Guidelines for Verification Strategies to Minimize RISK Based on Mission Environment, -Application and -Lifetime (MEAL)

There is a trend of compromising verification testing to address the cost and schedule constraints, which poses a high-risk posture for programs/projects. Current and emerging aerospace scientific and/or human exploration programs continue to pose new technological challenges. These technological challenges combined with finite budgets and truncated schedules are forcing designers, scientists, engineers, and managers to push technologies to their physical limits. In addition, budget and schedule pressures challenge how those technologies/missions are verified. A clear understanding of the different verification processes is needed to ensure the proper verification of the technology within the mission (i.e., capabilities, advantages, and limitations). The goal of verification is to prove through test, analysis, inspection, and/or demonstration that a product provides its required function while meeting the performance requirements. It is important that verification yield understanding of representative performance under worst-case conditions so that margins to failure can be evaluated for proposed applications. The capabilities, advantages, and limitations of the testing and inspection performed at each level are different, and the risk incurred by omitting a verification step depends on the level of integration as well as Mission, Environment, Application and Lifetime (MEAL). This paper focuses on verification processes. The goal of the verification process is to ensure the given avionics technology could be safely implemented on the given MEAL consistent with the program/project risk posture

Moderating Effect of the Neighborhood Physical Activity Environment on the Relation Between Psychosocial Factors and Physical Activity in Children: A Longitudinal Study

Background Few studies have examined the moderating role of neighbourhood environments on the relation between psychosocial factors and physical activity, and results of these studies are mixed. This study examined this relationship in 636 fifth to seventh graders from South Carolina, USA. Methods From 2010 to 2013, children and their parent/guardian completed annual self-reported surveys assessing psychosocial factors, and children wore accelerometers for 1 week each year. Neighbourhood environments were classified as supportive or non-supportive for physical activity (PA) based on in-person audits of facilities near children’s homes and windshield surveys of children’s streets. Growth curve analyses were completed to assess the moderating effect of the neighbourhood physical activity environment (NPAE) on the relation between psychosocial factors and total physical activity (TPA) over time. Results Significant interactions on TPA were found for (1) time, NPAE and parent-reported parent support for PA; (2) time, NPAE and child-reported equipment in the home; (3) child-reported parental support for PA and time; (4) child-reported parental support for PA and NPAE; (5) PA self-schema and time and (6) child-reported parental encouragement and time. Parental support and a supportive NPAE were important for TPA, especially as children transitioned to middle school, whereas home equipment and a supportive NPAE were important for fifth graders’ TPA. Conclusion Consistent with the socioecological model, PA behaviour was dependent on interacting effects across levels of influence. Generally, both a supportive NPAE and positive psychosocial factors were needed to support TPA. Factors influencing PA across multiple levels should be addressed in PA interventions

Toward a theory of repeat purchase drivers for consumer services

The marketing discipline’s knowledge about the drivers of service customers’ repeat purchase behavior is highly fragmented. This research attempts to overcome that fragmented state of knowledge by making major advances toward a theory of repeat purchase drivers for consumer services. Drawing on means–end theory, the authors develop a hierarchical classification scheme that organizes repeat purchase drivers into an integrative and comprehensive framework. They then identify drivers on the basis of 188 face-to-face laddering interviews in two countries (USA and Germany) and assess the drivers’ importance and interrelations through a national probability sample survey of 618 service customers. In addition to presenting an exhaustive and coherent set of hierarchical repeat-purchase drivers, the authors provide theoretical explanations for how and why drivers relate to one another and to repeat purchase behavior. This research also tests the boundary conditions of the proposed framework by accounting for different service types. In addition to its theoretical contribution, the framework provides companies with specific information about how to manage long-term customer relationships successfully

Population Dynamics of the Illinois Deer Herd: Illinois Forest Game Investigations W-87-R-12, 13, 14, Final Report 1 July 1989 through 30 June 1992

Project Title: Cooperative Forest Wildlife Research; Subproject No.: VII, Title: Illinois Deer Investigations; Study No. 1 Title: Population dynamics of the Illinois deer herdReport issued on: August 31, 1992INHS Technical Report prepared for unspecified recipien

Telemetry Tracking & Control (TT&C) - First TDRSS, then Commercial GEO & Big LEO and Now Through LEO

The advent of low earth orbit (LEO) commercial communication satellites provides an opportunity to dramatically reduce Telemetry, Tracking and Control (TT&C) costs of launch vehicles, Unpiloted Aerial Vehicles (UAVs), Research Balloons and spacecraft by reducing or eliminating ground infrastructure. Personnel from the Goddard Space Flight Center's Wallops Flight Facility (GSFC\WFF) have successfully used commercial Geostationary Earth Orbit (GEO) and Big LEO communications satellites for Long Duration Balloon Flight TT&C. The Flight Modem is a GSFC\WFF Advanced Range Technology initiative (ARTI) designed to streamline TT&C capability in the user community of these scientific data gathering platforms at low cost. Making use of existing LEO satellites and adapting and ruggedized commercially available components; two-way, over the horizon communications may be established with these vehicles at great savings due to reduced infrastructure. Initially planned as a means for permitting GPS data for tracking and recovery of sounding rocket and balloon payloads, expectations are that the bandwidth can soon be expanded to allow more comprehensive data transfer. The system architecture which integrates antennas, GPS receiver, commercial satellite packet data modem and a single board computer with custom software is described and technical challenges are discussed along with the plan for their resolution. A three-phase testing and development plan is outlined and the current results are reported. Results and status of ongoing flight tests on aircraft and sounding rockets are reported. Future applications on these platforms and the potential for satellite support are discussed along with an analysis of cost effectiveness of this method vs. other tracking and data transmission schemes

Titanium nitride and titanium films for nanoelectromechanical systems

Auf dem Gebiet der mikro- und besonders der nanoelektromechanischen Systeme (MEMS/NEMS) gibt es viele neue Entwicklungen. In Kombination mit metallischen Funktionsschichten, die monolithisch in die Metallisierungsebenen von CMOS-Schaltkreisen integriert werden, haben sie großes Potenzial für neue Anwendungen. Entscheidend für diese Integration sind Materialien, die kompatibel zu den CMOS-Fertigungsprozessen sind und gute mechanische und elektrische Eigenschaften besitzen. Aus diesem Grund sind Titan und speziell Titannitrid (TiN) attraktive Werkstoffe. Sie werden hauptsächlich als Diffusionsbarriere in der Aluminium- und Kupfermetallisierung oder als Antireflexionsschicht in der optischen Lithographie eingesetzt. Über die Wechselwirkung unterschiedlicher Herstellbedingungen auf die Materialeigenschaften in mikro- und nanomechanischen Anwendungen ist aber bisher wenig veröffentlicht. In der vorliegenden Arbeit wurde das DC-Magnetron-Sputtern von dünnen Titan- und TiN-Schichten systematisch untersucht. Ein Schwerpunkt war die Fragestellung, wie die Schichtspannung und der spezifische Widerstand über einen weiten Bereich mit den Sputterparametern kontrolliert werden kann. Allgemein wurde festgestellt, dass ein Kompromiss zwischen geforderter Schichtspannung und elektrischem Widerstand der gesputterten Materialien geschlossen werden muss. Im Rahmen dieser Arbeit wurde ein zweistufiger Abscheideprozess entwickelt, der sich als vielversprechend für die Einstellung und Kontrolle der Materialspannungen erwiesen hat. Dieser Prozess wurde zur Fertigung von strukturierten Mikrobalken mit verschiedenen Kombinationen aus Titan und Titannitrid eingesetzt und getestet. Die Möglichkeit, Zugspannungen in reinem Titan zu erzeugen, stellte ein zuverlässiges Mittel zur Kompensation der Druckspannungen des Titannitrids dar. Je nach Verhältnis der Schichtdicken im Zweischichtsystem konnten damit die resultierenden Spannungen zwischen Zug und Druck eingestellt werden. Das ermöglicht Mikroaktuatoren mit maßgeschneiderten elektromechanischen Eigenschaften. Als Beispiel wurden elektrostatische Schalter aus Mikrobalken mit einer Dicke von 100 nm und einer Breite von 500 nm hergestellt, die Grundelemente hochintegrierter elektromechanischer Nanorelais sein können.There have been many recent developments in microelectromechanical and especially nanoelectromechanical systems (MEMS/NEMS). They have shown great potential for new applications when combined with the monolithic integration of metallic functional layers in CMOS backend metallisation schemes. To achieve this integration, materials that are compatible with the CMOS backend processing and possessing good mechanical and electrical properties are critical. Titanium and in particular titanium nitride (TiN) are attractive for these reasons. These materials are currently known as a diffusion barrier in the aluminium and copper metallisation schemes and as an antireflective coating in optical lithography. Little work has been reported investigating the interaction of the process fabrication conditions on the properties of these materials in micro- and nanomechanical applications. In this thesis the DC magnetron sputtering of thin titanium and titanium nitride films has been studied systematically. The main characterisation was to establish how the film stress and resistivity could be controlled over a wide range of sputtering parameters. Overall, it was found that, a compromise has to be made between the required film stress and the desired electrical resistivity of the sputtered materials. In the course of the work, a two-step deposition process was developed and shown to be promising for the adjustment and control of the deposited material stresses. This deposition process has been applied to the fabrication of structured microbeams with various combinations of titanium and titanium nitride layers. The ability to create a tensile stress in pure titanium was shown to provide a means of compensating the compressive stress of the titanium nitride. Depending on the thickness ratio the resultant stresses could be adjusted between tensile and compressive in the two-layer system. This leads to microactuators with tailor-made electromechanical properties. As an example electrostatic switches with 100 nm thick and 500 nm wide microbeams were fabricated. These structures could form the basis of mechanical elements in highly integrated electromechanical nanorelays