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This study mainly focused on the key technologies, the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam (MCFSPB) model in the Accurate Radiotherapy System (ARTS). In the MCFSPB model, the acquisition of pencil beam kernel is one of the most important technologies. In this study, by analyzing the demerits of the clinical pencil beam dose calculation methods, a new pencil beam kernel model was developed based on the Monte Carlo (MC) simulation and the technology of medical accelerator energy spectrum reconstruction. which greatly improved the accuracy of calculated result. According to the axial symmetry principle, only part of simulation results was used for the data of pencil beam kernel, which greatly reduced the data quantity of the pencil beam and reduced calculated time. Based on the above studies, the MCFSPB method was designed and implemented by the Visual C++ development tool. With several tests including the comparisons among the American Association of Physicists in Medicine (AAPM) No. 55 Report sample and the ion chamber measurement of lung-simulating inhomogeneous phantom in clinical treatment plan, the results showed that the maximum error of most calculated point was less than 0.5% in the homogeneous phantom and less than 3% in the heterogeneous phantom. This method met the clinical criteria, and would be expected to be used as a fast and accurate dose engine for clinic TPS.
ZnO:Al (ZAO) films were deposited on quartz substrates by dc magnetron reactive sputtering from a Zn target mixed with Al. The effect of substrate temperature and Al doping content on the structural, electrical and optical properties of ZAO films were investigated. It was observed that the (002) peak position of all films shifts to lower angle comparable to that of bulk ZnO due to the residual stress change with deposition parameters. The dependences of electrical properties such as resistivity, carrier concentration and Hall mobility on substrate temperature and Al doping content were measured. The minimum resistivity is 4.23×10−4 ω.cm with the carrier concentration of 9.21×1020 cm−3 and Hall mobility of 16.0 cm2v−1s−1. The visible transmittance of above 80% was obtained. The optical band gap was observed to increase with increasing carrier concentration. The possible mechanisms are discussed.
Contributions of acoustical deformation scattering, ion impurity scattering and grain boundary potential scattering to the conductivity of TCO films have been calculated to discuss the predominant scattering mechanism, regardless of precise details of the preparation procedure. The results indicate that the effective mass of charge carriers has a strong dependence on carrier concentration. Based on the effective mass correction, as well as the carrier concentration-ionized impurity centers correction, scattering due to ion impurity has been developed to explain the upper limit of mobility or the lower limit of resistivity of TCO films. Two empirical expressions are introduced to depict the dependence of the upper limit of mobility and the lower limit of resistivity of TCO films on carrier concentration.
Electrochemically grown cadmium sulfide (CdS) nanorod arrays were studied with Raman spectroscopy. The resonant Raman spectroscopy unravels the enhanced electron-phonon interaction up to the fifth-order multiphonon process in the vertically aligned CdS nanorods after annealing. Resonant Raman scattering at room temperature reveals a surface phonon mode at 253 cm−1 in the annealed nanorod. This unprecedented observation is accounted for by the lateral confinement in the nanorod whose average aspect ratio is approximately 5. An intersubband transition near 3000 cm−1 is also observed. These results point to important optoelectronic applications of this material.
In this paper, we consider random dynamical systems (abbreviated as RDSs) generated by compositions of one-sided stationary random endomorphisms of class C^2 of a compact manifold. We will first introduce the notions of entropy and Lyapunov exponents for such RDSs, and then prove that the entropy formula of Pesin type holds if the sample measures of an invariant measure are absolutely continuous with respect to the Lebesgue measure on the manifold. Our result covers those obtained by Ledrappier and Young , and Liu  for i.i.d. random diffeomorphisms or (non-invertible) endomorphisms, and that obtained by  for two-sided stationary random endomorphisms. If the phase spaces are compact and finite-dimensional manifolds without boundary, this result may be considered as the almost-final form of Pesin entropy formula for RDSs with absolutely continuous invariant or sample measures.
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