Casimir-Lifshitz force out of thermal equilibrium
Antezza, M.; Pitaevskii, L.P.; Stringari, S.; Svetovoy, Vitaly
We study the Casimir-Lifshitz interaction out of thermal equilibrium, when the interacting objects are at different temperatures. The analysis is focused on the surface-surface, surface-rarefied body, and surface-atom configurations. A systematic investigation of the contributions to the force
Archimedes Force on Casimir Apparatus
Shevchenko, Vladimir
2016-01-01
We address a problem of Casimir apparatus in dense medium and weak gravitational field. The falling of the apparatus has to be governed by the equivalence principle, with proper account for contributions to the weight of the apparatus from its material part and from distorted quantum fields. We discuss general expression for the corresponding force in metric with cylindrical symmetry. By way of example we compute explicit expression for Archimedes force, acting on the Casimir apparatus of finite size, immersed into thermal bath of free scalar field. It is shown that besides universal term, proportional to the volume of the apparatus, there are non-universal quantum corrections, depending on the boundary conditions.
Thermal fluctuations and stability of a particle levitated by a repulsive Casimir force in a liquid.
Inui, Norio; Goto, Kosuke
2013-11-01
We study the vertical Brownian motion of a gold particle levitated by a repulsive Casimir force to a silica plate immersed in bromobenzene. The time evolution of the particle distribution starting from an equilibrium position, where the Casimir force and gravitational force are balanced, is considered by solving the Langevin equation using the Monte Carlo method. When the gold particle is very close to the silica plate, the Casimir force changes from repulsive to attractive, and the particle eventually sticks to the surface. The escape rate from a metastable position is calculated by solving the Fokker-Plank equation; it agrees with the value obtained by Kramers' escape theory. The duration of levitation increases as the particle radius increases up to around 2.3 μm. As an example, we show that a 1-μm-diameter gold particle can be levitated for a significantly long time by the repulsive Casimir force at room temperature.
Thermal Casimir-Polder forces on a V-type three-level atom
Xu, Chen-Ran; Xu, Jing-Ping; Al-amri, M.; Zhu, Cheng-Jie; Xie, Shuang-Yuan; Yang, Ya-Ping
2017-09-01
We study the thermal Casimir-Polder (CP) forces on a V-type three-level atom. The competition between the thermal effect and the quantum interference of the two transition dipoles on the force is investigated. To shed light onto the role of the quantum interference, we analyze two kinds of initial states of the atom, i.e., the superradiant state and the subradiant state. Considering the atom being in the thermal reservoir, the resonant CP force arising from the real photon emission dominates in the evolution of the CP force. Under the zero-temperature condition, the quantum interference can effectively modify the amplitude and the evolution of the force, leading to a long-time force or even the cancellation of the force. Our results reveal that in the finite-temperature case, the thermal photons can enhance the amplitude of all force elements, but have no influence on the net resonant CP force in the steady state, which means that the second law of thermodynamics still works. For the ideal degenerate V-type atom with parallel dipoles under the initial subradiant state, the robust destructive quantum interference overrides the thermal fluctuations, leading to the trapping of the atom in the subradiant state and the disappearance of the CP force. However, in terms of a realistic Zeeman atom, the thermal photons play a significant role during the evolution of the CP force. The thermal fluctuations can enhance the amplitude of the initial CP force by increasing the temperature, and weaken the influence of the quantum interference on the evolution of the CP force from the initial superradiant (subradiant) state to the steady state.
Energy Technology Data Exchange (ETDEWEB)
Messina, Riccardo [LNE-SYRTE, Observatoire de Paris, CNRS UMR 8630, UPMC, 61 avenue de l' Observatoire, F-75014 Paris (France); Antezza, Mauro [Universite Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier (France); CNRS, Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier (France)
2011-10-15
We study the radiative heat transfer and the Casimir-Lifshitz force occurring between two bodies in a system out of thermal equilibrium. We consider bodies of arbitrary shape and dielectric properties, held at two different temperatures and immersed in environmental radiation at a third different temperature. We derive explicit closed-form analytic expressions for the correlations of the electromagnetic field and for the heat transfer and Casimir-Lifshitz force in terms of the bodies' scattering matrices. We then consider some particular cases which we investigate in detail: the atom-surface and the slab-slab configurations.
Repulsive Casimir force between Weyl semimetals
Wilson, Justin H.; Allocca, Andrew A.; Galitski, Victor
2015-06-01
Weyl semimetals are a class of topological materials that exhibit a bulk Hall effect due to time-reversal symmetry breaking. We show that for the idealized semi-infinite case, the Casimir force between two identical Weyl semimetals is repulsive at short range and attractive at long range. Considering plates of finite thickness, we can reduce the size of the long-range attraction even making it repulsive for all distances when thin enough. In the thin-film limit, we study the appearance of an attractive Casimir force at shorter distances due to the longitudinal conductivity. Magnetic field, thickness, and chemical potential provide tunable nobs for this effect, controlling the Casimir force: whether it is attractive or repulsive, the magnitude of the effect, and the positions and existence of a trap and antitrap.
Casimir force between topological insulator slabs
Nie, Wenjie; Zeng, Ran; Lan, Yueheng; Zhu, Shiyao
2013-08-01
The Casimir force between two finite-thick topological insulator slabs and its dependence on the gap size between the slabs are investigated in detail. Two typical substrate materials including semi-infinite vacuum and silicon are used in the study, in which the Casimir force can always change from attractive to repulsive when the gap size decreases. The gap width at transition is a function of the slab thickness and also depends strongly on the electric permittivity and topological magnetoelectric polarizability of the slabs. In particular, in the absence of a substrate, this width increases with decreasing slab thickness and for thin slabs with large internal and external topological magnetoelectric polarizability the Casimir force is always repulsive where the surface topological magnetoelectric effect of the slabs plays a dominant role. In the presence of a semi-infinite silicon substrate, however, the attractive role of the silicon substrate becomes increasingly important, and thus the transition gap decreases with decreasing thickness of the slab. The characteristic features of the Casimir force may be detected experimentally through exploring its gradient with a certain dynamical method.
Oscillating Casimir force between two slabs in a Fermi sea
DEFF Research Database (Denmark)
Li-Wei, Chen; Guo-Zhen, Su; Jin-Can, Chen
2012-01-01
The Casimir effect for two parallel slabs immersed in an ideal Fermi sea is investigated at both zero and nonzero temperatures. It is found that the Casimir effect in a Fermi gas is distinctly different from that in an electromagnetic field or a massive Bose gas. In contrast to the familiar result...... that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude...
Extended Analysis of the Casimir Force
Directory of Open Access Journals (Sweden)
Lehnert B.
2014-04-01
Full Text Available There are several arguments for the conventional form of the Zero Point Energy fre- quency spectrum to be put in doubt. It has thus to be revised in to that of a self-consistent system in statistical equilibrium where the total energy de nsity and the equivalent pres- sure become finite. An extended form of the Casimir force is th ereby proposed to be used as a tool for determining the local magnitude of the same pressure. This can be done in terms of measurements on the force between a pair po lished plane plates consisting of different metals, the plates having very small or zero air gaps. T his corre- sponds to the largest possible Casimir force. Even then, the re may arise problems with other adhering forces, possibly to be clarified in further experiments.
Resource Letter VWCPF-1: Van der Waals and Casimir-Polder forces
Milton, Kimball A.
2011-01-01
This Resource Letter provides a guide to the literature on van der Waals and Casimir-Polder forces. Journal articles, books, and other documents are cited on the following topics: van der Waals forces, retarded dispersion forces or Casimir-Polder forces between atoms or molecules, Casimir-Polder forces between a molecule and a dielectric or conducting body, the summation of Casimir-Polder forces as leading to the Casimir and Lifshitz forces between conducting and dielectric bodies, Casimir fr...
Casimir force on an interacting Bose-Einstein condensate
Energy Technology Data Exchange (ETDEWEB)
Biswas, Shyamal; Majumder, Dwipesh; Saha, Kush [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Bhattacharjee, J K [S.N. Bose National Centre for Basic Sciences, Sector 3, JD Block, Salt Lake, Kolkata 700098 (India); Chakravarty, Nabajit, E-mail: tpsb2@iacs.res.i [Positional Astronomy Centre, Block AQ, Plot 8, Sector 5, Salt Lake, Kolkata 700091 (India)
2010-04-28
We have presented an analytic theory for the Casimir force on a Bose-Einstein condensate which is confined between two parallel plates. We have considered Dirichlet boundary conditions for the condensate wavefunction as well as for the phonon field. We have shown that the condensate wavefunction (which obeys the Gross-Pitaevskii equation) is responsible for the mean field part of the Casimir force, which usually dominates over the quantum (fluctuations) part of the Casimir force.
Casimir force on interacting Bose-Einstein condensate
Biswas, Shyamal; Bhattacharjee, J K; Majumder, Dwipesh; Saha, Kush; Chakravarty, Nabajit
2009-01-01
We have presented an analytic theory for the Casimir force on a Bose-Einstein condensate (BEC) which is confined between two parallel plates. We have considered Dirichlet boundary conditions for the condensate wave function as well as for the phonon field. We have shown that, the condensate wave function (which obeys the Gross-Pitaevskii equation) is responsible for the mean field part of Casimir force, which usually dominates over the quantum (fluctuations) part of the Casimir force.
Critical Casimir forces and anomalous wetting
Indian Academy of Sciences (India)
Laboratoire de Physique Statistique de l´Ecole Normale Supérieure, associé au CNRS et aux Universités Paris 6 et 7, 24 rue Lhomond, 75231 Paris Cedex 05, France. E-mail: balibar@lps.ens.fr. Abstract. We present a review of critical Casimir forces in connection with successive experiments on wetting near the critical ...
Three-body critical Casimir forces.
Mattos, T G; Harnau, L; Dietrich, S
2015-04-01
Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles in the direction normal to their axes, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover, we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces.
Energy Technology Data Exchange (ETDEWEB)
Ellingsen, Simen Andreas Aadnoey
2011-01-15
The present thesis focuses on several topics within three separate but related branches of the overall field of dispersion forces. The three branches are: temperature corrections to the Casimir force between real materials (Part 1), explicit calculation of Casimir energy in wedge geometries (Part 2), and Casimir-Polder forces on particles out of thermal equilibrium (Part 3). Part 1 deals primarily with analysis of a previously purported thermodynamic inconsistency in the Casimir-Lifshitz free energy of the interaction of two plane mirrors - violation of the third law of thermodynamics - when the latter's dielectric response is described with dissipative models. It is shown analytically and numerically that the Casimir entropy of the interaction between two metallic mirrors described by the Drude model does tend to zero at zero temperature, provided electronic relaxation does not vanish. The leading order terms at low temperature are found. A similar calculation is carried out for the interaction of semiconductors with small but non-zero DC conductivity. In a generalisation, it is shown that a violation of the third law can only occur for permittivities whose low-frequency behaviour is temperature dependent near zero temperature. A calculation using path integral methods shows that the low temperature behaviour of the interaction of fluctuating Foucault currents in two mirrors of Drude metal is identical to that of the full Casimir-Lifshitz free energy, reasserting a previous finding by Intravaia and Henkel that such fluctuating bulk currents are the physical reason for the anomalous entropy behaviour. In a related effort, an analysis of the frequency dependence of the Casimir force by Ford is generalised to imperfectly reflecting mirrors. A paradox is pointed out, in that the effects of a perturbation of the reflecting properties of the mirrors in a finite frequency window can be calculated in two ways giving different results. It is concluded that optimistic
Casimir forces and quantum electrodynamical torques: Physics and nanomechanics
Capasso, F.; Munday, J. N.; Iannuzzi, D.; Chan, H. B.
2007-01-01
This paper discusses recent developments on quantum electrodynamical (QED) phenomena, such as the Casimir effect, and their use in nanomechanics and nanotechnology in general. Casimir forces and torques arise from quantum fluctuations of vacuum or, more generally, from the zero-point energy of
Towards a Casimir Force Measurement between Micromachined Parallel Plate Structures
Directory of Open Access Journals (Sweden)
Remco J. Wiegerink
2012-11-01
Full Text Available Ever since its prediction, experimental investigation of the Casimir force has been of great scientific interest. Many research groups have successfully attempted quantifying the force with different device geometries; however, measurement of the Casimir force between parallel plates with sub-micron separation distance is still a challenging task, since it becomes extremely difficult to maintain sufficient parallelism between the plates. The Casimir force can significantly influence the operation of micro devices and to realize reliable and reproducible devices it is necessary to understand and experimentally verify the influence of the Casimir force at sub-micron scale. In this paper, we present the design principle, fabrication and characterization of micromachined parallel plate structures that could allow the measurement of the Casimir force with tunable separation distance in the range of 100 to 1000 nm. Initially, a gold coated parallel plate structure is explored to measure the Casimir force, but also other material combinations could be investigated. Using gold-silicon eutectic bonding, a reliable approach to bond chips with integrated suspended plates together with a well-defined separation distance in the order of 1–2 μm is developed.
Numerical vs. Semiclassical Evaluation of Casimir Forces in Piston Geometries
Schaden, Martin; Mateescu, Liviu
2008-05-01
Using a modified wordline approach[1] for a massless scalar field satisfying Dirichlet boundary conditions, we numerically obtain the Casimir force on a piston in a cylindrical cavity with a cylinder head of different radius. There are no contributions from arbitrarily short paths and the Casimir force on the piston is finite for all systems considered. Our algorithm for Casimir forces in closed concave geometries is numerically stable, fast and accurate. For a hemispherical cylinder head, we analytically and numerically obtain an attractive contribution to the Casimir force that is inversely proportional to the elevation of the piston and does not depend on the radius of the cylinder. This attractive contribution to the Casimir energy cannot be distinguished from one due to the presence of a charge. It is of higher semiclassical order and was not observed in the leading description by periodic orbits [2]. By changing the radius of the cylinder head compared to that of the cylinder, we numerically verify the semiclassical estimate [2] that the Casimir force on the piston is drastically reduced by a hemispherical cylinder head. We also present preliminary numerical studies for a massless scalar field satisfying Neumann boundary conditions. [1] H. Gies, K. Langfeld and L. Moyaerts, JHEP 0306, 018 (2003); H. Gies and K. Klingmuller, Phys. Rev. D74, 045002 (2006). [2] L Mateescu and M. Schaden, [quant-ph/0705.3435].
Critical Casimir force in the superfluid phase: effect of fluctuations
Biswas, Shyamal; Bhattacharjee, J K; Samanta, Himadri S.; Bhattacharyya, Saugata; Hu, Bambi
2008-01-01
We have considered the critical Casimir force on a $^4$He film below and above the bulk $\\lambda$ point. We have explored the role of fluctuations around the mean field theory in a perturbative manner, and have substantially improved the mean field result of Zandi et al [Phys. Rev. E {\\bf 76}, 030601(R) (2007)]. The Casimir scaling function obtained by us approaches a universal constant ($-\\frac{\\zeta(3)}{8\\pi}$) for $T\\lesssim 2.13~\\text{K}$.
Casimir forces in multilayer magnetodielectrics with both gain and loss
DEFF Research Database (Denmark)
Amooghorban, Ehsan; Wubs, Martijn; Mortensen, N. Asger
2011-01-01
A path-integral approach to the quantization of the electromagnetic field in a linearly amplifying magnetodielectric medium is presented. Two continua of inverted harmonic oscillators are used to describe the polarizability and magnetizability of the amplifying medium. The causal susceptibilities...... and Casimir forces for a multilayer magnetodielectric medium with both gain and loss. We point out the essential differences with a purely passive layered medium. For a single layer, we find different bounds on the Casimir force for fully amplifying and for lossy media. The force is attractive in both cases...
CASIMIR FORCE EXPERIMENTS IN AIR: TWO BIRDS WITH ONE STONE
De Man, S.; Heeck, K.; Smith, K.; Wijngaarden, R. J.; Iannuzzi, D.
2010-01-01
We present a short overview of the recent efforts of our group in the design of high precision Casimir force setups. We first describe our Atomic Force Microscope based technique that allows one to simultaneously and continuously calibrate the instrument, compensate for a residual electrostatic
Casimir force phase transitions in the graphene family
Rodriguez-Lopez, Pablo; Kort-Kamp, Wilton J. M.; Dalvit, Diego A. R.; Woods, Lilia M.
2017-03-01
The Casimir force is a universal interaction induced by electromagnetic quantum fluctuations between any types of objects. The expansion of the graphene family by adding silicene, germanene and stanene (2D allotropes of Si, Ge, and Sn), lends itself as a platform to probe Dirac-like physics in honeycomb staggered systems in such a ubiquitous interaction. We discover Casimir force phase transitions between these staggered 2D materials induced by the complex interplay between Dirac physics, spin-orbit coupling and externally applied fields. In particular, we find that the interaction energy experiences different power law distance decays, magnitudes and dependences on characteristic physical constants. Furthermore, due to the topological properties of these materials, repulsive and quantized Casimir interactions become possible.
Weak and Repulsive Casimir Force in Piston Geometries
Schaden, Martin; Mateescu, Liviu
2007-01-01
We study the Casimir force in piston-like geometries semiclassically. The force on the piston is finite and physical, but to leading semiclassical approximation depends strongly on the shape of the surrounding cavity. Whereas this force is attractive for pistons in a parallelepiped with flat cylinder head, for which the semiclassical approximation by periodic orbits is exact, this approximation to the force on the piston vanishes for a semi-cylindrical head and becomes repulsive for a cylinde...
Roughness correction to the Casimir force beyond perturbation theory
Broer, Wijnand; Palasantzas, George; Knoester, Jasper; Svetovoy, Vitaly B.
Up to now there has been no reliable method to calculate the Casimir force when surface roughness becomes comparable with the separation between bodies. Statistical analysis of rough Au films demonstrates rare peaks with heights considerably larger than the root-mean-square (rms) roughness. These
Effect of hydrogen-switchable mirrors on the Casimir force
Iannuzzi, D.; Lisanti, M.; Capasso, F.
2004-01-01
We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the
Lateral Casimir Force on a Rotating Particle near a Planar Surface
Manjavacas, Alejandro; Rodríguez-Fortuño, Francisco J.; García de Abajo, F. Javier; Zayats, Anatoly V.
2017-03-01
We study the lateral Casimir force experienced by a particle that rotates near a planar surface. The origin of this force lies in the symmetry breaking induced by the particle rotation in the vacuum and thermal fluctuations of its dipole moment, and therefore, in contrast to lateral Casimir forces previously described in the literature for corrugated surfaces, it exists despite the translational invariance of the planar surface. Working within the framework of fluctuational electrodynamics, we derive analytical expressions for the lateral force and analyze its dependence on the geometrical and material properties of the system. In particular, we show that the direction of the force can be controlled by adjusting the particle-surface distance, which may be exploited as a new mechanism to manipulate nanoscale objects.
Non-equilibrium Casimir force between vibrating plates.
Directory of Open Access Journals (Sweden)
Andreas Hanke
Full Text Available We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir effect of the electromagnetic field and possible experiments to measure the time-dependent Casimir force are discussed.
Measurement of the Casimir Force between Two Spheres
Garrett, Joseph L.; Somers, David A. T.; Munday, Jeremy N.
2018-01-01
Complex interaction geometries offer a unique opportunity to modify the strength and sign of the Casimir force. However, measurements have traditionally been limited to sphere-plate or plate-plate configurations. Prior attempts to extend measurements to different geometries relied on either nanofabrication techniques that are limited to only a few materials or slight modifications of the sphere-plate geometry due to alignment difficulties of more intricate configurations. Here, we overcome this obstacle to present measurements of the Casimir force between two gold spheres using an atomic force microscope. Force measurements are alternated with topographical scans in the x -y plane to maintain alignment of the two spheres to within approximately 400 nm (˜1 % of the sphere radii). Our experimental results are consistent with Lifshitz's theory using the proximity force approximation (PFA), and corrections to the PFA are bounded using nine sphere-sphere and three sphere-plate measurements with spheres of varying radii.
Proof that Casimir force does not originate from vacuum energy
Directory of Open Access Journals (Sweden)
Hrvoje Nikolić
2016-10-01
Full Text Available We present a simple general proof that Casimir force cannot originate from the vacuum energy of electromagnetic (EM field. The full QED Hamiltonian consists of 3 terms: the pure electromagnetic term Hem, the pure matter term Hmatt and the interaction term Hint. The Hem-term commutes with all matter fields because it does not have any explicit dependence on matter fields. As a consequence, Hem cannot generate any forces on matter. Since it is precisely this term that generates the vacuum energy of EM field, it follows that the vacuum energy does not generate the forces. The misleading statements in the literature that vacuum energy generates Casimir force can be boiled down to the fact that Hem attains an implicit dependence on matter fields by the use of the equations of motion and to the illegitimate treatment of the implicit dependence as if it was explicit. The true origin of the Casimir force is van der Waals force generated by Hint.
Numerical calculation of the force on some Generalized Casimir Pistons
Schaden, Martin
2009-04-01
In this talk I presented numerical calculations of the Casimir force due to a scalar field on a piston in a cylinder of radius τ with a spherical cap of radius R > τ. Geometrical subtractions give a finite interaction energy. Due to reflection positivity, the vacuum force on the piston by a scalar field satisfying Dirichlet boundary conditions is attractive for these geometries, but the strength and short-distance behavior of the force depends strongly on the shape of the piston casing. For a cylindrical casing with a hemispherical head of large radius, the attractive force on the piston is inversely proportional to the square of the height of the piston.
Tuning the Mass of Chameleon Fields in Casimir Force Experiments
Brax, Ph; Davis, A C; Shaw, D J; Iannuzzi, D
2010-01-01
We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long range Casimir force experiments.
Casimir Forces at Tricritical Points: Theory and Possible Experiments
Ritschel, Uwe; Gerwinski, Markus
1997-01-01
Using field-theoretical methods and exploiting conformal invariance, we study Casimir forces at tricritical points exerted by long-range fluctuations of the order-parameter field. Special attention is paid to the situation where the symmetry is broken by the boundary conditions (extraordinary transition). Besides the parallel-plate configuration, we also discuss the geometries of two separate spheres and a single sphere near a planar wall, which may serve as a model for colloidal particles im...
A verification of quantum field theory – measurement of Casimir force
Indian Academy of Sciences (India)
Abstract. Here we review our work on measurement of the Casimir force between a large alu- minum coated a sphere and flat plate using an atomic force microscope. The average statistical pre- cision is 1% of the force measured at the closest separation. We have also shown nontrival boundary dependence of the Casimir ...
CASIMIR FORCE IN CRITICAL TERNARY POLYMER SOLUTIONS
Directory of Open Access Journals (Sweden)
H.Ridouane
2004-01-01
Full Text Available Consider a mixture of two incompatible polymers A and B in a common good solvent, confined between two parallel plates separated by a finite distance L. We assume that these plates strongly attract one of the two polymers close to the consolute point (critical adsorption. The plates then experience an effective force resulting from strong fluctuations of the composition. To simplify, we suppose that either plates have the same preference to attract one component (symmetric plates or they have an opposed preference (asymmetric plates. The force is attractive for symmetric plates and repulsive for asymmetric ones. We first exactly compute the force using the blob model, and find that the attractive and repulsive forces decay similarly to L-4. To go beyond the blob model that is a mean-field theory, and in order to get a correct induced force, we apply the Renormalization-Group to a φ4-field theory (φ is the composition fluctuation, with two suitable boundary conditions at the surfaces. The main result is that the expected force is the sum of two contributions. The first one is the mean-field contribution decaying as L-4, and the second one is the force deviation originating from strong fluctuations of the composition that decreases rather as L-3. This implies the existence of some cross-over distance L* ~ aN φ1/2 (a is the monomer size, N is the polymerization degree of chains and φ is the monomer volumic fraction, which separates two distance-regimes. For small distances (LL* the fluctuation force is more important.
Casimir forces from conductive silicon carbide surfaces
Sedighi Ghozotkhar, Mehdi; Svetovoy, V. B.; Broer, W. H.; Palasantzas, G.
2014-01-01
Samples of conductive silicon carbide (SiC), which is a promising material due to its excellent properties for devices operating in severe environments, were characterized with the atomic force microscope for roughness, and the optical properties were measured with ellipsometry in a wide range of
Macroscopic approach to the Casimir friction force
Nesterenko, V. V.; Nesterenko, A. V.
2014-01-01
The general formula is derived for the vacuum friction force between two parallel perfectly flat planes bounding two material media separated by a vacuum gap and moving relative to each other with a constant velocity $\\mathbf{v}$. The material media are described in the framework of macroscopic electrodynamics whereas the nonzero temperature and dissipation are taken into account by making use of the Kubo formulae from non-equilibrium statistical thermodynamics. The formula obtained provides ...
Tuning Patchy Bonds Induced by Critical Casimir Forces
Directory of Open Access Journals (Sweden)
Truc A. Nguyen
2017-11-01
Full Text Available Experimental control of patchy interactions promises new routes for the assembly of complex colloidal structures, but remains challenging. Here, we investigate the role of patch width in the assembly of patchy colloidal particles assembled by critical Casimir forces. The particles are composed of a hydrophobic dumbbell with an equatorial hydrophilic polymer shell, and are synthesized to have well-defined patch-to-shell area ratios. Patch-to-patch binding is achieved in near-critical binary solvents, in which the particle interaction strength and range are controlled by the temperature-dependent solvent correlation length. Upon decreasing the patch-to-shell area ratio, we observe a pronounced change of the bonding morphology towards directed single-bonded configurations, as clearly reflected in the formation of chain-like structures. Computer simulations using an effective critical Casimir pair potential for the patches show that the morphology change results from the geometric exclusion of the increasingly thick hydrophilic particle shells. These results highlight the experimental control of patchy interactions through the engineering of the building blocks on the way towards rationally designed colloidal superstructures.
Modulation of the Casimir force by laser pulses: Influence of oxide films on the silicon surface
Klimchitskaya, G. L.; Bukina, M. N.; Churkin, Yu. V.; Yurova, V. A.
2010-10-01
The possibility of modulating the Casimir force that acts in an air medium between a gold sphere and a silicon plate irradiated by laser pulses has been studied. It has been demonstrated that the oxide film that is formed on the silicon surface in air hardly affects the possibility of modulating the Casimir force when the distances between interacting bodies are of the order of 100 nm. With an increase in the distance, the modulation depth decreases; however, this region is of less practical interest, because the Casimir forces become too weak.
Energy Technology Data Exchange (ETDEWEB)
Mohideen, Umar [Univ. of California, Riverside, CA (United States)
2015-04-14
Duration of award was from 4/15/10-4/14/15. In this grant period our contributions to the field of VdW/Casimir forces are 24 refereed publications in journals such as Physical Review Letters (4) [1-4], Physical Review B (10) [5-14], Physical Review D (2) [15,16], Applied Physics Letters (1) [17], Review of Scientific Instruments (1) [18] and the International Journal of Modern Physics A (5) [19-23] and B(1) (invited review article [24]). We presented 2 plenary conference talks, 3 lectures at the Pan American School on Frontiers in Casimir Physics, 2 conferences, 1 colloquium and 11 APS talks. If publications are restricted to only those with direct connection to the aims proposed in the prior grant period, then it will be a total of 12: Physical Review Letters (3) [2-4], Physical Review B (6) [6-8,12,13,25], Review of Scientific Instruments (1) [18], International Journal of Modern Physics A (1) [19] and B(1) [169]. A brief aggregated description of the directly connected accomplishments is below. The following topics are detailed: dispersion force measurements with graphene, dispersion force from ferromagnetic metals, conclusion on role of electrostatic patches, UV radiation induced modification of the Casimir force, low temperature measurement of the Casimir force, and Casimir force from thin fluctuating membranes.
Critical Steps in Data Analysis for Precision Casimir Force Measurements with Semiconducting Films
Banishev, A. A.; Chang, Chia-Cheng; Mohideen, U.
2011-06-01
Some experimental procedures and corresponding results of the precision measurement of the Casimir force between low doped Indium Tin Oxide (ITO) film and gold sphere are described. Measurements were performed using an Atomic Force Microscope in high vacuum. It is shown that the magnitude of the Casimir force decreases after prolonged UV treatment of the ITO film. Some critical data analysis steps such as the correction for the mechanical drift of the sphere-plate system and photodiodes are discussed.
Casimir force in the Goedel space-time and its possible induced cosmological inhomogeneity
Energy Technology Data Exchange (ETDEWEB)
Khodabakhshi, Sh. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Shojai, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of)
2017-07-15
The Casimir force between two parallel plates in the Goedel universe is computed for a scalar field at finite temperature. It is observed that when the plates' separation is comparable with the scale given by the rotation of the space-time, the force becomes repulsive and then approaches zero. Since it has been shown previously that the universe may experience a Goedel phase for a small period of time, the induced inhomogeneities from the Casimir force are also studied. (orig.)
Bimonte, G.; Klimchitskaya, G. L.; Mostepanenko, V. M.
2017-05-01
We propose a universal experiment to measure the differential Casimir force between a Au-coated sphere and two halves of a structured plate covered with a P-doped Si overlayer. The concentration of free charge carriers in the overlayer is chosen slightly below the critical one, for which the phase transition from dielectric to metal occurs. One half of the structured plate is insulating, while the second half is made of gold. For the former we consider two structures, one consisting of bulk high-resistivity Si and the other of a layer of SiO 2 followed by bulk high-resistivity Si. The differential Casimir force is computed within the Lifshitz theory using four approaches that have been proposed in the literature to account for the role of free charge carriers in metallic and dielectric materials interacting with quantum fluctuations. According to these approaches, Au at low frequencies is described by either the Drude or the plasma model, whereas the free charge carriers in dielectric materials at room temperature are either taken into account or disregarded. It is shown that the values of differential Casimir forces, computed in the micrometer separation range using these four approaches, are widely distinct from each other and can be easily discriminated experimentally. It is shown that for all approaches the thermal component of the differential Casimir force is sufficiently large for direct observation. The possible errors and uncertainties in the proposed experiment are estimated and its importance for the theory of quantum fluctuations is discussed.
The critical Casimir force in the superfluid phase: effect of fluctuations
Energy Technology Data Exchange (ETDEWEB)
Biswas, Shyamal [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata-700 009 (India); Bhattacharjee, J K [SN Bose National Centre for Basic Sciences, Sector 3, JD Block, Salt Lake, Kolkata-700 098 (India); Samanta, Himadri S [Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Bhattacharyya, Saugata [Department of Physics, Vidyasagar College, 39 Sankar Ghosh Lane, Kolkata-700 006 (India); Hu, Bambi, E-mail: sbiswas.phys.cu@gmail.co [Centre for Nonlinear Studies, and BHKS Joint Centre for Nonlinear and Complex Systems, Hong Kong Baptist University, Kowloon Tong (Hong Kong)
2010-06-15
We have considered the critical Casimir force on a {sup 4}He film below and above the bulk {lambda} point. We have explored the role of fluctuations around the mean field theory in a perturbative manner, and have substantially improved the mean field result of Zandi et al (2007 Phys. Rev. E 76 030601(R)). The Casimir scaling function obtained by us approaches a universal constant (-{zeta}(3)/8{pi}) for T{approx}<2.13 K.
Kinetic Roughening and Material Optical Properties Influence on Van der Waals/Casimir Forces
van Zwol, P. J.; Palasantzas, G.
Atomic force microscopy measurements and force theory calculations using the Lifshitz theory show that van der Waals/Casimir dispersive forces have a strong dependence on surface roughness and material optical properties. It is found that at separations below 100 nm the roughness effect is
Casimir force in the Gödel space-time and its possible induced cosmological inhomogeneity
Khodabakhshi, Sh.; Shojai, A.
2017-07-01
The Casimir force between two parallel plates in the Gödel universe is computed for a scalar field at finite temperature. It is observed that when the plates' separation is comparable with the scale given by the rotation of the space-time, the force becomes repulsive and then approaches zero. Since it has been shown previously that the universe may experience a Gödel phase for a small period of time, the induced inhomogeneities from the Casimir force are also studied.
Tunable Casimir-Polder Forces and Spontaneous Emission Rates
Rosa, Felipe; Kort-Kamp, Wilton; Pinheiro, Felipe; Cysne, Tarik; Oliver, Diego; Farina, Carlos
2015-03-01
We investigate the dispersive Casimir-Polder interaction between a Rubidium atom and a graphene sheet subjected to an external magnetic field B. We demonstrate that this concrete physical system allows for a high degree of control of dispersive interactions at micro and nanoscales. Indeed, we show that the application of an external magnetic field can induce a 80 % reduction of the Casimir-Polder energy relative to its value without the field. We also show that sharp discontinuities emerge in the Casimir-Polder interaction energy for certain values of the applied magnetic field at low temperatures. In addition, we also show that atomic spontaneous emission rates can be greatly modified by the action of the magnetic field, with an order of magnitude enhancement or suppression depending on the dipole's moment orientation.
Casimir-Lifshitz force for nonreciprocal media and applications to photonic topological insulators
Fuchs, Sebastian; Lindel, Frieder; Krems, Roman V.; Hanson, George W.; Antezza, Mauro; Buhmann, Stefan Yoshi
2017-12-01
Based on the theory of macroscopic quantum electrodynamics, we generalize the expression of the Casimir force for nonreciprocal media. The essential ingredient of this result is the Green's tensor between two nonreciprocal semi-infinite slabs, including a reflexion matrix with four coefficients that mixes optical polarizations. This Green's tensor does not obey Lorentz's reciprocity and thus violates time-reversal symmetry. The general result for the Casimir force is analyzed in the retarded and nonretarded limits, concentrating on the influences arising from reflections with or without change of polarization. In a second step, we apply our general result to a photonic topological insulator whose nonreciprocity stems from an anisotropic permittivity tensor, namely InSb. We show that there is a regime for the distance between the slabs where the magnitude of the Casimir force is tunable by an external magnetic field. Furthermore, the strength of this tuning depends on the orientation of the magnetic field with respect to the slab surfaces.
Exact results for the Casimir force in a model with Neumann-infinity boundary conditions
Djondjorov, P. A.; Dantchev, D. M.; Vassilev, V. M.
2017-10-01
The dependence of the critical Casimir force on two parameters (temperature and external ordering field) within the mean-field Ginzburg-Landau Ising type model is studied. Here, the case of a film geometry where one boundary of the film exhibits strong adsorption to one of the phases (components) of the system, whereas the first derivative of the order-parameter profile vanishes on the other one is studied. The results obtained herein are valid for both, simple fluids and binary liquid mixtures. In the present contribution, the order parameter profile and the Casimir force are presented in exact analytic form, expressed through the Weierstrass function. Using these results, the dependence of the critical Casimir force on the temperature and external ordering field are illustrated.
Influence of random roughness on the Casimir force at small separations
van Zwol, P. J.; Palasantzas, G.; De Hosson, J. Th. M.
The influence of random surface roughness of Au films on the Casimir force is explored with atomic force microscopy in the plate-sphere geometry. The experimental results are compared to theoretical predictions for separations ranging between 20 and 200 nm. The optical response and roughness of the
Transition from Casimir to van der Waals force between macroscopic bodies
Palasantzas, G.; van Zwol, P. J.; De Hosson, J. Th. M.
2008-01-01
The transition of van der Waals to Casimir forces between macroscopic gold surfaces is investigated by atomic force microscopy in the plane-sphere geometry. It was found that the transition appears to take place at separations similar to 10% the plasma wavelength lambda(p) for evaporated gold
Optical properties and kinetic roughening influence on dispersive casimir and van der Waals forces
Palasantzas, G.; Svetovoy, Vitaly; van Zwol, P.J.
2010-01-01
Casimir and van der Waals dispersive forces between real material surfaces can be strongly influenced by surface roughness and the frequency dependent dielectric functions of the interacting materials. The Lifshitz theory allows calculations of these forces between two flat plates if the frequency
Optical Properties and Kinetic Roughening Influence on Dispersive Casimir and van der Waals Forces
Palasantzas, G.; Svetovoy, V. B.; Van Zwol, P. J.
2010-01-01
Casimir and van der Waals dispersive forces between real material surfaces can be strongly influenced by surface roughness and the frequency dependent dielectric functions of the interacting materials. The Lifshitz theory allows calculations of these forces between two flat plates if the frequency
Casimir stress inside planar materials
Griniasty, Itay; Leonhardt, Ulf
2017-09-01
The Casimir force between macroscopic bodies is well understood, but not the Casimir force inside bodies. Guided by a physically intuitive picture, we develop the macroscopic theory of the renormalized Casimir stress inside planar materials (where the electromagnetic properties vary in one direction). Our theory may be applied in predicting how inhomogeneous fluids respond to Casimir forces.
Liang, Binbin; Zhang, Long; Wang, Binglei; Zhou, Shenjie
2015-07-01
A size-dependent model for the electrostatically actuated Nano-Electro-Mechanical Systems (NEMS) incorporating nonlinearities and Casimir force is presented by using a variational method. The governing equation and boundary conditions are derived with the help of strain gradient elasticity theory and Hamilton principle. Generalized differential quadrature (GDQ) method is employed to solve the problem numerically. The pull-in instability with Casimir force included is then studied. The results reveal that Casimir force, which is a spontaneous force between the two electrodes, can reduce the external applied voltage. With Casimir force incorporated, the pull-in instability occurs without voltage applied when the beam size is in nanoscale. The minimum gap and detachment length can be calculated from the present model for different beam size, which is important for NEMS design. Finally, discussions of size effect induced by the strain gradient terms reveal that the present model is more accurate since size effect play an important role when beam in nanoscale.
Broer, W.; Palasantzas, G.; Knoester, J.; Svetovoy, Vitaly
2012-01-01
So far there has been no reliable method to calculate the Casimir force at separations comparable to the root-mean square of the height fluctuations of the surfaces. Statistical analysis of rough gold samples has revealed the presence of peaks considerably higher than the root-mean-square roughness.
Broer, Wijnand; Palasantzas, George; Knoester, Jasper; Svetovoy, Vitaly B.
2012-01-01
So far there has been no reliable method to calculate the Casimir force at separations comparable to the root-mean square of the height fluctuations of the surfaces. Statistical analysis of rough gold samples has revealed the presence of peaks considerably higher than the root-mean-square roughness.
Influence of dielectric properties on van der Waals/Casimir forces in solid-liquid systems
van Zwol, P. J.; Palasantzas, G.; De Hosson, J. Th. M.
In this paper, we present calculations of van der Waals/Casimir forces, described by Lifshitz theory, for the solid-liquid-solid system using measured dielectric functions of all involved materials for the wavelength range from millimeters down to subnanometers. It is shown that even if the
Repulsive Casimir forces between solid materials with high-refractive-index intervening liquids
van Zwol, P. J.; Palasantzas, G.
2010-01-01
In order to explore repulsive Casimir or van der Waals forces between solid materials with liquid as the intervening medium, we analyze dielectric data for a wide range of materials as, for example, (p) olytetrafluoroethylene, polystyrene, silica, and more than 20 liquids. Although significant
van Zwol, P.J.; Svetovoy, Vitaly; Palasantzas, G.
2011-01-01
The Lifshitz theory provides a method to calculate the Casimir force between two flat plates if the frequency dependent dielectric function of the plates is known. In reality any plate is rough and its optical properties are known only to some degree. For high precision experiments the plates must
How to modify the van der Waals and Casimir forces without change of the dielectric permittivity.
Klimchitskaya, G L; Mohideen, U; Mostepanenko, V M
2012-10-24
We propose a new experiment on the measurement of the Casimir force and its gradient between a Au-coated sphere and two different plates made of doped semiconductors. The concentrations of charge carriers in the plates are chosen slightly below and above the critical density at which the Mott-Anderson insulator-metal transition occurs. We calculate changes in the Casimir force and the Casimir pressure due to the insulator-metal transition using the standard Lifshitz theory and the phenomenological approach neglecting the contribution of free charge carriers in the dielectric permittivity of insulator materials (this approach was recently supported by the measurement data of several experiments). It is demonstrated that for the special selection of semiconductor materials (S- or Se-doped Si, B-doped diamond) the calculation results using the two theoretical approaches differ significantly and the predicted effects are easily detectable using the existing laboratory setups. In the case that the prediction of the phenomenological approach is confirmed, this would open opportunities to modify the van der Waals and Casimir forces with almost no change of room temperature dielectric permittivity.
Esteso, Victoria; Carretero-Palacios, Sol; Míguez, Hernán
2015-03-12
We report on the theoretical analysis of equilibrium distances in real plane-parallel systems under the influence of Casimir and gravity forces at thermal equilibrium. Due to the balance between these forces, thin films of Teflon, silica, or polystyrene in a single-layer configuration and immersed in glycerol stand over a silicon substrate at certain stable or unstable positions depending on the material and the slab thickness. Hybrid systems containing silica and polystyrene, materials which display Casimir forces and equilibrium distances of opposite nature when considered individually, are analyzed in either bilayer arrangements or as composite systems made of a homogeneous matrix with small inclusions inside. For each configuration, equilibrium distances and their stability can be adjusted by fine-tuning of the volume occupied by each material. We find the specific conditions under which nanolevitation of realistic films should be observed. Our results indicate that thin films of real materials in plane-parallel configurations can be used to control suspension or stiction phenomena at the nanoscale.
Martinez, J. C.; Jalil, M. B. A.
2013-05-01
The axion coupling in topological insulators (TI), which couples electric polarization (magnetization) with the magnetic (electric) field, is known to support a small-distance Casimir repulsion and a large-distance Casimir attraction with a zero-force stable equilibrium between TI plates. By enhancing the reflection properties of the TI interface through mirrors that introduce multiple reflections, we show that it is possible to maintain these trends while tuning the position of the zero-force point and its binding energy: the former by an order of magnitude and latter by over four orders. Moreover, surface charge on the TI allows for intermediate tuning of the zero-force point between coarse settings determined by the axion coupling.
Casimir force between two parallel semiconductor slabs: Magnetic field effects in the Voigt geometry
Energy Technology Data Exchange (ETDEWEB)
Garcia-Serrano, R.; Palomino-Ovando, M. [Facultad de Ciencias Fisico-Matematicas, Universidad Autonoma de Puebla, Puebla (Mexico); Martinez, G.; Hernandez, P.H.; Cocoletzi, Gregorio H. [Instituto de Fisica, Universidad Autonoma de Puebla, Puebla (Mexico)
2009-06-15
We investigate the Casimir force F between two parallel semiconductor slabs taking into account magnetoplasmon effects. For our calculations we consider an external magnetic field applied in the Voigt geometry. Studies are carried out using the formula of F, which is written in terms of the reflectivities of the incident electromagnetic (EM) waves onto the surfaces of the semiconductor slabs, in the vacuum gap between slabs. Results show that the Casimir force depends strongly on the slab thickness as well as on the magnetic-field strength (or equivalently on the cyclotron frequency). At a constant cyclotron frequency and for small slab thickness F/F{sub 0} (F{sub 0} is the ideal force) displays a dip at small separation distances L between slabs. F/F{sub 0} increases with L up to saturation as the slab thickness increases. The curve with the strongest value of F/F{sub 0} corresponds to the semi-infinite medium geometry. For a constant slab thickness and small cyclotron frequency, F/F{sub 0} as a function of L shows a monotonic increase as L increases, and eventually reaches saturation. At high cyclotron frequency F/F{sub 0} displays a dip. The curve of F/F{sub 0} with no applied external field corresponds to the one with the strongest Casimir force. Therefore, magnetoplasmon effects, with an applied magnetic field in the Voigt geometry may inhibit the Casimir force. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Dubail, J.; Santachiara, R.; Emig, T.
2017-03-01
Systems as diverse as binary mixtures and inclusions in biological membranes, and many more, can be described effectively by interacting spins. When the critical fluctuations in these systems are constrained by boundary conditions, critical Casimir forces (CCF) emerge. Here we analyze CCF between boundaries with alternating boundary conditions in two dimensions, employing conformal field theory (CFT). After presenting the concept of boundary changing operators, we specifically consider two different boundary configurations for a strip of critical Ising spins: (I) alternating equi-sized domains of up and down spins on both sides of the strip, with a possible lateral shift, and (II) alternating domains of up and down spins of different size on one side and homogeneously fixed spins on the other side of the strip. Asymptotic results for the CCF at small and large distances are derived. We introduce a novel modified Szegö formula for determinants of real antisymmetric block Toeplitz matrices to obtain the exact CCF and the corresponding scaling functions at all distances. We demonstrate the existence of a surface renormalization group flow between universal force amplitudes of different magnitude and sign. The Casimir force can vanish at a stable equilibrium position that can be controlled by parameters of the boundary conditions. Lateral Casimir forces assume a universal simple cosine form at large separations.
Detecting Casimir torque with an optically levitated nanorod
Xu, Zhujing; Li, Tongcang
2017-09-01
The linear momentum and angular momentum of virtual photons of quantum vacuum fluctuations can induce the Casimir force and the Casimir torque, respectively. While the Casimir force has been measured extensively, the Casimir torque has not been observed experimentally though it was predicted over 40 years ago. Here we propose to detect the Casimir torque with an optically levitated nanorod near a birefringent plate in vacuum. The axis of the nanorod tends to align with the polarization direction of the linearly polarized optical tweezer. When its axis is not parallel or perpendicular to the optical axis of the birefringent crystal, it will experience a Casimir torque that shifts its orientation slightly. We calculate the Casimir torque and Casimir force acting on a levitated nanorod near a birefringent crystal. We also investigate the effects of thermal noise and photon recoils on the torque and force detection. We prove that a levitated nanorod in vacuum will be capable of detecting the Casimir torque under realistic conditions, and will be an important tool in precision measurements.
Stable levitation and alignment of compact objects by Casimir spring forces.
Rahi, Sahand Jamal; Zaheer, Saad
2010-02-19
We investigate a stable Casimir force configuration consisting of an object contained inside a spherical or spheroidal cavity filled with a dielectric medium. The spring constant for displacements from the center of the cavity and the dependence of the energy on the relative orientations of the inner object and the cavity walls are computed. We find that the stability of the force equilibrium-unlike the direction of the torque-can be predicted based on the sign of the force between two slabs of the same material.
Zwol, P.J. van; Palasantzas, G.
2010-01-01
Theory calculations using the Lifshitz theory and atomic force microscopy force measurements show that Casimir/van der Weals dispersive forces have a strong dependence on material optical properties and surface roughness. At separations below 100 nm the roughness effect is manifested through a
Farrokhabadi, Amin; Mokhtari, Javad; Rach, Randolph; Abadyan, Mohamadreza
2015-09-01
The Casimir force can strongly interfere with the pull-in performance of ultra-small structures. The strength of the Casimir force is significantly affected by the geometries of interacting bodies. Previous investigators have exclusively studied the effect of the Casimir force on the electromechanical instability of nanostructures with planar geometries. However no work has yet considered this effect on the pull-in instability of systems with cylindrical geometries such as nanotweezers fabricated from nanotube/nanowires. In our present work, the influence of the Casimir attraction on the electrostatic response and pull-in instability of nanotweezers fabricated from cylindrical conductive nanowires/nanotubes is theoretically investigated. An asymptotic solution, based on scattering theory, is applied to consider the effect of vacuum fluctuations in the theoretical model. The Euler-Bernoulli beam model is employed, in conjunction with the size-dependent modified couple stress continuum theory, to derive the governing equation of the nanotweezers. The governing nonlinear equations are solved by two different approaches, i.e., the modified Adomian-Padé method (MAD-Padé) and a numerical solution. Various aspects of the problem, i.e., the variation of pull-in parameters, effect of geometry, coupling between the Casimir force and size dependency effects and comparison with the van der Waals force regime are discussed.
Modifying the Casimir force between indium tin oxide film and Au sphere
Banishev, A. A.; Chang, C.-C.; Castillo-Garza, R.; Klimchitskaya, G. L.; Mostepanenko, V. M.; Mohideen, U.
2012-01-01
We present complete results of the experiment on measuring the Casimir force between an Au-coated sphere and an untreated or, alternatively, UV-treated indium tin oxide (ITO) film deposited on a quartz substrate. Measurements were performed using an atomic force microscope in a high vacuum chamber. The measurement system was calibrated electrostatically. Special analysis of the systematic deviations is performed, and respective corrections in the calibration parameters are introduced. The corrected parameters are free from anomalies discussed in the literature. The experimental data for the Casimir force from two measurement sets for both untreated and UV-treated samples are presented. The random, systematic, and total experimental errors are determined at a 95% confidence level. It is demonstrated that the UV treatment of an ITO plate results in a significant decrease in the magnitude of the Casimir force (from 21% to 35% depending on separation). However, ellipsometry measurements of the imaginary parts of dielectric permittivities of the untreated and UV-treated samples did not reveal any significant differences. The experimental data are compared with computations in the framework of the Lifshitz theory. It is found that the data for the untreated sample are in a very good agreement with theoretical results taking into account the free charge carriers in an ITO film. For the UV-treated sample the data exclude the theoretical results obtained with account of free charge carriers. These data are in very good agreement with computations disregarding the contribution of free carriers in the dielectric permittivity. According to the hypothetical explanation provided, this is caused by the phase transition of the ITO film from metallic to dielectric state caused by the UV treatment. Possible applications of the discovered phenomenon in nanotechnology are discussed.
Approximating the effect of the Casimir force on the instability of electrostatic nano-cantilevers
Energy Technology Data Exchange (ETDEWEB)
Abadyan, Mohamadreza [Islamic Azad University, Tonekabon Branch, Ramsar Center, Ramsar (Iran, Islamic Republic of); Novinzadeh, Alireza [Aerospace Engineering Department, K N Toosi University of Technology, East Vafadar Street, PO Box 16765-3381, Tehran (Iran, Islamic Republic of); Kazemi, AsiehSadat [School of Physics and Center for Solid State Research, Damghan University of Basic Sciences, PO Box 367164-167, Damghan (Iran, Islamic Republic of)], E-mail: novinzadeh@kntu.ac.ir
2010-01-15
In this paper, the homotopy perturbation method (HPM) is used to investigate the effect of the Casimir force on the pull-in instability of electrostatic actuators at nano-scale separations. The proposed HPM is employed to solve nonlinear constitutive equations of cantilever beam-type nanoactuators. An analytical solution is obtained in terms of convergent series with easily computable components. Basic design parameters such as critical cantilever tip deflection and pull-in voltage of the nano-cantilevers are computed. As special cases of this work, freestanding nanoactuators and electrostatic micro-actuators are investigated. The analytical HPM results agree well with numerical solutions and those from the literature.
Lateral-drag Casimir forces induced by anisotropy
Nefedov, Igor S
2016-01-01
We predict the existence of lateral drag forces near the flat surface of an absorbing slab of an anisotropic material. The forces originate from the fluctuations of the electromagnetic field, when the anisotropy axis of the material forms a certain angle with the surface. In this situation, the spatial spectra of the fluctuating electromagnetic fields becomes asymmetric, different for positive and negative transverse wave vectors components. Differently from the case of van der Waals interactions in which the forward-backward symmetry is broken due to the particle movement or in quantum noncontact friction where it is caused by the mutual motion of the bodies, in our case the lateral motion results merely from the anisotropy of the slab. This new effect, of particular significance in hyperbolic materials, could be used for the manipulation of nanoparticles.
Thermal corrections to the Casimir energy in a general weak gravitational field
Nazari, Borzoo
2016-12-01
We calculate finite temperature corrections to the energy of the Casimir effect of a two conducting parallel plates in a general weak gravitational field. After solving the Klein-Gordon equation inside the apparatus, mode frequencies inside the apparatus are obtained in terms of the parameters of the weak background. Using Matsubara’s approach to quantum statistical mechanics gravity-induced thermal corrections of the energy density are obtained. Well-known weak static and stationary gravitational fields are analyzed and it is found that in the low temperature limit the energy of the system increases compared to that in the zero temperature case.
Farrokhabadi, Amin; Abadian, Naeime; Rach, Randolph; Abadyan, Mohamadreza
2014-09-01
The Casimir force can induce instability and adhesion in freestanding nanostructures. Previous research efforts in this area have exclusively focused on modeling the instability in structures with planar or rectangular cross-section, while, to the best knowledge of the authors, no attention has been paid to investigate this phenomenon for nanowires with circular cross-section. In this study, effects of the Casimir force on the instability and adhesion of freestanding Cylinder-Plate and Cylinder-Cylinder geometries are investigated, which are commonly encountered in real nanodevices. To compute the Casimir force, two approaches, i.e. the proximity force approximation (PFA) for small separations and Dirichlet asymptotic approximation (scattering theory) for large separations, are considered. A continuum mechanics theory is employed, in conjunction with the Euler-beam model, to obtain constitutive equations of the systems. The governing nonlinear constitutive equations of the nanostructures are solved using two different approaches, i.e. the analytical modified Adomian decomposition (MAD) and the numerical finite difference method (FDM). The detachment length and minimum gap, both of which prevent the Casimir force-induced adhesion, are computed for both configurations.
Palasantzas, George
2007-01-01
In this work, we investigate the combined influence of electromagnetic and acoustic Casimir forces on the pull-in voltage of microswitches with self-affine rough plates. It is shown that for plate separations within the micron range the acoustic term arising from pressure fluctuations can influence
Energy Technology Data Exchange (ETDEWEB)
Torres-Guzman, Jose C [Centro de Ciencias FIsicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico); Mochan, W Luis [Centro de Ciencias FIsicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico)
2006-05-26
We develop a formalism for the calculation of the flow of angular momentum carried by the fluctuating electromagnetic field within a cavity bounded by two flat anisotropic materials. By generalizing a procedure employed recently for the calculation of the Casimir force between arbitrary materials, we obtain an expression for the torque between anisotropic plates in terms of their reflection amplitude matrices. We evaluate the torque in 1D for ideal and dispersive model materials.
Rodrigues, Janderson R; Gusso, Andre; Rosa, Felipe S S; Almeida, Vilson R
2018-02-09
Nano-optomechanical devices have enabled a lot of interesting scientific and technological applications. However, due to their nanoscale dimensions, they are vulnerable to the action of Casimir and van der Waals (dispersion) forces. This work presents a rigorous analysis of the dispersion forces on a nano-optomechanical device based on a silicon waveguide and a silicon dioxide substrate, surrounded by air and driven by optical forces. The dispersion forces are calculated using a modified Lifshitz theory with experimental optical data and validated by means of a rigorous 3D FDTD simulation. The mechanical nonlinearity of the nanowaveguide is taken into account and validated using a 3D FEM simulation. The results show that it is possible to attain a no pull-in critical point due to only the optical forces; however, the dispersion forces usually impose a pull-in critical point to the device and establish a minimal initial gap between the waveguide and the substrate. Furthermore, it is shown that the geometric nonlinearity effect may be exploited in order to avoid or minimize the pull-in and, therefore, the device collapse.
Uvarova, L. A.; Babarin, S. S.
2014-09-01
This work is devoted to the problem of dynamics of molecules and nanoparticles in fields in following potentials: the Casimir force, the van der Waals interactions, the Coulomb potential for charged particles, the potential energies for bonds, and the electric potential. In the general case, molecules or nanoparticles move in nano volumes with walls of different optical properties. In particular, the matter at boundary can be with zero refracted index (Vesseur E J R et al 2013 Phys. Rev. Lett. 110 013902; Uvarova L A 2005 AIP congress). Current model can be used to investigate dynamical and configuration properties of particle systems, and to determine influences of molecules interactions with the walls. It is accepted that the Casimir force affects the velocity distribution function, the total energy, and equilibrium properties that produce rise of temperature, pressure and energy deviations. In many-atom molecules or nanoparticles interactions with the Casimir force are more complex, but they give opportunity to control admixtures and modification of system under the influence of electromagnetic waves.
Nonlinear (Anharmonic Casimir Oscillator
Directory of Open Access Journals (Sweden)
Habibollah Razmi
2011-01-01
Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.
Force sensor for chameleon and Casimir force experiments with parallel-plate configuration
Almasi, A.; Brax, P.; Iannuzzi, D.; Sedmik, R.
2015-01-01
The search for non-Newtonian forces has been pursued following many different paths. Recently it was suggested that hypothetical chameleon interactions, which might explain the mechanisms behind dark energy, could be detected in a high-precision force measurement. In such an experiment, interactions
Interplay between geometry and temperature in the Casimir effect
Energy Technology Data Exchange (ETDEWEB)
Weber, Alexej
2010-06-23
In this thesis, we investigate the interplay between geometry and temperature in the Casimir effect for the inclined-plates, sphere-plate and cylinder-plate configurations. We use the worldline approach, which combines the string-inspired quantum field theoretical formalism with Monte Carlo techniques. The approach allows the precise computation of Casimir energies in arbitrary geometries. We analyze the dependence of the Casimir energy, force and torque on the separation parameter and temperature T, and find Casimir phenomena which are dominated by long-range fluctuations. We demonstrate that for open geometries, thermal energy densities are typically distributed on scales of thermal wavelengths. As an important consequence, approximation methods for thermal corrections based on local energy-density estimates, such as the proximity-force approximation, are found to become unreliable even at small surface-separations. Whereas the hightemperature behavior is always found to be linear in T, richer power-law behaviors at small temperatures emerge. In particular, thermal forces can develop a non-monotonic behavior. Many novel numerical as well as analytical results are presented. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Razmi, H. [Department of Physics, University of Qom, Qom 37185-359 (Iran, Islamic Republic of)], E-mail: razmi@qom.ac.ir; Abdollahi, M. [Department of Physics, University of Qom, Qom 37185-359 (Iran, Islamic Republic of)], E-mail: mah.abdollahi@gmail.com
2008-11-10
We want to introduce an atomic pendulum whose driving force (torque) is due to the quantum vacuum fluctuations. Applying the well-known Casimir-Polder effect to a special configuration (a combined structure of an atomic nanostring and a conducting plate), an atomic pendulum (Casimir atomic pendulum) is designed. Using practically acceptable data corresponding to the already known world of nanotechnology and based on reasonable/reliable numerical estimates, the period of oscillation for the pendulum is computed. This pendulum can be considered as both a new micro(nano)-electromechanical system and a new simple vacuum machine. Its design may be considered as a first step towards realizing the visualized vacuum (Casimir) clock{exclamation_point}.
Razmi, H.; Abdollahi, M.
2008-11-01
We want to introduce an atomic pendulum whose driving force (torque) is due to the quantum vacuum fluctuations. Applying the well-known Casimir-Polder effect to a special configuration (a combined structure of an atomic nanostring and a conducting plate), an atomic pendulum (Casimir atomic pendulum) is designed. Using practically acceptable data corresponding to the already known world of nanotechnology and based on reasonable/reliable numerical estimates, the period of oscillation for the pendulum is computed. This pendulum can be considered as both a new micro(nano)-electromechanical system and a new simple vacuum machine. Its design may be considered as a first step towards realizing the visualized vacuum (Casimir) clock!
Bose-Einstein condensation and the Casimir effect for an ideal Bose gas confined between two slabs
Energy Technology Data Exchange (ETDEWEB)
Biswas, Shyamal [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)
2007-08-17
We study the Casimir effect for a 3D system of ideal Bose gas in a slab geometry with a Dirichlet boundary condition. We calculate the temperature (T) dependence of the Casimir force below and above the Bose-Einstein condensation temperature (T{sub c}). At T {<=} T{sub c} the Casimir force vanishes as [T/T{sub c}]{sup 3/2}. For T {approx}> T{sub c} it weakly depends on temperature. For T >> T{sub c} it vanishes exponentially. At finite temperatures this force for thermalized photons in between two plates has a classical expression which is independent of {Dirac_h}. At finite temperatures the Casimir force for our system depends on {Dirac_h}.
Advances in the Casimir Effect
Bordag, Michael; Mohideen, Umar; Mostepanenko, Vladimir Mikhaylovich
2009-01-01
The subject of this book is the Casimir effect, a manifestation of zero-point oscillations of the quantum vacuum resulting in forces acting between closely spaced bodies. For the benefit of the reader, the book assembles field-theoretical foundations of this phenomenon, applications of the general theory to real materials, and a comprehensive description of all recently performed measurements of the Casimir force with a comparison between experiment and theory. There is an urgentneed for a book of this type, given the increase of interest in forces originating from the quantum vacuum. Numerous
A Generalization of Electromagnetic Fluctuation-Induced Casimir Energy
Directory of Open Access Journals (Sweden)
Yi Zheng
2015-01-01
Full Text Available Intermolecular forces responsible for adhesion and cohesion can be classified according to their origins; interactions between charges, ions, random dipole—random dipole (Keesom, random dipole—induced dipole (Debye are due to electrostatic effects; covalent bonding, London dispersion forces between fluctuating dipoles, and Lewis acid-base interactions are due to quantum mechanical effects; pressure and osmotic forces are of entropic origin. Of all these interactions, the London dispersion interaction is universal and exists between all types of atoms as well as macroscopic objects. The dispersion force between macroscopic objects is called Casimir/van der Waals force. It results from alteration of the quantum and thermal fluctuations of the electrodynamic field due to the presence of interfaces and plays a significant role in the interaction between macroscopic objects at micrometer and nanometer length scales. This paper discusses how fluctuational electrodynamics can be used to determine the Casimir energy/pressure between planar multilayer objects. Though it is confirmation of the famous work of Dzyaloshinskii, Lifshitz, and Pitaevskii (DLP, we have solved the problem without having to use methods from quantum field theory that DLP resorted to. Because of this new approach, we have been able to clarify the contributions of propagating and evanescent waves to Casimir energy/pressure in dissipative media.
Directory of Open Access Journals (Sweden)
Valchev Galin
2018-01-01
Full Text Available Here we study the interplay between the van der Waals (vdWF and critical Casimir forces (CCF, as well as the total force (TF between a conical colloid particle and a thick planar slab. We do that using general scaling arguments and mean-field type calculations utilizing the so-called “surface integration approach”, a generalization of the well known Derjaguin approximation. Its usage in the present research, requires knowledge on the forces between two parallel slabs, confining in between some fluctuating fluid medium characterized by its temperature T and chemical potential μ. The surfaces of the colloid particle and the slab are assumed coated by thin layers exerting strong preference to the liquid phase of a simple fluid, or one of the components of a binary mixture, modeled by strong adsorbing local surface potentials, ensuring the so-called (+,+ boundary conditions. On the other hand, the core region of the slab and the particle, influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloid-fluid, slab-fluid, and fluid-fluid coupling parameters the competition between the effects due to the coatings and the core regions of the objects, result, when one changes T or μ, in sign change of the Casimir force (CF and the TF acting between the colloid and the slab. Such an effect can provide a strategy for solving problems with handling, feeding, trapping and fixing of microparts in nanotechnology.
Fermions on the low-buckled honey-comb structured lattice plane and classical Casimir-Polder force
Goswami, Partha
2016-05-01
We start with the well-known expression for the vacuum polarization and suitably modify it for 2+1-dimensional spin-orbit coupled (SOC) fermions on the low-buckled honey-comb structured lattice plane described by the low-energy Liu-Yao-Feng-Ezawa (LYFE) model Hamiltonian involving the Dirac matrices in the chiral representation obeying the Clifford algebra. The silicene and germanene fit this description suitably. They have the Dirac cones similar to those of graphene and SOC is much stronger. The system could be normal or ferromagnetic in nature. The silicene turns into the latter type if there is exchange field arising due to the proximity coupling to a ferromagnet (FM) such as depositing Fe atoms to the silicene surface. For the silicene, we find that the many-body effects considerably change the bare Coulomb potential by way of the dependence of the Coulomb propagator on the real-spin, iso-spin and the potential due to an electric field applied perpendicular to the silicene plane. The computation aspect of the Casimir-Polder force (CPF) needs to be investigated in this paper. An important quantity in this process is the dielectric response function (DRF) of the material. The plasmon branch was obtained by finding the zeros of DRF in the long-wavelength limit. This leads to the plasmon frequencies. We find that the collective charge excitations at zero doping, i.e., intrinsic plasmons, in this system, are absent in the Dirac limit. The valley-spin-split intrinsic plasmons, however, come into being in the case of the massive Dirac particles with characteristic frequency close to 10 THz. Our scheme to calculate the Casimir-Polder interaction (CPI) of a micro-particle with a sheet involves replacing the dielectric constant of the sample in the CPI expression obtained on the basis of the Lifshitz theory by the static DRF obtained using the expressions for the polarization function we started with. Though the approach replaces a macroscopic constant by a microscopic
What the Casimir-Effect really is telling about Zero-Point Energy
Gruendler, Gerold
2013-01-01
The attractive force between metallic surfaces, predicted by Casimir in 1948, seems to indicate the physical existence and measurability of the quantized electromagnetic field's zero-point energy. It is shown in this article, that Casimir's derivation depends essentially on a misleading idealization. When that idealization is replaced by a realistic assumption, Casimir's argument turns to the exact opposite: The observed Casimir force does positively prove, that the electromagnetic field's zero-point energy does not exert forces onto metallic surfaces.
Casimir-Polder forces on atoms in the presence of magnetoelectronic bodies
Energy Technology Data Exchange (ETDEWEB)
Buhmann, S.Y.
2007-07-05
In this work, the CP force between a single neutral atom or molecule and neutral magnetoelectric bodies is studied. The focus lies on the pure vacuum CP force, i.e., the electromagnetic field is in general understood to be in its ground state. Furthermore, we assume that the atom-body separation is sufficiently large to ensure that the atom is adequately characterised as an electric dipole, while the body can be described by its macroscopic magnetoelectric properties; and that repulsive exchange forces due to the overlap between the electronic wave functions of the atom and the bodies can be neglected. Interactions due to non-vanishing net charges, permanent electric dipole moments, magnetisability, quadrupole (or higher multipole) polarisabilities of the atom and those resulting from non-local or anisotropic magnetoelectric properties of the bodies are ignored. (orig.)
Quantum thermal machines driven by vacuum forces
Terças, Hugo; Ribeiro, Sofia; Pezzutto, Marco; Omar, Yasser
2017-02-01
We propose a quantum thermal machine composed of two nanomechanical resonators (two membranes suspended over a trench in a substrate) placed a few μ m from each other. The quantum thermodynamical cycle is powered by the Casimir interaction between the resonators and the working fluid is the polariton resulting from the mixture of the flexural (out-of-plane) vibrations. With the help of piezoelectric cells, we select and sweep the polariton frequency cyclically. We calculate the performance of the proposed quantum thermal machines and show that high efficiencies are achieved thanks to (i) the strong coupling between the resonators and (ii) the large difference between the membrane stiffnesses. Our findings can be of particular importance for applications in nanomechanical technologies where a sensitive control of temperature is needed.
The Reality of Casimir Friction
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Kimball A. Milton
2016-04-01
Full Text Available For more than 35 years theorists have studied quantum or Casimir friction, which occurs when two smooth bodies move transversely to each other, experiencing a frictional dissipative force due to quantum electromagnetic fluctuations, which break time-reversal symmetry. These forces are typically very small, unless the bodies are nearly touching, and consequently such effects have never been observed, although lateral Casimir forces have been seen for corrugated surfaces. Partly because of the lack of contact with observations, theoretical predictions for the frictional force between parallel plates, or between a polarizable atom and a metallic plate, have varied widely. Here, we review the history of these calculations, show that theoretical consensus is emerging, and offer some hope that it might be possible to experimentally confirm this phenomenon of dissipative quantum electrodynamics.
Is zero-point energy physical? A toy model for Casimir-like effect
Nikolić, Hrvoje
2017-08-01
Zero-point energy is generally known to be unphysical. Casimir effect, however, is often presented as a counterexample, giving rise to a conceptual confusion. To resolve the confusion we study foundational aspects of Casimir effect at a qualitative level, but also at a quantitative level within a simple toy model with only 3 degrees of freedom. In particular, we point out that Casimir vacuum is not a state without photons, and not a ground state for a Hamiltonian that can describe Casimir force. Instead, Casimir vacuum can be related to the photon vacuum by a non-trivial Bogoliubov transformation, and it is a ground state only for an effective Hamiltonian describing Casimir plates at a fixed distance. At the fundamental microscopic level, Casimir force is best viewed as a manifestation of van der Waals forces.
Casimir interactions for anisotropic magnetodielectric metamaterials
Energy Technology Data Exchange (ETDEWEB)
Da Rosa, Felipe S [Los Alamos National Laboratory; Dalvit, Diego A [Los Alamos National Laboratory; Milonni, Peter W [Los Alamos National Laboratory
2008-01-01
We extend our previous work on the generalization of the Casimir-Lifshitz theory to treat anisotropic magnetodielectric media, focusing on the forces between metals and magnetodielectric metamaterials and on the possibility of inferring magnetic effects by measurements of these forces.
Frassino, Antonia M.; Nicolini, Piero; Panella, Orlando
2017-09-01
In this paper we present the un-Casimir effect, namely the study of the Casimir energy in the presence of an unparticle component in addition to the electromagnetic field contribution. The distinctive feature of the un-Casimir effect is a fractalization of metallic plates. This result emerges through a new dependence of the Casimir energy on the plate separation that scales with a continuous power controlled by the unparticle dimension. As long as the perfect conductor approximation is valid, we find bounds on the unparticle scale that are independent of the effective coupling constant between the scale invariant sector and ordinary matter. We find regions of the parameter space such that for plate distances around 5 μm and larger the un-Casimir bound wins over the other bounds.
Valchev, Galin; Dantchev, Daniel
2015-07-01
We study, using general scaling arguments and mean-field type calculations, the behavior of the critical Casimir force and its interplay with the van der Waals force acting between two parallel slabs separated at a distance L from each other, confining some fluctuating fluid medium, say a nonpolar one-component fluid or a binary liquid mixture. The surfaces of the slabs are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials ensuring the so-called (+,+) boundary conditions. The slabs, on the other hand, influence the fluid by long-range competing dispersion potentials, which represent irrelevant interactions in renormalization-group sense. Under such conditions, one usually expects attractive Casimir force governed by universal scaling function, pertinent to the extraordinary surface universality class of Ising type systems, to which the dispersion potentials provide only corrections to scaling. We demonstrate, however, that below a given threshold thickness of the system L(crit) for a suitable set of slabs-fluid and fluid-fluid coupling parameters the competition between the effects due to the coatings and the slabs can result in sign change of the Casimir force acting between the surfaces confining the fluid when one changes the temperature T, the chemical potential of the fluid μ, or L. The last implies that by choosing specific materials for the slabs, coatings, and the fluid for L≲L(crit) one can realize repulsive Casimir force with nonuniversal behavior which, upon increasing L, gradually turns into an attractive one described by a universal scaling function, depending only on the relevant scaling fields related to the temperature and the excess chemical potential, for L≫L(crit). We present arguments and relevant data for specific substances in support of the experimental feasibility of the predicted behavior of the force. It can
Macroscopic QED in linearly responding media and a Lorentz-Force approach to dispersion forces
Energy Technology Data Exchange (ETDEWEB)
Raabe, Christian
2008-07-08
In this thesis, a very general quantization scheme for the macroscopic electromagnetic field in arbitrary linearly responding media is presented. It offers a unified approach to QED in such media. Applying the quantization scheme, a theory of the dispersion forces on the basis of the Lorentz force is developed. By regarding the dispersion force as the (ground-state or thermal-state) expectation value of the Lorentz force that acts on appropriately defined charge and current densities, Casimir, Casimir-Polder, and van der Waals forces are united in a very natural way that makes transparent their common physical basis. Application of the theory to planar structures yields generalizations of well-known Lifschitz and Casimir-type formulas. (orig.)
Enhancing Casimir repulsion via topological insulator multilayers
Energy Technology Data Exchange (ETDEWEB)
Zeng, Ran, E-mail: ranzeng@hotmail.com [School of Communication Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Chen, Liang; Nie, Wenjie [Beijing Computational Science Research Center, Beijing 100084 (China); Bi, Meihua [School of Communication Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Yang, Yaping [Beijing Computational Science Research Center, Beijing 100084 (China); Department of Physics, Tongji University, Shanghai 200092 (China); Zhu, Shiyao [Beijing Computational Science Research Center, Beijing 100084 (China)
2016-08-19
We propose to observe the enhanced Casimir repulsion between two parallel multilayer walls made of alternating layers of a topological insulator (TI) and a normal insulator. Based on the transfer matrix method, the Fresnel coefficients matrix is generalized to apply to the TI multilayer structure. The Casimir repulsion under the influence of the magnetization orientation in the magnetic coatings on TI layer surfaces, the layer thicknesses, and the topological magnetoelectric polarizability, is investigated. We show that, for the multilayer structures with parallel magnetization on the TI layer surfaces, it is possible to enhance the repulsion by increasing the TI layer number, which is due to the accumulation of the contribution to the repulsion from the polarization rotation effect occurring on each TI layer surface. Generally, in the distance region where there is Casimir attraction between semi-infinite TIs, the force may turn into repulsion in TI multilayer structure, and in the region of repulsion for semi-infinite TI, the repulsive force can be enhanced in magnitude, the enhancement tends to a maximum while the structure contains sufficiently many layers. - Highlights: • Enhancement of Casimir repulsion for topological insulator (TI) multilayers is shown. • Fresnel coefficients matrix is generalized to apply to the TI multilayer structure. • Multilayer with parallel magnetization on TI surfaces is needed for the enhancement. • Enhancement is due to accumulation of polarization rotation effect on TI surfaces.
Valchev, Galin; Dantchev, Daniel
2017-08-01
We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The latter arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar one-component fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab and between two spherical colloid particles. We do that using general scaling arguments and mean-field-type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential μ . The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the so-called (+,+) boundary conditions. On the other hand, the core region of the slab and the particles influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters, the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , μ , or L , in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding
Casimir stress in materials: Hard divergency at soft walls
Griniasty, Itay; Leonhardt, Ulf
2017-11-01
The Casimir force between macroscopic bodies is well understood, but not the Casimir stress inside bodies. Suppose empty space or a uniform medium meets a soft wall where the refractive index is continuous but its derivative jumps. For this situation we predict a characteristic power law for the stress inside the soft wall and close to its edges. Our result shows that such edges are not tolerated in the aggregation of liquids at surfaces, regardless whether the liquid is attracted or repelled.
Casimir interactions between graphene sheets and metamaterials
Energy Technology Data Exchange (ETDEWEB)
Drosdoff, D.; Woods, Lilia M. [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States)
2011-12-15
The Casimir force between graphene sheets and metamaterials is studied. Theoretical results based on the Lifshitz theory for layered, planar, two-dimensional systems in media are presented. We consider graphene-graphene, graphene-metamaterial, and metal-graphene-metamaterial configurations. We find that quantum effects of the temperature-dependent force are not apparent until the submicron range. In contrast to results with bulk dielectric and bulk metallic materials, no Casimir repulsion is found when graphene is placed on top of a magnetically active metamaterial substrate, regardless of the strength of the low-frequency magnetic response. In the case of the metal-graphene-metamaterial setting, repulsion between the metamaterial and the metal-graphene system is possible only when the dielectric response from the metal contributes significantly.
Chaotic behavior in Casimir oscillators : A case study for phase-change materials
Tajik, Fatemeh; Sedighi, Mehdi; Khorrami, Mohammad; Masoudi, Amir Ali; Palasantzas, George
2017-01-01
Casimir forces between material surfaces at close proximity of less than 200 nm can lead to increased chaotic behavior of actuating devices depending on the strength of the Casimir interaction. We investigate these phenomena for phase-change materials in torsional oscillators, where the amorphous to
Directory of Open Access Journals (Sweden)
Amir R. Askari
2014-01-01
Full Text Available The influence of the Casimir excitation on dynamic pull-in instability of a nanoelectromechanical beam under ramp-input voltage is studied. The ramp-input actuation has applications in frequency sweeping of RF-N/MEMS. The presented model is nonlinear due to the inherent nonlinearity of electrostatics and the Casimir excitations as well as the geometric nonlinearity of midplane stretching. A Galerkin based reduced order modeling is utilized. It is found that the calculated dynamic pull-in ramp input voltage leads to dynamic pull-in step input voltage by increasing the slope of voltage-time diagram. This fact is utilized to verify the results of present study.
Enhancing Casimir repulsion via topological insulator multilayers
Zeng, Ran; Chen, Liang; Nie, Wenjie; Bi, Meihua; Yang, Yaping; Zhu, Shiyao
2016-08-01
We propose to observe the enhanced Casimir repulsion between two parallel multilayer walls made of alternating layers of a topological insulator (TI) and a normal insulator. Based on the transfer matrix method, the Fresnel coefficients matrix is generalized to apply to the TI multilayer structure. The Casimir repulsion under the influence of the magnetization orientation in the magnetic coatings on TI layer surfaces, the layer thicknesses, and the topological magnetoelectric polarizability, is investigated. We show that, for the multilayer structures with parallel magnetization on the TI layer surfaces, it is possible to enhance the repulsion by increasing the TI layer number, which is due to the accumulation of the contribution to the repulsion from the polarization rotation effect occurring on each TI layer surface. Generally, in the distance region where there is Casimir attraction between semi-infinite TIs, the force may turn into repulsion in TI multilayer structure, and in the region of repulsion for semi-infinite TI, the repulsive force can be enhanced in magnitude, the enhancement tends to a maximum while the structure contains sufficiently many layers.
Thermal Powered Reciprocating-Force Motor
Tatum, III, Paul F. (Inventor); McDow Elliott, Amelia (Inventor)
2015-01-01
A thermal-powered reciprocating-force motor includes a shutter switchable between a first position that passes solar energy and a second position that blocks solar energy. A shape memory alloy (SMA) actuator is coupled to the shutter to control switching thereof between the shutter's first and second position. The actuator is positioned with respect to the shutter such that (1) solar energy impinges on the SMA when the shutter is in its first position so that the SMA experiences contraction in length until the shutter is switched to its second position, and (2) solar energy is impeded from impingement on the SMA when the shutter is in its second position so that the SMA experiences extension in length. Elastic members coupled to the actuator apply a force to the SMA that aids in its extension in length until the shutter is switched to its first position.
Casimir-Polder interaction in second quantization
Energy Technology Data Exchange (ETDEWEB)
Schiefele, Juergen
2011-03-21
The Casimir-Polder interaction between a single neutral atom and a nearby surface, arising from the (quantum and thermal) fluctuations of the electromagnetic field, is a cornerstone of cavity quantum electrodynamics (cQED), and theoretically well established. Recently, Bose-Einstein condensates (BECs) of ultracold atoms have been used to test the predictions of cQED. The purpose of the present thesis is to upgrade single-atom cQED with the many-body theory needed to describe trapped atomic BECs. Tools and methods are developed in a second-quantized picture that treats atom and photon fields on the same footing. We formulate a diagrammatic expansion using correlation functions for both the electromagnetic field and the atomic system. The formalism is applied to investigate, for BECs trapped near surfaces, dispersion interactions of the van der Waals-Casimir-Polder type, and the Bosonic stimulation in spontaneous decay of excited atomic states. We also discuss a phononic Casimir effect, which arises from the quantum fluctuations in an interacting BEC. (orig.)
Thermal Forces in Simple and Complex Fluids
Piazza, Roberto; Giglio, Marzio
2004-11-01
common, and no model is so far able to give a general prediction of the direction of thermodiffusive motion. Efforts in understanding the physical origin of the Soret effect in model systems like colloidal systems will probably be of great relevance. At the same time, analyzing Soret-driven hydrodynamic effects in complex fluids, and exploiting thermophoresis as a macromolecular separation/concentration method (as already done by Thermal Field-Flow Fractionation) are promising research topics. This renovated interest in Soret-related phenomena is mirrored by the rather diversified list of contributions that appear in the present issue. These papers have been presented at the International Meeting IMT6 - Thermal Forces held in Villa Cipressi (Varenna, Italy) in July 2004, as the sixth edition of a series of conferences run under the auspices of the European Group of Research in Thermodiffusion (EGRT). The conference falls on the hundredth anniversary of Charles Soret death. Very duly, a commemorative contribution by Jean Platten and Pierre Costesèque, on behalf of EGRT, opens this issue. In detail, the contributions cover the following topics. Soret effects in simple fluid mixtures are discussed in the first two papers: subtle problems related to thermal diffusion in multicomponent mixtures are addressed by Saghir et al., while convection-free measurements of the Soret coefficient in porous media are described by Costesèque et al. The paper by Parola and Piazza presents a general theoretical approach to particle thermophoresis in liquids, while Enge and Köhler give a detailed analysis of thermal diffusion in polymer blends. Blums reviews coupled magnetic and Soret effects in ferrofluids, while Duhr et al. describe microfluidics methods for measuring DNA thermophoresis, and Steinbach et al. design an optical trap for studying particle thermophoresis in gases under microgravity conditions. The second part of the issue is dedicated to thermal diffusion effects on
Bellucci, S
2009-01-01
We evaluate the Casimir energy and force for a massive fermionic field in the geometry of two parallel plates on background of Minkowski spacetime with an arbitrary number of toroidally compactified spatial dimensions. The bag boundary conditions are imposed on the plates and periodicity conditions with arbitrary phases are considered along the compact dimensions. The Casimir energy is decomposed into purely topological, single plate and interaction parts. With independence of the lengths of the compact dimensions and the phases in the periodicity conditions, the interaction part of the Casimir energy is always negative. In order to obtain the resulting force, the contributions from both sides of the plates must be taken into account. Then, the forces coming from the topological parts of the vacuum energy cancel out and only the interaction term contributes to the Casimir force. Applications of the general formulae to Kaluza-Klein type models and carbon nanotubes are given. In particular, we show that for fin...
Nonlocal impedances and the casimir entropy at low temperatures
Svetovoy, Vitaly; Esquivel, R.
2005-01-01
The problem with the temperature dependence of the Casimir force is investigated. Specifically, the entropy behavior in the low temperature limit, which caused debates in the literature, is analyzed. It is stressed that the behavior of the relaxation frequency in the T0 limit does not play a
Forces exerted by a correlated fluid on embedded inclusions.
Bitbol, Anne-Florence; Fournier, Jean-Baptiste
2011-06-01
We investigate the forces exerted on embedded inclusions by a fluid medium with long-range correlations, described by an effective scalar field theory. Such forces are the basis for the medium-mediated Casimir-like force. To study these forces beyond thermal average, it is necessary to define them in each microstate of the medium. Two different definitions of these forces are currently used in the literature. We study the assumptions underlying them. We show that only the definition that uses the stress tensor of the medium gives the sought-after force exerted by the medium on an embedded inclusion. If a second inclusion is embedded in the medium, the thermal average of this force gives the usual Casimir-like force between the two inclusions. The other definition can be used in the different physical case of an object that interacts with the medium without being embedded in it. We show in a simple example that the two definitions yield different results for the variance of the Casimir-like force.
Casimir Effect Under Quasi-Periodic Boundary Condition Inspired by Nanotubes
Feng, Chao-Jun; Li, Xin-Zhou; Zhai, Xiang-Hua
2014-01-01
When one studies the Casimir effect, the periodic (anti-periodic) boundary condition is usually taken to mimic a periodic (anti-periodic) structure for a scalar field living in a flat space with a non-Euclidean topology. However, there could be an arbitrary phase difference between the value of the scalar field on one endpoint of the unit structure and that on the other endpoint, such as the structure of nanotubes. Then, in this paper, a periodic condition on the ends of the system with an additional phase factor, which is called the "quasi-periodic" condition, is imposed to investigate the corresponding Casimir effect. And an attractive or repulsive Casimir force is found, whose properties depend on the phase angle value. Especially, the Casimir effect disappears when the phase angle takes a particular value. High dimensional spacetime case is also investigated.
Noncommutative Complex Scalar Field and Casimir Effect
Khelili, Farid
2012-06-01
Using the noncommutative deformed canonical commutation relations proposed by Carmona et al. [J. M. Carmona, J. L. Cortés, J. Gamboa, and F. Mendez, J. High Energy Phys.JHEPFG1029-8479 03 (2003) 058.10.1088/1126-6708/2003/03/058][J. Gamboa, J. Lopéz-Sarrion, and A. P. Polychronakos, Phys. Lett. B 634, 471 (2006).PYLBAJ0370-269310.1016/j.physletb.2006.02.014][J. M. Carmona, J. L. Cortés, Ashok Das, J. Gamboa, and F. Mendez, Mod. Phys. Lett. A 21, 883 (2006).MPLAEQ0217-732310.1142/S0217732306020111], a model describing the dynamics of the noncommutative complex scalar field is proposed. The noncommutative field equations are solved, and the vacuum energy is calculated to the second order in the parameter of noncommutativity. As an application to this model, the Casimir effect, due to the zero-point fluctuations of the noncommutative complex scalar field, is considered. It turns out that in spite of its smallness, the noncommutativity gives rise to a repulsive force at the microscopic level, leading to a modified Casimir potential with a minimum at the point amin=(5)/(84)πθ.
Casimir amplitudes in topological quantum phase transitions
Griffith, M. A.; Continentino, M. A.
2018-01-01
Topological phase transitions constitute a new class of quantum critical phenomena. They cannot be described within the usual framework of the Landau theory since, in general, the different phases cannot be distinguished by an order parameter, neither can they be related to different symmetries. In most cases, however, one can identify a diverging length at these topological transitions. This allows us to describe them using a scaling approach and to introduce a set of critical exponents that characterize their universality class. Here we consider some relevant models of quantum topological transitions associated with well-defined critical exponents that are related by a quantum hyperscaling relation. We extend to these models a finite-size scaling approach based on techniques for calculating the Casimir force in electromagnetism. This procedure allows us to obtain universal Casimir amplitudes at their quantum critical points. Our results verify the validity of finite-size scaling in these systems and confirm the values of the critical exponents obtained previously.
Thermal Creep Force: Analysis And Application
2016-06-01
pressure does exist, it produces a small force and would tend to move the vanes with the black side leading contrary to the observed motion . The same year...the simulation. After the particles have completed their motion , particles are randomly selected for collision . The probability that an individual...of the mean free time between collisions at lower pressures. Each simulation ran 100 thousand time steps. We calculated the force by multiplying
The Importance of Boundary Conditions for Fluctuation Induced Forces between Colloids at Interfaces
Lehle, H.; Oettel, M.
2006-01-01
We calculate the effective fluctuation induced force between spherical or disk-like colloids trapped at a flat, fluid interface mediated by thermally excited capillary waves. This Casimir type force is determined by the partition function of the system which in turn is calculated in a functional integral approach, where the restrictions on the capillary waves imposed by the colloids are incorporated by auxiliary fields. In the long-range regime the fluctuation induced force is shown to depend...
Fluctuation-induced forces between inclusions in a fluid membrane under tension.
Lin, Hsiang-Ku; Zandi, Roya; Mohideen, Umar; Pryadko, Leonid P
2011-11-25
We develop an exact method to calculate thermal Casimir forces between inclusions of arbitrary shapes and separation, embedded in a fluid membrane whose fluctuations are governed by the combined action of surface tension, bending modulus, and Gaussian rigidity. Each object's shape and mechanical properties enter only through a characteristic matrix, a static analog of the scattering matrix. We calculate the Casimir interaction between two elastic disks embedded in a membrane. In particular, we find that at short separations the interaction is strong and independent of surface tension.
Effects of geometrical specification of microengineered surfaces to Casimir-Polder potential
Khaidir, A. F.; Sabki, S. N.; Halif, M. N. A.
2017-11-01
Cold atoms can be trapped and guided using nanofabricated wires on microengineered surfaces, achieving the scales required by quantum information proposals on the consequences of Casimir-Polder (CP) force to its stability and lifetime. The atoms are found to be less attractive to the thin films compared to dielectric half plate, where the attractive potential drops even further when the thickness of the surface is lower than both thermal wavelength and the spacing length. Amiably, for the spherical surface, the CP potential decays even further as radial thickness decreases. We approximate the CP potential using the analytical expression obtained from the pairwise summation (PWS) calculated by taking a sum of single atom with the jumbled atoms inside the surface, treating them as two-bodies system as a whole. The means of PWS are to calculate the possibilities of geometrical effect: planar and curved surface on the CP potential.
Effects of geometrical specification of microengineered surfaces to Casimir-Polder potential
Directory of Open Access Journals (Sweden)
Khaidir A.F
2017-01-01
Full Text Available Cold atoms can be trapped and guided using nanofabricated wires on microengineered surfaces, achieving the scales required by quantum information proposals on the consequences of Casimir-Polder (CP force to its stability and lifetime. The atoms are found to be less attractive to the thin films compared to dielectric half plate, where the attractive potential drops even further when the thickness of the surface is lower than both thermal wavelength and the spacing length. Amiably, for the spherical surface, the CP potential decays even further as radial thickness decreases. We approximate the CP potential using the analytical expression obtained from the pairwise summation (PWS calculated by taking a sum of single atom with the jumbled atoms inside the surface, treating them as two-bodies system as a whole. The means of PWS are to calculate the possibilities of geometrical effect: planar and curved surface on the CP potential.
Petrov, V M
2016-01-01
The objective of the meeting is to promote contacts between scientists working in the field of Relativity, Gravitation and Cosmology and related fields. It is well known that the important role in Gravitation and Cosmology is played by the Casimir effect. To underline this, special Satellite Symposia devoted to this effect have been included in the Programs of the 7th and 8th Friedmann Seminars. The Casimir effect is a multidisciplinary subject. Its applications extend from gravitation and cosmology to the van der Waals forces, materials properties and nanotechnology. All these subjects are traditionally touched at the Satellite Simposia on the Casimir effect.
Energy Technology Data Exchange (ETDEWEB)
Klimchitskaya, G.L. [Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, Saint Petersburg (Russian Federation); Peter the Great Saint Petersburg Polytechnic University, Institute of Physics, Nanotechnology and Telecommunications, Saint Petersburg (Russian Federation)
2017-05-15
The strongest constraints on the Yukawa-type corrections to Newton's gravitational law and on the coupling constants of axion-like particles to nucleons, following from recently performed experiments of Casimir physics, are presented. Specifically, the constraints obtained from measurements of the lateral and normal Casimir forces between sinusoidally corrugated surfaces, and from the isoelectronic experiment are considered, and the ranges of their greatest strength are refined. Minor modifications in the experimental setups are proposed which allow for strengthening the resultant constraints up to an order of magnitude. The comparison with some weaker constraints derived in the Casimir regime is also made. (orig.)
The Casimir effect physical manifestations of zero-point energy
Milton, K A
2001-01-01
In its simplest manifestation, the Casimir effect is a quantum force of attraction between two parallel uncharged conducting plates. More generally, it refers to the interaction - which may be either attractive or repulsive - between material bodies due to quantum fluctuations in whatever fields are relevant. It is a local version of the van der Waals force between molecules. Its sweep ranges from perhaps its being the origin of the cosmological constant to its being responsible for the confinement of quarks. This monograph develops the theory of such forces, based primarily on physically tran
Numerical and semiclassical analysis of some generalized Casimir pistons
Schaden, M.
2009-05-01
The Casimir force due to a scalar field in a cylinder of radius r with a spherical cap of radius R>r is computed numerically in the world-line approach. A geometrical subtraction scheme gives the finite interaction energy that determines the Casimir force. The spectral function of convex domains is obtained from a probability measure on convex surfaces that is induced by the Wiener measure on Brownian bridges the convex surfaces are the hulls of. Due to reflection positivity, the vacuum force on the piston by a scalar field satisfying Dirichlet boundary conditions is attractive in these geometries, but the strength and short-distance behavior of the force depend strongly on the shape of the piston casing. For a cylindrical casing with a hemispherical head, the force on the piston does not depend on the dimension of the casing at small piston elevation a≪R and numerically approaches Fcas(a≪R)=-0.00326(4)ℏc/a2 . Semiclassically this asymptotic force is due to short, closed, and nonperiodic trajectories that reflect just once off the piston near its periphery. A semiclassical estimate reproduces the numerical results for the small-distance behavior of the force within statistical errors, whereas the proximity force approximation is off by one order of magnitude when Rtilde r .
Thermal-induced force release in oxyhemoglobin.
Gevorkian, S G; Allahverdyan, A E; Gevorgyan, D S; Hu, Chin-Kun
2015-08-17
Oxygen is released to living tissues via conformational changes of hemoglobin from R-state (oxyhemoglobin) to T-state (desoxyhemoglobin). The detailed mechanism of this process is not yet fully understood. We have carried out micromechanical experiments on oxyhemoglobin crystals to determine the behavior of the Young's modulus and the internal friction for temperatures between 20 °C and 70 °C. We have found that around 49 °C oxyhemoglobin crystal samples undergo a sudden and strong increase of their Young's modulus, accompanied by a sudden decrease of the internal friction. This sudden mechanical change (and the ensuing force release) takes place in a partially unfolded state and precedes the full denaturation transition at higher temperatures. After this transformation, the hemoglobin crystals have the same mechanical properties as their initial state at room temperatures. We conjecture that it can be relevant for explaining the oxygen-releasing function of native oxyhemoglobin when the temperature is increased, e.g. due to active sport. The effect is specific for the quaternary structure of hemoglobin, and is absent for myoglobin with only one peptide sequence.
Casimir interaction between spheres in ( D + 1)-dimensional Minkowski spacetime
Teo, L. P.
2014-05-01
We consider the Casimir interaction between two spheres in ( D + 1)-dimensional Minkowski spacetime due to the vacuum fluctuations of scalar fields. We consider combinations of Dirichlet and Neumann boundary conditions. The TGTG formula of the Casimir interaction energy is derived. The computations of the T matrices of the two spheres are straightforward. To compute the two G matrices, known as translation matrices, which relate the hyper-spherical waves in two spherical coordinate frames differ by a translation, we generalize the operator approach employed in [39]. The result is expressed in terms of an integral over Gegenbauer polynomials. In contrast to the D=3 case, we do not re-express the integral in terms of 3 j-symbols and hyper-spherical waves, which in principle, can be done but does not simplify the formula. Using our expression for the Casimir interaction energy, we derive the large separation and small separation asymptotic expansions of the Casimir interaction energy. In the large separation regime, we find that the Casimir interaction energy is of order L -2 D+3, L -2 D+1 and L -2 D-1 respectively for Dirichlet-Dirichlet, Dirichlet-Neumann and Neumann-Neumann boundary conditions, where L is the center-to-center distance of the two spheres. In the small separation regime, we confirm that the leading term of the Casimir interaction agrees with the proximity force approximation, which is of order , where d is the distance between the two spheres. Another main result of this work is the analytic computations of the next-to-leading order term in the small separation asymptotic expansion. This term is computed using careful order analysis as well as perturbation method. In the case the radius of one of the sphere goes to infinity, we find that the results agree with the one we derive for sphere-plate configuration. When D=3, we also recover previously known results. We find that when D is large, the ratio of the next-to-leading order term to the leading
Pyramidal nanowire tip for atomic force microscopy and thermal imaging
Burouni, N.; Sarajlic, Edin; Siekman, Martin Herman; Abelmann, Leon; Tas, Niels Roelof
2012-01-01
We present a novel 3D nanowire pyramid as scanning microscopy probe for thermal imaging and atomic force microscopy. This probe is fabricated by standard micromachining and conventional optical contact lithography. The probe features an AFM-type cantilever with a sharp pyramidal tip composed of four
Nonperturbative Casimir effect and monopoles: Compact Abelian gauge theory in two spatial dimensions
Chernodub, M. N.; Goy, V. A.; Molochkov, A. V.
2017-04-01
We demonstrate that Casimir forces associated with zero-point fluctuations of quantum vacuum may be substantially affected by the presence of dynamical topological defects. In order to illustrate this nonperturbative effect we study the Casimir interactions between dielectric wires in a compact formulation of Abelian gauge theory in two spatial dimensions. The model possesses topological defects, instantonlike monopoles, which are known to be responsible for nonperturbative generation of a mass gap and for a linear confinement of electrically charged probes. Despite the fact the model has no matter fields, the Casimir energy depends on the value of the gauge coupling constant. We show, both analytically and numerically, that in the strong coupling regime the Abelian monopoles make the Casimir forces short ranged. Simultaneously, their presence increases the interaction strength between the wires at short distances for a certain range of values of the gauge coupling. The wires suppress monopole density in the space between them compared to the density outside the wires. In the weak coupling regime the monopoles become dilute and the Casimir potential reduces to a known theoretical result that does not depend on the gauge coupling.
Energy Technology Data Exchange (ETDEWEB)
Grueneberg, Daniel
2008-02-15
To study how the behavior of the thermodynamic Casimir force changes qualitatively and quantitatively due to the presence of such interactions - compared to systems with purely short-range interactions - is the aim of this work. Considering d-dimensional models belonging to the universality class of the O(n)-symmetrical systems, the thermodynamic Casimir force and its leading corrections are derived for temperatures at and above the transition temperature (T{>=}T{sub c,{infinity}}). The underlying pair potential is assumed to be isotropic and long-ranged, decaying asymptotically proportional to x{sup -(d+{sigma}}{sup )} for large separations x, where the value of the parameter {sigma} is restricted to the interval 2<{sigma}<4. By solving an appropriate spherical model in 2
Tuning the Casimir-Polder interaction via magneto-optical effects in graphene
Cysne, T.; Kort-Kamp, W. J. M.; Oliver, D.; Pinheiro, F. A.; Rosa, F. S. S.; Farina, C.
2014-11-01
We investigate the dispersive Casimir-Polder interaction between a rubidium atom and a suspended graphene sheet subjected to an external magnetic field B . We demonstrate that this concrete physical system allows for an unprecedented control of dispersive interactions at micro- and nanoscales. Indeed, we show that the application of an external magnetic field can induce an 80 % reduction in the Casimir-Polder energy relative to its value without the field. We also show that sharp discontinuities emerge in the Casimir-Polder interaction energy for certain values of the applied magnetic field at low temperatures. Moreover, for sufficiently large distances, these discontinuities show up as a plateau-like pattern with a quantized Casimir-Polder interaction energy, in a phenomenon that can be explained in terms of the quantum Hall effect. In addition, we point out the importance of thermal effects in the Casimir-Polder interaction, which we show must be taken into account even for considerably short distances. In this case, the discontinuities in the atom-graphene dispersive interaction do not occur, which by no means prevents the tuning of the interaction in ˜50 % by the application of the external magnetic field.
Supersymmetry Breaking Casimir Warp Drive
Obousy, Richard K.; Cleaver, Gerald
2007-01-01
This paper utilizes a recent model which relates the cosmological constant to the Casimir energy of the extra dimensions in brane-world theories. The objective of this paper is to demonstrate that, given some sufficiently advanced civilization with the ability to manipulate the radius of the extra dimension, a local adjustment of the cosmological constant could be created. This adjustment would facilitate an expansion/contraction of the spacetime around a spacecraft creating an exotic form of field-propulsion. This idea is analogous to the Alcubierre bubble, but differs entirely in the approach, utilizing the physics of higher dimensional quantum field theory, instead of general relativity.
Particles with nonlinear electric response: Suppressing van der Waals forces by an external field.
Soo, Heino; Dean, David S; Krüger, Matthias
2017-01-01
We study the classical thermal component of Casimir, or van der Waals, forces between point particles with highly anharmonic dipole Hamiltonians when they are subjected to an external electric field. Using a model for which the individual dipole moments saturate in a strong field (a model that mimics the charges in a neutral, perfectly conducting sphere), we find that the resulting Casimir force depends strongly on the strength of the field, as demonstrated by analytical results. For a certain angle between the external field and center-to-center axis, the fluctuation force can be tuned and suppressed to arbitrarily small values. We compare the forces between these particles with those between particles with harmonic Hamiltonians and also provide a simple formula for asymptotically large external fields, which we expect to be generally valid for the case of saturating dipole moments.
PREFACE: International Workshop '60 Years of the Casimir Effect'
Barton, Gabriel; Carugno, Giovanni; Dodonov, Victor; Man'ko, Margarita
2009-07-01
In 1948 Hendrick Casimir published a short article predicting that (neutral) ideal metallic plates attract each other. This attraction is widely ascribed to the quantum vacuum fluctuations of the electromagnetic field (even though away from the limit of ideal metals it depends demonstrably on the physics of the charge carriers vanishing when they cease to carry). Casimir's remarkable discovery, nowadays called the Casimir effect, has charmed several generations of physicists. In the last decade alone, more than a thousand publications have addressed its many consequences, generalizations, and possible applications in different areas from particle physics to cosmology. Interest in the field is still growing driven by impressive progress in experimental skills and its importance for the recently opened-up area of micro- and nano-electromechanical systems: according to the Thompson ISI Web of Science database, in 2005 the number of papers related to the Casimir effect or to Casimir forces jumped to over 125, compared to approximately 60 in 2000 and 30 in 1995. The increase continues, with more than 170 papers in 2008. The International Workshop '60 Years of the Casimir Effect' took place on 23-27June 2008, in Brasilia (Brazil) organized by the International Center for Condensed Matter Physics (ICCMP). The purpose was to celebrate this anniversary of Casimir's pioneering paper by inviting the leading specialists in the area, both theorists and experimentalists, together with young researchers and post-graduate students interested in hearing about the most recent achievements in the field. The Workshop was attended by 65 participants from 14 countries, who presented 41 talks and 12 posters. These Proceedings contain extended versions of almost all the talks and some posters, plus several papers by authors who had planned to attend but for various reasons could not. The contributions are divided (with some inevitable arbitrariness) into four groups. The largest one
Dynamical Casimir effect in a Josephson metamaterial
Lahteenmaki, Pasi; Paraoanu, G. S.; Hassel, Juha; Hakonen, Pertti J.
2013-01-01
The zero-point energy stored in the modes of an electromagnetic cavity has experimentally detectable effects, giving rise to an attractive interaction between the opposite walls, the static Casimir effect. A dynamical version of this effect was predicted to occur when the vacuum energy is changed either by moving the walls of the cavity or by changing the index of refraction, resulting in the conversion of vacuum fluctuations into real photons. Here, we demonstrate the dynamical Casimir effec...
Mokhtari, J.; Farrokhabadi, A.; Rach, R.; Abadyan, M.
2015-04-01
The presence of the quantum vacuum fluctuations, i.e. the Casimir attraction, can strongly affect the performance of ultra-small actuators. The strength of the Casimir force is significantly influenced by the geometries of interacting bodies. Previous research has exclusively studied the impact of the vacuum fluctuations on the instability of nanoactuators with planar geometries. However, no work has yet considered this phenomenon in actuators fabricated from nanowires/nanotubes with cylindrical geometries. In our present work, the influence of the Casimir attraction on the electrostatic stability of nanoactuators fabricated from cylindrical conductive nanowire/nanotube is investigated. The Dirichlet mode is considered and an asymptotic solution, based on scattering theory, is applied to consider the effect of vacuum fluctuations in the theoretical model. The size-dependent modified couple stress theory is employed to derive the constitutive equation of the actuator. The governing nonlinear equations are solved by two different approaches, i.e. the finite difference method and modified Adomian-Padé method. Various aspects of the problem, i.e. comparison with the van der Waals force regime, the variation of instability parameters, effect of geometry and coupling between the Casimir force and size dependency are discussed. This work is beneficial to determine the impact of Casimir force on nanowire/nanotube-fabricated actuators.
Assembling quantum dots via critical Casimir forces
Marino, E.; Kodger, T.E.; Hove, J.B. ten; Velders, A.H.; Schall, P.
2016-01-01
Programmed assembly of colloidal inorganic nanocrystal superstructures is crucial for the realization of future artificial solids as well as present optoelectronic applications. Here, we present a new way to assemble quantum dots reversibly using binary solvents. By tuning the temperature and
Critical Casimir forces and anomalous wetting
Indian Academy of Sciences (India)
Author Affiliations. S Balibar1 R Ishiguro1. Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, associé au CNRS et aux Universités Paris 6 et 7, 24 rue Lhomond, 75231 Paris Cedex 05, France ...
Casimir Friction between Dense Polarizable Media
Directory of Open Access Journals (Sweden)
Johan S. Høye
2013-07-01
Full Text Available The present paper—a continuation of our recent series of papers on Casimir friction for a pair of particles at low relative particle velocity—extends the analysis, so as to include dense media. The situation becomes, in this case, more complex, due to induced dipolar correlations, both within planes and between planes. We show that the structure of the problem can be simplified by regarding the two half-planes as a generalized version of a pair of particles. It turns out that macroscopic parameters, such as permittivity, suffice to describe the friction, also in the finite density case. The expression for the friction force per unit surface area becomes mathematically well-defined and finite at finite temperature. We give numerical estimates and compare them with those obtained earlier by Pendry (1997 and by Volokitin and Persson (2007. We also show in an appendix how the statistical methods that we are using correspond to the field theoretical methods more commonly in use.
Energy Technology Data Exchange (ETDEWEB)
Cowan, Nicolas B. [Center for Interdisciplinary Exploration and Research in Astrophysics and Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States); Voigt, Aiko [Max Planck Institute for Meteorology, Bundesstr. 53, D-20146 Hamburg (Germany); Abbot, Dorian S., E-mail: n-cowan@nortwestern.edu [Department of Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)
2012-09-20
In order to understand the climate on terrestrial planets orbiting nearby Sun-like stars, one would like to know their thermal inertia. We use a global climate model to simulate the thermal phase variations of Earth analogs and test whether these data could distinguish between planets with different heat storage and heat transport characteristics. In particular, we consider a temperate climate with polar ice caps (like the modern Earth) and a snowball state where the oceans are globally covered in ice. We first quantitatively study the periodic radiative forcing from, and climatic response to, rotation, obliquity, and eccentricity. Orbital eccentricity and seasonal changes in albedo cause variations in the global-mean absorbed flux. The responses of the two climates to these global seasons indicate that the temperate planet has 3 Multiplication-Sign the bulk heat capacity of the snowball planet due to the presence of liquid water oceans. The obliquity seasons in the temperate simulation are weaker than one would expect based on thermal inertia alone; this is due to cross-equatorial oceanic and atmospheric energy transport. Thermal inertia and cross-equatorial heat transport have qualitatively different effects on obliquity seasons, insofar as heat transport tends to reduce seasonal amplitude without inducing a phase lag. For an Earth-like planet, however, this effect is masked by the mixing of signals from low thermal inertia regions (sea ice and land) with that from high thermal inertia regions (oceans), which also produces a damped response with small phase lag. We then simulate thermal light curves as they would appear to a high-contrast imaging mission (TPF-I/Darwin). In order of importance to the present simulations, which use modern-Earth orbital parameters, the three drivers of thermal phase variations are (1) obliquity seasons, (2) diurnal cycle, and (3) global seasons. Obliquity seasons are the dominant source of phase variations for most viewing angles. A
Energy Technology Data Exchange (ETDEWEB)
Klimchitskaya, G.L.; Mostepanenko, V.M. [Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, St. Petersburg (Russian Federation); St. Petersburg State Polytechnical University, Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg (Russian Federation)
2015-04-01
We obtain improved constraints on the coupling constants of axion-like particles to nucleons from a recently performed Casimir-less experiment. For this purpose, the differential force between a Au-coated sphere and either the Au or the Si sector of a rotating disc, arising due to two-axion exchange, is calculated. Over a wide region of axion masses, from 1.7 x 10{sup -3} eV to 0.9 eV, the obtained constraints are up to a factor of 60 stronger than the previously known ones following from the Cavendish-type experiment and measurements of the effective Casimir pressure. (orig.)
Speeding up the antidynamical Casimir effect with nonstationary qutrits
Dodonov, A. V.; Díaz-Guevara, J. J.; Napoli, A.; Militello, B.
2017-09-01
The antidynamical Casimir effect (ADCE) is a term coined to designate the coherent annihilation of excitations due to resonant external perturbation of system parameters, allowing for extraction of quantum work from nonvacuum states of some field. Originally proposed for a two-level atom (qubit) coupled to a single-cavity mode in the context of the nonstationary quantum Rabi model, it suffered from a very low transition rate and correspondingly narrow resonance linewidth. In this paper we show analytically and numerically that the ADCE rate can be increased by at least one order of magnitude by replacing the qubit by an artificial three-level atom (qutrit) in a properly chosen configuration. For the cavity thermal state we demonstrate that the dynamics of the average photon number and atomic excitation is completely different from the qubit's case, while the behavior of the total number of excitations is qualitatively similar yet significantly faster.
Yano, Ryosuke
2015-01-01
We discuss the thermal conduction and convection of thermally relativistic fluids between two parallel walls under the gravitational force, both theoretically and numerically. In the theoretical discussion, we assume that the Lorentz contraction is ignored and spacetime is flat. For understanding of the thermal conduction and convection of thermally relativistic fluids between two parallel walls under the gravitational force, we solve the relativistic Boltzmann equation using the direct simulation Monte Carlo method. Numerical results indicate that strongly nonequilibrium states are formed in vicinities of two walls, which do not allow us to discuss the transition of the thermal conduction to the thermal convection of thermally relativistic fluids under the gravitational force in the framework of the relativistic Navier-Stokes-Fourier equation, when the flow-field is under the transition regime between the rarefied and continuum regimes, whereas such strongly nonequilibrium states are not formed in vicinities...
Comments on the Casimir energy in supersymmetric field theories
Lorenzen, Jakob; Martelli, Dario
2015-07-01
We study the Casimir energy of four-dimensional supersymmetric gauge theories in the context of the rigid limit of new minimal supergravity. Firstly, revisiting the computation of the localized partition function on S 1 × S 3, we recover the supersymmetric Casimir energy from its path integral definition. Secondly, we consider the same theories in the Hamiltonian formalism on , focussing on the free limit and including a one- parameter family of background gauge fields along . We compute the vacuum expectation value of the canonical Hamiltonian using zeta function regularization, and show that this interpolates between the supersymmetric Casimir energy and the ordinary Casimir energy of a supersymmetric free field theory.
Thermal imbalance force modelling for a GPS satellite using the finite element method
Vigue, Yvonne; Schutz, Bob E.
1991-01-01
Methods of analyzing the perturbation due to thermal radiation and determining its effects on the orbits of GPS satellites are presented, with emphasis on the FEM technique to calculate satellite solar panel temperatures which are used to determine the magnitude and direction of the thermal imbalance force. Although this force may not be responsible for all of the force mismodeling, conditions may work in combination with the thermal imbalance force to produce such accelerations on the order of 1.e-9 m/sq s. If submeter accurate orbits and centimeter-level accuracy for geophysical applications are desired, a time-dependent model of the thermal imbalance force should be used, especially when satellites are eclipsing, where the observed errors are larger than for satellites in noneclipsing orbits.
Casimir Energy, Extra Dimensions and Exotic Propulsion
Obousy, R.; Saharian, A.
It is well known that the Casimir effect is an excellent candidate for the stabilization of the extra dimensions. It has also been suggested that the Casimir effect in higher dimensions may be the underlying phenomenon that is responsible for the dark energy which is currently driving the accelerated expansion of the universe. In this paper we suggest that, in principle, it may be possible to directly manipulate the size of an extra dimension locally using Standard Model fields in the next generation of particle accelerators. This adjustment of the size of the higher dimension could serve as a technological mechanism to locally adjust the dark energy density and change the local expansion of spacetime. This idea holds tantalizing possibilities in the context of exotic spacecraft propulsion.
Casimir apparatuses in a weak gravitational field
DEFF Research Database (Denmark)
Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero
2009-01-01
We review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the resulting regularized and renormalized energy-momentum tensor...... is covariantly conserved, while the trace anomaly vanishes if the massless field is conformally coupled to gravity. Conformal coupling also ensures a finite Casimir energy and finite values of the pressure upon parallel plates. These results have been extended to an electromagnetic field subject to perfect...... conductor (hence idealized) boundary conditions on parallel plates, by various authors. The regularized and renormalized energy-momentum tensor has beene valuated up to second order in the gravity acceleration. In both the scalar and the electromagnetic case, studied to first order in the gravity...
Curved Casimir Operators and the BGG Machinery
Directory of Open Access Journals (Sweden)
Andreas Cap
2007-11-01
Full Text Available We prove that the Casimir operator acting on sections of a homogeneous vector bundle over a generalized flag manifold naturally extends to an invariant differential operator on arbitrary parabolic geometries. We study some properties of the resulting invariant operators and compute their action on various special types of natural bundles. As a first application, we give a very general construction of splitting operators for parabolic geometries. Then we discuss the curved Casimir operators on differential forms with values in a tractor bundle, which nicely relates to the machinery of BGG sequences. This also gives a nice interpretation of the resolution of a finite dimensional representation by (spaces of smooth vectors in principal series representations provided by a BGG sequence.
Casimir friction and near-field radiative heat transfer in graphene structures
Energy Technology Data Exchange (ETDEWEB)
Volokitin, A.I. [Forschungszentrum Juelich (Germany). Peter Gruenberg Inst.; Samara State Technical Univ. (Russian Federation). Physical Dept.
2017-05-01
The dependence of the Casimir friction force between a graphene sheet and a (amorphous) SiO{sub 2} substrate on the drift velocity of the electrons in the graphene sheet is studied. It is shown that the Casimir friction is strongly enhanced for the drift velocity above the threshold velocity when the friction is determined by the resonant excitation of the surface phonon-polaritons in the SiO{sub 2} substrate and the electron-hole pairs in graphene. The theory agrees well with the experimental data for the current-voltage dependence for unsuspended graphene on the SiO{sub 2} substrate. The theories of the Casimir friction and the near-field radiative energy transfer are used to study the heat generation and dissipation in graphene due to the interaction with phonon-polaritons in the (amorphous) SiO{sub 2} substrate and acoustic phonons in graphene. For suspended graphene, the energy transfer coefficient at nanoscale gap is ∝ three orders of magnitude larger than the radiative heat transfer coefficient of the blackbody radiation limit.
Atomic force microscope with combined FTIR-Raman spectroscopy having a micro thermal analyzer
Fink, Samuel D [Aiken, SC; Fondeur, Fernando F [North Augusta, SC
2011-10-18
An atomic force microscope is provided that includes a micro thermal analyzer with a tip. The micro thermal analyzer is configured for obtaining topographical data from a sample. A raman spectrometer is included and is configured for use in obtaining chemical data from the sample.
Measurement of the short-range attractive force between Ge plates using a torsion balance
Kim, W. J.; Sushkov, A. O.; Dalvit, D. A. R.; Lamoreaux, S. K.
2008-01-01
We have measured the short-range attractive force between crystalline Ge plates, and found contributions from both the Casimir force and an electrical force possibly generated by surface patch potentials. Using a model of surface patch effects that generates an additional force due to a distance dependence of the apparent contact potential, the electrical force was parameterized using data at distances where the Casimir force is relatively small. Extrapolating this model, to provide a correct...
Effect of permeability anisotropy on forced convection thermal ...
African Journals Online (AJOL)
Forced convective flow through anisotropic porous saturated circular tube was analysed to determine the entrance length to the hydrodynamic flow. The porous medium saturated with an incompressible viscous fluid was characterized by anisotropy permeability ratio, inclination angle of the principal axes and Prandtl ...
The repulsive Casimir effect in Weyl semimetals
Wilson, Justin; Allocca, Andrew; Galitski, Victor
2015-03-01
Weyl semimetals are a proposed topological material with broken time-reversal symmetry. Due to this, they experience a particular bulk Hall effect as well as a weak longitudinal conductance. In such a situation, one can see a repulsive Casimir effect between two Weyl semimetals (similar to what has been studied for topological insulators and quantum hall materials), and the effect can be tuned from attractive to repulsive with chemical potential or magnetic field. We consider, separately, a simplified bulk description and a thin film geometry taking into account the band structure. This work is supported by JQI-PFC.
Farrokhabadi, Amin; Mohebshahedin, Abed; Rach, Randolph; Duan, Jun-Sheng
2016-01-01
The influence of the surface energy on the instability of nano-structures under the electrostatic force has been investigated in recent years by different researchers. It appears that in all prior research, the response of all structures becomes softer due to the surface effects. In the present study, the pull-in instability of a NEMS device incorporating the electrostatic force and Casimir intermolecular attraction for different values of the surface parameter is investigated by the Duan-Rach method of determined coefficients (MDC) in order to identify the remarkable effect of the surface energy. Although the obtained results verify the behavior of such structures in presence of the fringing field and the Casimir attraction same as the previous investigations, however the incremental effects of the surface energy cause the aforementioned structures to behave more stiffly in contrast.
Dynamical Casimir effect for surface plasmon polaritons
Energy Technology Data Exchange (ETDEWEB)
Hizhnyakov, V.; Loot, A., E-mail: ardi.loot@ut.ee; Azizabadi, S.Ch.
2015-02-20
The emission of photon pairs by a metal–dielectric interface placed between the mirrors of the resonator and excited by a plane wave is considered. The excitation causes oscillations in time of the optical length of surface plasmon polaritons in the interface. This leads to the dynamical Casimir effect – the generation of pairs of surface plasmon polariton quanta, which transfer to photons outside the interface. In the case of a properly chosen interface, the yield of two-photon emission may exceed that of the usual spontaneous parametric down-conversion. - Highlights: • The theory of dynamical Casimir effect (DCE) in the metal–dielectric interface excited by a monochromatic wave is proposed. • It is shown that the field enhancement associated with surface plasmon polaritons strongly enhances the yield of the DCE. • The numerical calculations of the enhancement factor are made. • The scheme of experimental setup to observe the DCE in the metal–dielectric interface is proposed. • Additional methods to enhance the DCE in the metal–dielectric interface are discussed.
MHD Gauge Fields: Helicities and Casimirs
Hu, Q.; Webb, G. M.; Zank, G. P.; Anco, S.
2016-12-01
Clebsch potential gauge field theory for magnetohydrodynamics is developed based in part on the theory of Calkin (1963). It is shown how the polarization vector P in Calkin's approach, naturally arises from the Lagrange multiplier constraint equation for Faraday's equation for the magnetic induction B, or alternatively from the magnetic vector potential form of Faraday's equation. Gauss's equation, (divergence of Bis zero), is incorporated in the variational principle by means of a Lagrange multiplier constraint. Noether's theorem, and gauge symmetries are used to derive the conservation laws for (a) magnetic helicity (b) cross helicity, (c) fluid helicity for non-magnetized fluids, and (d) a class of conservation laws associated with curl and divergence equations, which applies to Faraday's equation and Gauss's equation. The magnetic helicity conservation law is due to a gauge symmetry in MHD and not due to a fluid relabelling symmetry. The analysis is carried out for a non-barotropic gas. The cross helicity and fluid helicity conservation are nonlocal conservation laws, that reduce to local conservation laws for the case of a barotropic gas. The connections between gauge symmetries, Clebsch potentials and Casimirs are developed. It is shown that the gauge symmetry functionals in the work of Henyey (1982) satisfy the Casimir equations.
Forced thermal cycling of catalytic reactions: experiments and modelling
DEFF Research Database (Denmark)
Jensen, Søren; Olsen, Jakob Lind; Thorsteinsson, Sune
2007-01-01
Recent studies of catalytic reactions subjected to fast forced temperature oscillations have revealed a rate enhancement increasing with temperature oscillation frequency. We present detailed studies of the rate enhancement up to frequencies of 2.5 Hz. A maximum in the rate enhancement is observed...... at about 1 Hz. A model for the rate enhancement that includes the surface kinetics and the dynamic partial pressure variations in the reactor is introduced. The model predicts a levelling off of the rate enhancement with frequency at about 1 Hz. The experimentally observed decrease above 1 Hz is explained...
Finite-temperature Casimir effect in the presence of nonlinear dielectrics
DEFF Research Database (Denmark)
Kheirandish, Fardin; Amooghorban, Ehsan; Soltani, Morteza
2011-01-01
Starting from a Lagrangian, the electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques, and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained, and their relations to coupl......Starting from a Lagrangian, the electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques, and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained, and their relations...... to coupling functions are determined. Finally, the Casimir energy and force in the presence of a nonlinear medium at finite temperature are calculated....
Casimir energy and the possibility of higher dimensional manipulation
Obousy, R. K.; Saharian, A. A.
2009-01-01
It is well known that the Casimir effect is an excellent candidate for the stabilization of the extra dimensions. It has also been suggested that the Casimir effect in higher dimensions may be the underlying phenomenon that is responsible for the dark energy which is currently driving the accelerated expansion of the universe. In this paper we suggest that, in principle, it may be possible to directly manipulate the size of an extra dimension locally using Standard Model fields in the next ge...
Charge-Induced Fluctuation Forces in Graphitic Nanostructures
Directory of Open Access Journals (Sweden)
D. Drosdoff
2016-01-01
Full Text Available Charge fluctuations in nanocircuits with capacitor components are shown to give rise to a novel type of long-ranged interaction, which coexist with the regular Casimir–van der Waals force. The developed theory distinguishes between thermal and quantum mechanical effects, and it is applied to capacitors involving graphene nanostructures. The charge fluctuations mechanism is captured via the capacitance of the system with geometrical and quantum mechanical components. The dependence on the distance separation, temperature, size, and response properties of the system shows that this type of force can have a comparable and even dominant effect to the Casimir interaction. Our results strongly indicate that fluctuation-induced interactions due to various thermodynamic quantities can have important thermal and quantum mechanical contributions at the microscale and the nanoscale.
Nonequilibrium Fluctuational Quantum Electrodynamics: Heat Radiation, Heat Transfer, and Force
Bimonte, Giuseppe; Emig, Thorsten; Kardar, Mehran; Krüger, Matthias
2017-03-01
Quantum-thermal fluctuations of electromagnetic waves are the cornerstone of quantum statistics and inherent to phenomena such as thermal radiation and van der Waals forces. Although the principles are found in elementary texts, recent experimental and technological advances make it necessary to come to terms with counterintuitive consequences at short scales—the so-called near-field regime. We focus on three manifestations: (a) The Stefan-Boltzmann law describes radiation from macroscopic bodies but fails for small objects. (b) The heat transfer between two bodies at close proximity is dominated by evanescent waves and can be orders of magnitude larger than the classical (propagating) contribution. (c) Casimir forces, dominant at submicron separation, are not sufficiently explored for objects at different temperatures (at least experimentally). We explore these phenomena using fluctuational quantum electrodynamics (QED), introduced by Rytov in the 1950s, combined with scattering formalisms. This enables investigation of different material properties, shapes, separations, and arrangements.
Casimir scaling and Yang-Mills glueballs
Hong, Deog Ki; Lee, Jong-Wan; Lucini, Biagio; Piai, Maurizio; Vadacchino, Davide
2017-12-01
We conjecture that in Yang-Mills theories the ratio between the ground-state glueball mass squared and the string tension is proportional to the ratio of the eigenvalues of quadratic Casimir operators in the adjoint and the fundamental representations. The proportionality constant depends on the dimension of the space-time only, and is henceforth universal. We argue that this universality, which is supported by available lattice results, is a direct consequence of area-law confinement. In order to explain this universal behavior, we provide three analytical arguments, based respectively on a Bethe-Salpeter analysis, on the saturation of the scale anomaly by the lightest scalar glueball and on QCD sum rules, commenting on the underlying assumptions that they entail and on their physical implications.
Effect of Knudsen thermal force on the performance of low-pressure micro gas sensor
Barzegar Gerdroodbary, M.; Ganji, D. D.; Taeibi-Rahni, M.; Vakilipour, Shidvash
2017-07-01
In this paper, Direct Simulation Monte Carlo (DSMC) simulations were applied to investigate the mechanism of the force generation inside a low-pressure gas sensor. The flow feature and force generation mechanism inside a rectangular enclosure with heat and cold arms as the non-isothermal walls are comprehensively explained. In addition, extensive parametric studies are done to study the effects of physical parameters on the performance and characteristics of this device in different operating conditions. In this research, the Knudsen number is varied from 0.1 to 4.5 (0.5 to 11torr) to reveal all the characteristics of the thermally driven force inside the MEMS sensor. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equations are applied to obtain high-precision results. The effects of ambient pressure and temperature difference of arms are comprehensively investigated. Our findings show that maximum force increases more than 7 times when the temperature difference of the cold and hot arms is increased from 10 to 100K. In addition, the results demonstrate that the thermal gradient at rarefied pressure induces complex structure, and the mechanism of force generation highly varies at different pressure conditions.
Directory of Open Access Journals (Sweden)
Johan Liakka
2012-01-01
Full Text Available This study examines mutual interactions between stationary waves and ice sheets using a dry atmospheric primitive-equation model coupled to a three-dimensional thermomechanical ice-sheet model. The emphasis is on how non-linear interactions between thermal and topographical forcing of the stationary waves influence the ice-sheet evolution by changing the ablation. Simulations are conducted in which a small ice cap, on an idealised Northern Hemisphere continent, evolves to an equilibrium continental-scale ice sheet. In the absence of stationary waves, the equilibrium ice sheet arrives at symmetric shape with a zonal equatorward margin. In isolation, the topographically induced stationary waves have essentially no impact on the equilibrium features of the ice sheet. The reason is that the temperature anomalies are located far from the equatorward ice margin. When forcing due to thermal cooling is added to the topographical forcing, thermally induced perturbation winds amplify the topographically induced stationary-wave response, which that serves to increase both the equatorward extent and the volume of the ice sheet. Roughly, a 10% increase in the ice volume is reported here. Hence, the present study suggests that the topographically induced stationary-wave response can be substantially enhanced by the high albedo of ice sheets.
Guarino, Stefano; Di Ilio, Giovanni; Venettacci, Simone
2017-08-05
In this paper, the heat transfer performances of aluminum metal foams, placed on horizontal plane surface, was evaluated in forced convection conditions. Three different types of contacts between the sample and the heated base plate have been investigated: simple contact, brazed contact and grease paste contact. First, in order to perform the study, an ad hoc experimental set-up was built. Second, the value of thermal contact resistance was estimated. The results show that both the use of a conductive paste and the brazing contact, realized by means of a copper electro-deposition, allows a great reduction of the global thermal resistance, increasing de facto the global heat transfer coefficient of almost 80%, compared to the simple contact case. Finally, it was shown that, while the contribution of thermal resistance is negligible for the cases of brazed and grease paste contact, it is significantly high for the case of simple contact.
Directory of Open Access Journals (Sweden)
Stefano Guarino
2017-08-01
Full Text Available In this paper, the heat transfer performances of aluminum metal foams, placed on horizontal plane surface, was evaluated in forced convection conditions. Three different types of contacts between the sample and the heated base plate have been investigated: simple contact, brazed contact and grease paste contact. First, in order to perform the study, an ad hoc experimental set-up was built. Second, the value of thermal contact resistance was estimated. The results show that both the use of a conductive paste and the brazing contact, realized by means of a copper electro-deposition, allows a great reduction of the global thermal resistance, increasing de facto the global heat transfer coefficient of almost 80%, compared to the simple contact case. Finally, it was shown that, while the contribution of thermal resistance is negligible for the cases of brazed and grease paste contact, it is significantly high for the case of simple contact.
Control of the South Atlantic Convergence Zone by extratropical thermal forcing
Talento, Stefanie; Barreiro, Marcelo
2017-03-01
The response of the South Atlantic Convergence Zone (SACZ) to an extratropical thermal forcing is investigated in a series of simulations performed with an atmospheric general circulation model coupled to a slab ocean model. Three sets of experiments are performed, varying the extratropical forcing. In the first the forcing consists of warming of the Northern Hemisphere (NH) and cooling of the Southern Hemisphere, with zero global average. In the second and third experiments, the former forcing is divided into its northern and southern components to asses their relative roles in affecting the SACZ. In all the cases realistic surface boundary conditions are implemented. We found that during its peak in austral summer the SACZ weakens in response to the extratropical forcing and that such weakening is mostly due to the NH component of the forcing. We found that 75% of the SACZ signal in response to the forcing is linked to the generation of a secondary tropical convergence zone in the Atlantic Ocean around 20°N-30°N, which generates an anomalous Hadley circulation with subsidence over the SACZ. This mechanism appears to be dependent on the upper level changes and tropical ocean response, as it weakens significantly when the simulation is repeated not allowing the tropical sea surface temperatures to change in response to the forcing. The remaining 25% of the signal can be explained through the development of a Walker-type of circulation between western tropical Africa and the SACZ, being this mechanism dependent on the African land surface temperature reaction to the remote forcing.
Shin, I; Wachtel, E; Roth, E; Bon, C; Silman, I; Weiner, L
2002-08-01
A monomeric form of acetylcholinesterase from the venom of Bungarus fasciatus is converted to a partially unfolded molten globule species by thermal inactivation, and subsequently aggregates rapidly. To separate the kinetics of unfolding from those of aggregation, single molecules of the monomeric enzyme were encapsulated in reverse micelles of Brij 30 in 2,2,4-trimethylpentane, or in large unilamellar vesicles of egg lecithin/cholesterol at various protein/micelle (vesicle) ratios. The first-order rate constant for thermal inactivation at 45 degrees C, of single molecules entrapped within the reverse micelles (0.031 min(-1)), was higher than in aqueous solution (0.007 min(-1)) or in the presence of normal micelles (0.020 min(-1)). This clearly shows that aggregation does not provide the driving force for thermal inactivation of BfAChE. Within the large unilamellar vesicles, at average protein/vesicle ratios of 1:1 and 10:1, the first-order rate constants for thermal inactivation of the encapsulated monomeric acetylcholinesterase, at 53 degrees C, were 0.317 and 0.342 min(-1), respectively. A crosslinking technique, utilizing the photosensitive probe, hypericin, showed that thermal denaturation produces a distribution of species ranging from dimers through to large aggregates. Consequently, at a protein/vesicle ratio of 10:1, aggregation can occur upon thermal denaturation. Thus, these experiments also demonstrate that aggregation does not drive the thermal unfolding of Bungarus fasciatus acetylcholinesterase. Our experimental approach also permitted monitoring of recovery of enzymic activity after thermal denaturation in the absence of a competing aggregation process. Whereas no detectable recovery of enzymic activity could be observed in aqueous solution, up to 23% activity could be obtained for enzyme sequestered in the reverse micelles.
Casimir effect for parallel plates in a Friedmann-Robertson-Walker universe
Bezerra de Mello, E. R.; Saharian, A. A.; Setare, M. R.
2017-03-01
We evaluate the Hadamard function, the vacuum expectation values (VEVs) of the field squared and the energy-momentum tensor for a massive scalar field with a general curvature coupling parameter in the geometry of two parallel plates on a spatially flat Friedmann-Robertson-Walker background with a general scale factor. On the plates, the field operator obeys the Robin boundary conditions with the coefficients depending on the scale factor. In all the spatial regions, the VEVs are decomposed into the boundary-free and boundary-induced contributions. Unlike the problem with the Minkowski bulk, in the region between the plates, the normal stress is not homogeneous and does not vanish in the geometry of a single plate. Near the plates, it has different signs for accelerated and decelerated expansions of the Universe. The VEV of the energy-momentum tensor, in addition to the diagonal components, has a nonzero off-diagonal component describing an energy flux along the direction normal to the boundaries. Expressions are derived for the Casimir forces acting on the plates. Depending on the Robin coefficients and on the vacuum state, these forces can be either attractive or repulsive. An important difference from the corresponding result in the Minkowski bulk is that the forces on the separate plates, in general, are different if the corresponding Robin coefficients differ. We give the applications of general results for the class of α vacua in the de Sitter bulk. It is shown that, compared with the Bunch-Davies vacuum state, the Casimir forces for a given α vacuum may change the sign.
The effect of power law body forces on a thermally-driven flow between concentric rotating spheres
Macaraeg, M. G.
1985-01-01
A numerical study is conducted to determine the effect of power-law body forces on a thermally-driven axisymmetric flow field confined between concentric co-rotating spheres. This study is motivated by Spacelab geophysical fluid-flow experiments, which use an electrostatic force on a dielectric fluid to simulate gravity; this force exhibits a (1/r)sup 5 distribution. Meridional velocity is found to increase when the electrostatic body force is imposed, relative to when the body force is uniform. Correlation among flow fields with uniform, inverse-square, and inverse-quintic force fields is obtained using a modified Grashof number.
The effect of power-law body forces on a thermally driven flow between concentric rotating spheres
Macaraeg, M. G.
1986-01-01
A numerical study is conducted to determine the effect of power-law body forces on a thermally-driven axisymmetric flow field confined between concentric co-rotating spheres. This study is motivated by Spacelab geophysical fluid-flow experiments, which use an electrostatic force on a dielectric fluid to simulate gravity; this force exhibits a (1/r)sup 5 distribution. Meridional velocity is found to increase when the electrostatic body force is imposed, relative to when the body force is uniform. Correlation among flow fields with uniform, inverse-square, and inverse-quintic force fields is obtained using a modified Grashof number.
Self assembly of anisotropic particles with critical Casimir forces
Nguyễn, Trúc Anh
2016-01-01
Building new materials with structures on the micron and nanoscale presents a grand challenge currently. It requires fine control in the assembly of well-designed building blocks, and understanding of the mechanical, thermodynamic, and opto-electronic properties of the resulting structures. Patchy
Parallel plate structures for optical modulation and casimir force measurement
Syed Nawazuddin, M.B.; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Elwenspoek, Michael Curt
2009-01-01
Integrated optical switches using mechano-optical sensing are gaining more attention in many fields due to their fast switching speed, large bandwidth and compact devices. In this paper, a micromachined electrostatically actuated metal plate to sense the evanescent field above the waveguide is
Top-down and bottom-up forces interact at thermal range extremes on American lobster.
Boudreau, Stephanie A; Anderson, Sean C; Worm, Boris
2015-05-01
Exploited marine populations are thought to be regulated by the effects of fishing, species interactions and climate. Yet, it is unclear how these forces interact and vary across a species' range. We conducted a meta-analysis of American lobster (Homarus americanus) abundance data throughout the entirety of the species' range, testing competing hypotheses about bottom-up (climate, temperature) vs. top-down (predation, fishing) regulation along a strong thermal gradient. Our results suggest an interaction between predation and thermal range - predation effects dominated at the cold and warm extremes, but not at the centre of the species' range. Similarly, there was consistent support for a positive climate effect on lobster recruitment at warm range extremes. In contrast, fishing effort followed, rather than led changes in lobster abundance over time. Our analysis suggests that the relative effects of top-down and bottom-up forcing in regulating marine populations may intensify at thermal range boundaries and weaken at the core of a species' range. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.
Importance of boundary conditions for fluctuation-induced forces between colloids at interfaces.
Lehle, Hartwig; Oettel, Martin
2007-01-01
We calculate the effective fluctuation-induced force between spherical or disklike colloids trapped at a flat, fluid interface mediated by thermally excited capillary waves. This Casimir-type force is determined by the partition function of the system which in turn is calculated in a functional integral approach, where the restrictions on the capillary waves imposed by the colloids are incorporated by auxiliary fields. In the long-range regime the fluctuation-induced force is shown to depend sensitively on the boundary conditions imposed at the three-phase contact line between the colloids and the two fluid phases. Separating the colloid fluctuations from the fluctuations of the capillary wave field leads to competing repulsive and attractive contributions, respectively, which give rise to cancellations of the leading terms. In a second approach based on a multipole expansion of the Casimir interaction, these cancellations can be understood from the vanishing of certain multipole moments enforced by the boundary conditions. We also discuss the connection of the different types of boundary conditions to certain external fields acting on the colloids which appear to be realizable by experimental techniques such as the laser tweezer method.
Influence of coupling on thermal forces and dynamic friction in plasmas with multiple ion species
Kagan, Grigory; Daligault, Jerome
2016-01-01
The recently proposed effective potential theory [Phys. Rev. Lett. 110, 235001 (2013)] is used to investigate the influence of coupling on inter-ion-species diffusion and momentum exchange in multi-component plasmas. Thermo-diffusion and the thermal force are found to diminish rapidly as strong coupling onsets. For the same coupling parameters, the dynamic friction coefficient is found to tend to unity. These results provide an impetus for addressing the role of coupling on diffusive processes in inertial confinement fusion experiments.
Influence of coupling on thermal forces and dynamic friction in plasmas with multiple ion species
Kagan, Grigory; Baalrud, Scott D.; Daligault, Jérôme
2017-07-01
The recently proposed effective potential theory [Phys. Rev. Lett. 110, 235001 (2013)] is used to investigate the influence of coupling on inter-ion-species diffusion and momentum exchange in multi-component plasmas. Thermo-diffusion and the thermal force are found to diminish rapidly as strong coupling onsets. For the same coupling parameters, the dynamic friction coefficient is found to tend to unity. These results provide an impetus for addressing the role of coupling on diffusive processes in inertial confinement fusion experiments.
Analysis of the step responses of laminar premixed flames to forcing by non-thermal plasma
Lacoste, Deanna A.
2016-07-16
The step responses of lean methane-air flames to non-thermal plasma forcing is reported. The experimental setup consists of an axisymmetric burner, with a nozzle made of a quartz tube. The equivalence ratio is 0.95, allowing stabilization of the flame in a V-shape or an M-shape geometry, over a central stainless steel rod. The plasma is produced by short pulses of 10-ns duration, 8-kV maximum voltage amplitude, applied at 10 kHz. The central rod is used as a cathode, while the anode is a stainless steel ring, fixed on the outer surface of the quartz tube. Plasma forcing is produced by positive or negative steps of plasma. The step response of the flame is investigated through heat release rate (HRR) fluctuations, to facilitate comparisons with flame response to acoustic perturbations. The chemiluminescence of CH* between two consecutive pulses was recorded using an intensified camera equipped with an optical filter to estimate the HRR fluctuations. First, the results show that the flame does not respond to each single plasma pulse, but is affected only by the average plasma power, confirming the step nature of the forcing. The temporal evolutions of HRR are analyzed and the flame transfer functions are determined. A forcing mechanism, as a local increase in the reactivity of the fluid close to the rod, is proposed and compared with numerical simulations. Experiments and numerical simulations are in good qualitative agreement. © 2016.
A Scheme for Solving the Plane–Plane Challenge in Force Measurements at the Nanoscale
Directory of Open Access Journals (Sweden)
Comin Fabio
2010-01-01
Full Text Available Abstract Non-contact interaction between two parallel flat surfaces is a central paradigm in sciences. This situation is the starting point for a wealth of different models: the capacitor description in electrostatics, hydrodynamic flow, thermal exchange, the Casimir force, direct contact study, third body confinement such as liquids or films of soft condensed matter. The control of parallelism is so demanding that no versatile single force machine in this geometry has been proposed so far. Using a combination of nanopositioning based on inertial motors, of microcrystal shaping with a focused-ion beam (FIB and of accurate in situ and real-time control of surface parallelism with X-ray diffraction, we propose here a “gedanken” surface-force machine that should enable one to measure interactions between movable surfaces separated by gaps in the micrometer and nanometer ranges.
A scheme for solving the plane-plane challenge in force measurements at the nanoscale.
Siria, Alessandro; Huant, Serge; Auvert, Geoffroy; Comin, Fabio; Chevrier, Joel
2010-05-19
Non-contact interaction between two parallel flat surfaces is a central paradigm in sciences. This situation is the starting point for a wealth of different models: the capacitor description in electrostatics, hydrodynamic flow, thermal exchange, the Casimir force, direct contact study, third body confinement such as liquids or films of soft condensed matter. The control of parallelism is so demanding that no versatile single force machine in this geometry has been proposed so far. Using a combination of nanopositioning based on inertial motors, of microcrystal shaping with a focused-ion beam (FIB) and of accurate in situ and real-time control of surface parallelism with X-ray diffraction, we propose here a "gedanken" surface-force machine that should enable one to measure interactions between movable surfaces separated by gaps in the micrometer and nanometer ranges.
Optical switching of a graphene mechanical switch using the Casimir effect
Inui, Norio
2017-09-01
We propose a method to control a graphene-based mechanical switch with light. By positioning a self-supporting graphene sheet parallel to a doped silicon membrane, irradiation of the membrane with light can bring the graphene into contact with the membrane. This operation is based on the enhancement of the Casimir force between the graphene sheet and a doped silicon membrane that results from photoionization; therefore, pull-in phenomena can occur even without applying any voltage. We theoretically investigated the dependence of the maximum displacement of a graphene sheet on the power of the irradiation light. Furthermore, the switching time is estimated by analyzing the time-evolution of the carrier density in a doped silicon membrane.
Dynamics of the Vacuum and Casimir Analogs to the Hydrogen Atom
White, Harold; Vera, Jerry; Bailey, Paul; March, Paul; Lawrence, Tim; Sylvester, Andre; Brady, David
2015-01-01
This paper will discuss the current viewpoint of the vacuum state and explore the idea of a "natural" vacuum as opposed to immutable, non-degradable vacuum. This concept will be explored for all primary quantum numbers to show consistency with observation at the level of Bohr theory. A comparison with the Casimir force per unit area will be made, and an explicit function for the spatial variation of the vacuum density around the atomic nucleus will be derived. This explicit function will be numerically modeled using the industry multi-physics tool, COMSOL(trademark), and the eigenfrequencies for the n = 1 to n = 7 states will be found and compared to expectation.
Fluctuation of a Piston in Vacuum Induced by Thermal Radiation Pressure
Inui, Norio
2017-10-01
We consider the displacement of a piston dividing a vacuum cavity at a finite temperature T induced by fluctuations in the thermal radiation pressure. The correlation function of the thermal radiation pressure is calculated using the theoretical framework developed by Barton, which was first applied to the fluctuation of the Casimir force at absolute zero. We show that the variance of the radiation pressure at a fixed point is proportional to T8 and evaluate the mean square displacement for a piston with a small cross section in a characteristic correlation timescale ħ/(kBT). At room temperature, the contribution of the thermal radiation to the fluctuation is larger than that of the vacuum fluctuation.
Abkenar, Masoud; Gray, Thomas H.; Zaccone, Alessio
2017-04-01
Theories that are used to extract energy-landscape information from single-molecule pulling experiments in biophysics are all invariably based on Kramers' theory of the thermally activated escape rate from a potential well. As is well known, this theory recovers the Arrhenius dependence of the rate on the barrier energy and crucially relies on the assumption that the barrier energy is much larger than kBT (limit of comparatively low thermal fluctuations). As was shown already in Dudko et al. [Phys. Rev. Lett. 96, 108101 (2006), 10.1103/PhysRevLett.96.108101], this approach leads to the unphysical prediction of dissociation time increasing with decreasing binding energy when the latter is lowered to values comparable to kBT (limit of large thermal fluctuations). We propose a theoretical framework (fully supported by numerical simulations) which amends Kramers' theory in this limit and use it to extract the dissociation rate from single-molecule experiments where now predictions are physically meaningful and in agreement with simulations over the whole range of applied forces (binding energies). These results are expected to be relevant for a large number of experimental settings in single-molecule biophysics.
Energy Technology Data Exchange (ETDEWEB)
Soroush, R [Electronics Engineering Department, Islamic Azad University, Lahijan Branch, Lahijan (Iran, Islamic Republic of); Koochi, A; Haddadpour, H [Department of Aerospace Engineering, and Center of Excellence in Aerospace Systems, Sharif University of Technology, Azadi Avenue, PO Box 11165-8639, Tehran (Iran, Islamic Republic of); Kazemi, A S [School of Physics and Center for Solid State Research, Damghan University for Basic Sciences, PO Box 367164-167, Damghan (Iran, Islamic Republic of); Noghrehabadi, A [Department of Mechanical Engineering, Shahid Chamran University, PO Box 613574-333, Ahvaz (Iran, Islamic Republic of); Abadyan, M, E-mail: A.R.Noghrehabadi@scu.ac.i, E-mail: Abadyan@yahoo.co [Mechanical Engineering Group, Islamic Azad University Ramsar Branch, Ramsar Center, Ramsar (Iran, Islamic Republic of)
2010-10-15
This paper investigates the effect of dispersion (van der Waals and Casimir) forces on the pull-in instability of cantilever nano-actuators by considering their range of application. Adomian decomposition is introduced to obtain an analytical solution of the distributed parameter model. Dispersion forces decrease the pull-in deflection and voltage of a nano-actuator. However, the fringing field increases the pull-in deflection while decreasing the pull-in voltage of the actuator. The minimum initial gap and the detachment length of the actuator that does not stick to the substrate due to van der Waals and Casimir attractions were determined. Furthermore, the proposed approach is capable of determining the stress distribution of the actuator at the onset of instability. It is seen that Casimir and van der Waals attractions effectively reduce the maximum value of stress resultants at the onset of instability. The results indicate that Adomian decomposition is a reliable method for simulating nano-structures at submicrometer ranges.
Casimir scaling and YangâMills glueballs
Directory of Open Access Journals (Sweden)
Deog Ki Hong
2017-12-01
Full Text Available We conjecture that in YangâMills theories the ratio between the ground-state glueball mass squared and the string tension is proportional to the ratio of the eigenvalues of quadratic Casimir operators in the adjoint and the fundamental representations. The proportionality constant depends on the dimension of the space-time only, and is henceforth universal. We argue that this universality, which is supported by available lattice results, is a direct consequence of area-law confinement. In order to explain this universal behavior, we provide three analytical arguments, based respectively on a BetheâSalpeter analysis, on the saturation of the scale anomaly by the lightest scalar glueball and on QCD sum rules, commenting on the underlying assumptions that they entail and on their physical implications. Keywords: Glueballs, YangâMills theories, Confinement, Casimir scaling
Xue, Pengfei; Schwab, David J.; Hu, Song
2015-07-01
Lake Superior, the largest lake in the world by surface area and third largest by volume, features strong spatiotemporal thermal variability due to its immense size and complex bathymetry. The objectives of this study are to document our recent modeling experiences on the simulation of the lake thermal structure and to explore underlying dynamic explanations of the observed modeling success. In this study, we use a three-dimensional hydrodynamic model (FVCOM—Finite Volume Community Ocean Model) and an assimilative weather forecasting model (WRF—Weather Research and Forecasting Model) to study the annual heating and cooling cycle of Lake Superior. Model experiments are carried out with meteorological forcing based on interpolation of surface weather observations, on WRF and on Climate Forecast System Reanalysis (CFSR) reanalysis data, respectively. Model performance is assessed through comparison with satellite products and in situ measurements. Accurate simulations of the lake thermal structure are achieved through (1) adapting the COARE algorithm in the hydrodynamic model to derive instantaneous estimates of latent/sensible heat fluxes and upward longwave radiation based on prognostic surface water temperature simulated within the model as opposed to precomputing them with an assumed surface water temperature; (2) estimating incoming solar radiation and downward longwave radiation based on meteorological measurements as opposed to meteorological model-based estimates; (3) using the weather forecasting model to provide high-resolution dynamically constrained wind fields as opposed to wind fields interpolated from station observations. Analysis reveals that the key to the modeling success is to resolve the lake-atmosphere interactions and apply appropriate representations of different meteorological forcing fields, based on the nature of their spatiotemporal variability. The close agreement between model simulation and observations also suggests that the 3-D
On the static Casimir effect with parity-breaking mirrors
Energy Technology Data Exchange (ETDEWEB)
Fosco, C.D. [Comision Nacional de Energia Atomica, Centro Atomico Bariloche and Instituto Balseiro, Bariloche (Argentina); Remaggi, M.L. [Universidad Nacional de Cuyo, Facultad de Ciencias Exactas y Naturales, Mendoza (Argentina)
2017-03-15
We study the Casimir interaction energy due to the vacuum fluctuations of the electromagnetic (EM) field in the presence of two mirrors, described by 2+1-dimensional, generally nonlocal actions, which may contain both parity-conserving and parity-breaking terms. We compare the results with the ones corresponding to Chern-Simons boundary conditions and evaluate the interaction energy for several particular situations. (orig.)
Wen, Mao-Yu; Yeh, Cheng-Hsiung
2017-06-01
This paper presents a numerical simulation of the heat transfer performance under forced convection for two different types of circular pin fin heat sinks with (Type A) and without (Type B) a hollow in the heated base. COMSOL Multiphysics, which is used for the thermal hydraulic analyses, has proven to be a powerful finite-element-based simulation tool for solving multiple physics-based systems of partial and ordinary differential equations. The standard κ - \\varepsilon two-equations turbulence model is employed to describe the turbulent structure and behavior. The numerical results are validated with the experimental results, and are shown to be in good agreement. The effects of the Reynolds number, height of the fin, finning factor and the perforated base plate on the heat-transfer coefficient are investigated and evaluated. The present study strongly recommends the use of a small hollow ( (Dh /Db ) heat sink.
Graybill, George
2007-01-01
Forces are at work all around us. Discover what a force is, and different kinds of forces that work on contact and at a distance. We use simple language and vocabulary to make this invisible world easy for students to ""see"" and understand. Examine how forces ""add up"" to create the total force on an object, and reinforce concepts and extend learning with sample problems.
Sakai, S.; Stramigioli, Stefano
2008-01-01
This paper gives a new passivity based control of hydraulic arms based on a new model using “natural��? Casimir functions. Not only passivity but also Casimir functions are used in the modeling and control as a new structural property. First, we refer port-Hamiltonian systems and their properties.
DEFF Research Database (Denmark)
Lindballe, Thue Bjerring; Kristensen, Martin V. G.; Keiding, Søren Rud
2013-01-01
is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our......An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 polystyrene bead, the laser pulse...
Short-range fundamental forces
Antoniadis, I; Buchner, M; Fedorov, V V; Hoedl, S; Lambrecht, A; Nesvizhevsky, V V; Pignol, G; Protasov, K V; Reynaud, S; Sobolev, Yu
2011-01-01
We consider theoretical motivations to search for extra short-range fundamental forces as well as experiments constraining their parameters. The forces could be of two types: 1) spin-independent forces, 2) spin-dependent axion-like forces. Differe nt experimental techniques are sensitive in respective ranges of characteristic distances. The techniques include measurements of gravity at short distances, searches for extra interactions on top of the Casimir force, precision atomic and neutron experim ents. We focus on neutron constraints, thus the range of characteristic distances considered here corresponds to the range accessible for neutron experiments.
Zhang, Xiaochun; Caldeira, Ken
2015-06-01
The Earth warms both when fossil fuel carbon is oxidized to carbon dioxide and when greenhouse effect of carbon dioxide inhibits longwave radiation from escaping to space. Various important time scales and ratios comparing these two climate forcings have not previously been quantified. For example, the global and time-integrated radiative forcing from burning a fossil fuel exceeds the heat released upon combustion within 2 months. Over the long lifetime of CO2 in the atmosphere, the cumulative CO2-radiative forcing exceeds the amount of energy released upon combustion by a factor >100,000. For a new power plant, the radiative forcing from the accumulation of released CO2 exceeds the direct thermal emissions in less than half a year. Furthermore, we show that the energy released from the combustion of fossil fuels is now about 1.71% of the radiative forcing from CO2 that has accumulated in the atmosphere as a consequence of historical fossil fuel combustion.
Directory of Open Access Journals (Sweden)
Florian Pielmeier
2014-04-01
Full Text Available In frequency modulation atomic force microscopy (FM-AFM the stability of the eigenfrequency of the force sensor is of key importance for highest precision force measurements. Here, we study the influence of temperature changes on the resonance frequency of force sensors made of quartz, in a temperature range from 4.8–48 K. The sensors are based on the qPlus and length extensional principle. The frequency variation with temperature T for all sensors is negative up to 30 K and on the order of 1 ppm/K, up to 13 K, where a distinct kink appears, it is linear. Furthermore, we characterize a new type of miniaturized qPlus sensor and confirm the theoretically predicted reduction in detector noise.
Casimir Friction between Dense Polarizable Media
National Research Council Canada - National Science Library
Johan S Høye; Iver Brevik
2013-01-01
.... The expression for the friction force per unit surface area becomes mathematically well-defined and finite at finite temperature. We give numerical estimates and compare them with those obtained earlier by Pendry (1997) and by Volokitin and Persson (2007). We also show in an appendix how the statistical methods that we are using correspond to the field theoretical methods more commonly in use.
Energy Technology Data Exchange (ETDEWEB)
Bradonjic, K [Physics Department, Boston University, Boston MA (United States); Swain, J D; Widom, A; Srivastava, Y N, E-mail: john.swain@cern.c [Physics Department, Northeastern University, Boston MA (United States)
2009-04-01
Despite the fact that red blood cells carry negative charges, under certain conditions they form cylindrical stacks, or 'rouleaux'. It is shown here that a form of the Casimir effect, generalizing the more well-known van der Waals forces, can provide the necessary attractive force to balance the electrostatic repulsion. Erythrocytes in plasma are modelled as negatively charged dielectric disks in an ionic solution, allowing predictions to be made about the conditions under which rouleaux will form. The results show qualitative agreement with observations which suggest that the basic idea is worth further pursuit. In addition to revealing a mechanism which may be widespread in biology at the cellular level, it also suggest new experiments and further applications to other biological systems, colloid chemistry and nanotechnology.
Bradonjić, K.; Swain, J. D.; Widom, A.; Srivastava, Y. N.
2009-04-01
Despite the fact that red blood cells carry negative charges, under certain conditions they form cylindrical stacks, or "rouleaux". It is shown here that a form of the Casimir effect, generalizing the more well-known van der Waals forces, can provide the necessary attractive force to balance the electrostatic repulsion. Erythrocytes in plasma are modelled as negatively charged dielectric disks in an ionic solution, allowing predictions to be made about the conditions under which rouleaux will form. The results show qualitative agreement with observations which suggest that the basic idea is worth further pursuit. In addition to revealing a mechanism which may be widespread in biology at the cellular level, it also suggest new experiments and further applications to other biological systems, colloid chemistry and nanotechnology.
Energy Technology Data Exchange (ETDEWEB)
Turner, C.W.; Klimas, S.J.; Brideau, M.G
2000-02-01
Degradation of the thermal performance of steam generators(SGs) is a serious problem in nuclear power stations throughout the world (Lovett and Dow, 1991). In pressurized-heavy-water reactors (PWHRs), the reduced thermal performance of the SGs is manifested by an increase of the primary coolant reactor inlet header temperature (RIHT). In pressurized-light-water reactors(PWRs), which operate with fixed primary coolant temperature, the loss of thermal performance is manifested by a reduction of the steam pressure. Degradation mechanisms that may contribute to the loss of SG thermal performance include: fouling of the boiler tube inner surfaces (primary-side fouling); fouling of the boiler tube outer surfaces (secondary-side fouling); divider and thermal plate leakage that causes the coolant to bypass either the SG or the integral preheater and fouling of the steam separators. The relative contribution of these various degradation mechanisms to the overall loss of thermal performance is still under investigation. Soulard et al. (1990) examined the relative contributions of tube bundle fouling, divider plate leakage, and thermal plate leakage to the increase in RIHT at the Point Lepreau Generating Station, and concluded that tube fouling contributes to a significant fraction of the loss of thermal performance. Corrosion products deposit on both the inner and outer surfaces of the boiler tubes. Thus a complete understanding of the reasons fro the loss of thermal performance and the development of strategies to mitigate this loss requires a knowledge of the thermal resistance of tube deposits under primary and secondary side heat transfer conditions. We present here the results of measurements of the thermal resistance of primary-side and secondary-side boiler tube deposits performed under single-phase forced convection and flow-boiling conditions, respectively. The results are discussed in terms of the physical properties of the deposit and the mode of heat transfer.
Phonon-induced diamagnetic force and its effect on the lattice thermal conductivity.
Jin, Hyungyu; Restrepo, Oscar D; Antolin, Nikolas; Boona, Stephen R; Windl, Wolfgang; Myers, Roberto C; Heremans, Joseph P
2015-06-01
Phonons are displacements of atoms around their rest positions in a crystalline solid. They carry sound and heat, but are not classically associated with magnetism. Here, we show that phonons are, in fact, sensitive to magnetic fields, even in diamagnetic materials. We do so by demonstrating experimentally that acoustic phonons in a diamagnetic semiconductor (InSb) scatter more strongly from one another when a magnetic field is applied. We attribute this observation to the magnetic-field sensitivity of the anharmonicity of the interatomic bonds that govern the probability of phonon-phonon interactions. The displacements of atoms locally affect the orbital motion of valence band electrons, which, in the presence of an external magnetic field, spatially modulates the orbital diamagnetism around the displaced atoms. The spatial gradient in magnetic moment results in an anharmonic magnetic force exerted on the displaced atom. The process is modelled by ab initio calculations that, without the use of a single adjustable parameter, reproduce the observed 12% decrease in the lattice thermal conductivity under a 7 T magnetic field at a temperature of 5.2 K.
Tian, Ye; Du, Jincheng; Han, Wei; Zu, Xiaotao; Yuan, Xiaodong; Zheng, Wanguo
2017-02-01
The thermal conductivity of vitreous silica is computed using the direct method in molecular dynamics simulations with three sets of empirical force fields, including the BKS, Teter, and ReaxFF, to investigate their performance in thermal characterization. Various heat flux and system sizes are used in the simulations to evaluate the statistical uncertainty and the finite-size effect. While all these potentials can reproduce realistic silica structures, the ReaxFF provides better agreement with experiments at 300 K than the BKS and Teter, which is due to its improved description of low-frequency vibrations. Increasing the heat flux and cross-sectional area tends to reduce the calculated standard deviation induced by thermal fluctuations, thus contributing to more accurate thermal conductivity predictions.
Molecular forces in electromechanical integrated electrostatic harmonic actuator
Directory of Open Access Journals (Sweden)
Lizhong Xu
2017-10-01
Full Text Available Authors invent an electromechanical integrated electrostatic harmonic actuator. It is more favorable for miniaturization of the electromechanical devices. As the dimensions of the actuator decreases, the effects of the Casimir and van der Waals forces become obvious. Here, effects of the molecular forces on the operating behavior of the actuator are investigated theoretically investigated by a parametric study. The equations of the radial displacements of the flexible ring and the output torque for the actuator are deduced for three different situations: only considering electrostatic force, considering electrostatic and van der Waals forces, and considering electrostatic and the Casimir forces. The effects of van der Waals or the Casimir force on the radial displacements of the flexible ring and the output torque for the actuator are analyzed. Results show that van der Waals or the Casimir forces has obvious effects on the output torque of the actuator for small structure dimension. The results are useful in theory and technique studies on further miniaturization of the actuator.
Molecular forces in electromechanical integrated electrostatic harmonic actuator
Xu, Lizhong; Shi, Xufei
2017-10-01
Authors invent an electromechanical integrated electrostatic harmonic actuator. It is more favorable for miniaturization of the electromechanical devices. As the dimensions of the actuator decreases, the effects of the Casimir and van der Waals forces become obvious. Here, effects of the molecular forces on the operating behavior of the actuator are investigated theoretically investigated by a parametric study. The equations of the radial displacements of the flexible ring and the output torque for the actuator are deduced for three different situations: only considering electrostatic force, considering electrostatic and van der Waals forces, and considering electrostatic and the Casimir forces. The effects of van der Waals or the Casimir force on the radial displacements of the flexible ring and the output torque for the actuator are analyzed. Results show that van der Waals or the Casimir forces has obvious effects on the output torque of the actuator for small structure dimension. The results are useful in theory and technique studies on further miniaturization of the actuator.
Maclay, G. Jordan
1999-01-01
Two infinite parallel uncharged conducting planes experience an attractive force between them (called the Casimir force) due to the alteration of the zero point electromagnetic field between the plates. Similarly, there are forces on the surfaces of a rectangular cavity with conductive walls of dimension a1,a2,a3. Recently a paradox was published describing a method for the extraction of mechanical energy from the zero point fluctuations of the electromagnetic field in a rectangular conductive cavity by cyclical changes in the dimensions of the walls without doing any work (Forward, 1998). The validity of the analysis depends on the implicit assumption that the energy density within the cavity is approximately isotropic, so that positive average energy densities within the cavity result in outward forces, and negative average energy densities result in attractive forces. However, detailed computations of the forces on the cavity walls show this assumption is not valid, and that there are positive energy regions in which there are outward forces on some faces and inward forces on other faces (Hacyan, 1993). Specifically, for a cavity with a1=a2=1 the energy is positive for 0.4average pressure P1 on the 1×1 faces and the average pressure P3 on the 1×a3 faces are both positive only if 0.71.6, P3>0, P10. The implications of these and other unusual features of rectangular cavities in the vacuum are discussed.
Rectification of a Casimir Nanomachine with a Triangular Wave Signal
Directory of Open Access Journals (Sweden)
ali moradian
2017-11-01
Full Text Available In this paper, we investigate the Casimir nano system composed of two quadrisected dielectric disks separated by a thin gap. Initially the two disks have the same surface dielectric distributions. We use scatting approach in the weak coupling limit and show that the top plate experiences a torque if it rotates about its axes by an angle. Consequently, we will be able to calculate. Quite interesting, such a nanomachine may be used to examine the dielectric dependence of the Casimir torque. Our small system can be used to measure small torques. We assume that the top disk is mounted on an axle and part of the rotational friction in the system comes from the axial friction and an external load is mounted on it. For such a system with specified parameters, we can estimate inertia and axial friction. Therefor we can neglect the inertia term and use the over damped regime to describe the dynamics of our system. We show that our small system can rectify a periodic square-wave angular velocity and we obtain the average angular velocity of the top plate.
Navarro-Urrios, Daniel; Gomis-Bresco, Jordi; Alzina, Francesc; Griol, Amadeu; Martinez, Alejandro; Torres, Clivia M Sotomayor
2014-01-01
Optical forces can set tiny objects in states of self-sustained oscillation. When more than one oscillator comes into play, even a very weak interaction among them may lead to synchronization. This work reports a novel spontaneous synchronization process within an optomechanical crystal, which involves thermal/free-carrier self-pulsing and coherent mechanical motion. Both oscillating systems are driven and coupled by the optical energy stored in the cavity. Multiple frequency entrainment regions are observed as a result of the wide tuneability of the natural frequency of the thermal/free-carrier self-pulsing and the comb nature of the optical forces. All these features are observed at ambient conditions of pressure and temperature in a silicon compatible platform, which would allow their exploitation for advanced clocking applications or in artificial neural networks.
On the Regularization independence of the Casimir energy for rectangular geometries
Manzoni, Luiz
2011-04-01
The Ramanujan sum of a divergent series is employed to investigate the regularization independence of the Casimir energy in d-dimensional rectangular geometries. As an specific application we consider the piston geometry for the scalar field.
Batra, Romesh C.; Porfiri, Maurizio; Spinello, Davide
2008-01-01
We study the influence of von Kármán nonlinearity, van der Waals force, and thermal stresses on pull-in instability and small vibrations of electrostatically actuated microplates. We use the Galerkin method to develop a tractable reduced-order model for electrostatically actuated clamped rectangular microplates in the presence of van der Waals forces and thermal stresses. More specifically, we reduce the governing two-dimensional nonlinear transient boundary-value problem to a single nonlinear ordinary differential equation. For the static problem, the pull-in voltage and the pull-in displacement are determined by solving a pair of nonlinear algebraic equations. The fundamental vibration frequency corresponding to a deflected configuration of the microplate is determined by solving a linear algebraic equation. The proposed reduced-order model allows for accurately estimating the combined effects of van der Waals force and thermal stresses on the pull-in voltage and the pull-in deflection profile with an extremely limited computational effort. PMID:27879752
Casimir effects for classical and quantum liquids in slab geometry: A brief review
Energy Technology Data Exchange (ETDEWEB)
Biswas, Shyamal, E-mail: sbsp@uohyd.ac.in [School of Physics, University of Hyderabad, C.R. Rao Road, Gachibowli, Hyderabad-500046 (India)
2015-05-15
We analytically explore Casimir effects for confinement of classical and quantum fluctuations in slab (film) geometry (i) for classical (critical) fluctuations over {sup 4}He liquid around the λ point, and (ii) for quantum (phonon) fluctuations of Bogoliubov excitations over an interacting Bose-Einstein condensate. We also briefly review Casimir effects for confinement of quantum vacuum fluctuations confined to two plates of different geometries.
Directory of Open Access Journals (Sweden)
Li-Ching Lin Hsien-Kuo Chang
2008-01-01
Full Text Available The paper presents an adaptive neuro fuzzy inference system for predicting sea level considering tide-generating forces and oceanic thermal expansion assuming a model of sea level dependence on sea surface temperature. The proposed model named TGFT-FN (Tide-Generating Forces considering sea surface Temperature and Fuzzy Neuro-network system is applied to predict tides at five tide gauge sites located in Taiwan and has the root mean square of error of about 7.3 - 15.0 cm. The capability of TGFT-FN model is superior in sea level prediction than the previous TGF-NN model developed by Chang and Lin (2006 that considers the tide-generating forces only. The TGFT-FN model is employed to train and predict the sea level of Hua-Lien station, and is also appropriate for the same prediction at the tide gauge sites next to Hua-Lien station.
Visualization of thermally activated nanocarriers using in situ atomic force microscopy
DEFF Research Database (Denmark)
Dong, M. D.; Howard, K. A.; Oupicky, D.
2007-01-01
Thermo-responsive nanocarriers aim to improve the delivery of drugs into target tissue by a process of size-mediated deposition activated by thermal stimuli. The direct imaging of thermally-induced changes in nanocarrier morphology was demonstrated using in situ liquid AFM over a nano-scale and t......Thermo-responsive nanocarriers aim to improve the delivery of drugs into target tissue by a process of size-mediated deposition activated by thermal stimuli. The direct imaging of thermally-induced changes in nanocarrier morphology was demonstrated using in situ liquid AFM over a nano...
Unifying Microscopic and Continuum Treatments of van der Waals and Casimir Interactions
Venkataram, Prashanth S.; Hermann, Jan; Tkatchenko, Alexandre; Rodriguez, Alejandro W.
2017-06-01
We present an approach for computing long-range van der Waals (vdW) interactions between complex molecular systems and arbitrarily shaped macroscopic bodies, melding atomistic treatments of electronic fluctuations based on density functional theory in the former with continuum descriptions of strongly shape-dependent electromagnetic fields in the latter, thus capturing many-body and multiple scattering effects to all orders. Such a theory is especially important when considering vdW interactions at mesoscopic scales, i.e., between molecules and structured surfaces with features on the scale of molecular sizes, in which case the finite sizes, complex shapes, and resulting nonlocal electronic excitations of molecules are strongly influenced by electromagnetic retardation and wave effects that depend crucially on the shapes of surrounding macroscopic bodies. We show that these effects together can modify vdW interaction energies and forces, as well as molecular shapes deformed by vdW interactions, by orders of magnitude compared to previous treatments based on Casimir-Polder, nonretarded, or pairwise approximations, which are valid only at macroscopically large or atomic-scale separations or in dilute insulating media, respectively.
Unifying Microscopic and Continuum Treatments of van der Waals and Casimir Interactions.
Venkataram, Prashanth S; Hermann, Jan; Tkatchenko, Alexandre; Rodriguez, Alejandro W
2017-06-30
We present an approach for computing long-range van der Waals (vdW) interactions between complex molecular systems and arbitrarily shaped macroscopic bodies, melding atomistic treatments of electronic fluctuations based on density functional theory in the former with continuum descriptions of strongly shape-dependent electromagnetic fields in the latter, thus capturing many-body and multiple scattering effects to all orders. Such a theory is especially important when considering vdW interactions at mesoscopic scales, i.e., between molecules and structured surfaces with features on the scale of molecular sizes, in which case the finite sizes, complex shapes, and resulting nonlocal electronic excitations of molecules are strongly influenced by electromagnetic retardation and wave effects that depend crucially on the shapes of surrounding macroscopic bodies. We show that these effects together can modify vdW interaction energies and forces, as well as molecular shapes deformed by vdW interactions, by orders of magnitude compared to previous treatments based on Casimir-Polder, nonretarded, or pairwise approximations, which are valid only at macroscopically large or atomic-scale separations or in dilute insulating media, respectively.
Casimir effect for the Higgs field at finite temperature
Santos, A. F.; Khanna, Faqir C.
2017-08-01
In early 1970, it was postulated that there exists a zero spin quantum field, called Higgs field, that is present in all universe. The potential energy of the Higgs field is transferred to particles. Hence they acquire mass. These ideas were essential in fulfilling the basic need for a particle, called Higgs, with mass. These particles are called Higgs particles with spin zero with its mass to be ˜125 GeV. This raises the question as to its physical effects. If these particles are present, will they exhibit a Casimir effect and also obey the Stefan-Boltzmann Law? Assuming the dynamics of this field, will these effects change with temperature. The present calculation uses thermo field dynamics formalism to calculate temperature effects.
Design and Analysis of a High Force, Low Voltage and High Flow Rate Electro-Thermal Micropump
Directory of Open Access Journals (Sweden)
Ghader Yosefi
2014-12-01
Full Text Available This paper presents the design and simulation of an improved electro-thermal micromachined pump for drug delivery applications. Thermal actuators, which are a type of Micro Electro Mechanical system (MEMS device, are highly useful because of their ability to deliver with great force and displacement. Thus, our structure is based on a thermal actuator that exploits the Joule heating effect and has been improved using the springy length properties of MEMS chevron beams. The Joule heating effect results in a difference in temperature and therefore displacement in the beams (actuators. Simulation results show that a maximum force of 4.4 mN and a maximum flow rate of 16 μL/min can be obtained by applying an AC voltage as low as 8 V at different frequencies ranging from 1 to 32 Hz. The maximum temperature was a problem at the chevron beams and the center shaft. Thus, to locally increase the temperature of the chevron beams alone and not that of the pumping diaphragm: (1 The air gaps 2 μm underneath and above the device layer were optimized for heat transfer. (2 Release holes and providing fins were created at the center shaft and actuator, respectively, to decrease the temperature by approximately 10 °C. (3 We inserted and used a polymer tube to serve as an insulator and eliminate leakage problems in the fluidic channel.
Lee, Ching Hua; Gan, Chee Kwan
2017-07-01
Phonon-mediated thermal conductivity, which is of great technological relevance, arises due fundamentally to anharmonic scattering from interatomic potentials. Despite its prevalence, accurate first-principles calculations of thermal conductivity remain challenging, primarily due to the high computational cost of anharmonic interatomic force constant (IFC) calculations. Meanwhile, the related anharmonic phenomenon of thermal expansion is much more tractable, being computable from the Grüneisen parameters associated with phonon frequency shifts due to crystal deformations. In this work, we propose an approach for computing the largest cubic IFCs from the Grüneisen parameter data. This allows an approximate determination of the thermal conductivity via a much less expensive route. The key insight is that although the Grüneisen parameters cannot possibly contain all the information on the cubic IFCs, being derivable from spatially uniform deformations, they can still unambiguously and accurately determine the largest and most physically relevant ones. By fitting the anisotropic Grüneisen parameter data along judiciously designed deformations, we can deduce (i.e., reverse-engineer) the dominant cubic IFCs and estimate three-phonon scattering amplitudes. We illustrate our approach by explicitly computing the largest cubic IFCs and thermal conductivity of graphene, especially for its out-of-plane (flexural) modes that exhibit anomalously large anharmonic shifts and thermal conductivity contributions. Our calculations on graphene not only exhibit reasonable agreement with established density-functional theory results, but they also present a pedagogical opportunity for introducing an elegant analytic treatment of the Grüneisen parameters of generic two-band models. Our approach can be readily extended to more complicated crystalline materials with nontrivial anharmonic lattice effects.
Nesic, Svetozar; Cuerno Rejado, Rodolfo; Moro Egido, Esteban
2013-11-01
It has been shown that, in the regime controlled by surface tension, the spreading dynamics of a thin viscous fluid droplet changes significantly when it is subjected to thermal fluctuations. Technically, this has been accomplished through the incorporation of appropriate stochastic terms into the standard lubrication equation. In practice, it leads to a modification of the classic Tanner's law for spreading, with implications for Micro and Nanofluidic systems. We have recently found a new law of spreading for the same kind of systems, but in the gravity-dominated regime. Moreover, in the deteministic case a finite contact angle is formed when a van der Waals attractive force is introduced to the system and we show that there is a slight change in contact angle when thermal fluctuations are taken into account. Ph.D student and a member of GISC (http://matematicas.uc3m.es/index.php/gisc).
Trolese, Matteo; Giordano, Guido; Cifelli, Francesca; Winkler, Aldo; Mattei, Massimo
2017-11-01
Few studies have detailed the thermal architecture of large-volume pyroclastic density current deposits, although such work has a clear importance for understanding the dynamics of eruptions of this magnitude. Here we examine the temperature of emplacement of large-volume caldera-forming ignimbrites related to magmatic and phreatomagmatic eruptions at the Colli Albani volcano, Italy, by using thermal remanent magnetization analysis on both lithic and juvenile clasts. Results show that all the magmatic ignimbrites were deposited at high temperature, between the maximum blocking temperature of the magnetic carrier (600-630 °C) and the glass transition temperature (about 710 °C). Temperature estimations for the phreatomagmatic ignimbrite range between 200 and 400 °C, with most of the clasts emplaced between 200 and 320 °C. Because all the investigated ignimbrites, magmatic and phreatomagmatic, share similar magma composition, volume and mobility, we attribute the temperature difference to magma-water interaction, highlighting its pronounced impact on thermal dissipation, even in large-volume eruptions. The homogeneity of the deposit temperature of each ignimbrite across its areal extent, which is maintained across topographic barriers, suggests that these systems are thermodynamically isolated from the external environment for several tens of kilometers. Based on these findings, we propose that these large-volume ignimbrites are dominated by the mass flux, which forces the lateral transport of mass, momentum, and thermal energy for distances up to tens of kilometers away from the vent. We conclude that spatial variation of the emplacement temperature can be used as a proxy for determining the degree of forced-convection flow.
The design of long range quantum electrodynamical forces and torques between macroscopic bodies
Iannuzzi, D.; Lisanti, M.; Munday, J. N.; Capasso, F.
2005-01-01
The interaction between electrically neutral surfaces at sub-micron separation is dominated by the force arising from quantum fluctuations of the electromagnetic field, known as the Casimir force. This effect has been witnessing a renewed interest because of its potential impact in micro- and
Weak dispersive forces between glass and gold macroscopic surfaces in alcohols
van Zwol, P. J.; Palasantzas, G.; DeHosson, J. Th. M.
In this work we concentrate on an experimental validation of the Lifshitz theory for the van der Waals and the Casimir forces in gold-alcohol-glass systems. From this theory weak dispersive forces are predicted when the dielectric properties of the intervening medium become comparable to one of the
Zare, Jamal; Shateri, Alireza
2017-06-01
The aim of this research work is to address the influences of dispersion forces and rippled configuration on the instability threshold of carbon nanotube (CNT) based nanotweezers. To this end, the Dirichlet and Neumann modes of Casimir force arisen from the electric and magnetic energies is developed for cylinder-cylinder geometry. Moreover, the CNTs rippling deformation which experimentally revealed is included in the Euler-Bernoulli beam model to modify the governing equations. The differential quadrature method (DQM) in conjunction with the 4th-order Runge-Kutta algorithm is employed to numerically simulate the non-linear partial differential equations. It is interestingly demonstrated that these phenomena remarkably affect the electromechanical behavior of nanotweezers fabricated from CNTs. By taking the rippling configuration and Casimir attraction between tubes into account, the pull-in voltage decreases. On the other hand, when the gas damping effect due to low vacuum environment is taken into consideration, the pull-in value increases. The accuracy of the present modeling is compared with those experimentally published in the literature, giving excellent results.
Bogerd, Cornelis P; Brühwiler, Paul A; Heus, Ronald
2008-05-01
Both radiant and forced convective heat flow were measured for a prototype rowing headgear and white and black cotton caps. The measurements were performed on a thermal manikin headform at a wind speed of 4.0 m . s(-1) (s = 0.1) in a climate chamber at 22.0 degrees C (s = 0.05), with and without radiant heat flow from a heat lamp, coming from either directly above (90 degrees ) or from above at an angle of 55 degrees . The effects of hair were studied by repeating selected measurements with a wig. All headgear reduced the radiant heat gain compared with the nude headform: about 80% for the caps and 95% for the prototype rowing headgear (P headgear (9%) (P headgear, showing that forced convective heat loss is the dominant heat transfer parameter under the chosen conditions. The results of the headgear - wig combinations were qualitatively similar, with lower absolute heat transfer.
Fahnestock, M. A.; Shuman, C. A.; Albert, M.; Scambos, T.
2004-12-01
An NSF-OPP funded research site in the megadunes occupied during the 2002-2003 and 2003-2004 field seasons provided an opportunity to monitor wind speed and direction, atmospheric pressure, air temperature, and the evolution of the thermal profile in the firn. In the first season this was done on the lee face of a megadune; in the second season it was done there and at an additional site on the windward face. Wind speed and temperature fluctuations were well correlated at the two sites with little lag. The thermal profiles provide a picture of the cold wave penetration at both sites. Firn in these areas was significantly recrystallized (see abstract by Courville et al., this session), had a surface character that included both large sastrugi (windward slopes) and very smooth surfaces (lee slopes), and showed numerous thermal contraction cracks that were likely sites of vertical air movement. In the first season the smooth lee slope was covered by a thin glaze; the spatial extent of this glaze and the surface roughness variations are detectable in satellite imagery from this period. Large area MODIS-based image maps show the dominance of katabatic-wind-generated features in the dune field. Satellite-based microwave emission time series show the source of emission to be extremely shallow and/or characteristic of rapid cooling to near isothermal conditions; these patterns have been used to map the extent of recrystallized firn. This will be revisited in light of the new time series of firn thermal profiles.
Energy Technology Data Exchange (ETDEWEB)
Loehle, C. (Argonne National Lab., IL (United States))
1994-01-15
Data from ice cores show that CO[sub 2] and air temperature are highly correlated over the last 157,000 yr. Although this correlation can be taken as evidence that CO[sub 2] amplifies orbital forcing of temperature and is thus a strong greenhouse gas, this paper argues that estimating the strength of the CO[sub 2] warming effect from statistical evaluations of past climates based on CO[sub 2] and orbital forcing is hampered by strong multiple correlations between CH[sub 4], CO[sub 2], ocean currents, ice volume (and therefore albedo), dust, and nonseasalt sulfate. To estimate the strength of the greenhouse warming effect of CO[sub 2] from historical data, these correlations and multiple forcings should be taken into account. 21 refs., 21 figs.
Modeling of strain in multifilamentary wires deformed by thermal contraction and transverse forces
ten Haken, Bernard; Zaitseva, Tatjana N.; ten Kate, Herman H.J.
1994-01-01
A previously published analytical model that describes a simplified wire geometry with three stacked cylinders is compared with finite element model calculations. The thermal strain from the matrix on the superconducting filaments is considered first. It appears that the analytical model is able to
Sader, John E; Lu, Jianing; Mulvaney, Paul
2014-11-01
Calibration of the optical lever sensitivities of atomic force microscope (AFM) cantilevers is especially important for determining the force in AFM measurements. These sensitivities depend critically on the cantilever mode used and are known to differ for static and dynamic measurements. Here, we calculate the ratio of the dynamic and static sensitivities for several common AFM cantilevers, whose shapes vary considerably, and experimentally verify these results. The dynamic-to-static optical lever sensitivity ratio is found to range from 1.09 to 1.41 for the cantilevers studied - in stark contrast to the constant value of 1.09 used widely in current calibration studies. This analysis shows that accuracy of the thermal noise method for the static spring constant is strongly dependent on cantilever geometry - neglect of these dynamic-to-static factors can induce errors exceeding 100%. We also discuss a simple experimental approach to non-invasively and simultaneously determine the dynamic and static spring constants and optical lever sensitivities of cantilevers of arbitrary shape, which is applicable to all AFM platforms that have the thermal noise method for spring constant calibration.
Mode Summation Approach to Casimir Effect Between Two Objects
Teo, L. P.
2012-10-01
In the last few years, several approaches have been developed to compute the exact Casimir interaction energy between two nonplanar objects, all lead to the same functional form, which is called the TGTG formula. In this paper, we explore the TGTG formula from the perspective of mode summation approach. Both scalar fields and electromagnetic fields are considered. In this approach, one has to first solve the equation of motion to find a wave basis for each object. The two T's in the TGTG formula are T-matrices representing the Lippmann-Schwinger T-operators, one for each of the objects. Each T-matrix can be found by matching the boundary conditions imposed on the object, and it is independent of the other object. However, it depends on whether the object is interacting with an object outside it, or an object inside it. The two G's in the TGTG formula are the translation matrices, relating the wave basis of an object to the wave basis of the other object. These translation matrices only depend on the wave basis chosen for each object, and they are independent of the boundary conditions on the objects. After discussing the general theory, we apply the prescription to derive the explicit formulas for the Casimir energies for the sphere-sphere, sphere-plane, cylinder-cylinder and cylinder-plane interactions. First the T-matrices for a plane, a sphere and a cylinder are derived for the following cases: the object is imposed with Dirichlet, Neumann or general Robin boundary conditions; the object is semitransparent; and the object is a magnetodielectric object immersed in a magnetodielectric media. Then the operator approach developed by R. C. Wittman [IEEE Trans. Antennas Propag.36, 1078 (1988)] is used to derive the translation matrices. From these, the explicit TGTG formula for each of the scenarios can be written down. On the one hand, we have summarized all the TGTG formulas that have been derived so far for the sphere-sphere, cylinder-cylinder, sphere-plane and
Shin, I; Wachtel, E.; Roth, E.; Bon, C; Silman, I.; Weiner, L
2002-01-01
A monomeric form of acetylcholinesterase from the venom of Bungarus fasciatus is converted to a partially unfolded molten globule species by thermal inactivation, and subsequently aggregates rapidly. To separate the kinetics of unfolding from those of aggregation, single molecules of the monomeric enzyme were encapsulated in reverse micelles of Brij 30 in 2,2,4-trimethylpentane, or in large unilamellar vesicles of egg lecithin/cholesterol at various protein/micelle (vesicle) ratios. The first...
Casimir free energy of dielectric films: classical limit, low-temperature behavior and control.
Klimchitskaya, G L; Mostepanenko, V M
2017-07-12
The Casimir free energy of dielectric films, both free-standing in vacuum and deposited on metallic or dielectric plates, is investigated. It is shown that the values of the free energy depend considerably on whether the calculation approach used neglects or takes into account the dc conductivity of film material. We demonstrate that there are material-dependent and universal classical limits in the former and latter cases, respectively. The analytic behavior of the Casimir free energy and entropy for a free-standing dielectric film at low temperature is found. According to our results, the Casimir entropy goes to zero when the temperature vanishes if the calculation approach with neglected dc conductivity of a film is employed. If the dc conductivity is taken into account, the Casimir entropy takes the positive value at zero temperature, depending on the parameters of a film, i.e. the Nernst heat theorem is violated. By considering the Casimir free energy of SiO2 and Al2O3 films deposited on a Au plate in the framework of two calculation approaches, we argue that physically correct values are obtained by disregarding the role of dc conductivity. A comparison with the well known results for the configuration of two parallel plates is made. Finally, we compute the Casimir free energy of SiO2, Al2O3 and Ge films deposited on high-resistivity Si plates of different thicknesses and demonstrate that it can be positive, negative and equal to zero. The effect of illumination of a Si plate with laser light is considered. Possible applications of the obtained results to thin films used in microelectronics are discussed.
Test of Zero-point Energy Emission from Gases Flowing Through Casimir Cavities
Dmitriyeva, Olga; Moddel, Garret
A recently issued patent [1] describes a method by which vacuum energy is extracted from gas flowing through a Casimir cavity. According to stochastic electrodynamics, the electronic orbitals in atoms are supported by the ambient zero-point (ZP) field. When the gas atoms are pumped into a Casimir cavity, where long-wavelength ZP field modes are excluded, the electrons spin down into lower energy orbitals and release energy in the process. This energy is collected in a local absorber. When the electrons exit the Casimir cavity they are re-energized to their original orbitals by the ambient ZP fields. The process is repeated to produce continuous power. In this way, the device functions like a heat pump for ZP energy, extracting it globally from the electromagnetic quantum vacuum and collecting it in a local absorber. This energy can be used for heating, or converted to electric power. We carried out a series of experiments to test whether energy is, in fact, radiated from Casimir cavities when the appropriate gas flows through them. The Casimir cavity devices we tested were nanopore polycarbonate membranes with submicron pores having a density of 3x108pores/cm2. Gas was pumped through the membranes in a stainless steel vacuum system, and emitted energy was measured using a broadband pyroelectric detector and lock-in amplifier. Emission in the infrared was clearly observed. We analyzed the emission from different gases and cavities to determine its origin. None of the conventional thermodynamic models we applied to our data fully explain it, leaving open the possibility that it is due to Casimir-cavity-induced emission from ZP fields.
Sierakowski, Andrzej; Kopiec, Daniel; Majstrzyk, Wojciech; Kunicki, Piotr; Janus, Paweł; Dobrowolski, Rafał; Grabiec, Piotr; Rangelow, Ivo W.; Gotszalk, Teodor
2017-03-01
In this paper the authors compare methods used for piezoresistive microcantilevers actuation for the atomic force microscopy (AFM) imaging in the dynamic shear force mode. The piezoresistive detection is an attractive technique comparing the optical beam detection of deflection. The principal advantage is that no external alignment of optical source and detector are needed. When the microcantilever is deflected, the stress is transferred into a change of resistivity of piezoresistors. The integration of piezoresistive read-out provides a promising solution in realizing a compact non-contact AFM. Resolution of piezoresistive read-out is limited by three main noise sources: Johnson, 1/f and thermomechanical noise. In the dynamic shear force mode measurement the method used for cantilever actuation will also affect the recorded noise in the piezoresistive detection circuit. This is the result of a crosstalk between an aluminium path (current loop used for actuation) and piezoresistors located near the base of the beam. In this paper authors described an elaborated in ITE (Institute of Electron Technology) technology of fabrication cantilevers with piezoresistive detection of deflection and compared efficiency of two methods used for cantilever actuation.
Casimir effect in rugby-ball type flux compactifications
Elizalde, Emilio; Minamitsuji, Masato; Naylor, Wade
2007-03-01
As a continuation of the work by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys.JHEPFG1029-8479 12 (2006) 07910.1088/1126-6708/2006/12/079], we discuss the Casimir effect for a massless bulk scalar field in a 4D toy model of a 6D warped flux compactification model, to stabilize the volume modulus. The one-loop effective potential for the volume modulus has a form similar to the Coleman-Weinberg potential. The stability of the volume modulus against quantum corrections is related to an appropriate heat kernel coefficient. However, to make any physical predictions after volume stabilization, knowledge of the derivative of the zeta function, ζ'(0) (in a conformally related spacetime) is also required. By adding up the exact mass spectrum using zeta-function regularization, we present a revised analysis of the effective potential. Finally, we discuss some physical implications, especially concerning the degree of the hierarchy between the fundamental energy scales on the branes. For a larger degree of warping our new results are very similar to the ones given by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys.JHEPFG1029-8479 12 (2006) 07910.1088/1126-6708/2006/12/079] and imply a larger hierarchy. In the nonwarped (rugby ball) limit the ratio tends to converge to the same value, independently of the bulk dilaton coupling.
A Toy Cosmology Using a Hubble-Scale Casimir Effect
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Michael E. McCulloch
2014-02-01
Full Text Available The visible mass of the observable universe agrees with that needed for a flat cosmos, and the reason for this is not known. It is shown that this can be explained by modelling the Hubble volume as a black hole that emits Hawking radiation inwards, disallowing wavelengths that do not fit exactly into the Hubble diameter, since partial waves would allow an inference of what lies outside the horizon. This model of “horizon wave censorship” is equivalent to a Hubble-scale Casimir effect. This incomplete toy model is presented to stimulate discussion. It predicts a minimum mass and acceleration for the observable universe which are in agreement with the observed mass and acceleration, and predicts that the observable universe gains mass as it expands and was hotter in the past. It also predicts a suppression of variation on the largest cosmic scales that agrees with the low-l cosmic microwave background anomaly seen by the Planck satellite.
On the Casimir scaling violation in the cusp anomalous dimension at small angle
Grozin, Andrey; Henn, Johannes; Stahlhofen, Maximilian
2017-10-01
We compute the four-loop n f contribution proportional to the quartic Casimir of the QCD cusp anomalous dimension as an expansion for small cusp angle ϕ. This piece is gauge invariant, violates Casimir scaling, and first appears at four loops. It requires the evaluation of genuine non-planar four-loop Feynman integrals. We present results up to O({φ}^4) . One motivation for our calculation is to probe a recent conjecture on the all-order structure of the cusp anomalous dimension. As a byproduct we obtain the four-loop HQET wave function anomalous dimension for this color structure.
Anisotropic atom-surface interactions in the Casimir-Polder regime
Taillandier-Loize, T.; Baudon, J.; Dutier, G.; Perales, F.; Boustimi, M.; Ducloy, M.
2014-05-01
The distance dependence of the anisotropic atom-wall interaction is studied. The central result is the 1/z6 quadrupolar anisotropy decay in the retarded Casimir-Polder regime. Analysis of the transition region between nonretarded van der Waals regime (in 1/z3) and Casimir-Polder regime shows that the anisotropy crossover occurs at very short distances from the surface, on the order of 0.03λ, where λ is the atom characteristic wavelength. Possible experimental verifications of this distance dependence using surface-induced inelastic transitions are discussed.
Anisotropic Atom-Surface Interactions in the Casimir-Polder Regime
Taillandier-Loize, T; Dutier, G; Perales, F; Boustimi, M; Ducloy, M
2014-01-01
The distance-dependence of the anisotropic atom-wall interaction is studied. The central result is the 1/z^6 quadrupolar anisotropy decay in the retarded Casimir-Polder regime. Analysis of the transition region between non-retarded van der Waals regime (in 1/z^3) and Casimir-Polder regime shows that the anisotropy cross-over occurs at very short distances from the surface, on the order of 0.03 Lambda, where Lambda is the atom characteristic wavelength. Possible experimental verifications of this distance dependence are discussed.
Tai, Tamin; Kertesz, Vilmos; Lin, Ming-Wei; Srijanto, Bernadeta R; Hensley, Dale K; Xiao, Kai; Van Berkel, Gary J
2017-07-30
As the spatial resolution of mass spectrometry imaging technologies has begun to reach into the nanometer regime, finding readily available or easily made resolution reference materials has become particularly challenging for molecular imaging purposes. This paper describes the fabrication, characterization and use of vertical line array polymeric spatial resolution test patterns for nano-thermal analysis/atomic force microscopy/mass spectrometry chemical imaging. Test patterns of varied line width (0.7 or 1.0 μm) and spacing (0.7 or 1.0 μm) were created in an ~1-μm-thick poly(methyl methacrylate) thin film using electron beam lithography. The patterns were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy topography and nano-thermal analysis/mass spectrometry imaging. The efficacy of these polymeric test patterns for the advancement of chemical imaging techniques was illustrated by their use to judge the spatial resolution improvement achieved by heating the ionization interface of the current instrument platform. The spatial resolution of the mass spectral chemical images was estimated to be 1.4 μm, based on the ability to statistically distinguish 0.7-μm-wide lines separated by 0.7-μm-wide spacings in those images when the interface cross was heated to 200°C. This work illustrates that e-beam lithography is a viable method to create spatial resolution test patterns in a thin film of high molecular weight polymer to allow unbiased judgment of intra-laboratory advancement and/or inter-laboratory comparison of instrument advances in nano-thermal analysis/atomic force microscopy/mass spectrometry chemical imaging. Published in 2017. This article is a U.S. Government work and is in the public domain in the USA. Published in 2017. This article is a U.S. Government work and is in the public domain in the USA.
Brissinger, D; Parent, G; Lacroix, D
2013-12-01
This Note describes a mechanical etching technique which can be used to prepare silicon tips used in atomic force microscopy apparatus. For such devices, dedicated tips with specific shapes are now commonly used to probe surfaces. Yet, the control of the tip morphology where characteristic scales are lower than 1 μm remains a real challenge. Here, we detail a controlled etching process of AFM probes apex allowing micrometer-sized sphere attachment. The technique used and influent parameters are discussed and SEM images of the achieved tips are given. Deceptive problems and drawbacks that might occur during the process are also covered.
Thermal and force loads on the vehicle surface in high-velocity motion in the earth's atmosphere
Tarnavskii, G. A.
2008-03-01
Consideration has been given to a number of aspects of mathematical modeling of a high-velocity flight in the earth’s atmosphere in a wide range of variation of the determining parameters. Super-and hypersonic gas flow past flying vehicles has been investigated based on computer-aided calculations with allowance for its actual properties. Data on the distribution of gasdynamic parameters in the flow field, including thermal and force loads on the surface, have been obtained and analyzed. The issues of applying today’s information technologies to archiving scientific knowledge obtained in electronic databases of a specialized Internet center and their dissemination via the Global Network have been discussed.
Finite element methodology for transient conduction/forced-convection thermal analysis
Thornton, E. A.; Wieting, A. R.
1979-01-01
Finite element methodology for steady state thermal analysis of convectively cooled structures has been extended for transient analysis. The finite elements are based on representing the fluid passages by fluid bulk-temperature nodes and fluid-solid interface nodes. The formulation of the finite element equations for a typical flow passage is based on the weighted residual method with upwind weighting functions. Computer implementation of the convective finite element methodology using explicit and implicit time integration algorithms is described. Accuracy and efficiency of the methodology is evaluated by comparisons with analytical solutions and finite-difference lumped-parameter analyses. The comparative analyses demonstrate that finite element conduction/conduction methodology may be used to predict transient temperatures with an accuracy equal or superior to the lumped-parameter finite-difference method.
Directory of Open Access Journals (Sweden)
Amnart Boonloi
2014-09-01
Full Text Available Thermal performance analysis for laminar forced convection in an isothermal wall square channel with 30° V-baffle is presented numerically. The parameters of the V-baffle, blockage ratio (b/H, BR, pitch ratio (P/H, PR, flow direction (V-Downstream and V-Upstream, and arrangement (in-line and staggered, are studied and compared with the previous works, 20° and 45° V-baffle. The Reynolds number based on the hydraulic diameter of the channel (Dh, Re = 100–2000, is used in range study. The results show that the flow configurations of 30° V-baffle are found similar as 20° and 45° V-baffle. The fully developed periodic flow and heat transfer are created around 7th-8th module, while the periodic flow and heat transfer profiles are found at 2nd module in all cases. Except for the periodic concept, the 30° V-baffle can help to reduce the pressure loss around 2.3 times in comparison with the 45° V-baffle at the maximum f/f0 value (BR = 0.3, PR = 1, V-Downstream. The optimum thermal enhancement factor for the 30° V-baffle is found around 4.25 at BR = 0.15, PR = 1, and Re = 2000 for V-Downstream case with in-line arrangement.
Atitoaie, Alexandru; Stoleriu, Laurentiu; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian
2016-04-01
The scientific community is manifesting a high research interest on spin crossover compounds and their recently synthesized nanoparticles, due to their various appealing properties, such as the bistability between a diamagnetic low spin state and a paramagnetic high spin state (HS), inter-switchable by temperature or pressure changes, light irradiation or magnetic field. The utility of these compounds showing hysteresis covers a broad area of applications, from the development of more efficient designs of temperature and pressure sensors to automotive and aeronautic industries and even a new type of molecular actuators. We are proposing in this work a study regarding the kinetic effects and the distribution of reversible and irreversible components on the thermal hysteresis of spin crossover nanoparticulated systems. We are considering here tridimensional systems with different sizes and also systems of nanoparticles with a Gaussian size distribution. The correlations between the kinetics of the thermal hysteresis, the distributions of sizes and intermolecular interactions and the transition temperature distributions were established by using the FORC (First Order Reversal Curves) method using a Monte Carlo technique within an Ising-like system.
Marcucci, Lorenzo; Washio, Takumi; Yanagida, Toshio
2016-09-01
Muscle contractions are generated by cyclical interactions of myosin heads with actin filaments to form the actomyosin complex. To simulate actomyosin complex stable states, mathematical models usually define an energy landscape with a corresponding number of wells. The jumps between these wells are defined through rate constants. Almost all previous models assign these wells an infinite sharpness by imposing a relatively simple expression for the detailed balance, i.e., the ratio of the rate constants depends exponentially on the sole myosin elastic energy. Physically, this assumption corresponds to neglecting thermal fluctuations in the actomyosin complex stable states. By comparing three mathematical models, we examine the extent to which this hypothesis affects muscle model predictions at the single cross-bridge, single fiber, and organ levels in a ceteris paribus analysis. We show that including fluctuations in stable states allows the lever arm of the myosin to easily and dynamically explore all possible minima in the energy landscape, generating several backward and forward jumps between states during the lifetime of the actomyosin complex, whereas the infinitely sharp minima case is characterized by fewer jumps between states. Moreover, the analysis predicts that thermal fluctuations enable a more efficient contraction mechanism, in which a higher force is sustained by fewer attached cross-bridges.
Uma introdução aos métodos de cálculo da energia de Casimir
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Passos Sobrinho J.J.
2001-01-01
Full Text Available O efeito Casimir é um dos aspectos mais intrigantes da física moderna. A previsão da existência de uma força macroscópica de origem quântica entre condutores neutros e sua posterior comprovação experimental é sem dúvida um dos triunfos da teoria quântica dos campos. Complementando uma introdução conceitual publicada recentemente nesta revista, apresentamos alguns métodos de cálculo da energia de Casimir, que é a grandeza fundamental que origina o efeito Casimir.
Directory of Open Access Journals (Sweden)
Ya Feng
2014-12-01
Full Text Available Molecular dynamics simulations are performed to evaluate the effect of van der Waals forces among single-wall carbon nanotubes (SWNTs on the interfacial thermal conductance between a SWNT array and silicon substrate. First, samples of SWNTs vertically aligned on silicon substrate are simulated, where both the number and arrangement of SWNTs are varied. Results reveal that the interfacial thermal conductance of a SWNT array/Si with van der Waals forces present is higher than when they are absent. To better understand how van der Waals forces affect heat transfer through the interface between SWNTs and silicon, further constructs of one SWNT surrounded by different numbers of other ones are studied, and the results show that the interfacial thermal conductance of the central SWNT increases with increasing van der Waals forces. Through analysis of the covalent bonds and vibrational density of states at the interface, we find that heat transfer across the interface is enhanced with a greater number of chemical bonds and that improved vibrational coupling of the two sides of the interface results in higher interfacial thermal conductance. Van der Waals forces stimulate heat transfer at the interface.
The Casimir effect in rugby-ball type flux compactifications
Minamitsuji, M.
2008-04-01
We discuss volume stabilization in a 6D braneworld model based on 6D supergravity theory. The internal space is compactified by magnetic flux and contains codimension two 3-branes (conical singularities) as its boundaries. In general the external 4D spacetime is warped and in the unwrapped limit the shape of the internal space looks like a 'rugby ball'. The size of the internal space is not fixed due to the scale invariance of the supergravity theory. We discuss the possibility of volume stabilization by the Casimir effect for a massless, minimally coupled bulk scalar field. The main obstacle in studying this case is that the brane (conical) part of the relevant heat kernel coefficient (a6) has not been formulated. Thus as a first step, we consider the 4D analog model with boundary codimension two 1-branes. The spacetime structure of the 4D model is very similar to that of the original 6D model, where now the relevant heat kernel coefficient is well known. We derive the one-loop effective potential induced by a scalar field in the bulk by employing zeta function regularization with heat kernel analysis. As a result, the volume is stabilized for most possible choices of the parameters. Especially, for a larger degree of warping, our results imply that a large hierarchy between the mass scales and a tiny amount of effective cosmological constant can be realized on the brane. In the non-warped limit the ratio tends to converge to the same value, independently of the bulk gauge coupling constant. Finally, we will analyze volume stabilization in the original model 6D by employing the same mode-sum technique.
Simulation of a Casimir-like effect in a granular pile with avalanches
Denisov, D.V.; Villanueva, Y. Y.; Wijngaarden, R.J.
2011-01-01
Using a modified Bak-Tang-Wiesenfeld model for sand piles, we simulate a Casimir-like effect in a granular pile with avalanches. Results obtained in the simulation are in good agreement with results previously acquired experimentally: two parallel walls are attracted to each other at small
Supersymmetric Casimir effect and quantum creation of the universe with nontrivial topology
Energy Technology Data Exchange (ETDEWEB)
Goncharov, Yu.P.; Bytsenko, A.A.
1985-10-17
We estimate the probability of quantum creation of the universe, having the spatial topology (S )T, and filled with the fields of minimal N=1 supergravity, in the semiclassical approximation. After creation, inflation of the universe occurs due to the topological Casimir effect. Creation of the universe with an isotropic topology is found to be the most preferable. (orig.).
Study of spin crossover nanoparticles thermal hysteresis using FORC diagrams on an Ising-like model
Atitoaie, Alexandru; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian
2014-11-01
Recent developments in the synthesis and characterization of spin crossover (SCO) nanoparticles and their prospects of switching at molecular level turned these bistable compounds into possible candidates for replacing the materials used in recording media industry for development of solid state pressure and temperature sensors or for bringing contributions in engineering. Compared to bulk samples with the same chemical structure, SCO nanoparticles display different characteristics of the hysteretic and relaxation properties like the shift of the transition temperature towards lower values along with decrease of the hysteresis width with nanoparticles size. Using an Ising-like model with specific boundary conditions within a Monte Carlo procedure, we here reproduce most of the hysteretic properties of SCO nanoparticles by considering the interaction between spin crossover edge molecules and embedding surfactant molecules and we propose a complex analysis concerning the effect of the interactions and sizes during the thermal transition in systems of SCO nanoparticles by using the First Order Reversal Curves diagram method and by comparison with similar effects in mixed crystal systems.
Li, Botong; Zhang, Wei; Zhu, Liangliang
2016-09-01
This paper presents an investigation of forced convection heat transfer in power-law non-Newtonian fluids between two semi-infinite plates with variable thermal conductivity. Three cases of different thermal conductivity models are considered: (i) thermal conductivity is a constant, (ii) thermal conductivity is a linear function of temperature, (iii) thermal conductivity is a power-law function of temperature gradient (Zheng's model). Governing equations are solved using the finite element method with the ‘ghost’ time introduced to the control equations, which does not affect the results because the velocity and temperature will remain unchanged when the steady state is reached. Results for the solutions of different variable models are presented as well as the analysis of the associated heat transfer characteristics. It is shown that the heat transfer behaviours are strongly dependent on the power-law index (n) in all models. For example, when n 1.
Tuning the effective coupling of an AFM lever to a thermal bath
Energy Technology Data Exchange (ETDEWEB)
Jourdan, G [Institut Neel CNRS Grenoble BP 166 38042, Grenoble Cedex 9 (France); Torricelli, G [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Chevrier, J [Institut Neel CNRS Grenoble BP 166 38042, Grenoble Cedex 9 (France); Comin, F [ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France)
2007-11-28
Fabrication of high quality nano-electromechanical systems (NEMS) is nowadays extremely efficient. These NEMS will be used as sensors and actuators in integrated systems. Their use, however, raises questions about their interface (actuation, detection, read out) with external detection and control systems. Their operation implies many fundamental questions related to single particle effects such as Coulomb blockade, light matter interactions such as radiation pressure, thermal effects, Casimir forces and the coupling of nanosystems to the external world (thermal fluctuations, back action effect). Here we specifically present how the damping of an oscillating cantilever can be tuned in two radically different ways: (i) through an electromechanical coupling in the presence of a strong Johnson noise, (ii) through an external feedback control of thermal fluctuations which is the cold damping closely related to Maxwell's demon. This shows how the interplay between external control of micro-EMS (MEMS) or NEMS and their coupling to a thermal bath can lead to a wealth of effects that are nowadays extensively studied in different areas.
Blaschek, M.; Renssen, H.
2012-01-01
The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene Thermal Maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveal a
Amiri Delouei, A.; Nazari, M.; Kayhani, M. H.; Succi, S.
2014-05-01
In this study, the immersed boundary-thermal lattice Boltzmann method has been used to simulate non-Newtonian fluid flow over a heated circular cylinder. The direct-forcing algorithm has been employed to couple the off-lattice obstacles and on-lattice fluid nodes. To investigate the effect of boundary sharpness, two different diffuse interface schemes are considered to interpolate the velocity and temperature between the boundary and computational grid points. The lattice Boltzmann equation with split-forcing term is applied to consider the effects of the discrete lattice and the body force to the momentum flux, simultaneously. A method for calculating the Nusselt number based on diffuse interface schemes is developed. The rheological and thermal properties of non-Newtonian fluids are investigated under the different power-law indices and Reynolds numbers. The effect of numerical parameters on the accuracy of the proposed method has been investigated in detail. Results show that the rheological and thermal properties of non-Newtonian fluids in the presence of a heated immersed body can be suitably captured using the immersed boundary thermal lattice Boltzmann method.
Towards measuring the Archimedes force of vacuum
Calloni, Enrico; De Rosa, Rosario; Di Fiore, Luciano; Esposito, Giampiero; Garufi, Fabio; Rosa, Luigi; Rovelli, Carlo; Ruggi, Paolo; Tafuri, Francesco
2014-01-01
We discuss the force exerted by the gravitational field on a Casimir cavity in terms of Archimedes' force of vacuum, we identify the force that can be tested against observation and we show that the present technology makes it possible to perform the first experimental tests. We motivate the use of suitable high-Tc superconductors as modulators of Archimedes' force. We analyze the possibility of using gravitational wave interferometers as detectors of the force, transported through an optical spring from the Archimedes vacuum force apparatus to the gravitational interferometers test masses to maintain the two systems well separated. We also analyze the use of balances to actuate and detect the force, we compare different solutions and discuss the most important experimental issues.
Chernykh, Elena; Kharintsev, Sergey; Fishman, Alexandr; Alekseev, Alexander; Salakhov, Myakzuym
2017-03-01
In this paper we introduce and apply the method for determination of the glass transition temperature of the sub-100 nm thick freestanding and supported polymer films based on thermally assisted atomic force microscopy (AFM). In proposed approach changes of the phase of an oscillating AFM cantilever are used to determine glass transition temperature. An anomalous decrease of the glass transition temperature for both free-standing and supported azobenzene-functionalized polymer thin films is shown.
Phillips, Nicholas G.; Hu, B. L.
2000-10-01
We present calculations of the variance of fluctuations and of the mean of the energy momentum tensor of a massless scalar field for the Minkowski and Casimir vacua as a function of an intrinsic scale defined by a smeared field or by point separation. We point out that, contrary to prior claims, the ratio of variance to mean-squared being of the order unity is not necessarily a good criterion for measuring the invalidity of semiclassical gravity. For the Casimir topology we obtain expressions for the variance to mean-squared ratio as a function of the intrinsic scale (defined by a smeared field) compared to the extrinsic scale (defined by the separation of the plates, or the periodicity of space). Our results make it possible to identify the spatial extent where negative energy density prevails which could be useful for studying quantum field effects in worm holes and baby universes, and for examining the design feasibility of real-life ``time machines.'' For the Minkowski vacuum we find that the ratio of the variance to the mean-squared, calculated from the coincidence limit, is identical to the value of the Casimir case at the same limit for spatial point separation while identical to the value of a hot flat space result with a temporal point separation. We analyze the origin of divergences in the fluctuations of the energy density and discuss choices in formulating a procedure for their removal, thus raising new questions about the uniqueness and even the very meaning of regularization of the energy momentum tensor for quantum fields in curved or even flat spacetimes when spacetime is viewed as having an extended structure.
Bednarz, Tomasz Piotr; Lei, Chengwang; Patterson, John C.
2009-07-01
The present experimental investigation is concerned with the transient flow response in a reservoir model to periodic heating and cooling at the water surface. The experiment reveals a stable stratification of the water body during the heating phase and an unsteady mixing flow in the reservoir during the cooling phase. It is shown that thermal instabilities play an important role in breaking up the residual circulation and initiating a reverse flow circulation in deep waters after the switch of thermal forcing from heating to cooling. Moreover, the heating from the water surface results in a stable large-scale convective roll that is clearly observed in the experiment. The present flow visualization is carried out with the application of thermo-chromic liquid crystals. Quantitative temperature and velocity fields are extracted using Particle Image Thermometry and Particle Image Velocimetry techniques. Understanding of the flow mechanisms pertinent to this problem is important for predicting the transport of nutrients and pollutants across reservoirs.
Buhmann, Stefan Yoshi
2012-01-01
In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...
Casimir effect at finite temperature for pure-photon sector of the minimal Standard Model Extension
Energy Technology Data Exchange (ETDEWEB)
Santos, A.F., E-mail: alesandroferreira@fisica.ufmt.br [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900, Cuiabá, Mato Grosso (Brazil); Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road Victoria, BC (Canada); Khanna, Faqir C., E-mail: khannaf@uvic.ca [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road Victoria, BC (Canada)
2016-12-15
Dynamics between particles is governed by Lorentz and CPT symmetry. There is a violation of Parity (P) and CP symmetry at low levels. The unified theory, that includes particle physics and quantum gravity, may be expected to be covariant with Lorentz and CPT symmetry. At high enough energies, will the unified theory display violation of any symmetry? The Standard Model Extension (SME), with Lorentz and CPT violating terms, has been suggested to include particle dynamics. The minimal SME in the pure photon sector is considered in order to calculate the Casimir effect at finite temperature.
Zeta Function Regularization in Casimir Effect Calculations and J. S. Dowker's Contribution
Elizalde, Emilio
2012-07-01
A summary of relevant contributions, ordered in time, to the subject of operator zeta functions and their application to physical issues is provided. The description ends with the seminal contributions of Stephen Hawking and Stuart Dowker and collaborators, considered by many authors as the actual starting point of the introduction of zeta function regularization methods in theoretical physics, in particular, for quantum vacuum fluctuation and Casimir effect calculations. After recalling a number of the strengths of this powerful and elegant method, some of its limitations are discussed. Finally, recent results of the so called operator regularization procedure are presented.
Casimir effect at finite temperature for pure-photon sector of the minimal Standard Model Extension
Santos, A. F.; Khanna, Faqir C.
2016-12-01
Dynamics between particles is governed by Lorentz and CPT symmetry. There is a violation of Parity (P) and CP symmetry at low levels. The unified theory, that includes particle physics and quantum gravity, may be expected to be covariant with Lorentz and CPT symmetry. At high enough energies, will the unified theory display violation of any symmetry? The Standard Model Extension (SME), with Lorentz and CPT violating terms, has been suggested to include particle dynamics. The minimal SME in the pure photon sector is considered in order to calculate the Casimir effect at finite temperature.
Tasawar Hayat; Awatif A. Hendi; Jacob A. Gbadeyan; Philip O. Olanrewaju
2011-01-01
In this paper we analyse the effects of internal heat generation, thermal radiation and buoyancy force on the laminar boundary layer about a vertical plate in a uniform stream of fluid under a convective surface boundary condition. In the analysis, we assumed that the left surface of the plate is in contact with a hot fluid whilst a stream of cold fluid flows steadily over the right surface; the heat source decays exponentially outwards from the surface of the plate. The similarity variable m...
Nome, Rene A.; Sorbello, Cecilia; Jobbágy, Matías; Barja, Beatriz C.; Sanches, Vitor; Cruz, Joyce S.; Aguiar, Vinicius F.
2017-03-01
The stochastic dynamics of individual co-doped Er:Yb upconversion nanoparticles (UCNP) were investigated from experiments and simulations. The UCNP were characterized by high-resolution scanning electron microscopy, dynamic light scattering, and zeta potential measurements. Single UCNP measurements were performed by fluorescence upconversion micro-spectroscopy and optical trapping. The mean-square displacement (MSD) from single UCNP exhibited a time-dependent diffusion coefficient which was compared with Brownian dynamics simulations of a viscoelastic model of harmonically bound spheres. Experimental time-dependent two-dimensional trajectories of individual UCNP revealed correlated two-dimensional nanoparticle motion. The measurements were compared with stochastic trajectories calculated in the presence of a non-conservative rotational force field. Overall, the complex interplay of UCNP adhesion, thermal fluctuations and optical forces led to a rich stochastic behavior of these nanoparticles.
Trinh, T.T.; Vlugt, T.J.H.; Kjelstrup, S.H.
2014-01-01
We report a systematic investigation of the thermal conductivity of various three-site models of carbon dioxide (CO2) using nonequilibrium molecular dynamics in the temperature range 300–1000 K and for pressures up to 200 MPa. A direct comparison with experimental data is made. Three popular CO2
Translationally symmetric extended MHD via Hamiltonian reduction: Energy-Casimir equilibria
Kaltsas, D. A.; Throumoulopoulos, G. N.; Morrison, P. J.
2017-09-01
The Hamiltonian structure of ideal translationally symmetric extended MHD (XMHD) is obtained by employing a method of Hamiltonian reduction on the three-dimensional noncanonical Poisson bracket of XMHD. The existence of the continuous spatial translation symmetry allows the introduction of Clebsch-like forms for the magnetic and velocity fields. Upon employing the chain rule for functional derivatives, the 3D Poisson bracket is reduced to its symmetric counterpart. The sets of symmetric Hall, Inertial, and extended MHD Casimir invariants are identified, and used to obtain energy-Casimir variational principles for generalized XMHD equilibrium equations with arbitrary macroscopic flows. The obtained set of generalized equations is cast into Grad-Shafranov-Bernoulli (GSB) type, and special cases are investigated: static plasmas, equilibria with longitudinal flows only, and Hall MHD equilibria, where the electron inertia is neglected. The barotropic Hall MHD equilibrium equations are derived as a limiting case of the XMHD GSB system, and a numerically computed equilibrium configuration is presented that shows the separation of ion-flow from electro-magnetic surfaces.
Vanapalli, Srinivas; ter Brake, Hermanus J.M.
2013-01-01
Nanofluids are considered for improving the heat exchange in forced convective flow. In literature, the benefit of nanofluids compared to the corresponding base fluid is represented by several figures-of-merit in which the heat transfer benefit and the cost of pumping the fluid are considered. These
Digital Repository Service at National Institute of Oceanography (India)
Gopalakrishna, V.V.; Murty, V.S.N.; Sarma, M.S.S.; Sastry, J.S.
Upper ocean response to forcing of a severe cyclonic storm during May 1990 in the western Bay of Bengal was studied using the XBT data sets collected (4 d after passage of storm) under Indian TOGA programme. A maximum lowering in the sea surface...
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Yubai Li
2017-07-01
Full Text Available In this paper, we study the effects of the Lorentz force and the induced anisotropic thermal conductivity due to a magnetic field on the flow and the heat transfer of a ferro-nanofluid. The ferro-nanofluid is modeled as a single-phase fluid, where the viscosity depends on the concentration of nanoparticles; the thermal conductivity shows anisotropy due to the presence of the nanoparticles and the external magnetic field. The anisotropic thermal conductivity tensor, which depends on the angle of the applied magnetic field, is suggested considering the principle of material frame indifference according to Continuum Mechanics. We study two benchmark problems: the heat conduction between two concentric cylinders as well as the unsteady flow and heat transfer in a rectangular channel with three heated inner cylinders. The governing equations are made dimensionless, and the flow and the heat transfer characteristics of the ferro-nanofluid with different angles of the magnetic field, Hartmann number, Reynolds number and nanoparticles concentration are investigated systematically. The results indicate that the temperature field is strongly influenced by the anisotropic behavior of the nanofluids. In addition, the magnetic field may enhance or deteriorate the heat transfer performance (i.e., the time-spatially averaged Nusselt number in the rectangular channel depending on the situations.
Giant vacuum forces via transmission lines.
Shahmoon, Ephraim; Mazets, Igor; Kurizki, Gershon
2014-07-22
Quantum electromagnetic fluctuations induce forces between neutral particles, known as the van der Waals and Casimir interactions. These fundamental forces, mediated by virtual photons from the vacuum, play an important role in basic physics and chemistry and in emerging technologies involving, e.g., microelectromechanical systems or quantum information processing. Here we show that these interactions can be enhanced by many orders of magnitude upon changing the character of the mediating vacuum modes. By considering two polarizable particles in the vicinity of any standard electric transmission line, along which photons can propagate in one dimension, we find a much stronger and longer-range interaction than in free space. This enhancement may have profound implications on many-particle and bulk systems and impact the quantum technologies mentioned above. The predicted giant vacuum force is estimated to be measurable in a coplanar waveguide line.
1981-01-01
anticyclonic circulations. During the summer seasons other secondary source regions of energy occur over Brazil, the Carribean and Africa. This...AD-AIL9 755 AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH F/6 4/2 DIAGNOSTICS OF THE HEAT SOURCES AND SINKS OF THE ASIATIC MONSOO-ETC(U) 1981 D R...RECIPIENT’S CATALOG NUMBER 81-35T / /- Al I.. 4. TITLE ( nd Subtitle) Diagnostics of the Heat Sources and S. TYPE OF REPORT & PERIOD COVERED Sinks of
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Tasawar Hayat
2011-09-01
Full Text Available In this paper we analyse the effects of internal heat generation, thermal radiation and buoyancy force on the laminar boundary layer about a vertical plate in a uniform stream of fluid under a convective surface boundary condition. In the analysis, we assumed that the left surface of the plate is in contact with a hot fluid whilst a stream of cold fluid flows steadily over the right surface; the heat source decays exponentially outwards from the surface of the plate. The similarity variable method was applied to the steady state governing non-linear partial differential equations, which were transformed into a set of coupled non-linear ordinary differential equations and were solved numerically by applying a shooting iteration technique together with a sixth-order Runge–Kutta integration scheme for better accuracy. The effects of the Prandtl number, the local Biot number, the internal heat generation parameter, thermal radiation and the local Grashof number on the velocity and temperature profiles are illustrated and interpreted in physical terms. A comparison with previously published results on similar special cases showed excellent agreement.
Sensitivity on materials optical properties of single beam torsional Casimir actuation
Tajik, Fatemeh; Sedighi, Mehdi; Palasantzas, George
2017-05-01
Here, we investigate the dynamical sensitivity of electrostatic torsional type microelectromechanical systems (MEMS) on the optical properties of interacting materials. This is accomplished by considering the combined effect of mechanical Casimir and electrostatic torques to drive the device actuation. The bifurcation curves and the phase portraits of the actuation dynamics have been analyzed to compare the sensitivity of a single beam torsional device operating between materials with conductivities that differ by several orders of magnitude. It is shown that the range of stable operation of torsional MEMS against stiction instabilities can increase by decreasing the conductivity of interacting materials. Moreover, the introduction of controlled dissipation, corresponding to a finite quality factor, in an otherwise unstable torsional system, could alter an unstable motion towards stiction to dissipative stable motion.
Casimir self-entropy of a spherical electromagnetic δ -function shell
Milton, Kimball A.; Kalauni, Pushpa; Parashar, Prachi; Li, Yang
2017-10-01
In this paper we continue our program of computing Casimir self-entropies of idealized electrical bodies. Here we consider an electromagnetic δ -function sphere ("semitransparent sphere") whose electric susceptibility has a transverse polarization with arbitrary strength. Dispersion is incorporated by a plasma-like model. In the strong-coupling limit, a perfectly conducting spherical shell is realized. We compute the entropy for both low and high temperatures. The transverse electric self-entropy is negative as expected, but the transverse magnetic self-entropy requires ultraviolet and infrared renormalization (subtraction), and, surprisingly, is only positive for sufficiently strong coupling. Results are robust under different regularization schemes. These rather surprising findings require further investigation.
Lotfipour, H.; Allameh, Z.; Roknizadeh, R.; Heydari, H.
2016-03-01
Using two different schemes, a non-classical-squeezed state of light is detected and characterized. In the first scheme, in a one-dimensional cavity with a moving mirror (non-stationary Casimir effect) in the principal mode, we study the photon generation rate for two modes (squeezed and coherent state) of a driving field. Since the cavity with the moving mirror (similar to an optomechanical system) can be considered an analogue to a Kerr-like medium, in the second scheme, the probability amplitude for multi-photon absorption in a nonlinear (Kerr) medium will be quantum mechanically calculated. It is shown that because of the presence of nonlinear effects, the responses of these two systems to the squeezed versus coherent state are considerably distinguishable. The drastic difference between the results of these two states of light can be viewed as a proposal for detecting non-classical states.
Brevik, Iver
2012-09-01
The main part of this paper is to present an updated review of the Casimir energy at zero and finite temperature for the transverse oscillations of a piecewise uniform closed string. We make use of three different regularizations: the cutoff method, the complex contour integration method and the zeta-function method. The string model is relativistic, in the sense that the velocity of sound is for each string piece set equal to the velocity of light. In this sense the theory is analogous to the electromagnetic theory in a dielectric medium in which the product of permittivity and permeability is equal to unity (an isorefractive medium). We demonstrate how the formalism works for a two-piece string, and for a 2N-piece string, and show how in the latter case a compact recursion relation serves to facilitate the formalism considerably. The Casimir energy turns out to be negative, and the more so the larger the number of pieces in the string. The two-piece string is quantized in D-dimensional spacetime, in the limit when the ratio between the two tensions is very small. We calculate the free energy and other thermodynamic quantities, demonstrate scaling properties, and comment finally on the meaning of the Hagedorn critical temperature for the two-piece string. Thereafter, as a novel development we present a scalar field theory for a real field in three-dimensional space in a potential rising linearly with a longitudinal coordinate z in the interval 0 article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker's 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’.
Fisher-Hubbard, Amanda O; Sung, LokMan; Hubbard, Sean A; Hlavaty, Leigh
2017-05-01
Heat-related deaths of children are most often encountered in the context of enclosed vehicles in summer months. Deviating from this, a 16-month-old boy was found unresponsive in a stroller that was placed adjacent to a space heater during mid-winter. The cause of death was hyperthermia and thermal injuries. Manner of death determination was difficult due to alleged surrounding circumstances. To understand the time-course of this child's injuries, a child death scene investigation was performed; the stroller and space heater were recovered. In a re-enactment of the events, a slaughtered pig approximating the child's size was warmed using a water bath and placed in the stroller beside the space heater. Cutaneous temperature measurements showed rapid initial temperature rise with subsequent steady increases. Tanning of the skin was seen on periodic direct observations. Internal temperature monitoring illustrated steady increases. This experiment was essential in classifying the manner of death as homicide. © 2016 American Academy of Forensic Sciences.
Are coarse-grained models apt to detect protein thermal stability? The case of OPEP force field.
Kalimeri, Maria; Derreumaux, Philippe; Sterpone, Fabio
2015-01-01
We present the first investigation of the kinetic and thermodynamic stability of two homologous thermophilic and mesophilic proteins based on the coarse-grained model OPEP. The object of our investigation is a pair of G-domains of relatively large size, 200 amino acids each, with an experimental stability gap of about 40 K. The OPEP force field is able to maintain stable the fold of these relatively large proteins within the hundrend-nanosecond time scale without including external constraints. This makes possible to characterize the conformational landscape of the folded protein as well as to explore the unfolding. In agreement with all-atom simulations used as a reference, we show that the conformational landscape of the thermophilic protein is characterized by a larger number of substates with slower dynamics on the network of states and more resilient to temperature increase. Moreover, we verify the stability gap between the two proteins using replica-exchange simulations and estimate a difference between the melting temperatures of about 23 K, in fair agreement with experiment. The detailed investigation of the unfolding thermodynamics, allows to gain insight into the mechanism underlying the enhanced stability of the thermophile relating it to a smaller heat capacity of unfolding.
Pull-in instability of paddle-type and double-sided NEMS sensors under the accelerating force
Keivani, M.; Khorsandi, J.; Mokhtari, J.; Kanani, A.; Abadian, N.; Abadyan, M.
2016-02-01
Paddle-type and double-sided nanostructures are potential for use as accelerometers in flying vehicles and aerospace applications. Herein the pull-in instability of the cantilever paddle-type and double-sided sensors in the Casimir regime are investigated under the acceleration. The D'Alembert principle is employed to transform the accelerating system into an equivalent static system by incorporating the accelerating force. Based on the couple stress theory (CST), the size-dependent constitutive equations of the sensors are derived. The governing nonlinear equations are solved by two approaches, i.e. modified variational iteration method and finite difference method. The influences of the Casimir force, geometrical parameters, acceleration and the size phenomenon on the instability performance have been demonstrated. The obtained results are beneficial to design and fabricate paddle-type and double-sided accelerometers.
Nonadditivity of van der Waals forces on liquid surfaces.
Venkataram, Prashanth S; Whitton, Jeremy D; Rodriguez, Alejandro W
2016-09-01
We present an approach for modeling nanoscale wetting and dewetting of textured solid surfaces that exploits recently developed, sophisticated techniques for computing exact long-range dispersive van der Waals (vdW) or (more generally) Casimir forces in arbitrary geometries. We apply these techniques to solve the variational formulation of the Young-Laplace equation and predict the equilibrium shapes of liquid-vacuum interfaces near solid gratings. We show that commonly employed methods of computing vdW interactions based on additive Hamaker or Derjaguin approximations, which neglect important electromagnetic boundary effects, can result in large discrepancies in the shapes and behaviors of liquid surfaces compared to exact methods.
Imbe, H; Kimura, A; Donishi, T; Kaneoke, Y
2014-02-14
Stress affects brain activity and promotes long-term changes in multiple neural systems. Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces lasting hyperalgesia. The insular (IC) and anterior cingulate cortices (ACC) are the regions exhibiting most reliable pain-related activity. And the IC and ACC play an important role in pain modulation via the descending pain modulatory system. In the present study we examined the expression of phospho-cAMP response element-binding protein (pCREB) and c-Fos in the IC and ACC after forced swim stress (FS) and complete Freund's adjuvant (CFA) injection to clarify changes in the cerebral cortices that affect the activity of the descending pain modulatory system in the rats with stress-induced hyperalgesia. FS (day 1, 10min; days 2-3, 20min) induced an increase in the expression of pCREB and c-Fos in the anterior IC (AIC). CFA injection into the hindpaw after the FS shows significantly enhanced thermal hyperalgesia and induced a decrease in the expression of c-Fos in the AIC and the posterior IC (PIC). Quantitative image analysis showed that the numbers of c-Fos-immunoreactive neurons in the left AIC and PIC were significantly lower in the FS+CFA group (L AIC, 95.9±6.8; L PIC, 181.9±23.1) than those in the naive group (L AIC, 151.1±19.3, pCFA-induced thermal hyperalgesia through dysfunction of the descending pain modulatory system. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Niekerken, Ole
2009-06-15
In this diploma thesis the Casimir-Polder force at zero temperature and at finite temperatures is calculated by using a well-defined quantum field theory (formulated in position space) and the method of image charges. For the calculations at finite temperature KMS-states are used. The so defined temperature describes the temperature of the electromagnetic background. A one oscillator model for inhomogeneous dispersive absorbing dielectric material is introduced and canonically quantized to calculate the Casimir-Polder force at a dielectric interface at finite temperature. The model fulfils causal commutation relations and the dielectric function of the model fulfils the Kramer-Kronig relations. We then use the same methods to calculate the van der Waals force between two neutral atoms at zero temperature and at finite temperatures. It is shown that the high temperature behaviour of the Casimir-Polder force and the van der Waals force are independent of {Dirac_h}. This means that they have to be understood classically, what is then shown in an algebraic statistical theory by using classical KMS states. (orig.)
Directory of Open Access Journals (Sweden)
M. Blaschek
2013-07-01
Full Text Available The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM, is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS, as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.
Macoveciuc, Ioana; Márquez-Grant, Nicholas; Horsfall, Ian; Zioupos, Peter
2017-06-01
Burning of human remains is one method used by perpetrators to conceal fatal trauma and expert opinions regarding the degree of skeletal evidence concealment are often disparate. This experiment aimed to reduce this incongruence in forensic anthropological interpretation of burned human remains and implicitly contribute to the development of research methodologies sufficiently robust to withstand forensic scrutiny in the courtroom. We have tested the influence of thermal alteration on pre-existing sharp and blunt trauma on twenty juvenile sheep radii in the laboratory using an automated impact testing system and an electric furnace. The testing conditions simulated a worst-case scenario where remains with pre-existing sharp or blunt trauma were exposed to burning with an intentional vehicular fire scenario in mind. All impact parameters as well as the burning conditions were based on those most commonly encountered in forensic cases and maintained constant throughout the experiment. The results have shown that signatures associated with sharp and blunt force trauma were not masked by heat exposure and highlights the potential for future standardization of fracture analysis in burned bone. Our results further emphasize the recommendation given by other experts on handling, processing and recording burned remains at the crime scene and mortuary. Copyright © 2017 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Fosco, César D. [Centro Atómico Bariloche, Instituto Balseiro, Comisión Nacional de Energía Atómica, R8402AGP, Bariloche (Argentina); Lombardo, Fernando C., E-mail: lombardo@df.uba.ar [Departamento de Física Juan José Giambiagi, FCEyN UBA and IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellón I, 1428, Buenos Aires (Argentina)
2015-12-17
We study the properties of the classical electromagnetic radiation produced by two physically different yet closely related systems, which may be regarded as classical analogues of the dynamical Casimir effect. They correspond to two flat, infinite, parallel planes, one of them static and imposing perfect-conductor boundary conditions, while the other performs a rigid oscillatory motion. The systems differ just in the electrical properties of the oscillating plane: one of them is just a planar dipole layer (representing, for instance, a small-width electret). The other, instead, has a dipole layer on the side which faces the static plane, but behaves as a conductor on the other side: this can be used as a representation of a conductor endowed with patch potentials (on the side which faces the conducting plane). We evaluate, in both cases, the dissipative flux of energy between the system and its environment, showing that, at least for small mechanical oscillation amplitudes, it can be written in terms of the dipole layer autocorrelation function. We show that there are resonances as a function of the frequency of the mechanical oscillation.
Energy Technology Data Exchange (ETDEWEB)
Fosco, Cesar D. [Comision Nacional de Energia Atomica, Centro Atomico Bariloche, Instituto Balseiro, Bariloche (Argentina); Lombardo, Fernando C. [Ciudad Universitaria, Departamento de Fisica Juan Jose Giambiagi, FCEyN UBA y IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2015-12-15
We study the properties of the classical electromagnetic radiation produced by two physically different yet closely related systems, which may be regarded as classical analogues of the dynamical Casimir effect. They correspond to two flat, infinite, parallel planes, one of them static and imposing perfect-conductor boundary conditions, while the other performs a rigid oscillatory motion. The systems differ just in the electrical properties of the oscillating plane: one of them is just a planar dipole layer (representing, for instance, a small-width electret). The other, instead, has a dipole layer on the side which faces the static plane, but behaves as a conductor on the other side: this can be used as a representation of a conductor endowed with patch potentials (on the side which faces the conducting plane). We evaluate, in both cases, the dissipative flux of energy between the system and its environment, showing that, at least for small mechanical oscillation amplitudes, it can be written in terms of the dipole layer autocorrelation function. We show that there are resonances as a function of the frequency of the mechanical oscillation. (orig.)
De vette jaren: de Commissie-Casimir en het Nederlandse wetenschapsbeleid 1957-1970
Directory of Open Access Journals (Sweden)
David Baneke
2012-11-01
Full Text Available The Years of Abundance: the Casimir Committee and Dutch Science Policy 1957–1970 In October 1958, a committee of six prominent Dutch scientists and industrial managers presented a brief report in which they requested a major increase of the science budget. This report has been described as a turning point in the history of science in the Netherlands, signaling the beginning of a decade of rapid growth of funding for ‘pure’ research. Surprisingly little is known about the backgrounds of this report, however. In this paper, I analyze its origin, its relation to contemporary higher education policy, and its consequences. As it turns out, the report was less revolutionary than is usually assumed: it mostly reinforced developments that had already begun earlier. Furthermore, Sputnik and the Cold War were not as important as is often claimed. This paper also suggests a reinterpretation of the justification of the government spending on academic research after the Second World War. Producing skilled researchers for industry was at least as important as produc- ing new knowledge.
Casimir meets Poisson: improved quark/gluon discrimination with counting observables
Frye, Christopher; Larkoski, Andrew J.; Thaler, Jesse; Zhou, Kevin
2017-09-01
Charged track multiplicity is among the most powerful observables for discriminating quark- from gluon-initiated jets. Despite its utility, it is not infrared and collinear (IRC) safe, so perturbative calculations are limited to studying the energy evolution of multiplicity moments. While IRC-safe observables, like jet mass, are perturbatively calculable, their distributions often exhibit Casimir scaling, such that their quark/gluon discrimination power is limited by the ratio of quark to gluon color factors. In this paper, we introduce new IRC-safe counting observables whose discrimination performance exceeds that of jet mass and approaches that of track multiplicity. The key observation is that track multiplicity is approximately Poisson distributed, with more suppressed tails than the Sudakov peak structure from jet mass. By using an iterated version of the soft drop jet grooming algorithm, we can define a "soft drop multiplicity" which is Poisson distributed at leading-logarithmic accuracy. In addition, we calculate the next-to-leading-logarithmic corrections to this Poisson structure. If we allow the soft drop groomer to proceed to the end of the jet branching history, we can define a collinear-unsafe (but still infrared-safe) counting observable. Exploiting the universality of the collinear limit, we define generalized fragmentation functions to study the perturbative energy evolution of collinear-unsafe multiplicity.
Energy Technology Data Exchange (ETDEWEB)
Wang, Sheng-Feng; Kao, Tzu-Hao [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 106, Taiwan, ROC (China); Cheng, Chih-Chia [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan, ROC (China); Chang, Chi-Jung [Department of Chemical Engineering, Feng Chia University, 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan, ROC (China); Chen, Jem-Kun, E-mail: jkchen@mail.ntust.edu.tw [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 106, Taiwan, ROC (China)
2015-12-01
Graphical abstract: We developed a simple approach, mixing TiO{sub 2} nanoparticles and 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (BA), to obtain a UV-responsive surfaces after thermal treatment. Because the wettability between TiO{sub 2} nanoparticles and BA, a nanoassembled structure was generated on the surface during the coating process. Results indicate that the mixing 30 wt% TiO{sub 2} nanoparticles into PBA matrix generated the superhydrophobic surface (static water contact angle > 150°) with ca. 1° of sliding angle. The superhydrophobic TiO{sub 2}/PBA nanoassembled surface can be converted by photocatalytic oxidation into a highly hydrophilic one (static water contact angle ∼ 0°) within five minimums. Interestingly, the hydrophilic surface can be converted back into a superhydrophobic surface by heat treatment. A water droplet can be transported among the surfaces that UV-irradiated for various times. Velocity of the droplet on the 15°-titled surface could be also manipulated with UV irradiation for various times. The correlations between PBA and TiO{sub 2} nanoparticles would provide insight into the designing and developing of light-responsive surfaces. - Highlights: • Nanoassembly of PBA and TiO{sub 2} NPs are generated with superhydrophobicity. • The superhydrophobicity can be converted to hydrophilic surface within 5 min. • The hydrophilic surface can be converted back into a superhydrophobic surface. • Adhesive force of the nanoassemblies can be manipulated by UV illumination time. - Abstract: In this study we mixed TiO{sub 2} nanoparticles (NPs) with 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (BA), as a precursor to a polybenzoxazine (PBA), to generate nanocomposite surfaces possessing low surface free energies. Because of extreme phase separation between the TiO{sub 2} NPs and BA, their mixtures featured nanoassembled structures on their surfaces. After thermal curing, we obtained PBA/TiO{sub 2} nanoassembled (PTN) surfaces possessing
Uses of zeta regularization in QFT with boundary conditions: a cosmo-topological Casimir effect
Energy Technology Data Exchange (ETDEWEB)
Elizalde, Emilio [Instituto de Ciencias del Espacio (CSIC) and Institut d' Estudis Espacials de Catalunya (IEEC/CSIC) Campus UAB, Facultat de Ciencies, Torre C5-Parell-2a planta E-08193 Bellaterra, Barcelona (Spain)
2006-05-26
Zeta regularization has proven to be a powerful and reliable tool for the regularization of the vacuum energy density in ideal situations. With the Hadamard complement, it has been shown to provide finite (and meaningful) answers too in more involved cases, as when imposing physical boundary conditions (BCs) in two- and higher-dimensional surfaces (being able to mimic, in a very convenient way, other ad hoc cut-offs, as non-zero depths). Recently, these techniques have been used in calculations of the contribution of the vacuum energy of the quantum fields pervading the universe to the cosmological constant (cc). Naive counting of the absolute contributions of the known fields lead to a value which is off by as much as 120 orders of magnitude, as compared with observational tests, what is known as the cosmological constant problem. This is very difficult to solve and we do not address that question directly. What we have considered-with relative success in several approaches of different nature-is the additional contribution to the cc coming from the non-trivial topology of space or from specific boundary conditions imposed on braneworld models (kind of cosmological Casimir effects). Assuming someone will be able to prove (some day) that the ground value of the cc is zero, as many had suspected until very recently, we will then be left with this incremental value coming from the topology or BCs. We show that this value can have the correct order of magnitude-corresponding to the one coming from the observed acceleration in the expansion of our universe-in a number of quite reasonable models involving small and large compactified scales and/or brane BCs, and supergravitons.
Directory of Open Access Journals (Sweden)
Michael A. Persinger
2015-09-01
Full Text Available The ~1.5 × 10−20 J which is considered a universal quantity and is associated with the movement of protons in water also relates to the ratio of the magnetic moment of a proton divided by its unit charge, multiplied by viscosity and applied over the O-H distance. There is quantitative evidence that thixotropy, the “spontaneous” increased viscosity in water when undisturbed, originates from the transformation of virtual particles or vacuum oscillations to real states through conversion of Casimir-magnetic energies that involve the frequency of the neutral hydrogen line and the upper bound threshold value for intergalactic magnetic fields. The results indicate that ½ of a single electron orbit is real (particle and the other ½ is virtual (wave. The matter equivalent per s for virtual-to-real states for electrons in 1 mL of water with a neutral pH is consistent with the numbers of protons (H+ and the measured range of molecules in the coherent domains for both width and duration of growth and is similar to widths of intergalactic dust grains from which planets and stars may condense. The de Broglie momentum for the lower boundary of the width of coherent domains multiplied by the fine structure velocity of an electron is concurrent with the quantum when one proton is being removed from another and when the upper boundary of the rest mass of a photon is transformed by the product of velocities for putative “entanglement” and light. Theoretical and experimental results indicate that components of thixotropy, such as specific domains of intercalated water molecules, could display excess correlations over very large distances. Because the energies of the universal quantity and water converge it may be a special conduit for discrete transformations from virtual to real states.
The Casimir Effect from the Point of View of Algebraic Quantum Field Theory
Energy Technology Data Exchange (ETDEWEB)
Dappiaggi, Claudio, E-mail: claudio.dappiaggi@unipv.it; Nosari, Gabriele [Università degli Studi di Pavia, Dipartimento di Fisica (Italy); Pinamonti, Nicola [Università di Genova, Dipartimento di Matematica (Italy)
2016-06-15
We consider a region of Minkowski spacetime bounded either by one or by two parallel, infinitely extended plates orthogonal to a spatial direction and a real Klein-Gordon field satisfying Dirichlet boundary conditions. We quantize these two systems within the algebraic approach to quantum field theory using the so-called functional formalism. As a first step we construct a suitable unital ∗-algebra of observables whose generating functionals are characterized by a labelling space which is at the same time optimal and separating and fulfils the F-locality property. Subsequently we give a definition for these systems of Hadamard states and we investigate explicit examples. In the case of a single plate, it turns out that one can build algebraic states via a pull-back of those on the whole Minkowski spacetime, moreover inheriting from them the Hadamard property. When we consider instead two plates, algebraic states can be put in correspondence with those on flat spacetime via the so-called method of images, which we translate to the algebraic setting. For a massless scalar field we show that this procedure works perfectly for a large class of quasi-free states including the Poincaré vacuum and KMS states. Eventually Wick polynomials are introduced. Contrary to the Minkowski case, the extended algebras, built in globally hyperbolic subregions can be collected in a global counterpart only after a suitable deformation which is expressed locally in terms of a *-isomorphism. As a last step, we construct explicitly the two-point function and the regularized energy density, showing, moreover, that the outcome is consistent with the standard results of the Casimir effect.
Energy Technology Data Exchange (ETDEWEB)
Sridharan, Kumar; Anderson, Mark; Allen, Todd; Corradini, Michael
2012-01-30
The goal of this NERI project was to perform research on high temperature fluoride and chloride molten salts towards the long-term goal of using these salts for transferring process heat from high temperature nuclear reactor to operation of hydrogen production and chemical plants. Specifically, the research focuses on corrosion of materials in molten salts, which continues to be one of the most significant challenges in molten salts systems. Based on the earlier work performed at ORNL on salt properties for heat transfer applications, a eutectic fluoride salt FLiNaK (46.5% LiF-11.5%NaF-42.0%KF, mol.%) and a eutectic chloride salt (32%MgCl2-68%KCl, mole %) were selected for this study. Several high temperature candidate Fe-Ni-Cr and Ni-Cr alloys: Hastelloy-N, Hastelloy-X, Haynes-230, Inconel-617, and Incoloy-800H, were exposed to molten FLiNaK with the goal of understanding corrosion mechanisms and ranking these alloys for their suitability for molten fluoride salt heat exchanger and thermal storage applications. The tests were performed at 850C for 500 h in sealed graphite crucibles under an argon cover gas. Corrosion was noted to occur predominantly from dealloying of Cr from the alloys, an effect that was particularly pronounced at the grain boundaries Alloy weight-loss due to molten fluoride salt exposure correlated with the initial Cr-content of the alloys, and was consistent with the Cr-content measured in the salts after corrosion tests. The alloys weight-loss was also found to correlate to the concentration of carbon present for the nominally 20% Cr containing alloys, due to the formation of chromium carbide phases at the grain boundaries. Experiments involving molten salt exposures of Incoloy-800H in Incoloy-800H crucibles under an argon cover gas showed a significantly lower corrosion for this alloy than when tested in a graphite crucible. Graphite significantly accelerated alloy corrosion due to the reduction of Cr from solution by graphite and formation
Recent advances in the surface forces apparatus (SFA) technique
Israelachvili, J.; Min, Y.; Akbulut, M.; Alig, A.; Carver, G.; Greene, W.; Kristiansen, K.; Meyer, E.; Pesika, N.; Rosenberg, K.; Zeng, H.
2010-03-01
The surface forces apparatus (SFA) has been used for many years to measure the physical forces between surfaces, such as van der Waals (including Casimir) and electrostatic forces in vapors and liquids, adhesion and capillary forces, forces due to surface and liquid structure (e.g. solvation and hydration forces), polymer, steric and hydrophobic interactions, bio-specific interactions as well as friction and lubrication forces. Here we describe recent developments in the SFA technique, specifically the SFA 2000, its simplicity of operation and its extension into new areas of measurement of both static and dynamic forces as well as both normal and lateral (shear and friction) forces. The main reason for the greater simplicity of the SFA 2000 is that it operates on one central simple-cantilever spring to generate both coarse and fine motions over a total range of seven orders of magnitude (from millimeters to ångstroms). In addition, the SFA 2000 is more spacious and modulated so that new attachments and extra parts can easily be fitted for performing more extended types of experiments (e.g. extended strain friction experiments and higher rate dynamic experiments) as well as traditionally non-SFA type experiments (e.g. scanning probe microscopy and atomic force microscopy) and for studying different types of systems.
Lacoste, Deanna
2016-06-23
The responses of laminar methane-air flames to forcing by acoustic waves, AC electric fields, and nanosecond repetitively pulsed (NRP) glow discharges are reported here. The experimental setup consists of an axisymmetric burner with a nozzle made from a quartz tube. Three different flame geometries have been studied: conical, M-shaped and V-shaped flames. A central stainless steel rod is used as a cathode for the electric field and plasma excitations. The acoustic forcing is obtained with a loudspeaker located at the bottom part of the burner. For forcing by AC electric fields, a metallic grid is placed above the rod and connected to an AC power supply. Plasma forcing is obtained by applying high-voltage pulses of 10-ns duration applied at 10 kHz, between the rod and an annular stainless steel ring, placed at the outlet of the quartz tube. The chemiluminescence of CH is used to determine the heat release rate fluctuations. For forcing by acoustic waves and plasma, the geometry of the flame plays a key role in the response of the combustion, while the flame shape does not affect the response of the combustion to electric field forcing. The flame response to acoustic forcing of about 10% of the incoming flow is similar to those obtained in the literature. The flames are found to be responsive to an AC electric field across the whole range of frequencies studied. A forcing mechanism, based on the generation of ionic wind, is proposed. The gain of the transfer function obtained for plasma forcing is found to be up to 5 times higher than for acoustic forcing. A possible mechanism of plasma forcing is introduced.
Lynn, Keith C.; Commo, Sean A.; Johnson, Thomas H.; Parker, Peter A,
2011-01-01
Wind tunnel research at NASA Langley Research Center s 31-inch Mach 10 hypersonic facility utilized a 5-component force balance, which provided a pressurized flow-thru capability to the test article. The goal of the research was to determine the interaction effects between the free-stream flow and the exit flow from the reaction control system on the Mars Science Laboratory aeroshell during planetary entry. In the wind tunnel, the balance was exposed to aerodynamic forces and moments, steady-state and transient thermal gradients, and various internal balance cavity pressures. Historically, these effects on force measurement accuracy have not been fully characterized due to limitations in the calibration apparatus. A statistically designed experiment was developed to adequately characterize the behavior of the balance over the expected wind tunnel operating ranges (forces/moments, temperatures, and pressures). The experimental design was based on a Taylor-series expansion in the seven factors for the mathematical models. Model inversion was required to calculate the aerodynamic forces and moments as a function of the strain-gage readings. Details regarding transducer on-board compensation techniques, experimental design development, mathematical modeling, and wind tunnel data reduction are included in this paper.
Energy Technology Data Exchange (ETDEWEB)
Fischer, D.J.
2008-01-15
We study the Casimir energy density of the Klein-Gordon-field in the case of two static geometries. We model the effect by coupling the free quantum field to a static classical scalar field. We work out the dependence on the coupling {lambda}, including the limit {lambda}={infinity} (Dirichlet boundary condition). The chosen geometries are described by a {delta}-funktion ({sigma}(x)={delta}(x{sub 3})) and a step function of finite height ({sigma}(x)= (1)/(2{epsilon})1{sub [{epsilon},{epsilon}]}(x{sub 3})), respectively. In the area outside the support of the background the density energy converges; calculations for the distorted area lead to divergent surface terms. (orig.)
Directory of Open Access Journals (Sweden)
Mohammad Yaghoub Abdollahzadeh Jamalabadi
2016-05-01
Full Text Available Numerical and analytical investigation of the effects of thermal radiation and viscous heating on a convective flow of a non-Newtonian, incompressible fluid in an axisymmetric stretching sheet with constant temperature wall is performed. The power law model of the blood is used for the non-Newtonian model of the fluid and the Rosseland model for the thermal radiative heat transfer in an absorbing medium and viscous heating are considered as the heat sources. The non-dimensional governing equations are transformed to similarity form and solved numerically. A parameter study on entropy generation in medium is presented based on the Second Law of Thermodynamics by considering various parameters such as the thermal radiation parameter, the Brinkman number, Prandtl number, Eckert number.
Directory of Open Access Journals (Sweden)
Yulong Yan
2016-03-01
Full Text Available The stability of partly liquid filled spacecraft with flexible attachment was investigated in this paper. Liquid sloshing dynamics was simplified as the spring–mass model, and flexible attachment was modeled as the linear shearing beam. The dynamic equations and Hamiltonian of the coupled spacecraft system were given by analyzing the rigid body, liquid fuel, and flexible appendage. Nonlinear stability conditions of the coupled spacecraft system were derived by computing the variation of Casimir function which was added to the Hamiltonian. The stable region of the parameter space was given and validated by numerical computation. Related results suggest that the change of inertia matrix, the length of flexible attachment, spacecraft spinning rate, and filled ratio of liquid fuel tank have strong influence on the stability of the spacecraft system.
Force Analysis and Energy Operation of Chaotic System of Permanent-Magnet Synchronous Motor
Qi, Guoyuan; Hu, Jianbing
2017-12-01
The disadvantage of a nondimensionalized model of a permanent-magnet synchronous Motor (PMSM) is identified. The original PMSM model is transformed into a Kolmogorov system to aid dynamic force analysis. The vector field of the PMSM is analogous to the force field including four types of torque — inertial, internal, dissipative, and generalized external. Using the feedback thought, the error torque between external torque and dissipative torque is identified. The pitchfork bifurcation of the PMSM is performed. Four forms of energy are identified for the system — kinetic, potential, dissipative, and supplied. The physical interpretations of the decomposition of force and energy exchange are given. Casimir energy is stored energy, and its rate of change is the error power between the dissipative energy and the energy supplied to the motor. Error torque and error power influence the different types of dynamic modes. The Hamiltonian energy and Casimir energy are compared to find the function of each in producing the dynamic modes. A supremum bound for the chaotic attractor is proposed using the error power and Lagrange multiplier.
Quantum Gravitational Force Between Polarizable Objects
Ford, L. H.; Hertzberg, Mark P.; Karouby, J.
2016-04-01
Since general relativity is a consistent low energy effective field theory, it is possible to compute quantum corrections to classical forces. Here we compute a quantum correction to the gravitational potential between a pair of polarizable objects. We study two distant bodies and compute a quantum force from their induced quadrupole moments due to two-graviton exchange. The effect is in close analogy to the Casimir-Polder and London-van der Waals forces between a pair of atoms from their induced dipole moments due to two photon exchange. The new effect is computed from the shift in vacuum energy of metric fluctuations due to the polarizability of the objects. We compute the potential energy at arbitrary distances compared to the wavelengths in the system, including the far and near regimes. In the far distance, or retarded, regime, the potential energy takes on a particularly simple form: V (r )=-3987 ℏc G2α1 Sα2 S/(4 π r11) , where α1 S , α2 S are the static gravitational quadrupole polarizabilities of each object. We provide estimates of this effect.
Furuya, M.
2006-01-01
Currently, 434 nuclear power plants are in operation worldwide. 21% of them are known as Boiling Water Reactors (BWRs). These BWRs have pumps that cool their reactor cores (the forced circulation BWRs). In the design of new BWRs, ways to cool the core by a natural circulation flow, without pumps,
Bakirov, M. B.; Levchuk, V. I.; Povarov, V. P.; Gromov, A. F.
2014-08-01
Inadmissible operational flaws occurring in the critical zones of heat-transfer and mechanical equipment are commonly revealed in all nuclear power plant units both in Russia and abroad. The number of such flaws will only grow in the future because the majority of nuclear power plants have been in operation for a time that is either close to or even exceeds the assigned service life. In this connection, establishing cause-and-effect relations with regard to accelerated incipience and growth of flaws, working out compensating measures aimed at reducing operational damageability, and setting up monitoring of equipment integrity degradation of during operation are becoming the matters of utmost importance. There is a need to introduce new approaches to comprehensive diagnostics of the technical state of important nuclear power plant equipment, including continuous monitoring of its operational damageability and the extent of its loading in the most critical zones. Starting from 2011, such a monitoring system has successfully been used for the Novovoronezh NPP Unit 5 in the zone of weld joint no. 111-1 of steam generator no. 4. Based on the results from operation of this system in 2011-2013, unsteady thermally induced force effects (periodic thermal shocks and temperature abnormalities) were reveled, which had not been considered in the design, and which have an essential influence on the operational loading of this part. Based on an analysis of cause-and-effect relations pertinent to temperature abnormalities connected with technological operations, a set of measures aimed at reducing the thermally induced force loads exerted on pipeline sections was developed, which includes corrections to the process regulations for safe operation and to the operating manuals (involving changes in the algorithms for manipulating with the stop and control valves in the steam generator blowdown system).
Directory of Open Access Journals (Sweden)
Rongjia Yang
2014-08-01
Full Text Available If we assume that the source of thermodynamic system, ρ and p, are also the source of gravity, then either thermal quantities, such as entropy, temperature, and chemical potential, can induce gravitational effects, or gravity can induce thermal effects. We find that gravity can be seen as entropic force only for systems with constant temperature and zero chemical potential. The case for Newtonian approximation is discussed.
1997-01-01
Gateway Technologies, Inc. is marketing and developing textile insulation technology originally developed by Triangle Research and Development Corporation. The enhanced thermal insulation stems from Small Business Innovation Research contracts from NASA's Johnson Space Center and the U.S. Air Force. The effectiveness of the insulation comes from the microencapsulated phase-change materials originally made to keep astronauts gloved hands warm. The applications for the product range from outer wear, housing insulation, and blankets to protective firefighting gear and scuba diving suits. Gateway has developed and begun marketing thermal regulating products under the trademark, OUTLAST. Products made from OUTLAST are already on the market, including boot and shoe liners, winter headgear, hats and caps for hunting and other outdoor sports, and a variety of men's and women's ski gloves.
Fluctuation-induced forces in confined ideal and imperfect Bose gases.
Diehl, H W; Rutkevich, Sergei B
2017-06-01
Fluctuation-induced ("Casimir") forces caused by thermal and quantum fluctuations are investigated for ideal and imperfect Bose gases confined to d-dimensional films of size ∞^{d-1}×D under periodic (P), antiperiodic (A), Dirichlet-Dirichlet (DD), Neumann-Neumann (NN), and Robin (R) boundary conditions (BCs). The full scaling functions Υ_{d}^{BC}(x_{λ}=D/λ_{th},x_{ξ}=D/ξ) of the residual reduced grand potential per area φ_{res,d}^{BC}(T,μ,D)=D^{-(d-1)}Υ_{d}^{BC}(x_{λ},x_{ξ}) are determined for the ideal gas case with these BCs, where λ_{th} and ξ are the thermal de Broglie wavelength and the bulk correlation length, respectively. The associated limiting scaling functions Θ_{d}^{BC}(x_{ξ})≡Υ_{d}^{BC}(∞,x_{ξ}) describing the critical behavior at the bulk condensation transition are shown to agree with those previously determined from a massive free O(2) theory for BC=P,A,DD,DN,NN. For d=3, they are expressed in closed analytical form in terms of polylogarithms. The analogous scaling functions Υ_{d}^{BC}(x_{λ},x_{ξ},c_{1}D,c_{2}D) and Θ_{d}^{R}(x_{ξ},c_{1}D,c_{2}D) under the RBCs (∂_{z}-c_{1})ϕ|_{z=0}=(∂_{z}+c_{2})ϕ|_{z=D}=0 with c_{1}≥0 and c_{2}≥0 are also determined. The corresponding scaling functions Υ_{∞,d}^{P}(x_{λ},x_{ξ}) and Θ_{∞,d}^{P}(x_{ξ}) for the imperfect Bose gas are shown to agree with those of the interacting Bose gas with n internal degrees of freedom in the limit n→∞. Hence, for d=3, Θ_{∞,d}^{P}(x_{ξ}) is known exactly in closed analytic form. To account for the breakdown of translation invariance in the direction perpendicular to the boundary planes implied by free BCs such as DDBCs, a modified imperfect Bose gas model is introduced that corresponds to the limit n→∞ of this interacting Bose gas. Numerically and analytically exact results for the scaling function Θ_{∞,3}^{DD}(x_{ξ}) therefore follow from those of the O(2n)ϕ^{4} model for n→∞.
Energy Technology Data Exchange (ETDEWEB)
Marks, P.J.; Noland, J.W.; Nielson, R.K.
1990-03-01
The patented Low Temperature Thermal Treatment (LT3) System was previously proven to be successful in treating soils contaminated with volatile organic compounds and petroleum hydrocarbons. This demonstration broadened the applicability to include soils contaminated with aviation fuel and other halogenated solvents. Several test were conducted to verify the effectiveness of the LT3 system. While meeting all goal cleanup objectives, a processing rate of 20,000 lb/hr was demonstrated with a projected LT3 System processing cost of $86/ton. A number of system changes and process improvements are recommended. The system proved to be an efficient, cost-effective, and commercially available remediation alternative for decontaminating soils.
Snap-through buckling of initially curved microbeam subject to an electrostatic force.
Chen, X; Meguid, S A
2015-05-08
In this paper, the snap-through buckling of an initially curved microbeam subject to an electrostatic force, accounting for fringing field effect, is investigated. The general governing equations of the curved microbeam are developed using Euler-Bernoulli beam theory and used to develop a new criterion for the snap-through buckling of that beam. The size effect of the microbeam is accounted for using the modified couple stress theory, and intermolecular effects, such as van der Waals and Casimir forces, are also included in our snap-through formulations. The snap-through governing equations are solved using Galerkin decomposition of the deflection. The results of our work enable us to carefully characterize the snap-through behaviour of the initially curved microbeam. They further reveal the significant effect of the beam size, and to a much lesser extent, the effect of fringing field and intermolecular forces, upon the snap-through criterion for the curved beam.
Forces between a partially coherent fluctuating source and a magnetodielectric particle
Auñon, Juan Miguel
2013-01-01
We address the forces exerted by the electromagnetic ?eld emitted by a planar uctuating source on dielectric particles that have arose much interest because of their recently shown magnetodielectric behavior. In this context, we analyze as a particular case the modi?cation of the Casimir and Van der Waals forces. We study the e?ect of the source coherence length as well as the interplay between the force from the radiated ?eld and that from the electric and magnetic dipoles induced on the particle. This allows a control of these interactions as well as of the weight and interference e?ects between the ?elds from both kinds of induced dipoles, in particular when large changes in their di?erential scattering cross section occur due to Kerker minimum forward or zero backward conditions; thus opening new paths to nanoparticle ensembling and manipulation. The influence of surface waves of the source is also studied.
Villar, Paula I.; Soba, Alejandro
2017-07-01
We present an alternative numerical approach to compute the number of particles created inside a cavity due to time-dependent boundary conditions. The physical model consists of a rectangular cavity, where a wall always remains still while the other wall of the cavity presents a smooth movement in one direction. The method relies on the setting of the boundary conditions (Dirichlet and Neumann) and the following resolution of the corresponding equations of modes. By a further comparison between the ground state before and after the movement of the cavity wall, we finally compute the number of particles created. To demonstrate the method, we investigate the creation of particle production in vibrating cavities, confirming previously known results in the appropriate limits. Within this approach, the dynamical Casimir effect can be investigated, making it possible to study a variety of scenarios where no analytical results are known. Of special interest is, of course, the realistic case of the electromagnetic field in a three-dimensional cavity, with transverse electric (TE)-mode and transverse magnetic (TM)-mode photon production. Furthermore, with our approach we are able to calculate numerically the particle creation in a tuneable resonant superconducting cavity by the use of the generalized Robin boundary condition. We compare the numerical results with analytical predictions as well as a different numerical approach. Its extension to three dimensions is also straightforward.
Chernodub, M. N.
2013-01-01
Recently, we have demonstrated that for a certain class of Casimir-type systems (“devices”) the energy of zero-point vacuum fluctuations reaches its global minimum when the device rotates about a certain axis rather than remains static. This rotational vacuum effect may lead to the emergence of permanently rotating objects provided the negative rotational energy of zero-point fluctuations cancels the positive rotational energy of the device itself. In this paper, we show that for massless electrically charged particles the rotational vacuum effect should be drastically (astronomically) enhanced in the presence of a magnetic field. As an illustration, we show that in a background of experimentally available magnetic fields the zero-point energy of massless excitations in rotating torus-shaped doped carbon nanotubes may indeed overwhelm the classical energy of rotation for certain angular frequencies so that the permanently rotating state is energetically favored. The suggested “zero-point-driven” devices—which have no internally moving parts—correspond to a perpetuum mobile of a new, fourth kind: They do not produce any work despite the fact that their equilibrium (ground) state corresponds to a permanent rotation even in the presence of an external environment. We show that our proposal is consistent with the laws of thermodynamics.
Moffat, Jonathan G; Qi, Sheng; Craig, Duncan Q M
2014-07-01
In this study we explore the use of nano-scale localized thermal analysis (LTA) and transition temperature microcopy (TTM) as a novel combined approach to studying phase separation in HME dispersions of cyclosporine A in Eudragit EPO. Modulated temperature differential scanning calorimetry (MTDSC), attenuated total reflectance FTIR spectroscopy, nano-LTA and TTM were performed on raw materials and dispersions prepared by hot melt extrusion (HME) and spin coating. For samples prepared by HME, two mixing temperatures (110°C and 150°C) and residence times (5 and 15 min) were investigated. Spin coated samples showed an intermediate T g for the mixed systems consistent with molecular dispersion formation. The HME samples prepared at 110°C showed evidence of inhomogeneity using MTDSC and FTIR, while those produced at 150°C h showed evidence for the formation of a single phase system using MTDSC. The nanothermal methods, however, indicated the presence of phase separated cyclosporine A at the higher preparation temperature while the TTM was able to map regions of differing penetration temperatures, indicating the presence of compositionally inhomogeneous regions in all but the high processing temperature/high residence time samples. TTM is a potentially important new method for studying phase separation and that such separation may remain undetected or poorly understood using conventional bulk analytical techniques.
Directory of Open Access Journals (Sweden)
Crislaine Alberton
2014-02-01
Full Text Available Starch is arguably the most investigated biopolymer in the world and the cassava starch that is extracted from Manihot esculenta Crantz, represents an important vegetal crop in tropical countries, where its roots and derivatives serve as food and a source of energy. The main composition of these roots is 70-80% water, 16-24% starch and small quantities (<4% of protein, lipids vitamins and minerals. Hydrocolloids, or gums, are substances consisting of a hydrophilic long-chain with colloidal properties that, in water-based systems, produce gels. Starches and hydrocolloids are often used together in food systems to provide texture, water mobility, control moisture, improve product quality and stability, facilitate processing and reduce costs. In this study, the interactions between cassava and starch-hydrocolloids (1% of the following gums: CMC, jatahy, pectin and xanthan were investigated. The TG/DTG method made it possible to determine the thermal decomposition of each sample, which under air atmosphere occurs in three steps. Little difference was observed in the degree of relative crystallinity (XRD and in the average roughness or average diameter of the starch granules (NC-AFM. The viscosity and pasting properties (RVA increased, and were higher for starch treated with jatahy gum. A large decrease was observed in peak temperature and gelatinisation enthalpy for the treated samples (DSC.
Multiphase forces on bend structures
Nennie, E.D.; Belfroid, S.P.C.
2016-01-01
Piping structures are generally subjected to high dynamic loading due to multiphase forces. In particular subsea structures are very vulnerable as large flexibility is required to cope for instance with thermal stresses. The forces due to multiphase flow are characterized by a broadband spectrum
Origin of Knudsen forces on heated microbeams
Zhu, Taishan
2010-09-09
The presented work probes the fundamentals of Knudsen forces. Using the direct simulation Monte Carlo (DSMC) method, the flows induced by temperature inhomogeneity within a representative configuration and the Knudsen force acting on a heated microbeam are captured as functions of Knudsen number in the entire flow regime. Both flow strength and Knudsen force peak in the transition regime and negative Knudsen force absent in experimental data is observed. The mechanisms of the thermally induced flows and Knudsen forces are studied. It has been found that thermal edge flow is the main driven source for the formation of the Knudsen force on microbeams and domain configuration plays an important role in the process.
Ultrasensitive Inertial and Force Sensors with Diamagnetically Levitated Magnets
Prat-Camps, J.; Teo, C.; Rusconi, C. C.; Wieczorek, W.; Romero-Isart, O.
2017-09-01
We theoretically show that a magnet can be stably levitated on top of a punctured superconductor sheet in the Meissner state without applying any external field. The trapping potential created by such induced-only superconducting currents is characterized for magnetic spheres ranging from tens of nanometers to tens of millimeters. Such a diamagnetically levitated magnet is predicted to be extremely well isolated from the environment. We propose to use it as an ultrasensitive force and inertial sensor. A magnetomechanical readout of its displacement can be performed by using superconducting quantum interference devices. An analysis using current technology shows that force and acceleration sensitivities on the order of 10-23 N /√{Hz } (for a 100-nm magnet) and 10-14 g /√{Hz } (for a 10-mm magnet) might be within reach in a cryogenic environment. Such remarkable sensitivities, both in force and acceleration, can be used for a variety of purposes, from designing ultrasensitive inertial sensors for technological applications (e.g., gravimetry, avionics, and space industry), to scientific investigations on measuring Casimir forces of magnetic origin and gravitational physics.
Thermal management for LED applications
Poppe, András
2014-01-01
Thermal Management for LED Applications provides state-of-the-art information on recent developments in thermal management as it relates to LEDs and LED-based systems and their applications. Coverage begins with an overview of the basics of thermal management including thermal design for LEDs, thermal characterization and testing of LEDs, and issues related to failure mechanisms and reliability and performance in harsh environments. Advances and recent developments in thermal management round out the book with discussions on advances in TIMs (thermal interface materials) for LED applications, advances in forced convection cooling of LEDs, and advances in heat sinks for LED assemblies. This book also: Presents a comprehensive overview of the basics of thermal management as it relates to LEDs and LED-based systems Discusses both design and thermal management considerations when manufacturing LEDs and LED-based systems Covers reliability and performance of LEDs in harsh environments Has a hands-on applications a...
Numerical simulation of the LAGEOS thermal behavior and thermal accelerations
Andrés, J.I.; Noomen, R.; Vecellio None, S.
2006-01-01
The temperature distribution throughout the LAGEOS satellites is simulated numerically with the objective to determine the resulting thermal force. The different elements and materials comprising the spacecraft, with their energy transfer, have been modeled with unprecedented detail. The radiation
Optical Near-field Interactions and Forces for Optoelectronic Devices
Kohoutek, John Michael
Throughout history, as a particle view of the universe began to take shape, scientists began to realize that these particles were attracted to each other and hence came up with theories, both analytical and empirical in nature, to explain their interaction. The interaction pair potential (empirical) and electromagnetics (analytical) theories, both help to explain not only the interaction between the basic constituents of matter, such as atoms and molecules, but also between macroscopic objects, such as two surfaces in close proximity. The electrostatic force, optical force, and Casimir force can be categorized as such forces. A surface plasmon (SP) is a collective motion of electrons generated by light at the interface between two mediums of opposite signs of dielectric susceptibility (e.g. metal and dielectric). Recently, surface plasmon resonance (SPR) has been exploited in many areas through the use of tiny antennas that work on similar principles as radio frequency (RF) antennas in optoelectronic devices. These antennas can produce a very high gradient in the electric field thereby leading to an optical force, similar in concept to the surface forces discussed above. The Atomic Force Microscope (AFM) was introduced in the 1980s at IBM. Here we report on its uses in measuring these aforementioned forces and fields, as well as actively modulating and manipulating multiple optoelectronic devices. We have shown that it is possible to change the far field radiation pattern of an optical antenna-integrated device through modification of the near-field of the device. This modification is possible through change of the local refractive index or reflectivity of the "hot spot" of the device, either mechanically or optically. Finally, we have shown how a mechanically active device can be used to detect light with high gain and low noise at room temperature. It is the aim of several of these integrated and future devices to be used for applications in molecular sensing
Occupational Outlook Quarterly, 2012
2012-01-01
The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…
Thermal transport in Si and Ge nanostructures in the `confinement' regime
Kwon, Soonshin; Wingert, Matthew C.; Zheng, Jianlin; Xiang, Jie; Chen, Renkun
2016-07-01
Reducing semiconductor materials to sizes comparable to the characteristic lengths of phonons, such as the mean-free-path (MFP) and wavelength, has unveiled new physical phenomena and engineering capabilities for thermal energy management and conversion systems. These developments have been enabled by the increasing sophistication of chemical synthesis, microfabrication, and atomistic simulation techniques to understand the underlying mechanisms of phonon transport. Modifying thermal properties by scaling physical size is particularly effective for materials which have large phonon MFPs, such as crystalline Si and Ge. Through nanostructuring, materials that are traditionally good thermal conductors can become good candidates for applications requiring thermal insulation such as thermoelectrics. Precise understanding of nanoscale thermal transport in Si and Ge, the leading materials of the modern semiconductor industry, is increasingly important due to more stringent thermal conditions imposed by ever-increasing complexity and miniaturization of devices. Therefore this Minireview focuses on the recent theoretical and experimental developments related to reduced length effects on thermal transport of Si and Ge with varying size from hundreds to sub-10 nm ranges. Three thermal transport regimes - bulk-like, Casimir, and confinement - are emphasized to describe different governing mechanisms at corresponding length scales.
Thermal-induced force release in oxyhemoglobin
S. G. Gevorkian; Allahverdyan, A.E.; Gevorgyan, D. S.; Chin-Kun Hu
2015-01-01
Oxygen is released to living tissues via conformational changes of hemoglobin from R-state (oxyhemoglobin) to T-state (desoxyhemoglobin). The detailed mechanism of this process is not yet fully understood. We have carried out micromechanical experiments on oxyhemoglobin crystals to determine the behavior of the Young?s modulus and the internal friction for temperatures between 20??C and 70??C. We have found that around 49??C oxyhemoglobin crystal samples undergo a sudden and strong increase o...
2007-06-01
Guidelines to help A&E staff and other healthcare professionals who suspect cases of forced marriage were launched this month by the government. The guidelines provide practical advice on how to recognise the warning signs, and what to do if patients disclose that they have been, or are about to be, forced to marry. The guidelines, Dealing with Cases of Forced Marriage, are available at www.fco.gov.uk/forcedmarriage.
Size Dependent Orientation of Knudsen Force
Zhu, Taishan
2012-03-03
Knudsen force acting on a heated microbeam adjacent to a cold substrate in a rarefied gas is a mechanical force created by unbalanced thermal gradients. The measured force has its direction pointing towards the side with a lower thermal gradient and its magnitude vanishes in both continuum and free-molecule limits. In our previous study, negative Knudsen forces were discovered at the high Knudsen regime before diminishing in the free-molecule limit. Such a phenomenon was however not observed in the experiment. In this paper, the existence of such a negative Knudsen force is further confirmed using both numerical simulation and theoretical analysis. The asymptotic order of the Knudsen force near the collisionless limit is analyzed and the analytical expression of its leading term is provided, from which approaches for the enhancement of negative Knudsen forces are proposed. Copyright © 2012 by ASME.
CSIR Research Space (South Africa)
Osburn, L
2010-01-01
Full Text Available wider range of temperature limits, saving energy while still satisfying the majority of building occupants. It is also noted that thermal comfort varies significantly between individuals and it is generally not possible to provide a thermal environment...
Thermal to electricity conversion using thermal magnetic properties
West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID
2010-04-27
A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.
Compliant electro-thermal microactuators
DEFF Research Database (Denmark)
Jonsmann, Jacques; Sigmund, Ole; Bouwstra, Siebe
1999-01-01
This paper describes design, microfabrication and characterisation of topology optimised compliant electro-thermal microactuators. The actuators are fabricated by a fast prototyping process using laser micromachining and electroplating. Actuators are characterised with respect to displacement......, force and work, by use of image analysis. Four different actuators are presented. These actuators are capable of displacements of 30 μm and forces of 15 mN. The most recent actuator designs function in reasonable accordance with design predictions....
Directory of Open Access Journals (Sweden)
Ya-Pu Zhao
2007-11-01
Full Text Available The influence of damping on the dynamical behavior of the electrostaticparallel-plate and torsional actuators with the van der Waals (vdW or Casimir force(torque is presented. The values of the pull-in parameters and the number of theequilibrium points do not change whether there is damping or not. The ability ofequilibrium points is varied with the appearance of damping. One equilibrium point is anunstable saddle with a different damping coefficient, the other equilibrium point is astable node when the damping coefficient is greater than some critical value, andotherwise it is a stable focus. Then there are two heteroclinic orbits passing from theunstable saddle point to the stable node or focus.
Energy Technology Data Exchange (ETDEWEB)
Canavan, G.H.
1998-12-31
This paper is concerned with rapid, continuous inspection of vehicles entering military facilities or compounds, searching for high explosives, or the rapid survey of facilities if it is found that security has been breached. The author reviews methods which are in use now, including: x-rays; x-ray tomography; thermal or fast neutrons; quadrupole resonance; trace detection; electron capture; chemiluminesence; ion mobility spectroscopy; mass spectroscopy; antibodies; and layered, synergistic approaches. He then discusses the limitations of these methods and proposes new approaches which are a combination of old techniques such as weighing vehicles with technological advances in some present methods.
Adaptation of thermal power plants
Bogmans, Christian W.J.; Dijkema, Gerard P.J.; Vliet, van Michelle T.H.
2017-01-01
When does climate change information lead to adaptation? We analyze thermal power plant adaptation by means of investing in water-saving (cooling) technology to prevent a decrease in plant efficiency and load reduction. A comprehensive power plant investment model, forced with downscaled climate
Analysis of thermally-degrading, confined HMX
Energy Technology Data Exchange (ETDEWEB)
Hobbs, M.L.; Schmitt, R.G.; Renlund, A.M.
1996-12-01
The response of a thermally-degrading, confined HMX pellet is analyzed using a Reactive Elastic-Plastic (REP) constitutive model which is founded on the collapse and growth of internal inclusions resulting from physical and chemical processes such as forced displacement, thermal expansion, and/or decomposition. Axial stress predictions compare adequately to data. Deficiencies in the model and future directions are discussed.
DEFF Research Database (Denmark)
Christensen, Thomas Budde
The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands......, Portugal and New Zealand have adopted the concept. Public sector interventions that aim to support cluster development in industries most often focus upon economic policy goals such as enhanced employment and improved productivity, but rarely emphasise broader societal policy goals relating to e.......g. sustainability or quality of life. The purpose of this paper is to explore how and to what extent public sector interventions that aim at forcing cluster development in industries can support sustainable development as defined in the Brundtland tradition and more recently elaborated in such concepts as eco-industrialism...
Marciuc, Daly; Solschi, Viorel
2017-04-01
Understanding the Coriolis effect is essential for explaining the movement of air masses and ocean currents. The lesson we propose aims to familiarize students with the manifestation of the Coriolis effect. Students are guided to build, using the GeoGebra software, a simulation of the motion of a body, related to a rotating reference system. The mathematical expression of the Coriolis force is deduced, for particular cases, and the Foucault's pendulum is presented and explained. Students have the opportunity to deepen the subject, by developing materials related to topics such as: • Global Wind Pattern • Ocean Currents • Coriolis Effect in Long Range Shooting • Finding the latitude with a Foucault Pendulum
Thermal coupling within LTP dynamics control loop
Energy Technology Data Exchange (ETDEWEB)
Nofrarias, M; Garcia Marin, A F; Heinzel, G; Hewitson, M; Danzmann, K [Max-Planck-Institut fuer Gravitationsphysik, Albert Einstein Institut (AEI), Callinstrasse 38, 30167 Hannover (Germany); Lobo, A; Sanjuan, J [Institut de Ciencies de l' Espai (ICE-CSIC), Facultat de Ciencies, Torre C5, 08193 Bellaterra (Spain); Ramos-Castro, J, E-mail: miquel.nofrarias@aei.mpg.d [Departament d' Enginyeria Electronica, UPC, Campus Nord, Edifici C4, Jordi Girona 1-3, 08034 Barcelona (Spain)
2009-03-01
The Diagnostic Subsytem in the LISA Technology Package (LTP) on board the LISA Pathfinder mission (LPF) will characterise those external disturbances with a potential impact on the performance of the experiment coming from either thermal, magnetic or charged particles perturbations. A correct design of the experiments to measure these effects in flight requires a closed loop analysis that takes into account the dynamics of the test masses, the force applied by the controllers and those noisy terms (coming from sensing or force noise) that enters into the loop. We describe this analysis in the thermal case and we give a first numerical example of the instrument response to controlled thermal inputs.
Force distribution in a semiflexible loop
Waters, James T
2016-01-01
Loops undergoing thermal fluctuations are prevalent in nature. Ring-like or cross-linked polymers, cyclic macromolecules, and protein-mediated DNA loops all belong to this category. Stability of these molecules are generally described in terms of free energy, an average quantity, but it may also be impacted by local fluctuating forces acting within these systems. The full distribution of these forces can thus give us insights into mechanochemistry beyond the predictive capability of thermodynamics. In this paper, we study the force exerted by an inextensible semiflexible polymer constrained in a looped state. By using a novel simulation method termed "phase-space sampling", we generate the equilibrium distribution of chain conformations in both position and momentum space. We compute the constraint forces between the two ends of the loop in this chain ensemble using Lagrangian mechanics, and show that the mean of these forces is equal to the thermodynamic force. By analyzing kinetic and potential contribution...
DEFF Research Database (Denmark)
d’Ambrosio Alfano, Francesca Romana; Olesen, Bjarne W.; Palella, Boris Igor
2014-01-01
Thermal comfort is one of the most important aspects of the indoor environmental quality due to its effects on well-being, people's performance and building energy requirements. Its attainment is not an easy task requiring advanced design and operation of building and HVAC systems, taking...... under specific conditions. At operation level, only few variables are taken into account with unpredictable effects on the assessment of comfort indices. In this paper, the main criteria for the design and assessment of thermal comfort are discussed in order to help building and HVAC systems designers...... into account all parameters involved. Even though thermal comfort fundamentals are consolidated topics for more than forty years, often designers seem to ignore or apply them in a wrong way. Design input values from standards are often considered as universal values rather than recommended values to be used...
Shi, Chen; Cui, Xin; Xie, Lei; Liu, Qingxia; Chan, Derek Y C; Israelachvili, Jacob N; Zeng, Hongbo
2015-01-27
A combination of atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) was used to measure simultaneously the interaction force and the spatiotemporal evolution of the thin water film between a bubble in water and mica surfaces with varying degrees of hydrophobicity. Stable films, supported by the repulsive van der Waals-Casimir-Lifshitz force were always observed between air bubble and hydrophilic mica surfaces (water contact angle, θ(w) bubble attachment occurred on hydrophobized mica surfaces. A theoretical model, based on the Reynolds lubrication theory and the augmented Young-Laplace equation including the effects of disjoining pressure, provided excellent agreement with experiment results, indicating the essential physics involved in the interaction between air bubble and solid surfaces can be elucidated. A hydrophobic interaction free energy per unit area of the form: WH(h) = -γ(1 - cos θ(w))exp(-h/D(H)) can be used to quantify the attraction between bubble and hydrophobized solid substrate at separation, h, with γ being the surface tension of water. For surfaces with water contact angle in the range 45° bubble and hydrophobic surfaces, and provided a feasible method for synchronous measurements of the interaction forces with sub-nN resolution and the drainage dynamics of thin films down to nm thickness.
Karimipour, I.; Kanani, A.; Koochi, A.; Keivani, M.; Abadyan, M.
2015-11-01
While few studies have been conducted on modeling the pull-in instability of cantilever nanoelectromechanical systems (NEMS) in electrolyte media, no researchers has investigated this phenomenon in double-clamped NEMS. Herein, the pull-in instability of the NEMS bridge immersed in ionic liquid electrolyte media is explored for the first time considering the size effect and dispersion forces. The strain gradient elasticity in conjunction with von-Karman strain is employed to incorporate the effect of size-dependency and beam stretching in the structural model. The presence of electrochemical force field and nano-scale attractions i.e. Casimir and van der Waals forces is incorporated in the model considering the presence of the liquid media. To solve the nonlinear constitutive equation of the system two different methods including the differential transformation method (DTM) and numerical solution are employed. The proposed model is validated by comparing with the results presented in literature. Impacts of various parameters i.e. the size dependency, dispersion forces, electrolyte ion concentration and potential ratio on the instability characteristics of the NEMS bridge are discussed. The results of present theory are compared with those predicted by the classic continuum theory as well as the modified couple stress theory.
Thermal cascaded lattice Boltzmann method
Fei, Linlin
2016-01-01
In this paper, a thermal cascaded lattice Boltzmann method (TCLBM) is developed in combination with the double-distribution-function (DDF) approach. A density distribution function relaxed by the cascaded scheme is employed to solve the flow field, and a total energy distribution function relaxed by the BGK scheme is used to solve temperature field, where two distribution functions are coupled naturally. The forcing terms are incorporated by means of central moments, which is consistent with the previous force scheme [Premnath \\emph{et al.}, Phys. Rev. E \\textbf{80}, 036702 (2009)] but the derivation is more intelligible and the evolution process is simpler. In the method, the viscous heat dissipation and compression work are taken into account, the Prandtl number and specific-heat ratio are adjustable, the external force is considered directly without the Boussinesq assumption, and the low-Mach number compressible flows can also be simulated. The forcing scheme is tested by simulating a steady Taylor-Green f...
Nonequilibrium Distribution of the Microscopic Thermal Current in Steady Thermal Transport Systems
Yukawa, Satoshi
2010-01-01
Nonequilibrium distribution of the microscopic thermal current is investigated by direct molecular dynamics simulations. The microscopic thermal current in this study is defined by a flow of kinetic energy carried by a single particle. Asymptotic parallel and antiparallel tails of the nonequilibrium distribution to an average thermal current are identical to ones of equilibrium distribution with different temperatures. These temperatures characterizing the tails are dependent on a characteristic length in which a memory of dynamics is completely erased by several particle collisions. This property of the tails of nonequilibrium distribution is confirmed in other thermal transport systems. In addition, statistical properties of a particle trapped by a harmonic potential in a steady thermal conducting state are also studied. This particle feels a finite force parallel to the average thermal current as a consequence of the skewness of the distribution of the current. This force is interpreted as the microscopic origin of thermophoresis.
Torun, H; Finkler, O; Degertekin, F L
2009-07-01
The authors describe a method for athermalization in atomic force microscope (AFM) based force spectroscopy applications using microstructures that thermomechanically match the AFM probes. The method uses a setup where the AFM probe is coupled with the matched structure and the displacements of both structures are read out simultaneously. The matched structure displaces with the AFM probe as temperature changes, thus the force applied to the sample can be kept constant without the need for a separate feedback loop for thermal drift compensation, and the differential signal can be used to cancel the shift in zero-force level of the AFM.
The negative perception some consumers hold regarding agricultural chemicals has resulted in an increased demand for organic foods and fibers, and in increasing political pressure for the regulation of agricultural production practices. This has revived interest in thermal defoliation of cotton and ...
Balasubramanian, V.; Bernamonti, A.; de Boer, J.; Copland, N.; Craps, B.; Keski-Vakkuri, E.; Müller, B.; Schäfer, A.; Shigemori, M.; Staessens, W.
2011-01-01
Using the AdS/CFT correspondence, we probe the scale-dependence of thermalization in strongly coupled field theories following a quench, via calculations of two-point functions, Wilson loops and entanglement entropy in d=2,3,4. In the saddlepoint approximation these probes are computed in AdS space
Thermal Hardware for the Thermal Analyst
Steinfeld, David
2015-01-01
The presentation will be given at the 26th Annual Thermal Fluids Analysis Workshop (TFAWS 2015) hosted by the Goddard Space Flight Center (GSFC) Thermal Engineering Branch (Code 545). NCTS 21070-1. Most Thermal analysts do not have a good background into the hardware which thermally controls the spacecraft they design. SINDA and Thermal Desktop models are nice, but knowing how this applies to the actual thermal hardware (heaters, thermostats, thermistors, MLI blanketing, optical coatings, etc...) is just as important. The course will delve into the thermal hardware and their application techniques on actual spacecraft. Knowledge of how thermal hardware is used and applied will make a thermal analyst a better engineer.
Energy Technology Data Exchange (ETDEWEB)
Alam, M.S.; Rahman, M.M. [Department of Mathematics, University of Dhaka, Dhaka-1000 (Bangladesh); Sattar, M.A. [Department of Computer Science and Engineering, North South University, 12 Kemal Ataturk Avenue, Banani, Dhaka-1213 (Bangladesh)
2008-06-15
A two-dimensional steady MHD mixed convection and mass transfer flow over a semi-infinite porous inclined plate in the presence of thermal radiation with variable suction and thermophoresis has been analyzed numerically. The governing fundamental equations are approximated by a system of non-linear locally similar ordinary differential equations which are solved numerically by applying Nachtsheim-Swigert shooting iteration technique along with sixth-order Runge-Kutta integration scheme. Favorable comparison with previously published work is performed. Numerical results for the dimensionless velocity, temperature and concentration profiles as well as for the skin-friction coefficient, wall heat transfer and particle deposition rate are obtained and displayed graphically for pertinent parameters to show interesting aspects of the solutions. (author)
Negative Knudsen force on heated microbeams
Zhu, Taishan
2011-11-18
Knudsen force acting on a heated microbeam adjacent to a cold substrate in a rarefied gas is a mechanical force created by unbalanced thermal gradients. The measured force has its direction pointing towards the side with a lower thermal gradient and its magnitude vanishes in both continuum and free-molecule limits. In our previous study, negative Knudsen forces were discovered at the high Knudsen regime before diminishing in the free-molecule limit. Such a phenomenon was, however, neither observed in experiment [A. Passian et al., Phys. Rev. Lett. 90, 124503 (2003)], nor captured in the latest numerical study [J. Nabeth et al., Phys. Rev. E 83, 066306 (2011)]. In this paper, the existence of such a negative Knudsen force is further confirmed using both numerical simulation and theoretical analysis. The asymptotic order of the Knudsen force near the collisionless limit is analyzed and the analytical expression of its leading term is provided, from which approaches for the enhancement of negative Knudsen forces are proposed. The discovered phenomenon could find its applications in novel mechanisms for pressure sensing and actuation.
Micha, Raphael; Micha, Raphael; Tkachev, Igor I.
2004-01-01
We study, analytically and with lattice simulations, the decay of coherent field oscillations and the subsequent thermalization of the resulting stochastic classical wave-field. The problem of reheating of the Universe after inflation constitutes our prime motivation and application of the results. We identify three different stages of these processes. During the initial stage of ``parametric resonance'', only a small fraction of the initial inflaton energy is transferred to fluctuations in the physically relevant case of sufficiently large couplings. A major fraction is transfered in the prompt regime of driven turbulence. The subsequent long stage of thermalization classifies as free turbulence. During the turbulent stages, the evolution of particle distribution functions is self-similar. We show that wave kinetic theory successfully describes the late stages of our lattice calculation. Our analytical results are general and give estimates of reheating time and temperature in terms of coupling constants and...
Forced air heat sink apparatus
Rippel, Wally E. (Inventor)
1989-01-01
A high efficiency forced air heat sink assembly employs a split feed transverse flow configuration to minimize the length of the air flow path through at least two separated fin structures. Different embodiments use different fin structure material configurations including honeycomb, corrugated and serpentine. Each such embodiment uses a thermally conductive plate having opposed exterior surfaces; one for receiving a component to be cooled and one for receiving the fin structures. The serpentine structured fin embodiment employs a plurality of fin supports extending from the plate and forming a plurality of channels for receiving the fin structures. A high thermal conductivity bondant, such as metal-filled epoxy, may be used to bond the fin structures to either the plate or the fin supports. Dip brazing and soldering may also be employed depending upon the materials selected.
Concentrating solar thermal power.
Müller-Steinhagen, Hans
2013-08-13
In addition to wind and photovoltaic power, concentrating solar thermal power (CSP) will make a major contribution to electricity provision from renewable energies. Drawing on almost 30 years of operational experience in the multi-megawatt range, CSP is now a proven technology with a reliable cost and performance record. In conjunction with thermal energy storage, electricity can be provided according to demand. To date, solar thermal power plants with a total capacity of 1.3 GW are in operation worldwide, with an additional 2.3 GW under construction and 31.7 GW in advanced planning stage. Depending on the concentration factors, temperatures up to 1000°C can be reached to produce saturated or superheated steam for steam turbine cycles or compressed hot gas for gas turbine cycles. The heat rejected from these thermodynamic cycles can be used for sea water desalination, process heat and centralized provision of chilled water. While electricity generation from CSP plants is still more expensive than from wind turbines or photovoltaic panels, its independence from fluctuations and daily variation of wind speed and solar radiation provides it with a higher value. To become competitive with mid-load electricity from conventional power plants within the next 10-15 years, mass production of components, increased plant size and planning/operating experience will be accompanied by technological innovations. On 30 October 2009, a number of major industrial companies joined forces to establish the so-called DESERTEC Industry Initiative, which aims at providing by 2050 15 per cent of European electricity from renewable energy sources in North Africa, while at the same time securing energy, water, income and employment for this region. Solar thermal power plants are in the heart of this concept.
National Research Council Canada - National Science Library
Arzura Idris
2012-01-01
This paper analyzes the phenomenon of "forced migration" in Malaysia. It examines the nature of forced migration, the challenges faced by Malaysia, the policy responses and their impact on the country and upon the forced migrants...
Stefanescu, Dan Mihai
2011-01-01
Part I introduces the basic ""Principles and Methods of Force Measurement"" acording to a classification into a dozen of force transducers types: resistive, inductive, capacitive, piezoelectric, electromagnetic, electrodynamic, magnetoelastic, galvanomagnetic (Hall-effect), vibrating wires, (micro)resonators, acoustic and gyroscopic. Two special chapters refer to force balance techniques and to combined methods in force measurement. Part II discusses the ""(Strain Gauge) Force Transducers Components"", evolving from the classical force transducer to the digital / intelligent one, with the inco
Thermally stable imaging channeled spectropolarimetry
Craven-Jones, Julia; Way, Brandyn M.; Hunt, Jeff; Kudenov, Michael W.; Mercier, Jeffrey A.
2013-09-01
Channeled spectropolarimetry can measure the complete polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the spectrally-dependent Stokes polarization information. A primary limitation of conventional channeled spectropolarimeters is related to the thermal variability of the retarders. Thermal variation often forces frequent system recalibration, particularly for field deployed systems. However, implementing thermally stable retarders results in an athermal channeled spectropolarimeter that relieves the need for frequent recalibration. Past work has addressed this issue by developing athermalized retarders using two or more uniaxial crystals. Recently, a retarder made of biaxial KTP and cut at a thermally insensitive angle was used to produce an athermal channeled spectropolarimeter. This paper presents the results of the biaxial crystal system and compares the two thermal stabilization techniques in the context of producing an imaging thermally stable channeled spectropolarimeter. A preliminary design for a snapshot imaging channeled spectropolarimeter is also presented.
The swim force as a body force
Yan, Wen; Brady, John
2015-11-01
Net (as opposed to random) motion of active matter results from an average swim (or propulsive) force. It is shown that the average swim force acts like a body force - an internal body force [Yan and Brady, Soft Matter, DOI:10.1039/C5SM01318F]. As a result, the particle-pressure exerted on a container wall is the sum of the swim pressure [Takatori et al., Phys. Rev. Lett., 2014, 113, 028103] and the `weight' of the active particles. A continuum mechanical description is possible when variations occur on scales larger than the run length of the active particles and gives a Boltzmann-like distribution from a balance of the swim force and the swim pressure. Active particles may also display `action at a distance' and accumulate adjacent to (or be depleted from) a boundary without any external forces. In the momentum balance for the suspension - the mixture of active particles plus fluid - only external body forces appear.
Energy Technology Data Exchange (ETDEWEB)
Yamamoto, R.; Asada, Y.; Matsuo, Y.; Mikoda, M.
1985-07-16
A thermal insulator comprises an expanded resin body having embedded therein an evacuated powder insulation portion which consists of fine powder and a container of film-like plastics or a film-like composite of plastics and metal for enclosing the powder. The resin body has been expanded by a Freon gas as a blowing agent. Since a Freon gas has a larger molecular diameter than the constituent gases of air, it is less likely to permeate through the container than air. Thus present invention provides a novel composite insulator which fully utilizes the benefits of vacuum insulation without necessitating a strong and costly material for a vacuum container.
Thermal lensing in ocular media
Vincelette, Rebecca Lee
2009-12-01
This research was a collaborative effort between the Air Force Research Laboratory (AFRL) and the University of Texas to examine the laser-tissue interaction of thermal lensing induced by continuous-wave, CW, near-infrared, NIR, laser radiation in the eye and its influence on the formation of a retinal lesion from said radiation. CW NIR laser radiation can lead to a thermal lesion induced on the retina given sufficient power and exposure duration as related to three basic parameters; the percent of transmitted energy to, the optical absorption of, and the size of the laser-beam created at the retina. Thermal lensing is a well-known phenomenon arising from the optical absorption, and subsequent temperature rise, along the path of the propagating beam through a medium. Thermal lensing causes the laser-beam profile delivered to the retina to be time dependent. Analysis of a dual-beam, multidimensional, high-frame rate, confocal imaging system in an artificial eye determined the rate of thermal lensing in aqueous media exposed to 1110, 1130, 1150 and 1318-nm wavelengths was related to the power density created along the optical axis and linear absorption coefficient of the medium. An adaptive optics imaging system was used to record the aberrations induced by the thermal lens at the retina in an artificial eye during steady-state. Though the laser-beam profiles changed over the exposure time, the CW NIR retinal damage thresholds between 1110--1319-nm were determined to follow conventional fitting algorithms which neglected thermal lensing. A first-order mathematical model of thermal lensing was developed by conjoining an ABCD beam propagation method, Beer's law of attenuation, and a solution to the heat-equation with respect to radial diffusion. The model predicted that thermal lensing would be strongest for small (retina. The model predicted thermal lensing would cause the retinal damage threshold for wavelengths above 1300-nm to increase with decreasing beam
Air Force Research Laboratory Cryocooler Technology Development
Davis, Thomas M.; Smith, D. Adam; Easton, Ryan M.
2004-06-01
This paper presents an overview of the cryogenic refrigerator and cryogenic integration programs in development and characterization under the Cryogenic Cooling Technology Group, Space Vehicles Directorate of the Air Force Research Laboratory (AFRL). The vision statement for the group is to support the space community as the center of excellence for developing and transitioning space cryogenic thermal management technologies. This paper will describe the range of Stirling, pulse tube; reverse Brayton, and Joule-Thomson cycle cryocoolers currently under development to meet current and future Air Force and Department of Defense requirements. Cooling requirements at 10K, 35K, 60K, 95K, and multistage cooling requirements at 35/85K are addressed. In order to meet these various requirements, the Air Force Research Laboratory, Space Vehicles Directorate is pursuing various strategic cryocooler and cryogenic integration options. The Air Force Research Laboratory, working with industry partners, is also developing several advanced cryogenic integration technologies that will result in the reduction in current cryogenic system integration penalties and design time. These technologies include the continued development of gimbaled transport systems, 35K and 10K thermal storage units, heat pipes, cryogenic straps, and thermal switches.
Microelectromechanical (MEM) thermal actuator
Garcia, Ernest J [Albuquerque, NM; Fulcher, Clay W. G. [Sandia Park, NM
2012-07-31
Microelectromechanical (MEM) buckling beam thermal actuators are disclosed wherein the buckling direction of a beam is constrained to a desired direction of actuation, which can be in-plane or out-of-plane with respect to a support substrate. The actuators comprise as-fabricated, linear beams of uniform cross section supported above the substrate by supports which rigidly attach a beam to the substrate. The beams can be heated by methods including the passage of an electrical current through them. The buckling direction of an initially straight beam upon heating and expansion is controlled by incorporating one or more directional constraints attached to the substrate and proximal to the mid-point of the beam. In the event that the beam initially buckles in an undesired direction, deformation of the beam induced by contact with a directional constraint generates an opposing force to re-direct the buckling beam into the desired direction. The displacement and force generated by the movement of the buckling beam can be harnessed to perform useful work, such as closing contacts in an electrical switch.
Luminescence Materials as Nanoparticle Thermal Sensors
2016-06-01
6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-16-71 Luminescence Materials as Nanoparticle Thermal Sensors ...10 12 joule (J) British thermal unit (Btu) (thermochemical) 1.054 350 × 10 3 joule (J) foot-pound-force (ft lbf) 1.355 818 joule (J) calorie...theoretical investigations on thermal history extraction III. Materials Testing TL in te ns ity Temperature (K) te m pe ra tu re time • nanophosphors
Laser Plasma Physics - Forces and Nonlinear Principle
Hora, Heinrich
2014-01-01
This work is an electronic pre-publication of a book manuscript being under consideration in order to provide information to interested researchers about a review of mechanical forces in plasmas by electro-dynamic fields. Beginning with Kelvin's ponderomotive force of 1845 in electrostatics, the hydrodynamic force in a plasma is linked with quadratic force quantities of electric and magnetic fields. Hydrodynamics is interlinked with single particle motion of plasma particles electric field generation and double layers and sheaths due to properties of inhomogeneous plasmas. Consequences relate to laser driven particle acceleration and fusion energy. Beyond the very broad research field of fusion using nanosecond laser pulses based on thermodynamics, the new picosecond pulses of ultrahigh power opened a categorically different non-thermal interaction finally permitting proton-boron fusion with eliminating problems of nuclear radiation.
Ridgely, Charles T.
2010-07-01
Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced by an observer in general coordinates. The general force is then applied to the local co-moving coordinate system of a uniformly accelerating observer, leading to an expression of the inertial force experienced by the observer. Next, applying the general force in Schwarzschild coordinates is shown to lead to familiar expressions of the gravitational force. As a more complex demonstration, the general force is applied to an observer in Boyer-Lindquist coordinates near a rotating, Kerr black hole. It is then shown that when the angular momentum of the black hole goes to zero, the force on the observer reduces to the force on an observer held stationary in Schwarzschild coordinates. As a final consideration, the force on an observer moving in rotating coordinates is derived. Expressing the force in terms of Christoffel symbols in rotating coordinates leads to familiar expressions of the centrifugal and Coriolis forces on the observer. It is envisioned that the techniques presented herein will be most useful to graduate level students, as well as those undergraduate students having experience with general relativity and tensor analysis.
Labor Force Participation Rate
City and County of Durham, North Carolina — This thematic map presents the labor force participation rate of working-age people in the United States in 2010. The 2010 Labor Force Participation Rate shows the...
Weltner, Klaus
1990-01-01
Describes some experiments showing both qualitatively and quantitatively that aerodynamic lift is a reaction force. Demonstrates reaction forces caused by the acceleration of an airstream and the deflection of an airstream. Provides pictures of demonstration apparatus and mathematical expressions. (YP)
Augereau, J F
2002-01-01
ENSEMBLE DE QUATRE ARTICLES - LARGE HADRON COLLIDER: Le monde des particules tel que nous le connaissons aujourd'hui est constitue de trois familles de quatre membres. Ces particules sont collees les unes aux autres par des forces. Celles-ci, au nombre de quatre - gravitation, force forte, force electromagnetique et force faible -, sont " portees " par d'autres particules dont certaines sont a decouvrir (graviton) et d'autres deja identifiees (gluons, photons, bosons W et Z) (1/2 page).
1984-05-05
International Defense Review, and Foreign Affairs have published articles treating various as- .1 pects of France’s Forces Nucleaires Strategiques(FNS...forces(La Force Nucleaire Strategique or FNS) consist of three systems similar to the American triad. France’s tactical nuclear forces(L’Arme... Nucleaire Tactique or ANT) include a variety of land- and carrier-based aircraft and a tactical missile--Pluton--deployed by the French Army. Thirty-four M
Thermal Oxidation of Structured Silicon Dioxide
DEFF Research Database (Denmark)
Christiansen, Thomas Lehrmann; Hansen, Ole; Jensen, Jørgen Arendt
2014-01-01
The topography of thermally oxidized, structured silicon dioxide is investigated through simulations, atomic force microscopy, and a proposed analytical model. A 357 nm thick oxide is structured by removing regions of the oxide in a masked etch with either reactive ion etching or hydrofluoric acid...
Global characterization of the Holocene Thermal Maximum
Renssen, H.; Seppä, H.; Crosta, X.; Goosse, H.; Roche, D.M.V.A.P.
2012-01-01
We analyze the global variations in the timing and magnitude of the Holocene Thermal Maximum (HTM) and their dependence on various forcings in transient simulations covering the last 9000 years (9 ka), performed with a global atmosphere-ocean-vegetation model. In these experiments, we consider the
Seasonal thermal energy storage
Energy Technology Data Exchange (ETDEWEB)
Allen, R.D.; Kannberg, L.D.; Raymond, J.R.
1984-05-01
This report describes the following: (1) the US Department of Energy Seasonal Thermal Energy Storage Program, (2) aquifer thermal energy storage technology, (3) alternative STES technology, (4) foreign studies in seasonal thermal energy storage, and (5) economic assessment.
Ridgely, Charles T.
2010-01-01
Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…
Fundamentals of Thermal Expansion and Thermal Contraction
Liu, Zi-Kui; Shang, Shun-Li; Wang, Yi
2017-01-01
Thermal expansion is an important property of substances. Its theoretical prediction has been challenging, particularly in cases the volume decreases with temperature, i.e., thermal contraction or negative thermal expansion at high temperatures. In this paper, a new theory recently developed by the authors has been reviewed and further examined in the framework of fundamental thermodynamics and statistical mechanics. Its applications to cerium with colossal thermal expansion and Fe3Pt with th...
Mechanotransduction: use the force(s)
National Research Council Canada - National Science Library
Paluch, Ewa K; Nelson, Celeste M; Biais, Nicolas; Fabry, Ben; Moeller, Jens; Pruitt, Beth L; Wollnik, Carina; Kudryasheva, Galina; Rehfeldt, Florian; Federle, Walter
2015-01-01
Mechanotransduction - how cells sense physical forces and translate them into biochemical and biological responses - is a vibrant and rapidly-progressing field, and is important for a broad range of biological phenomena...
Thermal state of the general time-dependent harmonic oscillator
Indian Academy of Sciences (India)
the thermal state. In Ü2, we investigate quantum mechanical solution of the general time-dependent har- monic oscillator. The thermal state of the system is discussed in Ü3 on the basis of. Liouville–von Neumann approach. InÜ4, we will apply our theory for a special case which is the forced Caldirola–Kanai oscillator.
Root cause analysis of thermal sleeve separation
Energy Technology Data Exchange (ETDEWEB)
Jo, J. C.; Jhung, M. J.; Yu, S. O.; Kim, H. J.; Yune, Y. K.; Park, J. Y
2006-01-15
Thermal sleeves in the shape of thin wall cylinder seated inside the nozzle part of each Safety Injection (SI) line at Pressurized Water Reactors (PWRs) have such functions as prevention and relief of potential excessive transient thermal stress in the wall of SI line nozzle part which is initially heated up with hot water flowing in the primary coolant piping system when cold water is injected into the system through the SI nozzles during the SI operation mode. Recently, mechanical failures that the sleeves were separated from the SI branch pipe and fell into the connected cold leg main pipe occurred in sequence at some typical PWR plants in Korea. To find out the root cause of thermal sleeve breakaway failures, the flow situation in the junction of primary coolant main pipe and SI branch pipe, and the vibration modal characteristics of the thermal sleeve are investigated in detail by using both Computational Fluid Dynamic (CFD) code and structure analysis finite element code. As the results, the transient response in fluid force exerting on the local part of thermal sleeve wall surface to the primary coolant flow through the pipe junction area during the normal reactor operation mode shows oscillatory characteristics with frequencies ranging from 17 to 18, which coincide with one of the lower mode natural frequencies of thermal sleeve having a pinned support condition on the circumferential prominence on the outer surface of thermal sleeve which is put into the circumferential groove on the inner surface of SI nozzle at the mid-height of the thermal sleeve. In addition, the variation of force on the thermal sleeve surface yields alternating torques in the directions of two rectangular axes which are perpendicular to the longitudinal axis of cylindrical thermal sleeve, which cause rolling, pitching and rotating motions of the thermal sleeve. Consequently, it is seen that this flow situation surrounding the thermal sleeve during the normal reactor operation can
Boettcher, Philipp Andreas
Accidental ignition of flammable gases is a critical safety concern in many industrial applications. Particularly in the aviation industry, the main areas of concern on an aircraft are the fuel tank and adjoining regions, where spilled fuel has a high likelihood of creating a flammable mixture. To this end, a fundamental understanding of the ignition phenomenon is necessary in order to develop more accurate test methods and standards as a means of designing safer air vehicles. The focus of this work is thermal ignition, particularly auto-ignition with emphasis on the effect of heating rate, hot surface ignition and flame propagation, and puffing flames. Combustion of hydrocarbon fuels is traditionally separated into slow reaction, cool flame, and ignition regimes based on pressure and temperature. Standard tests, such as the ASTM E659, are used to determine the lowest temperature required to ignite a specific fuel mixed with air at atmospheric pressure. It is expected that the initial pressure and the rate at which the mixture is heated also influences the limiting temperature and the type of combustion. This study investigates the effect of heating rate, between 4 and 15 K/min, and initial pressure, in the range of 25 to 100 kPa, on ignition of n-hexane air mixtures. Mixtures with equivalence ratio ranging from 0.6 to 1.2 were investigated. The problem is also modeled computationally using an extension of Semenov's classical auto-ignition theory with a detailed chemical mechanism. Experiments and simulations both show that in the same reactor either a slow reaction or an ignition event can take place depending on the heating rate. Analysis of the detailed chemistry demonstrates that a mixture which approaches the ignition region slowly undergoes a significant modification of its composition. This change in composition induces a progressive shift of the explosion limit until the mixture is no longer flammable. A mixture that approaches the ignition region
Molecular forces caused by the confinement of thermal noise
Morariu, MD; Schaffer, E; Steiner, U
2004-01-01
We have investigated spontaneous surface instabilities of very thin polymer films. Film stability and the wavelength of the dominating unstable mode were found to depend sensitively on the media adjacent to the film. Our experimental results cannot be explained by van der Waals interactions alone.
Recent Progress with the KWISP Force Sensor
Cantatore, G; Hoffmann, D.H.H.; Karuza, M.; Semertzidis, Y.K.; Zioutas, K.
2015-01-01
The KWISP opto-mechanical force sensor has been built and calibrated in the INFN Trieste optics laboratory and is now under off-beam commissioning at CAST. It is designed to detect the pressure exerted by a flux of solar Chameleons on a thin (100 nm) Si$_3$N$_4$ micromembrane thanks to their direct coupling to matter. A thermally-limited force sensitivity of $1.5 \\cdot 10^{-14}~\\mbox{N}/\\sqrt{\\mbox{Hz}}$, corresponding to $7.5 \\cdot 10^{-16}~\\mbox{m}/\\sqrt{\\mbox{Hz}}$ in terms of displacement, has been obtained. An originally developed prototype chameleon chopper has been used in combination with the KWISP force sensor to conduct preliminary searches for solar chamaleons.
TIGER: Development of Thermal Gradient Compensation Algorithms and Techniques
Hereford, James; Parker, Peter A.; Rhew, Ray D.
2004-01-01
In a wind tunnel facility, the direct measurement of forces and moments induced on the model are performed by a force measurement balance. The measurement balance is a precision-machined device that has strain gages at strategic locations to measure the strain (i.e., deformations) due to applied forces and moments. The strain gages convert the strain (and hence the applied force) to an electrical voltage that is measured by external instruments. To address the problem of thermal gradients on the force measurement balance NASA-LaRC has initiated a research program called TIGER - Thermally-Induced Gradients Effects Research. The ultimate goals of the TIGER program are to: (a) understand the physics of the thermally-induced strain and its subsequent impact on load measurements and (b) develop a robust thermal gradient compensation technique. This paper will discuss the impact of thermal gradients on force measurement balances, specific aspects of the TIGER program (the design of a special-purpose balance, data acquisition and data analysis challenges), and give an overall summary.
DEFF Research Database (Denmark)
Barendregt, Wolmet; Börjesson, Peter; Eriksson, Eva
2017-01-01
In this paper, we present the forced collaborative interaction game StringForce. StringForce is developed for a special education context to support training of collaboration skills, using readily available technologies and avoiding the creation of a "mobile bubble". In order to play String......Force two or four physically collocated tablets are required. These tablets are connected to form one large shared game area. The game can only be played by collaborating. StringForce extends previous work, both technologically and regarding social-emotional training. We believe String......Force to be an interesting demo for the IDC community, as it intertwines several relevant research fields, such as mobile interaction and collaborative gaming in the special education context....
Energy Technology Data Exchange (ETDEWEB)
Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa; Ali, H.
2016-08-15
Short-pulse laser heating of aluminum and silicon thin films pair with presence of a minute vacuum gap in between them is considered and energy transfer across the thin films pair is predicted. The frequency dependent Boltzmann equation is used to predict the phonon intensity distribution along the films pair for three cycles of the repetitive short-pulse laser irradiation on the aluminum film surface. Since the gap size considered is within the Casimir limit, thermal radiation and ballistic phonon contributions to energy transfer across the vacuum gap is incorporated. The laser irradiated field is formulated in line with the Lambert's Beer law and it is considered as the volumetric source in the governing equations of energy transport. In order to assess the phonon intensity distribution in the films pair, equivalent equilibrium temperature is introduced. It is demonstrated that thermal separation of electron and lattice sub-systems in the aluminum film, due to the short-pulse laser irradiation, takes place and electron temperature remains high in the aluminum film while equivalent equilibrium temperature for phonons decays sharply in the close region of the aluminum film interface. This behavior is attributed to the phonon boundary scattering at the interface and the ballistic phonon transfer to the silicon film across the vacuum gap. Energy transfer due to the ballistic phonon contribution is significantly higher than that of the thermal radiation across the vacuum gap.
1990-11-16
structural force is often observed on hydrophilic and hydrophobic surfaces, respectively. These forces are referred to in the literature as hydration and...47,481. One parameter, the effective molecular diffusivity in a pore (e.g., zeolite or polymer), has been indirectly related to transport limited rates...adhesion force (2 g.N) and a marked increase in rate of Fe(CN)6 -3 reduction. Both effects were ascribed to the more hydrophilic nature of the activated
Relativistic Linear Restoring Force
Clark, D.; Franklin, J.; Mann, N.
2012-01-01
We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…
Liu, Feifei; Lan, Fengchong; Chen, Jiqing
2016-07-01
Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a ;segmented; thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed ;segmented; model shows more precise than the ;non-segmented; model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the ;segmented; model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.
Intermolecular and surface forces
Israelachvili, Jacob N
2011-01-01
This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.· starts fr
Monitoring and thermal management.
Lenhardt, Rainer
2003-12-01
Anaesthesia alters normal thermoregulatory control of the body, usually leading to perioperative hypothermia. Hypothermia is associated with a large number of serious complications. To assess perianaesthetic hypothermia, core temperature should be monitored vigorously. Pulmonary artery, tympanic membrane, distal oesophageal or nasopharyngeal temperatures reflect core temperature reliably. Core temperatures can be often estimated with reasonable accuracy using oral, axillary and bladder temperatures, except during extreme thermal perturbations. The body site for measurements should be chosen according to the surgical procedure. Unless hypothermia is specifically indicated, efforts should be made to maintain intraoperative core temperatures above 36 degrees C. Forced air is the most effective, commonly available, non-invasive warming method. Resistive heating electrical blankets and circulating water garment systems are an equally effective alternative. Intravenous fluid warming is also helpful when large volumes are required. In some patients, induction of mild therapeutic hypothermia may become an issue for the future. Recent studies indicate that patients suffering from neurological disease may profit from rapid core cooling.
Thermal emissions and climate change: Cooler options for future energy technology
Cowern, Nick E. B.; Ahn, Chihak
2008-01-01
Global warming arises from 'temperature forcing', a net imbalance between energy fluxes entering and leaving the climate system and arising within it. Humanity introduces temperature forcing through greenhouse gas emissions, agriculture, and thermal emissions from fuel burning. Up to now climate projections, neglecting thermal emissions, typically foresee maximum forcing around the year 2050, followed by a decline. In this paper we show that, if humanity's energy use grows at 1%/year, slower ...
Dynamic thermal environment and thermal comfort.
Zhu, Y; Ouyang, Q; Cao, B; Zhou, X; Yu, J
2016-02-01
Research has shown that a stable thermal environment with tight temperature control cannot bring occupants more thermal comfort. Instead, such an environment will incur higher energy costs and produce greater CO2 emissions. Furthermore, this may lead to the degeneration of occupants' inherent ability to combat thermal stress, thereby weakening thermal adaptability. Measured data from many field investigations have shown that the human body has a higher acceptance to the thermal environment in free-running buildings than to that in air-conditioned buildings with similar average parameters. In naturally ventilated environments, occupants have reported superior thermal comfort votes and much greater thermal comfort temperature ranges compared to air-conditioned environments. This phenomenon is an integral part of the adaptive thermal comfort model. In addition, climate chamber experiments have proven that people prefer natural wind to mechanical wind in warm conditions; in other words, dynamic airflow can provide a superior cooling effect. However, these findings also indicate that significant questions related to thermal comfort remain unanswered. For example, what is the cause of these phenomena? How we can build a comfortable and healthy indoor environment for human beings? This article summarizes a series of research achievements in recent decades, tries to address some of these unanswered questions, and attempts to summarize certain problems for future research. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Two-Arm Flexible Thermal Strap
Urquiza, Eugenio; Vasquez, Cristal; Rodriquez, Jose I.; Leland, Robert S.; VanGorp, Byron E.
2011-01-01
Airborne and space infrared cameras require highly flexible direct cooling of mechanically-sensitive focal planes. A thermal electric cooler is often used together with a thermal strap as a means to transport the thermal energy removed from the infrared detector. While effective, traditional thermal straps are only truly flexible in one direction. In this scenario, a cooling solution must be highly conductive, lightweight, able to operate within a vacuum, and highly flexible in all axes to accommodate adjustment of the focal plane while transmitting minimal force. A two-armed thermal strap using three end pieces and a twisted section offers enhanced elastic movement, significantly beyond the motion permitted by existing thermal straps. This design innovation allows for large elastic displacements in two planes and moderate elasticity in the third plane. By contrast, a more conventional strap of the same conductance offers less flexibility and asymmetrical elasticity. The two-arm configuration reduces the bending moment of inertia for a given conductance by creating the same cross-sectional area for thermal conduction, but with only half the thickness. This reduction in the thickness has a significant effect on the flexibility since there is a cubic relationship between the thickness and the rigidity or bending moment of inertia. The novelty of the technology lies in the mechanical design and manufacturing of the thermal strap. The enhanced flexibility will facilitate cooling of mechanically sensitive components (example: optical focal planes). This development is a significant contribution to the thermal cooling of optics. It is known to be especially important in the thermal control of optical focal planes due to their highly sensitive alignment requirements and mechanical sensitivity; however, many other applications exist including the cooling of gimbal-mounted components.
Engineering thermal conductivity in polymer blends
Rashidi, Vahid; Coyle, Eleanor; Kieffer, John; Pipe, Kevin
Weak inter-chain bonding in polymers is believed to be a bottleneck for both thermal conductivity and mechanical strength. Most polymers have low thermal conductivity (~0.1 W/mK), hindering their performance in applications for which thermal management is critical (e.g., electronics packaging). In this work, we use computational methods to study how hydrogen bonding between polymer chains as well as water content can be used to engineer thermal transport in bulk polymers. We examine how changes in the number of hydrogen bonds, chain elongation, density, and vibrational density of states correlate with changes in thermal conductivity for polymer blends composed of different relative constituent fractions. We also consider the effects of bond strength, tacticity, and polymer chain mass. For certain blend fractions, we observe large increases in thermal conductivity, and we analyze these increases in terms of modifications to chain chemistry (e.g., inter-chain bonding) and chain morphology (e.g., chain alignment and radius of gyration). We observe that increasing the number of hydrogen bonds in the system results in better packing as well as better chain alignment and elongation that contribute to enhanced thermal conductivity. The Air Force Office of Scientific Research, Grant No. FA9550-14-1-0010.
Pereira, Maria J; Amaral, Joao S; Silva, Nuno J O; Amaral, Vitor S
2016-12-01
Determining and acting on thermo-physical properties at the nanoscale is essential for understanding/managing heat distribution in micro/nanostructured materials and miniaturized devices. Adequate thermal nano-characterization techniques are required to address thermal issues compromising device performance. Scanning thermal microscopy (SThM) is a probing and acting technique based on atomic force microscopy using a nano-probe designed to act as a thermometer and resistive heater, achieving high spatial resolution. Enabling direct observation and mapping of thermal properties such as thermal conductivity, SThM is becoming a powerful tool with a critical role in several fields, from material science to device thermal management. We present an overview of the different thermal probes, followed by the contribution of SThM in three currently significant research topics. First, in thermal conductivity contrast studies of graphene monolayers deposited on different substrates, SThM proves itself a reliable technique to clarify the intriguing thermal properties of graphene, which is considered an important contributor to improve the performance of downscaled devices and materials. Second, SThM's ability to perform sub-surface imaging is highlighted by thermal conductivity contrast analysis of polymeric composites. Finally, an approach to induce and study local structural transitions in ferromagnetic shape memory alloy Ni-Mn-Ga thin films using localized nano-thermal analysis is presented.
El-Kirat-Chatel, Sofiane; Beaussart, Audrey; Vincent, Stéphane P.; Abellán Flos, Marta; Hols, Pascal; Lipke, Peter N.; Dufrêne, Yves F.
2015-01-01
In the baker's yeast Saccharomyces cerevisiae, cell-cell adhesion (``flocculation'') is conferred by a family of lectin-like proteins known as the flocculin (Flo) proteins. Knowledge of the adhesive and mechanical properties of flocculins is important for understanding the mechanisms of yeast adhesion, and may help controlling yeast behaviour in biotechnology. We use single-molecule and single-cell atomic force microscopy (AFM) to explore the nanoscale forces engaged in yeast flocculation, focusing on the role of Flo1 as a prototype of flocculins. Using AFM tips labelled with mannose, we detect single flocculins on Flo1-expressing cells, showing they are widely exposed on the cell surface. When subjected to force, individual Flo1 proteins display two distinct force responses, i.e. weak lectin binding forces and strong unfolding forces reflecting the force-induced extension of hydrophobic tandem repeats. We demonstrate that cell-cell adhesion bonds also involve multiple weak lectin interactions together with strong unfolding forces, both associated with Flo1 molecules. Single-molecule and single-cell data correlate with microscale cell adhesion behaviour, suggesting strongly that Flo1 mechanics is critical for yeast flocculation. These results favour a model in which not only weak lectin-sugar interactions are involved in yeast flocculation but also strong hydrophobic interactions resulting from protein unfolding.
``Force-free'' electrophoresis?
Yariv, Ehud
2006-03-01
When a colloidal particle is exposed to an externally applied electric field, it acquires an electrophoretic velocity, resulting from fluid slip occurring across the Debye screening layer. When the field is uniformly applied, it is usually assumed that the net neutrality of the combined particle-layer system implies that the net electric force acting on it must vanish. This assumption of "force-free" phoretic motion has been employed extensively to describe electrophoresis in both unbounded and bounded fluid domains [J. L. Anderson, Annu. Rev. Fluid Mech. 21, 61 (1989)]. A careful inspection reveals here that this intuitive premise may fail when the fluid domain is bounded, in which case a nonzero electric force (resembling dielectrophoretic forces in nonuniformly applied fields) may actually exist. Such forces (represented via surface integrals of Maxwell stresses) result in particle motion above and beyond the one driven by the phoretic slip mechanism. A positive demonstration for the existence of a such a force is provided for a standard sphere-wall configuration, where the applied field acts parallel to the wall. In that scenario, particle motion consists of a (familiar) slip-driven contribution parallel to the wall, together with a superimposed force-driven drift away from the wall. An analogy with pressure forces occurring at incompressible and inviscid potential flows is presented.
DEFF Research Database (Denmark)
Bialynicki-Birula, I; Cirone, M.A.; Dahl, Jens Peder
2002-01-01
We present Heisenberg's equation of motion for the radial variable of a free non-relativistic particle in D dimensions. The resulting radial force consists of three contributions: (i) the quantum fictitious force which is either attractive or repulsive depending on the number of dimensions, (ii) ...
Multidomain proteins under force.
Valle-Orero, Jessica; Rivas-Pardo, Jaime Andrés; Popa, Ionel
2017-04-28
Advancements in single-molecule force spectroscopy techniques such as atomic force microscopy and magnetic tweezers allow investigation of how domain folding under force can play a physiological role. Combining these techniques with protein engineering and HaloTag covalent attachment, we investigate similarities and differences between four model proteins: I10 and I91-two immunoglobulin-like domains from the muscle protein titin, and two α + β fold proteins-ubiquitin and protein L. These proteins show a different mechanical response and have unique extensions under force. Remarkably, when normalized to their contour length, the size of the unfolding and refolding steps as a function of force reduces to a single master curve. This curve can be described using standard models of polymer elasticity, explaining the entropic nature of the measured steps. We further validate our measurements with a simple energy landscape model, which combines protein folding with polymer physics and accounts for the complex nature of tandem domains under force. This model can become a useful tool to help in deciphering the complexity of multidomain proteins operating under force.
Multidomain proteins under force
Valle-Orero, Jessica; Andrés Rivas-Pardo, Jaime; Popa, Ionel
2017-04-01
Advancements in single-molecule force spectroscopy techniques such as atomic force microscopy and magnetic tweezers allow investigation of how domain folding under force can play a physiological role. Combining these techniques with protein engineering and HaloTag covalent attachment, we investigate similarities and differences between four model proteins: I10 and I91—two immunoglobulin-like domains from the muscle protein titin, and two α + β fold proteins—ubiquitin and protein L. These proteins show a different mechanical response and have unique extensions under force. Remarkably, when normalized to their contour length, the size of the unfolding and refolding steps as a function of force reduces to a single master curve. This curve can be described using standard models of polymer elasticity, explaining the entropic nature of the measured steps. We further validate our measurements with a simple energy landscape model, which combines protein folding with polymer physics and accounts for the complex nature of tandem domains under force. This model can become a useful tool to help in deciphering the complexity of multidomain proteins operating under force.
Energy Technology Data Exchange (ETDEWEB)
Bell, R.E.; Hartley, D.S.III; Packard, S.L.
1999-05-01
This report documents refined requirements for tools to aid the process of force design in Operations Other Than War (OOTWs). It recommends actions for the creation of one tool and work on other tools relating to mission planning. It also identifies the governmental agencies and commands with interests in each tool, from whom should come the user advisory groups overseeing the respective tool development activities. The understanding of OOTWs and their analytical support requirements has matured to the point where action can be taken in three areas: force design, collaborative analysis, and impact analysis. While the nature of the action and the length of time before complete results can be expected depends on the area, in each case the action should begin immediately. Force design for OOTWs is not a technically difficult process. Like force design for combat operations, it is a process of matching the capabilities of forces against the specified and implied tasks of the operation, considering the constraints of logistics, transport and force availabilities. However, there is a critical difference that restricts the usefulness of combat force design tools for OOTWs: the combat tools are built to infer non-combat capability requirements from combat capability requirements and cannot reverse the direction of the inference, as is required for OOTWs. Recently, OOTWs have played a larger role in force assessment, system effectiveness and tradeoff analysis, and concept and doctrine development and analysis. In the first Quadrennial Defense Review (QDR), each of the Services created its own OOTW force design tool. Unfortunately, the tools address different parts of the problem and do not coordinate the use of competing capabilities. These tools satisfied the immediate requirements of the QDR, but do not provide a long-term cost-effective solution.
Solar Thermal Energy Technology
Energy Technology Data Exchange (ETDEWEB)
Cason, D.L.; Pitsenbarger, J. [eds.
1996-02-01
Solar Thermal Energy Technology (PST) announces on a bimonthly basis the current worldwide research and development information that would expand the technology base required for the advancement of solar thermal systems as a significant energy resource.
Ouellette Thermal Test Facility
Federal Laboratory Consortium — The Thermal Test Facility is a joint Army/Navy state-of-the-art facility (8,100 ft2) that was designed to:Evaluate and characterize the effect of flame and thermal...
Vekstein, G.
2017-10-01
This is a tutorial-style selective review explaining basic concepts of forced magnetic reconnection. It is based on a celebrated model of forced reconnection suggested by J. B. Taylor. The standard magnetohydrodynamic (MHD) theory of this process has been pioneered by Hahm & Kulsrud (Phys. Fluids, vol. 28, 1985, p. 2412). Here we also discuss several more recent developments related to this problem. These include energetics of forced reconnection, its Hall-mediated regime, and nonlinear effects with the associated onset of the secondary tearing (plasmoid) instability.
Comparison of frictional forces on graphene and graphite
Energy Technology Data Exchange (ETDEWEB)
Lee, Hyunsoo; Lee, Naesung; Seo, Yongho [Faculty of Nanotechnology and Advanced Material Engineering and Institute of Fundamental Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Eom, Jonghwa [Department of Physics and Institute of Fundamental Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lee, SangWook, E-mail: yseo@sejong.ac.k [Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul 143-107 (Korea, Republic of)
2009-08-12
We report on the frictional force between an SiN tip and graphene/graphite surfaces using lateral force microscopy. The cantilever we have used was made of an SiN membrane and has a low stiffness of 0.006 N m{sup -1}. We prepared graphene flakes on a Si wafer covered with silicon oxides. The frictional force on graphene was smaller than that on the Si oxide and larger than that on graphite (multilayer of graphene). Force spectroscopy was also employed to study the van der Waals force between the graphene and the tip. Judging that the van der Waals force was also in graphite-graphene-silicon oxide order, the friction is suspected to be related to the van der Waals interactions. As the normal force acting on the surface was much weaker than the attractive force, such as the van der Waals force, the friction was independent of the normal force strength. The velocity dependency of the friction showed a logarithmic behavior which was attributed to the thermally activated stick-slip effect.
Comparison of frictional forces on graphene and graphite
Lee, Hyunsoo; Lee, Naesung; Seo, Yongho; Eom, Jonghwa; Lee, Sang Wook
2009-08-01
We report on the frictional force between an SiN tip and graphene/graphite surfaces using lateral force microscopy. The cantilever we have used was made of an SiN membrane and has a low stiffness of 0.006 N m-1. We prepared graphene flakes on a Si wafer covered with silicon oxides. The frictional force on graphene was smaller than that on the Si oxide and larger than that on graphite (multilayer of graphene). Force spectroscopy was also employed to study the van der Waals force between the graphene and the tip. Judging that the van der Waals force was also in graphite-graphene-silicon oxide order, the friction is suspected to be related to the van der Waals interactions. As the normal force acting on the surface was much weaker than the attractive force, such as the van der Waals force, the friction was independent of the normal force strength. The velocity dependency of the friction showed a logarithmic behavior which was attributed to the thermally activated stick-slip effect.
Electric Motor Thermal Management
Energy Technology Data Exchange (ETDEWEB)
Bennion, Kevin S [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-09-01
Thermal management enables more efficient and cost-effective motors. This Annual Merit Review presentation describes the technical accomplishments and progress in electric motor thermal management R&D over the last year. This project supports a broad industry demand for data, analysis methods, and experimental techniques to improve and better understand motor thermal management.
Thermal Performance Benchmarking (Presentation)
Energy Technology Data Exchange (ETDEWEB)
Moreno, G.
2014-11-01
This project will benchmark the thermal characteristics of automotive power electronics and electric motor thermal management systems. Recent vehicle systems will be benchmarked to establish baseline metrics, evaluate advantages and disadvantages of different thermal management systems, and identify areas of improvement to advance the state-of-the-art.
Federal Laboratory Consortium — MIT Lincoln Laboratory occupies 75 acres (20 acres of which are MIT property) on the eastern perimeter of Hanscom Air Force Base, which is at the nexus of Lexington,...
DEFF Research Database (Denmark)
Pedersen, Preben Terndrup
1996-01-01
The purpose of these notes is to present a basis for the estimation of the internal collision forces between conventinal merchant vessels and large volume offshore structures in the form of gravity-supported offshore installations and bridges crossing international shipping routes.The main emphasis...... is on the presentation of impact loads on fixed offshore structures due to bow collisions. The crushing forces are determined as functions of vessels size, vessels speed, bow profile, collision angles and eccentric impacts....
Petrache, Horia I.
2012-01-01
This manuscript is written for students in introductory physics classes to address some of the common difficulties and misconceptions of the normal force, especially the relationship between normal and friction forces. Accordingly, it is intentionally informal and conversational in tone to teach students how to build an intuition to complement mathematical formalism. This is accomplished by beginning with common and everyday experience and then guiding students toward two realizations: (i) Th...
Air Force Leadership Diversity
2017-04-06
general officer statistics bear out that the group is 94% white and only 7% female as opposed to the overall Air Force population that is 72% white and 20...programmed, over time, to think about skin color and gender. The Air Force is trying to change this programming by adding other words to describe...Officer Corps, those officers in the ranks of O-7 through O-10 indicates that cohort of officers is 94% white and only 7% female. Since officer
Thermal Transport in Supported Graphene: Substrate Effects on Collective Excitations
France-Lanord, Arthur; Soukiassian, Patrick; Glattli, Christian; Wimmer, Erich
2017-03-01
A detailed computational analysis of thermal transport in supported graphene reveals the possibility of tuning its thermal conductivity by targeted chemical modifications of the substrate's surface. Based on classical molecular dynamics with an accurate charge-optimized bond-order force field and a time-domain normal-mode analysis, our approach allows us to distinguish collective from single-phonon excitations. The computations reveal a disproportional reduction of the thermal conductivity, due to the two different excitations, when graphene interacts with a substrate. Deposition of graphene on a bare silica surface leads to a dramatic reduction of the thermal conductivity and a change in the heat transport mechanism. Remarkably, partial hydroxylation of the silica surface almost doubles the thermal conductivity of the collective excitations. Thus, specific surface terminations allow for control of the thermal conductivity of graphene.
Bonde-Petersen, F
1975-01-01
The force platform consists of a sandwhich of steel, Rockwool and concrete plates about 900 X 700 mm in surface. Four steel rings were bolted to the under side of the steel plate in each corner. Each steel ring was furnished with only one strain gauge, two of which were placed on the outer- respectively on the inner side of each ring. The four strain gauges were connected to a measuring bridge. Before mounting the rings on the steel plate, the sensitivity to pressure of each ring was adjusted in such a way that they were all similar. Because of this the platform responded with a signal which was independent of where a pressure was applied within the surface of the platform. The platform showed a rectilinear response for static forces up to 500 kp with a stable zero value. In response to dynamic forces the platform showed a resononance frequency of about 50 Hz, with a damping factor of 0.15. Calibration of dynamic forces was carried out by calculation of the forces during a vertical jump compared with what would be expected from the time of flight also registered by the platform-measuring-bridge-ink-writer-set-up. The time of flight was significantly higher (11%) than exected from the time-force relations beforetake-off. This was esplained partly by the relatively low damping factor in the system, partly by the subjects not extending their knees at landing on the platform.
Carvalho, Filomena A; Martins, Ivo C; Santos, Nuno C
2013-03-01
Atomic force microscopy (AFM) applied to biological systems can, besides generating high-quality and well-resolved images, be employed to study protein folding via AFM-based force spectroscopy. This approach allowed remarkable advances in the measurement of inter- and intramolecular interaction forces with piconewton resolution. The detection of specific interaction forces between molecules based on the AFM sensitivity and the manipulation of individual molecules greatly advanced the understanding of intra-protein and protein-ligand interactions. Apart from the academic interest in the resolution of basic scientific questions, this technique has also key importance on the clarification of several biological questions of immediate biomedical relevance. Force spectroscopy is an especially appropriate technique for "mechanical proteins" that can provide crucial information on single protein molecules and/or domains. Importantly, it also has the potential of combining in a single experiment spatial and kinetic measurements. Here, the main principles of this methodology are described, after which the ability to measure interactions at the single-molecule level is discussed, in the context of relevant protein-folding examples. We intend to demonstrate the potential of AFM-based force spectroscopy in the study of protein folding, especially since this technique is able to circumvent some of the difficulties typically encountered in classical thermal/chemical denaturation studies. Copyright © 2012 Elsevier Inc. All rights reserved.
Energy, Power and Thermal Research Overview
2010-09-01
Watt power generation • Magnetic materials • Thermoelectric power generation • Mega-Watt power generation ‒ Superconducting and conventional...FeCo) • Multilayered structures for thermoelectric power generation ‒ Oxide materials ‒ Promote phonon scattering to inhibit thermal flow and increase...and space force. 4 AFRL’s Core Areas of Expertise Space Vehicles Materials Directed Energy Munitions Propulsion Human Effectiveness Information
Solar Thermal Propulsion for Microsatellite Manoeuvring
2004-09-01
kg), acetylene (614 kJ/kg), and xenon (96.3 kJ/kg) [Lide, 1995][ Air Liquide , 2004]. Solar Thermal Propulsion for Microsatellite Manoeuvring 197...Archives, Kirtland Air Force Base, New Mexico, 2004 [accessed 6 May 2004]. [ Air Liquide , 2004] http://www.airliquide.com/en/business/products/gases...gasdata/index.asp, “Gases,” Air Liquide , Paris, France, March 2004 [accessed 26 March 2004]. [Amass, 2000] http://www.lanternroom.com/misc
2014-03-27
reflectivity than water and because of snow and ice, greater latitudes have greater reflectivity. Albedo also tends to increase due to cloud cover and...15 Albedo Radiation ..................................................................................................... 16 Earth-Emitted Infrared...derivative control coefficient m mass, kg P pressure, Torr q heat rate, W combined direct and albedo solar heat rate absorbed by a spacecraft, W
Thermal Management and Thermal Protection Systems
Hasnain, Aqib
2016-01-01
During my internship in the Thermal Design Branch (ES3), I contributed to two main projects: i) novel passive thermal management system for future human exploration, ii) AVCOAT undercut thermal analysis. i) As NASA prepares to further expand human and robotic presence in space, it is well known that spacecraft architectures will be challenged with unprecedented thermal environments. Future exploration activities will have the need of thermal management systems that can provide higher reliability, mass and power reduction and increased performance. In an effort to start addressing the current technical gaps the NASA Johnson Space Center Passive Thermal Discipline has engaged in technology development activities. One of these activities was done through an in-house Passive Thermal Management System (PTMS) design for a lunar lander. The proposed PTMS, functional in both microgravity and gravity environments, consists of three main components: a heat spreader, a novel hybrid wick Variable Conductance Heat Pipe (VCHP), and a radiator. The aim of this PTMS is to keep electronics on a vehicle within their temperature limits (0 and 50 C for the current design) during all mission phases including multiple lunar day/night cycles. The VCHP was tested to verify its thermal performance. I created a thermal math model using Thermal Desktop (TD) and analyzed it to predict the PTMS performance. After testing, the test data provided a means to correlate the thermal math model. This correlation took into account conduction and convection heat transfer, representing the actual benchtop test. Since this PTMS is proposed for space missions, a vacuum test will be taking place to provide confidence that the system is functional in space environments. Therefore, the model was modified to include a vacuum chamber with a liquid nitrogen shroud while taking into account conduction and radiation heat transfer. Infrared Lamps were modelled and introduced into the model to simulate the sun
Joulain, Karl; Drevillon, Jérémie; Ezzahri, Younès; Ordonez-Miranda, Jose
2016-05-20
We demonstrate that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nanosystems.
Thermal Ablation Modeling for Silicate Materials
Chen, Yih-Kanq
2016-01-01
A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.
Confusion around the tidal force and the centrifugal force
Matsuda, Takuya; Boffin, Henri M J
2015-01-01
We discuss the tidal force, whose notion is sometimes misunderstood in the public domain literature. We discuss the tidal force exerted by a secondary point mass on an extended primary body such as the Earth. The tidal force arises because the gravitational force exerted on the extended body by the secondary mass is not uniform across the primary. In the derivation of the tidal force, the non-uniformity of the gravity is essential, and inertial forces such as the centrifugal force are not needed. Nevertheless, it is often asserted that the tidal force can be explained by the centrifugal force. If we literally take into account the centrifugal force, it would mislead us. We therefore also discuss the proper treatment of the centrifugal force.
A dark mode in scanning thermal microscopy
Ramiandrisoa, Liana; Allard, Alexandre; Joumani, Youssef; Hay, Bruno; Gomés, Séverine
2017-12-01
The need for high lateral spatial resolution in thermal science using Scanning Thermal Microscopy (SThM) has pushed researchers to look for more and more tiny probes. SThM probes have consequently become more and more sensitive to the size effects that occur within the probe, the sample, and their interaction. Reducing the tip furthermore induces very small heat flux exchanged between the probe and the sample. The measurement of this flux, which is exploited to characterize the sample thermal properties, requires then an accurate thermal management of the probe-sample system and to reduce any phenomenon parasitic to this system. Classical experimental methodologies must then be constantly questioned to hope for relevant and interpretable results. In this paper, we demonstrate and estimate the influence of the laser of the optical force detection system used in the common SThM setup that is based on atomic-force microscopy equipment on SThM measurements. We highlight the bias induced by the overheating due to the laser illumination on the measurements performed by thermoresistive probes (palladium probe from Kelvin Nanotechnology). To face this issue, we propose a new experimental procedure based on a metrological approach of the measurement: a SThM "dark mode." The comparison with the classical procedure using the laser shows that errors between 14% and 37% can be reached on the experimental data exploited to determine the heat flux transferred from the hot probe to the sample.
Radiative forcing by contrails
Directory of Open Access Journals (Sweden)
R. Meerkötter
1999-08-01
Full Text Available A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres. Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere, a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 Wm-2 daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude. The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.Key words. Atmospheric composition and structure (aerosols and particles · Meteorology and atmospheric dynamics (climatology · radiative processes
Radiative forcing by contrails
Directory of Open Access Journals (Sweden)
R. Meerkötter
Full Text Available A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres. Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere, a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 Wm^{-2} daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude. The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.
Key words. Atmospheric composition and structure (aerosols and particles · Meteorology and atmospheric dynamics (climatology · radiative processes
Radiative forcing by contrails
Energy Technology Data Exchange (ETDEWEB)
Meerkoetter, R.; Schumann, U. [DLR Oberpfaffenhofen, Wessling (Germany). Inst. fuer Phys. der Atmosphaere; Doelling, D.R.; Minnis, P. [National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center; Nakajima, T.; Tsushima, Y. [Tokyo Univ. (Japan). Center for Climate System Research
1999-08-01
A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, midlatitude, and subarctic summer and winter atmospheres. Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere, a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 Wm{sup -2} daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude. The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover. (orig.) 78 refs.
Radiative Forcing of Climate Change
Energy Technology Data Exchange (ETDEWEB)
Ramaswamy, V.; Boucher, Olivier; Haigh, J.; Hauglustaine, D.; Haywood, J.; Myhre, G.; Nakajima, Takahito; Shi, Guangyu; Solomon, S.; Betts, Robert E.; Charlson, R.; Chuang, C. C.; Daniel, J. S.; Del Genio, Anthony D.; Feichter, J.; Fuglestvedt, J.; Forster, P. M.; Ghan, Steven J.; Jones, A.; Kiehl, J. T.; Koch, D.; Land, C.; Lean, J.; Lohmann, Ulrike; Minschwaner, K.; Penner, Joyce E.; Roberts, D. L.; Rodhe, H.; Roelofs, G.-J.; Rotstayn, Leon D.; Schneider, T. L.; Schumann, U.; Schwartz, Stephen E.; Schwartzkopf, M. D.; Shine, K. P.; Smith, Steven J.; Stevenson, D. S.; Stordal, F.; Tegen, I.; van Dorland, R.; Zhang, Y.; Srinivasan, J.; Joos, Fortunat
2001-10-01
Chapter 6 of the IPCC Third Assessment Report Climate Change 2001: The Scientific Basis. Sections include: Executive Summary 6.1 Radiative Forcing 6.2 Forcing-Response Relationship 6.3 Well-Mixed Greenhouse Gases 6.4 Stratospheric Ozone 6.5 Radiative Forcing By Tropospheric Ozone 6.6 Indirect Forcings due to Chemistry 6.7 The Direct Radiative Forcing of Tropospheric Aerosols 6.8 The Indirect Radiative Forcing of Tropospheric Aerosols 6.9 Stratospheric Aerosols 6.10 Land-use Change (Surface Albedo Effect) 6.11 Solar Forcing of Climate 6.12 Global Warming Potentials hydrocarbons 6.13 Global Mean Radiative Forcings 6.14 The Geographical Distribution of the Radiative Forcings 6.15 Time Evolution of Radiative Forcings Appendix 6.1 Elements of Radiative Forcing Concept References.
DEFF Research Database (Denmark)
Lindemann, J.; Damkilde, Lars
2009-01-01
ForcePAD is a 2-dimensional finite element application that started as a concept application for finite element modeling. Over the course of 10 years the application has been evolved into an application that is used extensively in both an educational setting as well as a tool for design and engin......ForcePAD is a 2-dimensional finite element application that started as a concept application for finite element modeling. Over the course of 10 years the application has been evolved into an application that is used extensively in both an educational setting as well as a tool for design...... and engineering. In the latest version of ForcePAD an optimization module was added to enable to take advantage of topology optimization in the design process....
DEFF Research Database (Denmark)
Maffiuletti, Nicola A; Aagaard, Per; Blazevich, Anthony J
2016-01-01
The evaluation of rate of force development during rapid contractions has recently become quite popular for characterising explosive strength of athletes, elderly individuals and patients. The main aims of this narrative review are to describe the neuromuscular determinants of rate of force...... development and to discuss various methodological considerations inherent to its evaluation for research and clinical purposes. Rate of force development (1) seems to be mainly determined by the capacity to produce maximal voluntary activation in the early phase of an explosive contraction (first 50-75 ms......), particularly as a result of increased motor unit discharge rate; (2) can be improved by both explosive-type and heavy-resistance strength training in different subject populations, mainly through an improvement in rapid muscle activation; (3) is quite difficult to evaluate in a valid and reliable way...
DEFF Research Database (Denmark)
Steensen, Elmer Fly; Sanchez, Ron
2008-01-01
literature. Based on an extensive review of relevant theory and empirical work in strategic decision-making, organizational change theory, cognitive and social psychology, and strategy processes, seven kinds of ''forces'' - rational, imposed, teleological, learning, political, heuristic, and social......This chapter proposes that organizational strategy formation should be characterized theoretically as a process that is subject to several interacting forces, rather than represented by separate discrete decisionmodels or theoretic perspectives, as is commonly done in the strategic management...... - are identified as interacting in and having significant influence on the strategy formation process. It is further argued that by applying a holistic ''forces-view'' of the significant and interacting influences on strategy formation, we can better understand the dynamics and challenges in managing the process...
Electrochemical force microscopy
Kalinin, Sergei V.; Jesse, Stephen; Collins, Liam F.; Rodriguez, Brian J.
2017-01-10
A system and method for electrochemical force microscopy are provided. The system and method are based on a multidimensional detection scheme that is sensitive to forces experienced by a biased electrode in a solution. The multidimensional approach allows separation of fast processes, such as double layer charging, and charge relaxation, and slow processes, such as diffusion and faradaic reactions, as well as capturing the bias dependence of the response. The time-resolved and bias measurements can also allow probing both linear (small bias range) and non-linear (large bias range) electrochemical regimes and potentially the de-convolution of charge dynamics and diffusion processes from steric effects and electrochemical reactivity.
DEFF Research Database (Denmark)
Maffiuletti, Nicola A; Aagaard, Per; Blazevich, Anthony J
2016-01-01
), particularly as a result of increased motor unit discharge rate; (2) can be improved by both explosive-type and heavy-resistance strength training in different subject populations, mainly through an improvement in rapid muscle activation; (3) is quite difficult to evaluate in a valid and reliable way......The evaluation of rate of force development during rapid contractions has recently become quite popular for characterising explosive strength of athletes, elderly individuals and patients. The main aims of this narrative review are to describe the neuromuscular determinants of rate of force...
Multiphase forces on bend structures – overview of large scale 6”experiments
Belfroid, S.P.C.; Nennie, E.D.; Wijhe, A. van; Pereboom, H.P.; Lewis, M.
2016-01-01
Piping structures are generally subjected to high dynamic loading due to multiphase forces. In particular subsea structures are very vulnerable as large flexibility is required to cope for instance with thermal stresses. The forces due to multiphase flow are characterized by a broadband spectrum
High resolution magnetic force microscopy using focused ion beam modified tips
Phillips, G.N.; Siekman, Martin Herman; Abelmann, Leon; Lodder, J.C.
2002-01-01
Atomic force microscope tips coated by the thermal evaporation of a magnetic 30 nm thick Co film have been modified by focused ion beam milling with Ga+ ions to produce tips suitable for magnetic force microscopy. Such tips possess a planar magnetic element with high magnetic shape anisotropy, an
Air Force Security Forces Professionalism: Useful Insights for Leaders
2013-03-27
REPORT DOCUMENTATION PAGE Air Force Security Forces Professionalism· tns19hts for Leaders Secrest Justin D .. Major, USAF USMC Command and Staff...corporateness characteristics as theorized by Samuel P. Huntingon, yields helpful insights for current and future-generation leaders . Huntington theorizes...theory, this analysis examines professoonalism in Air Force Security Forces. Security Forces expertise developed as career field leaders constantly
SPONTANEOUS FRACTURE IN THERMALLY STRENGTHENED GLASS - A REVIEW AND OUTLOOK
Stefan Karlsson
2017-01-01
Thermal strengthening of glass is common for many different purposes including architecture, automotive, glasses for solar energy, tableware and occasionally also containers. It is an easy and relatively cheap method to make glasses stronger, however, with an Achilles heel that it can spontaneously fracture without the slightest applied external force. Though, fracture due to applied external force is the most common case, spontaneous fracture is rare. The current paper reviews the literature...
Directory of Open Access Journals (Sweden)
Marek Štumper
2015-10-01
Full Text Available This article focuses on the use of thermal imaging in aviation. In the never ending pursuit of lower costs, the Thermal Imaging offers shorter inspection times thanks to its application in aircraft inspections and can reduce the number of costly goarounds using the Enhanced Vision System, which also increases safety in one of the most dangerous parts of flight. Thermal Imaging also offers solutions for Airport Perimeter Security and it can be used for construction of ground surveillance system.
Lin, S T; Lin, Y Y; Wang, T D; Huang, Y C
2010-01-18
We report a mid-infrared, CW singly resonant optical parametric oscillator (OPO) with a thermally induced waveguide in its gain crystal. We measured a numerical aperture of 0.0062 for the waveguide at 80-W intracavity power at 3.2 microm. This thermal-guiding effect benefits to the stable operation of an OPO and improves the parametric conversion efficiency by more than a factor of two when compared with that without thermal guiding.
Thermal Hyperbolic Metamaterials
Guo, Yu; Jacob, Zubin
2013-01-01
We explore the near-field radiative thermal energy transfer properties of hyperbolic metamaterials. The presence of unique electromagnetic states in a broad bandwidth leads to super-planckian thermal energy transfer between metamaterials separated by a nano-gap. We consider practical phonon-polaritonic metamaterials for thermal engineering in the mid-infrared range and show that the effect exists in spite of the losses, absorption and finite unit cell size. For thermophotovoltaic energy conve...
Peabody, Hume L.
2017-01-01
This presentation is meant to be an overview of the model building process It is based on typical techniques (Monte Carlo Ray Tracing for radiation exchange, Lumped Parameter, Finite Difference for thermal solution) used by the aerospace industry This is not intended to be a "How to Use ThermalDesktop" course. It is intended to be a "How to Build Thermal Models" course and the techniques will be demonstrated using the capabilities of ThermalDesktop (TD). Other codes may or may not have similar capabilities. The General Model Building Process can be broken into four top level steps: 1. Build Model; 2. Check Model; 3. Execute Model; 4. Verify Results.
Thermal microactuator dimension analysis
Azman, N. D.; Ong, N. R.; Aziz, M. H. A.; Alcain, J. B.; Haimi, W. M. W. N.; Sauli, Z.
2017-09-01
The focus of this study was to analyse the stress and thermal flow of thermal microactuator with different type of materials and parameter using COMSOL Multiphysics software. Simulations were conducted on the existing thermal actuator and integrated it to be more efficient, low cost and low power consumption. In this simulation, the U-shaped actuator was designed and five different materials of the microactuator were studied. The result showed that Si Polycrystalline was the most suitable material used to produce thermal actuator for commercialization.
Thermal Performance Benchmarking
Energy Technology Data Exchange (ETDEWEB)
Feng, Xuhui; Moreno, Gilbert; Bennion, Kevin
2016-06-07
The goal for this project is to thoroughly characterize the thermal performance of state-of-the-art (SOA) in-production automotive power electronics and electric motor thermal management systems. Information obtained from these studies will be used to: evaluate advantages and disadvantages of different thermal management strategies; establish baseline metrics for the thermal management systems; identify methods of improvement to advance the SOA; increase the publicly available information related to automotive traction-drive thermal management systems; help guide future electric drive technologies (EDT) research and development (R&D) efforts. The thermal performance results combined with component efficiency and heat generation information obtained by Oak Ridge National Laboratory (ORNL) may then be used to determine the operating temperatures for the EDT components under drive-cycle conditions. In FY16, the 2012 Nissan LEAF power electronics and 2014 Honda Accord Hybrid power electronics thermal management system were characterized. Comparison of the two power electronics thermal management systems was also conducted to provide insight into the various cooling strategies to understand the current SOA in thermal management for automotive power electronics and electric motors.
Boley, Bruno A
1997-01-01
Highly regarded text presents detailed discussion of fundamental aspects of theory, background, problems with detailed solutions. Basics of thermoelasticity, heat transfer theory, thermal stress analysis, more. 1985 edition.
Manipulation of double-stranded DNA melting by force
Singh, Amit Raj; Granek, Rony
2017-09-01
By integrating elasticity—as described by the Gaussian network model—with bond binding energies that distinguish between different base-pair identities and stacking configurations, we study the force induced melting of a double-stranded DNA (dsDNA). Our approach is a generalization of our previous study of thermal dsDNA denaturation [J. Chem. Phys. 145, 144101 (2016), 10.1063/1.4964285] to that induced by force at finite temperatures. It allows us to obtain semimicroscopic information about the opening of the chain, such as whether the dsDNA opens from one of the ends or from the interior, forming an internal bubble. We study different types of force manipulation: (i) "end unzipping," with force acting at a single end base pair perpendicular to the helix, (ii) "midunzipping," with force acting at a middle base pair perpendicular to the helix, and (iii) "end shearing," where the force acts at opposite ends along the helix. By monitoring the free-energy landscape and probability distribution of intermediate denaturation states, we show that different dominant intermediate states are stabilized depending on the type of force manipulation used. In particular, the bubble state of the sequence L60B36, which we have previously found to be a stable state during thermal denaturation, is absent for end unzipping and end shearing, whereas very similar bubbles are stabilized by midunzipping, or when the force location is near the middle of the chain. Ours results offer a simple tool for stabilizing bubbles and loops using force manipulations at different temperatures, and may implicate on the mechanism in which DNA enzymes or motors open regions of the chain.
DEFF Research Database (Denmark)
Engell-Nørregård, Morten Pol; Erleben, Kenny
We present a method for simulating the active contraction of deformable models, usable for interactive animation of soft deformable objects. We present a novel physical principle as the governing equation for the coupling between the low dimensional 1D activation force model and the higher...
DEFF Research Database (Denmark)
Brüggemann, Dagmar Adeline; Risbo, Jens; Pierzynowski, Stefan G.
2008-01-01
Muscle contraction studies often focus solely on myofibres and the proteins known to be involved in the processes of sarcomere shortening and cross-bridge cycling, but skeletal muscle also comprises a very elaborate ancillary network of capillaries, which not only play a vital role in terms of nu...... contributor to force transfer within muscular tissue....
Forced Displacement and Refugee
African Journals Online (AJOL)
Rutinwa: Forced Displacement and Refugee Rights in the Great Lakes 1 3 with the new problems associated with refugees, such as those outlined above. An effective system for refugee protection must be holistic and address the refugee problem at the levels of pre- vention, response and solution. At the level of prevention, ...
Geddes, John B.; Black, Kelly
2008-01-01
We examine an experimental apparatus that is used to motivate the connections between the basic properties of vectors, potential functions, systems of nonlinear equations, and Newton's method for nonlinear systems of equations. The apparatus is an adaptation of a force table where we remove the center-pin and allow the center-ring to move freely.…
Perrin, Graham
2012-01-01
When providing training to teachers struggling with the concept of forces, the author encourages them to start with something within the experience of the children they are teaching. For example, show them photographs taken on windy days, such as that of a tree, and ask them to explain what is happening. This encourages the children to focus on…
Mattei, John P.; Buck, Peter A.; Williams, Michael D.
1990-01-01
Latching mechanism simultaneously applies force in two perpendicular directions to install or remove electronic-equipment modules. Used to simplify installation and removal of modular equipment where movement restricted by protective clothing as in hazardous environments or where installation and removal to be performed by robots or remote manipulators. Concept adaptable to hydraulic, pneumatic, and mechanical systems.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 7. Atomic Force Microscopy - A Tool to Unveil the Mystery of Biological Systems ... Transcription and Disease Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 ...
Abelmann, Leon
Principle of MFM In magnetic force microscopy (MFM), the magnetic stray field above a very flat specimen, or sample, is detected by placing a small magnetic element, the tip, mounted on a cantilever spring very close to the surface of the sample (Figure 1). Typical dimensions are a cantilever length
Eliminating thermal violin spikes from LIGO noise
Energy Technology Data Exchange (ETDEWEB)
Santamore, D. H.; Levin, Yuri
2001-08-15
We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally induced motion of a small portion of (a 'point' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than {approx}2 x 10{sup -13} cm/Hz. This sensitivity is two orders of magnitude greater than that of currently available sensors.
Thermal Impulse Sensors for use in Explosions
Eilers, Hergen; Gunawidjaja, Ray; Anderson, Benjamin
2017-06-01
We have developed temperature and thermal impulse (temperature and duration) sensors for use in explosive fireballs. These sensors are seeded into an explosive fireball and record temperature and duration via morphological phase changes that are optically probed. The thermal impulse sensors include two sensor materials with different phase transition kinetics, and may include a reference material which does not undergo temperature-induced phase changes, and can aid in the optical analysis. Analyzing the sensor materials allows us to determine heating temperature and heating duration of an explosion. The temperature sensors and thermal impulse sensors were recently tested and showed promising results. However, we found that the different components of the thermal impulse sensors tend to get separated during the explosion. We are now evaluating several approaches for redesigning our thermal impulse sensors so that the components remain together during the explosion. These approaches include a core/shell assembly, crosslinking, and co-synthesis. The integrity of the chemically bonded components is evaluated by subjecting the sensors to dispersing forces, while temperature-dependent phase changes of these sensors are assessed by rapid heating using a CO2 laser.
Variable pressure thermal insulating jacket
Nelson, Paul A.; Malecha, Richard F.; Chilenskas, Albert A.
1994-01-01
A device for controlled insulation of a thermal device. The device includes a thermal jacket with a closed volume able to be evacuated to form an insulating jacket around the thermal source. A getter material is in communcation with the closed volume of the thermal jacket. The getter material can absorb and desorb a control gas to control gas pressure in the volume of the thermal jacket to control thermal conductivity in the thermal jacket.
Resonant Optical Gradient Force Interaction for Nano-Imaging and-Spectroscopy
2016-07-19
gradient force off-resonance is below the thermal cantilever noise limit of a room temperature atomic forcemicroscope (AFM), we assess that in the cases of...the cantilever oscillation amplitude equals that induced by thermal noise given by ( ) w = ⎡ ⎣⎢ ⎤ ⎦⎥F k TkB Q 4 , 4min B 1 2 with Boltzmann’s...force is proportional to the local optical electricfield, while the thermal expansion/ absorption is due to resistive heating associatedwith electric
Biodegradable Piezoelectric Force Sensor.
Curry, Eli J; Ke, Kai; Chorsi, Meysam T; Wrobel, Kinga S; Miller, Albert N; Patel, Avi; Kim, Insoo; Feng, Jianlin; Yue, Lixia; Wu, Qian; Kuo, Chia-Ling; Lo, Kevin W-H; Laurencin, Cato T; Ilies, Horea; Purohit, Prashant K; Nguyen, Thanh D
2018-01-30
Measuring vital physiological pressures is important for monitoring health status, preventing the buildup of dangerous internal forces in impaired organs, and enabling novel approaches of using mechanical stimulation for tissue regeneration. Pressure sensors are often required to be implanted and directly integrated with native soft biological systems. Therefore, the devices should be flexible and at the same time biodegradable to avoid invasive removal surgery that can damage directly interfaced tissues. Despite recent achievements in degradable electronic devices, there is still a tremendous need to develop a force sensor which only relies on safe medical materials and requires no complex fabrication process to provide accurate information on important biophysiological forces. Here, we present a strategy for material processing, electromechanical analysis, device fabrication, and assessment of a piezoelectric Poly-l-lactide (PLLA) polymer to create a biodegradable, biocompatible piezoelectric force sensor, which only employs medical materials used commonly in Food and Drug Administration-approved implants, for the monitoring of biological forces. We show the sensor can precisely measure pressures in a wide range of 0-18 kPa and sustain a reliable performance for a period of 4 d in an aqueous environment. We also demonstrate this PLLA piezoelectric sensor can be implanted inside the abdominal cavity of a mouse to monitor the pressure of diaphragmatic contraction. This piezoelectric sensor offers an appealing alternative to present biodegradable electronic devices for the monitoring of intraorgan pressures. The sensor can be integrated with tissues and organs, forming self-sensing bionic systems to enable many exciting applications in regenerative medicine, drug delivery, and medical devices.
Thermal computations for electronics conductive, radiative, and convective air cooling
Ellison, Gordon
2010-01-01
IntroductionPrimary mechanisms of heat flowConductionApplication example: Silicon chip resistance calculationConvectionApplication example: Chassis panel cooled by natural convectionRadiationApplication example: Chassis panel cooled only by radiation 7Illustrative example: Simple thermal network model for a heat sinked power transistorIllustrative example: Thermal network circuit for a printed circuit boardCompact component modelsIllustrative example: Pressure and thermal circuits for a forced air cooled enclosureIllustrative example: A single chip package on a printed circuit board-the proble
Mechanochemical and Thermal Transformations of Amorphous and Crystalline Aluminosilicates
Directory of Open Access Journals (Sweden)
Subotić, B.
2007-01-01
Full Text Available Preparation of amorphous aluminosilicates precursors with defined properties is a very important factor for further studies of nucleation and crystal growth of zeolites during their thermal and hydrothermal transformation into zeolites and special ceramics. This study presents the effect of an intensive mechanical force (ball-milling on the properties of zeolite A and zeolite A with partially exchanged sodium ions with other cations (Li+, K+, Cs+, NH4+. The influence is studied of different cations on the mechanical and thermal stability of the zeolite framework and the formation of amorphous phases, as well as their transformation into nonzeolitic crystal phases after thermal treatment.
Effect of self-induced magnetic force in a coronal loop transient
Yeh, T.; Dryer, M.
1981-01-01
The distribution of the self-induced magnetic force in a section of a model coronal loop is examined and it is found that an axial current produces a pointwise magnetic force in the direction toward the axis of the loop. The direction of the pointwise magnetic force indicates that the effect of this force, acting alone, is to cause a contraction of the cross section of the magnetic loop toward the axis, but not the translation motion of the loop as a whole. It is concluded that forces other than the self-induced magnetic force, such as thermal force of pressure gradient or extra-induced magnetic force of magnetic buoyancy, must be involved in the acceleration mechanisms for the heliocentrifugal motion of coronal transients.
Influence of defects on thermal properties of stanene
Das, Sourav; Rakib, Tawfiqur; Mojumder, Satyajit; Islam, Md Mahbubul; Motalab, Mohammad Abdul
2017-06-01
Stanene is a two-dimensional, graphene-like honeycomb structure material, has been synthesized in a recent experimental study. Theoretically, it is expected to have a super conductive property near room temperature due to its spin orbital coupling effect. It is a potential material for the next generation nano-electronics application. Therefore, studying its thermal property is of particular interest. In this paper, we investigated the effect of different types of defects on the thermal conductivity of stanene nanosheets. Molecular Dynamics simulations are performed to calculate the thermal conductivity as a function of various types of defects. MEAM potential is used to describe the inter-atomic forces. It has been found that the presence of defects reduces the thermal conductivity significantly. Finally, vibrational density of states (DOS) are calculated to elucidate the underlying mechanisms of the reduction of thermal conductivity.
Yang, Tianzhi; Wu, Qinghe; Xu, Weikai; Liu, Di; Huang, Lujun; Chen, Fei
2016-02-01
The thermal cloak has been a long-standing scientific dream of researchers and engineers. Recently thermal metamaterials with man-made micro-structure have been presented based on the principle of transformation optics (TO). This new concept has received considerable attention, which is a powerful tool for manipulating heat flux in thermal imaging systems. However, the inherent material singularity has long been a captivation of experimental realization. As an alternative method, the scattering-cancellation-based cloak (or bi-layer thermal cloak) has been presented to remove the singularity for achieving the same cloaking performance. Nevertheless, such strategy needs prerequisite knowledge (geometry and conductivity) of the object to be cloaked. In this paper, a new thermal ground cloak is presented to overcome the limitations. The device is designed, fabricated and measured to verify the thermal cloaking performance. We experimentally show that the remarkably low complexity of the device can fully and effectively be manipulated using realizable transformation thermal devices. More importantly, this thermal ground cloak is designed to exclude heat flux without knowing the information of the cloaked object.
Power Electronics Thermal Management
Energy Technology Data Exchange (ETDEWEB)
Moreno, Gilberto [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-08-07
Thermal modeling was conducted to evaluate and develop thermal management strategies for high-temperature wide-bandgap (WBG)-based power electronics systems. WBG device temperatures of 175 degrees C to 250 degrees C were modeled under various under-hood temperature environments. Modeling result were used to identify the most effective capacitor cooling strategies under high device temperature conditions.
Thermally exfoliated graphite oxide
Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)
2011-01-01
A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.
Strijk, R.
2008-01-01
Present thermal design tools and methods insufficiently support the development of structural concepts engaged by typical practicing designers. Research described in this thesis identifies the main thermal design problems in practice. In addition, models and methods are developed that support an
1980-01-01
The planning and implementation of activities associated with lead center management role and the technical accomplishments pertaining to high temperature thermal energy storage subsystems are described. Major elements reported are: (1) program definition and assessment; (2) research and technology development; (3) industrial storage applications; (4) solar thermal power storage applications; and (5) building heating and cooling applications.
Elwenspoek, Michael Curt
1999-01-01
A review is given on sensors fabricated by silicon micromachining technology using the thermal domain for the measurement of fluid flow. Attention is paid especially to performance and geometry of the sensors. Three basic types of thermal flow sensors are discussed: anemometers, calorimetric flow
High Thermal Conductivity Materials
Shinde, Subhash L
2006-01-01
Thermal management has become a ‘hot’ field in recent years due to a need to obtain high performance levels in many devices used in such diverse areas as space science, mainframe and desktop computers, optoelectronics and even Formula One racing cars! Thermal solutions require not just taking care of very high thermal flux, but also ‘hot spots’, where the flux densities can exceed 200 W/cm2. High thermal conductivity materials play an important role in addressing thermal management issues. This volume provides readers a basic understanding of the thermal conduction mechanisms in these materials and discusses how the thermal conductivity may be related to their crystal structures as well as microstructures developed as a result of their processing history. The techniques for accurate measurement of these properties on large as well as small scales have been reviewed. Detailed information on the thermal conductivity of diverse materials including aluminum nitride (AlN), silicon carbide (SiC), diamond, a...
Paradoxes of Thermal Radiation
Besson, U.
2009-01-01
This paper presents an analysis of the thermal behaviour of objects exposed to a solar-type flux of thermal radiation. It aims to clarify certain apparent inconsistencies between theory and observation, and to give a detailed exposition of some critical points that physics textbooks usually treat in an insufficient or incorrect way. In particular,…
DEFF Research Database (Denmark)
Foged, Isak Worre; Pasold, Anke
2015-01-01
search procedure, the combination of materials and their bonding temperature is found in relation to the envelope effect on a thermal environment inside a defined space. This allows the designer to articulate dynamic composites with time-based thermal functionality, related to the material dynamics...
Principles and applications of force spectroscopy using atomic force microscopy
Energy Technology Data Exchange (ETDEWEB)
Kim, Young Kyu; Kim, Woong; Park, Joon Won [Dept. of Chemistry, Pohang University of Science and Technology, Pohang (Korea, Republic of)
2016-12-15
Single-molecule force spectroscopy is a powerful technique for addressing single molecules. Unseen structures and dynamics of molecules have been elucidated using force spectroscopy. Atomic force microscope (AFM)-based force spectroscopy studies have provided picoNewton force resolution, subnanometer spatial resolution, stiffness of substrates, elasticity of polymers, and thermodynamics and kinetics of single-molecular interactions. In addition, AFM has enabled mapping the distribution of individual molecules in situ, and the quantification of single molecules has been made possible without modification or labeling. In this review, we describe the basic principles, sample preparation, data analysis, and applications of AFM-based force spectroscopy and its future.
Radiative Bistability and Thermal Memory
Kubytskyi, Viacheslav; Biehs, Svend-Age; Ben-Abdallah, Philippe
2014-08-01
We predict the existence of a thermal bistability in many-body systems out of thermal equilibrium which exchange heat by thermal radiation using insulator-metal transition materials. We propose a writing-reading procedure and demonstrate the possibility to exploit the thermal bistability to make a volatile thermal memory. We show that this thermal memory can be used to store heat and thermal information (via an encoding temperature) for arbitrary long times. The radiative thermal bistability could find broad applications in the domains of thermal management, information processing, and energy storage.
Energy Technology Data Exchange (ETDEWEB)
Pesaran, Ahmad
2016-06-14
This presentation describes the thermal design of battery packs at the National Renewable Energy Laboratory. A battery thermal management system essential for xEVs for both normal operation during daily driving (achieving life and performance) and off-normal operation during abuse conditions (achieving safety). The battery thermal management system needs to be optimized with the right tools for the lowest cost. Experimental tools such as NREL's isothermal battery calorimeter, thermal imaging, and heat transfer setups are needed. Thermal models and computer-aided engineering tools are useful for robust designs. During abuse conditions, designs should prevent cell-to-cell propagation in a module/pack (i.e., keep the fire small and manageable). NREL's battery ISC device can be used for evaluating the robustness of a module/pack to cell-to-cell propagation.
Forced Vibration Analysis for a FGPM Cylindrical Shell
Directory of Open Access Journals (Sweden)
Hong-Liang Dai
2013-01-01
Full Text Available This article presents an analytical study for forced vibration of a cylindrical shell which is composed of a functionally graded piezoelectric material (FGPM. The cylindrical shell is assumed to have two-constituent material distributions through the thickness of the structure, and material properties of the cylindrical shell are assumed to vary according to a power-law distribution in terms of the volume fractions for constituent materials, the exact solution for the forced vibration problem is presented. Numerical results are presented to show the effect of electric excitation, thermal load, mechanical load and volume exponent on the static and force vibration of the FGPM cylindrical shell. The goal of this investigation is to optimize the FGPM cylindrical shell in engineering, also the present solution can be used in the forced vibration analysis of cylindrical smart elements.
Mechanically-forced dynamos (Invited)
Le Bars, M.
2013-12-01
It is a commonly accepted hypothesis that convection is responsible for planetary dynamos. However, the validity of the convective dynamo model can be questioned in various planets and moons as well as in asteroids, where the constraints from thermal evolution and compositional core models are sometimes difficult to reconcile with available data from paleomagnetism and in situ measurements. Over the last few years, researches have thus been pursued to find alternative mechanisms for sustaining intense three-dimensional motions in liquid cores, a necessary ingredient for planetary dynamo. In particular, mechanical forcings driven by libration, precession, nutation and tides, have received a renewed interest, following the first studies by Malkus in the 60's. A huge reservoir of energy is available in the rotational and orbital motions of all planetary systems. If planetary bodies were completely rigid and rotating at a constant spin rate, their fluid layers in the absence of convection would also behave rigidly and follow the spin of their boundaries. But small periodic perturbations of the shape of the core/mantle boundary (i.e. dynamic tides) and/or small periodic perturbations of the direction of the spin vector (i.e. precession and nutation) and/or small periodic perturbations of the spin rate (i.e. libration) systematically perturb this rigid state. Then, each of these small perturbations is capable of triggering instabilities in fluid layers, conveying energy from the spin and orbital motions to drive intense three-dimensional flows in the liquid cores. With the view to establish a general framework for planetary applications, I will present here the basic physical ingredients of these instabilities, which involve a resonance between the considered mechanical forcing and two inertial waves of the core. I will then review the numerical and experimental validations of this generic principle, and the few magnetohydrodynamic validations of their dynamo capacity
Energy Technology Data Exchange (ETDEWEB)
Redmond Clark
2009-04-30
Many metal parts manufacturers use large metal presses to shape sheet metal into finished products like car body parts, jet wing and fuselage surfaces, etc. These metal presses take sheet metal and - with enormous force - reshape the metal into a fully formed part in a manner of seconds. Although highly efficient, the forces involved in forming metal parts also damage the press itself, limit the metals used in part production, slow press operations and, when not properly controlled, cause the manufacture of large volumes of defective metal parts. To date, the metal-forming industry has not been able to develop a metal-holding technology that allows full control of press forces during the part forming process. This is of particular importance in the automotive lightweighting efforts under way in the US automotive manufacturing marketplace. Metalforming Controls Technology Inc. (MC2) has developed a patented press control system called the Force Modulator that has the ability to control these press forces, allowing a breakthrough in stamping process control. The technology includes a series of hydraulic cylinders that provide controlled tonnage at all points in the forming process. At the same time, the unique cylinder design allows for the generation of very high levels of clamping forces (very high tonnages) in very small spaces; a requirement for forming medium and large panels out of HSS and AHSS. Successful production application of these systems testing at multiple stamping operations - including Ford and Chrysler - has validated the capabilities and economic benefits of the system. Although this technology has been adopted in a number of stamping operations, one of the primary barriers to faster adoption and application of this technology in HSS projects is system cost. The cost issue has surfaced because the systems currently in use are built for each individual die as a custom application, thus driving higher tooling costs. This project proposed to better
1997-01-01
I-FORCE, a computer peripheral from Immersion Corporation, was derived from virtual environment and human factors research at the Advanced Displays and Spatial Perception Laboratory at Ames Research Center in collaboration with Stanford University Center for Design Research. Entrepreneur Louis Rosenberg, a former Stanford researcher, now president of Immersion, collaborated with Dr. Bernard Adelstein at Ames on studies of perception in virtual reality. The result was an inexpensive way to incorporate motors and a sophisticated microprocessor into joysticks and other game controllers. These devices can emulate the feel of a car on the skid, a crashing plane, the bounce of a ball, compressed springs, or other physical phenomenon. The first products incorporating I-FORCE technology include CH- Products' line of FlightStick and CombatStick controllers.
Pridmore, Saxby; Walter, Garry
2013-03-01
The prevailing view that the vast majority of those who complete suicide have an underlying psychiatric disorder has been recently challenged by research on the contribution of "predicaments", in the absence of mental illness, to suicide. In this paper, we sought data to support the notion that forced marriage may lead to suicide without the presence of psychiatric disorder. Historical records, newspapers, and the electronic media were searched for examples. Two examples from ancient times and six from the last hundred years were located and described. These cases suggest that forced marriage may lead to suicide and complements earlier findings that loss of fortune, health, liberty, and reputation may lead to suicide in the absence of mental disorder.
2017-10-19
bases and missions toward an enterprise solution for incorporating smart technologies in the future (defined in the Information Environment Mission... technology might enrich and protect our nation, businesses, and lives. As a human-centric design center, we seek out unique ways to connect Air Force...warfighters with current and future technology in meaningful ways. We look to transfer, license, and share promising prototypes, solutions, and knowledge
2015-11-01
for disease preven- tion which can also reduce the transmission of other sexually transmitted infec- tions (STIs). However, rates are considered con...65 HEALTH OF THE FORCE Chlamydia Sexually transmitted infections such as chla- mydia can impact medical readiness and Soldier well-being. Most...particularly among women , who may experience pelvic inflammatory disease , ec- topic pregnancy, and infertility. Therefore, it is rec- ommended that
Rao, Zhonghao; Wang, Qingchao; Zhao, Jiateng; Huang, Congliang
2017-10-01
To investigate the thermal performance of the closed oscillating heat pipe (OHP) as a passive heat transfer device in thermal management system, the gravitation force, surface tension, cooling section position and inclination angle were discussed with applied heating power ranging from 5 to 65 W. The deionized water was chosen as the working fluid and liquid-filling ratio was 50 ± 5%. The operation of the OHP mainly depends on the phase change of the working fluid. The working fluid within the OHP was constantly evaporated and cooled. The results show that the movement of the working fluid was similar to the forced damped mechanical vibration, it has to overcome the capillary resistance force and the stable oscillation should be that the OHP could successful startup. The oscillation frequency slowed and oscillation amplitude decreased when the inclination angle of the OHP increased. However, the thermal resistance increased. With the increment of the heating power, the average temperature of the evaporation and condensation section would be close. If the heating power was further increased, dry-out phenomenon within the OHP would appeared. With the decrement of the L, the start-up heating power also decreased and stable oscillation would be formed.
Thermally-related safety issues associated with thermal batteries.
Energy Technology Data Exchange (ETDEWEB)
Guidotti, Ronald Armand
2006-06-01
Thermal batteries can experience thermal runaway under certain usage conditions. This can lead to safety issues for personnel and cause damage to associated test equipment if the battery thermally self destructs. This report discusses a number of thermal and design related issues that can lead to catastrophic destruction of thermal batteries under certain conditions. Contributing factors are identified and mitigating actions are presented to minimize or prevent undesirable thermal runaway.
``Force,'' ontology, and language
Brookes, David T.; Etkina, Eugenia
2009-06-01
We introduce a linguistic framework through which one can interpret systematically students’ understanding of and reasoning about force and motion. Some researchers have suggested that students have robust misconceptions or alternative frameworks grounded in everyday experience. Others have pointed out the inconsistency of students’ responses and presented a phenomenological explanation for what is observed, namely, knowledge in pieces. We wish to present a view that builds on and unifies aspects of this prior research. Our argument is that many students’ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term “force” as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.
Lissuaer, D
One of the more congested areas in the ATLAS detector is the GAP region (the area between the Barrel Calorimeter and the End Cap calorimeter) where Inner Detector services, LAr Services and some Tile services all must co-habitat in a very limited area. It has been clear for some time that the space in the GAP region is not sufficient to accommodate all that is needed. In the last few month additional problems of routing all the services to Z=0 have been encountered due to the very limited space between the Tile Calorimeter and the first layer of Muon chambers. The Technical Management Board (TMB) and the Executive Board (EB) decided in the middle of March to establish a Task Force to look at this problem and come up with a solution within well-specified guidelines. The task force consisted of experts from the ID, Muon, Liquid Argon and Tile systems in addition to experts from the Technical Coordination team and the Physics coordinator. The task force held many meetings and in general there were some very l...
Directory of Open Access Journals (Sweden)
Jaka Ogorevc
2015-12-01
Full Text Available AbstractIntroduction: Body temperature monitoring is one of the oldest and still one of the most basic diagnostic methods in medicine. In recent years thermal imaging has been increasingly used in measurements of body temperature for diagnostic purposes. Thermal imaging is non-invasive, non-contact method for measuring surface body temperature. Method is quick, painless and patient is not exposed to ionizing radiation or any other body burden.Application of thermal imaging in medicine: Pathological conditions can be indicated as hyper- or hypothermic patterns in many cases. Thermal imaging is presented as a diagnostic method, which can detect such thermal anomalies. This article provides an overview of the thermal imaging applications in various fields of medicine. Thermal imaging has proven to be a suitable method for human febrile temperature screening, for the detection of sites of fractures and infections, a reliable diagnostic tool in the detection of breast cancer and determining the type of skin cancer tumour. It is useful in monitoring the course of a therapy after spinal cord injury, in the detection of food allergies and detecting complications at hemodialysis and is also very effective at the course of treatment of breast reconstruction after mastectomy. With thermal imaging is possible to determine the degrees of burns and early detection of osteomyelitis in diabetic foot phenomenon. The most common and the oldest application of thermal imaging in medicine is the field of rheumatology.Recommendations for use and standards: Essential performance of a thermal imaging camera, measurement method, preparation of a patient and environmental conditions are very important for proper interpretation of measurement results in medical applications of thermal imaging. Standard for screening thermographs was formed for the human febrile temperature screening application.Conclusion: Based on presented examples it is shown that thermal imaging can
Force transmission in epithelial tissues.
Vasquez, Claudia G; Martin, Adam C
2016-03-01
In epithelial tissues, cells constantly generate and transmit forces between each other. Forces generated by the actomyosin cytoskeleton regulate tissue shape and structure and also provide signals that influence cells' decisions to divide, die, or differentiate. Forces are transmitted across epithelia because cells are mechanically linked through junctional complexes, and forces can propagate through the cell cytoplasm. Here, we review some of the molecular mechanisms responsible for force generation, with a specific focus on the actomyosin cortex and adherens junctions. We then discuss evidence for how these mechanisms promote cell shape changes and force transmission in tissues. © 2016 Wiley Periodicals, Inc.
Evstigneev, M; Reimann, P
2015-04-01
Friction force microscopy and single-molecule force spectroscopy are experimental methods to explore multistable energy landscapes by means of a controlled reduction of the energy barriers between adjacent potential minima. This affects the system's interstate transition rates proportional to e(-ΔE(f)/kBT), with ΔE(f) being the barrier height, k(B)T the thermal energy, and f the elastic force applied. It is often assumed that, at large forces, the barrier height scales as (f(c) - f)(3/2), where f(c) is the critical force, at which the barrier vanishes. We show that, for the elastic forces produced by a pulling device of finite stiffness κ, this scaling relation is actually incorrect. Rather, the barrier is a double-valued function of force of the form E(f) ∝ (κ/κ(c) ±√1 − f/f(0))(3), where f(0) is the maximal force that the system potential can generate, and the characteristic stiffness κ(c) is not necessarily much larger than κ. In particular, for finite κ, the barrier vanishes at a certain force f(κ) force f0 can still be reached. We derive the relation between the most probable force at the moment of transition, fm, and the pulling velocity, v. The usually assumed scaling f(m) ∝ (ln v)(2/3) is recovered as the κ → 0 limit of our more general result, but becomes increasingly worse as κ grows. We introduce a new data analysis method that allows one to quantitatively characterize the system potential and evaluate the stiffness of the pulling device, κ, which is usually not known beforehand. We demonstrate the feasibility of our method by analyzing the results of a numerical experiment based on the standard Prandtl-Tomlinson model of nanoscale friction.
Energy Technology Data Exchange (ETDEWEB)
Calloni, E. [University of Napoli Federico II and INFN Napoli (Italy); Caprara, S. [University of Roma Sapienza and INFN Roma (Italy); Laurentis, M. De; Esposito, G. [University of Napoli Federico II and INFN Napoli (Italy); Grilli, M.; Majorana, E. [University of Roma Sapienza and INFN Roma (Italy); Pepe, G.P. [University of Napoli Federico II and INFN Napoli (Italy); Petrarca, S. [University of Roma Sapienza and INFN Roma (Italy); Puppo, P., E-mail: paola.puppo@roma1.infn.it [University of Roma Sapienza and INFN Roma (Italy); Rapagnani, P.; Ricci, F. [University of Roma Sapienza and INFN Roma (Italy); Rosa, L. [University of Napoli Federico II and INFN Napoli (Italy); Rovelli, C. [University of Aix-Marseille (France); Ruggi, P. [European Gravitational Observatory (EGO), Cascina (Pisa) (Italy); Saini, N.L. [University of Roma Sapienza and INFN Roma (Italy); Stornaiolo, C.; Tafuri, F. [University of Napoli Federico II and INFN Napoli (Italy)
2016-07-11
Archimedes is an INFN-funded pathfinder experiment aimed at verifying the feasibility of measuring the interaction of vacuum fluctuations with gravity. The final experiment will measure the force exerted by the gravitational field on a Casimir cavity whose vacuum energy is modulated with a superconductive transition, by using a balance as a small force detector. Archimedes is two-year project devoted to test the most critical experimental aspects, in particular the balance resonance frequency and quality factor, the thermal modulation efficiency and the superconductive sample realization. - Highlights: • Weight of the vacuum. • Superconductive stacks studies. • Thermal behavior studies at cryogenic temperatures.
Optimizing Global Force Management for Special Operations Forces
2016-12-01
FORCE MANAGEMENT FOR SPECIAL OPERATIONS FORCES by Emily A. LaCaille December 2016 Thesis Advisor: Paul L. Ewing Second Reader: Jeffrey...Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget...DATES COVERED Master’s thesis 4. TITLE AND SUBTITLE OPTIMIZING GLOBAL FORCE MANAGEMENT FOR SPECIAL OPERATIONS FORCES 5. FUNDING NUMBERS 6
NANOFLUID PROPERTIES FOR FORCED CONVECTION HEAT TRANSFER: AN OVERVIEW
Directory of Open Access Journals (Sweden)
W.H.Azmi
2013-06-01
Full Text Available Nanoﬂuids offer a significant advantage over conventional heat transfer ﬂuids and consequently, they have attracted much attention in recent years. The engineered suspension of nano-sized particles in a base liquid alters the properties of these nanofluids. Many researchers have measured and modeled the thermal conductivity and viscosity of nanofluids. The estimation of forced convective heat transfer coefficients is done through experiments with either metal or nonmetal solid particles dispersed in water. Regression equations are developed for the determination of the thermal conductivity and viscosity of nanofluids. The parameters influencing the decrease in convection heat transfer, observed by certain investigators, is explained.
Phonon and thermal properties of achiral single wall carbon ...
Indian Academy of Sciences (India)
A detailed theoretical study of the phonon and thermal properties of achiral single wall carbon nanotubes has been carried out using force constant model considering up to third nearest-neighbor interactions. We have calculated the phonon dispersions, density of states, radial breathing modes (RBM) and the specific heats ...
Thermal properties of nanofluids.
Philip, John; Shima, P D
2012-11-15
Colloidal suspensions of fine nanomaterials in the size range of 1-100 nm in carrier fluids are known as nanofluids. For the last one decade, nanofluids have been a topic of intense research due to their enhanced thermal properties and possible heat transfer applications. Miniaturization and increased operating speeds of gadgets warranted the need for new and innovative cooling concepts for better performance. The low thermal conductivity of conventional heat transfer fluid has been a serious impediment for improving the performance and compactness of engineering equipments. Initial studies on thermal conductivity of suspensions with micrometer-sized particles encountered problems of rapid settling of particles, clogging of flow channels and increased pressure drop in the fluid. These problems are resolved by using dispersions of fine nanometer-sized particles. Despite numerous experimental and theoretical studies, it is still unclear whether the thermal conductivity enhancement in nanofluids is anomalous or within the predictions of effective medium theory. Further, many reports on thermal conductivity of nanofluids are conflicting due to the complex issues associated with the surface chemistry of nanofluids. This review provides an overview of recent advances in the field of nanofluids, especially the important material properties that affect the thermal properties of nanofluids and novel approaches to achieve extremely high thermal conductivities. The background information is also provided for beginners to better understand the subject. Copyright © 2012 Elsevier B.V. All rights reserved.
Thermal transfer structures coupling electronics card(s) to coolant-cooled structure(s)
David, Milnes P; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Parida, Pritish R; Schmidt, Roger R
2014-12-16
Cooling apparatuses and coolant-cooled electronic systems are provided which include thermal transfer structures configured to engage with a spring force one or more electronics cards with docking of the electronics card(s) within a respective socket(s) of the electronic system. A thermal transfer structure of the cooling apparatus includes a thermal spreader having a first thermal conduction surface, and a thermally conductive spring assembly coupled to the conduction surface of the thermal spreader and positioned and configured to reside between and physically couple a first surface of an electronics card to the first surface of the thermal spreader with docking of the electronics card within a socket of the electronic system. The thermal transfer structure is, in one embodiment, metallurgically bonded to a coolant-cooled structure and facilitates transfer of heat from the electronics card to coolant flowing through the coolant-cooled structure.
2016-12-07
in enemy territory, working with indige - nous forces, and performing deep reconnais- sance, strikes, and raids. The 1993 version of the manual still...designated combat zones, like training and advising indig - enous security forces, and operating differently SPECIAL OPERATIONS FORCES AND CONVENTIONAL
Force modulation for improved conductive-mode atomic force microscopy
Koelmans, W.W.; Sebastian, Abu; Despont, Michel; Pozidis, Haris
We present an improved conductive-mode atomic force microscopy (C-AFM) method by modulating the applied loading force on the tip. Unreliable electrical contact and tip wear are the primary challenges for electrical characterization at the nanometer scale. The experiments show that force modulation
Force tracing: a method to sculpt the optical force
Akbarzadeh, Alireza; Caloz, Christophe
2017-08-01
A brief description of the long-standing problem of the optical momentum in media and its resolution is given. The method of force tracing to trace optical force fields along the trajectories of light rays is reviewed and a few illustrative examples are shown. Then, based on the method of force tracing, several graded-index devices performing interesting optical manipulations are reviewed.
Ferreira, Ricardo Z.; Notari, Alessio
2017-09-01
We analyze the dynamics of inflationary models with a coupling of the inflaton phi to gauge fields of the form phi F tilde F/f, as in the case of axions. It is known that this leads to an instability, with exponential amplification of gauge fields, controlled by the parameter ξ= dot phi/(2fH), which can strongly affect the generation of cosmological perturbations and even the background. We show that scattering rates involving gauge fields can become larger than the expansion rate H, due to the very large occupation numbers, and create a thermal bath of particles of temperature T during inflation. In the thermal regime, energy is transferred to smaller scales, radically modifying the predictions of this scenario. We thus argue that previous constraints on ξ are alleviated. If the gauge fields have Standard Model interactions, which naturally provides reheating, they thermalize already at ξgtrsim2.9, before perturbativity constraints and also before backreaction takes place. In absence of SM interactions (i.e. for a dark photon), we find that gauge fields and inflaton perturbations thermalize if ξgtrsim3.4 however, observations require ξgtrsim6, which is above the perturbativity and backreaction bounds and so a dedicated study is required. After thermalization, though, the system should evolve non-trivially due to the competition between the instability and the gauge field thermal mass. If the thermal mass and the instabilities equilibrate, we expect an equilibrium temperature of Teq simeq ξ H/bar g where bar g is the effective gauge coupling. Finally, we estimate the spectrum of perturbations if phi is thermal and find that the tensor to scalar ratio is suppressed by H/(2T), if tensors do not thermalize.
Radiative peristaltic flow of magneto nanofluid in a porous channel with thermal radiation
Directory of Open Access Journals (Sweden)
T. Hayat
Full Text Available Peristaltic flow of MHD nano fluid in a porous channel with velocity and thermal slip conditions is examined. Nanomaterial is comprised with water and copper/silver. Thermal radiation is present. The relevant problems have been solved for the velocity, temperature, pressure rise, frictional force and heat transfer rate. Physical impact of parameters in this study is analyzed.
Tuning thermal conductance of CNT interface junction via stretching and atomic bonding
Liao, Dongmei; Chen, Wen; Zhang, Jingchao; Yue, Yanan
2017-11-01
In this work, various effects of stretching and bonding strength on the thermal transport at CNT junctions are comprehensively studied by classical molecular dynamics (MD) simulations. The modeling is performed on a typical parallel-aligned junction formed by two single-walled (10, 10) CNTs. The overlap length is the first condition we studied and it is found that thermal conductance is significantly increased from 1.00 to 11.76 nW K‑1 with overlap length from 0.982 to 6.877 nm. Surprisingly, the thermal conductance per unit overlap length is increased rather than a constant value. The van der Waals interaction in non-bonded CNTs has a positive correlation on thermal conductance, which means thermal conductance can be effectively enhanced by applied force in the inter-tube direction. In the axial direction, the applied force is an important condition to adjust thermal conductance at bonded junction. Results show that the thermal conductance for overlap length of 1.966 nm can be enhanced from 2.81 to 3.42 nW K‑1 at the initial stage because of the combined squeezing force. However, as applied force approaches the breaking value, the atomic bonding at the junction is greatly weakened with a rapidly dropping thermal conductance from 3.42 to 1.88 nW K‑1.
Radiative peristaltic flow of magneto nanofluid in a porous channel with thermal radiation
Hayat, T.; Rani, Saima; Alsaedi, A.; Rafiq, M.
Peristaltic flow of MHD nano fluid in a porous channel with velocity and thermal slip conditions is examined. Nanomaterial is comprised with water and copper/silver. Thermal radiation is present. The relevant problems have been solved for the velocity, temperature, pressure rise, frictional force and heat transfer rate. Physical impact of parameters in this study is analyzed.
High-precision force sensing using a single trapped ion
Ivanov, Peter A.; Vitanov, Nikolay V.; Singer, Kilian
2016-06-01
We introduce quantum sensing schemes for measuring very weak forces with a single trapped ion. They use the spin-motional coupling induced by the laser-ion interaction to transfer the relevant force information to the spin-degree of freedom. Therefore, the force estimation is carried out simply by observing the Ramsey-type oscillations of the ion spin states. Three quantum probes are considered, which are represented by systems obeying the Jaynes-Cummings, quantum Rabi (in 1D) and Jahn-Teller (in 2D) models. By using dynamical decoupling schemes in the Jaynes-Cummings and Jahn-Teller models, our force sensing protocols can be made robust to the spin dephasing caused by the thermal and magnetic field fluctuations. In the quantum-Rabi probe, the residual spin-phonon coupling vanishes, which makes this sensing protocol naturally robust to thermally-induced spin dephasing. We show that the proposed techniques can be used to sense the axial and transverse components of the force with a sensitivity beyond the range, i.e. in the (xennonewton, 10-27). The Jahn-Teller protocol, in particular, can be used to implement a two-channel vector spectrum analyzer for measuring ultra-low voltages.
Advanced thermal management materials
Jiang, Guosheng; Kuang, Ken
2012-01-01
""Advanced Thermal Management Materials"" provides a comprehensive and hands-on treatise on the importance of thermal packaging in high performance systems. These systems, ranging from active electronically-scanned radar arrays to web servers, require components that can dissipate heat efficiently. This requires materials capable of dissipating heat and maintaining compatibility with the packaging and dye. Its coverage includes all aspects of thermal management materials, both traditional and non-traditional, with an emphasis on metal based materials. An in-depth discussion of properties and m
Alternatives to eigenstate thermalization.
Rigol, Marcos; Srednicki, Mark
2012-03-16
An isolated quantum many-body system in an initial pure state will come to thermal equilibrium if it satisfies the eigenstate thermalization hypothesis (ETH). We consider alternatives to ETH that have been proposed. We first show that von Neumann's quantum ergodic theorem relies on an assumption that is essentially equivalent to ETH. We also investigate whether, following a sudden quench, special classes of pure states can lead to thermal behavior in systems that do not obey ETH, namely, integrable systems. We find examples of this, but only for initial states that obeyed ETH before the quench.
Berdahl, C. M.; Thiele, C. L. (Inventor)
1979-01-01
For use in combination with a heat engine, a thermal energy transformer is presented. It is comprised of a flux receiver having a first wall defining therein a radiation absorption cavity for converting solar flux to thermal energy, and a second wall defining an energy transfer wall for the heat engine. There is a heat pipe chamber interposed between the first and second walls having a working fluid disposed within the chamber and a wick lining the chamber for conducting the working fluid from the second wall to the first wall. Thermal energy is transferred from the radiation absorption cavity to the heat engine.
Karimipour, I.; Beni, Yaghoub Tadi; Taheri, N.
2017-10-01
Plate-type clamped microplate is of the most common constructive elements for developing in-liquid-operating devices. While the electromechanical behavior of clamped microplate in non-liquid environments has exclusively been addressed in the literature, no theoretical studies have yet been conducted on precise modeling of the clamped microplate in electrolyte liquid. Herein, the electromechanical response and instability of the clamped microplate immersed in ionic electrolyte media are investigated. The electrochemical force field is determined using double layer theory and linearized Poisson-Boltzmann equation. The presence of dispersion forces, i.e., Casimir and van der Waals attractions, are included in the theoretical model considering the correction due to the presence of liquid media between the interacting surfaces (three-layer model). To this end, a kind of microplate has been designed, i.e., a square microplate with all edges clamped supported. The strain gradient elasticity is employed to model the size-dependent structural behavior of the clamped microplate. To solve the nonlinear constitutive equation of the system, Extended Kantorovich Method, is employed and the pull-in parameter of the microplate are extracted. Impacts of the dispersion forces and size effect on the instability characteristics are discussed as well as the effect of ion concentration and potential ratio. It is found that the significant difference between the pull-in instability parameters in the modified strain gradient theory and the classical theory for thin microplates is merely due to the consideration of size effect parameter in the modified strain gradient theory. To confirm the validity of formulations, the numerical values of the results are compared. The results predicted via the aforementioned approach are in excellent agreement with those in the literature. Some new examples are solved to demonstrate the applicability of the procedure.
Force Dynamics of Verb Complementation
Directory of Open Access Journals (Sweden)
Jacek Woźny
2015-12-01
Full Text Available Force Dynamics of Verb Complementation The concepts of motion and force are both extensively discussed in cognitive linguistics literature. But they are discussed separately. The first usually in the context of ‘motion situations’ (Talmy, Slobin, Zlatev, the other as part of the Force Dynamics framework, which was developed by Talmy. The aim of this paper is twofold: first, to argue that the concepts of force and motion should not be isolated but considered as two inseparable parts of force-motion events. The second goal is to prove that the modified Force Dynamics (force-motion framework can be used for precise characterization of the verb complementation patterns. To this end, a random sample of 50 sentences containing the verb ‘went’ is analyzed, demonstrating the differences between the categories of intensive and intransitive complementation with respect to the linguistically coded parameters of force and motion.
Grasping 2010 with Naval Forces
National Research Council Canada - National Science Library
Barnett, Roger
1998-01-01
This article focuses on how naval combat forces should be employed in 2010. Narrowing that focus presumes the Nation will want to maintain capable forces to underwrite its security and that of its allies and friends around the globe...
Modernization of African Armed Forces
DEFF Research Database (Denmark)
Mandrup, Thomas
2015-01-01
Concept paper framing the debate at the Dakar Forum Workshop on Modernization of Armed forces in Africa.......Concept paper framing the debate at the Dakar Forum Workshop on Modernization of Armed forces in Africa....
On the computation of the disruption forces in tokamaks
Pustovitov, V. D.; Rubinacci, G.; Villone, F.
2017-12-01
The currents and forces induced in the tokamak vacuum vessel (wall) during the disruption are calculated for different values of wall resistivity. Several consequences and new developments are derived from the general result that the global disruption force acting on the perfectly conducting wall must be exactly opposite to the similar force acting on the plasma, which is inherently small in tokamaks. This theoretical prediction is tested and confirmed here for the ITER tokamak with disruption modelled as the fast thermal quench followed by slower current quench that develops into the vertical displacement event. The plasma is simulated by the evolutionary equilibrium code CarMa0NL. One of the results is that the computed integral force on a perfectly conducting wall is zero at each instant during a disruption. This in turn highlights the importance of having good models for the plasma (in which the equilibrium constraint is explicitly imposed) and for the structures (able to correctly describe the induced currents and the resistive effects). The dependence of the disruption force on the magnetic field penetration through the wall is demonstrated. Also the concept of a disruption force damper is proposed, able to ‘absorb’ a significant part of the force that would arise on a resistive wall during a disruption.
The law of electromagnetic force
Directory of Open Access Journals (Sweden)
V.J. Kutkovetskyy
2014-06-01
Full Text Available Calculation peculiarities for Lorentz force, Ampere force, interaction of parallel electric currents, and the moment of electrical machines are analyzed. They have exceptions on application, and they are the rules which result from the law of electromagnetic force as coordinate derivative of the operating magnetic flow. An addition to the direction of electromagnetic force action is proposed. Standards of salient-pole electrical machine designing are considered.
Why is the magnetic force similar to a Coriolis force?
Royer, Antoine
2011-01-01
It is pointed out that the underlying reason why the magnetic force is similar to a Coriolis force is that it is caused by Thomas rotations, induced by successions of non-collinear Lorentz boosts. The magnetic force may even be viewed as a kind of Coriolis force (making perhaps more acceptable the apparent non-existence of magnetic monopoles). We also show that under a change of inertial frames, Faraday lines of force Lorentz contract as if 'etched' in space, while 'Coriolis' terms get added on.
Shen, Xiangying; Li, Ying; Jiang, Chaoran; Ni, Yushan; Huang, Jiping
2016-07-01
For macroscopically manipulating heat flow at will, thermal metamaterials have opened a practical way, which possesses a single function, such as either cloaking or concentrating the flow of heat even though environmental temperature varies. By developing a theory of transformation heat transfer for multiple functions, here we introduce the concept of intelligent thermal metamaterials with a dual function, which is in contrast to the existing thermal metamaterials with single functions. By assembling homogeneous isotropic materials and shape-memory alloys, we experimentally fabricate a kind of intelligent thermal metamaterials, which can automatically change from a cloak (or concentrator) to a concentrator (or cloak) when the environmental temperature changes. This work paves an efficient way for a controllable gradient of heat, and also provides guidance both for arbitrarily manipulating the flow of heat and for efficiently designing similar intelligent metamaterials in other fields.