2,486 research outputs found
A REAL TIME MONITORING MODEL OF THE CALCIUM CARBONATE FOULING INDUCTION PERIOD BASED ON THE CONDUCTANCE TITRATION
A new method has been developed to monitor the calcium carbonate fouling induction period (CCFIP) in real time. Based on the conductance titration, this paper investigated the forming process of CCFIP by a staticdynamic combined simulation experiment unit. With the help of titration analysis (that is titrimetry), an accurate definition of CCFIP and the corresponding real time monitoring model were built up. The investigation results show that the proposed model applies not only to measure the CCFIP in real time, but also applies to an investigation of the influence of various factors on the CCFIP
On the Heisenberg invariance and the Elliptic Poisson tensors
We study different algebraic and geometric properties of Heisenberg invariant
Poisson polynomial quadratic algebras. We show that these algebras are
unimodular. The elliptic Sklyanin-Odesskii-Feigin Poisson algebras
are the main important example. We classify all quadratic
invariant Poisson tensors on with and show that
for they coincide with the elliptic Sklyanin-Odesskii-Feigin Poisson
algebras or with their certain degenerations.Comment: 14 pages, no figures, minor revision, typos correcte
Recurrence and Polya number of general one-dimensional random walks
The recurrence properties of random walks can be characterized by P\'{o}lya
number, i.e., the probability that the walker has returned to the origin at
least once. In this paper, we consider recurrence properties for a general 1D
random walk on a line, in which at each time step the walker can move to the
left or right with probabilities and , or remain at the same position
with probability (). We calculate P\'{o}lya number of this
model and find a simple expression for as, , where is
the absolute difference of and (). We prove this rigorous
expression by the method of creative telescoping, and our result suggests that
the walk is recurrent if and only if the left-moving probability equals to
the right-moving probability .Comment: 3 page short pape
Distribution of exchange energy in a bond-alternating S=1 quantum spin chain
The quasi-one-dimensional bond-alternating S=1 quantum antiferromagnet NTENP
is studied by single crystal inelastic neutron scattering. Parameters of the
measured dispersion relation for magnetic excitations are compared to existing
numerical results and used to determine the magnitude of bond-strength
alternation. The measured neutron scattering intensities are also analyzed
using the 1st-moment sum rules for the magnetic dynamic structure factor, to
directly determine the modulation of ground state exchange energies. These
independently determined modulation parameters characterize the level of spin
dimerization in NTENP. First-principle DMRG calculations are used to study the
relation between these two quantities.Comment: 10 pages, 10 figure
Optimised limit for polarimetric calibration of fully polarised SAR systems
The optimised limit for polarimetric calibration of fully polarised synthetic aperture radar systems is derived by establishing an error model as a function of cross-talk, channel imbalance and system noise. Compared with noise equivalent sigma zero, the polarimetric error below the optimised limit is too small to affect the signal of cross-polarised channel. Thus, polarimetric calibration could be relaxed or even ignored in this case. With the backscatter model, optimised limits for cross-talk and channel imbalance at X, C and L-bands are presented. Moreover, when ignoring channel imbalance, the limit for cross-talk is given in a quantitative way. These results are very useful in practice, allowing significant reduction in calibration cost
Has the nonlinear Meissner effect been observed?
We examine recent high-precision experimental data on the magnetic field,
, dependence of the penetration depth in
(YBCO) for several field directions in the
plane. In a new theoretical analysis that incorporates the effects of
orthorhombic symmetry, we show that the data at sufficiently high magnetic
fields and low temperatures are in quantitative agreement with the theoretical
predictions of the nonlinear Meissner effect.Comment: 4 text pages plus 3 postscript figure
A unified approach to combinatorial key predistribution schemes for sensor networks
There have been numerous recent proposals for key predistribution schemes for wireless sensor networks based on various types of combinatorial structures such as designs and codes. Many of these schemes have very similar properties and are analysed in a similar manner. We seek to provide a unified framework to study these kinds of schemes. To do so, we define a new, general class of designs, termed “partially balanced t-designs”, that is sufficiently general that it encompasses almost all of the designs that have been proposed for combinatorial key predistribution schemes. However, this new class of designs still has sufficient structure that we are able to derive general formulas for the metrics of the resulting key predistribution schemes. These metrics can be evaluated for a particular scheme simply by substituting appropriate parameters of the underlying combinatorial structure into our general formulas. We also compare various classes of schemes based on different designs, and point out that some existing proposed schemes are in fact identical, even though their descriptions may seem different. We believe that our general framework should facilitate the analysis of proposals for combinatorial key predistribution schemes and their comparison with existing schemes, and also allow researchers to easily evaluate which scheme or schemes present the best combination of performance metrics for a given application scenario
Theoretical investigations of a highly mismatched interface: the case of SiC/Si(001)
Using first principles, classical potentials, and elasticity theory, we
investigated the structure of a semiconductor/semiconductor interface with a
high lattice mismatch, SiC/Si(001). Among several tested possible
configurations, a heterostructure with (i) a misfit dislocation network pinned
at the interface and (ii) reconstructed dislocation cores with a carbon
substoichiometry is found to be the most stable one. The importance of the slab
approximation in first-principles calculations is discussed and estimated by
combining classical potential techniques and elasticity theory. For the most
stable configuration, an estimate of the interface energy is given. Finally,
the electronic structure is investigated and discussed in relation with the
dislocation array structure. Interface states, localized in the heterostructure
gap and located on dislocation cores, are identified
Use of control to maintain period-1 motions during wind-up or wind-down operations of an impacting driven beam
We consider the dynamical response of a thin beam held fixed at one end while excited by an external driving force. A motion limiting constraint, or stop, causes the beam to impact. During wind-up or wind-down operations, in which the driving frequency is continuously altered, the system can undergo complicated motions close to the value of frequency at which impacts may first occur, the grazing bifurcation. In this region, the beam may experience several impacts within a long period-repeating solution or even chaotic behavior which, in practical terms, may be undesirable to the long-term integrity of the system. The first task is to identify the zones in the space of parameters (forcing amplitude or, alternatively, the gap between the beam and the stop) in which period-1 motions can be guaranteed. In this paper, in the areas in which complicated or chaotic motion occurs, a control strategy is proposed which stabilises unstable period-1 motions. As a consequence, numerical simulations indicate that, for any choice of parameter in the range, simple period-1 motions can be maintained, limiting the number of impacts (together with their velocity)
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