Current problems in the cultivation of Hydrogenomonas bacteria under controlled environments in the turbidostat
Environment effects on growth of Hydrogenomonas eutropha in dense culture
Foster, J. F.↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Current concepts of space flight induced changes in hormonal control of fluid and electrolyte metabolism
A systematic analysis of body fluid and renal dynamics during simulated space flight (head-down bedrest) was undertaken to increase understanding of the physiologic effects of acute cephalad fluid shifts. The earliest effects were increases in central venous pressure and decreases in plasma aldosterone, epinephrine and norepinephrine and glomerular filtration rate, 2 h after the beginning of bedrest. Decreases in plasma angiotensin I at 6 h may have resulted from the increased effective pressure and decreased sympathetic activity seen earlier in bedrest. The early decrease in aldosterone and ADH is thought to contribute to an increase, by 6 h, in urinary excretion of salt and water. Fluid and electrolyte losses occur during space flight, and analysis of body fluids from Space Shuttle crewmembers has indicated that conservation of these substances is begun almost immediately upon cessation of weightlessness. Operational medicine measures to counteract dehydration and electrolyte loss resulted in a less extreme physiologic response to the flight.
Leach, C. S.↗
Flight testing the X-29
A testing status report is presented for the X-29 forward-swept-wing experimental aircraft, which integrates such advanced technologies as an aeroelastically tailored composite wing, a thin supercritical airfoil, three-surface pitch control, discrete variable camber, full-authority close-coupled canards, static instability, and digital fly-by-wire flight controls. X-29 flight test results to date raise several issues pertinent to the design of future combat aircraft flight control systems; for example, they bring into question the current MIL-8785C requirements on control system time delays.
Smith, Rogers E.↗
Multivariable control of the Space Shuttle Remote Manipulator System using linearization by state feedback
This paper demonstrates an approach to nonlinear control system design that uses linearization by state feedback to allow faster maneuvering of payloads by the Shuttle Remote Manipulator System (SRMS). A nonlinear feedback law is defined to cancel the nonlinear plant dynamics so that a linear controller can be designed for the SRMS. First a nonlinear design model was generated via SIMULINK. This design model included nonlinear arm dynamics derived from the Lagrangian approach, linearized servo model, and linearized gearbox model. The current SRMS position hold controller was implemented on this system. Next, a trajectory was defined using a rigid body kinematics SRMS tool, KRMS. The maneuver was simulated. Finally, higher bandwidth controllers were developed. Results of the new controllers were compared with the existing SRMS automatic control modes for the Space Station Freedom Mission Build 4 Payload extended on the SRMS.
Gettman, Chang-Ching L.↗
Interplanetary magnetic field control of mantle precipitation and associated field-aligned currents
Dayside reconnection, which is particularly effective for a southward interplanetary magnetic field (IMF), allows magnetosheath particles to enter the magnetosphere where they form the plasma mantle. The motions of the reconnected flux tube produce convective flows in the ionosphere. It is known that the convection patterns in the polar cap are skewed to the dawnside for a positive IMF B(sub y) (or duskside for a negative IMF B(sub y)) in the northern polar cap. Correspondingly, one would expect to find asymmetric distributions of mantle particle precipitation, but previous results have been unclear. In this paper the correlation between B(sub y) and the distribution of mantle particle precipitation is studied for steady IMF conditions with southward IMF. Ion and electron data from the Defense Meteorological Satellite Program (DMSP) F6 and F7 satellites are used to identify the mantle region and IMP 8 is used as a solar wind monitor to characterize the IMF. We study the local time extension of mantle precipitation in the prenoon and postnoon regions. We find that, in accordance with theoretical expectations for a positive (negative) IMF B(sub y), mantle particle precipitation mainly appears in the prenoon region of the northern (southern) hemisphere. The mantle particle precipitation can extend to as early as 0600 magnetic local time (MLT) in the prenoon region but extends over a smaller local time region in the postnoon sector (we did not find mantle plasma beyond 1600 MLT in our data set although coverage is scant in this area). Magnetometer data from F7 are used to determine whether part of the region 1 current flows on open field lines. We find that at times part of the region 1 sense current extends into the region of mantle particle precipitation, and is therefore on open field lines. In other cases, region 1 currents are absent on open field lines. Most of the observed features can be readily interpreted in terms of the open magnetosphere model.
Xu, Dingan↗
A MEMS Nanopositioner With Integrated Tip for Scanning Tunneling Microscopy
Not provided.
Engineering↗
Spin-polarized currents in the tunnel contact of a normal conductor and a two-dimensional topological insulator
The spin filtering of electrons tunneling from the edge states of a two-dimensional topological insulator into a normal conductor under a magnetic field (external or induced due to proximity to a magnetic insulator) is studied. Calculations are performed for a tunnel contact of finite length between the topological insulator and an electronic multimode quantum strip. It is shown that the flow of tunneling electrons is split in the strip, so that spin-polarized currents arise in its left and right branches. These currents can be effectively controlled by the contact voltage and the chemical potential of the system. The presence of a magnetic field, which splits the spin subbands of the electron spectrum in the strip, gives rise to switching of the spin current between the strip branches.
36 MATERIALS SCIENCE↗
δ -Doping of oxygen vacancies dictated by thermodynamics in epitaxial SrTiO 3 films
Homoepitaxial SrTiO 3 (110) film is grown by molecular beam epitaxy in ultra-high vacuum with oxygen diffusing from substrate as the only oxidant. The resulted oxygen vacancies (V O s ) are found to be spatially confined within few subsurface layers only, forming a quasi-two-dimensional doped region with a tunable high concentration. Such a δ-function distribution of V O s is essentially determined by the thermodynamics associated with the surface reconstruction, and facilitated by the relatively high growth temperature. Here, our results demonstrate that it is feasible to tune V O s distribution at the atomic scale by controlling the lattice structure of oxide surfaces. Transition metal oxide interfaces have exhibited a variety of novel phenomena, including the high-mobility two-dimensional electron gas, superconductivity and unusual magnetism. While these phenomena are inherently related to the artificially designed architecture, oxygen vacancies (V O s ) are recognized to be particularly important in determining the exotic behaviors of the oxides systems. As electron donors in oxides, V O s were observed to be one of the major factors for the high carrier density at the LaAlO 3 /SrTiO 3 interface. V O s induce ferromagnetism in the epitaxial LaCoO 3 films via the ordering of excess electrons in Co 3d orbit. It was also suggested that the existence of V O s plays an important role in the formation of undesirable insulating phase in ultrathin films of many metallic oxide materials, referred to as the “dead layer” behavior. How V O s are involved in such complex phenomena is still unclear. One essential issue toward the design of emergent properties of oxide films is how to characterize and control V O s at the atomic scale. Recently, quantitative measurements of V O concentration have been realized with high spatial resolution benefited by the development of the state-of-the-art aberration-corrected scanning transmission microscope (STEM) and related spectroscopy techniques. However, tuning the V O density precisely by growth control is still extremely challenging. Different oxidants, i.e., molecular O 2 , O 3 and atomic O, have been used with different feeding pressure during the growth. This approach is limited by thermodynamics of the material since the pressure of oxidant has to coordinate with temperature and other parameters in order to ensure the formation of the desired phase. In many cases the optimal condition for oxygen stoichiometry cannot be reached, and residual V O s are inevitably formed. It has been reported that V O s even form inhomogeneous clusters in SrTiO 3 (STO) films. Post annealing is another thermodynamic approach and seems to be effective to reduce the V O density. However, it does not allow the precise control of V O s distribution at the atomic scale either. In the current work, to study the control of V O s at the atomic scale, we grow SrTiO 3 homoepitaxial films along the polar [110] direction. Atomically well-defined (4 × 1) reconstruction is maintained on the surface all through the growth [see Fig. 1 (a) and (b)], which compensates the polarity. More importantly, the energy configuration associated with the surface reconstruction results in the spatial confinement of V O s within only few subsurface layers of the film, while their concentration remains extremely low on the topmost surface and in the bulk of STO substrate. In conclusion, we show that such a quasi-two-dimensional (2D) V O -doped layer, mimicking the δ-doping case in conventional semiconductors, can be precisely controlled.
36 MATERIALS SCIENCE↗
Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling
We consider the generation of a pure spin-current at zero bias voltage with a single time-dependent potential. To such end we study a device made of a mesoscopic ring connected to electrodes and clarify the interplay between a magnetic flux, spin-orbit coupling, and non-adiabatic driving in the production of a spin and electrical current. By using Floquet theory, we show that the generated spin to charge current ratio can be controlled by tuning the spin-orbit coupling.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Controller modeling and evaluation for PCV electro-mechanical actuator
Hydraulic actuators are currently used to operate the propellant control valves (PCV) for the space shuttle main engine (SSME) and other rocket engines. These actuators are characterized by large power to weight ratios, large force capabilities, and rapid accelerations, which favor their use in control valve applications. However, hydraulic systems are also characterized by susceptibility to contamination, which leads to frequent maintenance requirements. The Control Mechanisms Branch (EP34) of the Component Development Division of the Propulsion Laboratory at the Marshall Space Flight Center (MSFC) has been investigating the application of electromechanical actuators as replacements for the hydraulic units in PCV's over the last few years. This report deals with some testing and analysis of a PCV electromechanical actuator (EMA) designed and fabricated by HR Textron, Inc. This prototype actuator has undergone extensive testing by EP34 personnel since early 1993. At this time, the performance of the HR Textron PCV EMA does not meet requirements for position tracking.
Parker, Joey K.↗
System Design and Performance of the Two-Gyro Science Mode For the Hubble Space Telescope
For fifteen years, the science mission of the Hubble Space Telescope (HST) required using at least three of the six on-board rate gyros for attitude control. Failed gyros were eventually replaced through Space Shuttle Servicing Missions. The tragic loss of the Space Shuttle Columbia has resulted in the cancellation of all planned Shuttle based missions to HST. While a robotic servicing mission is currently being planned instead, controlling with alternate sensors to replace failed gyros can extend the HST science gathering until a servicing mission can be performed, and also extend science at HST's end of life. Additionally, sufficient performance may allow a permanent transition to operations with less than 3 gyros (by intentionally turning off working gyros saving them for later use) allowing for an even greater science mission extension. To meet this need, a Two Gyro Science (TGS) mode has been designed and implemented using magnetometers (Magnetic Sensing System - MSS), Fixed Head Star Trackers (FHSTs), and Fine Guidance Sensors (FGSs) to control vehicle rate about the missing gyro input axis. The development of the TGS capability is the largest re-design of HST operations undertaken, since it affects several major spacecraft subsystems, the most heavily being the Pointing Control System (PCS) and Flight Software (FSW). Additionally, and equally important, are the extensive modifications and enhancements of the Planning and Scheduling system which must now be capable of scheduling science observations while taking into account several new constraints imposed by the TGS operational modes (such as FHST availability and magnetic field geometry) that will impact science gathering efficiency and target availability. This paper discusses the systems engineering design, development, and performance of the TGS mode, now in its final stages of completion.
Prior, Michael↗
System Design and Performance of the Two-Gyro Science Mode For the Hubble Space Telescope
For fifteen years, the science mission of the Hubble Space Telescope (HST) required using at least three of the six on-board rate gyros for attitude control. Failed gyros were eventually replaced through Space Shuttle Servicing Missions. The tragic loss of the Space Shuttle Columbia has resulted in the cancellation of all planned Shuttle based missions to HST. While a robotic servicing mission is currently being planned instead, controlling with alternate sensors to replace failed gyros can extend the HST science gathering until a servicing mission can be performed, and also extend science at HST s end of life. Additionally, sufficient performance may allow a permanent transition to operations with less than 3 gyros (by intentionally turning off working gyros saving them for later use) allowing for an even greater science mission extension. To meet this need, a Two Gyro Science (TGS) mode has been designed and implemented using magnetometers (Magnetic Sensing System - MSS), Fixed Head Star Trackers (FHSTs), and Fine Guidance Sensors (FGSs) to control vehicle rate about the missing gyro input axis. The development of the TGS capability is the largest re-design of HST operations undertaken, since it affects several major spacecraft subsystems, the most heavily being the Pointing Control System (PCS) and Flight Software (FSW). Additionally, and equally important, are the extensive modifications and enhancements of the Planning and Scheduling system which must now be capable of scheduling science observations while taking into account several new constraints imposed by the TGS operational modes (such as FHST availability and magnetic field geometry) that will impact science gathering efficiency and target availability. This paper discusses the systems engineering design, development, and performance of the TGS mode, now in its final stages of completion.
Prior, Michael↗
The microstructure and property variations of metals induced by electric current treatment: A review
Heat treatment has been widely applied for manipulating the microstructure and properties of metals with thermal energy. The thermal energy triggers the atomic diffusion accompanied by dislocation movement and results in the subsequent property variations in metals. One of the attractive efforts in the past decades is the development of a direct treatment of metals with electric current stressing as an alternative method for conventional heat treatment. Electric current treatment provides thermal energy from Joule heat (thermal effect) and kinetic energy from electron momentum (athermal effect). This article reviewed the practices of electric current treatment, microstructure-property variations and the physical metallurgy involved in a variety of metals. Both thermal and athermal effects have been well recognized in the literatures. An appropriate manipulation of the electric current treatment enables the control of both effects and thus the microstructure and properties of metals.
36 MATERIALS SCIENCE↗
Description of a magnetic bearing test fixture
A description of a microcomputer controlled magnetic bearing test fixture is presented. Parameters which are controlled are magnetic bearing current and gaps. Parameters which are measured are magnetic bearing gaps, magnetic flux in the bearing gaps, and bearing forces. The test fixture is configured for bearing elements similar to those used in a laboratory test model Annular Momentum Control Device (AMCD).
Groom, Nelson J.↗
Flight control actuation system
A flight control actuation system comprises a controller, electromechanical actuator and a pneumatic actuator. During normal operation, only the electromechanical actuator is needed to operate a flight control surface. When the electromechanical actuator load level exceeds 40 amps positive, the controller activates the pneumatic actuator to offset electromechanical actuator loads to assist the manipulation of flight control surfaces. The assistance from the pneumatic load assist actuator enables the use of an electromechanical actuator that is smaller in size and mass, requires less power, needs less cooling processes, achieves high output forces and adapts to electrical current variations. The flight control actuation system is adapted for aircraft, spacecraft, missiles, and other flight vehicles, especially flight vehicles that are large in size and travel at high velocities.
Wingett, Paul T.↗
Flight control actuation system
A flight control actuation system comprises a controller, electromechanical actuator and a pneumatic actuator. During normal operation, only the electromechanical actuator is needed to operate a flight control surface. When the electromechanical actuator load level exceeds 40 amps positive, the controller activates the pneumatic actuator to offset electromechanical actuator loads to assist the manipulation of flight control surfaces. The assistance from the pneumatic load assist actuator enables the use of an electromechanical actuator that is smaller in size and mass, requires less power, needs less cooling processes, achieves high output forces and adapts to electrical current variations. The flight control actuation system is adapted for aircraft, spacecraft, missiles, and other flight vehicles, especially flight vehicles that are large in size and travel at high velocities.
Wingett, Paul T.↗
Automated Eddy Current Inspection on Space Shuttle Hardware
Over the life time of the Space Shuttle program, metal parts used for the Reusable Solid Rocket Motors (RSRMs) have been nondestructively inspected for cracks and surface breaking discontinuities using magnetic particle (steel) and penetrant methods. Although these inspections adequately screened for critical sized cracks in most regions of the hardware, it became apparent after detection of several sub-critical flaws that the processes were very dependent on operator attentiveness and training. Throughout the 1990's, eddy current inspections were added to areas that had either limited visual access or were more fracture critical. In the late 1990's. a project was initiated to upgrade NDE inspections with the overall objective of improving inspection reliability and control. An automated eddy current inspection system was installed in 2001. A figure shows one of the inspection bays with the robotic axis of the system highlighted. The system was programmed to inspect the various case, nozzle, and igniter metal components that make up an RSRM. both steel and aluminum. For the past few years, the automated inspection system has been a part of the baseline inspection process for steel components. Although the majority of the RSRM metal part inventory ts free of detectable surface flaws, a few small, sub-critical manufacturing defects have been detected with the automated system. This paper will summarize the benefits that have been realized with the current automated eddy current system, as well as the flaws that have been detected.
Hartmann, John↗
Natural Language Understanding and Extraction of Flight Constraints Recorded in Letters of Agreement
This paper presents an automated information extraction and inference technique using natural language processing for extracting flight operational procedures and constraints embedded in heritage air traffic management documents. The extracted flight constraints can be digitized and fit into existing airspace information exchange models such as the Aeronautical Information Exchange Model (AIXM). This approach offers a digitized solution to disseminate airspace operating conditions to diverse air users and stakeholders in the National Airspace System (NAS). Furthermore, the digitized flight procedures can provide operational flexibility for emerging advanced air mobility providers and reduce traffic controller workload while maintaining current safety standards. To demonstrate this process, 1,972 Letters of Agreement (LOAs) have been selected for processing, named entity extraction, constraint identification and extraction. This dataset is derived from a subset of documents related to Air Route Traffic Control Centers (ARTCC) operations. We experimented with various traditional information extraction techniques, state-of-the-art machine learning and deep learning models to perform named entity recognition and pattern recognition on our dataset. We present the results from our experiments and demonstrate 99.0% F-1 score for named entity recognition, and a 96.6% accuracy for our entire workflow up to named entity recognition. We also discuss constraint definitions using generic patterned templates and extensions to this work in applying entity linking to digitally extracting relevant constraints.
Natural Language Processing↗