Physical Processes in the Outer Heliosphere

This chapter covers the theory of physical processes in the outer heliosphere that are particularly important for the IBEX Mission, excluding global magnetohydrodynamic/Boltzmann modeling of the entire heliosphere. Topics addressed include the structure and parameters of the solar wind termination shock, the transmission of ions through the termination shock including possible reflections at the shock electrostatic potential, the acceleration and transport of suprathermal ions and anomalous cosmic rays at the termination shock and in the heliosheath, charge-exchange interactions in the outer heliosphere including mass and momentum loading of the solar wind, the transport of interstellar pickup ions, and the production and anticipated intensities of energetic neutral atoms (ENAs) in the heliosphere.     

Step load response of a current-mode-controlled DC-to-DC converter

This paper analyzes the step load response of a current-mode-controlled pulsewidth modulation (PWM) converter and also presents design guidelines for obtaining a good step load response. Analytical expressions for the step load response are derived in terms of the power stage and feedback compensation parameters. Control design to minimize the overshoot and settling time of the output voltage is presented. Analysis results are verified by large-signal simulations.     

Microsatellite combined attitude/energy systems

We have constructed a high-temperature super conductor-magnet momentum wheel for microsatellites and propose a micro high-temperature superconductor energy storage and attitude control system for nano/pico satellites. The momentum wheel for micro satellites has a mass of 1.1 kg with an angular momentum capacity of 3.5 J sec. It occupies a volume of 12.7 cm in diameter and 5 cm in height. It operates within the restricted power budget of a microsatellite with a total power supply of only 10 watts. It consumes less than 1 watt for sustenance. The micro high-temperature superconductor flywheel for nano/pico satellites has an angular momentum capacity of 0.083 Js and stores 2.32 kJ at 530 krpm. Its energy storage capacity is approximately 45 Wh/kg with an energy density of around 370 kJ/L. The HTS systems can perform the dual function of a power/attitude control system and are ideally suited for low Earth orbit energy storage, power generation, and attitude control of spacecraft.     

In-flight entertainment-getting from wishlist to reality

Much of what we see in the consumer electronics stores will eventually find its way into airplanes in the form of In-Flight Entertainment (IFE). This consumer electronic equipment is often referred to as “the leading edge of technology”. Unfortunately, that same equipment that is the “leading edge” of consumer electronics, often stalls to feel like the “bleeding edge” when you try to integrate it into IFE systems for today's modern aircraft. Unlike Avionics Systems, the technologies behind IFE equipment are not usually mature before they are integrated into the aircraft. What may work well in a home environment, may not work well at all in the aircraft environment. Often this problem results in last minute redesign in an effort to make the equipment function as intended on the aircraft. Both the FAA and the aircraft manufacturer impose many requirements on the suppliers and products of IFE. Systems need to be designed for the aircraft environment. Many variations on IFE Systems have forced the creation of new standards for integration into commercial aircraft. Power, cooling, and EMC issues are becoming more of a concern as we move to fill aircraft implementations. Beyond the technical evaluations and lab/aircraft testing, one key component is customer satisfaction. This paper will cover some of the methods and tools we use to get IFE from wishlist to reality     

Detection of Changes in the Characteristics of a Gauss-Markov Process

By an extension to the theory of sequential detection with dependent measurements, it is possible to develop a sequential probability ratio test (SPRT) to detect changes in regime in a Gauss-Markov process rather than detecting which of the two regimes exists. It is shown how a posterior form of this extended SPRT may be simplified to reduce computational complexity. The simplified SPRT's are in fact modifications of the original SPRT detecting the regime and not the change. The tests are applied to the problem of fault detection in a gyro navigational system; the results of a detailed computer simulation are given.     

Altered expression of mRNAs implicated in osteogenesis under conditions of simulated microgravity is regulated by CD200:CD200R

Mouse calvarial cells grown under simulated microgravity conditions (neutral buoyancy) show preferential differentiation towards the osteoclast lineage, as defined by surrogate mRNAs, bone nodule growth and TRAP⁺ cells, when compared with cells cultured under normal gravity conditions. This effect was suppressed in cultures which contained the immunoregulatory molecule CD200, and conversely enhanced by anti-CD200 mAb. Concomitant increases occur in expression of inflammatory cytokines, and their mRNAs, under simulated microgravity conditions. Again cultures containing exogenous CD200 showed suppressed cytokine and cytokine mRNA expression. Further alterations in osteoclastogenesis were seen using cells isolated from cytokine-receptor knockout mice. We conclude that, as assessed by altered expression of mRNAs associated with osteoblast differentiation, CD200:CD200R interactions play an important regulatory role in the enhanced osteoclastogenesis seen under simulated microgravity conditions, with changes in cytokine expression further modulating this effect.     

Adaptive control for feedback-linearized missiles withuncertainties

A robust adaptive control scheme is proposed that can be applied to a practical autopilot design for feedback-linearized skid-to-turn (STT) missiles with aerodynamic uncertainties. The approach is to add a robust adaptive controller to a feedback-linearizing controller in order to reduce the influence of the aerodynamic uncertainties. The proposed robust adaptive control scheme is based on a sliding mode control technique with an adaptive law for estimating the unknown upper bounds of uncertain parameters. A feature of the proposed scheme is that missile systems with aerodynamic uncertainties can be controlled effectively over a wide operating range of flight conditions. It is shown, using Lyapunov stability theory, that the proposed scheme can give sufficient tracking capability and stability for a feedback-linearized STT missile with aerodynamic uncertainties. The six-degree-of-freedom nonlinear simulation results also show that good performance for several uncertainty models and engagement scenarios can be achieved by the proposed scheme in practical night conditions     

A multi-wavelength study of the merger candidate Abell S0721 and the activities of its member galaxies

We present a multi-wavelength study of the merging history and its influence on galaxy activities of a newly detected merger candidate – Abell S0721. This cluster was only known as a poor cluster in the Shapley Supercluster, but when several survey data of different wavelengths are combined, evidence of strong merging is revealed. We have analyzed the optical and X-ray structures of the cluster, as well as galaxy dynamics and properties of the radio galaxies in the cluster. The dynamics analysis shows the velocity distribution of this system is significantly deviated from a 1-Gaussian model, indicating the existence of 2–3 dynamically different sub-systems; in addition, both optical and X-ray structures of the cluster show an elongated and multi-clump structure, two X-ray clumps imaged by ROSAT All Sky Survey are well correlated with two galaxy density peaks. This cluster is possibly a merger of several groups; our analysis shows that the projection angle for two clumps in the main structure is possibly near the projection plane, and the substructure is seen at ∼30–75° from the projection plane. The merging process could also be the origin to boost the activities of its member galaxies. Finally, as compared with other merger candidates in the Shapley Supercluster, the radio galaxies identified in Abell S0721 are all optically luminous, and the fraction of luminous radio galaxies is only lower than one merger candidate (which is proposed to be at the very beginning of a merger event), this suggests Abell S0721 is also at the beginning of a merger event.     

A Probabilistic Strongest Neighbor Filter Algorithm for m Validated Measurements

A new form of the probabilistically strongest neighbor filter (PSNF) algorithm taking into account the number of validated measurements is proposed. The probabilistic nature of the strongest neighbor (SN) measurement in a cluttered environment is shown to be varied with respect to the number of validated measurements. Incorporating the number of validated measurements into design of the PSNF produces a consistent and cost effective data association method. Simulation studies show that the new filter is less sensitive to the unknown spatial clutter density and is more reliable for practical target tracking in nonhomogeneous clutter than the existing PSNF. It has similar performances to the probabilistic data association filter amplitude information (PDAF-AI) with much less computational complexities.