Rapid Annealing in Silicon Transistors

Rapid annealing data after a pulse of reactor neutrons for seven NPN planar transistors at room temperature and the 2N1613 at various temperatures down to dry ice were interpreted in terms of the motion of a single type of mobile defect. An equation was derived for the recombination of the defect with fixed defects in a spherical cluster and the subsequent diffusion of the defect outside the cluster. This treatment leads to an identification of two stages of annealing, with a transition time between stages at room temperature of a few milliseconds. The variation in the transition time with temperature for the 2N1613 is used to derive an activation energy of (0.28 ± 0.02) eV, which agrees, within error, with that for the vacancy in p-type silicon. A calculation of the cluster radius is in reasonable agreement with one-half the primary recoil range.     

Characterization of metal (Fe,Co, Ni,Cu) and fluorine codoped barium strontium titanate thick-films for microwave applications

The influence of codoping of Fe, Co, Ni, Cu as acceptors and F as donor on the dielectric properties of screen-printed Ba_0.6Sr_0.4TiO₃ ceramic thick-films has been investigated. The undoped and codoped Ba_0.6Sr_0.4TiO₃ powders were synthesized through a sol-gel route. The thermal gravimetric analysis revealed the difference of the thermal decomposition behaviour between the undoped and codoped precursors. The ceramic powders were characterized with x-ray diffraction, scanning electron microscopy and BET measurements. Larger crystallite sizes of the codoped powders were observed. The densification behaviour of the powders was recorded by dilatometry and indicated that codoping influences the sintering mechanism. The permittivity, dielectric loss and tunability of the undoped and codoped thick-films were characterized with coplanar waveguide structures up to 30 GHz.     

Scaling Effects of Inverter-Induced Bearing Currents in AC Machines

In this survey paper, we show by straightforward mathematical scaling considerations that small inverter-fed ac motors of up to typical 20 kW at 1500/min are likely to suffer from discharge (electric discharge machining) bearing currents, whereas larger motors are likely to be subjected to high-frequency (HF) circulating bearing currents. When comparing motors that operate at the same voltage level, the resulting bearing-current density is high for very small and very large motors. Smaller values occur in between these two extremes with medium size motors in the range of 10-100 kW. Therefore, electric bearing insulation is useful for larger motors to interrupt the HF circulating bearing-current path, whereas small motors need rotor shielding, common-mode voltage filters, or hybrid bearings.     

Chemically mediated ovipositional behaviors of the european corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

The volatile plant sesquiterpenoids farnesene, nerolidol, and farnesol were tested to determine their effect on European corn borer,Ostrinia nubilalis, oviposition during the first six nights of the adult stage. Adult European corn borers were released into cages designed to encourage oviposition on eight glass plates randomly arranged on top of the cage: four coated with either 80µg/cm² farnesene, nerolidol, or farnesol, and four coated with the solvent methylene chloride. The setup was used as a binary choice test. Farnesene was preferred by females because they deposited significantly more egg masses on plates coated with the compound. Nerolidol had no effect. Farnesol, by contrast, deterred oviposition: the number of egg masses was significantly lower on plates covered with that compound. These data show that structural modification at a single terminal functional group in these compounds affects the ovipositional behavior of European corn borer females.This paper reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by USDA.     

Conversion of methyl ricinoleate to methyl 12-ketostearate with Raney nickel

A convenient laboratory preparation of methyl 12-ketostearate is described. Methyl ricinoleate is converted to methyl 12-ketostearate in 70–75% yield by Raney nickel. The type and quantity of Raney nickel have a marked influence on the yield as well as on the time and temp required for the conversion. The reaction is not a direct isomerization as previously assumed but appears to be a two-step process. Methyl ricinoleate is hydrogenated rapidly to methyl 12-hydroxystearate which is then dehydrogenated slowly to the product. Hydrogenolysis of the alcohol function is a competing reaction which is minimized by the proper choice of reaction conditions. A laboratory of the W. Utiliz. Res. & Dev. Div., ARS, USDA.     

Saturated keto esters from lesquerolic,dimorphecolic, and densipolic acids

Summary The naturally occurring, unsaturated, hydroxy fatty esters, methyl lesquerolate (methyl 14-hydroxy-cis-11-eicosenoate), methyl dimorphecolate (methyl 9-hydroxy-trans, trans-10,12-octadecadienoate), and methyl densipolate (methyl 12-hydroxy-cis,cis-9,15-octadecadienoate) have been converted to the corresponding saturated keto esters by tow routes. The unsaturated esters were subjected to a hydrogenation-dehydrogenation reaction in the presence of Raney nickel or their saturated derivatives were dehydrogenated by copper chromite catalysis. Yields of the keto esters are 65–82% in the nickel-catalyzed reactions, and 71–94% by copper chromite-catalyzed dehydrogenation. In the hydrogenation-dehydrogenation system the order of reactivity is: methyl lesquerolate>methyl dimorphecolate>methyl densipolate. Relationships between structure and reactivity of these compounds, methyl 12-hydroxystearate, and methyl ricinoleate are discussed. W. Utiliz. Res. Dev. Div., ARS, USDA.     

A research frontier in landscape architecture: landscape performance and assessment of social benefits

This paper introduces a research frontier in landscape architecture—landscape performance benefits assessment. In an initiative proposed by the Landscape Architecture Foundation (LAF), leading landscape architecture firms and academic institutions have been collaborating on studies that quantitatively assess environmental, economic and social benefits of high-profile landscape design projects. This study describes the components and processes of LAF landscape performance research and specifically evaluates the status of social benefits assessment, a critical though under-investigated aspect of landscape design sustainability. Using 58 published LAF case studies, the study examines to what extent social benefits are quantified compared with stated design goals, the benefits across the LAF case portfolio (e.g. per benefit category and project type), and methods and data options available to perform the analyses. Finally, the study provides suggestions on improving landscape performance research, particularly social benefits, in the enterprise of achieving evidence-based designs that are anchored in quantitative performance measures.