Parents’ Expectations about Educational Institutions during the Pandemic: Results of Nationwide Questionnaire Research in Poland

(1) Background: The coronavirus pandemic has highlighted the problem of combining work and private life. The pandemic conditions have turned out to be particularly difficult for parents who, due to changes in the organization of the education system, have been forced to reconcile their professional duties with the raising of childcare. Thanks to the recommendations for cooperation between schools and parents proposed in this study, it will be possible to reduce the risk and uncertainty of achieving common goals of the education system. (2) Methods: In the preparation of nationwide research, a questionnaire was provided to a sample of 10,331 respondents, including 7800 professional parents, in a trial form before a transition to the study of children. (3) Results: The analysis of the data showed that educational institutions should shape their activities based on cooperation with the family environment of children. (4) Conclusions: Educational institutions can help working parents in times of increased uncertainty. Parents reported that in caring for children, it would be helpful to operate educational institutions in stationary mode. Moreover, they expect increases in extracurricular and extra-curricular activities.

Heat Exchange of the Cylindrical Liquid Body of a Limited Height with the Environment

The experimental investigations of the intensity of the heat exchange between the internal surface of the thin-wall metal cylinder and the studied liquid medium were carried out in conditions of its cooling (heating), i.e. under nonstationary heat exchange conditions. The existence of the regular thermal mode in the liquid medium surrounded by the thin-wall metal cylinder has been established. Local in time heat loss coefficients were derived using appropriate dimensionless equations for the stationary mode conditions of heat-exchange in a large volume. Heat loss coefficients were determined using regular thermal mode methods and computational-&-experimental heat loss coefficients. The changes in the relative values of the heat loss coefficients were analyzed using the method of regular thermal mode and computational-&-experimental heat loss coefficients. The deviations in the values of given coefficients in time are mainly within ± 10 %. Relative values of the heat loss coefficients deviate within ± 40 % using appropriate dimensionless equations for the conditions of the stationary mode of heat exchange in a large volume. This conclusion is natural because the cooling (heating) process is nonstationary.

Improving the unit for melting cheese masses

This paper reports the improved model of the unit for melting cheese masses. The device differs in the technique of heat supply to working tanks through the replacement of a steam jacket with heating by a flexible film resistive electric heater of radiative type (FFREhRT). The heat exchange surface of the working container was increased through heating the mixing device by FFREhRT. In addition, the unit is distinguished by utilizing secondary thermal energy of melting cheese masses (35...95 °C) by converting it with Peltier elements into a low-voltage power supply to autonomous fans (3.5...12 W) in order to cool the control unit. Such a solution would improve the efficiency of the proposed structure, which is explained by reducing the dimensional and weight parameters of the cheese melting unit by replacing the steam heating technique with an electric one. A decrease in the time to enter a stationary mode (85 °C) when melting cheese masses was experimentally confirmed: for the bowl of the examined unit ‒ 575 s, compared to the analog ‒ 725 s. That confirms the reduction in the time to enter a stationary mode by 21 % compared to the base unit B6-OPE-400. The estimation has established a 1.2-time decrease in the main indicator of resource efficiency of the specific energy consumption for heating the volume of a unit of product in the improved plant for melting cheese masses – 3,037.2 kJ/kg, compared to the base B6-OPE-400 – 3,672.5 kJ/kg. The results confirm an increase in resource efficiency that is achieved by the elimination of steam heat networks; the increased heat exchange surface of working bowls by heating the stirrer with the help of FFREhRT. The heat transfer that employs FFREhRT simplifies the operational indicators of the temperature stabilization system in the bowl of the cheese mass melting unit. The results reported here may prove useful when designing thermal equipment with electric heating while using secondary thermal energy.

CATALYTIC PROPERTIES IN THE HETEROGENEOUS FENTON REACTION OF THE SURFACE OF NANOPOROUS IRON OBTAINED BY ELECTROCHEMICAL DEALOIYNG IN MELTED CHLORIDE MIXTURES

Исследованы образцы частично окисленного микро- и нанопористого железа, полученного методом высокотемпературного деаллоинга железо-марганцевого сплава в солевом расплаве. При помощи электронной микроскопии получены данные о морфологии образцов и составе их поверхности, установлено, что уже после отмывки при комнатной температуре на воздухе образовались оксидные фазы железа в виде вискеров толщиной порядка 10 нм. В ходе получения образцов достигалось количественное удаление марганца из исходного сплава. Оценена каталитическая активность полученных образцов в гетерогенной реакции Фентона по окислению красителя метилового оранжевого пероксидом водорода. На первом этапе протекания реакции, описываемой уравнением реакции первого порядка, ее скорость определялась наиболее активной расходуемой частью образцов, далее реакция переходила в стационарный режим. Более высокой каталитической активностью обладали нанопористые образцы. The samples of partially oxidized micro- and nanoporous iron obtained by high-temperature dealloing of an iron-manganese alloy in a molten salt were investigated. The data concerning the structure of the samples and the composition of their surface were obtained by electron microscopy; it was found that after washing at room temperature in air the oxide phases of iron were formed as whiskers with a thickness of about 10 nm. During the preparation of the samples a quantitative removal of manganese from the initial alloy was achieved. The catalytic activity of the obtained samples in the heterogeneous Fenton reaction was estimated by oxidation of methyl orange by hydrogen peroxide. The rate of the first stage of the reaction, which was described by the first-order equation, was determined by the most active spent part of the samples, and then the reaction passed into the stationary mode. The nanoporous samples possessed a higher catalytic activity.

Control of thermal regime of thermoelectric coolers in uniform temperature field

The comparative analysis of means of control of a thermal mode at minimization of a complex of the basic parameters in various combinations with indicators of reliability and dynamics of functioning of one-stage thermoelectric cooler is resulted. The study was conducted for the operating range of temperature differences, standard heat load and different geometry of the branches of thermocouples. According to the results of research to minimize the sets of basic parameters in interaction with the indicators of reliability and dynamics of work, a number of current modes of operation have been developed. The developed mathematical models for the optimal operating current from the relative temperature difference and heat transfer of the radiator for the proposed operating modes are analyzed. The results of calculations of the main parameters, reliability indicators, and time of transition to stationary mode of operation for different current modes of operation in the range of temperature differences for different geometry of branches of thermoelements are given. The extremes of dependences of the cooling coefficient, heat dissipation capacity of the radiator, the amount of energy consumed on the relative operating current are determined, which is essential for the implementation of the control function. The possibility of choosing the current mode of operation for optimal control of the thermal regime of single-stage thermoelectric devices manufactured by the same technology, taking into account mass, size, energy, reliability and dynamic characteristics. The developed method of optimal regulation of the thermal regime of a single-stage thermoelectric cooler based on minimizing the set of basic parameters allows finding and choosing compromise solutions taking into account the importance of each of the limiting factors.

Метод определения параметров утечек в трубопроводах на основе гидродинамических моделей

It is known that on the basis of the pipeline non-stationary hydrodynamic model after identification of parameters included in it, it is possible to adequately reproduce the full-scale hydraulic characteristics of transported medium flow by resolving the primal problem of hydraulics, in particular, the primal problem of identifying leakage parameters. The numerical solution of the inverse problem, in contrast to the analytical solution, is usually reduced to a multiple solution of the primal problem. In the present work, the hydrodynamic mathematical model of a pipeline with two parameters that have been identified and fluid withdrawal in the set section is confined to differential equations of evolutionary type for medium cross-section pressure and mass flow. Based on the built partial analytical solutions of these equations, dependences have been obtained for calculation of pressure values in the oil pipeline operated in stationary mode with existing liquid withdrawal (leakage). Results of application of analytical solutions to the method of sensitivity functions in the inverse problem of identifying leakage parameters have been reviewed. Exact analytical solution (in implicit form) of the inverse problem has been obtained to make it possible to relate the location of the leak to readings of pressure sensors, to the pipeline and the transported fluid parameters. Известно, что на основе нестационарной гидродинамической модели трубопровода после идентификации входящих в нее параметров можно адекватно воспроизводить натурные гидравлические характеристики потока транспортируемой среды путем решения прямой задачи гидравлики, в частности, прямой задачи об утечке, когда местоположение и расход отбора заданы. Численное решение обратной задачи, в отличие от аналитического обычно сводится к многократному решению прямой задачи. В предлагаемой работе гидродинамическая математическая модель трубопровода с двумя параметрами, прошедшими идентификацию, и отбором жидкости в заданном сечении сведена к дифференциальным уравнениям эволюционного типа для среднего по сечению давления и массового расхода. На основе частных аналитических решений данных уравнений получены зависимости для определения давления в работающем в стационарном режиме нефтепроводе при наличии отбора (утечки). Рассмотрены результаты применения аналитических решений к методу функций чувствительности в обратной задаче утечки. Получено точное аналитическое решение (в неявной форме) обратной задачи, позволяющее связать местоположение утечки с показаниями датчиков давления, характеристиками трубопровода и транспортируемой среды.

Three-dimensional periodic thermoelastichydrodynamic modeling of hydrodynamic processes of a thrust bearing

The article presents the basic principles of three-dimensional mathematical modeling of the operation of a thrust plain bearing with fixed pads of the compressor. The model is based on the periodic thermoelastichydrodynamic (PTEHD) theory which allows calculating the temperature at the inlet to the pad and considering the complete thermal pattern. A description of the main provisions of the numerical implementation is given. In the stationary mode of the bearings operation, using the Sm2Px3Tx program, numerical experiments were carried out aimed at studying different boundary conditions to the Reynolds equation, the physics of the hydrodynamic process in the lubricating and boundary films of the bearing and the heat propagation in the body of the pad and thrust collar.

Study of the dependences of coal-wood composition, identification of combustion features of the obtained composite materials

In the study of the combustion of samples, it was found that, other things being equal, under the experimental conditions and with the fixed technical characteristics of the fuel, different parameters of the flame are observed, namely, the speed of reaching a stationary mode, the completeness of fuel combustion, the size and distribution of temperature zones strongly depend on the methods used to carry out the mechanical fuel processing. Comparison of the results showed that under the same experimental conditions, the temperature distribution along the length of the experimental stand, in a stationary mode of operation, is higher for the composite fuel. In the case of composite fuel, 70 percent of the fuel burned up was observed at a 1 m section, which is indicative of these fuel consumption and kindling processes at industrial thermal power plants.

Building a mathematical model of technological processes in the acetic acid synthesis reactor

The result of the study reported in this paper is the proposed mathematical model of technological processes occurring in the reactor for acetic acid synthesis. The initial parameters of the reactor considered were the value of the concentration of acetic acid at the reactor outlet, temperature, the level of reaction mass, and pressure in the reactor. The input parameters included the amount of methanol and carbon monoxide supplied. Material and thermal balances of reactor technological processes were used to construct the mathematical model of the reactor. Fisher criterion was applied to test the mathematical model for adequacy. At the specified 5 % level of significance, the value of Fisher criterion for the concentration of acetic acid, temperature, and the level of reaction mass in the reactor does not exceed its critical value for a stationary mode. The reproducibility of the modeling results was tested using the Cochran criterion. The value of the Cochrane criterion, at the predefined 5 % level of significance, for the concentration of acetic acid, temperature, and the level of reaction mass in the reactor does not exceed its critical value for different modes. The relative error for the modeled output parameters was calculated. The relative error of the initial parameters did not exceed the level of 10 %. The model built makes it possible to calculate with satisfactory accuracy the value of the concentration of acetic acid at the reactor output, the temperature and level of the reaction mass in the reactor under a stationary mode. The resulting model could be used to automate the control of technological processes in the acetic acid synthesis reactor under a stationary mode. The study results open additional opportunities to manage the stationary mode of the reactor