2,576 research outputs found
Post density functional theoretical studies of highly polar semiconductive Pb(TiNi)O solid solutions: The effects of cation arrangement on band gap
We use a combination of conventional density functional theory (DFT) and
post-DFT methods, including the local density approximation plus Hubbard
(LDA+), PBE0, and self-consistent to study the electronic properties of
Ni-substituted PbTiO (Ni-PTO) solid solutions. We find that LDA
calculations yield unreasonable band structures, especially for Ni-PTO solid
solutions that contain an uninterrupted NiO layer. Accurate treatment of
localized states in transition-metal oxides like Ni-PTO requires post-DFT
methods. -site Ni/Ti cation ordering is also investigated. The -site
cation arrangement alters the bonding between Ni and O, and therefore strongly
affects the band gap () of Ni-PTO. We predict that Ni-PTO solid
solutions should have a direct band gap in the visible light energy range, with
polarization similar to the parent PbTiO. This combination of properties
make Ni-PTO solid solutions promising candidate materials for solar energy
conversion devices.Comment: 19 pages, 6 figure
Existence of Mild Solutions for Fractional Nonlocal Evolution Equations With Delay in Partially Ordered Banach Spaces
This paper deals with the existence of mild solutions for the abstract fractional nonlocal evolution equations with noncompact semigroup in partially ordered Banach spaces. Under some mixed conditions, a group of sufficient conditions for the existence of abstract fractional nonlocal evolution equations are obtained by using a Krasnoselskii type fixed point theorem. The results we obtained are a generalization and continuation of the recent results on this issue. At the end, an example is given to illustrate the applicability of abstract result
Semi-analytical solution to the second-order wave loads on a vertical cylinder in bi-chromatic bi-directional waves
A complete solution is presented for the second-order wave loads experienced by a 15 uniform vertical cylinder in bi-chromatic bi-directional waves. The solution is obtained 16 based on the introduction of an assisting radiation potential without explicitly 17 evaluating the second-order diffraction potential. The semi-analytical formulation for 18 calculating the wave loads is provided and an efficient numerical technique is 19 developed to treat the oscillatory free-surface integral that appears in the force 20 formulation. After validating the present solution by comparing with the predictions 21 based on other methods, numerical studies are conducted for different combinations of 22 incident wave frequencies and wave headings, and the influence of frequencies and 23 headings of dual waves on the second-order wave loads is investigated. In addition, by 24 expressing the second-order wave loads in a power expansion with respect to the wave 25 frequency difference and wave heading difference which are both assumed to be small, 26 approximations on the calculation of wave loads are developed. The accuracy of 27 different approximations is assessed by comparing the approximate results with those 28 based on the complete solution
Modeling GRB 050904: Autopsy of a Massive Stellar Explosion at z=6.29
GRB 050904 at redshift z=6.29, discovered and observed by Swift and with
spectroscopic redshift from the Subaru telescope, is the first gamma-ray burst
to be identified from beyond the epoch of reionization. Since the progenitors
of long gamma-ray bursts have been identified as massive stars, this event
offers a unique opportunity to investigate star formation environments at this
epoch. Apart from its record redshift, the burst is remarkable in two respects:
first, it exhibits fast-evolving X-ray and optical flares that peak
simultaneously at t~470 s in the observer frame, and may thus originate in the
same emission region; and second, its afterglow exhibits an accelerated decay
in the near-infrared (NIR) from t~10^4 s to t~3 10^4 s after the burst,
coincident with repeated and energetic X-ray flaring activity. We make a
complete analysis of available X-ray, NIR, and radio observations, utilizing
afterglow models that incorporate a range of physical effects not previously
considered for this or any other GRB afterglow, and quantifying our model
uncertainties in detail via Markov Chain Monte Carlo analysis. In the process,
we explore the possibility that the early optical and X-ray flare is due to
synchrotron and inverse Compton emission from the reverse shock regions of the
outflow. We suggest that the period of accelerated decay in the NIR may be due
to suppression of synchrotron radiation by inverse Compton interaction of X-ray
flare photons with electrons in the forward shock; a subsequent interval of
slow decay would then be due to a progressive decline in this suppression. The
range of acceptable models demonstrates that the kinetic energy and circumburst
density of GRB 050904 are well above the typical values found for low-redshift
GRBs.Comment: 45 pages, 7 figures, and ApJ accepted. Revised version, minor
modifications and 1 extra figur
Numerical simulation of stress wave interaction in short-delay blasting with a single free surface
It is generally believed that stress wave superposition does occur and plays an important role in cutting blasting with a single free surface, in which explosive columns of several blast holes with short spacing are simultaneously initiated. However, considering the large scatter of pyrotechnic delay detonators that are used in most underground metal mines in China, the existence of stress wave superposition and the influence of this effect on rock fragmentation are questionable. In the present study, the stress wave interaction in short-delay blasting with a single free surface was studied through the use of the LS-DYNA code. Stress waves induced by two blast holes blasting with different delays were compared with the single blast hole case, and the effects of delay time, detonating location and spacing on stress wave superposition were investigated. The numerical results showed that for blast holes with a 1 m spacing, stress wave interaction only occurs when the delay time is 0 ms and does not occur for blasting with delays of more than 1 ms. An increase in the duration of a stress wave via optimizing the detonation location does not improve the stress wave interaction. For a 1 ms delay, stress wave superposition only occurs when the spacing is more than 4 m, which is a rare case in practice. The results indicated that the occurrence of stress wave superposition for blasting with a single free surface is strictly limited to conditions that would be difficult to achieve under the existing delay accuracy of detonators. Therefore, it is unrealistic to improve fragmentation via the stress wave interaction in field blasting. Furthermore, the numerical results of the stress wave interaction also show that there would be a great potential to reduce the hazardous vibrations induced by short-delay blasting by using electronic detonators with better control of delays in an order of several milliseconds
Molecular cloning and characterization of two genes - PHKG2 and IRAK4 from black-boned sheep (Ovis aries)
The complete coding sequences of two sheep genes-PHKG2 and IRAK4 were amplified using the rapid amplification of cDNA ends (RACE) method based on three sheep expressed sequence tags whose translated amino acids contain the mitochondrial carrier domain. The sequence analyses of these two genes revealed that the sheep PHKG2 gene encodes a protein of 406 amino acids which has high homology with the phosphorylase kinase, gamma 2 protein of five species: Cattle (99%), human (96%), mouse (92%), rat (91%) and chicken (63%). The sheep IRAK4 gene encodes a protein of 456 amino acids which has high homology with the interleukin-1 receptor-associated kinase 4 protein of six species: Cattle (94%), pig (88%), human (87%), mouse (79%), rat (79%) and chicken (54%). The tissue transcription profile analyses indicated that the Black-boned sheep PHKG2 and IRAK4 genes are generally but differentially expressed in the detected tissues including spleen, muscle, skin, kidney, lung, liver, heart, fat and small intestine. These data serve as a foundation for further insight into these two genes.Key words: Black-boned sheep, PHKG2 and IRAK4, tissue transcription profile
Lighting Analysis at Access Zone of Tunnel Entrance of Hong Kong-Zuhai-Macao Bridge (HZMB)
The study aimed to evaluate several shading schemes at access zone of the tunnel entrance of HZMB in order to find the best scenario to increase the user lighting comfort. The study analysed the luminance at the tunnel entrance (L20) and energy saving in the thereshold zone. For these analyses, four shading schemes have been simulated. The schemes were the Original Scheme (Zebra, 50% solid & 50% transparent), Option 1 (Gradation Glass), Option 2 (Perforated Material), and Option 3 (No Shading). The results shows that the Original scheme has the lowest L20 luminance and consequently the highest lighting energy saving. While the Option 3 (No Shading) has the highest L20 luminance and consequently the lowest lighting energy saving
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