Novel structure of a Photonic Crystal Fiber (PCF) is proposed for flattened dispersion characteristics. As compared with the conventional PCFs, the proposed PCF has no air holes in second ring area. Then the proposed PCF has a concentric missing ring PCF. Here silica glass is used as core material. It has been demonstrated that when we change the layer of PCF, dispersion is also changed. The ch...

a model for missing data in mixed binary and continuous responses, which can be used on cross-sectional data, is presented. in this model response indicator for the binary response can be dependent on the continuous response. a closed form for the likelihood is found. for data with a complicated pattern of missing responses some new residuals are also proposed. the model of multiplicative heter...

Meteorological stations usually contain some missing data for different reasons.There are several traditional methods for completing data, among them bivariate and multivariate linear and non-linear correlation analysis, double mass curve, ratio and difference methods, moving average and probability density functions are commonly used. In this paper a blended model comprising the bivariate expo...

a module m is called epi-retractable if every submodule of m is a homomorphic image of m. dually, a module m is called co-epi-retractable if it contains a copy of each of its factor modules. in special case, a ring r is called co-pli (resp. co-pri) if rr (resp. rr) is co-epi-retractable. it is proved that if r is a left principal right duo ring, then every left ideal of r is an epi-retractable ...

The most common congenital and developmental anomaly in teeth is the missing of one or more of them. Congenitally missing teeth (CMT) or teeth agenesis mentions failure of tooth formation due to disturbances during the early stages of tooth germ development. There are several definitive treatment options for these patients including fixed, removable or implant-supported prostheses. Economic lim...

the zero-divisor graph of a commutative ring r with respect to nilpotent elements is a simple undirected graph $gamma_n^*(r)$ with vertex set z_n(r)*, and two vertices x and y are adjacent if and only if xy is nilpotent and xy is nonzero, where z_n(r)={x in r: xy is nilpotent, for some y in r^*}. in this paper, we investigate the basic properties of $gamma_n^*(r)$. we discuss when it will be eu...

let r be an associative ring with unity. an element a in r is said to be r-clean if a = e+r, where e is an idempotent and r is a regular (von neumann) element in r. if every element of r is r-clean, then r is called an r-clean ring. in this paper, we prove that the concepts of clean ring and r-clean ring are equivalent for abelian rings. further we prove that if 0 and 1 are the only idempotents...

let r be an associative ring with unity. an element a in r is said to be r-clean if a = e+r, where e is an idempotent and r is a regular (von neumann) element in r. if every element of r is r-clean, then r is called an r-clean ring. in this paper, we prove that the concepts of clean ring and r-clean ring are equivalent for abelian rings. further we prove that if 0 and 1 are the only idempotents...

Missing values occur in studies of various disciplines such as social sciences, medicine, and economics. The missing mechanism in these studies should be investigated more carefully. In this article, some models, proposed in the literature on longitudinal data with dropout are reviewed and compared. In an applied example it is shown that the selection model of Hausman and Wise (1979, Econometri...