Evaluation of AMB Turbomachinery Auxiliary Bearings

1999 ◽  
Vol 121 (2) ◽  
pp. 156-161 ◽  
Author(s):  
R. G. Kirk
Keyword(s):  
Transient Response ◽  
Analytical Techniques ◽  
Contact Forces ◽  
Active Magnetic Bearings ◽  
Low Loss ◽  
The Past ◽  
Compressor Rotor ◽  
Auxiliary Bearing ◽  
On Line ◽  
Proper Design

The use of active magnetic bearings (AMB) for turbomachinery has experienced substantial growth during the past two decades. The advantages for many applications make AMB’s a very attractive solution for potentially low loss and efficient support for both radial and thrust loads. New machinery must be shop tested prior to shipment to the field for installation on-line. For AMB turbomachinery, one additional test is the operation of the auxiliary drop or overload bearings. A major concern is ability of the selected auxiliary bearing to withstand the contact forces following an at speed rotor drop. The proper design of AMB machinery requires the calculation of the anticipated loading for the auxiliary bearings. Analytical techniques to predict the rotor transient response are reviewed. Results of transient response evaluation of a full-size compressor rotor are presented to illustrate some of the important parameters in the design for rotor drop.

Evaluation of AMB Turbomachinery Auxiliary Bearings

1997 ◽  
Author(s):  
R. G. Kirk
Keyword(s):  
Transient Response ◽  
Analytical Techniques ◽  
Contact Forces ◽  
Active Magnetic Bearings ◽  
Low Loss ◽  
The Past ◽  
Compressor Rotor ◽  
Auxiliary Bearing ◽  
On Line ◽  
Proper Design

Abstract The use of active magnetic bearings (AMB) for turbomachinery has experienced substantial growth during the past two decades. The advantages for many applications make AMB’s a very attractive solution for potentially low loss and efficient support for both radial and thrust loads. New machinery must be shop tested prior to shipment to the field for installation on-line. For AMB turbomachinery, one additional test is the operation of the auxiliary drop or overload bearings. A major concern is ability of the selected auxiliary bearing to withstand the contact forces following an at speed rotor drop. The proper design of AMB machinery requires the calculation of the anticipated loading for the auxiliary bearings. Analytical techniques to predict the rotor transient response are reviewed. Results of transient response evaluation of a full-size compressor rotor are presented to illustrate some of the important parameters in the design for rotor drop.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

The on-line use of histogram data for high-speed correction and alignment of electron microscope images

1984 ◽  
Vol 42 ◽  
pp. 556-557
Author(s):  
William Krakow
Keyword(s):  
Power Spectrum ◽  
High Speed ◽  
Direct Memory Access ◽  
Digital Television ◽  
Contrast Transfer Function ◽  
The Past ◽  
High Resolution Tem ◽  
On Line ◽  
Correction Of Astigmatism ◽  
The Fourier Transform

In the past few years on-line digital television frame store devices coupled to computers have been employed to attempt to measure the microscope parameters of defocus and astigmatism. The ultimate goal of such tasks is to fully adjust the operating parameters of the microscope and obtain an optimum image for viewing in terms of its information content. The initial approach to this problem, for high resolution TEM imaging, was to obtain the power spectrum from the Fourier transform of an image, find the contrast transfer function oscillation maxima, and subsequently correct the image. This technique requires a fast computer, a direct memory access device and even an array processor to accomplish these tasks on limited size arrays in a few seconds per image. It is not clear that the power spectrum could be used for more than defocus correction since the correction of astigmatism is a formidable problem of pattern recognition.

Q & A. Lisa Randall. [interview]

2019 ◽  
Author(s):  
Adib Rifqi Setiawan
Keyword(s):  
New York ◽  
New York City ◽  
Particle Physics ◽  
Harvard University ◽  
The Past ◽  
Talent Search ◽  
Cosmological Inflation ◽  
On Line ◽  
Theoretical Physicist ◽  
Fundamental Forces

Lisa Randall is a theoretical physicist working in particle physics and cosmology. She was born in Queens, New York City, on June 18, 1962. Lisa Randall is an alumna of Hampshire College Summer Studies in Mathematics; and she graduated from Stuyvesant High School in 1980. She won first place in the 1980 Westinghouse Science Talent Search at the age of 18; and at Harvard University, Lisa Randall earned both a BA in physics (1983) and a PhD in theoretical particle physics (1987) under advisor Howard Mason Georgi III, a theoretical physicist. She is currently Frank B. Baird, Jr. Professor of Science on the physics faculty of Harvard University, where he has been for the past a decade. Her works concerns elementary particles and fundamental forces, and has involved the study of a wide variety of models, the most recent involving dimensions. She has also worked on supersymmetry, Standard Model observables, cosmological inflation, baryogenesis, grand unified theories, and general relativity. Consequently, her studies have made her among the most cited and influential theoretical physicists and she has received numerous awards and honors for her scientific endeavors. Since December 27, 2010 at 00:42 (GMT+7), Lisa Randall is Twitter’s user with account @lirarandall. “Thanks to new followers. Interesting how different it feels broadcasting on line vs.via book or article. Explanations? Pithiness? Rapidity?” is her first tweet.

On the Use of Actively Controlled Auxiliary Bearings in Magnetic Bearing Systems

2008 ◽  
Author(s):  
Iain S. Cade ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows ◽  
Patrick S. Keogh
Keyword(s):  
Controller Design ◽  
Control Strategies ◽  
Frictional Heating ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Active Magnetic Bearing ◽  
Physical Limit ◽  
Drop Tests ◽  
Auxiliary Bearing ◽  
And Control

Auxiliary bearings are used to prevent rotor/stator contact in active magnetic bearing systems. They are sacrificial components providing a physical limit on the rotor displacement. During rotor/auxiliary bearing contact significant forces normal to the contact zone may occur. Furthermore, rotor slip and rub can lead to localized frictional heating. Linear control strategies may also become ineffective or induce instability due to changes in rotordynamic characteristics during contact periods. This work considers the concept of using actively controlled auxiliary bearings in magnetic bearing systems. Auxiliary bearing controller design is focused on attenuating bearing vibration resulting from contact and reducing the contact forces. Controller optimization is based on the H∞ norm with appropriate weighting functions applied to the error and control signals. The controller is assessed using a simulated rotor/magnetic bearing system. Comparison of the performance of an actively controlled auxiliary bearing is made with that of a resiliently mounted auxiliary bearing. Rotor drop tests, repeated contact tests, and sudden rotor unbalance resulting in trapped contact modes, are considered.

Otolaryngology and the Internet

1996 ◽  
Vol 115 (1) ◽  
pp. 123-131 ◽  
Author(s):  
Michael Rothschild
Keyword(s):  
Clinical Medicine ◽  
Neck Surgery ◽  
Academic Departments ◽  
The Internet ◽  
Extensive Experience ◽  
The Past ◽  
National Organizations ◽  
On Line ◽  
Cultural Entity ◽  
Technical Terms

During the past 25 years, the Internet has grown tremendously. Starting as four academic computers linked by the Department of Defense, it has become a major technical and cultural entity that is accessible to millions of persons outside the realm of government and academia. The field of medicine has been well served by this telecommunications system, in which many applications have been developed to assist in research, clinical medicine, and education. More recently, resources of specific interest to otolaryngologists have been implemented at various academic departments and national organizations. This review is intended to simplify the Internet for otolaryngologists who do not have extensive experience in computers or telecommunication. The Internet is described in basic, minimally technical terms, and specific examples are provided of ways that on-line resources can be used in the practice of otolaryngology-head and neck surgery.

scholarly journals Establishment and functioning of the Vascular Registry in Hungary

2014 ◽  
Vol 155 (19) ◽  
pp. 755-760 ◽  
Author(s):  
Gábor Menyhei ◽  
Gábor Simó ◽  
Zoltán Szeberin ◽  
Gábor Bíró ◽  
Tamás Kováts
Keyword(s):  
Vascular Surgery ◽  
Organizational Development ◽  
Vascular Diseases ◽  
Artery Aneurysm ◽  
Population Based ◽  
The Past ◽  
Carotid Artery Aneurysm ◽  
Surgical Units ◽  
On Line ◽  
Scientific Results

Randomized controlled trials provide the best evidence in clinical trials; however, they do have limitations. In order to evaluate the effectiveness of treatments, population based registries may also yield useful information about the actual practice and they may enable users to carry out a dynamic follow-up. To evaluate the outcome of vascular procedures, the Vascular Registry in Hungary has been established in 2002. This article presents the establishment and functioning of the Vascular Registry and provides information about scientific results obtained during the past years. The Vascular Registry is an internet based database with on-line input. The backup server is provided by the National Institute for Quality and Organizational Development in Healthcare and Medicines. The database collects data in three different fields: interventions for carotid artery, aneurysm (any type) and lower extremity vascular diseases. Twenty five vascular surgical units record interventions in the registry, which corresponds to two thirds of the whole activity. Since joining the Vascunet Group of the European Society for Vascular Surgery, the registry has contributed to several publications based on evaluation of a large common dataset in different fields of vascular surgery. A validation process has been recently performed which confirmed the internal and external validity of the database. The authors conclude that despite unsolved problems related to financing issues, the Vascular Registry has proved to be a useful tool during the past years. In order to take advantage of the registry to its fullest, measures should be taken to achieve a more complete data recording, increase publication activity on the national dataset, improve the flow of information during operation and develop a system of regular feedback. Orv. Hetil., 2014, 155(19), 755–760.

Public Participation in E-Government

2010 ◽  
pp. 324-339
Author(s):  
Scott Baum ◽  
Arun Mahizhnan
Keyword(s):  
Public Participation ◽  
Digital Divide ◽  
International Comparisons ◽  
Significant Progress ◽  
The Past ◽  
The World ◽  
On Line

Singapore’s E-government model is considered to be among the best in the world. Over the past decade the Singapore government has constantly developed and re-developed its on-line presence. International comparisons have consistently rated Singapore as one of the most advanced E-government nations. However, despite significant progress towards full E-government maturity, some issues of full public participation remain. It is these issues which this chapter discusses. In particular, it will consider the ways in which a digital divide within the Singapore model has emerged, despite specific policies to address such a problem.

Writing about the Past, an Act of Resistance

2019 ◽  
pp. 21-42
Keyword(s):  
Communist Party ◽  
Chinese Communist Party ◽  
The Internet ◽  
Official Publication ◽  
Xi Jinping ◽  
The Third ◽  
The Past ◽  
On Line ◽  
Historical Truth ◽  
Historical Accounts

Since taking power in 1949, the Chinese Communist Party has consistently tried to enforce a monopoly on the writing and interpretation of history. However, since 1998 individual initiatives have increased in the field of memory. Confronting official amnesia, victims of Maoist movements have decided to write their versions of history before it is too late. This chapter presents a typology of these endeavours. Annals of the Yellow Emperor (Yanhuang chunqiu), an official publication, enjoyed some freedom to publish dissenting historical accounts but was suppressed in 2016. With the rise of the internet, unofficial journals appeared that were often dedicated to a specific period: Tie Liu’s Small traces of the Past (Wangshi weihen) published accounts of victims of the Anti-Rightist movement for almost a decade before the editor was arrested; Wu Di’s Remembrance (Jiyi) founded by former Red Guards and rusticated youth circulates on line. The third type is the samizdat: targets of repression during Mao’s reign recount their experience in books that are published at their own expense and circulated privately. Most of these “entrepreneurs of memory” are convinced that restoring historical truth is a pre-requisite to China’s democratization. Since Xi Jinping came to power, they have suffered repression.

Sign in / Sign up

Export Citation Format

Share Document