REVIEW—A Critical Review of Turbomachinery Noise

1977 ◽  
Vol 99 (2) ◽  
pp. 278-293 ◽  
Author(s):  
N. A. Cumpsty
Keyword(s):  
Critical Review ◽  
High Speed ◽  
Theoretical Models ◽  
Point Of View ◽  
Theory And Experiment

The review is written from the point of view of an engineer wanting to understand, reduce, and predict noise from turbomachines. In consequence knowledge gained by theory and, in particular, experiment is emphasized rather than the details of theoretical treatments. Attention is drawn to the surprisingly small interaction between theory and experiment and to the small amount of application that the theories have received. In describing the theoretical models it is the validity or applicability of their assumptions that is emphasized; despite the large number of theoretical treatments published the range of assumptions is quite small. Inevitably the review reflects the emphasis on funding for research by describing mainly high-speed, aeronautical turbomachinery noise. The overall conclusions drawn are rather depressing, with relatively little known even now about noise mechanisms for high speed machinery.

scholarly journals Theoretical Models of Teaching Creativity - Critical Review

2020 ◽  
Vol 7 (1) ◽  
pp. 54-72
Author(s):  
Krzysztof J. Szmidt ◽  
Anna Majewska-Owczarek
Keyword(s):  
Teaching Methods ◽  
Critical Review ◽  
Creative Thinking ◽  
Theoretical Models ◽  
Point Of View ◽  
Heuristic Model ◽  
Models Of Teaching

Abstract This paper is an attempt to present selected classifications of models of teaching creativity, which may have been found in literature over the last years. Models of teaching creativity are understood by the authors as well-developed systems of statements, based on a specific theory of creativity and concerning strategies and methods of teaching creative thinking and action, conditions of education, the role of a teacher in that process, and evaluation of education results. The paper describes several classifications of such models, including the authors’ own proposal, and presents a more detailed description of the heuristic model of teaching creativity. In the conclusion, the authors propose a thesis that the issue of methods of teaching creativity is open and the answer to the question about the best teaching methods in that obligation, which is interesting from the pedagogical point of view, should, as in the whole didactics, be answered by teachers, using their knowledge about creativity and its development.

scholarly journals Critical Review of the Methods to Measure the Condensed Systems Transient Regression Rate

2018 ◽  
Vol 20 (1) ◽  
pp. 45
Author(s):  
Vladimir Zarko
Keyword(s):  
Burning Rate ◽  
Critical Review ◽  
Energetic Materials ◽  
High Speed ◽  
Measurement Problem ◽  
Theoretical Models ◽  
Gas Generator ◽  
Regression Rate ◽  
High Speed Cinematography ◽  
Transient Burning Rate

Accurate knowledge of steady state and transient burning rate of solid fuels and energetic materials is very important for evaluating the performance of different propulsion and/or gas generator systems. The practical demands imply accuracy of available burning rate data on the level of 1% or better and proper temporal resolution. Unfortunately, existing theoretical models do not allow predicting the magnitude of the burning (regression) rate with needed accuracy. Therefore, numerous burning rate measurement methods have been developed by various research groups over the world in the past decades. This paper presents a critical review of existing techniques, including basic physical principles utilized for burning rate determination, an estimate of the temporal and spatial resolutions of the methods as well as their specific merits and limitations. There are known the methods for measuring linear regression rate via high speed cinematography, X-ray radiography and ultrasonic wave reflection technique. Actually, none of those methods could satisfy the practical demands. As an alternative is the microwave reflection method, which potentially possesses high spatial and temporal resolutions and may solve the measurement problem. In addition, there exist methods for measuring transient mass or weight of the burning material. They are based on recording the frequency of oscillations of elastic element with attached specimen or a cantilevered rod with a strain gauge pasted to the base. Practically, these methods could not provide needed accuracy. Much better parameters can be obtained when using the recoil force or microwave resonator techniques. Recommendations for special applications of certain methods are formulated.

scholarly journals A Critical Review of Supersonic Flow Control for High-Speed Applications

2021 ◽  
Vol 11 (15) ◽  
pp. 6899
Author(s):  
Abdul Aabid ◽  
Sher Afghan Khan ◽  
Muneer Baig
Keyword(s):  
Supersonic Flow ◽  
Flow Control ◽  
Active Control ◽  
Critical Review ◽  
High Speed ◽  
Passive Control ◽  
Control Method ◽  
Sudden Expansion ◽  
Control Approach ◽  
Cost Efficient

In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion duct. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent–divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems.

Comparison of the reluctance laminated and solid rotor synchronous machine operating at high temperatures

2019 ◽  
Vol 38 (4) ◽  
pp. 1111-1119 ◽  
Author(s):  
Marcin Lefik ◽  
Krzysztof Komeza ◽  
Ewa Napieralska-Juszczak ◽  
Daniel Roger ◽  
Piotr Andrzej Napieralski
Keyword(s):  
High Speed ◽  
Design Methodology ◽  
Three Dimensional ◽  
Synchronous Machine ◽  
Point Of View ◽  
Heat Sources ◽  
Model Calculations ◽  
Content Type ◽  
Thermal Phenomenon ◽  
Practical Implications

Purpose The purpose of this paper is to present a comparison between reluctance synchronous machine-enabling work at high internal temperature (HT° machine) with laminated and solid rotor. Design/methodology/approach To obtain heat sources for the thermal model, calculations of the electromagnetic field were made using the Opera 3D program including effect of rotation and the resulting eddy current losses. To analyse the thermal phenomenon, the 3D coupled thermal-fluid (CFD) model is used. Findings The presented results show clearly that laminated construction is much better from a point of view of efficiency and temperature. However, solid construction can be interesting for high speed machines due to their mechanical robustness. Research limitations/implications The main problem, despite the use of parallel calculations, is the long calculation time. Practical implications The obtained simulation and experimental results show the possibility of building a machine operating at a much higher ambient temperature than it was previously produced for example in the vicinity of the aircraft turbines. Originality/value The paper presents the application of fully three-dimensional coupled electromagnetic and thermal analysis of new machine constructions designed for elevated temperature.

Translation and interpretation in Abhidharmakośa

Diogenes ◽  
2021 ◽  
Vol 29 (2) ◽  
Author(s):  
Mitko Momov
Keyword(s):  
Critical Review ◽  
Point Of View ◽  
Literal Meaning ◽  
The Other ◽  
Young Scholar ◽  
Other Hand ◽  
The One

Rosemberg (1991) has made a critical review of a long-standing discussion between Eastern philologists and Buddhist philosophers. The discussion is centered around the translation of the doctrine on the one hand, and its philosophical systematization on the other hand. When scientific-philological translation prevails, the literal meaning of Buddhist terminology is declared to be its basis. The young scholar, who had specialized in Japan, studied Buddhism from Japanese and Chinese sources and collected lexicographic material from non-Hindu sources. After comparing them, he encountered inaccuracies in the translation. In an attempt to overcome them, he preferred the point of view of the philosophy of Buddhism. The conclusion that he has drawn in the preface of this edition is that the study should begin with a systematization of antiquity.

A Critical Review of Theories and Models of Technology Adoption and Acceptance in Information System Research

2015 ◽  
Vol 6 (4) ◽  
pp. 58-77 ◽  
Author(s):  
Ali Tarhini ◽  
Nalin Asanka Gamagedara Arachchilage ◽  
Ra'ed Masa'deh ◽  
Muhammad Sharif Abbasi
Keyword(s):  
Information System ◽  
Technology Adoption ◽  
Environmental Factors ◽  
Critical Review ◽  
Predictive Power ◽  
Theoretical Models ◽  
System Research ◽  
Information System Research ◽  
Individual Level ◽  
The Individual

Previous research shows that selecting an appropriate theory or model has always remained a critical task for IS researchers. To the best of the authors' knowledge, there are few papers that review and compare the acceptance theories and models at the individual level. Hence, this article aims to overcome this problem by providing a critical review of eight of the most influential theories that have been used to predict and explain human behaviour towards adoption of various technologies at the individual level. This article also summarizes their evolution; highlight the key constructs, extensions, strengths, and criticisms from a selective list of published articles appeared in the literature related to IS. This review provides a holistic picture for future researchers in selecting appropriate single/multiple theoretical models/constructs based on their strengths and weaknesses and in terms of predictive power and path significance. It is concluded that a well-established theory should consider the personal, social, cultural, technological, organizational and environmental factors

scholarly journals Capillary transfer of soft films

2020 ◽  
Vol 117 (10) ◽  
pp. 5210-5216 ◽  
Author(s):  
Yue Zhang ◽  
Mengtian Yin ◽  
Yongmin Baek ◽  
Kyusang Lee ◽  
Giovanni Zangari ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Analysis ◽  
Liquid Surface ◽  
Theoretical Models ◽  
Dynamic Contact ◽  
Surface Wetting ◽  
Motion Direction ◽  
Wetting Properties ◽  
Geometric Patterns ◽  
Solid Substrates

Existing transfer technologies in the construction of film-based electronics and devices are deeply established in the framework of native solid substrates. Here, we report a capillary approach that enables a fast, robust, and reliable transfer of soft films from liquid in a defect-free manner. This capillary transfer is underpinned by the transfer front of dynamic contact among receiver substrate, liquid, and film, and can be well controlled by a selectable motion direction of receiver substrates at a high speed. We demonstrate in extensive experiments, together with theoretical models and computational analysis, the robust capabilities of the capillary transfer using a versatile set of soft films with a broad material diversity of both film and liquid, surface-wetting properties, and complex geometric patterns of soft films onto various solid substrates in a deterministic manner.

scholarly journals New Dzungaria Gates for wmlt-corridor: historical necessity

2019 ◽  
Vol 5 (3) ◽  
pp. 36-44
Author(s):  
Viktor A. Bogachev ◽  
Yuri A. Terentyev ◽  
Viktor V. Koledov ◽  
Taras V. Bogachev
Keyword(s):  
Mathematical Models ◽  
Variational Methods ◽  
High Speed ◽  
Optimization Problem ◽  
Point Of View ◽  
The North ◽  
Computer Math ◽  
Pass Through ◽  
Historical Necessity ◽  
North Western

Background: Research is ongoing relating to the analysis of a set of issues that arise in connection with the creation of the operating on the basis of vacuum magnetic technologies a transcontinental high-speed land transport corridor, connecting the eastern regions of China with Russia. As part of the variation calculus task, the geopolitical, economic, social, logistic, geographic, geomorphological, seismological, topographic components of the project are considered, in which it is assumed that the high speed overland route will pass through the north-western part of the historical region of Dzungaria. Aim: Find the most optimal from the point of view of the above components the location of the most important section of high speed overland route passing through Central Asia. Methods: Variational methods for solving an optimization problem with the use of a computer math system. Results: After creating a fairly informative and versatile picture of the region in question, the foundations of the corresponding mathematical models are built. Conclusion: The New Dzungarian Gates is a key element in choosing the location of a high-speed overland route based on VMLT.

Object-Oriented Cognitive Complexity Measures

2017 ◽  
pp. 917-940
Author(s):  
Sanjay Misra ◽  
Adewole Adewumi
Keyword(s):  
Software Development ◽  
Comparative Study ◽  
Critical Review ◽  
Cognitive Complexity ◽  
Object Oriented ◽  
Point Of View ◽  
Complexity Measures ◽  
Cognitive Informatics ◽  
Validation Criteria ◽  
Object Oriented Metrics

This chapter presents the analysis of ten recently proposed object-oriented metrics based on cognitive informatics. The metrics based on cognitive informatics use cognitive weight. Cognitive weight is the representation of the understandability of the piece of software that evaluates the difficulty experienced in comprehending and/or performing the piece of software. Development of metrics based on Cognitive Informatics (CI) is a new area of research, and from this point of view, for the analysis of these metrics, it is important to know their acceptability from other existing evaluation and validation criteria. This chapter presents a critical review on existing object-oriented cognitive complexity measures. In addition, a comparative study based on some selected attributes is presented.

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