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排序方式: 共有238条查询结果,搜索用时 906 毫秒
81.
Mounir Aytouna Denis Bartolo Gerard Wegdam Daniel Bonn Salima Rafaï 《Experiments in fluids》2010,48(1):49-57
We study the impact and subsequent retraction of aqueous surfactant-laden drops upon high-speed impact on hydrophobic surfaces.
Without surfactants, a rapid expansion of the drop due to the fluid inertia is followed by a rapid retraction, due to the
wetting incompatibility. With surfactants, the retraction can be partly or completely inhibited. We provide quantitative measurements
showing that both the expansion and the retraction dynamics depend not only on the equilibrium surface tension (ST) but also
on the dynamic tension of the surfactant solutions; the latter varies significantly between different surfactants. 相似文献
82.
83.
Wireless access to Internet services will become typical, rather than the exception as it is today. Such a vision presents
great demands on mobile networks. Mobile IP represents a simple and scalable global mobility solution but lacks the support
for fast handoff control and paging found in cellular telephony networks. In contrast, second- and third-generation cellular
systems offer seamless mobility support but are built on complex and costly connection-oriented networking infrastructure
that lacks the inherent flexibility, robustness, and scalability found in IP networks. This paper presents an overview and
performance comparison of two of the main micro-mobility protocols, namely Cellular IP and Hierarchical Mobile IP with regards
to the handoff process for UDP applications. The differences in the handoff quality of the two protocols are small and can
be traced to design choices within the typical model. There are however significant differences regarding the processing requirement,
routing efficiency and parameters relating to implementation and deployment. 相似文献
84.
85.
Test decisions still constitute one of the most difficult and time-consuming design tasks. This is particularly true in the analog domain where some basic test questions have not yet been completely resolved. Since the gap between a good and a bad analog circuit is not always well-defined, extensive tests may result in the rejection of many fault-free ICs. The objective of this article is to propose fuzzy optimization models that can help in the more realistic formulation and resolution of the analog test problem. The set of good or fault-free ICs is considered as a fuzzy set. Each performance test is represented by a membership function. A global test measure is obtained by aggregating all the performance tests. An illustrative example using these concepts is provided. 相似文献
86.
87.
Carole C. Harrison Mounir A. Malati Nigel B. Smetham 《Journal of solution chemistry》1996,25(5):505-514
The rate of decomposition of NH4NO2 solutions, at pH 5–7, equals k[NH3] [HNO2]2 or k[NH
4
+
] [NO
2
–
][HNO2]. A plausible mechanism involves a ratedetermining attack of N2O3, derived from HNO2, on NH3. H++ and S++ are 82 kJ-mol–1 and –27 J-mol–1-K–1, respectively. On partially replacing the solvent water by methanol or ethanol, the change G++, coupled with the calculated standard Gibbs energy of transfer of the reactants from water to the mixed solvent indicated that, in the latter, there is a greater destabilization of the transition state compared to that of the reactants. This can be explained by assuming two hydrogen bonds from the same water molecule to the transition state and hence a loss of hydrogen bond energy in the mixed solvent compared to the aqueous solution. The rate constant for the reaction of ND4NO2 in D2O compared to the reaction of NH4NO2 in water, gave a composite isotope effect involving two acid-base equilibria, suggested in the proposed mechanism; in addition to primary isotope effects in the equilibrium: 2 HNO2N2O3+H2O. 相似文献
88.
Caroline Rmond Mounir Ferchichi Nathalie Aubry Richard Plantier-Royon Charles Portella Michael J. O'Donohue 《Tetrahedron letters》2002,43(52)
A thermostable α-l-arabinofuranosidase was tested for its ability to perform transglycosylation with different alcohol acceptors. Reactions were characterized by high rates with optimal synthesis being obtained within 10 min. Both primary and secondary alcohols could act as acceptors in transarabinosylation but yields of alkyl arabinosides decreased with increasing alkyl chain length. 相似文献
89.
Maaloum M Muller P Krafft MP 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2261-2264
It has recently been found that monodisperse surface micelles (hemimicelles) were formed in Langmuir monolayers of the semifluorinated alkane C8F17C16H33 (F8H16) after transfer onto silicon wafers. Grazing incidence X-ray diffraction studies have demonstrated that compression of mixed Langmuir monolayers made from combinations of dipalmitoyl phosphatidylethanolamine (DPPE) and diblock F8H16 in various molar ratios resulted in the complete expulsion of the diblock molecule at high surface pressure. F8H16 then formed a second layer on top of a DPPE-only monolayer, demonstrating a novel type of reversible, pressure-induced, vertical phase separation. Using atomic force microscopy and X-ray reflectivity, we show now that mixed DPPE/F8H16 (1:1.3) Langmuir-Blodgett films transferred onto silicon wafers below 10 mN m(-1) are laterally phase separated and consist of domains of F8H16 surface micelles in coexistence with a monolayer of DPPE. The density of the network of F8H16 surface micelles increases when the surface pressure of transfer increases. Around 10 mN m(-1), the F8H16 surface micelles start to glide on the DPPE monolayer, progressively overlying it, until total coverage is achieved. 相似文献
90.
Synthesis and properties of 7-formyl-8-hydroxyquinoline and its transition metal complexes 总被引:4,自引:0,他引:4
Ahmed A. El-Asmy Adel Z. El-Sonbati Abdulla A. Ba-Issa Mohamed Mounir 《Transition Metal Chemistry》1990,15(3):222-225
Summary CoII, NiII, CuII, CdII and HgII complexes of 7-formyl-8-hydroxyquinoline (HFHQ) have been prepared, and characterized by elemental analysis, molar conductivities, electronic and i.r. spectra, and magnetic measurements. It was found that the ligand acts as a neutral monodentate or a monobasic bidentate donor. The CoII, NiII and CuII complexes possess, respectively, tetrahedral, octahedral and square-planar structures based on their magnetic and electronic spectral data. The electrical conductivities of HFHQ and its metal complexes were measured at different temperatures and their activation energies were calculated. The values obtained for the CoII, NiII, CdII and HgII complexes agree fairly well with those reported for semiconductors. The ligand was tested as a corrosion inhibitor for aluminium; the limiting concentration of HFHQ to give maximum efficiency (99.2%) is 10–3 mole dm–3 at 22°C. The metal-ligand ratios and apparent formation constants for the species generated in ethanol solution were determined spectrophotometrically. 相似文献