Servers in SCADA applications

Data acquisition and supervisory control and data acquisition (SCADA) systems have evolved from mainframe-based systems to multilevel tiered systems to flat client-server architecture. This paper examines the necessity for this evolution and the technology that spurred it on. A rod mill is discussed as a case study     

Studien über den TBS-Test I: Seine Temperatur-Abhängigkeit und Anwendung auf Vakuum-destillierte Fettoxydationsprodukte

Studies on TBA-Test I: Its Relationship to Temperature and Application to Oxidation Products of Fats Obtained by Vacuum Distillation Few conditions involved in the procedure for carrying out TBA-test were investigated in order to determine its scope and limitations. Regarding the development of colour for measurement at 530 nm, it was found, that heating at 95° C should be preferred to that at a lower temperature in order to avoid the interference due to extinction at 450 nm. As regards the isolation of oxidation products, it was observed, that TBA reactive condensates whose extinctions at 530 nm agree well with the course of oxidation, can be obtained by vacuum distillation for 30 min.     

Radiation loss coefficients of asymmetric dielectric waveguides with shallow sinusoidal corrugations

Kiselev [10] has solved the boundary equations for an asymmetric slab waveguide with a shallow sinusoidal corrugation, and derived explicit, closed expressions for the TE radiation loss coefficients of various waveguide geometries. For many practical applications in integrated optics, the Rayleigh assumption justifying the boundary-matching procedure and the approximations of linear perturbation analysis employed in this derivation are both satisfied. We have extended this procedure to TM modes and found that the expressions for both TE and TM modes in all of the geometries so treated agree identically with those derived by coupled-mode theory. The dependence of the TM radiation loss coefficient in each waveguide geometry on the grating period, radiation angle, refractive index profile, and mode polarization is illustrated graphically, and compared with its TE counterpart.     

The effect of the ▿n2term on the modes of an optical square-law medium

Solutions of the mode problem of an optical waveguide with a square-law medium are usually based on the scalar wave equation. An exact derivation of the wave equation from Maxwell's equations results in an additional term containing the gradientnablan^{2}of the square of the refractive indexn. It is the purpose of this correspondence to evaluate the change of the propagation constants of the modes of the square-law medium that is caused by thenablan^{2}term. We find that the change is significant only for TM modes of low order, but insignificant for all other modes of a dielectric slab with parabolic index distribution.     

Directional couplers made of nonidentical asymmetric slabs. Part I: Synchronous couplers

We discuss TE and TM mode directional couplers made of nonidentical asymmetric slab waveguides. Approximate expressions are provided for the coupling coefficients of synchronous (no grating) couplers and their accuracy is checked by comparison with exact solutions that are based on solving the guided mode problem of the total structure consisting of the two slabs considered to be a single waveguide.     

Heterodyne detection with an injection laser I. principle ofoperation and conversion efficiency

If a light signal is passed into the resonant cavity of an actively oscillating injection laser, an electrical signal at the difference between the laser and light signal frequencies flows through the wire supplying the DC bias to the laser. A small-signal analysis of heterodyne detection with such a laser oscillator that is based solely on rate equations and introduces the externally applied signal as a source term into the photon rate equation is discussed. Since neither Maxwell's equations nor the wave equation are involved, this analysis is deemed simpler and more transparent than that reported earlier. Gain saturation of the active medium of the laser, which is responsible for broadening of the relaxation resonance, is taken into account     

Heterodyne detection with an injection laser. II. Signal-to-noiseratio

For pt.I see ibid., vol.26, p.85-93 (1990). In part I a theory of the conversion efficiency of the self-heterodyne laser detector that was first described by R.F. Kazarinov and R.A. Suris (1974) was presented. In this device a light signal is passed into the resonant cavity of an actively oscillating injection laser, causing an electrical signal at the difference frequency between laser and signal to flow through the wire supplying the DC bias to the laser. An expression is derived for the signal-to-noise ratio of the self-heterodyne laser detector. The result shows that in the limit of ideal operation (complete population inversion and no internal losses) the signal-to-noise ratio of the self-heterodyne laser detector reaches one-half of the quantum noise limit     

Computer model of a superluminescent LED with lateral confinement

We present a computer simulation of a strip-geometry superluminescent light emitting diode (SLD). One end of the strip waveguide has a finite reflectivity while the reflectivity vanishes at the other end because it is assumed that the strip waveguide terminates in a high-loss region. The gain of the structure is computed from the drive current and several intrinsic device parameters; gain saturation is taken into account. We discuss the dependence of the light power coupled into a fiber from an InGaAsP SLD at 1.3 μm as a function of the driving current, the reflectivity of one end of the strip waveguide, its numerical aperture (NA), and its length and width. A considerable improvement in power coupling efficiency can be realized when the waveguide NA equals the fiber NA or, in the absence of lateral confinement, when the fiber NA is much larger than the half-width to length ratio (times the refractive index) of the strip waveguide. Previous analyses have ignored lateral waveguiding effects.