Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Deterministics series

Statistical analysis, such as a two-way analysis of variance may be used to test whether differences between values at various times are significant. However, statistical analyses do not provide any information about the shape, phase, amplitude, or mean level of the rhythm they merely indicates whether the data are different from random variation. In order to quantify rhythm parameters, other mathematical techniques, such as Halberg s cosi-nor model, are required. Our hypothesis assumes that the measured data follow a deterministic series model. Deterministic series are obtained when successive observations are dependent variables and any future values may be predicted firom past observations (Chatfield, 1975). [Pg.221]

Wet-weather processes are subject to high variability. A simple deterministic model result in terms of the impacts on the water quality is out of scope. From a modeling point of view, a stochastic description is a realistic solution for producing relevant results. Furthermore, an approach based on a historical rainfall series as model input is needed to establish extreme event statistics for a critical CSO impact that can be compared to a water quality criterion. In terms of CSO design including water quality, this approach is a key point. [Pg.225]

Deterministic trend models are based on the assumption that the trend of a time series can be approximated closely by simple mathematical functions of time over the entire span of the series. The most common representation of a deterministic trend is by means of polynomials or of transcendental functions. The time series... [Pg.891]

Deterministic trend models are based on the assumption that the trend of a time series can be approximated closely by simple mathematical functions of time over the entire span of the series. The most common representation of a deterministic trend is by means of polynomials or of transcendental functions. The time series from which the trend is to be identified is assumed to be generated by a nonstationary process where the nonstationarity results from a deterministic trend. A classical model is the regression or error model (Anderson, 1971) where the observed series is treated as the sum of a systematic part or trend and a random part or irregular. This model can be written as... [Pg.939]

Thus, a deterministic answer assumes that the laws of physics and chemistry have causally and sequentially determined the obligatory series of events leading from inanimate matter to life - that each step is causally linked to the previous one and to the next one by the laws of nature. In principle, in a strictly deterministic situation, the state of a system at any point in time determines the future behavior of the system - with no random influences. In contrast, in a non-deterministic or stochastic system it is not generally possible to predict the future behavior exactly and instead of a linear causal pathway the sequence of steps may be determined by the set of parameters operating at each step. [Pg.4]

Internal noise is described by a master equation. When this equation cannot be solved exactly it is necessary to have a systematic approximation method - rather than the naive Fokker-Planck and Langevin approximations. Such a method will now be developed in the form of a power series expansion in a parameter Q. In lowest order it reproduces the macroscopic equation and thereby demonstrates how a deterministic equation emerges from the stochastic description. [Pg.244]

Regression analysis in time series analysis is a very useful technique if an explanatory variable is available. Explanatory variables may be any variables with a deterministic relationship to the time series. VAN STRATEN and KOUWENHOVEN [1991] describe the dependence of dissolved oxygen on solar radiation, photosynthesis, and the respiration rate of a lake and make predictions about the oxygen concentration. STOCK [1981] uses the temperature, biological oxygen demand, and the ammonia concentration to describe the oxygen content in the river Rhine. A trend analysis of ozone data was demonstrated by TIAO et al. [1986]. [Pg.219]

Since the susceptibility cannot be evaluated in a deterministic way, the exponential function is developed at p = 0 (which implies T —> oo) as a Taylor series ... [Pg.92]

G. Adomian developed the decomposition method to solve the deterministic or stochastic differential equations.3 The solutions obtained are approximate and fast to converge, as shown by Cherrault.8 In general, satisfactory results can be obtained by using the first few terms of the approximate, series solution. According to Adomian s theory, his polynomials can approximate the... [Pg.223]

XPPAUT (http //www.math.pitt.edu/ bard/xpp/xpp.html) offers deterministic simulations with a set of very good stiff solvers. It also offers fitting, stability analysis, nonlinear systems analysis, and time-series analysis, like histograms. The GUI is simple. It is mainly available under Linux, but also mns on Windows. [Pg.76]

Since this monograph is devoted only to the conception of mathematical models, the inverse problem of estimation is not fully detailed. Nevertheless, estimating parameters of the models is crucial for verification and applications. Any parameter in a deterministic model can be sensibly estimated from time-series data only by embedding the model in a statistical framework. It is usually performed by assuming that instead of exact measurements on concentration, we have these values blurred by observation errors that are independent and normally distributed. The parameters in the deterministic formulation are estimated by nonlinear least-squares or maximum likelihood methods. [Pg.372]

Fig. 1. Some examples of heterogeneous oscillations observed experimentally, (a) Sinusoidal time series for H2/O2 on a Pt wire (from Ref. 41). (b) Relaxation oscillations for CO/O2 on Pt/Al203 (from Ref. 100). (c) Oscillations after a single period doubling for CO/O2 on Pt(l 10) (from Ref. 231). (d) Model and experimental (inset) quasiperiodic oscillations for NO/CO on supported Pd (from Ref. 232). (e) Deterministic chaos produced by a period doubling sequence for CO/O2 on Pt(IlO) (from Ref. 231). Fig. 1. Some examples of heterogeneous oscillations observed experimentally, (a) Sinusoidal time series for H2/O2 on a Pt wire (from Ref. 41). (b) Relaxation oscillations for CO/O2 on Pt/Al203 (from Ref. 100). (c) Oscillations after a single period doubling for CO/O2 on Pt(l 10) (from Ref. 231). (d) Model and experimental (inset) quasiperiodic oscillations for NO/CO on supported Pd (from Ref. 232). (e) Deterministic chaos produced by a period doubling sequence for CO/O2 on Pt(IlO) (from Ref. 231).
Chaotic time series have been obtained from a wide variety of experimental systems. Figures 16 and 17 show examples of the irregular time series found in various cases. It is somewhat problematic to assign the term chaotic to these reported time series because it was rarely investigated whether the time series were deterministically chaotic in the strict sense of the word. Therefore, when we use the expression chaotic, we are well aware that there is, in many cases, no proof for chaos in the oscillation patterns. The few reports wherein a thorough analysis has been performed (64,104) do though show the existence of deterministically chaotic oscillations. It would be beyond the scope of this review to describe the methods... [Pg.107]

Complex time series have also been detected for Pd 129,131). In these studies, however, it was shown that the complex structure could be characterized by three or fewer superimposed frequencies (729) and was thus not deterministically chaotic. Chaotic oscillations have been reported for several other sterns, namely, NH3/O2 on Pt (40,211,212), H2/O2 on Ni (168,169) and Pt (752), CO/NO on Pt and Pd (91,123), C2H4/H2 on Pt (335), C3H6/O2 on Pt (194), l-hexene/02 on Pd (798), and the CH3NH2 decomposition over Pt, Rh, and Ir (24). This list, while incomplete, shows that irregular oscillations and often chaos are frequently encountered during heterogeneous catalytic studies. [Pg.109]

Chaotic behavior and synchronization in heterogeneous catalysis are closely related. Partial synchronization can lead to a complex time series, generated by superposition of several periodic oscillators, and can in some cases result in deterministically chaotic behavior. In addition to the fact that macroscopically observable oscillations exist (which demonstrates that synchronization occurs in these systems), a number of experiments show the influence of a synchronizing force on all the hierarchical levels mentioned earlier. Sheintuch (294) analyzed on a general level the problem of communication between two cells. He concluded that if the gas-phase concentration is the autocatalytic variable, then synchronization is attained in all cases. However, if the gas-phase concentration were the nonautocatalytic variable, then this would lead to symmetry breaking and the formation of spatial structures. When surface variables are the model variables, the existence of synchrony is dependent upon the size scale. Only two-variable models were analyzed, and no such strict analysis has been provided for models with two or more surface concentrations, mass balances, or heat balances. There are, however, several studies that focused on a certain system and a certain synchronization mechanism. [Pg.111]

SlMl.dat Section 1.4 Five data sets of 200 points each generated by SIM-GAUSS the deterministic time series sine wave, saw tooth, base line, GC-peak, and step function have stochastic (normally distributed) noise superimposed use with SMOOTH to test different filter functions (filer type, window). A comparison between the (residual) standard deviations obtained using SMOOTH respectively HISTO (or MSD) demonstrates that the straight application of the Mean/SD concept to a fundamentally unstable signal gives the wrong impression. [Pg.392]

To date, quantum theory, despite its many peculiar non-classical microscopic aberrations, has been used effectively to explain experimental observations and to predict accurately physical effects in advance of the experiment. Interestingly, many of the founders of quantum mechanics later rejected it, primarily because it was a non-deterministic theory. The break from their classical mechanics view of the universe appears to have been too severe for them to accept. But a new generation of physicists was prepared to embrace the quantum mechanics and apply the methods to chemical structures. With a series of novel concepts and observations, physics and chemistry were changed forever. [Pg.717]

Using a 15-minute SRV time series, from which the data depicted in Fig. 6 were taken, we apply the allometric aggregation procedure to determine the relation between the standard deviation and mean of the time series as shown in Fig. 7. In the latter figure, the curve for the SRV data is, as we did with the other data sets, contrasted with an uncorrelated random process (slope = 0.5) and a regular deterministic process (slope = 1.0). The slope of the data curve is 0.70,... [Pg.19]

Kaplan, D, T., and Glass, L. (1993) Coarse-grained embeddings of time series random walks, Gaussian random processes, and deterministic chaos. Physica D 64,431. [Pg.469]

In a series of impressive publications. Maxwell [65] [66] [67] [68] provided most of the fundamental concepts constituting the statistical theory recognizing that the molecular motion has a random character. When the molecular motion is random, the absolute molecular velocity cannot be described deterministically in accordance with a physical law so a probabilistic (stochastic) model is required. [Pg.190]

For a many-spin system, the solution of Equation (4.6) becomes very complicated and the individual coupling frequencies d cannot always be extracted from experimental data. Nevertheless, the sum polarization 2, S,j. remains time invariant and is called a constant of the motion. In principle, we must describe the time evolution of an initial nonequilibrium state tr(0) = 2, c,(0)S, as a series of rotations of the density operator in the Hilbert space of the entire spin system. At times t > 0 not only populations but also many-spin terms of the form riA S jnmSmri S appear in the density operator. Of course, this time evolution is fully deterministic and reversible. The reversibility was in fact demonstrated in the polarization-echo experiments [10] (Fig. 4.2) where two sequential time evolutions with a scaling factor of s =1 and s = -1/2 follow each other (see Equation (4.5)). If the second period has twice the length of the first period, the time evolution under the dipolar interaction is refocused and the density operator returns to the initial density operator. [Pg.87]


See other pages where Deterministics series is mentioned: [Pg.319]    [Pg.73]    [Pg.401]    [Pg.392]    [Pg.52]    [Pg.52]    [Pg.892]    [Pg.2]    [Pg.320]    [Pg.43]    [Pg.219]    [Pg.343]    [Pg.84]    [Pg.61]    [Pg.269]    [Pg.62]    [Pg.108]    [Pg.525]    [Pg.3290]    [Pg.383]    [Pg.288]    [Pg.298]    [Pg.25]    [Pg.28]    [Pg.151]    [Pg.479]    [Pg.298]    [Pg.413]    [Pg.173]   
See also in sourсe #XX -- [ Pg.90 ]




SEARCH



Deterministic

© 2024 chempedia.info