Roll angle measurement based on common path compensation principle

We propose a novel and compact roll angle displacement measurement method based on collimated laser position measurement and the common path compensation principle. The principles of the roll angle displacement measurement and the common path compensation are analyzed. The feasibility of the measurement method is verified, and the experimental results revealed a linear correlation coefficient of 0.99995 between the relative displacement of the measuring beam spot and the angular displacement. Furthermore, the theoretical measurement resolution is 0.013  arcsec. To test the performance of the compensation, a series of experiments, including one system stability experiment and two different environmental interference experiments, were performed. The experimental results indicated that the standard deviations of the measuring beam spot’s angular drift were improved by 82.6–87.2%. Thus, the stability of the system and the measurement resolution were improved.     

On Entropic Uncertainty Relations for Measurements of Energy and Its “Complement”

Heisenberg's uncertainty principle in application to energy and time is a powerful heuristics. This statement plays an important role in foundations of quantum theory and statistical physics. If some state exists for a finite interval of time, then it cannot have a completely definite value of energy. It is well known that the case of energy and time principally differs from more familiar examples of two non‐commuting observables. Since quantum theory was originated, many approaches to energy–time uncertainties have been proposed. Entropic way to formulate the uncertainty principle is currently the subject of active researches. Using the Pegg concept of complementarity of the Hamiltonian, uncertainty relations of the “energy–time” type are obtained in terms of Rényi and Tsallis entropies. Although this concept is somehow restricted in scope, derived relations can be applied to systems typically used in quantum information processing. Both the state‐dependent and state‐independent formulations are of interest. Some of the derived state‐independent bounds are similar to the results obtained within a more general approach on the basis of sandwiched relative entropies. The developed method allows us to address the case of detection inefficiencies.     

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.     

“It's been plenty of time ...”

Die Geburtsstunde der theoretischen Nanotechnologie wird heute gerne auf den 29. Dezember 1959 zurückdatiert. An diesem Tag äußerte der spätere Nobelpreisträger Richard Feynman in seiner Bankettansprache “There's Plenty of Room at the Bottom” erste Gedanken zu einer extremen Erhöhung von Datenspeicherdichten. Nanotechnologen sehen sich mit ihrer Arbeit in der Tradition seiner Ideen.     

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.     

Designing the “perfect” projection screen

A perfect diffuser would place 100% of the light leaving the projector in that small region of space where there will be audience eyes to observe it. It would not allow light from sources other than the projector to reach the eyes from the screen. The screen should be affordably priced and cosmetically unremarkable, e.g. seamless. The image seen by any observer should be equally bright over the whole screen. I discuss a way to approximate the perfect projection screen using kinoform diffusers, a Fresnel lens and a mirrored surface.     

“Proper Time” Method Calculation of the “One Loop” Thermodynamical Potential for QED in External Electromagnetic Field

The extension of the “proper time” method to the statistical field theory is obtained. The procedure is used to calculate the “one loop” contribution to the thermodynamical potential in electrodynamics, when the electron positron gas is located in a combination of an inhomogeneous electrostatic field and an uniform magnetic one. Also, a “proper time” representation of the temperature Green function for this problem is given.     

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.     

Optimum excitation of “enhanced” central transition populations

Central transition (CT) sensitivity enhancement schemes that transfer polarization from satellites to the CT through selective saturation or inversion of neighboring satellite transitions have provided a welcome improvement for magic-angle spinning spectra of half-integer quadrupole nuclei. While many researchers have investigated and developed different methods of creating enhanced CT populations, here we investigate the conversion of these enhanced CT populations into observable CT coherence. We show a somewhat unexpected result that a conversion pulse length optimized for maximum sensitivity on equilibrium populations may not be optimum for an enhanced (non-equilibrium) polarization. Furthermore, CT enhancements can be lost if excessive rf field strength is used to convert this enhanced polarization into CT coherence. While a maximally enhanced CT signal is expected when using a perfectly selective CT conversion pulse, we have found that significant sensitivity loss can occur when using surprisingly low rf field strengths, even for sites with relatively large quadrupole coupling constants. We have systematically investigated these issues, and present some general guidelines and expectations when optimizing the conversion of enhanced (non-equilibrium) CT populations into observable CT coherence.     

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.     

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.     

Voltage-controlled trapping of excitons and “storage of light” in lateral superlattices

Voltage-controlled lateral superlattices of various periods are employed to demonstrate the trapping of photogenerated excitons in quasi-one-dimensional regions and to store light in form of ionised excitons in the quantum well of a semiconductor heterostructure. The superlattices are induced by applying spatially alternating external voltages via interdigitated metal gates. Exciton localisation arises from a periodical modulation of the strength of the quantum confined Stark effect in the plane of the quantum well. At large superlattice potential amplitudes the excitons are ionised due to the strong lateral electric fields. The thus spatially separated electrons and holes can be stored efficiently in the structure. Resetting the potential amplitude to zero induces their radiative recombination after very long storage times.     

“Compensatory falsetto”: Effects on vocal quality

The term “compensatory falsetto”, for the purpose of this investigation, refers to the development of an abnormally high-pitched voice in the presence of laryngeal pathology where more socially acceptable lower pitched voice production is possible. The purpose of this investigation was to compare laryngeal compensations and their effects on objective measures of vocal function during production of compensatory falsetto voice. Eighteen patients with abnormally high-pitched voice in the presence of underlying laryngeal pathology were evaluated in the Department of Otolaryngology at the University of Miami School of Medicine from January 1988 through December 1992 and were diagnosed with “compensatory falsetto”. Vocal fold paralysis (n = 11) was the most common laryngeal pathology. Vibratory characteristics were evaluated through videostrobolaryngoscopic examination. Acoustic and aerodynamic parameters assessed included fundamental frequency, jitter rate, harmonic-to-noise ratio, glottal air flow, and maximum phonation time. Production of a higher-pitched voice appeared to improve glottic closure and decrease the amount of air loss during phonation. A corresponding increase in maximum phonation time and improvement in acoustic characteristics of jitter and harmonic-to-noise ratio was also observed.     

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.     

Generic phase diagram of “electron-doped” T′ cuprates

We investigated the generic phase diagram of the electron doped superconductor, Nd_2−xCe_xCuO₄, using films prepared by metal organic decomposition. After careful oxygen reduction treatment to remove interstitial O_ap atoms, we found that the T_c increases monotonically from 24 K to 29 K with decreasing x from 0.15 to 0.00, demonstrating a quite different phase diagram from the previous bulk one. The implication of our results is discussed on the basis of tremendous influence of O_ap “impurities” on superconductivity and also magnetism in T′ cuprates. Then we conclude that our result represents the generic phase diagram for oxygen-stoichiometric Nd_2−xCe_xCuO₄.