On Sensor Coverage by Mobile Sensors

We study the problem of using a small number of mobile sensors to monitor various threats in a geographical area. Using some recent results on stochastic sensor scheduling, we propose a stochastic sensor movement strategy. We present simple conditions under which it is not possible to maintain a bounded estimate error covariance for all the threats. We also study a simple sub-optimal algorithm to generate stochastic trajectories. Simulations are presented to illustrate the results

Redesigning for Usability: Information Architecture and Usability Testing for Georgia Tech Library's Website

Case study: Purpose: To describe the efforts by the Georgia Institute of Technology Library to keep its website relevant and current by incorporating user testing, both outsourced and in-house. Design/methodology/approach: A chronological history of the Library's web presence with a discussion of how user testing was conducted with a vendor and how future testing will be conducted by the Library itself. Findings: Illustrates issues the Georgia Institute of Technology Library has faced in regards to its website in the past, and future plans to test the site to maintain currency and strive to meet the users' needs. Originality/value: This paper offers practical information for undertaking usability testing of a library website

In Situ Trace Element Analysis of an Allende Type B1 CAI: EK-459-5-1

Variations in refractory major and trace element composition of calcium, aluminum-rich inclusions (CAIs) provide constraints on physical and chemical conditions and processes in the earliest stages of the Solar System. Previous work indicates that CAIs have experienced complex histories involving, in many cases, multiple episodes of condensation, evaporation, and partial melting. We have analyzed major and trace element abundances in two core to rim transects of the melilite mantle as well as interior major phases of a Type B1 CAI (EK-459-5-1) from Allende by electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to investigate the behavior of key trace elements with a primary focus on the REEs Tm and Yb

Mineralogy and Petrology of EK-459-5-1, A Type B1 CAI from Allende

Calcium-aluminum-rich inclusions (CAIs) are a type of coarse-grained clast composed of Ca-, Al-, and Mg-rich silicates and oxides found in chondrite meteorites. Type B (CAIs) are exclusively found in the CV chondrite meteorites and are the most well studied type of inclusion found in chondritic meteorites. Type B1 CAIs are distinguished by a nearly monomineralic rim of melilite that surrounds an interior predominantly composed of melilite, fassaite (Ti and Al-rich clinopyroxene), anorthite, and spinel with varying amounts of other minor primary and secondary phases. The formation of Type B CAIs has received considerable attention in the course of CAI research and quantitative models, experimental results and observations from Type B inclusions remain largely in disagreement. Recent experimental results and quantitative models have shown that the formation of B1 mantles could have occurred by the evaporative loss of Si and Mg during the crystallization of these objects. However, comparative studies suggest that the lower bulk SiO2 compositions in B1s result in more prior melilite crystallization before the onset of fassaite and anorthite crystallization leading to the formation of thick melilite rich rims in B1 inclusions. Detailed petrographic and cosmochemical studies of these inclusions will further our understanding of these complex objects

Stable Magnesium Isotope Variation in Melilite Mantle of Allende Type B1 CAI EK 459-5-1

Ca-Al-rich inclusions (CAIs) are the earliest formed crystalline material in our solar system and they record early Solar System processes. Here we present petrographic and delta Mg-25 data of melilite mantles in a Type B1 CAI that records early solar nebular processes

New Petrology, Mineral Chemistry and Stable MG Isotope Compositions of an Allende CAI: EK-459-7-2

Calcium-aluminum-rich inclusions (CAIs) are the key to understanding physical and chemical conditions in the nascent solar nebula. These inclusions have the oldest radiometric ages of solar system materials and are composed of phases that are predicted to condense early from a gas of solar composition. Thus, their chemistry and textures record conditions and processes in the earliest stages of development of the solar nebula. Type B inclusions are typically larger and more coarse grained than other types with substantial evidence that many of them were at least partially molten. Type B inclusions are further subdivided into Type B1 (possess thick melilite mantle) and Type B2 (lack melilite mantle). Despite being extensively studied, the origin of the melilite mantles of Type B1 inclusions remains uncertain. We present petrologic and chemical data for a Type B inclusion, EK-459-7-2, that bears features found in both Type B1 and B2 inclusions and likely represents an intermediate between the two types. Detailed studies of more of these intermediate objects may help to constrain models for Type B1 rim formation

Al-Mg Isotope Study of Allende 5241

The defining characteristic of type B1 CAIs is a large (.5- 3mm) concentric melilite mantle [1]. In [2] we presented two isochrons from separate traverses across the melilite mantle of Allende EK 459-5-1. The primary petrographic differences between the traverses was the preservation of strong oscillatory zoning. The traverse that crossed the distinctive oscillatory zone produced a pristine internal isochron, while the other that did not have a strongly preserved oscillatory zone produced a disturbed isochron indicated by more scatter (higher MSWD) and a positive (delta)26Mg* intercept. The implication simply being that the oscillatory zone may represent varying conditions during the mantle formation event. We targeted a similar texture in Allende 5241 using the same methodology in an attempt to achieve similar results

Supra-Canonical Initial 26Al/27Al from a Reprocessed Allende CAI

No abstract availabl

Experimental and analytical studies of advanced air cushion landing systems

Several concepts are developed for air cushion landing systems (ACLS) which have the potential for improving performance characteristics (roll stiffness, heave damping, and trunk flutter), and reducing fabrication cost and complexity. After an initial screening, the following five concepts were evaluated in detail: damped trunk, filled trunk, compartmented trunk, segmented trunk, and roll feedback control. The evaluation was based on tests performed on scale models. An ACLS dynamic simulation developed earlier is updated so that it can be used to predict the performance of full-scale ACLS incorporating these refinements. The simulation was validated through scale-model tests. A full-scale ACLS based on the segmented trunk concept was fabricated and installed on the NASA ACLS test vehicle, where it is used to support advanced system development. A geometrically-scaled model (one third full scale) of the NASA test vehicle was fabricated and tested. This model, evaluated by means of a series of static and dynamic tests, is used to investigate scaling relationships between reduced and full-scale models. The analytical model developed earlier is applied to simulate both the one third scale and the full scale response

Changes in inflammatory mediators in experimental periodontitis in the rhesus monkey.

Ligature-induced periodontitis was monitored for 6 months in eight Macaca mulatta monkeys to examine clinical status, radiographic bone level, and crevicular fluid (CF) levels of prostaglandin E2 (PGE2), thromboxane B2 (TxB2), interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha, and leukotriene B4 (LTB4). A split-mouth design was used, with eight ligated teeth and eight contralateral nonligated teeth which develop soft-chow-promoted (spontaneous) disease. Ligated sites experienced an average attachment loss of 0.94 mm per site and linear bone loss of 0.88 mm per site, with spontaneous-periodontitis sites experiencing approximately half the loss of ligated sites. The CF mediator levels showed increased levels of PGE2 and TxB2 at the ligated sites, as compared with the spontaneous sites, with no significant contralateral differences in the IL-1 beta or LTB4 responses. The concentrations of LTB4 in CF reached an early threefold peak over the baseline level at 1 month. By 2 months there was a statistically significant threefold elevation in CF-PGE2 in the ligated sites and a twofold elevation in the spontaneous sites as compared to the baseline level (P = 0.041 and 0.008, respectively). The monocyte product IL-1 beta increased sharply at 2 months and returned to the baseline level by 6 months at both ligated and nonligated sites. Tumor necrosis factor alpha in CF was below the limit of detection at all sites throughout the experiment (i.e., < 2 ng/ml). The selective elevation of both PGE2 and TxB2 in ligated sites, compared with levels in spontaneous sites, in the presence of similar levels of LTB4 and IL-1 beta provides further evidence that these molecules regulate the magnitude of the tissue-destructive response in progressive periodontitis