No abstract

We investigate the critical behavior of a one-dimensional diffusive epidemic propagation process by means of a Monte Carlo procedure. In the model, healthy (A) and sick (B) individuals diffuse on a lattice with diffusion constants D(A) and D(B), respectively. According to a Wilson renormalization calculation, the system presents a second-order phase transition between a steady reactive state and a vacuum state, with distinct universality classes for the cases D(A)=D(B) and D(A)D(B). In this work we perform a finite size scaling analysis of order parameter data at the vicinity of the critical point in dimension d=1. Our results show no signature of a first-order transition in the case of D(A)>D(B). A finite size scaling typical of second-order phase transitions fits well the data from all three regimes. We found that the correlation exponent nu=2 as predicted by field-theoretical arguments. Estimates for beta/nu are given for all relevant regimes.

No abstract

No abstract

Articles you may be interested inOptical temperature sensor based on upconversion emission in Er-doped ferroelectric 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic Appl. Phys. Lett.Evaluation of rare earth doped silica sub-micrometric spheres as optically controlled temperature sensors Characteristics of doped optical fiber for fluorescence-based fiber optic temperature systems Rev. Sci. Instrum. 74, 5212 (2003); 10.1063/1.1623624 Effects of high-temperature heat treatment on Nd 3+ -doped optical fibers for use in fluorescence intensity ratio based temperature sensing Rev. Sci. Instrum. 74, 3524 (2003); 10.1063/1.1578706Optical temperature sensing using upconversion fluorescence emission in Er 3+ /Yb 3+ -codoped chalcogenide glass Appl.In this work an optically integrated and compact point temperature sensor based upon upconversion fluorescence emission in an Er 3ϩ -doped silica-on-silicon waveguide is proposed. The sensing system relies upon the temperature information residing in the intensity ratio of two thermally coupled upconversion excited fluorescence emission signals around 530 and 550 nm due to the Er 3ϩ transitions 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 , respectively. The system was tested in the range of temperature from 20°C to 140°C. Under this circumstance the system have shown sensitivity close to 9.0ϫ10 Ϫ3 /°C with a coupled pump power around 800 nm as low as 7 mW and a maximum sensitivity of 0.010/°C is expected at 250°C.

No abstract

No abstract

No abstract