Controlling the Dynamic Characteristics of a Hydrostatic Bearing by Using a Pocket-Connected Accumulator

1983 ◽  
Vol 197 (4) ◽  
pp. 255-258 ◽  
Author(s):  
M J Goodwin ◽  
C J Hooke ◽  
J E T Penny
Keyword(s):  
Experimental Investigation ◽  
Dynamic Characteristics ◽  
System Performance ◽  
Journal Bearings ◽  
Careful Selection ◽  
Hydrostatic Bearing ◽  
Optimum System ◽  
Flexible Rotors ◽  
Rotor Support ◽  
Selection Of

This paper describes a theoretical and experimental investigation of the dynamic characteristics of a capillary-compensated oil-lubricated hydrostatic bearing which has an accumulator connected to the bearing pocket via a second capillary restrictor. Results show that by careful selection of accumulator and restrictor the bearing can be tuned to give an optimum system performance. Such a facility can be of considerable use if the hydrostatic bearing is being used to support other machinery, for example in the support of journal bearings used with flexible rotors. By tuning the hydrostatic bearing dynamic characteristics, optimum rotor support impedance might be achieved thereby giving the engineer some control over system resonances and stability.

Afterword

2020 ◽  
pp. 680-683
Author(s):  
Janice L. Waldron ◽  
Stephanie Horsley ◽  
Kari K. Veblen
Keyword(s):  
Social Media ◽  
Media Use ◽  
Careful Selection ◽  
Social Media Use ◽  
Pedagogical Tools ◽  
The Future ◽  
User Data ◽  
Selection Of ◽  
Data Surface

We all feel the implications of the force of social media—for good and for ill—in our lives and in our professional world. At the time of this writing, Facebook continues with its struggle to “clean up its act” as more revelations surrounding breaches of trust and hacked user data surface in the news and various countries attempt to hold Facebook to account. Despite this, social media use continues to grow exponentially, and the potential for responsible, ethical, and transparent social media to transform the ways in which we interact with and learn from each other increase with it. As we wait to see what the future holds for social media in society, we are reminded once again that it is the careful selection of pedagogical tools such as social media, as well the guided awareness of the challenges and benefits of those tools, that remains constant, even as tools may change, disappear, or fall out of fashion.

Comparative Evaluation of MoS2 and WS2 as Powder Lubricants in High Speed, Multi-Pad Journal Bearings

1999 ◽  
Vol 121 (3) ◽  
pp. 625-630 ◽  
Author(s):  
C. Fred Higgs ◽  
Crystal A. Heshmat ◽  
Hooshang Heshmat
Keyword(s):  
Comparative Evaluation ◽  
High Speed ◽  
Solid Lubricants ◽  
Extreme Environment ◽  
Journal Bearings ◽  
Lubricating Film ◽  
Constant Friction ◽  
Traction Coefficient ◽  
Limiting Value ◽  
Selection Of

As part of a program to develop solid/powder-lubricated journal bearings, a comparative evaluation has been performed to aid in determining whether MoS2 and WS2 powder are suitable lubricants for high-speed, extreme-environment multi-pad journal bearings. Plots of traction coefficients, friction, frictional power loss, and bearing pad temperature are presented as a means for comparing various powder lubricants. This paper primarily focuses on experiments carried out on a three-pad journal bearing and a disk-on-disk tribometer. Results showed that MoS2 traction curves resemble that of SAE 10 synthetic oil. Unlike liquid lubricants, powder films have a limiting shear strength property. Once the powder reaches this limiting value, the maximum traction coefficient is limited and the powder essentially shears along sliding walls. Experimental traction data shows evidence of this property in various powders. The thermal performance of the bearing was evaluated at speeds up to 30,000 rpm and loads up to 236 N. Although WS2 displayed constant friction coefficient and low temperature with increasing dimensionless load, MoS2 exhibited frictional behavior resembling that of a hydrodynamic lubricating film. In this paper, an attempt has been made to provide a criterion for the selection of solid lubricants for use in those tribosystems that may be operated in a high speed/load regime (i.e., high strain rates) as an alternative yard stick to conventional comparative approaches.

Catacomb culture wagons of the Eurasian steppes

Antiquity ◽  
2014 ◽  
Vol 88 (340) ◽  
pp. 378-394 ◽  
Author(s):  
N.I. Shishlina ◽  
D.S. Kovalev ◽  
E.R. Ibragimova
Keyword(s):  
Stable Isotope ◽  
Isotope Analysis ◽  
Burial Mound ◽  
Careful Selection ◽  
Southern Russia ◽  
The Subject ◽  
The Individual ◽  
Wheeled Vehicles ◽  
Selection Of ◽  
Catacomb Culture

The origin and development of wheeled vehicles continues to fascinate today no less than when Stuart Piggott (1974) first wrote about the subject inAntiquity40 years ago. A growing number of examples from the steppes of southern Russia and Ukraine are providing new insights into the design and construction of these complex artefacts. A recent example from the Ulan IV burial mound illustrates the techniques employed and the mastery of materials, with careful selection of the kinds of wood used for the wheels, axles and other elements. Stable isotope analysis of the individual interred in this grave showed that he had travelled widely, emphasising the mobility of steppe populations.

scholarly journals The Effects of Landscape Elements on the Breeding Sites of Bloodsucking Midge

2021 ◽  
Vol 13 (5) ◽  
pp. 2863
Author(s):  
Kaowen Grace Chang ◽  
Hungju Chien
Keyword(s):  
Ground Surface ◽  
Preventive Strategies ◽  
Careful Selection ◽  
Public Concern ◽  
Breeding Sites ◽  
Algae Growth ◽  
Potential Habitats ◽  
Landscape Factors ◽  
The Relationship ◽  
Selection Of

Forcipomyia taiwana, a bloodsucking midge that is one of the most irritating biting pests in Taiwan, has raised widespread public concern. However, we have little information about the extent to which landscape factors affect their potential habitats. As a result, landscape professionals do not have enough information to implement preventive strategies to control midges. The purpose of this study is to investigate the relationship between landscaping and algae growth for larval breeding sites of Forcipomyia taiwana. The intent is to determine the environmental strategies that make the planned landscape unsuitable for midges to breed. GIS based on data collected from 16 constructed landscape sites (317,187 m2 in total) was utilized to spatially examine the relationship between the occurrence of the algae for midge breeding sites and the ground surface types and planting characteristics in each landscape. The results revealed that the potential midge habitats can be controlled through careful selection of the ground surface, the improvement of the site drainage, and choosing plants with the appropriate characteristics. Apart from choosing the appropriate type of paving surface, the integrity of the paving installation and the coverage of the ecological surface also influence prevention efficacy.

WEIGHT GAINS IN THE FIRST FOUR WEEKS OF INFANCY: A COMPARISON OF THREE DIETS

PEDIATRICS ◽  
1956 ◽  
Vol 18 (3) ◽  
pp. 362-368
Author(s):  
Ruth T. Gross ◽  
Lincoln E. Moses
Keyword(s):  
Human Milk ◽  
Statistical Methods ◽  
Full Term ◽  
Clinical Judgement ◽  
Careful Selection ◽  
Term Infants ◽  
Weight Gains ◽  
The Many ◽  
Selection Of

Four hundred seven healthy, full-term infants were divided into three groups and fed, respectively, a formula of evaporated milk and water with 5% carbohydrate; human milk; and a special modified evaporated milk designed to simulate human milk. No other foods were added to the diet. A comparison of the three groups was made, based on weight gains from birth to the end of the first 4 weeks. The conclusions refer only to weight gains; no attempt was made to determine the superiority of any particular diet. The data show no significant differences in the 4-week weight gains among the three groups of infants, although sensitive statistical methods could be validly applied to the problem. These methods are explained. The authors wish to emphasize the many variables which must be taken into account in a study of this sort; the necessity for careful selection of valid statistical methods; the importance of critical clinical judgement in the evaluation of the results.

The Design for Assembly Guidelines Transform a Product Innovation From a Loser to a Winner

1998 ◽  
Author(s):  
David H. Myszka
Keyword(s):  
Product Innovation ◽  
Computer Models ◽  
Design For Assembly ◽  
Careful Selection ◽  
Significant Cost ◽  
Success Stories ◽  
Modeling Process ◽  
Design Activities ◽  
Manual Review ◽  
Selection Of

Abstract Several manufacturer’s are witnessing soaring profits as a result of cost reductions derived from Design for Manufacturing and Assembly (DFMA) analyses. These successes are prompting others to turn to more refined computer models of product assemblies. However, much can be gained from a very routine analysis, using nothing more than the basic Design for Assembly (DFA) guidelines. These gains can be realized at a mere fraction of the resources needed for the computer models. This method of analysis is especially appealing to engineers whose time constraints require careful selection of design activities. This paper argues that DFMA analysis does not need to be an elaborate modeling process to produce significant cost improvements. This point is illustrated with an example of a redesign of a cooking range door. A manual review of the DFA guidelines turned a design innovation from a loser into a winner. Success stories from such informal analyses should promote greater implementation across industries that are hesitant in adopting DFMA practices.

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Journal Bearing ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Derivatives Of ◽  
Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

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