Turbulent Lubrication—Its Genesis and Role in Modern Design

1974 ◽  
Vol 96 (1) ◽  
pp. 2-6 ◽  
Author(s):  
D. F. Wilcock
Keyword(s):  
Reynolds Number ◽  
Point Of View ◽  
Thrust Bearings ◽  
Viscous Forces ◽  
Taylor Vortices ◽  
Low Viscosity ◽  
Starting Point ◽  
Process Fluid ◽  
Inertia Forces ◽  
Lubricant Viscosity

Turbulence, a phenomenon well known in fluid flow, was first reported in journal bearings and thrust bearings in 1949. The observations were of higher torques and greater temperature rises than were expected from lower speed data. The transition from laminar behavior occurred at a Reynolds’ number corresponding to the predicted occurrence of Taylor vortices. This was the starting point for efforts to understand the phenomenon and to establish rules of behavior useful for predicting turbulent bearing performance. From an engineering point-of-view, good results in design have been achieved by treating turbulence as an increase in lubricant viscosity, the percent of increase being a function of the ratio of inertia forces to viscous forces, the Reynolds’ number. The effective result is greater film thickness and larger power losses in turbulent lubrication than would be anticipated from laminar theory. Where will the designer of the future encounter turbulence, and how will he treat its effects? Large turbogenerators have already reached a size where turbulent operation is experienced. The gradually increasing use of process-fluid-lubricated machinery, often involving low viscosity fluids such as water, liquid metal, and liquified gases, offers the designer fresh opportunities to understand and take advantage of turbulence in both hydrodynamic and hydrostatic designs.

Performance of Plain Journal Bearings Operating Under Vortex Flow Conditions

1974 ◽  
Vol 96 (1) ◽  
pp. 145-149 ◽  
Author(s):  
J. Freˆne ◽  
M. Godet
Keyword(s):  
Reynolds Number ◽  
Friction Torque ◽  
Point Of View ◽  
Taylor Vortex ◽  
Experimental Program ◽  
Frictional Torque ◽  
Taylor Vortices ◽  
Attitude Angle ◽  
Relative Eccentricity ◽  
High Reynolds

An experimental program conducted on an original device was undertaken to study the performance of plain bearings operating at sufficiently high Reynolds number to introduce Taylor vortices. Curves of relative eccentricity, attitude angle, and friction torque were obtained versus speed and load. Experimental results conducted for Reynolds number smaller than 1100 indicate that both laminar and Taylor vortex regimes are encountered. The occurrence of the vortices is identified by a break in the slope of the friction torque versus speed curves. The position of the break is in good agreement with the theoretical predictions of Di Prima and Ritchie. From the practical point of view, the data show that for constant viscosity the occurence of Taylor vortices does not alter the curves of eccentricity versus either speed or load but modifies the attitude angle and frictional torque. In turn, the increase in frictional torque, and subsequently of temperature may cause a decrease in viscosity and thus a drop in load carrying capacity for fluids such as oils whose variations of viscosity with temperature is large.

Inertia Forces in Lubricating Films

1955 ◽  
Vol 22 (3) ◽  
pp. 363-364
Author(s):  
R. S. Brand
Keyword(s):  
Reynolds Number ◽  
Hydrodynamic Lubrication ◽  
Equations Of Motion ◽  
Viscous Forces ◽  
Usual Theory ◽  
Inertia Forces

Abstract The usual theory of hydrodynamic lubrication is based on the assumption that the inertia forces in the equations of motion are negligible compared to the viscous forces. This paper shows that if the Reynolds number ρRω/μ is of the same order as R/h, then the inertia forces will be of the same order as the viscous forces.

LES AXES DE LA CRÉATION ET LA NAISSANCE DE LʹIMAGINAIRE COMME LANGAGE MYTHIQUE

Trictrac ◽  
2016 ◽  
Vol 9 ◽  
Author(s):  
Liliana Danciu ◽  
Petru Adrian Danciu
Keyword(s):  
Sacred Space ◽  
Physical World ◽  
Spoken Word ◽  
Point Of View ◽  
Philosophical Approach ◽  
Starting Point ◽  
Written Form ◽  
The Creation ◽  
Religious Systems ◽  
Rich Spectrum

The axes of the creation and birth of the imaginary as a mythical language. Our research follows the relationships of the concepts that are taking into account creation on the double axis of verticality and horizontality. We highlight those symbolic elements which would later constitute the mythical language about the sacred space-temporality. Inside this space-temporality a rich spectrum of mythical images develops; images capable of explaining the relationships of the creation plans. Without a religious perception of the temporality, the conceptualization of the axis would remain a philosophical approach. Through our point of view, the two are born simultaneously. Thanks to them, creation can be imagined. The first “frozen” formula of the mystical human spirit can be thought, brought to a palpable reality, expressed in an oral and then a written form. Studied together, temporality (sacred or not) and space are permanently imagined together. For example, a loss of mundane temporality in the secret ecstasy that offers to the soul an ascending direction does not mean getting out of universal temporality, but of its mundane section. In the sacred space the soul relates to time. Even the gods are submitted by the sacred, Aeon sometimes being synonymous to destiny. The universal creator seems to evade every touch, but not consistently, only when he avoids the descent into its created worlds. In sacredness, time and space seem or become confused, both expressing the same reality, by the immediate swing from thinking to deed. The mythical imagery conceives the displacement in the primary space-temporality by the spoken word. So, for something to appear and live, the spoken word is required. Even the divine dream appears as a pre-word of a creator’s thought. The thought follows the spoken word, the spoken word follows the gestures which finally indicate the meanings of the creative act, controlling the rhythm of the creation days. These three will later be adapted through imitation in rite. We are now situated at the limit of the physical world, a real challenge for the mythical imagery. The general feature of the mythical expression on the creation of the material world is the state of the divinity’s exhaustion, most often conceptualized by sacrifice or divine fatigue. The world geography identifies with the anatomy of a self-gutted god. Practically, material creation is most likely the complete revelation of God’s body autopsy. As each body decomposes, everything in it is an illusion. An axial approach of the phenomenon exists in all religious systems. The created element’s origin is exterior, with or without a pre-existing matter, by a god’s sacrifice or only because it has to be that way. This is the starting point of the discussion on the symbolism of axiality as a reason for the constitution of the language of creation, capable of retelling the imaginary construction of myth in an oral and then written form.

L’absence chez Michel Butor. L’Emploi du temps et Degrés

2012 ◽  
pp. 66-80
Author(s):  
Michał Mrozowicki
Keyword(s):  
Human Memory ◽  
Point Of View ◽  
Narrative Discourse ◽  
The Novel ◽  
Michel Butor ◽  
Starting Point ◽  
One Year ◽  
The Moment ◽  
Narrative Mode ◽  
The City

Michel Butor, born in 1926, one of the leaders of the French New Novel movement, has written only four novels between 1954 and 1960. The most famous of them is La Modification (Second thoughts), published in 1957. The author of the paper analyzes two other Butor’s novels: L’Emploi du temps (Passing time) – 1956, and Degrés (Degrees) – 1960. The theme of absence is crucial in both of them. In the former, the novel, presented as the diary of Jacques Revel, a young Frenchman spending a year in Bleston (a fictitious English city vaguely similar to Manchester), describes the narrator’s struggle to survive in a double – spatial and temporal – labyrinth. The first of them, formed by Bleston’s streets, squares and parks, is symbolized by the City plan. During his one year sojourn in the city, using its plan, Revel learns patiently how to move in its different districts, and in its strange labyrinth – strange because devoid any centre – that at the end stops annoying him. The other, the temporal one, symbolized by the diary itself, the labyrinth of the human memory, discovered by the narrator rather lately, somewhere in the middle of the year passed in Bleston, becomes, by contrast, more and more dense and complex, which is reflected by an increasinly complex narration used to describe the past. However, at the moment Revel is leaving the city, he is still unable to recall and to describe the events of the 29th of February 1952. This gap, this absence, symbolizes his defeat as the narrator, and, in the same time, the human memory’s limits. In Degrees temporal and spatial structures are also very important. This time round, however, the problems of the narration itself, become predominant. Considered from this point of view, the novel announces Gerard Genette’s work Narrative Discourse and his theoretical discussion of two narratological categories: narrative voice and narrative mode. Having transgressed his narrative competences, Pierre Vernier, the narrator of the first and the second parts of the novel, who, taking as a starting point, a complete account of one hour at school, tries to describe the whole world and various aspects of the human civilization for the benefit of his nephew, Pierre Eller, must fail and disappear, as the narrator, from the third part, which is narrated by another narrator, less audacious and more credible.

OWNERSHIP IN THE REPUBLIC OF MACEDONIA AND THE STATE AS THE HOLDER OF THE PROPERTY RIGHT UNDER THE CONSTITUTION IN 1991

2018 ◽  
Vol 28 (6) ◽  
pp. 1993-2005
Author(s):  
Shemsije Demiri ◽  
Rudina Kaja
Keyword(s):  
Legal Aspect ◽  
State Ownership ◽  
The State ◽  
Point Of View ◽  
State Function ◽  
Dominant Form ◽  
Republic Of Macedonia ◽  
General Terms ◽  
Starting Point ◽  
The Republic

This paper deals with the right to property in general terms from its source in Roman law, which is the starting point for all subsequent legal systems. As a result of this, the acquisition of property rights is handled from the historical point of view, with the inclusion of various local and international literature and studies, as well as the legal aspect devoted to the respective civil codes of the states cited in the paper.Due to such socio-economic developments, state ownership and its ownership function have changed. The state function as owner of property also changed in Macedonia's property law.The new constitutional sequence of the Republic of Macedonia since 1991 became privately owned as a dominant form of ownership, however, state ownership also exists.This process of transforming social property into state or private (dissolves), in Macedonia starts from Yugoslavia through privatization, return and denationalization measures, on which basis laws on privatization have been adopted. Because of this, there will be particularly intensive negotiations regaring the remaining state assets.

Enzyme Promiscuous Activity: How to Define it and its Evolutionary Aspects

2020 ◽  
Vol 27 (5) ◽  
pp. 400-410
Author(s):  
Valentina De Luca ◽  
Luigi Mandrich
Keyword(s):  
Gene Evolution ◽  
Sequence Divergence ◽  
High Specificity ◽  
Industrial Applications ◽  
Point Of View ◽  
Enzyme Promiscuity ◽  
Primary Activity ◽  
Starting Point ◽  
Main Activity

: Enzymes are among the most studied biological molecules because better understanding enzymes structure and activity will shed more light on their biological processes and regulation; from a biotechnological point of view there are many examples of enzymes used with the aim to obtain new products and/or to make industrial processes less invasive towards the environment. Enzymes are known for their high specificity in the recognition of a substrate but considering the particular features of an increasing number of enzymes this is not completely true, in fact, many enzymes are active on different substrates: this ability is called enzyme promiscuity. Usually, promiscuous activities have significantly lower kinetic parameters than to that of primary activity, but they have a crucial role in gene evolution. It is accepted that gene duplication followed by sequence divergence is considered a key evolutionary mechanism to generate new enzyme functions. In this way, promiscuous activities are the starting point to increase a secondary activity in the main activity and then get a new enzyme. The primary activity can be lost or reduced to a promiscuous activity. In this review we describe the differences between substrate and enzyme promiscuity, and its rule in gene evolution. From a practical point of view the knowledge of promiscuity can facilitate the in vitro progress of proteins engineering, both for biomedical and industrial applications. In particular, we report cases regarding esterases, phosphotriesterases and cytochrome P450.

Design of Inhibitors for Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH) Enzyme of Leishmania mexicana

2020 ◽  
Vol 16 (6) ◽  
pp. 784-795
Author(s):  
Krisnna M.A. Alves ◽  
Fábio José Bonfim Cardoso ◽  
Kathia M. Honorio ◽  
Fábio A. de Molfetta
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Binding Site ◽  
Point Of View ◽  
New Drugs ◽  
Leishmania Mexicana ◽  
Receptor Complexes ◽  
Starting Point ◽  
Dynamics Simulations ◽  
Selection Of

Background:: Leishmaniosis is a neglected tropical disease and glyceraldehyde 3- phosphate dehydrogenase (GAPDH) is a key enzyme in the design of new drugs to fight this disease. Objective:: The present study aimed to evaluate potential inhibitors of GAPDH enzyme found in Leishmania mexicana (L. mexicana). Methods: A search for novel antileishmanial molecules was carried out based on similarities from the pharmacophoric point of view related to the binding site of the crystallographic enzyme using the ZINCPharmer server. The molecules selected in this screening were subjected to molecular docking and molecular dynamics simulations. Results:: Consensual analysis of the docking energy values was performed, resulting in the selection of ten compounds. These ligand-receptor complexes were visually inspected in order to analyze the main interactions and subjected to toxicophoric evaluation, culminating in the selection of three compounds, which were subsequently submitted to molecular dynamics simulations. The docking results showed that the selected compounds interacted with GAPDH from L. mexicana, especially by hydrogen bonds with Cys166, Arg249, His194, Thr167, and Thr226. From the results obtained from molecular dynamics, it was observed that one of the loop regions, corresponding to the residues 195-222, can be related to the fitting of the substrate at the binding site, assisting in the positioning and the molecular recognition via residues responsible for the catalytic activity. Conclusion:: he use of molecular modeling techniques enabled the identification of promising compounds as inhibitors of the GAPDH enzyme from L. mexicana, and the results obtained here can serve as a starting point to design new and more effective compounds than those currently available.

Changes in the Prognosis of Functional Psychoses Since the Days of Kraepelin

1967 ◽  
Vol 113 (501) ◽  
pp. 813-822 ◽  
Author(s):  
Örnulv Ödegård
Keyword(s):  
Special Problem ◽  
Point Of View ◽  
General Point ◽  
Course Of Illness ◽  
Dynamic Reasoning ◽  
Starting Point ◽  
Functional Psychoses ◽  
External Conditions ◽  
Point Of Departure ◽  
The Universe

My choice of Kraepelin as a point of departure for this lecture has definite reasons. If one wants to stay within the field of clinical psychiatry (as opposed to psychiatric history), that is as far back as one can reasonably go. By this no slight is intended upon the pre-Kraepelinian psychiatrists. For our topic Henry Maudsley would indeed have been a most appropriate starting point, and by no means for reasons of courtesy. His general point of view is admirably sound as a basis for the scientific study of prognosis in psychiatry. I quote: “There is no accident in madness. Causality, not casualty, governs its appearance in the universe, and it is very far from being a good and sufficient practice simply to mark its phenomena and straightway to pass on as if they belonged not to an order but to a disorder of events that called for no explanation.” On the special problem of prognosis he shows his clinical acumen by stating that the outlook is poor when the course of illness is insidious, but this only means that these cases develop their psychoses on the basis of mental deviations which go very far back in the patient's life, so that in fact they are generally in a chronic stage at the time of their first admission to hospital. Here he actually corrects a mistake which is still quite often made. He shows his dynamic attitude when he says that prognosis is to a large extent modified by external conditions, in particular by the attitude of friends and relatives. Maudsley's dynamic reasoning was limited by the narrow framework of the degeneration hypothesis of those days. He had a sceptical attitude towards classification, which he regarded as artificial and dangerously pseudo-exact. His own classification was deliberately provisional, with very wide groups. He held that a description of various sub-forms of chronic insanity was useless, as it would mean nothing but a tiresome enumeration of unconnected details.

A Three-Dimensional Analysis of Thermohydrodynamic Performance of Sector-Shaped, Tilting-Pad Thrust Bearings

1983 ◽  
Vol 105 (3) ◽  
pp. 406-412 ◽  
Author(s):  
Kyung Woong Kim ◽  
Masato Tanaka ◽  
Yukio Hori
Keyword(s):  
Dimensional Analysis ◽  
Environmental Conditions ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Thrust Bearings ◽  
Tilting Pad ◽  
Dimensional Variation ◽  
Lubricant Viscosity

The thermohydrodynamic performance of the bearing is analyzed, taking into account the three-dimensional variation of lubricant viscosity and density. The effect of pivot position and operating and environmental conditions on the performance is studied. The present analysis is compared with the isoviscous or the two-dimensional analysis, and is found to predict the bearing performance more accurately.

Adapted Methodology for Evaluating EOR Reserves and Resources, Incorporated and Applied at an Oil and Gas Company

2021 ◽  
Author(s):  
Lilibeth Chiquinquira Perdomo ◽  
Carlos Alvarez ◽  
Maria Edith Gracia ◽  
Guillermo Danilo Salomone ◽  
Gilberto Ventuirini ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Large Body ◽  
Securities And Exchange Commission ◽  
Point Of View ◽  
Assessment Process ◽  
Pilot Projects ◽  
Oil Reserves ◽  
Track Record ◽  
Starting Point ◽  
Petroleum Resources

Abstract As other companies registered in the US stock market, the company reports oil and gas reserves, in compliance with the definitions of the Securities and Exchange Commission (SEC). In addition, it complies internally with the guidelines established by the Petroleum Resources Management System to certify its resources. The PRMS focuses on supporting consistent evaluation of oil resources based on technically sound industry practices, providing fundamental principles for the assessment and classification of oil reserves and resources, but does not provide specific guidance for the classification and categorization of quantities associated with IOR projects. Recently, the company has implemented EOR pilot projects, and their results seem to show commerciality for future development or expansion to new areas, displaying multiple opportunities and proposals to incorporate reserves and resources. So far, the pilot projects and their expansions have been addressed only from the point of view of incremental projects, as an improvement over the previous secondary recovery. The company does not have sufficient track record in booking reserves or resources from EOR projects, their quantities have been incorporated following bibliographic references and results of EOR projects with proven commerciality around the world. For this reason, the need arose to have a tool that provides the company with methodological criteria to evaluate the resources and reserves inherent in this type of project, that incorporate the "best practices" of the industry and that respect the guidelines and definitions of PRMS for incremental projects. That was how, the need to meet this challenging goal led company to develop its "EOR Resources and Reserves Assessment Guide" with the advice of a renowned consulting company. Although the Guide is not intended to be a review of the large body of existing IOR literature, it contains several useful references that serve as a starting point for understanding the IOR project for assessment process of resources and reserves. This document shows the process of development and implementation of the EOR guide, complementing the existing guides within the corporation and providing the company with a positive result within the internal processes of Audit, reserves and resources for this type of projects.

Sign in / Sign up

Export Citation Format

Share Document