Description and simulation of an integrated power and attitude control system concept for space-vehicle application

An Integrated Power and Attitude Control System (IPACS) concept with potential application to a broad class of space missions is discussed. A description is given of the basic concept of combining the onboard energy storage and attitude control functions by storing energy in spinning flywheels which are used to provide control torques. A shuttle-launched Research and Applications Module (RAM) A303B solar-observatory mission having stringent pointing requirements (1.0 arc second) is selected to investigate possible interactions between energy storage and attitude control. A simulation of this spacecraft involving actual laboratory-model control-system hardware is presented. Simulation results are discussed which indicate that the IPACS concept, even in a failure-mode configuration, can readily meet the RAM A303B pointing requirements

Quantification of microstructure during the phase transformation of dynamically cooled steels using the EMspec® sensor

Electromagnetic (EM) sensor signals are sensitive to changes in permeability and resistivity in steel, where both are determined by microstructure, chemical composition and temperature. EM sensors are currently being used in the steel industry to monitor the phase transformation of hot strip on the runout table. However, there are factors still not fully understood when it comes to the EM signal such as relationship between phase fraction transformed at high temperatures and the EM signal. The purpose of this research is to quantitatively relate the EM of zero crossing frequency to microstructure and more specifically phase fraction during transformation of steels at high temperature. The EMspec® industrial EM sensor which is currently used in industrial conditions on the run-out table of a hot strip mill has been installed into a run out table simulator that consists of a furnace and roller run out table. This system has been designed and constructed to allow the EMspec® sensor to be able to monitor various steels through transformation during dynamic cooling on a lab-based scale. A full 3D finite element model of the EMspec® sensor has been developed in a parallel project and is able to use permeability and resistivity values to predict zero crossing frequency. This model has been used in this project to along with measured resistivities and extrapolated permeabilities from the literature to predict zero crossing frequency. The power law was used along with the permeability values, resistivities and phase fraction obtained from dilatometry to predict zero crossing frequency. The EMspec® industrial sensor has been used to monitor the full phase transformation of various carbon steels including mild steels of 3, 6 and 10mm in thickness, a high carbon steel and medium carbon steel. The EMspec® sensor was able to distinguish between the mild steels of different thickness due to their different cooling rates in air and therefore transformation trajectory. The EMspec® sensor was also used to successfully monitor a 2.25 Cr- 1 Mo steel to measure the full transformation to bainite below the Curie temperature. The magnetic transformation of the duplex stainless steel was also monitored by the EMspec® as it cools through the Curie temperature. The EMspec® sensor was shown to be sensitive to the formation of sigma phase as a result of heat treatment of the duplex stainless steel. The sample with higher amount of sigma phase had a lower zero crossing frequency. When relating the ZCF to phase percentage transformed obtained from dilatometry, the 6mm and 10mm mild steels, the high carbon and the 2.25 Cr- 1Mo steel all needed to be approximately 30-40% transformed before an increase in ZCF would occur due to the need for ferromagnetic phase connectivity before permeability significantly increases. This agrees well with the literature for room temperature ferrite fractions however there is room for discrepancies when taking into the temperature difference between a dilatometry sample and a larger sample cooling on the ROT. For the mild steels, the ZCF would peak before dilatometry predicts the steels to be 100% transformed. The modelling data agreed well with the experimental data for steels that consisted of lower permeability phases such as the 2.25Cr-1Mo and high carbon steels. For the 3mm, 6mm and 10mm thick mild steels, the model could not solve for the high permeabilities which may be due to a more refined mesh being required. The model was able to solve for the duplex stainless steel however the modelled data did not agree with the experimental data due to the nature of the calculation of effective permeability. Power law was used however this does not consider the microstructural parameters such as the connectivity of ferrite. The permeabilities at lower phase fractions is higher as a result of this. The work in this project shows that the EMspec® industrial sensor can monitor the full transformation of multiple steels below the Curie temperature and the EMspec® signal can be related quantitatively to phase percentage transformed although the discrepancy between a dilatometry sample and a large sample with inhomogeneity in temperature cannot be ignored

It's Hard to Learn How Gravity and Electromagnetism Couple

We construct the most general effective Lagrangian coupling gravity and electromagnetism up to mass dimension 6 by enumerating all possible non-minimal coupling terms respecting both diffeomorphism and gauge invariance. In all, there are only two unique terms after field re-definitions; one is known to arise from loop effects in QED while the other is a parity violating term which may be generated by weak interactions within the standard model of particle physics. We show that neither the cosmological propagation of light nor, contrary to earlier claims, solar system tests of General Relativity are useful probes of these terms. These non-minimal couplings of gravity and electromagnetism may remain a mystery for the foreseeable future.Comment: 9 pages. Minor corrections made. To appear in Phys. Rev.

OSPACS: Ultrasound image management system

Ultrasound scanning uses the medical imaging format, DICOM, for electronically storing the images and data associated with a particular scan. Large health care facilities typically use a picture archiving and communication system (PACS) for storing and retrieving such images. However, these systems are usually not suitable for managing large collections of anonymized ultrasound images gathered during a clinical screening trial

Effects of a Tailored Follow-Up Intervention on Health Behaviors, Beliefs, and Attitudes

Background: The high rates of relapse that tend to occur after short-term behavioral interventions indicate the need for maintenance programs that promote long-term adherence to new behavior patterns. Computer-tailored health messages that are mailed to participants or given in brief telephone calls offer an innovative and time-efficient alternative to ongoing face-to-face contact with healthcare providers. Methods: Following a 1-year behavior change program, 22 North Carolina health departments were randomly assigned to a follow-up intervention or control condition. Data were collected from 1999 to 2001 by telephone-administered surveys at preintervention and postintervention for 511 low-income, midlife adult women enrolled in the Well-Integrated Screening and Evaluation for Women Across the Nation (WISEWOMAN) program at local North Carolina health departments. During the year after the behavior change program, intervention participants were mailed six sets of computer-tailored health messages and received two computer-tailored telephone counseling sessions. Main outcomes of dietary and physical activity behaviors, beliefs, and attitudes were measured. Results: Intervention participants were more likely to move forward into more advanced stages of physical activity change (p = 0.02); control participants were more likely to increase their level of dietary social support at follow-up (p = 0.05). Both groups maintained low levels of reported saturated fat and cholesterol intake at follow-up. No changes were seen in physical activity in either group. Conclusions: Mailed computer-tailored health messages and telephone counseling calls favorably modified forward physical activity stage movement but did not appreciably affect any other psychosocial or behavioral outcomes

Mapping the effect of variable HPT blade cooling on fuel burn, engine life and emissions for fleet optimization using active control

Modern aero engines have increasingly sophisticated control systems. The aim for next-generation aircraft is to have even more adaptive and flexible control systems to enable the optimization of economic aspects, operational aspects and fleet management. Among others, an engine control variable that has the potential to offer various life and fuel burn benefits at different flight phases is the High-Pressure Turbine (HPT) blade cooling air. The HPT blades have demanding cooling requirements to protect their life and decelerate HPT efficiency degradation. However, any engine bleed has a penalty in efficiency and results in increased fuel consumption. Previous generation aircraft have a fixed relative blade cooling flow based on a design choice for a trade-off between life and efficiency. However, with adaptive control systems, there is an opportunity to extract the maximum potential benefit under different flight phases and scenarios. With this opportunity comes the challenge of increased complexity in engine behavior necessitating detailed modeling to quantify effects on lifing, fuel burn and safety. This paper focuses on modeling the performance, lifing and emission effects of variable HPT blade cooling air at take-off, climb and cruise. First, the effect of variable cooling on the Turbine Entry Temperature (TET), Exhaust Gas Temperature (EGT), fuel flow, lifing and NOx emissions are modeled at operating point level while the thrust requirement is achieved. Subsequently, a Design of Experiment is performed at mission level with the relative cooling flow at take-off, climb and cruise as the independent variables to train surrogate, analytical models. The analytical models are applied in the probabilistic modeling of system failure rates under different cooling flows. Optimization of engine control variables, in this case, the HPT blade cooling, requires analytical expressions that can be used in objective functions. These analytical models will inform fleet optimizers and active control systems to facilitate the implementation of fleet decisions such as reducing direct operating costs (fuel cost, maintenance reserves, NOx taxation), meeting NOx requirements of airports and extending Time-on-Wing (TOW). The findings indicate that take-off offers an opportunity to protect HPT life with increased cooling, but caution should be exercised in regard to the damage increase at the downstream non-cooled hot gas path components. A decrease in cooling flow at cruise, which is less detrimental to engine life, can offer significant fuel savings and climb can be investigated for the optimum economic trade-off between life and fuel burn as a response to economic scenarios

Gravitomagnetism and the Clock Effect

The main theoretical aspects of gravitomagnetism are reviewed. It is shown that the gravitomagnetic precession of a gyroscope is intimately connected with the special temporal structure around a rotating mass that is revealed by the gravitomagnetic clock effect. This remarkable effect, which involves the difference in the proper periods of a standard clock in prograde and retrograde circular geodesic orbits around a rotating mass, is discussed in detail. The implications of this effect for the notion of ``inertial dragging'' in the general theory of relativity are presented. The theory of the clock effect is developed within the PPN framework and the possibility of measuring it via spaceborne clocks is examined.Comment: 27 pages, LaTeX, submitted to Proc. Bad Honnef Meeting on: GYROS, CLOCKS, AND INTERFEROMETERS: TESTING GENERAL RELATIVITY IN SPACE (22 - 27 August 1999; Bad Honnef, Germany

Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa

There are multiple hypotheses for human responses to glacial cycling in the Late Pleistocene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5-6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenvironments explain some, but not all temporal technological variability at PP5-6.Social Science and Humanities Research Council of Canada; NORAM; American-Scandinavian Foundation; Fundacao para a Ciencia e Tecnologia [SFRH/BPD/73598/2010]; IGERT [DGE 0801634]; Hyde Family Foundations; Institute of Human Origins; National Science Foundation [BCS-9912465, BCS-0130713, BCS-0524087, BCS-1138073]; John Templeton Foundation to the Institute of Human Origins at Arizona State Universit