scholarly journals Об устойчивости сильно заряженной капли, подвешенной в суперпозиции гравитационного и электростатического полей

2019 ◽  
Vol 89 (8) ◽  
pp. 1183
Author(s):  
С.О. Ширяева ◽  
Н.А. Петрушов ◽  
А.И. Григорьев
Keyword(s):  
Spherical Shape ◽  
Critical Value ◽  
Critical Parameters ◽  
Critical Conditions ◽  
Charged Drop ◽  
First Order ◽  
Electrostatic Fields ◽  
Dimensionless Amplitude ◽  
Free Drop ◽  
Density Coefficient

For strongly charged drop suspended in a fixed status in superposition gravitational and electrostatic fields, critical conditions of realization of its instability in relation to own and induced charges are found. All calculations are carried out in the fourth order of smallness on value of stationary deformation of spherical shape of a drop and first order on the dimensionless amplitude of its capillary oscillations. Dependences of values of critical parameters of Rayleigh and Taylor on radius, density, coefficient of surface tension, acceleration of the field of gravity and from number of a mode of oscillations, other than those for the free drop are found. With increase mode number the critical value of parameter of Rayleigh grows and comes to an asymptotic , and the critical value of Taylor parameter decreases and comes to an asymptotic . The specified changes and are explained by existence of a condition of immobility of the center of masses in a suspension connecting , and acceleration of the field of gravity.

Laser-Induced Pretransitional Ordering And Nonlinear Optical Properties Of Rigid-Rod Polymer Suspensions

1993 ◽  
Vol 328 ◽  
Author(s):  
Boris E. Vugmeister ◽  
Michelle S. Malcuit ◽  
John C. Kralik ◽  
Colleen Stevens
Keyword(s):  
Phase Transition ◽  
Colloidal Particles ◽  
Volume Fraction ◽  
Orientational Order ◽  
Critical Value ◽  
Orientational Relaxation ◽  
First Order ◽  
First Order Phase Transition ◽  
Rigid Rod ◽  
First Order Phase

ABSTRACTWe investigate the pretransitional behavior in laser-induced alignment of rigid rod-like polytetraflouroethylene (PTFE) suspensions. Using a laser-induced birefringence experiment, we measure both the orientational order parameter and the orientational relaxation time. We find that both increase as the volume fraction of colloidal particles approaches the critical value for the isotropic-nematic phase transition. Experimental results are compared with theory which takes into account the possibility of a first-order phase transition induced by a laser electric field.

scholarly journals ANALYTIC STUDY OF FIRST-ORDER PHASE TRANSITION IN HOLOGRAPHIC SUPERCONDUCTOR AND SUPERFLUID

2013 ◽  
Vol 28 (28) ◽  
pp. 1350140 ◽  
Author(s):  
WUNG-HONG HUANG
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Critical Value ◽  
Analytic Study ◽  
Matching Method ◽  
Holographic Superconductor ◽  
First Order ◽  
Numerical Result ◽  
First Order Phase Transition ◽  
First Order Phase

We use the matching method to investigate the first-order phase transition in holographic superconductor and superfluid. We first use the simple holographic superconductor model to describe the matching method and mention how to see the first-order phase transition. Next, we study the holographic superconductor with Stückelberg term and see that the analytic results indicate the existence of first-order phase transition. Finally, we study the holographic superfluid and show that the first-order phase transition can be found for some values of parameters. We determine the critical value analytically and compare it with the previous numerical result.

scholarly journals A theoretical study of a possible model of paramagnetic alums at low temperatures

1940 ◽  
Vol 176 (965) ◽  
pp. 203-213 ◽  
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Theoretical Study ◽  
Spontaneous Magnetization ◽  
Critical Value ◽  
Transition Curve ◽  
Thin Specimen ◽  
First Order ◽  
Freely Suspended ◽  
Line Of Critical Points

An attempt is made to examine theoretically the properties of paramagnetic alums at low temperatures. The model taken is a lattice of freely suspended magnets, all interactions except purely magnetic being neglected. Even with this simplification it is impossible at present to make rigorous calculations of the partition function, either on classical or quantum lines. A simple model is proposed, which is really a generalization of the Bragg - Williams theory enabling one to take account of the effect of a magnetic field. The few configurations whose energies are known are used to fix arbitrary constants in the expression assumed for the energy. The theory predicts that the state of lowest energy is either a spontaneously magnetized, state for a long thin specimen, or a state in which alternate rows of magnets point in opposite directions for a sphere, spontaneous magnetization appearing in an ellipsoid with an eccentricity greater than a certain critical value. The transition curve bounding the region in which the antiparallel state is stable consists partly of a line of Curie points corresponding to transitions of the second, order, passing smoothly into a line of critical points corresponding to a transition of the first order. The effect of shape on the magnetic properties of the specimen seems to be experimentally verified, but the rough nature of the theory prevents it being more than qualitative.

Characteristics and Photocatalytic Activity of Sm Doped ZnO Nanoparticles

2019 ◽  
Vol 799 ◽  
pp. 179-184 ◽  
Author(s):  
Pavels Rodionovs ◽  
Dzidra Jankovica ◽  
Jānis Grabis
Keyword(s):  
Photocatalytic Activity ◽  
Calcination Temperature ◽  
Zno Nanoparticles ◽  
Sol Gel ◽  
Spherical Shape ◽  
Order Rate Constant ◽  
X Ray Diffraction ◽  
First Order ◽  
Microwave Assisted ◽  
Gel Combustion

Sm2O3/ZnO nanoparticles were prepared via microwave-assisted hydrothermal and sol-gel combustion synthesis. Characteristics of obtained samples were compared in dependence of Sm2O3 content and calcination temperature. Prepared nanostructures were characterized with scanning electron microscopy and X-ray diffraction. Nanoparticles prepared via microwave-assisted hydrothermal and sol-gel method have flower-like and spherical shape respectively. The photocatalytic activity of samples under solar light simulated illumination was found to be affected by content of Sm2O3, calcination temperature and preparation method. The first-order rate constant of MB solution degradation of samples prepared via microwave-assisted hydrothermal method approximately three times exceeds that of sol-gel samples.

scholarly journals Tuning the Optical Band Gap of Semiconductor Nanocomposites—A Case Study with ZnS/Carbon

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4162
Author(s):  
Dominik Voigt ◽  
Larry Sarpong ◽  
Michael Bredol
Keyword(s):  
Surface Chemistry ◽  
Band Gap ◽  
Optical Band Gap ◽  
Bulk Composition ◽  
Optical Excitation ◽  
Careful Analysis ◽  
Critical Parameters ◽  
Surface Charges ◽  
Electrostatic Fields ◽  
Size Adjustment

The linear photochemical response of materials depends on two critical parameters: the size of the optical band gap determines the onset of optical excitation, whereas the absolute energetic positions of the band edges define the reductive or oxidative character of photo-generated electrons and holes. Tuning these characteristics is necessary for many potential applications and can be achieved through changes in the bulk composition or particle size, adjustment of the surface chemistry or the application of electrostatic fields. In this contribution the influence of surface chemistry and fields is investigated systematically with the help of standard DFT calculations for a typical case, namely composites prepared from ZnS quantum dots and functionalized carbon nanotubes. After comparing results with existing qualitative and quantitative experimental data, it is shown conclusively, that the details of the surface chemistry (especially defects) in combination with electrostatic fields have the largest influence. In conclusion, the development of novel or improved photoresponsive materials therefore will have to integrate a careful analysis of the interplay between surface chemistry, surface charges and interaction with the material environment or substrate.

ORIENTATION OF SYMMETRIC BODIES FALLING IN A SECOND-ORDER LIQUID AT NONZERO REYNOLDS NUMBER

2002 ◽  
Vol 12 (11) ◽  
pp. 1653-1690 ◽  
Author(s):  
GIOVANNI P. GALDI ◽  
ASHWIN VAIDYA ◽  
MILAN POKORNÝ ◽  
DANIEL D. JOSEPH ◽  
JIMMY FENG
Keyword(s):  
Prolate Spheroid ◽  
Critical Value ◽  
Second Order ◽  
The Body ◽  
Body Of Revolution ◽  
Translational Velocity ◽  
Homogeneous Body ◽  
First Order ◽  
The Stability ◽  
Elasticity Number

We study the steady translational fall of a homogeneous body of revolution around an axis a, with fore-and-aft symmetry, in a second-order liquid at nonzero Reynolds (Re) and Weissenberg (We) numbers. We show that, at first order in these parameters, only two orientations are allowed, namely, those with a either parallel or perpendicular to the direction of the gravity g. In both cases the translational velocity is parallel to g. The stability of the orientations can be described in terms of a critical value E c for the elasticity number E = We/Re , where E c depends only on the geometric properties of the body, such as size or shape, and on the quantity (Ψ1 + Ψ2)/Ψ1, where Ψ1 and Ψ2 are the first and second normal stress coefficients. These results are then applied to the case when the body is a prolate spheroid. Our analysis shows, in particular, that there is no tilt-angle phenomenon at first order in Re and We.

Transition in oscillating boundary layer flows

1967 ◽  
Vol 29 (1) ◽  
pp. 93-111 ◽  
Author(s):  
H. J. Obremski ◽  
A. A. Fejer
Keyword(s):  
Reynolds Number ◽  
Free Stream ◽  
Rapid Development ◽  
Transition Process ◽  
Critical Value ◽  
Boundary Layer Flows ◽  
Instability Waves ◽  
Dimensionless Amplitude ◽  
Oscillating Boundary ◽  
Tollmien Schlichting

An experimental investigation of transition phenomena in non-steady boundary layers of sinusoidally oscillating flows was conducted, and the effect of various parameters on the transition process was observed.The manner in which transition occurs appears to be related to a dimensionless grouping designated as the non-steady Reynolds number, (Re)NS= LΔU/2πvν. When this number exceeds a certain critical value, transition begins with turbulent bursts appearing periodically at the frequency of the free stream oscillation; these are preceded by instability waves having the appearance of a Tollmien-Schlichting instability. The transition Reynolds number depends, in this case, only on the amplitude of the free stream oscillations and not on their frequency, at least to the first order. Below a critical value of this parameter, transition occurs at a relatively constant Reynolds number which appears independent of the amplitude and frequency of the oscillation, at least over the range tested.When the bursts appear periodically, their development appears to occur in two succeeding phases: an initial or ‘creative’ phase marked by a sequential appearance of turbulence upstream and rapid development and a latter or ‘convective’ phase marked by turbulent spots having relatively constant leading and trailing edge velocities.The dimensionless amplitude, ΔU/U∞, of the imposed oscillations was varied from 0.014 to 0.29 while the oscillation frequencies extended from 4.5 to 62c/s.Pressure gradients imposed on the flat plate model during the course of the study are given bydCp/dx = − 0.004/ft., −0.081/ft. and 0.045/ft. whereCp= 2p/ρU2∞and x is the distance (ft.) along the plate.

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