The Polarisation Behaviour of Silver in Potassium Hydroxide Solution at Elevated Temperatures

<p>The Polarisation behaviour of silver in 1 mol kg-1 KOH solution over the temperature range 295-478 K was studied using cyclic voltammetry, potentiostatic, galvanostatic and a.c. impedance techniques. Thermodynamic data for the silver/water system at temperatures up to 573 K is presented in the form of potential-pH diagrams which assist in the interpretation of results at elevated temperatures. The cyclic voltammograms and galvanostatic charging curves indicate the principal changes to be the appearance of additional peaks and arrests, respectively, as the temperature is increased, followed by their disappearance at higher temperatures. The data obtained from cyclic voltammetry and also potentiostatic polarisation are analysed in terms of previously-derived relations for limiting rate control, in particular that due to diffusion. The impedance data are examined using equivalent circuit models from which it is shown that surface roughness of the electrodes has a significant effect on the reaction kinetics over the temperature range studied. It is proposed that substantial changes in the electrochemistry of silver at 478 K are associated with extensive surface roughness that a change in the kinetics of growth of the Ag2O multilayer takes place at elevated temperatures with the rate of nucleation of Ag2O growth centres becoming more important in relation to the rate of solid-state diffusion.</p>

The Polarisation Behaviour of Silver in Potassium Hydroxide Solution at Elevated Temperatures

<p>The Polarisation behaviour of silver in 1 mol kg-1 KOH solution over the temperature range 295-478 K was studied using cyclic voltammetry, potentiostatic, galvanostatic and a.c. impedance techniques. Thermodynamic data for the silver/water system at temperatures up to 573 K is presented in the form of potential-pH diagrams which assist in the interpretation of results at elevated temperatures. The cyclic voltammograms and galvanostatic charging curves indicate the principal changes to be the appearance of additional peaks and arrests, respectively, as the temperature is increased, followed by their disappearance at higher temperatures. The data obtained from cyclic voltammetry and also potentiostatic polarisation are analysed in terms of previously-derived relations for limiting rate control, in particular that due to diffusion. The impedance data are examined using equivalent circuit models from which it is shown that surface roughness of the electrodes has a significant effect on the reaction kinetics over the temperature range studied. It is proposed that substantial changes in the electrochemistry of silver at 478 K are associated with extensive surface roughness that a change in the kinetics of growth of the Ag2O multilayer takes place at elevated temperatures with the rate of nucleation of Ag2O growth centres becoming more important in relation to the rate of solid-state diffusion.</p>

Ship control in storm conditions

Приведены выражения для определения периодов собственных поперечных и продольных колебаний судна, как точные, так и приближённые, но в тоже время достаточные для их практического использования на судне. Представлены формулы для расчёта поперечной метацентрической высоты после принятия груза судном перед выходом в море. Выведены формулы для определения критических зон резонансной качки по крену и дифференту, как по скорости судна, так и по курсовому углу по отношению к направлению распространения штормового волнения моря. Представлены формулы для определения кажущегося периода встречи судна с волной, которые являются основой для расчёта резонансных зон. Выведенные соотношения для определения зоны резонанса по скорости судна при заданном курсовом угле и по курсовому углу при заданной скорости судна представлены при условии известного периода штормового волнения моря и курсового угла судна по отношению к направлению распространения волнения моря. Приведены формулы для определения амплитуды качки в условиях резонанса, если отношение периода собственных колебаний судна к кажущемуся периоду волны находится в пределах 0,7 – 1,3. Представлены выражения для определения амплитуд качки по крену и дифференту, вызывающие морскую болезнь у персонала, а также критические значения боковых перегрузок, влияющих на правильность его действия. Expressions for determining the periods of the natural transverse and longitudinal vibrations of the vessel, both exact and approximate, are given, but at the same time sufficient for their practical use on the vessel. The formulas for calculating the transverse metacentric height after the cargo has been accepted by the vessel before going to sea are presented. Formulas are derived for determining the critical zones of resonant pitching in terms of roll and trim, both in terms of the ship's speed and in the heading angle in relation to the direction of propagation of storm waves of the sea. The formulas for determining the apparent period of the ship's meeting with the wave are presented, which are the basis for calculating the resonance zones. The derived relations for determining the resonance zone by the speed of the vessel at a given heading angle and by the heading angle at a given speed of the vessel are presented under the condition of a known period of stormy sea waves and the heading angle of the vessel in relation to the direction of propagation of sea waves. Formulas are given for determining the amplitude of pitching under resonance conditions if the ratio of the period of natural oscillations of the vessel to the apparent period of the wave is within 0.7 - 1.3. Expressions for determining the amplitudes of roll and pitch that cause motion sickness in personnel, as well as the critical values of lateral g-forces that affect the correctness of its action, are presented.

Social Determinant Trends of COVID-19: An Analysis Using Knowledge Graphs from Published Evidence and Online Trends

This paper presents the results of a new approach to discover related health and social factors during the COVID-19 pandemic. The approach leverages a knowledge graph of related concepts mined from a corpus of published evidence (PubMed) prior to the pandemic. Population trends from online searches were used to identify social determinants of health (SDoH) concepts that trended high at the outset of the pandemic from a list of SDoH topics from the World Health Organization (WHO). The trending concepts were then mapped to the knowledge graph and a subsequent analysis of the derived insights, spanning two years, was conducted. This paper suggests an approach to derive new related health and social factors that may have either played a role in, or been affected by, the onset of the global COVID-19 pandemic. In particular, our results show how, from a list of SDoH topics, Food Security, Unemployment trended the highest at the start of the pandemic. Further work is needed to continue to ascertain the validity of the derived relations in a population health context and to improve mining insights from published evidence.

Enhanced Equivalence Projective Simulation: A Framework for Modeling Formation of Stimulus Equivalence Classes

Formation of stimulus equivalence classes has been recently modeled through equivalence projective simulation (EPS), a modified version of a projective simulation (PS) learning agent. PS is endowed with an episodic memory that resembles the internal representation in the brain and the concept of cognitive maps. PS flexibility and interpretability enable the EPS model and, consequently the model we explore in this letter, to simulate a broad range of behaviors in matching-to-sample experiments. The episodic memory, the basis for agent decision making, is formed during the training phase. Derived relations in the EPS model that are not trained directly but can be established via the network's connections are computed on demand during the test phase trials by likelihood reasoning. In this letter, we investigate the formation of derived relations in the EPS model using network enhancement (NE), an iterative diffusion process, that yields an offline approach to the agent decision making at the testing phase. The NE process is applied after the training phase to denoise the memory network so that derived relations are formed in the memory network and retrieved during the testing phase. During the NE phase, indirect relations are enhanced, and the structure of episodic memory changes. This approach can also be interpreted as the agent's replay after the training phase, which is in line with recent findings in behavioral and neuroscience studies. In comparison with EPS, our model is able to model the formation of derived relations and other features such as the nodal effect in a more intrinsic manner. Decision making in the test phase is not an ad hoc computational method, but rather a retrieval and update process of the cached relations from the memory network based on the test trial. In order to study the role of parameters on agent performance, the proposed model is simulated and the results discussed through various experimental settings.

Uncertainty Relations in Hydrodynamics

The qualitative behaviors of uncertainty relations in hydrodynamics are numerically studied for fluids with low Reynolds numbers in 1+1 dimensional system. We first give a review for the formulation of the generalized uncertainty relations in the stochastic variational method (SVM), following the work by two of the present authors [Phys. Lett. A 382, 1472 (2018)]. In this approach, the origin of the finite minimum value of uncertainty is attributed to the non-differentiable (virtual) trajectory of a quantum particle and then both of the Kennard and Robertson-Schrödinger inequalities in quantum mechanics are reproduced. The same non-differentiable trajectory is applied to the motion of fluid elements in the Navier-Stokes-Fourier equation or the Navier-Stokes-Korteweg equation. By introducing the standard deviations of position and momentum for fluid elements, the uncertainty relations in hydrodynamics are derived. These are applicable even to the Gross-Pitaevskii equation and then the field-theoretical uncertainty relation is reproduced. We further investigate numerically the derived relations and find that the behaviors of the uncertainty relations for liquid and gas are qualitatively different. This suggests that the uncertainty relations in hydrodynamics are used as a criterion to classify liquid and gas in fluid.