arXiv subjects

Erwin Lalik

Publications and source records attributed to Erwin Lalik.

3 recordsLinked to original sources

arXiv2022

Extracting the oscillatory component and defining a mean amplitude of thermokinetic oscillations in the H/Pd system

The mean value theorem for integrals has been applied in constructing a base curve for non-equilibrium thermokinetic oscillations, q(t), recorded in oscillatory sorptions of H2(D2) in Pd. The mean values are calculated for each period of q(t), followed by cubic spline interpolation, forming the new non-oscillatory curve, h(t), to be used as a baseline for the oscillatory component of the original thermokinetic time series. Crucially, areas, under both q(t) and h(t) are strictly identical. Subsequent pointwise subtraction q(t) h(t) yields another oscillatory time series g(t), considered the oscillatory component extracted from the thermokinetic data. The method has been applied to various experimental time series q(t). Using the g(t) curves, a new parameter, the mean amplitude has been defined and used as a descriptor correlating the intensity of thermokinetic oscillations with various experimental conditions. The mean amplitude turns out to be a linear function of the first ionization potential of noble gases, admixed intentionally to H2 before its contacting Pd.

physics.data-an↗

arXiv2012

Chaos in oscillatory heat evolution accompanying the sorption of hydrogen and deuterium in palladium

Aperiodic oscillations in the sorption of H2 or D2 in metallic Pd powder have been observed, and a novel method to confirm their deterministic rather than random character has been devised. A theorem relating the square of a function, with the derivative and integral with variable upper limit of the same function has been proved and proposed to be used as a base for a chaos-vs-random test. Both the experimental and the computed time series may be tested to detect determinism. The result is a single number within the interval [0,2]. The test is designed in such a way that its result is close to zero for the datasets that are deterministic and smooth, and close to 2 for the datasets that are non deterministic (random) or non smooth (discrete). A large variety of the test results has been obtained for the calorimetric time series recorded in thermokinetic oscillations, periodic and quasiperiodic, accompanying the sorption of H2 or D2 with Pd as well as for several non oscillatory calorimetric curves recorded in this reaction. These experimental datasets, all coming form presumably deterministic processes, yielded the results clustering around 0.001. On the other hand, certain databases that were presumably random or non smooth yielded the test results from 0.7 to 1.9. Against these benchmarks, the examined, experimental, aperiodic oscillations gave the test results between 0.004 and 0.01, which appear to be much closer to the deterministic behavior than to randomness. Consequently, it has been concluded that the examined cases of aperiodic oscillations in the heat evolution accompanying the sorption of H2 or D2 in palladium may represent an occurrence of mathematical chaos in the behavior of this system. Further applicability and limitations of the test have also been discussed, including its intrinsic inability to detect determinism in discrete time series.

physics.chem-ph↗

arXiv2011

An empirical dependence of frequency in the oscillatory sorption of H2 and D2 in Pd on the first ionization potential of noble gases

Oscillatory heat evolution in sorption of H2 and D2 in Pd can be induced by admixture of ca. 10 % vol. of inert gases He, Ne, Ar, Kr or N2 to either isotope prior to its contact with palladium powder. The oscillations are represented in a form of calorimetric time series, recorded using gas flow-through microcalorimeter at the temperatures of 75 °C for D2 and 106 °C for H2. For both D2 and H2, the oscillation parameters changes as a function of the kind of inert gas used: the amplitude increases and the frequency decreases in passing from He to Kr. An empirical dependence of the oscillation frequencies observed for various admixtures and normalized with respect to Kr has been found. Accordingly, the frequency is a function of a product of the first ionization potential and the square root of atomic mass of the inert gas (He, Ne, Ar, Kr or N2). On the other hand, invariance of the thermal effects of sorption is evident from the integrated areas under the calorimetric time series yielding the molar heats of sorption conserved, irrespective of the inert gas admixture. A novel calibration procedure has been devised in order to deal with an instability of calibration factor arising in desorption of H2 and D2 from Pd. A concept of dynamic calibration factor made it possible to obtain a good agreement between the heats of sorption and desorption of both H2 and D2 within individual sorption-desorption cycles for all inert gas admixtures.

physics.chem-ph↗