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181.
Heart rate oscillates on several different time scales and has long-term variability in the form of 1/f noise. The physiological control of heart rate is briefly reviewed, and several typical patterns of heart rate variability, in health and sickness, are described. Considered briefly are some possible dynamical mechanisms for heart rate variability. 相似文献
182.
Frequency differences of up to 170 GHz between a cw dye laser and a krypton laser at 568 nm were measured by mixing laser and microware radiation with a metalinsulator-metal point contact diode. Beat signals are well above noise and there is still great potential for improvement when better microwave oscillators are used. From the measurements reported it follows that the diode can be used for determining still higher frequency differences of visible laser radiation. 相似文献
183.
Summary. The iterative aggregation method
for the solution of linear systems is
extended in several directions:
to operators on Banach spaces; to the method with inexact correction, i.e.,
to methods where the (inner) linear system is in turn solved
iteratively; and to the problem of finding
stationary distributions of Markov operators.
Local convergence is shown in all cases.
Convergence results apply to the particular case of stochastic
matrices. Moreover, an argument is given which suggests why the
iterative aggregation method works so well for nearly
uncoupled Markov chains, as well as for Markov chains with
other zero-nonzero structures.
Received
May 25, 1991/Revised version received February 23, 1994 相似文献
184.
185.
Daniel B. Szyld 《Numerical Linear Algebra with Applications》1994,1(2):151-154
Equivalence is shown between different conditions for convergence of iterative methods for consistent singular systems of linear equations on Banach spaces. These systems appear in many applications, such as Markov chains and Markov processes. The conditions considered relate the range and null spaces of different operators. 相似文献
186.
187.
Side-on observations of the visible spectrum emitted by a helium plasma generated in a wall-stabilized arc are reported. Electron densities range from 0.2 to 1.3 × 1022m-3 and electron temperatures vary from 10,000 to 20,000 K. Most of the seventeen measured lines are “isolated” at the conditions of the experiment. Here, “isolated” refers to quantum levels which are non-degenerate even in the presence of perturbing fields. Electron densities derived from the Stark-widths of the isolated lines agree to within 15% of the values determined from Hβ and from the quasi-degenerate He(I) lines at 4471 and 4921 Å. Similar agreement is observed for the static-ion Stark broadening parameters. However, at the conditions of this experiment, the static-ion approximation is not valid near the center of some of the isolated lines. The observation of ion-dynamic effects in neutral isolated lines is reported here for the first time. In the isolated lines, the measured ion-dynamic effects are reasonably consistent with calculations based on an adiabatic “unified” theory for the ion perturbers. A simple parametric expression closely approximates the ion-dynamic contribution to the half-width of isolated lines. Hydrogenic (non-isolated) neutral helium lines exhibit a large discrepancy with theoretical profiles near the line center, where ion-dynamic effects are important. 相似文献
188.
Some Morera and mean-value type theorems are proved in the hyperbolic disk.
Partially supported by NSF grants DMS-9000619 and CDR-8803012.
Partially supported by NSF grants DMS-8703072 and DMS-9000619, and DGI-CYT grant PB 89-0311. 相似文献
189.
P. Ehrhart F. J. Hartmann E. Köhler H. Daniel 《Zeitschrift für Physik A Hadrons and Nuclei》1983,311(4):259-266
Muonic Coulomb capture ratios and x-ray intensity patterns in four binary mixtures of the gases N2, Ne, Ar, Kr, and Xe have been measured at three atomic ratios. An influence of the concentration has been established. The Lyman series intensity patterns of pure N2, Ne, Ar, Kr, and Xe were measured at pressures between 0.4 and 51 bar and found to depend on the pressure. Possible explanations are discussed. 相似文献
190.
Shlomo Havlin James E. Kiefer George H. Weiss Daniel Benavraham Yehoshua Glazer 《Journal of statistical physics》1985,41(3-4):489-496
We discuss and analyze a family of trees grown on a Cayley tree, that allows for a variable exponent in the expression for the mass as a function of chemical distance, M(l)l
dl
. For the suggested model, the corresponding exponent for the mass of the skeleton,d
l
s
, can be expressed in terms ofd
l
asd
l
s
= 1,d
l
d
l
c
= 2;d
l
s
= d
l
–1,d
1
d
l
c
= 2, which implies that the tree is finitely ramified ford
l
2 and infinitely ramified whend
l
2. Our results are derived using a recursion relation that takes advantage of the one-dimensional nature of the problem. We also present results for the diffusion exponents and probability of return to the origin of a random walk on these trees. 相似文献