Laser modulated optical reflectance of thin semiconductor films on glass

Semiconductor films, deposited by reactive magnetron sputtering on glass substrates have been analyzed with the help of laser-modulated optical reflectance. The results are discussed with respect to the thermal and charge carrier transport properties. Semiconductor properties have been identified both for micro-crystalline and amorphous film

Quantitative Contactless Photothermal Monitoring Of Drying In Foodstuff Materials

The role of a quantitative method, based on contactless photothermal monitoring, in the drying process of food products was described. The influence of moisture content on the effective thermal transport properties of the materials was used in the study. The transperency consideration in the foodstuff provided direct information related to the optical and thermal parameters. The infrared detection formed the basis for analyzing the frequency dependent thermal wave signals at different drying states.741 II744746Delgadillo-Holtfort, I., (2000) Quantitative Infrared Thermograph 5, QIRT 2000, pp. 103-104. , Reims, France, edited by D. Balageas et alDelgadillo-Holtfort, I., (2001) Anal. Sci., 17, p. 507Bein, B.K., (1999) BAM-DGZfP-Berichtsband, BB 69-CD, pp. M1Xiao, P., (2001) Anal. Sci., 17, pp. s349Bolte, J., (1997) High Temp.-High Press., 29, p. 567Bein, B.K., (1986) Can. J. Phys., 64, p. 1208Bein, B.K., (1997) High Temp.-High Press., 29, p. 43

Theory of Banana Liquid Crystal Phases and Phase Transitions

We study phases and phase transitions that can take place in the newly discovered banana (bow-shaped or bent-core) liquid crystal molecules. We show that to completely characterize phases exhibited by such bent-core molecules a third-rank tensor $T^{ijk}$ order parameter is necessary in addition to the vector and the nematic (second-rank) tensor order parameters. We present an exhaustive list of possible liquid phases, characterizing them by their space-symmetry group and order parameters, and catalog the universality classes of the corresponding phase transitions that we expect to take place in such bent-core molecular liquid crystals. In addition to the conventional liquid-crystal phases such as the nematic phase, we predict the existence of novel liquid phases, including the spontaneously chiral nematic $(N_T + 2)^*$ and chiral polar $(V_T + 2)^*$ phases, the orientationally-ordered but optically isotropic tetrahedratic $T$ phase, and a novel nematic $N_T$ phase with $D_{2d}$ symmetry that is neither uniaxial nor biaxial. Interestingly, the Isotropic-Tetrahedratic transition is {\em continuous} in mean-field theory, but is likely driven first-order by thermal fluctuations. We conclude with a discussion of smectic analogs of these phases and their experimental signatures.Comment: 28 pgs. RevTex, 32 eps figures, submitted to Phys. Rev.

Effective index of refraction, optical rotation, and circular dichroism in isotropic chiral liquid crystals

This paper concerns optical properties of the isotropic phase above the isotropic-cholesteric transition and of the blue phase BP III. We introduce an effective index, which describes spatial dispersion effects such as optical rotation, circular dichroism, and the modification of the average index due to the fluctuations. We derive the wavelength dependance of these spatial dispersion effects quite generally without relying on an expansion in powers of the chirality and without assuming that the pitch of the cholesteric $P$ is much shorter than the wavelength of the light $\lambda$, an approximation which has been made in previous studies of this problem. The theoretical predictions are supported by comparing them with experimental spectra of the optical activity in the BP III phase.Comment: 15 pages and 7 figures. Submitted to PR

Modulated photothermal measurements applied to multi-layer superinsulation foils

Abstract -Photothermal measurements based on modulated heating in the visible spectral range and IR detection of the thermal response are used to determine the effective thermal transport properties and the shielding properties of multi-layer superinsulation foils consisting of different numbers of aluminized mylar layers and spacer layers. The measurements have been run at ambient temperature, both at ambient pressure and at reduced pressures between 1 mbar and 300 mbar

Mathematical Properties of a New Levin-Type Sequence Transformation Introduced by \v{C}\'{\i}\v{z}ek, Zamastil, and Sk\'{a}la. I. Algebraic Theory

\v{C}\'{\i}\v{z}ek, Zamastil, and Sk\'{a}la [J. Math. Phys. \textbf{44}, 962 - 968 (2003)] introduced in connection with the summation of the divergent perturbation expansion of the hydrogen atom in an external magnetic field a new sequence transformation which uses as input data not only the elements of a sequence $\{s_n \}_{n=0}^{\infty}$ of partial sums, but also explicit estimates $\{\omega_n \}_{n=0}^{\infty}$ for the truncation errors. The explicit incorporation of the information contained in the truncation error estimates makes this and related transformations potentially much more powerful than for instance Pad\'{e} approximants. Special cases of the new transformation are sequence transformations introduced by Levin [Int. J. Comput. Math. B \textbf{3}, 371 - 388 (1973)] and Weniger [Comput. Phys. Rep. \textbf{10}, 189 - 371 (1989), Sections 7 -9; Numer. Algor. \textbf{3}, 477 - 486 (1992)] and also a variant of Richardson extrapolation [Phil. Trans. Roy. Soc. London A \textbf{226}, 299 - 349 (1927)]. The algebraic theory of these transformations - explicit expressions, recurrence formulas, explicit expressions in the case of special remainder estimates, and asymptotic order estimates satisfied by rational approximants to power series - is formulated in terms of hitherto unknown mathematical properties of the new transformation introduced by \v{C}\'{\i}\v{z}ek, Zamastil, and Sk\'{a}la. This leads to a considerable formal simplification and unification.Comment: 41 + ii pages, LaTeX2e, 0 figures. Submitted to Journal of Mathematical Physic

THERMAL-WAVE MEASUREMENTS OF MULTI-LAYER SUPERINSULATION FOILS

Abstract Thermal wave measurements rely on modulated laser heating and IR detection of the thermal response, using a MCT detector with IR optics and lock-in amplifier. Both, the amplitude and the phase retardation of the thermal wave response with respect to the heating modu-lation, provide information on the effective thermal transport properties of the measured samples. Here we apply this method to determine the shielding properties of multilayer superinsulation foils, used for the thermal insulation of superconducting magnetic coils in particle accelerators, e.g. in LHC at CERN. The measurements, performed at ambient temperature and ambient and reduced pressure, have been interpreted using a theoreti-cal model, including both conductive and radiative heat transport. The results show that the radiative heat transport can be well identified, although the conductive heat transport is dominant across multi-layer samples. At reduced pressures, the conductive heat transport decrea-ses considerably and, depending on the number of spacer layers, the radiative heat transport can become dominant. Applying this new photothermal technique, the shielding efficiencies of multi-layer superinsulation foils have been compared in this work for the first time

Convergence Acceleration via Combined Nonlinear-Condensation Transformations

A method of numerically evaluating slowly convergent monotone series is described. First, we apply a condensation transformation due to Van Wijngaarden to the original series. This transforms the original monotone series into an alternating series. In the second step, the convergence of the transformed series is accelerated with the help of suitable nonlinear sequence transformations that are known to be particularly powerful for alternating series. Some theoretical aspects of our approach are discussed. The efficiency, numerical stability, and wide applicability of the combined nonlinear-condensation transformation is illustrated by a number of examples. We discuss the evaluation of special functions close to or on the boundary of the circle of convergence, even in the vicinity of singularities. We also consider a series of products of spherical Bessel functions, which serves as a model for partial wave expansions occurring in quantum electrodynamic bound state calculations.Comment: 24 pages, LaTeX, 12 tables (accepted for publication in Comput. Phys. Comm.