FLOW OF WORKING MEDIA THROUGH THE CHANNELS IN THE BODY OF THE ELECTRODE-TOOL

Рассмотрен механизм течения жидких и газожидкостных рабочих сред через профильный инструмент для комбинированных методов обработки. Приведены типовые детали, для которых применимы электроды-инструменты с регулируемой подачей рабочей среды в зону обработки, обеспечивающей массовынос продуктов обработки из межэлектродного зазора. За счет применения аддитивных технологий решена проблема изготовления инструмента с внутренними каналами расчетного переменного сечения, обеспечивающими стабильную подачу жидкой (газожидкостной) среды и массовынос продуктов обработки. Предложены новые (на уровне изобретений) способ и электрод-инструмент с управляемой подачей по внутренним каналам рабочей среды, параметры которой рассчитаны с учетом специфики чистовой электроабразивной обработки по схеме копирования профиля детали. Расчетные зависимости для описания механизма течения рабочих сред и методы их использования позволили проектировать электроды-инструменты с профильными каналами, обеспечивающими применение технологических режимов для чистовой обработки инструментом с регулируемой подачей сред и выполнением критерия массовыноса продуктов обработки. Приведенные результаты расчета параметров течения рабочих сред через каналы в инструменте позволили расширить область эффективного использования аддитивных технологий и создать новые (на уровне изобретений) инструменты для электроабразивной обработки по методу копирования и высокопроизводительного одновременного профилирования нескольких поверхностей. Доказана возможность использования энергетической модели для расчета потенциальной составляющей энергии от реализации мощности, затрачиваемой на подкачку рабочей среды, и кинетической энергии от вращения инструмента для получения в зоне обработки требуемой скорости течения жидких (газожидкостных) сред We considered the mechanism of flow of liquid and gas-liquid working media through a profile tool for combined processing methods. We present typical parts for which electrodes-tools are applicable with an adjustable supply of the working medium to the processing zone, which ensures the mass removal of processing products from the interelectrode gap. Through the use of additive technologies, we solved the problem of making a tool with internal channels of a calculated variable cross-section, providing a stable supply of a liquid (gas-liquid) medium and mass removal of processing products. We propose a new (at the level of inventions) method and electrode-tool with a controlled feed through the internal channels of the working medium, the parameters of which are calculated taking into account the specifics of finishing electro-abrasive machining according to the pattern of copying the profile of the part. Calculated dependencies for describing the mechanism of flow of working media and methods of their use made it possible to design electrodes-tools with profile channels that ensure the use of technological modes for finishing with a tool with controlled supply of media and fulfillment of the criterion of mass removal of processing products. The presented results of calculating the parameters of the flow of working media through channels in the tool made it possible to expand the area of effective use of additive technologies and create new (at the level of inventions) tools for electro-abrasive processing using the copying method and high-performance simultaneous profiling of several surfaces. The possibility of using the energy model for calculating the potential component of energy from the implementation of the power spent on pumping the working medium and the kinetic energy from the rotation of the tool has been proved to obtain the required flow rate of liquid (gas-liquid) media in the processing zone

THE METHOD OF PROCESSING EXPERIMENTAL DATA AND THE ALGORITHM FOR ITS IMPLEMENTATION TO DETERMINE THE PARAMETERS OF THE RHEOLOGICAL MODEL OF A DILATANT LIQUID WITH THE EFFECT OF «SOLIDIFICATION»

В различных технических приложениях применяются рабочие среды типа суспензий, которые при достаточно высокой концентрации частиц твердой фазы демонстрируют аномалии вязкости. Существо этих аномалий заключается в том, что при приближении скорости сдвига к некоторому пороговому значению наблюдается явление резкого возрастания вязкости жидкости. При этом в соответствующих зонах течения рабочая среда начинает вести себя подобно твердому телу. Механическое поведение такой рабочей среды может быть описано в рамках реологической модели вязкопластической жидкости, которая позволяет учитывать проявление эффекта“упрочнения” или “отвердевания”. Рассмотрена методика определения параметров такой реологической модели на основе обработки экспериментальных данных зависимости касательного напряжения от скорости сдвига. Предложен алгоритм для реализации этой методики. In various technical applications, working media such as suspensions are used, which, at a sufficiently high concentration of solid phase particles, demonstrate viscosity anomalies. The essence of these anomalies lies in the fact that when the shear rate approaches a certain threshold value, the phenomenon of a sharp increase in the viscosity of the liquid is observed. At the same time, in the corresponding flow zones, the working medium begins to behave like a solid. The mechanical behavior of such a working medium can be described within the framework of a rheological model of a viscoplastic fluid, which allows for the manifestation of the effect of “hardening” or “solidification”. The method of determining the parameters of such a rheological model based on the processing of experimental data on the dependence of the shear stress on the shear rate is considered. An algorithm for the implementation of this technique is proposed

Modeling the working media flow in shut-off valves with displacement of the regulating body perpendicular to the flow axis

The mathematical model of the working fluid movement in the flow section of the wedge type two-disc parallel gate valve is developed. The simulation of the fluid flow through the valve cavity is carried out, as a result the flow parameters are obtained in a wide range of Reynolds numbers at the entrance to the calculated area. The dependence of the hydraulic resistance as a function of the Reynolds number for liquid and gas flow is calculated. The various positions of the shut-off body in the flow part of the valve are considered and the area of reduced pressures in which the effect of cavitation may occur during fluid flow is estimated.

Quantum Heat Engines with Complex Working Media, Complete Otto Cycles and Heuristics

Quantum thermal machines make use of non-classical thermodynamic resources, one of which include interactions between elements of the quantum working medium. In this paper, we examine the performance of a quasi-static quantum Otto engine based on two spins of arbitrary magnitudes subject to an external magnetic field and coupled via an isotropic Heisenberg exchange interaction. It has been shown earlier that the said interaction provides an enhancement of cycle efficiency, with an upper bound that is tighter than the Carnot efficiency. However, the necessary conditions governing engine performance and the relevant upper bound for efficiency are unknown for the general case of arbitrary spin magnitudes. By analyzing extreme case scenarios, we formulate heuristics to infer the necessary conditions for an engine with uncoupled as well as coupled spin model. These conditions lead us to a connection between performance of quantum heat engines and the notion of majorization. Furthermore, the study of complete Otto cycles inherent in the average cycle also yields interesting insights into the average performance.

“Going Virtual Helped Me Learn That I Can Handle Everything”: Campus Magazine Production as a High Impact Practice During the COVID-19 Pandemic

This case study documents a large, 4-year university magazine’s transition to virtual instruction during the initial months of the COVID-19 pandemic. Using theoretical frameworks from Kuh’s work on high impact practices (HIPs), this analysis offers empirical evidence that virtual student newsrooms may provide impactful learning experiences during crisis situations. Based on interviews, surveys, and newsroom observation, 23 magazine staff members reported improvements in their professional self-efficacy as they overcame logistics challenges and interpersonal hurdles similar to working media professionals. The case study also identifies strengths and weaknesses of crisis pedagogy. Implications for post-pandemic pedagogy and course planning are discussed.

High-Speed Joining of Tubes To Panel Sheets Using Electro-Hydraulic Forming

This study presents a new method for high-speed joining of the sheet to the end of a tube without the need for any additional processes. Joining of the AA3105 sheets to the AA1170 tube is carried out with a thickness of 0.5 mm. The process is performed using electro-hydraulic forming which is a local deformation of the tube and sheet. In this method, the mechanical force is transmitted by working media in a very short time. The shock wave accelerates the panel sheet towards the die and tube to create a form-fit joint. To avoid friction between the mandrel and the flat sheet, the panel sheet is pre-drilled. The experimental tests were performed to show the effect of process parameters including; washer housing angle, sheet hole diameter, and the gap between the mandrel and top of the sheet. In addition, pull-out test is utilized to determine the strength of the joints in different conditions. Accordingly, the usage of electro-hydraulic forming on joining thin tubular parts to flat sheets was successful and the feasibility of this technique as an advanced joining approach was verified.

Investigation and analysis of kinetic regularities of wear of internal surfaces of equipment under conditions of intense corrosion using different working media

The reasons for failures of technological equipment made of structural steels during long-term operation in various environments and fields of application are considered. Investigations of the intensity of wear of equipment failures through the rate of damaging processes are presented. Modeling the processes of wear and tear of steel equipment, its failures was carried out using regression and correlation analyzes. The results of diagnostics are presented in accordance with the theoretical principles of statistical analysis, experiment in the form of polynomial kinetic wear models. The results of comparison of experimental and theoretical data on the wear rate for various types of equipment are also presented. The results of the normal distribution of the experimental values of the degree of wear for various types of equipment are shown, which is confirmed by the general uniform corrosion.

Combined Paper-Based Substrates for Electrochemical Detection of Copper Ions in Serum

<p>The electroanalytical field has exploited great advantages in using paper-based substrates, even if the word “paper” might be general. In fact, the mainly adopted paper-based substrates are often chromatographic and office ones. They are characterized by main features (and drawbacks): chromatographic paper is well-established for storing reagents/treating samples but the sensitivity compared to traditional screen-printed is lower (due to porosity), while office paper represents a sustainable alternative to plastic (with similar sensitivity) but its porosity is not enough to load reagents. To overcome the limitations that might arise due to the adoption of a type of individual paper-based substrate, herein we describe for the first time, the development of a 2D merged paper-based devices for electrochemical copper ions detection in serum. In this work we report a novel configuration to produce an integrated all-in-one electrochemical device, in which no additional working media has to be added by the end user and the sensitivity can be tuned by rapid pre-concentration on porous paper, with the advantage of making the platform adaptable to real matrix scenario. The novel architecture has been obtained by combining office paper to screen-print a sustainable and robust electrochemical strip, the printed electrochemical strips and chromatographic one to 1) store the reagents, 2) collect real sample and 3) pre-concentrate the analyte of interest. The novel sensing platform has allowed to obtain a detection limit for copper ions down to 5 ppb in all the solutions that have been interrogated, namely standard solution and serum, and a repeatability of ca. 10% has been obtained.</p>

Combined Paper-Based Substrates for Electrochemical Detection of Copper Ions in Serum

<p>The electroanalytical field has exploited great advantages in using paper-based substrates, even if the word “paper” might be general. In fact, the mainly adopted paper-based substrates are often chromatographic and office ones. They are characterized by main features (and drawbacks): chromatographic paper is well-established for storing reagents/treating samples but the sensitivity compared to traditional screen-printed is lower (due to porosity), while office paper represents a sustainable alternative to plastic (with similar sensitivity) but its porosity is not enough to load reagents. To overcome the limitations that might arise due to the adoption of a type of individual paper-based substrate, herein we describe for the first time, the development of a 2D merged paper-based devices for electrochemical copper ions detection in serum. In this work we report a novel configuration to produce an integrated all-in-one electrochemical device, in which no additional working media has to be added by the end user and the sensitivity can be tuned by rapid pre-concentration on porous paper, with the advantage of making the platform adaptable to real matrix scenario. The novel architecture has been obtained by combining office paper to screen-print a sustainable and robust electrochemical strip, the printed electrochemical strips and chromatographic one to 1) store the reagents, 2) collect real sample and 3) pre-concentrate the analyte of interest. The novel sensing platform has allowed to obtain a detection limit for copper ions down to 5 ppb in all the solutions that have been interrogated, namely standard solution and serum, and a repeatability of ca. 10% has been obtained.</p>