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81.
M.H. Christmann G.H. Dierssen O.N. Salmon A.L. Taylor W.H. Thom 《Journal of Physics and Chemistry of Solids》1975,36(12):1371-1374
Physical properties of selected CdS single crystal platelets as-grown and after vacuum heat treatments at temperatures up to 600°C have been studied using u.v. excited edge emission, mass spectrometry, electrical resistivity and electron paramagnetic resonance (EPR). It was found that sulfur leaves the crystal at temperatures as low as 100°C creating a depletion layer. The native defect changes were monitored by edge emission studies at 4.2°K in combination with etch treatments. The defect structure throughout the crystal is not only dependent upon the temperature and atmosphere of the treatments, but is also strongly dependent upon the cooling rate. 相似文献
82.
83.
In this article we study cocycles of discrete countable groups with values in ℓ
2
G and the ring of affiliated operators UG\mathcal{U}G. We clarify properties of the first cohomology of a group G with coefficients in ℓ
2
G and answer several questions from De Cornulier et al. (Transform. Groups 13(1):125–147, 2008). Moreover, we obtain strong results about the existence of free subgroups and the subgroup structure, provided the group
has a positive first ℓ
2-Betti number. We give numerous applications and examples of groups which satisfy our assumptions. 相似文献
84.
85.
Herrington TJ Thom AJ White AJ Ashley AE 《Dalton transactions (Cambridge, England : 2003)》2012,41(30):9019-9022
Tris[3,5-bis(trifluoromethyl)phenyl]borane (1, BArF(18)), has been synthesised on a practical scale for the first time. According to the Gutmann-Beckett method it is a more powerful Lewis acid than B(C(6)F(5))(3). It forms a 'frustrated Lewis pair' with 2,2,6,6-tetramethylpiperidine which cleaves H(2) to form a salt containing the novel anion [μ-H(BArF(18))(2)](-). 相似文献
86.
Declémy A. Debelle A. Dupeyrat C. Thomé L. Monnet I. Eyidi D. 《Applied Physics A: Materials Science & Processing》2012,106(3):679-685
SiC single crystals were implanted with Fe ions and the effects of implantation temperature, Fe concentration, and subsequent
swift heavy ion irradiation on both dopant and damage depth distributions were evaluated by using RBS and channelling techniques.
It is found that an increase of the implantation temperature above the threshold temperature for amorphization can lead to
the formation of a broad layer (∼50 nm) containing a large concentration of implanted Fe atoms (∼2 at.%) but almost free of
implantation defects. This particular configuration is likely due to dynamic annealing during implantation combined with defect
annihilation at the surface. It is only observed when the implanted species concentration does not exceed a critical value
(which lies between 2 and 5 at.% in the present system). Post-implantation swift heavy ion irradiation leads to a further
decrease of the damage level, while the Fe distribution is not affected. The Fe substitutional fraction has been evaluated
in the different tested conditions. A maximum value of ∼50% is found when implantation is performed at the temperature above
that required to prevent amorphization (470 K in the present system). Swift-heavy ion irradiation seems to induce Fe atoms
relocation at substitutional positions. 相似文献
87.
We use techniques from both real and complex algebraic geometry to study K-theoretic and related invariants of the algebra C(X) of continuous complex-valued functions on a compact Hausdorff topological space X. For example, we prove a parameterized version of a theorem by Joseph Gubeladze; we show that if M is a countable, abelian, cancellative, torsion-free, semi-normal monoid, and X is contractible, then every finitely generated projective module over C(X)[M] is free. The particular case gives a parameterized version of the celebrated theorem proved independently by Daniel Quillen and Andrei Suslin that finitely
generated projective modules over a polynomial ring over a field are free. The conjecture of Jonathan Rosenberg which predicts
the homotopy invariance of the negative algebraic K-theory of C(X) follows from the particular case . We also give algebraic conditions for a functor from commutative algebras to abelian groups to be homotopy invariant on
C
*-algebras, and for a homology theory of commutative algebras to vanish on C
*-algebras. These criteria have numerous applications. For example, the vanishing criterion applied to nil K-theory implies that commutative C
*-algebras are K-regular. As another application, we show that the familiar formulas of Hochschild–Kostant–Rosenberg and Loday–Quillen for
the algebraic Hochschild and cyclic homology of the coordinate ring of a smooth algebraic variety remain valid for the algebraic
Hochschild and cyclic homology of C(X). Applications to the conjectures of Beĭlinson-Soulé and Farrell–Jones are also given. 相似文献
88.
We present a simple yet accurate method for the calculation of effective moments of inertia for large-amplitude low-frequency internal motions in molecules. Our technique makes use of the quantum-mechanical kinetic energy operator developed within the internal coordinate path Hamiltonian formalism, with the imposition of Eckart conditions on the molecular frame to separate the internal motion from overall molecular rotation. Numerical results are presented for several molecules possessing internal large-amplitude motions. These results are compared with those obtained from approximate analytic formulas proposed by Pitzer. We also give detailed examples where the conventional approximations in the current literature are not applicable for describing a single large-amplitude motion. Our straightforward algorithm yields results more accurate than those of Pitzer's method, especially for molecules with asymmetric internal rotors. 相似文献
89.
Iain A. Anderson Thom Hale Todd Gisby Tokushu Inamura Thomas McKay Benjamin O’Brien Scott Walbran Emilio P. Calius 《Applied Physics A: Materials Science & Processing》2010,98(1):75-83
Desirable rotary motor attributes for robotics include the ability to develop high torque in a low mass body and to generate
peak power at low rotational speeds. Electro-active polymer artificial muscles offer promise as actuator elements for robotic
motors. A promising artificial muscle technology for use as a driving mechanism for rotary motion is the dielectric elastomer
actuator (DEA). We present a membrane DEA motor in which phased actuation of electroded sectors of the motor membrane impart
orbital motion to a central drive that turns a rotor. The motor is inherently scalable, flexible, flat, silent in operation,
amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials. As a membrane it can also
form part of the skin of a robot.
We have investigated the torque and power of stacked membrane layers. Specific power and torque ratios when calculated using active membrane mass only were 20.8 W/kg
and 4.1 Nm/kg, respectively. These numbers compare favorably with a commercially available stepper motor. 相似文献
90.
Thom AJ 《Physical review letters》2010,105(26):263004
We describe a stochastic coupled cluster theory which represents excitation amplitudes as discrete excitors in the space of excitation amplitudes. Reexpressing the coupled cluster (CC) equations as the dynamics of excitors in this space, we show that a simple set of rules suffices to evolve a distribution of excitors to sample the CC solution and correctly evaluate the CC energy. These rules are not truncation specific and this method can calculate CC solutions to an arbitrary level of truncation. We present results of calculation on the neon atom, and nitrogen and water molecules showing the ability to recover both truncated and full CC results. 相似文献