Boundary Conditions for a Traveling Web Detaching From a Rotating Cylinder

2000 ◽  
Author(s):  
Christoph G. Reuter
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Wave Speed ◽  
Adhesion Forces ◽  
Plastic Foil ◽  
Mechanical Models ◽  
Simple Support ◽  
Eye Examination ◽  
Almost All ◽  
The Web

Abstract High speed traveling webs appear in a number of technical applications such as plastic foil or paper production machinery and printing machines. Almost all mechanical models for the dynamic behaviour used so far, assume simple support boundary conditions. In reality, in the case of two-dimensional webs immersed in a viscous fluid, a low pressure zone will be present under the web near the point where the web detaches from the rotating drum. Other effects such as adhesion forces may also contribute. Thus, as can often also be seen already by naked-eye examination, the web does not detach tangentially from the drum. In this paper a mechanical model for small amplitude vibrations of a traveling web with small sag is developed, which takes into account the effect of the above described upstream boundary condition. The web is modeled as a one-dimensional heavy string without bending stiffness. The assumption of quasi-static stretching is made, i.e. infinitely high wave speed is assumed for longitudinal waves.

scholarly journals Development of safety monitor from destructive influences of web–sites and social networks of internet

2021 ◽  
Vol 273 ◽  
pp. 08046
Author(s):  
Larisa Cherckesova ◽  
Alexandr Zelensky ◽  
Elena Revyakina ◽  
Olga Safaryan ◽  
Denis Korochentsev
Keyword(s):  
Social Networks ◽  
Programming Language ◽  
Web Sites ◽  
High Speed ◽  
Parental Control ◽  
The Internet ◽  
Age Related ◽  
Security Monitor ◽  
Almost All ◽  
The Web

This article discusses the main age-related features of the Internet use by adolescents and children. Today more and more computers are connected to the Internet. At the same time, connection via high-speed channels is becoming more common, both at work and at home. More and more children get the opportunity to work on the Internet. But at the same time, the problem of ensuring the safety of children on the Internet is becoming more acute. For this, a security monitor was developed, which has many functions that allow you to use the Internet more safely and under parental control. This security monitor is written in the web programming language JavaScript and PHP, which will allow using the system on almost all modern browsers and on any computer. The article also provides screenshots of the program's operation and a flowchart with a detailed description.

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

The C-start escape response ofPolypterus senegalus: bilateral muscle activity and variation during stage 1 and 2

2002 ◽  
Vol 205 (17) ◽  
pp. 2591-2603 ◽  
Author(s):  
Eric D. Tytell ◽  
George V. Lauder
Keyword(s):  
Muscle Activity ◽  
Escape Response ◽  
High Speed ◽  
Wave Speed ◽  
Activity Patterns ◽  
Motor Pattern ◽  
The Body ◽  
Wide Range ◽  
Fast Start ◽  
Stage 1

SUMMARYThe fast-start escape response is the primary reflexive escape mechanism in a wide phylogenetic range of fishes. To add detail to previously reported novel muscle activity patterns during the escape response of the bichir, Polypterus, we analyzed escape kinematics and muscle activity patterns in Polypterus senegalus using high-speed video and electromyography (EMG). Five fish were filmed at 250 Hz while synchronously recording white muscle activity at five sites on both sides of the body simultaneously (10 sites in total). Body wave speed and center of mass velocity, acceleration and curvature were calculated from digitized outlines. Six EMG variables per channel were also measured to characterize the motor pattern. P. senegalus shows a wide range of activity patterns, from very strong responses, in which the head often touched the tail, to very weak responses. This variation in strength is significantly correlated with the stimulus and is mechanically driven by changes in stage 1 muscle activity duration. Besides these changes in duration, the stage 1 muscle activity is unusual because it has strong bilateral activity, although the observed contralateral activity is significantly weaker and shorter in duration than ipsilateral activity. Bilateral activity may stiffen the body, but it does so by a constant amount over the variation we observed; therefore, P. senegalus does not modulate fast-start wave speed by changing body stiffness. Escape responses almost always have stage 2 contralateral muscle activity, often only in the anterior third of the body. The magnitude of the stage 2 activity is the primary predictor of final escape velocity.

The Bionic Vibration Damping Technology and its Inspiration for the High Speed Milling Cutter

2012 ◽  
Vol 226-228 ◽  
pp. 98-101
Author(s):  
Hong Qing Lv ◽  
Wei Xiao Tang ◽  
Qing Hua Song ◽  
Shan Shan Sun
Keyword(s):  
Vibration Control ◽  
High Speed ◽  
Vibration Damping ◽  
Control Technology ◽  
Ambient Vibrations ◽  
Milling Cutter ◽  
High Speed Milling ◽  
Important Concept ◽  
Good Ability ◽  
Mechanical Models

A review of research on the vibration control technology inspiration from the biological vibration damping mechanisms is described. First the important concept and background of the bionic vibration damping technology are briefly introduced. Then the basic theories and its applications in the engineering fields are elaborated from three aspects: vibration damping mechanisms of the creatures own the good ability to withstand the ambient vibrations, mechanical models of biological prototypes and its application progress in the practical occasions.

scholarly journals World Experience in Creating Mathematical Models of Air Springs: Advantages and Disadvantages

2021 ◽  
pp. 25-42
Author(s):  
A. Y Kuzyshyn ◽  
S. A Kostritsia ◽  
Yu. H Sobolevska ◽  
А. V Batih
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Mathematical Models ◽  
Dynamic Behavior ◽  
High Speed ◽  
Vertical Direction ◽  
Rolling Stock ◽  
Air Spring ◽  
Advantages And Disadvantages ◽  
Mechanical Models

Purpose. Taking into account the production and commissioning of modern high-speed rolling stock, the authors are aimed to analyze the currently created mathematical models describing the dynamic behavior of the air spring, systematize them and consider the advantages and disadvantages of each model type. Methodology. For the analysis, a comparative chronological method was used, which makes it possible to trace the development of several points of view, concepts, theories. In accordance with the adopted decision equations, the existing models of air springs were divided into three groups: mechanical, thermodynamic and finite-elements. When analyzing mathematical models, the influence of a number of parameters on the dynamic behavior of the air spring, such as disturbing force frequency, heat transfer, nonlinear characteristics of materials, the shape of the membrane, etc., was considered. Findings. A feature of mechanical models is the determination of input parameters based on the analysis of experimental results, requires access to complex measuring equipment and must be performed for each new model of an air spring separately. Unlike mechanical models, which allow taking into account the damping effect of an air spring in the horizontal and vertical direction, thermodynamic models are mainly focused on studying the dynamic behavior of an air spring in the vertical direction. The use of the finite element method makes it possible to most accurately reproduce the dynamic behavior of an air spring, however, it requires significant expenditures of time and effort to create a finite element model and perform calculations. Originality. Mathematical models of the dynamic behavior of an air spring are systematized, and the importance of their study in conjunction with a spatial mathematical model of high-speed rolling stock is emphasized. Practical value. The analysis of the mathematical models of the dynamic behavior of the air spring shows the ways of their further improvement, indicates the possibility of their use in the spatial mathematical model of the rolling stock in accordance with the tasks set. It will allow, even at the design stage of high-speed rolling stock, to evaluate its dynamic characteristic and traffic safety indicators when interacting with a railway track.

scholarly journals New Physics II: Spin Picture, Particle Structure, and Fundamental Interactions

2021 ◽  
Author(s):  
China Kang
Keyword(s):  
High Speed ◽  
New Physics ◽  
Particle Structure ◽  
Classical Counterpart ◽  
Fundamental Interactions ◽  
Wave Particle Duality ◽  
Theory Of Everything ◽  
Vorticity Flux ◽  
Quantum Phenomena ◽  
Almost All

Abstract Experimental data sometimes fails to render the expected truth, such as high-speed bullets smashing into pieces on a water surface cannot verify the water’s hardness. By re-examining the essence underneath quantum phenomena and analyzing their relevance to universal classical theory, this study has thoroughly revealed the classical counterpart of spin. Subsequently, the equivalence between spin angular momentum (of energy or charge) and vorticity flux (of energy or charge) has also been unveiled, thus intuitively clarifying many abstruse physical concepts, like spin magnetic moment, virtual electron, relativistic time dilation, neutrino chirality, quark origin, and fundamental interactions (including gravitons). From now on, almost all quantum puzzles (e.g., wave-particle duality, quantum entanglement, Schrödinger’s cat) can be understood classically, just as prominent physicists such as Planck, Einstein, and Schrödinger longed for back then. This paper can be considered a blueprint of the Theory of Everything (TOE).

System Dynamics of the Open-Draw With Web Adhesion: Particle Approach

2009 ◽  
Vol 77 (2) ◽  
Author(s):  
Sverker Edvardsson ◽  
Tetsu Uesaka
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Time Dependent ◽  
Temporal Fluctuation ◽  
Continuous Solutions ◽  
Continuous Growth ◽  
System Parameters ◽  
Paper Machines ◽  
Particle Approach ◽  
The Web

In the present work we propose a particle approach, which is designed to treat complex mechanics and dynamics of the open-draw sections that are still present in many of today’s paper machines. First, known steady-state continuous solutions are successfully reproduced. However, it is shown that since the boundary conditions depend on the solution itself, the solutions for web strain and web path in the open-draw section are generally time-dependent. With a certain set of system parameters, the nonsteady solutions are common. A temporal fluctuation of Young’s modulus, for example, destabilizes the system irreversibly, resulting in the continuous growth of web strain, i.e., break. Finally we exemplify with some strategic draw countermeasures how to prevent a dangerous evolution in the web strain.

Strains in Aluminum-Adhesive-Ceramic Trilayers

1990 ◽  
Vol 112 (4) ◽  
pp. 288-302 ◽  
Author(s):  
P. M. Hall ◽  
F. L. Howland ◽  
Y. S. Kim ◽  
L. H. Herring
Keyword(s):  
Elastic Modulus ◽  
High Speed ◽  
Theoretical Study ◽  
Alumina Ceramic ◽  
Strain Gages ◽  
Wire Bonds ◽  
Large Expansion ◽  
Trilayer Structure ◽  
Almost All ◽  
Increasing Temperature

In many of today’s high speed, high density circuits, there is a need to remove large amounts of heat. To facilitate this removal of heat, it is common to adhere a sheet of a high thermal conductivity material (such as aluminum or copper) to the substrate (which may be alumina ceramic). This can result in large expansion mismatches which cause stresses and bowing, with the possibility of delamination, cracking, stressing solder joints, loss of hermeticity, or shorting of a metal lid to wire bonds inside a cavity. One approach to this problem is to use a compliant adhesive to decouple the materials. The present paper is an experimental and theoretical study of the strains as a function of temperature from −40° C to 140° C in a trilayer structure of 0.030 in. or 0.76 mm thick aluminum, 0.006 in. or 0.15 mm thick adhesive, and 0.021 in. or 0.5 mm thick low-temperature cofired (glassy) ceramic. The strains are analyzed using E. Suhir’s theory, and they are measured using strain gages for three adhesives: an epoxy, a fabric-reinforced epoxy, and a silcone elastopolymer. If the adhesive has an elastic modulus below 10 psi or 70 kPa, theory predicts almost complete de-coupling. Between 100 and 105 psi or 700 kPa and 700 MPa, there is partial decoupling, depending on the in-plane dimensions. Above 10,000 psi or 700 MPa, the decoupling is negligible, and the same bowing results for any elastic modulus between 10,000 and 1,000,000 psi or 70 MPa and 7 GPa. For temperatures below 80° C, only the elastomer has enough compliance to provide any de-coupling. Above 80° C, the elastomer de-couples the most, and the unreinforced epoxy the least. Almost all of the observed effects are understandable in terms of the Suhir theory, along with the fact that the elastic modulus of the epoxy materials decreases with increasing temperature. In particular, when there is some decoupling of the materials, the amount of decoupling depends on the in-plane dimensions of the sample.

Subsonic and Intersonic Failure of Composites: High-Speed Optical and Thermographic Measurements and Numerical Simulations

2000 ◽  
Author(s):  
A. J. Rosakis ◽  
D. Coker ◽  
C. Yu ◽  
M. Ortiz
Keyword(s):  
Crack Growth ◽  
High Speed ◽  
Large Scale ◽  
Wave Speed ◽  
Epoxy Composite ◽  
Shear Crack ◽  
Crack Tip ◽  
Composite Plates ◽  
Crack Face ◽  
Shear Wave Speed

Abstract In this paper dynamic fracture behavior of unidirectional graphite-epoxy composite plates is investigated experimentally and numerically. Crack propagation experiments are conducted on thick unidirectional graphite-epoxy composite plates subjected to in-plane, symmetric and asymmetric, impact loading. The coherent gradient sensing technique (CGS) is used in conjunction with high-speed photography to visualize the crack growth events. Cracks are found to propagate at subsonic speeds in the Mode-I case, whereas in both mixed mode and Mode-II the crack tip speed clearly exceeds the shear wave speed of the laminate. In the case of symmetric loading (Mode-I), the crack tip speeds approach the Rayleigh wave speed of the composite (1500 m/s), however it never exceeds it as predicted by asymptotic analysis. The situation is found to be entirely different for growing shear (Mode-II) cracks. A shock wave emanating from the crack tip is observed in the optical patterns. This provides direct evidence that the crack propagates faster than the shear wave speed of the composite. The crack tip speed is then observed to jump to a level close to the axial longitudinal wave speed along the fibers (7500 m/s) and then to stabilize to a lower level of approximately 6500 m/s. This speed corresponds to the speed at which the energy release rate required for shear crack growth is non-zero as determined from asymptotic analysis. The CGS interferograms also reveal the existence of large-scale frictional contact of the crack faces behind the moving shear cracks. In addition high speed thermographic measurements are conducted that show concentrated hot spots behind the crack tip indicating crack face frictional contact. Finally, these experiments are modeled by a detailed dynamic finite element calculation involving cohesive elements, newly developed adaptive remeshing using subdivision and edge collapse, composites element, and penalty contact. The numerical calculations are calibrated on the basis of fundamental material properties measured in the laboratory. The numerical methodology is subsequently validated by direct comparison to optical experimental measurements (crack speed record and near tip deformation field structure). For shear crack growth the numerics also reveal the experimentally observed shock wave structure and confirm the optical observation of large-scale crack face contact.

Sign in / Sign up

Export Citation Format

Share Document