Search results for "direct method"
showing 10 items of 51 documents
Direct determination of Mancozeb by photoacoustic spectrometry
2006
Abstract A solvent free, fast and environmentally friendly photoacoustic-infrared-based methodology (PAS-FTIR) was developed for the determination of Mancozeb in agrochemicals. This methodology was based on the direct measurement of the transmittance spectra of solid samples and a multivariate calibration model to determine the active ingredient concentration. The proposed partial least squares (PLS) model was made using nine standards prepared by mixing different amounts of kaolin and Mancozeb, with concentrations between 5.43 and 88.10% (w/w). A hierarchical cluster analysis was made in order to classify the samples in terms of similarity in the PAS-FTIR spectra. From their spectra differ…
Comparison of two vibrational procedures for the direct determination of mancozeb in agrochemicals.
2007
The direct determination of mancozeb in agrochemicals has been made by diamond attenuated total reflectance (ATR) Fourier transform infrared spectroscopy in the middle range (DATR-MIR) and diffuse reflectance infrared Fourier transform spectroscopy in the near range (DR-NIR) methods using in both cases a previous identification of the samples using a dendrographic classification and an appropriate partial least squares (PLS) calibration established from a set of nine external standards and optimized for each type of sample. It was analyzed a heterogeneous population of 11 samples obtained from the Spanish market, containing different co-formulated products, such as fosetyl-Al, copper oxychl…
A direct impedance tomography algorithm for locating small inhomogeneities
2003
Impedance tomography seeks to recover the electrical conductivity distribution inside a body from measurements of current flows and voltages on its surface. In its most general form impedance tomography is quite ill-posed, but when additional a-priori information is admitted the situation changes dramatically. In this paper we consider the case where the goal is to find a number of small objects (inhomogeneities) inside an otherwise known conductor. Taking advantage of the smallness of the inhomogeneities, we can use asymptotic analysis to design a direct (i.e., non-iterative) reconstruction algorithm for the determination of their locations. The viability of this direct approach is documen…
Correspondences and Contrasts in Foreign Language Pedagogy and Translation Studies
2013
Correspondences and contrasts in foreign language pedagogy.- Correspondences and contrasts in translation studies.
A Comparison of Algorithms for Path Planning of Industrial Robots
2008
In this paper, the path planning problem for industrial robots in environ- ments with obstacles has been solved using four algorithms that implement different methodologies. Our objective is to analyze the characteristics of these algorithms. Consequently, the results (solutions) obtained with each of them are compared through the analysis of three operational parameters that are relevant to determine the qualities of the solutions. These parameters are: the computational time, the distance travelled by the robot and the number of generated configurations. One of the algorithms can be catalogued as indirect and the other three are variations of a direct method. The four algorithms have been…
Direct method for calculating temperature-dependent transport properties
2015
We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance and the spi…
Multicommutation Fourier transform infrared determination of benzene in gasoline
2004
A fully mechanized method to determine benzene in motor gasolines has been developed based on the use of Fourier transform infrared spectroscopy (FT-IR) and multicommutation. The flow network comprised a set of three-way solenoid valves and was controlled by means of a microcomputer furnished with an electronic interface and running by a software written in QUICK BASIC 4.5. The flow network and control software were designed to implement the multicommutation approach providing facilities to handle sample and reagent solutions, so that, sample dilution, external calibration and standard addition could be easily performed on-line. The method permits the direct determination of benzene without…
"Ab initio" structure solution from electron diffraction data obtained by a combination of automated diffraction tomography and precession technique
2009
Using a combination of our recently developed automated diffraction tomography (ADT) module with precession electron technique (PED), quasi-kinematical 3D diffraction data sets of an inorganic salt (BaSO(4)) were collected. The lattice cell parameters and their orientation within the data sets were found automatically. The extracted intensities were used for "ab initio" structure analysis by direct methods. The data set covered almost the complete set of possible symmetrically equivalent reflections for an orthorhombic structure. The structure solution in one step delivered all heavy (Ba, S) as well as light atoms (O). Results of the structure solution using direct methods, charge flipping …
Automated diffraction tomography combined with electron precession: a new tool forab initionanostructure analysis
2009
AbstractThree-dimensional electron diffraction data was collected with our recently developed module for automated diffraction tomography and used to solve inorganic as well as organic crystal structuresab initio. The diffraction data, which covers nearly the full relevant reciprocal space, was collected in the standard nano electron diffraction mode as well as in combination with the precession technique and was subsequently processed with a newly developed automated diffraction analysis and processing software package. Non-precessed data turned out to be sufficient forab initiostructure solution by direct methods for simple crystal structures only, while precessed data allowed structure s…
The role of electron diffraction in zeolite structure determination
2006
Because electron diffraction can sample individual microcrystals, it is clear that this single crystal method can facilitate, in at least two ways, structure determination for inorganic materials, such as zeolites, that are preferentially microcrystalline. First, in a qualitative application, three-dimensional tilts of individual small crystals, to map the reciprocal lattice, greatly facilitates unit cell and space group determination when powder diffraction indexing programs fail. If incoherent multiple scattering leads to violation of systematic absences, these absences can be restored by collection of precession diffraction patterns based on the Vincent-Midgley method [1], as demonstrate…