Schlieren “PIV” for turbulent flows

The possibility of using commercial PIV equipment combined with schlieren optics to measure the velocity fields of turbulent flows is explored. Given a sufficiently high Reynolds number and adequate refractive flow differences, turbulent eddies can serve as the PIV “particles” in a schlieren image or shadowgram. The PIV software analyzes motion between consecutive schlieren or shadowgraph frames to obtain velocity fields. Velocimetry examples of an axisymmetric sonic helium jet in air and a 2D turbulent boundary layer at Mach 3 are shown. Due to optical path integration, axisymmetric flows require the inverse Abel transform to extract center-plane velocity data. Conditions for optimum schlieren sensitivity are examined. In its present embodiment, “schlieren PIV” is not useful for laminar flows nor for fully 3D flows. Otherwise it functions much like standard PIV under conditions where individual particles are not resolved and velocimetry is instead based on correlation of the motion of turbulent structures. “Schlieren PIV” shows significant promise for general refractive turbulent flow velocimetry if its integrative nature can be overcome through sharp-focusing optics.     

Deformed “commutative” Chern–Simons’ system

Noncommutative Chern–Simons’ system is non-perturbatively investigated at a full deformed level. A deformed “commutative” phase space is found by a non-canonical change between two sets of deformed variables of noncommutative space. It is explored that in the “commutative” phase space all calculations are similar to the case in commutative space. Spectra of its energy and angular momentum of the Chern–Simons’ system are obtained at the full deformed level. The noncommutative–commutative correspondence is clearly showed. Formalism for the general dynamical system is briefly presented. Some subtle points are clarified.     

Study on some aspects of the “singer's formant” in north indian classical singing

This article deals with a spectrographic analysis of the singer's formant as occurred during singing of the vowels /a/, /i/, and /o/ in North Indian classical vocal music. The resonance balance, center frequency, and band-width are shown as a function of fundamental frequency for eight singers.Two new parameters have been defined viz. asymmetry parameter (A) and spectral energy balance (W). Their variation with fundamental frequency is shown.     

Geschwindigkeitsverteilung,Teilchendichte, transversale Driftgeschwindigkeit und Energiedichte des Neutralgases in der Freifallsäule unter Berücksichtigung der „Neutralgasaufzehrung”︁ durch die Ionisationsvorgänge

A neutral gas rarefaction caused by ionization processes occurs in the plasma of the low pressure gas discharges. The velocity distributions, the particle density, the transversal drift velocity and the energy density of the neutral gas are calculated both for the plane and for the cylindrical positive column under free fall conditions. The neutral gas rarefaction is taken into account. It is shown, that the velocity distributions is non-Maxwellian and anisotropic. The pressure tensor is anisotropic, too. Particle density and energy density of neutral gas decrease with increasing electron density and electron temperature relatively homogeneously over the cross section of the column. Only, if the degree of ionization is high, these densities are much smaller near the axis than at the wall. Decreasing neutral gas temperature causes a similar change in the particle density profile as increasing electron density and electron temperature do. The transverse neutral gas pressure decreases from the axis to the wall in all cases. In the steady-state column an upper limit exists for the transverse particle current density of the neutral gas and of the ion gas. This limit depends on the gas temperature, the filling pressure and the atomic mass of the filling gas. In the appendix the Boltzmann equation is given in a form, which is suitable to investigate cylindrical problems not only for simple examples.     

Comment on “A simple experiment to test Bell’s inequality”, J.-M. Vigoureux

In the above paper, it is claimed that with a particular use of the Bell inequality, a simple single photon experiment could be performed to show the impossibility of any deterministic hidden variable theory in quantum optics. A careful analysis of the concept of probability for hidden variables and a detailed discussion of the hidden variable model of de Broglie–Bohm show that the reasoning and main conclusion of this paper are not correct.     

Das CARNOTsche „Paradigma”︁ und seine erkenntnistheoretischen Implikationen

CARNOT's “Paradigm” and its Epistemological Implications The present historic-critical essay traces the pecularities of classical phenomenological thermodynamics back to the “paradigm”, created by CARNOT, and takes up some questions to which this paradigm gives rise.     

Comments concerning “Study of solute–solvent and solvent–solvent interactions in pure and mixed binary solvents”

A number of mathematical equations representing the solute solubility in monosolvent and binary solvent mixtures are discussed. This work is a commentary to the article of Maitra and Baghchi that appeared in this journal.     

High order “ZIP” differencing of convective terms

The ZIP flux form for differencing the term (wv)_x, where w is a convected quantity and v is a convective velocity, is observed to be equivalent to differencing the alternative expression wv_x + wx_v using centered second order finite differences. The advantage of this form is that one class of nonlinear computational instabilities is eliminated. Based on this observation, the extension of the ZIP flux concept to arbitrarily high order accuracy is given. Computational examples show the advantage both of the ZIP flux concept itself and of its higher order forms within the context of flux-corrected transport (FCT) algorithms.     

Erratum to: “Weak corrections to gluon-induced top–antitop hadro-production” [Phys. Lett. B 639 (2006) 513]

This is an Erratum to a Letter of ours [S. Moretti, M.R. Nolten, D.A. Ross, Phys. Lett. B 639 (2006) 513]. After its publication, we have discovered a mistake in a numerical program that affects the results presented therein. We provide here the corrected version.     

Sinn und Möglichkeiten der Theoretischen Physik. Zum 300. Jahrestag von Newtons „Philosophiae Naturalis Principia Mathematica”︁

The Meaning and Abilities of Theoretical Physics The Newtonean principles and — derived from them — the congnition of the exixtence of elementary constants according to Planck, Einstein and Bohr increasingly prove to be a strong base not only of physics and its apllication in technology but also of each kind of “exact” sciences in the broadest sense of the word. Since Newton the clarification of concepts with regard so their physical takes place in close connection with the development of mathematical methods. This combination proves to be further productive and ensures the progress of physics an of the “exact” sciences. Most likely all problems which may be of importance in the realm of life can be treated successfully — adequate expenditure taken for granted — with the existing fund of knowledge and methods. The connection between law and accident resting on reality proves to be a relation of complementarity (“there is no absolute accident”). This becomes evident in all branches in all branches of physics, not only in thermodynamics and quantum physics, and can be treated already on the level of the Newtonean principles and elementary constants. Theoretical physics as initiated by newton was designed to comprise all parts of nature. About that there is no contrast between classical physics and quantum physics. It is only a matter of differentiation with regard to the different physical contents and the appropriate mathematical methods, dependent of course on the choice problems. Theoretical physics represents a generally available concentration of the reliable knowledge of physics, which is at the same time the foundation of the “exact” sciences. In this way theoretical physics is the means of communication within the cooperation necessary for the solution of the great complex tasks of science and technology.     

Discovering and “rediscovering” the W boson

One of the first publications by the ATLAS collaboration using data from the Large Hadron Collider at CERN dealt with the measurement of the production cross section of the W boson. The collaboration “rediscovered” the W in order to, among other things, check whether the detector and analysis methods were working well. Originally, the discovery of the W had been announced in 1983 by the CERN management, referring mainly to work done by its UA1 collaboration. In both the discovery and the “rediscovery”, the convergence of two distinct sets of criteria of data selection was an important concern of the researchers. In 1983, this concern figured prominently in the published paper whereas in 2010 it was mainly dealt with inside the collaboration.     

Orientational dynamics of superfluid He: A “two-fluid” model. II. Orbital dynamics

We present a phenomenological theory of the homogeneous orbital dynamics of the class of “separable” anisotropic superfluid phases which includes the ABM state generally identified with ³He-A. The theory is developed by analogy with the spin dynamics described in the first paper of this series; the basic variables are the orientation of the Cooper-pair wavefunction (in the ABM phase, the l-vector) and a quantity K which we visualize as the “pseudo-angular momentum” of the Cooper pairs but which must be distinguished, in general, from the total orbital angular momentum of the system. In the ABM case l is the analog of d in the spin dynamics and K of the “superfluid spin” S_p. Important points of difference from the spin case which are taken into account include the fact that a rotation of l without a simultaneous rotation of the normal-component distribution strongly increases the energy of the system (“normal locking”), and that the equilibrium value of K is zero even for finite total angular momentum. The theory does not claim to handle correctly effects associated with any intrinsic angular momentum arising from particle-hole asymmetry, but it is shown that the magnitude of this quantity can be estimated directly from experimental data and is extremely small; also, the Landau damping does not emerge automatically from the theory, but can be put in in an ad hoc way. With these provisos the theory should be valid for all frequencies irrespective of the value of ωτ. (Δ = gap parameter, τ = quasi-particle relaxation time.) It disagrees with all existing phenomenological theories of comparable generality, although the disagreement with that of Volovik and Mineev is confined to the “gapless” region very close to T_c.The phenomenological equations of motion, which are similar in general form to those of the spin dynamics with damping, involve an “orbital susceptibility of the Cooper pairs” χ_orb(T). We give a possible microscopic definition of the variable K and use it to calculate χ_orb(T) for a general phase of the “separable” type. The theory is checked by inserting the resulting formula in the phenomenological equations for ωτ 1 and comparing with the results of a fully microscopic calculation based on the collisionless kinetic equation; precise agreement is obtained for both the ABM and the (real) polar phase, showing that the complex nature of the ABM phase and the associated “pair angular momentum” is largely irrelevant to its orbital dynamics. We note also that the phenomenological theory gives a good qualitative picture even when ω Δ(T), e.g., for the flapping mode near T_c. Our theory permits a simple and unified calculation of (1) the Cross-Anderson viscous torque in the overdamped regime, (2) the flapping-mode frequency near zero temperature, (3) orbital effects on the NMR, both at low temperatures and near T_c, (4) the orbit wave spectrum at zero temperature (this requires a generalization to inhomogeneous situations which is possible at T = 0 but probably not elsewhere). We also discuss the possibility of experiments of the Einstein-de Haas type. Generally speaking, our results for any one particular application can be also obtained from some alternative theory, but in the case of orbital and spin relaxation very close to T_c (within the “gapless” region) our predictions, while somewhat tentative and qualitative, appear to disagree with those of all existing theories. We discuss briefly how our approach could be extended to apply to more general phases.     

Nuclear track radiography of “Hot” aerosol particles

Nuclear track radiography was applied to identify aerosol “hot” particles which contain elements of nuclear fuel and fallout after Chernobyl NPP accident. For the determination of the content of transuranium elements in radioactive aerosols the measurement of the -activity of “hot” particles by SSNTD was used in this work, as well as radiography of fission fragments formed as a result of the reactions (n,f) and (γ,f) in the irradiation of aerosol filters by thermal neutrons and high energy gamma quanta. The technique allowed the sizes and alpha-activity of “hot” particles to be determined without extracting them from the filter, as well as the determination of the uranium content and its enrichment by ²³⁵U, ²³⁹Pu and ²⁴¹Pu isotopes. Sensitivity of determination of alpha activity by fission method is 5×10⁻⁶ Bq per particle. The software for the system of image analysis was created. It ensured the identification of track clusters on an optical image of the SSNTD surface obtained through a video camera and the determination of size and activity of “hot” particles.     

Weyl geometric gravity and electroweak symmetry “breaking”

A Weyl geometric scale covariant approach to gravity due to Omote, Dirac, and Utiyama (1971ff) is reconsidered. It can be extended to the electroweak sector of elementary particle fields, taking into account their basic scaling freedom. Already Cheng (1988) indicated that electroweak symmetry breaking, usually attributed to the Higgs field with a boson expected at 0.1–0.3 TeV, may be due to a coupling between Weyl geometric gravity and electroweak interactions. Weyl geometry seems to be well suited for treating questions of elementary particle physics, which relate to scale invariance and its “breaking”. This setting suggests the existence of a scalar field boson at the surprisingly low energy of ～ 1 eV. That may appear unlikely; but, as a payoff, the acquirement of mass arises as a result of coupling to gravity in agreement with the understanding of mass as the gravitational charge of fields.     

Feasibility of “intermittent” active control of combustion instabilities in liquid fueled combustors using a “smart” fuel injector

This paper describes an experimental investigation of the feasibility of an “intermittent” active control approach for suppressing combustion instabilities in liquid fueled combustors. The developed controller employs a “smart” fuel injector that can modify the spray properties in response to changes in combustor operating conditions. This action weakens or breaks up the coupling between the combustion process and combustor acoustic modes oscillations, thus preventing the excitation of large amplitude instabilities. This approach differs significantly from previously proposed active control methods, both in concept and implementation, as it requires only “intermittent” modification of the combustion process by a single control action as opposed to the continuous action required by most other active control methods. The “smart” fuel injector used in this study consisted of a double-staged, air-assisted atomizer in which counter swirling, primary (inner stage) and secondary (outer stage) air streams were supplied to the injector through separate sets of tangentially oriented orifices. Control of the ratio of air mass flow rates supplied to these two stages, by use of a diverter valve, resulted in significant changes in the spray shape and its axial, tangential, and radial velocity components. This variation in spray properties of the “smart” injector was characterized for different values of the inner to outer air flow rate ratio in cold flow tests with a PDPA system. These results were then correlated with the characteristics of the “intermittently” controlled combustor. Measured quantities included the instability amplitudes, axial dependence of the mean and oscillatory heat release amplitudes, and the characteristics of the recirculation zones, which were all shown to depend on the fuel spray properties. The results of this study demonstrate the feasibility of using “smart” fuel injectors with capabilities for varying the combustion process characteristics to reduce the amplitudes of detrimental combustion instabilities in real engines to acceptable levels.     

Non-perturbative optical response of a “fluctuating” single quantum dot

We present a model that treats the inter-band optical transitions within a non-perturbative framework which incorporates .both the coherent coupling to light and the incoherent coupling to different reservoirs. It allows us to calculate the photoluminescence line shape and also to simulate its excitation experiments on actual single dots.     

Reply to the paper “comments on the theory of phase-conjugated waves”, by E. Wolf and W.H. Carter

The NH₄Br crystal is irradiated simultaneously with a modulated red light and a steady UV light in the region of the fundamental absorption band. The resulting recombination luminescence of electrons with V_K centers is phase-sensitively detected, and compared with the emission which is directly excited by UV light. From measurements of the excitation spectra for recombination luminescence, it is pointed out that the dissociation of free excitons occurs efficiently in NH₄Br.     

“Loop the loop”

The applicability of the collective coordinate method (saddle-point approximation) for large-N planar models is discussed. Some unstated assumptions are clarified. Statements that Wilson loops form a complete set of gauge invariant operators are also examined and a set of generalized algebraic Mandelstam relations among Wilson loops is presented. The inclusion of loops that wind around themselves and cross many times, as independent variables, is stressed.