scholarly journals Modeling the process of force load generation at the initial periodic change in pressure (a plane problem)

2021 ◽  
Vol 258 ◽  
pp. 08020
Author(s):  
Mukhiddin Khudjaev ◽  
Erkin Nematov ◽  
Anorgul Karimova ◽  
Doston Khurramov ◽  
Botir Khasanov
Keyword(s):  
Plane Problem ◽  
Operational Calculus ◽  
Periodic Change ◽  
Working Fluid ◽  
Normal Velocity ◽  
Force Load ◽  
Molecular Transfer ◽  
The Law ◽  
Analytical Expressions ◽  
Load Generation

The article deals with modeling the process of force load generation at an initial periodic change in pressure (a plane problem). The subject of research is a pulsating flow in a flat channel at an initial periodic pressure change. The determination of flow parameters with a periodic change in the inlet pressure; the changes in the structure of the working fluid associated with the release of various particles from the pipe walls, the addition of impurities to prevent leaks, and the high-speed modes, are given in the article considering the law of molecular and molar transfer between layers. Research methods are based on Newton’s rheological law, according to which molecular transfer is described by the law of proportionality of stresses to the derivative of the normal velocity; on the method of accounting for molar transfer by proportionality of stresses to the derivative of normal acceleration; on the method of mathematical modeling and the analytical method for their solutions, based on the provisions of operational calculus. An analytical solution to the problem of pulsating fluid motion in a plane-parallel channel is obtained with allowance for single and group transfer of molecules in the flow. The application of the analytical expressions obtained for the velocities is not limited to the critical Reynolds number, i.e. they are applied for any values of this number. Analytical expressions are obtained for the transverse and longitudinal components of the flow velocity. The resulting solution describes two zones of flow: in the first zone, two types of transfer occur, depending on the flow pattern, either molecular or molar transfer of fluid volumes between the layers prevails. In the second zone, only molecular transfer occurs.

scholarly journals Researches on physical geology.—Part I. The figure and primitive formation of the earth

1851 ◽  
Vol 5 ◽  
pp. 659-659
Keyword(s):  
Chemical Changes ◽  
Fluid Mass ◽  
General Properties ◽  
The Earth ◽  
Figure Of The Earth ◽  
Ellipsoid Of Revolution ◽  
The Law ◽  
Physical Geology ◽  
Analytical Expressions ◽  
Different Parts

The author’s investigations of the figure of the earth proceed on the hypothesis of its having originally been a heterogeneous fluid mass, possessing only such general properties as those which have been established for fluids; and independently of the supposition, with which the theory has generally been complicated, that the vo­lume of the entire mass, and the law of the density of the fluid, have suffered no change in consequence of the solidification of a part of that fluid. Assuming the figure of the mass to be an ellipsoid of revolution, the author obtains general analytical expressions for its ellipticity, and for the variation of gravity at its surface. He gives a general sketch of the consequences that may result from the im­proved hypothesis of the primitive figure of the earth, to physical geology, that is, to the changes occurring upon the external crust of the earth during the process of its solidification, resulting both from calorific and chemical changes taking place among its different parts, and giving rise to a process of circulation throughout the fluid por­tions of the mass. The present memoir is only the first of a series which the author announces it is his intention to communicate to the Society on the same subject.

scholarly journals Analysis of steady flow in a circular cylindrical pipe with hydraulically smooth walls

2020 ◽  
Author(s):  
В.А. Павловский
Keyword(s):  
Steady Flow ◽  
Reynolds Numbers ◽  
Explicit Representation ◽  
Turbulent Regime ◽  
Cylindrical Pipe ◽  
Pipe Axis ◽  
Law Of Similarity ◽  
The Law ◽  
The Relationship ◽  
Analytical Expressions

Анализируются формулы для скоростей и сопротивлений при установившемся течении несжимаемой вязкой жидкости в круглой цилиндрической трубе. Используется закон подобия скоростей при турбулентном режиме течения для получения представления коэффициента сопротивления в явном виде. Рассматривается связь между числами Рейнольдса, вычисляемых по средней и по динамической скоростями. Сформулирован принцип нахождении профилей скорости по закону сопротивления. Приведены аналитические выражения для всего универсального профиля скоростей. Приводится алгоритм построения кривой сопротивления по профилю скоростей в универсальных координатах. Предлагается единая формула для коэффициента сопротивления при любом режиме течения и формула для учёта отклонения от логарифмики на профиле скоростей в области вблизи оси трубы. The formulas for the velocities and resistances in the steady flow of an incompressible viscous fluid in a round cylindrical pipe are analyzed. The law of similarity of velocities in the turbulent regime is used to obtain an explicit representation of the drag coefficient. The relationship between the Reynolds numbers calculated by the average and dynamic speeds is considered. The principle of finding velocity profiles according to the law of resistance is formulated. Analytical expressions are given for the for any flow regime and a formula for taking into account deviations from the logarithm on the velocity profile in the region near the pipe axis.

Effects of Irreversibility and Economics on the Performance of a Heat Engine

1992 ◽  
Vol 114 (4) ◽  
pp. 267-271 ◽  
Author(s):  
O. M. Ibrahim ◽  
S. A. Klein ◽  
J. W. Mitchell
Keyword(s):  
Heat Engine ◽  
Maximum Power ◽  
Working Fluid ◽  
Carnot Cycle ◽  
Transfer Coefficients ◽  
Maximum Power Point ◽  
Power Point ◽  
Method Of Lagrange Multipliers ◽  
Cycle Efficiency ◽  
Analytical Expressions

Previous investigators have shown that an internally reversible Carnot cycle, operating with heat transfer limitations between the heat source and heat sink at temperatures TH and TL, achieves maximum power at an efficiency equal to 1−TL/TH independent of the heat exchanger transfer coefficients. In this paper, optimization of the power output of an internally irreversible heat engine is considered for finite capacitance rates of the external fluid streams. The method of Lagrange multipliers is used to solve for working fluid temperatures which yield maximum power. Analytical expressions for the maximum power and the cycle efficiency at maximum power are obtained. The effects of irreversibility and economics on the performance of a heat engine are investigated. A relationship between the maximum power point and economically optimum design is identified. It is demonstrated that, with certain reasonable economic assumptions, the maximum power point of a heat engine corresponds to a point of minimum life-cycle costs.

Numerical Simulation and Experimental Research of Oil-Free Scroll Air Compressor Based on CFD

2021 ◽  
Vol 14 ◽  
Author(s):  
Sun Jian ◽  
Peng Bin ◽  
Zhu Bingguo
Keyword(s):  
Numerical Simulation ◽  
Thermodynamic Model ◽  
Volume Flow ◽  
Working Fluid ◽  
Working Process ◽  
Scroll Compressor ◽  
Working Chamber ◽  
Actual Working ◽  
Discharge Temperature ◽  
The Law

Background: Compared with other types of compressors, although the scroll compressor has a simple structure and low noise, due to the limitation of the structure, it has defects such as excessively high discharge temperature, and has extremely high requirements on the machining accuracy of parts. The oil-free scroll compressor is a new type of scroll machine, which does not contain oil during the working process; it can be applied to cases with low displacement requirements and a high-pressure ratio. Objective: Taking a scroll compressor with a rated displacement of 0.6 as the research object, the analysis and research of the working performance parameters of the scroll compressor in actual work provide a certain theoretical basis for the improvement and optimization of the test prototype. Methods: The thermodynamic model of the scroll compressor in the actual working process is established by the variable-mass system thermodynamics and the control volume method. Based on the CFD method, a three-dimensional unsteady-state numerical simulation of the flow characteristics of the working fluid in the scroll compressor's working chamber is carried out in order to verify the thermodynamic model. Considering the accuracy of numerical simulation, a test platform with air as the working fluid is set up. Results: Through the thermodynamic model and numerical simulation, the changes of temperature, pressure and velocity in the working chamber of the scroll compressor with the orbiting angle of the main shaft as well as the gas force and torque acting on the orbiting scroll tooth are obtained. Through experiments, the law of volume flow and shaft power of the scroll compressor with the speed of change, and the law of the change of discharge temperature with pressure at different speeds are obtained. Conclusion: At the same time, the thermodynamic model established by considering heat transfer and leakage is more in line with the actual working process of the compressor; the mass exchange between adjacent working chambers of the scroll compressor has a greater impact on the temperature and pressure in the working chamber. Due to internal leakage and irreversible loss, such as heat transmission, there is a deviation between the theoretical volume flow and the actual volume flow.

scholarly journals Researches in physical astronomy

1837 ◽  
Vol 3 ◽  
pp. 15-16
Keyword(s):  
Angular Velocity ◽  
The Other ◽  
Similar Solution ◽  
Axis Of Rotation ◽  
Geographical Latitude ◽  
The Law ◽  
The Stability ◽  
Revolving Body ◽  
Analytical Expressions

The author has shown in a former paper, published in the last part of the Philosophical Transactions for 1830, that the stability of a system of bodies subject to the law of gravitation, is always preserved, provided they move in a space absolutely devoid of resistance. This conclusion results from the analytical expressions for the variations of the elliptic constants in the theory of the Planetary Motions. In the present paper he extends his researches to the problem of the precession of the Equinoxes, which admits of a similar solution to the former. Of the six constants which determine the position of the revolving body, and the axis of instantaneous rotation, at any instant, three have only periodic inequalities; while the other three have each a term which varies as the time; but from the manner in which these constants enter into the resulting expressions, the equilibrium of the system may be inferred to be stable, as in the former case. By the stability of the system, the author wishes to be understood to mean that the pole of the axis of rotation has always nearly the same geographical latitude, and that the angular velocity of rotation, and the obliquity of the ecliptic vary within small limits; and that its variation is periodical.

scholarly journals Religious fundamentalism in its Christian-confessional manifestations

2013 ◽  
pp. 269-280
Author(s):  
Liudmyla O. Fylypovych
Keyword(s):  
Religious Life ◽  
Religious Fundamentalism ◽  
Periodic Change ◽  
History Of Religions ◽  
History Of ◽  
The Law ◽  
Maximal Points

Historically, the development of religions occurs according to the law of cyclic wave-like, where the maximal points of the sinusoid are represented by opposite states-markers. Thus, known periods in the history of religions, when dominated by internal or external signs of their development, when victory vulgar religion, in contrast to the elevation of theological revelations, when the teachings of modernity prevail, trying to get rid of orthodoxy anyway. In place of the newest trends in the understanding of God, man, their relationship comes fundamentalism as a decisive trend in their development228. To find absolute modernist or fundamentalist epochs in religiongege, to calculate the duration of each of them, to clearly periodize them difficultly. Both the religions themselves and the society in which they existed quickly "tired" from the severity of the requirements of purity of faith, and from the unrestricted liberalization of religious life, which led to a periodic change in sentiment and orientation, either on fundamentalism, or on the modernization of religions.

Layered and ion implantation specimens as possible reference materials for the electron-probe microanalysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1652-1653
Author(s):  
G. Remond ◽  
R.H. Packwood ◽  
C. Gilles ◽  
S. Chryssoulis
Keyword(s):  
Ion Implantation ◽  
Reference Materials ◽  
Analytical Techniques ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
X Ray ◽  
Spatially Resolved ◽  
Analytical Expressions ◽  
Original Approach ◽  
Depth Concentration

Merits and limitations of layered and ion implanted specimens as possible reference materials to calibrate spatially resolved analytical techniques are discussed and illustrated for the case of gold analysis in minerals by means of x-ray spectrometry with the EPMA. To overcome the random heterogeneities of minerals, thin film deposition and ion implantation may offer an original approach to the manufacture of controlled concentration/ distribution reference materials for quantification of trace elements with the same matrix as the unknown.In order to evaluate the accuracy of data obtained by EPMA we have compared measured and calculated x-ray intensities for homogeneous and heterogeneous specimens. Au Lα and Au Mα x-ray intensities were recorded at various electron beam energies, and hence at various sampling depths, for gold coated and gold implanted specimens. X-ray intensity calculations are based on the use of analytical expressions for both the depth ionization Φ (ρz) and the depth concentration C (ρz) distributions respectively.

A Simple Real-Space Channelling Theory for Electron Diffraction and HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 64-65
Author(s):  
D. Van Dyck
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Direct Method ◽  
Real Space ◽  
Zone Axis ◽  
Phase Object ◽  
High Resolution Images ◽  
The Many ◽  
Analytical Expressions ◽  
Electron Wavefunction

The computation of the many beam dynamical electron diffraction amplitudes or high resolution images can only be done numerically by using rather sophisticated computer programs so that the physical insight in the diffraction progress is often lost. Furthermore, it is not likely that in this way the inverse problem can be solved exactly, i.e. to reconstruct the structure of the object from the knowledge of the wavefunction at its exit face, as is needed for a direct method [1]. For this purpose, analytical expressions for the electron wavefunction in real or reciprocal space are much more useful. However, the analytical expressions available at present are relatively poor approximations of the dynamical scattering which are only valid either for thin objects ((weak) phase object approximation, thick phase object approximation, kinematical theory) or when the number of beams is very limited (2 or 3). Both requirements are usually invalid for HREM of crystals. There is a need for an analytical expression of the dynamical electron wavefunction which applies for many beam diffraction in thicker crystals. It is well known that, when a crystal is viewed along a zone axis, i.e. parallel to the atom columns, the high resolution images often show a one-to-one correspondence with the configuration of columns provided the distance between the columns is large enough and the resolution of the instrument is sufficient. This is for instance the case in ordered alloys with a column structure [2,3]. From this, it can be suggested that, for a crystal viewed along a zone axis with sufficient separation between the columns, the wave function at the exit face does mainly depend on the projected structure, i.e. on the type of atom columns. Hence, the classical picture of electrons traversing the crystal as plane-like waves in the directions of the Bragg beams which historically stems from the X-ray diffraction picture, is in fact misleading.

Ethical Challenges: Less About Moral Wrongdoing and More About Communication Breakdown

2015 ◽  
Vol 20 (3) ◽  
pp. 72-84 ◽  
Author(s):  
Paula Leslie ◽  
Mary Casper
Keyword(s):  
Ethical Challenges ◽  
Speech Language Pathology ◽  
Thickened Liquids ◽  
Communication Breakdown ◽  
Professional Duty ◽  
Language Pathology ◽  
The Law ◽  
Personal Case

“My patient refuses thickened liquids, should I discharge them from my caseload?” A version of this question appears at least weekly on the American Speech-Language-Hearing Association's Community pages. People talk of respecting the patient's right to be non-compliant with speech-language pathology recommendations. We challenge use of the word “respect” and calling a patient “non-compliant” in the same sentence: does use of the latter term preclude the former? In this article we will share our reflections on why we are interested in these so called “ethical challenges” from a personal case level to what our professional duty requires of us. Our proposal is that the problems that we encounter are less to do with ethical or moral puzzles and usually due to inadequate communication. We will outline resources that clinicians may use to support their work from what seems to be a straightforward case to those that are mired in complexity. And we will tackle fears and facts regarding litigation and the law.

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