INFLUENCE OF PAD GEOMETRY MODIFICATION ON THE PERFORMANCE OF THRUST BEARINGS LUBRICATED WITH MAGNETORHEOLOGICAL FLUID

Tribologia ◽  
2018 ◽  
Vol 278 (2) ◽  
pp. 29-35 ◽  
Author(s):  
Wojciech HORAK ◽  
Marcin SZCZĘCH ◽  
Józef SALWIŃSKI
Keyword(s):  
Sliding Friction ◽  
Experimental Tests ◽  
Magnetic Fluids ◽  
Performance Parameters ◽  
System Operation ◽  
Precise Control ◽  
Thrust Bearings ◽  
Wide Range ◽  
The Magnetic Field

Magnetic fluids belong to the class of controllable materials. The influence of magnetic fields on this type of substance results in a change in its internal structure and an almost immediate change in its rheological properties. The ability to control the rheological characteristics in a very wide range, in combination with the ease of generating and controlling the magnetic field, creates the possibility of using this type of substance in systems with controlled operating parameters. The use of magnetic fluids in bearings may allow the design of some types of bearings to be simplified and enable efficient, fast, and precise control of the system operation, with a much shorter response time and higher stiffness than is the case with conventional sliding friction bearings. The paper presents the results of experimental tests carried out on a laboratory stand designed for thrust bearings lubricated with magnetic fluids. The analyses carried out concerned the determination of how the pad surface modification of the slide bearing, lubricated with magnetorheological fluids, influences the system performance parameters.

Second Paper: Analysis of Spin/Roll Conditions and the Frictional-Energy Dissipation in Angular-Contact Thrust Ball Bearings

1966 ◽  
Vol 181 (1) ◽  
pp. 349-362 ◽  
Author(s):  
J. Hailing
Keyword(s):  
Sliding Friction ◽  
Paper Analysis ◽  
Rolling Contact ◽  
Ball Bearings ◽  
Thrust Bearings ◽  
Frictional Energy ◽  
Coefficient Of Sliding Friction ◽  
Tangential Surface ◽  
Frictional Energy Dissipation

In current analyses of the contact conditions in angular-contact ball bearings it is assumed that sliding occurs in all regions where tangential surface tractions are operative. Other work in similar rolling-contact situations has, however, demonstrated that some of this slip requirement may be accommodated by the elastic surface deformations. This type of analysis leads to areas of sliding and sticking coexisting within the contact areas. These concepts are here applied to angular-contact thrust ball bearings and lead to some interesting deviations from the results obtained using the complete slip analysis. In particular, these concepts of microslip enable the determination of the spin/roll ratio at each race contact. Detailed calculations for conical ball thrust bearings illustrate the main discrepancy of the full slip analysis in over-estimating the frictional-energy losses, such discrepancies being most marked with decreasing contact angle, increasing pitch/ball radii, and increasing coefficient of sliding friction.

THE INFLUENCE OF SELECTED FACTORS ON AXIAL FORCE AND FRICTION TORQUE IN A THRUST BEARING LUBRICATED WITH MAGNETORHEOLOGICAL FLUID

Tribologia ◽  
2016 ◽  
Vol 269 (5) ◽  
pp. 51-61 ◽  
Author(s):  
Wojciech HORAK ◽  
Józef SALWIŃSKI ◽  
Marcin SZCZĘCH
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Magnetic Fluid ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Magnetic Field Gradient ◽  
Magnetic Fluids ◽  
Carrier Fluid ◽  
Wide Range ◽  
The Magnetic Field

Magnetic fluids belong to the class of materials in which rheological properties can be controlled by magnetic fields. Magnetic fluids are suspensions of ferromagnetic particles in a carrier fluid, and the magnetic field can change their internal structure. This phenomenon is fully reversible, almost instantaneously. The test results of a hydrostatic bearing lubricated by magnetic fluid are shown in the publication [L. 7]. It has been shown that the use of MR fluids as a lubricant allows high stiffness of the bearing to be obtained regardless of the height of the bearing gap. The publication [L. 8] presents the results of a thrust bearing lubricated by magnetic fluid with no external feed pump. The load capacity of the bearing was achieved by a self-sealing effect. This effect is associated with the ability to hold a magnetic fluid in a predetermined position through the magnetic field. This is caused by the appropriate geometry of the bearing surface. This effect retains the flow of the magnetic fluid out of the bearing gap as a result of the occurrence of a magnetic barrier, which counteracts the movement of the magnetic fluid. This barrier is a result of a local increase or decrease in magnetic induction similar to magnetic fluid seals. Another phenomenon highlighted in [L. 9, 10, 11] is the generation in the magnetic fluid of additional pressure due to the interaction of the magnetic field gradient. The result is an additional buoyancy force. When selecting a magnetic fluid for application in the thrust bearing, a number of factors should be taken into account. In addition to the parameters describing the typical lubricant, such as lubricity, corrosion properties, and work at high temperatures, the magnetic fluid used in the friction zone should allow a wide range of the rheological properties to be obtained due to changes in the magnetic field intensity. It is also important that the magnetic fluids have the ability to generate the appropriate value of the normal force due to the magnetic field.

scholarly journals Importance of Experimental Tests for the Determination of Modeling Parameters in Fire Safety Engineering

2019 ◽  
Vol 290 ◽  
pp. 12025
Author(s):  
Vincenzo Torretta ◽  
Marco Barozzi ◽  
Luca Talamona ◽  
Sabrina Copelli ◽  
Fabio Conti ◽  
...  
Keyword(s):  
Fire Safety ◽  
Experimental Tests ◽  
Composition Analysis ◽  
Safety Engineering ◽  
Fire Safety Engineering ◽  
Wide Range ◽  
In Fire ◽  
Real Scale ◽  
Heat Released

In the field of Fire Safety Engineering, the application of mathematical models is crucial in order to properly estimate the severity of eventual fires occurring inside workplaces. Such models (like CFast, Ozone, FDS, CFX, Fluent), require a notable amount of specific parameters in order to work. Such parameters are usually available in the current literature, or they can be estimated via experimental tests. In this work, several experimental setups have been performed in order to evaluate such data in the burning of a wide range of materials: cotton, polyethylene and polyester in industrial rollers, flour, sugar, feed for dairy cows, and wood pallets. Cone Calorimeter, Mahler bomb, and real-scale tests have been performed in order to evaluate parameters such as Calorific Values, Total Heat Released, Heat Released Rate and smoke composition analysis. The real-scale tests have been performed with the aim of addressing fire occurring in warehouses, focusing then on an industrial environment. All the values have been compared with theoretical estimations made with the ClaRaf 2.0 software, and it was noticed that they tend to give overestimated values in comparison with empirical results.

scholarly journals DNA Nanodevices as Mechanical Probes of Protein Structure and Function

2021 ◽  
Vol 11 (6) ◽  
pp. 2802
Author(s):  
Nicholas Stephanopoulos ◽  
Petr Šulc
Keyword(s):  
Protein Structure ◽  
Protein Function ◽  
Cell Activation ◽  
Dna Nanotechnology ◽  
Future Directions ◽  
Precise Control ◽  
Wide Range ◽  
Promising Application ◽  
And Function

DNA nanotechnology has reported a wide range of structurally tunable scaffolds with precise control over their size, shape and mechanical properties. One promising application of these nanodevices is as probes for protein function or determination of protein structure. In this perspective we cover several recent examples in this field, including determining the effect of ligand spacing and multivalency on cell activation, applying forces at the nanoscale, and helping to solve protein structure by cryo-EM. We also highlight some future directions in the chemistry necessary for integrating proteins with DNA nanoscaffolds, as well as opportunities for computational modeling of hybrid protein-DNA nanomaterials.

Dynamic Characteristics of Externally Pressurized Rectangular Porous Gas Thrust Bearings

1976 ◽  
Vol 98 (1) ◽  
pp. 181-186 ◽  
Author(s):  
B. C. Majumdar
Keyword(s):  
Design Procedure ◽  
Theoretical Data ◽  
Periodic Load ◽  
Small Perturbations ◽  
Thrust Bearings ◽  
Design Variables ◽  
Wide Range ◽  
Stiffness And Damping ◽  
Compressible Lubricant

A theoretical study on the behavior of an externally pressurized rectangular porous thrust bearing is made using compressible lubricant. A periodic load is imposed on the bearing and the pressure distribution which leads to the determination of stiffness and damping is obtained by small perturbations. The results are calculated numerically using a digital computer. The tabulated theoretical data of a square pad given for a wide range of design variables enable one to use directly in the design. A design procedure of such a bearing is also indicated.

Monte Carlo calculation of the energy parameters and spatial distribution of the cathodic arc ions while passing through the macro-particles filters

2018 ◽  
Vol 1 (1) ◽  
pp. 30-34 ◽  
Author(s):  
Alexey Chernogor ◽  
Igor Blinkov ◽  
Alexey Volkhonskiy
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Monte Carlo ◽  
Monte Carlo Calculation ◽  
Inhomogeneous Magnetic Field ◽  
Flow Energy ◽  
Wide Range ◽  
Field Concentrator ◽  
Cathodic Arc ◽  
The Magnetic Field

The flow, energy distribution and concentrations profiles of Ti ions in cathodic arc are studied by test particle Monte Carlo simulations with considering the mass transfer through the macro-particles filters with inhomogeneous magnetic field. The loss of ions due to their deposition on filter walls was calculated as a function of electric current and number of turns in the coil. The magnetic field concentrator that arises in the bending region of the filters leads to increase the loss of the ions component of cathodic arc. The ions loss up to 80 % of their energy resulted by the paired elastic collisions which correspond to the experimental results. The ion fluxes arriving at the surface of the substrates during planetary rotating of them opposite the evaporators mounted to each other at an angle of 120° characterized by the wide range of mutual overlapping.

DINAMIKA POLITIK PERSETUJUAN BERSAMA TENTANG PENETAPAN DESA ADAT DI KABUPATEN ROKAN HULU TAHUN 2014

2017 ◽  
Vol 15 (1) ◽  
pp. 21
Author(s):  
Haryo Suganda ◽  
Raja Muhammad Amin
Keyword(s):  
Regulatory Region ◽  
Field Research ◽  
Analysis Techniques ◽  
Political Dynamics ◽  
Political Interests ◽  
Wide Range ◽  
Information Method ◽  
Qualitative Descriptive ◽  
The Village

This study is motivated the identification of policies issued by the regional Governmentof Rokan Hulu in the form of Regulatory region number 1 by 2015 on the determination of thevillage and Indigenous Village. Political dynamics based on various interests against themanufacture of, and decision-making in the process of formation of the corresponding localregulations determination of Indigenous Villages in the Rokan Hulu is impacted to a verysignificantamount of changes from the initial draft of the number i.e. 21 (twenty one) the villagebecame Customary 89 (eighty-nine) the Indigenous Villages who have passed. Type of thisresearch is a qualitative descriptive data analysis techniques. The research aims to describe theState of the real situation in a systematic and accurate fact analysis unit or related research, aswell as observations of the field based on the data (information). Method of data collectionwas done with interviews, documentation, and observations through fieldwork (field research).The results of the research on the process of discussion of the draft local regulations andmutual agreement about Designation of Indigenous Villages in the Rokan Hulu is, showed thatthe political dynamics that occur due to the presence of various political interests, rejectionorally by Villagers who were judged to have met the requirements of Draft Regulations to beformulated and the area for the set to be Indigenous Villages, and also there is a desire fromsome villages in the yet to Draft local regulations in order to set the Indigenous village , there isa wide range of interests of these aspects influenced the agreement to assign the entire localVillage which is in the Rokan Hulu become Indigenous village, and the village of Transmigrationinto administrative Villages where the initiator of the changes in the number of IndigenousVillages in the Rokan Hulu it is the desire of the local Government of its own.

scholarly journals Recent Developments in the Determination of Biomarkers of Tobacco Smoke Exposure in Biological Specimens: A Review

2021 ◽  
Vol 18 (4) ◽  
pp. 1768
Author(s):  
Hernâni Marques ◽  
Pedro Cruz-Vicente ◽  
Tiago Rosado ◽  
Mário Barroso ◽  
Luís A. Passarinha ◽  
...  
Keyword(s):  
Tobacco Smoke ◽  
Solid Phase ◽  
Smoke Exposure ◽  
Tobacco Smoke Exposure ◽  
World Health ◽  
Second Hand Smoke ◽  
Tobacco Exposure ◽  
Wide Range ◽  
Recent Developments

Environmental tobacco smoke exposure (ETS) and smoking have been described as the most prevalent factors in the development of certain diseases worldwide. According to the World Health Organization, more than 8 million people die every year due to exposure to tobacco, around 7 million due to direct ETS and the remaining due to exposure to second-hand smoke. Both active and second-hand exposure can be measured and controlled using specific biomarkers of tobacco and its derivatives, allowing the development of more efficient public health policies. Exposure to these compounds can be measured using different methods (involving for instance liquid- or gas-chromatographic procedures) in a wide range of biological specimens to estimate the type and degree of tobacco exposure. In recent years, a lot of research has been carried out using different extraction methods and different analytical equipment; this way, liquid–liquid extraction, solid-phase extraction or even miniaturized procedures have been used, followed by chromatographic analysis coupled mainly to mass spectrometric detection. Through this type of methodologies, second-hand smokers can be distinguished from active smokers, and this is also valid for e-cigarettes and vapers, among others, using their specific biomarkers. This review will focus on recent developments in the determination of tobacco smoke biomarkers, including nicotine and other tobacco alkaloids, specific nitrosamines, polycyclic aromatic hydrocarbons, etc. The methods for their detection will be discussed in detail, as well as the potential use of threshold values to distinguish between types of exposure.

scholarly journals Applicability of Cork as Novel Modifiers to Develop Electrochemical Sensor for Caffeine Determination

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 37
Author(s):  
Mayra K. S. Monteiro ◽  
Djalma R. Da Silva ◽  
Marco A. Quiroz ◽  
Vítor J. P. Vilar ◽  
Carlos A. Martínez-Huitle ◽  
...  
Keyword(s):  
Electrochemical Sensor ◽  
Linear Response ◽  
High Performance ◽  
Low Cost ◽  
Pharmaceutical Formulations ◽  
Caffeine Concentration ◽  
Real Samples ◽  
Wide Range ◽  
Potential Use

This study aims to investigate the applicability of a hybrid electrochemical sensor composed of cork and graphite (Gr) for detecting caffeine in aqueous solutions. Raw cork (RAC) and regranulated cork (RGC, obtained by thermal treatment of RAC with steam at 380 °C) were tested as modifiers. The results clearly showed that the cork-graphite sensors, GrRAC and GrRGC, exhibited a linear response over a wide range of caffeine concentration (5–1000 µM), with R2 of 0.99 and 0.98, respectively. The limits of detection (LOD), estimated at 2.9 and 6.1 µM for GrRAC and GrRGC, suggest greater sensitivity and reproducibility than the unmodified conventional graphite sensor. The low-cost cork-graphite sensors were successfully applied in the determination of caffeine in soft drinks and pharmaceutical formulations, presenting well-defined current signals when analyzing real samples. When comparing electrochemical determinations and high performance liquid chromatography measurements, no significant differences were observed (mean accuracy 3.0%), highlighting the potential use of these sensors to determine caffeine in different samples.

scholarly journals Differential Laboratory Diagnosis of Acute Fever in Guinea: Preparedness for the Threat of Hemorrhagic Fevers

2021 ◽  
Vol 18 (11) ◽  
pp. 6022
Author(s):  
Vladimir G. Dedkov ◽  
N’Faly Magassouba ◽  
Olga A. Stukolova ◽  
Victoria A. Savina ◽  
Jakob Camara ◽  
...  
Keyword(s):  
Ebola Virus ◽  
Febrile Illness ◽  
Laboratory Diagnosis ◽  
Acute Febrile Illness ◽  
Causative Pathogen ◽  
Hemorrhagic Fevers ◽  
Wide Range ◽  
Causative Agents ◽  
Pathognomonic Sign

Acute febrile illnesses occur frequently in Guinea. Acute fever itself is not a unique, hallmark indication (pathognomonic sign) of any one illness or disease. In the infectious disease context, fever’s underlying cause can be a wide range of viral or bacterial pathogens, including the Ebola virus. In this study, molecular and serological methods were used to analyze samples from patients hospitalized with acute febrile illness in various regions of Guinea. This analysis was undertaken with the goal of accomplishing differential diagnosis (determination of causative pathogen) in such cases. As a result, a number of pathogens, both viral and bacterial, were identified in Guinea as causative agents behind acute febrile illness. In approximately 60% of the studied samples, however, a definitive determination could not be made.

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