Multigigabit/s demultiplexing in optical domain using coherence properties of pulse trains from multiple, asynchronous mode-locked lasers

It is shown that the unique coherence properties of mode-locked lasers can be exploited to provide new opportunities for high-speed data transmission. Using passive Mach-Zehnder optical delay stages, very high bit rate optical data streams constructed from asynchronously combined transmitters can be demultiplexed directly in the optical domain, without imposing restrictions on the source wavelength. Potential implementation and performance of the technique are discussed.<>     

Crystallinity and lateral crystallite size of different UHMW PE materials

Nascent high-molecular-weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70–75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molecular weight of the sample and the higher the activity of the used catalyser. A melting / recooling treatment results in a reduction of crystallinity by about 15–25% and disappearance of the triclinic phase. Further, an irreversible conversion of nascent orthorhombic extended chain crystallites to orthorhombic folded chain crystallites of increased lateral dimensions and crystalline perfections takes place during the melting / recooling treatment. The results are compared to those obtained for lower-molecular-weight PE samples and for high-strength / modulus PE fibers of different origins.     

RESERVOIR POTENTIAL OF CRETACEOUS PLATFORM-MARGIN BRECCIAS, CENTRAL ITALIAN APENNINES

In this paper, we report on the characteristics of sedimentary breccias derived from, and deposited adjacent to, the Cretaceous Maiella carbonate platform in central Italy. Previous work has interpreted the northern platform margin to have been inherited from Early Jurassic rifting, and to have remained tectonically passive throughout the Cretaceous. However, our field studies show that the platform margin was segmented by north‐south oriented normal faults in the Late Cretaceous. Thick breccias composed of lithoclastic rudstones and floatstones were derived from the collapse of the shelf margin, and were deposited as rock avalanche and debris flow deposits in hangingwall depocentres. Four breccia units (thicknesses up to 250m, 130m, 60m and 20m) were mapped and studied in detail. Clasts consist of shallow‐water bioclastic limestones; textures vary within each breccia unit from rudstones in the bottom two‐thirds to floatstones above. Vuggy, late stage dissolution porosity is present throughout each unit, and probably developed in a meteoric environment after Pliocene thrusting and exhumation. Much earlier diagenesis, associated with a Late Cretaceous shallow‐marine to meteoric environment, generated the mouldic and intergranular porosity observed in the rudstones. The skeletal floatstones display biomouldic porosity which has likewise been preserved since the Late Cretaceous. Bulk porosity volumes have been estimated for three of the breccias at the time of expected hydrocarbon charge (Miocene‐Pliocene): they range between 72 × 10⁶ and 42 × 10⁶ m³. Oil seepage from these breccias can be observed at the present day in outcrops near to the study area, indicating that migration and charge are still active. The significance of the breccias as potential reservoirs is that high‐porosity platform margin facies clasts were transported into a depositional environment which would otherwise have been occupied by low‐porosity slope facies. This extends the platform margin reservoir fairway beyond the defined platform edge.     

A machine vision system for high speed object tracking using a moments algorithm

A system has been developed for tracking the motion of objects in two dimensions in real-time. The system consists of a conventional CCD camera linked to a transputer-based frame grabber and an array of nine transputers. A parallel moments algorithm is used to extract the co-ordinates of the object's centre of gravity and orientation at field rate, i.e. 60 Hz. Since the position data are made available in real-time—with a small time delay—the system has the potential for inclusion in a feedback loop. Results are presented for tracking the trajectory of a chocolate bar diverted by an air jet. The potential of the system for higher sampling rates—up to 200 Hz—is discussed.     

Current distribution, resistance, and inductance forsuperconducting strip transmission lines

A method for the calculation of the current distribution, resistance, and inductance matrices for a system of coupled superconducting transmission lines having finite rectangular cross-section is presented. These calculations allow accurate characterization of both high-T_c and low-T _c superconducting strip transmission lines. For a single stripline geometry with finite ground planes, the current distribution, resistance, inductance, and kinetic inductance are calculated as functions of the penetration depth for various film thicknesses. These calculations are then used to determine the penetration depth for Nb, NbN, and YBa₂Cu₃O_7-x superconducting thin films from the measured temperature dependence of the resonant frequency of a stripline resonator. The calculations are also used to convert measured temperature dependence of the quality factor to the intrinsic surface resistance as a function of temperature for an Nb stripline resonator     

Comparison of scene segmentations: SMAP, ECHO, and maximumlikelihood

Sequential maximum a posteriori (SMAP) and the extraction and classification of homogeneous objects (ECHO), two spectral/spatial scene segmentation algorithms, were compared with traditional maximum likelihood (ML) estimation in a supervised classification of multispectral data. SMAP generalized better than both ECHO and ML. Significant differences were found in all mean class classification accuracies: SMAP>ECHO>ML     

A menu-driven environment for automated urban and regional analysis: a GIS application for educational purposes

Geographical information systems (GIS) constitute an important development offering wide application potential in geography, urban and regional planning and associated disciplines. Current debates entail two kinds of criticism; the first involves GIS themselves and the fact that they are often cumbersome and difficult to use; the second involves the ‘poverty‘ of some GIS applications. The result is a worldwide endeavour to produce answers to both questions. The main objective of the system proposed here, known as URAP (urban and regional analysis for planning), is to make a contribution to these goals, by upgrading conventional GIS capabilities, while simplifying the means by which results from advanced statistical analysis are obtained and subsequently plotted. It entails a menu-driven environment and involves the dynamic formation of customised databases to meet the geographical, methodological and other choices made by the user. While the arguments in the paper involve an emphasis on education, the system is also suitable for supporting public policy making.     

Charge comparison protection of transmission lines-relayingconcepts

The authors describe the relaying concepts of charge comparison. Charge comparison is a new transmission line protection system. It is a form of current differential relaying. Charge comparison largely resolves the traditional problems of current differential relaying of transmission lines, which are that protection is lost if a channel fails, a large channel capacity is required, and precise channel delay compensation is required. This technique is suitable for the protection of two- or three-terminal AC transmission lines, of all lengths and voltage levels, with or without series of shunt compensation, with three-hole or single-pole tripping