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1.
A least‐squares meshfree method based on the first‐order velocity–pressure–vorticity formulation for two‐dimensional incompressible Navier–Stokes problem is presented. The convective term is linearized by successive substitution or Newton's method. The discretization of all governing equations is implemented by the least‐squares method. Equal‐order moving least‐squares approximation is employed with Gauss quadrature in the background cells. The boundary conditions are enforced by the penalty method. The matrix‐free element‐by‐element Jacobi preconditioned conjugate method is applied to solve the discretized linear systems. Cavity flow for steady Navier–Stokes problem and the flow over a square obstacle for time‐dependent Navier–Stokes problem are investigated for the presented least‐squares meshfree method. The effects of inaccurate integration on the accuracy of the solution are investigated. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
2.
Acidolytic cleavage of unsymmetrically substituted dithioacetal monoxides, ArCH(SR)S(O)Me has been used to prepare linear unsymmetrical disulfides RSSMe. Disproportionation was suppressed by the addition of a small amount of benzyl mercaptan. The required starting materials were conveniently obtained from appropriately substituted sulfines ArC(=SO)SR and methyl lithium. The following disulfides were prepared: R =n-C4H9 (73.5%), n-C7H15 (78%), Ph (77.3%), AcO(CH2)10 (81.5%).The unsymmetrical dithioacetal PhCH(SEt)SC7H15-n gave upon oxidation with one equivalent of peracid a mixture of two dithioacetal monoxides which on treatment with HClO4 led to three disulfides. This result is discussed in term of the mechanism of acidolysis. 相似文献
3.
T. A. Przylibski B. Kozłowska J. Dorda B. Kiełczawa 《Journal of Radioanalytical and Nuclear Chemistry》2002,253(1):11-19
This work characterizes the occurrence of radionuclides 222Rn and 226Ra in the mineralized groundwaters of Gorzanów. The village is situated in the Sudeten Mountains, which are known in Poland for having increased concentrations of the aforesaid radionuclides in their groundwaters. However, in Gorzanów, the measured concentrations of 226Ra were low both in the reservoir rocks and mineralized waters. Consequently, the 222Rn concentration in the groundwaters also turned out to be low. The 226Ra content of these waters should mainly be associated with the dissolution of this nuclide, together with other main ions, at large depths, at slightly enhanced temperature. Radon-222, on the other hand, penetrates into the water during its outflow to the surface, in the zones of intensive friable deformations near fault zones. Thus, in the groundwaters of Gorzanów, the concentrations of these nuclides, subsequent in the uranium series, do not have a common genesis and they are not correlated with each other. 相似文献
4.
Summary The highly complex matrix of diesel particulate extracts was analyzed for nitrated polycyclic aromatic hydrocarbons (nitro-PAH)
using fused-silica capillary-column gas chromatography along with a thermionic nitrogen-phosphorus detector (TID) and high-performance
liquid chromatography followed by on-line catalytic reduction of the nitro-PAH to amino-PAH and subsequent fluorescence detection.
Positive isomer identification and quantitation of nitro-PAH are from retention times of authentic standards and their mass
spectra. The ease of nitro-PAH formation by nitration of PAH raises the question regarding the origin of these species, whether
they are produced as “native” products during the engine combustion process and/or in the exhaust, or instead, formed as the
result of chemical conversion to produce artifacts during the sampling procedure. This problem is assessed examing 1-nitropyrene-concentration
in particulates of three light-duty diesel engines for different sampling times. 1-Nitropyrene concentrations show only a
moderate increase with sampling time under average sampling conditions.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
5.
D. KieΒling 《Colloid and polymer science》1961,176(2):119-128
Ohne Zusammenfassung
Herrn Prof. Dr.W. Holzmütter danke ich für sein stetes Interesse an dieser Arbeit und seine wertvollen Ratschl?ge. Au\erdem bin ich Herrn Dr.G. Geppert und seiner Mitarbeiterin, Frl.C. Roth, für die Unterstützung beim Aufnehmen der Ultrarotspektren zu Dank verpflichtet. Für die überlassung von Probematerial m?chte
ich folgenden Firmen danken: Eilenburger Celluloidwerk, Chemische Werke Buna, Badische Anilin- & Sodafabriken, Ludwigshafen,
Kalle & Co., Wiesbaden. 相似文献
6.
The garnet-type fluorides, Na3M2Li3F12 (M = Al, Cr, and Fe) were synthesized as the coprecipitates of ~1 to 10 μm powders from HF solutions. The garnet structures were always obtained under acidic conditions. The incorporation of water molecules into the structure of the Cr and Fe garnets was observed. After heat treatment at 300°C, very small unknown peaks were observed in the X-ray powder pattern in addition to the garnet phase which had a slightly smaller value of the lattice constant than that of hydrous garnets. From the measurement of magnetic properties and Mössbauer effects, the Fe and Cr garnets were found to be paramagnetic with both ions in the trivalent state. Presentation of infrared spectra of the garnets is also included. 相似文献
7.
Horiyama S Suwa K Yamaki M Kataoka H Katagi T Takayama M Takeuchi T 《Chemical & pharmaceutical bulletin》2002,50(7):996-1000
Hydroxylamines gradually undergo oxidation to their oximes on being dissolved in organic solvent (e.g. methanol). This phenomenon was followed by (1)H-NMR and liquid chromatography-mass spectrometry (LC-MS). The oxidation rate was estimated from the peak area observed on the mass chromatogram at the protonated molecule or fragment ion on LC-atmospheric pressure chemical ionization (APCI)-MS. The results showed that the oxidation rate of hydroxylamines depended on the solvent type. 相似文献
8.
Takeshi Suwa Terutaka Watanabe Jiro Okamoto Sueo Machi 《Journal of polymer science. Part A, Polymer chemistry》1978,16(11):2931-2944
The radiation-induced emulsifier-free emulsion polymerization of tetrafluoroethylene was carried out at an initial pressure of 2–25 kg/cm2, temperature of 30–110°C, and under a dose rate of 0.57 × 104?3.0 × 104 rad/hr. The rate of polymerization was shown to be proportional to 1.0 and 1.3 powers of the dose rate and initial pressure, respectively, and is maximal at about 70°C. The molecular weight of polytetrafluoroethylene (PTFE) lies in the range of 105?106, increases with reaction time in the early stage of polymerization, and is maximal at 70°C but is almost independent of the dose rate. An interesting discovery is that PTFE, a hydrophobic polymer, forms as a stable latex in the absence of emulsifier. When PTFE latex coagulates during polymerization under certain conditions, the polymerization rate decreases, probably because polymerization proceeds mainly on the polymer particle surface. The observed rate acceleration and successive increase in polymer molecular weight may be due to slow termination of propagating radicals in the rigid PTFE particles. 相似文献
9.
Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter
can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated
polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis
was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact
mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes
(ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times
and mass spectra.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
10.
Racemic phosphocarnitine 3 has been synthesized starting from diethyl 3-chloro-2-oxopropanephosphonate 4 in three steps involving reduction of 4 to the corresponding 2-hydroxyphosphonate 5, conversion of the latter to phosphonic acid 6, and final reaction with trimethylamine, affording the trimethylammonium salt of 3. Baker's yeast reduction of 4 and enzymatic kinetic resolution of (+/-)-5 afforded the enantiomerically pure precursors of phosphocarnitine, (R)-(+)-5 and (S)-(-)-5, which were converted to (S)-(-)- and (R)-(+)-phosphocarnitine 3, respectively. 相似文献