scholarly journals Triboelectric Effect of Polytetrafluoroethylene Fibers to Improve the Filtration Performance of Air-Purified Materials

2018 ◽  
Vol 13 (1) ◽  
pp. 155892501801300
Author(s):  
Shang Zhu ◽  
Yukang Xu ◽  
Chen Huang ◽  
Xiangyu Jin
Keyword(s):  
Charge Density ◽  
Contact Area ◽  
Applied Load ◽  
Static Charge ◽  
Filtration Property ◽  
Filtration Performance ◽  
Triboelectric Effect

The effect of triboelectric behavior of polytetrafluoroethylene (PTFE) on the filtration performance of common air-purified filters was studied. Variations of triboelectric charge density on PTFE films were analyzed by four typical parameters (cycle, applied load, contact area and velocity). The results demonstrated that the addition of PTFE fibers could significantly improve the filtration property of air-purified materials, owning to the accumulation of triboelectric static charge on the fibers.

scholarly journals Interpretations of ground-state symmetry breaking and strong correlation in wavefunction and density functional theories

2021 ◽  
Vol 118 (4) ◽  
pp. e2017850118 ◽  
Author(s):  
John P. Perdew ◽  
Adrienn Ruzsinszky ◽  
Jianwei Sun ◽  
Niraj K. Nepal ◽  
Aaron D. Kaplan
Keyword(s):  
Density Functional Theory ◽  
Charge Density ◽  
Ground State ◽  
Charge Density Wave ◽  
Density Functional ◽  
Density Wave ◽  
Static Charge ◽  
Functional Theory ◽  
Correlation Kernel ◽  
Frequency Moments

Strong correlations within a symmetry-unbroken ground-state wavefunction can show up in approximate density functional theory as symmetry-broken spin densities or total densities, which are sometimes observable. They can arise from soft modes of fluctuations (sometimes collective excitations) such as spin-density or charge-density waves at nonzero wavevector. In this sense, an approximate density functional for exchange and correlation that breaks symmetry can be more revealing (albeit less accurate) than an exact functional that does not. The examples discussed here include the stretched H2 molecule, antiferromagnetic solids, and the static charge-density wave/Wigner crystal phase of a low-density jellium. Time-dependent density functional theory is used to show quantitatively that the static charge-density wave is a soft plasmon. More precisely, the frequency of a related density fluctuation drops to zero, as found from the frequency moments of the spectral function, calculated from a recent constraint-based wavevector- and frequency-dependent jellium exchange-correlation kernel.

A New Technique for Contact Mechanics and Friction in Microstructures: Controllable Electrostatic Repulsive Forces From Capacitive Coupling to Electret

2005 ◽  
Author(s):  
Myongseob Kim ◽  
Chungho Lee ◽  
Edwin C. Kan
Keyword(s):  
Charge Density ◽  
Polymer Film ◽  
Contact Mechanics ◽  
Repulsive Force ◽  
Capacitive Coupling ◽  
Cantilever Beams ◽  
Static Charge ◽  
Actuation Mechanism ◽  
A New Technique ◽  
Repulsive Forces

The use of the electrostatically repulsive force from the capacitive coupling with electret polymer film is demonstrated experimentally. The repulsive forces can be utilized in controlling contact mechanics and friction in microstructures, and serve as an alternative MEMS actuation mechanism to overcome the limitations by the attractive forces. Simple parallel cantilever beams patterns are used to illustrate the magnitude of the repulsive forces and the associated static charge density from the electret polymer films coupling.

Model for a Sphere–Flat Elastic–Plastic Adhesion Contact

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Zhi Qian Wang ◽  
Jin Feng Wang
Keyword(s):  
Contact Area ◽  
Applied Load ◽  
Dissipated Energy ◽  
Polynomial Functions ◽  
Elastic Plastic ◽  
Adhesion Contact ◽  
Cubic Model ◽  
Cubic Polynomial ◽  
Plastic Displacement ◽  
Work Done

This paper presents a cubic model for the sphere–flat elastic–plastic contact without adhesion. In the cubic model, the applied load and the contact area are described by the cubic polynomial functions of the displacement to the power of 1/2 during loading and unloading, and the applied load is also expressed as the cubic polynomial function of the contact area to the power of 1/3 during loading. Utilizing these cubic polynomial functions, the elastic–plastic load (EPL) index, which is defined by the ratio between the dissipated energy due to plastic deformations and the work done to deform the sphere during loading, is calculated analytically. The calculated EPL index is just the ratio between the residue displacement after unloading and the maximum elastic–plastic displacement after loading. Using the cubic model, this paper extends the Johnson–Kendall–Roberts (JKR) model from the elastic regime to the elastic–plastic regime. Introducing the Derjaguin–Muller–Toporov (DMT) adhesion, the unified elastic–plastic adhesion model is obtained and compared with the simplified analytical model (SAM) and Kogut–Etsion (KE) model.

d-wave pairing in the doped static charge-density-wave state on a two-dimensional square lattice

2000 ◽  
Vol 62 (14) ◽  
pp. 9648-9653 ◽  
Author(s):  
Mikio Onozawa ◽  
Yoshiyuki Fukumoto ◽  
Akihide Oguchi ◽  
Yukio Mizuno
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Square Lattice ◽  
Two Dimensional ◽  
Static Charge ◽  
Wave State ◽  
Wave Pairing ◽  
D Wave

The effects of contact area and applied load on the morphology of in vitro worn ultra-high molecular weight knee prostheses: a micro-Raman and gravimetric study

2014 ◽  
Vol 45 (9) ◽  
pp. 781-787 ◽  
Author(s):  
Silvia Tozzi ◽  
Enrico Modena ◽  
Stefano Falcioni ◽  
Alessandra Sudanese ◽  
Saverio Affatato ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Contact Area ◽  
Applied Load ◽  
Knee Prostheses ◽  
Ultra High Molecular Weight

Study of Pressure Distribution in Compliant Coated Abrasive Tools for Robotic Polishing

2012 ◽  
Author(s):  
Muhammed Umer ◽  
Kushendarsyah Saptaji ◽  
Sathyan Subbiah
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Contact Area ◽  
Force Control ◽  
Applied Load ◽  
Element Model ◽  
Curved Surfaces ◽  
Abrasive Tool ◽  
Abrasive Grains ◽  
Abrasive Tools

Robotic polishing applications involve the use of coated abrasive tools along with a compliant backing pad. The compliance helps in conforming to curved surfaces and also in blending with unpolished areas. This compliance and its effect are currently controlled only by empirical choice of various backing pad designs and materials. A better understanding of this important characteristic of these tools will lead to better process control. One of the effects of the compliance or stiffness of the backing pad under a certain applied load (robotic force control) is on the contact area and pressure distribution applied on the abrasive grains in that area. This pressure distribution in turn dictates how material is removed in the area of contact. Here, we report preliminary results of the pressure distribution exerted by an abrasive tool mounted on a robot using pressure film sensors and compare results with a simple finite element model.

The Strain Generated on a Rubber Surface in the Course of Pattern Abrasion

2000 ◽  
Vol 28 (2) ◽  
pp. 96-105 ◽  
Author(s):  
T. Iwai ◽  
Y. Uchiyama
Keyword(s):  
Contact Area ◽  
Applied Load ◽  
Crack Surface ◽  
Optical Microscope ◽  
Surface Strain ◽  
Front Part ◽  
Breaking Strain ◽  
Outermost Surface ◽  
Rubber Surface ◽  
Isoprene Rubber

Abstract The surface strain on a rubbing rubber surface was examined in the course of pattern abrasion. Rubbing experiments between the outermost surface of a rotating isoprene rubber wheel and a cylindrical lens were conducted. Observations of the contact area were made through the lens. Markers were put on the rubbing rubber surface to measure strain. The maximum strains at the inclined rubber surface between the ridges were from around 40% to 100%. In order to measure the strain at the crack-propagating area, a marker was put on the lower front part of the ridge. It was found that the strain necessary for crack propagation underneath the ridge was 750%, which was almost equivalent to its breaking strain, irrespective of the applied load. At that moment, newly generated crack surface was confirmed. However, no visible crack was observed through an optical microscope when the strain was measure at 200% to 400%.

Experimental Investigations upon the Electrical Resistance of Microcontacts

2013 ◽  
Vol 705 ◽  
pp. 365-370 ◽  
Author(s):  
Marilena Glovnea ◽  
Cornel Suciu
Keyword(s):  
Contact Resistance ◽  
Contact Area ◽  
Electrical Resistance ◽  
Applied Load ◽  
Electrical Contact ◽  
Constant Current ◽  
Load Force ◽  
Experimental Investigations ◽  
Electrical Contact Resistance ◽  
Force Contact

An important parameter in MEMS design is the electrical contact resistance. This depends on material conductibility, on the geometry of the contacting surfaces, on the applied load and on the current passing through the contact. This work aims to experimentally investigate the dependence between: electrical contact resistance and contact load force, contact resistance and contact area and contact perimeter for constant current through a microcontact.

scholarly journals Experimental Evidence for Static Charge Density Waves in Iron Oxypnictides

2017 ◽  
Vol 118 (5) ◽  
Author(s):  
A. Martinelli ◽  
P. Manfrinetti ◽  
A. Provino ◽  
A. Genovese ◽  
F. Caglieris ◽  
...  
Keyword(s):  
Charge Density ◽  
Experimental Evidence ◽  
Charge Density Waves ◽  
Density Waves ◽  
Static Charge
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