Improved coupled-mode theory of anisotropic optical waveguides

A coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived. Numerical results comparing the exact calculations to those of the method of Hardy et al. (Opt. Lett., vol.11, 742-4, 1986) show that the same accuracy can be obtained not only for TE, but also for TM mode coupling in the case of anisotropic waveguides, and the improved coupled-mode theory is applicable to the situation when moderately strong coupling occurs under the condition where the edge-to-edge separation of two coupled guides D₂ is about 0.1 μm     

The fourth amendment and emerging communications technologies

The key US Supreme Court case that addresses the constitutionality of government surveillance is nearly four decades old. This overview considers how technological developments have strained the prevailing legal framework and highlights areas for reform.     

Constriction resistance at high signal frequencies

This paper describes the dependence of constriction resistance on signal frequency. This dependence was calculated for circular constrictions ranging in diameter from 10 to 100 /spl mu/m, and for frequencies ranging from dc to 1 GHz. The results indicate that the magnitude of constriction resistance does not deviate appreciably from values predicted by Holm's classical analytical expression, as long as the skin depth is large compared with the constriction radius. For skin depths that are much smaller than the constriction radius, constriction resistance decreases with increasing frequency to an apparent limiting value independent of the constriction radius. At high frequencies, constriction resistance constitutes only one of two components of the total connection resistance measured in practice. The second component of connection resistance is determined by details of the geometry and dimensions of the contact interface, and increases with signal frequency.     

A Proposed Receiver Structure for Optical Communication Systems that Employ Heterodyne Detection and a Semiconductor Laser as a Local Oscillator

Coherent heterodyne detection in optical communication is degraded by phase instabilities present when a semiconductor laser is used as a local oscillator. Postdetection processing that accounts for these instabilities is suggested, based on a diffusion-process model for oscillator instabilities and a maximum-likelihood sequence-estimator of information symbols modulating the received light.     

Fatty acid composition of phospholipids and neutral lipids during embryonic and early larval development in Atlantic herring (Clupea harengus,L.)

The fatty acid compositions of total polar and total neutral lipids of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Within 3 hr after fertilization the percentage of total PUFA in neutral lipid decreased from 33% to 20%, with a reciprocal increase in monoenes. Thereafter the percentage of PUFA in the neutral lipids increased progressively, attaining the original level in ripe eggs by the time of yolk sac absorption. During the larval stages the percentage of PUFA continued to increase in the neutral lipid, reaching almost 44% of the total by day 32 after fertilization, although it was reduced to 32% by day 36. The percentage of monoenes in the neutral lipid displayed a progressive decrease during the whole period of development from 3 hr after fertilization. Throughout all the developmental periods the fatty acid composition of total polar lipids remained essentially constant. The polar lipids of the yolk sac displayed virtually the same fatty acid composition as the larval bodies, but the neutral lipids of the yolk sac were low in PUFA compared to the larval bodies. The results are discussed with reference to changes in lipid class composition during development. The conservation of high levels of PUFA in lipids during embryogenesis and early larval development reflects the importance of these fatty acids during development.     

Induced chemiluminescence of oxidized fatty acids and oils

The injection of a strong organic base into milligram quantities of fats and oils dissolved in methylene chloride results in a burst of chemiluminescence whose peak intensity is a function of the previous thermal oxidation history and of the degree of unsaturation of the starting material. The flash of this induced chemiluminescence can be 10⁸ times higher than the steady-state “spontaneous” chemiluminescence. The kinetics of the induced chemiluminescence are first order in concentration and second order in time. The emission spectrum is broad and extends into the near infrared. A model based on dioxetane chemiluminescence is proposed to explain the observed kinetics.     

Shear deformation under impact conditions

The deformation behavior that results from falling weight impact testing with flat-headed darts is analyzed in terms of elasticity and plasticity. From a comparison of the time and temperature dependence of the yield stress that is observed during a falling weight test with the same dependences of the yield stress during simple shear tests, it is concluded that the use of flat-headed darts results in strong shear loading. Consequently most of the plastic deformation takes place by shear flow. Of practical interest is that this leads to a simple dependence of the yield stress during the impact test and the impact energy on the plate thickness. Furthermore, for a number of cases this result allows a direct conversion of temperature effects to time effects. In practice this means that it is possible to simulate the impact behavior at very high impact rates simply by performing impact tests at lower temperatures.     

Fine-line conductor manufacturing using drop-on demand PZT printingtechnology

An emerging selective metallization process to fabricate fine-line conductors based on drop-on-demand (DOD) ink jet printing and novel nano-particle fluid suspensions (NPFS) was studied. The suspensions consist of 1-10 nm silver or gold particulates that are homogeneously suspended in an organic carrier. A piezo-electric droplet generator driven by a bipolar voltage signal is used to dispense 50-70 μm diameter droplets traveling at 1-3 m/s before impacting a compliant polyimide substrate. The deposit/substrate composite is subsequently processed at 300°C for 15 min to allow for complete evaporation of the carrier and for sintering of the nano-particles, thereby yielding a finished circuit interconnect. Test vehicles created using this technique exhibit features as fine as 120 μm wide and 1 μm thick with resistivities on the order of 3.5×10^-5 Ωcm. The circuitry performed well under environmental conditioning. As expected, repeatability of circuitry fabrication showed sensitivity to the generation of steady, satellite-free droplets. In an effort to generate droplets consistently, it is essential to develop a strong fundamental understanding of the correlation between device excitation parameters and dispensed fluid properties, and to resolve the microrheological behavior of the NPFS when flowing through the droplet generator