1,809 research outputs found
Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study
An experimental study has been conducted to examine the interaction of compressible flow structures such as
shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure
ratios ofP4
=P1 = 4, 8, and 12 have been employed, whereP4
is the driver gas pressure andP1
is the pressure within
the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66,
respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and
driven gases. High-speed shadowgraphy was employed to visualize the induced flowfield. Pressure measurements
were taken at different locations along the test section to study theflow quantitatively. The induced flow is unsteady
and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm
Novel ionic liquid [Et3N-SO3H][MeSO3]: Synthesis, characterization and catalytic performance for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes
The main aim of this work is introducing a novel protic acidic ionic-liquid catalyst for organic synthesis. Thus, N,N-diethyl-N-sulfoethanaminium methanesulfonate ([Et3N-SO3H][MeSO3]) was synthesized by the reaction of triethylamine with chlorosulfonic acid, and then with methanesulfonic acid. The structure of this novel protic acidic ionic liquid was identified by FT-IR, 1H NMR, 13C NMR and mass spectral data. Its catalytic activity was examined for the solvent-free reaction of 2-naphthol with arylaldehydes to provide 14-aryl-14H-dibenzo[a,j]xanthenes. [Et3N-SO3H][MeSO3] efficiently catalyzed the reaction, and the products were obtained in high to excellent yields and in short reaction times. KEY WORDS: Protic acidic ionic liquid, N,N-Diethyl-N-sulfoethanaminium methanesulfonate ([Et3N-SO3H][MeSO3]), 2-Naphthol, Arylaldehyde, 14-Aryl-14H-dibenzo[a,j]xanthene Bull. Chem. Soc. Ethiop. 2019, 33(1), 69-76DOI: https://dx.doi.org/10.4314/bcse.v33i1.
Spin-squeezing and Dicke state preparation by heterodyne measurement
We investigate the quantum non-demolition (QND) measurement of an atomic
population based on a heterodyne detection and show that the induced
back-action allows to prepare both spin-squeezed and Dicke states. We use a
wavevector formalism to describe the stochastic process of the measurement and
the associated atomic evolution. Analytical formulas of the atomic distribution
momenta are derived in the weak coupling regime both for short and long time
behavior, and they are in good agreement with those obtained by a Monte-Carlo
simulation. The experimental implementation of the proposed heterodyne
detection scheme is discussed. The role played in the squeezing process by the
spontaneous emission is considered
Strong-field approximation for Coulomb explosion of H_2^+ by short intense laser pulses
We present a simple quantum mechanical model to describe Coulomb explosion of
H by short, intense, infrared laser pulses. The model is based on the
length gauge version of the molecular strong-field approximation and is valid
for pulses shorter than 50 fs where the process of dissociation prior to
ionization is negligible. The results are compared with recent experimental
results for the proton energy spectrum [I. Ben-Itzhak et al., Phys. Rev. Lett.
95, 073002 (2005), B. D. Esry et al., Phys. Rev. Lett. 97, 013003 (2006)]. The
predictions of the model reproduce the profile of the spectrum although the
peak energy is slightly lower than the observations. For comparison, we also
present results obtained by two different tunneling models for this process.Comment: 8 pages, 4 figure
Behavior analysis of factors affecting safety management to reduce incidents in the pelletizing industry using the system dynamics approach
The purpose of this study was to analyze the behavior of effective factors on safety management to reduce incidents in the pelletizing industry using the system dynamics approach. Risk assessment for the Sechahon pelletizing plant was performed using the FMEA method. A total of 625 risks were identified in this complex of which 286 are high risk RPNs and need to be scrutinized. These risks were categorized according to their nature and consequences in five physical categories, exposure to dust, ergonomics, emergencies and psychosocial risks, so that they can be reviewed in detail. The results showed that decreasing the number of incidents in the risk reduction scenario would reduce the incidence earlier, and is initially more than other policies. The scenario of risk reduction is the best scenario in the short term. The technology improvement scenario shows an incremental growth trend, but the scenario of the current situation can better decrease the number of incidents. The human resource management and safety management scenario will initially be on an upward trend and will continue to decline. The human resource management and safety management scenario is a good way to reduce disasters in the long run. Keywords: safety management, system dynamics, incident reduction, pelletizing industry. DOI: 10.7176/IEL/10-1-06 Publication date: February 29th 202
Exciton coherence lifetimes from electronic structure
We model the coherent energy transfer of an electronic excitation within
covalently linked aromatic homodimers from first-principles, to answer whether
the usual models of the bath calculated via detailed electronic structure
calculations can reproduce the key dynamics. For these systems the timescales
of coherent transport are experimentally known from time-dependent polarization
anisotropy measurements, and so we can directly assess the whether current
techniques might be predictive for this phenomenon. Two choices of electronic
basis states are investigated, and their relative merits discussed regarding
the predictions of the perturbative model. The coupling of the electronic
degrees of freedom to the nuclear degrees of freedom is calculated rather than
assumed, and the fluorescence anisotropy decay is directly reproduced.
Surprisingly we find that although TDDFT absolute energies are routinely in
error by orders of magnitude more than the coupling energy, the coherent
transport properties of these dimers can be semi-quantitatively reproduced from
first-principles. The directions which must be pursued to yield predictive and
reliable prediction of coherent transport are suggested.Comment: 22 pages, 7 figure
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