نشریه علوم پایه
سال بیست و سوم شماره 2 (1389)

The compound lead oxide α-PbO was prepared in this laboratory and used for XRD and electron microscopic investigations. A serie of calculations is made to refinemente the cell constants. Then were computed these dates with a computer program (LSUCRIPC). The cell constants were calculated more exactly. The received values are a=5.47045, b=4.72464, c=5.87024.

There are different models for discussion of nonlinear water waves. One oe them is know Benjamin-Bona-Mahony-Burgers(BBM-B) model. The main question of this model is the investigation of the water waves in low-deep environment. In this paper, we are going to find the probability distribution function and moments of velocity field of the BBM-B equation in (1+1) dimensions.

Design and construction of an optical sensor for liquid level control is reported here. Operation of this sensor is based on the intensity modulation. The modulated light intensity is detected by total internal reflection in a prism. The variation of output intensity is measured by an optical detector and is monitored by a digital voltmeter. This optical fiber sensor is used for water level measurement in this experiment. For a white light source, the output voltage in the case of low water level is equal to 480 mV and when the water level reaches to prism reduced to 8 mV. Height measurement accuracy in this system is about ±1mm.

In the frame work of fluid theory, in spite of the compressional shocks, it is commonly believed that the rarefacting shocks can propagate only in the regime of anomalous thermodynamics. Plasma a charged fluid is not an exception; so in the one dimensional plasma expansion accompany with the propagation of an electromagnetic (E. M.) field, in opposite direction. In this paper it is shown that the pressure of E. M wave through pondermotive force can modulate plasma density and as a result, the condition for propagation of a rarefaction shock preserved.

In this paper, electronic structural properties of LiBC are calculated by using a Full Potential -Linearized Augmented Plane waveFP-LAPW) method in the framework of density functional theory (DFT) with the generalized gradient approximation (GGA) by WIEN2k package.. The structural properties of LiBC such as lattice parameters, bulk module, compressibility and the derivative of bulk module relative to pressure were calculated using three different approximations of GGA, LDA and LSDA. The results indicate that the calculation done with GGA approximation is in better agreement with the experimental results and the results of the other methods.

Samples of YBa2Cu3-xAlxO7- with x=0, 0.01, 0.02, 0.03 and 0.045 are prepared by Sol-Gel method. Structural and superconducting properties of samples are studied by electrical resistivity (R-T), X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the samples show transition to superconducting state. R-T measurements show a small decrease of TC (zero) with increasing Al doping up to x=0.02, and followed by a faster decrease with increasing doping concentration. We suggest that substitution of Al at Cu(1) site, makes holes localized at Cu-O chains and decreases TC. The crystal structure of YBa2Cu3-xAlxO7- is refined by the MAUD analysis. The orthorhombicity decreases with increasing Al doping. The Critical current density increases with increasing Al doping up to x=0.02 and then decreases.

The detail of design, construction and test of a parabolic radio telescope is explained. It consists of a 2 meter parabolic dish with 1 meter focal length made by fiber glass. The dish is mounted on an alt-azimuth peer made by iron which is completely steer able. The device was tested to observe both terrestrial and astronomical sources.