Characterizing the Effect of Processing Parameters on Temperature Distribution of 7075 Aluminum Alloy Slurry Prepared by Enthalpy Control Process

There is a strong demand for high-strength aluminum alloys such as 7075 aluminum alloy to be applied for rheocasting industry. The overriding challenge for the application of 7075 alloy is that its solid fraction is very sensitive to the variation of temperature in the range of 40% ~ 50% solid fraction, which inevitably narrows down the processing window of slurry preparation for rheocasting process. Therefore, in this work, a novel method to prepare semi-solid slurry of the 7075 alloy, so called Enthalpy Control Process (ECP), has been developed to grapple with this issue. In the method, a medium-frequency electromagnetic field was applied on the outside of slurry preparation crucible to reduce the temperature difference throughout the slurry. The effect of processing parameters, including heating power, heating time, the initial temperature of crucible and melt weight, on the temperature field of the semi-solid slurry was investigated. The results exhibited that although the all the processing parameters had a great influence on the average temperature of the slurry, heating time was the main factor affecting the maximum temperature difference of the slurry. The optimum processing parameters during ECP were found to be heating power of 7.5 KW, the initial temperature of crucible of 30 °C ~ 200 °C and melt weight of 2 kg.

Influence of the initial parameters on the thermodynamic efficiency of carbon dioxide power cycles

This paper considers the main CO2 power cycle configurations based on the Allam and JIHT cycles. In particular, the authors of the article have proposed new configurations of the power cycle. The efficiency of these cycles is studied as a function of the initial temperature and pressure of the working fluid. The thermodynamic efficiency can reach 65–66%. It is shown that the presence of regenerative heat transfer and the properties of supercritical carbon dioxide have a great influence on the thermal efficiency.

Influence of Initial Temperature and Convective Heat Loss on the Self-Propagating Reaction in Al/Ni Multilayer Foils

A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed that all reactants reacted and formed a B2 NiAl phase. Finally, it is predicted that (1) increasing thermal conductivity of the final product increases the reaction front velocity; (2) effect of heat convection losses on reaction characteristics is insignificant, e.g., the foils can maintain their characteristics in water; and (3) with increasing initial temperature of the foils, the reaction front velocity and the reaction temperature increased.

A Modelling Study by Response Surface Methodology (RSM) on Turbidity Removal Optimization using Nanocellulose Filter Paper (Neolamarckia Cadamba)

This study observed the influence of initial turbidity, pH and initial temperature on the turbidity removal from the textile wastewater using nanocellulose filter paper from Neolamarckia Cadamba. Response Surface Methodology (RSM) model was employed to optimize and create a predictive model to evaluate the turbidity removal performance on the nanocellulose filter paper. The performance of the RSM model was statistically evaluated in terms of coefficient of determination, R2. The optimum value of turbidity removal of 99.39% were found at 66 NTU, pH 6.4 and 35.9°C. The value of prediction that obtained from modelling (RSM) was in agreement with the experimental values with R2 = 88.23%, AAD = 6.87% and RMSE = 0.18 towards the efficiency of turbidity removal.

Sudden increase in the degrees of freedom in dense QCD matter

In this paper, we analyzed charged particle transverse momentum spectra in high multiplicity events in proton–proton and nucleus–nucleus collisions at LHC energies from the ALICE experiment using the color string percolation model (CSPM). The color reduction factor and associated string density parameters are extracted for various multiplicity classes in [Formula: see text] collisions and centrality classes for heavy-ion collisions at various LHC energies to study the effect of collision geometry and collision energy. These parameters are used to extract the thermodynamical quantities temperature and the energy density of the hot nuclear matter. A universal scaling is observed in initial temperature when studied as a function of charged particle multiplicity scaled by transverse overlap area. From the measured initial energy density [Formula: see text] and the initial temperature T, a dimensionless quantity [Formula: see text] is constructed which is used to obtain the degrees of freedom (DOF) of the deconfined phase. A two-step behavior and a sudden increase in DOF of [Formula: see text]47 for the ideal gas, above the hadronization temperature (T [Formula: see text] 210[Formula: see text]MeV), are observed in case of heavy-ion collisions at LHC energies.

A change in the air temperature inside a 20-liter chamber when air is added from the receiver

Introduction. One of the reasons for the overestimation of the explosion hazard of dust inside a (20 ± 2)-liter chamber is the elevated initial temperature of the air suspension. The initial temperature is also raised by the process of filling the pre-emptied chamber with air from the receiver, used to distribute dust over the chamber. In this work, an increase in the air temperature inside an 18.7-liter chamber was identified in an experiment for the case of addition of air from the receiver.The methodology of an experiment. The air temperature in the chamber was measured at the time when the air from the receiver was added using a WR 5/20 thermoelectric converter (a thermocouple). The thermocouple junction was located at the distance of 70 mm from the inner wall of the chamber. The thermocouple signal was processed by an MCLab PRO programmable logic controller (the time resolution is 1 ms).Research results. The measuring instruments recorded an increase in the temperature of the thermocouple junction by +14 degrees. Due to the comparability of the inertia of the thermocouple (3 s) and the characteristic time of air cooling by the chamber walls (5 s), the measurement results underestimated the real value of a jump in the air temperature inside the chamber. Measurement results were refined using a simple model of heat transfer between the objects involved in the process (thermocouple junction – air – chamber wall) that entailed the exponential relaxation of the temperature difference over time. As a result, an estimated increase in the initial temperature inside the chamber of +30 degrees was identified.Results and discussion. The temperature jump by +30 degrees makes a noticeable contribution to the total jump in the initial temperature, which was previously tied solely to the burnout of the ignition source (+80 degrees).Conclusions. Given the known increase in the temperature inside the chamber caused by the burnout ofa standard ignition source (2 kJ), the real value of the initial temperature of the environment can reach 135 °C in the course of studying dust in a (20 ± 2)-liter chamber.

Selection of the optimal flow path and control program for the turbo drive of remotely operated underwater vehicle

Обеспечение высокой экономичности не только на режимах номинальной мощности, но и на частичных режимах при изменении внешних параметров приводит к необходимости оптимизации проточной части турбины с объективным учетом ее характеристик на переменных режимах. Приводятся результаты многорежимной оптимизации МРТ в составе ЭУ АНПА на базе подхода разработанного авторами. Представлены основные результаты сравнительного анализа многорежимной оптимизации МРТ с оптимизацией на i-тый режим и работающей на остальных режимах как переменных для различных программ регулирования мощности. Выявлено сильное влияние на результаты многорежимной оптимизации основного ограничения в виде равенства мощности турбины мощности задаваемой графиком нагрузки, а также программ регулирования. Возможность применения соплового регулирования приводит к ослаблению степени воздействия основного ограничения. Установлено, что оптимальные геометрические характеристики стремятся к режиму с большей работой. Представлены результаты многорежимной оптимизации МРТ для различных программ регулирования и графиков нагрузок по отношению к результатам многорежимной оптимизации с программой реализующей сопловое регулирование в сочетании с изменением начальных параметров перед турбиной. Многорежимная оптимизация для программы, реализующей сопловое регулирование в сочетании с изменением только начальной температуры перед турбиной, выявила узкую регулировочную способность начальной температуры, и невозможность в некоторых случаях удовлетворения основным ограничениям по равенству мощностей для всех исследуемых графиков нагрузки в пределах заданных ограничений на режимные параметры. Результаты численного эксперимента свидетельствуют, что разработанный автором подход к многорежимной оптимизации МРТ позволяет снизить расход топлива при условии обеспечения заданного графика нагрузок по сравнению с традиционными методами проектирования на номинальный режим. Ensuring high efficiency not only at nominal power modes, but also at partial modes when changing external parameters leads to the need to optimize the flow path of the turbine with objective consideration of its characteristics at variable modes. The results of multi-mode optimization of a low-consumption turbine as part of a power unit of remotely operated underwater vehicle based on the approach developed by the authors are presented. The main results of a comparative analysis of multi-mode optimization of a low-consumption turbine with optimization for the i-mode and operating in other modes as variables for various power control programs are presented. A strong influence on the results of multi-mode optimization of the main limitation in the form of equality of the turbine power to the power set by the load schedule, as well as control programs is revealed. The possibility of using nozzle regulation leads to a weakening of the degree of influence of the main restriction. It was found that the optimal geometric characteristics tend to the regime with more work. The results of multi-mode optimization of a low-consumption turbine for various control programs and load schedules are presented in relation to the results of multi-mode optimization with a program that implements nozzle control in combination with a change in the initial parameters in front of the turbine. Multimode optimization for a program that implements nozzle regulation in combination with changing only the initial temperature in front of the turbine revealed a narrow adjusting ability of the initial temperature and the impossibility, in some cases, of satisfying the basic constraints on the equality of powers for all the studied load curves within the specified constraints on operating parameters. The results of the numerical experiment indicate that the approach developed by the author to the multi-mode optimization of a low-consumption turbine makes it possible to reduce fuel consumption, provided that a given load schedule is provided in comparison with traditional design methods for the nominal mode.

Dark QCD matters

We investigate the nightmare scenario of dark sectors that are made of non-abelian gauge theories with fermions, gravitationally coupled to the Standard Model (SM). While testing these scenarios is experimentally challenging, they are strongly motivated by the accidental stability of dark baryons and pions, that explain the cosmological stability of dark matter (DM). We study the production of these sectors which are minimally populated through gravitational freeze-in, leading to a dark sector temperature much lower than the SM, or through inflaton decay, or renormalizable interactions producing warmer DM. Despite having only gravitational couplings with the SM these scenarios turn out to be rather predictive depending roughly on three parameters: the dark sector temperature, the confinement scale and the dark pion mass. In particular, when the initial temperature is comparable to the SM one these scenarios are very constrained by structure formation, ∆Neff and limits on DM self-interactions. Dark sectors with same temperature or warmer than SM are typically excluded.

Low-waste innovative production technology for canned quince compote, enriched with natural nutrients

The enterprises processing plant raw materials generate a fairly large amount of waste (secondary products), which can play an important role in solving food, environmental, and energy problems. This work improves the technology for the production of canned quince compote using a two-stage microwave heating of fruits and fruits filled with syrup prepared from infusion obtained from secondary products of cutting and peeling. It has been established that two-stage heating of fruits and microwave treatment of fruits filled with syrup in a glass jar promote an increase in the initial temperature of the product in the jars before sealing and thereby reduces the heat treatment modes. The infusion obtained from the secondary products of the heat-treated fruits provides a significant increase of biologically active components in the finished product. The experimental studies were used to construct a mathematical model for calculating the initial temperature of the product before sterilization, which makes it possible to establish intensive pasteurization modes. New modes of pasteurization of quince compote in various containers have been established. Physicochemical studies confirm the high quality of the finished product in terms of the content of biologically active components.