Novel,Printable Energetic Polymers

Novel, simple‐to‐make energetic mono‐ and bisvinylimidazolium perchlorate monomers are prepared and characterized. These energetic monomers offer the possibility to 3D print energetic polymers that may allow decreasing the content of the energetic filler in energetic devices without compromising their energetic properties. The new printable materials are suited for photocuring‐based additive manufacturing (AM), techniques, offering not only a large degree of control over the mechanical and energetic properties of the resulting solids, but also the production of complex geometries at high resolution.     

Harnessing “Click”‐Type Chemistry for the Preparation of Novel Electronic Materials

Sequence‐independent or “click”‐type chemistry is applied for the preparation of novel π‐conjugated oligomers. A variety of bi‐functional monomers for Wittig–Horner olefination are developed and applied in a sequential protection–deprotection process for the preparation of structurally similar π‐conjugated oligomers. Selected oligomers are incorporated as the organic semiconductors in light‐emitting diodes and a field‐effect transistor, demonstrating the potential of the approach.     

FM microwave multiplexed broad-band distribution systems using Er3+ fiber amplifiers and preamplifiers

The use of an Er³⁺ fiber preamplifier for microwave multiplexed systems and the use of an inline Er³⁺ amplifier in microwave multiplexed systems for signal distribution are reported. The improvement in receiver sensitivity as a preamplifier, without optical filtering, was 9 dB. No power penalty due to amplified spontaneous emission was found when the amplifier was used in a 30-channel signal distribution system     

Microwave-multiplexed wideband lightwave systems using opticalamplifiers for subscriber distribution

A lightwave systems analysis shows that microwave-multiplexed wideband services can be distributed to large numbers of subscribers by using optically amplified multiple-star lightwave distribution networks. Through the use of well developed, readily available microwave electronics, this technique enables lightwave systems to take advantage of the large available bandwidth of single-mode fibres, GaInAsP lasers and GaInAs photodetectors     

Semiconductor laser lineshape and parameter determination from fringe visibility measurements

The field autocorrelation function of single-mode 1.3 ?m InGaAsP lasers has been measured using a Michelson interferometer. Comparison with theory for semiconductor laser line broadening yields the relaxation oscillation frequency, its damping rate and the linewidth broadening factor. A comparison with other techniques for lineshape measurement is presented.     

Thickening kinetics of proeutectoid ferrite plates in Fe-C alloys

Thermionic electron emission microscopy was used to measure directly the thickening kinetics of proeutectoid ferrite sideplates in Fe-C alloys. These kinetics were found to be exceedingly irregular. During the first few seconds of growth, the thickening rate is 5 xl0^-5±1 cm/s; afterwards it usually diminishes to 1 - 30 × 10^-6 cm/s. As predicted by a general theory of precipitate morphology, thickening was shown to occur only by the ledge mechanism, despite the relatively poor matching of the austenite and the ferrite lattices. Ledges were observed to lengthen at rates controlled by the diffusion of carbon in austenite. Tent-shaped and other more complex surface relief effects, rather than the invariant plane strain relief, were found to predominate. These features are shown to be the expected result of a diffusional transformation occurring by means of a ledge mechanism. Formerly with the Scientific Research Staff Formerly with the Scientific Research Staff, Ford Motor Company     

Intrinsic lineshape and FM response of modulated semiconductor lasers

A new method for measuring the FM response and the intrinsic linewidth of modulated semiconductor lasers is reported. No additional stochastic line broadening has been observed for direct modulation of buried-heterostructure 1.3 ?m lasers with modulation depths of less than 20%. Thus FSK systems employing heterodyne detection are expected not to exhibit any additional phase noise penalty due to direct current modulation.     

Selective regrowth of a wide-bandwidth 1.3 μm integratedlossless tap and optical preamplifier

The authors report the first monolithically integrated wide-bandwidth lossless tap-that is, an optical semiconductor amplifier followed by a colinear reverse-biased waveguiding photodetector with fiber-coupled input and output. The integration was achieved by using off-axis selective epitaxial growth of ridge waveguides on a patterned dielectric layer. The tilted facets produced by the off-axis growth, along with photodetector absorption, serve to reduce the effective facet reflectivity to -36 dB without any antireflection coating. By adjusting the length of the absorbing photodetector section, part or all of the amplified light may be absorbed, allowing the device to function respectively as a lossless tap or an optical preamplifier. A lossless tap with an electrical bandwidth of 7 GHz, a responsivity of 26 A/W, and a fiber-to-fiber gain of 3 dB is shown to have a receiver sensitivity of -22 dB at 3 Gb/s     

The kinetics and mechanism of the thickening of κ plates in a Cu-Si alloy

Hot stage, polarized light microscopy studies have shown that hcp κ plates, formed in a fcc α Cu-Si matrix, thicken discontinuously. Abrupt, micron-sized increases in thickness take place during the initial minutes of transformation and occasionally thereafter. At all other times, the rate of thickening is, at most, exceedingly small. There are very few misfit dislocations at the broad face of κ plates. The combination of these experimental results and the very small free energy change attending κ precipitation rule out both conventional heterogeneous nucleation and most diffusional growth processes as significant contributors to the development of κ plates. The principal mechanism of this transformation appears to be the formation of bundles of stacking faults, evidently in response to cooling stresses. The fault bundles are then enriched to the composition of the κ phase by the inward diffusion of silicon.     

Energy use and conservation in the residential sector Methodological questions and policy prescriptions

Whatever future energy path is chosen in the USA, it will be critical to know energy supply and demand patterns at the micro (family) level. This article examines public surveys which gather information at this level and then suggests possibilities for further research.