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991.
992.
High-pressure phases of BC3 are studied within the local density approximation under the density functional theory framework. When the pressure reaches 20 GPa, the layered BC3 that is a semiconductor at ambient pressure, becomes metallic. As the pressure increases, the material changes into a network structure at about 35 GPa. To understand the mechanism of phase transitions, band structure and density of states are discussed. With the increase of pressure, the width of bands broadens and the dispersion of bands enlarges. Additionally, the density of states of the network bears great resemblance to that of diamond. Formation of the sp3 bonding in the network is the main reason for the structural transformation at 35 GPa. 相似文献
993.
The characteristics of radio-frequency (RF) plasma sheaths have been topics of much scientific study for decades, and have
also been of great importance in the manufacture of integrated circuits and fabricating microelectromechanical systems (MEMS),
as well as in the study of physical phenomena in dusty plasmas. The sheaths behave special properties under various situations
where they can be treated as collisionless or collisional, single-or dual-RF, one-or two-dimensional (1D or 2D) sheaths, etc.
This paper reviews our recent progress on the dynamics of RF plasma sheaths using a fluid method that includes the fluid equations
and Poission’s equation coupled with an equivalent circuit model and a hybrid method in which the fluid model is combined
with the Monte-Carlo (MC) method. The structures of RF sheaths behave differently in various situations and plasma parameters
such as the ion density, electron temperature, as well as the external parameters such as the applied frequency, power, gas
pressure, magnetic field, are crucial for determining the characteristics of plasma sheaths. 相似文献
994.
Different intermittent curing methods were conducted for pulsed laser induced photopolymerization reactions in a TMPTA acrylic
system. Two methods of curing were compared, named grouped pulses impingement (GPI) and consecutively pulsed curing (CPC),
respectively, in which the total number of the curing pulses were kept same. In GPI, a prominent light diffraction effect
was observed in the post curing process, but was absent in the CPC procedure. A condensed but limited sized core of polymeric
structure was the cause of the light diffraction. The amount of inhomogeneity in the refractive index for the core was about
90% of the cured background. Simulations based on Fresnel diffraction theory were performed, and the result was in good agreement
with the experimental observations.
PACS 42.25.Bs; 61.82.Pv; 82.35.-x 相似文献
995.
The potential energy curve of MgH+ and the potential energy surface of Mg2H+ are calculated by quantum chemical ab initio SCF MO method with STO-3G basis set. The electronic wave functions and populations are obtained. The eqilibrium internuclear distance of MgH+ is 1.60 Å. There are two possible configurations of Mg2H+: C and D . The former is (Mg-Mg-H)+, with bond length rMg-Mg = 2.41Å and rMg-H =1.63Å. The latter is (Mg-H-Mg)+, with bond length rMg-H = 1.73Å. The cause of the stability of these species is discussed. The result of calculation about the bond length of MgH+ agrees reasonably well with experimental value. The conclusion about the stability of (Mg-Mg-H)+ ion supports the hypothesis proposed by Porter, based on thermodynamical calculation. 相似文献
996.
997.
A relationship between the Berlekamp-Massey and the Euclidean algorithms for linear feedback shift register synthesis is established.
In fact, by refining a sequence of polynomials appearing in the Euclidean algorithm, the sequence of characteristic polynomials
computed by the Berlekamp-Massey algorithm will be achieved.
A preliminary version of this paper was presented at the Oberwolfach Information Theory Meeting, May 12–16, 1986. 相似文献
998.
999.
Consider the retarded difference equationx
n
−x
n−1
=F(−f(x
n
)+g(x
n−k
)), wherek is a positive integer,F,f,g:R→R are continuous,F andf are increasing onR, anduF(u)>0 for allu≠0. We show that whenf(y)≥g(y) (resp. f(y)≤g(y)) fory∈R, every solution of (*) tends to either a constant or −∞ (resp. ∞) asn→∞. Furthermore, iff(y)≡g(y) fory∈R, then every solution of (*) tends to a constant asn→∞.
Project supported by NNSF (19601016) of China and NSF (97-37-42) of Hunan 相似文献
1000.