Stall, Surge and 75 Years of Research

2015 ◽  
Author(s):  
I. J. Day
Keyword(s):  
High Speed ◽  
Second World War ◽  
Rotating Stall ◽  
World War ◽  
Flow Modelling ◽  
Future Developments ◽  
Fields Of Study ◽  
Performance Predictions ◽  
Stage Matching ◽  
Second World

Work on rotating stall and its related disturbances has been in progress since the Second World War. During this period, certain ‘hot topics’ have come to the fore — mostly in response to pressing problems associated with new engine designs. This paper will take a semi-historical look at some of these fields of study (stall, surge, active control, rotating instabilities etc.) and will examine the ideas which underpin each topic. Good progress can be reported, but the paper will not be an unrestricted celebration of our successes because, after 75 years of research, we are still unable to predict the stalling behaviour of a new compressor or to contribute much to the design a more stall resistant machine. Looking forward from where we are today, it is clear that future developments will come from CFD in the form of better performance predictions, better flow modelling and improved interpretation of experimental results. It is also clear that future experimental work will be most effective when focussed on real compressors with real problems — such as stage matching, large tip clearances, eccentricity and service life degradation. Today’s topics of interest are mostly associated with compressible effects and so further research will require more high speed testing.

Stall, Surge, and 75 Years of Research

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
I. J. Day
Keyword(s):  
High Speed ◽  
Second World War ◽  
Rotating Stall ◽  
Flow Modeling ◽  
World War ◽  
Future Developments ◽  
Fields Of Study ◽  
Performance Predictions ◽  
Stage Matching ◽  
Second World

Work on rotating stall and its related disturbances have been in progress since the Second World War. During this period, certain “hot topics” have come to the fore—mostly in response to pressing problems associated with new engine designs. This paper will take a semihistorical look at some of these fields of study (stall, surge, active control, rotating instabilities, etc.) and will examine the ideas which underpin each topic. Good progress can be reported, but the paper will not be an unrestricted celebration of our successes because, after 75 years of research, we are still unable to predict the stalling behavior of a new compressor or to contribute much to the design of a more stall-resistant machine. Looking forward from where we are today, it is clear that future developments will come from CFD in the form of better performance predictions, better flow modeling, and improved interpretation of experimental results. It is also clear that future experimental work will be most effective when focussed on real compressors with real problems—such as stage matching, large tip clearances, eccentricity, and service life degradation. Today’s topics of interest are mostly associated with compressible effects and so further research will require more high-speed testing.

Art archives: a common concern of archivists, librarians, and museum professionals

1989 ◽  
Vol 14 (2) ◽  
pp. 5-11 ◽  
Author(s):  
Antje B. Lemke
Keyword(s):  
New Technologies ◽  
Second World War ◽  
Critical Approach ◽  
World War ◽  
Future Developments ◽  
Single Person ◽  
Museum Professionals ◽  
Original Works ◽  
Finding Aids ◽  
Second World

The preservation of artists’ papers and other art source material has steadily increased since the Second World War. Art archives include national repositories, archives attached to museums and libraries, archives devoted to a single person or institution, and ‘multiple collection archives’. Archival materials range from manuscript and photographic records to original works of art. Some archival materials have been published in microform formats; many others have not, and potential users depend on being able to locate them by means of various finding aids. Unless supported by public funds, the archives themselves depend on grants or sponsorship. Art archives may be staffed by archivists, museum curators, or librarians; future developments require not merely cooperation but also a ‘harmonization’ of these three professions, and a critical approach to the application of new technologies.

scholarly journals Prediction of COVID-19 epidemic situation via fine-tuned IndRNN

2021 ◽  
Vol 7 ◽  
pp. e770
Author(s):  
Zhonghua Hong ◽  
Ziyang Fan ◽  
Xiaohua Tong ◽  
Ruyan Zhou ◽  
Haiyan Pan ◽  
...  
Keyword(s):  
High Speed ◽  
Low Complexity ◽  
Development Trend ◽  
Second World War ◽  
Fine Tuning ◽  
World War ◽  
Link Type ◽  
Epidemic Development ◽  
Tuning Strategy ◽  
Second World

The COVID-19 pandemic is the most serious catastrophe since the Second World War. To predict the epidemic more accurately under the influence of policies, a framework based on Independently Recurrent Neural Network (IndRNN) with fine-tuning are proposed for predict the epidemic development trend of confirmed cases and deaths in the United Stated, India, Brazil, France, Russia, China, and the world to late May, 2021. The proposed framework consists of four main steps: data pre-processing, model pre-training and weight saving, the weight fine-tuning, trend predicting and validating. It is concluded that the proposed framework based on IndRNN and fine-tuning with high speed and low complexity, has great fitting and prediction performance. The applied fine-tuning strategy can effectively reduce the error by up to 20.94% and time cost. For most of the countries, the MAPEs of fine-tuned IndRNN model were less than 1.2%, the minimum MAPE and RMSE were 0.05%, and 1.17, respectively, by using Chinese deaths, during the testing phase. According to the prediction and validation results, the MAPEs of the proposed framework were less than 6.2% in most cases, and it generated lowest MAPE and RMSE values of 0.05% and 2.14, respectively, for deaths in China. Moreover, Policies that play an important role in the development of COVID-19 have been summarized. Timely and appropriate measures can greatly reduce the spread of COVID-19; untimely and inappropriate government policies, lax regulations, and insufficient public cooperation are the reasons for the aggravation of the epidemic situations. The code is available at https://github.com/zhhongsh/COVID19-Precdiction. And the prediction by IndRNN model with fine-tuning are now available online (http://47.117.160.245:8088/IndRNNPredict).

scholarly journals 1.2kW Interleaved synchronous buck converter design for aviation systems

2020 ◽  
Vol 314 ◽  
pp. 02005
Author(s):  
Eralp Sener ◽  
Isil Yazar ◽  
Gurhan Ertasgin ◽  
Hasan Yamık
Keyword(s):  
Second World War ◽  
Buck Converter ◽  
Loss Reduction ◽  
World War ◽  
Passive Element ◽  
Dc System ◽  
Future Developments ◽  
Civil Aircraft ◽  
Converter Design ◽  
Second World

The principal aim of this work is to design a battery-operated 1.2kW interleaved synchronous buck converter for aviation systems to obtain lower losses compared to the existing topologies. It is desired to achieve at least a 5% loss reduction. Military aircrafts such as F-22 and civil aircraft as Boeing 787 are using the 270V DC for their battery systems. Although 270V DC system has some advantages such as reducing loses and the passive element sizes, old avionics that have been designed, produced and used since the second world war may not be compatible with the 270V DC system. Conversion from 270V to 28V appears to be quite promising for both old and new systems. Therefore, a buck converter design for 270 to 28V conversion is proposed in this study to adapt older avionics technology to accommodate new achievements. The analysis of the SiC MOSFET based interleaved synchronous buck converter with a double loop PI controller is presented. The paper demonstrates the principles of the design and discusses possible future developments. The concept is verified using simulations.

scholarly journals Enzo Collotti e l'Europa del Novecento

2011 ◽  
Keyword(s):  
Twentieth Century ◽  
Second World War ◽  
World War ◽  
Fields Of Study ◽  
Historic Memory ◽  
Eastern Border ◽  
Second World

Emerging from a convention in honour of Enzo Collotti, this book traces his interests and fields of study. These gravitate around the tragic experiences of the Second World War, always played out in a perspective where the horizon is a Europe centred on Germany and on the lacerations that rippled out from Germany itself to embrace the entire continent with the consolidation of Nazism as a totalitarian power grounded in an ideology that was intrinsically reactionary and violently racist. There are six axes of investigation, closely intermeshed, addressed in the various contributions: socialism between the two wars; the lacerations of Germany; the European manifestations of Fascism; the experience of the Shoah, the construction of a shared historic memory of the dramas of the twentieth century and the problems of the Italian "eastern border".

Gender and the Second World War

2017 ◽  
Author(s):  
Corinna Peniston-Bird ◽  
Emma Vickers
Keyword(s):  
Second World War ◽  
World War ◽  
Second World
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