Transmission distance of in-line amplifier systems withgroup-velocity-dispersion compensation

Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD     

Pyrolysis of tertiarybutylphosphine at low pressure

The pyrolysis of tertiarybutylphosphine (TBP) has been studied in the low pressure conditions used for chemical beam epitaxy (CBE). The pyrolysis studies were carried out in low pressure reactors of two different configurations, one of which is a cracker cell designed for use in a CBE system. The reaction products were studied using a quadrupole mass spectrometer. The products observed are accounted for by a reaction mechanism involving homolysis of the parent TBP molecule to produce PH₂ and C₄H₉ radicals. These undergo subsequent reactions to form the stable products C₄H₈, PH₃ and H₂, with smaller amounts of P and P₂ being produced. The production of the sub-hydride PH₂ using this cracker cell design indicates that the use of partially cracked TBP may be a promising technique for reducing the amount of carbon incorporated into the growing epitaxial layer.     

Sensitivity of torsional stress predictions of diesel generatorsets to critical parameter values

In the present paper a new method is presented for the evaluation of torsional stressing of diesel-generator sets consisting of components with uncertain torsional characteristics. A frequency scanning technique is implemented for eigenvalue analysis of the elastic system. Due to the uncertainty of the values of stiffness and damping coefficients, a sensitivity analysis method is also presented, suitable for the evaluation of the range of the mechanical stresses. Special consideration is given to the correct simulation of the coupling to the electric network, including the influence of generator regulators and possible network interactions. An exact formula is extracted for the synchronizing and damping torque coefficients. The method presented was checked in a diesel power station of the autonomous electric system of a Greek island     

On the broad band transmittance of direct irradiance in a cloudless sky and its application to the parameterization of atmospheric turbidity

The total atmospheric attenuation of direct irradiance is often expressed as the product of independent broad band transmittances pertaining to the different depleting materials in the atmosphere. In theory, it is clear however that the broad band transmittances of the two most important attenuating factors, aerosols and water vapour, cannot be considered independent of each other. This is most relevant when trying to isolate the effect of atmospheric aerosols from the measurement of broad band direct irradiance. These questions are addressed in an analytical approach. Several broad band direct transmittance equations and corresponding turbidity parameters are discussed with respect to the analytical results. Simulations made with the SMARTS2 spectral radiative transfer code are used to illustrate the broad band effects.     

A capacitor-based device for the measurement of shaft torque

This paper describes a capacitor technique for the measurement of torque in a rotating shaft. The passive rotating part incorporates a capacitor bridge which is connected capacitively to the static part. This device is simple in operation and is relatively easy to manufacture     

Effective scattering area of a three-faced corner cube reflector

Ray representations are used to refine a model for the equivalent aperture of a three-faced corner-cube reflector in which the faces are not perpendicular. This is used in calculating the actual value of the effective scattering area for such a reflector, which gives a correction factor to exclude the error component due to the nonperpendicularity. A table is given of calculated values for the correction factor together with experimental results. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 45–48, October, 1996.     

Optimization of a Reconstitutable Suspension of Rifampicin Using 24 Factorial Design

In this study 2⁴ factorial design associated with surface response methodology was used to develop and optimize a reconstitutable suspension of rifampicin. The study illustrated the effect of the percentage of each of sucrose, avicel RC-591, hydrophilic aerosil, and aerosol-OT on the flowability and the bulk density of the dry mixture as well as the viscosity, the sedimentation volume, and the redispersibility of the suspension. An empirical equation developed for each of the above responses was used with the aid of computer software to plot a contour map of the most significant effects and interactions. Five replicates at the center of the design were used to independently calculate the experimental error and to detect any curvature in the response surface. Three formulas which are not included in the design were prepared to check the validity of the model equation.     

Clinical applications compared in implantology

On the basis of their own experience and of orientation reported by literature, the authors display how important it is for professional men who practise implantology or who approach it, to have the possibility of knowing several implantologic systems. Indeed, what we want to demonstrate is, that in different situations of edentulous, in relation to the quantity and the quality of the available bones, to the gnotologic situation and to the aesthetic functional result they aim to, corresponds the choice of one or several implantologic systems. In that sense the basic research occupies a role of vital importance, because only through the knowledge of chemical, chemical-physical and biomechanical characteristics it is possible to recognize some essential chemical entities for an implantologic approach. Thus the several diagnostic instrumental means available enable the surgeon to make an exact clinical diagnosis. The TAC, in this case, assumes a determinant role, because, in addition to supplying exact dimensional and qualitative informations, also occupies an important medico-legal aspect. The resolution of some forms of edentulous programmed like that, will subsequently be illustrated. Finally, a control hypothesis is proposed for the rearrangement, of peri-implant bone. On this account, the SPECT (single photon emission computerized tomography), through a semi-quantitative research, could provide some specific indications about the osteotropic implantation activity.