1,831 research outputs found
Study on steady-state thermal conduction with singularities in multi-material composites
Increasing demand in material and mechanical properties has led to production of complex composite structures. The composite structures, made of different materials, possess a variety of properties derived from each material. This has brought challenges in both analytical and numerical studies in thermal conduction which is of significant importance for thermoelastic problems. Therefore, a unified and effective approach would be desirable. The present study makes a first attempt to determining the analytical symplectic eigen solution for steady-state thermal conduction problem of multi-material crack. Based on the obtained symplectic eigen solution (including higher order expanding eigen solution terms), a new symplectic analytical singular element (SASE) for numerical modeling is constructed. It is concluded that composite structures composed of multi-material with complex geometric shapes can be modeled by the developed method, and the generalized flux intensity factors (GFIFs) can be solved accurately and efficiently
Multi-neutron transfer coupling in sub-barrier 32S+90,96Zr fusion reactions
The role of neutron transfers is investigated in the fusion process below the
Coulomb barrier by analyzing 32S+90Zr and 32S+96Zr as benchmark reactions. A
full coupled-channel calculation of the fusion excitation functions has been
performed for both systems by using multi-neutron transfer coupling for the
more neutron-rich reaction. The enhancement of fusion cross sections for
32S+96Zr is well reproduced at sub-barrier energies by NTFus code calculations
including the coupling of the neutron-transfer channels following the Zagrebaev
semiclassical model. We found similar effects for 40Ca+90Zr and 40Ca+96Zr
fusion excitation functions.Comment: Minor corrections, 11 pages, 4 figures, Fusion11 Conference, Saint
Malo, France, 2-6 mai 201
Renormalization Effects in a Dilute Bose Gas
The low-density expansion for a homogeneous interacting Bose gas at zero
temperature can be formulated as an expansion in powers of ,
where is the number density and is the S-wave scattering length.
Logarithms of appear in the coefficients of the expansion. We show
that these logarithms are determined by the renormalization properties of the
effective field theory that describes the scattering of atoms at zero density.
The leading logarithm is determined by the renormalization of the pointlike scattering amplitude.Comment: 10 pages, 1 postscript figure, LaTe
The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced From Multi-Wavelength Observations
This paper presents measurements of the energy radiated by the lower solar
atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare
(SOL2011-02-15T01:56) in response to an injection of energy assumed to be in
the form of nonthermal electrons. Hard X-ray observations from RHESSI were used
to track the evolution of the parameters of the nonthermal electron
distribution to reveal the total power contained in flare accelerated
electrons. By integrating over the duration of the impulsive phase, the total
energy contained in the nonthermal electrons was found to be
erg. The response of the lower solar atmosphere was measured in the free-bound
EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II
at 304\AA\ and H I (Ly) at 1216\AA\ by SDO/EVE, the UV continua at
1600\AA\ and 1700\AA\ by SDO/AIA, and the WL continuum at 4504\AA, 5550\AA, and
6684\AA, along with the Ca II H line at 3968\AA\ using Hinode/SOT. The summed
energy detected by these instruments amounted to erg;
about 15% of the total nonthermal energy. The Ly line was found to
dominate the measured radiative losses. Parameters of both the driving electron
distribution and the resulting chromospheric response are presented in detail
to encourage the numerical modelling of flare heating for this event, to
determine the depth of the solar atmosphere at which these line and continuum
processes originate, and the mechanism(s) responsible for their generation.Comment: 14 pages, 18 figures. Accepted for publication in Astrophysics
Journa
Techniques for flexible radio-over-fibre networks
Radio-over-fibre systems can efficiently deliver broadband wireless services in access and in-building networks. RoF signal transport and routing techniques are presented which are robust against fibre dispersion and provide capacity-on-demand for high-capacity multi-tone radio signals
Aroma binding and stability in brewed coffee: A case study of 2-furfurylthiol
The aroma stability of fresh coffee brew was investigated during storage over 60 minutes, there was a substantial reduction in available 2-furfurylthiol (2-FFT) (84%), methanethiol (72%), 3-methyl-1H-pyrole (68%) and an increase of 2-pentylfuran (65%). It is proposed that 2-FFT was reduced through reversible chemical binding and irreversible losses. Bound 2-FFT was released after cysteine addition, thereby demonstrating that a reversible binding reaction was the dominant mechanism of 2-FFT loss in natural coffee brew. The reduction in available 2-FFT was investigated at different pH and temperatures. At high pH, the reversible binding of 2-FFT was shown to protect 2-FFT from irreversible losses, while irreversible losses led to the reduction of total 2-FFT at low pH. A model reaction system was developed and a potential conjugate, hydroxyhydroquinone, was reacted with 2-FFT. Hydroxyhydroquinone also showed 2-FFT was released after cysteine addition at high pH
Novel generation and transmission of 2 Gbps impulse radio ultra wideband over MMF for in-building networks application
We propose novel generation technique of IR-UWB pulse by linearly combining two monocycles using different pulse shapes. We experimentally demonstrate DSP based BER measurement of 2 Gbps IR-UWB over multimode fiber for in-building networks application.</p
Numerical determination of concrete crack width for corrosion-affected concrete structures
Corrosion-induced deterioration of reinforced concrete (RC) structures results in premature failure of the RC structures. In practice concrete crack width is one of the most important criteria for the assessment of the serviceability of RC structures. It is therefore desirable to predict the growth of the crack width over time so that better informed decisions can be made concerning the repairs due to concrete cracking. Literature review shows that little research has been undertaken on numerical prediction of concrete crack width. The intention of this study was to develop a numerical method to predict concrete crack width for corrosion-affected concrete structures. A cohesive crack model for concrete is implemented in the numerical formulation to simulate crack initiation and propagation in concrete. Choices for evaluating the parameters of cohesive elements are extensively discussed which is a key for developing a plausible model employing cohesive elements. The surface crack width is obtained as a function of service time. Accurate prediction of crack width can allow timely maintenance which prolongs the service life of the reinforced concrete structures
Coherent States and Modified de Broglie-Bohm Complex Quantum Trajectories
This paper examines the nature of classical correspondence in the case of
coherent states at the level of quantum trajectories. We first show that for a
harmonic oscillator, the coherent state complex quantum trajectories and the
complex classical trajectories are identical to each other. This congruence in
the complex plane, not restricted to high quantum numbers alone, illustrates
that the harmonic oscillator in a coherent state executes classical motion. The
quantum trajectories are those conceived in a modified de Broglie-Bohm scheme
and we note that identical classical and quantum trajectories for coherent
states are obtained only in the present approach. The study is extended to
Gazeau-Klauder and SUSY quantum mechanics-based coherent states of a particle
in an infinite potential well and that in a symmetric Poschl-Teller (PT)
potential by solving for the trajectories numerically. For the coherent state
of the infinite potential well, almost identical classical and quantum
trajectories are obtained whereas for the PT potential, though classical
trajectories are not regained, a periodic motion results as t --> \infty.Comment: More example
High-quality InP/ZnS nanocrystals with high photometric performance and their application to white quantum dot light-emitting diodes
Full visible range covering InP/ZnS core-shell nanocrystals with high photometric performance have been prepared. Making use of these nanocrystals, we demonstrate a white quantum dot LED with a high color rendering index of 91. © 2012 IEEE
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