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1.
We determine the structure of the partition algebra P
n( Q) (a generalized Temperley-Lieb algebra) for specific values of Q , focusing on the quotient which gives rise to the partition function of n site Q-state Potts models (in the continuous Q formulation) in arbitrarily high lattice dimensions (the mean field case). The algebra is nonsemisimple iff Q is a nonnegative integer less than 2 n-1. We determine the dimension of the key irreducible representation in every specialization.Work supported by the Packard Foundation. 相似文献
2.
Raman spectra of binary alkali silicates were measured at various temperatures from 1300°C to room temperature to investigate the relation between structural change and phase transformation phenomena. Distribution of structural units of Q n was estimated at each temperature by the deconvolution of spectra based on the equilibrium 2Q 3 ? Q 2 + Q 4. The Q n distributions of sodium and potassium silicate systems strongly depend on temperature and the equilibrium shifts to the left-hand side with decreasing temperature, but those of lithium silicate system were less sensitive to the temperature variation. In alkali disilicates (33?mol%?R 2O–67?mol%?SiO 2, where R=Li, Na or K), the Q n distributions near the melting point were independent of alkali ion species, and they held the relation [Q 2]?=?[Q 4]?≈?[Q 3]/4. This means that two of 6Q 3 units (six-memberd ring) in crystals are transformed into a pair of Q 2 and Q 4 in the melting process. Below the melting point, the Q n distribution in lithium disilicate melt remained while, in sodium and potassium disilicate melts, [Q 3] increased with decreasing temperature. Crystallization of the alkali disilicate melts is discussed considering the configuration entropy of Q n units. In 25?mol%?Li 2O–75?mol%?SiO 2, which is in the range of the immiscibility dome, the Q n distribution was maintained even when phase separation occurs in the cooling process. 相似文献
3.
A complete classification of all rotationally invariant operators of the two-dimensional unitary matrix model composed of gradients of the field Q and their anomalous dimensions are given in one-loop order. Similarly as in the orthogonal case and for the n-vector model the leading correction of operators with 2n factors Q grows with n( n–1).Work supported in part by the Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 123 Stochastic Mathematical Models 相似文献
4.
It is known that exp [iλ (Q1P1i/2)] is a unitary single-mode squeezing operator,where Q1,P1 are the coordinate and momentum operators,respectively.In this paper we employ Dirac’s coordinate representation to prove that the exponential operator S n ≡ exp [iλ sum((QiPi+1+Qi+1Pi))) from i=1 to n ],(Qn+1=Q1,Pn+1=P1),is an n-mode squeezing operator which enhances the standard squeezing.By virtue of the technique of integration within an ordered product of operators we derive S n ’s normally ordered expansion and obtain new n-mode squeezed vacuum states,its Wigner function is calculated by using the Weyl ordering invariance under similar transformations. 相似文献
5.
We consider algebraic geometrical properties of the integrable billiard on a quadric Q with elastic impacts along another quadric confocal to Q. These properties are in sharp contrast with those of the ellipsoidal Birkhoff billiards in
n
. Namely, generic complex invariant manifolds are not Abelian varieties, and the billiard map is no more algebraic. A Poncelet-like theorem for such system is known. We give explicit sufficient conditions both for closed geodesics and periodic billiard orbits on Q and discuss their relation with the elliptic KdV solutions and elliptic Calogero system. 相似文献
6.
We use methods of constructive field theory to generalize index theory to an infinite-dimensional setting. We study a family of Dirac operators Q on loop space. These operators arise in the context of supersymmetric nonlinear quantum field models with Hamiltonians H= Q 2. In these models Q is self-adjoint and Fredholm. A natural grading operator Γ exists such that Γ Q+ QΓ=0. We study Q += P ? QP +, where P ±=1/2 (1±Γ) are the orthogonal projections onto the eigenspaces of Γ. We calculate the index i( Q +) for Wess-Zumino models defined by a superpotential V(ω). Here V is a polynomial of degree n≧2. We establish that i( Q +)= n?1=degδ V. In particular, the field theory models have unbroken supersymmetry, and (for n≧3) they have degenerate vacua. We believe that this is the first index theorem for a Dirac operator that couples infinitely many degrees of freedom. 相似文献
7.
We present a review of our recent measurements of total cross sections ( Q
T's) for the scattering of positrons by Na, K, and Rb, and positronium-formation cross sections ( Q
Ps's) for Na and K. For our total cross section measurements, a beam transmission technique has been used. For our Q
Ps measurements, our approach involves setting upper and lower limits on Q
Ps using a combination of (1) measuring the transmission of the positron beam with the angular discrimination of the apparatus made as poor as possible, and (2) measuring the 511 keV annihilation gamma rays in coincidence produced by the decay of para-Ps formed in the scattering cell. Comparison with theoretical calculations shows that our measured Q
T's and Q
Ps's for Na and K agree reasonably well with a close coupling approximation (CCA) calculation which takes into account the formation of Ps in the n=1 and n=2 states. In the 3–10 eV energy range, this calculation predicts a peak in the Q
T's and Q
Ps's for K which also appears in our measurements. The absence of such a peak in our measured Q
T's and Q
Ps's (preliminary) for Na in this energy range is also consistent with the same theory. Comparisons with five-state CCA calculations of Q
T which do not take Ps-formation into account also show good agreement with our positron-Na, K, and Rb Q
T measurements for energies above 20 eV, but show dramatic departures from our measurements below 10 eV for K and Rb. 相似文献
8.
分析了自适应 Q值算法的防碰撞原理以及射频识别(RFID)通信的时序,定义防碰撞过程的识别效率、识别速度和标签数目及 Q值的数据状态( Q,n).在此基础上讨论并建立了多标签的状态转移过程的马尔科夫链模型.通过蒙特卡罗统计方法,对马尔科夫链模型求解,得出识别效率和识别速度.用软件无线电测试方案实现防碰撞测试,有效地实现了RFID防碰撞过程的识别效率和识别速度的量化分析.模型仿真结果和测试数据的一致证明了测试模型的有效性和测试方法的正确性.
关键词:
射频识别
防碰撞测试
马尔科夫链
时隙计数器 相似文献
9.
Creep experiments were conducted on Zn-22%?Al in which SiC particulates were introduced by variable co-deposition of multi-phase materials (VCM). The objective of the investigation is to determine the effect of SiC particulates on the creep behaviour in region I (the low-stress region) and region II (the intermediate-stress or superplastic region) of the sigmoidal plot between stress and strain rate, which was previously reported for the reinforcement-free Zn-22%?Al. The creep data show that the presence of SiC particulates has no effect on the sigmoidal trend between stress and strain rate; and that in region II, the stress exponent, n, and the activation energy for creep, Q, agree well with those reported for SiC-free grades of Zn-22%?Al; n?=?2.5 and Q?~? Q gb, where Q gb is energy for grain boundary diffusion in the alloy. However, the data indicate that the presence of the particulates results in narrowing region II and reducing maximum ductility. An analysis of the creep data reveals the presence of a threshold stress that depends strongly on temperature. The microstructural data inferred from an examination of the crept specimens by the means of transmission electron microscopy (TEM) suggest that the origin of τ 0 may be related to the interaction between moving dislocations and dispersion particles. These particles are introduced in the material as a result of processing the material by thermal spray and deposition. 相似文献
10.
A novel design method for high Q piezoelectric resonators was presented and proposed using the 3-D equations of linear piezoelectricity with quasi-electrostatic
approximation which include losses attributed to mechanical damping in solid and resistance in current conduction. There is
currently no finite element sofware for estimating the Q of a resonator without apriori assumptions of the resonator impedance or damping. There is a necessity for better and more
realistic modeling of resonators and filters due to miniaturization and the rapid advances in frequency ranges in telecommunication.
We presented new three-dimensional finite element models of quartz and barium titanate resonators with mechanical damping
and resistance in current conduction. Lee, Liu and Ballato’s 3-D equations of linear piezoelectricity with quasi-electrostatic
approximation which include losses attributed to mechanical damping in solid and resistance in current conduction were formulated
in a weak form and implemented in COMSOL. The resulting finite element model could predict the Q and other electrical parameters for any piezoelectric resonator without apriori assumptions of damping or resistance. Forced
and free vibration analyses were performed and the results for the Q and other electrical parameters were obtained. Comparisons of the Q and other electrical parameters obtained from the free vibration analysis with their corresponding values from the forced
vibration analysis were found to be in excellent agreement. Hence, the frequency spectra obtained from the free vibration
analysis could be used for designing high Q resonators. Results for quartz thickness shear AT-cut and SC-cut resonators and thickness stretch poled barium titanate resonators
were presented. An unexpected benefit of the model was the prediction of resonator Q with energy losses via the mounting supports. 相似文献
11.
We present supersymmetric, curved space, quantum mechanical models based on deformations of a parabolic subalgebra of osp(2 p+2| Q). The dynamics are governed by a spinning particle action whose internal coordinates are Lorentz vectors labeled by the fundamental
representation of osp(2 p| Q). The states of the theory are tensors or spinor-tensors on the curved background while conserved charges correspond to the
various differential geometry operators acting on these. The Hamiltonian generalizes Lichnerowicz’s wave/Laplace operator.
It is central, and the models are supersymmetric whenever the background is a symmetric space, although there is an osp(2 p| Q) superalgebra for any curved background. The lowest purely bosonic example (2 p, Q) = (2, 0) corresponds to a deformed Jacobi group and describes Lichnerowicz’s original algebra of constant curvature, differential
geometric operators acting on symmetric tensors. The case (2 p, Q) = (0, 1) is simply the superparticle whose supercharge amounts to the Dirac operator acting on spinors. The (2 p, Q) = (0, 2) model is the supersymmetric quantum mechanics corresponding to differential forms. (This latter pair of models are supersymmetric on any
Riemannian background.) When Q is odd, the models apply to spinor-tensors. The (2 p, Q) = (2, 1) model is distinguished by admitting a central Lichnerowicz-Dirac operator when the background is constant curvature.
The new supersymmetric models are novel in that the Hamiltonian is not just a square of super charges, but rather a sum of
commutators of supercharges and commutators of bosonic charges. These models and superalgebras are a very useful tool for
any study involving high rank tensors and spinors on manifolds.
Dedicated to the memory of Tom Branson 相似文献
12.
A class of multispin correlation functions of an Ising model with ferromagnetic nearest neighbor interactions K and constant (distance-independent) long-range interactions Q
1= Q, l=1,2,..., on the Sierpiski-gasket lattice is considered. Using an exact method for calculating thermodynamic functions of hierarchically constructed Ising systems, it is shown that, for a set of values of Q and for almost all values of K, some M
k-spin correlation functions, where M
k=3
k
+3 with k=1,2,..., n and n=1,2,... being the order of lattice construction, change chaotically as n, k, and thereby M
k increase to infinity. Accordingly, in the thermodynamic limit, these correlation functions prove to be nonanalytic for appropriate values of Q and K. Since M
k-point correlation functions with k being finite, i.e., correlation functions involving finite numbers of spins, remain analytic as n tends to infinity, there is a smooth crossover between analytic properties of correlation functions of the two types. 相似文献
13.
A new parameter is proposed for characterizing boundary friction between solids—the probability Q that some contact spot will be converted to a wear particle as the real contact area shifts by one mean contact-spot diameter.
A method is proposed for the phenomenological detection of optimum regimes of boundary friction, which are characterized by
the minimum wear intensity of the sample material, and for measuring the corresponding quantity Q= Q
opt. For babbitt, one of the most frictionless materials, the value of Q
opt is found to be ≈2×10 −10. When data on the linear wear intensity I
h
, the contact pressure p
n
, and the hardness H are available, Q can be calculated for the given test conditions. Deviations of Q from the value Q
opt (for a given material) can serve as a criterion for how closely a prepared surface structure approaches the optimal.
Zh. Tekh. Fiz. 68, 48–52 (April 1998) 相似文献
14.
I review some theories of the interaction of N Rydberg atoms interacting collectively with radiation in microwave cavities. The radiation may be incoherent (black body)
radiation or it may be coherent. In the former case theories of the steady state inversion and of the superradiance from initially
inverted atoms in low- Q cavities agree well with experimental observations. In the latter case in low- Q cavities ‘phase transitions’ of both first and second order types are predicted and should be observable by monitoring the
output of an atomic beam by an atomic ionisation detector. The first order transition which occurs at opposite detunings of
the cavity and atoms from the frequency of the coherent driving field is of “optically” bistable type but hysteresis is suppressed
by quantum fluctuations which can be large in the cavity field close to the transition. I also review a theory of the spectra
from single atoms in cavities of arbitrary Q containing a few microwave photons. A transition from a single peaked Lorentzian spectrum at low- Q to a double-peaked spectrum for Q≃10 6 is predicted and peaks representing one or more photon transitions of the Jaynes-Cummings model are also expected to be observable
at these or larger Q values. The collective theories are all based on N atom Dicke type models driven by the coherent or incoherent field. Substantial squeezing of the fluorescent radiation field
from these Dicke models is also predicted and may be observable with Rydberg atoms. 相似文献
15.
The mesostructure of transition-metal monogermanides Mn1 – xCo
x
Ge is studied by small-angle neutron scattering in a wide range of concentrations x = 0–0.95. These compounds were synthesized under high pressure and are metastable under normal conditions. The experimental dependences I(Q) obtained for the whole series of samples in the range of transferred momenta (6 × 10–2 nm–1 < Q< 2.5 nm–1) are described by the power dependence Q–n with an exponent n = 2.99 ± 0.02, uniquely related to the fractal properties of the system under study. The dependence obtained indicates that the superatomic structure of the samples is characterized by the presence of defects with a spatial organization described by a fractal model with a logarithmic dependence of the correlation function of the defect density. It is interesting to note that such defects are absent in the isostructural FeGe compound, i.e., the experimental dependences of the intensity are described well by the expression Q–n with an exponent n = 4.1 ± 0.1, which demonstrates the presence of crystallites with a uniform density distribution inside and a sharp boundary characterizing the surface. 相似文献
16.
The grand potential P(z)/kT of the cluster model at fugacity z, neglecting interactions between clusters, is defined by a power series
n
Q
n
z
n
, where Q
n
, which depends on the temperature T, is the partition function of a cluster of size n. At low temperatures this series has a finite radius of convergence z
s
. Some theorems are proved showing that if Q
n
, considered as a function of n, is the Laplace transform of a function with suitable properties, then P(z) can be analytically continued into the complex z plane cut along the real axis from z
s
to + and that (a) the imaginary part of P(z) on the cut is (apart from a relatively unimportant prefactor) equal to the rate of nucleation of the corresponding metastable state, as given by Becker-Döring theory, and (b) the real part of P(z) on the cut is approximately equal to the metastable grand potential as calculated by truncating the divergent power series at its smallest term. 相似文献
17.
The silicate speciation forms an important aspect of the structure of silicate melts, a subject of interest to both the earth‐ and materials science communities. In this study, the Q n speciation of binary cesium silicate glasses was studied by Raman spectroscopy. A method to extract the equilibrium constant from a set of Raman spectra is presented, and the least‐squares optimization algorithm is given (in Supporting Information). Log( K), the equilibrium constant of the speciation reaction, 2Q 3 = Q 4 + Q 2, equals −2.72 ± 0.11 at the glass transition. This extends the previously established correlation between log( K) and the inverse of the ionic radius of the network modifier to cesium. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
18.
High-resolution quasi-elastic neutron-scattering measurements have been made on two nematogens: DMBCA with a nematic range 108 to 119°C, and 5CB and a tail-deuteriated sample (D5CB), having a nematic range 22·6 to 35·1°C. Results on 5CB in the crystal phase at ~18°C showed no significant quasielastic broadening, which means that any random motions of the alkyl chain are slower than about 5 × 10 9 rad s -1. Measurements were made at a single temperature in the nematic phases on specimens aligned in a magnetic field of 0·25T; for DMBCA with scattering vector Q⊥ n ( n is the nematic director) and for 5CB and D5CB with Q⊥ n and Q∥ n and also on the isotropic liquid phase of D5CB at 45°C. Analysis of the coherent scattering from nematic D5CB at Q = 1·2 Å -1 and 25°C gave an order parameter < P 2>=0·55, close to the simple mean field value for this temperature. The coherent scattering from DMBCA is too weak to allow this experiment to be performed. The most remarkable qualitative feature of the results is the close similarity of the scattering law S( Q, ω) for D5CB (and 5CB) with Q⊥ n and Q∥ n. Analysis of the results in all cases was made using values for the translational diffusion constants measured previously. Corrections for multiple scattering are shown to be important and a single simple model has been devised which fits the line shapes of all the results for D5CB in nematic ( Q⊥ n and Q∥ n) and isotropic liquid phases and DMBCA. The model involves uniaxial rotational diffusion about the long molecular axis m coupled to a displacement along the rotation axis giving a net rotation in a plane whose normal makes an angle ∝ relative to the direction m. Values for the rotational diffusion constant D rd ns -1 are as follows: D5CB, 25°C, 6 (∝ ~ 50°); 45°C, 10. DMBCA, 112°C, 16, (all ±10–15 per cent). The results for D5CB and 5CB are so similar that no additional detailed model fitting was attempted for the fully hydrogenous sample and it is concluded that while the motion of the alkyl tails is freer, the time scale of the motions is not more than about a factor of 2 faster than that of the molecular cores. 相似文献
19.
We investigate the formation of a torus from a stationary state in an autonomous dynamical system with order-parameter dimension n=4 and symmetry group G=QC
2 ( Q =quaternion group). The quasi-periodic temporal states bifurcating from the origin due to a symmetry-induced hard-mode instability are characterized by two-independent frequencies.Dedicated to Professor Harry Thomas on the occasion of his 60th birthdayWork supported by the Sonderforschungsbereich 185 Frankfurt-Darmstadt 相似文献
20.
Lepton-quark mass may reflect a correspondence in spacetime structure described by a modular conformal scaling group. Stemming
in part from a spacetime line element correspondence ds → (exp λ
n) ds in which the eight quantities λ
0, λ
1, ..., λ
7 constitute a closed set under a modular addition, the associated formula for lepton-quark mass (yielding values at the 1
GeV scale for the leptons and lighter quarks and at the physical pole for the top) is conjectured to be m=m
fQ 2(exp − λ
n), where m
f=10.245 TeV is the progenitor fermion mass, Q is the charge number of the lepton or quark, and the modular group parameter λ
n is indexed by a fermion principal quantum number n that depends on three mutually independent projection operators. 相似文献
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