‎we call a ring $r$ right generalized semiperfect if every simple right $r$-module is an epimorphic image of a flat right $r$-module with small kernel‎, ‎that is‎, ‎every simple right $r$-module has a flat $b$-cover‎. ‎we give some properties of such rings along with examples‎. ‎we introduce flat strong covers as flat covers which are also flat $b$-covers and give characterizations of $a$-perfe...

This manual describes a procedure to align the cavity of our Ti:Sapphire ring laser and its injection with an Argon-Ion pump laser beam. The setup is shown in figure 1. An 8W Argon-Ion pump beam is adjusted in size and degree of divergence by a telescope consisting of a 62mm and an 88mm lens (L1 and L2). A periscope (mirrors P1 and P2) and a collimation lens C (f=175 mm) is used to inject the 5...

We report the study of infrared spectroscopy of intraband transitions in Ge/Si quantum dot superlattices. The superlattices, which were grown on (001) oriented Si substrates by a solid source molecular beam epitaxy system, are composed mainly of 20 or 30 periods of Ge dot layers and Si spacer films. The structural properties of them and of the uncapped Ge dots grown on the surfaces of some of t...

We report on the elastic contact between a spherical lens and a patterned substrate, composed of a hexagonal lattice of cylindrical pillars. The stress field and the size of the contact area are obtained by means of numerical methods: a superposition method of discrete pressure elements and an iterative bisection-like method. For small indentations, a transition from a Hertzian to a soft-flat-p...

In the standard flat cosmological constant (Λ) cold dark matter (CDM) cosmology, a model of two populations of lens halos for strong gravitational lensing can reproduce the results of the Jodrell-Bank VLA Astrometric Survey (JVAS) and the Cosmic Lens All-Sky Survey (CLASS) radio survey. In such a model, lensing probabilities are sensitive to three parameters: the concentration parameter c1, the...

We propose and demonstrate the concept of using a tuneable liquid crystal micro-lens (LCML) array to improve the image contrast of a pixelated thin film photo-transistor (TFPT) flat panel imager. Such a device can be used to image contents on paper-based media and display a magnified version on a flat panel display for elderly or visually impaired people. Practical aspects including device phys...

Nonlinear optical techniques (second-harmonic and sum-frequency generation) have been used to study the structure of organic molecules that are confined and compressed between a lens and a flat surface. The molecules studied include self-assembled monolayers of n-octadecyltriethoxysilane and Langmuir-Blodgett films of stearic acid, octadecylalcohol, octadecylamine, and a liquid-crystal molecule...

PURPOSE To determine the effect of the base curve radius (BCR) of therapeutic soft contact lens (T-lens) on epithelial healing after laser-assisted subepithelial keratectomy (LASEK). METHODS Ninety-two eyes in 47 patients with myopia were prospectively evaluated after LASEK. All the patients wore T-lenses with the BCR (R1) randomly chosen after LASEK. The T-lenses were removed after complete ...

Similar to their optic counterparts, acoustic components are anticipated to flexibly tailor the propagation of sound. However, the practical applications, e.g. for audible sound with large wavelengths, are frequently hampered by the issue of device thickness. Here we present an effective design of metasurface structures that can deflect the transmitted airborne sound in an anomalous way. This f...