652 research outputs found
Gas Wave Bearings: A Stable Alternative to Journal Bearings for High-Speed Oil-Free Machines
No full textTo run both smoothly and efficiently, high-speed machines need stable, low-friction bearings to support their rotors. In addition, an oil-free bearing system is a common requirement in today's designs. Therefore, self-acting gas film bearings are becoming the bearing of choice in high-performance rotating machinery, including that used in the machine tool industry. Although plain journal bearings carry more load and have superior lift and land characteristics, they suffer from instability problems. Since 1992, a new type of fluid film bearing, the wave bearing, has been under development at the NASA Lewis Research Center in Cleveland, Ohio, by Dr. Florin Dimofte, a Senior Research Associate of the University of Toledo. One unique characteristic of the waved journal bearing that gives it improved capabilities over conventional journal bearings is the low-amplitude waves of its inner diameter surface. The radial clearance is on the order of one thousandth of the shaft radius, and the wave amplitude is nominally up to one-half the clearance. This bearing concept offers a load capacity which is very close to that of a plain journal bearing, but it runs more stably at nominal speeds
Hydrodynamic Analyses and Evaluation of New Fluid Film Bearing Concepts
No full textOver the past several years, numerical and experimental investigations have been performed on a waved journal bearing. The research work was undertaken by Dr. Florin Dimofte, a Senior Research Associate in the Mechanical Engineering Department at the University of Toledo. Dr. Theo Keith, Distinguished University Professor in the Mechanical Engineering Department was the Technical Coordinator of the project. The wave journal bearing is a bearing with a slight but precise variation in its circular profile such that a waved profile is circumscribed on the inner bearing diameter. The profile has a wave amplitude that is equal to a fraction of the bearing clearance. Prior to this period of research on the wave bearing, computer codes were written and an experimental facility was established. During this period of research considerable effort was directed towards the study of the bearing's stability. The previously developed computer codes and the experimental facility were of critical importance in performing this stability research. A collection of papers and reports were written to describe the results of this work. The attached captures that effort and represents the research output during the grant period
Bulletin (Florin Japanese American Citizens League), no. 8 (May 16, 1942)
No full textNewsletter of the Florin chapter of the Japanese American Citizens League covering issues related to incarceration including an editorial by Mary Tsukamoto, news from Temporary Assembly Centers, care of pets, Japanese American soldiers, inoculation certificates, access to bank services, information about the Farm Security office, the Sacramento Workers Compensation Claims Administration, advice for incarcerees, work of the national Japanese American Citizens League, voting, verification papers, address changes, and recognition of individuals for their financial contributions. Newsletter labeled "Bulletin No. 8"The Japanese American Archival Collection documents the people, places, and daily life of Japanese Americans, primarily those who lived in the once thriving community of pre-war Florin in the Sacramento region, as well as the conditions in American incarceration camps during World War II. The approximately 7,000 original items include personal and official letters, photographs, diaries, arts and crafts, newsletters, textiles, camps artifacts, yearbooks and other publications
Bulletin (Florin Japanese American Citizens League), no. 9 (May 23, 1942)
No full textNewsletter of the Florin chapter of the Japanese American Citizens League covering issues related to evacuation including "Farewell" by Mary Tsukamoto, an editorial by John S. Hirohata, advice for evacuees, inoculation, want ads, social welfare, extra rice, access to bank services, recognition of volunteers and individuals for their financial contributions, information about the newsletter, care of pets, treasurers report, and information about control stations. Newsletter labeled "Bulletin No. 9."The Japanese American Archival Collection documents the people, places, and daily life of Japanese Americans, primarily those who lived in the once thriving community of pre-war Florin in the Sacramento region, as well as the conditions in American incarceration camps during World War II. The approximately 7,000 original items include personal and official letters, photographs, diaries, arts and crafts, newsletters, textiles, camps artifacts, yearbooks and other publications
Florin Chapter of Japanese American Citizens League newsletter, April 24, 1942
No full textNewsletter of the Florin chapter of the Japanese American Citizens League covering issues related to incarceration including storage of personal items, members trained in first aid, care of pets, and address changes. Also includes a memorial statement for Hiroyuki [Kato] and recognition of individuals for their financial contributions.The Japanese American Archival Collection documents the people, places, and daily life of Japanese Americans, primarily those who lived in the once thriving community of pre-war Florin in the Sacramento region, as well as the conditions in American incarceration camps during World War II. The approximately 7,000 original items include personal and official letters, photographs, diaries, arts and crafts, newsletters, textiles, camps artifacts, yearbooks and other publications
Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material
No full textIt has been estimated that the noise levels in aircraft engine transmissions can be reduced by as much as 10 dB through the use of journal bearings. The potential benefits of lower noise levels include reduced wear, longer gear life and enhanced comfort for passengers and crew. Based on this concept the journal-thrust wave bearing was analyzed and its performance was evaluated. Numerical codes, developed over the past 30 years by Dr. Dimofte, were used to predict the performance of the bearing. The wave bearing is a fluid film bearing and therefore was analyzed using the Reynolds pressure equation. The formulation includes turbulent flow concepts and possesses a viscosity-temperature correction. The centrifugal growth of the bearing diameter and the deformation of the bearing under gear loads were also incorporated into the code. An experimental rig was developed to test the journal-thrust wave bearing
Investigation of Pressurized Wave Bearings
No full textThe wave bearing has been pioneered and developed by Dr. Dimofte over the past several years. This bearing will be the main focus of this research. It is believed that the wave bearing offers a number of advantages over the foil bearing, which is the bearing that NASA is currently pursuing for turbomachinery applications. The wave bearing is basically a journal bearing whose film thickness varies around the circumference approximately sinusoidally, with usually 3 or 4 waves. Being a rigid geometry bearing, it provides precise control of shaft centerlines. The wave profile also provides good load capacity and makes the bearing very stable. Manufacturing techniques have been devised that should allow the production of wave bearings almost as cheaply as conventional full-circular bearings
Prof. Florin Popenţiu - Vlădicescu
No full textDr. Florin POPENTIU VLÃDICESCU is at present an associated Professor to Department of Control Engineering and Industrial Informatics, University Politehnica of Bucharest and Co-Chairholder to UNESCO Chair in Information Technologies , University of Oradea. Following the approved Joint Council of Europe/UNESCO Convention on the recognition of qualifications concerning Higher Education in the European Region (Lisbon, 1997), Dr. Florin POPENTIU VLÃDICESCU has been appointed as UNESCO Chairholder , by City University London, at the beginning of the academic year 1998/1999. Dr. Florin POPENTIU VLÃDICESCU has been a Visiting Professor at: Telecom Paris, ENST Ecole Nationale Superieure des Mines Paris, ENSMP Ecole Nationale Superieure de Techniques Avancees, ENSTA ETH - Zurich Université Pierre et Marie Curie Paris, UPMC Delft University of Technology University of Twente Enschede Technical University of Denmark Lyngby Sultan Qaboos University University of Calcutta
He was a member of the Programme Committees for , ESREL\u27 95, \u2797 - \u2703 and \u2710 - \u2712 , held in UK, Portugal, Norway, Germany, Scotland, Italy and Holland, Czech Republic, Greece, France and Finland. Also he was a member of the Programme Committee for ISSAT RQD, 2007, 2014-2020 in Ho Chi Minth City, Vietnam, Washinton, Philadelphia , USA and Toronto, Canada, Las Vegas, Nevada,Miami,Florida USA , MA RS-2007-2012, 2014, 2019-2020 in Saint-Petersburg, Russia, WMSCI 2008-2012 in Orlando, Florida, USA , IADIS 2012, in Lisbon, Portugal MCCSIS 2013, held in Prague,Czech Republic, WBC 2014-2018, held Lisbon, Portugal, MCCSIS 2015and MCCSIS 2020 in Las Palmas de Gran Canaria, Spain and and Zagreb, Croatia BDM & CC 2013 , ICCD 2014, ICCD 2020 and ICCC 2016 held in Bhubaneswar , ISDA 2018 , Vellore , eHaCON 2019 Kolkata, India, ICIEECT 2017 , Karachi, IMTIC \u2715 , Mehran University, Jamshoro, iCOMET 2019 , Sukkur IBA University, Pakistan, VECoS 2015 and eLSE 2012-2020, held in Bucharest, Romania, ICDSBA 2018 , in ChangSha, Hunan, ICCD 2018 in Guangzhou, China, ICIM 2019-202o , held in Cambridge and London UK, ICIC 2019-20, Mohali, Punjab,India, ICITEE 2019, Changsha, Human, China, ICIII2020, Puket, Thailand, ICICV 2020, Jaipur, India, ICIII 2020, Osaka, Japan, MMBD 2020, Beijing, China.
He has been invited in October 2014 to joint Steering Committee for Erasmus Mundus Action 2 Leading Mobility between Europe and Asia in Developing Engineering Education and Research ( LEADERS) project as the representative of the University of Oradea, for the period 2014 - 2018.
Prof. Florin POPENTIU VLÃDICESCU has published over 100 papers in International Journals and Conference Proceedings and is author of one book and co-author of 4 books.
He has worked for many years on problems associated with software reliability and has been Co-Director of two NATO research projects involving collaboration with partner institutions throughout Europe. He is on advisory board of several international journals, Reliability: Theory & Applications , IJCS , ARIV and Microelectronics Reliability . He is reviewer for ACM Computing Reviews, Neural Computing and Applications , IJCSIS, and Associated Editor to IJICT .
Also he is a member of ENBIS, IEE, IEEE and IEEE Communications Society. Dr. Florin POPENTIU VLÃDICESCU was elected active member of The New York Academy of Science in 1996 and of the ARA in 2004. Also Dr. Florin POPENTIU has been elected Fellow of the Academy of Romanian Scientists in 2008.
He is EU Expert for the H2020 and ALL EU Programme. His Research ID is E-5787-2010. Also in 2009 he has been nominated UNESCO Expert in the field of Higher Education, Research and Knowledge.
Prof. Florin POPENTIU VLÃDICESCU is currently Visiting Professor at ParisTech which includes the Grandes Ecoles , The ATHENS Programme , where he teaches courses on Software Reliability. He also lectures on Software Reliability at International Master of Science in Computer Systems Engineering - Technical University of Denmark.
Prof. Florin POPENTIU VLÃDICESCU has been Keynote Speaker to ICCRT 2017 Karachi and iCOMET 2019 , Sukkur IBA University, Pakistan , ICCD 2018 in Guangzhou, China, , WICT 2018 in Kochi , ICIC 2018 in Mohali, Punjab, India.https://www.interscience.in/mentors/1055/thumbnail.jp
Wave Journal Bearing. Part 1: Analysis
No full textA wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance
A waved journal bearing concept with improved steady-state and dynamic performance
No full textAnalysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. A three wave, waved journal bearing geometry is used to show the geometry of this concept. The performance of generic waved bearings having either three, four, six, or eight waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of dynamic coefficients and fluid film stability. It was found that the bearing wave amplitude has an important influence on both steady-state and dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases. Also, the waved bearing becomes more stable as the wave amplitude increases. In addition, increasing the number of waves reduces the waved bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the waved bearing design for a specific application. It is concluded that the stiffness of an air bearing, due to the hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance
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