Journal of Analytical Chemistry - In this article, a new spectrofluorometric method was developed for the determination of methamphetamine based on a turn-on luminescence response of captopril... 相似文献
Transport in Porous Media - We investigate viscous fluid flows and concurrent fluid-driven deformations in porous media. The hydro-mechanically (H-M) coupled pore-network model (PNM) is developed,... 相似文献
The problem of controlling the relative position and velocity in multi-spacecraft formation flying in the planetary orbits is an enabling technology for current and future research. This paper proposes a family of tracking controllers for different dynamics of Spacecraft Formation Flying (SFF) in the framework of port-Hamiltonian (pH) systems through application of timed Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). The leader–multi-follower architecture is used to address this problem. In this regard, first we model the spacecraft motion in the pH framework in the Earth Centered Inertial frame and then transform it to the Hill frame which is a special local coordinate system. By this technique, we may present a unified structure which encompasses linear/nonlinear dynamics, with/without perturbation. Then, using the timed IDA-PBC method and the contraction analysis, a new method for controlling a family of SFF dynamics is developed. The numerical simulations show the efficiency of the approach in two different cases of missions.
We demonstrate a three orders of magnitude increase and stability in the backscattered fluorescence signal from nitrogen molecules
by terawatt femtosecond laser pulse induced air filaments using a new method. The method is based on squeezing the initial
beam diameter using a telescope. The effect of laser shot-to-shot fluctuations was included in numerical simulations by a
random distribution of the initial intensity in both squeezed and non-squeezed beams. Statistical processing of the simulation
results shows that the average diameter of plasma channels as well as the total amount of free electrons generated in a bunch
of multiple filaments in air is larger in the squeezed beam. Shot-to-shot stability of the simulated plasma density increases
in the squeezed beam. The change of this plasma density with propagation distance is in good qualitative agreement with the
change of the range-corrected nitrogen fluorescence signal with distance.
PACS 42.65.Jx; 42.60.Jf; 42.68.Ay; 42.68.Wt 相似文献
Several planar waveguides have been fabricated. The waveguides have been polished for determination of their refractiveindex profiles (RIP) by wedge method. The RIP determined by inserting the sample in a Mach-Zehnder interferometer andapplying fringe analysis methods. 相似文献
Headspace solvent microextraction (HSME) into a single drop is developed for the determination of six trihalomethanes, CH2Cl2, CHCl3, C4H9Cl, CCl4, C2HCl3, and C2Cl4, in aqueous solution. A drop of benzyl alcohol containing bromoform, as an internal standard, is used for extraction. The analytes are extracted by suspending a 3-microL drop directly from the needle of a microsyringe. The needle passes through the septum of a vessel, and the needle tip appears above the surface of the solution. After the prescribed extraction time, the drop is drawn back into the syringe. The syringe is then removed, and its content is injected directly into a gas chromatography column for analysis. The main parameters affecting the HSME process, such as stirring speed, microdrop volume, sample solution temperature, microsyringe needle temperature, sample volume, solution pH, extracting solvent, and ionic strength of the solution, are studied. Also, the linear range and precision of the method are examined. 相似文献
A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency
inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate,
input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate
that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement
tube, are considerably altered by the changes in the torch operating conditions. 相似文献
A satisfactory method was described for separation and preconcentration of ultratrace amounts of fluoride ions enriched by
zirconia (ZrO2) as an inorganic ion exchanger. Fluoride ions can be adsorbed rapidly and selectively on zirconia from an acidic solution
(pH 4.8) then reversibly desorbed by increasing pH up to 13. A flow system consisting of a column packed with zirconia impregnated
on cellulose fibers and an ion-selective electrode was used for the determination of fluoride. The RSD was found to be 1.6%
and the detection limit defined by S/N = 3 was 3 × 10−9 mol L−1. The interference effects of various ions, such as nitrate, sulfate, halides, alkaline, and alkaline earth ions, which may
be found in the environmental water, were studied, and it was found that they were tolerated even at high concentrations.
The method was applied to determine fluoride in drinking water, which contains ultratrace amounts of fluoride. The concentration
of fluoride was found to be 42 μg L−1, which is confirmed by spiking 2 μmol fluoride to the drinking water with a recovery of 99%.
Published in Russian in Zhurnal Analiticheskoi Khimii, 2006, Vol. 61, No. 2, pp. 179–183.
The text was submitted by the authors in English. 相似文献
Some new N‐carbonyl, phosphoramidates with formula C6H5C(O)N(H)P(O)R2 (R = NC3H6 ( 1 ), NC6H12 ( 2 ), NHCH2CH=CH2 ( 3 ), N(C3H7)2 ( 4 )) and CCl3C(O)N(H)P(O)R′2 (R′ = NC3H6 ( 5 ), NHCH2CH=CH2 ( 6 )) were synthesized and characterized by 1H, 13C, 31P NMR and IR spectroscopy and elemental analysis. The structures were determined for compounds 1 and 2 . Compound 1 exists as two crystallographically independent molecules in crystal lattice. Both compounds 1 and 2 produced dimeric aggregates via intermolecular ‐P=O…H‐N‐ hydrogen bonds, which in compound 2 is a centrosymmetric dimer. In compounds with four‐membered ring amine groups, 3J(P,C)>2J(P,C), in agreement with our previous studies about five‐membered ring amine groups. Also, 3J(P,C) values in compounds 1 and 5 are greater than in compounds with five‐, six‐ and seven‐membered ring amine groups. 相似文献