3,707 research outputs found
Fluoride glasses : synthesis and properties
The discovery of heavy metal fluoride glasses has opened new prospects for fiber optics operating beyond 2 µm with expected losses less than 10(-2) dB/Km. The main interest of fluoride glasses lies in their infrared transmission up to 8 µm in the bulk form and 4.5 µm for optical fibers. We have reported here the preparation, the glass forming systems and properties of heavy metal fluoride glasses
Sensitivity and identifiability of hydraulic and geophysical parameters from streaming potential signals in unsaturated porous media
Fluid flow in a charged porous medium generates electric potentials called
streaming potential (SP). The SP signal is related to both hydraulic and
electrical properties of the soil. In this work, global sensitivity analysis
(GSA) and parameter estimation procedures are performed to assess the
influence of hydraulic and geophysical parameters on the SP signals and to
investigate the identifiability of these parameters from SP measurements.
Both procedures are applied to a synthetic column experiment involving a
falling head infiltration phase followed by a drainage phase.GSA is used through variance-based sensitivity indices, calculated using
sparse polynomial chaos expansion (PCE). To allow high PCE orders, we use an
efficient sparse PCE algorithm which selects the best sparse PCE from a
given data set using the Kashyap information criterion (KIC). Parameter
identifiability is performed using two approaches: the Bayesian approach
based on the Markov chain Monte Carlo (MCMC) method and the first-order
approximation (FOA) approach based on the Levenberg–Marquardt algorithm. The
comparison between both approaches allows us to check whether FOA can
provide a reliable estimation of parameters and associated uncertainties for
the highly nonlinear hydrogeophysical problem investigated.GSA results show that in short time periods, the saturated hydraulic conductivity
(Ks) and the voltage coupling coefficient at saturation Csat are the most influential parameters, whereas in long time periods, the
residual water content (θs), the Mualem–van Genuchten parameter
n and the Archie saturation exponent na
become influential, with strong interactions between them. The
Mualem–van Genuchten parameter α has a very weak
influence on the SP signals during the whole experiment.Results of parameter estimation show that although the studied problem is
highly nonlinear, when several SP data collected at different altitudes
inside the column are used to calibrate the model, all hydraulic (Ks, θs, α, n)
and geophysical parameters (na, Csat) can be reasonably estimated from the SP measurements. Further, in
this case, the FOA approach provides accurate estimations of both mean
parameter values and uncertainty regions. Conversely, when the number of SP
measurements used for the calibration is strongly reduced, the FOA approach
yields accurate mean parameter values (in agreement with MCMC results) but
inaccurate and even unphysical confidence intervals for parameters with
large uncertainty regions.</p
Synthesis and SomeReactions of 3-Methyl-4-aryl-1-phenyl-1H- pyrazolo[3,4-dipyrimidine-6-thiols
3-Methyl-4-aryl-1-phenyl-1H -pyrazolo[3,4-d]-pyrimidine-6-thiols(
11)were synthesised by the raction of thiourea with 3-methyl-\u27
-1-phenyl-4-arylidene-2-pyrazolin-5-ones(1) in ethanolic solution of
potassium hydroxide. The mechanism of this reaction is discussed
and further transformation of the products with different reagents
(S-methylation, substitution of SR-group by arylamines, hydrazine,
and azide) was carried out
Etude du lac collinaire de Sadine 1 : installations et premiers résultats
Rapport d'installation des 2 premiers enregistreurs pluviométrique et limnimétrique susceptibles d'être équipés d'émetteur ARGOS et de permettre une télétransmission des données. Ces 2 appareils ont été installés sur un lac collinaire de la région de Maktar. Définition des termes du bilan hydrologique en matière de retenue artificielle. Présentation de quelques résultats. (Résumé d'auteur
Heat and freezing pre-thermal treatments as a means of freeing potatoes from mosaic virus and its effects on potato plants quality characters
The aim of the study was to control of potato mosaic virus by using hot-air, hot-water and freezing as a physical pre-thermal treatments. Infected tubers of Lady Rosetta and Mondial potato (Solanum tuberosum L.) cultivars were treated by hot-air and hot-water treatments at 55± 2 ̊ C and freezing treatment at -18±2 ̊ C for 1, 2, 3 and 4 hours. Hot-air and freezing treatments showed complete elimination of mosaic virus from treated tubers. Hot-water treatment caused tuber damage at different exposure times. In this respect, hot-air treatment at 55± 2 ̊ C and freezing treatment at -18±2 ̊ C for two hours gave the best results of eliminating the virus from tubers and did not affect on economic characters of potato cultivars.
Should We Learn Probabilistic Models for Model Checking? A New Approach and An Empirical Study
Many automated system analysis techniques (e.g., model checking, model-based
testing) rely on first obtaining a model of the system under analysis. System
modeling is often done manually, which is often considered as a hindrance to
adopt model-based system analysis and development techniques. To overcome this
problem, researchers have proposed to automatically "learn" models based on
sample system executions and shown that the learned models can be useful
sometimes. There are however many questions to be answered. For instance, how
much shall we generalize from the observed samples and how fast would learning
converge? Or, would the analysis result based on the learned model be more
accurate than the estimation we could have obtained by sampling many system
executions within the same amount of time? In this work, we investigate
existing algorithms for learning probabilistic models for model checking,
propose an evolution-based approach for better controlling the degree of
generalization and conduct an empirical study in order to answer the questions.
One of our findings is that the effectiveness of learning may sometimes be
limited.Comment: 15 pages, plus 2 reference pages, accepted by FASE 2017 in ETAP
Synthesis of Fused Heterocyclic Derivatives from 5-Ethyl-3-Hydrazino-5H-1,2,4-Triazino[5,6-b]Indole
5-Ethyl-3-hydrazino-5H-1,2,4-triazino[5,6-b ]indole II was used for the synthesis of various heterocyclic derivatives. This was performed by reaction of its 3-hydrazino group with different reagents such as acid anhydrides, ethylacetate, diethyl oxalate, thioglycolic acid, aroyl esters and acid chlorides. The structure of the products was confirmed by different spectroscopic and analytical methods
Level densities and -ray strength functions in Yb
Level densities and radiative strength functions in Yb and Yb
nuclei have been measured using the
Yb(He,He)Yb and
Yb(He,)Yb reactions. New data on Yb
are compared to a previous measurement for Yb from the
Yb(He,)Yb reaction. Systematics of level
densities and radiative strength functions in Yb are
established. The entropy excess in Yb relative to the even-even nuclei
Yb due to the unpaired neutron quasiparticle is found to be
approximately 2. Results for the radiative strength function from the two
reactions lead to consistent parameters characterizing the ``pygmy''
resonances. Pygmy resonances in the Yb populated by the
(He,) reaction appear to be split into two components for both of
which a complete set of resonance parameters are obtained.Comment: 8 pages, 7 figure
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