Parametric Wavelength Conversion From Conventional Near-Infrared to Visible Band

The feasibility of distant wavelength conversion in photonic crystal fiber was explored. The one-pump parametric architecture was used to demonstrate translation from the conventional (1550 nm) to visible (500 nm) band. Experimental results are reported, which demonstrate the conventional-to-visible conversion of single- and multiple-channel signals encoded in the nonreturn-to-zero format     

Solving multiple objective quasi-convex goal programming problems by linear programming

This study presents a novel means of resolving multiple objective goal programming (GP) problems with quasi-convex linear penalty functions. The proposed method initially expresses a quasi-convex function by the maximum operator of two convex functions, then solves it via a linear programming technique. The proposed method does not contain any zero–one variables; nor does it require dividing the multi-objective quasi-convex GP problem into large sub-problems as in conventional methods. Some illustrative examples are provided.     

Tunable Parametric All-Fiber Short-Wavelength IR Transmitter

In this paper, the performance of an all-fiber short-wave IR (SWIR) transmitter with wideband tunability and high peak power is reported. Transmitter construction relied on parametric process in highly nonlinear fiber to convert a seed laser at 1260 nm to 2155 nm SWIR channel with record 39 dB efficiency and translation over 900 nm spectral range. We demonstrated 61 W of peak converted power at 2 $mu$m and 26 W at 2.15 $mu$ m. Efficient conversion was made possible by engineered fourth-order dispersion of the highly nonlinear fiber and construction of a low-noise pump source in a 1550 nm band.      

Fracture of laminates combining 2024-T3 and 7075-T6 aluminum alloys

Crack growth resistance curves have been determined for crack-divider laminates in which layers of 2024-T3 aluminum alloy are adhesively bonded to layers of 7075-T6 alloy. Results are compared with the fracture resistance of laminates consisting wholly of each material, the layer thickness being the same (1.54 mm) in all cases. The initial portions of the resistance curves are similar for both alloys; however those for 2024-T3 have steeper slopes at longer effective crack lengths. As a result, laminates consisting entirely of 2024-T3 alloy exhibit greater amounts of stable crack extension and higher toughnesses at instability. This is attributed in part to the greater strain hardening rate in 2024-T3 material. Laminates combining 2024-T3 and 7075-T6 layers are intermediate between those consisting entirely of one or the other alloy.     

Multicast Parametric Synchronous Sampling of 320-Gb/s Return-to-Zero Signal

Technology for simultaneous demultiplexing of subrate tributaries is described and applied to 320-Gb/s return-to-zero input. The parametric architecture is scalable with respect to processed input rate and relies on cascaded all-optical multicasting and subrate sampling. Processing of 320-Gb/s input was achieved by creating eight channel copies, followed by a 20-THz-wide parametric gate. Multicasting was based on a self-seeded two-pump broadband fiber-optic parametric amplifier. The architecture was used to demonstrate error-free parallel demultiplexing of eight 320-Gb/s tributary channels at 40 Gb/s.     

GAS-HYDRATE SYSTEMS AND GAS VOLUMETRIC ASSESSMENT IN THE LOWER FANGLIAO BASIN,TAIWAN ACCRETIONARY WEDGE

The accretionary wedge in the incipient arc-continent collisional zone offshore southwestern Taiwan is rich in gas hydrates as inferred from reflection seismic data and the geochemical analyses of shallow sediments. In this study, 2D and 3D seismic data were used to investigate the role of structural factors including mud diapirism on the formation of gas hydrates and associated free gas in the Quaternary Lower Fangliao Basin, a semi-enclosed slope basin situated on the upper accretionary wedge. Albeit limited drilling information on lithostratigraphy and petroleum potential in the area together with seismic reflection data show that mud diapirs have influenced the formation of bottom-simulating reflectors (BSRs) and the distribution of gas hydrates and free gas. On reflection seismic profiles, five seismic facies were observed and are characterised by: stratified parallel reflections; contorted reflections; semi-parallel, high-amplitude reflections; oblique, continuous high-amplitude reflections; and generally transparent reflections. These seismic facies were respectively interpreted as hemipelagic sediments, mass transport deposits (MTDs), sandstone-rich turbidites, overbank deposits and mud diapirs. The gas hydrate stability zone (GHSZ) is characterized by (i) high amplitude reflections with an analogous phase to that of seafloor, possibly indicating potential porous sandstone-rich turbidite reservoirs; (ii) BSRs showing polarity reversal relative to seafloor, suggesting higher impedance gas hydrates overlying lower impedance intervals with free gas; (iii) blanking reflections in fault zones, interpreted as gas-bearing fluid conduits; (iv) strong reflections on the flanks of mud diapirs (e.g. flank drags) and above buried mud diapirs, demonstrating the presence of gas hydrates; (v) high amplitude reflections dragging on diapiric flanks with reversed phase to that of seafloor, indicating free gas -charged zones abutting mud diapirs; and (vi) the presence of focused advection and diffusion flow through mud diapirs and faults, which is interpreted to control the migration of thermogenic gas. Based on the distribution of seismic amplitude characteristics and reflection strength with respect to depth of the BSRs, hydrocarbon prospects can be divided into gas-hydrate compartments above BSRs, free gas compartments above BSRs, and free gas compartments below BSRs. From a combination of geobody extraction and Monte Carlo simulation, the prospects appear to hold about 2048 Bcf (billion cubic feet) of total gas volume over a study area of 60 km². These observations provide first-order estimates of methane resources in the Lower Fangliao Basin offshore southwestern Taiwan.     

Effect of initial microstructure on high velocity and hypervelocity impact cratering and crater-related microstructures in thick copper targets: Part II Stainless steel projectiles

Three different, thick copper targets (an as-received, 98 m grain size containing 1010 dislocations/cm2 (Vickers hardness of 0.89 GPa); an annealed, 124 m grain size containing 109 dislocations/cm2 (Vicker's hardness of 0.69 GPa); and a 763 m grain size containing 109 dislocations/cm2 (Vickers hardness of 0.67 GPa) were impacted with 3.18 mm diameter ferritic stainless steel projectiles at nominal velocities of 0.7, 2 and 5 km s-1. Like companion experiments utilizing soda-lime glass projectiles (Part I), absolute grain size of the target was observed to be less important than the dislocation density in the cratering process. At low impact velocity, depth/diameter ratios were observed to increase dramatically in contrast to less dense soda-lime glass impactors, and the impactor behaviours were also very different. The ferritic stainless steel impactors spalled into small fragments at or above 2 km s-1 impact velocity and a significant fraction of these fragments remained in the craters. No significant melt phenomena were observed either in connection with projectile fragmentation or in the crater-related, residual microstructures. Dynamic recrystallization, dislocation cell structures and microbands were significant microstructural features in the targets. They extended from the crater walls and contributed to hardness profiles within the cratered targets. These hardness profiles and actual hardness zones generally increased in extent from the crater wall with both impact velocity and projectile density.     

Formation of fretting fatigue cracks in 7075-T7351 aluminum alloy

Fretted regions in 7075-T7351 aluminum alloy test specimens subjected to cyclic fatigue loading have been examined by scanning electron microscopy. Fatigue cracks generally formed at or near the boundaries of the fretted regions, often in patches of surface markings having a ripple or chevron-like appearance.     

Two-Pump Parametric Optical Delays

Continuously tunable optical delay lines based on parametric process in optical fibers are described theoretically and demonstrated experimentally. Performance limits are outlined and compared to alternative approaches capable of continually adjustable delay management. The current record of 105 ns tunable optical delay at 10 Gb/s is presented, with a delay-bandwidth product of 1055.