Lambda Curves Research Articles

Stochastic resonance in an optical bistable system subjected to cross-correlated additive white noise and multiplicative colored noise

The stochastic resonance (SR) of an optical bistable system with cross-correlated additive white and multiplicative colored noises and periodic signal is studied using the unified colored noise approximation and the theory of signal-to-noise ratio (SNR). Results show that cross-correlation intensity \lambda enforces the SR of the system. The position of the peak on the SNR-\tau curves moves to the right direction along with the increase of \lambda (\tau is the self-correlation time of the multiplicative colored noise). We find the SR phenomenon in the SNR-D and SNR-Q curves (D and Q are the intensities of the additive and multiplicative noises, respectively), but not in the SNR-\lambda curves.

Nonlinear scaling schemes for Lennard-Jones interactions in free energy calculations

Alchemical free energy calculations provide a means for the accurate determination of free energies from atomistic simulations and are increasingly used as a tool for computational studies of protein-ligand interactions. Much attention has been placed on efficient ways to deal with the "endpoint singularity" effect that can cause simulation instabilities when changing the number of atoms. In this study we compare the performance of linear and several nonlinear transformation methods, among them separation shifted "soft core" scaling, for a popular test system, the hydration free energy of an amino acid side chain. All the nonlinear methods yield similar results if extensive sampling is performed, but soft core scaling provides smooth lambda curves that are best suited for commonly used numerical integration schemes. Additionally, results from a more flexible solute, hexane, will also be discussed.

Processing effects on the microstructure and ferroelectric properties of strontium bismuth tantalate thin films

Ferroelectric thin films of strontium bismuth tantalate compositions with Bi/Sr ratios of 2.75 and 2.50 have been produced by deposition of solutions derived from sol-gels followed by crystallization using rapid thermal processing (RTP) at 650 °C. Single-step and two-step processes have been used for the RTP crystallization of the films. Both the composition and the heating process used affect the grain size, grain shape and compositional heterogeneity of the films, acting on their ferroelectric switching behaviour and dielectric properties. Larger and more elongated grains are obtained by crystallization using a single-step process. These films exhibit less slanted hysteresis loops. The combination of the study of the pure-ferroelectric-switching loop and the lambda curves through the application of a Curie–Weiss-like model gives a deeper insight into the influence of film heterogeneity on its ferroelectric properties. The observation of net polarisation without poling in all the films is attributed to the effects of 180° ferroelectric domains.

Control Model for Hydroelectric Energy-Value Optimization

A hydropower scheduling model that aims at minimizing thermal station-operation costs subject to various water- and power-demand constraints is described. The cost structure of the thermal power system is represented through incremental power-generation cost (or lambda) curves, which can be determined by running load-dispatching models. The model includes two control modules: one for the most efficient load allocation among the hydroplant turbines and another for the determination of the best hourly sequence of hydroplant power loads over the control horizon. These two modules are able to represent hydropower facilities and reservoir-management features in good detail, and the lambda curves effectively incorporate the essential elements of the thermal power system. The model is tested in the Lanier-Allatoona-Carters system in the southeastern United States and is shown to be computationally efficient even for very long control horizons.

Direct dynamical test for deterministic chaos and optimal embedding of a chaotic time series.

We propose here a local exponential divergence plot which is capable of providing an alternative means of characterizing a complex time series. The suggested plot defines a time-dependent exponent and a ''plus'' exponent. Based on their changes with the embedding dimension and delay time, a criterion for estimating simultaneously the minimal acceptable embedding dimension, the proper delay time, and the largest Lyapunov exponent has been obtained. When redefining the time-dependent exponent LAMBDA(k) curves on a series of shells, we have found that whether a linear envelope to the LAMBDA(k) curves exists can serve as a direct dynamical method of distinguishing chaos from noise.

Electrical resistivity, thermopower and thermal conductivity studies of (Sm1-xYx)Cu2 and RCu2 (R identical to Gd, Pr or Tb) systems

The authors report the electrical resistivity rho , thermopower S and thermal conductivity lambda studies of (Sm1-xYx)Cu2 and RCu2 (R identical to Gd, Pr or Tb) systems between 4.2 and 300 K. The value of the antiferromagnetic ordering temperature TN for the ((Sm1-xYx)Cu2 systems is found to become depressed, almost linearly, with Y substitution. The value of TN extrapolates to zero as x to 1. Such a behaviour is attributed solely to the dilution effects of Sm by Y atoms. Chemical pressure effects on the value of TN due to addition of Y atoms are found to be negligible. The lambda curves of SmCu2, GdCu2 and TbCu2 exhibit a peak for T < TN. This low-temperature peak at Tmaxlambda approximately= 10 K, in the lambda data of these compounds arises from the combined influence of the electronic and the magnetic contribution to the total lambda . This low-temperature peak becomes suppressed for x >or= 0.10. The S curves exhibit several extremum features, at T <or= TN, which is ascribed to the variation in the density of states at the Fermi level.

A precise and simple method, the relative transmission fringe depth method, of determining the optical constants and thickness of thin semitransparent films

This paper presents a new method (the relative transmission fringe depth (RTFD) method) of determining the optical constants and the thickness of semitransparent thin films. It has the following distinctive features: high precision, simplicity, and a self-examining function for the measured results. In order to meet the needs of application and engineering design, the n-F diagram (F is a new parameter which expresses the relative transmission fringe depth) is drawn. From it, n, k and d of films can be determined conveniently and precisely. With this method, the constants and thicknesses of SnO2:I heat mirror coatings, plastic films used in agriculture, and micasheets were determined. The results are in complete agreement with those obtained using a polarimetric meter. Also, the calculated T- lambda curves agree well with the T- lambda curves obtained using a spectrophotometer.

Spectrophotometric Determination of Some Preservatives in Milk

Benzoic acid, propyl p-hydroxybenzoate, and sorbic acid in milk have been determined by using the corresponding first derivative curves of absorption spectra of clarified milk samples. The delta A/delta lambda curves were computed and the concentration of each preservative was calculated using 1 point, 2 points, and/or 3 points. In all cases, the percentage error was within 2.4%.

Specific Heat of LiquidHe3/He4Mixtures Near the Junction of the Lambda and Phase-Separation Curves

Specific Heat of Liquid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>/<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Mixtures Near the Junction of the Lambda and Phase-Separation Curves