1,300 research outputs found
Noise Measurement Setup for Quartz Crystal Microbalance
Quartz crystal microbalance (QCM) is a high sensitive chemical sensor which has found widespread spectrum of applications. There are several mechanisms that are related to fluctuation phenomena. Since the aim of our research is oriented to study the sensitivity and influence of different kind of noises on sensor resolution, we modified an existing method to measure the small frequency fluctuation of QCM. The paper describes our measurement setup, in which a quartz crystal oscillator with coated active layers and a reference quartz oscillator are driven by two oscillator circuits. Each one regulates a frequency of a crystal at the minimum impedance which corresponds to the series resonance. A data-acquisition card triggers on the rise-edges of the output signal and stores these corresponding times on which the instantaneous frequency is estimated by own-written software. In comparison to other measurement setups, our approach can acquire immediate change of QCM frequency, thus, chemical processes can be even described on the basis of high-order statistics. The experiments were provided on quartz crystals with the sorption layer of polypyrrole, which is suitable for the construction of QCM humidity sensors
Noise in piezoelectric ceramics at the low temperatures
The piezoelectric ceramic belongs to materials with widespread spectrum of applications. It can be found in sensors as well as in ceramic capacitors. The main sources of voltage or current fluctuation in piezoelectric ceramics are thermal noise, polarization noise and low frequency 1/f noise. The observed spectra of fluctuating voltage or current can be very well described by the generalized Nyquist relation for linear dissipative system. In this work, we focused on validity of the Nyquist relation for piezoelectric ceramics in temperatures 150 K-270 K. The electrical impedance and noise spectral density are measured and compared in frequency range 100 kHz - 1 MHz. The measurements were made in thermal stable condition and under equilibrium conditions in the case of noise measurement
Surface Tension Driven Convection Experiment Completed
The Surface Tension Driven Convection Experiment (STDCE) was designed to study basic fluid mechanics and heat transfer on thermocapillary flows generated by temperature variations along the free surfaces of liquids in microgravity. STDCE first flew on the USML-1 mission in July 1992 and was rebuilt for the USML-2 mission that was launched in October 1995. This was a collaborative project with principal investigators from Case Western Reserve University (CWRU), Professors Simon Ostrach and Yasuhiro Kamotani, along with a team from the NASA Lewis Research Center composed of civil servants and contractors from Aerospace Design & Fabrication, Inc. (ADF), Analex, and NYMA, Inc
Magnetic Order in the 2D Heavy-Fermion System CePt2In7 studied by muSR
The low-temperature microscopic magnetic properties of the quasi-2D
heavyfermion compound, CePt2In7 are investigated by using a positive muon-spin
rotation and relaxation (?muSR) technique. Clear evidence for the formation of
a commensurate antiferromagnetic order below TN=5.40 K is presented. The
magnetic order parameter is shown to fit well to a modified BSC gap-energy
function in a strong-coupling scenario.Comment: Accepted in Journal of Physics: Conference Series (2014
The Effect of Calcining Temperature on Photocatalytic Activity of Porous ZnO Architecture
Zinc oxide (ZnO) nano crystals assembled porous architecture was prepared by thermal decomposition of zinc oxalate precursor at various temperatures ranging from 400-900°C. The effect of calcining temperature on structure and morphology was examined by scanning electron microscopy (SEM), X-ray diffractometry, thermogravimetry, and BET adsorption analysis. The porous nano crystalline ZnO morphology was developed due to the release of volatile precursor products, while the overall shape of ZnO micro crystals was retained as a legacy of the precursor. The average crystallite size increased with increasing temperature of calcination from approximately 21 nm to 79 nm, while the specific surface area decreased from 30 to 1.7 m2g-1. The photo catalytic performance of prepared ZnO powders was evaluated by degradation of methyl violet 2B, a model compound. The significantly highest photo catalytic activity was achieved with powder calcined at 500°C. This may be attributed to the sufficiently well-developed crystalline arrangement, while the specific surface area is still high enough
The Effect of Calcining Temperature on Photocatalytic Activity of Porous ZnO Architecture
Zinc oxide (ZnO) nano crystals assembled porous architecture was prepared by thermal decomposition of zinc oxalate precursor at various temperatures ranging from 400-900°C. The effect of calcining temperature on structure and morphology was examined by scanning electron microscopy (SEM), X-ray diffractometry, thermogravimetry, and BET adsorption analysis. The porous nano crystalline ZnO morphology was developed due to the release of volatile precursor products, while the overall shape of ZnO micro crystals was retained as a legacy of the precursor. The average crystallite size increased with increasing temperature of calcination from approximately 21 nm to 79 nm, while the specific surface area decreased from 30 to 1.7 m2g-1. The photo catalytic performance of prepared ZnO powders was evaluated by degradation of methyl violet 2B, a model compound. The significantly highest photo catalytic activity was achieved with powder calcined at 500°C. This may be attributed to the sufficiently well-developed crystalline arrangement, while the specific surface area is still high enough
Coherent Pion Radiation From Nucleon Antinucleon Annihilation
A unified picture of nucleon antinucleon annihilation into pions emerges from
a classical description of the pion wave produced in annihilation and the
subsequent quantization of that wave as a coherent state. When the constraints
of energy-momentum and iso-spin conservation are imposed on the coherent state,
the pion number distribution and charge ratios are found to be in excellent
agreement with experiment.Comment: LaTex, 8 text pages, 1 PostScript figure, PSI-PR-93-2
Microstructure of (Hf-Ta-Zr-Nb)C high-entropy carbide at micro and nano/atomic level
Support from the projects APVV-15-0469, APVV-15-0621, VEGA 2/0163/16, and VEGA 2/0082/17 is acknowledged. MJR and EGC acknowledge the support of EPSRC grant XMAT (EP/K008749/2)
Coherent state formulation of pion radiation from nucleon antinucleon annihilation
We assume that nucleon antinucleon annihilation is a fast process leading to
a classical coherent pion pulse. We develop the quantum description of such
pion waves based on the method of coherent states. We study the consequences of
such a description for averages of charge types and moments of distributions of
pion momenta with iso-spin and four-momentum conservation taken into account.
We briefly discuss the applicability of our method to annihilation at rest,
where we find agreement with experiment, and suggest other avenues for its use.Comment: 24 pages, 3 figures, 1 table, PSI-preprin
Seasonal and intra-diurnal variability of small-scale gravity waves in OH airglow at two Alpine stations
Between December 2013 and August 2017 the instrument FAIM (Fast Airglow
IMager) observed the OH airglow emission at two Alpine stations. A year of
measurements was performed at Oberpfaffenhofen, Germany (48.09∘ N,
11.28∘ E) and 2 years at Sonnblick, Austria (47.05∘ N,
12.96∘ E). Both stations are part of the network for the detection
of mesospheric change (NDMC). The temporal resolution is two frames per
second and the field-of-view is 55 km × 60 km and
75 km × 90 km at the OH layer altitude of 87 km with a spatial
resolution of 200 and 280 m per pixel, respectively. This resulted in two
dense data sets allowing precise derivation of horizontal gravity wave
parameters. The analysis is based on a two-dimensional fast Fourier transform
with fully automatic peak extraction. By combining the information of
consecutive images, time-dependent parameters such as the horizontal phase
speed are extracted. The instrument is mainly sensitive to high-frequency
small- and medium-scale gravity waves. A clear seasonal dependency concerning
the meridional propagation direction is found for these waves in summer in
the direction to the summer pole. The zonal direction of propagation is
eastwards in summer and westwards in winter. Investigations of the data set
revealed an intra-diurnal variability, which may be related to tides. The
observed horizontal phase speed and the number of wave events per
observation hour are higher in summer than in winter.</p
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