Topological defects in 1D elastic waves

It has been recently shown theoretically that a topological defect in a 1D periodic potential may give rise to two localized states within the energy gaps. In this work we present an experimental realization of this effect for the case of torsional waves in elastic rods. We also show numerically that three, or even more, localized states can be present if the parameters characterizing the topological defect are suitably varied.Comment: 3 pages, 4 figures, accepted in Physica

Geometric Analysis of Turbulent Macrostructure in Jets Laid on Flat Surfaces for Turbulence Intensity Calculation

У цій роботі ми розглянули інтенсивність турбулентності стінових струмів на плоских поверхностей, таких як стін або стель приміщень, без будь-яких експериментальних даних Результати співпадають з відомими експериментальними даними і можуть бути використані у розрахунках потоків у приміщенні.Європейські норми для вентиляції містять вимоги до інтенсивності турбулентності в номерах. Одним з визначальних факторів є інтенсивність турбулентності в вентиляційні потоки. Ми нашли підхід для геометричного аналізу турбулентних макроструктура дозвукових течій з великомасштабною стримуваністю, т. е. вентиляція струми та пограничні шари між потоками. Такий підхід потребує спрощеної діаграми турбулентної макроструктури та виконання геометричного аналіз В попередніх роботах, використовуючи підхід, який ми аналітично нашли, загальна характеристика вільних струмів, струми в потоках і струмах, закладених на різноманітних поверхнях без будь-яких експериментальних даних. Результати геометричний аналіз теплообміну між потоками використовуються в Українських норм. У цій роботі ми розглянули інтенсивність турбулентності стінових струмів на плоских поверхнях, таких як стін або стель приміщень, без будь-яких експериментальних даних Результати співпадають з відомими експериментальними даними і можуть бути використані у розрахунках потоків у приміщенні.European Norms for ventilation contain turbulence intensity requirements in rooms. One of the determining factors is turbulence intensity in ventilation jets. We found an approach for geometric analysis of turbulent macrostructure for subsonic flows with large-scale vorticity i.e. ventilation jets and boundary layers between flows. This approach requires building of simplified turbulent macrostructure chart and performing geometrical analysis of it. In previous works, using the approach we analytically found averaged characteristic of free jets, jets in flows and jets laid on different shape surfaces without requirements of any experimental data. The results of geometrical analysis of heat transfer between flows are used in Ukrainian norms. In this work we found turbulence intensity of wall jets on flat surfaces such as room walls or ceiling without any experimental values. The results are coincide with known experimental data and may be used in flow calculation in room.Европейские нормы для вентиляции содержат требования к интенсивности турбулентности в номерах. Одним из определяющих факторов является интенсивность турбулентности в вентиляционных потоках. Мы нашли подход для геометрического анализа турбулентных макроструктурах дозвуковых течений с крупномасштабной завихренностью, т. е. вентиляция струй и пограничных слоев между потоками. Такой подход требует упрощенной диаграммы турбулентной макроструктуры и выполнения геометрического анализа. В предыдущих работах, используя подход, который мы аналитически нашли, усредненная характеристика свободных струй, струй в потоках и струях, заложенных на разных поверхностях без каких-либо экспериментальных данных. Результаты геометрического анализа теплообмена между потоками используются в Украинских нормах. В этой работе мы рассмотрели интенсивность турбулентности стеновых струй на плоских поверхностях, таких как стены или потолки помещений, без каких-либо экспериментальных данных. Результаты совпадают с известными экспериментальными данными и могут быть используется при расчете потоков в помещении

Metafluid with anisotropic dynamic mass

We show that a fluid filling the space between metallic cylinders arranged in a two-dimensional lattice exhibits anisotropic dynamic mass for sound waves propagating through the lattice, if its unit cell is anisotropic. Using the plane-waves expansion method we derive (in the long wavelength limit) a formula for the effective mass tensor of the metafluid. The proposed formula is very general — it is valid for arbitrary Bravais lattices and arbitrary filling fractions of the cylinders. We apply our method to a periodic structure with very high anisotropy, when other known methods fail. In particular, we calculate the effective mass tensor for sound waves in air with embedded lattice of aluminum cylinders having rectangular cross sections, and obtain excellent agreement with experiment. The proposed method of calculation may find numerous applications for tailoring of metafluids with prescribed anisotropy

Index of refraction of a photonic crystal of carbon nanotubes and homogenization of optically anisotropic periodic composites

We consider the long-wavelength limit for a periodic arrangement of carbon nanotubes. Using the Fourier expansion method we develop an effective-medium theory for photonic crystal of aligned optically anisotropic cylinders. Exact analytical formulas for the effective dielectric constants for the E and H eigenmodes are obtained for arbitrary 2D Bravais lattice and arbitrary cross-section of anisotropic cylinders. It is shown that depending on the symmetry of the unit cell photonic crystal of anisotropic cylinders behaves in the low-frequency limit like uniaxial or biaxial optical crystal. The developed theory of homogenization is in a good agreement with existing experimental results for the dielectric tensor of photonic crystals of carbon nanotubes

Comparison of synchronisation and fertility after different modifications of the ovsynch protocol in cyclic dairy cows

The objectives of this study were to evaluate the effects of (1) double doses of PGF2α administration or (2) an exogenous progesterone (CIDR) applied concurrently with, or (3) the day after, first GnRH of Ovsynch (GnRH-1), on synchronisation and fertility during the Ovsynch protocol. All cows (n = 378) received the Ovsynch protocol (GnRH-7d-PGF2α-56h-GnRH-18h-TAI). The ‘OVS’ group (n = 105) received only the Ovsynch protocol. The ‘OVS-PGF’ group (n = 118, GnRH-7d-PGF2α-12h-PGF2α-44h-GnRH-18h-TAI) received an extra dose of PGF2α 12 h later on Day 7. The ‘OVS-7CIDR’ group (n = 78, GnRH+CIDR-7d-PGF2α-56h-GnRH-18h-TAI) received a CIDR for 7 days between GnRH-1 and PGF2α. In the ‘OVS-6CIDR’ group (n = 77, GnRH-24h-CIDR-6d-PGF2α-56h-GnRH-18h-TAI), CIDR was applied one day after GnRH-1 and removed 6 days later. When all cows were evaluated, the responses to GnRH-2 were higher (P = 0.005) in cows that responded to GnRH-1 (95.4%) compared to the cows that did not respond (87.6%). The pregnancy rates at 31 and 62 days for each group were 48.6% and 42.9% in the OVS, 54.2% and 52.5% in the OVS-PGF, 52.6% and 48.7% in the OVS-7CIDR, and 55.8% and 49.3% in the OVS-6CIDR groups. Thus, none of the three different treatments has an effect on increasing the out-comes of the Ovsynch protocol in cyclic lactating dairy cows

Speed of Sound in Periodic Elastic Composites

In this article, the authors consider the low-frequency limit (homogenization) for propagation of sound waves in periodic elastic medium (phononic crystals)

Low-frequency index of refraction for a two-dimensional metallodielectric photonic crystal

This article discusses the low-frequency index of refraction for a two-dimensional metallodialectric photonic crystal

A Study of Ground Deformation in the Guangzhou Urban Area with Persistent Scatterer Interferometry

The Interferometric Point Target Analysis (IPTA) technique and Advanced Synthetic Aperture Radar (ASAR) images acquired over Hong Kong from 2007–2008 were used to detect ground deformation in the urban area of Guangzhou city in South China. A ground deformation rate map with scattered distribution of point targets shows the maximum subsidence (rise) rate as high as -26 to -20 mma-1 (16–21 mma-1), implying that the study area is an active zone for ground deformation. Based on the point target map, a contour ground deformation rate map is generated. The map shows three major subsidence zones located in the middle-west, the east, and the southwest of the study area, respectively. All the six ground collapse accidents that occurred in 2007–2008 fall within the subsidence zones, qualitatively validating the IPTA results. Ground subsidence and geological conditions on Datansha Island are examined. The results indicate that the local geological conditions, such as limestone Karst geomorphology as well as silt layers characterized by high water content, high void ratio, high compressibility, low bearing capacity and low shear strength, and underground engineering projects are responsible for ground subsidence and ground collapse accidents occurred there

Electrostatic enhancement of light emitted by semiconductor quantum well

Carrier dynamics in metal-semiconductor structures is driven by electrodynamic coupling of carriers to the evanescent field of surface plasmons. Useful modifications in electron and hole dynamics due to presence of metallic inclusions show promise for applications from light emitters to communications. However, this picture does not include contributions from electrostatics. We propose here an electrostatic mechanism for enhancement of light radiated from semiconductor emitter which is comparable in effect to plasmonic mechanism Arising from Coulomb attraction of e-h pairs to their electrostatic images in metallic nanoparticles, this mechanism produces large carrier concentrations near the nanoparticle. A strong inhomogeneity in the carrier distribution and an increase in the internal quantum efficiency are predicted. In our experiments, this manifests as emission enhancement in InGaN quantum well (QW) radiating in the near-UV region. This fundamental mechanism provides a new perspective for improving the efficiency of broadband light emitters

Electrostatic enhancement of light emitted by semiconductor quantum well

Carrier dynamics in metal-semiconductor structures is driven by electrodynamic coupling of carriers to the evanescent field of surface plasmons. Useful modifications in electron and hole dynamics due to presence of metallic inclusions show promise for applications from light emitters to communications. However, this picture does not include contributions from electrostatics. We propose here an electrostatic mechanism for enhancement of light radiated from semiconductor emitter which is comparable in effect to plasmonic mechanism Arising from Coulomb attraction of e-h pairs to their electrostatic images in metallic nanoparticles, this mechanism produces large carrier concentrations near the nanoparticle. A strong inhomogeneity in the carrier distribution and an increase in the internal quantum efficiency are predicted. In our experiments, this manifests as emission enhancement in InGaN quantum well (QW) radiating in the near-UV region. This fundamental mechanism provides a new perspective for improving the efficiency of broadband light emitters