Fourier-transform-limited pulses from gain-switched distributed-Bragg-reflector lasers using simultaneous modulation of gain and phase sections

Fourier-transform-limited pulses ( Delta tau . Delta nu approximately=0.35) have been obtained from a microwave-modulated DBR laser at 1.56 mu m. The chirp of the gain-switched pulse is compensated for by applying a fraction of the microwave signal to the phase section, thereby creating an instantaneous frequency shift of opposite sign. The generation of short coherent pulses from such a monolithic source can be of great interest for long haul soliton transmission.<>     

New wire interface for graded 3-D TLM

A new 3-D graded TLM model for thin radiating wires is presented. The model differs from previous TLM models because the wire is modelled at the interfaces between cells, rather than through the centre of the node. The connection between the TLM symmetrical condensed-node link lines and the line forms a 'wire interface'. The scattering algorithm for the interface and simulation results are given.<>     

Über die Eignung der Wechselbiegemaschine „WEBI”︁ zur Ermittlung von Ermüdungskennwerten

On Alternating Bending Machine WEBI's Suitability for Determination of Fatigue Characteristics Already in 1966, experimental investigations revealed that the flat bending torsion testing machine ?FLATO”? (Schenck, Darmstadt) doesn't keep constant its torsional moment amplitude in case of specimen's fatigue softening or hardening, respectively. Thus. conclusions concerning the material's fatigue characteristics drawn from such experimental results might therefore be seriously false. Furthermore, also the alternating bending testing machine ?WEBI”? (Schenck, Darmstadt) shows an equivalent behaviour concerning its bending moment amplitude. For this reason. the main findings of a comprehensive experimental study carried out on WEBI with an unalloyed steel C 45 (0.45 mass perccnl C) in different heat treatment conditions are reported in this paper.     

A novel technique for fabrication of metallic structures on polyimide by selective electroless copper plating using ion implantation

The successful use of palladium ion implantation into polyimide to seed an electroless plated film of copper on the polyimide surface is reported. Polyimide (Hitachi PIX 3400) was implanted with palladium ions to doses of 1.5 × 10¹⁵ − 1.2 × 10¹⁷ ions cm⁻² using a MEVVA ion implanter. The implanted ions acted as sites for nucleation of copper film. A copper film was then deposited on implanted polyimide using a commercial electroless plating solution. The ion energy was kept low enough to facilitate a low critical ‘seed’ threshold dose that was measured to be 3.6× 10¹⁶ Pd ions cm⁻². Test patterns were made using polyimide to study the adaptability of this technique to form thick structures. Plated films were studied with optical microscopy, Rutherford Backscattering Spectrometry (RBS) and Profilometry. The adhesion of films was qualitatively assessed by a ‘scotch tape test’. The film growth (thickness) was observed to be linear with plating time. A higher implantation dose led to greater plating rates. The adhesion was found to improve with increasing dose.     

Manufacture of a high-quality alkylsalicylate additive at the Novokuibyshevsk Petroleum Refinery

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 16–17, April, 1992.     

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.