Temperature Variation Of Frequency Research Articles

Synthesis, optical and dielectric studies on novel semi organic nonlinear optical crystal by solution growth technique

Bisthiourea lead acetate Pb[SC(NH 2) 2] 2(CH 3COO) 2), a novel semi organic non linear optical crystal having dimensions 17 mm × 2 mm × 2 mm were grown using slow evaporation technique. The lattice parameters for the grown crystals were determined using single crystal XRD. The presence of functional groups for the grown crystals was confirmed using Fourier transform infrared (FT-IR) spectroscopy. The optical absorption studies show that the material has wide optical transparency in the entire visible region. The dielectric constant and dielectric loss has been studied as a function of frequency for various temperatures and the results were discussed in detail. The second harmonic generation was confirmed by Kurtz powder method and it is found to be 5 times than that of potassium dihydrogen phosphate (KDP) crystal.

Geothermal Climate Change Observatory in south India 2: Set-up and first results

A Geothermal Climate Change Observatory has been established in south India to quantify the inter-relationships between surface air temperatures, surface ground temperatures and subsurface temperatures on annual to decadal timescales and therefore contribute to better interpretation of the geothermal record of climate change. The observatory is located in the Choutuppal campus of National Geophysical Research Institute (17.29°N, 78.92°E), about 60 km to the east of Hyderabad. Surface meteorological parameters including air temperature, relative humidity, rainfall, solar radiation, wind speed and wind direction are being recorded continuously at an automatic weather station. At the same site, ground temperatures are being recorded continuously at depths of 0.015, 0.09, 0.19, 0.49, 0.99 and 1.19 m using a 1.2 m ground temperature probe buried into the granite regolith to track the diurnal changes in surface temperature. To track the seasonal and decadal changes, repeat temperature measurements are being carried out periodically in two boreholes CH-11 and CH-10 drilled to depths of 21 m and 210 m respectively and located within 3 m of the weather station. Surface meteorological data during the first year of operation indicate a general correlation between the time series for air temperature and incident solar radiation over the length of the record. Comparisons of the surface air temperature and ground temperatures measured at depths of a few cm to 21 m below the surface reveal both attenuation of high frequency temperature variations and time lag in the signals with increasing depth. These observations support a conductive heat transfer in the subsurface. Diurnal variations of surface air temperature decay to insignificant levels at a depth of ∼1 m, whereas the seasonal variations persist to depths of at least 10 m at the site. Ongoing measurements over the next few years would bring out a wealth of information on the nature and extent of tracking between the surface and subsurface temperature variations and lead to better understanding of the energy balance near the ground–air interface.

Rheology of asphalt and styrene–butadiene blends

In recent years, many authors have researched polymer-modified asphalt blends and tried to better understand the rheological behavior of these materials. In this work, the thermomechanical response of an asphalt formulation was researched trying to find better asphalt-modified blends that allow for the construction of improved asphalt roads. The experimentation included several polymer–maltene formulations developed at different polymer concentrations and temperatures where the asphaltenes of the original asphalt were removed. Such separation was carried out because the maltene fraction represents the portion of the asphalt that chemically reacts with the polymer modifier. The rheological behavior of the blends was determined from oscillatory shear flow data. Analysis of the G′, G′′, G* moduli and phase angle (δ) as a function of oscillatory frequency for various temperatures led to the conclusion that the maltenes behaved as a pseudo-homogeneous viscoelastic material that could dissipate stress without presenting structural changes. Furthermore, all maltenes–polymer blends behaved more viscoelastically than the non-blended maltenes depending on the amount of the polymer contained in the formulation. The blend viscosity increased with polymer concentration, and this increase was seen in both the viscous and elastic moduli. Furthermore, performance grade trials were also performed according to the AASHTO TP5 to determine the failing temperature. It was noticed that the limiting temperature increased with the modifier concentration with a δ between 50° and 60°, indirect value of elasticity found to have industrial applications for asphalt pavements.

Spin-coupled phonons in multiferroic YbMnO3 epitaxial films by Raman scattering

YbMnO3 epitaxial thin films were investigated by Raman scattering in the temperature range of 15-300K. We successfully observed some phonon modes (5A1+6E2) at 15K with mode assignment based on polarized Raman study. Furthermore, an E2 mode at 253 cm-1 which affected Mn-O-Mn bond angles showed anomalous temperature variation in frequency at temperature below ~80K. It suggested a spin-phonon coupling that occurred below TN.

Terrestrial Climate Evolution in Northwest Germany Over the Last 25 Million Years

Other| October 01, 2000 Terrestrial Climate Evolution in Northwest Germany Over the Last 25 Million Years TORSTEN UTESCHER; TORSTEN UTESCHER 1Institut für Geologie, Nussallee 8, 53115 Bonn, Germany Search for other works by this author on: GSW Google Scholar VOLKER MOSBRUGGER; VOLKER MOSBRUGGER 2Institut für Geologie und Paläontologie der Universität Tübingen, 72119 Tübingen, Germany Search for other works by this author on: GSW Google Scholar ABDUL R. ASHRAF ABDUL R. ASHRAF 2Institut für Geologie und Paläontologie der Universität Tübingen, 72119 Tübingen, Germany Search for other works by this author on: GSW Google Scholar PALAIOS (2000) 15 (5): 430–449. https://doi.org/10.1669/0883-1351(2000)015<0430:TCEING>2.0.CO;2 Article history accepted: 26 Jun 2000 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation TORSTEN UTESCHER, VOLKER MOSBRUGGER, ABDUL R. ASHRAF; Terrestrial Climate Evolution in Northwest Germany Over the Last 25 Million Years. PALAIOS 2000;; 15 (5): 430–449. doi: https://doi.org/10.1669/0883-1351(2000)015<0430:TCEING>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract The first detailed reconstruction of the continental paleoclimate evolution of the Northwest German Tertiary (Late Oligocene to Pliocene) is presented. The paleoclimate data are derived from the paleobotanical record using the coexistence approach, a method recently introduced that employs climatic requirements of the Nearest Living Relatives of a fossil flora. Twenty six megafloras (fruits and seeds, leaves, woods) from the Tertiary succession of the Lower Rhine Basin and neighboring areas are analyzed with respect to ten meteorological parameters. Additionally, two sample sets from Late Miocene to Early Pliocene sediments comprising 396 palynofloras are analyzed by the same method providing a higher temporal resolution. The temperature curves show a comparatively cooler phase in the Late Oligocene, a warm interval the Middle Miocene, and a cooling starting at 14 Ma. The cooling trend persisted until Late Pliocene with a few higher frequency temperature variations observed. From the beginning of Late Miocene to the present, the seasonality increases and climate appears to have been less stable. As indicated by the precipitation data, a Cfa climate with wet summers persisted in NW Germany from Late Oligocene to Late Pliocene.The results obtained are well in accordance with regional and global isotope curves derived from the marine record, and allow for a refined correlation of the Tertiary succession in the Lower Rhine Basin with the international standard. It is shown that the reconstructed data are largely consistent with the continental climate record for the Northern Hemisphere, as reported by various authors. Discrepancies with previous reconstructions are discussed in detail. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Alternating current conductivity and dielectric dispersion in copper-silica nanocomposites synthesized by electrodeposition

Composites of nanometer-sized copper metal with diameters varying from 3.2 to 11.4 nm dispersed in a silica gel medium were synthesized by an electrodeposition method. The ac conductivity and dielectric dispersion of these nanocomposites were measured over the frequency range 0.2 kHz–1.5 MHz at temperatures varying from 150 to 300 K. The ac conductivity showed a frequency dependence of ∝ωn where ω is the angular frequency and n∼0.62 the latter being temperature independent. The quantum mechanical tunneling model was used to explain this result. The dielectric modulus data were analyzed on the basis of a stretched exponential relaxation function. The values of the exponent β as extracted from such analysis were found to be in the range 0.31–0.42 and were temperature independent for different gel compositions. The activation energies were estimated from the temperature variation of frequency at which the imaginary part of the dielectric modulus was maximum. The activation energy value ∼0.24 eV could be explained satisfactorily on the basis of an electron tunneling mechanism.

Lattice vibrations in chlorobenzenes: Experimental dispersion curves for β-paradichlorobenzene by neutron scattering

Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p-C6D4Cl2 and p-C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K was applied in order to correct for anharmonic effects. Calculations based on the atom-atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either by consideration of electrostatic forces or by further anisotropy in the dispersion forces not described in the atom-atom model. Anharmonic effects are shown to be large, but the dominant features in the temperature variation of frequencies are describable by a quasiharmonic model.