Detachment Criterion for Static Axisymmetric Bubbles on Horizontal Flat Surfaces

2009 ◽  
Author(s):  
Shong-Leih Lee ◽  
Chao-Fu Yang
Keyword(s):  
Contact Area ◽  
Contact Angles ◽  
Maximum Volume ◽  
Flat Surfaces ◽  
Bubble Detachment ◽  
Numerical Result ◽  
Detachment Criterion ◽  
The Stability ◽  
The Many ◽  
Maximum Contact

The static Young-Laplace equation is solved with the geometry method to yield the bubble shape on a horizontal flat surface under various contact angles. Multi-solution modes are found. Among the many possible equilibrium shapes of the bubble, however, only the fundamental solution mode could occur naturally. The value of VAR (volume to contact area ratio) could be a good measure for stability of equilibrium bubbles. The bubble becomes less stable when VAR increases. The numerical result reveals that in the course of bubble growth (i.e. volume increases) the VAR of the bubble increases linearly until the maximum contact area is reached. After that, VAR has a sharp increase due to a decreasing contact area. Beyond the maximum volume, equilibrium bubble does not seem possible. Based on the finding, it is postulated that bubble detachment occurs somewhere between the maximum contact area and the maximum volume according to perturbations from environment. However, the postulation seems to underestimate the stability of the bubble significantly for contact angles of larger than 160 degrees. A correction is proposed in the paper. Numerical result of bubble detachment criterion is fitted with polynomial functions of the contact angle.

The stability of pendent liquid drops. Part 2. Axial symmetry

1974 ◽  
Vol 63 (3) ◽  
pp. 487-508 ◽  
Author(s):  
E. Pitts
Keyword(s):  
Surface Tension ◽  
Energy Change ◽  
Maximum Volume ◽  
Experimental Conditions ◽  
Liquid Drops ◽  
Stable Equilibria ◽  
Equilibrium Shapes ◽  
The Stability ◽  
The Many ◽  
Horizontal Support

In a drop of liquid which hangs below a horizontal support or a t the end of a tube, the forces due to surface tension, pressure and gravity are in equilibrium. Amongst the many possible equilibrium shapes of the drop, only those which are stable occur naturally. The calculus of variations has been used to determine theoretically the stable equilibria, by calculating the energy change when the liquid in equilibrium experiences axially symmetrical perturbations under physically realistic constraints. If the energy change can be made negative, the drop is unstable. With this criterion, stable equilibria have been identified through which the naturally growing drops evolve until they reach a maximum volume, when they become unstable. These results are illustrated by calculations relating to typical experimental conditions.

Experimental and Theoretical Study of the Contact Mechanics of Five Total Knee Joint Replacements

1995 ◽  
Vol 209 (4) ◽  
pp. 225-231 ◽  
Author(s):  
T Stewart ◽  
Z M Jin ◽  
D Shaw ◽  
D D Auger ◽  
M Stone ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Knee Joint ◽  
Contact Pressure ◽  
Contact Stress ◽  
Linear Elasticity ◽  
Contact Area ◽  
Elasticity Analysis ◽  
Joint Replacements ◽  
Total Knee ◽  
Maximum Contact

The tibio-femoral contact area in five current popular total knee joint replacements has been measured using pressure-sensitive film under a normal load of 2.5 kN and at several angles of flexion The corresponding maximum contact pressure has been estimated from the measured contact areas and found to exceed the point at which plastic deformation is expected in the ultra-high molecular weight polyethylene (UHMWPE) component particularly at flexion angles near 90°. The measured contact area and the estimated maximum contact stress have been found to be similar in magnitude for all of the five knee joint replacements tested. A significant difference, however, has been found in maximum contact pressure predicted from linear elasticity analysis for the different knee joints. This indicates that varying amounts of plastic deformation occurred in the polyethylene component in the different knee designs. It is important to know the extent of damage as knees with large amounts of plastic deformation are more likely to suffer low cycle fatigue failure. It is therefore concluded that the measurement of contact areas alone can be misleading in the design of and deformation in total knee joint replacements. It is important to modify geometries to reduce the maximum contact stress as predicted from the linear elasticity analysis, to below the linear elastic limit of the plastic component.

Consumer Behavior Changes Post Pandemic Covid-19

2020 ◽  
Vol 2 (2) ◽  
pp. 84-89
Author(s):  
Tati Maryati
Keyword(s):  
Consumer Behavior ◽  
Eating Habits ◽  
Supply And Demand ◽  
Health Economy ◽  
Behavior Changes ◽  
The World ◽  
The Stability ◽  
The Many ◽  
New Consumer ◽  
At Home

The Corona virus or Covid-19 which is unexpected will come to us, has an impact on health, economy and also humanity throughout the world and is able to fundamentally change the world. Supplements are disrupted because production is stopped, retail stores close, causing consumers to change their behavior, which had previously gone offline shopping. Not just shopping, when a pandemic, the way of thinking becomes different. Consumers around the world are looking for products and brands through new ways and new habits are formed. Online transactions focus more on basic products to make ends meet. The fact that Covid-19's anti-virus has not been found raises concerns about disrupted health and the Government's regulation to work and stay at home also raises concerns about disrupted businesses. Differences from habits and interests or preferences that are different for each person, provide different responses to the problems faced and solutions for the future. The habit of shopping offline has a tendency to continue for complementary products while food products are more directed towards offline. The rest eating habits at home can be continued because it provides more hygiene guarantees. The new habit of holding online meetings with distant relatives or colleagues will be increasingly considered given the many more positive things that can be obtained. Likewise with work problems, working from home is more interesting to consider because it is more efficient and effective and the results can be more productive. This new consumer behavior is adjusted to provide satisfaction for many parties, with the assistance of institutions or governments that oversee the security of supply and demand and maintain the stability of both. 

Coating of Particles in Spouted Bed: Flow Regime and Stability

2010 ◽  
Vol 660-661 ◽  
pp. 573-579
Author(s):  
J.L. Vieira Neto ◽  
J.E. Borges ◽  
Claudio Roberto Duarte ◽  
Marcos A.S. Barrozo
Keyword(s):  
Power Spectrum ◽  
Pressure Fluctuations ◽  
Flow Regimes ◽  
Main Flow ◽  
Agricultural Products ◽  
Soybean Seeds ◽  
Spouted Bed ◽  
Cyclical Motion ◽  
The Stability ◽  
The Many

The coating and encapsulating of particles presents many applications in the chemical, pharmaceutical, food and agricultural products industries. Among the many applications of seeds coating, the enlargement of small seeds is included in order to facilitate the planting, the addition of herbicides, fungicides, fertilizers, micronutrients and inoculation. The spouted bed has often been used in studies related to the coating of particles, due to the cyclical motion of the material, which promotes a fast axial mixture of particles and an excellent gas-particle contact. In this work, the coating of soybean seeds with inoculum and micronutrients in spouted bed has been studied. The different flow regimes were investigated using the pressure fluctuations and power spectrum. The results of the present work showed that it was possible to identify the main flow regimes and to analyze the influence of the coating in the stability of those regimes.

scholarly journals NECESSITY TO IMPROVE THE MATHEMATICAL MODEL OF FREIGHT CARS TO STUDY CASES OF ITS DERAILMENTS

2020 ◽  
pp. 442-451
Author(s):  
А.V. Batig ◽  
A. Ya. Kuzyshyn
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
Computer Experiment ◽  
Rolling Stock ◽  
Software Systems ◽  
Freight Car ◽  
The Stability ◽  
The Many ◽  
The Impact ◽  
The Mathematical Model

One of the most important problems that pose a serious threat to the functioning of railways is the problem of freight cars derailment. However, according to statistics, the number of cases of the derailments of freight cars in trains annually grows. Тo prevent such cases, the necessary preventive measures are developed, and to study the causes of their occurrence, a significant number of mathematical models, programs and software systems created by leading domestic and foreign scientists. Studies of such mathematical models by the authors of this work have led to the conclusion that they are not sufficiently detailed to the extent that it is necessary for analyze the reasons of its derailment. At the same time, an analysis of the causes of the rolling stock derailments on the railways of Ukraine over the past five years showed that in about 20 % of cases they are obvious, and in 7 % of cases they are not obvious and implicitly expressed. The study of such cases of rolling stock derailment during an official investigation by the railway and during forensic railway transport expertises requires the use of an improved mathematical model of a freight car, which would allow a quantitative assessment of the impact of its parameters and rail track on the conditions of railway accidents. Therefore, taking into account the main reasons that caused the occurrence of such railroad accidents over the last five years on the railways of Ukraine, the article selected the main directions for improving the mathematical model of a freight car, allowing to cover all the many factors (explicit and hidden) and identify the most significant ones regarding the circumstances of the derailment rolling stock off the track, established on the basis of a computer experiment. It is proposed in the mathematical model of a freight car to take into account the guiding force, the value of which is one of the main indicators of the stability of the rolling stock. The authors of the article noted that not taking into account the influence of the guiding forces on the dynamics of the freight car can lead to an erroneous determination of the reasons for the rolling stock derailment or even to the impossibility of establishing them.

scholarly journals Non-Hermitian physics for optical manipulation uncovers inherent instability of large clusters

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xiao Li ◽  
Yineng Liu ◽  
Zhifang Lin ◽  
Jack Ng ◽  
C. T. Chan
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Optical Forces ◽  
Exceptional Points ◽  
Complex Eigenvalues ◽  
Microscopic World ◽  
The Stability ◽  
The Many ◽  
Large Clusters ◽  
Conventional Systems

AbstractIntense light traps and binds small particles, offering unique control to the microscopic world. With incoming illumination and radiative losses, optical forces are inherently nonconservative, thus non-Hermitian. Contrary to conventional systems, the operator governing time evolution is real and asymmetric (i.e., non-Hermitian), which inevitably yield complex eigenvalues when driven beyond the exceptional points, where light pumps in energy that eventually “melts” the light-bound structures. Surprisingly, unstable complex eigenvalues are prevalent for clusters with ~10 or more particles, and in the many-particle limit, their presence is inevitable. As such, optical forces alone fail to bind a large cluster. Our conclusion does not contradict with the observation of large optically-bound cluster in a fluid, where the ambient damping can take away the excess energy and restore the stability. The non-Hermitian theory overturns the understanding of optical trapping and binding, and unveils the critical role played by non-Hermiticity and exceptional points, paving the way for large-scale manipulation.

Wetting Behavior and Drainage of Water Droplets on Microgrooved Brass Surface

2011 ◽  
Author(s):  
M. A. Rahman ◽  
A. M. Jacobi
Keyword(s):  
Aspect Ratio ◽  
End Milling ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Milling Process ◽  
Water Droplets ◽  
Sliding Angle ◽  
Flat Surfaces ◽  
Micro End Milling ◽  
Water Drops

In the present study, we report the contact angle hysteresis and drainage behavior of water drops on a number of brass surfaces with parallel microgrooves and compare them to the flat baseline surfaces. Parallel micro-grooves with different groove dimensions are fabricated by micro end-milling process without any modification of the surface chemistry. Advancing and receding contact angles in both parallel and perpendicular direction of the grooves and also the drainage behavior of water droplets on the microgrooved surfaces is found to be considerably affected by change in groove geometry parameters. Very high hysteresis is observed for both low (< 0.2) and high aspect ratio (> 0.7) of grooves and also for surfaces with lower groove spacing due to the droplets being in a Wenzel state. For intermediate aspect ratio (0.25–0.70) and larger spacing of the grooves, droplets remain in a Cassie state and the hysteresis is lower in both directions than that on the flat surfaces. Variation of critical sliding angle (angle at the point of incipient sliding of water droplets due to gravity) with groove geometry is investigated for a range of water droplet volume of 15 to 75 μl. Droplets of all volumes are found to slide much more readily on grooved surfaces than when placed on the flat baseline surfaces. Height and spacing of the grooves are also found to have significant influence on the sliding of the water droplets, as critical inclination angle decreased with groove height and increased with groove spacing. The results from this study may be useful in a broad range of applications where water retention plays an important role.

scholarly journals The General Factor of Psychopathology

2020 ◽  
Vol 16 (1) ◽  
pp. 75-98 ◽  
Author(s):  
Gregory T. Smith ◽  
Emily A. Atkinson ◽  
Heather A. Davis ◽  
Elizabeth N. Riley ◽  
Joshua R. Oltmanns
Keyword(s):  
Mental Health Treatment ◽  
Full Range ◽  
Empirical Support ◽  
Strong Relationship ◽  
General Factor ◽  
General Factor Of Personality ◽  
The Stability ◽  
The Many ◽  
P Factor ◽  
Empirical Approaches

An important advance in understanding and defining mental disorders has been the development of empirical approaches to mapping dimensions of dysfunction and their interrelatedness. Such empirical approaches have consistently observed intercorrelations among the many forms of psychopathology, leading to the identification of a general factor of psychopathology (the p factor). In this article, we review empirical support for p, including evidence for the stability and criterion validity of p. Further, we discuss the strong relationship between p and both the general factor of personality and the general factor of personality disorder, substantive interpretations of p, and the potential clinical utility of p. We posit that proposed substantive interpretations of p do not explain the full range of symptomatology typically included in p. The most plausible explanation is that p represents an index of impairment that has the potential to inform the duration and intensity of a client's mental health treatment.

Numerical Determination of the Response of a Linear Vibration System With a Singular Mass Matrix

1972 ◽  
Vol 94 (1) ◽  
pp. 64-69
Author(s):  
K. D. Willmert
Keyword(s):  
Multistep Methods ◽  
Mass Matrix ◽  
Linear Equations ◽  
Coefficient Matrix ◽  
Vibrational System ◽  
Wide Range ◽  
Mass Matrices ◽  
The Stability ◽  
The Many

In numerically determining the response of a linear second-order multidegree-of-freedom vibrational system subjected to a general excitation, the common approach of applying one of the many multistep methods of numerical analysis (e.g., Milne-Simpson, Adams-Bashforth, etc.) leads ultimately to the solution of a system of linear equations. However, when the mass matrix of the original vibrational system is singular, the coefficient matrix of the system of equations also becomes singular and thus the response cannot be determined. Presented is a means of applying these multistep methods to vibrational systems which results in a method that is capable of obtaining the response independent of the singularity of the mass matrix. This technique is particularly useful in optimization where the values of the parameters of the system are unknown in advance, and thus the method of determining the response must be applicable for a wide range of values of the parameters. In the development and investigation of this technique, the causes of the stability problems which develop from the application of multistep methods to systems with nearly singular mass matrices become apparent.

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