Review—Mechanisms of Cavitation Inception

1991 ◽  
Vol 113 (2) ◽  
pp. 163-175 ◽  
Author(s):  
E. P. Rood
Keyword(s):  
Pressure Field ◽  
Hydrodynamic Cavitation ◽  
Prediction Methods ◽  
Cavitation Inception ◽  
Physical Mechanisms ◽  
Bubble Cavitation ◽  
Passive Pressure ◽  
Flow Features ◽  
Physical Phenomena ◽  
Fundamental Physical

A review is made of progress in research during the period 1979–1989 on the fundamental physical mechanisms of hydrodynamic cavitation inception. During that decade identification of the physical phenomena has been made, and techniques have been developed to reproduce on laboratory scale selected forms of full scale cavitation inception. Understanding of the mechanisms remains shallow, and analytical/numerical prediction methods are nonexistent except for the restricted case of travelling bubble cavitation inception in a passive pressure field. The control of inception is seen to be related in part to control of the underlying viscous flow features. A growing body of experimental evidence points to microscale vortex cavitation as a primal inception event.

Focused Ion Beam Irradiation Induced Damages on CMOS and Bipolar Technologies

1998 ◽  
Author(s):  
J. Benbrik ◽  
G. Rolland ◽  
P. Perdu ◽  
B. Benteo ◽  
M. Casari ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Electronic Devices ◽  
Complete Characterization ◽  
Bipolar Transistors ◽  
Ion Beam Irradiation ◽  
Physical Mechanisms ◽  
Dc Characteristics ◽  
Electrical Degradation ◽  
Physical Phenomena

Abstract Focused Ion Beam is commonly used for IC repairs and modifications. However, FIB operation may also induce a damaging impact which can takes place far from the working area due to the charge-up phenomenon. A complete characterization joined to an in-depth understanding of the physical phenomena arising from FIB irradiation is therefore necessary to take into account spurious FIB induced effects and to enhance the success of FIB modifications. In this paper, we present the effects of FIB irradiation on the electrical DC performances of different electronic devices such as nMOS and pMOS transistors, CMOS inverters, PN junctions and bipolar transistors. From the observed behavior of the DC characteristics evolution of the devices, some suggestions about physical mechanisms inducing the electrical degradation are proposed.

Nonlinear Refractive Index of Silicon Nanoparticles: A Short Review

2014 ◽  
Vol 1 (2) ◽  
pp. 87-97
Author(s):  
Sudakshina Prusty
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Phase Modulation ◽  
Silicon Nanoparticles ◽  
Nonlinear Coefficient ◽  
Short Review ◽  
Self Phase Modulation ◽  
Physical Mechanisms ◽  
Self Focusing ◽  
Physical Phenomena

This article discusses the nonlinear refractive index of silicon nanoparticles starting from the basic formalism to some of the consequent physical phenomena like self focusing and self phase modulation. Several experimental techniques mainly based on Z-scan are discussed to measure the nonlinear refractive index. Another less explored technique for silicon nanoparticles, which studies the far-field optical fringe pattern formed by spatial self-phase modulation, is also discussed. Computation of the nonlinear refractive index is shown in detail by employing these two techniques. While Z-scan can estimate the nonlinear coefficient of a medium in a chosen time scale, the optical fringe method can predict the overall nonlinear refractive index due to all possible physical mechanisms. Some of the recent results for silicon nanoparticles using these two techniques are also discussed.

scholarly journals A new hybridization filtering-based linear-nonlinear models for time series forecasting

2021 ◽  
Author(s):  
Mehrnaz Ahmadi ◽  
◽  
Mehdi Khashei ◽  
Keyword(s):  
Hybrid Methods ◽  
Nonlinear Models ◽  
Prediction Methods ◽  
Short Term ◽  
Forecasting Methods ◽  
Primary Relationships ◽  
Time Dependencies ◽  
Physical Laws ◽  
Face Time ◽  
Physical Phenomena

In recent years, the idea of using a mathematical model to describe the behavior of physical phenomena has been very much considered. Specifically, a definitive model, based on physical laws, enables researchers to calculate the number of time dependencies precisely at any moment in time. However, in the real world, we often face time-dependent phenomena with many unknown or unavailable factors (Lindley, 2010; Roulston et al., 2003). In this case, when it is not possible to achieve a definite - model, the prediction methods are wide used, especially when the past observations of a variable and primary relationships between specific observations are available. Forecasting methods that are used in different fields of science can be categorized based on various aspects. For example, the prediction methods used in the field of wind energy can be divided into four categories of 1) ultra short term (several seconds to four hours), 2) short term (4 to 24 hours), 3) medium-term (1 to 7 days), and 4) long term (more than 7 days) (Zack, 2003; Soman et al., 2010). Also, the structure of forecasting methods can be divided into two types of 1) single methods and 2) hybrid methods. Each of these categories can also be subdivided into smaller subgroups.

Study on reconstruction and prediction methods of pressure field on blade surfaces for oil-filling process in a hydrodynamic retarder

2016 ◽  
Vol 26 (6) ◽  
pp. 1843-1870 ◽  
Author(s):  
Hongbin Mu ◽  
Wei Wei ◽  
Alexandrina Untaroiu ◽  
Qingdong Yan
Keyword(s):  
Numerical Method ◽  
Pressure Field ◽  
Structural Features ◽  
Accurate Prediction ◽  
Dynamics Simulation ◽  
Prediction Methods ◽  
Flow Data ◽  
Transient Pressure ◽  
Filling Process ◽  
Content Type

Purpose – Traditional three-dimensional numerical methods require a long time for transient computational fluid dynamics simulation on oil-filling process of hydrodynamic braking. The purpose of this paper is to investigate reconstruction and prediction methods for the pressure field on blade surfaces to explore an accurate and rapid numerical method to solve transient internal flow in a hydrodynamic retarder. Design/methodology/approach – Dynamic braking performance for the oil-filling process was simulated and validated using experimental results. With the proper orthogonal decomposition (POD) method, the dominant modes of transient pressure distribution on blades were extracted using their spatio-temporal structural features from the knowledge of computed flow data. Pressure field on blades was reconstructed. Based on the approximate model (AM), transient pressure field on blades was predicted in combination with POD. The causes of reconstruction and prediction error were, respectively, analyzed. Findings – Results show that reconstruction with only a few dominant POD modes could represent all flow samples with high accuracy. POD method demonstrates an efficient simplification for accurate prediction of the instantaneous variation of pressure field in a hydrodynamic retarder, especially at the stage of high oil-filling rate. Originality/value – The paper presents a novel numerical method, which combines POD and AM approaches for rapid and accurate prediction of braking characteristics during the oil-filling period, based on the knowledge of computed flow data.

Towards the concept of hydrodynamic cavitation control

1997 ◽  
Vol 332 ◽  
pp. 377-394 ◽  
Author(s):  
Dhiman Chatterjee ◽  
Vijay H. Arakeri
Keyword(s):  
Acoustic Field ◽  
Bubble Dynamics ◽  
Hydrodynamic Cavitation ◽  
Careful Study ◽  
Potential Control ◽  
Cavitation Phenomenon ◽  
Bubble Cavitation ◽  
First Results ◽  
Hydrodynamic Field ◽  
Pass Through

A careful study of the existing literature available in the field of cavitation reveals the potential of ultrasonics as a tool for controlling and, if possible, eliminating certain types of hydrodynamic cavitation through the manipulation of nuclei size present in a flow. A glass venturi is taken to be an ideal device to study the cavitation phenomenon at its throat and its potential control. A piezoelectric transducer, driven at the crystal resonant frequency, is used to generate an acoustic pressure field and is termed an ‘ultrasonic nuclei manipulator (UNM)'. Electrolysis bubbles serve as artificial nuclei to produce travelling bubble cavitation at the venturi throat in the absence of a UNM but this cavitation is completely eliminated when a UNM is operative. This is made possible because the nuclei, which pass through the acoustic field first, cavitate, collapse violently and perhaps fragment and go into dissolution before reaching the venturi throat. Thus, the potential nuclei for travelling bubble cavitation at the venturi throat seem to be systematically destroyed through acoustic cavitation near the UNM. From the solution to the bubble dynamics equation, it has been shown that the potential energy of a bubble at its maximum radius due to an acoustic field is negligible compared to that for the hydrodynamic field. Hence, even though the control of hydrodynamic macro cavitation achieved in this way is at the expense of acoustic micro cavitation, it can still be considered to be a significant gain. These are some of the first results in this direction.

scholarly journals Mathematical modeling of the impact of forest fires on buildings and structures

2018 ◽  
Vol 209 ◽  
pp. 00021
Author(s):  
Valeriy Perminov ◽  
Victoria Marzaeva
Keyword(s):  
Mathematical Modeling ◽  
Forest Fire ◽  
Forest Fires ◽  
Fire Behavior ◽  
Fire Intensity ◽  
Physical Mechanisms ◽  
Important Concern ◽  
Fire Initiation ◽  
The Impact ◽  
Fundamental Physical

The protection of buildings and structures in a community from destruction by forest fires is a very important concern. This paper addresses the development of a mathematical model for fires in the wildland-urban intermix. The forest fire is a very complicated phenomenon. At present, fire services can forecast the danger rating of, or the specific weather elements relating to, forest fire. There is need to understand and predict forest fire initiation, behavior and impact of fire on the buildings and constructions. This paper’s purposes are the improvement of knowledge on the fundamental physical mechanisms that control forest fire behavior. The mathematical modeling of forest fires actions on buildings and structures has been carried out to study the effects of fire intensity and wind speed on possibility of ignition of buildings.

Optically Induced Electrohydrodynamics and Electrokinetic Colloidal Aggregation

2009 ◽  
Author(s):  
Stuart J. Williams ◽  
Aloke Kumar ◽  
Steven T. Wereley
Keyword(s):  
Laser Beam ◽  
Electrode Surface ◽  
Parallel Plate ◽  
Near Infrared ◽  
Lab On A Chip ◽  
Particle Manipulation ◽  
Colloidal Aggregation ◽  
Physical Mechanisms ◽  
Fundamental Physical ◽  
Optically Induced

Recently, we have demonstrated a novel optically induced AC electrokinetic technique that rapidly, continuously and selectively concentrates micro and nanoparticles on an electrode surface [1–3]. This is demonstrated with a highly focused near-infrared (1,064 nm) laser beam applied to parallel plate electrodes separated by 50 μm without the need for photosensitive materials. This dynamic optically-induced technique can be applied towards a variety of lab-on-a-chip applications. This paper will explain the fundamental physical mechanisms involved, necessary in order to replicate and implement this technique. This dynamic fluid and particle manipulation technique may prove valuable to a variety of applications in micro- and nanotechnology.

scholarly journals A bird's-eye view on turbulence: seabird foraging associations with evolving surface flow features

2021 ◽  
Vol 288 (1949) ◽  
Author(s):  
Lilian Lieber ◽  
Roland Langrock ◽  
W. Alex M. Nimmo-Smith
Keyword(s):  
Markov Model ◽  
Foraging Ecology ◽  
Hidden Markov ◽  
Surface Flow ◽  
Coastal Change ◽  
Physical Mechanisms ◽  
Flow Features ◽  
Evolving Surface ◽  
In Transit ◽  
Foraging Associations

Understanding physical mechanisms underlying seabird foraging is fundamental to predict responses to coastal change. For instance, turbulence in the water arising from natural or anthropogenic structures can affect foraging opportunities in tidal seas. Yet, identifying ecologically important localized turbulence features (e.g. upwellings approximately 10–100 m) is limited by observational scale, and this knowledge gap is magnified in volatile predators. Here, using a drone-based approach, we present the tracking of surface-foraging terns (143 trajectories belonging to three tern species) and dynamic turbulent surface flow features in synchrony. We thereby provide the earliest evidence that localized turbulence features can present physical foraging cues. Incorporating evolving vorticity and upwelling features within a hidden Markov model, we show that terns were more likely to actively forage as the strength of the underlying vorticity feature increased, while conspicuous upwellings ahead of the flight path presented a strong physical cue to stay in transit behaviour. This clearly encapsulates the importance of prevalent turbulence features as localized foraging cues. Our quantitative approach therefore offers the opportunity to unlock knowledge gaps in seabird sensory and foraging ecology on hitherto unobtainable scales. Finally, it lays the foundation to predict responses to coastal change to inform sustainable ocean development.

Physical basis of measurements and standards

2017 ◽  
Author(s):  
Афанасьев ◽  
Aleksandr Afanas'ev ◽  
Погонин ◽  
Anatoliy Pogonin
Keyword(s):  
Uncertainty Relation ◽  
Fundamental Physical Constants ◽  
Reference Base ◽  
Measurement Systems ◽  
The World ◽  
Heisenberg Uncertainty ◽  
The Stability ◽  
Physical Phenomena ◽  
Fundamental Physical ◽  
Principle Of Complementarity

The manual presents elements of the theory of similarity and dimensions, presents concepts of classical measurement systems, elements of the modern physical picture of the world, stability of fundamental physical constants. The Heisenberg uncertainty relation, the principle of complementarity, the principles of creating a modern reference base based on the stability of micro-world objects, the essence of physical phenomena and effects, and the physical foundations of measuring con-verters in engineering are con-sidered.

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