Qualitative behaviour of a ratio-dependent predator–prey system

This paper deals with the qualitative properties of an autonomous system of differential equations, modeling ratio-dependent predator–prey interactions.This model differs from traditional ratio dependent models essentially in the predator mortality term, the death rate of the predator is not constant but instead increases when there is overcrowding.We incorporate delay(s) into the system. The most important observation is that as the delay(s) is (are) increased the originally asymptotic stable interior equilibrium loses its stability. Furthermore at a certain critical value a Hopf bifurcation takes place: small amplitude periodic solutions arise.     

Ellipsometry of silica nanoparticulate Langmuir-Blodgett films for the verification of the validity of effective medium approximations

The validity of various effective medium approximations (EMAs) (Bruggeman, Maxwell-Garnett) was studied for nanostructured systems, where the scale of inhomogeneities is comparable to the wavelength. Langmuir-Blodgett (LB) layers of St?ber silica nanospheres of diameters between 40 and 129 nm are excellent model structures for the experimental verification of the validity of the EMA methods in spectroscopic ellipsometry (SE) evaluation. Nanostructured mono- and multilayered silica films were investigated by SE and reflectance spectroscopy. The effective refractive index and film thickness were determined from the results of multiparameter fitting of SE spectra in the 300-759 nm wavelength region. The distribution of the effective refractive index in the particulate films was calculated assuming an ideal close-packed arrangement of particles. The average deviation from such a structure was deduced from the corrected model by introducing a "fill factor". In the EMA approximation, the spherical shape of the silica particle determines the optical behavior, rather than the "depth distribution" of silica or porosity. Therefore, the shape of particles has a dominant effect on the optical properties of nanoparticulate LB films.     

On the multi‐colored Ramsey numbers of cycles

For a graph L and an integer k≥2, R_k(L) denotes the smallest integer N for which for any edge‐coloring of the complete graph K_N by k colors there exists a color i for which the corresponding color class contains L as a subgraph. Bondy and Erdos conjectured that, for an odd cycle C_n on n vertices, They proved the case when k = 2 and also provided an upper bound R_k(C_n)≤(k+ 2)!n. Recently, this conjecture has been verified for k = 3 if n is large. In this note, we prove that for every integer k≥4, When n is even, Sun Yongqi, Yang Yuansheng, Xu Feng, and Li Bingxi gave a construction, showing that R_k(C_n)≥(k?1)n?2k+ 4. Here we prove that if n is even, then © 2011 Wiley Periodicals, Inc. J Graph Theory 69: 169‐175, 2012     

Increment sizes of the principal value of Brownian local time

Let W be a standard Brownian motion, and define Y(t)= ∫₀ ^t ds/W(s) as Cauchy's principal value related to local time. We determine: (a) the modulus of continuity of Y in the sense of P. Lévy; (b) the large increments of Y. Received: 1 April 1999 / Revised version: 27 September 1999 / Published online: 14 June 2000     

Fire Retarded Insulating Sheets from Recycled Materials

In this work we aimed at forming partially recycled polymer composites of appropriate mechanical properties and flame retardancy. Multilayer composite structures proved to be suitable to fulfill all of these requirements. Core-shell structures presented here contain two-component thermosets, i.e. epoxy, recycled polyurethane and polyisocyanurate, as matrices reinforced with waste fillers such as short basalt fibers and wood chips. Flame retardancy and mechanical properties of the core-shell structures were investigated by the conventional methods of characterization. The developed cost-effective multilayer composites can be applied as heat and sound insulating panels e.g. multifunctional sheets for construction or automotive industry.     

The latest international recognition of the Hungarian thermal analysis,the Judit Simon ESTAC Award

Journal of Thermal Analysis and Calorimetry -     

Determination of thermal transport properties of thin metal films from pulsed thermoreflectance measurements in the picosecond regime

Picosecond transient thermoreflectance (PTTR) of metals is shown to depend strongly on the temperature coefficients of the complex dielectric constant. The properties of PTTR are studied for TE and TM waves as a function of the angle of incidence. A method is suggested for subtracting the thermal transport properties of thin films from PTTR measurements.     

Windowless resonant acoustic chamber for laser-photoacoustic applications

A windowless resonant photoacoustic chamber is described for environmental and agricultural applications. The windowless design is a solution to the lack of perfect windows in the infrared region. The design was made insensitive to external noise with the help of acoustic filters. The chamber was designed to have a high quality factor of about 400. Experimental results show good agreement with the theoretical calculations.     

Double-exchange ferromagnetism in the partially-filled one-dimensional Kondo lattice model

We investigate the incompletely saturated ferromagnetic phase which occurs at strong-coupling in the partially-filled one-dimensional (1D) Kondo lattice model. The double-exchange interaction responsible for the ferromagnetic ordering is absent in dilute Kondo systems, and is a missing element in nearly all theoretical treatments of the model. We discuss how: 1) double-exchange arises in the system, even though the Kondo coupling is antiferromagnetic, and show that at strong-coupling it favors an alignment of the spins of unpaired localized moments; and 2) how this determines the ground-state phase diagram, and properties of the localized moments.     

When Can Statistical Theories Be Causally Closed?

The notion of common cause closedness of a classical, Kolmogorovian probability space with respect to a causal independence relation between the random events is defined, and propositions are presented that characterize common cause closedness for specific probability spaces. It is proved in particular that no probability space with a finite number of random events can contain common causes of all the correlations it predicts; however, it is demonstrated that probability spaces even with a finite number of random events can be common cause closed with respect to a causal independence relation that is stronger than logical independence. Furthermore it is shown that infinite, atomless probability spaces are always common cause closed in the strongest possible sense. Open problems concerning common cause closedness are formulated and the results are interpreted from the perspective of Reichenbach's Common Cause Principle (RCCP).