Iranian Journal of Science
Year:2004 | Volume:28 | Issue:A2|Papers Count:11

A simple new closed form of the Green function for axisymmetric magnetostatic problems is found analytically in cylindrical coordinates. The result is verified by applying several examples.  

We propose a new ring resonator side-coupled M-Z interferometer all-optical switch through the pumped nonlinear directional coupler. By controlling pump power P to lead the coupler reflectivity r approaching to 1, the resonator finesse will be enhanced dramatically, and then the minimum switching power in silica-based practice devices can be obtained. As a sample, we use a nonlinear coupler made by two erbium-doped fibers, and launch a 514.5nm-pump light into one of the cores to make the reflective- index difference between two cores. Based on the asymmetric-coupler theory, we simulate the relationship between r and P, and show that the required pump power is only 0.8Mw for r →1.

In this paper, strong laws of large numbers (SLLN) are obtained for the sums Σn i=1Xi , under certain conditions, where {Xn ,n≥1} n is a sequence of pairwise negatively dependent random variables.

A chaos control method suggested by Erjaee has been reviewed. It has been shown that this technique can be applied in various evolutionary systems of 2-dimensional types. The method has been applied for cases of the Henon map, as well as Burger’s map. The limitations of the control technique have also been discussed by considering the Standard Map and the Gumowski-Mira map. The results obtained through numerical calculations are very interesting and significant. This technique has some advantages over many other techniques of chaos control in discrete systems.

In this experimental work, by using the method of plasma-chemical etching, we have dealt with the causes of the creation of a distorted layer on the surface of silicon wafers during mechanical machining processes, in addition, the elucidation of connections between the structure of this layer and characteristic parameters of the mechanical strength of these wafers have been studied. Experimental results obtained at room temperature show that after cutting and grinding processes, the mean value of mechanical strength σ, which is apparently independent of the types of conductivity, is significantly lower than its theoretical value. Analysis of the dependence of mechanical parameters on the time of plasma-chemical etching indicates that the lower values obtained for the mechanical strength of silicon wafers is basically due to the existence of a distorted layer and corresponding internal stresses created on the surface of these wafers after mechanical machining. Plasma-chemical etching leads to an increase in σ value. Dependency of σ on the etching time is qualitatively described by the microstructure of the distorted layer and parameters of the micro relief surface of the wafers. Correlation between parameters σ, H, K and the microstructure of the distorted layer allows us to suggest the method of plasma chemical etching as a method of investigating the microstructure of the distorted layer after the echanical machining processes.  

Several tables have been given due to α − minimal sets. Our main aim in this paper is to complete these tables by employing several examples.  

An improved MIT bag model with hyper central interactions is used to calculate the static properties of hadrons containing u, d, s and c quarks. We present a theoretical approach to the internal structure of three-body hyper central interacting quarks in a hadron, in which we take hadron as a bag. We discuss a few of the results obtained using a six-dimension harmonic oscilator (h.o) potential, having a two-body character, which turns out to be a hyper central confinement part. The other potential is six dimensional, which is attractive for small separation, originating from the color charge of hyper color term. However the potential can easily be generalized in order to allow a systematic analysis. We calculate the relativistic wave function for quarks in a scalar-vector hyper central potential, analytically. Finally, vanishing the normal component of vector current at the surface of the baryon bag as a boundary condition equivalent to confinement, results in the static properties and the strength of hyper Coulomb like potential parameter. This depends on the mass parameters contrary to almost all previous versions. The calculated static properties for baryon are better than in the uncorrected versions of the model PACS index 12.39 .Ba, 12.39. Ki, 12.39. Pn

The largest class of algebraic hyper structures satisfying the module like axioms is the Hv-module. In this paper, we consider the category of Hv-modules and prove that the direct limit always exists in this category. Direct limits are defined by a universal property, and so are unique. The most powerful tool in order to obtain a module from a given Hv-module is the quotient out procedure. To use this method we consider the fundamental equivalence relation ε * , and then prove some of the results about the connection between the fundamental modules, direct systems and direct limits.

In the analysis of spatial point patterns, complete spatial randomness (CSR) hypothesis, which is a restriction of a homogenous Poisson process to study region A, operates as a dividing hypothesis between “regular” and “aggregated” patterns. Meanwhile, many alternatives to CSR in aggregated patterns are extensions of homogenous Poisson processes themselves. Therefore, when the CSR hypothesis is rejected, results related to Poisson processes may be used to formulate plausible alternatives to CSR. In this paper, we propose a new statistic for testing CSR and then by applying it in conjunction with a notion of kernels of a point pattern, we determine the “parents” of a Poisson cluster process when the CSR hypothesis is rejected and a Neyman-Scott process is assumed for the point pattern under alternative hypothesis. We have made power studies for our test statistic by simulation, and have also surveyed the performance of our method on a certain point pattern. Finally, the whole method is carried on certain real life data.

In this paper we initiate the study of real group algebras and investigate some of its aspects. Let L1 (G) be a group algebra of a locally compact group G, τ :G → G be a group homeomorphism such that τ2 =τοτ = 1, the identity map, and Lp (G, τ ) = { ƒ Є Lp (G) : ƒοτ = ƒ } ( p ≥ 1) . In this paper, among other results, we clarify the structure of Lp (G, τ ) and characterize amenability of L1 (G, τ ) and identify its multipliers.

Analysis of time series data can involve the inversion of large covariance matrices. For the class of ARMA (p, q) processes there are no exact explicit expressions for these inverses, except for The MA (1) process. In practice, the sample covariance matrix can be very large and inversion can be computationally time consuming and so approximate explicit expressions for the inverse are desirable. This paper offers some of these approximations.