Simulation of solar PV surface temperature with dimpled fin cooling

A significant number of cooling technologies have been developed to maintain the PV module temperature within subscribed limits. This paper represents the simulation study of active cooling forced air convection with fins attached to the back of the solar panel using CFD SimScale software. It has been first carefully validated against experimental and numerical results available in the literature. The number of fins and the shape of perforated and dimpled in each fin were varied to compare cooling performance. Three types of fins were adapted into this simulation: traditional fins, circular, and triangle perforated/dimpled fins. The effect of solar irradiation and velocity inlet was also reviewed by applying the nominal operating condition from the experimental works. Results indicated that fin channels are a very effective cooling technique, which significantly reduces the average temperature of the PV cell, especially when increasing the number of fins from 20 to 26 fins. Also, the results show that the dimpled triangle fin had the highest average temperature drop with a percentage difference of 6% compared with the solar panel cooling with traditional fins.

Термодинамические свойства жидкого цезия: поиск аномалий

The polymorphism of liquid cesium at atmospheric pressure in the temperature range of ~ 590 K in the form of a second-order phase transition, announced in the late 90s, is not confirmed in new experimental works and in computer simulations of its properties. At the same time, the question whether the change in the properties of liquid cesium with a decrease or increase in density up to two times is monotonous or is accompanied by various anomalies needs further research.

Żelazo meteorytowe w starożytnym Egipcie przed okresem późnym

The aim of the article is to present an unusual raw material, which is the meteorite iron and its specific status in the culture of ancient Egypt. The presentation of this extraordinary material, highlighting the features allowing to recognize it, the interpretation of the artifacts made of it (taking into account the physicochemical analyzes), and the development of the results of experimental works recreating the methods of its processing allow us to obtain the necessary information about the delineation of meteorite iron metallurgy in ancient Egypt up to the beginning of the Late Period. An important source for achieving the article’s goal are also texts. Text analysis highlights the ambiguity of the terminology used to describe meteorite iron. By reviewing the contexts of its use, they allow us to enrich knowledge about its metallurgy and help to characterize the status of this metal in the consciousness of the Egyptians.

Effect of hydrogen peroxide solutions on growth of micromycetes Saprolegniaceae on egg membranes of beluga (Huso huso) embryos and on indicators of its embryonic development during incubation

The article describes the data of the experimental works on assessing the influence of hydrogen peroxide so-lutions (0.05, 0.10, 0.20, 0.30, 0.40%) in different concentrations on the growth of the micromycetes Saprolegniaceae on egg membranes of beluga embryos and its embryonic development. In conditions of increasing intensification of aquacultures there is an acute problem regarding to the shortage of approved drugs for treating a common disease in fish farming - saprolegniosis. This disease is caused by species of different genus, the most common of which are the genus Achlya and Saprolegnia belonging to the biological kingdom Chromista (Stramenopila), the Oomycota phylum, the Oomycetes class, the Saprolegniales order, the Saprolegniaceae family. The impact of experimental hydrogen peroxide solutions on the beluga embryonic development and infection with saprolegnial micromycetes was assessed by fish-breeding biological indicators: the number of inseminated oocytes, number of survived embryos and hatched prelarvae, number of embryos infected with the micromycetes Saprolegniaceae and abnormally developing fish. Histological analysis of embryos at different stages of development was also carried out. The experimental works were carried out under production conditions in an incubation apparatus of “Sturgeon” type. The experimental groups were formed in accordance with the experimental solutions’ concentrations. Upon the result of the studies it has been inferred that using a 0.05% hydrogen peroxide solution with a 10-minute-exposure proves effective. This solution sup-pressed growth of micromycetes Saprolegniaceae without any negative impact on the embryonic development. Other experimental solutions had a negative impact on beluga (Huso huso) embryonic development of in most cases, causing the increased mortality and, as a consequence, the increased infection rate.

MATHEMATICAL MODEL OF THE DEVELOPMENT OF A SINGLE TWIN LAYER IN METAL CRYSTALS

By analyzing the experimental data available in the scientific literature, a mathematical model of the development of a single twin layer in metal crystals has been obtained. The model has the form of a differential equation, the order of which is determined by the required accuracy of obtaining the results associated with the solution of this equation. Even in the linear approximation of one of the main parameters of the phenomenological model, the latter gives qualitatively the same dependences of the development of single twins under different loading conditions compared to the experiment. Despite a large number of experimental works devoted to twinning, there is still no rigorous quantitative theory of the development of twinning layers in different media and under different conditions. However, in these works, the mathematical approach was demonstrated only in relation to elastic twins. This work is an introduction to the creation of a quantitative theory of twinning in metal crystals. Comparisons with the experimental results of the proposed phenomenological model were limited in this work to the task of demonstrating the performance of the model in the sense of predicting the most specific effects of the development of twins under various conditions and loading modes. In particular, the model implies the effect of loss and subsequent restoration of hardening by twin boundaries during stress pulsations, the Bauschinger effect upon a change in the sign of the applied voltage, and a number of other effects observed experimentally on a number of different metal crystals.

Operating conditions of container cars in railway trains of special formation

The article considers main technical characteristics, indicators of dynamic qualities and parameters of braking effciency of special railway rolling stock of container cars (container transporters) intended for the transportation of radioactive materials — spent nuclear fuel. In accordance with the current regulatory documents of JSC Russian Railways, it is currently allowed forming special trains exclusively from container transporters of any one type, which is associated with the peculiarities of the technology for handling and transporting spent nuclear fuel, which is within the competence of the state corporation Rosatom. However, this signifcantly increases the timing of the delivery of special trains due to the need to wait for the readiness of transporters, due to the non-simultaneous delivery of any one type of assembly kits with spent nuclear fuel. The practice of handling has shown that the transportation of some types of spent nuclear fuel can be carried out with a combination of the transport operation, which implies the combination of various types of container transporters in one echelon, but at the same time it is necessary to correct certain regulatory documents of Russian Railways. For this purpose, at the request of the Rosatom corporation, a necessary set of experimental works was carried out. Authors presented results of control running dynamic, stationary and running braking tests of container transporters of various types, following as part of the same echelon, on the infrastructure of the Test Loop of JSC “VNIIZHT”, including when running along the frst ring track and along various combinations of turnouts along a tangent line (main) and lateral directions. It has been experimentally proved that it is possible to operate container transporters of various types as part of the same echelon in compliance with the conditions for ensuring traffc safety in accordance with the standards of dynamic qualities and braking effciency. Based on the test results, a regulatory document of JSC Russian Railways was developed — the Regulation on the conditions for joint operation of special freight cars (transporters) as part of one echelon, approved by the order of JSC Russian Railways dated July 22, 2021 No. 1591/r. components. Interstate standard, put into effect as nat. standard of the Russian Federation by order of the Federal Agency for Technical Regulation and Metrology dated March 17, 2016 No. 162-st. Moscow, Standartinform Publ., 2016, 54 p. (in Russ.).

The Relation between Burning Time and Burning Energy of HTPB - Based Composite Propellant

This paper represented a result of several visions of chemical phenomenon and several extractions and extrapolations of experimental works which included a relationship between energy related to a chemical process and the relevant time which is required to achieve this process, but it must be taken into account that those mentioned experimental works hadn’t aimed substantially to study and state this relationship neither implicitly nor explicitly, but the results of those works have been exploited for another field after being compared with the relevant thermodynamic calculations. The selected case study for this paper was the relation between the burning time of Hydroxyl terminated poly butadiene propellant ( HTPB) and the caloric value of this material. The results reflected some relationship between the burning time and the change of the system energy during the burning process.

Cyclic Photoisomerization of Azobenzene in Atomistic Simulations: Modeling the Effect of Light on Columnar Aggregates of Azo Stars

This computational study investigates the influence of light on supramolecular aggregates of three-arm azobenzene stars. Every star contains three azobenzene (azo) moieties, each able to undergo reversible photoisomerization. In solution, the azo stars build column-shaped supramolecular aggregates. Previous experimental works report severe morphological changes of these aggregates under UV–Vis light. However, the underlying molecular mechanisms are still debated. Here we aim to elucidate how light affects the structure and stability of the columnar stacks on the molecular scale. The system is investigated using fully atomistic molecular dynamics (MD) simulations. To implement the effects of light, we first developed a stochastic model of the cyclic photoisomerization of azobenzene. This model reproduces the collective photoisomerization kinetics of the azo stars in good agreement with theory and previous experiments. We then apply light of various intensities and wavelengths on an equilibrated columnar stack of azo stars in water. The simulations indicate that the aggregate does not break into separate fragments upon light irradiation. Instead, the stack develops defects in the form of molecular shifts and reorientations and, as a result, it eventually loses its columnar shape. The mechanism and driving forces behind this order–disorder structural transition are clarified based on the simulations. In the end, we provide a new interpretation of the experimentally observed morphological changes.

Columnar Aggregates of Azobenzene Stars: Exploring Intermolecular Interactions, Structure, and Stability in Atomistic Simulations

We present a simulation study of supramolecular aggregates formed by three-arm azobenzene (Azo) stars with a benzene-1,3,5-tricarboxamide (BTA) core in water. Previous experimental works by other research groups demonstrate that such Azo stars assemble into needle-like structures with light-responsive properties. Disregarding the response to light, we intend to characterize the equilibrium state of this system on the molecular scale. In particular, we aim to develop a thorough understanding of the binding mechanism between the molecules and analyze the structural properties of columnar stacks of Azo stars. Our study employs fully atomistic molecular dynamics (MD) simulations to model pre-assembled aggregates with various sizes and arrangements in water. In our detailed approach, we decompose the binding energies of the aggregates into the contributions due to the different types of non-covalent interactions and the contributions of the functional groups in the Azo stars. Initially, we investigate the origin and strength of the non-covalent interactions within a stacked dimer. Based on these findings, three arrangements of longer columnar stacks are prepared and equilibrated. We confirm that the binding energies of the stacks are mainly composed of π–π interactions between the conjugated parts of the molecules and hydrogen bonds formed between the stacked BTA cores. Our study quantifies the strength of these interactions and shows that the π–π interactions, especially between the Azo moieties, dominate the binding energies. We clarify that hydrogen bonds, which are predominant in BTA stacks, have only secondary energetic contributions in stacks of Azo stars but remain necessary stabilizers. Both types of interactions, π–π stacking and H-bonds, are required to maintain the columnar arrangement of the aggregates.