Characterizing performance of ultra-sensitive accelerometers

An overview is given of methodology and test results pertaining to the characterization of ultra sensitive accelerometers. Two issues are of primary concern. The terminology ultra sensitive accelerometer is used to imply instruments whose noise floors and resolution are at the state of the art. Hence, the typical approach of verifying an instrument's performance by measuring it with a yet higher quality instrument (or standard) is not practical. Secondly, it is difficult to find or create an environment with sufficiently low background acceleration. The typical laboratory acceleration levels will be at several orders of magnitude above the noise floor of the most sensitive accelerometers. Furthermore, this background must be treated as unknown since the best instrument available is the one to be tested. A test methodology was developed in which two or more like instruments are subjected to the same but unknown background acceleration. Appropriately selected spectral analysis techniques were used to separate the sensors' output spectra into coherent components and incoherent components. The coherent part corresponds to the background acceleration being measured by the sensors being tested. The incoherent part is attributed to sensor noise and data acquisition and processing noise. The method works well for estimating noise floors that are 40 to 50 dB below the motion applied to the test accelerometers. The accelerometers being tested are intended for use as feedback sensors in a system to actively stabilize an inertial guidance component test platform

Animal-Inspired Agile Flight Using Optical Flow Sensing

There is evidence that flying animals such as pigeons, goshawks, and bats use optical flow sensing to enable high-speed flight through forest clutter. This paper discusses the elements of a theory of controlled flight through obstacle fields in which motion control laws are based on optical flow sensing. Performance comparison is made with feedback laws that use distance and bearing measurements, and practical challenges of implementation on an actual robotic air vehicle are described. The related question of fundamental performance limits due to clutter density is addressed.Comment: 20 pages, 7 figure

Spreading Sequences Generated Using Asymmetrical Integer-Number Maps

Chaotic sequences produced by piecewise linear maps can be transformed to binary sequences. The binary sequences are optimal for the asynchronous DS/CDMA systems in case of certain shapes of the maps. This paper is devoted to the one-to-one integer-number maps derived from the suitable asymmetrical piecewise linear maps. Such maps give periodic integer-number sequences, which can be transformed to the binary sequences. The binary sequences produced via proposed modified integer-number maps are perfectly balanced and embody good autocorrelation and crosscorrelation properties. The number of different binary sequences is sizable. The sequences are suitable as spreading sequences in DS/CDMA systems

The Effects of Fire on Spore Viability of Lygodium microphyllum (Old World Climbing Fern)

Lygodium microphyllum, native to the Old World tropics, has invaded central and southern Florida, destroying native habitats, reducing biodiversity and altering fire regimes. Prescribed fire, one of several methods used to manage L. microphyllum infestations, reduces fern biomass over large areas, but its effects on spore viability are unknown. To provide tools to evaluate whether fire-dispersed spores are viable, this research determined how heat affects spore viability. Spores were exposed to temperatures of 50°C to 300°C for durations of 5 seconds to 1 hour, then allowed to germinate on agar in petri plates. Percent germination was assayed after two weeks. Temperatures of 50°C had little effect; 300°C killed spores for all durations. Results indicate that while viability of unburnt spores decreases with increasing temperature and duration of heat exposure, spores are killed when exposed to relatively low temperatures compared to those in fires

Invasion Ecology and Response to Fire of the Nonnative Fern Lygodium microphyllum in the South Florida Everglades

Lygodium microphyllum (Old World Climbing Fern (OWCF)) is a climbing fern native to tropical and subtropical regions of Australia, Asia, and Africa. First introduced to Florida as an ornamental in the 1960s, the fern has become a serious invasive in numerous Florida habitats, severely degrading native herbaceous and woody vegetation and altering fire behavior. One area with the greatest increase in OWCF cover is the sawgrass marsh of southern Everglades National Park (ENP), where prescribed fire is used for both maintenance of sawgrass marshes and management of OWCF infestations. However, the efficacy of OWCF control using fire in this habitat is uncertain. This dissertation investigated the response of individual OWCF plants in coastal sawgrass marshes over two years following a prescribed burn. As some OWCF occurs in brackish conditions, salinity tolerance of the fern was assessed under greenhouse conditions. Additionally, nectar production, which can influence biological control agent success, was examined in OWCF and related species. Following the prescribed burn, surviving OWCF recovered to pre-burn sizes between 6 and 15 months after burning, depending on the burn season. Mortality was size-dependent, with smaller plants suffering highest mortality rates. Sexual reproduction and biocontrol mite presence were both reduced for approximately 9 months post-burn. Saline conditions of 10 ppt reduced growth rates of greenhouse-grown OWCF within 6 weeks and resulted in significantly reduced biomass after 3 months as compared to plants in both 0 and 5 ppt. Spores had reduced and delayed germination in saline conditions compared to 0 ppt, and were completely prevented from germinating in 15 ppt. Foliar nectar production, previously discovered on OWCF, was documented on three additional species, including the other major Florida invasive, Lygodium japonicum. The findings of the dissertation suggest that fire is an effective management strategy for OWCF and may be improved in certain habitats by combination with biocontrol releases. Although OWCF is found in mildly brackish habitats, higher salinity hinders its survival, suggesting limited invasion potential in more saline areas. Finally, if foliar nectar production occurs in the field, further study of its effects on biocontrol agent success is warranted

Descriptive Sensory Analysis and Composition of Blackberry Genotypes

Consumer interest in blackberries has been increasing due in part to reputed health-promoting factors. Appearance, flavor, and texture attributes of blackberry fruits are important to consumers. The objective of this study was to investigate correlations among sensory and composition attributes of blackberry genotypes from the University of Arkansas Division of Agriculture breeding program. Descriptive panelists evaluated attributes of 20 blackberry genotypes. Composition attributes were evaluated for these and two additional genotypes. ‘Natchez’ had the most pyrenes/berry and the highest levels of total ellagitannins. Selection A-2215 was scored highest for descriptive-evaluated sweetness and had the highest soluble solids content. Total ellagitannins (r= 0.57; p\u3c0.0095) and ORAC (r= 0.54; p\u3c0.0146) were moderately correlated to seediness, which may reflect the value of ORAC factors in pyrenes. These initial investigations of the relationship between sensory and composition of blackberry genotypes provide insights that can be used for future blackberry cultivar assessments

Mobile Communication Networks and Digital Television Broadcasting Systems in the Same Frequency Bands – Advanced Co-Existence Scenarios

The increasing demand for wireless multimedia services provided by modern communication systems with stable services is a key feature of advanced markets. On the other hand, these systems can many times operate in a neighboring or in the same frequency bands. Therefore, numerous unwanted co-existence scenarios can occur. The aim of this paper is to summarize our results which were achieved during exploration and measurement of the co-existences between still used and upcoming mobile networks (from GSM to LTE) and digital terrestrial television broadcasting (DVB) systems. For all of these measurements and their evaluation universal measurement testbed has been proposed and used. Results presented in this paper are a significant part of our activities in work package WP5 in the ENIAC JU project “Agile RF Transceivers and Front-Ends for Future Smart Multi-Standard Communications Applications (ARTEMOS)”

Clara Schumann-Wieck: ihre drei Männer und der lange Weg zur Freiheit

Clara Schumann-Wieck: ihre drei Männer und der lange Weg zur Freihei

Characterization of seediness attributes of blackberry genotypes

Fresh market blackberries can feel “seedy” when consumed. This “seediness” is associated with the presence of pyrenes which are comprised of a single seed enclosed in an endocarp. Small pyrene size

Quantifying substructures in {\it Hubble Frontier Field} clusters: comparison with ΛCDM\Lambda CDM simulations

The Hubble Frontier Fields (HFF) are six clusters of galaxies, all showing indications of recent mergers, which have recently been observed for lensed images. As such they are the natural laboratories to study the merging history of galaxy clusters. In this work, we explore the 2D power spectrum of the mass distribution $P_{\rm M}(k)$ as a measure of substructure. We compare $P_{\rm M}(k)$ of these clusters (obtained using strong gravitational lensing) to that of $\Lambda$CDM simulated clusters of similar mass. To compute lensing $P_{\rm M}(k)$, we produced free-form lensing mass reconstructions of HFF clusters, without any light traces mass (LTM) assumption. The inferred power at small scales tends to be larger if (i)~the cluster is at lower redshift, and/or (ii)~there are deeper observations and hence more lensed images. In contrast, lens reconstructions assuming LTM show higher power at small scales even with fewer lensed images; it appears the small scale power in the LTM reconstructions is dominated by light information, rather than the lensing data. The average lensing derived $P_{\rm M}(k)$ shows lower power at small scales as compared to that of simulated clusters at redshift zero, both dark-matter only and hydrodynamical. The possible reasons are: (i)~the available strong lensing data are limited in their effective spatial resolution on the mass distribution, (ii)~HFF clusters have yet to build the small scale power they would have at $z\sim 0$, or (iii)~simulations are somehow overestimating the small scale power.Comment: 13 pages, 10 figures, 1 table; Accepted for publication in MNRA