Justification of coal mines conveyor line parameters

Purpose. Increasing the efficiency of the conveyor transport system of the mine due to the application of rational parameters, which are calculated objectively on the basis of the reliable output data of random freight flow in the conveyor transport line, taking into account the velocity of minerals transportation, including a perfect theoretical model application of the freight flow distribution. Methodology. Complex research: - statistical studies on the actual distribution of random freight flow in the highly productive stages of the PSU Mine “n.a Heroiv Kosmosu” PJSC “DTEK Pavlohradvuhillia”; - description of histograms of the distribution of random freight flow by various indicative algebraic functions, normal and gamma distribution of a random variable and a specially constructed function with separately defined parameters of its branches; - analysis of research results regarding the correctness of the theoretical model of the distribution of random freight flow according to various criteria of genuineness, a center of grouping, amplitude, velocity of rise and fall, and deviation. Findings. A perfect theoretical model was built in the form of an indicative algebraic function, whose branches are described by the normal distribution law of a random variable with separately determined parameters. It describes well the distribution of random freight flow in the conveyor transport line of the mine and ensures the determination of its parameters by the methods of probability theory. Originality. A theoretical model of the distribution of random freight flow in the conveyor transport line of the mine has been obtained for the first time, which describes well various cases of its distribution, including symmetric and asymmetric ones, and provides the determination of the freight flow parameters by the methods of probability theory. Practical value. The actual value of the coefficient of nonuniformity of the freight flow in the conveyor transport line of the mine, which was determined by a perfect theoretical model, exceeds, by almost a quarter, the value inherent in the model accepted in practice, the normal law of the distribution of a random variable. The coefficient of nonuniformity of the freight flow in the highly productive longwalls of only the specified mine reaches a value of 2.012, which already exceeds the normative value limit for conveyor transport lines along horizontal and inclined preparatory workings of mining areas (2.0). Reliable initial data on the variation of the random freight flow in the conveyor transport line of the mine, which is substantiated by a perfect theoretical model of its distribution, have a positive effect on the calculation of its parameters and contribute to increasing the efficiency and reliability of the functioning of the conveyor transport system.

吉林蛟河阔叶红松林物种多度分布模型研究

This study has been conducted to explore grade 10 th students\' misconceptions about conservation of mechanical energy which is a subject included in secondary school physics curriculum in Turkey. For this purpose, the conceptual test of conservation of mechanical energy was developed. This conceptual test was given to 10th graders in 6 selected high schools in the city of Ankara. The analysis of the data revealed that the students had conceptual difficulties about conservation of mechanical energy. In this paper, in one part of the study, students\' misconceptions about conservation of mechanical energy in simple pendulum system have been discussed. It is clear from study that students had delevoped misconceptions about conservation of mechanical energy and transformations of different energy forms to each other. For this reason, it is important for teachers to use new teachiMekanik enerjinin korunumu, kavram yanilgilariConservation of mechanical energy, misconceptions Tam Metin

The purpose of this study was to explore the effectiveness of the conventional high school instruction about conservation of mechanical energy in Canton Sarajevo. To that end we tested 441 high school students from six different schools in Sarajevo (Bosnia and Herzegovina) for their competence to apply the law of conservation of mechanical energy. Concretely, students were expected to solve 5 open-ended tasks that covered conceptually different situations. In each task we asked a set of sub-questions to check whether the students possess all the prerequisite sub-competencies for systematic reasoning about conservation of mechanical energy. In addition, we investigated how students’ ideas about conservation of mechanical energy were affected by the choice of the physical system, as well as by the choice of the observed time interval. Data analysis was performed on the level of individual tasks. The students’ written answers were analyzed and the frequencies of most prominent student responses were reported. Generally, it has been shown that most high school students from Sarajevo fail to identify and distinguish internal, external, conservative and non-conservative forces. Also, many students think that applicability of the conservation law does not depend on the chosen physical system and its evolution over time. We could conclude that high school students’ use of the conservation law is mostly based on remembering similar problem solving experiences, rather than on relevant strategic knowledge.

In the theory of thin fluid sheets, governing equations are derived with specific reference to an assumed simple kinematic structure of the flow. There is a separate set of governing equations associated with each degree of complexity of the kinematic structure, forming a hierarchy of models (Green and Naghdi [3] and Shields and Webster [8]). If one is interested in the velocity profile across the sheet, the kinematic structure can be used again to interpret the variables in the governing equations as an approximate flow. This paper is concerned with the properties of this approximate flow. Two important consequences of the field equations (Euler's equations) in the classical, three-dimensional theory of ideal fluids are: conservation of mechanical energy, and conservation of circulation (Kelvin's theorem). The research reported herein provides a proof that mechanical energy is exactly conserved for the approximate flow in each level in this hierarchy. Two types of circulation are considered in the approximate flow: “in-sheet” circulation which is computed about circuits lying a fixed fractional distance between the top and bottom surfaces of the sheet, and “cross-sheet” circulation which is computed about circuits lying in a vertical cylindrical surface. It was found that K moments of the in-sheet circulation and K − 1 weighted moments of the cross-sheet circulation are conserved in the Kth level approximate flow.

The random distribution model (RDM) and uniform distribution model (UDM) were used to simulate the thermal sterilization of canned fruit. The RDM was established with the radiation function, and the stability of RDM results was analyzed by simulating temperature change during thermal sterilization and determining the sterilization parameter F value of the slowest heating zone (SHZ). The performance of the distribution models in simulating thermal sterilization heating process of canned fruit with different shapes was studied using the UDM and RDM of canned yellow peach (hemispherical shell), pear (sphere), and coconut (cube). Simulation results were compared with experimental results. The flow field and temperature field distributions were used in analyzing the influence of fruits shape on the accuracy of the models. The simulation results of different RDMs were consistent with the temperature change and F value, indicating that the RDMs had stable simulation results. When the contact between two types of fruit was a point, the UDM can be used in the numerical simulation of thermal sterilization. When the contact was a non-point, the RDM was more accurate in simulating thermal sterilization. This study provides constructive suggestions for the simulation of thermal sterilization of canned fruit with different shapes.

A common method that scientists use to validate a theory is to utilize known principles and laws to produce results on specific settings, which can be assessed using the appropriate experimental methods and apparatuses. Smartphones have various sensors built-in and could be used for measuring and logging data in physics experiments. In this work, we propose the use of smartphones for students to study a simple pendulum’s conservation of mechanical energy. It is well known that common smartphones do not have a velocity sensor, which could make the verification of the conservation of mechanical energy a simpler task. To overcome this, one can use an accelerometer to measure the centripetal acceleration on the mass and from that, deduce the maximum velocity. In this study, we show that this can be achieved with reasonable uncertainty, using a mobile device. Thus, we developed an experiment which corroborates with the conservation of mechanical energy and can be performed in the classroom.

The relativistic and the hidden momentum of Minkowski and Abraham in relativistic energy wave

In this study, our aim was to identify high school and university students’ postinstruction conceptions about the law of conservation of mechanical energy (LCME). A cross-sectional survey design was used. Firstly, a test consisting of 14 multiple-choice questions was developed. 23 physics teachers analysed the test and concluded that our questions are useful for measuring understanding about the LCME. Next, the test was administered to a convenient sample of high school and university students who had already received conventional instruction about the energy concept. The sample consisted of 138 students from the University of Zagreb (Croatia), and 115 high school students from two different schools in Sarajevo (Bosnia and Herzegovina). While the distribution of item difficulties was good, the reliability of test scores proved to be barely acceptable. Therefore, we primarily focused on analysing how frequently the students chose the individual distractors and drew corresponding conclusions about students’ conceptions. It has been shown that many students associate conservation of mechanical energy with certain surface features of physical problems (e.g., “pulley problems”), instead of reasoning about the processes a chosen system undergoes over time. Students often believe that mechanical energy is conserved even for phenomena in which air resistance cannot be neglected. Similarly, they sometimes do not recognize that most collisions of everyday objects necessarily include the conversion of mechanical energy into thermal energy. We could conclude that many students from all educational levels in Bosnia and Herzegovina and Croatia still fail to apply a system-based approach to energy analysis.

Presentamos un análisis crítico de los enfoques clásicos de los contenidos de energía, basado en elteorema trabajo-energía y la conservación de la energía mecánica que se proponen en los cursosde los primeros años de educación terciaria. Mostramos cómo estos enfoques presentan una seriede inconsistencias y errores que son fuente de dificultades conceptuales en los estudiantes. Analizamosluego un tratamiento moderno dirigido a cursos de mecánica basado en los resultados delas investigaciones en educación de la Física de los últimos 40 años. Hacemos especial énfasis en elprincipio de conservación de la energía como uno de los principios fundamentales de la naturaleza,jerarquizando los conceptos de sistema, ambiente, transferencia y transformación de energía.

Purpose of study: This research aims to analyze students' answers about the conservation of mechanical energy assessment in the form of essay tests.
 Methodology: Descriptive quantitative methods chosen by the researchers involving 46 students of physics education in physics education at Bengkulu University. Students are asked to answer tests on the conservation of mechanical energy consisting of 5 essay questions, which involve verbal, mathematical, and picture representations. Interviews will also be conducted to ascertain student answers.
 Main findings: This research found that 38% of students answered correctly and others still answered incorrectly because they asked for difficulties in mastering the concepts of physics.
 Applications of this study: The implication of this research is to help students improve their conceptual understanding, so students can solve problems about physics correctly.
 The novelty of this study: The researcher explains about what is important in building students' conceptions in-depth and directing students to solve problems about physics, especially about the conservation of mechanical energy.

Energy concepts are fundamentally important for describing and analyzing systems ranging from subatomic particles to spiral galaxies. In general, students first encounter such concepts in introductory courses that typically focus on forms of energy, energy transfer, and conservation laws. Within these courses, conservation of mechanical energy is particularly useful for solving problems (since the physical quantities being analyzed do not require vector analysis). However, strictly speaking, conservation of mechanical energy is valid only when no energy is transferred across the boundary of the system being considered.

Measurements of gravitational acceleration in this study use the concepts of free-fall motion and mechanical energy conservation. The purpose of this study is to compare the values of gravitational acceleration obtained from the two experiments and to determine the factors that cause deviations from the measurements of the gravitational acceleration value from free-fall motion experiments and the law of mechanical energy conservation. The research method used was a descriptive analysis of primary data in the Applied Physics Laboratory of Politeknik Negeri Bandung. The data was collected using free-fall motion equipment and the law of mechanical energy conservation. Height is the independent variable, and time is the dependent variable. The data were processed using a computer-aided device, and it is obtained the g value with the concept of free-fall and mechanical energy conservation by 9.54 m/s2 and 10.1 m/s2. The deviation of g value in the free-fall motion is caused by the presence of magnetic remanence that holds the ball from falling immediately when the time calculator was operated. The t result, which is too large, causes the value of g becomes too small. The result of g deviation in mechanical energy conservation is obtained by determining the location of the light source when the ball is in a stable condition. Meanwhile, in the real measurement, the ball moves as it passes through the light sensor, which results in a large tension force so that the sensor position moves in a higher state. The result is Δt becomes smaller than the real one so that v becomes too large. As a consequence, the value of g becomes too large.

To analyze the deflector-jet servo valve’s internal flow characteristics, a theoretical model of the complicated flow distribution in the deflector plate is established based on the offset jet attachment theory. When the deflector plate offsets, jet attachment parameters are attained to figure out the jet’s bending and colliding process. On this basis, an analytical method of acquiring the pilot valve’s pressure gain is derived. According to an actual pilot stage’s structure, pressure gain calculations are carried out. Meanwhile, the pilot valve’s mesh model is established for numerical simulation in order to examine the accuracy of the theoretical model. Calculation and numerical simulation show that the final oil jet is not sensitive to the deflector plate’s movement, which directly reveals the pressure stabilizing effect of the V-shaped structure on the deflector plate. Moreover, the experiment on the pressure gain is accomplished and experiment results verify the accuracy of the analytical calculation.

An analytical study is made of the perforated pipe distributor for the admission of high-energy fluids to a surface steam condenser. The results show that for all perforated pipes there is a general characteristic parameter MkD/Lf, which depends on the pipe geometry and flow properties. Four cases are considered based on the value of the characteristic parameter M. (1) When M⩾1/4, momentum controls and the main channel static pressure will increase in the direction of the streamline. (2) When 1/6⩽M<1/4, the momentum effect balances friction losses and the pressure will decrease to a minimum, and then increase in the direction of flow to a positive value. (3) When 0<M<1/6, friction controls and the pressure will decrease to a minimum, then increase slowly, but the total pipe static pressure difference will always be negative. (4) When M=0, a limiting case when the ratio of the length to the diameter is infinite. This analysis is useful not only for the design of perforated pipe distributors for turbine condensers over a wide range of dimensions, fluid properties, and side hole pressure but also for many other technical systems requiring branching flow distribution.