paul Dorin Popa Marius Dobromir Felicia Iacomi 《Materials Science and Engineering: B》2013,178(19):1334-1338
The influence of Co2+ ions content on structure and sensing properties of Ni1−xCoxFe2O4 (x = 0.25, 0.5, 0.75) thin films deposited on glass substrates by spin coating is presented. Structural characterization evidenced thin films with cubic spinel structures and morphologies dependent on cobalt content. Repartition of cations in spinel tetrahedral and octahedral sites was determined and was found that the presence of Co2+ ions in octahedral sites favor the formation of Fe2+ species. The sensitivity to some reducing vapor gases (acetone, liquefied petroleum gas LPG, ethyl alcohol and methyl alcohol) was investigated and was found that thin films with x = 0.75 exhibit high sensitivity to ethyl alcohol and thin films with x = 0.25 have high sensitivity to acetone. This sensitivity largely depends on the temperature and test gas concentration and was related to the Fe2+ species formed in octahedral sites. 相似文献
109.
Gheorghe Juncu Aurelian Nicola Constantin Popa Elena Stroila 《Numerical Heat Transfer, Part A: Applications》2013,63(11):1268-1296
In a series of two papers, we analyze the numerical performances of the preconditioned conjugate gradient algorithms (BICGSTAB and GMRES) and multigrid method in solving two-dimensional multicomponent mass transfer equations. The present test problems are steady-state, linear and nonlinear diffusion-reaction equations. The nonlinear algorithm used in connection with the preconditioned conjugate gradient methods is the modified Picard iteration. Theoretical results about the preconditioning are presented. The multigrid algorithm used is the Full Approximation Storage algorithm. The finite difference method was used to discretize the mathematical model equations. The numerical results obtained show good numerical performances. 相似文献
110.
Krapal AM Popa OP Iorgu EI Costache M Popa LO 《International journal of molecular sciences》2012,13(2):2515-2520
The invasive softshell clam (Mya arenaria Linnaeus, 1758) is native to the northwestern region of the Atlantic Ocean. This species has been introduced in the northeast Pacific and along the European coasts, due to intense naval transports and aquaculture, and it is now present in all the European seas. In this paper we describe seven new microsatellite loci for Mya arenaria. The isolated loci are polymorphic with a number of alleles per locus between 6 and 14. The observed and expected heterozygosities ranged from 0.417 to 0.951, and from 0.643 to 0.895, with an average of 0.716 and 0.775, respectively. These microsatellite markers should be useful in analyzing this species' genetic diversity, which could explain various processes of its invasion history. 相似文献