266 research outputs found
Thermoelectric energy recovery at ionic-liquid/electrode interface
A Thermally Chargeable Capacitor containing a binary solution of
1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide (EMIMTFSI) in
acetonitrile is electrically charged by applying a tempera- ture gradient to
two ideally polarisable electrodes. The corresponding thermoelectric
coefficient is -1.7 mV/K for platinum foil electrodes and -0.3 mV/K for
nanoporous carbon electrodes. Stored electrical energy is extracted by
discharging the capacitor through a resistor. The measured capacitance of the
electrode/ionic- liquid interface is 5 micro F for each platinum electrode
while it becomes four orders of magnitude larger mF for a single
nanoporous carbon electrode. Reproducibility of the effect through repeated
charging-discharging cycles under a steady-state temperature gradient
demonstrates the robustness of the electrical charging pro- cess at the
liquid/electrode interface. The acceleration of the charging by convective
flows is also observed. This offers the possibility to convert waste-heat into
electric energy without exchanging electrons between ions and electrodes, in
contrast to what occurs in most thermogalvanic cells.Comment: 8 pages, 11 figure
Fifth-order susceptibility unveils growth of thermodynamic amorphous order in glass-formers
Glasses are ubiquitous in daily life and technology. However the microscopic
mechanisms generating this state of matter remain subject to debate: Glasses
are considered either as merely hyper-viscous liquids or as resulting from a
genuine thermodynamic phase transition towards a rigid state. We show that
third- and fifth-order susceptibilities provide a definite answer to this
longstanding controversy. Performing the corresponding high-precision nonlinear
dielectric experiments for supercooled glycerol and propylene carbonate, we
find strong support for theories based upon thermodynamic amorphous order.
Moreover, when lowering temperature, we find that the growing transient domains
are compact - that is their fractal dimension d_f = 3. The glass transition may
thus represent a class of critical phenomena different from canonical
second-order phase transitions for which d_f < 3.Comment: 9 pages, 3 figure
A Robust Iterative Unfolding Method for Signal Processing
There is a well-known series expansion (Neumann series) in functional
analysis for perturbative inversion of specific operators on Banach spaces.
However, operators that appear in signal processing (e.g. folding and
convolution of probability density functions), in general, do not satisfy the
usual convergence condition of that series expansion. This article provides
some theorems on the convergence criteria of a similar series expansion for
this more general case, which is not covered yet by the literature.
The main result is that a series expansion provides a robust unbiased
unfolding and deconvolution method. For the case of the deconvolution, such a
series expansion can always be applied, and the method always recovers the
maximum possible information about the initial probability density function,
thus the method is optimal in this sense. A very significant advantage of the
presented method is that one does not have to introduce ad hoc frequency
regulations etc., as in the case of usual naive deconvolution methods. For the
case of general unfolding problems, we present a computer-testable sufficient
condition for the convergence of the series expansion in question.
Some test examples and physics applications are also given. The most
important physics example shall be (which originally motivated our survey on
this topic) the case of pi^0 --> gamma+gamma particle decay: we show that one
can recover the initial pi^0 momentum density function form the measured single
gamma momentum density function by our series expansion.Comment: 23 pages, 9 figure
PCN83 PERFORMANCE AND ADEQUACY OF PATIENT-PERSPECTIVE CRITERIA IN THE ASSESSMENT OF TEST-RETEST RELIABILITY: THE CASE OF THE PERFORM QUESTIONNAIRE
Generation of magnetic field by dynamo action in a turbulent flow of liquid sodium
We report the observation of dynamo action in the VKS experiment, i.e., the
generation of magnetic field by a strongly turbulent swirling flow of liquid
sodium. Both mean and fluctuating parts of the field are studied. The dynamo
threshold corresponds to a magnetic Reynolds number Rm \sim 30. A mean magnetic
field of order 40 G is observed 30% above threshold at the flow lateral
boundary. The rms fluctuations are larger than the corresponding mean value for
two of the components. The scaling of the mean square magnetic field is
compared to a prediction previously made for high Reynolds number flows.Comment: 4 pages, 5 figure
Data driven optimal filtering for phase and frequency of noisy oscillations: application to vortex flowmetering
A new method for extracting the phase of oscillations from noisy time series
is proposed. To obtain the phase, the signal is filtered in such a way that the
filter output has minimal relative variation in the amplitude (MIRVA) over all
filters with complex-valued impulse response. The argument of the filter output
yields the phase. Implementation of the algorithm and interpretation of the
result are discussed. We argue that the phase obtained by the proposed method
has a low susceptibility to measurement noise and a low rate of artificial
phase slips. The method is applied for the detection and classification of mode
locking in vortex flowmeters. A novel measure for the strength of mode locking
is proposed.Comment: 12 pages, 10 figure
Obesity: A Biobehavioral Point of View
Excerpt: If you ask an overweight person, “Why are you fat?’, you will, almost invariably, get the answer, “Because 1 eat too much.” You will get this answer in spite of the fact that of thirteen studies, six find no significant differences in the caloric intake of obese versus nonobese subjects, five report that the obese eat significantly less than the nonobese, and only two report that they eat significantly more
Labelled Tableaux For Non-Normal Modal Logics
In this paper we show how to extend KEM, a tableaux-like proof system for normal modal logic, in order to deal with classes of non-normal modal logic, such as monotonic and regular, in a uniform and modular way
MHD in von Kármán swirling flows, development and first run of the sodium experiment
URL: http://www-spht.cea.fr/articles/s01/004 MHD dans les écoulements de von Kármán | Collaboration VKSNATO Science Series II 26, 35-50 (2001). NATO Advanced Research Workshop, Dynamo and Dynamics, A Mathematical ChallengeWe describe the motivations, development and first run of the Von Kármán Sodium (VKS) experiment built to study high Reynolds number magnetohydrodynamics and applications to the dynamo effect. The flow is optimized using water experiments at scale 1/2 and kinematic dynamo simulations. In VKS run1, induction measurements are made in the presence of an externally applied field. Results are reported concerning the geometry of the induced field and its fluctuations in time
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