An investigation on planar dielectric light collectors for illumination and solar energy applications

In this paper the performances of inhomogeneous dielectric slabs as solar light collectors for both illumination and solar energy applications are analysed.     

Three terminals optoelectronics devices integrated into a silicon on silicon waveguide

In this paper we describe two different kind of optoelectronic devices both based on a three terminals active device and exploit the plasma dispersion effect to achieve the desired working. The first device exploits this effect in order to obtain an optical modulation. The second device is an optoelectronic router based on the mode-mixing principle together with the injection-induced optical phase shift. Both devices are integrated into a Silicon on Silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III–V Optoelectronics. The active three terminal device used is a Bipolar Mode Field Effect Transistor (BMFET). Numerical simulation results are presented on both devices.     

Cladding mode reorganization in high-refractive-index-coated long-period gratings: effects on the refractive-index sensitivity

We theoretically and experimentally investigated the reorganization of cladding modes in high-refractive-index- (HRI-) coated long-period gratings (LPGs), focusing on the influence of refractive-index sensitivity. When azimuthally symmetric nanoscale HRI coatings are deposited along LPG devices, a significant modification of the distribution of cladding modes occurs, depending on the layers' features (refractive index and thickness) and on the external refractive index. In particular, if these parameters are properly chosen, a transition between cladding modes and overlay modes occurs. Numerical and experimental effects of the mode transition on the sensitivity of the surrounding refractive index are described.     

On a new general theory of earthquakes

Summary Some phenomena have been observed a very brief time before an intense earthquake: variations of the terrestrial magnetic and electric fields, rumble and also often animal nervousness. In order to give a sole explanation of all these phenomena, a general theory of the earthquake has been built, based on separation of the electric charges when the internal terrestrial masses are subject to strong compressive stress for piezoelectric effect. If the separation of the electric charges takes place on very large masses, intense electric fields are produced so to generate strong electric potential differences. If these differences are higher that the dielectric rigidity of the materials, a strong disruptive discharge can occur between the terrestrial masses. The destruction of some masses allows other masses to move generating intense seismic waves. The discharge produces the rumble and electromagnetic waves with frequencies depending on the dimensions on the focus. The tables show that the calculated frequencies (ultra-audible vibrations) are 35, 23, 17, 14, 12 kHz. (This abstract was published on Bulletin of S.I.F. on 10 September 1982, N. 127).     

Locally Finite Groups All of Whose Subgroups are Boundedly Finite over Their Cores

For n a positive integer, a group G is called core-n if H/H_Ghas order at most n for every subgroup H of G (where H_G is thenormal core of H, the largest normal subgroup of G containedin H). It is proved that a locally finite core-n group G hasan abelian subgroup whose index in G is bounded in terms ofn. 1991 Mathematics Subject Classification 20D15, 20D60, 20F30.     

Processing of product forms for the large-scale manufacturing of advanced thermoplastic composites

In the field of large-volume applications today, injection-moldable polymers, reinforced with short or long fibers, are used for semi-structural components. Additional use is made of glass mat thermoplastic sheets, for which the processing technologies have already been established in a large number of applications. Advanced thermoplastic composites based on highly aligned, continuous fibers represent, with their high fiber content, a big step in terms of mechanical performance and offer thermoplastic polymers the chance to become structural components. In spite of a great deal of work carried out in this category of materials, in particular with carbon fiber-based products for defense and aerospace applications, the business is still at an early stage of development due to the high price of intermediate products (small plants and not fully optimized production processes) and to embrionic manufacturing technologies for mess production applications. Conversion of the various continuous fiber reinforced thermoplastic materials into useful parts and components is dependent on the intermediate product forms: boardy tape, flexible two, fabric or sheet. Some general technologies exist for the thermoplastic composites and their subsequent processing methods; however, in many cases because of the peculiarity of these products (i.e. fabric deformation under stamping) they require different approaches. The scope of this work is to describe those methods that are most promising for large-volume applications, in particular products forms (containing powder) for post-shaping impregnation, and to analyze some of the fundamental mechanisms of flow and deformation that drive the processing behavior.     

Optical characterization of the recombination process in silicon wafers, epilayers and devices

In this paper we present various approaches to the measurement of recombinative parameters in silicon wafers, epitaxial layers and solar cells. In particular our techniques are able to measure the bulk lifetime and the surface recombination velocity at low injection levels. We also show that the techniques presented are a reliable tool to monitor the fabrication process of a standard crystalline silicon solar cell. In all the methodologies presented there are no stringent requirements concerning the state of wafer surface.     

The basic principles of intracavity photothermal spectroscopy

The basic theory of intracavity photothermal deflection is analysed. Its main applications to linear spectroscopy and high power laser beam modulation are briefly discussed.     

Groups with a maximality condition for some non-normal subgroups

We describe (generalized) soluble-by-finite groups in which the set of non-normal subgroups which are not finitely generated satisfies the maximal condition.     

The cofinality of the least Berkeley cardinal and the extent of dependent choice

This paper is concerned with the possible values of the cofinality of the least Berkeley cardinal. Berkeley cardinals are very large cardinal axioms incompatible with the Axiom of Choice, and the interest in the cofinality of the least Berkeley arises from a result in [1], showing it is connected with the failure of . In fact, by a theorem of Bagaria, Koellner and Woodin, if γ is the cofinality of the least Berkeley cardinal then γ‐ fails. We shall prove that this result is optimal for or . In particular, it will follow that the cofinality of the least Berkeley is independent of .