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51.
J. W. Kooi G. Chattopadhyay M. Thielman T. G. Phillips R. Schieder 《International Journal of Infrared and Millimeter Waves》2000,21(5):689-716
There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability. 相似文献
52.
对生长在Si和MgO单晶基片上的不同厚度的单层NbN薄膜、双层薄膜AlN/NbN以及三层薄膜NbN/AlN/NbN应用透射电子显微镜(Transmission Electron Microscope,TEM)技术进行了分析研究,对这几种薄膜样品的微观结构、薄膜厚度以及各个边界的一些直观细节给出了较为清晰的图像。由透射电子显微镜的电子衍射图案计算了薄膜和单晶衬底的晶格常数,并与我们以前采用X射线衍射技术分析的结果进行了比较,结果有很好的吻合。 相似文献
53.
54.
C. Benjamin T. Jonckheere A. Zazunov T. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):279-289
We consider a model for a single molecule with a large frozen spin
sandwiched in between two BCS superconductors at equilibrium, and
show that this system has a π junction behavior at low
temperature. The π shift can be reversed by varying the other
parameters of the system, e.g., temperature or the position of the
quantum dot level, implying a controllable π junction with
novel application as a Josephson current switch. We show that the mechanism
leading to the π shift can be explained simply in terms of the contributions
of the Andreev bound states and of the continuum of states above the superconducting gap.
The free energy for certain configuration of parameters shows a
bistable nature, which is a necessary pre-condition for
achievement of a qubit. 相似文献
55.
Z. Barticevic M. Pacheco C. A. Duque L. E. Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):303-309
A theoretical study, within the effective-mass approximation, of the
effects of applied magnetic fields on excitons in disk-shaped
GaAs-Ga1-xAlxAs quantum dots is presented. Magnetic fields
are applied in the growth direction of the semiconductor
heterostructure. The parity of the excitonic envelope function
related to the simultaneous exchange of ze→-ze and
zh→-zh is a good quantum number and the wave
function, both the odd and even parity, can be expanded as
combination of products of the quantum well electron and hole
function that preserves the parity with appropriate Gaussian
functions. We have simultaneously obtained the energies of the
excitonic ground and excited states and discuss the behavior of
these energies as a function of the magnetic field. 相似文献
56.
Nominally pure and Tm3+-doped LiCaAlF6 crystals were grown by the Czochralski technique in a reducing atmosphere. The optical properties of transparent single crystals were studied using absorption and time-resolved luminescence spectroscopy in the VUV spectral range (330-100 nm). The strongest VUV emission peaking at 60 800 cm−1 with a decay time of 5.6 μs (7 μs) at 300 K (7.4 K) was assigned to the spin-forbidden 4f115d-4f12 transition of Tm3+. The fine structure observed in the VUV emission and corresponding excitation spectra indicate intermediate strength of electron-phonon coupling in this system. The efficient excitation of f-f emissions above 72 000 cm−1, higher than the onset of f-d absorption at 63 000 cm−1, is mainly caused by the F− to Tm3+ charge transfer absorption. The nature of various host-related excitation processes in the energy transfer to the Tm3+ ions is discussed. 相似文献
57.
ThehydrogenatomtransferreactionNH H-N H,isanimportantreactioninradicalreactionsandthegas-phrasethermatdecompositionofammonia.Therewereseveralstudiesonthisreactioninexperiment]andtheory='3.Inthispaper,wehaveemployedtheunifiedstatisticaltheory'(UST)tos... 相似文献
58.
G.P. Pepe G. Peluso R. Scaldaferri L. Parlato C. Granata E. Esposito M. Russo 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):421-425
A new fabrication process for three-terminal superconducting devices consisting of two Josephson junctions in a stacked configuration
is reported. The process is based on the deposition of the whole Nb/AlxOy/Nb-Al/AlxOy/Nb multilayer on a Si crystalline wafer without any vacuum breaking. Lift-off techniques, anodization processes and a SiO
film deposition have been adopted for patterning and insulating the two tunnel stacked junctions. Devices have been characterized
in terms of current-voltage (I-V) curves and Josephson critical current vs. the externally applied magnetic field. They show high quality factors (V
m values up to 65 mV at 4.2 K), and good current uniformity.
Received 5 June 2001 相似文献
59.
D. Shaltiel H.-A. Krug von Nidda B.Ya. Shapiro B. Bogoslavsky B. Rosenstein I. Shapiro T. Tamegai 《Physica C: Superconductivity and its Applications》2010,470(21):1937-1942
Following the discovery of high Tc superconductors, many researchers have applied EPR spectrometers to investigate their properties using the regular instructions to operate the spectrometer. As no substantial information was obtained it was soon practically abandoned. Investigations performed recently with the EPR technique, using a different operating method than the conventional one and the introduction of a detailed theoretical study related to the interaction of the JV with the microwave magnetic field lead to new and important results related to properties of high anisotropy superconductors indicating that the EPR spectrometer can be used to investigate properties of high anisotropy superconductors. The failures when using conventional operating method to obtain meaningful results and the method used in the present work to carry out the measurements in a proper manner are presented. Some important results obtained in investigating high anisotropy superconductors by the EPR technique are presented. 相似文献
60.
Gary F. Birkenmeier 《代数通讯》2013,41(12):5134-5151
In this paper the idea of an intrinsic extension of a ring, first proposed by Faith and Utumi, is generalized and studied in its own right. For these types of ring extensions, it is shown that, with relatively mild conditions on the base ring, R, a complete set of primitive idempotents (a complete set of left triangulating idempotents, a complete set of centrally primitive idempotents) can be constructed for an intrinsic extension, T, from a corresponding set in the base ring R. Examples and applications are given for rings that occur in functional analysis and group ring theory. 相似文献