Development of a digital electronic rebalance loop for a dry tuned-rotor two degree-of-freedom gyroscope

Digital electronic rebalance loops were designed and implemented in brassboard form to capture both X and Y axes of the Kearfott Gyroflex. The loops were width-modulated binary types using a 614.4 kHz keying signal and a 2.4 kHz sample frequency. The loops were designed for a torquing rate of 2 deg/sec (70.6 mA torquing current) and a data resolution of 23.4 milli-arc-sec per data pulse. Design considerations, implementation details, and preliminary experimental results are presented

On the Concept of a Notational Variant

In the study of modal and nonclassical logics, translations have frequently been employed as a way of measuring the inferential capabilities of a logic. It is sometimes claimed that two logics are “notational variants” if they are translationally equivalent. However, we will show that this cannot be quite right, since first-order logic and propositional logic are translationally equivalent. Others have claimed that for two logics to be notational variants, they must at least be compositionally intertranslatable. The definition of compositionality these accounts use, however, is too strong, as the standard translation from modal logic to first-order logic is not compositional in this sense. In light of this, we will explore a weaker version of this notion that we will call schematicity and show that there is no schematic translation either from first-order logic to propositional logic or from intuitionistic logic to classical logic

Embryo Culture of Lycopersicon esculentum × L. peruvianum Hybrid Genotypes Possessing Heat-stable Resistance to Meloidogyne incognita

Genotypes of Lycopersicon peruvianum (L.) Mill. and L. peruvianum var. glandulosum (Rick), selected from accessions that possess resistance to Meloidogyne incognita [(Kofoid and White) Chitwood] at high soil temperature (30C), were used as male parents in crosses with L. esculentum (Mill.) susceptible cultivars UC82, Lukullus, Tropic, and male-sterile line ms-31, respectively. The incongruity barrier between the two plant species was overcome by embryo callus and embryo cloning techniques. Hybridity of the F, progeny obtained from each cross was confirmed by differences in leaf and flower morphology, plant growth habits, and by acid phosphatase isozyme phenotypes using polyacrylamide gel electrophoresis. In greenhouse inoculation experiments, F1 plants were highly resistant to M. incognita in soil at 25 and 30C. These results confirmed the successful transfer and expression of heat-stable resistance to M. incognita from L. peruvianum to hybrids with L. esculentum as a preliminary step to introgressing additional root-knot nematode resistance into tomato.EEA AMBAFil: Cap, Guillermo Bartolome. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Área Metropolitana de Buenos Aires. Agencia de Extensión Rural La Plata; ArgentinaFil: Roberts, P.A. University of California, Riverside. Department of Hematology; Estados UnidosFil: Thomason, I.J. University of California, Riverside. Department of Hematology; Estados UnidosFil: Murashige, T. University of California, Riverside. Department of Hematology; Estados Unido

Earthworm populations in a wheat-soybean double-crop system under seven years of established residue management practices

Earthworms improve soil structure, distribute litter and microbes, stimulate microbial activity, facilitate decomposition, and increase nitrogen (N) availability for plant growth. Earthworm density is often reduced in low organic matter soils that are intensively managed to grow row crops. This study was designed to relate earthworm density and community composition to residue management after seven years of established management practices in a wheat (Triticum aestivum L.)-soybean (Glycine max (L.) Merr.) double-crop system maintained in Marianna, Ark. Residue management practices included conventional tillage (CT) and no-tillage (NT), N fertilization to produce high and low wheat residue amounts left in the field, and burning and non-burning of residue after wheat harvest. Total earthworm densities ranged from 271 to 508 m-2 across treatments. Both exotic Aporrectodea trapezoides (Duges) and native Diplocardia sylvicola (Gates) adult earthworms were present with very little difference in diversity among sampled communities; however, more than 50 % of adults were D. sylvicola in all treatments. Residue level and burning influenced total, juvenile, and native earthworm densities differently in CT and NT. Adult native earthworms predominated over a common exotic species in a wheat-soybean double-crop system in Arkansas with residue management practices interacting to impact the density of earthworms

A New Model for Void Coalescence by Internal Necking

A micromechanical model for predicting the strain increment required to bring a damaged material element from the onset of void coalescence up to final fracture is developed based on simple kinematics arguments. This strain increment controls the unloading slope and the energy dissipated during the final step of material failure. Proper prediction of the final drop of the load carrying capacity is an important ingredient of any ductile fracture model, especially at high stress triaxiality. The model has been motivated and verified by comparison to a large set of finite element void cell calculations.

A simple chemical approach to regenerating strength of thermally damaged glass fibre for reuse in composites

A key technical barrier to the reuse of thermally recycled glass fibres in composite applications is their low mechanical strength. This research study looks into the effect of alkaline treatments in regenerating the strength of glass fibres which were heated in a furnace to simulate thermal recycling conditions. Up to 100% strength increase of the fibres can be achieved through a simple treatment in alkaline solution. It was found that the nature of alkali, concentration, and treatment duration had a significant effect on the extent of strength recovery of the fibres. These treatments could potentially be implemented to thermally recycled glass fibres on an industrial scale, to allow their reprocessing into second-life composite materials. As well as optimising the reaction conditions to regenerate fibre strength, an examination of the surface morphology was carried out using various techniques. In addition, the kinetics of dissolution of glass fibres in alkaline solutions was investigated in order to further understand the strength regeneration mechanism

On the vanishing of negative K-groups

Let k be an infinite perfect field of positive characteristic p and assume that strong resolution of singularities holds over k. We prove that, if X is a d-dimensional noetherian scheme whose underlying reduced scheme is essentially of finite type over the field k, then the negative K-group K_q(X) vanishes for every q < -d. This partially affirms a conjecture of Weibel.Comment: Math. Ann. (to appear

Embedding Four-directional Paths on Convex Point Sets

A directed path whose edges are assigned labels "up", "down", "right", or "left" is called \emph{four-directional}, and \emph{three-directional} if at most three out of the four labels are used. A \emph{direction-consistent embedding} of an \mbox{$n$-vertex} four-directional path $P$ on a set $S$ of $n$ points in the plane is a straight-line drawing of $P$ where each vertex of $P$ is mapped to a distinct point of $S$ and every edge points to the direction specified by its label. We study planar direction-consistent embeddings of three- and four-directional paths and provide a complete picture of the problem for convex point sets.Comment: 11 pages, full conference version including all proof

Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2022) observations of smoke in the stratosphere

Using a common analysis approach for data sets produced by the Stratospheric Aerosol and Gas Experiment instruments SAGE II and SAGE III/ISS, we identify 13 likely smoke events based on enhancements in the aerosol extinction coefficient. Nine of these are sufficiently large compared to ambient aerosol levels to compute mean mid-latitude 1020 nm optical depth enhancements that range from 0.0005 to 0.011. We also note that, for large events, the 525 to 1020 nm aerosol extinction coefficient ratio asymptotes at a high extinction coefficient to values between 2 and 3, suggesting that the aerosol radius is relatively small (&lt; 0.3 µm) and relatively consistent from event to event. Most of these events are primarily confined to the lower stratosphere and rarely can be observed above 20 km. We also infer an increase in the frequency of smoke events between the SAGE II (1984–1991, 1996–2005) and SAGE III/ISS (2017-present) periods by almost a factor of 2 and also note that the two largest events occur in the latter data set. However, given the low frequencies overall, we are not confident that the differences can be attributed to changes between the two periods. We also attempt to disentangle the mixing of aerosol in the Northern Hemisphere summer of 1991 from a pyrocumulus event (Baie-Comeau, Quebec) and Mt. Pinatubo and conclude that, while there is evidence for smoke in the lower stratosphere, virtually all of the enhanced aerosol observations in the northern mid-latitudes in the summer of 1991 are associated with the Mt. Pinatubo eruption.</p

Іноземні інвестиції у контексті економічного зростання

The eruption of Mount Pinatubo in 1991 injected a large amount of SO2 into the stratosphere, which formed sulfate aerosols. Increased scattering and absorption of UV radiation by the enhanced stratospheric SO2 and aerosols decreased the amount of UV radiation reaching the troposphere, causing changes in tropospheric photochemistry. These changes affected the oxidizing capacity of the atmosphere and the removal rate of CH4 in the years following the eruption. We use the three-dimensional chemistry transport model TM5 coupled to the aerosol microphysics module M7 to simulate the evolution of SO2 and sulfate aerosols from the Pinatubo eruption. Their effect on tropospheric photolysis frequencies and concentrations of OH and CH4 is quantified for the first time. We find that UV attenuation by stratospheric sulfur decreased the photolysis frequencies of both ozone and NO2 by about 2% globally, decreasing global OH concentrations by a similar amount in the first 2 years after the eruption. SO2 absorption mainly affects OH primary production by ozone photolysis, while aerosol scattering also alters OH recycling. The effect of stratospheric sulfur on global OH and CH4 is dominated by the effect of aerosol extinction, while SO2 absorption contributes by 12.5% to the overall effect in the first year after the eruption. The reduction in OH concentrations causes an increase in the CH4 growth rate of 4 and 2 ppb/yr in the first and second years after the eruption, respectively, contributing 11 Tg to the 27 Tg observed CH4 burden change in late 1991 and early 1992. Key Points We modeled the effect of Pinatubo sulfur on tropospheric photochemistry SO2 absorption and aerosol extinction reduce tropospheric UV levels The tropospheric OH sink of CH4 decreased by 17.8 Tg during June 1991-June 199