11,922 research outputs found
Wavelet transform for the evaluation of peak intensities in flow-injection analysis
The application of the wavelet transform in the determination of peak intensities in flow-injection analysis was studied with regard to its properties of minimizing the effects of noise and baseline drift. The results indicate that for white noise and a favourable peak shape a signal-to-noise ratio of 2 can be tolerated at the 5% error level, which means that a significant reduction in the detection limit can be obtained in comparison with the classical signal-processing methods. With regard to the influence of a changing baseline it was found that its d.c. level has a negligible effect, but a linear or exponentially rising baseline introduces an error that depends on the chosen frequency of the wavelet that is used to determine the peak intensity. The optimum choice of this frequency, in turn, depends on the shape of the peak that is studied. In this respect significant differences were observed for pure Gaussian and exponentially modified Gaussian peaks
The behaviour of a single catalyst pellet for the selective hydrogenation of ethyne in ethene
The steady-state and dynamic behaviour of a single Pd---Al2O3 catalyst particle is studied for the selective hydrogenation of ethyne in the presence of ethene, without addition of carbon monoxide. The particle-to-gas heat transfer in the reactor is characterized. During selective hydrogenation, not only the ignition and the extinction phenomena but also oscillatory behaviour is observed. The nature of the single and multipeak oscillations is discussed. With a dynamic model, based on relatively simple kinetic equations and an additional slow mechanism, e.g. the formation of ethylidyne on the catalyst surface, the qualitative features of this system can be described
Structural selection in implicit learning of artificial grammars
In the contextual cueing paradigm, Endo and Takeda (in Percept Psychophys 66:293–302, 2004) provided evidence that implicit learning involves selection of the aspect of a structure that is most useful to one’s task. The present study attempted to replicate this finding in artificial grammar learning to investigate whether or not implicit learning commonly involves such a selection. Participants in Experiment 1 were presented with an induction task that could be facilitated by several characteristics of the exemplars. For some participants, those characteristics included a perfectly predictive feature. The results suggested that the aspect of the structure that was most useful to the induction task was selected and learned implicitly. Experiment 2 provided evidence that, although salience affected participants’ awareness of the perfectly predictive feature, selection for implicit learning was mainly based on usefulness
A knowledge-based system for the automatic chronopotentiometric elucidation of electrode reaction mechanisms
A knowledge-based system for the elucidation of electrode reaction mechanisms based on chronopotentiometric experiments is described. The system runs the diagnostic experiments and uses the results in the reasoning process. New mechanistic knowledge can be added directly to its knowledge base in the form of production rules. The system is fully modular and its domain- specific modules can easily be changed for application to other electrochemical techniques. Correct operation of the system is demonstrated with the familiar reduction mechanisms of cadmium (II), zinc (II), cystamine and cinnamaldehyde
Background information and biorefinery status, potential and Sustainability: Task 2.1.2 Market and Consumers; Carbohydrates
This report was produced to give an overview of present and future market for biorefinery products based on carbohydrates. Various studies show that there is a wealth of possible molecules and products that can be produced from carbohydrates. Carbohydrates already find significant application in starch products and cellulose plastics and fibres. However, for a biorefinery to operate in an economically sustainable way, applications for (preferably all) biomass ingredients need to be found. Presumably the optimal mix of applications will be a combination of larger volume/smaller value and smaller volume/higher value applications. For this study we therefore have taken a molecular approach. Looking at the size of possible end markets for the molecules that can be based on carbohydrates a number of main products come into view: dialcohols, dioic acids, 2,5 furan dicarboxylic acid and ethanol. These molecules with a wide application range can serve as basis targets for the carbohydrate stream of a biorefinery, provided the production processes are optimised to make them competitive to the petrochemical counterparts. Speciality applications for the resulting side streams will then need to be found on a case by case basis
The LHCb Track Extrapolator Tools
This note describes the LHCb track propagation models and their implementation in the track extrapolator tools. Their usability and configuration options are discussed. The code referred to is that associated with Brunel release v31r11
Bayesian cosmic density field inference from redshift space dark matter maps
We present a self-consistent Bayesian formalism to sample the primordial
density fields compatible with a set of dark matter density tracers after
cosmic evolution observed in redshift space. Previous works on density
reconstruction did not self-consistently consider redshift space distortions or
included an additional iterative distortion correction step. We present here
the analytic solution of coherent flows within a Hamiltonian Monte Carlo
posterior sampling of the primordial density field. We test our method within
the Zel'dovich approximation, presenting also an analytic solution including
tidal fields and spherical collapse on small scales using augmented Lagrangian
perturbation theory. Our resulting reconstructed fields are isotropic and their
power spectra are unbiased compared to the true one defined by our mock
observations. Novel algorithmic implementations are introduced regarding the
mass assignment kernels when defining the dark matter density field and
optimization of the time step in the Hamiltonian equations of motions. Our
algorithm, dubbed barcode, promises to be specially suited for analysis of the
dark matter cosmic web down to scales of a few Megaparsecs. This large scale
structure is implied by the observed spatial distribution of galaxy clusters
--- such as obtained from X-ray, SZ or weak lensing surveys --- as well as that
of the intergalactic medium sampled by the Lyman alpha forest or perhaps even
by deep hydrogen intensity mapping. In these cases, virialized motions are
negligible, and the tracers cannot be modeled as point-like objects. It could
be used in all of these contexts as a baryon acoustic oscillation
reconstruction algorithm.Comment: 34 pages, 25 figures, 1 table. Submitted to MNRAS. Accompanying code
at https://github.com/egpbos/barcod
The Detection of a 3.5-h Period in the Classical Nova Velorum 1999 (V382 Vel) and the Long Term Behavior of the Nova Light Curve
We present CCD photometry, light curve and time series analysis of the
classical nova V382 Vel (N Vel 1999). The source was observed for 2 nights in
2000, 21 nights in 2001 and 7 nights in 2002 using clear filters. We report the
detection of a distinct period in the light curve of the nova P=0.146126(18) d
(3.5 h). The period is evident in all data sets, and we interpret it as the
binary period of the system. We also measured an increase in the amplitude
modulation of the optical light (in magnitude) by more than 55% from 2000 to
2001 and about 64% from 2001 to 2002. The pulse profiles in 2001 show
deviations from a pure sinusoidal shape which progressively become more
sinusoidal by 2002. The main cause of the variations in 2001 and 2002 can be
explained with the occultation of the accretion disk by the secondary star. We
interpret the observed deviations from a pure sinusoidal shape as additional
flux resulting from the aspect variations of the irradiated face of the
secondary star.Comment: 16 pages and 4 figures, accepted as it stands to be published in the
Astronomical Journal (AJ
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