مجله فیزیک کاربردی
سال دوم شماره 2 (پیاپی 3، پاییز و زمستان 1391)

When a plane wavefront of a monochromatic and semi coherent is incident on a step، the reflected beam of light diffracted from the step because of the abrupt changes in the amplitude and phase of wave at the boundary of the step therefore fringes pattern is formed in perpendicular of propagation of light that can be described by Fresnel- Kirchhoff integrals. Recently numerous applications of this kind of Fresnel diffraction has been investigated involving measurement of thickness of thin films by accuracy of nanometers، accurate measurement of refractive index of solids and liquids، determination of dispersion relation of materials، measurement of nanometer displacement and measurement of wavelength by angstrom accuracy. In this report we will be shown that when two sides of a phase step which its boundary is perpendicular to the plane of incidence are two different materials، the intensity distribution in the fringes pattern of diffraction from a step is a function of optical constants of materials and height of the step. Numerical simulations of this case indicates that by having the intensity distribution of fringes pattern in several incident angels for polarized beam of light parallel or normal to the plane of incident we can determine optical constants of materials of both sides of step and its height. These simulations are performed for cases of one side dielectric and other side conductor، both side’s conductor and both side dielectric. Primary experimental results are in good agreement with theoretical and numerical results.

Carbon nanotubes (CNT) were synthesized by CVD method based on Ni (NO3) 2. 6H2O and Co (NO3) 2. 6H2O solution with two different ratios [Ni/Co = (1/ 0. 5)، (1/ 0. 0)]. We obtained the magnetic properties of the samples، such as coercivity field، saturate magnetization، retentivity magnetization and magnetic susceptibility by using of the magnetic hysteresis loops. It was found that carbon nano tubes were synthesized by using combination of Ni (NO3) 2. 6H2O and Co (NO3) 2. 6H2O catalysts، have much higher coercivity field، but less retentivity magnetization and saturation magnetization compared with the nanotubes were synthesized by using of the only Ni (NO3) 2. 6H2O catalyst

Strong experimental evidences and scaling analysis have shown that tumors growth belongs to the molecular beam epitaxy (MBE) universality class. This type of growth is described by three characteristics: 1) linear growth rate 2) the constraint of cell proliferation to the tumor border 3) surface diffusion of cells at the growing edge. All of these features have been experimentally seen. Stochastic partial differential equations with correct geometrical symmetries are reproduced some of the fundamental mechanisms of the tumor growth as a statistical approach. In the present article we presented a more general model in (1+1) dimension by adding 1 r term to the deterministic term . By solving this equation، we understand that with this approximation tumor reach faster to radially symmetric solution and its growth will become more favorable.

In this paper the NiO/PVC nanohybride composites with different concentration of organic matter have been synthesized with sol-gel method in the 80 °C. Nanocrystallites phases، crystallinity and electrical properties were characterized with using X-ray diffraction (XRD)، Fourier transfer infrared radiation (FTIR) and Atomic force microscopy (AFM) techniques. Electrical property characterization was also performed with prepared a wafer of NiO/PVC nanopowder and calculated the dielectric constant by application of GPS 132 A. The obtained 3results indicated that the NiO/PVC sample with weight rate 1:250 has higher dielectric constant، better morphology، less roughness surface، less leakage current، and can be used as a good gate dielectric for the future of OFET (Organic Field Effect Transistor) devices.