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111.
For a stationary nonlinear Boltzmann equation in a slab with a particular truncation in the collision operator, the Milne problem for the boundary layer together with a weak type of hydrodynamic behavior in the interior of the slab are studied by nonperturbative methods in the small-mean-free-path limit. 相似文献
112.
Boundary conditions for multidimensional scalar conservation laws are obtained in the context of hydrodynamic limits from a kinetic point of view. The initial boundary value kinetic problem is well posed since inward and outward characteristics of the domain can be distinguished. The convergence of the first momentum of the distribution function to an entropy solution of the conservation law is established. Boundary conditions are obtained. The equivalence with the Bardos, Leroux, and Nedelec conditions is studied. 相似文献
113.
L. Arkeryd R. Esposito R. Marra A. Nouri 《Archive for Rational Mechanics and Analysis》2010,198(1):125-187
We consider the Boltzmann equation for a gas in a horizontal slab, subject to a gravitational force. The boundary conditions
are of diffusive type, specifying the wall temperatures, so that the top temperature is lower than the bottom one (Benard
setup). We consider a 2-dimensional convective stationary solution, which for small Knudsen numbers is close to the convective
stationary solution of the Oberbeck–Boussinesq equations, near and above the bifurcation point, and prove its stability under
2-d small perturbations, for Rayleigh numbers above and close to the bifurcation point and for small Knudsen numbers. 相似文献
114.
115.
Mir Ali Farajzadeh Djavanshir Djozan Nina Nouri Mehdi Bamorowat Mohammad Safi Shalamzari 《Journal of separation science》2010,33(12):1816-1828
Stir bar sorptive extraction (SBSE) combined with dispersive liquid–liquid microextraction (DLLME) has been developed as a new approach for the extraction of six triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, triticonazole and difenconazole) in aqueous samples prior to GC‐flame ionization detection (GC‐FID). A series of parameters that affect the performance of both steps were thoroughly investigated. Under optimized conditions, aqueous sample was stirred using a stir bar coated with octadecylsilane (ODS) and then target compounds on the sorbent (stir bar) were desorbed with methanol. The extract was mixed with 25 μL of 1,1,2,2‐tetrachloroethane and the mixture was rapidly injected into sodium chloride solution 30% w/v. After centrifugation, an aliquot of the settled organic phase was analyzed by GC‐FID. The methodology showed broad linear ranges for the six triazole pesticides studied, with correlation coefficients higher than 0.993, lower LODs and LOQs between 0.53–24.0 and 1.08–80.0 ng/mL, respectively, and suitable precision (RSD < 5.2%). Moreover, the developed methodology was applied for the determination of target analytes in several samples, including tap, river and well waters, wastewater (before and after purification), and grape and apple juices. Also, the presented SBSE‐DLLME procedure followed by GC‐MS determination was performed on purified wastewater. Penconazole, hexaconazole and diniconazole were detected in the purified wastewater that confirmed the obtained results by GC‐FID determination. In short, by coupling SBSE with DLLME, advantages of two methods are combined to enhance the selectivity and sensitivity of the method. This method showed higher enrichment factors (282–1792) when compared with conventional methods of sample preparation to screen pesticides in aqueous samples. 相似文献
116.
Four new ligands, (4-methyl-phenyl)-pyridin-2-ylmethylene-amine (A), (2,3-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (B), (2,4-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (C) and (2,5-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (D), and their corresponding copper(I) complexes, [Cu(A)2]ClO4 (1a), [Cu(B)2]ClO4 (1b), [Cu(C)2]ClO4 (1c), [Cu(D)2]ClO4 (1d), [Cu(A)(PPh3)2]ClO4 (2a), [Cu(B)(PPh3)2]ClO4 (2b), [Cu(C)(PPh3)2]ClO4 (2c) and [Cu(D)(PPh3)2]ClO4 (2d), have been synthesized and characterized by CHN analyses, 1H and 13C NMR, IR and UV–Vis spectroscopy. The crystal structures of [Cu(B)2]ClO4 (1b), [Cu(C)2]ClO4 (1c) and [Cu(A)(PPh3)2]ClO4 · 1/2CH3CN (2a) were determined from single crystal X-ray diffraction. The coordination polyhedron about the copper(I) center in the three complexes is best described as a distorted tetrahedron. A quasireversible redox behavior is observed for the complexes. 相似文献
117.
Hassan NM Murimboh JD Sekaly AL Mandal R Chakrabarti CL Grégoire DC 《Analytical and bioanalytical chemistry》2006,384(7-8):1558-1566
Kinetic speciation of nickel, aluminium, and iron in fresh water has been investigated by cascade ultrafiltration followed by competing ligand exchange of the ultrafiltered fractions. Graphite furnace atomic absorption spectrometry was used to measure the kinetics of metal complex dissociation. Dissolved metal species were fractionated by cascade ultrafiltration. Metal speciation in each ultrafiltered fraction was then characterized as free metal ions, “labile” metal complexes (with dissociation rate constants ≥10−3 s−1), “slowly labile” metal complexes (with dissociation rate constants >10−6 s−1), and “inert” metal complexes (with dissociation rate constants <10−6 s−1). The experimental results were compared with the predictions of a computer-based equilibrium speciation model, the Windermere humic aqueous model (WHAM) V. Cascade ultrafiltration coupled with kinetic speciation of the metal species in each molecular weight cut-off (MWCO) fraction provided a more comprehensive picture and insight into the physical and the chemical characteristics of the metal species than either ultrafiltration or measurement of dissociation kinetics alone. 相似文献
118.
Khadijeh Didehban Elham Yarahmadi Farshid Nouri‐Ahangarani Seyed Amin Mirmohammadi Naeimeh Bahri‐Laleh 《中国化学会会志》2015,62(9):826-831
A nitrate? citrate gel was prepared from metallic nitrates and citric acid by sol? gel process and was further used to synthesize Ni0.5Zn0.5Fe2O4 nanocrystalline powder by auto‐combustion. Then, two novel 15 and 35% (w/w) magnetic Ni0.5Zn0.5Fe2O4 containing polyaniline nanocomposites, named as PANI‐Ni15 and PANI‐Ni35, respectively, were prepared via in‐situ polymerization of aniline in an aqueous solution containing proper amount of Ni0.5Zn0.5Fe2O4 magnetic powder. The incorporation of the nanopowders to PANI matrix was confirmed by X‐ray diffraction (XRD), IR and SEM. Synthesized PANI‐NiZn ferrite composite particles were subsequently added to an epoxy resin matrix to produce related nanocomposites. The morphological properties of these nanocomposite materials were investigated by SEM and TEM. The electromagnetic‐absorbing properties were studied by measuring the reflection loss in the frequency range of 8.0 to 12.0 GHz. Results showed the reflection loss of the PANI‐Ni35 composite is higher than pure polyaniline and PANI‐Ni15. The good reflection loss of the nanocomposites suggests their potential applicability as radar absorber. 相似文献
119.
Self-broadening coefficients of NH3 in the ν2 and ν4 bands and absolute line intensities in the ν2 band have been measured at room temperature for some selected lines in the P- and R-branches. Using a Fourier transform spectrometer, line intensities and collisional widths were obtained by fitting Voigt profiles to the measured shapes of the lines. The results of self-broadening coefficients are in reasonable agreement with calculated linewidths using a semiclassical model which reproduce rather well the systematic experimental J and K quantum numbers dependencies. Satisfactory agreement was also obtained for line intensities with previous measurements in the ν2 band. From the intensity measurements, we have determined effective transition dipole moments as well as Herman–Wallis parameters for the ν2 band. 相似文献
120.
Since its innovation in 2006, the dispersive liquid-liquid microextraction (DLLME) method has attracted the attention of analytical chemists in the field of sample preparation. This method has been successfully applied to determine trace amounts of pollutants in various matrices, but the restriction in the choice of suitable disperser and extraction solvents, and high disperser solvent consumption leading to decreased partition coefficients of the analytes between aqueous phase and extractant are its problems. To solve these drawbacks and develop environmentally friendly techniques, various alternatives for the conventional DLLME have been presented. The current review will begin with an introduction to the sample preparation, implementation of DLLME, and its advantages. Then, we focus on its drawbacks, which result mainly from the use of disperser solvent. Afterward, some of the most interesting approaches that have been employed and published until now are reviewed. Finally, an outlook on the future of these techniques will be given. 相似文献