124 research outputs found
The Effects of Thermal Procedure on Transformation Temperature, Crystal Structure and Microstructure of Cu-Al-Co Shape Memory Alloy
The purpose of this study is to investigate the effects of different thermal procedures of the Cu-Al-Co shape memory alloy on its crystal structure, transformation temperature and microstructure. The alloys were subjected to a heat treatment and then cooling was applied at four different conditions. After the thermal process, XRD, DSC, optical microscopy and micro-hardness measurements were carried out. The experimental studies showed that crystal structure, microstructure and transformation temperature of Cu-Al-Co alloy were changed from the cooling conditions
On the physical nudging equations
In this work we show how it is possible to derive a new set of nudging equations, a tool still used in many data assimilation problems, starting from statistical physics considerations and availing ourselves of stochastic parameterizations that take into account unresolved interactions. The fluctuations used are thought of as Gaussian white noise with zero mean. The derivation is based on the conditioned Langevin dynamics technique. Exploiting the relation between the Fokker-Planck and the Langevin equations, the nudging equations are derived for a maximally observed system that converges towards the observations in finite time. The new nudging term found is the analog of the so called quantum potential of the Bohmian mechanics. In order to make the new nudging equations feasible for practical computations, two approximations are developed and used as bases from which extending this tool to non-perfectly observed systems. By means of a physical framework, in the zero noise limit, all the physical nudging parameters are fixed by the model under study and there is no need to tune other free ad-hoc variables. The limit of zero noise shows that also for the classical nudging equations it is necessary to use dynamical information to correct the typical relaxation term. A comparison of these approximations with a 3DVar scheme, that use a conjugate gradient minimization, is then shown in a series of four twin experiments that exploit low order chaotic models
Comparison of the calculated absorption and the measured field strength of HF waves reflected from the ionosphere
The absorption (L) of the wave in the ionosphere has been calculated. The 5.47MHz wave is transmitted from Ercis, Turkey (39.03°N, 43.37°E)and received at Elazıg, Turkey (38.70°N, 39.20°E). The field strength of this wave is measured by ITU-Compliant HF Field Strength Monitoring Terminal, and the absorption L in the ionosphere has been calculated. It is observed that the field strength of the wave is least around noon time and it increases at night times at all seasons. The diurnal and seasonal variations of the calculated absorption L shows that the maximum absorption in the wave occurs around noon time. The behaviour of the diurnal and seasonal variations of the field strength of the wave can be explained with the diurnal and seasonal variations of the calculated absorption L in the ionosphere. Equation (22) in this paper can be used to obtain the imaginary part (β) of the refractive index of the ionospheric plasma, and it can be applied to the HF radio waves propagations in the ionosphere for absorption L
Scattering of Woods-Saxon Potential in Schrodinger Equation
The scattering solutions of the one-dimensional Schrodinger equation for the
Woods-Saxon potential are obtained within the position-dependent mass
formalism. The wave functions, transmission and reflection coefficients are
calculated in terms of Heun's function. These results are also studied for the
constant mass case in detail.Comment: 14 page
Factors associated with non-invasive ventilation response on the first day of therapy in patients with hypercapnic respiratory failure
Low computational complexity for optimizing energy efficiency in mm-wave hybrid precoding system for 5G
Millimeter-wave (mm-wave) communication is the spectral frontier to meet the anticipated
significant volume of high data traffic processing in next-generation systems. The primary challenges in
mm-wave can be overcome by reducing complexity and power consumption by large antenna arrays for
massive multiple-input multiple-output (mMIMO) systems. However, the circuit power consumption is
expected to increase rapidly. The precoding in mm-wave mMIMO systems cannot be successfully achieved
at baseband using digital precoders, owing to the high cost and power consumption of signal mixers and
analog-to-digital converters. Nevertheless, hybrid analog–digital precoders are considered a cost-effective
solution. In this work, we introduce a novel method for optimizing energy efficiency (EE) in the upper-bound
multiuser (MU) - mMIMO system and the cost efficiency of quantized hybrid precoding (HP) design.
We propose effective alternating minimization algorithms based on the zero gradient method to establish
fully-connected structures (FCSs) and partially-connected structures (PCSs). In the alternating minimization
algorithms, low complexity is proposed by enforcing an orthogonal constraint on the digital precoders
to realize the joint optimization of computational complexity and communication power. Therefore, the
alternating minimization algorithm enhances HP by improving the performance of the FCS through
advanced phase extraction, which involves high complexity. Meanwhile, the alternating minimization
algorithm develops a PCS to achieve low complexity using HP. The simulation results demonstrate that the
proposed algorithm for MU - mMIMO systems improves EE. The power-saving ratio is also enhanced for
PCS and FCS by 48.3% and 17.12%, respectively
Tumour necrosis factor-alpha, haptoglobin, serum amyloid a and neopterin levels in cattle with lumpy skin disease
Quantitatively Assessed Spontaneous Echo Contrast Density Predicts Left Atrial Thrombus Formation in Patients with Rheumatismal Mitral Stenosis: An Integrated Backscatter Analysis Study
Approximate k-state solutions to the Dirac-Yukawa problem based on the spin and pseudospin symmetry
Using an approximation scheme to deal with the centrifugal
(pseudo-centrifugal) term, we solve the Dirac equation with the screened
Coulomb (Yukawa) potential for any arbitrary spin-orbit quantum number
{\kappa}. Based on the spin and pseudospin symmetry, analytic bound state
energy spectrum formulas and their corresponding upper- and lower-spinor
components of two Dirac particles are obtained using a shortcut of the
Nikiforov-Uvarov method. We find a wide range of permissible values for the
spin symmetry constant C_{s} from the valence energy spectrum of particle and
also for pseudospin symmetry constant C_{ps} from the hole energy spectrum of
antiparticle. Further, we show that the present potential interaction becomes
less (more) attractive for a long (short) range screening parameter {\alpha}.
To remove the degeneracies in energy levels we consider the spin and pseudospin
solution of Dirac equation for Yukawa potential plus a centrifugal-like term. A
few special cases such as the exact spin (pseudospin) symmetry Dirac-Yukawa,
the Yukawa plus centrifugal-like potentials, the limit when {\alpha} becomes
zero (Coulomb potential field) and the non-relativistic limit of our solution
are studied. The nonrelativistic solutions are compared with those obtained by
other methods.Comment: 21 pages, 6 figure
Long-baseline, sub-decimeter kinematic GPS positioning of moving object, with potential application to monitor ocean surface wave
Precise relative kinematic positioning of moving platforms using GPS carrier phase
observables has numerous applications. One prominent application is utilization of highly
stabilized GPS technology mounted on the buoy, which is specially designed for detecting
tsunami wave at open sea. The essential point of this research is to investigate a potential use of a
GPS tsunami buoy for the purpose of tsunami early warning system with long-baseline kinematic
GPS processing method.
The rule of thumb GPS positioning concept, GPS position results are affected by. baseline
length mostly due to de-correlation of atmospheric errors. As baseline lengths increase, position
results degrade due to the difficulty to correctly fix the cariier phase ambiguity to its integer
value. carrier phase fixed ambiguity solutions are more accurate that float arnbiguify solutions. It
is generally accepted that carrier phase can be successfUlly fixed for baselines of up to 10 km.
After that, fixing ambiguities becomes more difficult and risky. It would be certainty more
advantageous to have a reliable float solution rather than an unreliable fixed solution.
In this study, we have developed a new quasi-real time long-baseline kinematic analysis
method using dual-frequency carrier phase with floated ambiguities, implemented in the Bernese
GPS Software Version 5.0. We demonstrate that early detection of a damaging tsunami can be
achieved by tracking the anomalous changes in sea surface height. The movements of a GPS
buoy relative to a base station with baseline length of 500 km have been monitored in quasi-real
time mode, and the tsunami waves caused by the 5th September 2004 Off Kii Peninsula
earthquake, Japan, have been successful detected as they went by, even though these were only 15 cm high. The filtered record of the solution closely resembles that of short baseline, with
RMS of 3.4 cm over 2.5 hours.
To test the robustness of our Iong-baseline kinematic GPS method under various
meteorological, we conducted the GPS tsunami buoy data analysis continuously for 8 days to
monitor the motion of the buoy. The average scatterings of GPS buoy heights by the low-pass
filtered 1 -Hz positioning result after tidal correction are about 3.4 cm and 1.2 cm under both
typhoon and calm weather conditions. This accuracy is precise enough to be applicable to a
tsunami early warning system. Since our long-baseline kinematic GPS analysis is effective to a
long baseline up to 500 km, we can place a GPS buoy far offshore, which ensures an adequate
evacuation time even, for people living on the coast
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