WorldWideScience

Sample records for spacecraft gains momentum

  1. Spacecraft momentum control systems

    CERN Document Server

    Leve, Frederick A; Peck, Mason A

    2015-01-01

    The goal of this book is to serve both as a practical technical reference and a resource for gaining a fuller understanding of the state of the art of spacecraft momentum control systems, specifically looking at control moment gyroscopes (CMGs). As a result, the subject matter includes theory, technology, and systems engineering. The authors combine material on system-level architecture of spacecraft that feature momentum-control systems with material about the momentum-control hardware and software. This also encompasses material on the theoretical and algorithmic approaches to the control of space vehicles with CMGs. In essence, CMGs are the attitude-control actuators that make contemporary highly agile spacecraft possible. The rise of commercial Earth imaging, the advances in privately built spacecraft (including small satellites), and the growing popularity of the subject matter in academic circles over the past decade argues that now is the time for an in-depth treatment of the topic. CMGs are augmented ...

  2. Hydrogen gains further momentum

    International Nuclear Information System (INIS)

    Anon.

    2017-01-01

    As first industrial production projects should become a reality in the next few years, hydrogen as a source of energy will find important applications with mobility, which momentum is rapid and irresistible. Next steps will be the (large capacity) storage of hydrogen associated to power-to-gas systems and the generalization of renewable energies. This document presents 5 articles, which themes are: Description and explanation of the process of hydrogen production; Presentation of the H2V project for the construction, in Normandy, of the first operational industrial hydrogen production plant using electric power 100 pc generated by renewable energies; The conversion of electric power from renewable energies through hydrogen storage and fuel cells for buildings applications (Sylfen project); The development of a reversible fuel cell at Mines-Paris Tech University, that will be adapted to the storage of renewable electric power; Hydrogen as a lever for the development of zero-emission vehicles, from trucks to cars and bicycles

  3. High Gain Antenna Calibration on Three Spacecraft

    Science.gov (United States)

    Hashmall, Joseph A.

    2011-01-01

    This paper describes the alignment calibration of spacecraft High Gain Antennas (HGAs) for three missions. For two of the missions (the Lunar Reconnaissance Orbiter and the Solar Dynamics Observatory) the calibration was performed on orbit. For the third mission (the Global Precipitation Measurement core satellite) ground simulation of the calibration was performed in a calibration feasibility study. These three satellites provide a range of calibration situations-Lunar orbit transmitting to a ground antenna for LRO, geosynchronous orbit transmitting to a ground antenna fer SDO, and low Earth orbit transmitting to TDRS satellites for GPM The calibration results depend strongly on the quality and quantity of calibration data. With insufficient data the calibration Junction may give erroneous solutions. Manual intervention in the calibration allowed reliable parameters to be generated for all three missions.

  4. Alternative Fuels Data Center: Little Rock Gains Momentum with Natural Gas

    Science.gov (United States)

    Buses Little Rock Gains Momentum with Natural Gas Buses to someone by E-mail Share Alternative Fuels Data Center: Little Rock Gains Momentum with Natural Gas Buses on Facebook Tweet about Alternative Fuels Data Center: Little Rock Gains Momentum with Natural Gas Buses on Twitter Bookmark Alternative

  5. Development of a Hardware-In-Loop (HIL Simulator for Spacecraft Attitude Control Using Momentum Wheels

    Directory of Open Access Journals (Sweden)

    Dohee Kim

    2008-12-01

    Full Text Available In this paper, a Hardware-In-the-Loop simulator to simulate attitude control of spacecraft using momentum wheels is developed. The simulator consists of a spherical air bearing system allowing rotation and tilt in all three axes, three momentum wheels for actuation, and an AHRS (Attitude Heading Reference System. The simulator processes various types of data in PC104 and wirelessly communicates with a host PC using TCP/IP protocol. A simple low-cost momentum wheel assembly set and its drive electronics are also developed. Several experiments are performed to test the performance of the momentum wheels. For the control performance test of the simulator, a PID controller is implemented. The results of experimental demonstrations confirm the feasibility and validity of the Hardware-In-the-Loop simulator developed in the current study.

  6. A feedback linearization approach to spacecraft control using momentum exchange devices. Ph.D. Thesis

    Science.gov (United States)

    Dzielski, John Edward

    1988-01-01

    Recent developments in the area of nonlinear control theory have shown how coordiante changes in the state and input spaces can be used with nonlinear feedback to transform certain nonlinear ordinary differential equations into equivalent linear equations. These feedback linearization techniques are applied to resolve two problems arising in the control of spacecraft equipped with control moment gyroscopes (CMGs). The first application involves the computation of rate commands for the gimbals that rotate the individual gyroscopes to produce commanded torques on the spacecraft. The second application is to the long-term management of stored momentum in the system of control moment gyroscopes using environmental torques acting on the vehicle. An approach to distributing control effort among a group of redundant actuators is described that uses feedback linearization techniques to parameterize sets of controls which influence a specified subsystem in a desired way. The approach is adapted for use in spacecraft control with double-gimballed gyroscopes to produce an algorithm that avoids problematic gimbal configurations by approximating sets of gimbal rates that drive CMG rotors into desirable configurations. The momentum management problem is stated as a trajectory optimization problem with a nonlinear dynamical constraint. Feedback linearization and collocation are used to transform this problem into an unconstrainted nonlinear program. The approach to trajectory optimization is fast and robust. A number of examples are presented showing applications to the proposed NASA space station.

  7. A parametric study of the behavior of the angular momentum vector during spin rate changes of rigid body spacecraft

    Science.gov (United States)

    Longuski, J. M.

    1982-01-01

    During a spin-up or spin-down maneuver of a spinning spacecraft, it is usual to have not only a constant body-fixed torque about the desired spin axis, but also small undesired constant torques about the transverse axes. This causes the orientation of the angular momentum vector to change in inertial space. Since an analytic solution is available for the angular momentum vector as a function of time, this behavior can be studied for large variations of the dynamic parameters, such as the initial spin rate, the inertial properties and the torques. As an example, the spin-up and spin-down maneuvers of the Galileo spacecraft was studied and as a result, very simple heuristic solutions were discovered which provide very good approximations to the parametric behavior of the angular momentum vector orientation.

  8. Spacecraft Angular Rates Estimation with Gyrowheel Based on Extended High Gain Observer

    Directory of Open Access Journals (Sweden)

    Xiaokun Liu

    2016-04-01

    Full Text Available A gyrowheel (GW is a kind of electronic electric-mechanical servo system, which can be applied to a spacecraft attitude control system (ACS as both an actuator and a sensor simultaneously. In order to solve the problem of two-dimensional spacecraft angular rate sensing as a GW outputting three-dimensional control torque, this paper proposed a method of an extended high gain observer (EHGO with the derived GW mathematical model to implement the spacecraft angular rate estimation when the GW rotor is working at large angles. For this purpose, the GW dynamic equation is firstly derived with the second kind Lagrange method, and the relationship between the measurable and unmeasurable variables is built. Then, the EHGO is designed to estimate and calculate spacecraft angular rates with the GW, and the stability of the designed EHGO is proven by the Lyapunov function. Moreover, considering the engineering application, the effect of measurement noise in the tilt angle sensors on the estimation accuracy of the EHGO is analyzed. Finally, the numerical simulation is performed to illustrate the validity of the method proposed in this paper.

  9. Robust control for spacecraft rendezvous system with actuator unsymmetrical saturation: a gain scheduling approach

    Science.gov (United States)

    Wang, Qian; Xue, Anke

    2018-06-01

    This paper has proposed a robust control for the spacecraft rendezvous system by considering the parameter uncertainties and actuator unsymmetrical saturation based on the discrete gain scheduling approach. By changing of variables, we transform the actuator unsymmetrical saturation control problem into a symmetrical one. The main advantage of the proposed method is improving the dynamic performance of the closed-loop system with a region of attraction as large as possible. By the Lyapunov approach and the scheduling technology, the existence conditions for the admissible controller are formulated in the form of linear matrix inequalities. The numerical simulation illustrates the effectiveness of the proposed method.

  10. A Preliminary Model for Spacecraft Propulsion Performance Analysis Based on Nuclear Gain and Subsystem Mass-Power Balances

    Science.gov (United States)

    Chakrabarti, Suman; Schmidt, George R.; Thio, Y. C.; Hurst, Chantelle M.

    1999-01-01

    A preliminary model for spacecraft propulsion performance analysis based on nuclear gain and subsystem mass-power balances are presented in viewgraph form. For very fast missions with straight-line trajectories, it has been shown that mission trip time is proportional to the cube root of alpha. Analysis of spacecraft power systems via a power balance and examination of gain vs. mass-power ratio has shown: 1) A minimum gain is needed to have enough power for thruster and driver operation; and 2) Increases in gain result in decreases in overall mass-power ratio, which in turn leads to greater achievable accelerations. However, subsystem mass-power ratios and efficiencies are crucial: less efficient values for these can partially offset the effect of nuclear gain. Therefore, it is of interest to monitor the progress of gain-limited subsystem technologies and it is also possible that power-limited systems with sufficiently low alpha may be competitive for such ambitious missions. Topics include Space flight requirements; Spacecraft energy gain; Control theory for performance; Mission assumptions; Round trips: Time and distance; Trip times; Vehicle acceleration; and Minimizing trip times.

  11. Gaining Momentum: How Media Influences Public Opinion To Push Civil-Military Decision Makers Into Formulating Foreign Policy

    Science.gov (United States)

    2016-02-09

    1 AIR WAR COLLEGE AIR UNIVERSITY GAINING MOMENTUM: HOW MEDIA INFLUENCES PUBLIC OPINION TO PUSH CIVIL-MILITARY DECISION MAKERS INTO...engagements from the past, evidence suggest the media or press does have an influence over public opinion, especially during times of war and humanitarian...changes and that leaders must take into consideration that public opinion and the media may provide a large amount of influence over how the nation

  12. An Application of the "Virtual Spacecraft" Concept in Evaluation of the Mars Pathfinder Lander Low Gain Antenna

    Science.gov (United States)

    Pogorzelski, R. J.; Beckon, R. J.

    1997-01-01

    The virtual spacecraft concept is embodied in a set of subsystems, either in the form of hardware or computational models, which together represent all, or a portion of, a spacecraft. For example, the telecommunications transponder may be a hardware prototype while the propulsion system may exist only as a simulation. As the various subsystems are realized in hardware, the spacecraft becomes progressively less virtual. This concept is enabled by JPL's Mission System Testbed which is a set of networked workstations running a message passing operating system called "TRAMEL" which stands for Task Remote Asynchronous Message Exchange Layer. Each simulation on the workstations, which may in fact be hardware controlled by the workstation, "publishes" its operating parameters on TRAMEL and other simulations requiring those parameters as input may "subscribe" to them. In this manner, the whole simulation operates as a single virtual system. This paper describes a simulation designed to evaluate a communications link between the earth and the Mars Pathfinder Lander module as it descends under a parachute through the Martian atmosphere toward the planet's surface. This link includes a transmitter and a low gain antenna on the spacecraft and a receiving antenna and receiver on the earth as well as a simulation of the dynamics of the spacecraft. The transmitter, the ground station antenna, the receiver and the dynamics are all simulated computationally while the spacecraft antenna is implemented in hardware on a very simple spacecraft mockup. The dynamics simulation is a record of one output of the ensemble of outputs of a Monte Carlo simulation of the descent. Additionally, the antenna/spacecraft mock-up system was simulated using APATCH, a shooting and bouncing ray code developed by Demaco, Inc. The antenna simulation, the antenna hardware, and the link simulation are all physically located in different facilities at JPL separated by several hundred meters and are linked via

  13. Mission Capability Gains from Multi-Mode Propulsion Thrust Variations on a Variety Spacecraft Orbital Maneuvers

    Science.gov (United States)

    2011-03-01

    Geocentric -Equatorial Reference Frame2 ....................................................................... 31  Figure 8: Perifocal and Geocentric ...67  Figure 25: Mission 3 Geocentric Equatorial Reference Frame ...................................................... 69  Figure 26: Mission 3...but at the cost of the propellant required. Spacecraft electric propulsion systems provide high specific impulse which result in low propellant

  14. Megawatt wind turbines gaining momentum

    International Nuclear Information System (INIS)

    Oehlenschlaeger, K.; Madsen, B.T.

    1996-01-01

    Through the short history of the modern wind turbine, electric utilities have made it amply clear that they have held a preference for large scale wind turbines over smaller ones, which is why wind turbine builders through the years have made numerous attempts develop such machines - machines that would meet the technical, aesthetic and economic demands that a customer would require. Considerable effort was put into developing such wind turbines in the early 1980s. There was the U.S. Department of Energy's MOD 1-5 program, which ranged up to 3.2 MW, Denmark's Nibe A and B, 630 kW turbine and the 2 MW Tjaereborg machine, Sweden's Naesudden, 3 MW, and Germany's Growian, 3 MW. Most of these were dismal failures, though some did show the potential of MW technology. (au)

  15. Alpha Momentum and Price Momentum

    Directory of Open Access Journals (Sweden)

    Hannah Lea Hühn

    2018-05-01

    Full Text Available We analyze a novel alpha momentum strategy that invests in stocks based on three-factor alphas which we estimate using daily returns. The empirical analysis for the U.S. and for Europe shows that (i past alpha has power in predicting the cross-section of stock returns; (ii alpha momentum exhibits less dynamic factor exposures than price momentum and (iii alpha momentum dominates price momentum only in the U.S. Connecting both strategies to behavioral explanations, alpha momentum is more related to an underreaction to firm-specific news while price momentum is primarily driven by price overshooting due to momentum trading.

  16. Angular Momentum

    Science.gov (United States)

    Shakur, Asif; Sinatra, Taylor

    2013-01-01

    The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

  17. Open Access publishing in physics gains momentum

    CERN Multimedia

    2006-01-01

    The first meeting of European particle physics funding agencies took place on 3 November at CERN to establish a consortium for Open Access publishing in particle physics, SCOAP3 (Sponsoring Consortium for Open Access Publishing in Particle Physics). Open Access could transform the academic publishing world, with a great impact on research. The traditional model of research publication is funded through reader subscriptions. Open Access will turn this model on its head by changing the funding structure of research results, without increasing the overall cost of publishing. Instead of demanding payment from readers, publications will be distributed free of charge, financed by funding agencies via laboratories and the authors. This new concept will bring greater benefits and broaden opportunities for researchers and funding agencies by providing unrestricted distribution of the results of publicly funded research. The meeting marked a positive step forward, with international support from laboratories, fundin...

  18. 1999 Annual report: Gaining momentum, creating value

    International Nuclear Information System (INIS)

    2000-01-01

    Danoil Energy is an oil and gas company engaged in exploration, development and acquisition of both oil and natural gas reserves in western Canada. The company is based in Calgary. In 1999, the company had revenues of $29.5 million from natural gas sales and from the sale of crude oil and natural gas liquids, an increase of 56 per cent over the previous year. Net earnings amounted to $2.7 million, or 12 cents a share. Production also increased about 15 per cent in 1999 and is forecast to increase 32 per cent over 1999 levels in 2000. Production has been replaced by 150 per cent, bringing current total reserves to 29,239 MMcf/d of natural gas and 11,238 Mbbls of crude oil and natural gas liquids. The company has 71,149 acres of undeveloped lands. The report contains a review of the property, a review of operations, consolidated financial statements, and management's analysis and discussion of operating and financial results

  19. Open access publishing in physics gains momentum

    CERN Multimedia

    2006-01-01

    "The first meeting of European particle physics funding agencies took place today at CERN to establish a consortium for Open Access publishing in particle physics, SCOAP3. This is the first time an antire scientific field is exploring the conversion of its reader-paid journals into an author-paid Open Access format." (1 page)

  20. Open Access publishing in physics gains momentum

    CERN Multimedia

    2006-01-01

    "As if inventing the World-Wide Web were not revolutionary enough, the European Organisation for Nuclear Research (CERN) is now on its way to unleashing a paradigm shift in the world of academic publishing. For the first time ever, an entire scientific field is exploring the possibility of converting its reader-paid journals into an author-pai Open Access format." (1 page)

  1. Possibilities for private facility gain momentum

    International Nuclear Information System (INIS)

    Tompkins, B.

    1994-01-01

    In a resounding show of support for the development of a private monitored retrievable storage (MRS) facility for the storage of spent commercial nuclear fuel, 33 utilities and two nuclear industry contractors have signed on with the Mescalero Apache Tribe and Northern States Power Company to further explore such a project. Representatives from 34 utilities gathered on the Mescalero Apache Reservation in southern New Mexico on March 10-11 to hear the tribe's proposal for a privately owned and operated MRS. The preliminary business plan developed for the project sets forth the terms of facility use for utilities that are interested in joining, estimates implementation costs, and describes storage capacity requirements. The Mescaleros would have majority ownership in the venture, and a board of directors would represent equity holders. Completion of the project would be contingent on the ability of NSP and the Mescaleros to site and license the facility; to agree on a design; to finish construction and begin operation; to ensure an adequate system for transport of spent fuel to the site; and to plan for site remediation

  2. Seamless service: maintaining momentum.

    Science.gov (United States)

    Grinstead, N; Timoney, R

    1994-01-01

    Describes the process used by the Mater Infirmorum Hospital in Belfast in 1992-1994 to achieve high quality care (Seamless Service), motivate staff to deliver and measure performance. Aims of the project include focusing the organization on the customer, improving teamwork and motivation at all levels. After comprehensive data collection from GPs, patients and staff management forums developed a full TQM strategy to gain support and maintain momentum including innovative staff events (every staff member was given the opportunity to attend) where multilevel, multidisciplinary workshops enabled staff to design customer care standards, develop teams and lead customer-driven change.

  3. Spacecraft operations

    CERN Document Server

    Sellmaier, Florian; Schmidhuber, Michael

    2015-01-01

    The book describes the basic concepts of spaceflight operations, for both, human and unmanned missions. The basic subsystems of a space vehicle are explained in dedicated chapters, the relationship of spacecraft design and the very unique space environment are laid out. Flight dynamics are taught as well as ground segment requirements. Mission operations are divided into preparation including management aspects, execution and planning. Deep space missions and space robotic operations are included as special cases. The book is based on a course held at the German Space Operation Center (GSOC).

  4. Spacecraft radiator systems

    Science.gov (United States)

    Anderson, Grant A. (Inventor)

    2012-01-01

    A spacecraft radiator system designed to provide structural support to the spacecraft. Structural support is provided by the geometric "crescent" form of the panels of the spacecraft radiator. This integration of radiator and structural support provides spacecraft with a semi-monocoque design.

  5. Large momentum transfer phenomena

    International Nuclear Information System (INIS)

    Imachi, Masahiro; Otsuki, Shoichiro; Matsuoka, Takeo; Sawada, Shoji.

    1978-01-01

    The large momentum transfer phenomena in hadron reaction drastically differ from small momentum transfer phenomena, and are described in this paper. Brief review on the features of the large transverse momentum transfer reactions is described in relation with two-body reactions, single particle productions, particle ratios, two jet structure, two particle correlations, jet production cross section, and the component of momentum perpendicular to the plane defined by the incident protons and the triggered pions and transverse momentum relative to jet axis. In case of two-body process, the exponent N of the power law of the differential cross section is a value between 10 to 11.5 in the large momentum transfer region. The breaks of the exponential behaviors into the power ones are observed at the large momentum transfer region. The break would enable to estimate the order of a critical length. The large momentum transfer phenomena strongly suggest an important role of constituents of hadrons in the hard region. Hard rearrangement of constituents from different initial hadrons induces large momentum transfer reactions. Several rules to count constituents in the hard region have been proposed so far to explain the power behavior. Scale invariant quark interaction and hard reactions are explained, and a summary of the possible types of hard subprocess is presented. (Kato, T.)

  6. Introducing Conservation of Momentum

    Science.gov (United States)

    Brunt, Marjorie; Brunt, Geoff

    2013-01-01

    The teaching of the principle of conservation of linear momentum is considered (ages 15 + ). From the principle, the momenta of two masses in an isolated system are considered. Sketch graphs of the momenta make Newton's laws appear obvious. Examples using different collision conditions are considered. Conservation of momentum is considered…

  7. Attention and Representational Momentum

    OpenAIRE

    Hayes, Amy; Freyd, Jennifer J

    1995-01-01

    Representational momentum, the tendency for memory to be distorted in the direction of an implied transformation, suggests that dynamics are an intrinsic part of perceptual representations. We examined the effect of attention on dynamic representation by testing for representational momentum under conditions of distraction. Forward memory shifts increase when attention is divided. Attention may be involved in halting but not in maintaining dynamic representations.

  8. On momentum conservation

    International Nuclear Information System (INIS)

    Karastoyanov, A.

    1990-01-01

    The relativistic law of momentum transformation shows that the sum of momenta of even isolated particles is not invariable in all inertial reference systems. This is connected with the relativistic change of kinetic energy and mass of a system of particles in result of internal interactions. The paper proposes a short and simple proof on the necessity of potential momentum. The momentum conservation law (for all interactions in the Minkowski world) is expressed in a generalized form. The constancy of the sum of kinetic and potential momentum of closed system of particles is shown. The energy conservation is a necessary condition. The potential momentum is defined as usual (e.g. as in the Berkeley Physics Course). (author). 13 refs

  9. Momentum fractionation on superstrata

    International Nuclear Information System (INIS)

    Bena, Iosif; Martinec, Emil; Turton, David; Warner, Nicholas P.

    2016-01-01

    Superstrata are bound states in string theory that carry D1, D5, and momentum charges, and whose supergravity descriptions are parameterized by arbitrary functions of (at least) two variables. In the D1-D5 CFT, typical three-charge states reside in high-degree twisted sectors, and their momentum charge is carried by modes that individually have fractional momentum. Understanding this momentum fractionation holographically is crucial for understanding typical black-hole microstates in this system. We use solution-generating techniques to add momentum to a multi-wound supertube and thereby construct the first examples of asymptotically-flat superstrata. The resulting supergravity solutions are horizonless and smooth up to well-understood orbifold singularities. Upon taking the AdS_3 decoupling limit, our solutions are dual to CFT states with momentum fractionation. We give a precise proposal for these dual CFT states. Our construction establishes the very nontrivial fact that large classes of CFT states with momentum fractionation can be realized in the bulk as smooth horizonless supergravity solutions.

  10. Quark Orbital Angular Momentum

    Directory of Open Access Journals (Sweden)

    Burkardt Matthias

    2015-01-01

    Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.

  11. Optical Angular Momentum

    International Nuclear Information System (INIS)

    Arimondo, Ennio

    2004-01-01

    For many years the Institute of Physics has published books on hot topics based on a collection of reprints from different journals, including some remarks by the editors of each volume. The book on Optical Angular Momentum, edited by L Allen, S M Barnett and M J Padgett, is a recent addition to the series. It reproduces forty four papers originally published in different journals and in a few cases it provides direct access to works not easily accessible to a web navigator. The collection covers nearly a hundred years of progress in physics, starting from an historic 1909 paper by Poynting, and ending with a 2002 paper by Padgett, Barnett and coworkers on the measurement of the orbital angular momentum of a single photon. The field of optical angular momentum has expanded greatly, creating an interdisciplinary attraction for researchers operating in quantum optics, atomic physics, solid state physics, biophysics and quantum information theory. The development of laser optics, especially the control of single mode sources, has made possible the specific design of optical radiation modes with a high degree of control on the light angular momentum. The editors of this book are important figures in the field of angular momentum, having contributed to key progress in the area. L Allen published an historical paper in 1999, he and M J Padgett (together with M Babiker) produced few years ago a long review article which is today still the most complete basic introduction to the angular momentum of light, while S M Barnett has contributed several high quality papers to the progress of this area of physics. The editors' choice provides an excellent overview to all readers, with papers classified into eight different topics, covering the basic principles of the light and spin and orbital angular momentum, the laboratory tools for creating laser beams carrying orbital angular momentum, the optical forces and torques created by laser beams carrying angular momentum on

  12. Momentum, March 2016

    OpenAIRE

    2016-01-01

    Momentum is the quarterly magazine of the Department of Mechanical Engineering at Virginia Tech. In this issue: Lead-free piezoelectric material in development; Harnessing the energy of ocean waves; Meet the Hyperloop team; Maleshia Jones - Graduate student with focus.

  13. MD 2179: Scraping of off-momentum halo after injection

    CERN Document Server

    Garcia Morales, Hector; Patecki, Marcin; Wretborn, Sven Joel; CERN. Geneva. ATS Department

    2018-01-01

    In this MD, a beam scraping was performed using the momentum primary collimator in IR3 where dispersion is high. A second scraping was performed using a TCSG in IR7 where dispersion is almost negligible. In such a way, we aim to disentangle the contribution of off-momentum particles to halo population. These scrapings will provide useful information to better understand the usual off-momentum losses we see at the start of the ramp. The MD results would also be used to benchmark simulations of off-momentum beam losses in order to gain confidence in simulation models.

  14. Computational design gains momentum in enzyme catalysis engineering

    NARCIS (Netherlands)

    Wijma, Hein J.; Janssen, Dick B.

    Computational protein design is becoming a powerful tool for tailoring enzymes for specific biotechnological applications. When applied to existing enzymes, computational re-design makes it possible to obtain orders of magnitude improvement in catalytic activity towards a new target substrate.

  15. Gaining Momentum, Losing Ground. Tapping America's Potential, Progress Report 2008

    Science.gov (United States)

    Tapping America's Potential, 2008

    2008-01-01

    In July 2005, 15 of America's most prominent business organizations joined together to express their deep concern about the ability of the United States to sustain its scientific and technological leadership in a world where newly energized foreign competitors are investing in the capacity for innovation--the key driver of productivity and…

  16. Exports of Finnish wind power technology gaining momentum

    International Nuclear Information System (INIS)

    2005-01-01

    In the 1990s, Finnish companies in the wind power sector focused on supplying advanced components and materials. This capability has now extended to cover entire turbines and wind farms. Winwind Oy, based in northern Finland, has developed a new type of solution for the export market, combining the advantages of modem direct drives with those of traditional high-speed gear systems

  17. "Genetic Engineering" Gains Momentum (Science/Society Case Study).

    Science.gov (United States)

    Moore, John W.; Moore, Elizabeth A., Eds.

    1980-01-01

    Reviews the benefits and hazards of genetic engineering, or "recombinant-DNA" research. Recent federal safety rules issued by NIH which ease the strict prohibitions on recombinant-DNA research are explained. (CS)

  18. Selling and Building Linked Data: Drive Value and Gain Momentum

    Science.gov (United States)

    Harris, Kristen

    Data inside enterprises is exploding. Routinely key decision makers state, "one of the most valuable assets of our organization is actionable information." Paradoxically, it is often challenging to gather the necessary metrics to build a business case to justify a Linked Data initiative for improved data quality in the face of the well-documented shortcomings of traditional enterprise approaches to data management. Internet standards have matured considerably in the last decade. The number of linked data sets is growing daily and already exceeds well in excess of ten thousand data sets, over 400 of which are published via the US Government at gov as of April 2010. Many of these linked data sets are high quality. Best practices for linking data within the enterprise are increasingly being published in articles, blogs and technical books. One of the pioneering linked enterprise data projects was undertaken by a Fortune 500 company in the early 2000 timeframe. The lessons learned about how to navigate the management and organizational dynamics are relevant today. This chapter outlines the successful strategies for a linked enterprise data initiative, including a consistent metadata management strategy across lines of business, definition and documentation of data ownership and the value of cross-functional teams in the definition, development and deployment of the project.

  19. Angular momentum in general relativity

    International Nuclear Information System (INIS)

    Cresswell, A.; Zimmerman, R.L.; Oregon Univ., Eugene

    1986-01-01

    It is argued that the correct expressions for the angular momentum flux carried by gravitational radiation should follow directly from the momentum currents. Following this approach, the authors compute the angular momentum associated with several different choices of energy-momentum prescriptions. (author)

  20. Electron momentum spectroscopy

    International Nuclear Information System (INIS)

    McCarthy, I.E.

    1986-03-01

    For electron energies greater than a few hundred eV and recoil momenta less than a few atomic units, the differential cross section for the non-coplanar symmetric (e,2e) reaction on an atom or molecule depends on the target and ion structure only through the target-ion overlap. Experimental criteria for the energy and momentum are that the apparent structure information does not change when the energy and momentum are varied. The plane-wave impulse approximation is a sufficient description of the reaction mechanism for determining spherically-averaged squares of momentum-space orbitals for atoms and molecules and for coefficients describing initial and final state correlations

  1. Value and Momentum Everywhere

    DEFF Research Database (Denmark)

    Asness, Clifford S.; Moskowitz, Tobias J.; Heje Pedersen, Lasse

    across asset classes than passive exposures to the asset classes themselves. However, value and momentum are negatively correlated both within and across asset classes. Our results indicate the presence of common global risks that we characterize with a three factor model. Global funding liquidity risk...... is a partial source of these patterns, which are identifiable only when examining value and momentum simultaneously across markets. Our findings present a challenge to existing behavioral, institutional, and rational asset pricing theories that largely focus on U.S. equities....

  2. Spacecraft Spin Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides the capability to correct unbalances of spacecraft by using dynamic measurement techniques and static/coupled measurements to provide products of...

  3. Momentum accumulation due to solar radiation torque, and reaction wheel sizing, with configuration optimization

    Science.gov (United States)

    Hablani, Hari B.

    1993-01-01

    This paper has a two-fold objective: determination of yearly momentum accumulation due to solar radiation pressure, and optimum reaction wheel sizing. The first objective is confronted while determining propellant consumption by the attitude control system over a spacecraft's lifetime. This, however, cannot be obtained from the daily momentum accumulation and treating that constant throughout the year, because the orientation of the solar arrays relative to the spacecraft changes over a wide range in a year, particularly if the spacecraft has two arrays, one normal and the other off-normal to different extent at different times to the sun rays. The paper first develops commands for the arrays for tracking the sun, the arrays articulated to earth-pointing spacecraft with two rotational degrees of freedom, and spacecraft in an arbitrary circular orbit. After developing expressions for solar radiation torque due to one or both arrays, arranged symmetrically or asymmetrically relative to the spacecraft bus, momentum accumulation over an orbit and then over a year are determined. The remainder of the paper is concerned with designing reaction wheel configurations. Four-, six-, and three-wheel configurations are considered, and for given torque and momentum requirements, their cant angles with the roll/yaw plane are optimized for minimum power consumption. Finally, their momentum and torque capacities are determined for one-wheel failure scenario, and six configurations are compared and contrasted.

  4. Maximum Torque and Momentum Envelopes for Reaction Wheel Arrays

    Science.gov (United States)

    Markley, F. Landis; Reynolds, Reid G.; Liu, Frank X.; Lebsock, Kenneth L.

    2009-01-01

    Spacecraft reaction wheel maneuvers are limited by the maximum torque and/or angular momentum that the wheels can provide. For an n-wheel configuration, the torque or momentum envelope can be obtained by projecting the n-dimensional hypercube, representing the domain boundary of individual wheel torques or momenta, into three dimensional space via the 3xn matrix of wheel axes. In this paper, the properties of the projected hypercube are discussed, and algorithms are proposed for determining this maximal torque or momentum envelope for general wheel configurations. Practical strategies for distributing a prescribed torque or momentum among the n wheels are presented, with special emphasis on configurations of four, five, and six wheels.

  5. Rotations and angular momentum

    International Nuclear Information System (INIS)

    Nyborg, P.; Froyland, J.

    1979-01-01

    This paper is devoted to the analysis of rotational invariance and the properties of angular momentum in quantum mechanics. In particular, the problem of addition of angular momenta is treated in detail, and tables of Clebsch-Gordan coefficients are included

  6. Momentum constraint relaxation

    International Nuclear Information System (INIS)

    Marronetti, Pedro

    2006-01-01

    Full relativistic simulations in three dimensions invariably develop runaway modes that grow exponentially and are accompanied by violations of the Hamiltonian and momentum constraints. Recently, we introduced a numerical method (Hamiltonian relaxation) that greatly reduces the Hamiltonian constraint violation and helps improve the quality of the numerical model. We present here a method that controls the violation of the momentum constraint. The method is based on the addition of a longitudinal component to the traceless extrinsic curvature A ij -tilde, generated by a vector potential w i , as outlined by York. The components of w i are relaxed to solve approximately the momentum constraint equations, slowly pushing the evolution towards the space of solutions of the constraint equations. We test this method with simulations of binary neutron stars in circular orbits and show that it effectively controls the growth of the aforementioned violations. We also show that a full numerical enforcement of the constraints, as opposed to the gentle correction of the momentum relaxation scheme, results in the development of instabilities that stop the runs shortly

  7. Momentum, Fall 2016

    OpenAIRE

    2016-01-01

    Momentum is the quarterly magazine of the Department of Mechanical Engineering at Virginia Tech. In this issue: Nano engineering - Scaling up; Coating 3D objects quickly Energy Harvesting - from soldier's backpacks to nuclear monitoring Hyperloop - team readies pod, university to build test track.

  8. Our Theme for 2016: Sustaining Momentum

    Science.gov (United States)

    2016-03-01

    of design architectures and interfaces to make both open sys- tems and modularity a reality. This is “owning the technical baseline,” and the devil... write this year, although we will be implementing the changes required in the Fiscal Year (FY) 2016 National Defense Au- thorization Act. We still...Defense for Acquisition, Technology, and Logistics on the momentum we have gained as we get ready for a new administration next year. Promote Technical

  9. Fission fragment angular momentum

    International Nuclear Information System (INIS)

    Frenne, D. De

    1991-01-01

    Most of the energy released in fission is converted into translational kinetic energy of the fragments. The remaining excitation energy will be distributed among neutrons and gammas. An important parameter characterizing the scission configuration is the primary angular momentum of the nascent fragments. Neutron emission is not expected to decrease the spin of the fragments by more than one unit of angular momentum and is as such of less importance in the determination of the initial fragment spins. Gamma emission is a suitable tool in studying initial fragment spins because the emission time, number, energy, and multipolarity of the gammas strongly depend on the value of the primary angular momentum. The main conclusions of experiments on gamma emission were that the initial angular momentum of the fragments is large compared to the ground state spin and oriented perpendicular to the fission axis. Most of the recent information concerning initial fragment spin distributions comes from the measurement of isomeric ratios for isomeric pairs produced in fission. Although in nearly every mass chain isomers are known, only a small number are suitable for initial fission fragment spin studies. Yield and half-life considerations strongly limit the number of candidates. This has the advantage that the behavior of a specific isomeric pair can be investigated for a number of fissioning systems at different excitation energies of the fragments and fissioning nuclei. Because most of the recent information on primary angular momenta comes from measurements of isomeric ratios, the global deexcitation process of the fragments and the calculation of the initial fragment spin distribution from measured isomeric ratios are discussed here. The most important results on primary angular momentum determinations are reviewed and some theoretical approaches are given. 45 refs., 7 figs., 2 tabs

  10. Spacecraft Charge Monitor

    Science.gov (United States)

    Goembel, L.

    2003-12-01

    We are currently developing a flight prototype Spacecraft Charge Monitor (SCM) with support from NASA's Small Business Innovation Research (SBIR) program. The device will use a recently proposed high energy-resolution electron spectroscopic technique to determine spacecraft floating potential. The inspiration for the technique came from data collected by the Atmosphere Explorer (AE) satellites in the 1970s. The data available from the AE satellites indicate that the SCM may be able to determine spacecraft floating potential to within 0.1 V under certain conditions. Such accurate measurement of spacecraft charge could be used to correct biases in space plasma measurements. The device may also be able to measure spacecraft floating potential in the solar wind and in orbit around other planets.

  11. Large transverse momentum phenomena

    International Nuclear Information System (INIS)

    Brodsky, S.J.

    1977-09-01

    It is pointed out that it is particularly significant that the quantum numbers of the leading particles are strongly correlated with the quantum numbers of the incident hadrons indicating that the valence quarks themselves are transferred to large p/sub t/. The crucial question is how they get there. Various hadron reactions are discussed covering the structure of exclusive reactions, inclusive reactions, normalization of inclusive cross sections, charge correlations, and jet production at large transverse momentum. 46 references

  12. Angular momentum projected semiclassics

    International Nuclear Information System (INIS)

    Hasse, R.W.

    1986-10-01

    By using angular momentum projected plane waves as wave functions, we derive semiclassical expressions for the single-particle propagator, the partition function, the nonlocal density matrix, the single-particle density and the one particle- one hole level density for fixed angular momentum and fixed z-component or summed over the z-components. Other quantities can be deduced from the propagator. In coordinate space (r, r') the relevant quantities depend on vertical stroker - r 3 vertical stroke instead of vertical stroker - r'vertical stroke and in Wigner space (R, P) they become proportional to the angular momentum constraints δ(vertical strokeRxPvertical stroke/ℎ - l) and δ((RxP) z /ℎ - m). As applications we calculate the single-particle and one particle- one hole level densities for harmonic oscillator and Hill-Wheeler box potentials and the imaginary part of the optical potential and its volume integral with an underlying harmonic oscillator potential and a zero range two-body interaction. (orig.)

  13. Momentum distributions: opening remarks

    International Nuclear Information System (INIS)

    Weigold, E.

    1982-01-01

    The problem of the hydrogen atom has played a central role in the development of quantum mechanics, beginning with Bohr's daring speculations. It was also the first problem tackled by Schroedinger with his new wave mechanics and similarly it was used by Heisenberg in his first papers as a prime example of the success of quantum mechanics. It has always played a central role in the teaching of quantum physics and has served as a most important heuristic tool, shaping our intuition and inspiring many expositions. The Schroedinger equation for the hydrogen atom is usually solved in the position representation, the solution to the equation being the wave functions psi/sub nlm/(r). If Schroedinger's equation is solved in the momentum representation instead of the coordinate representation, the absolute square of the corresponding momentum state wave function phi/sub nlm/(p) would give the momentum probability distribution of the electron in the state defined by the quantum numbers n, l and m. Three different types of collisions which can take place in the (e,2e) reaction on atomic hydrogen, which is a three body problem, are discussed

  14. Optical angular momentum and atoms.

    Science.gov (United States)

    Franke-Arnold, Sonja

    2017-02-28

    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).

  15. Kalman Filter for Spinning Spacecraft Attitude Estimation

    Science.gov (United States)

    Markley, F. Landis; Sedlak, Joseph E.

    2008-01-01

    This paper presents a Kalman filter using a seven-component attitude state vector comprising the angular momentum components in an inertial reference frame, the angular momentum components in the body frame, and a rotation angle. The relatively slow variation of these parameters makes this parameterization advantageous for spinning spacecraft attitude estimation. The filter accounts for the constraint that the magnitude of the angular momentum vector is the same in the inertial and body frames by employing a reduced six-component error state. Four variants of the filter, defined by different choices for the reduced error state, are tested against a quaternion-based filter using simulated data for the THEMIS mission. Three of these variants choose three of the components of the error state to be the infinitesimal attitude error angles, facilitating the computation of measurement sensitivity matrices and causing the usual 3x3 attitude covariance matrix to be a submatrix of the 6x6 covariance of the error state. These variants differ in their choice for the other three components of the error state. The variant employing the infinitesimal attitude error angles and the angular momentum components in an inertial reference frame as the error state shows the best combination of robustness and efficiency in the simulations. Attitude estimation results using THEMIS flight data are also presented.

  16. Fractionated Spacecraft Architectures Seeding Study

    National Research Council Canada - National Science Library

    Mathieu, Charlotte; Weigel, Annalisa

    2006-01-01

    .... Models were developed from a customer-centric perspective to assess different fractionated spacecraft architectures relative to traditional spacecraft architectures using multi-attribute analysis...

  17. Spacecraft Material Outgassing Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This compilation of outgassing data of materials intended for spacecraft use were obtained at the Goddard Space Flight Center (GSFC), utilizing equipment developed...

  18. Spacecraft Fire Safety Demonstration

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the Spacecraft Fire Safety Demonstration project is to develop and conduct large-scale fire safety experiments on an International Space Station...

  19. Quick spacecraft charging primer

    International Nuclear Information System (INIS)

    Larsen, Brian Arthur

    2014-01-01

    This is a presentation in PDF format which is a quick spacecraft charging primer, meant to be used for program training. It goes into detail about charging physics, RBSP examples, and how to identify charging.

  20. Deployable Brake for Spacecraft

    Science.gov (United States)

    Rausch, J. R.; Maloney, J. W.

    1987-01-01

    Aerodynamic shield that could be opened and closed proposed. Report presents concepts for deployable aerodynamic brake. Brake used by spacecraft returning from high orbit to low orbit around Earth. Spacecraft makes grazing passes through atmosphere to slow down by drag of brake. Brake flexible shield made of woven metal or ceramic withstanding high temperatures created by air friction. Stored until needed, then deployed by set of struts.

  1. Time Series Momentum

    DEFF Research Database (Denmark)

    Moskowitz, Tobias J.; Ooi, Yao Hua; Heje Pedersen, Lasse

    2012-01-01

    We document significant “time series momentum” in equity index, currency, commodity, and bond futures for each of the 58 liquid instruments we consider. We find persistence in returns for one to 12 months that partially reverses over longer horizons, consistent with sentiment theories of initial...... under-reaction and delayed over-reaction. A diversified portfolio of time series momentum strategies across all asset classes delivers substantial abnormal returns with little exposure to standard asset pricing factors and performs best during extreme markets. Examining the trading activities...

  2. Optical angular momentum and atoms

    Science.gov (United States)

    2017-01-01

    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom’s angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light’s OAM, aiding our fundamental understanding of light–matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069766

  3. Prediction of Lunar Reconnaissance Orbiter Reaction Wheel Assembly Angular Momentum Using Regression Analysis

    Science.gov (United States)

    DeHart, Russell

    2017-01-01

    This study determines the feasibility of creating a tool that can accurately predict Lunar Reconnaissance Orbiter (LRO) reaction wheel assembly (RWA) angular momentum, weeks or even months into the future. LRO is a three-axis stabilized spacecraft that was launched on June 18, 2009. While typically nadir-pointing, LRO conducts many types of slews to enable novel science collection. Momentum unloads have historically been performed approximately once every two weeks with the goal of maintaining system total angular momentum below 70 Nms; however flight experience shows the models developed before launch are overly conservative, with many momentum unloads being performed before system angular momentum surpasses 50 Nms. A more accurate model of RWA angular momentum growth would improve momentum unload scheduling and decrease the frequency of these unloads. Since some LRO instruments must be deactivated during momentum unloads and in the case of one instrument, decontaminated for 24 hours there after a decrease in the frequency of unloads increases science collection. This study develops a new model to predict LRO RWA angular momentum. Regression analysis of data from October 2014 to October 2015 was used to develop relationships between solar beta angle, slew specifications, and RWA angular momentum growth. The resulting model predicts RWA angular momentum using input solar beta angle and mission schedule data. This model was used to predict RWA angular momentum from October 2013 to October 2014. Predictions agree well with telemetry; of the 23 momentum unloads performed from October 2013 to October 2014, the mean and median magnitude of the RWA total angular momentum prediction error at the time of the momentum unloads were 3.7 and 2.7 Nms, respectively. The magnitude of the largest RWA total angular momentum prediction error was 10.6 Nms. Development of a tool that uses the models presented herein is currently underway.

  4. Galaxy angular momentum

    International Nuclear Information System (INIS)

    Thompson, L.A.

    1974-01-01

    In order to test the theories which purport to explain the origin of galaxy angular momentum, this study presents new data for about 1000 individual galaxies in eight rich clusters. The clusters which are studied include Virgo, A 119, A 400, A 1656 (Coma), A 2147, A 2151 (Hercules), A 2197, and A 2199. Selected samples of these data are used to investigate systematic alignment effects in clusters of galaxies and to investigate the intrinsic ellipticities of E, SO, and spiral galaxies. The following new results are reported: Galaxies in the cluster A 2197 show a significant alignment effect (chi 2 probability less than 0.0002), and the preferential direction of alignment corresponds approximately to the major axis of the overall cluster elongation. None of the other seven clusters show any significant alignment trends. The spiral galaxy samples in four clusters (Virgo, A 1656, A 2151, and A 2197) were large enough to analyze the number distributions of forward and reverse winding spirals. Large and small spiral galaxies have identical ellipticity distributions. Large E and SO galaxies tend to be more spherical, and small E and SO galaxies more flattened. The intrinsic ellipticities of E, SO, and spiral galaxies are the same for galaxies in the ''field'' and for galaxies in rich clusters. Six models of galaxy formation are reviewed, and the major []mphasis is placed on how each model explains the origin of galaxy angular momentum. (Diss. Abstr. Int., B)

  5. Transport of momentum in full f gyrokinetics

    International Nuclear Information System (INIS)

    Parra, Felix I.; Catto, Peter J.

    2010-01-01

    Full f electrostatic gyrokinetic formulations employ two gyrokinetic equations, one for ions and the other for electrons, and quasineutrality to obtain the ion and electron distribution functions and the electrostatic potential. We demonstrate with several examples that the long wavelength radial electric field obtained with full f approaches is extremely sensitive to errors in the ion and electron density since small deviations in density give rise to large, nonphysical deviations in the conservation of toroidal angular momentum. For typical tokamak values, a relative error of 10 -7 in the ion or electron densities is enough to obtain the incorrect toroidal rotation. Based on the insights gained with the examples considered, three simple tests to check transport of toroidal angular momentum in full f simulations are proposed.

  6. Internet Technology on Spacecraft

    Science.gov (United States)

    Rash, James; Parise, Ron; Hogie, Keith; Criscuolo, Ed; Langston, Jim; Powers, Edward I. (Technical Monitor)

    2000-01-01

    The Operating Missions as Nodes on the Internet (OMNI) project has shown that Internet technology works in space missions through a demonstration using the UoSAT-12 spacecraft. An Internet Protocol (IP) stack was installed on the orbiting UoSAT-12 spacecraft and tests were run to demonstrate Internet connectivity and measure performance. This also forms the basis for demonstrating subsequent scenarios. This approach provides capabilities heretofore either too expensive or simply not feasible such as reconfiguration on orbit. The OMNI project recognized the need to reduce the risk perceived by mission managers and did this with a multi-phase strategy. In the initial phase, the concepts were implemented in a prototype system that includes space similar components communicating over the TDRS (space network) and the terrestrial Internet. The demonstration system includes a simulated spacecraft with sample instruments. Over 25 demonstrations have been given to mission and project managers, National Aeronautics and Space Administration (NASA), Department of Defense (DoD), contractor technologists and other decisions makers, This initial phase reached a high point with an OMNI demonstration given from a booth at the Johnson Space Center (JSC) Inspection Day 99 exhibition. The proof to mission managers is provided during this second phase with year 2000 accomplishments: testing the use of Internet technologies onboard an actual spacecraft. This was done with a series of tests performed using the UoSAT-12 spacecraft. This spacecraft was reconfigured on orbit at very low cost. The total period between concept and the first tests was only 6 months! On board software was modified to add an IP stack to support basic IP communications. Also added was support for ping, traceroute and network timing protocol (NTP) tests. These tests show that basic Internet functionality can be used onboard spacecraft. The performance of data was measured to show no degradation from current

  7. Mechanical Design of Spacecraft

    Science.gov (United States)

    1962-01-01

    In the spring of 1962, engineers from the Engineering Mechanics Division of the Jet Propulsion Laboratory gave a series of lectures on spacecraft design at the Engineering Design seminars conducted at the California Institute of Technology. Several of these lectures were subsequently given at Stanford University as part of the Space Technology seminar series sponsored by the Department of Aeronautics and Astronautics. Presented here are notes taken from these lectures. The lectures were conceived with the intent of providing the audience with a glimpse of the activities of a few mechanical engineers who are involved in designing, building, and testing spacecraft. Engineering courses generally consist of heavily idealized problems in order to allow the more efficient teaching of mathematical technique. Students, therefore, receive a somewhat limited exposure to actual engineering problems, which are typified by more unknowns than equations. For this reason it was considered valuable to demonstrate some of the problems faced by spacecraft designers, the processes used to arrive at solutions, and the interactions between the engineer and the remainder of the organization in which he is constrained to operate. These lecture notes are not so much a compilation of sophisticated techniques of analysis as they are a collection of examples of spacecraft hardware and associated problems. They will be of interest not so much to the experienced spacecraft designer as to those who wonder what part the mechanical engineer plays in an effort such as the exploration of space.

  8. Spacecraft Attitude Determination

    DEFF Research Database (Denmark)

    Bak, Thomas

    This thesis describes the development of an attitude determination system for spacecraft based only on magnetic field measurements. The need for such system is motivated by the increased demands for inexpensive, lightweight solutions for small spacecraft. These spacecraft demands full attitude...... determination based on simple, reliable sensors. Meeting these objectives with a single vector magnetometer is difficult and requires temporal fusion of data in order to avoid local observability problems. In order to guaranteed globally nonsingular solutions, quaternions are generally the preferred attitude...... is a detailed study of the influence of approximations in the modeling of the system. The quantitative effects of errors in the process and noise statistics are discussed in detail. The third contribution is the introduction of these methods to the attitude determination on-board the Ørsted satellite...

  9. Revamping Spacecraft Operational Intelligence

    Science.gov (United States)

    Hwang, Victor

    2012-01-01

    The EPOXI flight mission has been testing a new commercial system, Splunk, which employs data mining techniques to organize and present spacecraft telemetry data in a high-level manner. By abstracting away data-source specific details, Splunk unifies arbitrary data formats into one uniform system. This not only reduces the time and effort for retrieving relevant data, but it also increases operational visibility by allowing a spacecraft team to correlate data across many different sources. Splunk's scalable architecture coupled with its graphing modules also provide a solid toolset for generating data visualizations and building real-time applications such as browser-based telemetry displays.

  10. Dips spacecraft integration issues

    International Nuclear Information System (INIS)

    Determan, W.R.; Harty, R.B.

    1988-01-01

    The Department of Energy, in cooperation with the Department of Defense, has recently initiated the dynamic isotope power system (DIPS) demonstration program. DIPS is designed to provide 1 to 10 kW of electrical power for future military spacecraft. One of the near-term missions considered as a potential application for DIPS was the boost surveillance and tracking system (BSTS). A brief review and summary of the reasons behind a selection of DIPS for BSTS-type missions is presented. Many of these are directly related to spacecraft integration issues; these issues will be reviewed in the areas of system safety, operations, survivability, reliability, and autonomy

  11. Momentum density maps for molecules

    International Nuclear Information System (INIS)

    Cook, J.P.D.; Brion, C.E.

    1982-01-01

    Momentum-space and position-space molecular orbital density functions computed from LCAO-MO-SCF wavefunctions are used to rationalize the shapes of some momentum distributions measured by binary (e,2e) spectroscopy. A set of simple rules is presented which enable one to sketch the momentum density function and the momentum distribution from a knowledge of the position-space wavefunction and the properties and effects of the Fourier Transform and the spherical average. Selected molecular orbitals of H 2 , N 2 and CO 2 are used to illustrate this work

  12. Force As A Momentum Current

    International Nuclear Information System (INIS)

    Munera, Hector A.

    2010-01-01

    Advantages of a neo-Cartesian approach to classical mechanics are noted. If conservation of linear momentum is the fundamental principle, Newton's three laws become theorems. A minor paradox in static Newtonian mechanics is identified, and solved by reinterpreting force as a current of momentum. Contact force plays the role of a mere midwife in the exchange of momentum; however, force cannot be eliminated from physics because it provides the numerical value for momentum current. In this sense, in a neo-Cartesian formulation of mechanics the concept of force becomes strengthened rather than weakened.

  13. The momentum distribution inside nucleus

    International Nuclear Information System (INIS)

    Fujita, T.

    1985-01-01

    Discussions are made on several reactions which can determine the momentum distribution inside nucleus. The first reaction discussed is the high energy heavy ion collision. This reaction involves many nucleons which interact strongly. Therefore, one must be careful for any possible final state interactions. The expression for the single particle momentum distribution is given. And it can be said that the expression is consistent with the description of the energetic neutrons from muon capture by heavy nucleus. The best way to determine the momentum distribution would be the lepton-nucleus scattering since it does not involve the strong interaction in the initial channel. Another reaction discussed is the backward proton production, which is governed by quite complicated reaction processes. Therefore, the determination of the momentum distribution is only indirect. Noverthless, it is found that this reaction presents a very interesting and important information on the momentum distribution. (Aoki, K.)

  14. Automating Trend Analysis for Spacecraft Constellations

    Science.gov (United States)

    Davis, George; Cooter, Miranda; Updike, Clark; Carey, Everett; Mackey, Jennifer; Rykowski, Timothy; Powers, Edward I. (Technical Monitor)

    2001-01-01

    missions such as DRACO with the intent that mission operations costs be significantly reduced. The goal of the Constellation Spacecraft Trend Analysis Toolkit (CSTAT) project is to serve as the pathfinder for a fully automated trending system to support spacecraft constellations. The development approach to be taken is evolutionary. In the first year of the project, the intent is to significantly advance the state of the art in current trending systems through improved functionality and increased automation. In the second year, the intent is to add an expert system shell, likely through the adaptation of an existing commercial-off-the-shelf (COTS) or government-off-the-shelf (GOTS) tool to implement some level of the trending intelligence that humans currently provide in manual operations. In the third year, the intent is to infuse the resulting technology into a near-term constellation or formation-flying mission to test it and gain experience in automated trending. The lessons learned from the real missions operations experience will then be used to improve the system, and to ultimately incorporate it into a fully autonomous, closed-loop mission operations system that is truly capable of supporting large constellations. In this paper, the process of automating trend analysis for spacecraft constellations will be addressed. First, the results of a survey on automation in spacecraft mission operations in general, and in trending systems in particular will be presented to provide an overview of the current state of the art. Next, a rule-based model for implementing intelligent spacecraft subsystem trending will be then presented, followed by a survey of existing COTS/GOTS tools that could be adapted for implementing such a model. The baseline design and architecture of the CSTAT system will be presented. Finally, some results obtained from initial software tests and demonstrations will be presented.

  15. General Navier–Stokes-like momentum and mass-energy equations

    Energy Technology Data Exchange (ETDEWEB)

    Monreal, Jorge, E-mail: jmonreal@mail.usf.edu

    2015-03-15

    A new system of general Navier–Stokes-like equations is proposed to model electromagnetic flow utilizing analogues of hydrodynamic conservation equations. Such equations are intended to provide a different perspective and, potentially, a better understanding of electromagnetic mass, energy and momentum behaviour. Under such a new framework additional insights into electromagnetism could be gained. To that end, we propose a system of momentum and mass-energy conservation equations coupled through both momentum density and velocity vectors.

  16. Spacecraft Thermal Management

    Science.gov (United States)

    Hurlbert, Kathryn Miller

    2009-01-01

    In the 21st century, the National Aeronautics and Space Administration (NASA), the Russian Federal Space Agency, the National Space Agency of Ukraine, the China National Space Administration, and many other organizations representing spacefaring nations shall continue or newly implement robust space programs. Additionally, business corporations are pursuing commercialization of space for enabling space tourism and capital business ventures. Future space missions are likely to include orbiting satellites, orbiting platforms, space stations, interplanetary vehicles, planetary surface missions, and planetary research probes. Many of these missions will include humans to conduct research for scientific and terrestrial benefits and for space tourism, and this century will therefore establish a permanent human presence beyond Earth s confines. Other missions will not include humans, but will be autonomous (e.g., satellites, robotic exploration), and will also serve to support the goals of exploring space and providing benefits to Earth s populace. This section focuses on thermal management systems for human space exploration, although the guiding principles can be applied to unmanned space vehicles as well. All spacecraft require a thermal management system to maintain a tolerable thermal environment for the spacecraft crew and/or equipment. The requirements for human rating and the specified controlled temperature range (approximately 275 K - 310 K) for crewed spacecraft are unique, and key design criteria stem from overall vehicle and operational/programatic considerations. These criteria include high reliability, low mass, minimal power requirements, low development and operational costs, and high confidence for mission success and safety. This section describes the four major subsystems for crewed spacecraft thermal management systems, and design considerations for each. Additionally, some examples of specialized or advanced thermal system technologies are presented

  17. Momentum confinement at low torque

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, W M [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Burrell, K H [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); De Grassie, J S [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Budny, R [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Groebner, R J [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Kinsey, J E [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Kramer, G J [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Luce, T C [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Makowski, M A [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Mikkelsen, D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Nazikian, R [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Petty, C C [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Politzer, P A [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Scott, S D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Zeeland, M A Van [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Zarnstorff, M C [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States)

    2007-12-15

    Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized beta {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. GLF23 modeling suggests that the role of E x B shearing is quite different between the two plasmas, which may help to explain the different dependence of the momentum confinement on torque.

  18. Angular momentum of dwarf galaxies

    Science.gov (United States)

    Kurapati, Sushma; Chengalur, Jayaram N.; Pustilnik, Simon; Kamphuis, Peter

    2018-05-01

    Mass and specific angular momentum are two fundamental physical parameters of galaxies. We present measurements of the baryonic mass and specific angular momentum of 11 void dwarf galaxies derived from neutral hydrogen (HI) synthesis data. Rotation curves were measured using 3D and 2D tilted ring fitting routines, and the derived curves generally overlap within the error bars, except in the central regions where, as expected, the 3D routines give steeper curves. The specific angular momentum of void dwarfs is found to be high compared to an extrapolation of the trends seen for higher mass bulge-less spirals, but comparable to that of other dwarf irregular galaxies that lie outside of voids. As such, our data show no evidence for a dependence of the specific angular momentum on the large scale environment. Combining our data with the data from the literature, we find a baryonic threshold of ˜109.1 M⊙ for this increase in specific angular momentum. Interestingly, this threshold is very similar to the mass threshold below which the galaxy discs start to become systematically thicker. This provides qualitative support to the suggestion that the thickening of the discs, as well as the increase in specific angular momentum, are both results of a common physical mechanism, such as feedback from star formation. Quantitatively, however, the amount of star formation observed in our dwarfs appears insufficient to produce the observed increase in specific angular momentum. It is hence likely that other processes, such as cold accretion of high angular momentum gas, also play a role in increasing the specific angular momentum.

  19. Trajectory Control of Rendezvous with Maneuver Target Spacecraft

    Science.gov (United States)

    Zhou, Zhinqiang

    2012-01-01

    In this paper, a nonlinear trajectory control algorithm of rendezvous with maneuvering target spacecraft is presented. The disturbance forces on the chaser and target spacecraft and the thrust forces on the chaser spacecraft are considered in the analysis. The control algorithm developed in this paper uses the relative distance and relative velocity between the target and chaser spacecraft as the inputs. A general formula of reference relative trajectory of the chaser spacecraft to the target spacecraft is developed and applied to four different proximity maneuvers, which are in-track circling, cross-track circling, in-track spiral rendezvous and cross-track spiral rendezvous. The closed-loop differential equations of the proximity relative motion with the control algorithm are derived. It is proven in the paper that the tracking errors between the commanded relative trajectory and the actual relative trajectory are bounded within a constant region determined by the control gains. The prediction of the tracking errors is obtained. Design examples are provided to show the implementation of the control algorithm. The simulation results show that the actual relative trajectory tracks the commanded relative trajectory tightly. The predicted tracking errors match those calculated in the simulation results. The control algorithm developed in this paper can also be applied to interception of maneuver target spacecraft and relative trajectory control of spacecraft formation flying.

  20. Angular momentum from tidal torques

    International Nuclear Information System (INIS)

    Barnes, J.; Efstathiou, G.; Cambridge Univ., England)

    1987-01-01

    The origin of the angular momentum of bound objects in large N-body simulations is studied using three sets of models. One model with white-noise initial conditions is analyzed as well as two in which the initial conditions have more power on large scales, as predicted in models with cold dark matter. The growth and distribution of angular momentum in individual objects is studied and it is found that the specific angular momentum distribution of bound clumps increases in a near linear fashion with radius while the orientation of the angular momentum in the inner high-density regions is often poorly correlated with that of the outer parts. It is also found that the dimensionless spin parameter is insensitive to the initial perturbation spectrum and has a median value of about 0.05. 61 references

  1. Lidar Orbital Angular Momentum Sensor

    Data.gov (United States)

    National Aeronautics and Space Administration — The recognition in recent decades that electromagnetic fields have angular momentum (AM) in the form of not only polarization (or spin AM) but also orbital (OAM) has...

  2. Angular Momentum in Dwarf Galaxies

    Directory of Open Access Journals (Sweden)

    Del Popolo A.

    2014-06-01

    Full Text Available We study the “angular momentum catastrophe” in the framework of interaction among baryons and dark matter through dynamical friction. By means of Del Popolo (2009 model we simulate 14 galaxies similar to those investigated by van den Bosch, Burkert and Swaters (2001, and calculate the distribution of their spin parameters and the angular momenta. Our model gives the angular momentum distribution which is in agreement with the van den Bosch et al. observations. Our result shows that the “angular momentum catastrophe” can be naturally solved in a model that takes into account the baryonic physics and the exchange of energy and angular momentum between the baryonic clumps and dark matter through dynamical friction.

  3. Higgs boson transverse momentum distribution

    CERN Multimedia

    CERN. Geneva

    2018-01-01

    I will review  the recent progress in understanding Higgs boson transverse momentum distribution focusing on effects that go beyond the point-like approximation for the Higgs-glue interaction vertex.

  4. Forecast Accuracy Uncertainty and Momentum

    OpenAIRE

    Bing Han; Dong Hong; Mitch Warachka

    2009-01-01

    We demonstrate that stock price momentum and earnings momentum can result from uncertainty surrounding the accuracy of cash flow forecasts. Our model has multiple information sources issuing cash flow forecasts for a stock. The investor combines these forecasts into an aggregate cash flow estimate that has minimal mean-squared forecast error. This aggregate estimate weights each cash flow forecast by the estimated accuracy of its issuer, which is obtained from their past forecast errors. Mome...

  5. Spacecraft exploration of asteroids

    International Nuclear Information System (INIS)

    Veverka, J.; Langevin, Y.; Farquhar, R.; Fulchignoni, M.

    1989-01-01

    After two decades of spacecraft exploration, we still await the first direct investigation of an asteroid. This paper describes how a growing international interest in the solar system's more primitive bodies should remedy this. Plans are under way in Europe for a dedicated asteroid mission (Vesta) which will include multiple flybys with in situ penetrator studies. Possible targets include 4 Vesta, 8 Flora and 46 Hestia; launch its scheduled for 1994 or 1996. In the United States, NASA plans include flybys of asteroids en route to outer solar system targets

  6. Spacecraft rendezvous and docking

    DEFF Research Database (Denmark)

    Jørgensen, John Leif

    1999-01-01

    The phenomenons and problems encountered when a rendezvous manoeuvre, and possible docking, of two spacecrafts has to be performed, have been the topic for numerous studies, and, details of a variety of scenarios has been analysed. So far, all solutions that has been brought into realization has...... been based entirely on direct human supervision and control. This paper describes a vision-based system and methodology, that autonomously generates accurate guidance information that may assist a human operator in performing the tasks associated with both the rendezvous and docking navigation...

  7. Toward autonomous spacecraft

    Science.gov (United States)

    Fogel, L. J.; Calabrese, P. G.; Walsh, M. J.; Owens, A. J.

    1982-01-01

    Ways in which autonomous behavior of spacecraft can be extended to treat situations wherein a closed loop control by a human may not be appropriate or even possible are explored. Predictive models that minimize mean least squared error and arbitrary cost functions are discussed. A methodology for extracting cyclic components for an arbitrary environment with respect to usual and arbitrary criteria is developed. An approach to prediction and control based on evolutionary programming is outlined. A computer program capable of predicting time series is presented. A design of a control system for a robotic dense with partially unknown physical properties is presented.

  8. Momentum Confinement at Low Torque

    International Nuclear Information System (INIS)

    Solomon, W.M.; Burrell, K.H.; deGrassie, J.S.; Budny, R.; Groebner, R.J.; Heidbrink, W.W.; Kinsey, J.E.; Kramer, G.J.; Makowski, M.A.; Mikkelsen, D.; Nazikian, R.; Petty, C.C.; Politzer, P.A.; Scott, S.D.; Van Zeeland, M.A.; Zarnstorff, M.C.

    2007-01-01

    Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized β N , by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q min show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

  9. Dual electromagnetism: helicity, spin, momentum and angular momentum

    International Nuclear Information System (INIS)

    Bliokh, Konstantin Y; Nori, Franco; Bekshaev, Aleksandr Y

    2013-01-01

    The dual symmetry between electric and magnetic fields is an important intrinsic property of Maxwell equations in free space. This symmetry underlies the conservation of optical helicity and, as we show here, is closely related to the separation of spin and orbital degrees of freedom of light (the helicity flux coincides with the spin angular momentum). However, in the standard field-theory formulation of electromagnetism, the field Lagrangian is not dual symmetric. This leads to problematic dual-asymmetric forms of the canonical energy–momentum, spin and orbital angular-momentum tensors. Moreover, we show that the components of these tensors conflict with the helicity and energy conservation laws. To resolve this discrepancy between the symmetries of the Lagrangian and Maxwell equations, we put forward a dual-symmetric Lagrangian formulation of classical electromagnetism. This dual electromagnetism preserves the form of Maxwell equations, yields meaningful canonical energy–momentum and angular-momentum tensors, and ensures a self-consistent separation of the spin and orbital degrees of freedom. This provides a rigorous derivation of the results suggested in other recent approaches. We make the Noether analysis of the dual symmetry and all the Poincaré symmetries, examine both local and integral conserved quantities and show that only the dual electromagnetism naturally produces a complete self-consistent set of conservation laws. We also discuss the observability of physical quantities distinguishing the standard and dual theories, as well as relations to quantum weak measurements and various optical experiments. (paper)

  10. A January angular momentum balance in the OSU two-level atmospheric general circulation model

    Science.gov (United States)

    Kim, J.-W.; Grady, W.

    1982-01-01

    The present investigation is concerned with an analysis of the atmospheric angular momentum balance, based on the simulation data of the Oregon State University two-level atmospheric general circulation model (AGCM). An attempt is also made to gain an understanding of the involved processes. Preliminary results on the angular momentum and mass balance in the AGCM are shown. The basic equations are examined, and questions of turbulent momentum transfer are investigated. The methods of analysis are discussed, taking into account time-averaged balance equations, time and longitude-averaged balance equations, mean meridional circulation, the mean meridional balance of relative angular momentum, and standing and transient components of motion.

  11. Streamlined Modeling for Characterizing Spacecraft Anomalous Behavior

    Science.gov (United States)

    Klem, B.; Swann, D.

    2011-09-01

    from both the sun and the underlying earth surface. The objects are modeled to be either tumbling or spin stabilized at key orientations in order to capture the complexity of the solar/earth incident illumination and the sensor viewing aspect conditions. Although these geometries and processes appear to be specialized and limited, they are sufficient to capture the principal observable features that are necessary for gaining insight into the complex issues of interpreting non-imaging sensor signals for monitoring the actual on-orbit spacecraft behavior changes. This talk has been prepared as a poster paper, to allow for engagement with conference participants on the presentation contents, and discussions for expansion of the material to include additional topical areas for future work, as appropriate. All discussions have been limited only to topics that could be discussed in the open format of the conference.

  12. The NEOTωIST mission (Near-Earth Object Transfer of angular momentum spin test)

    Science.gov (United States)

    Drube, Line; Harris, Alan W.; Engel, Kilian; Falke, Albert; Johann, Ulrich; Eggl, Siegfried; Cano, Juan L.; Ávila, Javier Martín; Schwartz, Stephen R.; Michel, Patrick

    2016-10-01

    We present a concept for a kinetic impactor demonstration mission, which intends to change the spin rate of a previously-visited asteroid, in this case 25143 Itokawa. The mission would determine the efficiency of momentum transfer during an impact, and help mature the technology required for a kinetic impactor mission, both of which are important precursors for a future space mission to deflect an asteroid by collisional means in an emergency situation. Most demonstration mission concepts to date are based on changing an asteroid's heliocentric orbit and require a reconnaissance spacecraft to measure the very small orbital perturbation due to the impact. Our concept is a low-cost alternative, requiring only a single launch. Taking Itokawa as an example, an estimate of the order of magnitude of the change in the spin period, δP, with such a mission results in δP of 4 min (0.5%), which could be detectable by Earth-based observatories. Our preliminary study found that a mission concept in which an impactor produces a change in an asteroid's spin rate could provide valuable information for the assessment of the viability of the kinetic-impactor asteroid deflection concept. Furthermore, the data gained from the mission would be of great benefit for our understanding of the collisional evolution of asteroids and the physics behind crater and ejecta-cloud development.

  13. Spacecraft Conceptual Design for the 8-Meter Advanced Technology Large Aperture Space Telescope (ATLAST)

    Science.gov (United States)

    Hopkins, Randall C.; Capizzo, Peter; Fincher, Sharon; Hornsby, Linda S.; Jones, David

    2010-01-01

    The Advanced Concepts Office at Marshall Space Flight Center completed a brief spacecraft design study for the 8-meter monolithic Advanced Technology Large Aperture Space Telescope (ATLAST-8m). This spacecraft concept provides all power, communication, telemetry, avionics, guidance and control, and thermal control for the observatory, and inserts the observatory into a halo orbit about the second Sun-Earth Lagrange point. The multidisciplinary design team created a simple spacecraft design that enables component and science instrument servicing, employs articulating solar panels for help with momentum management, and provides precise pointing control while at the same time fast slewing for the observatory.

  14. A Shaftless Magnetically Levitated Multifunctional Spacecraft Flywheel Storage System

    Science.gov (United States)

    Stevens, Ken; Thornton, Richard; Clark, Tracy; Beaman, Bob G.; Dennehy, Neil; Day, John H. (Technical Monitor)

    2002-01-01

    Presently many types of spacecraft use a Spacecraft Attitude Control System (ACS) with momentum wheels for steering and electrochemical batteries to provide electrical power for the eclipse period of the spacecraft orbit. Future spacecraft will use Flywheels for combined use in ACS and Energy Storage. This can be done by using multiple wheels and varying the differential speed for ACS and varying the average speed for energy storage and recovery. Technology in these areas has improved since the 1990s so it is now feasible for flywheel systems to emerge from the laboratory for spacecraft use. This paper describes a new flywheel system that can be used for both ACS and energy storage. Some of the possible advantages of a flywheel system are: lower total mass and volume, higher efficiency, less thermal impact, improved satellite integration schedule and complexity, simplified satellite orbital operations, longer life with lower risk, less pointing jitter, and greater capability for high-rate slews. In short, they have the potential to enable new types of missions and provide lower cost. Two basic types of flywheel configurations are the Flywheel Energy Storage System (FESS) and the Integrated Power and Attitude Control System (IPACS).

  15. Should I Gain Weight?

    Science.gov (United States)

    ... Videos for Educators Search English Español Should I Gain Weight? KidsHealth / For Teens / Should I Gain Weight? ... something about it. Why Do People Want to Gain Weight? Some of the reasons people give for ...

  16. Momentum-Space Josephson Effects

    Science.gov (United States)

    Hou, Junpeng; Luo, Xi-Wang; Sun, Kuei; Bersano, Thomas; Gokhroo, Vandna; Mossman, Sean; Engels, Peter; Zhang, Chuanwei

    2018-03-01

    The Josephson effect is a prominent phenomenon of quantum supercurrents that has been widely studied in superconductors and superfluids. Typical Josephson junctions consist of two real-space superconductors (superfluids) coupled through a weak tunneling barrier. Here we propose a momentum-space Josephson junction in a spin-orbit coupled Bose-Einstein condensate, where states with two different momenta are coupled through Raman-assisted tunneling. We show that Josephson currents can be induced not only by applying the equivalent of "voltages," but also by tuning tunneling phases. Such tunneling-phase-driven Josephson junctions in momentum space are characterized through both full mean field analysis and a concise two-level model, demonstrating the important role of interactions between atoms. Our scheme provides a platform for experimentally realizing momentum-space Josephson junctions and exploring their applications in quantum-mechanical circuits.

  17. Momentum transport in gyrokinetic turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, Rico

    2016-07-01

    In this thesis, the gyrokinetic-Vlasov code GKW is used to study turbulent transport, with a focus on radial transport of toroidal momentum. To support the studies on turbulent transport an eigenvalue solver has been implemented into GKW. This allows to find, not only the most unstable mode, but also subdominant modes. Furthermore it is possible to follow the modes in parameter scans. Furthermore, two fundamental mechanisms that can generate an intrinsic rotation have been investigated: profile shearing and the velocity nonlinearity. The study of toroidal momentum transport in a tokamak due to profile shearing reveals that the momentum flux can not be accurately described by the gradient in the turbulent intensity. Consequently, a description using the profile variation is used. A linear model has been developed that is able to reproduce the variations in the momentum flux as the profiles of density and temperature vary, reasonably well. It uses, not only the gradient length of density and temperature profile, but also their derivative, i.e. the second derivative of the logarithm of the temperature and the density profile. It is shown that both first as well as second derivatives contribute to the generation of a momentum flux. A difference between the linear and nonlinear simulations has been found with respect to the behaviour of the momentum flux. In linear simulations the momentum flux is independent of the normalized Larmor radius ρ{sub *}, whereas it is linear in ρ{sub *} for nonlinear simulations, provided ρ{sub *} is small enough (≤4.10{sup -3}). Nonlinear simulations reveal that the profile shearing can generate an intrinsic rotation comparable to that of current experiments. Under reactor conditions, however, the intrinsic rotation from the profile shearing is expected to be small due to the small normalized Larmor radius ρ{sub *}

  18. Estimating the Backup Reaction Wheel Orientation Using Reaction Wheel Spin Rates Flight Telemetry from a Spacecraft

    Science.gov (United States)

    Rizvi, Farheen

    2013-01-01

    A report describes a model that estimates the orientation of the backup reaction wheel using the reaction wheel spin rates telemetry from a spacecraft. Attitude control via the reaction wheel assembly (RWA) onboard a spacecraft uses three reaction wheels (one wheel per axis) and a backup to accommodate any wheel degradation throughout the course of the mission. The spacecraft dynamics prediction depends upon the correct knowledge of the reaction wheel orientations. Thus, it is vital to determine the actual orientation of the reaction wheels such that the correct spacecraft dynamics can be predicted. The conservation of angular momentum is used to estimate the orientation of the backup reaction wheel from the prime and backup reaction wheel spin rates data. The method is applied in estimating the orientation of the backup wheel onboard the Cassini spacecraft. The flight telemetry from the March 2011 prime and backup RWA swap activity on Cassini is used to obtain the best estimate for the backup reaction wheel orientation.

  19. Automated Angular Momentum Recoupling Algebra

    Science.gov (United States)

    Williams, H. T.; Silbar, Richard R.

    1992-04-01

    We present a set of heuristic rules for algebraic solution of angular momentum recoupling problems. The general problem reduces to that of finding an optimal path from one binary tree (representing the angular momentum coupling scheme for the reduced matrix element) to another (representing the sub-integrals and spin sums to be done). The method lends itself to implementation on a microcomputer, and we have developed such an implementation using a dialect of LISP. We describe both how our code, called RACAH, works and how it appears to the user. We illustrate the use of RACAH for several transition and scattering amplitude matrix elements occurring in atomic, nuclear, and particle physics.

  20. Momentum anisotropy at freeze out

    International Nuclear Information System (INIS)

    Feld, S.; Borghini, N.; Lang, C.

    2017-01-01

    The transition from a hydrodynamical modeling to a particle-based approach is a crucial element of the description of high-energy heavy-ion collisions. Assuming this “freeze out” happens instantaneously at each point of the expanding medium, we show that the local phase-space distribution of the emitted particles is asymmetric in momentum space. This suggests the use of anisotropic hydrodynamics for the last stages of the fluid evolution. We discuss how observables depend on the amount of momentum-space anisotropy at freeze out and how smaller or larger anisotropies allow for different values of the freeze-out temperature. (paper)

  1. Bound-state momentum distributions

    International Nuclear Information System (INIS)

    Alexander, Y.; Redish, E.F.; Wall, N.S.

    1977-01-01

    Proposed forms for nuclear momentum distributions are investigated. Calculations of (p,p') reactions using those forms are done in a plane-wave impulse approximation at angles where the quasielastic peak is seen and also at back angles. The parameters used are derived from (e,e') data, where the nuclear momenta probed overlap with those of the low angle (p,p') experiment. Although there is reasonable agreement for the (p,p') data at 180 0 , the inclusion of distortion necessitates a different parameter set to obtain agreement for the quasifree process. We conclude that the (p,p') reaction cannot be readily understood with a simple momentum distribution

  2. Overview of toroidal momentum transport

    International Nuclear Information System (INIS)

    Peeters, A.G.; Hornsby, W.A.; Angioni, C.; Hein, T.; Kluy, N.; Strintzi, D.; Tardini, G.; Bortolon, A.; Camenen, Y.; Casson, F.J.; Snodin, A.P.; Szepesi, G.; Duval, B.; Fiederspiel, L.; Idomura, Y.; Mantica, P.; Parra, F.I.; Tala, T.; De Vries, P.; Weiland, J.

    2011-01-01

    Toroidal momentum transport mechanisms are reviewed and put in a broader perspective. The generation of a finite momentum flux is closely related to the breaking of symmetry (parity) along the field. The symmetry argument allows for the systematic identification of possible transport mechanisms. Those that appear to lowest order in the normalized Larmor radius (the diagonal part, Coriolis pinch, E x B shearing, particle flux, and up-down asymmetric equilibria) are reasonably well understood. At higher order, expected to be of importance in the plasma edge, the theory is still under development.

  3. Small Spacecraft for Planetary Science

    Science.gov (United States)

    Baker, John; Castillo-Rogez, Julie; Bousquet, Pierre-W.; Vane, Gregg; Komarek, Tomas; Klesh, Andrew

    2016-07-01

    As planetary science continues to explore new and remote regions of the Solar system with comprehensive and more sophisticated payloads, small spacecraft offer the possibility for focused and more affordable science investigations. These small spacecraft or micro spacecraft (attitude control and determination, capable computer and data handling, and navigation are being met by technologies currently under development to be flown on CubeSats within the next five years. This paper will discuss how micro spacecraft offer an attractive alternative to accomplish specific science and technology goals and what relevant technologies are needed for these these types of spacecraft. Acknowledgements: Part of this work is being carried out at the Jet Propulsion Laboratory, California Institute of Technology under contract to NASA. Government sponsorship acknowledged.

  4. Dividing Attention Increases Operational Momentum

    Directory of Open Access Journals (Sweden)

    Koleen McCrink

    2017-12-01

    Full Text Available When adding or subtracting two quantities, adults often compute an estimated outcome that is larger or smaller, respectively, than the actual outcome, a bias referred to as “operational momentum”. The effects of attention on operational momentum were investigated. Participants viewed a display in which two arrays of objects were added, or one array was subtracted from another array, and judged whether a subsequent outcome (probe array contained the correct or incorrect number of objects. In a baseline condition, only the arrays to be added or subtracted were viewed. In divided attention conditions, participants simultaneously viewed a sequence of colors or shapes, and judged which color (a non-spatial judgment or shape (a spatial judgment was repeated. Operational momentum occurred in all conditions, but was higher in divided attention conditions than in the baseline condition, primarily for addition problems. This pattern suggests that dividing attention, rather than decreasing operational momentum by decreasing attentional shifts, actually increased operational momentum. These results are consistent with a heightened use of arithmetic heuristics under conditions of divided attention.

  5. Angular momentum projection with Pfaffian

    International Nuclear Information System (INIS)

    Oi, M.

    2011-01-01

    Recent developments to rewrite the Onishi formula for an evaluation of the so-called norm overlap kernel necessary in angular momentum projection are to be discussed. The essential ingredients in the development, that is, the Fermion coherent states, the Grassmann numbers, and the Pfaffian, are explained. (author)

  6. Representational Momentum in Older Adults

    Science.gov (United States)

    Piotrowski, Andrea S.; Jakobson, Lorna S.

    2011-01-01

    Humans have a tendency to perceive motion even in static images that simply "imply" movement. This tendency is so strong that our memory for actions depicted in static images is distorted in the direction of implied motion--a phenomenon known as representational momentum (RM). In the present study, we created an RM display depicting a pattern of…

  7. Printed Spacecraft Separation System

    Energy Technology Data Exchange (ETDEWEB)

    Dehoff, Ryan R [ORNL; Holmans, Walter [Planetary Systems Corporation

    2016-10-01

    In this project Planetary Systems Corporation proposed utilizing additive manufacturing (3D printing) to manufacture a titanium spacecraft separation system for commercial and US government customers to realize a 90% reduction in the cost and energy. These savings were demonstrated via “printing-in” many of the parts and sub-assemblies into one part, thus greatly reducing the labor associated with design, procurement, assembly and calibration of mechanisms. Planetary Systems Corporation redesigned several of the components of the separation system based on additive manufacturing principles including geometric flexibility and the ability to fabricate complex designs, ability to combine multiple parts of an assembly into a single component, and the ability to optimize design for specific mechanical property targets. Shock absorption was specifically targeted and requirements were established to attenuate damage to the Lightband system from shock of initiation. Planetary Systems Corporation redesigned components based on these requirements and sent the designs to Oak Ridge National Laboratory to be printed. ORNL printed the parts using the Arcam electron beam melting technology based on the desire for the parts to be fabricated from Ti-6Al-4V based on the weight and mechanical performance of the material. A second set of components was fabricated from stainless steel material on the Renishaw laser powder bed technology due to the improved geometric accuracy, surface finish, and wear resistance of the material. Planetary Systems Corporation evaluated these components and determined that 3D printing is potentially a viable method for achieving significant cost and savings metrics.

  8. Spectra and spacecraft

    Science.gov (United States)

    Moroz, V. I.

    2001-02-01

    In June 1999, Dr. Regis Courtin, Associate Editor of PSS, suggested that I write an article for the new section of this journal: "Planetary Pioneers". I hesitated , but decided to try. One of the reasons for my doubts was my primitive English, so I owe the reader an apology for this in advance. Writing took me much more time than I supposed initially, I have stopped and again returned to manuscript many times. My professional life may be divided into three main phases: pioneering work in ground-based IR astronomy with an emphasis on planetary spectroscopy (1955-1970), studies of the planets with spacecraft (1970-1989), and attempts to proceed with this work in difficult times. I moved ahead using the known method of trials and errors as most of us do. In fact, only a small percentage of efforts led to some important results, a sort of dry residue. I will try to describe below how has it been in my case: what may be estimated as the most important, how I came to this, what was around, etc.

  9. Angular momentum in general relativity

    International Nuclear Information System (INIS)

    Prior, C.R.

    1977-01-01

    The definition of angular momentum proposed in part I of this series (Prior. Proc. R. Soc. Lond.; A354:379 (1977)) is investigated when applied to rotating black holes. It is shown how to use the formula to evaluate the angular momentum of a stationary black hole. This acts as a description of a background space on which the effect of first matter and then gravitational perturbations is considered. The latter are of most interest and the rate of change of angular momentum, dJ/dt, is found as an expression in the shear induced in the event horizon by the perturbation and in its time integral. Teukolsky's solutions (Astrophys. J.; 185:635 (1973)) for the perturbed component of the Weyl tensor are then used to find this shear and hence to give an exact answer for dJ/dt. One of the implications of the result is a direct verification of Bekenstein's formula (Phys. Rev.; 7D:949 (1973)) relating in a simple way the rate of change of angular momentum to the rate of change of mass caused by a plane wave. A more general expression is also given for dM/dt. Considering only stationary perturbations, it is shown how to generalize the definition of angular momentum so as to include information about its direction as well. Three problems are particularly discussed - a single moon, two or more moons and a ring of matter causing the perturbation - since they provide illustrations of all the main features of the black hole's behaviour. In every case it is found that the black hole realigns its axis of rotation so that the final configuration is axisymmetric if possible; otherwise is slows down completely to reach a static state. (author)

  10. Energy, momentum and angular momentum conservations in de Sitter gravity

    International Nuclear Information System (INIS)

    Lu, Jia-An

    2016-01-01

    In de Sitter (dS) gravity, where gravity is a gauge field introduced to realize the local dS invariance of the matter field, two kinds of conservation laws are derived. The first kind is a differential equation for a dS-covariant current, which unites the canonical energy-momentum (EM) and angular momentum (AM) tensors. The second kind presents a dS-invariant current which is conserved in the sense that its torsion-free divergence vanishes. The dS-invariant current unites the total (matter plus gravity) EM and AM currents. It is well known that the AM current contains an inherent part, called the spin current. Here it is shown that the EM tensor also contains an inherent part, which might be observed by its contribution to the deviation of the dust particle’s world line from a geodesic. All the results are compared to the ordinary Lorentz gravity. (paper)

  11. Momentum

    DEFF Research Database (Denmark)

    Korsbek, Lisa; Tønder, Esben Sandvik

    2016-01-01

    OBJECTIVE: The aim of the pilot study was to examine the use of a smartphone application as a modern decision aid to support shared decision making in mental health. METHOD: 78 people using mental health services and 116 of their providers participated in a 4-month pilot study. At the end...... FOR PRACTICE: The results indicate the relevance of using modern technology to support shared decision making (SDM) and the recovery model, though raise the question of how the actual use in the study is to be understood. The study thereby points to a need of further research into the understanding...... relating to the power asymmetry between people using mental health services and staff. Contrary to our hypothesis that peer support would be crucial, the use of the application was most widespread when it was presented to consumers by providers who found it was a useful tool. CONCLUSIONS AND IMPLICATIONS...

  12. Spacecraft Charging and the Microwave Anisotropy Probe Spacecraft

    Science.gov (United States)

    Timothy, VanSant J.; Neergaard, Linda F.

    1998-01-01

    The Microwave Anisotropy Probe (MAP), a MIDEX mission built in partnership between Princeton University and the NASA Goddard Space Flight Center (GSFC), will study the cosmic microwave background. It will be inserted into a highly elliptical earth orbit for several weeks and then use a lunar gravity assist to orbit around the second Lagrangian point (L2), 1.5 million kilometers, anti-sunward from the earth. The charging environment for the phasing loops and at L2 was evaluated. There is a limited set of data for L2; the GEOTAIL spacecraft measured relatively low spacecraft potentials (approx. 50 V maximum) near L2. The main area of concern for charging on the MAP spacecraft is the well-established threat posed by the "geosynchronous region" between 6-10 Re. The launch in the autumn of 2000 will coincide with the falling of the solar maximum, a period when the likelihood of a substorm is higher than usual. The likelihood of a substorm at that time has been roughly estimated to be on the order of 20% for a typical MAP mission profile. Because of the possibility of spacecraft charging, a requirement for conductive spacecraft surfaces was established early in the program. Subsequent NASCAP/GEO analyses for the MAP spacecraft demonstrated that a significant portion of the sunlit surface (solar cell cover glass and sunshade) could have nonconductive surfaces without significantly raising differential charging. The need for conductive materials on surfaces continually in eclipse has also been reinforced by NASCAP analyses.

  13. Field momentum, inertial momentum and gravitational momentum of a system of bodies in the post-Newtonian approximation

    Energy Technology Data Exchange (ETDEWEB)

    Jankiewicz, Cz; Sikora, D [Wyzsza Szkola Pedagogiczna, Rzeszow (Poland)

    1980-01-01

    It is shwon that in the post-Newtonian approximation the gravitational momentum of a system of point particles is equal to the sum of field momentum and inertial momentum only in two classes of coordinate systems. This equality may be treated as a natural condition on a coordinate system in which the generally covariant Einstein equations are to be solved.

  14. Angular momentum in QGP holography

    Directory of Open Access Journals (Sweden)

    Brett McInnes

    2014-10-01

    Full Text Available The quark chemical potential is one of the fundamental parameters describing the quark–gluon plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account.

  15. Angular momentum content of galaxies

    International Nuclear Information System (INIS)

    Shaya, E.J.; Tully, R.B.

    1984-01-01

    A schema of galaxy formation is developed in which the environmental influence of large-scale structure plays a dominant role. This schema was motivated by the observation that the fraction of E and S0 galaxies is much higher in clusters than in low-density regions and by an inference that those spirals that are found in clusters probably have fallen in relatively recently from the low-density regions. It is proposed that the tidal field of the Local Supercluster acts to determine the morphology of galaxies through two complementary mechanisms. In the first place, the supercluster can apply torques to protogalaxies. Galaxies which collapsed while expanding away from the central cluster decoupled from the external tidal field and conserved the angular momentum that they acquired before collapse. Galaxies which formed in the cluster while the cluster collapsed continued to feel the tidal field. In the latter case, the spin of outer collapsing layers can be halted and reversed, and tends to cancel the spin of inner layers. The result is a reduction of the total angular momentum content of the galaxy. In addition, the supercluster tidal field can regulate accretion of fresh material onto the galaxies since the field creates a Roche limit about galaxies and material beyond this limit is lost. Any material that has not collapsed onto a galaxy by the time the galaxy falls into a cluster will be tidally stripped. The angular momentum content of that part of the protogalactic cloud which has not yet collapsed . continues to grow linearly with time due to the continued torquing by the supercluster and neighbors. Galaxies at large distances from the cluster core can continue to accrete this high angular momentum material until the present, but galaxies that enter the cluster are cut off from replenishing material

  16. Blade-element/momentum theory

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær

    2016-01-01

    Although there exists a large variety of methods for predicting performance and loadings of wind turbines, the only approach used today by wind turbine manufacturers is based on the blade-element/momentum (BEM) theory by Glauert (Aerodynamic theory. Springer, Berlin, pp. 169-360, 1935). A basic...... assumption in the BEM theory is that the flow takes place in independent stream tubes and that the loading is determined from two-dimensional sectional airfoil characteristics....

  17. Spacecraft Environmental Interactions Technology, 1983

    Science.gov (United States)

    1985-01-01

    State of the art of environment interactions dealing with low-Earth-orbit plasmas; high-voltage systems; spacecraft charging; materials effects; and direction of future programs are contained in over 50 papers.

  18. Gravity Probe B spacecraft description

    International Nuclear Information System (INIS)

    Bennett, Norman R; Burns, Kevin; Katz, Russell; Kirschenbaum, Jon; Mason, Gary; Shehata, Shawky

    2015-01-01

    The Gravity Probe B spacecraft, developed, integrated, and tested by Lockheed Missiles and Space Company and later Lockheed Martin Corporation, consisted of structures, mechanisms, command and data handling, attitude and translation control, electrical power, thermal control, flight software, and communications. When integrated with the payload elements, the integrated system became the space vehicle. Key requirements shaping the design of the spacecraft were: (1) the tight mission timeline (17 months, 9 days of on-orbit operation), (2) precise attitude and translational control, (3) thermal protection of science hardware, (4) minimizing aerodynamic, magnetic, and eddy current effects, and (5) the need to provide a robust, low risk spacecraft. The spacecraft met all mission requirements, as demonstrated by dewar lifetime meeting specification, positive power and thermal margins, precision attitude control and drag-free performance, reliable communications, and the collection of more than 97% of the available science data. (paper)

  19. Transverse spin and momentum correlations in quantum ...

    Indian Academy of Sciences (India)

    asymmetry for a longitudinally polarized target in semi-inclusive deep inelastic scattering. Keywords. .... integrate out ξ and perform the momentum integration over the diquark momentum ...... [53] European Muon: M Arneodo et al, Z. Phys. C34 ...

  20. Intelligent spacecraft module

    Science.gov (United States)

    Oungrinis, Konstantinos-Alketas; Liapi, Marianthi; Kelesidi, Anna; Gargalis, Leonidas; Telo, Marinela; Ntzoufras, Sotiris; Paschidi, Mariana

    2014-12-01

    The paper presents the development of an on-going research project that focuses on a human-centered design approach to habitable spacecraft modules. It focuses on the technical requirements and proposes approaches on how to achieve a spatial arrangement of the interior that addresses sufficiently the functional, physiological and psychosocial needs of the people living and working in such confined spaces that entail long-term environmental threats to human health and performance. Since the research perspective examines the issue from a qualitative point of view, it is based on establishing specific relationships between the built environment and its users, targeting people's bodily and psychological comfort as a measure toward a successful mission. This research has two basic branches, one examining the context of the system's operation and behavior and the other in the direction of identifying, experimenting and formulating the environment that successfully performs according to the desired context. The latter aspect is researched upon the construction of a scaled-model on which we run series of tests to identify the materiality, the geometry and the electronic infrastructure required. Guided by the principles of sensponsive architecture, the ISM research project explores the application of the necessary spatial arrangement and behavior for a user-centered, functional interior where the appropriate intelligent systems are based upon the existing mechanical and chemical support ones featured on space today, and especially on the ISS. The problem is set according to the characteristics presented at the Mars500 project, regarding the living quarters of six crew-members, along with their hygiene, leisure and eating areas. Transformable design techniques introduce spatial economy, adjustable zoning and increased efficiency within the interior, securing at the same time precise spatial orientation and character at any given time. The sensponsive configuration is

  1. Weight Gain during Pregnancy

    Science.gov (United States)

    ... Global Map Premature Birth Report Cards Careers Archives Pregnancy Before or between pregnancies Nutrition, weight & fitness Prenatal ... fitness > Weight gain during pregnancy Weight gain during pregnancy E-mail to a friend Please fill in ...

  2. Preventing Weight Gain

    Science.gov (United States)

    ... Local Programs Related Topics Diabetes Nutrition Preventing Weight Gain Language: English (US) Español (Spanish) Recommend on Facebook ... cancer. Choosing an Eating Plan to Prevent Weight Gain So, how do you choose a healthful eating ...

  3. Large transverse momentum behavior of gauge theories

    International Nuclear Information System (INIS)

    Coquereaux, Robert; De Rafael, Eduardo.

    1977-05-01

    The large transverse momentum behavior of Compton scattering and Moeller scattering in Quantum Electrodynamics; and of elastic quark-quark scattering in Quantum Chromodynamics are examined in perturbation theory. The results strongly suggest that the large transverse momentum regime in gauge theories is governed by a differential equation of the Callan-Symanzik type with a suitable momentum dependent anomalous dimension term. An explicit solution for the quark-quark elastic scattering amplitude at large transverse momentum is given

  4. Transverse Momentum Distributions for Heavy Quark Pairs

    OpenAIRE

    Berger, Edmond L.; Meng, Ruibin

    1993-01-01

    We study the transverse momentum distribution for a $pair$ of heavy quarks produced in hadron-hadron interactions. Predictions for the large transverse momentum region are based on exact order $\\alpha_s^3$ QCD perturbation theory. For the small transverse momentum region, we use techniques for all orders resummation of leading logarithmic contributions associated with initial state soft gluon radiation. The combination provides the transverse momentum distribution of heavy quark pairs for all...

  5. Momentum in Transformation of Technical Infrastructure

    DEFF Research Database (Denmark)

    Nielsen, Susanne Balslev; Elle, Morten

    1999-01-01

    Current infrastructure holds a considerable momentum and this momentum is a barrier of transformation towards more sustainable technologies and more sustainable styles of network management. Using the sewage sector in Denmark as an example of a technical infrastructure system this paper argues...... that there are technical, economical and social aspects of the current infrastructures momentum....

  6. Wigner Functions and Quark Orbital Angular Momentum

    Directory of Open Access Journals (Sweden)

    Mukherjee Asmita

    2015-01-01

    Full Text Available Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs and transverse momentum dependent parton distributions (TMDs. We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.

  7. Wigner Functions and Quark Orbital Angular Momentum

    OpenAIRE

    Mukherjee, Asmita; Nair, Sreeraj; Ojha, Vikash Kumar

    2014-01-01

    Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.

  8. Angular-momentum transport in nuclear collisions

    International Nuclear Information System (INIS)

    Wolschin, G.; Ayik, S.; Noerenberg, W.

    1978-01-01

    Among the various relaxation processes that can be observed in heavy-ion collisions, the dissipation of relative angular momentum into intrinsic angular momentum of the fragments attracts increasing attention. Here we present a transport theoretical description of angular-momentum and mass transport that allows for a transparent interpretation of the data. (orig.) [de

  9. An Empirical Comparison between Two Recursive Filters for Attitude and Rate Estimation of Spinning Spacecraft

    Science.gov (United States)

    Harman, Richard R.

    2006-01-01

    The advantages of inducing a constant spin rate on a spacecraft are well known. A variety of science missions have used this technique as a relatively low cost method for conducting science. Starting in the late 1970s, NASA focused on building spacecraft using 3-axis control as opposed to the single-axis control mentioned above. Considerable effort was expended toward sensor and control system development, as well as the development of ground systems to independently process the data. As a result, spinning spacecraft development and their resulting ground system development stagnated. In the 1990s, shrinking budgets made spinning spacecraft an attractive option for science. The attitude requirements for recent spinning spacecraft are more stringent and the ground systems must be enhanced in order to provide the necessary attitude estimation accuracy. Since spinning spacecraft (SC) typically have no gyroscopes for measuring attitude rate, any new estimator would need to rely on the spacecraft dynamics equations. One estimation technique that utilized the SC dynamics and has been used successfully in 3-axis gyro-less spacecraft ground systems is the pseudo-linear Kalman filter algorithm. Consequently, a pseudo-linear Kalman filter has been developed which directly estimates the spacecraft attitude quaternion and rate for a spinning SC. Recently, a filter using Markley variables was developed specifically for spinning spacecraft. The pseudo-linear Kalman filter has the advantage of being easier to implement but estimates the quaternion which, due to the relatively high spinning rate, changes rapidly for a spinning spacecraft. The Markley variable filter is more complicated to implement but, being based on the SC angular momentum, estimates parameters which vary slowly. This paper presents a comparison of the performance of these two filters. Monte-Carlo simulation runs will be presented which demonstrate the advantages and disadvantages of both filters.

  10. Non-analog Monte Carlo estimators for radiation momentum deposition

    International Nuclear Information System (INIS)

    Hykes, Joshua M.; Densmore, Jeffery D.

    2009-01-01

    The standard method for calculating radiation momentum deposition in Monte Carlo simulations is the analog estimator, which tallies the change in a particle's momentum at each interaction with the matter. Unfortunately, the analog estimator can suffer from large amounts of statistical error. In this paper, we present three new non-analog techniques for estimating momentum deposition. Specifically, we use absorption, collision, and track-length estimators to evaluate a simple integral expression for momentum deposition that does not contain terms that can cause large amounts of statistical error in the analog scheme. We compare our new non-analog estimators to the analog estimator with a set of test problems that encompass a wide range of material properties and both isotropic and anisotropic scattering. In nearly all cases, the new non-analog estimators outperform the analog estimator. The track-length estimator consistently yields the highest performance gains, improving upon the analog-estimator figure of merit by factors of up to two orders of magnitude.

  11. ICNTS. Benchmarking of momentum correction techniques

    International Nuclear Information System (INIS)

    Beidler, Craig D.; Isaev, Maxim Yu.; Kasilov, Sergei V.

    2008-01-01

    In the traditional neoclassical ordering, mono-energetic transport coefficients are evaluated using the simplified Lorentz form of the pitch-angle collision operator which violates momentum conservation. In this paper, the parallel momentum balance with radial parallel momentum transport and viscosity terms is analysed, in particular with respect to the radial electric field. Next, the impact of momentum conservation in the stellarator lmfp-regime is estimated for the radial transport and the parallel electric conductivity. Finally, momentum correction techniques are described based on mono-energetic transport coefficients calculated e.g. by the DKES code, and preliminary results for the parallel electric conductivity and the bootstrap current are presented. (author)

  12. On the Classical and Quantum Momentum Map

    DEFF Research Database (Denmark)

    Esposito, Chiara

    In this thesis we study the classical and quantum momentum maps and the theory of reduction. We focus on the notion of momentum map in Poisson geometry and we discuss the classification of the momentum map in this framework. Furthermore, we describe the so-called Poisson Reduction, a technique...... that allows us to reduce the dimension of a manifold in presence of symmetries implemented by Poisson actions. Using techniques of deformation quantization and quantum groups, we introduce the quantum momentum map as a deformation of the classical momentum map, constructed in such a way that it factorizes...

  13. Recoil-ion momentum spectroscopy

    International Nuclear Information System (INIS)

    Ullrich, J.; Moshammer, R.; Doerner, R.; Jagutzki, O.; Mergel, V.; Schmidt-Boecking, H.; Spielberger, L.

    1996-10-01

    High-resolution recoil-ion momentum spectroscopy (RIMS) is a novel technique to determine the charge state and the complete final momentum vector P R of a recoiling target ion emerging from an ionising collision of an atom with any kind of radiation. It offers a unique combination of superior momentum resolution in all three spatial directions of ΔP R = 0.07 a.u. with a large detection solid angle of ΔΩ R /4π≥ 98%. Recently, low-energy electron analysers based on rigorously new concepts and reaching similar specifications were successfully integrated into RIM spectrometers yielding so-called ''reaction microscopes''. Exploiting these techniques, a large variety of atomic reactions for ion, electron, photon and antiproton impact have been explored in unprecedented detail and completeness. Among them first kinematically complete experiments on electron capture, single and double ionisation in ion-atom collisions at projectile energies between 5 keV and 1.4 GeV. Double photoionisation of He has been investigated at energies E γ close to the threshold (E γ = 80 eV) up to E γ = 58 keV. At E γ >8 keV the contributions to double ionisation after photoabsorption and Compton scattering were kinematically separated for the first time. These and many other results will be reviewed in this article. In addition, the experimental technique is described in some detail and emphasis is given to envisage the rich future potential of the method in various fields of atomic collision physics with atoms, molecules and clusters. (orig.)

  14. Rechargeable metal hydrides for spacecraft application

    Science.gov (United States)

    Perry, J. L.

    1988-01-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  15. Workshop on momentum distributions: Summary

    International Nuclear Information System (INIS)

    Simmons, R.O.

    1988-01-01

    This has been an extraordinary Workshop touching many branches of physics. The Workshop has treated momentum distributions in fluid and solid condensed matter, in nuclei, and in electronic systems. Both theoretical and experimental concepts and methods have been considered in all these branches. A variety of specific illustrations and applications in physical systems have been presented. One finds that some common unifying themes emerge. One finds, also, that some examples are available to illustrate where one branch is more mature than others and to contrast where expectations for future progress may be most encouraged. 6 refs., 2 figs

  16. Large transverse momentum hadronic processes

    International Nuclear Information System (INIS)

    Darriulat, P.

    1977-01-01

    The possible relations between deep inelastic leptoproduction and large transverse momentum (psub(t)) processes in hadronic collisions are usually considered in the framework of the quark-parton picture. Experiments observing the structure of the final state in proton-proton collisions producing at least one large transverse momentum particle have led to the following conclusions: a large fraction of produced particles are uneffected by the large psub(t) process. The other products are correlated to the large psub(t) particle. Depending upon the sign of scalar product they can be separated into two groups of ''towards-movers'' and ''away-movers''. The experimental evidence are reviewed favouring such a picture and the properties are discussed of each of three groups (underlying normal event, towards-movers and away-movers). Some phenomenological interpretations are presented. The exact nature of away- and towards-movers must be further investigated. Their apparent jet structure has to be confirmed. Angular correlations between leading away and towards movers are very informative. Quantum number flow, both within the set of away and towards-movers, and between it and the underlying normal event, are predicted to behave very differently in different models

  17. Artist concept of Galileo spacecraft

    Science.gov (United States)

    1988-01-01

    Galileo spacecraft is illustrated in artist concept. Gallileo, named for the Italian astronomer, physicist and mathematician who is credited with construction of the first complete, practical telescope in 1620, will make detailed studies of Jupiter. A cooperative program with the Federal Republic of Germany the Galileo mission will amplify information acquired by two Voyager spacecraft in their brief flybys. Galileo is a two-element system that includes a Jupiter-orbiting observatory and an entry probe. Jet Propulsion Laboratory (JPL) is Galileo project manager and builder of the main spacecraft. Ames Research Center (ARC) has responsibility for the entry probe, which was built by Hughes Aircraft Company and General Electric. Galileo will be deployed from the payload bay (PLB) of Atlantis, Orbiter Vehicle (OV) 104, during mission STS-34.

  18. Charging Effects on Fluid Stream Droplets for Momentum Exchange Between Spacecraft

    Science.gov (United States)

    2009-01-01

    temperature where liquid polymers transition to a brittle glass like state and solid polymers transition to a rubbery state. A technical... Glen Research Center, Thermo Mechanical Systems Branch http://www.grc.nasa.gov/WWW/tmsb/concentrators.html [accessed Sep 29, 2006]. Purcell, E

  19. Gestational weight gain.

    Science.gov (United States)

    Kominiarek, Michelle A; Peaceman, Alan M

    2017-12-01

    Prenatal care providers are advised to evaluate maternal weight at each regularly scheduled prenatal visit, monitor progress toward meeting weight gain goals, and provide individualized counseling if significant deviations from a woman's goals occur. Today, nearly 50% of women exceed their weight gain goals with overweight and obese women having the highest prevalence of excessive weight gain. Risks of inadequate weight gain include low birthweight and failure to initiate breast-feeding whereas the risks of excessive weight gain include cesarean deliveries and postpartum weight retention for the mother and large-for-gestational-age infants, macrosomia, and childhood overweight or obesity for the offspring. Prenatal care providers have many resources and tools to incorporate weight and other health behavior counseling into routine prenatal practices. Because many women are motivated to improve health behaviors, pregnancy is often considered the optimal time to intervene for issues related to eating habits and physical activity to prevent excessive weight gain. Gestational weight gain is a potentially modifiable risk factor for a number of adverse maternal and neonatal outcomes and meta-analyses of randomized controlled trials report that diet or exercise interventions during pregnancy can help reduce excessive weight gain. However, health behavior interventions for gestational weight gain have not significantly improved other maternal and neonatal outcomes and have limited effectiveness in overweight and obese women. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Net gains with Somos@Telecentros | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2011-02-03

    Feb 3, 2011 ... In this slum area, street children use the Internet to learn to read and write, as well as for multimedia, music, and other digital work. ... in number and substance as the telecentres movement gains momentum. ... We need to continue to develop relationships to be effective as a network within global forums ...

  1. Training for spacecraft technical analysts

    Science.gov (United States)

    Ayres, Thomas J.; Bryant, Larry

    1989-01-01

    Deep space missions such as Voyager rely upon a large team of expert analysts who monitor activity in the various engineering subsystems of the spacecraft and plan operations. Senior teammembers generally come from the spacecraft designers, and new analysts receive on-the-job training. Neither of these methods will suffice for the creation of a new team in the middle of a mission, which may be the situation during the Magellan mission. New approaches are recommended, including electronic documentation, explicit cognitive modeling, and coached practice with archived data.

  2. Calculating the momentum enhancement factor for asteroid deflection studies

    International Nuclear Information System (INIS)

    Heberling, Tamra; Gisler, Galen; Plesko, Catherine; Weaver, Robert

    2017-01-01

    The possibility of kinetic-impact deflection of threatening near-Earth asteroids will be tested for the first time in the proposed AIDA (Asteroid Impact Deflection Assessment) mission, involving NASAs DART (Double Asteroid Redirection Test). The impact of the DART spacecraft onto the secondary of the binary asteroid 65803 Didymos at a speed of 5 to 7 km/s is expected to alter the mutual orbit by an observable amount. Furthermore, the velocity transferred to the secondary depends largely on the momentum enhancement factor, typically referred to as beta. Here, we use two hydrocodes developed at Los Alamos, RAGE and PAGOSA, to calculate an approximate value for beta in laboratory-scale benchmark experiments. Convergence studies comparing the two codes show the importance of mesh size in estimating this crucial parameter.

  3. Results from active spacecraft potential control on the Geotail spacecraft

    International Nuclear Information System (INIS)

    Schmidt, R.; Arends, H.; Pedersen, A.

    1995-01-01

    A low and actively controlled electrostatic potential on the outer surfaces of a scientific spacecraft is very important for accurate measurements of cold plasma electrons and ions and the DC to low-frequency electric field. The Japanese/NASA Geotail spacecraft carriers as part of its scientific payload a novel ion emitter for active control of the electrostatic potential on the surface of the spacecraft. The aim of the ion emitter is to reduce the positive surface potential which is normally encountered in the outer magnetosphere when the spacecraft is sunlit. Ion emission clamps the surface potential to near the ambient plasma potential. Without emission control, Geotail has encountered plasma conditions in the lobes of the magnetotail which resulted in surface potentials of up to about +70 V. The ion emitter proves to be able to discharge the outer surfaces of the spacecraft and is capable of keeping the surface potential stable at about +2 V. This potential is measured with respect to one of the electric field probes which are current biased and thus kept at a potential slightly above the ambient plasma potential. The instrument uses the liquid metal field ion emission principle to emit indium ions. The ion beam energy is about 6 keV and the typical total emission current amounts to about 15 μA. Neither variations in the ambient plasma conditions nor operation of two electron emitters on Geotail produce significant variations of the controlled surface potential as long as the resulting electron emission currents remain much smaller than the ion emission current. Typical results of the active potential control are shown, demonstrating the surface potential reduction and its stability over time. 25 refs., 5 figs

  4. Charging in the environment of large spacecraft

    International Nuclear Information System (INIS)

    Lai, S.T.

    1993-01-01

    This paper discusses some potential problems of spacecraft charging as a result of interactions between a large spacecraft, such as the Space Station, and its environment. Induced electric field, due to VXB effect, may be important for large spacecraft at low earth orbits. Differential charging, due to different properties of surface materials, may be significant when the spacecraft is partly in sunshine and partly in shadow. Triple-root potential jump condition may occur because of differential charging. Sudden onset of severe differential charging may occur when an electron or ion beam is emitted from the spacecraft. The beam may partially return to the ''hot spots'' on the spacecraft. Wake effects, due to blocking of ambient ion trajectories, may result in an undesirable negative potential region in the vicinity of a large spacecraft. Outgassing and exhaust may form a significant spacecraft induced environment; ionization may occur. Spacecraft charging and discharging may affect the electronic components on board

  5. Fragment separator momentum compression schemes

    Energy Technology Data Exchange (ETDEWEB)

    Bandura, Laura, E-mail: bandura@anl.gov [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); National Superconducting Cyclotron Lab, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Erdelyi, Bela [Argonne National Laboratory, Argonne, IL 60439 (United States); Northern Illinois University, DeKalb, IL 60115 (United States); Hausmann, Marc [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Kubo, Toshiyuki [RIKEN Nishina Center, RIKEN, Wako (Japan); Nolen, Jerry [Argonne National Laboratory, Argonne, IL 60439 (United States); Portillo, Mauricio [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Sherrill, Bradley M. [National Superconducting Cyclotron Lab, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States)

    2011-07-21

    We present a scheme to use a fragment separator and profiled energy degraders to transfer longitudinal phase space into transverse phase space while maintaining achromatic beam transport. The first order beam optics theory of the method is presented and the consequent enlargement of the transverse phase space is discussed. An interesting consequence of the technique is that the first order mass resolving power of the system is determined by the first dispersive section up to the energy degrader, independent of whether or not momentum compression is used. The fragment separator at the Facility for Rare Isotope Beams is a specific application of this technique and is described along with simulations by the code COSY INFINITY.

  6. Fragment separator momentum compression schemes

    International Nuclear Information System (INIS)

    Bandura, Laura; Erdelyi, Bela; Hausmann, Marc; Kubo, Toshiyuki; Nolen, Jerry; Portillo, Mauricio; Sherrill, Bradley M.

    2011-01-01

    We present a scheme to use a fragment separator and profiled energy degraders to transfer longitudinal phase space into transverse phase space while maintaining achromatic beam transport. The first order beam optics theory of the method is presented and the consequent enlargement of the transverse phase space is discussed. An interesting consequence of the technique is that the first order mass resolving power of the system is determined by the first dispersive section up to the energy degrader, independent of whether or not momentum compression is used. The fragment separator at the Facility for Rare Isotope Beams is a specific application of this technique and is described along with simulations by the code COSY INFINITY.

  7. Airborne particulate matter in spacecraft

    Science.gov (United States)

    1988-01-01

    Acceptability limits and sampling and monitoring strategies for airborne particles in spacecraft were considered. Based on instances of eye and respiratory tract irritation reported by Shuttle flight crews, the following acceptability limits for airborne particles were recommended: for flights of 1 week or less duration (1 mg/cu m for particles less than 10 microns in aerodynamic diameter (AD) plus 1 mg/cu m for particles 10 to 100 microns in AD); and for flights greater than 1 week and up to 6 months in duration (0.2 mg/cu m for particles less than 10 microns in AD plus 0.2 mg/cu m for particles 10 to 100 microns in AD. These numerical limits were recommended to aid in spacecraft atmosphere design which should aim at particulate levels that are a low as reasonably achievable. Sampling of spacecraft atmospheres for particles should include size-fractionated samples of 0 to 10, 10 to 100, and greater than 100 micron particles for mass concentration measurement and elementary chemical analysis by nondestructive analysis techniques. Morphological and chemical analyses of single particles should also be made to aid in identifying airborne particulate sources. Air cleaning systems based on inertial collection principles and fine particle collection devices based on electrostatic precipitation and filtration should be considered for incorporation into spacecraft air circulation systems. It was also recommended that research be carried out in space in the areas of health effects and particle characterization.

  8. Orbital angular momentum in phase space

    International Nuclear Information System (INIS)

    Rigas, I.; Sanchez-Soto, L.L.; Klimov, A.B.; Rehacek, J.; Hradil, Z.

    2011-01-01

    Research highlights: → We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. → We present a simple and useful toolkit for the practitioner. → We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.

  9. Momentum management strategy during Space Station buildup

    Science.gov (United States)

    Bishop, Lynda; Malchow, Harvey; Hattis, Philip

    1988-01-01

    The use of momentum storage devices to control effectors for Space Station attitude control throughout the buildup sequence is discussed. Particular attention is given to the problem of providing satisfactory management of momentum storage effectors throughout buildup while experiencing variable torque loading. Continuous and discrete control strategies are compared and the effects of alternative control moment gyro strategies on peak momentum storage requirements and on commanded maneuver characteristics are described.

  10. A Study of Large Transverse Momentum Phenomena

    CERN Multimedia

    2002-01-01

    This experiment studies the structure of those p-p and @*-p collisions which are characterized by a very high transverse momentum flow in the central region. Some specific items studied are:\\\\ \\\\ \\item -~~Structure of events, where the high transverse momentum is shared by charged and neutral hadron (``jets''). Transverse momentum distribution, correlations and momentum balance for such events. \\item -~~Structure of events, where the high transverse momentum is mostly carried by one identified particle. Quantum number dependence and quantum number correlations of the high transverse momentum events. \\item -~~Structure of events containing large transverse momentum leptons or lepton pairs or direct photons. \\end{enumerate}.sk -~~Study of low momentum electrons and photons. -~~Search for gluonium states. -~~Search for new and rare particles. \\\\ \\\\ A conventional C-type magnet with a 0.5 T field in the direction of the beams together with a 42-layer cylindrical drift chamber detector is used for momentum analysi...

  11. Microbiological sampling of spacecraft cabling, antennas, solar panels and thermal blankets

    Science.gov (United States)

    Koukol, R. C.

    1973-01-01

    Sampling procedures and techniques described resulted from various flight project microbiological monitoring programs of unmanned planetary spacecraft. Concurrent with development of these procedures, compatibility evaluations were effected with the cognizant spacecraft subsystem engineers to assure that degradation factors would not be induced during the monitoring program. Of significance were those areas of the spacecraft configuration for which special handling precautions and/or nonstandard sample gathering techniques were evolved. These spacecraft component areas were: cabling, high gain antenna, solar panels, and thermal blankets. The compilation of these techniques provides a historical reference for both the qualification and quantification of sampling parameters as applied to the Mariner Spacecraft of the late 1960's and early 1970's.

  12. Modelling the reflective thermal contribution to the acceleration of the Pioneer spacecraft

    Energy Technology Data Exchange (ETDEWEB)

    Francisco, F., E-mail: frederico.francisco@ist.utl.pt [Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Bertolami, O., E-mail: orfeu.bertolami@fc.up.pt [Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Gil, P.J.S., E-mail: p.gil@dem.ist.utl.pt [Departamento de Engenharia Mecanica and IDMEC - Instituto de Engenharia Mecanica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Paramos, J., E-mail: paramos@ist.edu [Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

    2012-05-23

    We present an improved method to compute the radiative momentum transfer in the Pioneer 10 and 11 spacecraft that takes into account both diffusive and specular reflection. The method allows for more reliable results regarding the thermal acceleration of the deep-space probes, confirming previous findings. A parametric analysis is performed in order to set upper and lower bounds for the thermal acceleration and its evolution with time.

  13. Modelling the reflective thermal contribution to the acceleration of the Pioneer spacecraft

    International Nuclear Information System (INIS)

    Francisco, F.; Bertolami, O.; Gil, P.J.S.; Páramos, J.

    2012-01-01

    We present an improved method to compute the radiative momentum transfer in the Pioneer 10 and 11 spacecraft that takes into account both diffusive and specular reflection. The method allows for more reliable results regarding the thermal acceleration of the deep-space probes, confirming previous findings. A parametric analysis is performed in order to set upper and lower bounds for the thermal acceleration and its evolution with time.

  14. Antidepressants and Weight Gain

    Science.gov (United States)

    ... 2015;37:46. Blumenthal SR, et al. An electronic health records study of long-term weight gain following antidepressant ... your agreement to the Terms and Conditions and Privacy Policy linked below. Terms and Conditions Privacy Policy ...

  15. Weight gain - unintentional

    Science.gov (United States)

    ... diabetes Hormone changes or medical problems can also cause unintentional weight gain. This may be due to: Cushing syndrome Underactive thyroid, or low thyroid (hypothyroidism) Polycystic ovary syndrome Menopause Pregnancy Bloating, or swelling ...

  16. Detection of gravitational radiation by the Doppler tracking of spacecraft

    International Nuclear Information System (INIS)

    Mashhoon, B.

    1979-01-01

    It has been suggested that the residual Doppler shift in the precision electromagnetic tracking of spacecraft be used to search for gravitational radiation that may be incident on the Earth-spacecraft system. The influence of a gravitational wave on the Doppler shift is calculated, and it is found that the residual shift is dominated by two terms: one is due to the passage of electromagnetic waves through the gravitational radiation field, and the other depends on the change in the relative velocity of the Earth and the spacecraft caused by the external wave. A detailed analysis is given of the influence of gravitational radiation on a binary system with an orbital size small compared to the wavelength of the incident radiation. It is shown that, as a consequence of the interaction with the external wave, the system makes a transition from one Keplerian orbit into another which, in general, has a different energy and angular momentum. It is therefore proposed to search for such effects in the solar system. Observations of the orbit of an artificial Earth satellite, the lunar orbit, and especially the planetary orbits offer exciting possibilities for the detection of gravitational waves of various wavelengths. From the results of the lunar laser ranging experiment and the range measurement to Mars, certain interesting limits may be established on the frequency of incidence of gravitational waves of a given flux on the Earth-Moon and the Earth-Mars systems. This is followed by a brief and preliminary analysis of the possibility of detecting gravitational radiation by measuring a residual secular Doppler shift in the satellite-to-satellite Doppler tracking of two counterorbiting drag-free spacecraft around the Earth as in the Van Patten-Everitt experiment

  17. Temperature control of the Mariner class spacecraft - A seven mission summary.

    Science.gov (United States)

    Dumas, L. N.

    1973-01-01

    Mariner spacecraft have completed five missions of scientific investigation of the planets. Two additional missions are planned. A description of the thermal design of these seven spacecraft is given herein. The factors which have influenced the thermal design include the mission requirements and constraints, the flight environment, certain programmatic considerations and the experience gained as each mission is completed. These factors are reviewed and the impact of each on thermal design and developmental techniques is assessed. It is concluded that the flight success of these spacecraft indicates that adequate temperature control has been obtained, but that improvements in design data, hardware performance and analytical techniques are needed.

  18. Quick Spacecraft Thermal Analysis Tool, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — For spacecraft design and development teams concerned with cost and schedule, the Quick Spacecraft Thermal Analysis Tool (QuickSTAT) is an innovative software suite...

  19. Transverse momentum distributions of identified particles produced ...

    Indian Academy of Sciences (India)

    We assume that the transverse momentum distributions of identified particles measured in final state are contributed by a few energy sources which can be regarded as partons or quarks in the interacting system. The particle is contributed by each source with gluons which have transverse momentum distributions in an ...

  20. Momentum sum rules for fragmentation functions

    International Nuclear Information System (INIS)

    Meissner, S.; Metz, A.; Pitonyak, D.

    2010-01-01

    Momentum sum rules for fragmentation functions are considered. In particular, we give a general proof of the Schaefer-Teryaev sum rule for the transverse momentum dependent Collins function. We also argue that corresponding sum rules for related fragmentation functions do not exist. Our model-independent analysis is supplemented by calculations in a simple field-theoretical model.

  1. Momentum and hamiltonian in complex action theory

    DEFF Research Database (Denmark)

    Nagao, Keiichi; Nielsen, Holger Frits Bech

    2012-01-01

    $-parametrized wave function, which is a solution to an eigenvalue problem of a momentum operator $\\hat{p}$, in FPI with a starting Lagrangian. Solving the eigenvalue problem, we derive the momentum and Hamiltonian. Oppositely, starting from the Hamiltonian we derive the Lagrangian in FPI, and we are led...

  2. Representational momentum in memory for pitch.

    Science.gov (United States)

    Freyd, J J; Kelly, M H; DeKay, M L

    1990-11-01

    When a visual pattern is displayed at successively different orientations such that a rotation or translation is implied, an observer's memory for the final position is displaced forward. This phenomenon of representational momentum shares some similarities with physical momentum. For instance, the amount of memory shift is proportional to the implied velocity of the inducing display; representational momentum is specifically proportional to the final, not the average, velocity; representational momentum follows a continuous stopping function for the first 250 ms or so of the retention interval. In a previous paper (Kelly & Freyd, 1987) we demonstrated a forward memory asymmetry using implied changes in pitch, for subjects without formal musical training. In the current paper we replicate our earlier finding and show that the forward memory asymmetry occurs for subjects with formal musical training as well (Experiment 1). We then show the structural similarity between representational momentum in memory for pitch with previous reports of parametric effects using visual stimuli. We report a velocity effect for auditory momentum (Experiment 2), we demonstrate specifically that the velocity effect depends on the implied acceleration (Experiment 3), and we show that the stopping function for auditory momentum is qualitatively the same as that for visual momentum (Experiment 4). We consider the implications of these results for theories of mental representation.

  3. Angular momentum projected wave-functions

    International Nuclear Information System (INIS)

    Bengtsson, R.; Haakansson, H.B.

    1978-01-01

    Angular momentum projection has become a vital link between intrinsic model-wavefunctions and the physical states one intends to describe. We discuss in general terms some aspects of angular momentum projection and present results from projection on e.g. cranking wavefunctions. Mass densities and spectroscopic factors are also presented for some cases. (author)

  4. Essays on Momentum Strategies in Finance

    NARCIS (Netherlands)

    J.A. van Oord (Arco)

    2016-01-01

    textabstractThis section briefly summarizes in which way we have investigated momentum in this thesis. In Chapter 2 we alter the momentum strategy to improve its performance, while in Chapter 3 we leave the strategy as is, but aim at improving its performance by hedging. In Chapter 4 we develop a

  5. Multiple spacecraft Michelson stellar interferometer

    Science.gov (United States)

    Stachnik, R. V.; Arnold, D.; Melroy, P.; Mccormack, E. F.; Gezari, D. Y.

    1984-01-01

    Results of an orbital analysis and performance assessment of SAMSI (Spacecraft Array for Michelson Spatial Interferometry) are presented. The device considered includes two one-meter telescopes in orbits which are identical except for slightly different inclinations; the telescopes achieve separations as large as 10 km and relay starlight to a central station which has a one-meter optical delay line in one interferometer arm. It is shown that a 1000-km altitude, zero mean inclination orbit affords natural scanning of the 10-km baseline with departures from optical pathlength equality which are well within the corrective capacity of the optical delay line. Electric propulsion is completely adequate to provide the required spacecraft motions, principally those needed for repointing. Resolution of 0.00001 arcsec and magnitude limits of 15 to 20 are achievable.

  6. Spacecraft Tests of General Relativity

    Science.gov (United States)

    Anderson, John D.

    1997-01-01

    Current spacecraft tests of general relativity depend on coherent radio tracking referred to atomic frequency standards at the ground stations. This paper addresses the possibility of improved tests using essentially the current system, but with the added possibility of a space-borne atomic clock. Outside of the obvious measurement of the gravitational frequency shift of the spacecraft clock, a successor to the suborbital flight of a Scout D rocket in 1976 (GP-A Project), other metric tests would benefit most directly by a possible improved sensitivity for the reduced coherent data. For purposes of illustration, two possible missions are discussed. The first is a highly eccentric Earth orbiter, and the second a solar-conjunction experiment to measure the Shapiro time delay using coherent Doppler data instead of the conventional ranging modulation.

  7. Attitude Fusion Techniques for Spacecraft

    DEFF Research Database (Denmark)

    Bjarnø, Jonas Bækby

    Spacecraft platform instability constitutes one of the most significant limiting factors in hyperacuity pointing and tracking applications, yet the demand for accurate, timely and reliable attitude information is ever increasing. The PhD research project described within this dissertation has...... served to investigate the solution space for augmenting the DTU μASC stellar reference sensor with a miniature Inertial Reference Unit (IRU), thereby obtaining improved bandwidth, accuracy and overall operational robustness of the fused instrument. Present day attitude determination requirements are met...... of the instrument, and affecting operations during agile and complex spacecraft attitude maneuvers. As such, there exists a theoretical foundation for augmenting the high frequency performance of the μASC instrument, by harnessing the complementary nature of optical stellar reference and inertial sensor technology...

  8. Autonomous spacecraft rendezvous and docking

    Science.gov (United States)

    Tietz, J. C.; Almand, B. J.

    A storyboard display is presented which summarizes work done recently in design and simulation of autonomous video rendezvous and docking systems for spacecraft. This display includes: photographs of the simulation hardware, plots of chase vehicle trajectories from simulations, pictures of the docking aid including image processing interpretations, and drawings of the control system strategy. Viewgraph-style sheets on the display bulletin board summarize the simulation objectives, benefits, special considerations, approach, and results.

  9. Nonlinearity-induced spacecraft tumbling

    International Nuclear Information System (INIS)

    Amos, A.K.

    1994-01-01

    An existing tumbling criterion for the dumbbell satellite in planar librations is reexamined and modified to reflect a recently identified tumbling mode associated with the horizontal attitude orientation. It is shown that for any initial attitude there exists a critical angular rate below which the motion is oscillatory and harmonic and beyond which a continuous tumbling will ensue. If the angular rate is at the critical value the spacecraft drifts towards the horizontal attitude from which a spontaneous periodic tumbling occurs

  10. Population momentum across vertebrate life histories

    Science.gov (United States)

    Koons, D.N.; Grand, J.B.; Arnold, J.M.

    2006-01-01

    Population abundance is critically important in conservation, management, and demographic theory. Thus, to better understand how perturbations to the life history affect long-term population size, we examined population momentum for four vertebrate classes with different life history strategies. In a series of demographic experiments we show that population momentum generally has a larger effect on long-term population size for organisms with long generation times than for organisms with short generation times. However, patterns between population momentum and generation time varied across taxonomic groups and according to the life history parameter that was changed. Our findings indicate that momentum may be an especially important aspect of population dynamics for long-lived vertebrates, and deserves greater attention in life history studies. Further, we discuss the importance of population momentum in natural resource management, pest control, and conservation arenas. ?? 2006 Elsevier B.V. All rights reserved.

  11. Momentum Maps and Stochastic Clebsch Action Principles

    Science.gov (United States)

    Cruzeiro, Ana Bela; Holm, Darryl D.; Ratiu, Tudor S.

    2018-01-01

    We derive stochastic differential equations whose solutions follow the flow of a stochastic nonlinear Lie algebra operation on a configuration manifold. For this purpose, we develop a stochastic Clebsch action principle, in which the noise couples to the phase space variables through a momentum map. This special coupling simplifies the structure of the resulting stochastic Hamilton equations for the momentum map. In particular, these stochastic Hamilton equations collectivize for Hamiltonians that depend only on the momentum map variable. The Stratonovich equations are derived from the Clebsch variational principle and then converted into Itô form. In comparing the Stratonovich and Itô forms of the stochastic dynamical equations governing the components of the momentum map, we find that the Itô contraction term turns out to be a double Poisson bracket. Finally, we present the stochastic Hamiltonian formulation of the collectivized momentum map dynamics and derive the corresponding Kolmogorov forward and backward equations.

  12. Momentum of the Pure Radiation Field

    Directory of Open Access Journals (Sweden)

    Lehnert B.

    2007-01-01

    Full Text Available The local momentum equation of the pure radiation field is considered in terms of an earlier elaborated and revised electromagnetic theory. In this equation the contribution from the volume force is found to vanish in rectangular geometry, and to become nonzero but negligible in cylindrical geometry. Consequently the radiated momentum is due to the Poynting vector only, as in conventional electrodynamics. It results in physically relevant properties of a photon model having an angular momentum (spin. The Poynting vector concept is further compared to the quantized momentum concept for a free particle, as represented by a spatial gradient operator acting on the wave function. However, this latter otherwise successful concept leads to difficulties in the physical interpretation of known and expected photon properties such as the spin, the negligible loss of transverse momentum across a bounding surface, and the Lorentz invariance.

  13. Worldwide Spacecraft Crew Hatch History

    Science.gov (United States)

    Johnson, Gary

    2009-01-01

    The JSC Flight Safety Office has developed this compilation of historical information on spacecraft crew hatches to assist the Safety Tech Authority in the evaluation and analysis of worldwide spacecraft crew hatch design and performance. The document is prepared by SAIC s Gary Johnson, former NASA JSC S&MA Associate Director for Technical. Mr. Johnson s previous experience brings expert knowledge to assess the relevancy of data presented. He has experience with six (6) of the NASA spacecraft programs that are covered in this document: Apollo; Skylab; Apollo Soyuz Test Project (ASTP), Space Shuttle, ISS and the Shuttle/Mir Program. Mr. Johnson is also intimately familiar with the JSC Design and Procedures Standard, JPR 8080.5, having been one of its original developers. The observations and findings are presented first by country and organized within each country section by program in chronological order of emergence. A host of reference sources used to augment the personal observations and comments of the author are named within the text and/or listed in the reference section of this document. Careful attention to the selection and inclusion of photos, drawings and diagrams is used to give visual association and clarity to the topic areas examined.

  14. Study of the mode of angular velocity damping for a spacecraft at non-standard situation

    Science.gov (United States)

    Davydov, A. A.; Sazonov, V. V.

    2012-07-01

    Non-standard situation on a spacecraft (Earth's satellite) is considered, when there are no measurements of the spacecraft's angular velocity component relative to one of its body axes. Angular velocity measurements are used in controlling spacecraft's attitude motion by means of flywheels. The arising problem is to study the operation of standard control algorithms in the absence of some necessary measurements. In this work this problem is solved for the algorithm ensuring the damping of spacecraft's angular velocity. Such a damping is shown to be possible not for all initial conditions of motion. In the general case one of two possible final modes is realized, each described by stable steady-state solutions of the equations of motion. In one of them, the spacecraft's angular velocity component relative to the axis, for which the measurements are absent, is nonzero. The estimates of the regions of attraction are obtained for these steady-state solutions by numerical calculations. A simple technique is suggested that allows one to eliminate the initial conditions of the angular velocity damping mode from the attraction region of an undesirable solution. Several realizations of this mode that have taken place are reconstructed. This reconstruction was carried out using approximations of telemetry values of the angular velocity components and the total angular momentum of flywheels, obtained at the non-standard situation, by solutions of the equations of spacecraft's rotational motion.

  15. Integrating standard operating procedures with spacecraft automation, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Spacecraft automation has the potential to assist crew members and spacecraft operators in managing spacecraft systems during extended space missions. Automation can...

  16. Building Momentum in Student Engagement: Alternative Breaks and Students' Social Justice and Diversity Orientation

    Science.gov (United States)

    Niehaus, Elizabeth

    2017-01-01

    Drawing from the theory of academic momentum, the purpose of this study is to explore the relationship between what happens before, during, and after an alternative break (AB) experience and students' reported gains in diversity and social justice orientations 1 year after their AB. Findings point to the importance of considering how these types…

  17. Receiver gain function: the actual NMR receiver gain

    OpenAIRE

    Mo, Huaping; Harwood, John S.; Raftery, Daniel

    2010-01-01

    The observed NMR signal size depends on the receiver gain parameter. We propose a receiver gain function to characterize how much the raw FID is amplified by the receiver as a function of the receiver gain setting. Although the receiver is linear for a fixed gain setting, the actual gain of the receiver may differ from what the gain setting suggests. Nevertheless, for a given receiver, we demonstrate that the receiver gain function can be calibrated. Such a calibration enables accurate compar...

  18. Physical approach to price momentum and its application to momentum strategy

    Science.gov (United States)

    Choi, Jaehyung

    2014-12-01

    We introduce various quantitative and mathematical definitions for price momentum of financial instruments. The price momentum is quantified with velocity and mass concepts originated from the momentum in physics. By using the physical momentum of price as a selection criterion, the weekly contrarian strategies are implemented in South Korea KOSPI 200 and US S&P 500 universes. The alternative strategies constructed by the physical momentum achieve the better expected returns and reward-risk measures than those of the traditional contrarian strategy in weekly scale. The portfolio performance is not understood by the Fama-French three-factor model.

  19. Receiver Gain Modulation Circuit

    Science.gov (United States)

    Jones, Hollis; Racette, Paul; Walker, David; Gu, Dazhen

    2011-01-01

    A receiver gain modulation circuit (RGMC) was developed that modulates the power gain of the output of a radiometer receiver with a test signal. As the radiometer receiver switches between calibration noise references, the test signal is mixed with the calibrated noise and thus produces an ensemble set of measurements from which ensemble statistical analysis can be used to extract statistical information about the test signal. The RGMC is an enabling technology of the ensemble detector. As a key component for achieving ensemble detection and analysis, the RGMC has broad aeronautical and space applications. The RGMC can be used to test and develop new calibration algorithms, for example, to detect gain anomalies, and/or correct for slow drifts that affect climate-quality measurements over an accelerated time scale. A generalized approach to analyzing radiometer system designs yields a mathematical treatment of noise reference measurements in calibration algorithms. By treating the measurements from the different noise references as ensemble samples of the receiver state, i.e. receiver gain, a quantitative description of the non-stationary properties of the underlying receiver fluctuations can be derived. Excellent agreement has been obtained between model calculations and radiometric measurements. The mathematical formulation is equivalent to modulating the gain of a stable receiver with an externally generated signal and is the basis for ensemble detection and analysis (EDA). The concept of generating ensemble data sets using an ensemble detector is similar to the ensemble data sets generated as part of ensemble empirical mode decomposition (EEMD) with exception of a key distinguishing factor. EEMD adds noise to the signal under study whereas EDA mixes the signal with calibrated noise. It is mixing with calibrated noise that permits the measurement of temporal-functional variability of uncertainty in the underlying process. The RGMC permits the evaluation of EDA by

  20. Spacecraft Jitter Attenuation Using Embedded Piezoelectric Actuators

    Science.gov (United States)

    Belvin, W. Keith

    1995-01-01

    Remote sensing from spacecraft requires precise pointing of measurement devices in order to achieve adequate spatial resolution. Unfortunately, various spacecraft disturbances induce vibrational jitter in the remote sensing instruments. The NASA Langley Research Center has performed analysis, simulations, and ground tests to identify the more promising technologies for minimizing spacecraft pointing jitter. These studies have shown that the use of smart materials to reduce spacecraft jitter is an excellent match between a maturing technology and an operational need. This paper describes the use of embedding piezoelectric actuators for vibration control and payload isolation. In addition, recent advances in modeling, simulation, and testing of spacecraft pointing jitter are discussed.

  1. Momentum scale in the HARP TPC

    CERN Document Server

    Catanesi, M G; Edgecock, R; Ellis, M; Soler, F J P; Gössling, C; Bunyatov, S; Krasnoperov, A; Popov, B; Serdiouk, V; Tereschenko, V; Di Capua, E; Vidal-Sitjes, G; Artamonov, A; Giani, S; Gilardoni, S; Gorbunov, P; Grant, A; Grossheim, A; Ivanchenko, V; Kayis-Topaksu, A; Panman, J; Papadopoulos, I; Chernyaev, E; Tsukerman, I; Veenhof, R; Wiebusch, C; Zucchelli, P; Blondel, A; Borghi, S; Morone, M C; Prior, G; Schroeter, R; Meurer, C; Gastaldi, Ugo; Mills, G B; Graulich, J S; Grégoire, G; Bonesini, M; Ferri, F; Kirsanov, M; Bagulya, A; Grichine, V; Polukhina, N; Palladino, V; Coney, L; Schmitz, D; Barr, G; De Santo, A; Bobisut, F; Gibin, D; Guglielmi, A; Mezzetto, M; Dumarchez, J; Dore, U; Orestano, D; Pastore, F; Tonazzo, A; Tortora, L; Booth, C; Howlett, L; Bogomilov, M; Chizhov, M; Kolev, D; Tsenov, R; Piperov, S; Temnikov, P; Apollonio, M; Chimenti, P; Giannini, G; Burguet-Castell, J; Cervera-Villanueva, A; Gómez-Cadenas, J J; Martín-Albo, J; Novella, P; Sorel, M

    2007-01-01

    Recently a claim was made that the reconstruction of the large angle tracks in the HARP TPC was affected by a momentum bias as large as 15% at 500 MeV/c transverse momentum. In the following we recall the main issues with the momentum measurement in the HARP TPC, and describe the cross-checks made to validate the momentum scale. Proton-proton elastic scattering data off the hydrogen target are used to alibrate the momentum of charged particles with a precision evaluated to be 3.5%. A full description of the time development of the dynamic distortions in the TPC during physics spills is now available together with a correction algorithm. This allows a new cross-check using an enlarged data set made by comparing positive and negative pion elasticscattering data collected with negative polarity of the solenoid magnet. These data confirm the absence of a bias in the sagitta measurement. The dE/dx versus momentum curves are revisited, and shown to provide a confirmation that the HARP momentum calibration is correc...

  2. Searching sequences of resonant orbits between a spacecraft and Jupiter

    International Nuclear Information System (INIS)

    Formiga, J K S; Prado, A F B A

    2013-01-01

    This research shows a study of the dynamical behavior of a spacecraft that performs a series of close approaches with the planet Jupiter. The main idea is to find a sequence of resonant orbits that allows the spacecraft to stay in the region of the space near the orbit of Jupiter around the Sun gaining energy from each passage by the planet. The dynamical model considers the existence of only two massive bodies in the systems, which are the Sun and Jupiter. They are assumed to be in circular orbits around their center of mass. Analytical equations are used to obtain the values of the parameters required to get this sequence of close approaches. Those equations are useful, because they show which orbits are physically possible when taking into account that the periapsis distances have to be above the surface of the Sun and that the closest approach distances during the passage by Jupiter have to be above its surface

  3. Photomultiplier gain stabilisation

    International Nuclear Information System (INIS)

    Le Baud, P.; Sautiez, B.

    1958-07-01

    By the control and adjustment of magnetic deflection applied to the electron beam of a photomultiplier it has proved possible to flatten the gain curve, forming plateaux at levels dependent upon the voltage at intake. It should be possible to add this simple device to most photomultipliers on the market today. (author) [fr

  4. Photon momentum and optical forces in cavities

    DEFF Research Database (Denmark)

    Partanen, Mikko; Häyrynen, Teppo; Oksanen, Jani

    2016-01-01

    During the past century, the electromagnetic field momentum in material media has been under debate in the Abraham-Minkowski controversy as convincing arguments have been advanced in favor of both the Abraham and Minkowski forms of photon momentum. Here we study the photon momentum and optical....... When describing the steady-state nonequilibrium field distributions we use the recently developed quantized fluctuational electrodynamics (QFED) formalism. While allowing detailed studies of light propagation and quantum field fluctuations in interfering structures, our methods also provide practical...

  5. Angular momentum conservation for uniformly expanding flows

    International Nuclear Information System (INIS)

    Hayward, Sean A

    2007-01-01

    Angular momentum has recently been defined as a surface integral involving an axial vector and a twist 1-form, which measures the twisting around the spacetime due to a rotating mass. The axial vector is chosen to be a transverse, divergence-free, coordinate vector, which is compatible with any initial choice of axis and integral curves. Then a conservation equation expresses the rate of the change of angular momentum along a uniformly expanding flow as a surface integral of angular momentum densities, with the same form as the standard equation for an axial Killing vector, apart from the inclusion of an effective energy tensor for gravitational radiation

  6. Pengembangan Alat Peraga Momentum dengan Sistem Sensor

    Directory of Open Access Journals (Sweden)

    Upik Rahma

    2015-12-01

    Full Text Available Abstract This research aims to develop the props with the concept of momentum by using motion sensors. The method used is a method of research and development (Research and Development. In the implementation of the study outlines the development of research carried out in two stages: Theoretical and Empirical. Results of this research is a props momentum that has been developed and can be used by high school teachers who will perform physical demonstration of the momentum of an object. This tool can also be used as a media demonstration teacher for high school students to explain the physics of matter other. From the test results Viewer tool development momentum in SMAN 100 Jakarta indicate that the tool has been able to meet the expectations of teachers and learners in the orientation of the development of the various needs of props for high school students in the learning process of physics. Based on the results of this study concluded that, with the development of props momentum sensor system has met the criteria of props as a medium of learning physics. Keywords: learning media devlopment, learning media momentum with sensor systems, instructional media. Abstrak Penelitian ini bertujuan mengembangkan alat peraga dengan konsep momentum dengan menggunakan sensor gerak. Metode penelitian yang digunakan adalah metode penelitian pengembangan (Research and Development. Dalam pelaksanaan penelitian secara garis besar penelitian pengembangan dilaksanakan dalam dua tahap yaitu Teoritik dan Empiris. Hasil penelitian ini adalah sebuah alat peraga momentum yang sudah dikembangkan dan dapat digunakan oleh guru SMA yang akan melakukan peragaan fisika tentang momentum suatu benda. Alat ini juga dapat dipakai guru sebagai media demonstrasi bagi siswa SMA untuk menjelaskan materi fisika lainnya. Dari hasil uji coba pengembangan Alat Peraga Momentum di SMAN 100 Jakarta menunjukan bahwa alat telah mampu memenuhi harapan bagi guru dan peserta didik dalam

  7. The electromagnetic impulse pendulum and momentum conservation

    International Nuclear Information System (INIS)

    Graneau, P.; Graneau, P.N.

    1986-01-01

    Largely quantitative experiments by Pappas have indicated that the momentum imparted to an electrodynamic impulse pendulum was not balanced by an equal and opposite momentum change of field energy as required by the special theory of relativity. The authors repeated Pappas' experiment using discharge currents from a capacitor bank which contained a known amount of stored energy. It turned out that, for momentum conservation, the magnetic-field energy required would have been 1000 to 2000 times as large as the energy that was actually stored in the capacitors. In the second part of the paper the pendulum experiments are interpreted in terms of Ampere's force law

  8. Deuterium electrodisintegration at high recoil momentum

    International Nuclear Information System (INIS)

    Steenholen, G.

    1996-01-01

    The availability of continuous electron beams made it possible to carry out various deuterium electro-disintegration experiments in kinematical domains corresponding to a high recoil momentum. Three such experiments are discussed: 1) the left-right asymmetry with respect to the direction of the momentum transfer has been measured with good precision; 2) cross sections have been obtained in a kinematical region well above the quasi-elastic peak; 3) data have been taken in quasi-elastic kinematics that can be used to study high-momentum components in the deuterium wave function [ru

  9. Spacecraft Design Thermal Control Subsystem

    Science.gov (United States)

    Miyake, Robert N.

    2008-01-01

    The Thermal Control Subsystem engineers task is to maintain the temperature of all spacecraft components, subsystems, and the total flight system within specified limits for all flight modes from launch to end-of-mission. In some cases, specific stability and gradient temperature limits will be imposed on flight system elements. The Thermal Control Subsystem of "normal" flight systems, the mass, power, control, and sensing systems mass and power requirements are below 10% of the total flight system resources. In general the thermal control subsystem engineer is involved in all other flight subsystem designs.

  10. Gaining momentum : advanced multilateral technology touted as key to unlocking Manville CBM

    International Nuclear Information System (INIS)

    Smith, M.

    2006-01-01

    A new technology developed by a Louisiana-based company called Gardes Energy Services Inc. may be used to develop Canada's Manville coalbed methane (CBM) play. Two Canadian companies have recently agreed to test the patented technology in the Manville play, which has a permeability of only 3 to 4 millidarcies in shallower Manville targets and less than 1 millidarcy in deeper targets. The technology entails the drilling of multiple, radial wells with lateral branches. The 2-string dual injection drilling technique allows non-damaging underbalanced drilling of multiple lateral branches in each seam when combined with the patented Upstock process. The Upstock is then lowered to the lowest seam on a carrier string to redirect the drilling assembly into the first coal seam. Drilling fluid is pumped down the drillstring, activating the drilling assembly's mud motor and guidance system. Injection rates are adjusted according to downhole measurement-while drilling pressure sensors to maintain underbalanced drilling. Continuous circulation through the concentric casing system eliminates the potentially damaging surging that occurs in conventional drilling. By reorienting the bent housing on the drilling motor, branch laterals are added in each coal seam. Once completed, the drilling assembly is pulled, the Upstock is lifted on the carrier string to the next seam of interest, and the process is repeated. The dual annulus process lowers the equivalent circulating density below that of the formation pressure, preventing drilling fluid from invading and damaging the formation. Formation water is typically used as the drilling fluid. Once drilling is completed, an electric submersible pump (ESP) is lowered on tubing to the sump area and water is pumped to surface, allowing the methane to desorb and be produced through perforations into and up the inner annulus. The technique reduces the environmental impact of drilling, as 1 area can be used to drain an area the equivalent of 16 locations. It was concluded that the company is now looking to supply the technology and capital to develop CBM properties with other partners. 3 figs

  11. Gaining momentum: GeoGebra inspires educators and students around the world

    Directory of Open Access Journals (Sweden)

    Zsolt Lavicza

    2010-05-01

    Full Text Available The use of technology is slowly becoming a substantial part of today’s education. Although due to the increased accessibility of affordable computing technologies in the 1980s and 90s it was predicted that computers would become rapidly integrated into mathematics teaching and learning (Kaput, 1992, technology uptake in schools has been considerably slow. The current expansion of technology use took a new unconventional direction: a bottom-up, community-based collaborative development, catalyzed by Internet-based communities and increasingly available community-developed software packages. During the past decades it has been demonstrated that a large number of enthusiasts can alter conventional thinking and models of development and innovation. The success of open source projects like Linux, Firefox, Moodle, and Wikipedia shows that collaboration and sharing can produce valuable resources in a variety of areas of life. While working on the open-source project GeoGebra we are witnessing the emergence of an enthusiastic international community around the software.

  12. Post-genomics nanotechnology is gaining momentum: nanoproteomics and applications in life sciences.

    Science.gov (United States)

    Kobeissy, Firas H; Gulbakan, Basri; Alawieh, Ali; Karam, Pierre; Zhang, Zhiqun; Guingab-Cagmat, Joy D; Mondello, Stefania; Tan, Weihong; Anagli, John; Wang, Kevin

    2014-02-01

    The post-genomics era has brought about new Omics biotechnologies, such as proteomics and metabolomics, as well as their novel applications to personal genomics and the quantified self. These advances are now also catalyzing other and newer post-genomics innovations, leading to convergences between Omics and nanotechnology. In this work, we systematically contextualize and exemplify an emerging strand of post-genomics life sciences, namely, nanoproteomics and its applications in health and integrative biological systems. Nanotechnology has been utilized as a complementary component to revolutionize proteomics through different kinds of nanotechnology applications, including nanoporous structures, functionalized nanoparticles, quantum dots, and polymeric nanostructures. Those applications, though still in their infancy, have led to several highly sensitive diagnostics and new methods of drug delivery and targeted therapy for clinical use. The present article differs from previous analyses of nanoproteomics in that it offers an in-depth and comparative evaluation of the attendant biotechnology portfolio and their applications as seen through the lens of post-genomics life sciences and biomedicine. These include: (1) immunosensors for inflammatory, pathogenic, and autoimmune markers for infectious and autoimmune diseases, (2) amplified immunoassays for detection of cancer biomarkers, and (3) methods for targeted therapy and automatically adjusted drug delivery such as in experimental stroke and brain injury studies. As nanoproteomics becomes available both to the clinician at the bedside and the citizens who are increasingly interested in access to novel post-genomics diagnostics through initiatives such as the quantified self, we anticipate further breakthroughs in personalized and targeted medicine.

  13. Morse Potential in the Momentum Representation

    Institute of Scientific and Technical Information of China (English)

    孙国华; 董世海

    2012-01-01

    The momentum representation of the Morse potential is presented analytically by hypergeometric function. The properties with respect to the momentum p and potential parameter β are studied. Note that [q2(p)l is a nodeless function and the mutual orthogonality of functions is ensured by the phase functions arg[(p)], It is interesting to see that the [~ (p)[ is symmetric with respect to the axis p = 0 and the number of wave crest of [ (p)[ is equal to n + 1. We also study the variation of ]k(p)l with respect to . The arnplitude of |ψ(p)] first increases with the quantum number n and then deceases. Finally, we notice that the discontinuity in phase occurs at some points of the momentum p and the position and momentum probability densities are symmetric with respect to their arguments.

  14. Photon-momentum transfer in molecular photoionization

    Science.gov (United States)

    Chelkowski, Szczepan; Bandrauk, André D.

    2018-05-01

    In most models and theoretical calculations describing multiphoton ionization by infrared light, the dipole approximation is used. This is equivalent to setting the very small photon momentum to zero. Using numerical solutions of the (nondipole) three-dimensional time-dependent Schrödinger equation for one electron in a H2+ molecular ion we investigate the effect the photon-momentum transfer to the photoelectron in an H2+ ion in various regimes. We find that the photon-momentum transfer in a molecule is very different from the transfer in atoms due to two-center interference effects. The photon-momentum transfer is very sensitive to the symmetry of the initial electronic state and is strongly dependent on the internuclear distance and on the ellipticity of the laser.

  15. Amplitude damping channel for orbital angular momentum

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2010-03-01

    Full Text Available Since the pioneering work on the entanglement of the orbital angular momentum (OAM) states of light, much attention has been devoted to the subject, with particular attention into the quantum aspects of information processing using OAM. Furthermore...

  16. Energy-momentum tensor in scalar QED

    International Nuclear Information System (INIS)

    Joglekar, S.D.; Misra, A.

    1988-01-01

    We consider the renormalization of the energy-momentum tensor in scalar quantum electrodynamics. We show the need for adding an improvement term to the conventional energy-momentum tensor. We consider two possible forms for the improvement term: (i) one in which the improvement coefficient is a finite function of bare parameters of the theory (so that the energy-momentum tensor can be obtained from an action that is a finite function of bare quantities); (ii) one in which the improvement coefficient is a finite quantity, i.e., a finite function of renormalized parameters. We establish a negative result; viz., neither form leads to a finite energy-momentum tensor to O(e 2 λ/sup n/). .AE

  17. Morse Potential in the Momentum Representation

    International Nuclear Information System (INIS)

    Sun Guohua; Dong Shihai

    2012-01-01

    The momentum representation of the Morse potential is presented analytically by hypergeometric function. The properties with respect to the momentum p and potential parameter β are studied. Note that |Ψ(p)| is a nodeless function and the mutual orthogonality of functions is ensured by the phase functions arg[Ψ(p)]. It is interesting to see that the |Ψ(p)| is symmetric with respect to the axis p = 0 and the number of wave crest of |Ψ(p)| is equal to n + 1. We also study the variation of |Ψ(p)| with respect to β. The amplitude of |Ψ(p)| first increases with the quantum number n and then deceases. Finally, we notice that the discontinuity in phase occurs at some points of the momentum p and the position and momentum probability densities are symmetric with respect to their arguments.

  18. Constituent models and large transverse momentum reactions

    International Nuclear Information System (INIS)

    Brodsky, S.J.

    1975-01-01

    The discussion of constituent models and large transverse momentum reactions includes the structure of hard scattering models, dimensional counting rules for large transverse momentum reactions, dimensional counting and exclusive processes, the deuteron form factor, applications to inclusive reactions, predictions for meson and photon beams, the charge-cubed test for the e/sup +-/p → e/sup +-/γX asymmetry, the quasi-elastic peak in inclusive hadronic reactions, correlations, and the multiplicity bump at large transverse momentum. Also covered are the partition method for bound state calculations, proofs of dimensional counting, minimal neutralization and quark--quark scattering, the development of the constituent interchange model, and the A dependence of high transverse momentum reactions

  19. Orbital-angular-momentum entanglement in turbulence

    CSIR Research Space (South Africa)

    Hamadou Ibrahim, A

    2013-06-01

    Full Text Available The turbulence-induced decay of orbital-angular-momentum (OAM) entanglement between two photons is investigated numerically and experimentally. To compare our resultswith previouswork,we simulate the turbulent atmosphere with a single phase screen...

  20. Momentum sharing in imbalanced Fermi systems

    Science.gov (United States)

    Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.; Hakobyan, H.; Higinbotham, D. W.; Braverman, M.; Brooks, W. K.; Gilad, S.; Adhikari, K. P.; Arrington, J.; Asryan, G.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Beck, A.; Beck, S. May-Tal; Bedlinskiy, I.; Bertozzi, W.; Biselli, A.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Colaneri, L.; Cole, P. L.; Crede, V.; D'Angelo, A.; De Vita, R.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Forest, T.; Garillon, B.; Garcon, M.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Girod, F. X.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkanov, B. I.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Korover, I.; Kuhn, S. E.; Kubarovsky, V.; Lenisa, P.; Levine, W. I.; Livingston, K.; Lowry, M.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mokeev, V.; Movsisyan, A.; Camacho, C. Munoz; Mustapha, B.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Roy, P.; Rossi, P.; Sabatié, F.; Schott, D.; Schumacher, R. A.; Sharabian, Y. G.; Smith, G. D.; Shneor, R.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tkachenko, S.; Ungaro, M.; Vlassov, A. V.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Wood, S. A.; Zachariou, N.; Zana, L.; Zhao, Z. W.; Zheng, X.; Zonta, I.; aff16

    2014-10-01

    The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using 12C, 27Al, 56Fe, and 208Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

  1. Momentum sharing in imbalanced Fermi systems

    Energy Technology Data Exchange (ETDEWEB)

    Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.; Hakobyan, H.; Higinbotham, D. W.; Braverman, M.; Brooks, W. K.; Gilad, S.; Adhikari, K. P.; Arrington, J.; Asryan, G.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Beck, A.; Beck, S. M. -T.; Bedlinskiy, I.; Bertozzi, W.; Biselli, A.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Colaneri, L.; Cole, P. L.; Crede, V.; D' Angelo, A.; De Vita, R.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Forest, T.; Garillon, B.; Garcon, M.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Girod, F. X.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkanov, B. I.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Korover, I.; Kuhn, S. E.; Kubarovsky, V.; Lenisa, P.; Levine, W. I.; Livingston, K.; Lowry, M.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mokeev, V.; Movsisyan, A.; Camacho, C. M.; Mustapha, B.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Roy, P.; Rossi, P.; Sabatie, F.; Schott, D.; Schumacher, R. A.; Sharabian, Y. G.; Smith, G. D.; Shneor, R.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tkachenko, S.; Ungaro, M.; Vlassov, A. V.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Wood, S. A.; Zachariou, N.; Zana, L.; Zhao, Z. W.; Zheng, X.; Zonta, I.

    2014-10-16

    The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using C-12, Al-27, Fe-56, and Pb-208 targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

  2. Exclusive processes at high momentum transfer

    CERN Document Server

    Radyushkin, Anatoly; Stoker, Paul

    2002-01-01

    This book focuses on the physics of exclusive processes at high momentum transfer and their description in terms of generalized parton distributions, perturbative QCD, and relativistic quark models. It covers recent developments in the field, both theoretical and experimental.

  3. THE MOMENTUM EFFECT EXEMPLIFIES THE INFLUENCE OF INVESTORS’ IRRATIONAL BEHAVIOUR ON CHANGING PRICES OF SHARES AND STOCKS: AN ANALYSIS OF THE MOMENTUM EFFECT ON THE WARSAW STOCK EXCHANGE

    Directory of Open Access Journals (Sweden)

    Paweł Merło

    2015-08-01

    Full Text Available An efficient market should not show any anomalies. When new information reaches a market which is efficient, it should automatically translate into prices of assets, which ought to eliminate the possibility of gaining an advantage over other investors, thus preventing excess profits. However, studies on capital markets indicate that in reality it is possible to earn unusually high profits by taking advantage of certain anomalies which occur on a given market. Among such anomalies there is the momentum effect. This study performed on the Stock Exchange in Warsaw has shown that the momentum effect occurred throughout the entire analyzed time period. Positive returns demonstrated for investment strategies based on the momentum effect were unexplainable by the classical theory of finances. A correlation was found between the economic situation on the stock exchange and portfolio return rates, but it was too weak to attribute the effect to a single decisive factor. In addition, the returns from investments based on the momentum effect were statistically higher in January than in the other months, which was caused by the January effect, stimulating the occurrence of statistically higher returns at the beginning of a year rather than later on during the analyzed period of time. Research in this field carried out in other countries justifies the claim that there are many irrational factors which together create the momentum effect on the stock exchange. Thus, it is possible to conclude that irrational decisions may have strong impact on the pricing of stocks on the capital market. The momentum effect persisted throughout the entire analyzed period, although its power changed cyclically, which coincides with results of research carried out in other countries. The fact that the momentum effect did not disappear may suggest that the factors involved in its creation are an indispensable part of the market, and this seems to undermine the commonly accepted

  4. Benefits of Spacecraft Level Vibration Testing

    Science.gov (United States)

    Gordon, Scott; Kern, Dennis L.

    2015-01-01

    NASA-HDBK-7008 Spacecraft Level Dynamic Environments Testing discusses the approaches, benefits, dangers, and recommended practices for spacecraft level dynamic environments testing, including vibration testing. This paper discusses in additional detail the benefits and actual experiences of vibration testing spacecraft for NASA Goddard Space Flight Center (GSFC) and Jet Propulsion Laboratory (JPL) flight projects. JPL and GSFC have both similarities and differences in their spacecraft level vibration test approach: JPL uses a random vibration input and a frequency range usually starting at 5 Hz and extending to as high as 250 Hz. GSFC uses a sine sweep vibration input and a frequency range usually starting at 5 Hz and extending only to the limits of the coupled loads analysis (typically 50 to 60 Hz). However, both JPL and GSFC use force limiting to realistically notch spacecraft resonances and response (acceleration) limiting as necessary to protect spacecraft structure and hardware from exceeding design strength capabilities. Despite GSFC and JPL differences in spacecraft level vibration test approaches, both have uncovered a significant number of spacecraft design and workmanship anomalies in vibration tests. This paper will give an overview of JPL and GSFC spacecraft vibration testing approaches and provide a detailed description of spacecraft anomalies revealed.

  5. Do Momentum Strategies Work?: - Australian Evidence

    OpenAIRE

    Michael E. Drew; Madhu Veeraraghavan; Min Ye

    2004-01-01

    This paper investigates the profitability of momentum investment strategy and the predictive power of trading volume for equities listed in the Australian Stock Exchange. Recent research finds that momentum and trading volume appear to predict subsequent returns in U.S. market and past volume helps to reconcile intermediate-horizon “under reaction” and long-horizon “overreaction” effects. However, bulk of the evidence on this important relationship between past returns and future returns is l...

  6. The gluon propagator in momentum space

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, C. [Washington Univ., St. Louis, MO (United States). Dept. of Physics; Parrinello, C. [New York Univ., NY (United States). Dept. of Physics]|[Brookhaven National Lab., Upton, NY (United States); Soni, A. [Brookhaven National Lab., Upton, NY (United States)

    1992-12-31

    We consider quenched QCD on a 16{sup 3}{times}40 lattice at {beta}=6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others.

  7. The gluon propagator in momentum space

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, C. (Washington Univ., St. Louis, MO (United States). Dept. of Physics); Parrinello, C. (New York Univ., NY (United States). Dept. of Physics Brookhaven National Lab., Upton, NY (United States)); Soni, A. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    We consider quenched QCD on a 16[sup 3][times]40 lattice at [beta]=6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others.

  8. The gluon propagator in momentum space

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, C. (Dept. of Physics, Washington Univ., St. Louis, MO (United States)); Parrinello, C. (Physics Dept., New York Univ., NY (United States) Physics Dept., Brookhaven National Lab., Upton, NY (United States)); Soni, A. (Physics Dept., Brookhaven National Lab., Upton, NY (United States))

    1993-03-01

    We consider quenched QCD on a 16[sup 3] x 40 lattice at [beta] = 6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others. (orig.)

  9. Behavioral momentum in the treatment of noncompliance.

    OpenAIRE

    Mace, F C; Hock, M L; Lalli, J S; West, B J; Belfiore, P; Pinter, E; Brown, D K

    1988-01-01

    Behavioral momentum refers to the tendency for behavior to persist following a change in environmental conditions. The greater the rate of reinforcement, the greater the behavioral momentum. The intervention for noncompliance consisted of issuing a sequence of commands with which the subject was very likely to comply (i.e., high-probability commands) immediately prior to issuing a low-probability command. In each of five experiments, the high-probability command sequence resulted in a "moment...

  10. Momentum distribution in the nucleus. II

    International Nuclear Information System (INIS)

    Amado, R.D.; Woloshyn, R.M.

    1977-01-01

    We calculate the single particle momentum distribution n(q) for a one-dimensional model with delta forces. There is a domain of q for which n(q) has an exponential falloff; but, after allowance is made for the nonsaturation in the model, that domain does not grow significantly with particle number. The relation of this result to large momentum scattering from the nucleus and to the Hartree approximation is briefly discussed

  11. The gluon propagator in momentum space

    International Nuclear Information System (INIS)

    Bernard, C.; Soni, A.

    1992-01-01

    We consider quenched QCD on a 16 3 x40 lattice at β=6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others

  12. Average Transverse Momentum Quantities Approaching the Lightfront

    OpenAIRE

    Boer, Daniel

    2015-01-01

    In this contribution to Light Cone 2014, three average transverse momentum quantities are discussed: the Sivers shift, the dijet imbalance, and the $p_T$ broadening. The definitions of these quantities involve integrals over all transverse momenta that are overly sensitive to the region of large transverse momenta, which conveys little information about the transverse momentum distributions of quarks and gluons inside hadrons. TMD factorization naturally suggests alternative definitions of su...

  13. Hybrid spacecraft attitude control system

    Directory of Open Access Journals (Sweden)

    Renuganth Varatharajoo

    2016-02-01

    Full Text Available The hybrid subsystem design could be an attractive approach for futurespacecraft to cope with their demands. The idea of combining theconventional Attitude Control System and the Electrical Power System ispresented in this article. The Combined Energy and Attitude ControlSystem (CEACS consisting of a double counter rotating flywheel assemblyis investigated for small satellites in this article. Another hybrid systemincorporating the conventional Attitude Control System into the ThermalControl System forming the Combined Attitude and Thermal ControlSystem (CATCS consisting of a "fluid wheel" and permanent magnets isalso investigated for small satellites herein. The governing equationsdescribing both these novel hybrid subsystems are presented and theironboard architectures are numerically tested. Both the investigated novelhybrid spacecraft subsystems comply with the reference missionrequirements.The hybrid subsystem design could be an attractive approach for futurespacecraft to cope with their demands. The idea of combining theconventional Attitude Control System and the Electrical Power System ispresented in this article. The Combined Energy and Attitude ControlSystem (CEACS consisting of a double counter rotating flywheel assemblyis investigated for small satellites in this article. Another hybrid systemincorporating the conventional Attitude Control System into the ThermalControl System forming the Combined Attitude and Thermal ControlSystem (CATCS consisting of a "fluid wheel" and permanent magnets isalso investigated for small satellites herein. The governing equationsdescribing both these novel hybrid subsystems are presented and theironboard architectures are numerically tested. Both the investigated novelhybrid spacecraft subsystems comply with the reference missionrequirements.

  14. Analysis of angular momentum properties of photons emitted in fundamental atomic processes

    Science.gov (United States)

    Zaytsev, V. A.; Surzhykov, A. S.; Shabaev, V. M.; Stöhlker, Th.

    2018-04-01

    Many atomic processes result in the emission of photons. Analysis of the properties of emitted photons, such as energy and angular distribution as well as polarization, is regarded as a powerful tool for gaining more insight into the physics of corresponding processes. Another characteristic of light is the projection of its angular momentum upon propagation direction. This property has attracted a special attention over the past decades due to studies of twisted (or vortex) light beams. Measurements being sensitive to this projection may provide valuable information about the role of angular momentum in the fundamental atomic processes. Here we describe a simple theoretical method for determination of the angular momentum properties of the photons emitted in various atomic processes. This method is based on the evaluation of expectation value of the total angular momentum projection operator. To illustrate the method, we apply it to the textbook examples of plane-wave, spherical-wave, and Bessel light. Moreover, we investigate the projection of angular momentum for the photons emitted in the process of the radiative recombination with ionic targets. It is found that the recombination photons do carry a nonzero projection of the orbital angular momentum.

  15. Learn and gain

    CERN Document Server

    Al-Alami, Suhair Eyad Jamal

    2013-01-01

    Initiating the slogan ""love it, live it"", Learn and Gain includes eight short stories, chosen to illustrate various modes of narration, as well as to provoke reflection and discussion on a range of issues. All texts utilized here illustrate how great writers can, with their insight and gift for words, help us to see the world we live in, in new probing and exciting ways. What characterises the book, the author believes, is the integration of the skills of literary competence, communicative c...

  16. Universal spin-momentum locked optical forces

    Energy Technology Data Exchange (ETDEWEB)

    Kalhor, Farid [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 1H9 (Canada); Thundat, Thomas [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1H9 (Canada); Jacob, Zubin, E-mail: zjacob@purdue.edu [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 1H9 (Canada); Birck Nanotechnology Center, Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906 (United States)

    2016-02-08

    Evanescent electromagnetic waves possess spin-momentum locking, where the direction of propagation (momentum) is locked to the inherent polarization of the wave (transverse spin). We study the optical forces arising from this universal phenomenon and show that the fundamental origin of recently reported non-trivial optical chiral forces is spin-momentum locking. For evanescent waves, we show that the direction of energy flow, the direction of decay, and the direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and HE{sub 11} mode of an optical fiber. Furthermore, we explain how the recently reported phenomena of lateral optical force on chiral and achiral particles are caused by the transverse spin of the evanescent field and the spin-momentum locking phenomenon. Finally, we propose an experiment to identify the unique lateral forces arising from the transverse spin in the optical fiber and point to fundamental differences of the spin density from the well-known orbital angular momentum of light. Our work presents a unified view on spin-momentum locking and how it affects optical forces on chiral and achiral particles.

  17. Transverse angular momentum in topological photonic crystals

    Science.gov (United States)

    Deng, Wei-Min; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2018-01-01

    Engineering local angular momentum of structured light fields in real space enables applications in many fields, in particular, the realization of unidirectional robust transport in topological photonic crystals with a non-trivial Berry vortex in momentum space. Here, we show transverse angular momentum modes in silicon topological photonic crystals when considering transverse electric polarization. Excited by a chiral external source with either transverse spin angular momentum or transverse phase vortex, robust light flow propagating along opposite directions is observed in several kinds of sharp-turn interfaces between two topologically-distinct silicon photonic crystals. A transverse orbital angular momentum mode with alternating phase vortex exists at the boundary of two such photonic crystals. In addition, unidirectional transport is robust to the working frequency even when the ring size or location of the pseudo-spin source varies in a certain range, leading to the superiority of the broadband photonic device. These findings enable one to make use of transverse angular momentum, a kind of degree of freedom, to achieve unidirectional robust transport in the telecom region and other potential applications in integrated photonic circuits, such as on-chip robust delay lines.

  18. Studies of Fission Fragment Rocket Engine Propelled Spacecraft

    Science.gov (United States)

    Werka, Robert O.; Clark, Rodney; Sheldon, Rob; Percy, Thomas K.

    2014-01-01

    The NASA Office of Chief Technologist has funded from FY11 through FY14 successive studies of the physics, design, and spacecraft integration of a Fission Fragment Rocket Engine (FFRE) that directly converts the momentum of fission fragments continuously into spacecraft momentum at a theoretical specific impulse above one million seconds. While others have promised future propulsion advances if only you have the patience, the FFRE requires no waiting, no advances in physics and no advances in manufacturing processes. Such an engine unequivocally can create a new era of space exploration that can change spacecraft operation. The NIAC (NASA Institute for Advanced Concepts) Program Phase 1 study of FY11 first investigated how the revolutionary FFRE technology could be integrated into an advanced spacecraft. The FFRE combines existent technologies of low density fissioning dust trapped electrostatically and high field strength superconducting magnets for beam management. By organizing the nuclear core material to permit sufficient mean free path for escape of the fission fragments and by collimating the beam, this study showed the FFRE could convert nuclear power to thrust directly and efficiently at a delivered specific impulse of 527,000 seconds. The FY13 study showed that, without increasing the reactor power, adding a neutral gas to the fission fragment beam significantly increased the FFRE thrust through in a manner analogous to a jet engine afterburner. This frictional interaction of gas and beam resulted in an engine that continuously produced 1000 pound force of thrust at a delivered impulse of 32,000 seconds, thereby reducing the currently studied DRM 5 round trip mission to Mars from 3 years to 260 days. By decreasing the gas addition, this same engine can be tailored for much lower thrust at much higher impulse to match missions to more distant destinations. These studies created host spacecraft concepts configured for manned round trip journeys. While the

  19. Estimating Torque Imparted on Spacecraft Using Telemetry

    Science.gov (United States)

    Lee, Allan Y.; Wang, Eric K.; Macala, Glenn A.

    2013-01-01

    There have been a number of missions with spacecraft flying by planetary moons with atmospheres; there will be future missions with similar flybys. When a spacecraft such as Cassini flies by a moon with an atmosphere, the spacecraft will experience an atmospheric torque. This torque could be used to determine the density of the atmosphere. This is because the relation between the atmospheric torque vector and the atmosphere density could be established analytically using the mass properties of the spacecraft, known drag coefficient of objects in free-molecular flow, and the spacecraft velocity relative to the moon. The density estimated in this way could be used to check results measured by science instruments. Since the proposed methodology could estimate disturbance torque as small as 0.02 N-m, it could also be used to estimate disturbance torque imparted on the spacecraft during high-altitude flybys.

  20. Computer simulation of spacecraft/environment interaction

    International Nuclear Information System (INIS)

    Krupnikov, K.K.; Makletsov, A.A.; Mileev, V.N.; Novikov, L.S.; Sinolits, V.V.

    1999-01-01

    This report presents some examples of a computer simulation of spacecraft interaction with space environment. We analysed a set data on electron and ion fluxes measured in 1991-1994 on geostationary satellite GORIZONT-35. The influence of spacecraft eclipse and device eclipse by solar-cell panel on spacecraft charging was investigated. A simple method was developed for an estimation of spacecraft potentials in LEO. Effects of various particle flux impact and spacecraft orientation are discussed. A computer engineering model for a calculation of space radiation is presented. This model is used as a client/server model with WWW interface, including spacecraft model description and results representation based on the virtual reality markup language

  1. Computer simulation of spacecraft/environment interaction

    CERN Document Server

    Krupnikov, K K; Mileev, V N; Novikov, L S; Sinolits, V V

    1999-01-01

    This report presents some examples of a computer simulation of spacecraft interaction with space environment. We analysed a set data on electron and ion fluxes measured in 1991-1994 on geostationary satellite GORIZONT-35. The influence of spacecraft eclipse and device eclipse by solar-cell panel on spacecraft charging was investigated. A simple method was developed for an estimation of spacecraft potentials in LEO. Effects of various particle flux impact and spacecraft orientation are discussed. A computer engineering model for a calculation of space radiation is presented. This model is used as a client/server model with WWW interface, including spacecraft model description and results representation based on the virtual reality markup language.

  2. Nonlinear model and attitude dynamics of flexible spacecraft with large amplitude slosh

    Science.gov (United States)

    Deng, Mingle; Yue, Baozeng

    2017-04-01

    This paper is focused on the nonlinearly modelling and attitude dynamics of spacecraft coupled with large amplitude liquid sloshing dynamics and flexible appendage vibration. The large amplitude fuel slosh dynamics is included by using an improved moving pulsating ball model. The moving pulsating ball model is an equivalent mechanical model that is capable of imitating the whole liquid reorientation process. A modification is introduced in the capillary force computation in order to more precisely estimate the settling location of liquid in microgravity or zero-g environment. The flexible appendage is modelled as a three dimensional Bernoulli-Euler beam and the assumed modal method is employed to derive the nonlinear mechanical model for the overall coupled system of liquid filled spacecraft with appendage. The attitude maneuver is implemented by the momentum transfer technique, and a feedback controller is designed. The simulation results show that the liquid sloshing can always result in nutation behavior, but the effect of flexible deformation of appendage depends on the amplitude and direction of attitude maneuver performed by spacecraft. Moreover, it is found that the liquid sloshing and the vibration of flexible appendage are coupled with each other, and the coupling becomes more significant with more rapid motion of spacecraft. This study reveals that the appendage's flexibility has influence on the liquid's location and settling time in microgravity. The presented nonlinear system model can provide an important reference for the overall design of the modern spacecraft composed of rigid platform, liquid filled tank and flexible appendage.

  3. Optimal Autonomous Spacecraft Resiliency Maneuvers Using Metaheuristics

    Science.gov (United States)

    2014-09-15

    This work was accepted for published by the American Institute of Aeronautics and Astronautics (AIAA) Journal of Spacecraft and Rockets in July 2014...publication in the AIAA Journal of Spacecraft and Rockets . Chapter 5 introduces an impulsive maneuvering strategy to deliver a spacecraft to its final...upon arrival r2 and v2 , respectively. The variable T2 determines the time of flight needed to make the maneuver, and the variable θ2 determines the

  4. Energy and momentum management of the Space Station using magnetically suspended composite rotors

    Science.gov (United States)

    Eisenhaure, D. B.; Oglevie, R. E.; Keckler, C. R.

    1985-01-01

    The research addresses the feasibility of using magnetically suspended composite rotors to jointly perform the energy and momentum management functions of an advanced manned Space Station. Recent advancements in composite materials, magnetic suspensions, and power conversion electronics have given flywheel concepts the potential to simultaneously perform these functions for large, long duration spacecraft, while offering significant weight, volume, and cost savings over conventional approaches. The Space Station flywheel concept arising out of this study consists of a composite-material rotor, a large-angle magnetic suspension (LAMS) system, an ironless armature motor/generator, and high-efficiency power conversion electronics. The LAMS design permits the application of appropriate spacecraft control torques without the use of conventional mechanical gimbals. In addition, flywheel systems have the growth potential and modularity needed to play a key role in many future system developments.

  5. Development of model for studies on momentum transfer in electrochemical cells with entry region coil as turbulence promoter

    Science.gov (United States)

    Penta Rao, Tamarba; Rajendra Prasad, P.

    2018-04-01

    Entry region swirl promoters gain importance in industry because of its effectiveness in augmentation of mass and heat transfer augmentation. Design of equipment needs momentum transfer data along with mass or heat transfer data. Hence an experimental investigation was carried out with coaxially placed entry region spiral coil as turbulence promoters on momentum transfer in forced convection flow of electrolyte in circular conduits. Aqueous solution of sodium hydroxide and 0.01 M equimolal Ferri-ferro cyanide system was chosen for the study. The study covered parameters like effect of pitch of the coil, effect of length of the coil, diameter of the coil, diameter of the coil wire, diameter of the annular rod. The promoter is measured by limiting current technique using diffusion controlled electrochemical reactions. The study comprises of evaluation of momentum transfer rates at the outer wall of the electrochemical cell. Pressure drop measurements were also made to obtain the energy consumption pattern. Within the range of variables covered. The results are correlated by the momentum transfer similarity function. Momentum transfer coefficients were evaluated from measured limiting currents. Effect of each parameter was studied in terms of friction factor. A model was developed for momentum transfer. The experimental data on momentum transfer was modeled in terms of momentum transfer function and Reynolds number, geometric parameters.

  6. Ulysses spacecraft control and monitoring system

    Science.gov (United States)

    Hamer, P. A.; Snowden, P. J.

    1991-01-01

    The baseline Ulysses spacecraft control and monitoring system (SCMS) concepts and the converted SCMS, residing on a DEC/VAX 8350 hardware, are considered. The main functions of the system include monitoring and displaying spacecraft telemetry, preparing spacecraft commands, producing hard copies of experimental data, and archiving spacecraft telemetry. The SCMS system comprises over 20 subsystems ranging from low-level utility routines to the major monitoring and control software. These in total consist of approximately 55,000 lines of FORTRAN source code and 100 VMS command files. The SCMS major software facilities are described, including database files, telemetry processing, telecommanding, archiving of data, and display of telemetry.

  7. Operationally Responsive Spacecraft Subsystem, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Saber Astronautics proposes spacecraft subsystem control software which can autonomously reconfigure avionics for best performance during various mission conditions....

  8. Gains from quota trade

    DEFF Research Database (Denmark)

    Andersen, Jesper Levring; Bogetoft, Peter

    2007-01-01

    We provide a framework for evaluating potential effects of introducing tradable quotas to a sector. The effects depend on the economies of scale and scope of the production technology, and on firms' ability and willingness to learn best practice methods (catching up) and to change their input...... and output composition (mix). To illustrate our approach, data from the Danish fishery are used to calculate the potential gains from introducing individually transferable fishing quotas. Data envelopment analysis is used to model the production technology. We find that pure reallocation is as important...

  9. Gaining Relational Competitive Advantages

    DEFF Research Database (Denmark)

    Hu, Yimei; Zhang, Si; Li, Jizhen

    2015-01-01

    Establishing strategic technological partnerships (STPs) with foreign partners is an increasingly studied topic within the innovation management literature. Partnering firms can jointly create sources of relational competitive advantage. Chinese firms often lack research and development (R......&D) capabilities but are increasingly becoming preferred technological partners for transnational corporations. We investigate an STP between a Scandinavian and a Chinese firm and try to explore how to gain relational competitive advantage by focusing on its two essential stages: relational rent generation...... and appropriation. Based on an explorative case study, we develop a conceptual framework that consists of process, organizational alliance factors, and coordination modes that we propose lead to relational competitive advantage....

  10. Physics gains attraction?

    Science.gov (United States)

    2000-01-01

    A recent report from the American Institute of Physics has indicated that high school enrolments in physics in the USA have reached their highest level since World War II. Figures for the last decade show an increase in the proportion of high school students taking physics from 20 to 28% (800Â 000 students now), according to Physics Today (October 1999, p 68). The report, Maintaining Momentum: High School Physics for a New Millennium , was based on a 1997 survey of high school physics teachers, the fourth such since the mid-1980s. One conclusion drawn by the report's authors was that a broader range of physics courses is now offered, with increased popularity of `conceptual' physics courses using little algebra or trigonometry over the last ten years. The proportion of students with the strongest maths abilities now taking advanced placement or second-year physics has doubled since 1987. In addition the physics appeal has been noted among high school girls, where the percentage taking physics has risen from 39 to 47% in the ten years to 1997. These female students do not, however, seem to extend their studies into advanced placements or even into teaching physics (women constitute just a quarter of high school teachers of the subject). Sadly the good news is outweighed by the fact that physics still registers the lowest enrolments of all the high school sciences - about half those in chemistry for example. Indeed only around 1% of high school students have taken two years of physics before they graduate, which represents a much lower proportion than in many European and Asian countries. The full report can be viewed at the AIP's statistics division's homepage: www.aip.org/statistics/trends/hstrends.htm whilst summaries of the document are available free from the AIP, Education and Employment Statistics Division, One Physics Ellipse, College Park, MD 20740, USA.

  11. Nucleon internal structure: a new set of quark, gluon momentum, angular momentum operators and parton distribution functions

    International Nuclear Information System (INIS)

    Wang Fan; Sun Weimin; Chen Xiangsong; Lu Xiaofu; Goldman, T.

    2009-01-01

    It is unavoidable to deal with the quark and gluon momentum and angular momentum contributions to the nucleon momentum and spin in the study of nucleon internal structure. However we never have the quark and gluon momentum, orbital angular momentum and gluon spin operators which satisfy both the gauge invariance and the canonical momentum and angular momentum commutation relation. The conflicts between the gauge invariance and canonical quantization requirement of these operators are discussed. A new set of quark and gluon momentum, orbital angular momentum and spin operators, which satisfy both the gauge invariance and canonical momentum and angular momentum commutation relation, are proposed. The key point to achieve such a proper decomposition is to separate the gauge field into the pure gauge and the gauge covariant parts. The same conflicts also exist in QED and quantum mechanics and have been solved in the same manner. The impacts of this new decomposition to the nucleon internal structure are discussed. (authors)

  12. Mass and momentum conservation for fluid simulation

    KAUST Repository

    Lentine, Michael; Aanjaneya, Mridul; Fedkiw, Ronald

    2011-01-01

    Momentum conservation has long been used as a design principle for solid simulation (e.g. collisions between rigid bodies, mass-spring elastic and damping forces, etc.), yet it has not been widely used for fluid simulation. In fact, semi-Lagrangian advection does not conserve momentum, but is still regularly used as a bread and butter method for fluid simulation. In this paper, we propose a modification to the semi-Lagrangian method in order to make it fully conserve momentum. While methods of this type have been proposed earlier in the computational physics literature, they are not necessarily appropriate for coarse grids, large time steps or inviscid flows, all of which are common in graphics applications. In addition, we show that the commonly used vorticity confinement turbulence model can be modified to exactly conserve momentum as well. We provide a number of examples that illustrate the benefits of this new approach, both in conserving fluid momentum and passively advected scalars such as smoke density. In particular, we show that our new method is amenable to efficient smoke simulation with one time step per frame, whereas the traditional non-conservative semi-Lagrangian method experiences serious artifacts when run with these large time steps, especially when object interaction is considered. Copyright © 2011 by the Association for Computing Machinery, Inc.

  13. Momentum considerations on the New MEXICO experiment

    Science.gov (United States)

    Parra, E. A.; Boorsma, K.; Schepers, J. G.; Snel, H.

    2016-09-01

    The present paper regards axial and angular momentum considerations combining detailed loads from pressure sensors and the flow field mapped with particle image velocimetry (PIV) techniques. For this end, the study implements important results leaning on experimental data from wind tunnel measurements of the New MEXICO project. The measurements, taken on a fully instrumented rotor, were carried out in the German Dutch Wind tunnel Organisation (DNW) testing the MEXICO rotor in the open section. The work revisits the so-called momentum theory, showing that the integral thrust and torque measured on the rotor correspond with an extent of 0.7 and 2.4% respectively to the momentum balance of the global flow field using the general momentum equations. Likewise, the sectional forces combined with the local induced velocities are found to plausibly obey the annular streamtube theory, albeit some limitations in the axial momentum become more apparent at high inductions after a=0.3. Finally, azimuth induced velocities are measured and compared to predictions from models of Glauert and Burton et al., showing close-matching forecasts for blade spans above 25%.

  14. The amplituhedron from momentum twistor diagrams

    International Nuclear Information System (INIS)

    Bai, Yuntao; He, Song

    2015-01-01

    We propose a new diagrammatic formulation of the all-loop scattering amplitudes/Wilson loops in planar N=4 SYM, dubbed the “momentum-twistor diagrams”. These are on-shell-diagrams obtained by gluing trivalent black and white vertices in momentum twistor space, which, in the reduced diagram case, are known to be related to diagrams in the original twistor space. The new diagrams are manifestly Yangian invariant, and they naturally represent factorization and forward-limit contributions in the all-loop BCFW recursion relations in momentum twistor space, in a fashion that is completely different from those in momentum space. We show how to construct and evaluate momentum-twistor diagrams, and how to use them to obtain tree-level amplitudes and loop-level integrands; in particular the latter involve isolated bubble-structures for loop variables arising from forward limits, or the entangled removal of particles. From each diagram, the generalized “boundary measurement” directly gives the C, D matrices, thus a cell in the amplituhedron associated with the amplitude, and we expect that our diagrammatic representations of the amplitude provide triangulations of the amplituhedron. To demonstrate the computational power of the formalism, we give explicit results for general two-loop integrands, and the cells of the amplituhedron for two-loop MHV amplitudes.

  15. Momentum and Stochastic Momentum for Stochastic Gradient, Newton, Proximal Point and Subspace Descent Methods

    KAUST Repository

    Loizou, Nicolas

    2017-12-27

    In this paper we study several classes of stochastic optimization algorithms enriched with heavy ball momentum. Among the methods studied are: stochastic gradient descent, stochastic Newton, stochastic proximal point and stochastic dual subspace ascent. This is the first time momentum variants of several of these methods are studied. We choose to perform our analysis in a setting in which all of the above methods are equivalent. We prove global nonassymptotic linear convergence rates for all methods and various measures of success, including primal function values, primal iterates (in L2 sense), and dual function values. We also show that the primal iterates converge at an accelerated linear rate in the L1 sense. This is the first time a linear rate is shown for the stochastic heavy ball method (i.e., stochastic gradient descent method with momentum). Under somewhat weaker conditions, we establish a sublinear convergence rate for Cesaro averages of primal iterates. Moreover, we propose a novel concept, which we call stochastic momentum, aimed at decreasing the cost of performing the momentum step. We prove linear convergence of several stochastic methods with stochastic momentum, and show that in some sparse data regimes and for sufficiently small momentum parameters, these methods enjoy better overall complexity than methods with deterministic momentum. Finally, we perform extensive numerical testing on artificial and real datasets, including data coming from average consensus problems.

  16. Momentum and Stochastic Momentum for Stochastic Gradient, Newton, Proximal Point and Subspace Descent Methods

    KAUST Repository

    Loizou, Nicolas; Richtarik, Peter

    2017-01-01

    In this paper we study several classes of stochastic optimization algorithms enriched with heavy ball momentum. Among the methods studied are: stochastic gradient descent, stochastic Newton, stochastic proximal point and stochastic dual subspace ascent. This is the first time momentum variants of several of these methods are studied. We choose to perform our analysis in a setting in which all of the above methods are equivalent. We prove global nonassymptotic linear convergence rates for all methods and various measures of success, including primal function values, primal iterates (in L2 sense), and dual function values. We also show that the primal iterates converge at an accelerated linear rate in the L1 sense. This is the first time a linear rate is shown for the stochastic heavy ball method (i.e., stochastic gradient descent method with momentum). Under somewhat weaker conditions, we establish a sublinear convergence rate for Cesaro averages of primal iterates. Moreover, we propose a novel concept, which we call stochastic momentum, aimed at decreasing the cost of performing the momentum step. We prove linear convergence of several stochastic methods with stochastic momentum, and show that in some sparse data regimes and for sufficiently small momentum parameters, these methods enjoy better overall complexity than methods with deterministic momentum. Finally, we perform extensive numerical testing on artificial and real datasets, including data coming from average consensus problems.

  17. The laser elevator - Momentum transfer using an optical resonator

    Science.gov (United States)

    Meyer, Thomas R.; Mckay, Christopher P.; Mckenna, Paul M.

    1987-01-01

    In a conventional laser lightsail system the payload is propelled by the momentum imparted to it by the reflection of a laser beam without the use of any propellant. Because of the unfavorable relationship between energy and momentum in a light beam, these systems are very inefficient. The efficiency can be greatly improved, in principle, if the photons that impact the payload mirror are returned to the source and then redirected back toward the payload again. This system, which recirculates the laser beam, is defined as the 'laser elevator'. The gain of the laser elevator over conventional lightsails depends on the number of times the beam is recycled which is limited by the reflectance of the mirrors used, any losses in the transmission of the beam, and diffraction. Due to the increase pathlength of the folded beam, diffraction losses occur at smaller separations of the payload and the source mirror than for conventional lightsail system. The laser elevator has potential applications in launching to low earth orbit, orbital transfer, and rapid interplanetary delivery of small payloads.

  18. Staggering of angular momentum distribution in fission

    Science.gov (United States)

    Tamagno, Pierre; Litaize, Olivier

    2018-03-01

    We review here the role of angular momentum distributions in the fission process. To do so the algorithm implemented in the FIFRELIN code [?] is detailed with special emphasis on the place of fission fragment angular momenta. The usual Rayleigh distribution used for angular momentum distribution is presented and the related model derivation is recalled. Arguments are given to justify why this distribution should not hold for low excitation energy of the fission fragments. An alternative ad hoc expression taking into account low-lying collectiveness is presented as has been implemented in the FIFRELIN code. Yet on observables currently provided by the code, no dramatic impact has been found. To quantify the magnitude of the impact of the low-lying staggering in the angular momentum distribution, a textbook case is considered for the decay of the 144Ba nucleus with low excitation energy.

  19. Borel resummation of transverse momentum distributions

    International Nuclear Information System (INIS)

    Bonvini, Marco; Forte, Stefano; Ridolfi, Giovanni

    2009-01-01

    We present a new prescription for the resummation of contributions due to soft gluon emission to the transverse momentum distribution of processes such as Drell-Yan production in hadronic collisions. We show that familiar difficulties in obtaining resummed results as a function of transverse momentum starting from impact-parameter space resummation are related to the divergence of the perturbative expansion of the momentum-space result. We construct a resummed expression by Borel resummation of this divergent series, removing the divergence in the Borel inversion through the inclusion of a suitable higher twist term. The ensuing resummation prescription is free of numerical instabilities, is stable upon the inclusion of subleading terms, and the original divergent perturbative series is asymptotic to it. We compare our results to those obtained using alternative prescriptions, and discuss the ambiguities related to the resummation procedure

  20. Borel resummation of transverse momentum distributions

    CERN Document Server

    Bonvini, Marco; Ridolfi, Giovanni

    2009-01-01

    We present a new prescription for the resummation of contributions due to soft gluon emission to the trasverse momentum distribution of processes such as Drell-Yan production in hadronic collisions. We show that familiar difficulties in obtaining resummed results as a function of transverse momentum starting from impact-parameter space resummation are related to the divergence of the perturbative expansion of the momentum-space result. We construct a resummed expression by Borel resummation of this divergent series, removing the divergence in the Borel inversion through the inclusion of a suitable higher twist term. The ensuing resummation prescription is free of numerical instabilities, is stable upon the inclusion of subleading terms, and the original divergent perturbative series is asymptotic to it. We compare our results to those obtained using alternative prescriptions, and discuss the ambiguities related to the resummation procedure.

  1. A Very High Momentum Particle Identification Detector

    CERN Document Server

    Acconcia, T.V.; Barile, F.; Barnaföldi, G.G.; Bellwied, R.; Bencedi, G.; Bencze, G.; Berenyi, D.; Boldizsar, L.; Chattopadhyay, S.; Cindolo, F.; Chinellato, D.D.; D'Ambrosio, S.; Das, D.; Das, K.; Das-Bose, L.; Dash, A.K.; De Cataldo, G.; De Pasquale, S.; Di Bari, D.; Di Mauro, A.; Futo, E.; Garcia, E.; Hamar, G.; Harton, A.; Iannone, G.; Jimenez, R.T.; Kim, D.W.; Kim, J.S.; Knospe, A.; Kovacs, L.; Levai, P.; Nappi, E.; Markert, C.; Martinengo, P.; Mayani, D.; Molnar, L.; Olah, L.; Paic, G.; Pastore, C.; Patimo, G.; Patino, M.E.; Peskov, V.; Pinsky, L.; Piuz, F.; Pochybova, S.; Sgura, I.; Sinha, T.; Song, J.; Takahashi, J.; Timmins, A.; Van Beelen, J.B.; Varga, D.; Volpe, G.; Weber, M.; Xaplanteris, L.; Yi, J.; Yoo, I.K.

    2014-01-01

    The construction of a new detector is proposed to extend the capabilities of ALICE in the high transverse momentum (pT) region. This Very High Momentum Particle Identification Detector (VHMPID) performs charged hadron identification on a track-by-track basis in the 5 GeV/c < p < 25 GeV/c momentum range and provides ALICE with new opportunities to study parton-medium interactions at LHC energies. The VHMPID covers up to 30% of the ALICE central barrel and presents sufficient acceptance for triggered- and tagged-jet studies, allowing for the first time identified charged hadron measurements in jets. This Letter of Intent summarizes the physics motivations for such a detector as well as its layout and integration into ALICE.

  2. The price momentum of stock in distribution

    Science.gov (United States)

    Liu, Haijun; Wang, Longfei

    2018-02-01

    In this paper, a new momentum of stock in distribution is proposed and applied in real investment. Firstly, assuming that a stock behaves as a multi-particle system, its share-exchange distribution and cost distribution are introduced. Secondly, an estimation of the share-exchange distribution is given with daily transaction data by 3 σ rule from the normal distribution. Meanwhile, an iterative method is given to estimate the cost distribution. Based on the cost distribution, a new momentum is proposed for stock system. Thirdly, an empirical test is given to compare the new momentum with others by contrarian strategy. The result shows that the new one outperforms others in many places. Furthermore, entropy of stock is introduced according to its cost distribution.

  3. Staggering of angular momentum distribution in fission

    Directory of Open Access Journals (Sweden)

    Tamagno Pierre

    2018-01-01

    Full Text Available We review here the role of angular momentum distributions in the fission process. To do so the algorithm implemented in the FIFRELIN code [?] is detailed with special emphasis on the place of fission fragment angular momenta. The usual Rayleigh distribution used for angular momentum distribution is presented and the related model derivation is recalled. Arguments are given to justify why this distribution should not hold for low excitation energy of the fission fragments. An alternative ad hoc expression taking into account low-lying collectiveness is presented as has been implemented in the FIFRELIN code. Yet on observables currently provided by the code, no dramatic impact has been found. To quantify the magnitude of the impact of the low-lying staggering in the angular momentum distribution, a textbook case is considered for the decay of the 144Ba nucleus with low excitation energy.

  4. Plasma electron hole kinematics. I. Momentum conservation

    Energy Technology Data Exchange (ETDEWEB)

    Hutchinson, I. H.; Zhou, C. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-08-15

    We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, which behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

  5. Transverse momentum distributions and nuclear effects

    Directory of Open Access Journals (Sweden)

    Pace Emanuele

    2015-01-01

    Full Text Available A distorted spin-dependent spectral function for 3He is considered to take care of the final state interaction in the extraction of the quark transverse-momentum distributions in the neutron from semi-inclusive deep inelastic electron scattering off polarized 3He at finite momentum transfers. The generalization of the analysis in a Poincaré covariant framework within the light-front dynamics is outlined. The definition of the light-front spin-dependent spectral function for a J=1/2 system, as the nucleon, allows us to show that within the light-front dynamics and in the valence approximation only three of the six leading twist T-even transverse-momentum distributions are independent.

  6. TTEthernet for Integrated Spacecraft Networks

    Science.gov (United States)

    Loveless, Andrew

    2015-01-01

    Aerospace projects have traditionally employed federated avionics architectures, in which each computer system is designed to perform one specific function (e.g. navigation). There are obvious downsides to this approach, including excessive weight (from so much computing hardware), and inefficient processor utilization (since modern processors are capable of performing multiple tasks). There has therefore been a push for integrated modular avionics (IMA), in which common computing platforms can be leveraged for different purposes. This consolidation of multiple vehicle functions to shared computing platforms can significantly reduce spacecraft cost, weight, and design complexity. However, the application of IMA principles introduces significant challenges, as the data network must accommodate traffic of mixed criticality and performance levels - potentially all related to the same shared computer hardware. Because individual network technologies are rarely so competent, the development of truly integrated network architectures often proves unreasonable. Several different types of networks are utilized - each suited to support a specific vehicle function. Critical functions are typically driven by precise timing loops, requiring networks with strict guarantees regarding message latency (i.e. determinism) and fault-tolerance. Alternatively, non-critical systems generally employ data networks prioritizing flexibility and high performance over reliable operation. Switched Ethernet has seen widespread success filling this role in terrestrial applications. Its high speed, flexibility, and the availability of inexpensive commercial off-the-shelf (COTS) components make it desirable for inclusion in spacecraft platforms. Basic Ethernet configurations have been incorporated into several preexisting aerospace projects, including both the Space Shuttle and International Space Station (ISS). However, classical switched Ethernet cannot provide the high level of network

  7. Ghost Imaging Using Orbital Angular Momentum

    Institute of Scientific and Technical Information of China (English)

    赵生妹; 丁建; 董小亮; 郑宝玉

    2011-01-01

    We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum. In the signal arm, object spatial information is encoded as a phase matrix. For an N-grey-scale object, different phase matrices, varying from 0 to K with increment n/N, are used for different greyscales, and then they are modulated to a signal beam by a spatial light modulator. According to the conservation of the orbital angular momentum in the ghost imaging system, these changes will give different coincidence rates in measurement, and hence the object information can be extracted in the idler arm. By simulations and experiments, the results show that our scheme can improve the resolution of the image effectively. Compared with another encoding method using orbital angular momentum, our scheme has a better performance for both characters and the image object.%We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum.In the signal arm,object spatial information is encoded as a phase matrix.For an N-grey-scale object,different phase matrices,varying from 0 to π with increment π/N,are used for different greyscales,and then they are modulated to a signal beam by a spatial light modulator.According to the conservation of the orbital angular momentum in the ghost imaging system,these changes will give different coincidence rates in measurement,and hence the object information can be extracted in the idler arm.By simulations and experiments,the results show that our scheme can improve the resolution of the image effectively.Compared with another encoding method using orbital angular momentum,our scheme has a better performance for both characters and the image object.

  8. Spacecraft command and control using expert systems

    Science.gov (United States)

    Norcross, Scott; Grieser, William H.

    1994-01-01

    This paper describes a product called the Intelligent Mission Toolkit (IMT), which was created to meet the changing demands of the spacecraft command and control market. IMT is a command and control system built upon an expert system. Its primary functions are to send commands to the spacecraft and process telemetry data received from the spacecraft. It also controls the ground equipment used to support the system, such as encryption gear, and telemetry front-end equipment. Add-on modules allow IMT to control antennas and antenna interface equipment. The design philosophy for IMT is to utilize available commercial products wherever possible. IMT utilizes Gensym's G2 Real-time Expert System as the core of the system. G2 is responsible for overall system control, spacecraft commanding control, and spacecraft telemetry analysis and display. Other commercial products incorporated into IMT include the SYBASE relational database management system and Loral Test and Integration Systems' System 500 for telemetry front-end processing.

  9. Maximum entropy method in momentum density reconstruction

    International Nuclear Information System (INIS)

    Dobrzynski, L.; Holas, A.

    1997-01-01

    The Maximum Entropy Method (MEM) is applied to the reconstruction of the 3-dimensional electron momentum density distributions observed through the set of Compton profiles measured along various crystallographic directions. It is shown that the reconstruction of electron momentum density may be reliably carried out with the aid of simple iterative algorithm suggested originally by Collins. A number of distributions has been simulated in order to check the performance of MEM. It is shown that MEM can be recommended as a model-free approach. (author). 13 refs, 1 fig

  10. Turbulent momentum transport due to neoclassical flows

    International Nuclear Information System (INIS)

    Lee, Jungpyo; Barnes, Michael; Parra, Felix I; Belli, Emily; Candy, Jeff

    2015-01-01

    Intrinsic toroidal rotation in a tokamak can be driven by turbulent momentum transport due to neoclassical flow effects breaking a symmetry of turbulence. In this paper we categorize the contributions due to neoclassical effects to the turbulent momentum transport, and evaluate each contribution using gyrokinetic simulations. We find that the relative importance of each contribution changes with collisionality. For low collisionality, the dominant contributions come from neoclassical particle and parallel flows. For moderate collisionality, there are non-negligible contributions due to neoclassical poloidal electric field and poloidal gradients of density and temperature, which are not important for low collisionality. (paper)

  11. Valence electron momentum distributions in cadmium

    International Nuclear Information System (INIS)

    Frost, L.; Weigold, E.; Mitroy, J.

    1982-08-01

    The valence 5s and 4d electron momentum distributions in cadmium have been measured using noncoplanar symmetric (e, 2e) electron coincidence spectroscopy at a total energy of 1200eV. They are in close agreement with Hartree-Fock momentum distributions both in shape and relative magnitudes. Some satellite lines of very low intensity have been detected. A CI calculation of the Cd ground state and several Cd + ion states has been carried out to predict cross reactions for the ground state and various satellite transitions. The predictions are in agreement with the data

  12. Total angular momentum from Dirac eigenspinors

    International Nuclear Information System (INIS)

    Szabados, Laszlo B

    2008-01-01

    The eigenvalue problem for Dirac operators, constructed from two connections on the spinor bundle over closed spacelike 2-surfaces, is investigated. A class of divergence-free vector fields, built from the eigenspinors, are found, which, for the lowest eigenvalue, reproduce the rotation Killing vectors of metric spheres, and provide rotation BMS vector fields at future null infinity. This makes it possible to introduce a well-defined, gauge invariant spatial angular momentum at null infinity, which reduces to the standard expression in stationary spacetimes. The general formula for the angular momentum flux carried away by the gravitational radiation is also derived

  13. A momentum filter for atomic gas

    International Nuclear Information System (INIS)

    Xiong, Wei; Zhou, Xiaoji; Yue, Xuguang; Zhai, Yueyang; Chen, Xuzong

    2013-01-01

    We propose and demonstrate a momentum filter for atomic gas-based on a designed Talbot–Lau interferometer. It consists of two identical optical standing-wave pulses separated by a delay equal to odd multiples of the half Talbot time. The one-dimensional momentum width along the long direction of a cigar-shaped condensate is rapidly and greatly purified to a minimum, which corresponds to the ground state energy of the confining trap in our experiment. We find good agreement between theoretical analysis and experimental results. The filter is also effective for non-condensed cold atoms and could be applied widely. (paper)

  14. The blade element momentum (BEM) method

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The current chapter presents the blade element momentum (BEM) method. The BEM method for a steady uniform inflow is presented in a first section. Some of the ad-hoc corrections that are usually added to the algorithm are discussed in a second section. An exception is made to the tip-loss correction...... which is introduced early in the algorithm formulation for practical reasons. The ad-hoc corrections presented are: the tip-loss correction, the high-thrust correction (momentum breakdown) and the correction for wake rotation. The formulation of an unsteady BEM code is given in a third section...

  15. Momentum sharing in imbalanced Fermi systems

    OpenAIRE

    Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.; Hakobyan, H.; Higinbotham, D. W.; Braverman, M.; Brooks, W. K.; Gilad, S.; Adhikari, K. P.; Arrington, J.; Asryan, G.; Avakian, H.; Ball, J.; Baltzell, N. A.

    2014-01-01

    The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in ne...

  16. Conceptual Design of an Electric Sail Technology Demonstration Mission Spacecraft

    Science.gov (United States)

    Wiegmann, Bruce M.

    2017-01-01

    There is great interest in examining the outer planets of our solar system and Heliopause region (edge of Solar System) and beyond regions of interstellar space by both the Planetary and Heliophysics communities. These needs are well docu-mented in the recent National Academy of Sciences Decadal Surveys. There is significant interest in developing revolutionary propulsion techniques that will enable such Heliopause scientific missions to be completed within 10 to15 years of the launch date. One such enabling propulsion technique commonly known as Electric Sail (E-Sail) propulsion employs positively charged bare wire tethers that extend radially outward from a rotating spacecraft spinning at a rate of one revolution per hour. Around the positively charged bare-wire tethers, a Debye Sheath is created once positive voltage is applied. This sheath stands off of the bare wire tether at a sheath diameter that is proportional to the voltage in the wire coupled with the flux density of solar wind ions within the solar system (or the location of spacecraft in the solar system. The protons that are expended from the sun (solar wind) at 400 to 800 km/sec are electrostatically repelled away from these positively charged Debye sheaths and propulsive thrust is produced via the resulting momentum transfer. The amount of thrust produced is directly proportional to the total wire length. The Marshall Space Flight Center (MSFC) Electric Sail team is currently funded via a two year Phase II NASA Innovative Advanced Concepts (NIAC) awarded in July 2015. The team's current activities are: 1) Developing a Particle in Cell (PIC) numeric engineering model from the experimental data collected at MSFC's Solar Wind Facility on the interaction between simulated solar wind interaction with a charged bare wire that can be applied to a variety of missions, 2) The development of the necessary tether deployers and tethers to enable successful de-ployment of multiple, multi km length bare tethers

  17. Acting to gain information

    Science.gov (United States)

    Rosenchein, Stanley J.; Burns, J. Brian; Chapman, David; Kaelbling, Leslie P.; Kahn, Philip; Nishihara, H. Keith; Turk, Matthew

    1993-01-01

    This report is concerned with agents that act to gain information. In previous work, we developed agent models combining qualitative modeling with real-time control. That work, however, focused primarily on actions that affect physical states of the environment. The current study extends that work by explicitly considering problems of active information-gathering and by exploring specialized aspects of information-gathering in computational perception, learning, and language. In our theoretical investigations, we analyzed agents into their perceptual and action components and identified these with elements of a state-machine model of control. The mathematical properties of each was developed in isolation and interactions were then studied. We considered the complexity dimension and the uncertainty dimension and related these to intelligent-agent design issues. We also explored active information gathering in visual processing. Working within the active vision paradigm, we developed a concept of 'minimal meaningful measurements' suitable for demand-driven vision. We then developed and tested an architecture for ongoing recognition and interpretation of visual information. In the area of information gathering through learning, we explored techniques for coping with combinatorial complexity. We also explored information gathering through explicit linguistic action by considering the nature of conversational rules, coordination, and situated communication behavior.

  18. What is the transverse momentum of partons

    International Nuclear Information System (INIS)

    Close, F.E.; Halzen, F.; Scott, D.M.

    1977-01-01

    Theoretical arguments for a picture where the average transverse momentum of partons inside hadrons increases when x increases towards x=0.4 approximately 0.5, peaks and subsequently decreases when x approaches 1. This result is contrary to that suggested by asymptotic freedom arguments. Phenomenological support for this is discussed. (Auth.)

  19. Experimental determination of high angular momentum states

    International Nuclear Information System (INIS)

    Barreto, J.L.V.

    1985-01-01

    The current knowledge of the atomic nucleus structure is summarized. A short abstract of the nuclear properties at high angular momentum and a more detailed description of the experimental methods used in the study of high angular momenta is made. (L.C.) [pt

  20. Observation of Polarization Vortices in Momentum Space

    Science.gov (United States)

    Zhang, Yiwen; Chen, Ang; Liu, Wenzhe; Hsu, Chia Wei; Wang, Bo; Guan, Fang; Liu, Xiaohan; Shi, Lei; Lu, Ling; Zi, Jian

    2018-05-01

    The vortex, a fundamental topological excitation featuring the in-plane winding of a vector field, is important in various areas such as fluid dynamics, liquid crystals, and superconductors. Although commonly existing in nature, vortices were observed exclusively in real space. Here, we experimentally observed momentum-space vortices as the winding of far-field polarization vectors in the first Brillouin zone of periodic plasmonic structures. Using homemade polarization-resolved momentum-space imaging spectroscopy, we mapped out the dispersion, lifetime, and polarization of all radiative states at the visible wavelengths. The momentum-space vortices were experimentally identified by their winding patterns in the polarization-resolved isofrequency contours and their diverging radiative quality factors. Such polarization vortices can exist robustly on any periodic systems of vectorial fields, while they are not captured by the existing topological band theory developed for scalar fields. Our work provides a new way for designing high-Q plasmonic resonances, generating vector beams, and studying topological photonics in the momentum space.

  1. High Momentum Probes of Nuclear Matter

    Energy Technology Data Exchange (ETDEWEB)

    Fries, R.

    2009-07-24

    We discuss how the chemical composition of QCD jets is altered by final state interactions in surrounding nuclear matter. We describe this process through conversions of leading jet particles. We find that conversions lead to an enhancement of kaons at high transverse momentum in Au+Au collisions at RHIC, while their azimuthal asymmetry v{sub 2} is suppressed.

  2. The Das-Popowicz Moyal momentum algebra

    International Nuclear Information System (INIS)

    Boulahoual, A.; Sedra, M.B.

    2002-08-01

    We introduce in this short note some aspects of the Moyal momentum algebra that we call the Das-Popowicz Mm algebra. Our interest on this algebra is motivated by the central role that it can play in the formulation of integrable models and in higher conformal spin theories. (author)

  3. Angular-momentum-bearing modes in fission

    International Nuclear Information System (INIS)

    Moretto, L.G.; Peaslee, G.F.; Wozniak, G.J.

    1989-03-01

    The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs

  4. Angular and linear momentum of excited ferromagnets

    NARCIS (Netherlands)

    Yan, P.; Kamra, A.; Cao, Y.; Bauer, G.E.W.

    2013-01-01

    The angular momentum vector of a Heisenberg ferromagnet with isotropic exchange interaction is conserved, while under uniaxial crystalline anisotropy the projection of the total spin along the easy axis is a constant of motion. Using Noether's theorem, we prove that these conservation laws persist

  5. ''Turbulent Equipartition'' Theory of Toroidal Momentum Pinch

    International Nuclear Information System (INIS)

    Hahm, T.S.; Diamond, P.H.; Gurcan, O.D.; Rewaldt, G.

    2008-01-01

    The mode-independent part of magnetic curvature driven turbulent convective (TuroCo) pinch of the angular momentum density (Hahm et al., Phys. Plasmas 14,072302 (2007)) which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of 'magnetically weighted angular momentum density', nm i U # parallel# R/B 2 , and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustrated that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms which exist in a simpler geometry.

  6. Orbital momentum and topological phase transformation

    Czech Academy of Sciences Publication Activity Database

    Středa, Pavel; Kučera, Jan

    2015-01-01

    Roč. 92, č. 23 (2015), "235152-1"-"235152-6" ISSN 1098-0121 R&D Projects: GA ČR GA15-13436S Institutional support: RVO:68378271 Keywords : orbital momentum * anomalous Hall effect * topological phase transformation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  7. Elastic electron scattering at large momentum transfer

    International Nuclear Information System (INIS)

    Arnold, R.G.

    1979-05-01

    A review is given of elastic electron scattering at large momentum transfer (Q 2 > 20 fm -2 ) from nuclei with A less than or equal to 4. Recent experimental results are reviewed and the current problems in interpretation of these results are pointed out. Some questions for future experiments are posed, and a preview of possible future measurements is presented. 28 references

  8. ANGULAR MOMENTUM ACQUISITION IN GALAXY HALOS

    International Nuclear Information System (INIS)

    Stewart, Kyle R.; Brooks, Alyson M.; Bullock, James S.; Maller, Ariyeh H.; Diemand, Jürg; Wadsley, James; Moustakas, Leonidas A.

    2013-01-01

    We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky-Way-sized galaxies. We find that cold mode accreted gas enters a galaxy halo with ∼70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by λ ∼ 0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms ''cold flow disks.'' We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.

  9. W UMa stars and angular momentum loss

    International Nuclear Information System (INIS)

    Vilhu, O.; Rahunen, T.

    1980-01-01

    The structure and evolution of W UMa stars is still unsolved although considerable progress has been achieved in recent years. The authors aim is to find out whether it is possible to obtain more extreme mass ratios, what is the angular momentum needed and what is the time scale. (Auth.)

  10. Momentum transfer in a Brillouin surface scattering

    International Nuclear Information System (INIS)

    Khater, A.F.

    1980-01-01

    The theory of acoustic excitation scattering in the surface of Brilloiun of opaque materials, is related to the question of momentum transfexed from radiation fields to the material when the incident eight is scattered in a measurable spectrum. (A.C.A.S.) [pt

  11. Anomalous momentum transport from drift waves

    International Nuclear Information System (INIS)

    Dominguez, R.R.; Staebler, G.M.

    1993-01-01

    A sheared slab magnetic field model B = B 0 [z + (x/L s )y], with inhomogeneous flows in the y and z directions, is used to perform a fully-kinetic stability analysis of the ion temperature gradient (ITG) and dissipative trapped electron (DTE) modes. The concomitant quasilinear stress components that couple to the local perpendicular (y-component) and parallel (z-component) momentum transport are also calculated and the anomalous perpendicular and parallel viscous stresses obtained. A breakdown of the ITG-induced perpendicular viscous stress is generally observed at moderate values of the sheared perpendicular flow. The ITG-induced parallel viscous stress is generally larger and strongly dependent on the sheared flows. The DTE-induced perpendicular viscous stress may sometimes be negative, tending to cancel the ITG contributions while the DTE-induced parallel viscous stress is generally small. The effect of the perpendicular stress component in the momentum balance equations is generally small while the parallel stress component can dominate the usual neoclassical viscous stress terms. The dominant contribution to parallel viscous stress by the ITG mode suggests that bulk plasma toroidal momentum confinement, like energy confinement, is governed by an anomalous ion loss mechanism. Furthermore, the large anomalous effect suggests that the neoclassical explanation of poloidal flows in tokamaks may be incorrect. The present results are in general agreement with existing experimental observations on momentum transport in tokamaks

  12. Method II : The energy-momentum map

    NARCIS (Netherlands)

    Broer, H.; Hoveijn, I.; Lunter, G.; Vegter, G.

    2003-01-01

    In this chapter we apply the energy–momentum map reduction method to the same class of systems as in Chap. 2, namely two degree-of-freedom systems with optional symmetry, near equilibrium and close to resonance. We calculate the tangent space and nondegeneracy conditions for the 1:2, 1:3 and 1:4

  13. Submarines, spacecraft and exhaled breath.

    Science.gov (United States)

    Pleil, Joachim D; Hansel, Armin

    2012-03-01

    Foreword The International Association of Breath Research (IABR) meetings are an eclectic gathering of researchers in the medical, environmental and instrumentation fields; our focus is on human health as assessed by the measurement and interpretation of trace chemicals in human exhaled breath. What may have escaped our notice is a complementary field of research that explores the creation and maintenance of artificial atmospheres practised by the submarine air monitoring and air purification (SAMAP) community. SAMAP is comprised of manufacturers, researchers and medical professionals dealing with the engineering and instrumentation to support human life in submarines and spacecraft (including shuttlecraft and manned rockets, high-altitude aircraft, and the International Space Station (ISS)). Here, the immediate concerns are short-term survival and long-term health in fairly confined environments where one cannot simply 'open the window' for fresh air. As such, one of the main concerns is air monitoring and the main sources of contamination are CO(2) and other constituents of human exhaled breath. Since the inaugural meeting in 1994 in Adelaide, Australia, SAMAP meetings have been held every two or three years alternating between the North American and European continents. The meetings are organized by Dr Wally Mazurek (a member of IABR) of the Defense Systems Technology Organization (DSTO) of Australia, and individual meetings are co-hosted by the navies of the countries in which they are held. An overriding focus at SAMAP is life support (oxygen availability and carbon dioxide removal). Certainly, other air constituents are also important; for example, the closed environment of a submarine or the ISS can build up contaminants from consumer products, cooking, refrigeration, accidental fires, propulsion and atmosphere maintenance. However, the most immediate concern is sustaining human metabolism: removing exhaled CO(2) and replacing metabolized O(2). Another

  14. Leading Gainful Employment Metric Reporting

    Science.gov (United States)

    Powers, Kristina; MacPherson, Derek

    2016-01-01

    This chapter will address the importance of intercampus involvement in reporting of gainful employment student-level data that will be used in the calculation of gainful employment metrics by the U.S. Department of Education. The authors will discuss why building relationships within the institution is critical for effective gainful employment…

  15. Foot Pedals for Spacecraft Manual Control

    Science.gov (United States)

    Love, Stanley G.; Morin, Lee M.; McCabe, Mary

    2010-01-01

    Fifty years ago, NASA decided that the cockpit controls in spacecraft should be like the ones in airplanes. But controls based on the stick and rudder may not be best way to manually control a vehicle in space. A different method is based on submersible vehicles controlled with foot pedals. A new pilot can learn the sub's control scheme in minutes and drive it hands-free. We are building a pair of foot pedals for spacecraft control, and will test them in a spacecraft flight simulator.

  16. General Attitude Control Algorithm for Spacecraft Equipped with Star Camera and Reaction Wheels

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    A configuration consisting of a star camera, four reaction wheels and magnetorquers for momentum unloading has become standard for many spacecraft missions. This popularity has motivated numerous agencies and private companies to initiate work on the design of an imbedded attitude control system...... realized on an integrated circuit. This paper considers two issues: slew maneuver with a feature of avoiding direct exposure of the camera's CCD chip to the Sun %, three-axis attitude control and optimal control torque distribution in a reaction wheel assembly. The attitude controller is synthesized...

  17. Dirac states for unit position and momentum: Phase consistency of their angular momentum representations

    International Nuclear Information System (INIS)

    Snider, R.F.

    1982-01-01

    It is shown that the position and momentum directional representations of angular momentum states must satisfy Σ/sub lambdas/ = Σ/sub lambdas/(i)/sup lambda/Y/sub lambdas/(r)Y/sub lambdas/ (p)*. This imposes phase constraints on the relation between , , Y/sub lambdas/ (r), and Y/sub lambdas/(p). In the accompanying paper, it is shown that this resolves a problem in the centrifugal sudden approximation of molecular collision theory

  18. Distributed Autonomous Control of Multiple Spacecraft During Close Proximity Operations

    National Research Council Canada - National Science Library

    McCamish, Shawn B

    2007-01-01

    This research contributes to multiple spacecraft control by developing an autonomous distributed control algorithm for close proximity operations of multiple spacecraft systems, including rendezvous...

  19. Spacecraft Swarm Coordination and Planning Tool, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Fractionated spacecraft architectures to distribute mission performance from a single, monolithic satellite across large number of smaller spacecraft, for missions...

  20. Spacecraft Cabin Particulate Monitor, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — We have built and tested an optical extinction monitor for the detection of spacecraft cabin particulates. This sensor sensitive to particle sizes ranging from a few...

  1. SSTI- Lewis Spacecraft Nickel-Hydrogen Battery

    Science.gov (United States)

    Tobias, R. F.

    1997-01-01

    Topics considered include: NASA-Small Spacecraft Technology Initiative (SSTI) objectives, SSTI-Lewis overview, battery requirement, two cells Common Pressure Vessel (CPV) design summary, CPV electric performance, battery design summary, battery functional description, battery performance.

  2. Spacecraft Cabin Particulate Monitor, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design, build and test an optical extinction monitor for the detection of spacecraft cabin particulates. This monitor will be sensitive to particle...

  3. Automated constraint checking of spacecraft command sequences

    Science.gov (United States)

    Horvath, Joan C.; Alkalaj, Leon J.; Schneider, Karl M.; Spitale, Joseph M.; Le, Dang

    1995-01-01

    Robotic spacecraft are controlled by onboard sets of commands called "sequences." Determining that sequences will have the desired effect on the spacecraft can be expensive in terms of both labor and computer coding time, with different particular costs for different types of spacecraft. Specification languages and appropriate user interface to the languages can be used to make the most effective use of engineering validation time. This paper describes one specification and verification environment ("SAVE") designed for validating that command sequences have not violated any flight rules. This SAVE system was subsequently adapted for flight use on the TOPEX/Poseidon spacecraft. The relationship of this work to rule-based artificial intelligence and to other specification techniques is discussed, as well as the issues that arise in the transfer of technology from a research prototype to a full flight system.

  4. Computational Model for Spacecraft/Habitat Volume

    Data.gov (United States)

    National Aeronautics and Space Administration — Please note that funding to Dr. Simon Hsiang, a critical co-investigator for the development of the Spacecraft Optimization Layout and Volume (SOLV) model, was...

  5. Industry perspectives on Plug-& -Play Spacecraft Avionics

    Science.gov (United States)

    Franck, R.; Graven, P.; Liptak, L.

    This paper describes the methodologies and findings from an industry survey of awareness and utility of Spacecraft Plug-& -Play Avionics (SPA). The survey was conducted via interviews, in-person and teleconference, with spacecraft prime contractors and suppliers. It focuses primarily on AFRL's SPA technology development activities but also explores the broader applicability and utility of Plug-& -Play (PnP) architectures for spacecraft. Interviews include large and small suppliers as well as large and small spacecraft prime contractors. Through these “ product marketing” interviews, awareness and attitudes can be assessed, key technical and market barriers can be identified, and opportunities for improvement can be uncovered. Although this effort focuses on a high-level assessment, similar processes can be used to develop business cases and economic models which may be necessary to support investment decisions.

  6. Spacecraft Multiple Array Communication System Performance Analysis

    Science.gov (United States)

    Hwu, Shian U.; Desilva, Kanishka; Sham, Catherine C.

    2010-01-01

    The Communication Systems Simulation Laboratory (CSSL) at the NASA Johnson Space Center is tasked to perform spacecraft and ground network communication system simulations, design validation, and performance verification. The CSSL has developed simulation tools that model spacecraft communication systems and the space and ground environment in which the tools operate. In this paper, a spacecraft communication system with multiple arrays is simulated. Multiple array combined technique is used to increase the radio frequency coverage and data rate performance. The technique is to achieve phase coherence among the phased arrays to combine the signals at the targeting receiver constructively. There are many technical challenges in spacecraft integration with a high transmit power communication system. The array combining technique can improve the communication system data rate and coverage performances without increasing the system transmit power requirements. Example simulation results indicate significant performance improvement can be achieved with phase coherence implementation.

  7. Formation of disintegration particles in spacecraft recorders

    International Nuclear Information System (INIS)

    Kurnosova, L.V.; Fradkin, M.I.; Razorenov, L.A.

    1986-01-01

    Experiments performed on the spacecraft Salyut 1, Kosmos 410, and Kosmos 443 enable us to record the disintegration products of particles which are formed in the material of the detectors on board the spacecraft. The observations were made by means of a delayed coincidence method. We have detected a meson component and also a component which is apparently associated with the generation of radioactive isotopes in the detectors

  8. Power requirements for commercial communications spacecraft

    Science.gov (United States)

    Billerbeck, W. J.

    1985-01-01

    Historical data on commercial spacecraft power systems are presented and their power requirements to the growth of satellite communications channel usage are related. Some approaches for estimating future power requirements of this class of spacecraft through the year 2000 are proposed. The key technology drivers in satellite power systems are addressed. Several technological trends in such systems are described, focusing on the most useful areas for research and development of major subsystems, including solar arrays, energy storage, and power electronics equipment.

  9. A Reconfigurable Testbed Environment for Spacecraft Autonomy

    Science.gov (United States)

    Biesiadecki, Jeffrey; Jain, Abhinandan

    1996-01-01

    A key goal of NASA's New Millennium Program is the development of technology for increased spacecraft on-board autonomy. Achievement of this objective requires the development of a new class of ground-based automony testbeds that can enable the low-cost and rapid design, test, and integration of the spacecraft autonomy software. This paper describes the development of an Autonomy Testbed Environment (ATBE) for the NMP Deep Space I comet/asteroid rendezvous mission.

  10. Radiation Effects on Spacecraft Structural Materials

    International Nuclear Information System (INIS)

    Wang, Jy-An J.; Ellis, Ronald J.; Hunter, Hamilton T.; Singleterry, Robert C. Jr.

    2002-01-01

    Research is being conducted to develop an integrated technology for the prediction of aging behavior for space structural materials during service. This research will utilize state-of-the-art radiation experimental apparatus and analysis, updated codes and databases, and integrated mechanical and radiation testing techniques to investigate the suitability of numerous current and potential spacecraft structural materials. Also included are the effects on structural materials in surface modules and planetary landing craft, with or without fission power supplies. Spacecraft structural materials would also be in hostile radiation environments on the surface of the moon and planets without appreciable atmospheres and moons around planets with large intense magnetic and radiation fields (such as the Jovian moons). The effects of extreme temperature cycles in such locations compounds the effects of radiation on structural materials. This paper describes the integrated methodology in detail and shows that it will provide a significant technological advance for designing advanced spacecraft. This methodology will also allow for the development of advanced spacecraft materials through the understanding of the underlying mechanisms of material degradation in the space radiation environment. Thus, this technology holds a promise for revolutionary advances in material damage prediction and protection of space structural components as, for example, in the development of guidelines for managing surveillance programs regarding the integrity of spacecraft components, and the safety of the aging spacecraft. (authors)

  11. Standardizing the information architecture for spacecraft operations

    Science.gov (United States)

    Easton, C. R.

    1994-01-01

    This paper presents an information architecture developed for the Space Station Freedom as a model from which to derive an information architecture standard for advanced spacecraft. The information architecture provides a way of making information available across a program, and among programs, assuming that the information will be in a variety of local formats, structures and representations. It provides a format that can be expanded to define all of the physical and logical elements that make up a program, add definitions as required, and import definitions from prior programs to a new program. It allows a spacecraft and its control center to work in different representations and formats, with the potential for supporting existing spacecraft from new control centers. It supports a common view of data and control of all spacecraft, regardless of their own internal view of their data and control characteristics, and of their communications standards, protocols and formats. This information architecture is central to standardizing spacecraft operations, in that it provides a basis for information transfer and translation, such that diverse spacecraft can be monitored and controlled in a common way.

  12. Attitude Estimation in Fractionated Spacecraft Cluster Systems

    Science.gov (United States)

    Hadaegh, Fred Y.; Blackmore, James C.

    2011-01-01

    An attitude estimation was examined in fractioned free-flying spacecraft. Instead of a single, monolithic spacecraft, a fractionated free-flying spacecraft uses multiple spacecraft modules. These modules are connected only through wireless communication links and, potentially, wireless power links. The key advantage of this concept is the ability to respond to uncertainty. For example, if a single spacecraft module in the cluster fails, a new one can be launched at a lower cost and risk than would be incurred with onorbit servicing or replacement of the monolithic spacecraft. In order to create such a system, however, it is essential to know what the navigation capabilities of the fractionated system are as a function of the capabilities of the individual modules, and to have an algorithm that can perform estimation of the attitudes and relative positions of the modules with fractionated sensing capabilities. Looking specifically at fractionated attitude estimation with startrackers and optical relative attitude sensors, a set of mathematical tools has been developed that specify the set of sensors necessary to ensure that the attitude of the entire cluster ( cluster attitude ) can be observed. Also developed was a navigation filter that can estimate the cluster attitude if these conditions are satisfied. Each module in the cluster may have either a startracker, a relative attitude sensor, or both. An extended Kalman filter can be used to estimate the attitude of all modules. A range of estimation performances can be achieved depending on the sensors used and the topology of the sensing network.

  13. Air Bag Momentum Force Including Aspiration

    Directory of Open Access Journals (Sweden)

    Guy Nusholtz

    1995-01-01

    Full Text Available A gas-jet momentum force drives the air bag into position during a crash. The magnitude of this force can change as a result of aspiration. To determine the potential magnitude of the effect on the momentum force and mass flow rate in an aspirated system, a series of experiments and simulations of those experiments was conducted. The simulation consists of a two-dimensional unsteady isentropic CFD model with special “infinite boundaries”. One of the difficulties in simulating the gas-jet behavior is determining the mass flow rate. To improve the reliability of the mass flow rate input to the simulation, a sampling procedure involving multiple tests was used, and an average of the tests was adopted.

  14. Dynamics of high momentum transfer processes

    International Nuclear Information System (INIS)

    Efremov, A.V.

    1977-01-01

    The high momentum transfer processes are considered in terms of field theory of quarks interacting through scalar or pseudoscalar gluons. This approach is based on an algorithm involving the consideration of the Feynman diagram asymptotical behaviour and its summation. The Parton model and quark counting power are an approximation of not too high momentum transfer when anti g 2 (q 2 )ln(-q 2 /Λ) 2 -invariant charge, Λ-boundary parameter. The violation of scaling beyond this region depends on the character of charge renormalization and is of the same kind as in the Wilson expansion approach. Scaling in this region is suppressed by anti g 4 factor for high psub(UPSILON) hadroproduction and wide angle elastic scattering, and by anti g 2 factor for inclusive lepton production and wide angle electro- and photoproduction. Parameter Λ is controlled by hadron masses and can be essential for not too high psub(UPSILON)

  15. Transverse Momentum Correlations in Hadronic Z decays

    CERN Document Server

    Buskulic, Damir; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Nief, J Y; Odier, P; Pietrzyk, B; Casado, M P; Chmeissani, M; Crespo, J M; Delfino, M C; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Garrido, L; Juste, A; Martínez, M; Orteu, S; Padilla, C; Park, I C; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Nuzzo, S; Ranieri, A; Raso, G; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Tricomi, A; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Alemany, R; Bazarko, A O; Bonvicini, G; Bright-Thomas, P G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Lutters, G; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Mir, L M; Moneta, L; Oest, T; Pacheco, A; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rizzo, G; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schmitt, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wagner, A; Ajaltouni, Ziad J; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rosnet, P; Rossignol, J M; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Rensch, B; Wäänänen, A; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Casper, David William; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Dorris, S J; Halley, A W; Knowles, I G; Lynch, J G; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Teixeira-Dias, P; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Geweniger, C; Graefe, G; Hanke, P; Hansper, G; Hepp, V; Kluge, E E; Putzer, A; Schmidt, M; Sommer, J; Tittel, K; Werner, S; Wunsch, M; Abbaneo, D; Beuselinck, R; Binnie, David M; Cameron, W; Dornan, Peter J; Moutoussi, A; Nash, J; Sedgbeer, J K; Stacey, A M; Williams, M D; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Betteridge, A P; Bowdery, C K; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Williams, M I; Galla, A; Giehl, I; Greene, A M; Hoffmann, C; Jakobs, K; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, H G; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Konstantinidis, N P; Payre, P; Rousseau, D; Talby, M; Sadouki, A; Thulasidas, M; Trabelsi, K; Aleppo, M; Ragusa, F; Bauer, C; Berlich, R; Blum, Walter; Büscher, V; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Choi, Y; Cordier, A; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Höcker, A; Jacholkowska, A; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Nikolic, I A; Park, H J; Schune, M H; Simion, S; Veillet, J J; Videau, I; Zerwas, D; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Palla, Fabrizio; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Vannini, C; Verdini, P G; Walsh, J; Blair, G A; Bryant, L M; Cerutti, F; Chambers, J T; Gao, Y; Green, M G; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Maley, P; Norton, P R; Thompson, J C; Wright, A E; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Black, S N; Dann, J H; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Booth, C N; Boswell, R; Brew, C A J; Cartwright, S L; Combley, F; Köksal, A; Lehto, M H; Newton, W M; Reeve, J; Thompson, L F; Böhrer, A; Brandt, S; Cowan, G D; Grupen, Claus; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Greening, T C; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Scott, I J; Walsh, A M; Wu Sau Lan; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G

    1997-01-01

    Using data obtained with the ALEPH detector at the Z resonance, a measure based on transverse momentum is shown to exhibit a correlation between the two halves of a hadronic event which cannot be explained by energy-momentum conservation, flavour conservation, the imposition of an event axis or imperfect event reconstruction. Two possible explanations based on Monte Carlo models are examined: a) ARIADNE, with the correlation forming early in the parton shower and with the transition from partons to hadrons playing only a minor part; b) JETSET, with the correlation forming at the fragmentation stage. A correlation technique based on a jet cluster analysis is used to make a comparison of the models with the data. It is concluded that both non-perturbative and perturbative effects make important contributions to the observed correlation.

  16. Momentum transfer dependence of generalized parton distributions

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Neetika [Indian Institute of Science Education and Research Mohali, S.A.S. Nagar, Punjab (India)

    2016-11-15

    We revisit the model for parametrization of the momentum dependence of nucleon generalized parton distributions in the light of recent MRST measurements of parton distribution functions (A.D. Martin et al., Eur. Phys. J. C 63, 189 (2009)). Our parametrization method with a minimum set of free parameters give a sufficiently good description of data for Dirac and Pauli electromagnetic form factors of proton and neutron at small and intermediate values of momentum transfer. We also calculate the GPDs for up- and down-quarks by decomposing the electromagnetic form factors for the nucleon using the charge and isospin symmetry and also study the evolution of GPDs to a higher scale. We further investigate the transverse charge densities for both the unpolarized and transversely polarized nucleon and compare our results with Kelly's distribution. (orig.)

  17. Quantum scattering theory on the momentum lattice

    International Nuclear Information System (INIS)

    Rubtsova, O. A.; Pomerantsev, V. N.; Kukulin, V. I.

    2009-01-01

    A new approach based on the wave-packet continuum discretization method recently developed by the present authors for solving quantum-mechanical scattering problems for atomic and nuclear scattering processes and few-body physics is described. The formalism uses the complete continuum discretization scheme in terms of the momentum stationary wave-packet basis, which leads to formulation of the scattering problem on a lattice in the momentum space. The solution of the few-body scattering problem can be found in the approach from linear matrix equations with nonsingular matrix elements, averaged on energy over lattice cells. The developed approach is illustrated by the solution of numerous two- and three-body scattering problems with local and nonlocal potentials below and well above the three-body breakup threshold.

  18. Angular momentum alignment in molecular beam scattering

    International Nuclear Information System (INIS)

    Treffers, M.A.

    1985-01-01

    It is shown how the angular momentum alignment in a molecular beam can be determined using laser-induced fluorescence in combination with precession of the angular momenta in a magnetic field. After a general analysis of the method, some results are presented to illustrate the possibilities of the method. Experimental data are presented on the alignment production for Na 2 molecules that made a collision induced angular momentum transition. Magnitude as well as direction of the alignment have been determined for scattering with several scattering partners and for a large number of scattering angles and transitions. The last chapter deals with the total alignment production in a final J-state, i.e. without state selection of the initial rotational state. (orig.)

  19. Measuring momentum for charged particle tomography

    Science.gov (United States)

    Morris, Christopher; Fraser, Andrew Mcleod; Schultz, Larry Joe; Borozdin, Konstantin N.; Klimenko, Alexei Vasilievich; Sossong, Michael James; Blanpied, Gary

    2010-11-23

    Methods, apparatus and systems for detecting charged particles and obtaining tomography of a volume by measuring charged particles including measuring the momentum of a charged particle passing through a charged particle detector. Sets of position sensitive detectors measure scattering of the charged particle. The position sensitive detectors having sufficient mass to cause the charged particle passing through the position sensitive detectors to scatter in the position sensitive detectors. A controller can be adapted and arranged to receive scattering measurements of the charged particle from the charged particle detector, determine at least one trajectory of the charged particle from the measured scattering; and determine at least one momentum measurement of the charged particle from the at least one trajectory. The charged particle can be a cosmic ray-produced charged particle, such as a cosmic ray-produced muon. The position sensitive detectors can be drift cells, such as gas-filled drift tubes.

  20. Double-slit experiment in momentum space

    Science.gov (United States)

    Ivanov, I. P.; Seipt, D.; Surzhykov, A.; Fritzsche, S.

    2016-08-01

    Young's classic double-slit experiment demonstrates the reality of interference when waves and particles travel simultaneously along two different spatial paths. Here, we propose a double-slit experiment in momentum space, realized in the free-space elastic scattering of vortex electrons. We show that this process proceeds along two paths in momentum space, which are well localized and well separated from each other. For such vortex beams, the (plane-wave) amplitudes along the two paths acquire adjustable phase shifts and produce interference fringes in the final angular distribution. We argue that this experiment can be realized with the present-day technology. We show that it gives experimental access to the Coulomb phase, a quantity which plays an important role in all charged particle scattering but which usual scattering experiments are insensitive to.

  1. Hadronic currents in the infinite momentum frame

    International Nuclear Information System (INIS)

    Toth, K.

    1975-01-01

    The problem of the transformation properties of hadronic currents in the infinite momentum frame (IMF) is investigated. A general method is proposed to deal with the problem which is based upon the concept of group contraction. The two-dimensional aspects of the IMF description are studied in detail, and the current matrix elements of a three-dimensional Poincare covariant theory are reduced to those of a two-dimensional one. It is explicitlyshown that the covariance group of the two-dimensional theory may either be a 'non-relativistic' (Galilei) group, or a 'relativistic' (Poincare) one depending on the value of a parameter reminiscent of the light velocity in the three-dimensional theory. The value of this parameter cannot be determined by kinematical argument. These results offer a natural generalization of models which assume Galilean symmetry in the infinite momentum frame

  2. Behavior of nuclei at high angular momentum

    International Nuclear Information System (INIS)

    Stephens, F.S.

    1982-07-01

    The present report begins with a brief overview of nuclear shapes and level structures at high-spin values. The new spectroscopy associated with angular-momentum alignments is described, and some of the exciting possibilities of this spectroscopy are explored. Nuclear moments of inertia are discussed and a somewhat different one is defined, together with a method for measuring it and some early results. Finally a few comments on the future prospects for high-spin physics are offered

  3. Relativistic neoclassical transport coefficients with momentum correction

    International Nuclear Information System (INIS)

    Marushchenko, I.; Azarenkov, N.A.

    2016-01-01

    The parallel momentum correction technique is generalized for relativistic approach. It is required for proper calculation of the parallel neoclassical flows and, in particular, for the bootstrap current at fusion temperatures. It is shown that the obtained system of linear algebraic equations for parallel fluxes can be solved directly without calculation of the distribution function if the relativistic mono-energetic transport coefficients are already known. The first relativistic correction terms for Braginskii matrix coefficients are calculated.

  4. Longitudinal momentum distributions in transverse coordinate space

    International Nuclear Information System (INIS)

    Kumar, Narinder; Mondal, Chandan

    2016-01-01

    In the present work, we study the longitudinal momentum distributions in the transverse coordinate space in a light-front quark-diquark model inspired by soft-wall AdS/QCD. We take the phenomenological light-front quark-diquark model proposed by Gutsche et. al. In this model, the light-front wave functions (LFWFs) for the proton are constructed from the two particle wave functions obtained in soft-wall AdS/QCD

  5. On transverse momentum dependence of average multiplicity

    International Nuclear Information System (INIS)

    Slepchenko, L.A.; Matveev, V.A.; Sissakian, A.N.

    1975-01-01

    The behaviour of the mean associated multiplicity of the secondary particles as function of the transverse momentum is considered. New scaling regularities of the cross-sections of the semi-inclusive reactions are predicted and compared with the experimental data obtained in the two-meter propane chamber of JINR, irradiated by π - -mesons with p=40 GeV/c at the Serpukhov accelerator

  6. Production of baryons with large transverse momentum

    International Nuclear Information System (INIS)

    Landshoff, P.V.; Polkinghorne, J.C.; Scott, D.M.

    1975-01-01

    The multiple scattering of constituent quarks provides a natural mechanism for fairly copious production of large-transverse-momentum baryons in nucleon--nucleon collisions. The predicted scaling law agrees well with available data, and the mechanism provides a qualitative explanation of nuclear-target effects. In comparison with previous parton models, correlations are predicted to be qualitatively different, and large-p/sub T/ baryon production by meson beams is relatively suppressed

  7. Energy-momentum-tensor in quantumelectrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Schott, T

    1974-01-01

    This work deals with the operator properties of the energy-momentum-tensor (ET) in the framework of quantum electrodynamics. The principles of construction of the ET are discussed for quantized fields in the Schwinger variation principle. Dealing with the conserved quantities for quantized fields operator problems are coming up in the Coulomb gauge because Dirac- and Maxwellfield do not commute completely. Further on contemporary commutators of the ET components are investigated mutually. Finally non-canonical methods are developed.

  8. Transverse momentum signatures for heavy Higgs bosons

    International Nuclear Information System (INIS)

    Cahn, R.N.; Ellis, S.D.; Kleiss, R.; Stirling, W.J.

    1986-01-01

    Heavy Higgs bosons produced by WW fusion at the SSC will have transverse mementum of order M/sub w/. The background due to q anti q → ZZ will produce pairs with characteristically less transverse momentum. This provides a useful discriminator. It may be possible to tag the WW fusion events in a manner analogous to that used in two photon physics. 12 refs., 4 figs

  9. High momentum transfer processes in QCD

    International Nuclear Information System (INIS)

    Efremov, A.V.; Radyushkin, A.V.

    1978-01-01

    A unified approach to the investigation of inclusive high momentum transfer processes in the QCD framework is proposed. A modified parton model (with parton distribution functions depending on an additional renormalization parameter) is shown to be valid in all orders of perturbation theory. The approach is also applicable for studying wide-angle elastic scattering processes of colourless bound states of quarks (the hadrons). The asymptotic behaviour of pion electromagnetic form factor is calculated as an example

  10. High Angular Momentum Rydberg Wave Packets

    Science.gov (United States)

    Wyker, Brendan

    2011-12-01

    High angular momentum Rydberg wave packets are studied. Application of carefully tailored electric fields to low angular momentum, high- n (n ˜ 300) Rydberg atoms creates coherent superpositions of Stark states with near extreme values of angular momentum, ℓ. Wave packet components orbit the parent nucleus at rates that depend on their energy, leading to periods of localization and delocalization as the components come into and go out of phase with each other. Monitoring survival probability signals in the presence of position dependent probing leads to observation of characteristic oscillations based on the composition of the wave packet. The discrete nature of electron energy levels is observed through the measurement of quantum revivals in the wave packet localization signal. Time-domain spectroscopy of these signals allows determination of both the population and phase of individual superposition components. Precise manipulation of wave packets is achieved through further application of pulsed electric fields. Decoherence effects due to background gas collisions and electrical noise are also detailed. Quantized classical trajectory Monte-Carlo simulations are introduced and agree remarkably well with experimental results.

  11. On the angular momentum in star formation

    International Nuclear Information System (INIS)

    Horedt, G.P.

    1978-01-01

    The author discusses the rotation of interstellar clouds which are in a stage immediately before star formation. Cloud collisions seem to be the principal cause of the observed rotation of interstellar clouds. The rotational motion of the clouds is strongly influenced by turbulence. Theories dealing with the resolution of the angular momentum problem in star formation are classified into five major groups. The old idea that the angular momentum of an interstellar cloud passes during star formation into the angular momentum of double star systems and/or circumstellar clouds, is developed. It is suggested that a rotating gas cloud contracts into a ring-like structure which fragments into self-gravitating subcondensations. By collisions and gas accretion these subcondensations accrete into binary systems surrounded by circumstellar clouds. Using some rough approximations the authors find analytical expressions for the semi-major axis of the binary system and for the density of the circumstellar clouds as a function of the initial density and of the initial angular velocity of an interstellar cloud. The obtained values are well within the observational limits. (Auth.)

  12. Asymmetric Extreme Tails and Prospective Utility of Momentum Returns

    NARCIS (Netherlands)

    Stork, P.A.; Gregory-Allen, R.; Lu, H.

    2012-01-01

    We use extreme value theory to analyse the tails of a momentum strategy's return distribution. The asymmetry between the fat left tail and thin right tail strongly reduces a momentum strategy's prospective utility levels. © 2012 Elsevier B.V.

  13. Sorting and quantifying orbital angular momentum of laser beams

    CSIR Research Space (South Africa)

    Schulze, C

    2013-10-01

    Full Text Available We present a novel tool for sorting the orbital angular momentum and to determine the orbital angular momentum density of laser beams, which is based on the use of correlation filters....

  14. Large-Scale Spacecraft Fire Safety Tests

    Science.gov (United States)

    Urban, David; Ruff, Gary A.; Ferkul, Paul V.; Olson, Sandra; Fernandez-Pello, A. Carlos; T'ien, James S.; Torero, Jose L.; Cowlard, Adam J.; Rouvreau, Sebastien; Minster, Olivier; hide

    2014-01-01

    An international collaborative program is underway to address open issues in spacecraft fire safety. Because of limited access to long-term low-gravity conditions and the small volume generally allotted for these experiments, there have been relatively few experiments that directly study spacecraft fire safety under low-gravity conditions. Furthermore, none of these experiments have studied sample sizes and environment conditions typical of those expected in a spacecraft fire. The major constraint has been the size of the sample, with prior experiments limited to samples of the order of 10 cm in length and width or smaller. This lack of experimental data forces spacecraft designers to base their designs and safety precautions on 1-g understanding of flame spread, fire detection, and suppression. However, low-gravity combustion research has demonstrated substantial differences in flame behavior in low-gravity. This, combined with the differences caused by the confined spacecraft environment, necessitates practical scale spacecraft fire safety research to mitigate risks for future space missions. To address this issue, a large-scale spacecraft fire experiment is under development by NASA and an international team of investigators. This poster presents the objectives, status, and concept of this collaborative international project (Saffire). The project plan is to conduct fire safety experiments on three sequential flights of an unmanned ISS re-supply spacecraft (the Orbital Cygnus vehicle) after they have completed their delivery of cargo to the ISS and have begun their return journeys to earth. On two flights (Saffire-1 and Saffire-3), the experiment will consist of a flame spread test involving a meter-scale sample ignited in the pressurized volume of the spacecraft and allowed to burn to completion while measurements are made. On one of the flights (Saffire-2), 9 smaller (5 x 30 cm) samples will be tested to evaluate NASAs material flammability screening tests

  15. Operational gain : measuring the capture of genetic gain ...

    African Journals Online (AJOL)

    The concept of operational gain is more than the weighted average of the genetic quality of planted hectares, and encompasses tree breeding efficiencies, propagation efficiencies, matching of species and genotype to site, plant use efficiency and early measures of stand density and growth. To test the operational gain ...

  16. Dimensional Effects on the Momentum distribution of Bosonic Trimer States

    DEFF Research Database (Denmark)

    F. Bellotti, F.; Frederico, T.; T. Yamashita, M.

    2013-01-01

    -body contact parameter is universal and then demonstrate that the momentum distribution at next-to-leading order has a logarithmic dependence on momentum which is vastly different from the three-dimensional case. Based on this, we propose a scheme for measuring the effective dimensionality of a quantum many......-body system by exploiting the functional form of the momentum distribution....

  17. Parametric dependences of momentum pinch and Prandtl number in JET

    NARCIS (Netherlands)

    Tala, T.; Salmi, A.; Angioni, C.; Casson, F. J.; Corrigan, G.; Ferreira, J.; Giroud, C.; Mantica, P.; Naulin, V.; Peeters, A.G.; Solomon, W. M.; Strintzi, D.; Tsalas, M.; Versloot, T. W.; de Vries, P. C.; Zastrow, K. D.

    2011-01-01

    Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density

  18. REIT Momentum and the Performance of Real Estate Mutual Funds

    NARCIS (Netherlands)

    J. Derwall (Jeroen); J.J. Huij (Joop); W.A. Marquering (Wessel)

    2009-01-01

    textabstractREITs exhibit a strong and prevalent momentum effect that is not captured by conventional factor models. This REIT momentum anomaly hampers proper judgments about the performance of actively managed REIT portfolios. In contrast, a REIT momentum factor adds incremental explanatory power

  19. Fragmentation and momentum correlations in heavy-ion collisions

    Indian Academy of Sciences (India)

    The role of momentum correlations in the production of light and medium mass fragments is studied by imposing momentum cut in the clusterization of the phase space. Our detailed investigation shows that momentum cut has a major role to play in the emission of fragments. A comparison with the experimental data is also ...

  20. REQUIREMENTS FOR IMAGE QUALITY OF EMERGENCY SPACECRAFTS

    Directory of Open Access Journals (Sweden)

    A. I. Altukhov

    2015-05-01

    Full Text Available The paper deals with the method for formation of quality requirements to the images of emergency spacecrafts. The images are obtained by means of remote sensing of near-earth space orbital deployment in the visible range. of electromagnetic radiation. The method is based on a joint taking into account conditions of space survey, characteristics of surveillance equipment, main design features of the observed spacecrafts and orbital inspection tasks. Method. Quality score is the predicted linear resolution image that gives the possibility to create a complete view of pictorial properties of the space image obtained by electro-optical system from the observing satellite. Formulation of requirements to the numerical value of this indicator is proposed to perform based on the properties of remote sensing system, forming images in the conditions of outer space, and the properties of the observed emergency spacecraft: dimensions, platform construction of the satellite, on-board equipment placement. For method implementation the authors have developed a predictive model of requirements to a linear resolution for images of emergency spacecrafts, making it possible to select the intervals of space shooting and get the satellite images required for quality interpretation. Main results. To verify the proposed model functionality we have carried out calculations of the numerical values for the linear resolution of the image, ensuring the successful task of determining the gross structural damage of the spacecrafts and identifying changes in their spatial orientation. As input data were used with dimensions and geometric primitives corresponding to the shape of deemed inspected spacecrafts: Resurs-P", "Canopus-B", "Electro-L". Numerical values of the linear resolution images have been obtained, ensuring the successful task solution for determining the gross structural damage of spacecrafts.

  1. Poynting Theorem, Relativistic Transformation of Total Energy-Momentum and Electromagnetic Energy-Momentum Tensor

    Science.gov (United States)

    Kholmetskii, Alexander; Missevitch, Oleg; Yarman, Tolga

    2016-02-01

    We address to the Poynting theorem for the bound (velocity-dependent) electromagnetic field, and demonstrate that the standard expressions for the electromagnetic energy flux and related field momentum, in general, come into the contradiction with the relativistic transformation of four-vector of total energy-momentum. We show that this inconsistency stems from the incorrect application of Poynting theorem to a system of discrete point-like charges, when the terms of self-interaction in the product {\\varvec{j}} \\cdot {\\varvec{E}} (where the current density {\\varvec{j}} and bound electric field {\\varvec{E}} are generated by the same source charge) are exogenously omitted. Implementing a transformation of the Poynting theorem to the form, where the terms of self-interaction are eliminated via Maxwell equations and vector calculus in a mathematically rigorous way (Kholmetskii et al., Phys Scr 83:055406, 2011), we obtained a novel expression for field momentum, which is fully compatible with the Lorentz transformation for total energy-momentum. The results obtained are discussed along with the novel expression for the electromagnetic energy-momentum tensor.

  2. Dependence of two-neutron momentum densities on total pair momentum

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, Joseph A [Los Alamos National Laboratory; Wiringa, R B [ANL; Schiavilla, R [JEFFERSON LAB; Pieper, Steven C [ANL

    2008-01-01

    Two-nucleon momentum distributions are calculated for the ground states of {sup 3}He and {sup 4}He as a function of the nucleons' relative and total momenta. We use variational Monte Carlo wave functions derived from a realistic Hamiltonian with two- and three-nucleon potentials. The momentum distribution of pp pairs is found to be much smaller than that of pn pairs for values of the relative momentum in the range (300--500) MeV/c and vanishing total momentum. Howeer, as the totalmomentum increases to 400 MeV/c, the ratio of pp to pn pairs in this relative momentum range grows and approaches the limit 1/2 for {sup 3}He and 1/4 for {sup 4}He, corresponding to the ratio of pp to pn pairs in these nuclei. This behavior should be easily observable in two-nucleon knock-out processes, such as A(e, e'pN).

  3. Low eddy loss axial hybrid magnetic bearing with gimballing control ability for momentum flywheel

    International Nuclear Information System (INIS)

    Tang, Jiqiang; Sun, Jinji; Fang, Jiancheng; Shuzhi Sam, Ge

    2013-01-01

    For a magnetically suspended momentum flywheel (MSMF), the spinning rotor can be tilted by a pair of the presented axial hybrid magnetic bearing (AHMB) with eight poles and rotates around the radial axes to generate a large torque to maneuver the spacecraft. To improve the control performance and gimballing control ability of the AHMB, characteristics such as magnetic suspension force, angular stiffness and tilting momentum are researched. These segmented stator poles cause the magnetic density in the thrust rotor plate to be uneven unavoidably and the rotational loss is large at high speed, but we optimized the stator poles configuration and caused the thrust rotor plate formed by bulk DT4C and laminated material to make the magnetic density in the thrust rotor plate change less and be smoother. Laminated material such as 1J50 film with a thickness of 0.1 mm can make the variation of the magnetic density in DT4C become very small and the eddy loss of it be negligible, but the stress produced in the “O” shape stacks by reeling has a bad effect on its power loss. Nanocrystalline can reduce eddy losses and is not affected by the reeling process. Based on the AHBM consisting of the stator with eight improved poles and the presented thrust rotor plate with DT4 and nanocrystalline, the rotational loss of 5-DOF magnetically suspended momentum flywheel with angular momentum of 15 N m s at 5000 rpm has reduced from 23.4 W to 3.2 W, which proved that this AHMB has low eddy loss for the gimballing control ability. - Highlights: ► Control methods of rotor driven by AHMBs and their characteristics are researched. ► Optimized stator and rotor of AHMB reduce its eddy losses greatly. ► Presented the factors affecting the eddy losses of AHMBs. ► The good performances of AHMB with low eddy loss are proved by experiments.

  4. Modeling the fundamental characteristics and processes of the spacecraft functioning

    Science.gov (United States)

    Bazhenov, V. I.; Osin, M. I.; Zakharov, Y. V.

    1986-01-01

    The fundamental aspects of modeling of spacecraft characteristics by using computing means are considered. Particular attention is devoted to the design studies, the description of physical appearance of the spacecraft, and simulated modeling of spacecraft systems. The fundamental questions of organizing the on-the-ground spacecraft testing and the methods of mathematical modeling were presented.

  5. Robust Spacecraft Component Detection in Point Clouds

    Directory of Open Access Journals (Sweden)

    Quanmao Wei

    2018-03-01

    Full Text Available Automatic component detection of spacecraft can assist in on-orbit operation and space situational awareness. Spacecraft are generally composed of solar panels and cuboidal or cylindrical modules. These components can be simply represented by geometric primitives like plane, cuboid and cylinder. Based on this prior, we propose a robust automatic detection scheme to automatically detect such basic components of spacecraft in three-dimensional (3D point clouds. In the proposed scheme, cylinders are first detected in the iteration of the energy-based geometric model fitting and cylinder parameter estimation. Then, planes are detected by Hough transform and further described as bounded patches with their minimum bounding rectangles. Finally, the cuboids are detected with pair-wise geometry relations from the detected patches. After successive detection of cylinders, planar patches and cuboids, a mid-level geometry representation of the spacecraft can be delivered. We tested the proposed component detection scheme on spacecraft 3D point clouds synthesized by computer-aided design (CAD models and those recovered by image-based reconstruction, respectively. Experimental results illustrate that the proposed scheme can detect the basic geometric components effectively and has fine robustness against noise and point distribution density.

  6. Robust Spacecraft Component Detection in Point Clouds.

    Science.gov (United States)

    Wei, Quanmao; Jiang, Zhiguo; Zhang, Haopeng

    2018-03-21

    Automatic component detection of spacecraft can assist in on-orbit operation and space situational awareness. Spacecraft are generally composed of solar panels and cuboidal or cylindrical modules. These components can be simply represented by geometric primitives like plane, cuboid and cylinder. Based on this prior, we propose a robust automatic detection scheme to automatically detect such basic components of spacecraft in three-dimensional (3D) point clouds. In the proposed scheme, cylinders are first detected in the iteration of the energy-based geometric model fitting and cylinder parameter estimation. Then, planes are detected by Hough transform and further described as bounded patches with their minimum bounding rectangles. Finally, the cuboids are detected with pair-wise geometry relations from the detected patches. After successive detection of cylinders, planar patches and cuboids, a mid-level geometry representation of the spacecraft can be delivered. We tested the proposed component detection scheme on spacecraft 3D point clouds synthesized by computer-aided design (CAD) models and those recovered by image-based reconstruction, respectively. Experimental results illustrate that the proposed scheme can detect the basic geometric components effectively and has fine robustness against noise and point distribution density.

  7. High Gain Advanced GPS Receiver

    National Research Council Canada - National Science Library

    Brown, Alison; Zhang, Gengsheng

    2006-01-01

    NAVSYS High Gain Advanced GPS Receiver (HAGR) uses a digital beam-steering antenna array to enable up to eight GPS satellites to be tracked, each with up to 10 dBi of additional antenna gain over a conventional receiver solution...

  8. Attitude coordination for spacecraft formation with multiple communication delays

    Directory of Open Access Journals (Sweden)

    Guo Yaohua

    2015-04-01

    Full Text Available Communication delays are inherently present in information exchange between spacecraft and have an effect on the control performance of spacecraft formation. In this work, attitude coordination control of spacecraft formation is addressed, which is in the presence of multiple communication delays between spacecraft. Virtual system-based approach is utilized in case that a constant reference attitude is available to only a part of the spacecraft. The feedback from the virtual systems to the spacecraft formation is introduced to maintain the formation. Using backstepping control method, input torque of each spacecraft is designed such that the attitude of each spacecraft converges asymptotically to the states of its corresponding virtual system. Furthermore, the backstepping technique and the Lyapunov–Krasovskii method contribute to the control law design when the reference attitude is time-varying and can be obtained by each spacecraft. Finally, effectiveness of the proposed methodology is illustrated by the numerical simulations of a spacecraft formation.

  9. Energy-momentum tensor in the fermion-pairing model

    International Nuclear Information System (INIS)

    Kawati, S.; Miyata, H.

    1980-01-01

    The symmetric energy-momentum tensor for the self-interacting fermion theory (psi-barpsi) 2 is expressed in terms of the collective mode within the Hartree approximation. The divergent part of the energy-momentum tensor for the fermion theory induces an effective energy-momentum tensor for the collective mode, and this effective energy-momentum tensor automatically has the Callan-Coleman-Jackiw improved form. The renormalized energy-momentum tensor is structurally equivalent to the Callan-Coleman-Jackiw improved tensor for the Yukawa theory

  10. First-principles momentum-dependent local ansatz wavefunction and momentum distribution function bands of iron

    International Nuclear Information System (INIS)

    Kakehashi, Yoshiro; Chandra, Sumal

    2016-01-01

    We have developed a first-principles local ansatz wavefunction approach with momentum-dependent variational parameters on the basis of the tight-binding LDA+U Hamiltonian. The theory goes beyond the first-principles Gutzwiller approach and quantitatively describes correlated electron systems. Using the theory, we find that the momentum distribution function (MDF) bands of paramagnetic bcc Fe along high-symmetry lines show a large deviation from the Fermi–Dirac function for the d electrons with e g symmetry and yield the momentum-dependent mass enhancement factors. The calculated average mass enhancement m*/m = 1.65 is consistent with low-temperature specific heat data as well as recent angle-resolved photoemission spectroscopy (ARPES) data. (author)

  11. First-Principles Momentum-Dependent Local Ansatz Wavefunction and Momentum Distribution Function Bands of Iron

    Science.gov (United States)

    Kakehashi, Yoshiro; Chandra, Sumal

    2016-04-01

    We have developed a first-principles local ansatz wavefunction approach with momentum-dependent variational parameters on the basis of the tight-binding LDA+U Hamiltonian. The theory goes beyond the first-principles Gutzwiller approach and quantitatively describes correlated electron systems. Using the theory, we find that the momentum distribution function (MDF) bands of paramagnetic bcc Fe along high-symmetry lines show a large deviation from the Fermi-Dirac function for the d electrons with eg symmetry and yield the momentum-dependent mass enhancement factors. The calculated average mass enhancement m*/m = 1.65 is consistent with low-temperature specific heat data as well as recent angle-resolved photoemission spectroscopy (ARPES) data.

  12. Angular Momentum and Galaxy Formation Revisited

    Science.gov (United States)

    Romanowsky, Aaron J.; Fall, S. Michael

    2012-12-01

    Motivated by a new wave of kinematical tracers in the outer regions of early-type galaxies (ellipticals and lenticulars), we re-examine the role of angular momentum in galaxies of all types. We present new methods for quantifying the specific angular momentum j, focusing mainly on the more challenging case of early-type galaxies, in order to derive firm empirical relations between stellar j sstarf and mass M sstarf (thus extending earlier work by Fall). We carry out detailed analyses of eight galaxies with kinematical data extending as far out as 10 effective radii, and find that data at two effective radii are generally sufficient to estimate total j sstarf reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j sstarf in their outer regions owing to angular momentum transport in major mergers. We then carry out a comprehensive analysis of extended kinematic data from the literature for a sample of ~100 nearby bright galaxies of all types, placing them on a diagram of j sstarf versus M sstarf. The ellipticals and spirals form two parallel j sstarf-M sstarf tracks, with log-slopes of ~0.6, which for the spirals are closely related to the Tully-Fisher relation, but for the ellipticals derives from a remarkable conspiracy between masses, sizes, and rotation velocities. The ellipticals contain less angular momentum on average than spirals of equal mass, with the quantitative disparity depending on the adopted K-band stellar mass-to-light ratios of the galaxies: it is a factor of ~3-4 if mass-to-light ratio variations are neglected for simplicity, and ~7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j sstarf-M sstarf trends similar to the overall ones for spirals and ellipticals. The lenticulars have an intermediate trend, and we propose that the morphological types of galaxies reflect disk and bulge subcomponents that follow separate, fundamental j sstarf

  13. Guidance and control of swarms of spacecraft

    Science.gov (United States)

    Morgan, Daniel James

    There has been considerable interest in formation flying spacecraft due to their potential to perform certain tasks at a cheaper cost than monolithic spacecraft. Formation flying enables the use of smaller, cheaper spacecraft that distribute the risk of the mission. Recently, the ideas of formation flying have been extended to spacecraft swarms made up of hundreds to thousands of 100-gram-class spacecraft known as femtosatellites. The large number of spacecraft and limited capabilities of each individual spacecraft present a significant challenge in guidance, navigation, and control. This dissertation deals with the guidance and control algorithms required to enable the flight of spacecraft swarms. The algorithms developed in this dissertation are focused on achieving two main goals: swarm keeping and swarm reconfiguration. The objectives of swarm keeping are to maintain bounded relative distances between spacecraft, prevent collisions between spacecraft, and minimize the propellant used by each spacecraft. Swarm reconfiguration requires the transfer of the swarm to a specific shape. Like with swarm keeping, minimizing the propellant used and preventing collisions are the main objectives. Additionally, the algorithms required for swarm keeping and swarm reconfiguration should be decentralized with respect to communication and computation so that they can be implemented on femtosats, which have limited hardware capabilities. The algorithms developed in this dissertation are concerned with swarms located in low Earth orbit. In these orbits, Earth oblateness and atmospheric drag have a significant effect on the relative motion of the swarm. The complicated dynamic environment of low Earth orbits further complicates the swarm-keeping and swarm-reconfiguration problems. To better develop and test these algorithms, a nonlinear, relative dynamic model with J2 and drag perturbations is developed. This model is used throughout this dissertation to validate the algorithms

  14. Chirality and angular momentum in optical radiation

    Science.gov (United States)

    Coles, Matt M.; Andrews, David L.

    2012-06-01

    This paper develops, in precise quantum electrodynamic terms, photonic attributes of the “optical chirality density,” one of several measures long known to be conserved quantities for a vacuum electromagnetic field. The analysis lends insights into some recent interpretations of chiroptical experiments, in which this measure, and an associated chirality flux, have been treated as representing physically distinctive “superchiral” phenomena. In the fully quantized formalism the chirality density is promoted to operator status, whose exploration with reference to an arbitrary polarization basis reveals relationships to optical angular momentum and helicity operators. Analyzing multimode beams with complex wave-front structures, notably Laguerre-Gaussian modes, affords a deeper understanding of the interplay between optical chirality and optical angular momentum. By developing theory with due cognizance of the photonic character of light, it emerges that only the spin-angular momentum of light is engaged in such observations. Furthermore, it is shown that these prominent measures of the helicity of chiral electromagnetic radiation have a common basis in differences between the populations of optical modes associated with angular momenta of opposite sign. Using a calculation of the rate of circular dichroism as an example, with coherent states to model the electromagnetic field, it is discovered that two terms contribute to the differential effect. The primary contribution relates to the difference in left- and right-handed photon populations; the only other contribution, which displays a sinusoidal distance dependence corresponding to the claim of nodal enhancements, is connected with the quantum photon number-phase uncertainty relation. From the full analysis, it appears that the term “superchiral” can be considered redundant.

  15. Electron--molecule scattering in momentum space

    International Nuclear Information System (INIS)

    Ritchie, B.

    1979-01-01

    We examine the Fourier transform of the Schroedinger equation for electron--molecule scattering, treated as potential scattering from a multicenter distribution of charged fixed in space. When the angle theta between R,the internuclear vector of a diatomic target, and q, the momentum transfer, is held fixed during the collision, then the directions of incidence and scattering are fixed relative to R. The process is then described as having a dynamical dependence on the magnitude of q, q, from which the scattering angle is determined, and a parametric dependence on q's direction relative to R. This approximation is used routinely at high energies in the calculation of the Born amplitude. Fixed--nuclei coordinate--space studies suggest that this approximation can be extended to low energies, provided the amplitude is taken from the solution of the integral equation of momentum space rather than from its inhomogeneity, proportional to the Born amplitude. We constrain R to be in the same direction relative to q', a virtual momentum transfer belonging to the kernel, as it is to q.Calculations are performed for the e, H 2 scattering in the static approximation, and cross sections averaged over theta/sub R/ are shown to be in good agreement with cross sections calculated by use of coupled spherical and coupled spheroidal partial wave theories. The angular distribution in the static approximation is also calculated at an incident energy close to 7 eV, where exchange is relatively unimportant. This result is in reasonably good agreement with that of R matrix theory in the static--exchange approximation. The extension of the theory to treat exchange is formulated and discussed. Also its extension to treat more complicated molecular targets is discussed

  16. Parasitic momentum flux in the tokamak core

    Science.gov (United States)

    Stoltzfus-Dueck, T.

    2017-10-01

    Tokamak plasmas rotate spontaneously without applied torque. This intrinsic rotation is important for future low-torque devices such as ITER, since rotation stabilizes certain instabilities. In the mid-radius `gradient region,' which reaches from the sawtooth inversion radius out to the pedestal top, intrinsic rotation profiles may be either flat or hollow, and can transition suddenly between these two states, an unexplained phenomenon referred to as rotation reversal. Theoretical efforts to explain the mid-radius rotation shear have largely focused on quasilinear models, in which the phase relationships of some selected instability result in a nondiffusive momentum flux (``residual stress''). In contrast, the present work demonstrates the existence of a robust, fully nonlinear symmetry-breaking momentum flux that follows from the free-energy flow in phase space and does not depend on any assumed linear eigenmode structure. The physical origin is an often-neglected portion of the radial ExB drift, which is shown to drive a symmetry-breaking outward flux of co-current momentum whenever free energy is transferred from the electrostatic potential to ion parallel flows. The fully nonlinear derivation relies only on conservation properties and symmetry, thus retaining the important contribution of damped modes. The resulting rotation peaking is counter-current and scales as temperature over plasma current. As first demonstrated by Landau, this free-energy transfer (thus also the corresponding residual stress) becomes inactive when frequencies are much higher than the ion transit frequency, which allows sudden transitions between hollow and flat profiles. Simple estimates suggest that this mechanism may be consistent with experimental observations. This work was funded in part by the Max-Planck/Princeton Center for Plasma Physics and in part by the U.S. Dept. of Energy, Office of Science, Contract No. DE-AC02-09CH11466.

  17. Developing Sustainable Spacecraft Water Management Systems

    Science.gov (United States)

    Thomas, Evan A.; Klaus, David M.

    2009-01-01

    It is well recognized that water handling systems used in a spacecraft are prone to failure caused by biofouling and mineral scaling, which can clog mechanical systems and degrade the performance of capillary-based technologies. Long duration spaceflight applications, such as extended stays at a Lunar Outpost or during a Mars transit mission, will increasingly benefit from hardware that is generally more robust and operationally sustainable overtime. This paper presents potential design and testing considerations for improving the reliability of water handling technologies for exploration spacecraft. Our application of interest is to devise a spacecraft wastewater management system wherein fouling can be accommodated by design attributes of the management hardware, rather than implementing some means of preventing its occurrence.

  18. Embedded Thermal Control for Spacecraft Subsystems Miniaturization

    Science.gov (United States)

    Didion, Jeffrey R.

    2014-01-01

    Optimization of spacecraft size, weight and power (SWaP) resources is an explicit technical priority at Goddard Space Flight Center. Embedded Thermal Control Subsystems are a promising technology with many cross cutting NSAA, DoD and commercial applications: 1.) CubeSatSmallSat spacecraft architecture, 2.) high performance computing, 3.) On-board spacecraft electronics, 4.) Power electronics and RF arrays. The Embedded Thermal Control Subsystem technology development efforts focus on component, board and enclosure level devices that will ultimately include intelligent capabilities. The presentation will discuss electric, capillary and hybrid based hardware research and development efforts at Goddard Space Flight Center. The Embedded Thermal Control Subsystem development program consists of interrelated sub-initiatives, e.g., chip component level thermal control devices, self-sensing thermal management, advanced manufactured structures. This presentation includes technical status and progress on each of these investigations. Future sub-initiatives, technical milestones and program goals will be presented.

  19. Low power arcjet system spacecraft impacts

    Science.gov (United States)

    Pencil, Eric J.; Sarmiento, Charles J.; Lichtin, D. A.; Palchefsky, J. W.; Bogorad, A. L.

    1993-01-01

    Potential plume contamination of spacecraft surfaces was investigated by positioning spacecraft material samples relative to an arcjet thruster. Samples in the simulated solar array region were exposed to the cold gas arcjet plume for 40 hrs to address concerns about contamination by backstreaming diffusion pump oil. Except for one sample, no significant changes were measured in absorptance and emittance within experimental error. Concerns about surface property degradation due to electrostatic discharges led to the investigation of the discharge phenomenon of charged samples during arcjet ignition. Short duration exposure of charged samples demonstrated that potential differences are consistently and completely eliminated within the first second of exposure to a weakly ionized plume. The spark discharge mechanism was not the discharge phenomenon. The results suggest that the arcjet could act as a charge control device on spacecraft.

  20. Relativistic Spacecraft Propelled by Directed Energy

    Science.gov (United States)

    Kulkarni, Neeraj; Lubin, Philip; Zhang, Qicheng

    2018-04-01

    Achieving relativistic flight to enable extrasolar exploration is one of the dreams of humanity and the long-term goal of our NASA Starlight program. We derive a relativistic solution for the motion of a spacecraft propelled by radiation pressure from a directed energy (DE) system. Depending on the system parameters, low-mass spacecraft can achieve relativistic speeds, thus enabling interstellar exploration. The diffraction of the DE system plays an important role and limits the maximum speed of the spacecraft. We consider “photon recycling” as a possible method to achieving higher speeds. We also discuss recent claims that our previous work on this topic is incorrect and show that these claims arise from an improper treatment of causality.

  1. Numerical Analysis of Magnetic Sail Spacecraft

    International Nuclear Information System (INIS)

    Sasaki, Daisuke; Yamakawa, Hiroshi; Usui, Hideyuki; Funaki, Ikkoh; Kojima, Hirotsugu

    2008-01-01

    To capture the kinetic energy of the solar wind by creating a large magnetosphere around the spacecraft, magneto-plasma sail injects a plasma jet into a strong magnetic field produced by an electromagnet onboard the spacecraft. The aim of this paper is to investigate the effect of the IMF (interplanetary magnetic field) on the magnetosphere of magneto-plasma sail. First, using an axi-symmetric two-dimensional MHD code, we numerically confirm the magnetic field inflation, and the formation of a magnetosphere by the interaction between the solar wind and the magnetic field. The expansion of an artificial magnetosphere by the plasma injection is then simulated, and we show that the magnetosphere is formed by the interaction between the solar wind and the magnetic field expanded by the plasma jet from the spacecraft. This simulation indicates the size of the artificial magnetosphere becomes smaller when applying the IMF.

  2. Energy-momentum density of graphite by electron-momentum spectroscopy

    International Nuclear Information System (INIS)

    Vos, M.; Fang, Z.; Canney, S.; Kheifets, A.; McCarthy, I.E.; Weigold, E.

    1996-11-01

    The energy-resolved electron momentum density of graphite has been measured along a series of well-defined directions using electron momentum spectroscopy (EMS). This is the first measurement of this kind performed on a single-crystal target with a thoroughly controlled orientation which clearly demonstrates the different nature of the σ and π bands in graphite. Good agreement between the calculated density and the measured one is found, further establishing that fact that EMS yields more direct and complete information on the valence electronic structure that any other method. 12 refs., 2 figs

  3. The angular momentum of isolated white dwarfs

    Directory of Open Access Journals (Sweden)

    Brassard P.

    2013-03-01

    Full Text Available This is a very brief report on an ongoing program aimed at mapping the internal rotation profiles of stars through asteroseismology. Three years ago, we developed and applied successfully a new technique to the pulsating GW Vir white dwarf PG 1159−035, and were able to infer that it rotates very slowly and rigidly over some 99% of its mass. We applied the same approach to the three other GW Vir pulsators with available rotational splitting data, and found similar results. We discuss the implications of these findings on the question of the angular momentum of white dwarfs resulting from single star evolution.

  4. Projection of angular momentum via linear algebra

    Science.gov (United States)

    Johnson, Calvin W.; O'Mara, Kevin D.

    2017-12-01

    Projection of many-body states with good angular momentum from an initial state is usually accomplished by a three-dimensional integral. We show how projection can instead be done by solving a straightforward system of linear equations. We demonstrate the method and give sample applications to 48Cr and 60Fe in the p f shell. This new projection scheme, which is competitive against the standard numerical quadrature, should also be applicable to other quantum numbers such as isospin and particle number.

  5. MINET [momentum integral network] code documentation

    International Nuclear Information System (INIS)

    Van Tuyle, G.J.; Nepsee, T.C.; Guppy, J.G.

    1989-12-01

    The MINET computer code, developed for the transient analysis of fluid flow and heat transfer, is documented in this four-part reference. In Part 1, the MINET models, which are based on a momentum integral network method, are described. The various aspects of utilizing the MINET code are discussed in Part 2, The User's Manual. The third part is a code description, detailing the basic code structure and the various subroutines and functions that make up MINET. In Part 4, example input decks, as well as recent validation studies and applications of MINET are summarized. 32 refs., 36 figs., 47 tabs

  6. Optical communication beyond orbital angular momentum

    CSIR Research Space (South Africa)

    Trichili, A

    2016-06-01

    Full Text Available :27674 | DOI: 10.1038/srep27674 www.nature.com/scientificreports Optical communication beyond orbital angular momentum Abderrahmen Trichili1, Carmelo Rosales-Guzmán2, Angela Dudley2,3, Bienvenu Ndagano2, Amine Ben Salem1, Mourad Zghal1,4 & Andrew Forbes2 Mode....rosalesguzman@wits.ac.za) received: 29 March 2016 Accepted: 24 May 2016 Published: 10 June 2016 OPEN www.nature.com/scientificreports/ 2Scientific RepoRts | 6:27674 | DOI: 10.1038/srep27674 Results Consider a LG mode in cylindrical coordinates, at its waist plane (z = 0), described...

  7. The QCD vacuum at infinite momentum

    International Nuclear Information System (INIS)

    White, A.R.

    1988-01-01

    We outline how ''topological confinement'' can be seen by the analysis of Regge limit infra-red divergences. We suggest that it is a necessary bridge between conventional confinement and the parton model at infinite momentum. It is produced by adding a chiral doublet of color sextet quarks to conventional QCD. An immediate signature of the resultant electroweak symmetry breaking would be large cross-sections for W + W/sup /minus// and Z 0 Z 0 pairs at the CERN and Fermilab /bar p/p colliders. 24 refs

  8. Angular momentum effects in subbarrier fusion

    International Nuclear Information System (INIS)

    Halbert, M.L.; Beene, J.R.; Hensley, D.C.; Honkanen, K.; Semkow, T.M.; Abenante, V.; Sarantites, D.G.; Li, Z.

    1987-01-01

    The authors discuss angular-momentum distributions σ l for the compound nucleus 164 Yb deduced from measurements of γ-ray multiplicity for all significant evaporation residues from fusion of 64 Ni and 100 Mo and 16 O + 148 Sm. At the lowest bombarding energies the σ l extend to higher l values than do predictions that include coupling of the principal inelastic channels, even if the coupling strengths are increased to match the experimental excitation function. Likewise, σ l from an energy-dependent real potential fitted to the excitation function fails to reproduce the experimental σ l distribution. No effects attributed to superdeformation were observed

  9. Symmetry and bifurcations of momentum mappings

    International Nuclear Information System (INIS)

    Arms, J.M.; Marsden, J.E.; Moncrief, V.

    1981-01-01

    The zero set of a momentum mapping is shown to have a singularity at each point with symmetry. The zero set is diffeomorphic to the product of a manifold and the zero set of a homogeneous quadratic function. The proof uses the Kuranishi theory of deformations. Among the applications, it is shown that the set of all solutions of the Yang-Mills equations on a Lorentz manifold has a singularity at any solution with symmetry, in the sense of a pure gauge symmetry. Similarly, the set of solutions of Einstein's equations has a singularity at any solution that has spacelike Killing fields, provided the spacetime has a compact Cauchy surface. (orig.)

  10. External momentum expansion in NJL model

    International Nuclear Information System (INIS)

    Huang Mei; Zhao Weiqin; Zhuang Pengfei

    1999-01-01

    In the large N c expansion beyond mean-field approximation, the authors develop a general scheme of SU(2) NJL model including current quark mass explicitly. In the scheme, the constituent quark's propagator is expanded in pions external momentum k, and all the Feynman diagrams are naturally expanded to k 2 term in a unified way. The numerical results show that in the mean field approximation, the effect of current quark mass is invisible, however, the effect of current quark mass can be seen explicitly beyond mean-field approximation for reasonable choices of the parameters in NJL model

  11. Symmetry and bifurcations of momentum mappings

    Science.gov (United States)

    Arms, Judith M.; Marsden, Jerrold E.; Moncrief, Vincent

    1981-01-01

    The zero set of a momentum mapping is shown to have a singularity at each point with symmetry. The zero set is diffeomorphic to the product of a manifold and the zero set of a homogeneous quadratic function. The proof uses the Kuranishi theory of deformations. Among the applications, it is shown that the set of all solutions of the Yang-Mills equations on a Lorentz manifold has a singularity at any solution with symmetry, in the sense of a pure gauge symmetry. Similarly, the set of solutions of Einstein's equations has a singularity at any solution that has spacelike Killing fields, provided the spacetime has a compact Cauchy surface.

  12. Splitting Functions at High Transverse Momentum

    CERN Document Server

    Moutafis, Rhea Penelope; CERN. Geneva. TH Department

    2017-01-01

    Among the production channels of the Higgs boson one contribution could become significant at high transverse momentum which is the radiation of a Higgs boson from another particle. This note focuses on the calculation of splitting functions and cross sections of such processes. The calculation is first carried out on the example $e\\rightarrow e\\gamma$ to illustrate the way splitting functions are calculated. Then the splitting function of $e\\rightarrow eh$ is calculated in similar fashion. This procedure can easily be generalized to processes such as $q\\rightarrow qh$ or $g\\rightarrow gh$.

  13. Autonomous Spacecraft Communication Interface for Load Planning

    Science.gov (United States)

    Dever, Timothy P.; May, Ryan D.; Morris, Paul H.

    2014-01-01

    Ground-based controllers can remain in continuous communication with spacecraft in low Earth orbit (LEO) with near-instantaneous communication speeds. This permits near real-time control of all of the core spacecraft systems by ground personnel. However, as NASA missions move beyond LEO, light-time communication delay issues, such as time lag and low bandwidth, will prohibit this type of operation. As missions become more distant, autonomous control of manned spacecraft will be required. The focus of this paper is the power subsystem. For present missions, controllers on the ground develop a complete schedule of power usage for all spacecraft components. This paper presents work currently underway at NASA to develop an architecture for an autonomous spacecraft, and focuses on the development of communication between the Mission Manager and the Autonomous Power Controller. These two systems must work together in order to plan future load use and respond to unanticipated plan deviations. Using a nominal spacecraft architecture and prototype versions of these two key components, a number of simulations are run under a variety of operational conditions, enabling development of content and format of the messages necessary to achieve the desired goals. The goals include negotiation of a load schedule that meets the global requirements (contained in the Mission Manager) and local power system requirements (contained in the Autonomous Power Controller), and communication of off-plan disturbances that arise while executing a negotiated plan. The message content is developed in two steps: first, a set of rapid-prototyping "paper" simulations are preformed; then the resultant optimized messages are codified for computer communication for use in automated testing.

  14. Spacecraft-to-Earth Communications for Juno and Mars Science Laboratory Critical Events

    Science.gov (United States)

    Soriano, Melissa; Finley, Susan; Jongeling, Andre; Fort, David; Goodhart, Charles; Rogstad, David; Navarro, Robert

    2012-01-01

    Deep Space communications typically utilize closed loop receivers and Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK). Critical spacecraft events include orbit insertion and entry, descent, and landing.---Low gain antennas--> low signal -to-noise-ratio.---High dynamics such as parachute deployment or spin --> Doppler shift. During critical events, open loop receivers and Multiple Frequency Shift Keying (MFSK) used. Entry, Descent, Landing (EDL) Data Analysis (EDA) system detects tones in real-time.

  15. Dye gain gold NW array of surface plasmon polariton waveguide

    Directory of Open Access Journals (Sweden)

    Jun Zhu

    Full Text Available Plasmon lasers can support ultrasmall mode confinement and ultrafast dynamics with device feature sizes below the diffraction limit. At present in the single visible light frequency, the optical gain method of constraint SPP on metal nanowires structure reported less. We design the gold nanowire array structure, consisting of PMMA and R6G dye molecules as gain, by 488 nm pump in the middle of the nanowires position for wide range of light, use symmetry broken overcome that momentum does not match the photonic and SPP energy conversion. Theoretical analysis shows that dyes provide coherent optical feedback, resulting in nanowires face will observe laser properties of surface plasmons. Feature analysis: the incident light and pump joint strength is greater than the sum of strength which is the incident light, pump respectively. Under the effect of dye molecules gain effective, length of SPP transmission can increase 1 µm. The results achieved in a single optical frequency of stimulated radiation, application of dye optical gain can achieve continuous gain effect. This is for the future development of plasma amplifier and the wavelength laser. Keywords: SPP, Stimulated radiation, Gold nanowires array, Dye molecules

  16. Operational Philosophy Concerning Manned Spacecraft Cabin Leaks

    Science.gov (United States)

    DeSimpelaere, Edward

    2011-01-01

    The last thirty years have seen the Space Shuttle as the prime United States spacecraft for manned spaceflight missions. Many lessons have been learned about spacecraft design and operation throughout these years. Over the next few decades, a large increase of manned spaceflight in the commercial sector is expected. This will result in the exposure of commercial crews and passengers to many of the same risks crews of the Space Shuttle have encountered. One of the more dire situations that can be encountered is the loss of pressure in the habitable volume of the spacecraft during on orbit operations. This is referred to as a cabin leak. This paper seeks to establish a general cabin leak response philosophy with the intent of educating future spacecraft designers and operators. After establishing a relative definition for a cabin leak, the paper covers general descriptions of detection equipment, detection methods, and general operational methods for management of a cabin leak. Subsequently, all these items are addressed from the perspective of the Space Shuttle Program, as this will be of the most value to future spacecraft due to similar operating profiles. Emphasis here is placed upon why and how these methods and philosophies have evolved to meet the Space Shuttle s needs. This includes the core ideas of: considerations of maintaining higher cabin pressures vs. lower cabin pressures, the pros and cons of a system designed to feed the leak with gas from pressurized tanks vs. using pressure suits to protect against lower cabin pressures, timeline and consumables constraints, re-entry considerations with leaks of unknown origin, and the impact the International Space Station (ISS) has had to the standard Space Shuttle cabin leak response philosophy. This last item in itself includes: procedural management differences, hardware considerations, additional capabilities due to the presence of the ISS and its resource, and ISS docking/undocking considerations with a

  17. Testing programs for the Multimission Modular Spacecraft

    Science.gov (United States)

    Greenwell, T. J.

    1978-01-01

    The Multimission Modular Spacecraft (MMS) provides a standard spacecraft bus to a user for a variety of space missions ranging from near-earth to synchronous orbits. The present paper describes the philosophy behind the MMS module test program and discusses the implementation of the test program. It is concluded that the MMS module test program provides an effective and comprehensive customer buy-off at the subsystem contractor's plant, is an optimum approach for checkout of the subsystems prior to use for on-orbit servicing in the Shuttle Cargo Bay, and is a cost-effective technique for environmental testing.

  18. Robust Parametric Control of Spacecraft Rendezvous

    Directory of Open Access Journals (Sweden)

    Dake Gu

    2014-01-01

    Full Text Available This paper proposes a method to design the robust parametric control for autonomous rendezvous of spacecrafts with the inertial information with uncertainty. We consider model uncertainty of traditional C-W equation to formulate the dynamic model of the relative motion. Based on eigenstructure assignment and model reference theory, a concise control law for spacecraft rendezvous is proposed which could be fixed through solving an optimization problem. The cost function considers the stabilization of the system and other performances. Simulation results illustrate the robustness and effectiveness of the proposed control.

  19. Spacecraft charging: incoming and outgoing electrons

    CERN Document Server

    Lai, Shu T.

    2013-04-22

    This paper presents an overview of the roles played by incoming and outgoing electrons in spacecraft surface and stresses the importance of surface conditions for spacecraft charging. The balance between the incoming electron current from the ambient plasma and the outgoing currents of secondary electrons, backscattered electrons, and photoelectrons from the surfaces determines the surface potential. Since surface conditions significantly affect the outgoing currents, the critical temperature and the surface potential are also significantly affected. As a corollary, high level differential charging of adjacent surfaces with very different surface conditions is a space hazard.

  20. Event-triggered attitude control of spacecraft

    Science.gov (United States)

    Wu, Baolin; Shen, Qiang; Cao, Xibin

    2018-02-01

    The problem of spacecraft attitude stabilization control system with limited communication and external disturbances is investigated based on an event-triggered control scheme. In the proposed scheme, information of attitude and control torque only need to be transmitted at some discrete triggered times when a defined measurement error exceeds a state-dependent threshold. The proposed control scheme not only guarantees that spacecraft attitude control errors converge toward a small invariant set containing the origin, but also ensures that there is no accumulation of triggering instants. The performance of the proposed control scheme is demonstrated through numerical simulation.

  1. The spacecraft encounters of Comet Halley

    Science.gov (United States)

    Asoka Mendis, D.; Tsurutani, Bruce T.

    1986-01-01

    The characteristics of the Comet Halley spacecraft 'fleet' (VEGA 1 and VEGA 2, Giotto, Suisei, and Sakigake) are presented. The major aims of these missions were (1) to discover and characterize the nucleus, (2) to characterize the atmosphere and ionosphere, (3) to characterize the dust, and (4) to characterize the nature of the large-scale comet-solar wind interaction. While the VEGA and Giotto missions were designed to study all four areas, Suisei addressed the second and fourth. Sakigake was designed to study the solar wind conditions upstream of the comet. It is noted that NASA's Deep Space Network played an important role in spacecraft tracking.

  2. A proposed measurement of optical orbital and spin angular momentum and its implications for photon angular momentum

    Science.gov (United States)

    Leader, Elliot

    2018-04-01

    The expression for the total angular momentum carried by a laser optical vortex beam, splits, in the paraxial approximation, into two terms which seem to represent orbital and spin angular momentum respectively. There are, however, two very different competing versions of the formula for the spin angular momentum, one based on the use of the Poynting vector, as in classical electrodynamics, the other related to the canonical expression for the angular momentum which occurs in Quantum Electrodynamics. I analyze the possibility that a sufficiently sensitive optical measurement could decide which of these corresponds to the actual physical angular momentum carried by the beam.

  3. Orbital angular momentum of general astigmatic modes

    International Nuclear Information System (INIS)

    Visser, Jorrit; Nienhuis, Gerard

    2004-01-01

    We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere

  4. The LANSCE Low Momentum Beam Monitor

    CERN Document Server

    Merl, R

    2004-01-01

    A diagnostic has been developed at the Los Alamos Neutron Science Center (LANSCE) for the purpose of identifying low momentum beam tails in the linear accelerator. These tails must be eliminated in order to maintain the transverse and longitudinal beam size. Instead of the currently used phosphor camera system, this instrument consists of a Multi Wire Proportional Chamber (MWPC) front end coupled to an EPICS compliant VME-based electronics package. Low momentum tails are detected with a resolution of 5 mm in the MWPC at a high dispersion point near a bending magnet. While phosphor is typically not sensitive in the nano amp range, the MWPC is sensitive down to about a pico amp. The electronics package processes the signals from each of the MWPC wires to generate an array of beam currents at each of the lower energies. The electronics has an analog front end with a high-speed analog to digital converter for each wire. Data from multiple wires are processed with an embedded digital signal processor and results p...

  5. Relativistic meson spectroscopy in momentum space

    International Nuclear Information System (INIS)

    Hersbach, H.

    1994-01-01

    In this paper a relativistic constituent-quark model based on the Ruijgrok--de Groot formalism is presented. The quark model is not defined in configuration space, but in momentum space. The complete meson spectrum, with the exception of the self-conjugate light unflavored mesons, is calculated. The potential used consists of a one-gluon exchange (OGE) part and a confining part. For the confining part a relativistic generalization of the linear plus constant potential was used, which is well defined in momentum space without introducing any singularities. For the OGE part several potentials were investigated. Retardations were included at all places. By the use of a fitting procedure involving 52 well-established mesons, but results were obtained for a potential consisting of a purely vector Richardson potential and a purely scalar confining potential. Reasonable results were also obtained for a modified Richardson potential. Most meson masses, with the exception of the π, the K, and the K 0 * , were found to be quite well described by the model

  6. Momentum Cogging at the Fermilab Booster

    International Nuclear Information System (INIS)

    Seiya, K.; Drennan, C.C.; Pellico, W.; Triplett, A.K.; Waller, A.M.

    2012-01-01

    The Fermilab Booster has an upgrade plan called the Proton Improvement Plan (PIP). The flux throughput goal is 2E17 protons/hour which, is almost double the present flux, 1.1E17 protons/hour. The beam loss in the machine is going to be an issue. The Booster accelerates beam from 400 MeV to 8 GeV and extracts to the Main Injector (MI). The current cogging process synchronizes the extraction kicker gap to the MI by changing radial position of the beam during the cycle. The gap creation occurs at about 700 MeV, which is about 6 ms into the cycle. The cycle-to-cycle variations of the Booster are larger at lower energy. However, changing the radial position at low energy for cogging is limited because of aperture. Momentum cogging is able to move the gap creation to an earlier time by using dipole correctors and radial position feedback, and is able to control the revolution frequency and radial position at the same time. The new cogging is expected to reduce beam loss and not be limited by aperture. The progress of the momentum cogging system development is going to be discussed in this paper.

  7. Brane world black holes in teleparallel theory equivalent to general relativity and their Killing vectors, energy, momentum and angular momentum

    International Nuclear Information System (INIS)

    Nashed, Gamal G. L.

    2010-01-01

    The energy–momentum tensor, which is coordinate-independent, is used to calculate energy, momentum and angular momentum of two different tetrad fields. Although, the two tetrad fields reproduce the same space-time their energies are different. Therefore, a regularized expression of the gravitational energy–momentum tensor of the teleparallel equivalent of general relativity (TEGR), is used to make the energies of the two tetrad fields equal. The definition of the gravitational energy–momentum is used to investigate the energy within the external event horizon. The components of angular momentum associated with these space–times are calculated. In spite of using a static space–time, we get a non-zero component of angular momentum! Therefore, we derive the Killing vectors associated with these space–times using the definition of the Lie derivative of a second rank tensor in the framework of the TEGR to make the picture more clear. (general)

  8. Apparatus for Investigating Momentum and Energy Conservation With MBL and Video Analysis

    Science.gov (United States)

    George, Elizabeth; Vazquez-Abad, Jesus

    1998-04-01

    We describe the development and use of a laboratory setup that is appropriate for computer-aided student investigation of the principles of conservation of momentum and mechanical energy in collisions. The setup consists of two colliding carts on a low-friction track, with one of the carts (the target) attached to a spring, whose extension or compression takes the place of the pendulum's rise in the traditional ballistic pendulum apparatus. Position vs. time data for each cart are acquired either by using two motion sensors or by digitizing images obtained with a video camera. This setup allows students to examine the time history of momentum and mechanical energy during the entire collision process, rather than simply focusing on the before and after regions. We believe that this setup is suitable for helping students gain understanding as the processes involved are simple to follow visually, to manipulate, and to analyze.

  9. Inefficient Angular Momentum Transport in Accretion Disk Boundary Layers: Angular Momentum Belt in the Boundary Layer

    Science.gov (United States)

    Belyaev, Mikhail A.; Quataert, Eliot

    2018-04-01

    We present unstratified 3D MHD simulations of an accretion disk with a boundary layer (BL) that have a duration ˜1000 orbital periods at the inner radius of the accretion disk. We find the surprising result that angular momentum piles up in the boundary layer, which results in a rapidly rotating belt of accreted material at the surface of the star. The angular momentum stored in this belt increases monotonically in time, which implies that angular momentum transport mechanisms in the BL are inefficient and do not couple the accretion disk to the star. This is in spite of the fact that magnetic fields are advected into the BL from the disk and supersonic shear instabilities in the BL excite acoustic waves. In our simulations, these waves only carry a small fraction (˜10%) of the angular momentum required for steady state accretion. Using analytical theory and 2D viscous simulations in the R - ϕ plane, we derive an analytical criterion for belt formation to occur in the BL in terms of the ratio of the viscosity in the accretion disk to the viscosity in the BL. Our MHD simulations have a dimensionless viscosity (α) in the BL that is at least a factor of ˜100 smaller than that in the disk. We discuss the implications of these results for BL dynamics and emission.

  10. Momentum and Angular Momentum Transfer in Oblique Impacts: Implications for Asteroid Rotations

    Science.gov (United States)

    Yanagisawa, Masahisa; Hasegawa, Sunao; Shirogane, Nobutoshi

    1996-09-01

    We conducted a series of high velocity oblique impact experiments (0.66-6.7 km/s) using polycarbonate (plastic) projectiles and targets made of mortar, aluminum alloy, and mild steel. We then calculated the efficiencies of momentum transfer for small cratering impacts. They are η = (M‧Vn‧)/(mvn) and ζ = (M‧Vt‧)/(mvt), wheremandvare the mass and velocity of a projectile, andM‧ andV‧ represent those of a postimpact target. Subscripts “n” and “t” denote the components normal and tangential to the target surface at the impact point, respectively. The main findings are: (1) η increases with increasing impact velocity; (2) η is larger for mortar than for ductile metallic targets; (3) ζ for mortar targets seems to increase with the impact velocity in the velocity range less than about 2 km/s and decrease with it in the higher velocity range; (4) ζ for the aluminum alloy targets correlates negatively with incident zenith angle of the projectile. In addition to these findings on the momentum transfer, we show theoretically that “ζL” can be expressed by η and ζ for small cratering impact. Here, ζLis the spin angular momentum that the target acquires at impact divided by the collisional angular momentum due to the projectile. This is an important parameter to study the collisional evolution of asteroid rotation. For a spherical target, ζLis shown to be well approximated by ζ.

  11. Energy-momentum structure of the krypton valence shell by electron-momentum spectroscopy

    International Nuclear Information System (INIS)

    Nicholson, R.; Braidwood, S.W.; McCathy, I.E.; Weigold, E.; Brunger, M.J.

    1996-03-01

    Momentum distributions and spectroscopic factors are obtained in a high resolution electron-momentum spectroscopy study of krypton at 1000 eV. The shapes and relative magnitudes of the momentum profiles are in good agreement with the results of calculations made within the distorted-wave impulse approximation (DWIA) framework. The DWIA describes the relative magnitudes of the 4p and 4s manifolds as well as giving a good representation of the shapes of the respective 4p and 4s cross sections. Results for the momentum profiles belonging to excited 2 P o and 2 S e manifolds are also presented. Spectroscopic factors for transitions belonging to the 2 p o and 2 S e manifolds are assigned up to a binding energy of 42 eV. The spectroscopic factor for the lowest 4s transition is 0.51 ± 0.01, whereas that for the ground-state 4p transition is 0.98± 0.01. Comparisons of the present binding energies and spectroscopic factors are made against the results of several many-body calculations and photoelectron spectroscopy (PES) results. In addition, a new procedure is outlined, utilising the experimental 4p and 4s manifold cross sections, that provides information on possible initial state configuration interaction effects in krypton. 50 refs., 2 tabs., 10 figs

  12. RCS Diversity of Electromagnetic Wave Carrying Orbital Angular Momentum.

    Science.gov (United States)

    Zhang, Chao; Chen, Dong; Jiang, Xuefeng

    2017-11-13

    An electromagnetic (EM) wave with orbital angular momentum (OAM) has a helical wave front, which is different from that of the plane wave. The phase gradient can be found perpendicular to the direction of propagation and proportional to the number of OAM modes. Herein, we study the backscattering property of the EM wave with different OAM modes, i.e., the radar cross section (RCS) of the target is measured and evaluated with different OAM waves. As indicated by the experimental results, different OAM waves have the same RCS fluctuation for the simple target, e.g., a small metal ball as the target. However, for complicated targets, e.g., two transverse-deployed small metal balls, different RCSs can be identified from the same incident angle. This valuable fact helps to obtain RCS diversity, e.g., equal gain or selective combining of different OAM wave scattering. The majority of the targets are complicated targets or expanded targets; the RCS diversity can be utilized to detect a weak target traditionally measured by the plane wave, which is very helpful for anti-stealth radar to detect the traditional stealth target by increasing the RCS with OAM waves.

  13. Spacecraft attitude maneuver control using two parallel mounted 3-DOF spherical actuators

    Directory of Open Access Journals (Sweden)

    Guidan Li

    2017-02-01

    Full Text Available A parallel configuration using two 3-degree-of-freedom (3-DOF spherical electromagnetic momentum exchange actuators is investigated for large angle spacecraft attitude maneuvers. First, the full dynamic equations of motion for the spacecraft system are derived by the Newton-Euler method. To facilitate computation, virtual gimbal coordinate frames are established. Second, a nonlinear control law in terms of quaternions is developed via backstepping method. The proposed control law compensates the coupling torques arising from the spacecraft rotation, and is robust against the external disturbances. Then, the singularity problem is analyzed. To avoid singularities, a modified weighed Moore-Pseudo inverse velocity steering law based on null motion is proposed. The weighted matrices are carefully designed to switch the actuators and redistribute the control torques. The null motion is used to reorient the rotor away from the tilt angle saturation state. Finally, numerical simulations of rest-to-rest maneuvers are performed to validate the effectiveness of the proposed method.

  14. Toward a general theory of momentum-like effects.

    Science.gov (United States)

    Hubbard, Timothy L

    2017-08-01

    The future actions, behaviors, and outcomes of objects, individuals, and processes can often be anticipated, and some of these anticipations have been hypothesized to result from momentum-like effects. Five types of momentum-like effects (representational momentum, operational momentum, attentional momentum, behavioral momentum, psychological momentum) are briefly described. Potential similarities involving properties of momentum-like effects (continuation, coherence, role of chance or guessing, role of sensory processing, imperviousness to practice or error feedback, shifts in memory for position, effects of changes in velocity, rapid occurrence, effects of retention interval, attachment to an object rather than an abstract frame of reference, nonrigid transformation) are described, and potential constraints on a future theory of momentum-like effects (dynamic representation, nature of extrapolation, sensitivity to environmental contingencies, bridging gaps between stimulus and response, increasing adaptiveness to the environment, serving as a heuristic for perception and action, insensitivity to stimulus format, importance of subjective consequences, role of knowledge and belief, automaticity of occurrence, properties of functional architecture) are discussed. The similarity and ubiquity of momentum-like effects suggests such effects might result from a single or small number of mechanisms that operate over different dimensions, modalities, and time-scales and provide a fundamental adaptation for perception and action. Copyright © 2017. Published by Elsevier B.V.

  15. Quantum-mechanical analysis of low-gain free-electron laser oscillators

    Science.gov (United States)

    Fares, H.; Yamada, M.; Chiadroni, E.; Ferrario, M.

    2018-05-01

    In the previous classical theory of the low-gain free-electron laser (FEL) oscillators, the electron is described as a point-like particle, a delta function in the spatial space. On the other hand, in the previous quantum treatments, the electron is described as a plane wave with a single momentum state, a delta function in the momentum space. In reality, an electron must have statistical uncertainties in the position and momentum domains. Then, the electron is neither a point-like charge nor a plane wave of a single momentum. In this paper, we rephrase the theory of the low-gain FEL where the interacting electron is represented quantum mechanically by a plane wave with a finite spreading length (i.e., a wave packet). Using the concepts of the transformation of reference frames and the statistical quantum mechanics, an expression for the single-pass radiation gain is derived. The spectral broadening of the radiation is expressed in terms of the spreading length of an electron, the relaxation time characterizing the energy spread of electrons, and the interaction time. We introduce a comparison between our results and those obtained in the already known classical analyses where a good agreement between both results is shown. While the correspondence between our results and the classical results are shown, novel insights into the electron dynamics and the interaction mechanism are presented.

  16. Software for Engineering Simulations of a Spacecraft

    Science.gov (United States)

    Shireman, Kirk; McSwain, Gene; McCormick, Bernell; Fardelos, Panayiotis

    2005-01-01

    Spacecraft Engineering Simulation II (SES II) is a C-language computer program for simulating diverse aspects of operation of a spacecraft characterized by either three or six degrees of freedom. A functional model in SES can include a trajectory flight plan; a submodel of a flight computer running navigational and flight-control software; and submodels of the environment, the dynamics of the spacecraft, and sensor inputs and outputs. SES II features a modular, object-oriented programming style. SES II supports event-based simulations, which, in turn, create an easily adaptable simulation environment in which many different types of trajectories can be simulated by use of the same software. The simulation output consists largely of flight data. SES II can be used to perform optimization and Monte Carlo dispersion simulations. It can also be used to perform simulations for multiple spacecraft. In addition to its generic simulation capabilities, SES offers special capabilities for space-shuttle simulations: for this purpose, it incorporates submodels of the space-shuttle dynamics and a C-language version of the guidance, navigation, and control components of the space-shuttle flight software.

  17. How Spacecraft Fly Spaceflight Without Formulae

    CERN Document Server

    Swinerd, Graham

    2009-01-01

    About half a century ago a small satellite, Sputnik 1, was launched. The satellite did very little other than to transmit a radio signal to announce its presence in orbit. However, this humble beginning heralded the dawn of the Space Age. Today literally thousands of robotic spacecraft have been launched, many of which have flown to far-flung regions of the Solar System carrying with them the human spirit of scientific discovery and exploration. Numerous other satellites have been launched in orbit around the Earth providing services that support our technological society on the ground. How Spacecraft Fly: Spaceflight Without Formulae by Graham Swinerd focuses on how these spacecraft work. The book opens with a historical perspective of how we have come to understand our Solar System and the Universe. It then progresses through orbital flight, rocket science, the hostile environment within which spacecraft operate, and how they are designed. The concluding chapters give a glimpse of what the 21st century may ...

  18. Microgravity Flammability Experiments for Spacecraft Fire Safety

    DEFF Research Database (Denmark)

    Legros, Guillaume; Minster, Olivier; Tóth, Balazs

    2012-01-01

    As fire behaviour in manned spacecraft still remains poorly understood, an international topical team has been created to design a validation experiment that has an unprecedented large scale for a microgravity flammability experiment. While the validation experiment is being designed for a re-sup...

  19. Parameter Estimation of Spacecraft Fuel Slosh Model

    Science.gov (United States)

    Gangadharan, Sathya; Sudermann, James; Marlowe, Andrea; Njengam Charles

    2004-01-01

    Fuel slosh in the upper stages of a spinning spacecraft during launch has been a long standing concern for the success of a space mission. Energy loss through the movement of the liquid fuel in the fuel tank affects the gyroscopic stability of the spacecraft and leads to nutation (wobble) which can cause devastating control issues. The rate at which nutation develops (defined by Nutation Time Constant (NTC can be tedious to calculate and largely inaccurate if done during the early stages of spacecraft design. Pure analytical means of predicting the influence of onboard liquids have generally failed. A strong need exists to identify and model the conditions of resonance between nutation motion and liquid modes and to understand the general characteristics of the liquid motion that causes the problem in spinning spacecraft. A 3-D computerized model of the fuel slosh that accounts for any resonant modes found in the experimental testing will allow for increased accuracy in the overall modeling process. Development of a more accurate model of the fuel slosh currently lies in a more generalized 3-D computerized model incorporating masses, springs and dampers. Parameters describing the model include the inertia tensor of the fuel, spring constants, and damper coefficients. Refinement and understanding the effects of these parameters allow for a more accurate simulation of fuel slosh. The current research will focus on developing models of different complexity and estimating the model parameters that will ultimately provide a more realistic prediction of Nutation Time Constant obtained through simulation.

  20. Spacecraft 3D Augmented Reality Mobile App

    Science.gov (United States)

    Hussey, Kevin J.; Doronila, Paul R.; Kumanchik, Brian E.; Chan, Evan G.; Ellison, Douglas J.; Boeck, Andrea; Moore, Justin M.

    2013-01-01

    The Spacecraft 3D application allows users to learn about and interact with iconic NASA missions in a new and immersive way using common mobile devices. Using Augmented Reality (AR) techniques to project 3D renditions of the mission spacecraft into real-world surroundings, users can interact with and learn about Curiosity, GRAIL, Cassini, and Voyager. Additional updates on future missions, animations, and information will be ongoing. Using a printed AR Target and camera on a mobile device, users can get up close with these robotic explorers, see how some move, and learn about these engineering feats, which are used to expand knowledge and understanding about space. The software receives input from the mobile device's camera to recognize the presence of an AR marker in the camera's field of view. It then displays a 3D rendition of the selected spacecraft in the user's physical surroundings, on the mobile device's screen, while it tracks the device's movement in relation to the physical position of the spacecraft's 3D image on the AR marker.

  1. Special Semaphore Scheme for UHF Spacecraft Communications

    Science.gov (United States)

    Butman, Stanley; Satorius, Edgar; Ilott, Peter

    2006-01-01

    A semaphore scheme has been devised to satisfy a requirement to enable ultrahigh- frequency (UHF) radio communication between a spacecraft descending from orbit to a landing on Mars and a spacecraft, in orbit about Mars, that relays communications between Earth and the lander spacecraft. There are also two subsidiary requirements: (1) to use UHF transceivers, built and qualified for operation aboard the spacecraft that operate with residual-carrier binary phase-shift-keying (BPSK) modulation at a selectable data rate of 8, 32, 128, or 256 kb/s; and (2) to enable low-rate signaling even when received signals become so weak as to prevent communication at the minimum BPSK rate of 8 kHz. The scheme involves exploitation of Manchester encoding, which is used in conjunction with residual-carrier modulation to aid the carrier-tracking loop. By choosing various sequences of 1s, 0s, or 1s alternating with 0s to be fed to the residual-carrier modulator, one would cause the modulator to generate sidebands at a fundamental frequency of 4 or 8 kHz and harmonics thereof. These sidebands would constitute the desired semaphores. In reception, the semaphores would be detected by a software demodulator.

  2. Accelerated life testing of spacecraft subsystems

    Science.gov (United States)

    Wiksten, D.; Swanson, J.

    1972-01-01

    The rationale and requirements for conducting accelerated life tests on electronic subsystems of spacecraft are presented. A method for applying data on the reliability and temperature sensitivity of the parts contained in a sybsystem to the selection of accelerated life test parameters is described. Additional considerations affecting the formulation of test requirements are identified, and practical limitations of accelerated aging are described.

  3. Rotational Motion Control of a Spacecraft

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    2001-01-01

    The paper adopts the energy shaping method to control of rotational motion. A global representation of the rigid body motion is given in the canonical form by a quaternion and its conjugate momenta. A general method for motion control on a cotangent bundle to the 3-sphere is suggested. The design...... algorithm is validated for three-axis spacecraft attitude control...

  4. Rotational motion control of a spacecraft

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    2003-01-01

    The paper adopts the energy shaping method to control of rotational motion. A global representation of the rigid body motion is given in the canonical form by a quaternion and its conjugate momenta. A general method for motion control on a cotangent bundle to the 3-sphere is suggested. The design...... algorithm is validated for three-axis spacecraft attitude control. Udgivelsesdato: APR...

  5. Small Spacecraft Technology Initiative Education Program

    Science.gov (United States)

    1995-01-01

    A NASA engineer with the Commercial Remote Sensing Program (CRSP) at Stennis Space Center works with students from W.P. Daniels High School in New Albany, Miss., through NASA's Small Spacecraft Technology Initiative Program. CRSP is teaching students to use remote sensing to locate a potential site for a water reservoir to offset a predicted water shortage in the community's future.

  6. Spacecraft Attitude Control in Hamiltonian Framework

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    2000-01-01

    The objective of this paper is to give a design scheme for attitude control algorithms of a generic spacecraft. Along with the system model formulated in the Hamilton's canonical form the algorithm uses information about a required potential energy and a dissipative term. The control action...

  7. Generalized Momentum Control of the Spin-Stabilized Magnetospheric Multiscale Formation

    Science.gov (United States)

    Queen, Steven Z.; Shah, Neerav; Benegalrao, Suyog S.; Blackman, Kathie

    2015-01-01

    The Magnetospheric Multiscale (MMS) mission consists of four identically instrumented, spin-stabilized observatories elliptically orbiting the Earth in a tetrahedron formation. The on-board attitude control system adjusts the angular momentum of the system using a generalized thruster-actuated control system that simultaneously manages precession, nutation and spin. Originally developed using Lyapunov control-theory with rate-feedback, a published algorithm has been augmented to provide a balanced attitude/rate response using a single weighting parameter. This approach overcomes an orientation sign-ambiguity in the existing formulation, and also allows for a smoothly tuned-response applicable to both a compact/agile spacecraft, as well as one with large articulating appendages.

  8. Magneto optical trap recoil ion momentum spectroscopy: application to ion-atom collisions

    International Nuclear Information System (INIS)

    Blieck, J.

    2008-10-01

    87 Rb atoms have been cooled, trapped and prepared as targets for collision studies with 2 and 5 keV Na + projectiles. The physics studied deals with charge exchange processes. The active electron, which is generally the most peripheral electron of the atomic target, is transferred from the target onto the ionic projectile. The ionized target is called recoil ion. The technique used to study this physics is the MOTRIMS (Magneto Optical Trap Recoil Ion Momentum Spectroscopy) technique, which combines a magneto optical trap and a recoil ion momentum spectrometer. The spectrometer is used for the measurement of the recoil ions momentum, which gives access to all the information of the collision: the Q-value (which is the potential energy difference of the active electron on each particle) and the scattering angle of the projectile. The trap provides extremely cold targets to optimize the measurement of the momentum, and to release the latter from thermal motion. Through cinematically complete experiments, the MOTRIMS technique gives access to better resolutions on momentum measurements. Measurements of differential cross sections in initial and final capture states and in scattering angle have been done. Results obtained for differential cross sections in initial and final states show globally a good agreement with theory and an other experiment. Nevertheless, discrepancies with theory and this other experiment are shown for the measurements of doubly differential cross sections. These discrepancies are not understood yet. The particularity of the experimental setup designed and tested in this work, namely a low background noise, allows a great sensitivity to weak capture channels, and brings a technical and scientific gain compared with previous works. (author)

  9. Developmental gains in visuospatial memory predict gains in mathematics achievement.

    Science.gov (United States)

    Li, Yaoran; Geary, David C

    2013-01-01

    Visuospatial competencies are related to performance in mathematical domains in adulthood, but are not consistently related to mathematics achievement in children. We confirmed the latter for first graders and demonstrated that children who show above average first-to-fifth grade gains in visuospatial memory have an advantage over other children in mathematics. The study involved the assessment of the mathematics and reading achievement of 177 children in kindergarten to fifth grade, inclusive, and their working memory capacity and processing speed in first and fifth grade. Intelligence was assessed in first grade and their second to fourth grade teachers reported on their in-class attentive behavior. Developmental gains in visuospatial memory span (d = 2.4) were larger than gains in the capacity of the central executive (d = 1.6) that in turn were larger than gains in phonological memory span (d = 1.1). First to fifth grade gains in visuospatial memory and in speed of numeral processing predicted end of fifth grade mathematics achievement, as did first grade central executive scores, intelligence, and in-class attentive behavior. The results suggest there are important individual differences in the rate of growth of visuospatial memory during childhood and that these differences become increasingly important for mathematics learning.

  10. Developmental gains in visuospatial memory predict gains in mathematics achievement.

    Directory of Open Access Journals (Sweden)

    Yaoran Li

    Full Text Available Visuospatial competencies are related to performance in mathematical domains in adulthood, but are not consistently related to mathematics achievement in children. We confirmed the latter for first graders and demonstrated that children who show above average first-to-fifth grade gains in visuospatial memory have an advantage over other children in mathematics. The study involved the assessment of the mathematics and reading achievement of 177 children in kindergarten to fifth grade, inclusive, and their working memory capacity and processing speed in first and fifth grade. Intelligence was assessed in first grade and their second to fourth grade teachers reported on their in-class attentive behavior. Developmental gains in visuospatial memory span (d = 2.4 were larger than gains in the capacity of the central executive (d = 1.6 that in turn were larger than gains in phonological memory span (d = 1.1. First to fifth grade gains in visuospatial memory and in speed of numeral processing predicted end of fifth grade mathematics achievement, as did first grade central executive scores, intelligence, and in-class attentive behavior. The results suggest there are important individual differences in the rate of growth of visuospatial memory during childhood and that these differences become increasingly important for mathematics learning.

  11. Developmental Gains in Visuospatial Memory Predict Gains in Mathematics Achievement

    Science.gov (United States)

    Li, Yaoran; Geary, David C.

    2013-01-01

    Visuospatial competencies are related to performance in mathematical domains in adulthood, but are not consistently related to mathematics achievement in children. We confirmed the latter for first graders and demonstrated that children who show above average first-to-fifth grade gains in visuospatial memory have an advantage over other children in mathematics. The study involved the assessment of the mathematics and reading achievement of 177 children in kindergarten to fifth grade, inclusive, and their working memory capacity and processing speed in first and fifth grade. Intelligence was assessed in first grade and their second to fourth grade teachers reported on their in-class attentive behavior. Developmental gains in visuospatial memory span (d = 2.4) were larger than gains in the capacity of the central executive (d = 1.6) that in turn were larger than gains in phonological memory span (d = 1.1). First to fifth grade gains in visuospatial memory and in speed of numeral processing predicted end of fifth grade mathematics achievement, as did first grade central executive scores, intelligence, and in-class attentive behavior. The results suggest there are important individual differences in the rate of growth of visuospatial memory during childhood and that these differences become increasingly important for mathematics learning. PMID:23936154

  12. On the spacecraft attitude stabilization in the orbital frame

    Directory of Open Access Journals (Sweden)

    Antipov Kirill A.

    2012-01-01

    Full Text Available The paper deals with spacecraft in the circular near-Earth orbit. The spacecraft interacts with geomagnetic field by the moments of Lorentz and magnetic forces. The octupole approximation of the Earth’s magnetic field is accepted. The spacecraft electromagnetic parameters, namely the electrostatic charge moment of the first order and the eigen magnetic moment are the controlled quasiperiodic functions. The control algorithms for the spacecraft electromagnetic parameters, which allows to stabilize the spacecraft attitude position in the orbital frame are obtained. The stability of the spacecraft stabilized orientation is proved both analytically and by PC computations.

  13. Untangling Galaxy Components - The Angular Momentum Parameter

    Science.gov (United States)

    Tabor, Martha; Merrifield, Michael; Aragon-Salamanca, Alfonso

    2017-06-01

    We have developed a new technique to decompose Integral Field spectral data cubes into separate bulge and disk components, allowing us to study the kinematic and stellar population properties of the individual components and how they vary with position. We present here the application of this method to a sample of fast rotator early type galaxies from the MaNGA integral field survey, and demonstrate how it can be used to explore key properties of the individual components. By extracting ages, metallicities and the angular momentum parameter lambda of the bulges and disks, we show how this method can give us new insights into the underlying structure of the galaxies and discuss what this can tell us about their evolution history.

  14. Intrinsic Orbital Angular Momentum States of Neutrons

    Science.gov (United States)

    Cappelletti, Ronald L.; Jach, Terrence; Vinson, John

    2018-03-01

    It has been shown that single-particle wave functions, of both photons and electrons, can be created with a phase vortex, i.e., an intrinsic orbital angular momentum (OAM). A recent experiment has claimed similar success using neutrons [C. W. Clark et al., Nature, 525, 504 (2015), 10.1038/nature15265]. We show that their results are insufficient to unambiguously demonstrate OAM, and they can be fully explained as phase contrast interference patterns. Furthermore, given the small transverse coherence length of the neutrons in the original experiment, the probability that any neutron was placed in an OAM state is vanishingly small. We highlight the importance of the relative size of the coherence length, which presents a unique challenge for neutron experiments compared to electron or photon work, and we suggest improvements for the creation of neutron OAM states.

  15. China-The Momentum Keeps Building

    Institute of Scientific and Technical Information of China (English)

    Li Wei; Stephen Green; Judy H Zhu

    2009-01-01

    @@ China's August data came in better than July's.In particular,new loans were CNY 410bn(USD 60bn),allaying concerns about the negative impact of slower loan growth.We expect the momentum to remain strong for at least two more quarters.We look for the domestic private sector and exports to pick up some of the slack as the stimulus effect fades in H2-2010.Real tightening-by which we mean a hard constraint on loan availability-is at least three quarters away.However,in the meantime,we expect reserve requirements and rate hikes to be a shot across the bow,the latter possibly starting in Q2.

  16. Angular momentum of dark matter black holes

    Energy Technology Data Exchange (ETDEWEB)

    Frampton, Paul H., E-mail: paul.h.frampton@gmail.com

    2017-04-10

    We provide strongly suggestive evidence that the halo constituents of dark matter are Primordial Intermediate-Mass Black Holes (PIMBHs). PIMBHs are described by a Kerr metric with two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at PIMBH detection by microlensing. Nevertheless J does play a central role in understanding their previous lack of detection, especially by CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for PIMBHs with J non-vanishing and that, provided almost no dark matter black holes originate from stellar collapse, excessive CMB distortion is avoided.

  17. Topological photonic orbital-angular-momentum switch

    Science.gov (United States)

    Luo, Xi-Wang; Zhang, Chuanwei; Guo, Guang-Can; Zhou, Zheng-Wei

    2018-04-01

    The large number of available orbital-angular-momentum (OAM) states of photons provides a unique resource for many important applications in quantum information and optical communications. However, conventional OAM switching devices usually rely on precise parameter control and are limited by slow switching rate and low efficiency. Here we propose a robust, fast, and efficient photonic OAM switch device based on a topological process, where photons are adiabatically pumped to a target OAM state on demand. Such topological OAM pumping can be realized through manipulating photons in a few degenerate main cavities and involves only a limited number of optical elements. A large change of OAM at ˜10q can be realized with only q degenerate main cavities and at most 5 q pumping cycles. The topological photonic OAM switch may become a powerful device for broad applications in many different fields and motivate a topological design of conventional optical devices.

  18. Behavioral momentum theory: equations and applications.

    Science.gov (United States)

    Nevin, John A; Shahan, Timothy A

    2011-01-01

    Behavioral momentum theory provides a quantitative account of how reinforcers experienced within a discriminative stimulus context govern the persistence of behavior that occurs in that context. The theory suggests that all reinforcers obtained in the presence of a discriminative stimulus increase resistance to change, regardless of whether those reinforcers are contingent on the target behavior, are noncontingent, or are even contingent on an alternative behavior. In this paper, we describe the equations that constitute the theory and address their application to issues of particular importance in applied settings. The theory provides a framework within which to consider the effects of interventions such as extinction, noncontingent reinforcement, differential reinforcement of alternative behavior, and other phenomena (e.g., resurgence). Finally, the theory predicts some counterintuitive and potentially counterproductive effects of alternative reinforcement, and can serve as an integrative guide for intervention when its terms are identified with the relevant conditions of applied settings.

  19. Anderson localization and momentum-space entanglement

    International Nuclear Information System (INIS)

    Andrade, Eric C; Steudtner, Mark; Vojta, Matthias

    2014-01-01

    We consider Anderson localization and the associated metal–insulator transition for non-interacting fermions in D = 1, 2 space dimensions in the presence of spatially correlated on-site random potentials. To assess the nature of the wave function, we follow a recent proposal to study momentum-space entanglement. For a D = 1 model with long-range disorder correlations, both the entanglement spectrum and the entanglement entropy allow us to clearly distinguish between extended and localized states based upon a single realization of disorder. However, for other models, including the D = 2 case with long-range correlated disorder, we find that the method is not similarly successful. We analyze the reasons for its failure, concluding that the much desired generalization to higher dimensions may be problematic. (paper)

  20. Fourier transform of momentum distribution in vanadium

    International Nuclear Information System (INIS)

    Singh, A.K.; Manuel, A.A.; Peter, M.; Singru, R.M.

    1985-01-01

    Experimental Compton profile and 2D-angular correlation of positron annihilation radiation data from vanadium are analyzed by the mean of their Fourier transform. They are compared with the functions calculated with the help of both the linear muffin-tin orbital and the Hubbard-Mijnarends band structure methods. The results show that the functions are influenced by the positron wave function, by the e + -e - many-body correlations and by the differences in the electron wave functions used for the band structure calculations. It is concluded that Fourier analysis is a sensitive approach to investigate the momentum distributions in transition metals and to understnad the effects of the positron. (Auth.)

  1. Symmetry and bifurcations of momentum mappings

    Energy Technology Data Exchange (ETDEWEB)

    Arms, J.M.; Marsden, J.E.; Moncrief, V.

    1981-01-01

    The zero set of a momentum mapping is shown to have a singularity at each point with symmetry. The zero set is diffeomorphic to the product of a manifold and the zero set of a homogeneous quadratic function. The proof uses the Kuranishi theory of deformations. Among the applications, it is shown that the set of all solutions of the Yang-Mills equations on a Lorentz manifold has a singularity at any solution with symmetry, in the sense of a pure gauge symmetry. Similarly, the set of solutions of Einstein's equations has a singularity at any solution that has spacelike Killing fields, provided the spacetime has a compact Cauchy surface.

  2. Anomalous transport and holographic momentum relaxation

    Science.gov (United States)

    Copetti, Christian; Fernández-Pendás, Jorge; Landsteiner, Karl; Megías, Eugenio

    2017-09-01

    The chiral magnetic and vortical effects denote the generation of dissipationless currents due to magnetic fields or rotation. They can be studied in holographic models with Chern-Simons couplings dual to anomalies in field theory. We study a holographic model with translation symmetry breaking based on linear massless scalar field backgrounds. We compute the electric DC conductivity and find that it can vanish for certain values of the translation symmetry breaking couplings. Then we compute the chiral magnetic and chiral vortical conductivities. They are completely independent of the holographic disorder couplings and take the usual values in terms of chemical potential and temperature. To arrive at this result we suggest a new definition of energy-momentum tensor in presence of the gravitational Chern-Simons coupling.

  3. Application of Space Environmental Observations to Spacecraft Pre-Launch Engineering and Spacecraft Operations

    Science.gov (United States)

    Barth, Janet L.; Xapsos, Michael

    2008-01-01

    This presentation focuses on the effects of the space environment on spacecraft systems and applying this knowledge to spacecraft pre-launch engineering and operations. Particle radiation, neutral gas particles, ultraviolet and x-rays, as well as micrometeoroids and orbital debris in the space environment have various effects on spacecraft systems, including degradation of microelectronic and optical components, physical damage, orbital decay, biasing of instrument readings, and system shutdowns. Space climate and weather must be considered during the mission life cycle (mission concept, mission planning, systems design, and launch and operations) to minimize and manage risk to both the spacecraft and its systems. A space environment model for use in the mission life cycle is presented.

  4. Orbital Propagation of Momentum Exchange Tether Systems

    Science.gov (United States)

    Westerhoff, John

    2002-01-01

    An advanced concept in in-space transportation currently being studied is the Momentum-Exchange/Electrodynamic Reboost Tether System (MXER). The system acts as a large momentum wheel, imparting a Av to a payload in low earth orbit (LEO) at the expense of its own orbital energy. After throwing a payload, the system reboosts itself using an electrodynamic tether to push against Earth's magnetic field and brings itself back up to an operational orbit to prepare for the next payload. The ability to reboost itself allows for continued reuse of the system without the expenditure of propellants. Considering the cost of lifting propellant from the ,ground to LEO to do the same Av boost at $10000 per pound, the system cuts the launch cost of the payload dramatically, and subsequently, the MXER system pays for itself after a small number of missions.1 One of the technical hurdles to be overcome with the MXER concept is the rendezvous maneuver. The rendezvous window for the capture of the payload is on the order of a few seconds, as opposed to traditional docking maneuvers, which can take as long ets necessary to complete a precise docking. The payload, therefore, must be able to match its orbit to meet up with the capture device on the end of the tether at a specific time and location in the future. In order to be able to determine that location, the MXER system must be numerically propagated forward in time to predict where the capture device will be at that instant. It should be kept in mind that the propagation computation must be done faster than real-time. This study focuses on the efforts to find and/or build the tools necessary to numerically propagate the motion of the MXER system as accurately as possible.

  5. Angular momentum of circularly polarized light in dielectric media

    OpenAIRE

    Mansuripur, Masud

    2014-01-01

    A circularly polarized plane-wave is known to have no angular momentum when examined through Maxwell's equations. This, however, contradicts the experimentally observed facts, where finite segments of plane waves are known to be capable of imparting angular momentum to birefringent platelets. Using a superposition of four plane-waves propagating at slightly different angles to a common direction, we derive an expression for the angular momentum density of a single plane-wave in the limit when...

  6. Momentum and mass relaxation in heavy-ion collisions

    International Nuclear Information System (INIS)

    Gregoire, C.; Scheuter, F.; Remaud, B.; Sebille, F.

    1984-01-01

    The momentum and mass relaxation are shown to be described by transport equations. The momentum relaxation, which can be studied in the intermediate energy regime by the particle emissions, refers to a microscopic slowing down and diffusion process in the momentum space. The mass relaxation refers to the coupling of the collective mass asymmetry degree of freedom and the intrinsic system. It can be illustrated by the fast fission of light and very heavy systems

  7. Momentum Injection in Tokamak Plasmas and Transitions to Reduced Transport

    International Nuclear Information System (INIS)

    Parra, F. I.; Highcock, E. G.; Schekochihin, A. A.; Barnes, M.; Cowley, S. C.

    2011-01-01

    The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.

  8. Momentum transfer in relativistic heavy ion charge-exchange reactions

    Science.gov (United States)

    Townsend, L. W.; Wilson, J. W.; Khan, F.; Khandelwal, G. S.

    1991-01-01

    Relativistic heavy ion charge-exchange reactions yield fragments (Delta-Z = + 1) whose longitudinal momentum distributions are downshifted by larger values than those associated with the remaining fragments (Delta-Z = 1, -2,...). Kinematics alone cannot account for the observed downshifts; therefore, an additional contribution from collision dynamics must be included. In this work, an optical model description of collision momentum transfer is used to estimate the additional dynamical momentum downshift. Good agreement between theoretical estimates and experimental data is obtained.

  9. Off-momentum loss maps with one beam

    CERN Document Server

    Garcia Morales, Hector; Salvachua Ferrando, Belen Maria; CERN. Geneva. ATS Department

    2016-01-01

    The aim of this MD is the benchmarking of simulation of off-momentum loss maps. This will help us to further understand the dynamics of the off-momentum collimation cleaning and give input to the determination of the operational settings of the off-momentum cleaning insertion. The MD was carried out during different end-of-fills of other MDs. In this note we summarize the procedures and the measurements taken during the MD week.

  10. Transverse Momentum Distributions of Electron in Simulated QED Model

    Science.gov (United States)

    Kaur, Navdeep; Dahiya, Harleen

    2018-05-01

    In the present work, we have studied the transverse momentum distributions (TMDs) for the electron in simulated QED model. We have used the overlap representation of light-front wave functions where the spin-1/2 relativistic composite system consists of spin-1/2 fermion and spin-1 vector boson. The results have been obtained for T-even TMDs in transverse momentum plane for fixed value of longitudinal momentum fraction x.

  11. A proposed measurement of optical orbital and spin angular momentum and its implications for photon angular momentum

    Directory of Open Access Journals (Sweden)

    Elliot Leader

    2018-04-01

    Full Text Available The expression for the total angular momentum carried by a laser optical vortex beam, splits, in the paraxial approximation, into two terms which seem to represent orbital and spin angular momentum respectively. There are, however, two very different competing versions of the formula for the spin angular momentum, one based on the use of the Poynting vector, as in classical electrodynamics, the other related to the canonical expression for the angular momentum which occurs in Quantum Electrodynamics. I analyze the possibility that a sufficiently sensitive optical measurement could decide which of these corresponds to the actual physical angular momentum carried by the beam. Keywords: Photon, Angular momentum, Laser optics, Particle physics

  12. The Effects of Minimal Length, Maximal Momentum, and Minimal Momentum in Entropic Force

    Directory of Open Access Journals (Sweden)

    Zhong-Wen Feng

    2016-01-01

    Full Text Available The modified entropic force law is studied by using a new kind of generalized uncertainty principle which contains a minimal length, a minimal momentum, and a maximal momentum. Firstly, the quantum corrections to the thermodynamics of a black hole are investigated. Then, according to Verlinde’s theory, the generalized uncertainty principle (GUP corrected entropic force is obtained. The result shows that the GUP corrected entropic force is related not only to the properties of the black holes but also to the Planck length and the dimensionless constants α0 and β0. Moreover, based on the GUP corrected entropic force, we also derive the modified Einstein’s field equation (EFE and the modified Friedmann equation.

  13. DOD Recovery personnel and NASA technicians inspect Friendship 7 spacecraft

    Science.gov (United States)

    1964-01-01

    Department of Defense Recovery personnel and spacecraft technicians from NASA adn McDonnell Aircraft Corp., inspect Astronaut John Glenn's Mercury spacecraft, Friendship 7, following its return to Cape Canaveral after recovery in the Atlantic Ocean.

  14. High-Performance Fire Detector for Spacecraft, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The danger from fire aboard spacecraft is immediate with only moments for detection and suppression. Spacecraft are unique high-value systems where the cost of...

  15. Space tribology: its role in spacecraft mechanisms

    International Nuclear Information System (INIS)

    Roberts, E W

    2012-01-01

    The subject of tribology encompasses the friction, wear and lubrication of mechanical components such as bearings and gears. Tribological practices are aimed at ensuring that such components operate with high efficiency (low friction) and achieve long lives. On spacecraft mechanisms the route to achieving these goals brings its own unique challenges. This review describes the problems posed by the space environment, the types of tribological component used on spacecraft and the approaches taken to their lubrication. It is shown that in many instances lubrication needs can be met by synthetic oils having exceedingly low volatilities, but that at temperature extremes the only means of reducing friction and wear is by solid lubrication. As the demands placed on space engineering increase, innovatory approaches will be needed to solve future tribological problems. The direction that future developments might take is anticipated and discussed.

  16. MIDN: A spacecraft Micro-dosimeter mission

    International Nuclear Information System (INIS)

    Pisacane, V. L.; Ziegler, J. F.; Nelson, M. E.; Caylor, M.; Flake, D.; Heyen, L.; Youngborg, E.; Rosenfeld, A. B.; Cucinotta, F.; Zaider, M.; Dicello, J. F.

    2006-01-01

    MIDN (Micro-dosimetry instrument) is a payload on the MidSTAR-I spacecraft (Midshipman Space Technology Applications Research) under development at the United States Naval Academy. MIDN is a solid-state system being designed and constructed to measure Micro-dosimetric spectra to determine radiation quality factors for space environments. Radiation is a critical threat to the health of astronauts and to the success of missions in low-Earth orbit and space exploration. The system will consist of three separate sensors, one external to the spacecraft, one internal and one embedded in polyethylene. Design goals are mass <3 kg and power <2 W. The MidSTAR-I mission in 2006 will provide an opportunity to evaluate a preliminary version of this system. Its low power and mass makes it useful for the International Space Station and manned and unmanned interplanetary missions as a real-time system to assess and alert astronauts to enhanced radiation environments. (authors)

  17. Galileo spacecraft power management and distribution system

    International Nuclear Information System (INIS)

    Detwiler, R.C.; Smith, R.L.

    1990-01-01

    It has been twelve years since two Voyager spacecraft began the direct route to the outer planets. In October 1989 a single Galileo spacecraft started the return to Jupiter. Conceived as a simple Voyager look-alike, the Galileo power management and distribution (PMAD) system has undergone many iterations in configuration. Major changes to the PMAD resulted from dual spun slip ring limitations, variations in launch vehicle thrust capabilities, and launch delays. Lack of an adequate launch vehicle for an interplanetary mission of Galileo's size has resulted in an extremely long flight duration. A Venus-Earth-Earth Gravity Assist (VEEGA) tour, vital to attain the required energy, results in a 6 year trip to Jupiter and its moons. This paper provides a description of the Galileo PMAD and documents the design drivers that established the final as-built hardware

  18. Improved techniques for predicting spacecraft power

    International Nuclear Information System (INIS)

    Chmielewski, A.B.

    1987-01-01

    Radioisotope Thermoelectric Generators (RTGs) are going to supply power for the NASA Galileo and Ulysses spacecraft now scheduled to be launched in 1989 and 1990. The duration of the Galileo mission is expected to be over 8 years. This brings the total RTG lifetime to 13 years. In 13 years, the RTG power drops more than 20 percent leaving a very small power margin over what is consumed by the spacecraft. Thus it is very important to accurately predict the RTG performance and be able to assess the magnitude of errors involved. The paper lists all the error sources involved in the RTG power predictions and describes a statistical method for calculating the tolerance

  19. Data combinations accounting for LISA spacecraft motion

    International Nuclear Information System (INIS)

    Shaddock, Daniel A.; Tinto, Massimo; Estabrook, Frank B.; Armstrong, J.W.

    2003-01-01

    The laser interferometer space antenna is an array of three spacecraft in an approximately equilateral triangle configuration which will be used as a low-frequency gravitational wave detector. We present here new generalizations of the Michelson- and Sagnac-type time-delay interferometry data combinations. These combinations cancel laser phase noise in the presence of different up and down propagation delays in each arm of the array, and slowly varying systematic motion of the spacecraft. The gravitational wave sensitivities of these generalized combinations are the same as previously computed for the stationary cases, although the combinations are now more complicated. We introduce a diagrammatic representation to illustrate that these combinations are actually synthesized equal-arm interferometers

  20. The Stardust spacecraft arrives at KSC

    Science.gov (United States)

    1998-01-01

    After arrival at the Shuttle Landing Facility in the early morning hours, the crated Stardust spacecraft waits to be unloaded from the aircraft. Built by Lockheed Martin Astronautics near Denver, Colo., for the Jet Propulsion Laboratory (JPL) NASA, the spacecraft Stardust will use a unique medium called aerogel to capture comet particles flying off the nucleus of comet Wild 2 in January 2004, plus collect interstellar dust for later analysis. Stardust will be launched aboard a Boeing Delta 7426 rocket from Complex 17, Cape Canaveral Air Station, targeted for Feb. 6, 1999. The collected samples will return to Earth in a re- entry capsule to be jettisoned from Stardust as it swings by in January 2006.

  1. Close-Range Photogrammetry & Next Generation Spacecraft

    Science.gov (United States)

    Pappa, Richard S.

    2002-01-01

    NASA is focusing renewed attention on the topic of large, ultra-lightweight space structures, also known as 'gossamer' spacecraft. Nearly all of the details of the giant spacecraft are still to be worked out. But it's already clear that one of the most challenging aspects will be developing techniques to align and control these systems after they are deployed in space. A critical part of this process is creating new ground test methods to measure gossamer structures under stationary, deploying and vibrating conditions for validation of corresponding analytical predictions. In addressing this problem, I considered, first of all, the possibility of simply using conventional displacement or vibration sensor that could provide spatial measurements. Next, I turned my attention to photogrammetry, a method of determining the spatial coordinates of objects using photographs. The success of this research and development has convinced me that photogrammetry is the most suitable method to solve the gossamer measurement problem.

  2. Large Scale Experiments on Spacecraft Fire Safety

    DEFF Research Database (Denmark)

    Urban, David L.; Ruff, Gary A.; Minster, Olivier

    2012-01-01

    -based microgravity facilities or has been limited to very small fuel samples. Still, the work conducted to date has shown that fire behaviour in low-gravity is very different from that in normal-gravity, with differences observed for flammability limits, ignition delay, flame spread behaviour, flame colour and flame......Full scale fire testing complemented by computer modelling has provided significant knowhow about the risk, prevention and suppression of fire in terrestrial systems (cars, ships, planes, buildings, mines, and tunnels). In comparison, no such testing has been carried out for manned spacecraft due...... to the complexity, cost and risk associ-ated with operating a long duration fire safety experiment of a relevant size in microgravity. Therefore, there is currently a gap in knowledge of fire behaviour in spacecraft. The entire body of low-gravity fire research has either been conducted in short duration ground...

  3. Evaluation of Ultrafiltration for Spacecraft Water Reuse

    Science.gov (United States)

    Pickering, Karen D.; Wiesner, Mark R.

    2001-01-01

    Ultrafiltration is examined for use as the first stage of a primary treatment process for spacecraft wastewater. It is hypothesized that ultrafiltration can effectively serve as pretreatment for a reverse osmosis system, removing the majority of organic material in a spacecraft wastewater. However, it is believed that the interaction between the membrane material and the surfactant found in the wastewater will have a significant impact on the fouling of the ultrafiltration membrane. In this study, five different ultrafiltration membrane materials are examined for the filtration of wastewater typical of that expected to be produced onboard the International Space Station. Membranes are used in an unstirred batch cell. Flux, organic carbon rejection, and recovery from fouling are measured. The results of this evaluation will be used to select the most promising membranes for further study.

  4. FORTE spacecraft vibration mitigation. Final report

    International Nuclear Information System (INIS)

    Maly, J.R.

    1996-02-01

    This report documents work that was performed by CSA Engineering, Inc., for Los Alamos National Laboratory (LANL), to reduce vibrations of the FORTE spacecraft by retrofitting damped structural components into the spacecraft structure. The technical objective of the work was reduction of response at the location of payload components when the structure is subjected to the dynamic loading associated with launch and proto-qualification testing. FORTE is a small satellite that will be placed in orbit in 1996. The structure weighs approximately 425 lb, and is roughly 80 inches high and 40 inches in diameter. It was developed and built by LANL in conjunction with Sandia National Laboratories Albuquerque for the United States Department of Energy. The FORTE primary structure was fabricated primarily with graphite epoxy, using aluminum honeycomb core material for equipment decks and solar panel substrates. Equipment decks were bonded and bolted through aluminum mounting blocks to adjoining structure

  5. Momentum and angular momentum in the H-space of asymptotically flat, Einstein-Maxwell space-time

    International Nuclear Information System (INIS)

    Hallidy, W.; Ludvigsen, M.

    1979-01-01

    New definitions are proposed for the momentum and angular momentum of Einstein-Maxwell fields that overcome the deficiencies of earlier definitions of these terms and are appropriate to the new H-space formulations of space-time. Definitions are made in terms of the Winicour-Tamburino linkages applied to the good cuts of Cj + . The transformations between good cuts then correspond to the translations and Lorentz transformations at points in H-space. For the special case of Robinson-Trautman type II space-times, it is shown that the definitions of momentum and angular momentum yield previously published results. (author)

  6. Redundancy for electric motors in spacecraft applications

    Science.gov (United States)

    Smith, Robert J.; Flew, Alastair R.

    1986-01-01

    The parts of electric motors which should be duplicated in order to provide maximum reliability in spacecraft application are identified. Various common types of redundancy are described. The advantages and disadvantages of each are noted. The principal types are illustrated by reference to specific examples. For each example, constructional details, basic performance data and failure modes are described, together with a discussion of the suitability of particular redundancy techniques to motor types.

  7. Research on spacecraft electrical power conversion

    Science.gov (United States)

    Wilson, T. G.

    1983-01-01

    The history of spacecraft electrical power conversion in literature, research and practice is reviewed. It is noted that the design techniques, analyses and understanding which were developed make today's contribution to power computers and communication installations. New applications which require more power, improved dynamic response, greater reliability, and lower cost are outlined. The switching mode approach in electronic power conditioning is discussed. Technical aspects of the research are summarized.

  8. Schema for Spacecraft-Command Dictionary

    Science.gov (United States)

    Laubach, Sharon; Garcia, Celina; Maxwell, Scott; Wright, Jesse

    2008-01-01

    An Extensible Markup Language (XML) schema was developed as a means of defining and describing a structure for capturing spacecraft command- definition and tracking information in a single location in a form readable by both engineers and software used to generate software for flight and ground systems. A structure defined within this schema is then used as the basis for creating an XML file that contains command definitions.

  9. Additive Manufacturing: Ensuring Quality for Spacecraft Applications

    Science.gov (United States)

    Swanson, Theodore; Stephenson, Timothy

    2014-01-01

    Reliable manufacturing requires that material properties and fabrication processes be well defined in order to insure that the manufactured parts meet specified requirements. While this issue is now relatively straightforward for traditional processes such as subtractive manufacturing and injection molding, this capability is still evolving for AM products. Hence, one of the principal challenges within AM is in qualifying and verifying source material properties and process control. This issue is particularly critical for applications in harsh environments and demanding applications, such as spacecraft.

  10. Wheel speed management control system for spacecraft

    Science.gov (United States)

    Goodzeit, Neil E. (Inventor); Linder, David M. (Inventor)

    1991-01-01

    A spacecraft attitude control system uses at least four reaction wheels. In order to minimize reaction wheel speed and therefore power, a wheel speed management system is provided. The management system monitors the wheel speeds and generates a wheel speed error vector. The error vector is integrated, and the error vector and its integral are combined to form a correction vector. The correction vector is summed with the attitude control torque command signals for driving the reaction wheels.

  11. The Manned Spacecraft Center and medical technology

    Science.gov (United States)

    Johnston, R. S.; Pool, S. L.

    1974-01-01

    A number of medically oriented research and hardware development programs in support of manned space flights have been sponsored by NASA. Blood pressure measuring systems for use in spacecraft are considered. In some cases, complete new bioinstrumentation systems were necessary to accomplish a specific physiological study. Plans for medical research during the Skylab program are discussed along with general questions regarding space-borne health service systems and details concerning the Health Services Support Control Center.

  12. Artificial Intelligence and Spacecraft Power Systems

    Science.gov (United States)

    Dugel-Whitehead, Norma R.

    1997-01-01

    This talk will present the work which has been done at NASA Marshall Space Flight Center involving the use of Artificial Intelligence to control the power system in a spacecraft. The presentation will include a brief history of power system automation, and some basic definitions of the types of artificial intelligence which have been investigated at MSFC for power system automation. A video tape of one of our autonomous power systems using co-operating expert systems, and advanced hardware will be presented.

  13. THE FUTURE OF SPACECRAFT NUCLEAR PROPULSION

    OpenAIRE

    Jansen, Frank

    2014-01-01

    This paper summarizes the advantages of space nuclear power and propulsion systems. It describes the actual status of international power level dependent spacecraft nuclear propulsion missions, especially the high power EU-Russian MEGAHIT study including the Russian Megawatt-Class Nuclear Power Propulsion System, the NASA GRC project and the low and medium power EU DiPoP study. Space nuclear propulsion based mission scenarios of these studies are sketched as well.

  14. Whole-body angular momentum during stair ascent and descent.

    Science.gov (United States)

    Silverman, Anne K; Neptune, Richard R; Sinitski, Emily H; Wilken, Jason M

    2014-04-01

    The generation of whole-body angular momentum is essential in many locomotor tasks and must be regulated in order to maintain dynamic balance. However, angular momentum has not been investigated during stair walking, which is an activity that presents a biomechanical challenge for balance-impaired populations. We investigated three-dimensional whole-body angular momentum during stair ascent and descent and compared it to level walking. Three-dimensional body-segment kinematic and ground reaction force (GRF) data were collected from 30 healthy subjects. Angular momentum was calculated using a 13-segment whole-body model. GRFs, external moment arms and net joint moments were used to interpret the angular momentum results. The range of frontal plane angular momentum was greater for stair ascent relative to level walking. In the transverse and sagittal planes, the range of angular momentum was smaller in stair ascent and descent relative to level walking. Significant differences were also found in the ground reaction forces, external moment arms and net joint moments. The sagittal plane angular momentum results suggest that individuals alter angular momentum to effectively counteract potential trips during stair ascent, and reduce the range of angular momentum to avoid falling forward during stair descent. Further, significant differences in joint moments suggest potential neuromuscular mechanisms that account for the differences in angular momentum between walking conditions. These results provide a baseline for comparison to impaired populations that have difficulty maintaining dynamic balance, particularly during stair ascent and descent. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Spacecraft early design validation using formal methods

    International Nuclear Information System (INIS)

    Bozzano, Marco; Cimatti, Alessandro; Katoen, Joost-Pieter; Katsaros, Panagiotis; Mokos, Konstantinos; Nguyen, Viet Yen; Noll, Thomas; Postma, Bart; Roveri, Marco

    2014-01-01

    The size and complexity of software in spacecraft is increasing exponentially, and this trend complicates its validation within the context of the overall spacecraft system. Current validation methods are labor-intensive as they rely on manual analysis, review and inspection. For future space missions, we developed – with challenging requirements from the European space industry – a novel modeling language and toolset for a (semi-)automated validation approach. Our modeling language is a dialect of AADL and enables engineers to express the system, the software, and their reliability aspects. The COMPASS toolset utilizes state-of-the-art model checking techniques, both qualitative and probabilistic, for the analysis of requirements related to functional correctness, safety, dependability and performance. Several pilot projects have been performed by industry, with two of them having focused on the system-level of a satellite platform in development. Our efforts resulted in a significant advancement of validating spacecraft designs from several perspectives, using a single integrated system model. The associated technology readiness level increased from level 1 (basic concepts and ideas) to early level 4 (laboratory-tested)

  16. Determination of Realistic Fire Scenarios in Spacecraft

    Science.gov (United States)

    Dietrich, Daniel L.; Ruff, Gary A.; Urban, David

    2013-01-01

    This paper expands on previous work that examined how large a fire a crew member could successfully survive and extinguish in the confines of a spacecraft. The hazards to the crew and equipment during an accidental fire include excessive pressure rise resulting in a catastrophic rupture of the vehicle skin, excessive temperatures that burn or incapacitate the crew (due to hyperthermia), carbon dioxide build-up or accumulation of other combustion products (e.g. carbon monoxide). The previous work introduced a simplified model that treated the fire primarily as a source of heat and combustion products and sink for oxygen prescribed (input to the model) based on terrestrial standards. The model further treated the spacecraft as a closed system with no capability to vent to the vacuum of space. The model in the present work extends this analysis to more realistically treat the pressure relief system(s) of the spacecraft, include more combustion products (e.g. HF) in the analysis and attempt to predict the fire spread and limiting fire size (based on knowledge of terrestrial fires and the known characteristics of microgravity fires) rather than prescribe them in the analysis. Including the characteristics of vehicle pressure relief systems has a dramatic mitigating effect by eliminating vehicle overpressure for all but very large fires and reducing average gas-phase temperatures.

  17. Probing interferometric parallax with interplanetary spacecraft

    Science.gov (United States)

    Rodeghiero, G.; Gini, F.; Marchili, N.; Jain, P.; Ralston, J. P.; Dallacasa, D.; Naletto, G.; Possenti, A.; Barbieri, C.; Franceschini, A.; Zampieri, L.

    2017-07-01

    We describe an experimental scenario for testing a novel method to measure distance and proper motion of astronomical sources. The method is based on multi-epoch observations of amplitude or intensity correlations between separate receiving systems. This technique is called Interferometric Parallax, and efficiently exploits phase information that has traditionally been overlooked. The test case we discuss combines amplitude correlations of signals from deep space interplanetary spacecraft with those from distant galactic and extragalactic radio sources with the goal of estimating the interplanetary spacecraft distance. Interferometric parallax relies on the detection of wavefront curvature effects in signals collected by pairs of separate receiving systems. The method shows promising potentialities over current techniques when the target is unresolved from the background reference sources. Developments in this field might lead to the construction of an independent, geometrical cosmic distance ladder using a dedicated project and future generation instruments. We present a conceptual overview supported by numerical estimates of its performances applied to a spacecraft orbiting the Solar System. Simulations support the feasibility of measurements with a simple and time-saving observational scheme using current facilities.

  18. On-orbit supervisor for controlling spacecraft

    Science.gov (United States)

    Vandervoort, Richard J.

    1992-07-01

    Spacecraft systems of the 1990's and beyond will be substantially more complex than their predecessors. They will have demanding performance requirements and will be expected to operate more autonomously. This underscores the need for innovative approaches to Fault Detection, Isolation and Recovery (FDIR). A hierarchical expert system is presented that provides on-orbit supervision using intelligent FDIR techniques. Each expert system in the hierarchy supervises the operation of a local set of spacecraft functions. Spacecraft operational goals flow top down while responses flow bottom up. The expert system supervisors have a fairly high degree of autonomy. Bureaucratic responsibilities are minimized to conserve bandwidth and maximize response time. Data for FDIR can be acquired local to an expert and from other experts. By using a blackboard architecture for each supervisor, the system provides a great degree of flexibility in implementing the problem solvers for each problem domain. In addition, it provides for a clear separation between facts and knowledge, leading to an efficient system capable of real time response.

  19. Delamination Assessment Tool for Spacecraft Composite Structures

    Science.gov (United States)

    Portela, Pedro; Preller, Fabian; Wittke, Henrik; Sinnema, Gerben; Camanho, Pedro; Turon, Albert

    2012-07-01

    Fortunately only few cases are known where failure of spacecraft structures due to undetected damage has resulted in a loss of spacecraft and launcher mission. However, several problems related to damage tolerance and in particular delamination of composite materials have been encountered during structure development of various ESA projects and qualification testing. To avoid such costly failures during development, launch or service of spacecraft, launcher and reusable launch vehicles structures a comprehensive damage tolerance verification approach is needed. In 2009, the European Space Agency (ESA) initiated an activity called “Delamination Assessment Tool” which is led by the Portuguese company HPS Lda and includes academic and industrial partners. The goal of this study is the development of a comprehensive damage tolerance verification approach for launcher and reusable launch vehicles (RLV) structures, addressing analytical and numerical methodologies, material-, subcomponent- and component testing, as well as non-destructive inspection. The study includes a comprehensive review of current industrial damage tolerance practice resulting from ECSS and NASA standards, the development of new Best Practice Guidelines for analysis, test and inspection methods and the validation of these with a real industrial case study. The paper describes the main findings of this activity so far and presents a first iteration of a Damage Tolerance Verification Approach, which includes the introduction of novel analytical and numerical tools at an industrial level. This new approach is being put to the test using real industrial case studies provided by the industrial partners, MT Aerospace, RUAG Space and INVENT GmbH

  20. Adaptive nonlinear robust relative pose control of spacecraft autonomous rendezvous and proximity operations.

    Science.gov (United States)

    Sun, Liang; Huo, Wei; Jiao, Zongxia

    2017-03-01

    This paper studies relative pose control for a rigid spacecraft with parametric uncertainties approaching to an unknown tumbling target in disturbed space environment. State feedback controllers for relative translation and relative rotation are designed in an adaptive nonlinear robust control framework. The element-wise and norm-wise adaptive laws are utilized to compensate the parametric uncertainties of chaser and target spacecraft, respectively. External disturbances acting on two spacecraft are treated as a lumped and bounded perturbation input for system. To achieve the prescribed disturbance attenuation performance index, feedback gains of controllers are designed by solving linear matrix inequality problems so that lumped disturbance attenuation with respect to the controlled output is ensured in the L 2 -gain sense. Moreover, in the absence of lumped disturbance input, asymptotical convergence of relative pose are proved by using the Lyapunov method. Numerical simulations are performed to show that position tracking and attitude synchronization are accomplished in spite of the presence of couplings and uncertainties. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  1. Developmental Gains in Visuospatial Memory Predict Gains in Mathematics Achievement

    OpenAIRE

    Li, Yaoran; Geary, David C.

    2013-01-01

    Visuospatial competencies are related to performance in mathematical domains in adulthood, but are not consistently related to mathematics achievement in children. We confirmed the latter for first graders and demonstrated that children who show above average first-to-fifth grade gains in visuospatial memory have an advantage over other children in mathematics. The study involved the assessment of the mathematics and reading achievement of 177 children in kindergarten to fifth grade, inclusiv...

  2. Space Environments and Spacecraft Effects Organization Concept

    Science.gov (United States)

    Edwards, David L.; Burns, Howard D.; Miller, Sharon K.; Porter, Ron; Schneider, Todd A.; Spann, James F.; Xapsos, Michael

    2012-01-01

    The National Aeronautics and Space Administration (NASA) is embarking on a course to expand human presence beyond Low Earth Orbit (LEO) while also expanding its mission to explore the solar system. Destinations such as Near Earth Asteroids (NEA), Mars and its moons, and the outer planets are but a few of the mission targets. Each new destination presents an opportunity to increase our knowledge of the solar system and the unique environments for each mission target. NASA has multiple technical and science discipline areas specializing in specific space environments disciplines that will help serve to enable these missions. To complement these existing discipline areas, a concept is presented focusing on the development of a space environments and spacecraft effects (SENSE) organization. This SENSE organization includes disciplines such as space climate, space weather, natural and induced space environments, effects on spacecraft materials and systems and the transition of research information into application. This space environment and spacecraft effects organization will be composed of Technical Working Groups (TWG). These technical working groups will survey customers and users, generate products, and provide knowledge supporting four functional areas: design environments, engineering effects, operational support, and programmatic support. The four functional areas align with phases in the program mission lifecycle and are briefly described below. Design environments are used primarily in the mission concept and design phases of a program. Engineering effects focuses on the material, component, sub-system and system-level selection and the testing to verify design and operational performance. Operational support provides products based on real time or near real time space weather to mission operators to aid in real time and near-term decision-making. The programmatic support function maintains an interface with the numerous programs within NASA, other federal

  3. Large Scale Experiments on Spacecraft Fire Safety

    Science.gov (United States)

    Urban, David; Ruff, Gary A.; Minster, Olivier; Fernandez-Pello, A. Carlos; Tien, James S.; Torero, Jose L.; Legros, Guillaume; Eigenbrod, Christian; Smirnov, Nickolay; Fujita, Osamu; hide

    2012-01-01

    Full scale fire testing complemented by computer modelling has provided significant knowhow about the risk, prevention and suppression of fire in terrestrial systems (cars, ships, planes, buildings, mines, and tunnels). In comparison, no such testing has been carried out for manned spacecraft due to the complexity, cost and risk associated with operating a long duration fire safety experiment of a relevant size in microgravity. Therefore, there is currently a gap in knowledge of fire behaviour in spacecraft. The entire body of low-gravity fire research has either been conducted in short duration ground-based microgravity facilities or has been limited to very small fuel samples. Still, the work conducted to date has shown that fire behaviour in low-gravity is very different from that in normal gravity, with differences observed for flammability limits, ignition delay, flame spread behaviour, flame colour and flame structure. As a result, the prediction of the behaviour of fires in reduced gravity is at present not validated. To address this gap in knowledge, a collaborative international project, Spacecraft Fire Safety, has been established with its cornerstone being the development of an experiment (Fire Safety 1) to be conducted on an ISS resupply vehicle, such as the Automated Transfer Vehicle (ATV) or Orbital Cygnus after it leaves the ISS and before it enters the atmosphere. A computer modelling effort will complement the experimental effort. Although the experiment will need to meet rigorous safety requirements to ensure the carrier vehicle does not sustain damage, the absence of a crew removes the need for strict containment of combustion products. This will facilitate the possibility of examining fire behaviour on a scale that is relevant to spacecraft fire safety and will provide unique data for fire model validation. This unprecedented opportunity will expand the understanding of the fundamentals of fire behaviour in spacecraft. The experiment is being

  4. Multiple-choice test of energy and momentum concepts

    OpenAIRE

    Singh, Chandralekha; Rosengrant, David

    2016-01-01

    We investigate student understanding of energy and momentum concepts at the level of introductory physics by designing and administering a 25-item multiple choice test and conducting individual interviews. We find that most students have difficulty in qualitatively interpreting basic principles related to energy and momentum and in applying them in physical situations.

  5. Relating inclusive and exclusive meson photoproduction at large transverse momentum

    International Nuclear Information System (INIS)

    Scott, D.M.

    1975-01-01

    Inclusive and exclusive meson photoproduction at large transverse momentum are related by a local application of the correspondence principle of Bjorken and Kogut. The recent predictions for the inclusive process by Escobar are thus compared with wide angle exclusive data. The inclusive photoproduction of (rho 0 +ω) at large transverse momentum is discussed. (Auth.)

  6. [Analysis of momentum and impurity confinment in TFTR (1990)

    International Nuclear Information System (INIS)

    1990-01-01

    Work during the present grant period has been concentrated in two areas and are discussed in this report: (1) a review of momentum confinement experiments in tokamaks, of momentum confinement theories and of previous comparisons of the two; and (2) analysis and documentation of the dedicated power-scan rotation experiment performed on TFTR in September 1988

  7. Non-linear variation of the beta function with momentum

    International Nuclear Information System (INIS)

    Parzen, G.

    1983-07-01

    A theory is presented for computing the non-linear dependence of the β-functions on momentum. Results are found for the quadratic term. The results of the theory are compared with computed results. A procedure is proposed for computing the strengths of the sextupole correctors to correct the dependence of the β-function on momentum

  8. Energy-momentum tensor in quantum field theory

    International Nuclear Information System (INIS)

    Fujikawa, K.

    1981-01-01

    The definition of the energy-momentum tensor as a source current coupled to the background gravitational field receives an important modification in quantum theory. In the path-integral approach, the manifest covariance of the integral measure under general coordinate transformations dictates that field variables with weight 1/2 should be used as independent integration variables. An improved energy-momentum tensor is then generated by the variational derivative, and it gives rise to well-defined gravitational conformal (Weyl) anomalies. In the flat--space-time limit, all the Ward-Takahashi identities associated with space-time transformations including the global dilatation become free from anomalies in terms of this energy-momentum tensor, reflecting the general covariance of the integral measure; the trace of this tensor is thus finite at zero momentum transfer for renormalizable theories. The Jacobian for the local conformal transformation, however, becomes nontrivial, and it gives rise to an anomaly for the conformal identity. All the familiar anomalies are thus reduced to either chiral or conformal anomalies. The consistency of the dilatation and conformal identities at vanishing momentum transfer determines the trace anomaly of this energy-momentum tensor in terms of the renormalization-group b function and other parameters. In contrast, the trace of the conventional energy-momentum tensor generally diverges even at vanishing momentum transfer depending on the regularization scheme, and it is subtractively renormalized. We also explain how the apparently different renormalization properties of the chiral and trace anomalies arise

  9. Angular momentum dependence of the distribution of shell model eigenenergies

    International Nuclear Information System (INIS)

    Yen, M.K.

    1974-01-01

    In the conventional shell model calculation the many-particle energy matrices are constructed and diagonalized for definite angular momentum and parity. However the resulting set of eigenvalues possess a near normal behavior and hence a simple statistical description is possible. Usually one needs only about four parameters to capture the average level densities if the size of the set is not too small. The parameters are essentially moments of the distribution. But the difficulty lies in the yet unsolved problem of calculating moments in the fixed angular momentum subspace. We have derived a formula to approximate the angular momentum projection dependence of any operator averaged in a shell model basis. This approximate formula which is a truncated series in Hermite polynomials has been proved very good numerically and justified analytically for large systems. Applying this formula to seven physical cases we have found that the fixed angular momentum projection energy centroid, width and higher central moments can be obtained accurately provided for even-even nuclei the even and odd angular momentum projections are treated separately. Using this information one can construct the energy distribution for fixed angular momentum projection assuming normal behavior. Then the fixed angular momentum level densities are deduced and spectra are extracted. Results are in reasonably good agreement with the exact values although not as good as those obtained using exact fixed angular momentum moments. (Diss. Abstr. Int., B)

  10. Energy-momentum distribution: A crucial problem in general relativity

    NARCIS (Netherlands)

    Sharif, M.; Fatima, T.

    2005-01-01

    This paper is aimed to elaborate the problem of energy–momentum in general relativity. In this connection, we use the prescriptions of Einstein, Landau–Lifshitz, Papapetrou and Möller to compute the energy–momentum densities for two exact solutions of Einstein field equations. The space–times under

  11. Non-physical momentum sources in slab geometry gyrokinetics

    International Nuclear Information System (INIS)

    Parra, Felix I; Catto, Peter J

    2010-01-01

    We investigate momentum transport in the Hamiltonian electrostatic gyrokinetic formulation of Dubin et al (1983 Phys. Fluids 26 3524). We prove that the long wavelength electric field obtained from the gyrokinetic quasineutrality introduces a non-physical momentum source in the low flow ordering.

  12. Energy-momentum tensor in quantum field theory

    International Nuclear Information System (INIS)

    Fujikawa, Kazuo.

    1980-12-01

    The definition of the energy-momentum tensor as a source current coupled to the background gravitational field receives an important modification in quantum theory. In the path integral approach, the manifest covariance of the integral measure under general coordinate transformations dictates that field variables with weight 1/2 should be used as independent integration variables. An improved energy-momentum tensor is then generated by the variational derivative, and it gives rise to well-defined gravitational conformal (Weyl) anomalies. In the flat space-time limit, all the Ward-Takahashi identities associate with space-time transformations including the global dilatation become free from anomalies, reflecting the general covariance of the integral measure; the trace of this energy-momentum tensor is thus finite at the zero momentum transfer. The Jacobian for the local conformal transformation however becomes non-trivial, and it gives rise to an anomaly for the conformal identity. All the familiar anomalies are thus reduced to either chiral or conformal anomalies. The consistency of the dilatation and conformal identities at the vanishing momentum transfer determines the trace anomaly of this energy-momentum tensor in terms of the renormalization group β-function and other parameters. In contrast, the trace of the conventional energy-momentum tensor generally diverges even at the vanishing momentum transfer depending on the regularization scheme, and it is subtractively renormalized. We also explain how the apparently different renormalization properties of the chiral and trace anomalies arise. (author)

  13. A new uncertainty relation for angular momentum and angle

    International Nuclear Information System (INIS)

    Kranold, H.U.

    1984-01-01

    An uncertainty relation of the form ΔL 2 ΔSo >=sup(h/2π)/sub(2) is derived for angular momentum and angle. The non-linear operator So measures angles and has a simple interpretation. Subject to very general conditions of rotational invariance the above relation is unique. Radial momentum is not quantized

  14. The resummed Higgs boson transverse momentum distribution at the LHC

    CERN Document Server

    Kulesza, A; Vogelsang, W

    2003-01-01

    We apply QCD resummation techniques to study the transverse momentum distribution of Higgs bosons produced via gluon-gluon fusion at the LHC. In particular we focus on the joint resummation formalism which resums both threshold and transverse momentum corrections simultaneously. A comparison of results obtained in the joint and the standard recoil resummation frameworks is presented.

  15. Implications of conformal invariance in momentum space

    Science.gov (United States)

    Bzowski, Adam; McFadden, Paul; Skenderis, Kostas

    2014-03-01

    We present a comprehensive analysis of the implications of conformal invariance for 3-point functions of the stress-energy tensor, conserved currents and scalar operators in general dimension and in momentum space. Our starting point is a novel and very effective decomposition of tensor correlators which reduces their computation to that of a number of scalar form factors. For example, the most general 3-point function of a conserved and traceless stress-energy tensor is determined by only five form factors. Dilatations and special conformal Ward identities then impose additional conditions on these form factors. The special conformal Ward identities become a set of first and second order differential equations, whose general solution is given in terms of integrals involving a product of three Bessel functions (`triple- K integrals'). All in all, the correlators are completely determined up to a number of constants, in agreement with well-known position space results. In odd dimensions 3-point functions are finite without renormalisation while in even dimensions non-trivial renormalisation in required. In this paper we restrict ourselves to odd dimensions. A comprehensive analysis of renormalisation will be discussed elsewhere. This paper contains two parts that can be read independently of each other. In the first part, we explain the method that leads to the solution for the correlators in terms of triple- K integrals while the second part contains a self-contained presentation of all results. Readers interested only in results may directly consult the second part of the paper.

  16. Nuclear structure at high angular momentum

    International Nuclear Information System (INIS)

    Stephens, F.S.

    1976-08-01

    There is considerable interest in high angular-momentum states of nuclei, and some recent progress in three areas is discussed. Part I considers transitional nuclei, where two types of rotational bands--decoupled and strongly coupled--are found to occur very frequently. These can be described by several collective models, but the required potential-energy surfaces seem to differ somewhat from those calculated microscopically. In Part II the processes that might cause backbending (irregularities in the rotational levels of certain nuclei) are discussed, and alignment of individual nucleons now seems to be the cause in most cases. The mixing of the ground band with this aligned band can be studied in some detail using Coulomb excitation with very heavy ions. Part III deals with the very high-spin states where effective moments of inertia have been obtained for spins up to 50h. Also structure has been seen in the spectra around these spin values which can be tentatively related to calculated shell effects. 74 references, 61 figures

  17. Angular-momentum effects in subbarrier fusion

    International Nuclear Information System (INIS)

    Halbert, M.L.; Beene, J.R.

    1993-01-01

    It has been known since about 1980 that fusion of heavy ions is greatly enhanced below the Coulomb barrier compared with normal barrier-penetration expectations. The excitation function for fusion of 64 Ni + 100 Mo measured in collaboration with a group at Washington University shows the effect clearly. The barrier energy is about 142 MeV; the lowest point is at about 90% of the barrier energy. The dotted curve is the prediction of a one-dimensional-barrier-penetration calculation of a type that reproduces the fusion of light projectiles very well. Several theoretical approaches have been successful in explaining the enhancement seen in much of the excitation-function data, but it cannot be said that a full understanding of the physics is in hand even after more than a decade of hard work. In fact, the reasonable success of several rather different models shows that the underlying phenomena are not well understood. Other types of data might be helpful in distinguishing among the many different theoretical approaches. An important kind of information not measured in most of the experiments is the dependence on ell, the angular momentum of the fusing system. We obtained such information on the cross sections, σ ell, as a function of ell for the fusion of 64 Ni and 100 Mo using the Spin Spectrometer. This paper will first review the experimental method and data and then present results from a more sophisticated analysis of the same data

  18. Cyclic transformation of orbital angular momentum modes

    International Nuclear Information System (INIS)

    Schlederer, Florian; Krenn, Mario; Fickler, Robert; Malik, Mehul; Zeilinger, Anton

    2016-01-01

    The spatial modes of photons are one realization of a QuDit, a quantum system that is described in a D-dimensional Hilbert space. In order to perform quantum information tasks with QuDits, a general class of D-dimensional unitary transformations is needed. Among these, cyclic transformations are an important special case required in many high-dimensional quantum communication protocols. In this paper, we experimentally demonstrate a cyclic transformation in the high-dimensional space of photonic orbital angular momentum (OAM). Using simple linear optical components, we show a successful four-fold cyclic transformation of OAM modes. Interestingly, our experimental setup was found by a computer algorithm. In addition to the four-cyclic transformation, the algorithm also found extensions to higher-dimensional cycles in a hybrid space of OAM and polarization. Besides being useful for quantum cryptography with QuDits, cyclic transformations are key for the experimental production of high-dimensional maximally entangled Bell-states. (paper)

  19. Angular momentum transport by tidal acoustic wave

    International Nuclear Information System (INIS)

    Sakurai, T.

    1976-01-01

    An analytical expression of the braking torque on a Jacobian ellipsoid rotating steadily in an enviromental gas is given, based on the assumption that the ellipsoid rotates around its shortest principal axis with an angular momentum slightly larger than that at the bifurcation point of the Maclaurin spheroid. This braking torque is effected by the gravitational interaction between the ellipsoid matter and a spiral density configuration in the environmental gas. This spiral configuration which is called a tidal acoustic wave, is caused by the zone of silence effect in a supersonic flow. With respect to a coordinates system rotating with the ellipsoid, a supersonic region appears outside a certain radius. In this supersonic region, the effect of the non-axisymmetric fluctuation in the ellipsoid potential propagates along the downstream branches of the Mach waves. This one-sided response of the supersonic part causes the tidal acoustic wave. The discussion is restricted to the equatorial plane, and an acoustic approximation of the basic equations is used under the assumption that the self-gravity effect of the environmental gas is negligable in comparison to the main gravity of the ellipsoid. The results are applied to the pre- and post-Main sequence phases of a rotating star, and relating astrophysical problems are discussed. (Auth.)

  20. Angular momentum transport by tidal acoustic wave

    Energy Technology Data Exchange (ETDEWEB)

    Sakurai, T [Kyoto Univ. (Japan). Faculty of Engineering

    1976-05-01

    An analytical expression of the braking torque on a Jacobian ellipsoid rotating steadily in an enviromental gas is given, based on the assumption that the ellipsoid rotates around its shortest principal axis with an angular momentum slightly larger than that at the bifurcation point of the Maclaurin spheroid. This braking torque is effected by the gravitational interaction between the ellipsoid matter and a spiral density configuration in the environmental gas. This spiral configuration which is called a tidal acoustic wave, is caused by the zone of silence effect in a supersonic flow. With respect to a coordinates system rotating with the ellipsoid, a supersonic region appears outside a certain radius. In this supersonic region, the effect of the non-axisymmetric fluctuation in the ellipsoid potential propagates along the downstream branches of the Mach waves. This one-sided response of the supersonic part causes the tidal acoustic wave. The discussion is restricted to the equatorial plane, and an acoustic approximation of the basic equations is used under the assumption that the self-gravity effect of the environmental gas is negligable in comparison to the main gravity of the ellipsoid. The results are applied to the pre- and post-Main sequence phases of a rotating star, and relating astrophysical problems are discussed.

  1. Continuous Wheel Momentum Dumping Using Magnetic Torquers and Thrusters

    Science.gov (United States)

    Oh, Hwa-Suk; Choi, Wan-Sik; Eun, Jong-Won

    1996-12-01

    Two momentum management schemes using magnetic torquers and thrusters are sug-gested. The stability of the momentum dumping logic is proved at a general attitude equilibrium. Both momentum dumping control laws are implemented with Pulse-Width- Pulse-Frequency Modulated on-off control, and shown working equally well with the original continuous and variable strength control law. Thrusters are assummed to be asymmetrically configured as a contingency case. Each thruster is fired following separated control laws rather than paired thrusting. Null torque thrusting control is added on the thrust control calculated from the momentum control law for the gener-ation of positive thrusting force. Both magnetic and thrusting control laws guarantee the momentum dumping, however, the wheel inner loop control is needed for the "wheel speed" dumping, The control laws are simulated on the KOrea Multi-Purpose SATellite (KOMPSAT) model.

  2. Relativistic differential-difference momentum operators and noncommutative differential calculus

    International Nuclear Information System (INIS)

    Mir-Kasimov, R.M.

    2011-01-01

    Full text: (author)The relativistic kinetic momentum operators are introduced in the framework of the Quantum Mechanics in the relativistic configuration space (RCS). These operators correspond to the half of the non-Euclidean distance in the Lobachevsky momentum space. In terms of kinetic momentum operators the relativistic kinetic energy is separated from the total Hamiltonian. The role of the plane wave (wave function of the motion with definite value of momentum and energy) plays the generation function for the matrix elements of the unitary irreps of Lorentz group (generalized Jacobi polynomials). The kinetic momentum operators are the interior derivatives in the framework of the non-commutative differential calculus over the commutative algebra generated by the coordinate functions over the RCS

  3. LDPC-coded orbital angular momentum (OAM) modulation for free-space optical communication.

    Science.gov (United States)

    Djordjevic, Ivan B; Arabaci, Murat

    2010-11-22

    An orbital angular momentum (OAM) based LDPC-coded modulation scheme suitable for use in FSO communication is proposed. We demonstrate that the proposed scheme can operate under strong atmospheric turbulence regime and enable 100 Gb/s optical transmission while employing 10 Gb/s components. Both binary and nonbinary LDPC-coded OAM modulations are studied. In addition to providing better BER performance, the nonbinary LDPC-coded modulation reduces overall decoder complexity and latency. The nonbinary LDPC-coded OAM modulation provides a net coding gain of 9.3 dB at the BER of 10(-8). The maximum-ratio combining scheme outperforms the corresponding equal-gain combining scheme by almost 2.5 dB.

  4. Debuncher Momentum Cooling Systems Signal to Noise Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Pasquinelli, Ralph J.; /Fermilab

    2001-12-18

    The Debuncher Momentum cooling systems were carefully measured for signal to noise. It was observed that cooling performance was not optimum. Closer inspection shows that the installed front-end bandpass filters are wider than the pickup response. (The original filters were specified to be wider so that none of the available bandwidth would be clipped.) The end result is excess noise is amplified and passed onto the kickers unimpeded, hence, reducing the achievable system gain. From this data, new filters should be designed to improve performance. New system bandwidths are specified on the data figures. Also included are the transfer function measurements that clearly show adjacent band response. In band 4 upper, the adjacent lobes are strong and out of phase. This is also degrading the system performance. The correlation between spectrum analyzer signal to noise and network analyzer system transfer functions is very strong. The table below has a calculation of expected improvement of front noise reduction by means of building new front-end bandpass filters. The calculation is based on a flat input noise spectrum and is a linear estimation of improvement. The listed 3dB bandwidths of the original filters are from measured data. The expected bandwidth is taken from the linear spectrum analyzer plots and is closer to a 10 dB bandwidth making the percentage improvement conservative. The signal to noise measurements are taken with circulating pbars in the Debuncher. One cooling system was measured at a time with all others off. Beam currents are below ten microamperes.

  5. Debuncher Momentum Cooling Systems Signal to Noise Measurements

    International Nuclear Information System (INIS)

    Pasquinelli, Ralph J.

    2001-01-01

    The Debuncher Momentum cooling systems were carefully measured for signal to noise. It was observed that cooling performance was not optimum. Closer inspection shows that the installed front-end bandpass filters are wider than the pickup response. (The original filters were specified to be wider so that none of the available bandwidth would be clipped.) The end result is excess noise is amplified and passed onto the kickers unimpeded, hence, reducing the achievable system gain. From this data, new filters should be designed to improve performance. New system bandwidths are specified on the data figures. Also included are the transfer function measurements that clearly show adjacent band response. In band 4 upper, the adjacent lobes are strong and out of phase. This is also degrading the system performance. The correlation between spectrum analyzer signal to noise and network analyzer system transfer functions is very strong. The table below has a calculation of expected improvement of front noise reduction by means of building new front-end bandpass filters. The calculation is based on a flat input noise spectrum and is a linear estimation of improvement. The listed 3dB bandwidths of the original filters are from measured data. The expected bandwidth is taken from the linear spectrum analyzer plots and is closer to a 10 dB bandwidth making the percentage improvement conservative. The signal to noise measurements are taken with circulating pbars in the Debuncher. One cooling system was measured at a time with all others off. Beam currents are below ten microamperes.

  6. SMART-1: the first spacecraft of the future

    Science.gov (United States)

    2003-09-01

    for the geostationary transfer orbit (GTO), from which the Moon can be reached. Last but not least, the spiral orbit which SMART-1 has to take to reach the Moon from GTO is a long and complex trajectory, so that the ion engine will be fully tested in conditions representative of a deep-space mission. Good news for the whole space sector The technology to be tested on SMART-1 is a strategic investment for ESA. In particular, development of the solar-electric propulsion technology was followed by ESA directly. The experience gained with SMART-1 will be useful to many aspects of space technology, providing thorough groundwork for future ESA programmes. As ESA engineer Denis Estublier explains, "SMART-1 will provide answers to technological questions that affect the whole sector. It will demonstrate the use and the lifetime in space of electric thrusters; the ground control of a quasi-continuously thrusting satellite, the performance of the solar panels in the radiation belts; the interactions of the ion beam with the spacecraft surface and instruments." Many kinds of spacecraft, including commercial telecommunication satellites, will benefit from such technology. Ion engines will find an immediate application in future ESA scientific missions to distant destinations that could not be reached otherwise, as conventional chemical-propulsion spacecraft could not carry the required payload mass. Other scientific missions will have to rely completely on the accurate spacecraft control provided by the very gentle thrust of the ion engines. SMART-1’s journey starts on Saturday 27 September at 08.02 p.m. local time in Kourou (Sunday 28 September at 01:02 a.m. CEST) with a launch an Ariane 5 rocket from the European launch base in Kourou, French Guiana. The trip itself will be part of the adventure, with the engineers checking on the performance of the new technology. But for the scientifically curious the real thrill will begin in December 2004, when SMART-1 reaches the Moon

  7. Contemporary state of spacecraft/environment interaction research

    CERN Document Server

    Novikov, L S

    1999-01-01

    Various space environment effects on spacecraft materials and equipment, and the reverse effects of spacecrafts and rockets on space environment are considered. The necessity of permanent updating and perfection of our knowledge on spacecraft/environment interaction processes is noted. Requirements imposed on models of space environment in theoretical and experimental researches of various aspects of the spacecraft/environment interaction problem are formulated. In this field, main problems which need to be solved today and in the nearest future are specified. The conclusion is made that the joint analysis of both aspects of spacecraft/environment interaction problem promotes the most effective solution of the problem.

  8. Spacecraft Charging: Hazard Causes, Hazard Effects, Hazard Controls

    Science.gov (United States)

    Koontz, Steve.

    2018-01-01

    Spacecraft flight environments are characterized both by a wide range of space plasma conditions and by ionizing radiation (IR), solar ultraviolet and X-rays, magnetic fields, micrometeoroids, orbital debris, and other environmental factors, all of which can affect spacecraft performance. Dr. Steven Koontz's lecture will provide a solid foundation in the basic engineering physics of spacecraft charging and charging effects that can be applied to solving practical spacecraft and spacesuit engineering design, verification, and operations problems, with an emphasis on spacecraft operations in low-Earth orbit, Earth's magnetosphere, and cis-Lunar space.

  9. Slew Maneuver Control for Spacecraft Equipped with Star Camera and Reaction Wheels

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    2005-01-01

    A configuration consisting of a star camera, four reaction wheels and magnetorquers for momentum unloading has become standard for many spacecraft missions. This popularity has motivated numerous agencies and private companies to initiate work on the design of an imbedded attitude control system...... realized on an integrated circuit. This paper provides an easily implementable control algorithm for this type of configuration. The paper considers two issues: slew maneuver with a feature of avoiding direct exposure of the camera's CCD chip to the Sun %, three-axis attitude control and optimal control...... torque distribution in a reaction wheel assembly. The attitude controller is synthesized applying the energy shaping technique, where the desired potential function is carefully designed using a physical insight into the nature of the problem. The system stability is thoroughly analyzed and the control...

  10. Adaptive super twisting vibration control of a flexible spacecraft with state rate estimation

    Science.gov (United States)

    Malekzadeh, Maryam; Karimpour, Hossein

    2018-05-01

    The robust attitude and vibration control of a flexible spacecraft trying to perform accurate maneuvers in spite of various sources of uncertainty is addressed here. Difficulties for achieving precise and stable pointing arise from noisy onboard sensors, parameters indeterminacy, outer disturbances as well as un-modeled or hidden dynamics interactions. Based on high-order sliding-mode methods, the non-minimum phase nature of the problem is dealt with through output redefinition. An adaptive super-twisting algorithm (ASTA) is incorporated with its observer counterpart on the system under consideration to get reliable attitude and vibration control in the presence of sensor noise and momentum coupling. The closed-loop efficiency is verified through simulations under various indeterminate situations and got compared to other methods.

  11. Study to adapt solar electric propulsion to the Pioneer F and G spacecraft

    Science.gov (United States)

    1972-01-01

    The addition of an electric thrust subsystem to the spin-stabilized Pioneer F and G spacecraft to improve performance capability for certain missions is discussed. The evaluation was performed for the Atlas and Titan launch vehicles with Centaur and TE-364-4 stages and for electric thrust stages of 8- and 5-kw with three 30- and five 15-cm thrusters respectively. The combination of a spinning spacecraft with electric propulsion is a concept only recently evaluated and the penalty from spinning over three-axis stabilized is not as significant as might initally be thought. There are major gains in weight, cost, and reliability, the disadvantages being lower data rate during the thrust phase and less efficient pointing. A variety of missions were evaluated from a solar approach mission into 0.14 AU to a flyby mission of Neptune at approximately 30 AU. Performance improvements were present for all missions evaluated.

  12. Electric force on plasma ions and the momentum of the ion-neutrals flow

    Science.gov (United States)

    Makrinich, G.; Fruchtman, A.; Zoler, D.; Boxman, R. L.

    2018-05-01

    The electric force on ions in plasma and the momentum flux carried by the mixed ion-neutral flow were measured and found to be equal. The experiment was performed in a direct-current gas discharge of cylindrical geometry with applied radial electric field and axial magnetic field. The unmagnetized plasma ions, neutralized by magnetized electrons, were accelerated radially outward transferring part of the gained momentum to neutrals. Measurements were taken for various argon gas flow rates between 13 and 100 Standard Cubic Centimeter per Minute, for a discharge current of 1.9 A and a magnetic field intensity of 136 G. The plasma density, electron temperature, and plasma potential were measured at various locations along the flow. These measurements were used to determine the local electric force on the ions. The total electric force on the plasma ions was then determined by integrating radially the local electric force. In parallel, the momentum flux of the mixed ion-neutral flow was determined by measuring the force exerted by the flow on a balance force meter (BFM). The maximal plasma density was between 6 × 1010 cm-3 and 5 × 1011 cm-3, the maximal electron temperature was between 8 eV and 25 eV, and the deduced maximal electric field was between 2200 V/m and 5800 V/m. The force exerted by the mixed ion-neutral flow on the BFM agreed with the total electric force on the plasma ions. This agreement showed that it is the electric force on the plasma ions that is the source of the momentum acquired by the mixed ion-neutral flow.

  13. Angular momentum branching ratios for electron-induced ionization: Atomic and model calculations

    International Nuclear Information System (INIS)

    Mehl, M.J.; Einstein, T.L.

    1987-01-01

    We present calculations of the matrix elements for electron-induced ionization of core electrons of atoms. We use both self-consistent atomic potentials for accuracy and model potentials to gain physical insight. We pay particular attention to the angular momentum distribution of the two final-state electrons, especially when one of them lies near what would be the Fermi energy in a solid (i.e., as in an absorption fine-structure experiment). For nodeless core wave functions, in the dominant channel both final-state electrons have angular momentum one greater than that of the initial core state. For sufficiently deeply bound states, this first approximate selection rule holds until the incident electron energy exceeds the ionization threshold by at least 500 eV, i.e., over the experimentally relevant range. It is also possible to determine the angular momentum distribution of the final-state electron. The EXAFS-like electron tends to have angular momentum one greater than that of the initial core state, even in some cases where the first approximate selection rule does not hold. (EXAFS is extended x-ray-absorption fine structure.) The strongest trend is that the dipole component in a partial-wave expansion of the Coulomb interaction dominates the matrix element. In these studies, careful treatment of not just the core state but also the unbound states is crucial; we show that the conventional orthogonalized plane-wave approximation is inadequate, giving incorrect ordering of the channels. For model potentials with an adjustable screening length, low-lying bound resonances are found to play an important role

  14. Effects of trees on momentum exchange within and above a real urban environment

    Science.gov (United States)

    Salesky, S.; Giometto, M. G.; Christen, A.; Egli, P. E.; Schmid, M. F.; Tooke, T. R.; Coops, N. C.; Parlange, M. B.

    2017-12-01

    Large-eddy simulations (LES) are used to gain insight into the effects of trees on momentum transfer rates characterizing the atmosphere within and above a real urban canopy. Several areas are considered that are part of a neighbourhood in the city of Vancouver, BC, Canada where a small fraction of trees are taller than buildings. In this area, eight years of continuous wind and turbulence measurements are available from a 30 m meteorological tower. Buildings and vegetation geometries are obtained from airborne light detection and ranging (LiDAR) data. In the LES algorithm, buildings are accounted through an immersed boundary method, whereas vegetation is parameterized via a location-specific leaf area density. LES are performed varying wind direction and leaf area densities. Surface roughness lengths (z0) from both LES and tower measurements are sensitive to the 0 ≤ LAI/λ lower than the 27% increase featured by LES for the most representative canopy (leaves-off LAI/λ = 0.74, leaves-on LAI/λ = 2.24). Removing vegetation from such a canopy would cause a dramatic drop of approximately 50% in z0 when compared to the reference summer value. The momentum displacement height (d) from LES also consistently increases as LAI/λ increases, due to the disproportionate amount of drag that the (few) relatively taller trees exert on the flow. Within the urban canopy, the effects of trees are twofold: on one hand, they act as a direct momentum sink for the mean flow; on the other, they reduce downward turbulent transport of high-momentum fluid, significantly reducing the wind intensity at the heights where people live and buildings consume energy.

  15. SHARP - Automated monitoring of spacecraft health and status

    Science.gov (United States)

    Atkinson, David J.; James, Mark L.; Martin, R. G.

    1990-01-01

    Briefly discussed here are the spacecraft and ground systems monitoring process at the Jet Propulsion Laboratory (JPL). Some of the difficulties associated with the existing technology used in mission operations are highlighted. A new automated system based on artificial intelligence technology is described which seeks to overcome many of these limitations. The system, called the Spacecraft Health Automated Reasoning Prototype (SHARP), is designed to automate health and status analysis for multi-mission spacecraft and ground data systems operations. The system has proved to be effective for detecting and analyzing potential spacecraft and ground systems problems by performing real-time analysis of spacecraft and ground data systems engineering telemetry. Telecommunications link analysis of the Voyager 2 spacecraft was the initial focus for evaluation of the system in real-time operations during the Voyager spacecraft encounter with Neptune in August 1989.

  16. SHARP: Automated monitoring of spacecraft health and status

    Science.gov (United States)

    Atkinson, David J.; James, Mark L.; Martin, R. Gaius

    1991-01-01

    Briefly discussed here are the spacecraft and ground systems monitoring process at the Jet Propulsion Laboratory (JPL). Some of the difficulties associated with the existing technology used in mission operations are highlighted. A new automated system based on artificial intelligence technology is described which seeks to overcome many of these limitations. The system, called the Spacecraft Health Automated Reasoning Prototype (SHARP), is designed to automate health and status analysis for multi-mission spacecraft and ground data systems operations. The system has proved to be effective for detecting and analyzing potential spacecraft and ground systems problems by performing real-time analysis of spacecraft and ground data systems engineering telemetry. Telecommunications link analysis of the Voyager 2 spacecraft was the initial focus for evaluation of the system in real-time operations during the Voyager spacecraft encounter with Neptune in August 1989.

  17. Research-Based Monitoring, Prediction, and Analysis Tools of the Spacecraft Charging Environment for Spacecraft Users

    Science.gov (United States)

    Zheng, Yihua; Kuznetsova, Maria M.; Pulkkinen, Antti A.; Maddox, Marlo M.; Mays, Mona Leila

    2015-01-01

    The Space Weather Research Center (http://swrc. gsfc.nasa.gov) at NASA Goddard, part of the Community Coordinated Modeling Center (http://ccmc.gsfc.nasa.gov), is committed to providing research-based forecasts and notifications to address NASA's space weather needs, in addition to its critical role in space weather education. It provides a host of services including spacecraft anomaly resolution, historical impact analysis, real-time monitoring and forecasting, tailored space weather alerts and products, and weekly summaries and reports. In this paper, we focus on how (near) real-time data (both in space and on ground), in combination with modeling capabilities and an innovative dissemination system called the integrated Space Weather Analysis system (http://iswa.gsfc.nasa.gov), enable monitoring, analyzing, and predicting the spacecraft charging environment for spacecraft users. Relevant tools and resources are discussed.

  18. Optomechanical transistor with mechanical gain

    Science.gov (United States)

    Zhang, X. Z.; Tian, Lin; Li, Yong

    2018-04-01

    We study an optomechanical transistor, where an input field can be transferred and amplified unidirectionally in a cyclic three-mode optomechanical system. In this system, the mechanical resonator is coupled simultaneously to two cavity modes. We show that it only requires a finite mechanical gain to achieve the nonreciprocal amplification. Here the nonreciprocity is caused by the phase difference between the linearized optomechanical couplings that breaks the time-reversal symmetry of this system. The amplification arises from the mechanical gain, which provides an effective phonon bath that pumps the mechanical mode coherently. This effect is analogous to the stimulated emission of atoms, where the probe field can be amplified when its frequency is in resonance with that of the anti-Stokes transition. We show that by choosing optimal parameters, this optomechanical transistor can reach perfect unidirectionality accompanied with strong amplification. In addition, the presence of the mechanical gain can result in ultralong delay in the phase of the probe field, which provides an alternative to controlling light transport in optomechanical systems.

  19. Cluster PEACE observations of electrons of spacecraft origin

    Directory of Open Access Journals (Sweden)

    S. Szita

    2001-09-01

    Full Text Available The two PEACE (Plasma Electron And Current Experiment sensors on board each Cluster spacecraft sample the electron velocity distribution across the full 4 solid angle and the energy range 0.7 eV to 26 keV with a time resolution of 4 s. We present high energy and angular resolution 3D observations of electrons of spacecraft origin in the various environments encountered by the Cluster constellation, including a lunar eclipse interval where the spacecraft potential was reduced but remained positive, and periods of ASPOC (Active Spacecraft POtential Control operation which reduced the spacecraft potential. We demonstrate how the spacecraft potential may be found from a gradient change in the PEACE low energy spectrum, and show how the observed spacecraft electrons are confined by the spacecraft potential. We identify an intense component of the spacecraft electrons with energies equivalent to the spacecraft potential, the arrival direction of which is seen to change when ASPOC is switched on. Another spacecraft electron component, observed in the sunward direction, is reduced in the eclipse but unaffected by ASPOC, and we believe this component is produced in the analyser by solar UV. We find that PEACE anodes with a look direction along the spacecraft surfaces are more susceptible to spacecraft electron contamination than those which look perpendicular to the surface, which justifies the decision to mount PEACE with its field-of-view radially outward rather than tangentially.Key words. Magnetosheric physics (general or miscellaneous Space plasma physics (spacecraft sheaths, wakes, charging

  20. Correction of the deterministic part of space–charge interaction in momentum microscopy of charged particles

    Energy Technology Data Exchange (ETDEWEB)

    Schönhense, G., E-mail: schoenhense@uni-mainz.de [Institut für Physik, Johannes Gutenberg-Universität, 55128 Mainz (Germany); Medjanik, K. [Institut für Physik, Johannes Gutenberg-Universität, 55128 Mainz (Germany); Tusche, C. [Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle (Germany); Loos, M. de; Geer, B. van der [Pulsar Physics, Burghstraat 47, 5614 BC Eindhoven (Netherlands); Scholz, M.; Hieke, F.; Gerken, N. [Physics Department and Center for Free-Electron Laser Science, Univ. Hamburg, 22761 Hamburg (Germany); Kirschner, J. [Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle (Germany); Wurth, W. [Physics Department and Center for Free-Electron Laser Science, Univ. Hamburg, 22761 Hamburg (Germany); DESY Photon Science, 22607 Hamburg (Germany)

    2015-12-15

    Ultrahigh spectral brightness femtosecond XUV and X-ray sources like free electron lasers (FEL) and table-top high harmonics sources (HHG) offer fascinating experimental possibilities for analysis of transient states and ultrafast electron dynamics. For electron spectroscopy experiments using illumination from such sources, the ultrashort high-charge electron bunches experience strong space–charge interactions. The Coulomb interactions between emitted electrons results in large energy shifts and severe broadening of photoemission signals. We propose a method for a substantial reduction of the effect by exploiting the deterministic nature of space–charge interaction. The interaction of a given electron with the average charge density of all surrounding electrons leads to a rotation of the electron distribution in 6D phase space. Momentum microscopy gives direct access to the three momentum coordinates, opening a path for a correction of an essential part of space–charge interaction. In a first experiment with a time-of-flight momentum microscope using synchrotron radiation at BESSY, the rotation in phase space became directly visible. In a separate experiment conducted at FLASH (DESY), the energy shift and broadening of the photoemission signals were quantified. Finally, simulations of a realistic photoemission experiment including space–charge interaction reveals that a gain of an order of magnitude in resolution is possible using the correction technique presented here. - Highlights: • Photoemission spectromicroscopy with high-brightness pulsed sources is examined. • Deterministic interaction of an electron with the average charge density can be corrected. • Requires a cathode-lens type microscope optimized for best k-resolution in reciprocal plane. • Extractor field effectively separates pencil beam of secondary electrons from true signal. • Simulations reveal one order of magnitude gain in resolution.

  1. Linear momentum, angular momentum and energy in the linear collision between two balls

    Science.gov (United States)

    Hanisch, C.; Hofmann, F.; Ziese, M.

    2018-01-01

    In an experiment of the basic physics laboratory, kinematical motion processes were analysed. The motion was recorded with a standard video camera having frame rates from 30 to 240 fps the videos were processed using video analysis software. Video detection was used to analyse the symmetric one-dimensional collision between two balls. Conservation of linear and angular momentum lead to a crossover from rolling to sliding directly after the collision. By variation of the rolling radius the system could be tuned from a regime in which the balls move away from each other after the collision to a situation in which they re-collide.

  2. Electromagnetic Dissociation and Spacecraft Electronics Damage

    Science.gov (United States)

    Norbury, John W.

    2016-01-01

    When protons or heavy ions from galactic cosmic rays (GCR) or solar particle events (SPE) interact with target nuclei in spacecraft, there can be two different types of interactions. The more familiar strong nuclear interaction often dominates and is responsible for nuclear fragmentation in either the GCR or SPE projectile nucleus or the spacecraft target nucleus. (Of course, the proton does not break up, except possibly to produce pions or other hadrons.) The less familiar, second type of interaction is due to the very strong electromagnetic fields that exist when two charged nuclei pass very close to each other. This process is called electromagnetic dissociation (EMD) and primarily results in the emission of neutrons, protons and light ions (isotopes of hydrogen and helium). The cross section for particle production is approximately defined as the number of particles produced in nucleus-nucleus collisions or other types of reactions. (There are various kinematic and other factors which multiply the particle number to arrive at the cross section.) Strong, nuclear interactions usually dominate the nuclear reactions of most interest that occur between GCR and target nuclei. However, for heavy nuclei (near Fe and beyond) at high energy the EMD cross section can be much larger than the strong nuclear interaction cross section. This paper poses a question: Are there projectile or target nuclei combinations in the interaction of GCR or SPE where the EMD reaction cross section plays a dominant role? If the answer is affirmative, then EMD mechanisms should be an integral part of codes that are used to predict damage to spacecraft electronics. The question can become more fine-tuned and one can ask about total reaction cross sections as compared to double differential cross sections. These issues will be addressed in the present paper.

  3. Spacecraft fabrication and test MODIL. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Saito, T.T.

    1994-05-01

    This report covers the period from October 1992 through the close of the project. FY 92 closed out with the successful briefing to industry and with many potential and important initiatives in the spacecraft arena. Due to the funding uncertainties, we were directed to proceed as if our funding would be approximately the same as FY 92 ($2M), but not to make any major new commitments. However, the MODIL`s FY 93 funding was reduced to $810K and we were directed to concentrate on the cryocooler area. The cryocooler effort completed its demonstration project. The final meetings with the cryocooler fabricators were very encouraging as we witnessed the enthusiastic reception of technology to help them reduce fabrication uncertainties. Support of the USAF Phillips Laboratory cryocooler program was continued including kick-off meetings for the Prototype Spacecraft Cryocooler (PSC). Under Phillips Laboratory support, Gill Cruz visited British Aerospace and Lucas Aerospace in the United Kingdom to assess their manufacturing capabilities. In the Automated Spacecraft & Assembly Project (ASAP), contracts were pursued for the analysis by four Brilliant Eyes prime contractors to provide a proprietary snap shot of their current status of Integrated Product Development. In the materials and structure thrust the final analysis was completed of the samples made under the contract (``Partial Automation of Matched Metal Net Shape Molding of Continuous Fiber Composites``) to SPARTA. The Precision Technologies thrust funded the Jet Propulsion Laboratory to prepare a plan to develop a Computer Aided Alignment capability to significantly reduce the time for alignment and even possibly provide real time and remote alignment capability of systems in flight.

  4. Spacecraft computer technology at Southwest Research Institute

    Science.gov (United States)

    Shirley, D. J.

    1993-01-01

    Southwest Research Institute (SwRI) has developed and delivered spacecraft computers for a number of different near-Earth-orbit spacecraft including shuttle experiments and SDIO free-flyer experiments. We describe the evolution of the basic SwRI spacecraft computer design from those weighing in at 20 to 25 lb and using 20 to 30 W to newer models weighing less than 5 lb and using only about 5 W, yet delivering twice the processing throughput. Because of their reduced size, weight, and power, these newer designs are especially applicable to planetary instrument requirements. The basis of our design evolution has been the availability of more powerful processor chip sets and the development of higher density packaging technology, coupled with more aggressive design strategies in incorporating high-density FPGA technology and use of high-density memory chips. In addition to reductions in size, weight, and power, the newer designs also address the necessity of survival in the harsh radiation environment of space. Spurred by participation in such programs as MSTI, LACE, RME, Delta 181, Delta Star, and RADARSAT, our designs have evolved in response to program demands to be small, low-powered units, radiation tolerant enough to be suitable for both Earth-orbit microsats and for planetary instruments. Present designs already include MIL-STD-1750 and Multi-Chip Module (MCM) technology with near-term plans to include RISC processors and higher-density MCM's. Long term plans include development of whole-core processors on one or two MCM's.

  5. Soyuz Spacecraft Transported to Launch Pad

    Science.gov (United States)

    2003-01-01

    The Soyuz TMA-3 spacecraft and its booster rocket (rear view) is shown on a rail car for transport to the launch pad where it was raised to a vertical launch position at the Baikonur Cosmodrome, Kazakhstan on October 16, 2003. Liftoff occurred on October 18th, transporting a three man crew to the International Space Station (ISS). Aboard were Michael Foale, Expedition-8 Commander and NASA science officer; Alexander Kaleri, Soyuz Commander and flight engineer, both members of the Expedition-8 crew; and European Space agency (ESA) Astronaut Pedro Duque of Spain. Photo Credit: 'NASA/Bill Ingalls'

  6. Effects of Spacecraft Landings on the Moon

    Science.gov (United States)

    Metzger, Philip T.; Lane, John E.

    2013-01-01

    The rocket exhaust of spacecraft landing on the Moon causes a number of observable effects that need to be quantified, including: disturbance of the regolith and volatiles at the landing site; damage to surrounding hardware such as the historic Apollo sites through the impingement of high-velocity ejecta; and levitation of dust after engine cutoff through as-yet unconfirmed mechanisms. While often harmful, these effects also beneficially provide insight into lunar geology and physics. Some of the research results from the past 10 years is summarized and reviewed here.

  7. Fault Detection and Isolation for Spacecraft

    DEFF Research Database (Denmark)

    Jensen, Hans-Christian Becker; Wisniewski, Rafal

    2002-01-01

    This article realizes nonlinear Fault Detection and Isolation for actuators, given there is no measurement of the states in the actuators. The Fault Detection and Isolation of the actuators is instead based on angular velocity measurement of the spacecraft and knowledge about the dynamics...... of the satellite. The algorithms presented in this paper are based on a geometric approach to achieve nonlinear Fault Detection and Isolation. The proposed algorithms are tested in a simulation study and the pros and cons of the algorithms are discussed....

  8. Aircraft, ships, spacecraft, nuclear plants and quality

    International Nuclear Information System (INIS)

    Patrick, M.G.

    1984-05-01

    A few quality assurance programs outside the purview of the Nuclear Regulatory Commission were studied to identify features or practices which the NRC could use to enhance its program for assuring quality in the design and construction of nuclear power plants. The programs selected were: the manufacture of large commercial transport aircraft, regulated by the Federal Aviation Administration; US Navy shipbuilding; commercial shipbuilding regulated by the Maritime Administration and the US Coast Guard; Government-owned nuclear plants under the Department of Energy; spacecraft under the National Aeronautics and Space Administration; and the construction of nuclear power plants in Canada, West Germany, France, Japan, Sweden, and the United Kingdom

  9. SSS-A spacecraft and experiment description.

    Science.gov (United States)

    Longanecker, G. W.; Hoffman, R. A.

    1973-01-01

    The scientific objectives of the Explorer-45 mission are discussed. The primary objective is the study of the ring current responsible for the main phase of magnetic storms. Closely associated with this objective is the determination of the relationship between magnetic storms, substorms, and the acceleration of charged particles in the magnetosphere. Further objectives are the measurement of a wide range of proton, electron and alpha-particle energies, and studies of wave-particle interactions responsible for particle transport and loss in the inner magnetosphere. The orbital parameters, the spacecraft itself, and some of its unique features, such as the data handling system, which is programmable from the ground, are described.

  10. Scaling function, spectral function and nucleon momentum distribution in nuclei

    International Nuclear Information System (INIS)

    Antonov, A.N.; Ivanov, M.V.; Caballero, J.A.; Barbaro, M.B.; Udias, J.M.; Moya de Guerra, E.; Donnelly, T.W.

    2010-01-01

    The aim of the study is to find a good simultaneous description of the spectral function and the momentum distribution in relation to the realistic scaling function obtained from inclusive electron-nuclei scattering experiments. We start with a modified Hartree-Fock spectral function in which the energy dependent part (δ-function) is replaced by the Gaussian distributions with hole state widths as free parameters. We calculate the scaling function and the nucleon momentum distribution on the basis of the spectral function constructed in this way, trying to find a good description of the experimental data. The obtained scaling function has a weak asymmetry and the momentum distribution has not got a high-momentum tail in the case when harmonic-oscillator single-particle wave functions are used. So, to improve the behavior of the momentum distribution we used the basis of natural orbitals (NO) in which short-range correlations are partly incorporated. The results for the scaling function show again a weak asymmetry, but in this case the momentum distribution has a high-momentum tail. As a next step we include final-state interactions (FSI) in the calculations to reproduce the experimentally observed asymmetry of the scaling function. (author)

  11. Spacecraft intercept guidance using zero effort miss steering

    Science.gov (United States)

    Newman, Brett

    The suitability of proportional navigation, or an equivalent zero effort miss formulation, for spacecraft intercepts during midcourse guidance, followed by a ballistic coast to the endgame, is addressed. The problem is formulated in terms of relative motion in a general 3D framework. The proposed guidance law for the commanded thrust vector orientation consists of the sum of two terms: (1) along the line of sight unit direction and (2) along the zero effort miss component perpendicular to the line of sight and proportional to the miss itself and a guidance gain. If the guidance law is to be suitable for longer range targeting applications with significant ballistic coasting after burnout, determination of the zero effort miss must account for the different gravitational accelerations experienced by each vehicle. The proposed miss determination techniques employ approximations for the true differential gravity effect. Theoretical results are applied to a numerical engagement scenario and the resulting performance is evaluated in terms of the miss distances determined from nonlinear simulation.

  12. Spacecraft contamination programs within the Air Force Systems Command Laboratories

    Science.gov (United States)

    Murad, Edmond

    1990-01-01

    Spacecraft contamination programs exist in five independent AFSC organizations: Geophysics Laboratory (GL), Arnold Engineering and Development Center (AEDC), Rome Air Development Center (RADC/OSCE), Wright Research and Development Center (MLBT), Armament Laboratory (ATL/SAI), and Space Systems Division (SSD/OL-AW). In addition, a sizable program exists at Aerospace Corp. These programs are complementary, each effort addressing a specific area of expertise: GL's effort is aimed at addressing the effects of on-orbit contamination; AEDC's effort is aimed at ground simulation and measurement of optical contamination; RADC's effort addresses the accumulation, measurement, and removal of contamination on large optics; MLBT's effort is aimed at understanding the effect of contamination on materials; ATL's effort is aimed at understanding the effect of plume contamination on systems; SSD's effort is confined to the integration of some contamination experiments sponsored by SSD/CLT; and Aerospace Corp.'s effort is aimed at supporting the needs of the using System Program Offices (SPO) in specific areas, such as contamination during ground handling, ascent phase, laboratory measurements aimed at understanding on-orbit contamination, and mass loss and mass gain in on-orbit operations. These programs are described in some detail, with emphasis on GL's program.

  13. A condensed matter electron momentum spectrometer with parallel detection in energy and momentum

    Energy Technology Data Exchange (ETDEWEB)

    Storer, P; Caprari, R S; Clark, S A.C.; Vos, M; Weigold, E

    1994-03-01

    An electron momentum spectrometer has been constructed which measures electron binding energies and momenta by fully determining the kinematics of the incident, scattered and ejected electrons resulting from (e,2e) ionizing collisions in a thin solid foil. The spectrometer operates with incident beam energies of 20-30 keV in an asymmetric, non-coplanar scattering geometry. Bethe ridge kinematics are used. The technique uses transmission through the target foil, but it is most sensitive to the surface from which the 1.2 keV electrons emerge, to a depth of about 5 nm. Scattered and ejected electron energies and azimuthal angles are detected in parallel using position sensitive detection, yielding true coincidence count rates of 6 Hz from a 5.5 nm thick evaporated carbon target and an incident beam current of around 100 nA. The energy resolution is approximately 1.3 eV and momentum resolution approximately 0.15 a{sub 0}{sup -1}. The energy resolution could readily be improved by monochromating the incident electron beam. 28 refs., 15 figs.

  14. A condensed matter electron momentum spectrometer with parallel detection in energy and momentum

    International Nuclear Information System (INIS)

    Storer, P.; Caprari, R.S.; Clark, S.A.C.; Vos, M.; Weigold, E.

    1994-03-01

    An electron momentum spectrometer has been constructed which measures electron binding energies and momenta by fully determining the kinematics of the incident, scattered and ejected electrons resulting from (e,2e) ionizing collisions in a thin solid foil. The spectrometer operates with incident beam energies of 20-30 keV in an asymmetric, non-coplanar scattering geometry. Bethe ridge kinematics are used. The technique uses transmission through the target foil, but it is most sensitive to the surface from which the 1.2 keV electrons emerge, to a depth of about 5 nm. Scattered and ejected electron energies and azimuthal angles are detected in parallel using position sensitive detection, yielding true coincidence count rates of 6 Hz from a 5.5 nm thick evaporated carbon target and an incident beam current of around 100 nA. The energy resolution is approximately 1.3 eV and momentum resolution approximately 0.15 a 0 -1 . The energy resolution could readily be improved by monochromating the incident electron beam. 28 refs., 15 figs

  15. Enhanced Portfolio Performance Using a Momentum Approach to Annual Rebalancing

    Directory of Open Access Journals (Sweden)

    Michael D. Mattei

    2018-02-01

    Full Text Available After diversification, periodic portfolio rebalancing has become one of the most widely practiced methods for reducing portfolio risk and enhancing returns. Most of the rebalancing strategies found in the literature are generally regarded as contrarian approaches to rebalancing. A recent article proposed a rebalancing approach that incorporates a momentum approach to rebalancing. The momentum approach had a better risk adjusted return than either the traditional approach or a Buy-and-Hold approach. This article identifies an improvement to the momentum approach and then examines the impact of transactions costs and taxes on the portfolio performance of four active rebalancing approaches.

  16. Momentum integral network method for thermal-hydraulic transient analysis

    International Nuclear Information System (INIS)

    Van Tuyle, G.J.

    1983-01-01

    A new momentum integral network method has been developed, and tested in the MINET computer code. The method was developed in order to facilitate the transient analysis of complex fluid flow and heat transfer networks, such as those found in the balance of plant of power generating facilities. The method employed in the MINET code is a major extension of a momentum integral method reported by Meyer. Meyer integrated the momentum equation over several linked nodes, called a segment, and used a segment average pressure, evaluated from the pressures at both ends. Nodal mass and energy conservation determined nodal flows and enthalpies, accounting for fluid compression and thermal expansion

  17. Transverse momentum in semi-inclusive deep inelastic scattering

    International Nuclear Information System (INIS)

    Ceccopieri, Federico Alberto; Trentadue, Luca

    2006-01-01

    Within the framework of perturbative quantum chromodynamics we derive the evolution equations for transverse momentum dependent distributions and apply them to the case of semi-inclusive deep inelastic scattering. The evolution equations encode the perturbative component of transverse momentum generated by collinear parton branchings. The current fragmentation is described via transverse momentum dependent parton densities and fragmentation functions. Target fragmentation instead is described via fracture functions. We present, to leading logarithmic accuracy, the corresponding semi-inclusive deep inelastic scattering cross-section, which applies to the entire phase space of the detected hadron. Some phenomenological implications and further developments are briefly outlined

  18. Electron momentum spectroscopy of the core state of solid carbon

    International Nuclear Information System (INIS)

    Caprari, R.S.; Clark, S.A.C.; McCarthy, I.E.; Storer, P.J.; Vos, M.; Weigold, E.

    1994-08-01

    Electron momentum spectroscopy (binary encounter (e,2e)) experimental results are presented for the core state of an amorphous carbon allotrope. The (e,2e) cross section has two identifiable regions. One is a narrow energy width 'core band peak' that does not disperse with momentum. At higher binding energies there is an energy diffuse 'multiple scattering continuum', which is a consequence of (e,2e) collisions with core electrons that are accompanied by inelastic scattering of one or more of the incoming or outgoing electrons. Comparisons of experimental momentum distributions with the Hartree-Fock atomic carbon ls orbital are presented for both regions. 16 refs., 4 figs

  19. Evidence of Inward Toroidal Momentum Convection in the JET Tokamak

    DEFF Research Database (Denmark)

    Tala, T.; Zastrow, K.-D.; Ferreira, J.

    2009-01-01

    Experiments have been carried out on the Joint European Torus tokamak to determine the diffusive and convective momentum transport. Torque, injected by neutral beams, was modulated to create a periodic perturbation in the toroidal rotation velocity. Novel transport analysis shows the magnitude...... and profile shape of the momentum diffusivity are similar to those of the ion heat diffusivity. A significant inward momentum pinch, up to 20 m/s, has been found. Both results are consistent with gyrokinetic simulations. This evidence is complemented in plasmas with internal transport barriers....

  20. GAIN Technology Workshops Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Braase, Lori Ann [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-08-01

    National and global demand for nuclear energy is increasing and United States (U.S.) global leadership is eroding. There is a sense of urgency with respect to the deployment of the innovative nuclear energy technologies. The Gateway for Accelerated Innovation in Nuclear (GAIN) initiative is based on the simultaneous achievement of three strategic goals. The first is maintaining global technology leadership within the U.S. Department of Energy (DOE). The second is enabling global industrial leadership for nuclear vendors and suppliers. The third is focused on utility optimization of nuclear energy within the clean energy portfolio. An effective public-private partnership is required to achieve these goals. DOEs recognizes the recent sense of urgency new developers and investors have in getting their concepts to market. They know that time to market for nuclear technology takes too long and the facilities needed to conduct the necessary research, development and demonstration (RD&D) activities are very expensive to develop and maintain. Early technologies, in the lower technology readiness levels (TRL) need materials testing, analysis, modeling, code development, etc., most of which currently exists in the DOE national laboratory system. However, mature technologies typically need large component testing and demonstration facilities, which are expensive and long-lead efforts. By understanding the needs of advanced nuclear technology developers, GAIN will connect DOE national laboratory capabilities (e.g., facilities, expertise, materials, and data) with industry RD&D needs. In addition, GAIN is working with the Nuclear Regulatory Commission (NRC) to streamline processes and increase understanding of the licensing requirements for advanced reactors.