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Sample records for earth-like tidally locked

  1. Atmospheric dynamics of Earth-like tidally locked aquaplanets

    CERN Document Server

    Merlis, Timothy M

    2010-01-01

    We present simulations of atmospheres of Earth-like aquaplanets that are tidally locked to their star, that is, planets whose orbital period is equal to the rotation period about their spin axis, so that one side always faces the star and the other side is always dark. As extreme cases illustrating the effects of slow and rapid rotation, we consider planets with rotation periods equal to one current Earth year and one current Earth day. The dynamics responsible for the surface climate (e.g., winds, temperature, precipitation) and the general circulation of the atmosphere are discussed in light of existing theories of atmospheric circulations. For example, as expected from the increasing importance of Coriolis accelerations relative to inertial accelerations as the rotation rate increases, the winds are approximately isotropic and divergent at leading order in the slowly rotating atmosphere but are predominantly zonal and rotational in the rapidly rotating atmosphere. Free-atmospheric horizontal temperature va...

  2. Atmospheric dynamics of Earth-like tidally locked aquaplanets

    Directory of Open Access Journals (Sweden)

    Tapio Schneider

    2010-12-01

    Full Text Available We present simulations of atmospheres of Earth-like aquaplanets that are tidally locked to their star, that is, planets whose orbital period is equal to the rotation period about their spin axis, so that one side always faces the star and the other side is always dark. Such simulations are of interest in the study of tidally locked terrestrial exoplanets and as illustrations of how planetary rotation and the insolation distribution shape climate. As extreme cases illustrating the effects of slow and rapid rotation, we consider planets with rotation periods equal to one current Earth year and one current Earth day. The dynamics responsible for the surface climate (e.g., winds, temperature, precipitation and the general circulation of the atmosphere are discussed in light of existing theories of atmospheric circulations. For example, as expected from the increasing importance of Coriolis accelerations relative to inertial accelerations as the rotation rate increases, the winds are approximately isotropic and divergent at leading order in the slowly rotating atmosphere but are predominantly zonal and rotational in the rapidly rotating atmosphere. Free-atmospheric horizontal temperature variations in the slowly rotating atmosphere are generally weaker than in the rapidly rotating atmosphere. Interestingly, the surface temperature on the night side of the planets does not fall below ~240 K in either the rapidly or slowly rotating atmosphere; that is, heat transport from the day side to the night side of the planets efficiently reduces temperature contrasts in either case. Rotational waves and eddies shape the distribution of winds, temperature, and precipitation in the rapidly rotating atmosphere; in the slowly rotating atmosphere, these distributions are controlled by simpler divergent circulations. Both the slowly and rapidly rotating atmospheres exhibit equatorial superrotation. Systematic variation of the planetary rotation rate shows that the

  3. Characterising the three-dimensional ozone distribution of a tidally locked Earth-like planet

    Science.gov (United States)

    Proedrou, Elisavet; Hocke, Klemens

    2016-06-01

    We simulate the 3D ozone distribution of a tidally locked Earth-like exoplanet using the high-resolution, 3D chemistry-climate model CESM1(WACCM) and study how the ozone layer of a tidally locked Earth (TLE) (Ω _{TLE}= 1/365 days) differs from that of our present-day Earth (PDE) (Ω _{PDE}= 1/1 day). The middle atmosphere reaches a steady state asymptotically within the first 80 days of the simulation. An upwelling, centred on the subsolar point, is present on the day side while a downwelling, centred on the antisolar point, is present on the night side. In the mesosphere, we find similar global ozone distributions for the TLE and the PDE, with decreased ozone on the day side and enhanced ozone on the night side. In the lower mesosphere, a jet stream transitions into a large-scale vortex around a low-pressure system, located at low latitudes of the TLE night side. In the middle stratosphere, the concentration of odd oxygen is approximately equal to that of the ozone [({O}x) ≈ ({O}3)]. At these altitudes, the lifetime of odd oxygen is ˜16 h and the transport processes significantly contribute to the global distribution of stratospheric ozone. Compared to the PDE, where the strong Coriolis force acts as a mixing barrier between low and high latitudes, the transport processes of the TLE are governed by jet streams variable in the zonal and meridional directions. In the middle stratosphere of the TLE, we find high ozone values on the day side, due to the increased production of atomic oxygen on the day side, where it immediately recombines with molecular oxygen to form ozone. In contrast, the ozone is depleted on the night side, due to changes in the solar radiation distribution and the presence of a downwelling. As a result of the reduced Coriolis force, the tropical and extratropical air masses are well mixed and the global temperature distribution of the TLE stratosphere has smaller horizontal gradients than the PDE. Compared to the PDE, the total ozone column

  4. The middle atmospheric circulation of a tidally locked Earth-like planet and the role of the sea surface temperature

    Science.gov (United States)

    Proedrou, Elisavet; Hocke, Klemens; Wurz, Peter

    2016-12-01

    We investigate the influence of the sea surface temperature (SST) changes on the middle atmosphere of a tidally locked Earth-like planet orbiting a G star using the coupled 3D chemistry-climate model CESM1(WACCM). We perform three 90 day simulations. The first simulation is a present-day Earth (PDE) simulation, the second is a simulation of a tidally locked Earth-like planet with a tidally locked aquaplanet sea surface temperature (cold TLE (CLTE)) and the third is a hybrid simulation of a tidally locked Earth-like planet with a present-day Earth sea surface temperature (warm TLE (WTLE)). Our results show that changes in the SST have an influence on the lower stratospheric temperature and the secondary ozone layer. Both atmospheres exhibit a dayside upwelling and a nightside downwelling extending from the surface to the mesosphere. They are also characterised by comparable lower and middle stratospheric horizontal winds and relatively different mesospheric horizontal winds. The temperature of the WTLE atmosphere is altered as a result of the SST changes, compared to the CTLE. Specifically, the WTLE lower tropospheric temperature is increased by 3.7 K on average, due to the absorption of the increased upwelling longwave radiation and the increased sensible and latent heat. The WTLE upper troposphere temperature is decreased by 4 K on average, is adiabatic in nature, and is generated by the increased WTLE upwelling. The WLTE lower stratospheric temperature is increased by 3.8 K on average due to the absorption of the increased upwelling longwave radiation. The lower mesospheric temperature is decreased by 1.13 K on average due to increased mesospheric wave breaking. The upper mesospheric temperature is increased by 4.3 K, and its generation mechanism is currently unknown. Furthermore, the secondary ozone volume mixing ratio is increased by 40.5 %. The occurrence of large-scale vortices and variable jet streams depends, to some extent, on the SST distribution.

  5. Assessing the Chemistry of Tidally Locked Earth-like Planets around M-type Stars Using a 3D Coupled Chemistry-Climate Model (CESM/WACCM)

    Science.gov (United States)

    Lanzano, Alexander

    2016-10-01

    Given recent discoveries there is a very real potential for tidally-locked Earth-like planets to exist orbiting M stars. To determine whether these planets may be habitable it is necessary to understand the nature of their atmospheres. In our investigation we simulate the evolution of present-day Earth while placed in tidally-locked orbit (meaning the same side of the planet always faces the star) around an M dwarf star. We are particularly interested in the evolution of the planet's ozone layer and whether it will shield the planet, and therefore life, from harmful radiation.To accomplish the above objectives we use a state-of-the-art 3-D terrestrial model, the Whole Atmosphere Community Climate Model (WACCM), which fully couples chemistry and climate, and therefore allows self-consistent simulations of atmospheric constituents and their effects on a planet's climate, surface radiation and thus habitability. Preliminary results show that this model is stable and that a tidally-locked Earth is protected from harmful UV radiation produced by G stars. The next step shall be to adapt this model for an M star by including its UV and visible spectrum.This investigation will both provide an insight into the potential for habitable exoplanets and further define the nature of the habitable zones for M class stars. We will also be able to narrow the definition of the habitable zones around distant stars, which will help us identify these planets in the future. Furthermore, this project will allow for a more thorough analysis of data from past and future exoplanet observing missions by defining the atmospheric composition of Earth-like planets around a variety of types of stars.

  6. Coupled thermo-orbital evolution of tidally-evolved Earth-like planets

    Science.gov (United States)

    Behounkova, Marie; Walterova, Michaela; Cadek, Ondrej; Tobie, Gabriel; Choblet, Gael

    2016-10-01

    Progress in detection techniques of exoplanets inspired increasing number of studies focused on their internal dynamics and evolution. The detection methods tend to favor the discovery of short-period exoplanets, that are predicted to get rapidly tidally locked. During the locking process planets despin and a significant amount of tidal heating may contribute to the thermal budget of the planet. Moreover, tidally locked exoplanets exhibit large surface temperature contrasts between sub-stellar and anti-stellar sides due to uneven insolation which influence the convection pattern and cooling of the planet. Here, we will present the evolution of tidally locked Earth-like exoplanets using numerical tool Antigone (Behounkova et al., 2010, 2011) coupling long-term internal evolution, tidal dissipation (taking into account Maxwell or Andrade rheology) and uneven insolation pattern. For constant orbital parameters, we will focus on numerical simulation of the heat transfer in exoEarths for various rheological properties of planet and various values of spin-orbit resonance, semi-major axis, eccentricity and luminosity of star. In the case of effective heat transfer, our results suggest that the melting is mainly observed within the upper part of the mantle for tidal heating lower than 100TW . For tidal heating higher than 100TW, the melt is produced also within the deep part of the mantle and degree-2 convection is enhanced due to tidal heating pattern. For large tidal heating (larger than 1000TW), global melting is observed and temperature field is homogenized due to global melting, the heat transfer is mainly due to melt extraction and advection is suppressed. We will further present first results of coupled orbital-internal evolution of planets without companion using numerical model of orbital evolution with realistic (Maxwell or Andrade) rheology (Walterova et al., in prep). We will concentrate on the capture into the spin-orbit resonance. Special attention will be

  7. Climate instability on tidally locked exoplanets

    CERN Document Server

    Kite, Edwin S; Manga, Michael

    2011-01-01

    Feedbacks that can destabilize the climates of synchronously-rotating rocky planets may arise on planets with strong day-night surface temperature contrasts. Earth-like habitable-zone (HZ) planets maintain stable surface liquid water over geological time. This requires equilibrium between the temperature-dependent rate of greenhouse-gas consumption by weathering,and greenhouse-gas resupply by other processes. Detected small-radius exoplanets, and anticipated M-dwarf HZ rocky planets, are expected to be tidally locked. We investigate two feedbacks that can destabilize climate on tidally-locked planets. (1) If small changes in pressure alter the temperature distribution across a planet's surface such that the weathering rate increases when the pressure decreases, a positive feedback occurs involving increasing weathering rate near the substellar point, decreasing pressure, and increasing substellar surface temperature. (2) When decreases in pressure increase the surface area above the melting point (through red...

  8. No Snowball on Habitable Tidally Locked Planets

    Science.gov (United States)

    Checlair, Jade; Menou, Kristen; Abbot, Dorian S.

    2017-08-01

    The TRAPPIST-1, Proxima Centauri, and LHS 1140 systems are the most exciting prospects for future follow-up observations of potentially inhabited planets. All of the planets orbit nearby M-stars and are likely tidally locked in 1:1 spin-orbit states, which motivates the consideration of the effects that tidal locking might have on planetary habitability. On Earth, periods of global glaciation (snowballs) may have been essential for habitability and remote signs of life (biosignatures) because they are correlated with increases in the complexity of life and in the atmospheric oxygen concentration. In this paper, we investigate the snowball bifurcation (sudden onset of global glaciation) on tidally locked planets using both an energy balance model and an intermediate-complexity global climate model. We show that tidally locked planets are unlikely to exhibit a snowball bifurcation as a direct result of the spatial pattern of insolation they receive. Instead, they will smoothly transition from partial to complete ice coverage and back. A major implication of this work is that tidally locked planets with an active carbon cycle should not be found in a snowball state. Moreover, this work implies that tidally locked planets near the outer edge of the habitable zone with low CO2 outgassing fluxes will equilibrate with a small unglaciated substellar region rather than cycling between warm and snowball states. More work is needed to determine how the lack of a snowball bifurcation might affect the development of life on a tidally locked planet.

  9. CLIMATE INSTABILITY ON TIDALLY LOCKED EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Kite, Edwin S.; Manga, Michael [Department of Earth and Planetary Science, University of California at Berkeley, CA 94720 (United States); Gaidos, Eric, E-mail: edwin.kite@gmail.com [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

    2011-12-10

    Feedbacks that can destabilize the climates of synchronously rotating rocky planets may arise on planets with strong day-night surface temperature contrasts. Earth-like habitable planets maintain stable surface liquid water over geologic time. This requires equilibrium between the temperature-dependent rate of greenhouse-gas consumption by weathering, and greenhouse-gas resupply by other processes. Detected small-radius exoplanets, and anticipated M-dwarf habitable-zone rocky planets, are expected to be in synchronous rotation (tidally locked). In this paper, we investigate two hypothetical feedbacks that can destabilize climate on planets in synchronous rotation. (1) If small changes in pressure alter the temperature distribution across a planet's surface such that the weathering rate goes up when the pressure goes down, a runaway positive feedback occurs involving increasing weathering rate near the substellar point, decreasing pressure, and increasing substellar surface temperature. We call this feedback enhanced substellar weathering instability (ESWI). (2) When decreases in pressure increase the fraction of surface area above the melting point (through reduced advective cooling of the substellar point), and the corresponding increase in volume of liquid causes net dissolution of the atmosphere, a further decrease in pressure will occur. This substellar dissolution feedback can also cause a runaway climate shift. We use an idealized energy balance model to map out the conditions under which these instabilities may occur. In this simplified model, the weathering runaway can shrink the habitable zone and cause geologically rapid 10{sup 3}-fold atmospheric pressure shifts within the habitable zone. Mars may have undergone a weathering runaway in the past. Substellar dissolution is usually a negative feedback or weak positive feedback on changes in atmospheric pressure. It can only cause runaway changes for small, deep oceans and highly soluble atmospheric

  10. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions.

    Science.gov (United States)

    Driscoll, P E; Barnes, R

    2015-09-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the "tidal zone," where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life.

  11. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions

    Science.gov (United States)

    Barnes, R.

    2015-01-01

    Abstract The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the “tidal zone,” where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life. Key Words

  12. Tidal heating of Earth-like exoplanets around M stars: Thermal, magnetic, and orbital evolutions

    CERN Document Server

    Driscoll, Peter

    2015-01-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low mass M stars whose radiative habitable zone overlaps with the "tidal zone". We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a visco-elastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within $0.07$ AU circularize before 10 G...

  13. Atmospheric heat redistribution and collapse on tidally locked rocky planets

    CERN Document Server

    Wordsworth, Robin

    2014-01-01

    Atmospheric collapse is likely to be of fundamental importance to tidally locked rocky exoplanets but remains understudied. Here, general results on the heat transport and stability of tidally locked terrestrial-type atmospheres are reported. First, the problem is modeled with an idealized 3D general circulation model (GCM) with gray gas radiative transfer. It is shown that over a wide range of parameters the atmospheric boundary layer, rather than the large-scale circulation, is the key to understanding the planetary energy balance. Through a scaling analysis of the interhemispheric energy transfer, theoretical expressions for the day-night temperature difference and surface wind speed are created that reproduce the GCM results without tuning. Next, the GCM is used with correlated-k radiative transfer to study heat transport for two real gases (CO2 and CO). For CO2, empirical formulae for the collapse pressure as a function of planetary mass and stellar flux are produced, and critical pressures for atmospher...

  14. Connecting the dots II: Phase changes in the climate dynamics of tidally locked terrestrial exoplanets

    CERN Document Server

    Carone, Ludmila; Decin, Leen

    2015-01-01

    We investigate 3D atmosphere dynamics for tidally locked terrestrial planets with an Earth-like atmosphere and irradiation for different rotation periods ($P_{rot}=1-100$ days) and planet sizes ($R_P=1-2 R_{Earth}$) with unprecedented fine detail. We could precisely identify three climate state transition regions that are associated with phase transitions in standing tropical and extra tropical Rossby waves. We confirm that the climate on fast rotating planets may assume multiple states ($P_{rot}\\leq 12$ days for $R_P=2 R_{Earth}$). Our study is, however, the first to identify the type of planetary wave associated with different climate states: The first state is dominated by standing tropical Rossby waves with fast equatorial superrotation. The second state is dominated by standing extra tropical Rossby waves with high latitude westerly jets with slower wind speeds. For very fast rotations ($P_{rot}\\leq 5$~days for $R_P=2 R_{Earth}$), we find another climate state transition, where the standing tropical and ...

  15. Connecting the dots III: Night side cooling and surface friction affect climates of tidally locked terrestrial planets

    CERN Document Server

    Carone, L; Decin, L

    2016-01-01

    We investigate how night side cooling and surface friction impact surface temperatures and large scale circulation for tidally locked Earth-like planets. For each scenario, we vary the orbital period between $P_{rot}=1-100$~days and capture changes in climate states. We find drastic changes in climate states for different surface friction scenarios. For very efficient surface friction ($t_{s,fric}=$ 0.1 days), the simulations for short rotation periods ($P_{rot} \\leq$ 10 days) show predominantly standing extra tropical Rossby waves. These waves lead to climate states with two high latitude westerly jets and unperturbed meridional direct circulation. In most other scenarios, simulations with short rotation periods exhibit instead dominance by standing tropical Rossby waves. Such climate states have a single equatorial westerly jet, which disrupts direct circulation. Experiments with weak surface friction ($t_{s,fric}=~10 -100$ days) show decoupling between surface temperatures and circulation, which leads to s...

  16. Water Trapping on Tidally Locked Terrestrial Planets Requires Special Conditions

    CERN Document Server

    Yang, Jun; Hu, Yongyun; Abbot, Dorian S

    2014-01-01

    Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea-ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, night-side sea ice remains O(10 m) thick and night-side water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's w...

  17. DECIPHERING THERMAL PHASE CURVES OF DRY, TIDALLY LOCKED TERRESTRIAL PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Koll, Daniel D. B.; Abbot, Dorian S., E-mail: dkoll@uchicago.edu [Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States)

    2015-03-20

    Next-generation space telescopes will allow us to characterize terrestrial exoplanets. To do so effectively it will be crucial to make use of all available data. We investigate which atmospheric properties can, and cannot, be inferred from the broadband thermal phase curve of a dry and tidally locked terrestrial planet. First, we use dimensional analysis to show that phase curves are controlled by six nondimensional parameters. Second, we use an idealized general circulation model to explore the relative sensitivity of phase curves to these parameters. We find that the feature of phase curves most sensitive to atmospheric parameters is the peak-to-trough amplitude. Moreover, except for hot and rapidly rotating planets, the phase amplitude is primarily sensitive to only two nondimensional parameters: (1) the ratio of dynamical to radiative timescales and (2) the longwave optical depth at the surface. As an application of this technique, we show how phase curve measurements can be combined with transit or emission spectroscopy to yield a new constraint for the surface pressure and atmospheric mass of terrestrial planets. We estimate that a single broadband phase curve, measured over half an orbit with the James Webb Space Telescope, could meaningfully constrain the atmospheric mass of a nearby super-Earth. Such constraints will be important for studying the atmospheric evolution of terrestrial exoplanets as well as characterizing the surface conditions on potentially habitable planets.

  18. Habitability of Exomoons at the Hill or Tidal Locking Radius

    CERN Document Server

    Hinkel, Natalie R

    2013-01-01

    Moons orbiting extrasolar planets are the next class of object to be observed and characterized for possible habitability. Like the host-planets to their host-star, exomoons have a limiting radius at which they may be gravitationally bound, or the Hill radius. In addition, they also have a distance at which they will become tidally locked and therefore in synchronous rotation with the planet. We have examined the flux phase profile of a simulated, hypothetical moon orbiting at a distant radius around the confirmed exoplanets mu Ara b, HD 28185 b, BD +14 4559 b, and HD 73534 b. The irradiated flux on a moon at it's furthest, stable distance from the planet achieves it's largest flux gradient, which places a limit on the flux ranges expected for subsequent (observed) moons closer in orbit to the planet. We have also analyzed the effect of planetary eccentricity on the flux on the moon, examining planets that traverse the habitable zone either fully or partially during their orbit. Looking solely at the stellar ...

  19. WATER TRAPPING ON TIDALLY LOCKED TERRESTRIAL PLANETS REQUIRES SPECIAL CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jun; Abbot, Dorian S. [Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States); Liu, Yonggang [Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544 (United States); Hu, Yongyun, E-mail: junyang28@uchicago.edu [Laboratory for Climate and Atmosphere-Ocean Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing (China)

    2014-12-01

    Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld, we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, nightside sea ice remains O(10 m) thick and nightside water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete dayside dessiccation. Only planets with a geothermal heat flux lower than Earth's, much of their surface covered by continents, and a surface water reservoir O(10%) of Earth's would be susceptible to complete water trapping.

  20. Connecting the dots - III. Nightside cooling and surface friction affect climates of tidally locked terrestrial planets

    Science.gov (United States)

    Carone, L.; Keppens, R.; Decin, L.

    2016-09-01

    We investigate how nightside cooling and surface friction affect surface temperatures and large-scale circulation for tidally locked Earth-like planets. For each scenario, we vary the orbital period between Prot = 1 and 100 d and capture changes in climate states. We find drastic changes in climate states for different surface friction scenarios. For very efficient surface friction (ts,fric = 0.1 d), the simulations for short rotation periods (Prot ≤ 10 d) show predominantly standing extratropical Rossby waves. These waves lead to climate states with two high-latitude westerly jets and unperturbed meridional direct circulation. In most other scenarios, simulations with short rotation periods exhibit instead dominance by standing tropical Rossby waves. Such climate states have a single equatorial westerly jet, which disrupts direct circulation. Experiments with weak surface friction (ts,fric = 10-100 d) show decoupling between surface temperatures and circulation, which leads to strong cooling of the nightside. The experiment with ts,fric = 100 d assumes climate states with easterly flow (retrograde rotation) for medium and slow planetary rotations Prot = 12-100 d. We show that an increase of nightside cooling efficiency by one order of magnitude compared to the nominal model leads to a cooling of the nightside surface temperatures by 80-100 K. The dayside surface temperatures only drop by 25 K at the same time. The increase in thermal forcing suppresses the formation of extratropical Rossby waves on small planets (RP = 1REarth) in the short rotation period regime (Prot ≤ 10 d).

  1. Resonance locking as the source of rapid tidal migration in the Jupiter and Saturn moon systems

    CERN Document Server

    Fuller, Jim; Quataert, Eliot

    2016-01-01

    The inner moons of Jupiter and Saturn migrate outwards due to tidal energy dissipation within the planets, the details of which remain poorly understood. We demonstrate that resonance locking between moons and internal oscillation modes of the planet can produce rapid tidal migration. Resonance locking arises due to the internal structural evolution of the planet and typically produces an outward migration rate comparable to the age of the solar system. Resonance locking predicts a similar migration timescale but a different effective tidal quality factor Q for each moon. It also predicts nearly constant migration timescales a function of semi-major axis, such that effective Q values were larger in the past. Recent measurements of Jupiter and Saturn's moon systems find effective Q values that are smaller than expected (and are different between moons), and which correspond to migration timescales of roughly 10 Gyr. If confirmed, the measurements are broadly consistent with resonance locking as the dominant so...

  2. HABITABILITY OF EXOMOONS AT THE HILL OR TIDAL LOCKING RADIUS

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    Hinkel, Natalie R.; Kane, Stephen R., E-mail: natalie.hinkel@gmail.com [NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)

    2013-09-01

    Moons orbiting extrasolar planets are the next class of object to be observed and characterized for possible habitability. Like the host-planets to their host-star, exomoons have a limiting radius at which they may be gravitationally bound, or the Hill radius. In addition, they also have a distance at which they will become tidally locked and therefore in synchronous rotation with the planet. We have examined the flux phase profile of a simulated, hypothetical moon orbiting at a distant radius around the confirmed exoplanets {mu} Ara b, HD 28185 b, BD +14 4559 b, and HD 73534 b. The irradiated flux on a moon at its furthest, stable distance from the planet achieves its largest flux gradient, which places a limit on the flux ranges expected for subsequent (observed) moons closer in orbit to the planet. We have also analyzed the effect of planetary eccentricity on the flux on the moon, examining planets that traverse the habitable zone either fully or partially during their orbit. Looking solely at the stellar contributions, we find that moons around planets that are totally within the habitable zone experience thermal equilibrium temperatures above the runaway greenhouse limit, requiring a small heat redistribution efficiency. In contrast, exomoons orbiting planets that only spend a fraction of their time within the habitable zone require a heat redistribution efficiency near 100% in order to achieve temperatures suitable for habitability. This means that a planet does not need to spend its entire orbit within the habitable zone in order for the exomoon to be habitable. Because the applied systems comprise giant planets around bright stars, we believe that the transit detection method is most likely to yield an exomoon discovery.

  3. Resonance locking as the source of rapid tidal migration in the Jupiter and Saturn moon systems

    Science.gov (United States)

    Fuller, Jim; Luan, Jing; Quataert, Eliot

    2016-10-01

    The inner moons of Jupiter and Saturn migrate outwards due to tidal energy dissipation within the planets, the details of which remain poorly understood. We demonstrate that resonance locking between moons and internal oscillations of the planet can produce rapid tidal migration. Resonance locking arises due to the structural evolution of the planet and typically produces an outward migration rate comparable to the age of the solar system. Resonance locking predicts a similar migration timescale but a different effective tidal quality factor Q governing the migration of each moon. It also predicts nearly constant migration timescales a function of semi-major axis, such that effective Q values were larger in the past. Recent measurements of Jupiter and Saturn's moon systems find effective Q values that are much smaller than expected (and are different between moons), and which correspond to migration timescales of ~10 Gyr. If confirmed, the measurements are broadly consistent with resonance locking as the dominant source of tidal dissipation in Jupiter and Saturn. Resonance locking also provides solutions to several problems posed by current measurements: it naturally explains the exceptionally small Q governing Rhea's migration, it allows the large heating rate of Enceladus to be achieved in an equilibrium eccentricity configuration, and it resolves evolutionary problems arising from present-day migration/heating rates.

  4. A low-order model of water vapor, clouds, and thermal emission for tidally locked terrestrial planets

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jun; Abbot, Dorian S., E-mail: junyang28@uchicago.edu [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)

    2014-04-01

    In the spirit of minimal modeling of complex systems, we develop an idealized two-column model to investigate the climate of tidally locked terrestrial planets with Earth-like atmospheres in the habitable zone of M-dwarf stars. The model is able to approximate the fundamental features of the climate obtained from three-dimensional (3D) atmospheric general circulation model (GCM) simulations. One important reason for the two-column model's success is that it reproduces the high cloud albedo of the GCM simulations, which reduces the planet's temperature and delays the onset of a runaway greenhouse state. The two-column model also clearly illustrates a secondary mechanism for determining the climate: the nightside acts as a 'radiator fin' through which infrared energy can be lost to space easily. This radiator fin is maintained by a temperature inversion and dry air on the nightside, and plays a similar role to the subtropics on modern Earth. Since one-dimensional radiative-convective models cannot capture the effects of the cloud albedo and radiator fin, they are systematically biased toward a narrower habitable zone. We also show that cloud parameters are the most important in the two-column model for determining the day-night thermal emission contrast, which decreases and eventually reverses as the stellar flux increases. This reversal is important because it could be detected by future extrasolar planet characterization missions, which would suggest that the planet has Earth-like water clouds and is potentially habitable.

  5. A Low-order Model of Water Vapor, Clouds, and Thermal Emission for Tidally Locked Terrestrial Planets

    CERN Document Server

    Yang, Jun

    2014-01-01

    In the spirit of minimal modeling of complex systems, we develop an idealized two-column model to investigate the climate of tidally locked terrestrial planets with Earth-like atmospheres in the habitable zone of M-dwarf stars. The model is able to approximate the fundamental features of the climate obtained from three-dimensional (3D) atmospheric general circulation model (GCM) simulations. One important reason for the two-column model's success is that it reproduces the high cloud albedo of the GCM simulations, which reduces the planet's temperature and delays the onset of a runaway greenhouse state. The two-column model also clearly illustrates a secondary mechanism for determining the climate: the nightside acts as a ``radiator fin'' through which infrared energy can be lost to space easily. This radiator fin is maintained by a temperature inversion and dry air on the nightside, and plays a similar role to the subtropics on modern Earth. Since 1D radiative-convective models cannot capture the effects of t...

  6. Connecting the dots: A versatile terrestrial planet benchmark for the atmospheres of tidally locked Super-Earths

    CERN Document Server

    Carone, Ludmila; Decin, Leen

    2014-01-01

    We develop a benchmark for quantifying sustained global dynamics in the atmospheres of tidally locked terrestrial planets using the MITgcm core as the basis of a dry 3D-GCM with simplified thermal forcing. Our forcing employs a Newtonian relaxation scheme based on a simple greenhouse model. Our model is of the same conceptional simplicity than the model of Held& Suarez1994 and is thus versatile and computationally fast. As a case study relevant for Super-Earths, we investigate a Gl581g-like planet with Earth-like atmosphere and irradiation, and present all details on the obtained thermodynamics for representative rotation periods of $P_{rot}=10$ days and $P_{rot}=36.5$ days. This provides proof of concept and identifies interesting dynamical features for the rotating regime $3

  7. Cosmic ray impact on extrasolar earth-like planets in close-in habitable zones.

    Science.gov (United States)

    Griessmeier, J-M; Stadelmann, A; Motschmann, U; Belisheva, N K; Lammer, H; Biernat, H K

    2005-10-01

    Because of their different origins, cosmic rays can be subdivided into galactic cosmic rays and solar/stellar cosmic rays. The flux of cosmic rays to planetary surfaces is mainly determined by two planetary parameters: the atmospheric density and the strength of the internal magnetic moment. If a planet exhibits an extended magnetosphere, its surface will be protected from high-energy cosmic ray particles. We show that close-in extrasolar planets in the habitable zone of M stars are synchronously rotating with their host star because of the tidal interaction. For gravitationally locked planets the rotation period is equal to the orbital period, which is much longer than the rotation period expected for planets not subject to tidal locking. This results in a relatively small magnetic moment. We found that an Earth-like extrasolar planet, tidally locked in an orbit of 0.2 AU around an M star of 0.5 solar masses, has a rotation rate of 2% of that of the Earth. This results in a magnetic moment of less than 15% of the Earth's current magnetic moment. Therefore, close-in extrasolar planets seem not to be protected by extended Earth-like magnetospheres, and cosmic rays can reach almost the whole surface area of the upper atmosphere. Primary cosmic ray particles that interact with the atmosphere generate secondary energetic particles, a so-called cosmic ray shower. Some of the secondary particles can reach the surface of terrestrial planets when the surface pressure of the atmosphere is on the order of 1 bar or less. We propose that, depending on atmospheric pressure, biological systems on the surface of Earth-like extrasolar planets at close-in orbital distances can be strongly influenced by secondary cosmic rays.

  8. Atmospheric circulation of tidally-locked exoplanets: a suite of benchmark tests for dynamical solvers

    CERN Document Server

    Heng, Kevin; Phillipps, Peter J

    2010-01-01

    The complexity of atmospheric modelling and its inherent non-linearity, together with the limited amount of data of exoplanets available, motivate model intercomparisons and benchmark tests. In the geophysical community, the Held-Suarez test is a standard benchmark for comparing dynamical core simulations of the Earth's atmosphere with different solvers, based on statistically-averaged flow quantities. In the present study, we perform analogues of the Held-Suarez test for tidally-locked exoplanets with the GFDL-Princeton Flexible Modeling System (FMS) by subjecting both the spectral and finite difference dynamical cores to a suite of tests, including the standard benchmark for Earth, a hypothetical tidally-locked Earth, a "shallow" hot Jupiter model and a "deep" model of HD 209458b. We find qualitative and quantitative agreement between the solvers for the Earth, tidally-locked Earth and shallow hot Jupiter benchmarks, but the agreement is less than satisfactory for the deep model of HD 209458b. Further inves...

  9. Atmospheric tides in Earth-like planets

    CERN Document Server

    Auclair-Desrotour, Pierre; Mathis, Stéphane

    2016-01-01

    Atmospheric tides can strongly affect the rotational dynamics of planets. In the family of Earth-like planets, such as Venus, this physical mechanism coupled with solid tides makes the angular velocity evolve over long timescales and determines the equilibrium configurations of their spin. Contrary to the solid core, the atmosphere is submitted to both tidal gravitational potential and insolation flux coming from the star. The complex response of the gas is intrinsically linked to its physical properties. This dependence has to be characterized and quantified to study the large variety of extrasolar planetary systems. We develop a theoretical global model where radiative losses, which are predominant in slowly rotating atmospheres, are taken into account. We analytically compute the tidal perturbation of pressure, density, temperature and velocity field from which we deduce the expressions of atmospheric Love numbers and tidal torque exerted by the star. The dynamics of atmospheric tides depends on the freque...

  10. Atmospheric tides in Earth-like planets

    Science.gov (United States)

    Auclair-Desrotour, P.; Laskar, J.; Mathis, S.

    2017-07-01

    Context. Atmospheric tides can strongly affect the rotational dynamics of planets. In the family of Earth-like planets, which includes Venus, this physical mechanism coupled with solid tides makes the angular velocity evolve over long timescales and determines the equilibrium configurations of their spin. Aims: Unlike the solid core, the atmosphere of a planet is subject to both tidal gravitational potential and insolation flux coming from the star. The complex response of the gas is intrinsically linked to its physical properties. This dependence has to be characterized and quantified for application to the wide variety of extrasolar planetary systems. Methods: We develop a theoretical global model where radiative losses, which are predominant in slowly rotating atmospheres, are taken into account. We analytically compute the perturbation of pressure, density, temperature, and velocity field caused by a thermogravitational tidal perturbation. From these quantities, we deduce the expressions of atmospheric Love numbers and tidal torque exerted on the fluid shell by the star. The equations are written for the general case of a thick envelope and the simplified one of a thin isothermal atmosphere. Results: The dynamics of atmospheric tides depends on the frequency regime of the tidal perturbation: the thermal regime near synchronization and the dynamical regime characterizing fast-rotating planets. Gravitational and thermal perturbations imply different responses of the fluid, i.e. gravitational tides and thermal tides, which are clearly identified. The dependence of the torque on the tidal frequency is quantified using the analytic expressions of the model for Earth-like and Venus-like exoplanets and is in good agreement with the results given by global climate models (GCM) simulations.Introducing dissipative processes such as radiation regularizes the tidal response of the atmosphere, otherwise it is singular at synchronization. Conclusions: We demonstrate the

  11. Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars.

    Science.gov (United States)

    Hu, Yongyun; Yang, Jun

    2014-01-14

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere-ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an "eyeball." For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs' habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets.

  12. Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars

    Science.gov (United States)

    Hu, Yongyun; Yang, Jun

    2014-01-01

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere–ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an “eyeball.” For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs’ habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets. PMID:24379386

  13. Temperature Structure and Atmospheric Circulation of Dry, Tidally Locked Rocky Exoplanets

    CERN Document Server

    Koll, Daniel D B

    2016-01-01

    Next-generation space telescopes will observe the atmospheres of rocky planets orbiting nearby M-dwarfs. Understanding these observations will require well-developed theory in addition to numerical simulations. Here we present theoretical models for the temperature structure and atmospheric circulation of dry, tidally locked rocky exoplanets with grey radiative transfer and test them using a general circulation model (GCM). First, we develop a radiative-convective model that captures surface temperatures of slowly rotating and cool atmospheres. Second, we show that the atmospheric circulation acts as a global heat engine, which places strong constraints on large-scale wind speeds. Third, we develop a radiative-convective-subsiding model which extends our radiative-convective model to hot and thin atmospheres. We find that rocky planets develop large day-night temperature gradients at a ratio of wave-to-radiative timescales up to two orders of magnitude smaller than the value suggested by work on hot Jupiters....

  14. Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

    CERN Document Server

    Yang, Jun; Abbot, Dorian S

    2013-01-01

    The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phen...

  15. The carbonate-silicate cycle and CO2/climate feedbacks on tidally locked terrestrial planets.

    Science.gov (United States)

    Edson, Adam R; Kasting, James F; Pollard, David; Lee, Sukyoung; Bannon, Peter R

    2012-06-01

    Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.

  16. Roche tomography of cataclysmic variables - VI. Differential rotation of AE Aqr - Not tidally locked!

    CERN Document Server

    Hill, Colin; Shahbaz, Tariq; Steeghs, Danny; Dhillon, Vik

    2014-01-01

    We present Roche tomograms of the K4V secondary star in the cataclysmic variable AE Aqr, reconstructed from two datasets taken 9 days apart, and measure the differential rotation of the stellar surface. The tomograms show many large, cool starspots, including a large high-latitude spot and a prominent appendage down the trailing hemisphere. We find two distinct bands of spots around 22$^{\\circ}$ and 43$^{\\circ}$ latitude, and estimate a spot coverage of 15.4-17% on the northern hemisphere. Assuming a solar-like differential rotation law, the differential rotation of AE Aqr was measured using two different techniques. The first method yields an equator-pole lap time of 269 d and the second yields a lap time of 262 d. This shows the star is not fully tidally locked, as was previously assumed for CVs, but has a co-rotation latitude of $\\sim 40^{\\circ}$. We discuss the implications that these observations have on stellar dynamo theory, as well as the impact that spot traversal across the first Lagrangian point ma...

  17. STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jun; Abbot, Dorian S. [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States); Cowan, Nicolas B., E-mail: abbot@uchicago.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

    2013-07-10

    The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phenomenon a stabilizing climate feedback. Substellar clouds also effectively block outgoing radiation from the surface, reducing or even completely reversing the thermal emission contrast between dayside and nightside. The presence of substellar water clouds and the resulting clement surface conditions will therefore be detectable with the James Webb Space Telescope.

  18. Temperature Structure and Atmospheric Circulation of Dry Tidally Locked Rocky Exoplanets

    Science.gov (United States)

    Koll, Daniel D. B.; Abbot, Dorian S.

    2016-07-01

    Next-generation space telescopes will observe the atmospheres of rocky planets orbiting nearby M-dwarfs. Understanding these observations will require well-developed theory in addition to numerical simulations. Here we present theoretical models for the temperature structure and atmospheric circulation of dry, tidally locked rocky exoplanets with gray radiative transfer and test them using a general circulation model (GCM). First, we develop a radiative-convective (RC) model that captures surface temperatures of slowly rotating and cool atmospheres. Second, we show that the atmospheric circulation acts as a global heat engine, which places strong constraints on large-scale wind speeds. Third, we develop an RC-subsiding model which extends our RC model to hot and thin atmospheres. We find that rocky planets develop large day-night temperature gradients at a ratio of wave-to-radiative timescales up to two orders of magnitude smaller than the value suggested by work on hot Jupiters. The small ratio is due to the heat engine inefficiency and asymmetry between updrafts and subsidence in convecting atmospheres. Fourth, we show, using GCM simulations, that rotation only has a strong effect on temperature structure if the atmosphere is hot or thin. Our models let us map out atmospheric scenarios for planets such as GJ 1132b, and show how thermal phase curves could constrain them. Measuring phase curves of short-period planets will require similar amounts of time on the James Webb Space Telescope as detecting molecules via transit spectroscopy, so future observations should pursue both techniques.

  19. Evolution of Earth Like Planets

    Science.gov (United States)

    Monroy-Rodríguez, M. A.; Vega, K. M.

    2017-07-01

    In order to study and explain the evolution of our own planet we have done a review of works related to the evolution of Earth-like planets. From the stage of proto-planet to the loss of its atmosphere. The planetary formation from the gas and dust of the proto-planetary disk, considering the accretion by the process of migration, implies that the material on the proto-planet is very mixed. The newborn planet is hot and compact, it begins its process of stratification by gravity separation forming a super dense nucleus, an intermediate layer of convective mantle and an upper mantle that is less dense, with material that emerges from zones at very high pressure The surface with low pressure, in this process the planet expands and cools. This process also releases gas to the surface, forming the atmosphere, with the gas gravitationally bounded. The most important thing for the life of the planet is the layer of convective mantle, which produces the magnetic field, when it stops the magnetic field disappears, as well as the rings of van allen and the solar wind evaporates the atmosphere, accelerating the evolution and cooling of the planet. In a natural cycle of cataclysms and mass extinctions, the solar system crosses the galactic disk every 30 million years or so, the increase in the meteorite fall triggers the volcanic activity and the increase in the release of CO2 into the atmosphere reaching critical levels (4000 billion tons) leads us to an extinction by overheating that last 100 000 years, the time it takes CO2 to sediment to the ocean floor. Human activity will lead us to reach critical levels of CO2 in approximately 300 years.

  20. Atmospheric circulation of tidally locked exoplanets II: dual-band radiative transfer and convective adjustment

    CERN Document Server

    Heng, Kevin; Phillipps, Peter J

    2011-01-01

    Improving upon our purely dynamical work, we present three-dimensional simulations of the atmospheric circulation on Earth-like (exo)planets and hot Jupiters using the GFDL-Princeton Flexible Modeling System (FMS). As the first steps away from the purely dynamical benchmarks of Heng, Menou & Phillipps (2011), we add dual-band radiative transfer and dry convective adjustment schemes to our computational setup. Our treatment of radiative transfer assumes stellar irradiation to peak at a wavelength shorter than and distinct from that at which the exoplanet re-emits radiation ("shortwave" versus "longwave"), and also uses a two-stream approximation. Convection is mimicked by adjusting unstable lapse rates to the dry adiabat. The bottom of the atmosphere is bounded by an uniform slab with a finite thermal inertia. For our hot Jupiter models, we include an analytical formalism for calculating temperature-pressure profiles, in radiative equilibrium, which accounts for the effect of collision-induced absorption v...

  1. 3D Structures of equatorial waves and the resulting superrotation in the atmosphere of a tidally locked hot Jupiter

    CERN Document Server

    Tsai, Shang-Min; Gu, Pin-Gao

    2014-01-01

    Three-dimensional equatorial trapped waves excited by stellar isolation and the resulting equatorial superrotating jet in a vertical stratified atmosphere of a tidally-locked hot Jupiter are investigated. Taking the hot Jupiter HD 189733b as a fiducial example, we analytically solve a set of linear equations subject to stationary stellar heating with a uniform zonal-mean flow included. We also extract wave information in the final equilibrium state of the atmosphere from the radiative hydrodynamical simulation for HD 189733b by Dobbs-Dixon & Agol (2013). We find that the analytic wave solutions are able to qualitatively explain the three-dimensional simulation results. Studying the vertical structure of waves allows us to explore new wave features such as the westward tilt of wavefronts related to the Rossby-wave resonance as well as double gyres of dispersive Rossby waves. We also make an attempt to apply our linear wave analysis to explain some numerical features associated with the equatorial jet devel...

  2. Earth-like Habitats in Planetary Systems

    CERN Document Server

    Fritz, Jörg; Kührt, Ekkehard; Morbidelli, Alessandro; Tornow, Carmen; Wünnemann, Kai; Fernandes, Vera A; Grenfell, Lee J; Rauer, Heike; Wagner, Roland; Werner, Stephanie C

    2014-01-01

    Understanding the concept of habitability is related to an evolutionary knowledge of the particular planet-in-question. Additional indications so-called "systemic aspects" of the planetary system as a whole governs a particular planet's claim on habitability. Here we focus on such systemic aspects and discuss their relevance to the formation of an 'Earth-like' habitable planet. We summarize our results obtained by lunar sample work and numerical models within the framework of the Research Alliance "Planetary Evolution and Life". We consider various scenarios which simulate the dynamical evolution of the Solar System and discuss the likelihood of forming an Earth-like world orbiting another star. Our model approach is constrained by observations of the modern Solar System and the knowledge of its history. Results suggest that the long-term presence of terrestrial planets is jeopardized due to gravitational interactions if giant planets are present. But habitability of inner rocky planets may be supported in th...

  3. Transits of Earth-Like Planets

    CERN Document Server

    Kaltenegger, L

    2009-01-01

    Transmission spectroscopy of Earth-like exoplanets is a potential tool for habitability screening. Transiting planets are present-day "Rosetta Stones" for understanding extrasolar planets because they offer the possibility to characterize giant planet atmospheres and should provide an access to biomarkers in the atmospheres of Earth-like exoplanets, once they are detected. Using the Earth itself as a proxy we show the potential and limits of the transiting technique to detect biomarkers on an Earth-analog exoplanet in transit. We quantify the Earths cross section as a function of wavelength, and show the effect of each atmospheric species, aerosol, and Rayleigh scattering. Clouds do not significantly affect this picture because the opacity of the lower atmosphere from aerosol and Rayleigh losses dominates over cloud losses. We calculate the optimum signal-to-noise ratio for spectral features in the primary eclipse spectrum of an Earth-like exoplanet around a Sun-like star and also M stars, for a 6.5-m telesco...

  4. Giant Impacts on Earth-Like Worlds

    Science.gov (United States)

    Kohler, Susanna

    2016-05-01

    Earth has experienced a large number of impacts, from the cratering events that may have caused mass extinctions to the enormous impact believed to have formed the Moon. A new study examines whether our planets impact history is typical for Earth-like worlds.N-Body ChallengesTimeline placing the authors simulations in context of the history of our solar system (click for a closer look). [Quintana et al. 2016]The final stages of terrestrial planet formation are thought to be dominated by giant impacts of bodies in the protoplanetary disk. During this stage, protoplanets smash into one another and accrete, greatly influencing the growth, composition, and habitability of the final planets.There are two major challenges when simulating this N-body planet formation. The first is fragmentation: since computational time scales as N^2, simulating lots of bodies that split into many more bodies is very computationally intensive. For this reason, fragmentation is usually ignored; simulations instead assume perfect accretion during collisions.Total number of bodies remaining within the authors simulations over time, with fragmentation included (grey) and ignored (red). Both simulations result in the same final number of bodies, but the ones that include fragmentation take more time to reach that final number. [Quintana et al. 2016]The second challengeis that many-body systems are chaotic, which means its necessary to do a large number of simulations to make statistical statements about outcomes.Adding FragmentationA team of scientists led by Elisa Quintana (NASA NPP Senior Fellow at the Ames Research Center) has recently pushed at these challenges by modeling inner-planet formation using a code that does include fragmentation. The team ran 140 simulations with and 140 without the effects of fragmentation using similar initial conditions to understand how including fragmentation affects the outcome.Quintana and collaborators then used the fragmentation-inclusive simulations to

  5. On the Method to Infer an Atmosphere on a Tidally-Locked Super Earth Exoplanet and Upper limits to GJ 876d

    CERN Document Server

    Seager, S

    2009-01-01

    We develop a method to infer or rule out the presence of an atmosphere on a tidally-locked hot super Earth. The question of atmosphere retention is a fundamental one, especially for planets orbiting M stars due to the star's long-duration active phase and corresponding potential for stellar-induced planetary atmospheric escape and erosion. Tidally-locked planets with no atmosphere are expected to show a Lambertian-like thermal phase curve, causing the combined light of the planet-star system to vary with planet orbital phase. We report Spitzer 8 micron IRAC observations of GJ 876 taken over 32 continuous hours and reaching a relative photometric precision of 3.9e-04 per point for 25.6 s time sampling. This translates to a 3 sigma limit of 5.13e-05 on a planet thermal phase curve amplitude. Despite the almost photon-noise limited data, we are unable to conclusively infer the presence of an atmosphere or rule one out on the non-transiting short-period super Earth GJ 876d. The limiting factor in our observations...

  6. On the protection of extrasolar Earth-like planets around K/M stars against galactic cosmic rays

    CERN Document Server

    Grießmeier, J M; Grenfell, J L; Lammer, H; Motschmann, U; 10.1016/j.icarus.2008.09.015

    2009-01-01

    Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is strongly reduced by tidal locking. Therefore, such a close-in extrasolar planet is not protected by an extended magnetosphere. (b) The small orbital distance of the planet exposes it to a much denser stellar wind than that prevailing at larger orbital distances. This dense stellar wind leads to additional compression of the magnetosphere, which can further reduce the shielding efficiency against GCRs. In this work, we analyse and compare the effect of (a) and (b), showing that the stellar wind variation with orbital distance has little influence on the cosmic ray shielding. Instead, the weak shielding of M star planets can...

  7. Lightning chemistry on Earth-like exoplanets

    Science.gov (United States)

    Ardaseva, Aleksandra; Rimmer, Paul B.; Waldmann, Ingo; Rocchetto, Marco; Yurchenko, Sergey N.; Helling, Christiane; Tennyson, Jonathan

    2017-09-01

    We present a model for lightning shock-induced chemistry that can be applied to atmospheres of arbitrary H/C/N/O chemistry, hence for extrasolar planets and brown dwarfs. The model couples hydrodynamics and the STAND2015 kinetic gas-phase chemistry. For an exoplanet analogue to the contemporary Earth, our model predicts NO and NO2 yields in agreement with observation. We predict height-dependent mixing ratios during a storm soon after a lightning shock of NO ≈10-3 at 40 km and NO2 ≈10-4 below 40 km, with O3 reduced to trace quantities (≪10-10). For an Earth-like exoplanet with a CO2/N2 dominated atmosphere and with an extremely intense lightning storm over its entire surface, we predict significant changes in the amount of NO, NO2, O3, H2O, H2 and predict a significant abundance of C2N. We find that, for the Early Earth, O2 is formed in large quantities by lightning but is rapidly processed by the photochemistry, consistent with previous work on lightning. The chemical effect of persistent global lightning storms are predicted to be significant, primarily due to NO2, with the largest spectral features present at ∼3.4 and ∼6.2 μm. The features within the transmission spectrum are on the order of 1 ppm and therefore are not likely detectable with the James Webb Space Telescope. Depending on its spectral properties, C2N could be a key tracer for lightning on Earth-like exoplanets with a N2/CO2 bulk atmosphere, unless destroyed by yet unknown chemical reactions.

  8. On the equilibrium rotation of Earth-like extra-solar planets

    CERN Document Server

    Correia, Alexandre C M; Laskar, Jacques

    2008-01-01

    The equilibrium rotation of tidally evolved "Earth-like" extra-solar planets is often assumed to be synchronous with their orbital mean motion. The same assumption persisted for Mercury and Venus until radar observations revealed their true spin rates. As many of these planets follow eccentric orbits and are believed to host dense atmospheres, we expect the equilibrium rotation to differ from the synchronous motion. Here we provide a general description of the allowed final equilibrium rotation states of these planets, and apply this to already discovered cases in which the mass is lower than twelve Earth-masses. At low obliquity and moderate eccentricity, it is shown that there are at most four distinct equilibrium possibilities, one of which can be retrograde. Because most presently known "Earth-like" planets present eccentric orbits, their equilibrium rotation is unlikely to be synchronous.

  9. Dynamical Effects on the Habitable Zone for Earth-like Exomoons

    CERN Document Server

    Forgan, Duncan

    2013-01-01

    With the detection of extrasolar moons (exomoons) on the horizon, it is important to consider their potential for habitability. If we consider the circumstellar Habitable Zone (HZ, often described in terms of planet semi-major axis and orbital eccentricity), we can ask, "How does the HZ for an Earth-like exomoon differ from the HZ for an Earth-like exoplanet?" For the first time, we use 1D latitudinal energy balance modelling to address this question. The model places an Earth-like exomoon in orbit around a Jupiter mass planet, which in turn orbits a Sun-like star. The exomoon's surface temperature is evolved under the action of stellar insolation, atmospheric cooling, heat diffusion, eclipses and tidal heating. We use this model to carry out two separate investigations. In the first, four test cases are run to investigate in detail the dependence of the exomoon climate on orbital direction, orbital inclination, and on the frequency of stellar eclipse by the host planet. We find that lunar orbits which are re...

  10. The Search for Extrasolar Earth-like planets

    CERN Document Server

    Seager, S

    2003-01-01

    The search for extrasolar Earth-like planets is underway. Over 100 extrasolar giant planets are known to orbit nearby sun-like stars, including several in multiple-planet systems. These planetary systems are stepping stones for the search for Earth-like planets; the technology development, observational strategies, and science results can all be applied to Earth-like planets. Stars much less massive than the sun the most common stars in our Galaxy are being monitored for the gravitational influence of Earth-like planets. Although Earth-like planets orbiting sun-like stars are much more difficult to detect, space missions are being built to detect them indirectly due to their effects on the parent star and to quantify fundamental factors such as terrestrial planet frequency, size distribution, and mass distribution. Extremely ambitious space programs are being developed to directly detect Earth-like planets orbiting sun-like stars, and must tackle the immense technological challenge of blocking out the light o...

  11. Un-Earth-like interiors of the Earth-like planets

    Science.gov (United States)

    Shim, S. H. D.; Nisr, C.; Pagano, M.; Chen, H.; Ko, B.; Noble, S.; Leinenweber, K. D.; Young, P.; Desch, S. J.

    2015-12-01

    A number of exoplanets have been described as "Earth-like" planets (or even exo-earths) based on the mass-radius relations. Yet, significant variations have been documented in elemental abundances of planet-hosting stars, which will result in very different structures and processes in the interiors of rocky exoplanets. Recent data suggest that the Mg/Si ratio can be as small as less than 1 and as large as more than 2, opening the possibilities for the upper mantles to be dominated by pyroxene and olivine, respectively, and the lower mantles to be dominated by bridgmanite and ferropericlase, respectively. The changes in mineralogy will alter key properties, such as discontinuity structures (and therefore scale of mantle mixing), viscosity, and volatiles storage, of the mantle. Partial melting of such mantles would result in different compositions of the crusts, affecting the tectonics. However, the prediction should be made carefully because oxygen fugacity and contents of volatiles can change the mineralogy even for the same bulk composition. In extremely reducing proto-planetary disks, carbides will form instead of oxides and silicates, and become main constituents of planets in the system. Because carbides have high thermal conductivity and low thermal expansivity, internal heat transport of such planets may be dominated by conduction and mantle mixing would be much more limited than that of the Earth. However, the behaviors and properties of carbides need to be understood better at high pressure and high temperature. Some rocky exoplanets may have very thick layers of water and other icy materials. Interactions between ice (or fluid) and rock at extreme conditions would be the key to understand dynamics and habitability of such exoplanets.

  12. Uncovering the Chemistry of Earth-like Planets

    Science.gov (United States)

    Zeng, L.; Jacobsen, S. B.; Sasselov, D. D.

    2015-12-01

    We propose to use the evidence from our solar system to understand exoplanets, and in particular, to predict their surface chemistry and thereby the possibility of life. An Earth-like planet, born from the same nebula as its host star, is composed primarily of silicate rocks and an iron-nickel metal core, and depleted in volatile content in a systematic manner. The more volatile (easier to vaporize or dissociate into gas form) an element is in an Earth-like planet, the more depleted the element is compared to its host star. After depletion, an Earth-like planet would go through the process of core formation due to heat from radioactive decay and collisions. Core formation depletes a planet's rocky mantle of siderophile (iron-loving) elements, in addition to the volatile depletion. After that, Earth-like planets likely accrete some volatile-rich materials, called "late veneer". The late veneer could be essential to the origins of life on Earth and Earth-like planets, as it also delivers the volatiles such as nitrogen, sulfur, carbon and water to the planet's surface, which are crucial for life to occur. Here we build an integrative model of Earth-like planets from the bottom up. Thus the chemical compositions of Earth-like planets could be inferred from their mass-radius relations and their host stars' elemental abundances, and the origins of volatile contents (especially water) on their surfaces could be understood, and thereby shed light on the origins of life on them. This elemental abundance model could be applied to other rocky exoplanets in exoplanet systems.

  13. Can Red Dwarf stars support Earth-like vegetation?

    Science.gov (United States)

    Gale, Joseph; Wandel, Amri

    2016-07-01

    The Kepler mission has shown that Earthlike planets are common. Of particular interest in our search for extra-solar-system, life-clement conditions, are planets orbiting Red Dwarf (RD) stars, the most numerous stellar type in the Milky Way galaxy. Early considerations indicated that conditions on RD planets would be inimical to life, as their Habitable Zones would be so close as to make planets tidally locked to their star. This was expected to engender tempestuous climates and to expose life forms to flares of ionizing electro-magnetic radiation and charged particles. Moreover, the less photon energy of the radiation of the relatively cool RDs would be too low in the 300-700nm waveband required for Oxygenic Photosynthesis (OP). Recent calculations show that these negative factors are less severe than originally estimated. Many authors have suggested that OP may evolve on RP planets to utilize infrared photons in the 700-1000nm waveband. However, projecting from OP and the vegetation in analogous regions on Earth, we argue that the evolutionary pressure to do so would be small. On RD planets there will be regions receiving continuous illumination, of moderate intensity, containing a significant component of photosynthetic 400-700nm radiation. On Earth, OP has been an essential factor in producing the Biosphere environment that enabled the appearance and evolution of complex life. We conclude that the conditions for OP could exist on RD planets and consequently the evolution of vegetation and complex life is possible (albeit not necessary). Furthermore, the huge number of RDs and their long lifetimes, make advanced vegetation, OP and consequently complex life on RD planets probable, and statistically more likely than on planets of solar type stars.

  14. Earth-Like Exoplanets: The Science of NASA's Navigator Program

    Science.gov (United States)

    Lawson, Peter R. (Editor); Traub, Wesley A. (Editor)

    2006-01-01

    This book outlines the exoplanet science content of NASA's Navigator Program, and it identifies the exoplanet research priorities. The goal of Navigator Program missions is to detect and characterize Earth-like planets in the habitable zone of nearby stars and to search for signs of life on those planets.

  15. Kepler Mission to Detect Earth-like Planets

    Science.gov (United States)

    Kondo, Yoji

    2002-01-01

    Kepler Mission to detect Earth-like planets in our Milky Way galaxy was approved by NASA in December 2001 for a 4-5 year mission. The launch is planned in about 5 years. The Kepler observatory will be placed in an Earth-trailing orbit. The unique feature of the Kepler Mission is its ability to detect Earth-like planets orbiting around solar-type stars at a distance similar to that of Earth (from our Sun); such an orbit could provide an environment suitable for supporting life as we know it. The Kepler observatory accomplishes this feat by looking for the transits of planetary object in front of their suns; Kepler has a photometric precision of 10E-5 (0.00001) to achieve such detections. Other ongoing planetary detection programs (based mostly on a technique that looks for the shifting of spectral lines of the primary star due to its planetary companions' motions around it) have detected massive planets (with masses in the range of Jupiter); such massive planets are not considered suitable for supporting life. If our current theories for the formation of planetary systems are valid, we expect to detect about 50 Earth-like planets during Kepler's 4-year mission (assuming a random distribution of the planetary orbital inclinations with respect to the line of sight from Kepler). The number of detection will increase about 640 planets if the planets to be detected are Jupiter-sized.

  16. Spectral fingerprints of Earth-like planets around FGK stars.

    Science.gov (United States)

    Rugheimer, Sarah; Kaltenegger, Lisa; Zsom, Andras; Segura, Antígona; Sasselov, Dimitar

    2013-03-01

    We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from Teff=4250 K to Teff=7000 K in 250 K intervals. We have modeled the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1 AU equivalent distance from the VIS to IR (0.4 to 20 μm) to compare detectability of features in different wavelength ranges in accordance with the James Webb Space Telescope and future design concepts to characterize exo-Earths. We have also explored the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere, concentrating on detectable atmospheric features that indicate habitability on Earth, namely, H2O, O3, CH4, N2O, and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O, and CH3Cl, whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase is a lower surface temperature of the planet due to a bigger part of the stellar flux being reflected at short wavelengths, as well as increased photolysis. Earth-like atmosphere models show more O3 and OH but less stratospheric CH4, N2O, CH3Cl, and tropospheric H2O (but more stratospheric H2O) with increasing effective temperature of main sequence stars. The corresponding detectable spectral features, on the other hand, show different detectability depending on the wavelength observed. We concentrate on directly imaged planets here as a framework to interpret future light curves, direct imaging, and secondary eclipse measurements of atmospheres of terrestrial planets in the habitable zone at varying orbital positions.

  17. An Earth-Like Planet in GJ 832 System

    CERN Document Server

    Satyal, S; Musielak, Z E

    2016-01-01

    Stability of planetary orbits around GJ 832 star system, which contains inner (GJ 832c) and outer (GJ 832b) planets, is investigated numerically and the detailed phase-space analysis are performed. The stability of the system is de?ned in terms of its lifetime, which is its survival time during the orbital integration period, and the maximum eccentricity, emax attained by the orbits during the evolution processes. A special emphasis is given to the existence of stable orbits for an Earth-like planet that is injected between the inner and outer planets. Thus, numerical simulations are performed for three and four bodies in elliptical orbits (or circular for special cases), and a large number of initial conditions that covers the whole phase-space of the existing bodies are used. The results presented in the phase-space maps for GJ 832c indicates the least deviation of the eccentricity from its nominal value, which is then used to determine its inclination regime. Also, the Earth-like planet displays stable orb...

  18. Spectral Fingerprints of Earth-like Planets Around FGK Stars

    CERN Document Server

    Rugheimer, Sarah; Zsom, Andras; Segura, Antígona; Sasselov, Dimitar

    2012-01-01

    We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from Teff = 4250K to Teff = 7000K in 250K intervals. We model the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1AU equivalent distance from the VIS to IR (0.4 {\\mu}m - 20 {\\mu}m) to compare detectability of features in different wavelength ranges in accordance with JWST and future design concepts to characterize exo-Earths. We also explore the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere concentrating on detectable atmospheric features that indicate habitability on Earth, namely: H2O, O3, CH4, N2O and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O and CH3Cl whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase, is a lower surface temperature of the planet du...

  19. Climate Stability of Habitable Earth-like Planets

    CERN Document Server

    Menou, Kristen

    2014-01-01

    The carbon-silicate cycle regulates the atmospheric $CO_2$ content of terrestrial planets on geological timescales through a balance between the rates of $CO_2$ volcanic outgassing and planetary intake from rock weathering. It is thought to act as an efficient climatic thermostat on Earth and, by extension, on other habitable planets. If, however, the weathering rate increases with the atmospheric $CO_2$ content, as expected on planets lacking land vascular plants, the carbon-silicate cycle feedback can become severely limited. Here we show that Earth-like planets receiving less sunlight than current Earth may no longer possess a stable warm climate but instead repeatedly cycle between unstable glaciated and deglaciated climatic states. This has implications for the search for life on exoplanets in the habitable zone of nearby stars.

  20. Climate stability of habitable Earth-like planets

    Science.gov (United States)

    Menou, Kristen

    2015-11-01

    The carbon-silicate cycle regulates the atmospheric CO2 content of terrestrial planets on geological timescales through a balance between the rates of CO2 volcanic outgassing and planetary intake from rock weathering. It is thought to act as an efficient climatic thermostat on Earth and, by extension, on other habitable planets. If, however, the weathering rate increases with the atmospheric CO2 content, as expected on planets lacking land vascular plants, the carbon-silicate cycle feedback can become severely limited. Here we show that Earth-like planets receiving less sunlight than current Earth may no longer possess a stable warm climate but instead repeatedly cycle between unstable glaciated and deglaciated climatic states. This has implications for the search for life on exoplanets in the habitable zone of nearby stars.

  1. Climate variations on Earth-like circumbinary planets

    Science.gov (United States)

    Popp, Max; Eggl, Siegfried

    2017-04-01

    The discovery of planets orbiting double stars at close distances has sparked increasing scientific interest in determining whether Earth-analogues can remain habitable in such environments and how their atmospheric dynamics is influenced by the rapidly changing insolation. In this work we present results of the first three-dimensional numerical experiments of a water-rich planet orbiting a double star. We find that the periodic forcing of the atmosphere has a noticeable impact on the planet's climate. Signatures of the forcing frequencies related to the planet's as well as to the binary's orbital periods are present in a variety of climate indicators such as temperature and precipitation, making the interpretation of potential observables challenging. However, for Earth-like greenhouse gas concentrations, the variable forcing does not change the range of insolation values allowing for habitable climates substantially.

  2. Space vehicle with artificial gravity and earth-like environment

    Science.gov (United States)

    Gray, V. H. (Inventor)

    1973-01-01

    A space vehicle adapted to provide an artificial gravity and earthlike atmospheric environment for occupants is disclosed. The vehicle comprises a cylindrically shaped, hollow pressure-tight body, one end of which is tapered from the largest diameter of the body, the other end is flat and transparent to sunlight. The vehicle is provided with thrust means which rotates the body about its longitudinal axis, generating an artificial gravity effect upon the interior walls of the body due to centrifugal forces. The walls of the tapered end of the body are maintained at a temperature below the dew point of water vapor in the body and lower than the temperature near the transparent end of the body. The controlled environment and sunlight permits an earth like environment to be maintained wherein the CO2/O2 is balanced, and food for the travelers is supplied through a natural system of plant life grown on spacecraft walls where soil is located.

  3. Climate variations on Earth-like circumbinary planets.

    Science.gov (United States)

    Popp, Max; Eggl, Siegfried

    2017-04-06

    The discovery of planets orbiting double stars at close distances has sparked increasing scientific interest in determining whether Earth-analogues can remain habitable in such environments and how their atmospheric dynamics is influenced by the rapidly changing insolation. In this work we present results of the first three-dimensional numerical experiments of a water-rich planet orbiting a double star. We find that the periodic forcing of the atmosphere has a noticeable impact on the planet's climate. Signatures of the forcing frequencies related to the planet's as well as to the binary's orbital periods are present in a variety of climate indicators such as temperature and precipitation, making the interpretation of potential observables challenging. However, for Earth-like greenhouse gas concentrations, the variable forcing does not change the range of insolation values allowing for habitable climates substantially.

  4. Climate of an Earth-Like World with Changing Eccentricity

    Science.gov (United States)

    Kohler, Susanna

    2017-02-01

    Having a giant planet like Jupiter next door can really wreak havoc on your orbit! A new study examines what such a bad neighbor might mean for the long-term climate of an Earth-like planet.Influence of a Bad NeighborThe presence of a Jupiter-like giant planet in a nearby orbit can significantly affect how terrestrial planets evolve dynamically, causing elements like the planets orbital eccentricities and axial tilts to change over time. Earth is saved this inconvenience Jupiter isnt close enough to significantly influence us, and our large moon stabilizes our orbit against Jupiters tugs.Top panels: Authors simulationoutcomes for Case1, in which the planets eccentricity varies from 0 to 0.283 over 6500 years. Bottom panels: Outcomes for Case 2, in which the planets eccentricity varies from 0 to 0.066 over 4500 years. The highereccentricities reached in Case 1 causes the climate parameters to vary more widely. Click for a better look! [Way Georgakarakos 2017]Mars, on the other hand, isnt as lucky: its possible that Jupiters gravitational pull causes Marss axial tilt, for instance, to evolve through a range as large as 0 to 60 degrees on timescales of millions of years! Marss orbital eccentricity is similarly thought to vary due to Jupiters influence, and both of these factors play a major role in determining Marss climate.As exoplanet missions discover more planets many of which are Earth-like we must carefully consider which among these are most likely to be capable of sustaining life. If having a nearby neighbor like a Jupiter can tug an Earth-like world into an orbit with varying eccentricity, how does this affect the planets climate? Will the planet remain temperate? Or will it develop a runaway heating or cooling effect as it orbits, rendering it uninhabitable?Oceans and OrbitsTo examine these questions, two scientists have built the first ever 3D global climate model simulations of an Earth-like world using a fully coupled ocean (necessary for understanding

  5. Mantle convection and plate tectonics on Earth-like exoplanets

    Science.gov (United States)

    Sotin, C.; Schubert, G.

    2009-12-01

    The likelihood of plate tectonics on exoplanets larger than Earth can be assessed using either scaling laws or numerical models describing mantle thermal convection. We investigate the parameters which control the ratio of convective driving forces to lithosphere resisting forces. Two papers, Valencia et al. (AstroPhys. J., 670, L45-L48, 2007) and O’Neill and Lenardic (Geophys. Res. Lett., 34, L19204, 2007), came to opposite conclusions based on scaling laws and numerical calculations, respectively. The different assumptions and parameters used in each study are compared. The definition of thermal boundary layer and lithosphere and the use of their characteristics in the scaling laws are clarified. We show that Valencia et al. (2007) overestimate the ratio of driving forces to resistive forces because they infer too large values for both the thickness of the thermal boundary layer and the length of the plate and too small a value for the yield strength. We show that this ratio is so weakly dependent on the size of an Earth-like planet that other parameters such as presence of water, heating per unit mass, upper mantle thickness, etc., may actually determine the occurrence or not of plate tectonics. The numerical calculations of O’Neill and Lenardic (2007) show the importance of 2D simulations for determining the values of the velocity below the lithosphere, the convective stresses, and the plate dimensions. It demonstrates the need for 3D spherical numerical simulations. Their conclusion that super-Earths would not have plate tectonics depends on a number of assumptions including the constancy of heat-flux as a function of planetary size. We present a 3D spherical scaling including the increase of heat flux with the size of a planet showing that larger Earth-like planets would be marginally in the mobile lid convection regime reinforcing our caution that other factors may tip the balance. The present study points out the importance of the distance between

  6. Modeling the surface temperature of Earth-like planets

    CERN Document Server

    Vladilo, G; Murante, G; Filippi, L; Provenzale, A

    2015-01-01

    We introduce a novel Earth-like planet surface temperature model (ESTM) for habitability studies based on the spatial-temporal distribution of planetary surface temperatures. The ESTM adopts a surface Energy Balance Model complemented by: radiative-convective atmospheric column calculations, a set of physically-based parameterizations of meridional transport, and descriptions of surface and cloud properties more refined than in standard EBMs. The parameterization is valid for rotating terrestrial planets with shallow atmospheres and moderate values of axis obliquity (epsilon >= 45^o). Comparison with a 3D model of atmospheric dynamics from the literature shows that the equator-to-pole temperature differences predicted by the two models agree within ~5K when the rotation rate, insolation, surface pressure and planet radius are varied in the intervals 0.5 <= Omega/Omega_o <= 2, 0.75 <= S/S_o <= 1.25, 0.3 <= p/(1 bar) <= 10, and 0.5 <= R/R_o <= 2, respectively. The ESTM has an extremely l...

  7. Biosignatures from Earth-Like Planets Around M Dwarfs

    CERN Document Server

    Segura, A; Meadows, V; Cohen, M; Scalo, J; Crisp, D; Butler, R A H; Tinetti, G; Segura, Antigona; Kasting, James F.; Meadows, Victoria; Cohen, Martin; Scalo, John; Crisp, David; Butler, Rebecca A.H.; Tinetti, Giovana

    2005-01-01

    Coupled one-dimensional photochemical-climate calculations have been performed for hypothetical Earth-like planets around M dwarfs. Visible, near-infrared and thermal-infrared synthetic spectra of these planets were generated to determine which biosignature gases might be observed by a future, space-based telescope. Our star sample included two observed active M dwarfs, AD Leo and GJ 643, and three quiescent model stars. The spectral distribution of these stars in the ultraviolet generates a different photochemistry on these planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially longer lifetimes and higher mixing ratios than on Earth, making them potentially observable by space-based telescopes. On the active M-star planets, an ozone layer similar to Earth's was developed that resulted in a spectroscopic signature comparable to the terrestrial one. The simultaneous detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been suggested as strong evidence for life. Planet...

  8. The Maximal Runaway Temperature of Earth-like Planets

    CERN Document Server

    Shaviv, Nir J; Wehrse, Rainer

    2012-01-01

    We generalize the problem of the semi-gray model to cases in which a non-negligible fraction of the stellar radiation falls on the long-wavelength range, and/or that the planetary long-wavelength emission penetrates into the transparent short wavelength domain of the absorption. Second, applying the most general assumptions and independently of any particular properties of an absorber, we show that the greenhouse effect saturates and any Earth-like planet has a maximal temperature which depends on the type of and distance to its main-sequence star, its albedo and the primary atmospheric components which determine the cutoff frequency below which the atmosphere is optically thick. For example, a hypothetical convection-less planet similar to Venus, that is optically thin in the visible, could have at most a surface temperature of 1200-1300K irrespective of the nature of the greenhouse gas. We show that two primary mechanisms are responsible for the saturation of the runaway greenhouse effect, depending on the ...

  9. Characterizing Earth-like Planets with Terrestrial Planet Finder

    CERN Document Server

    Seager, S; Turner, E L

    2002-01-01

    For the first time in human history the possibility of detecting and studying Earth-like planets is on the horizon. Terrestrial Planet Finder (TPF), with a launch date in the 2015 timeframe, is being planned by NASA to find and characterize planets in the habitable zones of nearby stars. The mission Darwin from ESA has similar goals. The motivation for both of these space missions is the detection and spectroscopic characterization of extrasolar terrestrial planet atmospheres. Of special interest are atmospheric biomarkers--such as O2, O3, H2O, CO and CH4--which are either indicative of life as we know it, essential to life, or can provide clues to a planet's habitability. A mission capable of measuring these spectral features would also obtain sufficient signal-to-noise to characterize other terrestrial planet properties. For example, physical characteristics such as temperature and planetary radius can be constrained from low- resolution spectra. In addition, planet characteristics such as weather, rotation...

  10. Biosignatures from Earth-like planets around M dwarfs.

    Science.gov (United States)

    Segura, Antígona; Kasting, James F; Meadows, Victoria; Cohen, Martin; Scalo, John; Crisp, David; Butler, Rebecca A H; Tinetti, Giovanna

    2005-12-01

    Coupled one-dimensional photochemical-climate calculations have been performed for hypothetical Earth-like planets around M dwarfs. Visible/near-infrared and thermal-infrared synthetic spectra of these planets were generated to determine which biosignature gases might be observed by a future, space-based telescope. Our star sample included two observed active M dwarfs-AD Leo and GJ 643-and three quiescent model stars. The spectral distribution of these stars in the ultraviolet generates a different photochemistry on these planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially longer lifetimes and higher mixing ratios than on Earth, making them potentially observable by space-based telescopes. On the active M-star planets, an ozone layer similar to Earth's was developed that resulted in a spectroscopic signature comparable to the terrestrial one. The simultaneous detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been suggested as strong evidence for life. Planets circling M stars may be good locations to search for such evidence.

  11. The Occurrence of Earth-Like Planets Around Other Stars

    CERN Document Server

    Farr, Will M; Aldridge, Chris; Stroud, Kirsty

    2014-01-01

    The quantity $\\eta_\\oplus$, the number density of planets per star per logarithmic planetary radius per logarithmic orbital period at one Earth radius and one year period, describes the occurrence of Earth-like extrasolar planets. Here we present a measurement of $\\eta_\\oplus$ from a parameterised forward model of the (correlated) period-radius distribution and the observational selection function in the most recent (Q17) data release from the Kepler satellite. We find $\\eta_\\oplus = 3.9_{-1.6}^{+2.2}\\%$ (90% CL). We conclude that each star hosts $3.83_{-0.62}^{+0.76}$ planets with $P \\lesssim 3 \\mathrm{yr}$ and $R \\gtrsim 0.2 R_\\oplus$. Our empirical model for false-positive contamination is consistent with the dominant source being background eclipsing binary stars. The distribution of planets we infer is consistent with a highly-stochastic planet formation process producing many correlated, fractional changes in planet sizes and orbits.

  12. Extrasolar Giant Planet in Earth-like Orbit

    Science.gov (United States)

    1999-07-01

    companion . iota Hor b has an orbital period of 320 days. From this period, the known mass of the central star (1.03 solar masses) and the amplitude of the velocity changes, a mass of at least 2.26 times that of planet Jupiter is deduced for the planet. It revolves around the host star in a somewhat elongated orbit (the eccentricity is 0.16). If it were located in our own solar system, this orbit would stretch from just outside the orbit of Venus (at 117 million km or 0.78 Astronomical Units from the Sun) to just outside the orbit of the Earth (the point farthest from the Sun, at 162 million km or 1.08 Astronomical Units) The new giant planet is thus moving in an orbit not unlike that of the Earth. In fact, of all the planets discovered so far, the orbit of iota Hor b is the most Earth-like. Also, with a spectral type of G0 V , its host star is quite similar to the Sun (G2 V). iota Hor b is, however, at least 720 times more massive than the Earth and it is probably more similar to planet Jupiter in our own solar system. While the radial velocity technique described above only determines a minimum value for the planet's mass, an analysis of the velocity with which the star turns around its own axis suggests that the true mass of iota Hor b is unlikely to be much higher. A difficult case Natural phenomena with periods near one solar year always present a particular challenge to astronomers. This is one of the reasons why it has been necessary to observe the iota Hor system for such a long time to be absolutely sure about the present result. First, special care must be taken to verify that the radial velocity variations found in the data are not an artefact of the Earth's movement around the Sun. In any case, the effect of this movement on the measurements must be accurately accounted for; it reaches about ± 30 km/sec over one year, i.e. much larger than the effect of the new planet. In the present case of iota Hor , this was thoroughly tested and any residual influence of

  13. Star Masses and Star-Planet Distances for Earth-like Habitability

    Science.gov (United States)

    Waltham, David

    2017-01-01

    This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M⊙ planets with at least simple life is 0.57 M⊙ < M < 1.64 M⊙.

  14. Star Masses and Star-Planet Distances for Earth-like Habitability.

    Science.gov (United States)

    Waltham, David

    2017-01-01

    This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M⊙ < M < 1.04 M⊙, and the range for planets with at least simple life is 0.57 M⊙ < M < 1.64 M⊙. Key Words: Habitability-Habitable zone-Anthropic-Red dwarfs-Initial mass function. Astrobiology 17, 61-77.

  15. Star Masses and Star-Planet Distances for Earth-like Habitability

    Science.gov (United States)

    2017-01-01

    Abstract This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M⊙ planets with at least simple life is 0.57 M⊙ < M < 1.64 M⊙. Key Words: Habitability—Habitable zone—Anthropic—Red dwarfs—Initial mass function. Astrobiology 17, 61–77. PMID:28103107

  16. Tidal Forms

    Science.gov (United States)

    Bolla Pittaluga, M.; Seminara, G.; Tambroni, N.

    2003-04-01

    We give an overview of some recent investigations on the mechanics of the processes whereby forms develop in tidal environments. The viewpoint taken here is mechanistic. Some of the questions which deserve an answer may be summarised as follows: i) do tidal channels tend to some altimetric long term equilibrium? ii) why are they typically convergent and weakly meandering? iii) how is such equilibrium affected by the hydrodynamics and morphodynamics of tidal inlets? iv) what is the hydrodynamic and morphodynamic role played by tidal flats adjacent to the channels? Some of the above questions have received a considerable attention in the last few years. Schuttelaars and de Swart (1996), Lanzoni and Seminara (2002) and, more recently, Bolla Pittaluga (2003) have investigated the first problem. In particular, the latter two contributions have shown that a straight tidal channel connected to a tidal sea at one end and closed at the other end tends to reach a long term equilibrium profile, which is slightly concave seaward and convex landward where a beach forms. The equilibrium profile is strongly sensitive to the harmonic content of the tidal forcing as well as to the value of sediment concentration established by the coastal hydrodynamics in the far field of the inlet region. Less important are the effect of channel convergence and the role of settling lag in the transport of suspended load. Insufficient attention has been devoted to the understanding of what mechanisms control channel convergence and meandering, though some similarities and differences between tidal and fluvial channels have emerged from some recent works. In particular, free bars form in tidal channels due to an instability mechanism essentially similar to that occurring under steady conditions though the oscillatory character of the flow field makes the bar pattern non migrating (Seminara and Tubino, 2001). Similarly, forced bars in curved tidal channels are driven by the development of

  17. Tidal obliquity evolution of potentially habitable planets

    CERN Document Server

    Heller, René; Barnes, Rory

    2011-01-01

    Stellar insolation has been used as the main constraint on a planet's habitability. However, as more Earth-like planets are discovered around low-mass stars (LMSs), a re-examination of the role of tides on the habitability of exoplanets has begun. Those studies have yet to consider the misalignment between a planet's rotational axis and the orbital plane normal, i.e. the planetary obliquity. We apply two equilibrium tide theories to compute the obliquity evolution of terrestrial planets orbiting in the habitable zones around LMSs. The time for the obliquity to decrease from an Earth-like obliquity of 23.5 deg to 5 deg, the 'tilt erosion time', is compared to the traditional insolation habitable zone (IHZ) as a function of semi-major axis, eccentricity, and stellar mass. We also compute tidal heating and equilibrium rotation caused by obliquity tides. The Super-Earth Gl581d and the planet candidate Gl581g are studied as examples for tidal processes. Earth-like obliquities of terrestrial planets in the IHZ arou...

  18. Anelastic tidal dissipation in multi-layer planets

    CERN Document Server

    Remus, F; Zahn, J -P; Lainey, V

    2012-01-01

    Earth-like planets have viscoelastic mantles, whereas giant planets may have viscoelastic cores. The tidal dissipation of such solid regions, gravitationally perturbed by a companion body, highly depends on their rheology and on the tidal frequency. Therefore, modelling tidal interactions presents a high interest to provide constraints on planets' properties and to understand their history and their evolution, in our Solar System or in exoplanetary systems. We examine the equilibrium tide in the anelastic parts of a planet whatever the rheology, taking into account the presence of a fluid envelope of constant density. We show how to obtain the different Love numbers that describe its tidal deformation. Thus, we discuss how the tidal dissipation in solid parts depends on the planet's internal structure and rheology. Finally, we show how the results may be implemented to describe the dynamical evolution of planetary systems. The first manifestation of the tide is to distort the shape of the planet adiabatically...

  19. A high-contrast coronagraph for earth-like exoplanet direct imaging: design and test

    CERN Document Server

    Liu, C C; Dou, J P; Zhu, Y T; Zhang, X; Zhao, G; Wu, Zh; Chen, R

    2014-01-01

    The high-contrast coronagraph for direct imaging earth-like exoplanet at the visible needs a contrast of 10^(-10) at a small angular separation of 4 lambda/D or less. Here we report our recent laboratory experiment that is close to the limits. The test of the high-contrast imaging coronagraph is based on our step-transmission apodized filter. To achieve the goal, we use a liquid crystal array (LCA) as a phase corrector to create a dark hole based on our dedicated focal dark algorithm. We have suppressed the diffracted and speckle noise near the star point image to a level of 1.68 x 10^(-9) at 4 lambda/D, which can be immediately used for the direct imaging of Jupiter like exoplanets. This demonstrates that high-contrast coronagraph telescope in space has the potentiality to detect and characterize earth-like planets.

  20. 3D climate modeling of Earth-like extrasolar planets orbiting different types of host stars

    CERN Document Server

    Godolt, M; Hamann-Reinus, A; Kitzmann, D; Kunze, M; Langematz, U; von Paris, P; Patzer, A B C; Rauer, H; Stracke, B

    2015-01-01

    The potential habitability of a terrestrial planet is usually defined by the possible existence of liquid water on its surface. The potential presence of liquid water depends on many factors such as, most importantly, surface temperatures. The properties of the planetary atmosphere and its interaction with the radiative energy provided by the planet's host star are thereby of decisive importance. In this study we investigate the influence of different main-sequence stars upon the climate of Earth-like extrasolar planets and their potential habitability by applying a 3D Earth climate model accounting for local and dynamical processes. The calculations have been performed for planets with Earth-like atmospheres at orbital distances where the total amount of energy received from the various host stars equals the solar constant. In contrast to previous 3D modeling studies, we include the effect of ozone radiative heating upon the vertical temperature structure of the atmospheres. The global orbital mean results o...

  1. Habitable Zones for Earth-Like Planets in the 47UMa Planetary System

    Science.gov (United States)

    Ji, Jianghui; Liu, Lin

    The Habitable zones are usually believed to be appropriate environment for terrestrial planets that can provide the liquid-water, subtle temperature, atmosphere components of CO2, H2O, and N2 [Kasting et al., Icarus 101 (1993) 108], supporting the development and biological evolution of life on their surfaces. In this work [see an accompanied paper, Ji et al., Astrophysical Journal 631 (2005) 1191 for details], we investigated the dynamical architecture of 47 UMa with the planetary configuration of the best-fit orbital solutions by Fischer et al. [Astrophysical Journal 586 (2003) 1394], to study the existence of the Earth-like planets in the region for 0.05 AU ≤ a ≤ 2.0 AU for 47 UMa by numerical simulations. In the study, we found that the “hot Earths” at 0.05 AU ≤ a ≤ 0.4 AU can dynamically survive at least for 1 Myr. The Earth-like planets can eventually remain in the system for 10 Myr at the areas involved in mean motion resonance (MMR) (e.g., 3:2 MMR and 9:5 MMR) with the inner companion. Moreover, we showed that the 2:1 and 3:1 resonances could be marginally stable, but the 5:2 MMR is unstable. In a dynamical sense, we point out that the most possible candidate habitable environment is that the Earth-like planets may bear the orbits of 0.8 AU ≤ a ≤ 1.0 AU and 1.0 AU ≤ a ≤ 1.30 AU (except 5:2 MMR) for relatively lower eccentricities. We also conducted similar studies in other multi-planet systems and found the potential existence of the Earth-like planets in habitable zones.

  2. Effects of Variable Eccentricity on the Climate of an Earth-like World

    Science.gov (United States)

    Way, M. J.; Georgakarakos, Nikolaos

    2017-01-01

    The Kepler era of exoplanetary discovery has presented the astronomical community with a cornucopia of planetary systems that are very different from the one that we inhabit. It has long been known that Jupiter plays a major role in the orbital parameters of Mars and its climate, but there is also a long-standing belief that Jupiter would play a similar role for Earth if not for the Moon. Using a three-dimensional general circulation model (3D GCM) with a fully coupled ocean, we simulate what would happen to the climate of an Earth-like world if Mars did not exist, but a Jupiter-like planet was much closer to Earth’s orbit. We investigate two scenarios that involve the evolution of the Earth-like planet’s orbital eccentricity from 0 to 0.283 over 6500 years, and from 0 to 0.066 on a timescale of 4500 years. In both cases we discover that they would maintain relatively temperate climates over the timescales simulated. More Earth-like planets in multi-planet systems will be discovered as we continue to survey the skies and the results herein show that the proximity of large gas giant planets may play an important role in the habitability of these worlds. These are the first such 3D GCM simulations using a fully coupled ocean with a planetary orbit that evolves over time due to the presence of a giant planet.

  3. Tidal meanders

    Science.gov (United States)

    Marani, Marco; Lanzoni, Stefano; Zandolin, Diego; Seminara, Giovanni; Rinaldo, Andrea

    2002-11-01

    Observational evidence is presented on the geometry of meandering tidal channels evolved within coastal wetlands characterized by different tidal, hydrodynamic, topographic, vegetational and ecological features. New insight is provided on the geometrical properties of tidal meanders, with possible dynamic implications on their evolution. In particular, it is shown that large spatial gradients of leading flow rates induce important spatial variabilities of meander wavelengths and widths, while their ratio remains remarkably constant in the range of scales of observation. This holds regardless of changes in width and wavelength up to two orders of magnitude. This suggests a locally adapted evolution, involving the morphological adjustment to the chief landforming events driven by local hydrodynamics. The spectral analysis of local curvatures reveals that Kinoshita's model curve does not fit tidal meanders due to the presence of even harmonics, in particular the second mode. Geometric parameters are constructed that are suitable to detect possible geomorphic signatures of the transitions from ebb- to flood-dominated hydrodynamics, here related to the skewness of the tidal meander. Trends in skewness, however, prove elusive to measure and fail to show detectable patterns. We also study comparatively the spatial patterns of evolution of the ratios of channel width to depth, and the ratio of width to local radius of curvature. Interestingly, the latter ratio exhibits consistency despite sharp differences in channel incision. Since the degree of incision, epitomized by the width-to-depth ratio, responds to the relevant erosion and migrations mechanisms and is much sensitive to vegetation and sediment properties, it is noticeable that we observe a great variety of landscape carving modes and yet recurrent planar features like constant width/curvature and wavelength/width ratios.

  4. Effects of Variable Eccentricity on the Climate of an Earth-Like World

    Science.gov (United States)

    Way, M. J.; Georgakarakos, Nikolaos

    2017-01-01

    The Kepler era of exoplanetary discovery has presented the Astronomical community with a cornucopia of planetary systems very different from the one which we inhabit. It has long been known that Jupiter plays a major role in the orbital parameters of Mars and its climate, but there is also a long-standing belief that Jupiter would play a similar role for Earth if not for its large moon. Using a three dimensional general circulation model (3-D GCM) with a fully-coupled ocean we simulate what would happen to the climate of an Earth-like world if Mars did not exist, but a Jupiter-like planet was much closer to Earths orbit. We investigate two scenarios that involve evolution of the Earth-like planets orbital eccentricity from 0 to 0.066 on a time scale of 4500 years, and from 0 to 0.283 over 6500 years. We discover that during most of the 6500 year scenario the planet would experience a moist greenhouse effect when near periastron. This could have implications for the ability of such a world to retain an ocean on time scales of 109 years. More Earth-like planets in multi-planet systems will be discovered as we continue to survey the skies and the results herein show that the proximity of large gas giant planets may play an important role in the habitabilty of these worlds. These are the first such 3-D GCM simulations using a fully-coupled ocean with a planetary orbit that evolves over time due to the presence of a giant planet.

  5. 3D climate modeling of Earth-like extrasolar planets orbiting different types of host stars

    Science.gov (United States)

    Godolt, M.; Grenfell, J. L.; Hamann-Reinus, A.; Kitzmann, D.; Kunze, M.; Langematz, U.; von Paris, P.; Patzer, A. B. C.; Rauer, H.; Stracke, B.

    2015-06-01

    The potential habitability of a terrestrial planet is usually defined by the possible existence of liquid water on its surface, since life as we know it needs liquid water at least during a part of its life cycle. The potential presence of liquid water on a planetary surface depends on many factors such as, most importantly, surface temperatures. The properties of the planetary atmosphere and its interaction with the radiative energy provided by the planet's host star are thereby of decisive importance. In this study we investigate the influence of different main-sequence stars (F, G, and K-type stars) upon the climate of Earth-like extrasolar planets and their potential habitability by applying a state-of-the-art three-dimensional (3D) Earth climate model accounting for local and dynamical processes. The calculations have been performed for planets with Earth-like atmospheres at orbital distances (and corresponding orbital periods) where the total amount of energy received from the various host stars equals the solar constant. In contrast to previous 3D modeling studies, we include the effect of ozone radiative heating upon the vertical temperature structure of the atmospheres. The global orbital mean results obtained have been compared to those of a one-dimensional (1D) radiative convective climate model to investigate the approximation of global mean 3D results by those of 1D models. The different stellar spectral energy distributions lead to different surface temperatures and due to ozone heating to very different vertical temperature structures. As previous 1D studies we find higher surface temperatures for the Earth-like planet around the K-type star, and lower temperatures for the planet around the F-type star compared to an Earth-like planet around the Sun. However, this effect is more pronounced in the 3D model results than in the 1D model because the 3D model accounts for feedback processes such as the ice-albedo and the water vapor feedback. Whether the

  6. Searching for Earth-like planets in this solar system and beyond

    Science.gov (United States)

    Stofan, E. R.

    2014-12-01

    Earth sits in a narrow habitable zone, and its future habitability depends on the actions of those who inhabit the planet today. Earth's complex climate reflects interactions between its interior, surface, oceans, biosphere, atmosphere and its star - our sun. Studying the climates of other planets around our sun - Mars, Venus and Titan - can help us better understand the processes that control climate here on Earth. These three bodies provide compelling targets for future study as we explore beyond our solar system to find Earth-like worlds around other stars.

  7. EPIC212521166 b: a Neptune-mass planet with Earth-like density

    CERN Document Server

    Osborn, H P; Barros, S C C; Armstrong, D J; Santos, N C; Hojjatpanah, S; Demangeon, O; Adibekyan, V; Almenara, J M; Barrado, D; Bayliss, D; Boisse, I; Bouchy, F; Brown, D J A; Deleuil, M; Mena, E Delgado; Hébrard, G; Kirk, J; King, G W; Lam, K W F; Lillo-Box, J; Louden, T M; Lovis, C; Marmier, M; McCormac, J; Pollacco, D; Sousa, S G; Udry, S; Walker, S R

    2016-01-01

    We report the discovery of the exoplanet EPIC212521166 b from K2 photometry orbiting on a 13.8637d period around an old, metal-poor K3 dwarf star. A joint analysis of K2 photometry and high-precision RVs from HARPS reveals it to have a radius of 2.6$\\pm 0.1 R_{\\oplus}$ and a mass of 18.3$\\pm 2.8 M_{\\oplus}$, making it the most massive planet with a sub-Neptune radius (i.e. mini-Neptune) yet found. When accounting for compression, the resulting Earth-like density is best fit by a $0.2M_{\\oplus}$ hydrogen atmosphere over an $18M_{\\oplus}$ Earth-like core, although the planet could also have significant water content. At 0.1AU, even taking into account the old stellar age of $8 \\pm 3$ Gyr, the planet is unlikely to have been significantly affected by EUV evaporation or tides. However the planet likely disc-migrated to its current position making the lack of a thick H$_2$ atmosphere puzzling. With a V-band magnitude of 11.9 it is particularly amenable to follow-up observations, making EPIC-1166 b a rare and extre...

  8. Effects of variable eccentricity on the climate of an Earth-like world

    CERN Document Server

    Way, Michael J

    2016-01-01

    The Kepler era of exoplanetary discovery has presented the Astronomical community with a cornucopia of planetary systems very different from the one which we inhabit. It has long been known that Jupiter plays a major role in the orbital parameters of Mars and it's climate, but there is also a long-standing belief that Jupiter would play a similar role for Earth if not for its large moon. Using a three dimensional general circulation model (3-D GCM) with a fully-coupled ocean we simulate what would happen to the climate of an Earth-like world if Mars did not exist, but a Jupiter-like planet was much closer to Earth's orbit. We investigate two scenarios that involve evolution of the Earth-like planet's orbital eccentricity from 0--0.066 on a time scale of 4500 years, and from 0--0.283 over 6500 years. We discover that during most of the 6500 year scenario the planet would experience a moist greenhouse effect when near periastron. This could have implications for the ability of such a world to retain an ocean on...

  9. 3D climate simulations of an Earth-like circumbinary planet

    Science.gov (United States)

    Popp, Max; Eggl, Siegfried

    2017-04-01

    Planets orbiting close binary-star systems experience strong variations in insolation that are due to the non-trivial evolution of the distance between the planet and the two stars. Previous studies have suggested that these variations in insolation could influence the habitability of Earth-like circumbinary planets. In contrast to previous work using one-dimensional models that lack important climate dynamics, we performed for the first time simulations of a hypothetical Earth-like circumbinary planet with a three-dimensional atmospheric general circulation model coupled to an analytical orbital propagator. We choose a Kepler-35-like setup without the gas-giant that is present in the actual system in order to investigate the effects of the variable total solar irradiance (TSI) originating from the double star on the planet's climate. For fixed CO2 concentrations we find that an aqua-planet (a fully water-covered planet) can maintain a habitable climate at TSI values similar to those an identical planet receives orbiting our sun. The variations in TSI have, however, various effects on the climate of the planet. Signatures of these periodic variations are clearly visible in important climate indicators such as surface temperature and precipitation. Moreover, the periodic forcing leads to a cooling of the mean climate, especially in cold climate regimes.

  10. Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs

    CERN Document Server

    Rugheimer, S; Segura, A; Linsky, J; Mohanty, S

    2015-01-01

    We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with $T_{eff}$ = 2300K to $T_{eff}$ = 3800K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1AU equivalent distance and show spectra from the VIS to IR (0.4$\\mu$m - 20$\\mu$m) to compare detectability of features in different wavelength ranges with JWST and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely: H$_2$O, O$_3$, CH$_4$, N$_2$O and CH$_3$Cl. To observe signatures of life - O$_2$/O$_3$ in combination with reducing species like CH$_4$, we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O$_2$ spectral feature at 0.76$\\mu$m is increasingly difficult to detect in reflected light of later M dwarfs due to low stellar flux in ...

  11. A Laboratory Demonstration of the Capability to Image an Earth-like Extrasolar Planet

    Science.gov (United States)

    Trauger, John T.; Wesley, A. Traub

    2007-01-01

    The detection and characterization of an Earth-like planet orbiting a nearby star requires a telescope with an extraordinarily large contrast at small angular separations. At visible wavelengths, an Earth-like planet would be 1 times 10-10 times fainter than the star at angular separations of typically 0.1 arcsecond or less. There are several proposed space telescope systems that could, in principle, achieve this. Here we report a laboratory experiment that reaches these limits. We have suppressed the diffracted and scattered light near a star-like source to a level of 6 times 10-10 times the peak intensity in individual coronagraph images. In a series of such images, together with simple image processing, we have effectively reduced this to a residual noise level of about 0.1 times 10-10. This demonstrates that a coronagraphic telescope in space could detect and spectroscopically characterize nearby exoplanetary systems, with the sensitivity to image an 'Earth-twin' orbiting a nearby star.

  12. Dynamical Stability of Earth-Like Planetary Orbits in Binary Systems

    CERN Document Server

    David, E M; Fatuzzo, M; Adams, F C; David, Eva-Marie; Quintana, Elisa V.; Fatuzzo, Marco; Adams, Fred C.

    2003-01-01

    This paper explores the stability of an Earth-like planet orbiting a solar mass star in the presence of an outer-lying intermediate mass companion. The overall goal is to estimate the fraction of binary systems that allow Earth-like planets to remain stable over long time scales. We numerically determine the planet's ejection time $\\tauej$ over a range of companion masses ($M_C$ = 0.001 -- 0.5 $M_\\odot$), orbital eccentricities $\\epsilon$, and semi-major axes $a$. This suite of $\\sim40,000$ numerical experiments suggests that the most important variables are the companion's mass $M_C$ and periastron distance $\\rmin$ = $a(1-\\epsilon)$ to the primary star. At fixed $M_C$, the ejection time is a steeply increasing function of $\\rmin$ over the range of parameter space considered here (although the ejection time has a distribution of values for a given $\\rmin$). Most of the integration times are limited to 10 Myr, but a small set of integrations extend to 500 Myr. For each companion mass, we find fitting formulae ...

  13. Exomoon Climate Models with the Carbonate-Silicate Cycle and Viscoelastic Tidal Heating

    CERN Document Server

    Forgan, Duncan

    2016-01-01

    The habitable zone for exomoons with Earth-like properties is a non-trivial manifold, compared to that of Earth-like exoplanets. The presence of tidal heating, eclipses and planetary illumination in the exomoon energy budget combine to produce both circumstellar and circumplanetary habitable regions. Analytical calculations suggest that the circumplanetary habitable region is defined only by an inner edge (with its outer limits determined by orbital stability). Subsequent calculations using 1D latitudinal climate models indicated that the combined effect of eclipses and ice-albedo feedback can produce an outer edge to the circumplanetary habitable zone. But is this outer edge real, or an artefact of the climate model's relative simplicity? We present an upgraded 1D climate model of Earth-like exomoon climates, containing the carbonate-silicate cycle and viscoelastic tidal heating. We conduct parameter surveys of both the circumstellar and circumplanetary habitable zones, and we find that the outer circumplane...

  14. CO2 condensation is a serious limit to the deglaciation of Earth-like planets

    Science.gov (United States)

    Turbet, Martin; Forget, Francois; Leconte, Jeremy; Charnay, Benjamin; Tobie, Gabriel

    2017-10-01

    It is widely believed that the carbonate-silicate cycle is the main agent, through volcanism, to trigger deglaciations by CO2 greenhouse warming on Earth and on Earth-like planets when they get in a frozen state. Here we use a 3D Global Climate Model to simulate the ability of planets initially completely frozen to escape from glaciation episodes by accumulating enough gaseous CO2. The model includes CO2 condensation and sublimation processes and the water cycle. We find that planets with Earth-like characteristics (size, mass, obliquity, rotation rate, etc.) orbiting a Sun-like star may never be able to escape from a glaciation era, if their orbital distance is greater than ∼1.27 Astronomical Units (Flux pressures ( 0.6), this critical limit could occur at a significantly lower equivalent distance (or higher insolation). For each possible configuration, we show that the amount of CO2 that can be trapped in the polar caps depends on the efficiency of CO2 ice to flow laterally as well as its gravitational stability relative to subsurface water ice. We find that a frozen Earth-like planet located at 1.30 AU of a Sun-like star could store as much as 1.5, 4.5 and 15 bars of dry ice at the poles, for internal heat fluxes of 100, 30 and 10 mW m-2, respectively. But these amounts are in fact lower limits. For planets with a significant water ice cover, we show that CO2 ice deposits should be gravitationally unstable. They get buried beneath the water ice cover in geologically short timescales of ∼104 yrs, mainly controlled by the viscosity of water ice. CO2 would be permanently sequestered underneath the water ice cover, in the form of CO2 liquids, CO2 clathrate hydrates and/or dissolved in subglacial water reservoirs (if any). This would considerably increase the amount of CO2 trapped and further reduce the probability of deglaciation.

  15. Galactic cosmic rays on extrasolar Earth-like planets: II. Atmospheric implications

    CERN Document Server

    Grießmeier, J --M; Stadelmann, A; Grenfell, J L; Atri, D

    2016-01-01

    (abridged abstract) Theoretical arguments indicate that close-in terrestial exoplanets may have weak magnetic fields. As described in the companion article (Paper I), a weak magnetic field results in a high flux of galactic cosmic rays to the top of the planetary atmosphere. We investigate effects that may result from a high flux of galactic cosmic rays both throughout the atmosphere and at the planetary surface. Using an air shower approach, we calculate how the atmospheric chemistry and temperature change under the influence of galactic cosmic rays for Earth-like (N_2-O_2 dominated) atmospheres. We evaluate the production and destruction rate of atmospheric biosignature molecules. We derive planetary emission and transmission spectra to study the influence of galactic cosmic rays on biosignature detectability. We then calculate the resulting surface UV flux, the surface particle flux, and the associated equivalent biological dose rates. We find that up to 20% of stratospheric ozone is destroyed by cosmic-ra...

  16. Wavefront error correction and Earth-like planet detection by Self-Coherent Camera in space

    CERN Document Server

    Galicher, R; Rousset, G

    2008-01-01

    In the context of exoplanet detection, the performance of coronagraphs is limited by wavefront errors. To efficiently correct for these aberrations with a deformable mirror, it is mandatory to measure them using the science detector with a very high accuracy. The Self-Coherent Camera which is based on light incoherence between star and its environment enables an estimation of these wavefront errors. That estimation is directly derived from the encoded speckles in the science image. This avoids differential errors due to beam separation and non common optics. Earth-like planet detection is demonstrated by numerical simulations under realistic assumptions for a space telescope. The Self-Coherent Camera is an attractive technique for future space telescopes. It is also one of the techniques under investigation for the E-ELT planet finder so-called EPICS.

  17. Is the Pale Blue Dot unique? Optimized photometric bands for identifying Earth-like exoplanets

    CERN Document Server

    Krissansen-Totton, Joshua; Charnay, Benjamin; Arney, Giada; Robinson, Tyler D; Meadows, Victoria; Catling, David C

    2015-01-01

    The next generation of ground and space-based telescopes will image habitable planets around nearby stars. A growing literature describes how to characterize such planets with spectroscopy, but less consideration has been given to the usefulness of planet colors. Here, we investigate whether potentially Earth-like exoplanets could be identified using UV-visible-to-NIR wavelength broadband photometry (350-1000 nm). Specifically, we calculate optimal photometric bins for identifying an exo-Earth and distinguishing it from uninhabitable planets including both Solar System objects and model exoplanets. The color of some hypothetical exoplanets - particularly icy terrestrial worlds with thick atmospheres - is similar to Earth's because of Rayleigh scattering in the blue region of the spectrum. Nevertheless, subtle features in Earth's reflectance spectrum appear to be unique. In particular, Earth's reflectance spectrum has a 'U-shape' unlike all our hypothetical, uninhabitable planets. This shape is partly biogenic...

  18. Increased insolation threshold for runaway greenhouse processes on Earth like planets

    CERN Document Server

    Leconte, Jérémy; Charnay, Benjamin; Wordsworth, Robin; Pottier, Alizée

    2013-01-01

    Because the solar luminosity increases over geological timescales, Earth climate is expected to warm, increasing water evaporation which, in turn, enhances the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can "runaway" until all the oceans are evaporated. Through increases in stratospheric humidity, warming may also cause oceans to escape to space before the runaway greenhouse occurs. The critical insolation thresholds for these processes, however, remain uncertain because they have so far been evaluated with unidimensional models that cannot account for the dynamical and cloud feedback effects that are key stabilizing features of Earth's climate. Here we use a 3D global climate model to show that the threshold for the runaway greenhouse is about 375 W/m$^2$, significantly higher than previously thought. Our model is specifically developed to quantify the climate response of Earth-like planets to increased insolation in hot and extremely moist atmo...

  19. EXPRES: A Next Generation RV Spectrograph in the Search for Earth-like Worlds

    CERN Document Server

    Jurgenson, C; McCracken, T; Sawyer, D; Szymkowiak, A; Davis, A B; Muller, G; Santoro, F

    2016-01-01

    The EXtreme PREcision Spectrograph (EXPRES) is an optical fiber fed echelle instrument being designed and built at the Yale Exoplanet Laboratory to be installed on the 4.3-meter Discovery Channel Telescope operated by Lowell Observatory. The primary science driver for EXPRES is to detect Earth-like worlds around Sun-like stars. With this in mind, we are designing the spectrograph to have an instrumental precision of 15 cm/s so that the on-sky measurement precision (that includes modeling for RV noise from the star) can reach to better than 30 cm/s. This goal places challenging requirements on every aspect of the instrument development, including optomechanical design, environmental control, image stabilization, wavelength calibration, and data analysis. In this paper we describe our error budget, and instrument optomechanical design.

  20. Quantum degenerate mixtures of alkali and alkaline-earth-like atoms.

    Science.gov (United States)

    Hara, Hideaki; Takasu, Yosuke; Yamaoka, Yoshifumi; Doyle, John M; Takahashi, Yoshiro

    2011-05-20

    We realize simultaneous quantum degeneracy in mixtures consisting of the alkali and alkaline-earth-like atoms Li and Yb. This is accomplished within an optical trap by sympathetic cooling of the fermionic isotope ⁶Li with evaporatively cooled bosonic ¹⁷⁴Yb and, separately, fermionic ¹⁷³Yb. Using cross-thermalization studies, we also measure the elastic s-wave scattering lengths of both Li-Yb combinations, |a(⁶Li-¹⁷⁴Yb)| = 1.0 ± 0.2 nm and |a(⁶Li-¹⁷³Yb)| = 0.9 ± 0.2 nm. The equality of these lengths is found to be consistent with mass-scaling analysis. The quantum degenerate mixtures of Li and Yb, as realized here, can be the basis for creation of ultracold molecules with electron spin degrees of freedom, studies of novel Efimov trimers, and impurity probes of superfluid systems.

  1. Free oscillations of the earth-like planets in the presence of magnetic field

    Directory of Open Access Journals (Sweden)

    Y. Abedini

    2005-12-01

    Full Text Available   we study the free oscillations of a non-rotating earth-like planet in the presence of a force free magnetic field. The model consists of a solid inner core, a liquid outer core and a solid mantle which is spherically symmetric. The lagrangian displacements are decomposed into scaloidal, poloidal and toroidal components using a gauged version of Helmholtz theorem. These components are identified, with P- , g and t- modes, respectively. The normal modes of the model are determined using a Rayleigh-Ritz variational technique. The consequence of the presence of the solid parts and the magnetic field is the emergence of pure t- oscillations. The magnetic field, in addition to exciting t- modes, couples the everpresent p- and g -modes together. As an application of the model, the real seismic data of the earth is used to calculate eigenvalues and eigenvectors for different modes.

  2. Photon Hall Scattering from Alkaline-earth-like atoms and Alkali-like ions

    CERN Document Server

    van Tiggelen, B A

    2016-01-01

    We investigate the possibility of observing a magneto-transverse scattering of photons from alkaline-earth-like atoms as well as alkali-like ions and provide orders of magnitude. The transverse magneto-scattering is physically induced by the interference between two possible quantum transitions of an outer electron in a S-state, one dispersive electric-dipole transition to a P-orbital state and a second resonant electric-quadrupole transition to a P-orbital state. In contrast with previous mechanisms proposed for such an atomic photonic Hall effect, no real photons are scattered by the electric-dipole allowed transition, which increases the ratio of Hall current to background photons significantly. The main experimental challenge is to overcome the small detection threshold, with only 10^{-5} photons scattered per atom per second.

  3. Geodynamics and Rate of Volcanism on Massive Earth-like Planets

    CERN Document Server

    Kite, Edwin S; Gaidos, Eric

    2008-01-01

    We provide estimates of volcanism versus time for planets with Earth-like composition and masses from 0.25 to 25 times Earth, as a step toward predicting atmospheric mass on extrasolar rocky planets. Volcanism requires melting of the silicate mantle. We use a thermal evolution model, calibrated against Earth, in combination with standard melting models, to explore the dependence of convection-driven decompression mantle melting on planet mass. Here we show that (1) volcanism is likely to proceed on massive planets with plate tectonics over the main-sequence lifetime of the parent star; (2) crustal thickness (and melting rate normalized to planet mass) is weakly dependent on planet mass; (3) stagnant lid planets can have higher rates of melting than their plate tectonic counterparts early in their thermal evolution, but melting shuts down after a few Gyr; (4) plate tectonics may not operate on high mass planets because of the production of buoyant crust which is difficult to subduct; and (5) melting is necessa...

  4. Control of Earth-like magnetic fields on the transformation of ferrihydrite to hematite and goethite.

    Science.gov (United States)

    Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J; Barrón, Vidal; Torrent, José; Roberts, Andrew P

    2016-07-26

    Hematite and goethite are the two most abundant iron oxides in natural environments. Their formation is controlled by multiple environmental factors; therefore, their relative concentration has been used widely to indicate climatic variations. In this study, we aimed to test whether hematite and goethite growth is influenced by ambient magnetic fields of Earth-like values. Ferrihydrite was aged at 95 °C in magnetic fields ranging from ~0 to ~100 μT. Our results indicate a large influence of the applied magnetic field on hematite and goethite growth from ferrihydrite. The synthesized products are a mixture of hematite and goethite for field intensities fields favour hematite formation by accelerating ferrimagnetic ferrihydrite aggregation. Additionally, hematite particles growing in a controlled magnetic field of ~100 μT appear to be arranged in chains, which may be reduced to magnetite keeping its original configuration, therefore, the presence of magnetic particles in chains in natural sediments cannot be used as an exclusive indicator of biogenic magnetite. Hematite vs. goethite formation in our experiments is influenced by field intensity values within the range of geomagnetic field variability. Thus, geomagnetic field intensity could be a source of variation when using iron (oxyhydr-)oxide concentrations in environmental magnetism.

  5. Atmospheric effects of stellar cosmic rays on Earth-like exoplanets orbiting M-dwarfs

    CERN Document Server

    Tabataba-Vakili, F; Grießmeier, J -M; Rauer, H

    2016-01-01

    M-dwarf stars are generally considered favourable for rocky planet detection. However, such planets may be subject to extreme conditions due to possible high stellar activity. The goal of this work is to determine the potential effect of stellar cosmic rays on key atmospheric species of Earth-like planets orbiting in the habitable zone of M-dwarf stars and show corresponding changes in the planetary spectra. We build upon the cosmic rays model scheme of Grenfell et al. (2012), who considered cosmic ray induced NOx production, by adding further cosmic ray induced production mechanisms (e.g. for HOx) and introducing primary protons of a wider energy range (16 MeV - 0.5 TeV). Previous studies suggested that planets in the habitable zone that are subject to strong flaring conditions have high atmospheric methane concentrations, while their ozone biosignature is completely destroyed. Our current study shows, however, that adding cosmic ray induced HOx production can cause a decrease in atmospheric methane abundanc...

  6. VizieR Online Data Catalog: Catalog of Earth-Like Exoplanet Survey Targets (Chandler+, 2016)

    Science.gov (United States)

    Chandler, C. O.; McDonald, I.; Kane, S. R.

    2016-07-01

    We present the Catalog of Earth-Like Exoplanet Survey Targets (CELESTA), a database of habitable zones around 37000 nearby stars. The first step in creating CELESTA was assembling the input data. The Revised Hipparcos Catalog (van Leeuwen 2007, Cat. I/311) is a stellar catalog based on the original Hipparcos mission (Perryman et al. 1997, Cat. I/239) data set. Hipparcos, launched in 1989, recorded with great precision the parallax of nearby stars, ultimately leading to a database of 118218 stars. McDonald et al. 2012 (cat. J/MNRAS/427/343) calculated effective temperatures and luminosities for the Hipparcos stars. The next step was selecting appropriate stars for the construction of CELESTA. The Stellar Parameter Catalog of 103663 stars included many stars that were not suitable for our purposes, especially stars off the Main-Sequence (MS) branch, e.g., giants. Please refer to Section 3.2 in the paper for additional details about the star selection. The final CELESTA catalog contains 37354 stars (see Table2), each with a set of associated attributes, e.g., estimated mass, measured distance. The complete database can also be found online at a dedicated host (http://www.celesta.info/). (2 data files).

  7. Science cases for the OWL Earth-like planet imager and spectrograph (EPICS)

    Science.gov (United States)

    Beuzit, J.-L.; Gratton, R.; Kasper, M.; Desidera, S.; Kerber, F.; Rahoui, F.; Mouillet, D.; Rouan, D.; Turatto, M.; Feldt, M.; Schmid, H.-M.; Stam, D.; Selsis, F.; Hubin, N.; Vérinaud, C.

    The extreme contrast in mass and luminosity between the extra-solar planets and their host stars make detailed studies of these planets very challenging. In particular, direct observations of extra-solar planets is still beyond the capabilities of the currently available instrumentation, save for perhaps a few extreme cases of very young and massive planets at large distances from the central star. While progress in instrumentation might allow significant progress in detection capabilities either with the 8 and 10-m ground-based telescopes (Planet Finder instruments on the VLT and Gemini) or with the next generation space telescope (JWST), imaging of extra-solar planets over a wide range of parameters, and possibly down to terrestrial planets, will require extremely large ground-based telescopes like OWL or dedicated space instrumentation (TPF or Darwin for instance). We outline here the scientific objectives of EPICS, the OWL Earth-like Planet Imager and Spectrograph, summarize the corresponding high level requirements, present the foreseen observing modes and give a first estimate of its performance.

  8. UV SURFACE ENVIRONMENT OF EARTH-LIKE PLANETS ORBITING FGKM STARS THROUGH GEOLOGICAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Rugheimer, S.; Sasselov, D. [Harvard Smithsonian Center for Astrophysics, 60 Garden st., 02138 MA Cambridge (United States); Segura, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México (Mexico); Kaltenegger, L., E-mail: srugheimer@cfa.harvard.edu [Carl Sagan Institute, Cornell University, Ithaca, NY 14853 (United States)

    2015-06-10

    The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars in the circumstellar Habitable Zone for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early-Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present-day levels at 2.0 Gyr ago, 0.8 Gyr ago, and modern Earth. In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth–Sun levels. A pre-biotic Earth orbiting GJ 581 (M3.5 V) receives 300 times less biologically effective radiation, about 2 times modern Earth–Sun levels. The UV fluxes calculated here provide a grid of model UV environments during the evolution of an Earth-like planet orbiting a range of stars. These models can be used as inputs into photo-biological experiments and for pre-biotic chemistry and early life evolution experiments.

  9. The habitable zone of Earth-like planets with different levels of atmospheric pressure

    CERN Document Server

    Vladilo, Giovanni; Silva, Laura; Provenzale, Antonello; Ferri, Gaia; Ragazzini, Gregorio

    2013-01-01

    As a contribution to the study of the habitability of extrasolar planets, we implemented a 1-D Energy Balance Model (EBM), the simplest seasonal model of planetary climate, with new prescriptions for most physical quantities. Here we apply our EBM to investigate the surface habitability of planets with an Earth-like atmospheric composition but different levels of surface pressure. The habitability, defined as the mean fraction of the planet's surface on which liquid water could exist, is estimated from the pressure-dependent liquid water temperature range, taking into account seasonal and latitudinal variations of surface temperature. By running several thousands of EBM simulations we generated a map of the habitable zone (HZ) in the plane of the orbital semi-major axis, a, and surface pressure, p, for planets in circular orbits around a Sun-like star. As pressure increases, the HZ becomes broader, with an increase of 0.25 AU in its radial extent from p=1/3 bar to p=3 bar. At low pressure, the habitability is...

  10. THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Bagnulo, S. [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom); Kowalski, P. M. [GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam (Germany); Shulyak, D. V. [Institute of Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Sterzik, M. F., E-mail: l.fossati@open.ac.uk, E-mail: C.A.Haswell@open.ac.uk, E-mail: M.R.Patel@open.ac.uk, E-mail: r.busuttil@open.ac.uk, E-mail: sba@arm.ac.uk, E-mail: kowalski@gfz-potsdam.de, E-mail: denis.shulyak@gmail.com, E-mail: msterzik@eso.org [European Southern Observatory, Casilla 19001, Santiago 19 (Chile)

    2012-09-20

    Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for {approx}8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10{sup 2} (10{sup 4}) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M{sub Sun} white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

  11. Detecting industrial pollution in the atmospheres of earth-like exoplanets

    CERN Document Server

    Lin, Henry W; Loeb, Abraham

    2014-01-01

    Detecting biomarkers, such as molecular oxygen, in the atmospheres of transiting exoplanets has been a major focus in the search for alien life. We point out that in addition to these generic indicators, anthropogenic pollution could be used as a novel biomarker for intelligent life. To this end, we identify pollutants in the Earth's atmosphere that have significant absorption features in the spectral range covered by the James Webb Space Telescope (JWST). We estimate that for an Earth-mass planet in the habitable zone of a white dwarf, methane (CH4) and nitrous oxide (N2O) can be detected at earth-like concentrations with an integration time of ~1.5 hrs and 12 hrs respectively. Detecting pollutants that are produced nearly exclusively by anthropogenic activities will be significantly more challenging. Of these pollutants, we focus on tetrafluoromethane (CF4) and trichlorofluoromethane (CCl3F), which will be the easiest to detect. We estimate that ~1.5 days (~3 days) of total integration time will be sufficie...

  12. Control of Earth-like magnetic fields on the transformation of ferrihydrite to hematite and goethite

    Science.gov (United States)

    Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J.; Barrón, Vidal; Torrent, José; Roberts, Andrew P.

    2016-07-01

    Hematite and goethite are the two most abundant iron oxides in natural environments. Their formation is controlled by multiple environmental factors; therefore, their relative concentration has been used widely to indicate climatic variations. In this study, we aimed to test whether hematite and goethite growth is influenced by ambient magnetic fields of Earth-like values. Ferrihydrite was aged at 95 °C in magnetic fields ranging from ~0 to ~100 μT. Our results indicate a large influence of the applied magnetic field on hematite and goethite growth from ferrihydrite. The synthesized products are a mixture of hematite and goethite for field intensities <~60 μT. Higher fields favour hematite formation by accelerating ferrimagnetic ferrihydrite aggregation. Additionally, hematite particles growing in a controlled magnetic field of ~100 μT appear to be arranged in chains, which may be reduced to magnetite keeping its original configuration, therefore, the presence of magnetic particles in chains in natural sediments cannot be used as an exclusive indicator of biogenic magnetite. Hematite vs. goethite formation in our experiments is influenced by field intensity values within the range of geomagnetic field variability. Thus, geomagnetic field intensity could be a source of variation when using iron (oxyhydr-)oxide concentrations in environmental magnetism.

  13. Modeling the Entry of Micrometeoroids into the Atmospheres of Earth-like Planets

    Science.gov (United States)

    Pevyhouse, A. R.; Kress, M. E.

    2011-01-01

    The temperature profiles of micrometeors entering the atmospheres of Earth-like planets are calculated to determine the altitude at which exogenous organic compounds may be released. Previous experiments have shown that flash-heated micrometeorite analogs release organic compounds at temperatures from roughly 500 to 1000 K [1]. The altitude of release is of great importance because it determines the fate of the compound. Organic compounds that are released deeper in the atmosphere are more likely to rapidly mix to lower altitudes where they can accumulate to higher abundances or form more complex molecules and/or aerosols. Variables that are explored here are particle size, entry angle, atmospheric density profiles, spectral type of the parent star, and planet mass. The problem reduces to these questions: (1) How much atmosphere does the particle pass through by the time it is heated to 500 K? (2) Is the atmosphere above sufficient to attenuate stellar UV such that the mixing timescale is shorter than the photochemical timescale for a particular compound? We present preliminary results that the effect of the planetary and particle parameters have on the altitude of organic release.

  14. Influence of Sudden Change of Solar Mass in the PN Stage on the Orbit of Earth-Like Planet

    Indian Academy of Sciences (India)

    Yunfeng Zhu; Caijuan Pan; Dasheng Pan; Hongqiang Huang; Zhi-Fu Chen

    2014-09-01

    Assuming that the terminated mass is confined within the range 0.4551-0.5813⊙ when the sun is going to evolve into a white dwarf, the velocity of the sun projecting the shell in the PN stage is much greater than the revolving velocity of the earth-like planet, therefore, we think that the solar mass change is instantaneous.

  15. Increased insolation threshold for runaway greenhouse processes on Earth-like planets.

    Science.gov (United States)

    Leconte, Jérémy; Forget, Francois; Charnay, Benjamin; Wordsworth, Robin; Pottier, Alizée

    2013-12-12

    The increase in solar luminosity over geological timescales should warm the Earth's climate, increasing water evaporation, which will in turn enhance the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can 'run away' until the oceans have completely evaporated. Through increases in stratospheric humidity, warming may also cause evaporative loss of the oceans to space before the runaway greenhouse state occurs. The critical insolation thresholds for these processes, however, remain uncertain because they have so far been evaluated using one-dimensional models that cannot account for the dynamical and cloud feedback effects that are key stabilizing features of the Earth's climate. Here we use a three-dimensional global climate model to show that the insolation threshold for the runaway greenhouse state to occur is about 375 W m(-2), which is significantly higher than previously thought. Our model is specifically developed to quantify the climate response of Earth-like planets to increased insolation in hot and extremely moist atmospheres. In contrast with previous studies, we find that clouds have a destabilizing feedback effect on the long-term warming. However, subsident, unsaturated regions created by the Hadley circulation have a stabilizing effect that is strong enough to shift the runaway greenhouse limit to higher values of insolation than are inferred from one-dimensional models. Furthermore, because of wavelength-dependent radiative effects, the stratosphere remains sufficiently cold and dry to hamper the escape of atmospheric water, even at large fluxes. This has strong implications for the possibility of liquid water existing on Venus early in its history, and extends the size of the habitable zone around other stars.

  16. Atmospheric effects of stellar cosmic rays on Earth-like exoplanets orbiting M-dwarfs

    Science.gov (United States)

    Tabataba-Vakili, F.; Grenfell, J. L.; Grießmeier, J.-M.; Rauer, H.

    2016-01-01

    M-dwarf stars are generally considered favourable for rocky planet detection. However, such planets may be subject to extreme conditions due to possible high stellar activity. The goal of this work is to determine the potential effect of stellar cosmic rays on key atmospheric species of Earth-like planets orbiting in the habitable zone of M-dwarf stars and show corresponding changes in the planetary spectra. We build upon the cosmic rays model scheme of previous works, who considered cosmic ray induced NOx production, by adding further cosmic ray induced production mechanisms (e.g. for HOx) and introducing primary protons of a wider energy range (16 MeV-0.5 TeV). Previous studies suggested that planets in the habitable zone that are subject to strong flaring conditions have high atmospheric methane concentrations, while their ozone biosignature is completely destroyed. Our current study shows, however, that adding cosmic ray induced HOx production can cause a decrease in atmospheric methane abundance of up to 80%. Furthermore, the cosmic ray induced HOx molecules react with NOx to produce HNO3, which produces strong HNO3 signals in the theoretical spectra and reduces NOx-induced catalytic destruction of ozone so that more than 25% of the ozone column remains. Hence, an ozone signal remains visible in the theoretical spectrum (albeit with a weaker intensity) when incorporating the new cosmic ray induced NOx and HOx schemes, even for a constantly flaring M-star case. We also find that HNO3 levels may be high enough to be potentially detectable. Since ozone concentrations, which act as the key shield against harmful UV radiation, are affected by cosmic rays via NOx-induced catalytic destruction of ozone, the impact of stellar cosmic rays on surface UV fluxes is also studied.

  17. SCIENCE PARAMETRICS FOR MISSIONS TO SEARCH FOR EARTH-LIKE EXOPLANETS BY DIRECT IMAGING

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Robert A., E-mail: rbrown@stsci.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2015-01-20

    We use N{sub t} , the number of exoplanets observed in time t, as a science metric to study direct-search missions like Terrestrial Planet Finder. In our model, N has 27 parameters, divided into three categories: 2 astronomical, 7 instrumental, and 18 science-operational. For various ''27-vectors'' of those parameters chosen to explore parameter space, we compute design reference missions to estimate N{sub t} . Our treatment includes the recovery of completeness c after a search observation, for revisits, solar and antisolar avoidance, observational overhead, and follow-on spectroscopy. Our baseline 27-vector has aperture D = 16 m, inner working angle IWA = 0.039'', mission time t = 0-5 yr, occurrence probability for Earth-like exoplanets η = 0.2, and typical values for the remaining 23 parameters. For the baseline case, a typical five-year design reference mission has an input catalog of ∼4700 stars with nonzero completeness, ∼1300 unique stars observed in ∼2600 observations, of which ∼1300 are revisits, and it produces N {sub 1} ∼ 50 exoplanets after one year and N {sub 5} ∼ 130 after five years. We explore offsets from the baseline for 10 parameters. We find that N depends strongly on IWA and only weakly on D. It also depends only weakly on zodiacal light for Z < 50 zodis, end-to-end efficiency for h > 0.2, and scattered starlight for ζ < 10{sup –10}. We find that observational overheads, completeness recovery and revisits, solar and antisolar avoidance, and follow-on spectroscopy are all important factors in estimating N.

  18. THE HABITABLE ZONE OF EARTH-LIKE PLANETS WITH DIFFERENT LEVELS OF ATMOSPHERIC PRESSURE

    Energy Technology Data Exchange (ETDEWEB)

    Vladilo, Giovanni; Murante, Giuseppe; Silva, Laura [INAF-Trieste Astronomical Observatory, Trieste (Italy); Provenzale, Antonello [Institute of Atmospheric Sciences and Climate-CNR, Torino (Italy); Ferri, Gaia; Ragazzini, Gregorio, E-mail: vladilo@oats.inaf.it [Department of Physics, University of Trieste, Trieste (Italy)

    2013-04-10

    As a contribution to the study of the habitability of extrasolar planets, we implemented a one-dimensional energy balance model (EBM), the simplest seasonal model of planetary climate, with new prescriptions for most physical quantities. Here we apply our EBM to investigate the surface habitability of planets with an Earth-like atmospheric composition but different levels of surface pressure. The habitability, defined as the mean fraction of the planet's surface on which liquid water could exist, is estimated from the pressure-dependent liquid water temperature range, taking into account seasonal and latitudinal variations of surface temperature. By running several thousands of EBM simulations we generated a map of the habitable zone (HZ) in the plane of the orbital semi-major axis, a, and surface pressure, p, for planets in circular orbits around a Sun-like star. As pressure increases, the HZ becomes broader, with an increase of 0.25 AU in its radial extent from p = 1/3 to 3 bar. At low pressure, the habitability is low and varies with a; at high pressure, the habitability is high and relatively constant inside the HZ. We interpret these results in terms of the pressure dependence of the greenhouse effect, the efficiency of horizontal heat transport, and the extent of the liquid water temperature range. Within the limits discussed in the paper, the results can be extended to planets in eccentric orbits around non-solar-type stars. The main characteristics of the pressure-dependent HZ are modestly affected by variations of planetary properties, particularly at high pressure.

  19. The Stability of Hydrogen-Rich Atmospheres of Earth-Like Planets

    Science.gov (United States)

    Zahnle, Kevin

    2016-01-01

    Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydro- dynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than 1.6 Earth radii.

  20. Lost Treasures: Locks

    Directory of Open Access Journals (Sweden)

    Semra SARAÇOĞLU ÇELİK

    2015-03-01

    Full Text Available Locks have been widely used in our daily life. In this paper an attempt is made to study the history of locks and to give the kinds of locks and samples from past to present: Ancient Egypt, Chinese, Iran, Roman, Turk-Islam Locks. Ancient locks relied on the pin tumbler principle that many of today's locks use. Many early Roman Keys were made to be worn as rings, because clothing of Romans did not have pockets. It is hoped that this article can simulate more research and publications regarding the development of ancient locks.

  1. Crustal decoupling and mantle dynamics on Venus: implications for Earth-like planets

    Science.gov (United States)

    Ghail, Richard

    2013-04-01

    (intraplate) continental interiors. The higher background heat flux results in a higher incidence of intraplate volcanism than on Earth, in a relatively random distribution that mirrors the near-random distribution of impact craters and results in the observed mean surface age. While these conditions occur on Venus in basaltic crust because of its extreme surface conditions, it offers insight into mantle dynamics beneath Pangaea or an Earth-like planet entirely covered by continental crust. An ESA M-class mission, EnVision, is proposed to undertake InSAR measurements at Venus to determine rates of ground displacement in order to distinguish between these two models.

  2. Assessing the habitability of planets with Earth-like atmospheres with 1D and 3D climate modeling

    CERN Document Server

    Godolt, M; Kitzmann, D; Kunze, M; Langematz, U; Patzer, A B C; Rauer, H; Stracke, B

    2016-01-01

    The habitable zone (HZ) describes the range of orbital distances around a star where the existence of liquid water on the surface of an Earth-like planet is in principle possible. While 3D climate studies can calculate the water vapor, ice albedo, and cloud feedback self-consistently and therefore allow for a deeper understanding and the identification of relevant climate processes, 1D model studies rely on fewer model assumptions and can be more easily applied to the large parameter space possible for exoplanets. We evaluate the applicability of 1D climate models to estimate the potential habitability of Earth-like exoplanets by comparing our 1D model results to those of 3D climate studies in the literature. We applied a cloud-free 1D radiative-convective climate model to calculate the climate of Earth-like planets around different types of main-sequence stars with varying surface albedo and relative humidity profile. These parameters depend on climate feedbacks that are not treated self-consistently in most...

  3. Overview of locking systems

    Energy Technology Data Exchange (ETDEWEB)

    Gee, K.T.; Scott, S.H.; Wilde, M.G. [Sandia National Labs., Albuquerque, NM (United States); Highland, S.E. [Albuquerque Safe Co., Albuquerque, NM (United States)

    1993-12-01

    The purpose of this document is to present technical information that should be useful for understanding and applying locking systems for physical protection and control. There are major sections on hardware for locks, vaults, safes, and security containers. Other topics include management of lock systems and safety considerations. This document also contains notes on standards and specifications and a glossary.

  4. Development of a model to compute the extension of life supporting zones for Earth-like exoplanets.

    Science.gov (United States)

    Neubauer, David; Vrtala, Aron; Leitner, Johannes J; Firneis, Maria G; Hitzenberger, Regina

    2011-12-01

    A radiative convective model to calculate the width and the location of the life supporting zone (LSZ) for different, alternative solvents (i.e. other than water) is presented. This model can be applied to the atmospheres of the terrestrial planets in the solar system as well as (hypothetical, Earth-like) terrestrial exoplanets. Cloud droplet formation and growth are investigated using a cloud parcel model. Clouds can be incorporated into the radiative transfer calculations. Test runs for Earth, Mars and Titan show a good agreement of model results with observations.

  5. Assessing the habitability of planets with Earth-like atmospheres with 1D and 3D climate modeling

    Science.gov (United States)

    Godolt, M.; Grenfell, J. L.; Kitzmann, D.; Kunze, M.; Langematz, U.; Patzer, A. B. C.; Rauer, H.; Stracke, B.

    2016-07-01

    Context. The habitable zone (HZ) describes the range of orbital distances around a star where the existence of liquid water on the surface of an Earth-like planet is in principle possible. The applicability of one-dimensional (1D) climate models for the estimation of the HZ boundaries has been questioned by recent three-dimensional (3D) climate studies. While 3D studies can calculate the water vapor, ice albedo, and cloud feedback self-consistently and therefore allow for a deeper understanding and the identification of relevant climate processes, 1D model studies rely on fewer model assumptions and can be more easily applied to the large parameter space possible for extrasolar planets. Aims: We evaluate the applicability of 1D climate models to estimate the potential habitability of Earth-like extrasolar planets by comparing our 1D model results to those of 3D climate studies in the literature. We vary the two important planetary properties, surface albedo and relative humidity, in the 1D model. These depend on climate feedbacks that are not treated self-consistently in most 1D models. Methods: We applied a cloud-free 1D radiative-convective climate model to calculate the climate of Earth-like planets around different types of main-sequence stars with varying surface albedo and relative humidity profile. We compared the results to those of 3D model calculations available in the literature and investigated to what extent the 1D model can approximate the surface temperatures calculated by the 3D models. Results: The 1D parameter study results in a large range of climates possible for an Earth-sized planet with an Earth-like atmosphere and water reservoir at a certain stellar insolation. At some stellar insolations the full spectrum of climate states could be realized, i.e., uninhabitable conditions due to surface temperatures that are too high or too low as well as habitable surface conditions, depending only on the relative humidity and surface albedo assumed. When

  6. Climate of Earth-Like Planets With and Without Ocean Heat Transport Orbiting a Range of M and K Stars

    Science.gov (United States)

    Kiang, N. Y.; Jablonski, Emma R.; Way, Michael J.; Del Genio, Anthony; Roberge, Aki

    2015-01-01

    The mean surface temperature of a planet is now acknowledged as insufficient to surmise its full potential habitability. Advancing our understanding requires exploration with 3D general circulation models (GCMs), which can take into account how gradients and fluxes across a planet's surface influence the distribution of heat, clouds, and the potential for heterogeneous distribution of liquid water. Here we present 3D GCM simulations of the effects of alternative stellar spectra, instellation, model resolution, and ocean heat transport, on the simulated distribution of heat and moisture of an Earth-like planet (ELP).

  7. Perpetual long libration of terrestrial planets in tidal resonances

    Science.gov (United States)

    Makarov, Valeri

    2015-11-01

    On the example of Mercury, I show that firm planets of terrestrial composition, locked in the 3:2 or higher spin-orbit resonances, undergo long-period perpetual libration in longitude without any influence of third bodies. This non-damped libration at the natural frequency is driven by a secular tidal torque, which is increasing with frequency within a narrow interval around the resonance. The spectrum of regular forced, eccentricity-driven, libration defines the conditions for the perpetual long libration. The possibility of validating the tidal theory from the observable amplitude of perpetual libration is discussed.

  8. Tidal river dynamics

    NARCIS (Netherlands)

    Hoitink, A.J.F.; Jay, D.A.

    2016-01-01

    Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity

  9. Cosmic Tidal Reconstruction

    CERN Document Server

    Zhu, Hong-Ming; Yu, Yu; Er, Xinzhong; Chen, Xuelei

    2015-01-01

    The gravitational coupling of a long wavelength tidal field with small scale density fluctuations leads to anisotropic distortions of the locally measured small scale matter correlation function. Since the local correlation function is statistically isotropic in the absence of such tidal interactions, the tidal distortions can be used to reconstruct the long wavelength tidal field and large scale density field in analogy with the cosmic microwave background lensing reconstruction. In this paper we present in detail a formalism for the cosmic tidal reconstruction and test the reconstruction in numerical simulations. We find that the density field on large scales can be reconstructed with good accuracy and the cross correlation coefficient between the reconstructed density field and the original density field is greater than 0.9 on large scales ($k\\lesssim0.1h/\\mathrm{Mpc}$). This is useful in the 21cm intensity mapping survey, where the long wavelength radial modes are lost due to foreground subtraction proces...

  10. The O2 A-Band in the Fluxes and Polarization of Starlight Reflected by Earth-Like Exoplanets

    Science.gov (United States)

    Fauchez, Thomas; Rossi, Loic; Stam, Daphne M.

    2017-06-01

    Earth-like, potentially habitable exoplanets are prime targets in the search for extraterrestrial life. Information about their atmospheres and surfaces can be derived by analyzing the light of the parent star reflected by the planet. We investigate the influence of the surface albedo A s, the optical thickness b cloud, the altitude of water clouds, and the mixing ratio of biosignature O2 on the strength of the O2 A-band (around 760 nm) in the flux and polarization spectra of starlight reflected by Earth-like exoplanets. Our computations for horizontally homogeneous planets show that small mixing ratios (η clouds will usually decrease the band depth in flux and the band strength in polarization. However, cloud influence will be strongly dependent on properties such as optical thickness, top altitude, particle phase, coverage fraction, and horizontal distribution. Depending on the surface albedo and cloud properties, different O2 mixing ratios η can give similar absorption-band depths in flux and band strengths in polarization, especially if the clouds have moderate-to-high optical thicknesses. Measuring both the flux and the polarization is essential to reduce the degeneracies, although it will not solve them, especially not for horizontally inhomogeneous planets. Observations at a wide range of phase angles and with a high temporal resolution could help to derive cloud properties and, once those are known, the mixing ratio of O2 or any other absorbing gas.

  11. DETECTABILITY OF EARTH-LIKE PLANETS IN CIRCUMSTELLAR HABITABLE ZONES OF BINARY STAR SYSTEMS WITH SUN-LIKE COMPONENTS

    Energy Technology Data Exchange (ETDEWEB)

    Eggl, Siegfried; Pilat-Lohinger, Elke [University of Vienna, Institute for Astrophysics, Tuerkenschanzstr. 17, A-1180 Vienna (Austria); Haghighipour, Nader, E-mail: siegfried.eggl@univie.ac.at [Institute for Astronomy and NASA Astrobiology Institute, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2013-02-20

    Given the considerable percentage of stars that are members of binaries or stellar multiples in the solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the {alpha} Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones (HZ), especially in close S-type binary systems, can be rather inaccurate. Recent progress in this field, however, allows us to identify regions around the star permitting permanent habitability. While the discovery of {alpha} Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogs in HZs. We provide analytical expressions for the maximum and rms values of radial velocity and astrometric signals, as well as transit probabilities of terrestrial planets in such systems, showing that the dynamical interaction of the second star with the planet may indeed facilitate the planets' detection. As an example, we discuss the detectability of additional Earth-like planets in the averaged, extended, and permanent HZs around both stars of the {alpha} Centauri system.

  12. Rotational mixing in tidally locked massive main-sequence binaries

    CERN Document Server

    de Mink, S E; Langer, N; Pols, O R

    2008-01-01

    One of the main uncertainties in evolutionary calculations of massive stars is the efficiency of internal mixing. It changes the chemical profile inside the star and can therefore affect the structure and further evolution. We demonstrate that eclipsing binaries, in which the tides synchronize the rotation period of the stars and the orbital period, constitute a potentially strong test for the efficiency of rotational mixing. We present detailed stellar evolutionary models of massive binaries assuming the composition of the Small Magellanic Cloud. In these models we find enhancements in the surface nitrogen abundance of up to 0.6 dex.

  13. Swansong Biospheres: The biosignatures of inhabited earth-like planets nearing the end of their habitable lifetimes

    Science.gov (United States)

    O'Malley-James, Jack T.; Greaves, Jane S.; Raven, John A.; Cockell, Charles S.

    2014-01-01

    The biosignatures of life on Earth are not fixed, but change with time as environmental conditions change and life living within those environments adapts to the new conditions. A latitude-based climate model, incorporating orbital parameter variations, was used to simulate conditions on the far-future Earth as the Sun enters the late main sequence. Over time, conditions increasingly favour a unicellular microbial biosphere, which can persist for a maximum of 2.8 Gyr from present. The biosignature changes associated with the likely biosphere changes are evaluated using a biosphere-atmosphere gas exchange model and their detectability is discussed. As future Earth-like exoplanet discoveries could be habitable planets nearing the end of their habitable lifetimes, this helps inform the search for the signatures of life beyond Earth

  14. The Catalog of Earth-Like Exoplanet Survey TArgets (CELESTA): A Database of Habitable Zones around Nearby Stars

    CERN Document Server

    Chandler, Colin Orion; Kane, Stephen R

    2015-01-01

    Locating planets in circumstellar Habitable Zones is a priority for many exoplanet surveys. Space-based and ground-based surveys alike require robust toolsets to aid in target selection and mission planning. We present the Catalog of Earth-Like Exoplanet Survey Targets (CELESTA), a database of Habitable Zones around 36,000 nearby stars. We calculated stellar parameters, including effective temperatures, masses, and radii, and we quantified the orbital distances and periods corresponding to the circumstellar Habitable Zones. We gauged the accuracy of our predictions by contrasting CELESTA's computed parameters to observational data. We ascertain a potential return on investment by computing the number of Habitable Zones probed for a given survey duration. A versatile framework for extending the functionality of CELESTA into the future enables ongoing comparisons to new observations, and recalculations when updates to Habitable Zone models, stellar temperatures, or parallax data become available. We expect to u...

  15. Earth-like aqueous debris-flow activity on Mars at high orbital obliquity in the last million years.

    Science.gov (United States)

    de Haas, T; Hauber, E; Conway, S J; van Steijn, H; Johnsson, A; Kleinhans, M G

    2015-06-23

    Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years. This is testified by the widespread occurrence of mid-latitude gullies: small catchment-fan systems. However, there are no direct estimates of the amount and frequency of liquid water generation during these periods. Here we determine debris-flow size, frequency and associated water volumes in Istok crater, and show that debris flows occurred at Earth-like frequencies during high-obliquity periods in the last million years on Mars. Results further imply that local accumulations of snow/ice within gullies were much more voluminous than currently predicted; melting must have yielded centimetres of liquid water in catchments; and recent aqueous activity in some mid-latitude craters was much more frequent than previously anticipated.

  16. Holberg, lecteur de Locke

    DEFF Research Database (Denmark)

    Schøsler, Jørn

    2009-01-01

      En undersøgelse af John Lockes modtagelse i dansk Oplysningsfilosofi med særligt henblik på Holberg......  En undersøgelse af John Lockes modtagelse i dansk Oplysningsfilosofi med særligt henblik på Holberg...

  17. Locke on measurement.

    Science.gov (United States)

    Anstey, Peter R

    2016-12-01

    Like many virtuosi in his day, the English philosopher John Locke maintained an active interest in metrology. Yet for Locke, this was no mere hobby: questions concerning measurement were also implicated in his ongoing philosophical project to develop an account of human understanding. This paper follows Locke's treatment of four problems of measurement from the early Drafts A and B of the Essay concerning Human Understanding to the publication of this famous book and its aftermath. It traces Locke's attempt to develop a natural or universal standard for the measure of length, his attempts to grapple with the measurement of duration, as well as the problems of determining comparative measures for secondary qualities, and the problem of discriminating small differences in the conventional measures of his day. It is argued that the salient context for Locke's treatment of these problems is the new experimental philosophy and its method of experimental natural history.

  18. Tidal alignment of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  19. Properties of an Earth-like planet orbiting a Sun-like star: Earth observed by the EPOXI mission.

    Science.gov (United States)

    Livengood, Timothy A; Deming, L Drake; A'hearn, Michael F; Charbonneau, David; Hewagama, Tilak; Lisse, Carey M; McFadden, Lucy A; Meadows, Victoria S; Robinson, Tyler D; Seager, Sara; Wellnitz, Dennis D

    2011-11-01

    NASA's EPOXI mission observed the disc-integrated Earth and Moon to test techniques for reconnoitering extrasolar terrestrial planets, using the Deep Impact flyby spacecraft to observe Earth at the beginning and end of Northern Hemisphere spring, 2008, from a range of ∼1/6 to 1/3 AU. These observations furnish high-precision and high-cadence empirical photometry and spectroscopy of Earth, suitable as "ground truth" for numerically simulating realistic observational scenarios for an Earth-like exoplanet with finite signal-to-noise ratio. Earth was observed at near-equatorial sub-spacecraft latitude on 18-19 March, 28-29 May, and 4-5 June (UT), in the range of 372-4540 nm wavelength with low visible resolving power (λ/Δλ=5-13) and moderate IR resolving power (λ/Δλ=215-730). Spectrophotometry in seven filters yields light curves at ∼372-948 nm filter-averaged wavelength, modulated by Earth's rotation with peak-to-peak amplitude of ≤20%. The spatially resolved Sun glint is a minor contributor to disc-integrated reflectance. Spectroscopy at 1100-4540 nm reveals gaseous water and carbon dioxide, with minor features of molecular oxygen, methane, and nitrous oxide. One-day changes in global cloud cover resulted in differences between the light curve beginning and end of ≤5%. The light curve of a lunar transit of Earth on 29 May is color-dependent due to the Moon's red spectrum partially occulting Earth's relatively blue spectrum. The "vegetation red edge" spectral contrast observed between two long-wavelength visible/near-IR bands is ambiguous, not clearly distinguishing between the verdant Earth diluted by cloud cover versus the desolate mineral regolith of the Moon. Spectrophotometry in at least one other comparison band at short wavelength is required to distinguish between Earth-like and Moon-like surfaces in reconnaissance observations. However, measurements at 850 nm alone, the high-reflectance side of the red edge, could be sufficient to

  20. LOCKS AND KEYS SERVICE

    CERN Multimedia

    Locks and Keys Service

    2002-01-01

    The Locks and Keys service (ST/FM) will move from building 55 to building 570 from the 2nd August to the 9th August 2002 included. During this period the service will be closed. Only in case of extreme urgency please call the 164550. Starting from Monday, 12th August, the Locks and Keys Service will continue to follow the activities related to office keys (keys and locks) and will provide the keys for furniture. The service is open from 8h30 to 12h00 and from 13h00 to 17h30. We remind you that your divisional correspondents can help you in the execution of the procedures. We thank you for your comprehension and we remain at your service to help you in solving all the matters related to keys for offices and furniture. Locks and Keys Service - ST Division - FM Group

  1. Quantum Noise Locking

    CERN Document Server

    McKenzie, K; Goda, K; Lam, P K; Grosse, N; Gray, M B; Mavalvala, N; McClelland, D E; Kenzie, Kirk Mc; Mikhailov, Eugeniy; Goda, Keisuke; Lam, Ping Koy; Grosse, Nicolai; Gray, Malcolm B.; Mavalvala, Nergis; Clelland, David E. Mc

    2005-01-01

    Quantum optical states which have no coherent amplitude, such as squeezed vacuum states, can not rely on standard readout techniques to generate error signals for control of the quadrature phase. Here we investigate the use of asymmetry in the quadrature variances to obtain a phase-sensitive readout and to lock the phase of a squeezed vacuum state, a technique which we call noise locking (NL). We carry out a theoretical derivation of the NL error signal and the associated stability of the squeezed and anti-squeezed lock points. Experimental data for the NL technique both in the presence and absence of coherent fields are shown, including a comparison with coherent locking techniques. Finally, we use NL to enable a stable readout of the squeezed vacuum state on a homodyne detector.

  2. Quantum noise locking

    Energy Technology Data Exchange (ETDEWEB)

    McKenzie, Kirk [Center for Gravitational Physics, Department of Physics, Faculty of Science, Australian National University, ACT 0200 (Australia); Mikhailov, Eugeniy E [LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Goda, Keisuke [LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Lam, Ping Koy [Quantum Optics Group, Department of Physics, Faculty of Science, Australian National University, ACT 0200 (Australia); Grosse, Nicolai [Quantum Optics Group, Department of Physics, Faculty of Science, Australian National University, ACT 0200 (Australia); Gray, Malcolm B [Center for Gravitational Physics, Department of Physics, Faculty of Science, Australian National University, ACT 0200 (Australia); Mavalvala, Nergis [LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); McClelland, David E [Center for Gravitational Physics, Department of Physics, Faculty of Science, Australian National University, ACT 0200 (Australia)

    2005-10-01

    Quantum optical states which have no coherent amplitude, such as squeezed vacuum states, cannot rely on standard readout techniques to generate error signals for control of the quadrature phase. Here we investigate the use of asymmetry in the quadrature variances to obtain a phase-sensitive readout and to lock the phase of a squeezed vacuum state, a technique which we call noise locking (NL). We carry out a theoretical derivation of the NL error signal and the associated stability of the squeezed and anti-squeezed lock points. Experimental data for the NL technique both in the presence and absence of coherent fields are shown, including a comparison with coherent locking techniques. Finally, we use NL to enable a stable readout of the squeezed vacuum state on a homodyne detector.

  3. Introduction to Tidal Streams

    Science.gov (United States)

    Newberg, Heidi Jo

    Dwarf galaxies that come too close to larger galaxies suffer tidal disruption; the differential gravitational force between one side of the galaxy and the other serves to rip the stars from the dwarf galaxy so that they instead orbit the larger galaxy. This process produces "tidal streams" of stars, which can be found in the stellar halo of the Milky Way, as well as in halos of other galaxies. This chapter provides a general introduction to tidal streams, including the mechanism through which the streams are created, the history of how they were discovered, and the observational techniques by which they can be detected. In addition, their use in unraveling galaxy formation histories and the distribution of dark matter in galaxies is discussed, as is the interaction between these dwarf galaxy satellites and the disk of the larger galaxy.

  4. Experimental quantum data locking

    Science.gov (United States)

    Liu, Yang; Cao, Zhu; Wu, Cheng; Fukuda, Daiji; You, Lixing; Zhong, Jiaqiang; Numata, Takayuki; Chen, Sijing; Zhang, Weijun; Shi, Sheng-Cai; Lu, Chao-Yang; Wang, Zhen; Ma, Xiongfeng; Fan, Jingyun; Zhang, Qiang; Pan, Jian-Wei

    2016-08-01

    Classical correlation can be locked via quantum means: quantum data locking. With a short secret key, one can lock an exponentially large amount of information in order to make it inaccessible to unauthorized users without the key. Quantum data locking presents a resource-efficient alternative to one-time pad encryption which requires a key no shorter than the message. We report experimental demonstrations of a quantum data locking scheme originally proposed by D. P. DiVincenzo et al. [Phys. Rev. Lett. 92, 067902 (2004), 10.1103/PhysRevLett.92.067902] and a loss-tolerant scheme developed by O. Fawzi et al. [J. ACM 60, 44 (2013), 10.1145/2518131]. We observe that the unlocked amount of information is larger than the key size in both experiments, exhibiting strong violation of the incremental proportionality property of classical information theory. As an application example, we show the successful transmission of a photo over a lossy channel with quantum data (un)locking and error correction.

  5. Locke and botany.

    Science.gov (United States)

    Anstey, Peter R; Harris, Stephen A

    2006-06-01

    This paper argues that the English philosopher John Locke, who has normally been thought to have had only an amateurish interest in botany, was far more involved in the botanical science of his day than has previously been known. Through the presentation of new evidence deriving from Locke's own herbarium, his manuscript notes, journal and correspondence, it is established that Locke made a modest contribution to early modern botany. It is shown that Locke had close and ongoing relations with the Bobarts, keepers of the Oxford Botanic Garden, and that Locke distributed seeds and plant parts to other botanists, seeds of which the progeny almost certainly ended up in the most important herbaria of the period. Furthermore, it is claimed that the depth of Locke's interest in and practice of botany has a direct bearing on our understanding of his views on the correct method of natural philosophy and on the interpretation of his well known discussion of the nature of species in Book III of his Essay concerning human understanding.

  6. Pressure locking test results

    Energy Technology Data Exchange (ETDEWEB)

    DeWall, K.G.; Watkins, J.C.; McKellar, M.G.; Bramwell, D. [Idaho National Engineering Lab., Idaho Falls, ID (United States)] [and others

    1996-12-01

    The U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research, is funding the Idaho National Engineering Laboratory (INEL) in performing research to provide technical input for their use in evaluating responses to Generic Letter 95-07, {open_quotes}Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves.{close_quotes} Pressure locking and thermal binding are phenomena that make a closed gate valve difficult to open. This paper discusses only the pressure locking phenomenon in a flexible-wedge gate valve; the authors will publish the results of their thermal binding research at a later date. Pressure locking can occur when operating sequences or temperature changes cause the pressure of the fluid in the bonnet (and, in most valves, between the discs) to be higher than the pressure on the upstream and downstream sides of the disc assembly. This high fluid pressure presses the discs against both seats, making the disc assembly harder to unseat than anticipated by the typical design calculations, which generally consider friction at only one of the two disc/seat interfaces. The high pressure of the bonnet fluid also changes the pressure distribution around the disc in a way that can further contribute to the unseating load. If the combined loads associated with pressure locking are very high, the actuator might not have the capacity to open the valve. The results of the NRC/INEL research discussed in this paper show that the relationship between bonnet pressure and pressure locking stem loads appears linear. The results also show that for this valve, seat leakage affects the bonnet pressurization rate when the valve is subjected to thermally induced pressure locking conditions.

  7. Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

    CERN Document Server

    Barnes, Rory; Goldblatt, Colin; Meadows, Victoria S; Kasting, James F; Heller, Rene

    2012-01-01

    Traditionally stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at high enough levels to induce a runaway greenhouse for a long enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets "Tidal Venuses," and the phenomenon a "tidal greenhouse." Tidal effects also circularize the orbit, which decreases tidal heating. Hence, some planets may form with large eccentricity, with its accompanying large tidal heating, and lose their water, but eventually settle into nearly circular orbits in the habitable zone (HZ). However, these planets are not habitable as past tidal heating desiccated them, and hence should not be ranked highly for detailed follow-up observations aimed at detecting biosignatures. We simulate the evolution of hypothetical planetary systems in a quasi-continuous ...

  8. Resonance vector mode locking

    CERN Document Server

    Kolpakov, Stanislav A; Loika, Yuri; Tarasov, Nikita; Kalashnikov, Vladimir; Agrawal, Govind P

    2015-01-01

    A mode locked fibre laser as a source of ultra-stable pulse train has revolutionised a wide range of fundamental and applied research areas by offering high peak powers, high repetition rates, femtosecond range pulse widths and a narrow linewidth. However, further progress in linewidth narrowing seems to be limited by the complexity of the carrier-envelope phase control. Here for the first time we demonstrate experimentally and theoretically a new mechanism of resonance vector self-mode locking where tuning in-cavity birefringence leads to excitation of the longitudinal modes sidebands accompanied by the resonance phase locking of sidebands with the adjacent longitudinal modes. An additional resonance with acoustic phonons provides the repetition rate tunability and linewidth narrowing down to Hz range that drastically reduces the complexity of the carrier-envelope phase control and so will open the way to advance lasers in the context of applications in metrology, spectroscopy, microwave photonics, astronomy...

  9. Tidal Evolution of Exoplanets

    CERN Document Server

    Correia, Alexandre C M

    2010-01-01

    Tidal effects arise from differential and inelastic deformation of a planet by a perturbing body. The continuous action of tides modify the rotation of the planet together with its orbit until an equilibrium situation is reached. It is often believed that synchronous motion is the most probable outcome of the tidal evolution process, since synchronous rotation is observed for the majority of the satellites in the Solar System. However, in the 19th century, Schiaparelli also assumed synchronous motion for the rotations of Mercury and Venus, and was later shown to be wrong. Rather, for planets in eccentric orbits synchronous rotation is very unlikely. The rotation period and axial tilt of exoplanets is still unknown, but a large number of planets have been detected close to the parent star and should have evolved to a final equilibrium situation. Therefore, based on the Solar System well studied cases, we can make some predictions for exoplanets. Here we describe in detail the main tidal effects that modify the...

  10. Reasoning about Java's Reentrant Locks

    NARCIS (Netherlands)

    Haack, C.; Huisman, Marieke; Hurlin, C.; Ramalingam, G.

    2008-01-01

    This paper presents a verification technique for a concurrent Java-like language with reentrant locks. The verification technique is based on permission-accounting separation logic. As usual, each lock is associated with a resource invariant, i.e. when acquiring the lock the resources are obtained

  11. Locks and Keys Service

    CERN Multimedia

    Claude Ducastel

    The GS-LS-SEM section is pleased to inform you that as from Monday 30 November 2009, the opening hours of the Locks and Keys service will be the following: 08h30 - 12h30 / 13h30 - 16:30, Mondays to Fridays. GS-SEM-LS 73333

  12. LOCKE Detailed Specification Tables

    CERN Document Server

    Menezo, Lucia G; Gregorio, Jose-Angel

    2012-01-01

    This document shows the detailed specification of LOCKE coherence protocol for each cache controller, using a table-based technique. This representation provides clear, concise visual information yet includes sufficient detail (e.g., transient states) arguably lacking in the traditional, graphical form of state diagrams.

  13. Heartbeat Stars and the Ringing of Tidal Pulsations

    Directory of Open Access Journals (Sweden)

    Hambleton Kelly

    2015-01-01

    Full Text Available With the advent of high precision photometry from satellites such as Kepler and CoRoT, a whole new layer of interesting and astounding astronomical objects has been revealed: heartbeat stars are an example of such objects. Heartbeat stars are eccentric ellipsoidal variables that undergo strong tidal interactions when the stars are almost in contact at the time of closest approach. These interactions deform of the stars and cause a notable light curve variation in the form of a tidal pulse. A subset of these objects (~20% show prominent tidally induced pulsations: pulsations forced by the binary orbit. We now have a fully functional code that models binary star features (using PHOEBE and stellar pulsations simultaneously, enabling a complete and accurate heartbeat star model to be determined. In this paper we show the results of our new code, which uses emcee, a variant of mcmc, to generate a full set of stellar parameters. We further highlight the interesting features of KIC 8164262, including its tidally induced pulsations and resonantly locked pulsations.

  14. Tidal dissipation within hot Jupiters: a new appraisal

    CERN Document Server

    Levrard, B; Chabrier, G; Baraffe, I; Selsis, F; Laskar, J; Levrard, Benjamin; Correia, Alexandre Morgado; Chabrier, Gilles; Baraffe, Isabelle; Selsis, Franck; Laskar, Jacques

    2006-01-01

    Eccentricity or obliquity tides have been proposed as the missing energy source that may explain the anomalously large radius of some transiting ``hot Jupiters''. To maintain a non-zero and large obliquity, it was argued that the planets can be locked in a Cassini state, i.e. a resonance between spin and orbital precessions. We compute the tidal heating within ``inflated'' close-in giant planets with a non-zero eccentricity or obliquity. We further inspect whether the spin of a ``hot Jupiter'' could have been trapped and maintained in a Cassini state during its early despinning and migration. We estimate the capture probability in a spin-orbit resonance between $\\sim$ 0.5 AU (a distance where tidal effects become significant) and 0.05 AU for a wide range of secular orbital frequencies and amplitudes of gravitational perturbations. Numerical simulations of the spin evolution are performed to explore the influence of tidal despinning and migration processes on the resonance stability. We find that tidal heating...

  15. Tidal synchronization of the subdwarf B binary PG 0101+039

    CERN Document Server

    Geier, S; Heber, U; Randall, S K; Edelmann, H; Green, E M

    2007-01-01

    Tidally locked rotation is a frequently applied assumption that helps to measure masses of invisible compact companions in close binaries. The calculations of synchronization times are affected by large uncertainties in particular for stars with radiative envelopes calling for observational constraints. We aim at verifying tidally locked rotation for the binary PG 0101+039, a subdwarf B star + white dwarf binary from its tiny (0.025 %) light variations measured with the MOST satellite (Randall et al. 2005). Binary parameters were derived from the mass function, apparent rotation and surface gravity of PG 0101+039 assuming a canonical mass of 0.47 Mo and tidally locked rotation. The light curve was then synthesised and was found to match the observed amplitude well. We verified that the light variations are due to ellipsoidal deformation and that tidal synchronization is established for PG 0101+039. We conclude that this assumption should hold for all sdB binaries with orbital periods of less than half a day. ...

  16. Origin and Ubiquity of Short-Period Earth-like Planets: Evidence for the Sequential-Accretion Theory of Planet Formation

    OpenAIRE

    Zhou, J. L.; Aarseth, S. J.; Lin, D. N. C.; Nagasawa, M.

    2005-01-01

    The formation of gas giant planets is assumed to be preceded by the emergence of solid cores in the conventional sequential-accretion paradigm. This hypothesis implies that the presence of earth-like planets can be inferred from the detection of gas giants. A similar prediction cannot be made with the gravitational instability (hereafter GI) model which assumes that gas giants (hereafter giants) formed from the collapse of gas fragments analogous to their host stars. We propose an observation...

  17. Tidal Energy Research

    Energy Technology Data Exchange (ETDEWEB)

    Stelzenmuller, Nickolas [Univ of Washington; Aliseda, Alberto [Univ of Washington; Palodichuk, Michael [Univ of Washington; Polagye, Brian [Univ of Washington; Thomson, James [Univ of Washington; Chime, Arshiya [Univ of Washington; Malte, Philip [Univ of washington

    2014-03-31

    This technical report contains results on the following topics: 1) Testing and analysis of sub-scale hydro-kinetic turbines in a flume, including the design and fabrication of the instrumented turbines. 2) Field measurements and analysis of the tidal energy resource and at a site in northern Puget Sound, that is being examined for turbine installation. 3) Conceptual design and performance analysis of hydro-kinetic turbines operating at high blockage ratio, for use for power generation and flow control in open channel flows.

  18. Locked-in syndrome.

    Science.gov (United States)

    Sepcić, J; Sepić-Grahovac, D; Strenja-Grubesić, J; Antonelli, L; Andrasević, D

    1992-01-01

    A patient, young fisherman, with a locked-in syndrome is reported, in whom intact consciousness, quadriplegia of spastic type, voluntary eye blinking, (de)sursumvergence and anarthria were observed. Thrombosis of the basilar artery and slightly disturbed bioelectrogenesis of the cerebral cortex were proved by clinical examination. The patient died after 41 days. At the autopsy thrombosis a. basilaris and ventrobasal pontine infarction were confirmed. Differential diagnosis of this and similar syndromes has been discussed.

  19. Avoiding lock-in

    DEFF Research Database (Denmark)

    Henriksen, Ingrid

    1999-01-01

    The paper investigates the initial phase of the cooperative organisation of agricultural processing firms in Denmark. It argues that the variations observed can be explained within the framework of the theory of industrial organisation. The focus is on the success of cooperative creameries. In 19...... of gathering information and of preserving and transporting a perishable product, were ideally suited to overcome the problems of potential lock-in and of asymmetric information...

  20. Data port security lock

    Science.gov (United States)

    Quinby, Joseph D.; Hall, Clarence S.

    2008-06-24

    In a security apparatus for securing an electrical connector, a plug may be fitted for insertion into a connector receptacle compliant with a connector standard. The plug has at least one aperture adapted to engage at least one latch in the connector receptacle. An engagement member is adapted to partially extend through at least one aperture and lock to at least one structure within the connector receptacle.

  1. Tidal evolution of the Moon from a high-obliquity, high-angular-momentum Earth

    Science.gov (United States)

    Ćuk, Matija; Hamilton, Douglas P.; Lock, Simon J.; Stewart, Sarah T.

    2016-11-01

    In the giant-impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however, the current lunar orbital inclination of five degrees requires a subsequent dynamical process that is still unclear. In addition, the giant-impact theory has been challenged by the Moon’s unexpectedly Earth-like isotopic composition. Here we show that tidal dissipation due to lunar obliquity was an important effect during the Moon’s tidal evolution, and the lunar inclination in the past must have been very large, defying theoretical explanations. We present a tidal evolution model starting with the Moon in an equatorial orbit around an initially fast-spinning, high-obliquity Earth, which is a probable outcome of giant impacts. Using numerical modelling, we show that the solar perturbations on the Moon’s orbit naturally induce a large lunar inclination and remove angular momentum from the Earth-Moon system. Our tidal evolution model supports recent high-angular-momentum, giant-impact scenarios to explain the Moon’s isotopic composition and provides a new pathway to reach Earth’s climatically favourable low obliquity.

  2. Tidal evolution of the Moon from a high-obliquity, high-angular-momentum Earth.

    Science.gov (United States)

    Ćuk, Matija; Hamilton, Douglas P; Lock, Simon J; Stewart, Sarah T

    2016-11-17

    In the giant-impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however, the current lunar orbital inclination of five degrees requires a subsequent dynamical process that is still unclear. In addition, the giant-impact theory has been challenged by the Moon's unexpectedly Earth-like isotopic composition. Here we show that tidal dissipation due to lunar obliquity was an important effect during the Moon's tidal evolution, and the lunar inclination in the past must have been very large, defying theoretical explanations. We present a tidal evolution model starting with the Moon in an equatorial orbit around an initially fast-spinning, high-obliquity Earth, which is a probable outcome of giant impacts. Using numerical modelling, we show that the solar perturbations on the Moon's orbit naturally induce a large lunar inclination and remove angular momentum from the Earth-Moon system. Our tidal evolution model supports recent high-angular-momentum, giant-impact scenarios to explain the Moon's isotopic composition and provides a new pathway to reach Earth's climatically favourable low obliquity.

  3. 49 CFR 236.338 - Mechanical locking required in accordance with locking sheet and dog chart.

    Science.gov (United States)

    2010-10-01

    ... locking sheet and dog chart. 236.338 Section 236.338 Transportation Other Regulations Relating to... in accordance with locking sheet and dog chart. Mechanical locking shall be in accordance with locking sheet and dog chart currently in effect....

  4. Innovation and Lock-in

    DEFF Research Database (Denmark)

    Cantner, Uwe; Vannuccini, Simone

    2016-01-01

    , especially when innovation is concerned. Also, we address the question if lock-in is a well-defined concept at all. To offer a fresh view on lock-in and to tackle the issues just raised, we employ the replicator dynamics model. By making a parallel between monopolization in the replicator dynamics...... and the occurrence of lock-ins, we show that the convergence of a system to a given outcome can be reversed, under certain conditions. We highlight the need for a more precise demarcation of the conceptual boundaries of lock-in and path dependence, both from the formal and the empirical side, and suggest...

  5. Locked nucleic acid

    DEFF Research Database (Denmark)

    Jepsen, Jan Stenvang; Sørensen, Mads D; Wengel, Jesper

    2004-01-01

    Locked nucleic acid (LNA) is a class of nucleic acid analogs possessing very high affinity and excellent specificity toward complementary DNA and RNA, and LNA oligonucleotides have been applied as antisense molecules both in vitro and in vivo. In this review, we briefly describe the basic...... physiochemical properties of LNA and some of the difficulties that may be encountered when applying LNA technology. The central part of the review focuses on the use of LNA molecules in regulation of gene expression, including delivery to cells, stability, unspecific effects, toxicity, pharmacokinetics...

  6. Evolution of Earth-like Extrasolar Planetary Atmospheres: Assessing the Atmospheres and Biospheres of Early Earth Analog Planets with a Coupled Atmosphere Biogeochemical Model

    Science.gov (United States)

    Gebauer, S.; Grenfell, J. L.; Stock, J. W.; Lehmann, R.; Godolt, M.; von Paris, P.; Rauer, H.

    2017-01-01

    Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models. In this work, we present results from our newly developed Coupled Atmosphere Biogeochemistry model in which atmospheric O2 concentrations are fixed to values inferred by geological evidence. Applying a unique tool (Pathway Analysis Program), ours is the first quantitative analysis of catalytic cycles that governed O2 in early Earth's atmosphere near the Great Oxidation Event. Complicated oxidation pathways play a key role in destroying O2, whereas in the upper atmosphere, most O2 is formed abiotically via CO2 photolysis. The O2 bistability found by Goldblatt et al. (2006) is not observed in our calculations likely due to our detailed CH4 oxidation scheme. We calculate increased CH4 with increasing O2 during the Great Oxidation Event. For a given atmospheric surface flux, different atmospheric states are possible; however, the net primary productivity of the biosphere that produces O2 is unique. Mixing, CH4 fluxes, ocean solubility, and mantle/crust properties strongly affect net primary productivity and surface O2 fluxes. Regarding exoplanets, different "states" of O2 could exist for similar biomass output. Strong geological activity could lead to false negatives for life (since our analysis suggests that reducing gases remove O2 that

  7. Evolution of Earth-like Extrasolar Planetary Atmospheres: Assessing the Atmospheres and Biospheres of Early Earth Analog Planets with a Coupled Atmosphere Biogeochemical Model.

    Science.gov (United States)

    Gebauer, S; Grenfell, J L; Stock, J W; Lehmann, R; Godolt, M; von Paris, P; Rauer, H

    2017-01-01

    Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models. In this work, we present results from our newly developed Coupled Atmosphere Biogeochemistry model in which atmospheric O2 concentrations are fixed to values inferred by geological evidence. Applying a unique tool (Pathway Analysis Program), ours is the first quantitative analysis of catalytic cycles that governed O2 in early Earth's atmosphere near the Great Oxidation Event. Complicated oxidation pathways play a key role in destroying O2, whereas in the upper atmosphere, most O2 is formed abiotically via CO2 photolysis. The O2 bistability found by Goldblatt et al. ( 2006 ) is not observed in our calculations likely due to our detailed CH4 oxidation scheme. We calculate increased CH4 with increasing O2 during the Great Oxidation Event. For a given atmospheric surface flux, different atmospheric states are possible; however, the net primary productivity of the biosphere that produces O2 is unique. Mixing, CH4 fluxes, ocean solubility, and mantle/crust properties strongly affect net primary productivity and surface O2 fluxes. Regarding exoplanets, different "states" of O2 could exist for similar biomass output. Strong geological activity could lead to false negatives for life (since our analysis suggests that reducing gases remove O2 that

  8. Tidal controls on riverbed denitrification along a tidal freshwater zone

    Science.gov (United States)

    Knights, Deon; Sawyer, Audrey H.; Barnes, Rebecca T.; Musial, Cole T.; Bray, Samuel

    2017-01-01

    In coastal rivers, tidal pumping enhances the exchange of oxygen-rich river water across the sediment-water interface, controlling nitrogen cycling in riverbed sediment. We developed a one-dimensional, fluid flow and solute transport model that quantifies the influence of tidal pumping on nitrate removal and applied it to the tidal freshwater zone (TFZ) of White Clay Creek (Delaware, USA). In field observations and models, both oxygenated river water and anoxic groundwater deliver nitrate to carbon-rich riverbed sediment. A zone of nitrate removal forms beneath the aerobic interval, which expands and contracts over daily timescales due to tidal pumping. At high tide when oxygen-rich river water infiltrates into the bed, denitrification rates decrease by 25% relative to low tide. In the absence of tidal pumping, our model predicts that the aerobic zone would be thinner, and denitrification rates would increase by 10%. As tidal amplitude increases toward the coast, nitrate removal rates should decrease due to enhanced oxygen exchange across the sediment-water interface, based on sensitivity analysis. Denitrification hot spots in TFZs are more likely to occur in less permeable sediment under lower tidal ranges and higher rates of ambient groundwater discharge. Our models suggest that tidal pumping is not efficient at removing surface water nitrate but can remove up to 81% of nitrate from discharging groundwater in the TFZ of White Clay Creek. Given the high population densities of coastal watersheds, the reactive riverbeds of TFZs play a critical role in mitigating new nitrogen loads to coasts.

  9. On luminescence bleaching of tidal channel sediments

    DEFF Research Database (Denmark)

    Fruergaard, Mikkel; Pejrup, Morten; Murray, Andrew S.

    2015-01-01

    We investigate the processes responsible for bleaching of the quartz OSL signal from tidal channel sediment. Tidal dynamics are expected to play an important role for complete bleaching of tidal sediments. However, no studies have examined the amount of reworking occurring in tidal channels and o...

  10. Breaking Carbon Lock-in

    DEFF Research Database (Denmark)

    Driscoll, Patrick Arthur

    2014-01-01

    This central focus of this paper is to highlight the ways in which path dependencies and increasing returns (network effects) serve to reinforce carbon lock-in in large-scale road transportation infrastructure projects. Breaking carbon lock-in requires drastic changes in the way we plan future...

  11. Enceladus' tidal dissipation revisited

    Science.gov (United States)

    Tobie, Gabriel; Behounkova, Marie; Choblet, Gael; Cadek, Ondrej; Soucek, Ondrej

    2016-10-01

    A series of chemical and physical evidence indicates that the intense activity at Enceladus' South Pole is related to a subsurface salty water reservoir underneath the tectonically active ice shell. The detection of a significant libration implies that this water reservoir is global and that the average ice shell thickness is about 20-25km (Thomas et al. 2016). The interpretation of gravity and topography data further predicts large variations in ice shell thickness, resulting in a shell potentially thinner than 5 km in the South Polar Terrain (SPT) (Cadek et al. 2016). Such an ice shell structure requires a very strong heat source in the interior, with a focusing mechanism at the SPT. Thermal diffusion through the ice shell implies that at least 25-30 GW is lost into space by passive diffusion, implying a very efficient dissipation mechanism in Enceladus' interior to maintain such an ocean/ice configuration thermally stable.In order to determine in which conditions such a large dissipation power may be generated, we model the tidal response of Enceladus including variable ice shell thickness. For the rock core, we consider a wide range of rheological parameters representative of water-saturated porous rock materials. We demonstrate that the thinning toward the South Pole leads to a strong increase in heat production in the ice shell, with a optimal thickness obtained between 1.5 and 3 km, depending on the assumed ice viscosity. Our results imply that the heat production in the ice shell within the SPT may be sufficient to counterbalance the heat loss by diffusion and to power eruption activity. However, outside the SPT, a strong dissipation in the porous core is required to counterbalance the diffusive heat loss. We show that about 20 GW can be generated in the core, for an effective viscosity of 1012 Pa.s, which is comparable to the effective viscosity estimated in water-saturated glacial tills on Earth. We will discuss the implications of this revisited tidal

  12. Homodyne locking of a squeezer

    CERN Document Server

    Heurs, M; James, M R; Huntington, E H

    2009-01-01

    We report on the successful implementation of a new approach to locking the frequencies of an OPO-based squeezed-vacuum source and its driving laser. The technique allows the simultaneous measurement of the phase-shifts induced by a cavity, which may be used for the purposes of frequency-locking, as well as the simultaneous measurement of the sub-quantum-noise-limited (sub-QNL) phase quadrature output of the OPO. The homodyne locking technique is cheap, easy to implement and has the distinct advantage that subsequent homodyne measurements are automatically phase-locked. The homodyne locking technique is also unique in that it is a sub-QNL frequency discriminator.

  13. Tidal Creek Sentinel Habitat Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ecological Research, Assessment and Prediction's Tidal Creeks: Sentinel Habitat Database was developed to support the National Oceanic and Atmospheric...

  14. Tidal disruption of inviscid planetesimals

    Science.gov (United States)

    Boss, A. P.; Cameron, A. G. W.; Benz, W.

    1991-01-01

    In view of previous efforts' demonstration that strongly dissipative planetesimals are immune to tidal disruption, an examination is presently conducted of the complementary case of inviscid planetesimals arising from collisions that are sufficiently energetic to entirely melt the resulting planetesimal and debris. The tidal disruption is numerically simulated by means of the smoothed particle hydrodynamics (SPH) code of Cameron and Benz (1991), concentrating on the tidal disruption of 0.01 earth-mass planetesimals passing by the earth with variations in the impact parameter at perigee and velocity at infinity. The SPH models show that tidal forces during a close encounter can efficiently convert orbital angular momentum into spin angular momentum, thereby initiating equatorial mass-shedding to inviscid planetesimals that have been spun up beyond the limit of rotational stability.

  15. Parametric Dwarf Spheroidal Tidal Interaction

    CERN Document Server

    Fleck, J J; Fleck, Jean-Julien; Kuhn, Jeff R.

    2003-01-01

    The time dependent tidal interaction of the Local Group Dwarf Spheroidal (dS) Galaxies with the Milky Way (MW) can fundamentally affect their dynamical properties. The model developed here extends earlier numerical descriptions of dS-MW tidal interactions. We explore the dynamical evolution of dS systems in circular or elliptical MW orbits in the framework of a parametric oscillator. An analytic model is developed and compared with more general numerical solutions and N-body simulation experiments.

  16. Harnessing Tidal Energy Using Vertical Axis Tidal Turbine

    Directory of Open Access Journals (Sweden)

    Syed Shah Khalid

    2013-01-01

    Full Text Available An overview of the current design practices in the field of Renewable Energy (RE is presented; also paper delineates the background to the development of unique and novel techniques for power generation using the kinetic energy of tidal streams and other marine currents. Also this study focuses only on vertical axis tidal turbine. Tidal stream devices have been developed as an alternative method of extracting the energy from the tides. This form of tidal power technology poses less threat to the environment and does not face the same limiting factors associated with tidal barrage schemes, therefore making it a more feasible method of electricity production. Large companies are taking interest in this new source of power. There is a rush to research and work with this new energy source. Marine scientists are looking into how much these will affect the environment, while engineers are developing turbines that are harmless for the environment. In addition, the progression of technological advancements tracing several decades of R & D efforts on vertical axis turbines is highlighted.

  17. Tidal disruption event demographics

    Science.gov (United States)

    Kochanek, C. S.

    2016-09-01

    We survey the properties of stars destroyed in tidal disruption events (TDEs) as a function of black hole (BH) mass, stellar mass and evolutionary state, star formation history and redshift. For M_{BH} ≲ 10^7 M_{⊙}, the typical TDE is due to a M* ˜ 0.3 M⊙ M-dwarf, although the mass function is relatively flat for M_{ast } ≲ M_{⊙}. The contribution from older main-sequence stars and sub-giants is small but not negligible. From MBH ≃ 107.5-108.5 M⊙, the balance rapidly shifts to higher mass stars and a larger contribution from evolved stars, and is ultimately dominated by evolved stars at higher BH masses. The star formation history has little effect until the rates are dominated by evolved stars. TDE rates should decline very rapidly towards higher redshifts. The volumetric rate of TDEs is very high because the BH mass function diverges for low masses. However, any emission mechanism which is largely Eddington-limited for low BH masses suppresses this divergence in any observed sample and leads to TDE samples dominated by MBH ≃ 106.0-107.5 M⊙ BHs with roughly Eddington peak accretion rates. The typical fall-back time is relatively long, with 16 per cent having tfb plausible if tfb has any relation to the transient rise time. For almost any BH mass function, systematic searches for fainter, faster time-scale TDEs in smaller galaxies, and longer time-scale TDEs in more massive galaxies are likely to be rewarded.

  18. Is John Locke a democrat?

    DEFF Research Database (Denmark)

    Svensson, Palle

      Over recent years there has been a tendency to present John Locke as an equalitarian democrat (Ashcraft) and being close to the political views of the levellers (Waldron). This is not a completely new interpretation (Kendall, 1941), but contrasts with the prevalent view presented in textbooks...... (Holden, Held, Ball and Dagger) and monographs on Locke (Dunn, Parry, Marshall). In this paper a new approach to the democratic character of John Locke's political theory is suggested, as his Second Treatise is analysed with Robert A. Dahl's conceptual framework on assumptions for a democratic order...

  19. 49 CFR 236.765 - Locking, mechanical.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking, mechanical. 236.765 Section 236.765 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Locking, mechanical. An arrangement of locking bars, dogs, tappets, cross locking and other apparatus...

  20. 49 CFR 236.336 - Locking bed.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking bed. 236.336 Section 236.336 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Instructions § 236.336 Locking bed. The various parts of the locking bed, locking bed supports, and tappet...

  1. 49 CFR 236.330 - Locking dog of switch-and-lock movement.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking dog of switch-and-lock movement. 236.330 Section 236.330 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... Rules and Instructions § 236.330 Locking dog of switch-and-lock movement. Locking dog of...

  2. 49 CFR 236.337 - Locking faces of mechanical locking; fit.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking faces of mechanical locking; fit. 236.337 Section 236.337 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... Rules and Instructions § 236.337 Locking faces of mechanical locking; fit. Locking faces shall...

  3. Sensitivity of Biosignatures on Earth-like Planets orbiting in the Habitable Zone of Cool M-Dwarf Stars to varying Stellar UV Radiation and Surface Biomass Emissions

    CERN Document Server

    Grenfell, John Lee; von Paris, Philip; Godolt, Mareike; Rauer, Heike

    2015-01-01

    We find that variations in the UV emissions of cool M-dwarf stars have a potentially large impact upon atmospheric biosignatures in simulations of Earth-like exoplanets i.e. planets with Earths development, and biomass and a molecular nitrogen-oxygen dominated atmosphere. Starting with an assumed black-body stellar emission for an M7 class dwarf star, the stellar UV irradiation was increased stepwise and the resulting climate-photochemical response of the planetary atmosphere was calculated. Results suggest a Goldilocks effect with respect to the spectral detection of ozone. At weak UV levels, the ozone column was weak (due to weaker production from the Chapman mechanism) hence its spectral detection was challenging. At strong UV levels, ozone formation is stronger but its associated stratospheric heating leads to a weakening in temperature gradients between the stratosphere and troposphere, which results in weakened spectral bands. Also, increased UV levels can lead to enhanced abundances of hydrogen oxides ...

  4. Response of Atmospheric Biomarkers to NOx-induced Photochemistry Generated by Stellar Cosmic Rays for Earth-like Planets in the Habitable Zone of M-Dwarf Stars

    CERN Document Server

    Grenfell, John Lee; von Paris, Philip; Patzer, Beate; Lammer, Helmut; Stracke, Barbara; Gebauer, Stefanie; Schreier, Franz; Rauer, Heike

    2015-01-01

    Understanding whether M-dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M-dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N2), which leads to production of nitrogen oxides in the planetary atmosphere, hence affecting biomarkers such as ozone. We apply a stationary model, that is, without a time-dependence, hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by t...

  5. Apodized Pupil Lyot Coronagraphs for Arbitrary Apertures. V. Hybrid Shaped Pupil Designs for Imaging Earth-like planets with Future Space Observatories

    Science.gov (United States)

    N'Diaye, Mamadou; Soummer, Rémi; Pueyo, Laurent; Carlotti, Alexis; Stark, Christopher C.; Perrin, Marshall D.

    2016-02-01

    We introduce a new class of solutions for Apodized Pupil Lyot Coronagraphs (APLC) with segmented aperture telescopes to remove broadband diffracted light from a star with a contrast level of 1010. These new coronagraphs provide a key advance to enabling direct imaging and spectroscopy of Earth twins with future large space missions. Building on shaped pupil (SP) apodization optimizations, our approach enables two-dimensional optimizations of the system to address any aperture features such as central obstruction, support structures, or segment gaps. We illustrate the technique with a design that could reach a 1010 contrast level at 34 mas for a 12 m segmented telescope over a 10% bandpass centered at a wavelength of {λ }0 = 500 nm. These designs can be optimized specifically for the presence of a resolved star and, in our example, for stellar angular size up to 1.1 mas. This would allow one to probe the vicinity of Sun-like stars located beyond 4.4 pc, therefore, fully retiring this concern. If the fraction of stars with Earth-like planets is {η }\\oplus =0.1, with 18% throughput, assuming a perfect, stable wavefront and considering photon noise only, 12.5 exo-Earth candidates could be detected around nearby stars with this design and a 12 m space telescope during a five-year mission with two years dedicated to exo-Earth detection (one total year of exposure time and another year of overheads). Our new hybrid APLC/SP solutions represent the first numerical solution of a coronagraph based on existing mask technologies and compatible with segmented apertures, and that can provide contrast compatible with detecting and studying Earth-like planets around nearby stars. They represent an important step forward toward enabling these science goals with future large space missions.

  6. Innovation and Lock-in

    DEFF Research Database (Denmark)

    Cantner, Uwe; Vannuccini, Simone

    2016-01-01

    , especially when innovation is concerned. Also, we address the question if lock-in is a well-defined concept at all. To offer a fresh view on lock-in and to tackle the issues just raised, we employ the replicator dynamics model. By making a parallel between monopolization in the replicator dynamics...... that further structural features - for example users heterogeneity - may play a relevant role in affecting the outcome of dynamic allocation and competition processes....

  7. John locke on personal identity.

    Science.gov (United States)

    Nimbalkar, Namita

    2011-01-01

    John Locke speaks of personal identity and survival of consciousness after death. A criterion of personal identity through time is given. Such a criterion specifies, insofar as that is possible, the necessary and sufficient conditions for the survival of persons. John Locke holds that personal identity is a matter of psychological continuity. He considered personal identity (or the self) to be founded on consciousness (viz. memory), and not on the substance of either the soul or the body.

  8. John locke on personal identity

    Directory of Open Access Journals (Sweden)

    Nimbalkar Namita

    2011-01-01

    Full Text Available John Locke speaks of personal identity and survival of consciousness after death. A criterion of personal identity through time is given. Such a criterion specifies, insofar as that is possible, the necessary and sufficient conditions for the survival of persons. John Locke holds that personal identity is a matter of psychological continuity. He considered personal identity (or the self to be founded on consciousness (viz. memory, and not on the substance of either the soul or the body.

  9. John locke on personal identity

    Directory of Open Access Journals (Sweden)

    Namita Nimbalkar

    2011-03-01

    Full Text Available John Locke speaks of personal identity and survival of consciousness after death. A criterion of personal identity through time is given. Such a criterion specifies, insofar as that is possible, the necessary and sufficient conditions for the survival of persons. John Locke holds that personal identity is a matter of psychological continuity. He considered personal identity (or the self to be founded on consciousness (viz. memory, and not on the substance of either the soul or the body.

  10. Passively mode locked Raman laser

    CERN Document Server

    Liang, W; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2010-01-01

    We report on the observation of a novel mode locked optical comb generated at the Raman offset (Raman comb) in an optically pumped crystalline whispering gallery mode resonator. Mode locking is confirmed via measurement of the radio-frequency beat note produced by the optical comb on a fast photodiode. Neither the conventional Kerr comb nor hyper-parametric oscillation is observed when the Raman comb is present.

  11. Is John Locke a democrat?

    DEFF Research Database (Denmark)

    Svensson, Palle

    (Holden, Held, Ball and Dagger) and monographs on Locke (Dunn, Parry, Marshall). In this paper a new approach to the democratic character of John Locke's political theory is suggested, as his Second Treatise is analysed with Robert A. Dahl's conceptual framework on assumptions for a democratic order......, criteria for a democratic process, and the institutions of polyarchy. The conclusion has implications for the relationship between political liberalism and constitutionalism on the one hand and democracy on the other....

  12. Tidal disruption of inviscid protoplanets

    Science.gov (United States)

    Boss, Alan P.; Cameron, A. G. W.; Benz, W.

    1991-01-01

    Roche showed that equilibrium is impossible for a small fluid body synchronously orbiting a primary within a critical radius now termed the Roche limit. Tidal disruption of orbitally unbound bodies is a potentially important process for planetary formation through collisional accumulation, because the area of the Roche limit is considerably larger then the physical cross section of a protoplanet. Several previous studies were made of dynamical tidal disruption and different models of disruption were proposed. Because of the limitation of these analytical models, we have used a smoothed particle hydrodynamics (SPH) code to model the tidal disruption process. The code is basically the same as the one used to model giant impacts; we simply choose impact parameters large enough to avoid collisions. The primary and secondary both have iron cores and silicate mantles, and are initially isothermal at a molten temperature. The conclusions based on the analytical and numerical models are summarized.

  13. The distribution and tapping tidal energy

    Directory of Open Access Journals (Sweden)

    Zygmunt Kowalik

    2004-09-01

    Full Text Available Tidal power along tidal shores has been used for centuries to run small tidal mills. Generating electricity by tapping tidal power proved to be very successful only in the last century through the tidal power plant constructed in 1967 in La Rance, France. This used a large barrier to generate the sea level head necessary for driving turbines. Construction of such plants evolved very slowly because of prohibitive costs and concerns about the environmental impact. Developments in the construction of small, efficient and inexpensive underwater turbines admit the possibility of small scale operations that will use local tidal currents to bring electricity to remote locations. Since the generation of such electricity is concerned with the tidal energy in local water bodies, it is important to understand the site-specific energy balance, i.e., the energy flowing in through open boundaries, and the energy generated and dissipated within the local domain. The question is how to tap the tidal energy while keeping possible changes in the present tidal regimes to a minimum. The older approach of constructing barrages may still be quite useful in some locations. The basics of such tidal power plants constructed in a small bay are analyzed in order to understand the principal parameter for tidal plant evaluation, i.e., the power produced.     The new approach is to place turbines - devices similar to windmills - in the pathway of tidal currents. Theoretically, the amount of power available by such turbines for electricity generation is proportional to the water density and velocity cubed of the tidal flow. The naturally dissipated tidal power due to bottom friction forces is also proportional to the cube of the velocity. Because of this similarity, the exploitation of tidal energy can be directed to reinvesting the naturally dissipated power into tidal power for the generation of electricity. This approach to tidal power exploitation is better tuned

  14. Relativistic theory of tidal Love numbers

    OpenAIRE

    Binnington, Taylor; Poisson, Eric

    2009-01-01

    In Newtonian gravitational theory, a tidal Love number relates the mass multipole moment created by tidal forces on a spherical body to the applied tidal field. The Love number is dimensionless, and it encodes information about the body's internal structure. We present a relativistic theory of Love numbers, which applies to compact bodies with strong internal gravities; the theory extends and completes a recent work by Flanagan and Hinderer, which revealed that the tidal Love number of a neut...

  15. The concept of locking plates.

    Science.gov (United States)

    Cronier, P; Pietu, G; Dujardin, C; Bigorre, N; Ducellier, F; Gerard, R

    2010-05-01

    After a short historical review of locking bone plates since their inception more than a century ago to the success of the concept less than 15 years ago with today's plates, the authors present the main locking mechanisms in use. In the two broad categories - plates with fixed angulation and those with variable angulation - the screw head is locked in the plate with a locknut by screwing in a threaded chamber on the plate or by screwing through an adapted ring. The authors then provide a concrete explanation, based on simple mechanical models, of the fundamental differences between conventional bone plates and locking plates and why a locking screw system presents greater resistance at disassembly, detailing the role played by the position and number of screws. The advantages of epiphyseal fixation are then discussed, including in cases of mediocre-quality bone. For teaching purposes, the authors also present assembly with an apple fixed with five locking screws withstanding a 47-kg axial load with no resulting disassembly. The principles of plate placement are detailed for both the epiphysis and diaphysis, including the number and position of screws and respect of the soft tissues, with the greatest success assured by the minimally invasive and even percutaneous techniques. The authors then present the advantages of locking plates in fixation of periprosthetic fractures where conventional osteosynthesis often encounters limited success. Based on simplified theoretical cases, the economic impact in France of this type of implant is discussed, showing that on average it accounts for less than 10% of the overall cost of this pathology to society. Finally, the possible problems of material ablation are discussed as well as the means to remediate these problems.

  16. Medicine in John Locke's philosophy.

    Science.gov (United States)

    Sanchez-Gonzalez, M A

    1990-12-01

    John Locke's philosophy was deeply affected by medicine of his times. It was specially influenced by the medical thought and practice of Thomas Sydenham. Locke was a personal friend of Sydenham, expressed an avid interest in his work and shared his views and methods. The influence of Sydenham's medicine can be seen in the following areas of Locke's philosophy: his "plain historical method"; the emphasis on observation and sensory experience instead of seeking the essence of things; the rejection of hypotheses and principles; the refusal of research into final causes and inner mechanisms; the ideal of irrefutable evidence and skepticism on the possibilities of certainty in science. The science which for Locke held the highest paradigmatic value in his theory of knowledge was precisely medicine. To a great extent, Locke's Essay on Human Understanding can be understood as an attempt to justify, substantiate, and promote Sydenham's medical method. This method, generalized, was then proposed as an instrument for the elaboration of all natural sciences.

  17. The healing philosopher: John Locke's medical ethics.

    Science.gov (United States)

    Short, Bradford William

    2004-01-01

    This article examines a heretofore unexplored facet of John Locke's philosophy. Locke was a medical doctor and he also wrote about medical issues that are controversial today. Despite this, Locke's medical ethics has yet to be studied. An analysis of Locke's education and his teachers and colleagues in the medical profession, of the 17th century Hippocratic Oath, and of the reaction to the last recorded outbreak of the bubonic plague in London, shines some light on the subject of Locke's medical ethics. The study of Locke's medical ethics confirms that he was a deontologist who opposed all suicide and abortion through much of pregnancy.

  18. General relativistic tidal heating for Moller pseudotensor

    CERN Document Server

    So, Lau Loi

    2015-01-01

    Thorne elucidated that the relativistic tidal heating is the same as the Newtonian theory. Moreover, Thorne also claimed that the tidal heating is independent of how one localizes gravitational energy and is unambiguously given by a certain formula. Purdue and Favata calculated the tidal heating for different classical pseudotensors including Moller and obtained the results all matched with the Newtonian perspective. After re-examined this Moller pseudotensor, we find that there does not exist any tidal heating value. Thus we claim that the relativistic tidal heating is pseudotensor independent under the condition that if the peusdotensor is a Freud typed superpotential.

  19. Coupled optical resonance laser locking.

    Science.gov (United States)

    Burd, S C; du Toit, P J W; Uys, H

    2014-10-20

    We have demonstrated simultaneous laser frequency stabilization of a UV and IR laser, to coupled transitions of ions in the same spectroscopic sample, by detecting only the absorption of the UV laser. Separate signals for locking the different lasers are obtained by modulating each laser at a different frequency and using lock-in detection of a single photodiode signal. Experimentally, we simultaneously lock a 369 nm and a 935 nm laser to the (2)S(1/2) → (2)(P(1/2) and (2)D(3/2) → (3)D([3/2]1/2) transitions, respectively, of Yb(+) ions generated in a hollow cathode discharge lamp. Stabilized lasers at these frequencies are required for cooling and trapping Yb(+) ions, used in quantum information and in high precision metrology experiments. This technique should be readily applicable to other ion and neutral atom systems requiring multiple stabilized lasers.

  20. Maine Tidal Power Initiative: Environmental Impact Protocols For Tidal Power

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Michael Leroy [Univ. of Maine, Orono, ME; Zydlewski, Gayle Barbin [Univ. of Maine, Orono, ME; Xue, Huijie [Univ. of Maine, Orono, ME; Johnson, Teresa R. [Univ. of Maine, Orono, ME

    2014-02-02

    The Maine Tidal Power Initiative (MTPI), an interdisciplinary group of engineers, biologists, oceanographers, and social scientists, has been conducting research to evaluate tidal energy resources and better understand the potential effects and impacts of marine hydro-kinetic (MHK) development on the environment and local community. Project efforts include: 1) resource assessment, 2) development of initial device design parameters using scale model tests, 3) baseline environmental studies and monitoring, and 4) human and community responses. This work included in-situ measurement of the environmental and social response to the pre-commercial Turbine Generator Unit (TGU®) developed by Ocean Renewable Power Company (ORPC) as well as considering the path forward for smaller community scale projects.

  1. Tidal flow separation at protruding beach nourishments

    Science.gov (United States)

    Radermacher, Max; de Schipper, Matthieu A.; Swinkels, Cilia; MacMahan, Jamie H.; Reniers, Ad J. H. M.

    2017-01-01

    In recent years, the application of large-scale beach nourishments has been discussed, with the Sand Motor in the Netherlands as the first real-world example. Such protruding beach nourishments have an impact on tidal currents, potentially leading to tidal flow separation and the generation of tidal eddies of length scales larger than the nourishment itself. The present study examines the characteristics of the tidal flow field around protruding beach nourishments under varying nourishment geometry and tidal conditions, based on extensive field observations and numerical flow simulations. Observations of the flow field around the Sand Motor, obtained with a ship-mounted current profiler and a set of fixed current profilers, show that a tidal eddy develops along the northern edge of the mega-nourishment every flood period. The eddy is generated around peak tidal flow and gradually gains size and strength, growing much larger than the cross-shore dimension of the coastline perturbation. Based on a 3 week measurement period, it is shown that the intensity of the eddy modulates with the spring-neap tidal cycle. Depth-averaged tidal currents around coastline perturbations are simulated and compared to the field observations. The occurrence and behavior of tidal eddies is derived for a large set of simulations with varying nourishment size and shape. Results show that several different types of behavior exist, characterized by different combinations of the nourishment aspect ratio, the size of the nourishment relative to the tidal excursion length, and the influence of bed friction.

  2. Locking mechanism for orthopedic braces

    Science.gov (United States)

    Chao, J. I.; Epps, C. H., Jr.

    1981-01-01

    An orthopedic brace locking mechanism is described which under standing or walking conditions cannot be unlocked, however under sitting conditions the mechanism can be simply unlocked so as to permit bending of the patient's knee. Other features of the device include: (1) the mechanism is rendered operable, and inoperable, dependent upon the relative inclination of the brace with respect to the ground; (2) the mechanism is automatically locked under standing or walking conditions and is manually unlocked under sitting conditions; and (3) the mechanism is light in weight and is relatively small in size.

  3. The Effect of a Strong Stellar Flare on the Atmospheric Chemistry of an Earth-like Planet Orbiting an M dwarf

    CERN Document Server

    Segura, Antígona; Meadows, Victoria; Kasting, James; Hawley, Suzanne

    2010-01-01

    Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf, AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect we estimated a proton flux associated with the flare of $5.9\\times 10^{8}$ protons cm$^{-2}$ sr$^{-1}$ s$^{-1}$ for particles with energies >10 MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the "Carrington event". The simulations were performed using a 1-D photochemical model coupled to a 1-D radiative/co...

  4. Spectral features of Earth-like planets and their detectability at different orbital distances around F, G, and K-type stars

    CERN Document Server

    Hedelt, Pascal; Godolt, Mareike; Gebauer, Stefanie; Grenfell, John Lee; Rauer, Heike; Schreier, Franz; Selsis, Franck; Trautmann, Thomas

    2013-01-01

    We investigate the spectral appearance of Earth-like exoplanets in the HZ of different main sequence stars at different orbital distances. We furthermore discuss for which of these scenarios biomarker absorption bands may be detected during primary or secondary transit with near-future telescopes and instruments.We analyze the spectra taking into account different filter bandpasses of two photometric instruments planned to be mounted to the JWST. We analyze in which filters and for which scenarios molecular absorption bands are detectable when using the space-borne JWST or the ground-based telescope E-ELT. Absorption bands of CO2, H2O, CH4 and O3 are clearly visible in high-resolution spectra as well as in the filters of photometric instruments. However, only during primary eclipse bands of CO2, H2O and O3 are detectable for all scenarios when using photometric instruments and an E-ELT telescope setup. CH4 is only detectable at the outer HZ of the K star since here the atmospheric modeling results in very hig...

  5. Origin and Ubiquity of Short-Period Earth-like Planets: Evidence for the Sequential-Accretion Theory of Planet Formation

    CERN Document Server

    Zhou, J L; Lin, D N C; Nagasawa, M

    2005-01-01

    The formation of gas giant planets is assumed to be preceded by the emergence of solid cores in the conventional sequential-accretion paradigm. This hypothesis implies that the presence of earth-like planets can be inferred from the detection of gas giants. A similar prediction cannot be made with the gravitational instability (hereafter GI) model which assumes that gas giants (hereafter giants) formed from the collapse of gas fragments analogous to their host stars. We propose an observational test for the determination of the dominant planet-formation channel. Based on the sequential-accretion (hereafter SA) model, we identify several potential avenues which may lead to the prolific formation of a population of close-in earth-mass ($M_\\oplus$) planets (hereafter close-in earths) around stars with 1) short-period or 2) solitary eccentric giants and 3) systems which contain intermediate-period resonant giants. In contrast, these close-in earths are not expected to form in systems where giants originated rapid...

  6. Abiotic production of nitrous oxide by lightning. Implications for a false positive identification of life on Earth-Like Planets around quiescent M Dwarfs

    Science.gov (United States)

    Navarro, Karina F.; Navarro-Gonzalez, Rafael; McKay, Christopher P.

    Nitrous oxide (N _{2}O) is uniformly mixed in the troposphere with a concentration of about 310 ppb but disappears in the stratosphere (Prinn et al., 1990); N _{2}O is mostly emitted at a rate of 1x10 (13) g yr (-1) as a byproduct of microbial activity in soils and in the ocean by two processes: a) denitrification (reduction of nitrate and nitrite), and b) nitrification (oxidation of ammonia) (Maag and Vinther, 1996). The abiotic emission of N _{2}O in the contemporaneous Earth is small, mostly arising from lightning activity (2x10 (9) g yr (-1) , Hill et al., 1984) and by reduction of nitrite by Fe(II)-minerals in soils in Antarctica (Samarkin et al., 2010). Since N _{2}O has absorption bands in the mid-IR (7.8, 8.5, and 17 mumm) that makes it detectable by remote sensing (Topfer et al., 1997; Des Marais et al., 2002), it has been suggested as a potential biosignature in the search for life in extrasolar planets (Churchill and Kasting, 2000). However, the minimum required concentration for positive identification is 10,000 ppb with missions like Terrestrial Planet Finder and Darwin (Churchill and Kasting, 2000). Therefore, it is not a suitable biomarker for extrasolar Earth-like planets orbiting stars similar to the Sun. Because N _{2}O is protected in the troposphere from UV photolysis by the stratospheric ozone layer, its concentration would decrease with decreasing oxygen (O _{2}) concentrations, if the biological source strength remains constant (Kasting and Donahue, 1980). For a primitive Earth-like (Hadean) atmosphere dominated by CO _{2}, and no free O _{2}, the expected N _{2}O concentration would be about 3 ppb with the current microbial N _{2}O flux (Churchill and Kasting, 2000). The resulting N _{2}O spectral signature of this atmosphere would be undetectable unless the N _{2}O microbial flux would be 10 (4) greater than its present value (Churchill and Kasting, 2000). Since this flux is unlikely, it is impossible to use it as a biomarker in anoxic CO

  7. Frequency-Locking in Coupled Chaotic Systems

    Institute of Scientific and Technical Information of China (English)

    HU Bam-Bi; LIU Zong-Hua; ZHENG Zhi-Gang

    2001-01-01

    A novel approach is presented for measuring the phase synchronization (frequency-locking) of coupled N nonidentical oscillators, which can characterize frequency-locking for chaotic systems without well-defined phase by measuring the mean frequency. Numerical simulations confirm the existence of frequency-locking. The relations between the mean frequency and the coupling strength and the frequency mismatch are given. For the coupled hyperchaotic systems, the frequency-locking can be better characterized by more than one mean frequency curves.

  8. Tidal Evolution of Planetary Systems

    Science.gov (United States)

    Rodríguez, A.

    2017-07-01

    We review the orbital and rotational evolution of single and two-planet systems under tidal dissipation. In the framework of mutual gravitational perturbation and tidal interaction between the star and the innermost planet, we shall present the main results for the variations of eccentricities in both cases. These results are obtained through the numerical solution of the exact equations of motions. Moreover, we will also give an analysis of the planetary rotation, which can be temporarily trapped in special configurations such as spin-orbit resonances. Results will be shown using a Maxwell viscoelastic deformation law for the inner planet. This rheology is characterized by a viscous relaxation time, τ, that can be seen as the characteristic average time that the planet requires to achieve a new equilibrium shape after being disturbed by an external forcing (tides of the star).

  9. Prediction of CBS tidal evolution

    Science.gov (United States)

    Dryomova, G. N.

    The time series of basic processes, accompanying the tidal evolution of star components of Close Binary Systems (CBS) are predicted in the framework of evolutionary stellar models by Claret (2004). The series includes the apsidal motion period, timescale of synchronization of axial rotation of a star with the orbital revolution, the orbit circularization timescale, and the age. Data from the catalogues by Svechnikov & Perevozkina (1999) and by Torres, Andersen, Gimenez (2010) are used for testing the sensitivity of the numerical prediction algorithm.

  10. Tidal peritoneal dialysis: preliminary experience.

    Science.gov (United States)

    Flanigan, M J; Doyle, C; Lim, V S; Ullrich, G

    1992-01-01

    To determine the feasibility of home tidal peritoneal dialysis (TPD) and to assess whether eight hours of TPD can achieve uremia control and urea removal equal to that of continuous cycling peritoneal dialysis (CCPD). An open enrollment pilot study. The Home Dialysis Training Center of the University of Iowa Hospitals and Clinics, a tertiary care teaching hospital. Nine patients experienced with CCPD and living 80 km to 280 km from the dialysis center began TPD, because they wished to decrease their dialysis time. Following baseline measurements, each patient was taught to perform TPD. TPD consisted of an initial fill volume of 40 mL/kg, a residual volume approximately 20 mL/kg, and tidal exchanges of 10 to 20 mL/kg to achieve the desired hourly flow rate. Clinic assessments took place every four to six weeks, and prescriptions were subsequently altered to attain urea removal equal to that of CCPD. Patient interviews were used to determine TPD acceptance. Prior to each clinic visit, dialysate effluent volume and dialysis duration were recorded, and a sterile sample of the effluent was obtained for urea, creatinine, and total nitrogen measurement. Urea and creatinine clearances increased with dialysate flow. Dialysate nonurea nitrogen was 3.0 +/- 0.2 mmol/kg/D and changed minimally with increasing dialysate volumes. Eight hours of TPD (initial fill: 40 mL/kg; residual volume: 20 mL/kg; tidal inflow: 20 mL/kg) with hourly tidal flow exceeding 40 mL/kg/hr and no daytime volume achieved urea removal equal to that of the patient's prior CCPD prescription. TPD can provide dialysis equal to that of CCPD within a shorter amount of time (eight vs ten hours), but uses a greater volume of dialysate (16.0 L for TPD vs 9.5 L for CCPD).

  11. Trans World Tidal Gravity Profile.

    Science.gov (United States)

    1984-12-31

    America Curitiba (BraziZ) This station, situated at the Universidade Federal do Parana, in the Instituto de Ciencias Geod6sicas under Professor C...SUL COMPOSANTE VEPTICALE ERESIL 29 40 17S 53 49 22W H 700M P 2M 0 330KM DEPOTS SEDIMENTAIRES SUk BASALTE DEPT* DE INGENIERIA RURAL-UNIV. FED. DE SANTA...PRECAMBRIENIGNEISS * UNIVERSIDADE FEDERAL DO RIO GRANDE DO NORTE - DEPARTAMENTO DE FISICA TRANS WORLD TIDAL GRAVITY PROFILES P. MELCHIOR CENTRO POLITECNICO

  12. Bilateral locked facets in the thoracic spine

    NARCIS (Netherlands)

    M.H.A. Willems; Braakman, R. (Reinder); B. van Linge (Bert)

    1984-01-01

    textabstractTwo cases of traumatic bilateral locked facets in the thoracic spine are reported. Both patients had only minor neurological signs. They both made a full neurological recovery after surgical reduction of the locked facets. Bilateral locked facets are very uncommon in the thoracic spine.

  13. 49 CFR 236.769 - Locking, traffic.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking, traffic. 236.769 Section 236.769... Locking, traffic. Electric locking which prevents the manipulation of levers or other devices for changing the direction of traffic on a section of track while that section is occupied or while a signal...

  14. 49 CFR 236.381 - Traffic locking.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Traffic locking. 236.381 Section 236.381 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... and Tests § 236.381 Traffic locking. Traffic locking shall be tested when placed in service and...

  15. 49 CFR 236.768 - Locking, time.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking, time. 236.768 Section 236.768... Locking, time. A method of locking, either mechanical or electrical, which, after a signal has been caused to display an aspect to proceed, prevents, until after the expiration of a predetermined...

  16. 49 CFR 236.761 - Locking, electric.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking, electric. 236.761 Section 236.761 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Locking, electric. The combination of one or more electric locks and controlling circuits by means...

  17. 49 CFR 236.105 - Electric lock.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Electric lock. 236.105 Section 236.105 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION...: All Systems Inspections and Tests; All Systems § 236.105 Electric lock. Electric lock, except...

  18. 49 CFR 236.757 - Lock, electric.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Lock, electric. 236.757 Section 236.757... Lock, electric. A device to prevent or restrict the movement of a lever, a switch or a movable bridge, unless the locking member is withdrawn by an electrical device, such as an electromagnet, solenoid...

  19. 75 FR 2129 - Lock+TM

    Science.gov (United States)

    2010-01-14

    ... Energy Regulatory Commission Lock+ TM Hydro Friends Fund XXX, LLC; Notice of Preliminary Permit... January 6, 2010. On November 13, 2009, Lock+ TM Hydro Friends Fund XXX, LLC filed an application, pursuant...,018 megawatt-hours. Applicant Contact: Wayne F. Krouse, Lock+ TM Hydro Friends Fund XXX, LLC, 5090...

  20. Chaotic Dispersal of Tidal Debris

    CERN Document Server

    Price-Whelan, Adrian M; Valluri, Monica; Pearson, Sarah; Kupper, Andreas H W; Hogg, David W

    2015-01-01

    Several long, dynamically cold stellar streams have been observed around the Milky Way Galaxy, presumably formed from the tidal disruption of globular clusters. In integrable potentials---where all orbits are dynamically regular---tidal debris phase-mixes close to the orbit of the progenitor system. However, cosmological simulations of structure formation suggest that the Milky Way's dark matter halo is expected not to be fully integrable; an appreciable fraction of orbits will be chaotic. This paper examines the influence of chaos on the phase-space morphology of cold tidal streams. We find very stark results: Streams in chaotic regions look very different from those in regular regions. We find that streams (simulated using test particle ensembles of nearby orbits) can be sensitive to chaos on a much shorter time-scale than any standard prediction (from the Lyapunov or frequency-diffusion times). For example, on a weakly chaotic orbit with a chaotic timescale predicted to be >1000 orbital periods (>1000 Gyr)...

  1. Tidal Limits to Planetary Habitability

    CERN Document Server

    Barnes, Rory; Greenberg, Richard; Raymond, Sean N

    2009-01-01

    The habitable zones of main sequence stars have traditionally been defined as the range of orbits that intercept the appropriate amount of stellar flux to permit surface water on a planet. Terrestrial exoplanets discovered to orbit M stars in these zones, which are close-in due to decreased stellar luminosity, may also undergo significant tidal heating. Tidal heating may span a wide range for terrestrial exoplanets and may significantly affect conditions near the surface. For example, if heating rates on an exoplanet are near or greater than that on Io (where tides drive volcanism that resurface the planet at least every 1 Myr) and produce similar surface conditions, then the development of life seems unlikely. On the other hand, if the tidal heating rate is less than the minimum to initiate plate tectonics, then CO_2 may not be recycled through subduction, leading to a runaway greenhouse that sterilizes the planet. These two cases represent potential boundaries to habitability and are presented along with th...

  2. North American tidal power prospects

    Science.gov (United States)

    Wayne, W. W., Jr.

    1981-07-01

    Prospects for North American tidal power electrical generation are reviewed. Studies by the US Army Corps of Engineers of 90 possible generation schemes in Cobscook Bay, ME, indicated that maximum power generation rather than dependable capacity was the most economic method. Construction cost estimates for 15 MW bulb units in a single effect mode from basin to the sea are provided; five projects were considered ranging from 110-160 MW. Additional tidal power installations are examined for: Half-Moon Cove, ME (12 MW, 18 ft tide); Cook Inlet, AK, which is shown to pose severe environmental and engineering problems due to fish migration, earthquake hazards, and 300 ft deep silt deposits; and the Bay of Fundy, Canada. This last has a 17.8 MW plant under construction in a 29 ft maximum tide area. Other tidal projects of the Maritime Provinces are reviewed, and it is noted that previous economic evaluations based on an oil price of $16/barrel are in need of revision.

  3. Advances phase-lock techniques

    CERN Document Server

    Crawford, James A

    2008-01-01

    From cellphones to micrprocessors, to GPS navigation, phase-lock techniques are utilized in most all modern electronic devices. This high-level book takes a systems-level perspective, rather than circuit-level, which differentiates it from other books in the field.

  4. A Synthesis of Environmental and Plant Community Data for Tidal Wetland Restoration Planning in the Lower Columbia River and Estuary

    Energy Technology Data Exchange (ETDEWEB)

    Diefenderfer, Heida L.; Borde, Amy B.; Cullinan, Valerie I.

    2013-12-01

    This report reanalyzes and synthesizes previously existing environmental and plant community data collected by PNNL at 55 tidal wetlands and 3 newly restored sites in the lower Columbia River and estuary (LCRE) between 2005 and 2011. Whereas data were originally collected for various research or monitoring objectives of five studies, the intent of this report is to provide only information that will have direct utility in planning tidal wetland restoration projects. Therefore, for this report, all tidal wetland data on plants and the physical environment, which were originally developed and reported by separate studies, were tabulated and reanalyzed as a whole. The geographic scope of the data collected in this report is from Bonneville Lock and Dam to the mouth of the Columbia River

  5. 类地行星偏振特性研究∗%Study of Polarimetries of the Earth-like Exoplanet

    Institute of Scientific and Technical Information of China (English)

    宋伟; 屈中权

    2016-01-01

    相比于其他探测手段,行星的偏振探测能够提供更多有关行星表面以及大气的细节信息,而地球的偏振测量则有助于寻找系外类地行星以及对其大气和表面特征的鉴定.将地球看成一颗与其寄主星(太阳)可分辨但其自身圆面不可分辨的行星来研究其在太阳照射后辐射进入太空的偏振特性.采用PARASOL的670 nm (662.4 nm∼677.4 nm)波段的观测结果,得到不同地表类型和云层的偏振度和反照率随散射角和相对方位角的变化,然后根据辐射偏振的Stokes参量可叠加特性,求得在90◦散射角下,地球整体辐射的偏振度随自转的变化.结果发现:影响地球偏振的最大因素是海洋和云层,地球偏振度可以在18.6%到49%之间变化.由于气候变化导致的云层分布的随机性使得地球偏振度的变化具有快速多变的特点.揭示的这一特征有助于辨别系外类地行星.%Compared with other diagnostic techniques, the planetary polarimetry becomes more efficient to probe the details about the surface features of an exoplanet, and especially the polarimetry of our planet, the Earth, is useful to search for the Earth-like exoplanet. In this paper, the Earth is treated as a planet resolvable from its host star but its disk is unresolved. The data from the polarimeter boarding French satellite PARASOL are used to get the polarimetric results of 5 surface features as well as cloud within the band of 662.4–677.4 nm. The results are expressed in the curves which reflect the variations of linear polarization degree and albedo with the scattering and azimuth angles, respectively. Under the special case that the scattering angle is set to be 90 degrees, the polarization curves of the Earth in a rotation period are obtained. It is found that the polarization degree is mainly influenced by the ocean as well as the cloud, ranging from 18.6%to 49%. And due to the rapid climate change on the Earth, the

  6. Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars.

    Science.gov (United States)

    Kasting, James F; Kopparapu, Ravikumar; Ramirez, Ramses M; Harman, Chester E

    2014-09-02

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, "Dune" planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, S(eff), the recently recalculated HZ boundaries are: recent Venus--1.78; runaway greenhouse--1.04; moist greenhouse--1.01; maximum greenhouse--0.35; and early Mars--0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4-0.5.

  7. Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars

    Science.gov (United States)

    Kasting, James F.; Kopparapu, Ravikumar; Ramirez, Ramses M.; Harman, Chester E.

    2014-09-01

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, "Dune" planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, Seff, the recently recalculated HZ boundaries are: recent Venus-1.78; runaway greenhouse-1.04; moist greenhouse-1.01; maximum greenhouse-0.35; and early Mars-0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4-0.5.

  8. The effect of a strong stellar flare on the atmospheric chemistry of an earth-like planet orbiting an M dwarf.

    Science.gov (United States)

    Segura, Antígona; Walkowicz, Lucianne M; Meadows, Victoria; Kasting, James; Hawley, Suzanne

    2010-09-01

    Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high-energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect, we estimated a proton flux associated with the flare of 5.9 × 10⁸ protons cm⁻² sr⁻¹ s⁻¹ for particles with energies >10 MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the Carrington event. The simulations were performed with a 1-D photochemical model coupled to a 1-D radiative/convective model. Our results indicate that the UV radiation emitted during the flare does not produce a significant change in the ozone column depth of the planet. When the action of protons is included, the ozone depletion reaches a maximum of 94% two years after the flare for a planet with no magnetic field. At the peak of the flare, the calculated UV fluxes that reach the surface, in the wavelength ranges that are damaging for life, exceed those received on Earth during less than 100 s. Therefore, flares may not present a direct hazard for life on the surface of an orbiting habitable planet. Given that AD Leo is one of the most magnetically active M dwarfs known, this conclusion should apply to planets around other M dwarfs with lower levels of chromospheric activity.

  9. Biomarker response to galactic cosmic ray-induced NOx and the methane greenhouse effect in the atmosphere of an Earth-like planet orbiting an M dwarf star.

    Science.gov (United States)

    Grenfell, John Lee; Griessmeier, Jean-Mathias; Patzer, Beate; Rauer, Heike; Segura, Antigona; Stadelmann, Anja; Stracke, Barbara; Titz, Ruth; Von Paris, Philip

    2007-02-01

    Planets orbiting in the habitable zone of M dwarf stars are subject to high levels of galactic cosmic rays (GCRs), which produce nitrogen oxides (NOx) in Earth-like atmospheres. We investigate to what extent these NO(Mx) species may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources). Our model results suggest that such signals are robust, changing in the M star world atmospheric column due to GCR NOx effects by up to 20% compared to an M star run without GCR effects, and can therefore survive at least the effects of GCRs. We have not, however, investigated stellar cosmic rays here. CH4 levels are about 10 times higher on M star worlds than on Earth because of a lowering in hydroxyl (OH) in response to changes in the ultraviolet. The higher levels of CH4 are less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH4 fluxes compared to those studies. Unlike on Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M star world. We calculate a CH4 greenhouse heating effect of up to 4K. O3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M star world differs considerably compared with that of Earth.

  10. Numerically modelling tidal dissipation with bottom drag in the oceans of Titan and Enceladus

    Science.gov (United States)

    Hay, Hamish C. F. C.; Matsuyama, Isamu

    2017-01-01

    Icy satellites that contain subsurface oceans require sufficient thermal energy to prevent the liquid portion of their interiors from freezing. We develop a numerical finite difference model to solve the Laplace Tidal Equations on a sphere in order to simulate tidal flow and thermal energy dissipation in these oceans, neglecting the presence of an icy lid. The model is applied to Titan and Enceladus, where we explore how Rayleigh (linear) and bottom (quadratic) drag terms affect dissipation. The latter drag regime can only be applied numerically. We find excellent agreement between our results and recent analytical work. Obliquity tide Rossby-wave resonant features become independent of ocean thickness under the bottom drag regime for thick oceans. We show that for Titan, dissipation from this Rossby-wave resonance can act to dampen the rate of outward orbital migration by up to 40% for Earth-like values of bottom drag coefficient. Gravity-wave resonances can act to cause inward migration, although this is unlikely due to the thin oceans required to form such resonances. The same is true of all eccentricity tide resonances on Enceladus, such that dissipation becomes negligible for thick oceans under the bottom drag regime.

  11. Morbus-Locke's early essay on disease.

    Science.gov (United States)

    Walmsley, J

    2000-01-01

    John Locke engaged in a systematic study of medicine from the late 1650's. In this period he acquainted himself with the three main competing natural philosophical theories of the time -Galenism, Paracelsianism and Mechanism. He was particularly interested in the work of Sennert, Helmont and Doyle. In 1666, just after the publication of Boyle's The Origine of Formes and Qualities, Locke wrote a short paper entitled Morbus. This paper gave Locke's own view of the nature of disease. Locke went out of his way to criticise Boyle's attempts to give mechanical explanations for biological phenomena. He endorsed Helmont's theory that disease was caused by "ferments" and "Archei" and re-introduced Galenic temperaments as factors of susceptibility in seminal diseases. Locke did not endorse a mechanical corpuscularianism at this stage in his career, when his contact with Boyle was most frequent. Consequently, Locke's espousal of the corpuscular philosophy in the Essay cannot be attributed to Locke's association with Boyle at this time.

  12. Tidal friction in close-in planets

    Science.gov (United States)

    Rodríguez, Adrián; Ferraz-Mello, Sylvio; Hussmann, Hauke

    2008-05-01

    We use Darwin's theory (Darwin, 1880) to derive the main results on the orbital and rotational evolution of a close-in companion (exoplanet or planetary satellite) due to tidal friction. The given results do not depend on any assumption linking the tidal lags to the frequencies of the corresponding tide harmonics (except that equal frequency harmonics are assumed to span equal lags). Emphasis is given to the study of the synchronization of the planetary rotation in the two possible final states for a non-zero eccentricity : (1) the super-synchronous stationary rotation resulting from the vanishing of the average tidal torque; (2) the capture into a 1:1 spin-orbit resonance (true synchronization), which is only possible if an additional torque exists acting in opposition to the tidal torque. Results are given under the assumption that this additional torque is produced by a non-tidal permanent equatorial asymmetry of the planet. The indirect tidal effects and some non-tidal effects due to that asymmetry are considered. For sake of comparison with other works, the results obtained when tidal lags are assumed proportional to the corresponding tidal wave frequencies are also given.

  13. Calculating lunar retreat rates using tidal rhythmites

    Science.gov (United States)

    Kvale, E.P.; Johnson, H.W.; Sonett, C.P.; Archer, A.W.; Zawistoski, A.N.N.

    1999-01-01

    Tidal rhythmites are small-scale sedimenta??r}- structures that can preserve a hierarchy of astronomically induced tidal periods. They can also preserve a record of periodic nontidal sedimentation. If properly interpreted and understood, tidal rhjthmites can be an important component of paleoastronomy and can be used to extract information on ancient lunar orbital dynamics including changes in Earth-Moon distance through geologic time. Herein we present techniques that can be used to calculate ancient Earth-Moon distances. Each of these techniques, when used on a modern high-tide data set, results in calculated estimates of lunar orbital periods and an EarthMoon distance that fall well within 1 percent of the actual values. Comparisons to results from modern tidal data indicate that ancient tidal rhythmite data as short as 4 months can provide suitable estimates of lunar orbital periods if these tidal records are complete. An understanding of basic tidal theory allows for the evaluation of completeness of the ancient tidal record as derived from an analysis of tidal rhythmites. Utilizing the techniques presented herein, it appears from the rock record that lunar orbital retreat slowed sometime during the midPaleozoic. Copyright ??1999, SEPM (Society for Sedimentary Geology).

  14. Comparing the Overhead of Lock-based and Lock-free Implementations of Priority Queues

    DEFF Research Database (Denmark)

    Passas, Stavros; Karlsson, Sven

    2011-01-01

    structures is to allow multiple cores to safely access the data structure. Traditionally, mutual exclusion using lock primitives has been used to avoid interference between cores. However, lock primitives cause a high synchronization overhead in situations with high contention. More recently, lock-free data...... structures have been proposed as a solution to decrease the synchronization overhead. Lock-free data structures are more complex than their lock-based counterparts. It is not evident if the benefits of lower synchronization overhead can offset the higher sequential execution time caused by the complexity....... In this paper, we compare a lock-free implementation of a priority queue with a lock-based implementation. We perform experiments with processors of different generations and observe large performance differences for lock-free data structures depending on the processor generation. The lock-free implementation...

  15. Tidal Constraints on Planetary Habitability

    CERN Document Server

    Barnes, Rory; Greenberg, Richard; Raymond, Sean N; Heller, Rene

    2009-01-01

    We review how tides may impact the habitability of terrestrial-like planets. If such planets form around low-mass stars, then planets in the circumstellar habitable zone will be close enough to their host stars to experience strong tidal forces. We discuss 1) decay of semi-major axis, 2) circularization of eccentric orbits, 3) evolution toward zero obliquity, 4) fixed rotation rates (not necessarily synchronous), and 5) internal heating. We briefly describe these effects using the example of a 0.25 solar mass star with a 10 Earth-mass companion. We suggest that the concept of a habitable zone should be modified to include the effects of tides.

  16. Jaw locking after maxillofacial trauma

    Directory of Open Access Journals (Sweden)

    David B. Kamadjaja

    2007-09-01

    Full Text Available The purpose of this report is to present two cases of jaw locking with two different etiologies. In case #1, jaw locking occured 5.5 months after a surgical reduction and internal fixation on the fractured maxilla and mandible. Some plain radiographic x-ray were made but failed to give adequate information in establishing the cause of trismus. The three dimensional computed tomography (3D-CT was finally made and able to help guide the pre-operative diagnosis and treatment. Two-steps gap arthroplasty were done comprising a gap arthroplasty leading to acceptable outcome. An adult patient in case #2 with a history of trauma at his childhood and bird-like face apprearance clinically, was unable to open the mouth since the time of accident. The patient was diagnosed with bilateral ankylosis of temporomandibular joints. One side (right gap arthroplasty was done and resulted in normal mouth opening.

  17. Hydraulic Modeling of Lock Approaches

    Science.gov (United States)

    2016-08-01

    cation was that the guidewall design changed from a solid wall to one on pilings in which water was allowed to flow through and/or under the wall ...develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the...magnitudes and directions at lock approaches for open river conditions. The meshes were developed using the Surface- water Modeling System. The two

  18. Subharmonic Fourier domain mode locking.

    Science.gov (United States)

    Eigenwillig, Christoph M; Wieser, Wolfgang; Biedermann, Benjamin R; Huber, Robert

    2009-03-15

    We demonstrate a subharmonically Fourier domain mode-locked wavelength-swept laser source with a substantially reduced cavity fiber length. In contrast to a standard Fourier domain mode-locked configuration, light is recirculated repetitively in the delay line with the optical bandpass filter used as switch. The laser has a fundamental optical round trip frequency of 285 kHz and can be operated at integer fractions thereof (subharmonics). Sweep ranges up to 95 nm full width centred at 1317 nm are achieved at the 1/5th subharmonic. A maximum sensitivity of 116 dB and an axial resolution of 12 microm in air are measured at an average sweep power of 12 mW. A sensitivity roll-off of 11 dB over 4 mm and 25 dB over 10 mm is observed and optical coherence tomography imaging is demonstrated. Besides the advantage of a reduced fiber length, subharmonic Fourier domain mode locking (shFDML) enables simple scaling of the sweep speed by extracting light from the delay part of the resonator. A sweep rate of 570 kHz is achieved. Characteristic features of shFDML operation, such as power leakage during fly-back and cw breakthrough, are investigated.

  19. Storm surge and tidal range energy

    Science.gov (United States)

    Lewis, Matthew; Angeloudis, Athanasios; Robins, Peter; Evans, Paul; Neill, Simon

    2017-04-01

    The need to reduce carbon-based energy sources whilst increasing renewable energy forms has led to concerns of intermittency within a national electricity supply strategy. The regular rise and fall of the tide makes prediction almost entirely deterministic compared to other stochastic renewable energy forms; therefore, tidal range energy is often stated as a predictable and firm renewable energy source. Storm surge is the term used for the non-astronomical forcing of tidal elevation, and is synonymous with coastal flooding because positive storm surges can elevate water-levels above the height of coastal flood defences. We hypothesis storm surges will affect the reliability of the tidal range energy resource; with negative surge events reducing the tidal range, and conversely, positive surge events increasing the available resource. Moreover, tide-surge interaction, which results in positive storm surges more likely to occur on a flooding tide, will reduce the annual tidal range energy resource estimate. Water-level data (2000-2012) at nine UK tide gauges, where the mean tidal amplitude is above 2.5m and thus suitable for tidal-range energy development (e.g. Bristol Channel), were used to predict tidal range power with a 0D modelling approach. Storm surge affected the annual resource estimate by between -5% to +3%, due to inter-annual variability. Instantaneous power output were significantly affected (Normalised Root Mean Squared Error: 3%-8%, Scatter Index: 15%-41%) with spatial variability and variability due to operational strategy. We therefore find a storm surge affects the theoretical reliability of tidal range power, such that a prediction system may be required for any future electricity generation scenario that includes large amounts of tidal-range energy; however, annual resource estimation from astronomical tides alone appears sufficient for resource estimation. Future work should investigate water-level uncertainties on the reliability and

  20. The runaway Greenhouse revisited: it's "theoretically possible for an Earth-like planet at 1 AU", plus implications for more diverse planets

    Science.gov (United States)

    Goldblatt, C.; Zahnle, K. J.; Crisp, D.; Robinson, T. D.

    2013-12-01

    For water-vapour rich atmospheres, there is an asymptotic limit on thermal emission to space. If more sunlight is absorbed than this limit, energy balance is no longer possible and runaway heating occurs, evaporating the ocean and sterilizing the planet en route. Here, we present recently published work (Goldblatt et al., 2013) which was the first full re-evaluation of the problem since classic 1980's era work (e.g. Watson et al., 1984; Abe & Matsui, 1988; Kasting, 1988). With modern molecular absorption databases and a line-by-line resolution model, we find that the thermal limit is lower than previous estimates (282Wm-2, down from 310Wm-2) and that much more sunlight is absorbed by a steam atmosphere (294Wm-2, up from 222Wm-2). The immediate implication is that a cloud-free moist atmosphere on Earth would cause a runaway greenhouse. Triggering it would simply be a matter of sufficient heating, with around 30,000ppmv being sufficient in our most Earth-like model. This is substantially different than previous calculations, where weak solar absorption meant that a higher solar flux was required. Our published calculations are for the limit of clear-skies; any clouds would reduce both the thermal radiation emitted and the solar radiation absorbed, so clouds could make the runaway greenhouse either more or less likely. It can be shown that and excess of cloud reflection over cloud greenhouse is required to maintain temperate climate on Earth today - but how clouds will change in a warming atmosphere is far from clear. Work in progress (and hopefully ready by December!) on cloudy runaway greenhouse models will hopefully constrain this better. Wider implications for planetary stability will also be discussed. For example, water-world planets, with minimal background gas in the atmosphere may be highly susceptible to runaway greenhouses (heating Europa might take it directly from a snowball to a runaway). High CO2 levels after previous Snowball Earth events did not

  1. Response of atmospheric biomarkers to NO(x)-induced photochemistry generated by stellar cosmic rays for earth-like planets in the habitable zone of M dwarf stars.

    Science.gov (United States)

    Grenfell, John Lee; Grießmeier, Jean-Mathias; von Paris, Philip; Patzer, A Beate C; Lammer, Helmut; Stracke, Barbara; Gebauer, Stefanie; Schreier, Franz; Rauer, Heike

    2012-12-01

    Understanding whether M dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N(2)), which leads to production of nitrogen oxides (NO(x)) in the planetary atmosphere, hence affecting biomarkers such as ozone (O(3)). We apply a stationary model, that is, without a time dependence; hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by the impinging stellar flares. This point should be further explored in future work with time-dependent models. We estimate the NO(x) production using an air shower approach and evaluate the implications using a climate-chemical model of the planetary atmosphere. O(3) formation proceeds via the reaction O+O(2)+M→O(3)+M. At high NO(x) abundances, the O atoms arise mainly from NO(2) photolysis, whereas on Earth this occurs via the photolysis of molecular oxygen (O(2)). For the flaring case, O(3) is mainly destroyed via direct titration, NO+O(3)→NO(2)+O(2), and not via the familiar catalytic cycle photochemistry, which occurs on Earth. For scenarios with low O(3), Rayleigh scattering by the main atmospheric gases (O(2), N(2), and CO(2)) became more important for shielding the planetary surface from UV radiation. A major result of this work is that the biomarker O(3) survived all the stellar-activity scenarios considered except for the strong

  2. Tidal mixing in Dahej creek waters

    Digital Repository Service at National Institute of Oceanography (India)

    Swamy, G.N.; Sarma, R.V.

    Mixing characteristics of a tidal inlet near Dahej at the mouth of Narmada River, Gujarat, India are examined in terms of tides, currents and bathymetry. The dilution potential of the Dahej Creek waters during a tidal march for a given rate...

  3. Time-dependent solution for reorientation of rotating tidally deformed visco-elastic bodies

    Science.gov (United States)

    Hu, Haiyang; van der Wal, Wouter; Vermeersen, Bert

    2017-04-01

    Many icy satellites or planets contain features which suggest a (past) reorientation of the body, such as the tiger stripes on Enceladus and the heart-shaped Sputnik Planum on Pluto. Most of these icy bodies are tidally locked and this creates a large tidal bulge which is about three times of its centrifugal (equatorial) bulge. To study the reorientation of such rotating tidally deformed body is complicated and most previous studies apply the so-called fluid limit method. The fluid limit approach ignores the viscous response of the body and assumes that it immediately reaches its fluid limit when simulating the reorientation due to a changing load. As a result, this method can only simulate cases when the change in the load is much slower than the dominant viscous modes of the body. For other kinds of load, for instance, a Heaviside load due to an impact which creates an instant relocation of mass, it does not give us a prediction of how the reorientation is accomplished (e.g. How fast? Along which path?). We establish a new method which can give an accurate time-dependent solution for reorientation of rotating tidally deformed bodies. Our method can be applied both semi-analytically or numerically (with finite element method) to include features such as lateral heterogeneity or non-linear material. We also present an extension of our method to simulate the e ffect of a fossil bulge. With our method, we show that reorientation of a tidally deformed body driven by a positive mass anomaly near the poles has a preference for rotating around the tidal axis instead of towards it, contrary to predictions in previous studies. References Hu, H., W. van der Wal and L.L.A. Vermeersen (2017). A numerical method for reorientation of rotating tidally deformed visco-elastic bodies. Journal of Geophysical Research: Planets, doi:10.1002/2016JE005114, 2016JE005114. Matsuyama, I. and Nimmo, F. (2007). Rotational stability of tidally deformed planetary bodies. Journal of Geophysical

  4. Tidal Tales of Minor Mergers: Star Formation in the Tidal Debris of Minor Mergers

    CERN Document Server

    Knierman, Karen A

    2009-01-01

    How does the tidal debris of minor galaxy mergers contribute to structures in spiral galaxies or in the intergalactic medium? While major mergers are known to create structures such as tidal dwarf galaxies and star clusters within their tidal debris, less is known about minor mergers (mass ratios between a dwarf galaxy and disk galaxy of less than one-third) and their tidal debris. This work surveys 6 nearby minor mergers using optical broad-band and H-alpha narrow-band imaging to characterize star formation in their tidal debris. Young star clusters with ages less than the dynamical age of the tidal tails are found in all 6 mergers, indicating that the star clusters formed in situ. Even if minor mergers contribute less tidal debris per interaction than major mergers, they are more common and possibly contribute structure to all types of galaxies and to the intergalactic medium throughout the history of the universe.

  5. Hardware locks for a real-time Java chip multiprocessor

    DEFF Research Database (Denmark)

    Strøm, Torur Biskopstø; Puffitsch, Wolfgang; Schoeberl, Martin

    2016-01-01

    mechanisms are compared with a software locking solution as well as the original locking system of the processor. The hardware cost and performance are evaluated for all presented locking mechanisms. The performance of the better-performing hardware locks is comparable with that of the original single global...... lock when contending for the same lock. When several noncontending locks are used, the hardware locks enable true concurrency for critical sections. Benchmarks show that using the hardware locks yields performance ranging from no worse than the original locks to more than twice their best performance...... and may void a task set's schedulability. This paper presents 2 hardware locking mechanisms to reduce the worst-case time required to acquire and release synchronization locks. These solutions are implemented for the chip-multiprocessor version of the Java Optimized Processor. The 2 hardware locking...

  6. Is one hair lock really representative?

    Science.gov (United States)

    Dussy, Franz; Carson, Nicholas; Hangartner, Sarah; Briellmann, Thomas

    2014-06-01

    When investigating someone's hair a single lock is cut, washed, extracted and analysed. The forensic institutes in Switzerland agreed to retain a second lock for a possible reassessment. We were interested in the reproducibility of the concentrations of analytes in hair locks taken from different areas of the head of the same person covering the same time period. Therefore we analysed ethyl glucuronide and caffeine as model substances in 10 hair locks from three individuals categorised as social drinkers. The individual coefficients of variation varied between 14% and 28% for ethyl glucuronide and between 13% and 62% for caffeine corresponding to factors of 1.6 to 4.2 for the highest to the lowest concentrations between the hair locks. This finding has a significant importance both when the second hair lock has to be analysed in a forensic case and if the interpretation of the result is depending on a cut-off value.

  7. Diffuser Augmented Horizontal Axis Tidal Current Turbines

    Directory of Open Access Journals (Sweden)

    Nasir Mehmood

    2012-09-01

    Full Text Available The renewal energy technologies are increasingly popular to ensure future energy sustenance and address environmental issues. The tides are enormous and consistent untapped resource of renewable energy. The growing interest in exploring tidal energy has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The tidal energy industry is undergoing an increasing shift towards diffuser augmented turbines. The reason is the higher power output of diffuser augmented turbines compared to conventional open turbines. The purpose of this study is to present a comprehensive review of diffuser augmented horizontal axis tidal current turbines. The components, relative advantages, limitations and design parameters of diffuser augmented horizontal axis tidal current turbines are presented in detail. CFD simulation of NACA 0016 airfoil is carried out to explore its potential for designing a diffuser. The core issues associated with diffuser augmented horizontal axis tidal current turbines are also discussed.

  8. Tidal deformations of a spinning compact object

    CERN Document Server

    Pani, Paolo; Maselli, Andrea; Ferrari, Valeria

    2015-01-01

    The deformability of a compact object induced by a perturbing tidal field is encoded in the tidal Love numbers, which depend sensibly on the object's internal structure. These numbers are known only for static, spherically-symmetric objects. As a first step to compute the tidal Love numbers of a spinning compact star, here we extend powerful perturbative techniques to compute the exterior geometry of a spinning object distorted by an axisymmetric tidal field to second order in the angular momentum. The spin of the object introduces couplings between electric and magnetic deformations and new classes of induced Love numbers emerge. For example, a spinning object immersed in a quadrupolar, electric tidal field can acquire some induced mass, spin, quadrupole, octupole and hexadecapole moments to second order in the spin. The deformations are encoded in a set of inhomogeneous differential equations which, remarkably, can be solved analytically in vacuum. We discuss certain subtleties in defining the multipole mom...

  9. Relativistic theory of tidal Love numbers

    CERN Document Server

    Binnington, Taylor

    2009-01-01

    In Newtonian gravitational theory, a tidal Love number relates the mass multipole moment created by tidal forces on a spherical body to the applied tidal field. The Love number is dimensionless, and it encodes information about the body's internal structure. We present a relativistic theory of Love numbers, which applies to compact bodies with strong internal gravities; the theory extends and completes a recent work by Flanagan and Hinderer, which revealed that the tidal Love number of a neutron star can be measured by Earth-based gravitational-wave detectors. We consider a spherical body deformed by an external tidal field, and provide precise and meaningful definitions for electric-type and magnetic-type Love numbers; and these are computed for polytropic equations of state. The theory applies to black holes as well, and we find that the relativistic Love numbers of a nonrotating black hole are all zero.

  10. Treatment of cervical dislocation with locked facets

    Institute of Scientific and Technical Information of China (English)

    YU Ze-sheng; James J.Yue; WEI Feng; LIU Zhong-jun; CHEN Zhong-qiang; DANG Geng-ting

    2007-01-01

    Background Lower cervical dislocation with locked facets is common in cervical injury. The locked facets include unilateral and bilateral types. Different successful closed reduction rates has been achieved between unilateral and bilateral types by using rapid skull traction, which was commonly used to reduce the cervical dislocation. It is important to investigate a suitable management specific to patients with different types of cervical locked facets.Methods A total of 38 patients with cervical dislocation with locked facet due to cervical injury treated by rapid skull traction and operation from 1988 to 2005 were reviewed. Rapid skull traction was used in all the patients. Successful closed reduction rate was 88.0% in patients with bilateral cervical locked facets and that was 15.4% in those with unilateral cervical locked facets. These data were then statistically compared by Chi-square test. Patients who were reduced successfully underwent anterior cervical discectomy and fusion at the injured level, and those who failed in closed reduction received posterior open reduction and fixation.Results In this series, there was statistically significant difference (P<0.05) in the rate of successful closed skull traction reduction between unilateral and bilateral locked facets dislocation. Unilateral cervical locked facets dislocation was not easily reduced by skull traction which was suitable for reduction of bilateral cervical locked facets dislocation. However,unilateral cervical locked facets dislocation can be reduced by posterior open reduction.Conclusions Unilateral cervical locked facets dislocation should be treated immediately with posterior open reduction and instrumentation. Bilateral cervical locked facets dislocation can be reduced by rapid skull traction firstly and anterior cervical discectomy and interbody fusion later.

  11. All Digital Phase-Locked Loop

    OpenAIRE

    Marijan Jurgo

    2013-01-01

    The paper reviews working principles of phase-locked loop and drawbacks of classical PLL structure in nanometric technologies. It is proposed to replace the classical structure by all-digital phase-locked loop structure. Authors described the main blocks of all-digital phase-locked loop (time to digital converter and digitally controlled oscillator) and overviewed the quantization noise arising in these blocks as well as its minimization strategies. The calculated inverter delay in 65 nm CMOS...

  12. The Thermal Phase Curve Offset on Tidally and Nontidally Locked Exoplanets: A Shallow Water Model

    Science.gov (United States)

    Penn, James; Vallis, Geoffrey K.

    2017-06-01

    Using a shallow water model with time-dependent forcing, we show that the peak of an exoplanet thermal phase curve is, in general, offset from the secondary eclipse when the planet is rotating. That is, the planetary hot spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset are functions of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady state in the reference frame of the moving forcing. The model is an extension of the well-studied Matsuno-Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planet’s surface) exceeds that of the gravity waves, then the hot spot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wave speed of the system, the hottest point may lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics, as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.

  13. Double pass locking and spatial mode locking for gravitational wave detectors

    CERN Document Server

    Cusack, B J; Slagmolen, B; Vine, G D; Gray, M B; McClelland, D E

    2002-01-01

    We present novel techniques for overcoming problems relating to the use of high-power lasers in mode cleaner cavities for second generation laser interferometric gravitational wave detectors. Rearranging the optical components into a double pass locking regime can help to protect locking detectors from damage. Modulator thermal lensing can be avoided by using a modulation-free technique such as tilt locking, or its recently developed cousin, flip locking.

  14. Double pass locking and spatial mode locking for gravitational wave detectors

    Energy Technology Data Exchange (ETDEWEB)

    Cusack, Benedict J; Shaddock, Daniel A; Slagmolen, Bram J J; Vine, Glenn de; Gray, Malcolm B; McClelland, David E [Department of Physics, Faculty of Science, The Australian National University, ACT 0200 (Australia)

    2002-04-07

    We present novel techniques for overcoming problems relating to the use of high-power lasers in mode cleaner cavities for second generation laser interferometric gravitational wave detectors. Rearranging the optical components into a double pass locking regime can help to protect locking detectors from damage. Modulator thermal lensing can be avoided by using a modulation-free technique such as tilt locking, or its recently developed cousin, flip locking.

  15. Field Experience with Lock Culvert Valves

    Science.gov (United States)

    2013-12-01

    interesting accounts regarding their lock culvert valves. ST. LAWRENCE SEAWAY Eisenhower and Snell Locks. The valves on the Eisenhower and Snell Locks...Tainter Valve Design Lift, ft Eisenhower St. Lawrence Seaway 80 x 860 12 x 14 21.0 DSP 43 Snell St. Lawrence Seaway 80 x 860 12 x 14 21.0 3 DSP, 1 VF 49...vertical-frame valves were furnished to the SLSDC in January 2011, and one was installed in the south filling-valve location at Snell Lock. An option

  16. Robust quantum data locking from phase modulation

    Science.gov (United States)

    Lupo, Cosmo; Wilde, Mark M.; Lloyd, Seth

    2014-08-01

    Quantum data locking is a uniquely quantum phenomenon that allows a relatively short key of constant size to (un)lock an arbitrarily long message encoded in a quantum state, in such a way that an eavesdropper who measures the state but does not know the key has essentially no information about the message. The application of quantum data locking in cryptography would allow one to overcome the limitations of the one-time pad encryption, which requires the key to have the same length as the message. However, it is known that the strength of quantum data locking is also its Achilles heel, as the leakage of a few bits of the key or the message may in principle allow the eavesdropper to unlock a disproportionate amount of information. In this paper we show that there exist quantum data locking schemes that can be made robust against information leakage by increasing the length of the key by a proportionate amount. This implies that a constant size key can still lock an arbitrarily long message as long as a fraction of it remains secret to the eavesdropper. Moreover, we greatly simplify the structure of the protocol by proving that phase modulation suffices to generate strong locking schemes, paving the way to optical experimental realizations. Also, we show that successful data locking protocols can be constructed using random code words, which very well could be helpful in discovering random codes for data locking over noisy quantum channels.

  17. Literature Survey on Door Lock Security Systems

    National Research Council Canada - National Science Library

    Pradnya R Nehete; J P Chaudhari; S R Pachpande; K P Rane

    2016-01-01

    .... Due to the advancement in recent techniques, some door lock security systems are based on microcontroller, GSM, GPS, many sensors, software like MATLAB, PROTEUS, biometrics like face recognition...

  18. Microcontroller-based locking in optics experiments

    Energy Technology Data Exchange (ETDEWEB)

    Huang, K. [Laboratoire Kastler Brossel, UPMC-Sorbonne Universités, CNRS, ENS-PSL Research University, Collège de France, 4 place Jussieu, 75005 Paris (France); State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Le Jeannic, H.; Ruaudel, J.; Morin, O.; Laurat, J., E-mail: julien.laurat@upmc.fr [Laboratoire Kastler Brossel, UPMC-Sorbonne Universités, CNRS, ENS-PSL Research University, Collège de France, 4 place Jussieu, 75005 Paris (France)

    2014-12-15

    Optics experiments critically require the stable and accurate locking of relative phases between light beams or the stabilization of Fabry-Perot cavity lengths. Here, we present a simple and inexpensive technique based on a stand-alone microcontroller unit to perform such tasks. Easily programmed in C language, this reconfigurable digital locking system also enables automatic relocking and sequential functioning. Different algorithms are detailed and applied to fringe locking and to low- and high-finesse optical cavity stabilization, without the need of external modulations or error signals. This technique can readily replace a number of analog locking systems advantageously in a variety of optical experiments.

  19. Lock Culvert Valves; Hydraulic Design Considerations

    Science.gov (United States)

    2011-06-01

    the U.S. Army Engineer Waterways Experiment Station and U.S. Army Engineer Districts, St. Paul and Walla Walla . The prototype data suggest that the...been issued (U.S. Army Engineer District, Walla Walla 1955). 4.4.2 Lock No. 19 Lock 19 has a lift of 38.2 ft and flow is controlled with 14.5- by...Army Engineer Waterways Experiment Station. U.S. Army Engineer District, Walla Walla . 1955. Synchronization of lock filling valves, McNary Lock

  20. Microcontroller-based locking in optics experiments

    CERN Document Server

    Huang, K; Ruaudel, J; Morin, O; Laurat, J

    2014-01-01

    Optics experiments critically require the stable and accurate locking of relative phases between light beams or the stabilization of Fabry-Perot cavity lengths. Here, we present a simple and inexpensive technique based on a stand-alone microcontroller unit to perform such tasks. Easily programmed in C language, this reconfigurable digital locking system also enables automatic relocking and sequential functioning. Different algorithms are detailed and applied to fringe locking and to low- and high-finesse optical cavity stabilization, without the need of external modulations or error signals. This technique can readily replace a number of analog locking systems advantageously in a variety of optical experiments.

  1. Microcontroller-based locking in optics experiments.

    Science.gov (United States)

    Huang, K; Le Jeannic, H; Ruaudel, J; Morin, O; Laurat, J

    2014-12-01

    Optics experiments critically require the stable and accurate locking of relative phases between light beams or the stabilization of Fabry-Perot cavity lengths. Here, we present a simple and inexpensive technique based on a stand-alone microcontroller unit to perform such tasks. Easily programmed in C language, this reconfigurable digital locking system also enables automatic relocking and sequential functioning. Different algorithms are detailed and applied to fringe locking and to low- and high-finesse optical cavity stabilization, without the need of external modulations or error signals. This technique can readily replace a number of analog locking systems advantageously in a variety of optical experiments.

  2. «Réception de Locke au Danemark: Holberg, lecteur de Locke»

    DEFF Research Database (Denmark)

    Schøsler, Jørn

    Der gives en analyse af Holbergs læsning af Locke i Moralske Tanker og Epistler. Der fokuseres på hans holdning til Locke's Essay, hvor han synes fascineret af 'hypotesen om den tænkende materie' og problemet om de 'medfødte ideer'. Han tilslutter sig Locke's empirisme, men forsvarer dog en medfødt...

  3. Influence of Abrupt Change of Solar Mass on the Earth-like Planetary Orbit%太阳质量突变对类地行星轨道的影响

    Institute of Scientific and Technical Information of China (English)

    潘彩娟; 朱云锋; 马游

    2013-01-01

    Assuming that the terminated mass is confined within the range 0.4551~0.5813M⊙when sun is going to evolve into White Dwarf, the velocity sun ejecting the shell is much greater than the revolving velocity of earth-like planet, therefore we think that the solar mass change is instantaneous. Under the model of sun ejecting the shell, the radial velocity of earth-like planet has the same order of magnitude as its revolving velocity, the orbital eccentricity of earth-like planet varies with the range 1.7949~0.7240.%假设太阳演化为白矮星的终止质量范围是0.4551~0.5813 M⊙,太阳抛射壳层的速率远大于类地行星的公转速率,认为太阳的质量变化是瞬间的。在太阳抛射壳层的模型下,类地行星获得的径向速率的数值与其公转速率的数值在同一量级,类地行星的轨道偏心率的变化范围是1.7949~0.7240。

  4. Tidal river dynamics: Implications for deltas

    Science.gov (United States)

    Hoitink, A. J. F.; Jay, D. A.

    2016-03-01

    Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity intrusion, a realm that can extend inland hundreds of kilometers. One key phenomenon resulting from this interaction is the emergence of large fortnightly tides, which are forced long waves with amplitudes that may increase beyond the point where astronomical tides have become extinct. These can be larger than the linear tide itself at more landward locations, and they greatly influence tidal river water levels and wetland inundation. Exploration of the spectral redistribution and attenuation of tidal energy in rivers has led to new appreciation of a wide range of consequences for fluvial and coastal sedimentology, delta evolution, wetland conservation, and salinity intrusion under the influence of sea level rise and delta subsidence. Modern research aims at unifying traditional harmonic tidal analysis, nonparametric regression techniques, and the existing understanding of tidal hydrodynamics to better predict and model tidal river dynamics both in single-thread channels and in branching channel networks. In this context, this review summarizes results from field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia. A description of state-of-the-art methods for a comprehensive analysis of water levels, wave propagation, discharges, and inundation extent in tidal rivers is provided. Implications for lowland river deltas are also discussed in terms of sedimentary deposits, channel bifurcation, avulsion, and salinity intrusion, addressing contemporary research challenges.

  5. On the Tidal Dissipation of Obliquity

    CERN Document Server

    Rogers, T M

    2013-01-01

    We investigate tidal dissipation of obliquity in hot Jupiters. Assuming an initial random orientation of obliquity and parameters relevant to the observed population, the obliquity of hot Jupiters does not evolve to purely aligned systems. In fact, the obliquity evolves to either prograde, retrograde or 90^{o} orbits where the torque due to tidal perturbations vanishes. This distribution is incompatible with observations which show that hot jupiters around cool stars are generally aligned. This calls into question the viability of tidal dissipation as the mechanism for obliquity alignment of hot Jupiters around cool stars.

  6. Tidal flow separation at protruding beach nourishments

    OpenAIRE

    Rademacher, Max; de Schipper, Matthieu A.; Swinkels, Cilia; MacMahan, Jamie H.; Reniers, Ad J.H.M.

    2017-01-01

    The article of record as published may be found at http://dx.doi.org/10.1002/2016JC011942 In recent years, the application of large-scale beach nourishments has been discussed, with the Sand Motor in the Netherlands as the first real-world example. Such protruding beach nourishments have an impact on tidal currents, potentially leading to tidal flow separation and the generation of tidal eddies of length scales larger than the nourishment itself. The present study examines the cha...

  7. A quasilocal calculation of tidal heating

    CERN Document Server

    Booth, I S; Booth, Ivan S.; Creighton, Jolien D. E.

    2000-01-01

    We present a method for computing the flux of energy through a closed surfacecontaining a gravitating system. This method, which is based on the quasilocalformalism of Brown and York, is illustrated by two applications: a calculationof (i) the energy flux, via gravitational waves, through a surface nearinfinity and (ii) the tidal heating in the local asymptotic frame of a bodyinteracting with an external tidal field. The second application represents thefirst use of the quasilocal formalism to study a non-stationary spacetime andshows how such methods can be used to study tidal effects in isolatedgravitating systems.

  8. Dynamical response to a stationary tidal field

    CERN Document Server

    Landry, Philippe

    2015-01-01

    We demonstrate that a slowly rotating compact body subjected to a stationary tidal field undergoes a dynamical response, in which the fluid variables and the interior metric vary on the time scale of the rotation period. This dynamical response requires the tidal field to have a gravitomagnetic component generated by external mass currents; the response to a gravitoelectric tidal field is stationary. We confirm that in a calculation carried out to first order in the body's rotation, the exterior geometry bears no trace of this internal dynamics; it remains stationary in spite of the time-dependent interior.

  9. High-Order Frequency-Locked Loops

    DEFF Research Database (Denmark)

    Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack......) as well as a unification between FLLs and PLLs is presented....

  10. An automatic mode-locked system for passively mode-locked fiber laser

    Science.gov (United States)

    Li, Sha; Xu, Jun; Chen, Guoliang; Mei, Li; Yi, Bo

    2013-12-01

    This paper designs and implements one kind of automatic mode-locked system. It can adjust a passively mode-locked fiber laser to keep steady mode-locked states automatically. So the unsteadiness of traditional passively mode-locked fiber laser can be avoided. The system transforms optical signals into electrical pulse signals and sends them into MCU after processing. MCU calculates the frequency of the signals and judges the state of the output based on a quick judgment algorithm. A high-speed comparator is used to check the signals and the comparison voltage can be adjusted to improve the measuring accuracy. Then by controlling two polarization controllers at an angle of 45degrees to each other, MCU extrudes the optical fibers to change the polarization until it gets proper mode-locked output. So the system can continuously monitor the output signal and get it back to mode-locked states quickly and automatically. States of the system can be displayed on the LCD and PC. The parameters of the steady mode-locked states can be stored into an EEPROM so that the system will get into mode-locked states immediately next time. Actual experiments showed that, for a 6.238MHz passively mode-locked fiber lasers, the system can get into steady mode-locked states automatically in less than 90s after starting the system. The expected lock time can be reduced to less than 20s after follow up improvements.

  11. Downstream hydraulic geometry of a tidally influenced river delta

    NARCIS (Netherlands)

    Sassi, M.G.; Hoitink, A.J.F.; Brye, de B.; Deleersnijder, E.

    2012-01-01

    Channel geometry in tidally influenced river deltas can show a mixed scaling behavior between that of river and tidal channel networks, as the channel forming discharge is both of river and tidal origin. We present a method of analysis to quantify the tidal signature on delta morphology, by extendin

  12. The oscillations of ship lock bottom

    Directory of Open Access Journals (Sweden)

    N.Yu. Kuzmin

    2012-06-01

    Full Text Available The article deals with the dynamic characteristics of the ship lock. The accurate design relations intended to study the natural and forced vibrations of the bottom of the ship lock are provided. The degree of filling of the lock, as well as the added mass of water is considered. The various coupling conditions of the bottom and walls of buildings are taken into account. A concrete example of the calculation is given.An exact, in the framework of the adopted design scheme, solution of the problem of the own and forced vibrations of the bottom of the ship lock is found. The frequency of the first five tones of vibrations and the associated mass of liquid according to thickness of the structure and coupling conditions of the bottom and sides of the lock are analyzed. A significant effect of liquids on low-frequency part of the spectrum and the dynamic response of the bottom is determined.

  13. Commonwealth Edison Company pressure locking test report

    Energy Technology Data Exchange (ETDEWEB)

    Bunte, B.D.; Kelly, J.F.

    1996-12-01

    Pressure Locking is a phenomena which can cause the unseating thrust for a gate valve to increase dramatically from its typical static unseating thrust. This can result in the valve actuator having insufficient capability to open the valve. In addition, this can result in valve damage in cases where the actuator capability exceeds the valve structural limits. For these reasons, a proper understanding of the conditions which may cause pressure locking and thermal binding, as well as a methodology for predicting the unseating thrust for a pressure locked or thermally bound valve, are necessary. This report discusses the primary mechanisms which cause pressure locking. These include sudden depressurization of piping adjacent to the valve and pressurization of fluid trapped in the valve bonnet due to heat transfer. This report provides a methodology for calculating the unseating thrust for a valve which is pressure locked. This report provides test data which demonstrates the accuracy of the calculation methodology.

  14. Optical Estimation of Depth and Current in a Ebb Tidal Delta Environment

    Science.gov (United States)

    Holman, R. A.; Stanley, J.

    2012-12-01

    A key limitation to our ability to make nearshore environmental predictions is the difficulty of obtaining up-to-date bathymetry measurements at a reasonable cost and frequency. Due to the high cost and complex logistics of in-situ methods, research into remote sensing approaches has been steady and has finally yielded fairly robust methods like the cBathy algorithm for optical Argus data that show good performance on simple barred beach profiles and near immunity to noise and signal problems. In May, 2012, data were collected in a more complex ebb tidal delta environment during the RIVET field experiment at New River Inlet, NC. The presence of strong reversing tidal currents led to significant errors in cBathy depths that were phase-locked to the tide. In this paper we will test methods for the robust estimation of both depths and vector currents in a tidal delta domain. In contrast to previous Fourier methods, wavenumber estimation in cBathy can be done on small enough scales to resolve interesting nearshore features.

  15. Hydrodynamics and sediment suspension in shallow tidal channels intersecting a tidal flat

    Science.gov (United States)

    Pieterse, Aline; Puleo, Jack A.; McKenna, Thomas E.

    2016-05-01

    A field study was conducted on a tidal flat intersected by small tidal channels (depth stress and turbulent kinetic energy were computed from high frequency velocity measurements. Maximum water depth at the field site varied from 0.11 m during the lowest neap high tide to 0.58 m during a storm event. In the channel intersecting the tidal flat, the shear stress, turbulence and along-channel velocity were ebb dominant; e.g. 0.33 m/s peak velocity for ebb compared to 0.19 m/s peak velocity for flood. Distinct pulses in velocity occurred when the water level was near the tidal flat level. The velocity pulse during flood tide occurred at a higher water level than during ebb tide. No corresponding velocity pulse on the tidal flat was observed. Sediment concentrations peaked at the beginning and end of each tidal cycle, and often had a secondary peak close to high tide, assumed to be related to sediment advection. The influence of wind waves on bed shear stress and sediment suspension was negligible. Water levels were elevated during a storm event such that the tidal flat remained inundated for 4 tidal cycles. The water did not drain from the tidal flat into the channels during the storm, and no velocity pulses occurred. Along-channel velocities, turbulent kinetic energy, and shear stresses were therefore smaller in the channels during storm conditions than during non-storm conditions.

  16. Microbial quality of a marine tidal pool

    CSIR Research Space (South Africa)

    Genthe, Bettina

    1995-01-01

    Full Text Available In this study the source of microbial pollution to a tidal pool was investigated. Both adjacent seawater which could contribute to possible faecal pollution and potential direct bather pollution were studied. The microbial quality of the marine...

  17. Tides and tidal harmonics at Umbharat, Gujarat

    Digital Repository Service at National Institute of Oceanography (India)

    Suryanarayana, A.; Swamy, G.N.

    A part of the data on tides recorded at Machiwada near Umbharat, Gulf of Cambay during April 1978 was subjected to harmonic analysis following the Admiralty procedure. The general tidal characteristics and the value of four major harmonic...

  18. Analysis of 19-year tidal data

    Institute of Scientific and Technical Information of China (English)

    黄祖珂; 陈宗镛; 司鸿业; 叶琳

    1997-01-01

    19-year tidal data of the 3 stations, Huludao, Qinhuangdao and Kanmen, have totally been analysed, and the amplitudes and phases of 472 tidal constituents have been calculated with a resolution of Δ≥ 0.002 2 /h. Based on the draconitic tide, the anomalistic tide and pole tide obtained, the ultra-long-period variations of the mean sea level have been predicted. The annual tidal analysis of 19-year data at the above-mentioned stations and at Tanggu, Longkou has been carried out. The stability of the annual tidal analysis has been investigated with regard to the astronomical factors, the nonlinear effects and the variations of sea-bottom topography.

  19. Tidal Response of Preliminary Jupiter Model

    OpenAIRE

    Wahl, Sean M; Hubbard, Willam B.; Militzer, Burkhard

    2016-01-01

    In anticipation of improved observational data for Jupiter's gravitational field from the Juno spacecraft, we predict the static tidal response for a variety of Jupiter interior models based on ab initio computer simulations of hydrogen-helium mixtures. We calculate hydrostatic-equilibrium gravity terms using the non-perturbative concentric Maclaurin Spheroid (CMS) method that eliminates lengthy expansions used in the theory of figures. Our method captures terms arising from the coupled tidal...

  20. Assessment of Soil Quality of Tidal Marshes in Shanghai City

    Institute of Scientific and Technical Information of China (English)

    Qing; WANG; Juan; TAN; Jianqiang; WU; Chenyan; SHA; Junjie; RUAN; Min; WANG; Shenfa; HUANG

    2013-01-01

    We take three types of tidal marshes in Shanghai City as the study object:tidal marshes in mainland,tidal marshes in the rim of islands,and shoal in Yangtze estuary.On the basis of assessing nutrient quality and environmental quality,respectively,we use soil quality index(SQI)to assess the soil quality of tidal flats,meanwhile formulate the quality grading standards,and analyze the current situation and characteristics of it.The results show that except the north of Hangzhou Bay,Nanhui and Jiuduansha with low soil nutrient quality,there are not obvious differences in soil nutrient quality between other regions;the heavy metal pollution of tidal marshes in mainland is more serious than that of tidal marshes in the rim of islands;in terms of the comprehensive soil quality index,the regions are sequenced as follows:Jiuduansha wetland>Chongming Dongtan wetland>Nanhui tidal flat>tidal flat on the periphery of Chongming Island>tidal flat on the periphery of Hengsha Island>Pudong tidal flat>Baoshan tidal flat>tidal flat on the periphery of Changxing Island>tidal flat in the north of Hangzhou Bay.Among them,Jiuduansha wetland and Chongming Dongtan wetland have the best soil quality,belonging to class III,followed by Nanhui tidal flat,tidal flat on the periphery of Chongming Island and tidal flat on the periphery of Hengsha Island,belonging to class IV;tidal flat on the periphery of Changxing Island,Pudong tidal flat,Baoshan tidal flat and tidal flat in the north of Hangzhou Bay belong to class V.

  1. Spatial patterns of tidal heating

    CERN Document Server

    Beuthe, Mikael

    2012-01-01

    In a body periodically strained by tides, heating produced by viscous friction is far from homogeneous. I show here that the distribution of the dissipated power within a spherically stratified body is a linear combination of three angular functions. These angular functions depend only on the tidal potential whereas the radial weights are specified by the internal structure of the body. The 3D problem of predicting spatial patterns of dissipation at all radii is thus reduced to the 1D problem of computing weight functions. I compute spatial patterns in various toy models without assuming a specific rheology: a viscoelastic thin shell stratified in conductive and convective layers, an incompressible homogeneous body and a two-layer model of uniform density with a liquid or rigid core. For a body in synchronous rotation undergoing eccentricity tides, dissipation in a mantle surrounding a liquid core is highest at the poles. Within a softer layer (asthenosphere or icy layer), the same tides generate maximum heat...

  2. Half Moon Cove Tidal Project. Feasibility report

    Energy Technology Data Exchange (ETDEWEB)

    1980-11-01

    The proposed Half Moon Cove Tidal Power Project would be located in a small cove in the northern part of Cobscook Bay in the vicinity of Eastport, Maine. The project would be the first tidal electric power generating plant in the United States of America. The basin impounded by the barrier when full will approximate 1.2 square miles. The average tidal range at Eastport is 18.2 feet. The maximum spring tidal range will be 26.2 feet and the neap tidal range 12.8 feet. The project will be of the single pool-type single effect in which generation takes place on the ebb tide only. Utilizing an average mean tidal range of 18.2 feet the mode of operation enables generation for approximately ten and one-half (10-1/2) hours per day or slightly in excess of five (5) hours per tide. The installed capacity will be 12 MW utilizing 2 to 6 MW units. An axial flow, or Bulb type of turbine was selected for this study.

  3. Can Tidal Current Energy Provide Base Load?

    Directory of Open Access Journals (Sweden)

    Simone Giorgi

    2013-06-01

    Full Text Available Tidal energy belongs to the class of intermittent but predictable renewable energy sources. In this paper, we consider a compact set of geographically diverse locations, which have been assessed to have significant tidal stream energy, and attempt to find the degree to which the resource in each location should be exploited so that the aggregate power from all locations has a low variance. An important characteristic of the locations chosen is that there is a good spread in the peak tidal flow times, though the geographical spread is relatively small. We assume that the locations, all on the island of Ireland, can be connected together and also assume a modular set of tidal turbines. We employ multi-objective optimisation to simultaneously minimise variance, maximise mean power and maximise minimum power. A Pareto front of optimal solutions in the form of a set of coefficients determining the degree of tidal energy penetration in each location is generated using a genetic algorithm. While for the example chosen the total mean power generated is not great (circa 100 MW, the case study demonstrated a methodology that can be applied to other location sets that exhibit similar delays between peak tidal flow times.

  4. VISCOELASTIC MODELS OF TIDALLY HEATED EXOMOONS

    Energy Technology Data Exchange (ETDEWEB)

    Dobos, Vera [Konkoly Thege Miklos Astronomical Institute, Research Centre of Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Konkoly Thege Miklós út 15-17, Budapest (Hungary); Turner, Edwin L., E-mail: dobos@konkoly.hu [Department of Astrophysical Sciences, Princeton University, 08544, 4 Ivy Lane, Peyton Hall, Princeton, NJ (United States)

    2015-05-01

    Tidal heating of exomoons may play a key role in their habitability, since the elevated temperature can melt the ice on the body even without significant solar radiation. The possibility of life has been intensely studied on solar system moons such as Europa or Enceladus where the surface ice layer covers a tidally heated water ocean. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. To study the tidally heated surface temperature of exomoons, we used a viscoelastic model for the first time. This model is more realistic than the widely used, so-called fixed Q models because it takes into account the temperature dependence of the tidal heat flux and the melting of the inner material. Using this model, we introduced the circumplanetary Tidal Temperate Zone (TTZ), which strongly depends on the orbital period of the moon and less on its radius. We compared the results with the fixed Q model and investigated the statistical volume of the TTZ using both models. We have found that the viscoelastic model predicts 2.8 times more exomoons in the TTZ with orbital periods between 0.1 and 3.5 days than the fixed Q model for plausible distributions of physical and orbital parameters. The viscoelastic model provides more promising results in terms of habitability because the inner melting of the body moderates the surface temperature, acting like a thermostat.

  5. Viscoelastic Models of Tidally Heated Exomoons

    CERN Document Server

    Dobos, Vera

    2015-01-01

    Tidal heating of exomoons may play a key role in their habitability, since the elevated temperature can melt the ice on the body even without significant solar radiation. The possibility of life is intensely studied on Solar System moons such as Europa or Enceladus, where the surface ice layer covers tidally heated water ocean. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. For studying the tidally heated surface temperature of exomoons, we used a viscoelastic model for the first time. This model is more realistic than the widely used, so-called fixed Q models, because it takes into account the temperature dependency of the tidal heat flux, and the melting of the inner material. With the use of this model we introduced the circumplanetary Tidal Temperate Zone (TTZ), that strongly depends on the orbital period of the moon, and less on its radius. We compared the results with the fixed Q model and investigated the statistical volume of the TTZ usi...

  6. Delay locked loop integrated circuit.

    Energy Technology Data Exchange (ETDEWEB)

    Brocato, Robert Wesley

    2007-10-01

    This report gives a description of the development of a Delay Locked Loop (DLL) integrated circuit (IC). The DLL was developed and tested as a stand-alone IC test chip to be integrated into a larger application specific integrated circuit (ASIC), the Quadrature Digital Waveform Synthesizer (QDWS). The purpose of the DLL is to provide a digitally programmable delay to enable synchronization between an internal system clock and external peripherals with unknown clock skew. The DLL was designed and fabricated in the IBM 8RF process, a 0.13 {micro}m CMOS process. It was designed to operate with a 300MHz clock and has been tested up to 500MHz.

  7. Unusual Cause of Knee Locking

    Directory of Open Access Journals (Sweden)

    Gazi Huri

    2013-01-01

    Full Text Available We report a case of partial intrasubstance tear of popliteus tendon as an unusual cause of pseudolocking of the knee. A 13-year-old semiprofessional soccer player applied to our clinic with a locked right knee in spite of the therapy applied (cold pack, NSAID, and immobilization in another institution 20 days after the injury. Significant extension loss was observed in his right knee with 30∘–90∘ ROM. Magnetic resonance imaging (MRI and arthroscopy confirmed the intrasubstance tear of popliteus tendon and synovitis. The ruptured part of the tendon was debrided, and the inflammatory tissue around the tendon, which may lead to pseudolocking, was gently removed with a shaver in order to regain the normal ROM. The patient was discharged with full ROM and weight bearing first day after the surgery. To our knowledge, this is the first case demonstrating intrasubstance tear of popliteus tendon causing pseudolocking of the knee.

  8. Turbulent lock release gravity current

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The time evolution of a turbulent lock release gravity current, formed by a finite volume ofhomogeneous fluid released instantaneously into another fluid of slightly lower density, was studied byexperimental measurements of the density structure via elaborate digital image processing and by a nu-merical simulation of the flow and mixing using a two-equation turbulence model. The essential fact thatthe gravity current passes through an initial slumping phase in which the current head advances steadilyand a second self-similar phase in which the front velocity decreases like the negative third power of thetime after release is satisfactorily presented by the laboratory observation. An overall entrainment ratioproportional to the distance from the release point is found by the numerical simulation. The renormal-ization group (RNG) k- ε model for Reynolds-stress closure is validated to characterize the gravitycurrent with transitional and localized turbulence.

  9. Opto-mechanical door locking system

    Science.gov (United States)

    Patil, Saurabh S.; Rodrigues, Vanessa M.; Patil, Ajeetkumar; Chidangil, Santhosh

    2015-09-01

    We present an Opto-mechanical Door Locking System which is an optical system that combines a simple combination of a coherent light source (Laser) and a photodiode based sensor with focus toward security applications. The basic construct of the KEY comprises a Laser source in a cylindrical enclosure that slides perfectly into the LOCK. The Laser is pulsed at a fixed encrypted frequency unique to that locking system. Transistor-transistor logic (TTL) circuitry is used to achieve encryption. The casing of the key is designed in such a way that it will power the pulsing laser only when the key is inserted in the slot provided for it. The Lock includes a photo-sensor that will convert the detected light intensity to a corresponding electrical signal by decrypting the frequency. The lock also consists of a circuit with a feedback system that will carry the digital information regarding the encryption frequency code. The information received from the sensor is matched with the stored code; if found a perfect match, a signal will be sent to the servo to unlock the mechanical lock or to carry out any other operation. This technique can be incorporated in security systems for residences and safe houses, and can easily replace all conventional locks which formerly used fixed patterns to unlock. The major advantage of this proposed optomechanical system over conventional ones is that it no longer relies on a solid/imprinted pattern to perform its task and hence makes it almost impossible to tamper with.

  10. Correlations between locked modes and impurity influxes

    Energy Technology Data Exchange (ETDEWEB)

    Fishpool, G.M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Lawson, K.D. [UKAEA Culham Lab., Abingdon (United Kingdom)

    1994-07-01

    An analysis of pulses that were disturbed by medium Z impurity influxes (Cl, Cr, Fe and Ni) recorded during the 91/92 JET operations, has demonstrated that such influxes can result in MHD modes which subsequently ``lock``. A correlation is found between the power radiated by the influx and the time difference between the start of the influx and the beginning of the locked mode. The growth in the amplitude of the locked mode itself can lead to further impurity influxes. A correlation is noted between intense influxes (superior to 10 MW) and the mode ``unlocking``. (authors). 4 refs., 4 figs.

  11. Parallel Digital Phase-Locked Loops

    Science.gov (United States)

    Sadr, Ramin; Shah, Biren N.; Hinedi, Sami M.

    1995-01-01

    Wide-band microwave receivers of proposed type include digital phase-locked loops in which band-pass filtering and down-conversion of input signals implemented by banks of multirate digital filters operating in parallel. Called "parallel digital phase-locked loops" to distinguish them from other digital phase-locked loops. Systems conceived as cost-effective solution to problem of filtering signals at high sampling rates needed to accommodate wide input frequency bands. Each of M filters process 1/M of spectrum of signal.

  12. $\\mathcal{PT}$-symmetric mode-locking

    CERN Document Server

    Longhi, Stefano

    2016-01-01

    Parity-time ($\\mathcal{PT}$) symmetry is one of the most important accomplishments in optics over the past decade. Here the concept of $\\mathcal{PT}$ mode-locking of a laser is introduced, in which active phase locking of cavity axial modes is realized by asymmetric mode coupling in a complex time crystal. $\\mathcal{PT}$ mode-locking shows a transition from single to double pulse emission as the $\\mathcal{PT}$ symmetry breaking point is crossed. The transition can show a turbulent behavior, depending on a dimensionless modulation parameter that plays the same role as the Reynolds number in hydrodynamic flows.

  13. Seasonal variability of tidal and non-tidal currents off Beypore, SW coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DineshKumar, P.K.; Srinivas, K.; AnilKumar, N.

    Analyses of current meter records generated in the coastal waters off Beypore (11 degrees 10 minutes S; 75 degrees 48 minutes E) on the southwest coast of India have been made to understand the tidal and non-tidal variability during premonsoon...

  14. Biogeomorphology of tidal landforms: physical and biological processes shaping the tidal landscape

    Science.gov (United States)

    Marani, M.; D'Alpaos, A.; Da Lio, C.

    2011-12-01

    The equilibrium states and transient dynamics of tidal landforms are the result of many concurring physical and biological forcings, such as tidal range, wind climate, sediment supply, vegetation and microphytobenthos development, and rates of relative sea level rise (RSLR). A 0D model of the coupled elevation-vegetation dynamics is used to explore the relative role of the physical and biological factors shaping these systems. We find that salt marshes exposed to large tidal ranges are more stable, and therefore more resilient to increasing rates of RSLR, than marshes subjected to low tidal ranges and that subtidal platforms in macrotidal systems are less exposed to wind-induced erosion processes than their counterparts in systems with smaller tidal fluctuations. Notably, we find that vegetation crucially affects both the equilibrium marsh elevation, through dissipation of wind waves and organic accumulation, and marsh resilience to accelerations in RSLR rates, important differences being associated with different vegetation types. Furthermore, our results show that the existence and stability of equilibrium states fundamentally depend on the local wind and tidal regime, even within the same tidal system. Finally, we propose a modelling framework to study how biological evolution lead to the emergence of tidal landforms as we know them.

  15. Dynamics of tidal and non-tidal currents along the southwest continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Aruna, C.; Ravichandran, C.; Srinivas, K.; Rasheed, P.A.A; Lekshmi, S.

    are predominantly mixed, semidiurnal in nature. Motion over any continental shelf is governed by the tide-driven oscillatory flow. In this paper, tidal and non-tidal characteristics of the waters of Southwest continental shelf of India are assessed using...

  16. Three-dimensional semi-idealized model for tidal motion in tidal estuaries

    NARCIS (Netherlands)

    Kumar, M.; Schuttelaars, H.M.; Roos, P.C.; Möller, M.

    2015-01-01

    In this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the firs

  17. Stability of unicortical locked fixation versus bicortical non-locked fixation for forearm fractures

    Institute of Scientific and Technical Information of China (English)

    Timothy J.Pater; Steve I Grindel; Gregory J.Schmeling; Mei Wang

    2014-01-01

    Locking plate fixation is being widely applied for fixation of forearm fractures and has many potential advantages, such as fixed angle fixation and improved construct stability, especially in osteoporotic bone. Biomechanical data comparing locking devices to commonly used Low Contact Dynamic Compression (LCDCP) plates for the fixation of forearm fractures has been lacking. The purpose of this study was to compare the fixation stability of a 3.5-mm unicortical locked plate with bicortical non-locked LCDCP plates. Six matched pairs of fresh frozen cadaveric forearms were randomly assigned to unicortical locked and bicortical unlocked groups. Non-destructive four-point bending and torsional test was performed on the ulna and radius separately, using a servohydraulic testing system to obtain construct stiffness of the intact specimens and specimens after osteotomy and plating. The specimens were then loaded to failure to test the fixation strength. The locked unicortical fixation showed significantly higher bending stiffness than the unlocked bicortical fixation, but with significantly lower stiffness and strength in torsion. Fixation strength was comparable between the two groups under bending, but significantly greater in the bicortical non-locked group under torsion. Findings from this study suggest that postoperative rehabilitation protocols may need modification to limit torsional loading in the early stage when using locked unicortical fixation. The study also points out the potential advantage of a hybrid fixation that combines locked unicortical and unlocked bicortical screws.

  18. Universal Spin-Momentum Locked Optical Forces

    CERN Document Server

    Kalhor, Farid; Jacob, Zubin

    2015-01-01

    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, direction of decay, and direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and $HE_{11}$ mode of an optical fiber. Furthermore, we explain how the recently reported phenomena of lateral optical force on chiral and achiral particles is 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...

  19. 49 CFR 236.408 - Route locking.

    Science.gov (United States)

    2010-10-01

    ..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Traffic Control Systems... locking shall be effective when the first pair of wheels of a locomotive or car passes a point not...

  20. Poder constitucional e democracia em Locke

    Directory of Open Access Journals (Sweden)

    Joel Ulhôa

    2007-12-01

    Full Text Available O artigo analisa os princípios pelos quais são delimitados os poderes do Estado e assegurado o respeito aos direitos individuais, no Segundo tratado sobre o governo,de John Locke.

  1. LOCKING-FREE DEGENERATED ISOPARAMETRIC SHELL ELEMENT

    Institute of Scientific and Technical Information of China (English)

    章向明; 王安稳; 何汉林

    2001-01-01

    An 8-noded locking-free degenerated isoparametric shell element is presented.A revised interpolation for shear strain terms was constructed in natural co-ordinate system such that all necessary modes ( translation, rotation and constant curvature ) are preserved,which can be used to eliminate shear locking. A revised interpolation for membrane strains was produced in the local Cartesian co-ordinate system to overcome membrane locking behavior. The new 8-noded element has the proper rank, with the requisite number of zero eigenvalues each associated with a rigid mode. The element does not exhibit membrane or shear locking for large span-thickness ratio. The element does not form element mechanisms or extra spurious zero energy modes. Therefore, it can be used for both thin and thick shells.

  2. High power coherent polarization locked laser diode.

    Science.gov (United States)

    Purnawirman; Phua, P B

    2011-03-14

    We have coherently combined a broad area laser diode array to obtain high power single-lobed output by using coherent polarization locking. The single-lobed coherent beam is achieved by spatially combining four diode emitters using walk-off crystals and waveplates while their phases are passively locked via polarization discrimination. While our previous work focused on coherent polarization locking of diode in Gaussian beams, we demonstrate in this paper, the feasibility of the same polarization discrimination for locking multimode beams from broad area diode lasers. The resonator is designed to mitigate the loss from smile effect by using retro-reflection feedback in the cavity. In a 980 nm diode array, we produced 7.2 W coherent output with M2 of 1.5x11.5. The brightness of the diode is improved by more than an order of magnitude.

  3. Validation of Modeling Flow Approaching Navigation Locks

    Science.gov (United States)

    2013-08-01

    instrumentation, direction vernier . ........................................................................ 8  Figure 11. Plan A lock approach, upstream approach...13-9 8 Figure 9. Tools and instrumentation, bracket attached to rail. Figure 10. Tools and instrumentation, direction vernier . Numerical model

  4. Tidal stress and failure in the moon of binary asteroid systems: Application to asteroid (65803) Didymos

    Science.gov (United States)

    Sophal Pou, Laurent; Garcia, Raphael F.; Mimoun, David; Murdoch, Naomi; Karatekin, Ozgur

    2017-04-01

    Rocky remnants left over from the early formation of the Solar System, asteroids are a target of choice for planetary science since much about the history of planetary formation and small body evolution processes can be learnt by studying them. Here we consider the case of the binary asteroid (65803) Didymos, the target of several mission proposals e.g., AIM [1] and DART [2]. A mission to Didymos would be a great opportunity for in-situ geophysical investigation, providing information on the surface and interior of asteroids. Such studies would improve our knowledge of binary asteroid formation and subsequent evolution of asteroids, thus of the history of the Solar System. As Didymos is a binary asteroid [3] with the main 800-meter diameter asteroid named Didymain and a 150-meter sized moon named Didymoon, both are subject to tidal stress. Recent investigations suggest that Didymoon is tidally locked and moves in a retrograde motion around Didymain along an elliptic orbit with a 0.03 eccentricity at most. In the case of an eccentric orbit, the tidal stress varies periodically and may be strong enough to cause tidal quakes on Didymoon at some points of the orbit. For this study, we modelled Didymoon as a spherical, layered body with different internal structures: a homogeneous model, and two models with a 1-meter and 10-meter regolith layer on top of a stronger internal core. Simulations show that, for a cohesionless body with an internal friction angle of 30°, tidal stress is strong enough to cause failure at the surface of Didymoon. A maximal stress is reached around the poles and for a mean anomaly of 90°. These results would mean that if tidal quakes occur on Didymoon, then they are likely to happen at these locations. An extension of these results to an ellipsoidal model of Didymoon is also presented for comparison with the spherical case and for application to other bodies. [1]: P. Michel et al., Science case for the asteroid impact mission (aim): A

  5. Harnessing Ocean Energy by Tidal Current Technologies

    Directory of Open Access Journals (Sweden)

    Nasir Mehmood

    2012-09-01

    Full Text Available The world is heavily dependent on fossil fuels since most of its energy requirements are fulfilled by conventional methods of burning these fuels. The energy demand is increasing by day with growing population. The energy production by fossil fuels is devastating the environment and survival of life on globe is endangered. The renewal energy technologies are vital to ensure future energy sustenance and environmental issues. Ocean is a vast resource of renewable energy. The technology today makes it possible to extract energy from tides. The growing interest in exploring tidal current technologies has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The purpose of this study is to present a comprehensive review of tidal current technologies to harness ocean energy. The ocean energy resources are presented. The author discusses tidal energy technologies. The tidal current turbines are discussed in detail. The author reviews today’s popular tidal current technologies. The present status of ocean energy development is also reported.

  6. Carbon sequestration by Australian tidal marshes

    KAUST Repository

    Macreadie, Peter I.

    2017-03-10

    Australia\\'s tidal marshes have suffered significant losses but their recently recognised importance in CO2 sequestration is creating opportunities for their protection and restoration. We compiled all available data on soil organic carbon (OC) storage in Australia\\'s tidal marshes (323 cores). OC stocks in the surface 1 m averaged 165.41 (SE 6.96) Mg OC ha-1 (range 14-963 Mg OC ha-1). The mean OC accumulation rate was 0.55 ± 0.02 Mg OC ha-1 yr-1. Geomorphology was the most important predictor of OC stocks, with fluvial sites having twice the stock of OC as seaward sites. Australia\\'s 1.4 million hectares of tidal marshes contain an estimated 212 million tonnes of OC in the surface 1 m, with a potential CO2-equivalent value of $USD7.19 billion. Annual sequestration is 0.75 Tg OC yr-1, with a CO2-equivalent value of $USD28.02 million per annum. This study provides the most comprehensive estimates of tidal marsh blue carbon in Australia, and illustrates their importance in climate change mitigation and adaptation, acting as CO2 sinks and buffering the impacts of rising sea level. We outline potential further development of carbon offset schemes to restore the sequestration capacity and other ecosystem services provided by Australia tidal marshes.

  7. The tidal tails of NGC 2298

    CERN Document Server

    Balbinot, Eduardo; da Costa, Luiz N; Makler, Martin; Maia, Marcio A G

    2011-01-01

    We present an implementation of the matched-filter technique to detect tidal tails of globular clusters. The method was tested using SDSS data for the globular cluster Palomar 5 revealing its well known tidal tails. We also ran a simulation of a globular cluster with a tidal tail where we successfully recover the tails for a cluster at the same position and with the same characteristics of NGC 2298. Based on the simulation we estimate that the matched-filter increases the contrast of the tail relative to the background of stars by a factor of 2.5 for the case of NGC 2298. We also present the photometry of the globular cluster NGC 2298 using the MOSAIC2 camera installed on the CTIO 4m telescope. The photometry covers ~ 3deg2 reaching V ~ 23. A fit of a King profile to the radial density profile of NGC 2298 shows that this cluster has a tidal radius of 15.91' \\pm 1.07' which is twice as in the literature. The application of the matched-filter to NGC 2298 reveals several extra-tidal structures, including a leadi...

  8. Tidally Heated Terrestrial Exoplanets: Viscoelastic Response Models

    CERN Document Server

    Henning, Wade G; Sasselov, Dimitar D; 10.1088/0004-637X/707/2/1000

    2009-01-01

    Tidal friction in exoplanet systems, driven by orbits that allow for durable nonzero eccentricities at short heliocentric periods, can generate internal heating far in excess of the conditions observed in our own solar system. Secular perturbations or a notional 2:1 resonance between a Hot Earth and Hot Jupiter can be used as a baseline to consider the thermal evolution of convecting bodies subject to strong viscoelastic tidal heating. We compare results first from simple models using a fixed Quality factor and Love number, and then for three different viscoelastic rheologies: the Maxwell body, the Standard Anelastic Solid, and the Burgers body. The SAS and Burgers models are shown to alter the potential for extreme tidal heating by introducing the possibility of new equilibria and multiple response peaks. We find that tidal heating tends to exceed radionuclide heating at periods below 10-30 days, and exceed insolation only below 1-2 days. Extreme cases produce enough tidal heat to initiate global-scale parti...

  9. Carbon sequestration by Australian tidal marshes

    Science.gov (United States)

    Macreadie, Peter I.; Ollivier, Q. R.; Kelleway, J. J.; Serrano, O.; Carnell, P. E.; Ewers Lewis, C. J.; Atwood, T. B.; Sanderman, J.; Baldock, J.; Connolly, R. M.; Duarte, C. M.; Lavery, P. S.; Steven, A.; Lovelock, C. E.

    2017-03-01

    Australia’s tidal marshes have suffered significant losses but their recently recognised importance in CO2 sequestration is creating opportunities for their protection and restoration. We compiled all available data on soil organic carbon (OC) storage in Australia’s tidal marshes (323 cores). OC stocks in the surface 1 m averaged 165.41 (SE 6.96) Mg OC ha-1 (range 14-963 Mg OC ha-1). The mean OC accumulation rate was 0.55 ± 0.02 Mg OC ha-1 yr-1. Geomorphology was the most important predictor of OC stocks, with fluvial sites having twice the stock of OC as seaward sites. Australia’s 1.4 million hectares of tidal marshes contain an estimated 212 million tonnes of OC in the surface 1 m, with a potential CO2-equivalent value of $USD7.19 billion. Annual sequestration is 0.75 Tg OC yr-1, with a CO2-equivalent value of $USD28.02 million per annum. This study provides the most comprehensive estimates of tidal marsh blue carbon in Australia, and illustrates their importance in climate change mitigation and adaptation, acting as CO2 sinks and buffering the impacts of rising sea level. We outline potential further development of carbon offset schemes to restore the sequestration capacity and other ecosystem services provided by Australia tidal marshes.

  10. Tidal Response of Preliminary Jupiter Model

    Science.gov (United States)

    Wahl, Sean M.; Hubbard, William B.; Militzer, Burkhard

    2016-11-01

    In anticipation of improved observational data for Jupiter’s gravitational field, from the Juno spacecraft, we predict the static tidal response for a variety of Jupiter interior models based on ab initio computer simulations of hydrogen-helium mixtures. We calculate hydrostatic-equilibrium gravity terms, using the non-perturbative concentric Maclaurin Spheroid method that eliminates lengthy expansions used in the theory of figures. Our method captures terms arising from the coupled tidal and rotational perturbations, which we find to be important for a rapidly rotating planet like Jupiter. Our predicted static tidal Love number, {k}2=0.5900, is ˜10% larger than previous estimates. The value is, as expected, highly correlated with the zonal harmonic coefficient J 2, and is thus nearly constant when plausible changes are made to the interior structure while holding J 2 fixed at the observed value. We note that the predicted static k 2 might change, due to Jupiter’s dynamical response to the Galilean moons, and find reasons to argue that the change may be detectable—although we do not present here a theory of dynamical tides for highly oblate Jovian planets. An accurate model of Jupiter’s tidal response will be essential for interpreting Juno observations and identifying tidal signals from effects of other interior dynamics of Jupiter’s gravitational field.

  11. How Reliable Are The Threaded Locking Screws?

    OpenAIRE

    Karaarslan, Ahmet; Karakaslı, Ahmet; Karcı, Tolga; Aycan, Hakan; Sesli, Erhan

    2015-01-01

    Objectives: A frequent problem for interlocking nailing, that affects the treatment of the fracture is locking screw deformation. The research question is whether bending resistance is different between high, low and unthreaded locking screws of interlocking femoral nails. Materials and methods. : We used 90 screws for nine groups, ten screws for each group in this experimental study. We performed three-point bending tests on six group of 5 mm screws (titanium, stainless steel, crossed with u...

  12. Self-mode-locking semiconductor disk laser.

    Science.gov (United States)

    Gaafar, Mahmoud; Richter, Philipp; Keskin, Hakan; Möller, Christoph; Wichmann, Matthias; Stolz, Wolfgang; Rahimi-Iman, Arash; Koch, Martin

    2014-11-17

    The development of mode-locked semiconductor disk lasers received striking attention in the last 14 years and there is still a vast potential of such pulsed lasers to be explored and exploited. While for more than one decade pulsed operation was strongly linked to the employment of a saturable absorber, self-mode-locking emerged recently as an effective and novel technique in this field - giving prospect to a reduced complexity and improved cost-efficiency of such lasers. In this work, we highlight recent achievements regarding self-mode-locked semiconductor devices. It is worth to note, that although nonlinear effects in the active medium are expected to give rise to self-mode-locking, this has to be investigated with care in future experiments. However, there is a controversy whether results presented with respect to self-mode-locking truly show mode-locking. Such concerns are addressed in this work and we provide a clear evidence of mode-locking in a saturable-absorber-free device. By using a BBO crystal outside the cavity, green light originating from second-harmonic generation using the out-coupled laser beam is demonstrated. In addition, long-time-span pulse trains as well as radiofrequency-spectra measurements are presented for our sub-ps pulses at 500 MHz repetition rate which indicate the stable pulse operation of our device. Furthermore, a long-time-span autocorrelation trace is introduced which clearly shows absence of a pedestal or double pulses. Eventually, a beam-profile measurement reveals the excellent beam quality of our device with an M-square factor of less than 1.1 for both axes, showing that self-mode-locking can be achieved for the fundamental transverse mode.

  13. Phase-locked laser coherent interference

    Institute of Scientific and Technical Information of China (English)

    Jingjing Wang; Xiaobo Wang; Bo He; Liantuan Mao; Suotang Jia

    2011-01-01

    A method of locking the relative phase to provide stable constructive or destructive interference between the phase-modulated sidebands from a pair of phase modulators is demonstrated. It is discussed theoretically for optimal fringe visibility related to the phase noise from faulty system. After phase locking using the phase modulating and lock-in technique, the drift of the relative phase is focalized around ±0.0016 rad and the fringe visibility is restricted to 2×l0-4.%@@ A method of locking the relative phase to provide stable constructive or destructive interference between the phase-modulated sidebands from a pair of phase modulators is demonstrated.It is discussed theoretically for optimal fringe visibility related to the phase noise from faulty system.After phase locking using the vhase modulating and lock-in technique.the drift of the relative phase is focalized around±0.0016 rad and the fringe visibility is restricted to 2×10-4.

  14. Information locking in black holes

    CERN Document Server

    Smolin, J; Smolin, John; Oppenheim, Jonathan

    2005-01-01

    The black hole information loss paradox has plagued physicists since Hawking's discovery that black holes evaporate. The calculation suggests that information thrown into a black hole is evaporated away as thermal radiation, and is destroyed: either the unitary laws of quantum theory break down, or we must modify the laws of general relativity. Here we show that one of the central presumptions of the debate is incorrect. Ensuring that information not escape during the semi-classical evaporation process does not require that all the information remain in the black hole until the final stages of evaporation. By taking into account recent results in quantum information theory, we find that the amount of information that must remain in the black hole until the final stages of evaporation can be very small, even though the amount of information which has already radiated away is negligible. Quantum effects mean that information need not be additive: a small number of quanta can lock a large amount of information, ...

  15. Ocean energy. Tide and tidal power

    Energy Technology Data Exchange (ETDEWEB)

    Finkl, Charles W. [Coastal Planning and Engineering, Inc., Boca Raton, FL (United States); Charlier, Roger H.

    2009-07-01

    Engineers' dreams and fossil energy replacement schemes can come true. Man has been tapping the energy of the sea to provide power for his industries for centuries. Tidal energy combined with that of waves and marine winds rank among those most successfully put the work. Large scale plants are capital intensive but smaller ones, particularly built in China, have proven profitable. Since the initiation of the St Malo project in France, similar projects have gone into active service where methods have been devised to cut down on costs, new types of turbines developed and cost competitiveness considerably improved. Tidal power has enormous potential. The book reviews recent progress in extracting power from the ocean, surveys the history of tidal power harnessing and updates a prior publication by the author. (orig.)

  16. On Tidal Inference in the Diurnal Band

    Science.gov (United States)

    Ray, R. D.

    2017-01-01

    Standard methods of tidal inference should be revised to account for a known resonance that occurs mostly within the K(sub 1) tidal group in the diurnal band. The resonance arises from a free rotational mode of Earth caused by the fluid core. In a set of 110 bottom-pressure tide stations, the amplitude of the P(sub 1) tidal constituent is shown to be suppressed relative to K(sub 1), which is in good agreement with the resonance theory. Standard formulas for the K(sub 1) nodal modulation remain essentially unaffected. Two examples are given of applications of the refined inference methodology: one with monthly tide gauge data and one with satellite altimetry. For some altimeter-constrained tide models, an inferred P(sub 1) constituent is found to be more accurate than a directly determined one.

  17. The wave and tidal resource of Scotland

    Science.gov (United States)

    Neill, Simon; Vogler, Arne; Lewis, Matt; Goward-Brown, Alice

    2017-04-01

    As the marine renewable energy industry evolves, in parallel with an increase in the quantity of available data and improvements in validated numerical simulations, it is occasionally appropriate to re-assess the wave and tidal resource of a region. This is particularly true for Scotland - a leading nation that the international community monitors for developments in the marine renewable energy industry, and which has witnessed much progress in the sector over the last decade. With 7 leased wave and 17 leased tidal sites, Scotland is well poised to generate significant levels of electricity from its abundant natural marine resources. In this review of Scotland's wave and tidal resource, I present the theoretical and technical resource, and provide an overview of commercial progress. I also discuss issues that affect future development of the marine energy seascape in Scotland, applicable to other regions of the world, including the potential for developing lower energy sites, and grid connectivity.

  18. HI Recycling Formation of Tidal Dwarf Galaxies

    CERN Document Server

    Duc, P A; Duc, Pierre-Alain; Brinks, Elias

    2000-01-01

    Galactic collisions trigger a number of phenomena, such as transportation inward of gas from distances of up to kiloparsecs from the center of a galaxy to the nuclear region, fuelling a central starburst or nuclear activity. The inverse process, the ejection of material into the intergalactic medium by tidal forces, is another important aspect and can be studied especially well through detailed HI observations of interacting systems which have shown that a large fraction of the gaseous component of colliding galaxies can be expelled. Part of this tidal debris might fall back, be dispersed throughout the intergalactic medium or recondense to form a new generation of galaxies: the so-called tidal dwarf galaxies. The latter are nearby examples of galaxies in formation. The properties of these recycled objects are reviewed here and different ways to identify them are reviewed.

  19. Double tidal disruptions in galactic nuclei

    CERN Document Server

    Mandel, Ilya

    2015-01-01

    A star on a nearly radial trajectory approaching a massive black hole (MBH) gets tidally disrupted if it comes sufficiently close to the MBH. Here we explore what happens to binary stars whose centers of mass approach the MBH on nearly radial orbits. The interaction with the MBH often leads to both stars being disrupted in sequence. We argue that such events could produce light curves that are substantially different from those of the single disruptions, with possible features such as two local maxima. Tidal forces from the MBH can also lead the binary components to collide; these merger products can form highly magnetized stars, whose subsequent tidal disruption may enable prompt jet formation.

  20. DOUBLE TIDAL DISRUPTIONS IN GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Mandel, Ilya [School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT (United Kingdom); Levin, Yuri, E-mail: imandel@star.sr.bham.ac.uk, E-mail: yuri.levin@monash.edu [Monash Center for Astrophysics and School of Physics, Monash University, Clayton, VIC 3800 (Australia)

    2015-05-20

    A star on a nearly radial trajectory approaching a massive black hole (MBH) gets tidally disrupted if it comes sufficiently close to the MBH. Here we explore what happens to binary stars whose centers of mass approach the MBH on nearly radial orbits. The interaction with the MBH often leads to both stars being disrupted in sequence. We argue that such events could produce light curves that are substantially different from those of the single disruptions, with possible features such as two local maxima. Tidal forces from the MBH can also lead the binary components to collide; these merger products can form highly magnetized stars, whose subsequent tidal disruption may enable prompt jet formation.

  1. Tidal Forces in Naked Singularity Backgrounds

    CERN Document Server

    Goel, Akash; Roy, Pratim; Sarkar, Tapobrata

    2015-01-01

    The end stage of a gravitational collapse process can generically result in a black hole or a naked singularity. Here we undertake a comparative analysis of the nature of tidal forces in these backgrounds. The effect of such forces is generically exemplified by the Roche limit, which predicts the distance within which a celestial object disintegrates due to the tidal effects of a second more massive object. In this paper, using Fermi normal coordinates, we numerically compute the Roche limit for a class of non-rotating naked singularity backgrounds, and compare them with known results for Schwarzschild black holes. Our analysis indicates that there might be substantially large deviations in the magnitudes of tidal forces in naked singularity backgrounds, compared to the black hole cases. If observationally established, these can prove to be an effective indicator of the nature of the singularity at a galactic centre.

  2. Tidal response of Europa's subsurface ocean

    Science.gov (United States)

    Karatekin, Özgür; Comblen, Richard; Toubeau, Jonathan; Deleersnijder, Eric; van Hoolst, Tim; Dehant, Veronique

    2010-05-01

    Observations of Cassini and Galileo spacecrafts suggest the presence of subsurface global water oceans under the icy shells of several satellites of Jupiter and Saturn. Previous studies have shown that in the presence of subsurface oceans, time-variable tides cause large periodic surface displacements and that tidal dissipation in the icy shell becomes a major energy source that can affect long-term orbital evolution. However, in most studies so far, the dynamics of these satellite oceans have been neglected. In the present study, we investigate the tidal response of the subsurface ocean of Europa to a time-varying potential. Two-dimensional nonlinear shallow water equations are solved on a sphere by means of a finite element code. The resulting ocean tidal flow velocities and surface displacements will be presented.

  3. Tidal Response of Preliminary Jupiter Model

    CERN Document Server

    Wahl, Sean M; Militzer, Burkhard

    2016-01-01

    In anticipation of improved observational data for Jupiter's gravitational field from the Juno spacecraft, we predict the static tidal response for a variety of Jupiter interior models based on ab initio computer simulations of hydrogen-helium mixtures. We calculate hydrostatic-equilibrium gravity terms using the non-perturbative concentric Maclaurin Spheroid (CMS) method that eliminates lengthy expansions used in the theory of figures. Our method captures terms arising from the coupled tidal and rotational perturbations, which we find to be important for a rapidly-rotating planet like Jupiter. Our predicted static tidal Love number $k_2 = 0.5900$ is $\\sim$10\\% larger than previous estimates. The value is, as expected, highly correlated with the zonal harmonic coefficient $J_2$, and is thus nearly constant when plausible changes are made to interior structure while holding $J_2$ fixed at the observed value. We note that the predicted static $k_2$ might change due to Jupiter's dynamical response to the Galilea...

  4. The assessment of extactable tidal energy and the effect of tidal energy turbine deployment on the hydrodynamics in Zhoushan

    Institute of Scientific and Technical Information of China (English)

    HOU Fang; BAO Xianwen; LI Benxia; LIU Qianqian

    2015-01-01

    In this study, we construct one 2–dimensional tidal simulation, using an unstructured Finite Volume Coastal Ocean Model (FVCOM). In the 2–D model, we simulated the tidal turbines through adding additional bottom drag in the element where the tidal turbines reside. The additional bottom drag was calculated from the relationship of the bottom friction dissipation and the rated rotor efficiency of the tidal energy turbine. This study analyzed the effect of the tidal energy turbine to the hydrodynamic environment, and calculated the amount of the extractable tidal energy resource at the Guishan Hangmen Channel, considering the rotor wake effect.

  5. Tidal forces in Kiselev black hole

    Energy Technology Data Exchange (ETDEWEB)

    Shahzad, M.U. [University of Central Punjab, CAMS, UCP Business School, Lahore (Pakistan); Jawad, Abdul [COMSATS Institute of Information Technology, Department of Mathematics, Lahore (Pakistan)

    2017-06-15

    The aim of this paper is to examine the tidal forces occurring in a Kiselev black hole surrounded by radiation and dust fluids. It is noted that the radial and angular components of the tidal force change the sign between event and Cauchy horizons. We solve the geodesic deviation equation for radially free-falling bodies toward Kiselev black holes. We explain the geodesic deviation vector graphically and point out the location of the event and Cauchy horizons for specific values of the radiation and dust parameters. (orig.)

  6. CFD for wind and tidal offshore turbines

    CERN Document Server

    Montlaur, Adeline

    2015-01-01

    The book encompasses novel CFD techniques to compute offshore wind and tidal applications. Computational fluid dynamics (CFD) techniques are regarded as the main design tool to explore the new engineering challenges presented by offshore wind and tidal turbines for energy generation. The difficulty and costs of undertaking experimental tests in offshore environments have increased the interest in the field of CFD which is used to design appropriate turbines and blades, understand fluid flow physical phenomena associated with offshore environments, predict power production or characterise offshore environments, amongst other topics.

  7. Cycloidal tidal power generation - Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    This report summarises the findings of a project investigating the economic and technical viability of a cycloidal tidal stream generator and developing a performance prediction model to assess the applicability of cycloidal turbines to power generation. The concept of cycloidal power generation is described along with the use of the model to examine the performance of six designs in the tidal flow off the west coast of Scotland. Details are given of the estimated power generated and cost reductions using optimised designs. Areas to be examined for design optimisation are listed.

  8. Investigation on Tidal Components in GPS Coordinates

    Science.gov (United States)

    Araszkiewicz, Andrzej; Bogusz, Janusz; Figurski, Mariusz

    2009-01-01

    This paper presents analyses on the GPS coordinates from sub-diurnal solutions of EPN data provided by Warsaw Military University of Technology. The aim of this research is to investigate the way the tidal models used in Bernese software (solid Earth and ocean tides as well) fit to the individual conditions of EPN stations. The 1-hour solution technique of GPS data processing was utilized to obtain coordinates of above 70 EPN stations. Additionally several Polish permanent sites with clearly seen oscillations were examined. This processing technique allowed us to recognize diurnal and sub-diurnal residual oscillations which could be next utilized for validation of the tidal models.

  9. Tidal forces in Reissner-Nordstroem spacetimes

    Energy Technology Data Exchange (ETDEWEB)

    Crispino, Luis C.B.; Oliveira, Ednilton S. de [Universidade Federal do Para, Faculdade de Fisica, Belem, Para (Brazil); Higuchi, Atsushi; Oliveira, Leandro A. [University of York, Department of Mathematics, York (United Kingdom)

    2016-03-15

    We analyze the tidal forces produced in the spacetime of Reissner-Nordstroem black holes. We point out that the radial component of the tidal force changes sign just outside the event horizon if the charge-to-mass ratio is close to 1, unlike in Schwarzschild spacetime of uncharged black holes, and that the angular component changes sign between the outer and inner horizons. We solve the geodesic deviation equations for radially falling bodies toward the charged black hole. We find, for example, that the radial component of the geodesic deviation vector starts decreasing inside the event horizon unlike in the Schwarzschild case. (orig.)

  10. Transition from the locked in to the completely locked-in state: A physiological analysis

    NARCIS (Netherlands)

    Murguialday, A.R.; Hill, J.; Bensch, M.; Martens, S.; Halder, S.; Nijboer, Femke; Schoelkopf, B.; Birbaumer, N.; Gharabaghi, A.

    Objective To clarify the physiological and behavioral boundaries between locked-in (LIS) and the completely locked-in state (CLIS) (no voluntary eye movements, no communication possible) through electrophysiological data and to secure brain–computer-interface (BCI) communication. Methods

  11. Adelie penguin foraging location predicted by tidal regime switching.

    Directory of Open Access Journals (Sweden)

    Matthew J Oliver

    Full Text Available Penguin foraging and breeding success depend on broad-scale environmental and local-scale hydrographic features of their habitat. We investigated the effect of local tidal currents on a population of Adélie penguins on Humble Is., Antarctica. We used satellite-tagged penguins, an autonomous underwater vehicle, and historical tidal records to model of penguin foraging locations over ten seasons. The bearing of tidal currents did not oscillate daily, but rather between diurnal and semidiurnal tidal regimes. Adélie penguins foraging locations changed in response to tidal regime switching, and not to daily tidal patterns. The hydrography and foraging patterns of Adélie penguins during these switching tidal regimes suggest that they are responding to changing prey availability, as they are concentrated and dispersed in nearby Palmer Deep by variable tidal forcing on weekly timescales, providing a link between local currents and the ecology of this predator.

  12. Tidal propagation off the central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.

    Present study reviews the characteristics of tidal propagation on the continental shelf off the central west coast of India. Available observations from tide gauges are used to describe the variations of tidal ranges along the west coast. Amplitudes...

  13. NOAA Tidal Current Data for the Coastal United States

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Knowledge of the timing and strength of tidal currents is extremely important for safe navigation in coastal waters. Tidal currents are almost always the strongest...

  14. NOAA Historical Tidal Current Data for the Coastal United States

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Knowledge of the timing and strength of tidal currents is extremely important for safe navigation in coastal waters. Tidal currents are almost always the strongest...

  15. Tidal flow characteristics at Kasheli (Kalwa/ Bassein creek), Bombay

    Digital Repository Service at National Institute of Oceanography (India)

    Swamy, G.N.; Suryanarayana, A.

    Tidal flow characteristics of waters at Kasheli, connected to the sea through Thane and Bassein Creeks in Bombay, Maharashtra, India are investigated based on tide and current observations carried out in 1980-81. The results establish that the tidal...

  16. Don't Cross the (Tidal) Streams

    Science.gov (United States)

    Kohler, Susanna

    2015-09-01

    In a tidal disruption event (TDE), an unfortunate star passes too close to a dormant supermassive black hole (BH) and gets torn apart by tidal forces, feeding the BH for a short time. Oddly, were not finding nearly as many TDEs typically detected due to their distinctive observational signatures as theory says we should. A recent study suggests that we might be missing many of these events, due to the way the streams of shredded stars fall onto the BHs.Signatures of ShreddingWhen a BH tears a star apart, the stars material is stretched out into whats known as a tidal stream. That stream continues on a trajectory around the BH, with roughly half the material eventually falling back on the BH, whipping around it in a series of orbits. Where those orbits intersect each other, the material smashes together and circularizes, forming a disk that then accretes onto the BH.What does a TDE look like? We dont observe anything until after the tidal streams collide and the material begins to accrete onto the BH. At that point we observe a sudden peak in luminosity, which then gradually decreases (scaling roughly as time-5/3) as the tail end of whats left of the star accretes and the BHs food source eventually runs out.So why have we only been observing about a tenth as many TDEs as theory predicts we should see? By studying the structure of tidal streams in TDEs, James Guillochon (Harvard-Smithsonian Center for Astrophysics) and Enrico Ramirez-Ruiz (UC Santa Cruz) have found a potential reason and the culprit is general relativity.Dark YearsThe authors run a series of simulations of TDEs around black holes of varying masses and spins to see what form the resulting tidal streams take over time. They find that precession of the tidal stream due to the BHs gravitational effects changes how the stream interacts with itself, and therefore what we observe. Some cases behave like what we expect for whats currently considered a typical TDE but some dont.Example from simulations of a

  17. Assessment of Soil Quality of Tidal Marshes in Shanghai City

    OpenAIRE

    Wang, Qing; TAN, JUAN; SHA, Chenyan; RUAN, Junjie; Min WANG; HUANG, Shenfa; Wu, Jianqiang

    2013-01-01

    We take three types of tidal marshes in Shanghai City as the study object: tidal marshes in mainland, tidal marshes in the rim of islands, and shoal in Yangtze estuary. On the basis of assessing nutrient quality and environmental quality, respectively, we use soil quality index (SQI) to assess the soil quality of tidal flats, meanwhile formulate the quality grading standards, and analyze the current situation and characteristics of it. The results show that except the north of Hangzhou Bay, N...

  18. Tidal freshwater wetlands, the fresh dimension of the estuary

    NARCIS (Netherlands)

    Barendregt, A.

    2016-01-01

    Upstream in the estuary, where the river ends, the tidal energy is still present but the constant input from the river creates permanent fresh water conditions. The physical, chemical and biological conditions differ from the brackish part of the tidal area, but by processes from the tidal wave also

  19. Ecological consequences of diurnal flooding in tidal freshwater wetlands

    NARCIS (Netherlands)

    Barendregt, A.; Wassen, M.J.

    2010-01-01

    Diurnal flooding can be observed in the upper end of tidal estuaries, where flooding water originating from the river is constantly fresh. Here, the input from the river is confronted with a tidal wave, so that the sand banks, mud flats, low and high marshes and tidal forests are flooded mostly

  20. Subtidal flow division at a shallow tidal junction

    NARCIS (Netherlands)

    Buschman, F.A.; Hoitink, A.J.F.; Vegt, van der M.; Hoekstra, P.

    2010-01-01

    Tides influence distribution of river discharge at tidally affected channel junctions. At the apex of a channel network in an Indonesian delta, observations of flow division suggest that tidally averaged flow division depends on the tidal range. To understand the mechanisms governing the subtidal fl

  1. Development of Tidal areas: some principles and issues towards systainability

    NARCIS (Netherlands)

    Sang Hyun, P.; Simm, J.; Ritzema, H.P.

    2009-01-01

    The coastal zone comprises only 3% of the earth's surface, but contains a disproportionately high amount of its assets. Tidal areas include all those coastal areas where the tidal processes are capable of affecting man's activity or of being influenced by man. Tidal areas differ greatly depending on

  2. Salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

  3. Methane emission from tidal freshwater marshes

    NARCIS (Netherlands)

    Van der Nat, F.J.; Middelburg, J.J.

    2000-01-01

    In two tidal freshwater marshes, methane emission, production and accumulation in the pore-water have been studied. The two sites differ in their dominant vegetation, i.e., reed and bulrush, and in their heights above sea level. The reed site was elevated in relation to the bulrush site and had

  4. Methane emission from tidal freshwater marshes

    NARCIS (Netherlands)

    Van der Nat, F.J.; Middelburg, J.J.

    2000-01-01

    In two tidal freshwater marshes, methane emission, production and accumulation in the pore-water have been studied. The two sites differ in their dominant vegetation, i.e., reed and bulrush, and in their heights above sea level. The reed site was elevated in relation to the bulrush site and had high

  5. 2008 NWFSC Tidal Freshwater Genetics Results

    Energy Technology Data Exchange (ETDEWEB)

    David Teel

    2009-05-01

    Genetic Analysis of Juvenile Chinook Salmon for inclusion in 'Ecology of Juvenile Salmon in Shallow Tidal Freshwater Habitats in the Vicinity of the Sandy River Delta, Lower Columbia River, 2008. Annual Report to Bonneville Power Administration, Contract DE-AC05-76RL01830.'

  6. An optimal tuning strategy for tidal turbines

    Science.gov (United States)

    Vennell, Ross

    2016-11-01

    Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This `impatient-tuning strategy' results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing `patient-tuning strategy' which maximizes the power output averaged over the tidal cycle. This paper presents a `smart patient tuning strategy', which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine's average power output.

  7. Modeling the hydrodynamics in tidal networks

    NARCIS (Netherlands)

    Alebregtse, N.C.

    2016-01-01

    This thesis covers tidal propagation through networks of channels. Such networks are widespread and are often subject to discordant human and natural interests. First, the effect of a secondary channel on the tides in a main channel is explained with the use of an idealized model and the responsible

  8. Tidal evolution of planets around brown dwarfs

    CERN Document Server

    Bolmont, Emeline; Leconte, Jérémy

    2011-01-01

    The tidal evolution of planets orbiting brown dwarfs (BDs) presents an interesting case study because BDs' terrestrial planet forming region is located extremely close-in. In fact, the habitable zones of BDs range from roughly 0.001 to 0.03 AU and for the lowest-mass BDs are located interior to the Roche limit. In contrast with stars, BDs spin up as they age. Thus, the corotation distance moves inward. This has important implications for the tidal evolution of planets around BDs. We used a standard equilibrium tidal model to compute the orbital evolution of a large ensemble of planet-BD systems. We tested the effect of numerous parameters such as the initial semi-major axis and eccentricity, the rotation period of the BD, the masses of both the BD and planet, and the tidal dissipation factors. We find that all planets that form at or beyond the corotation distance and with initial eccentricities smaller than \\sim 0.1 are repelled from the BD. Some planets initially interior to corotation can survive if their ...

  9. On the superradiance-tidal friction correspondence

    CERN Document Server

    Glampedakis, K; Kennefick, D

    2013-01-01

    Since the work of Hartle in the 1970s, and the subsequent development of the the Membrane Paradigm approach to black hole physics it has been widely accepted that superradiant scattering of gravitational waves bears strong similarities with the phenomenon of ``tidal friction'' (well-known from Newtonian gravity) operating in binary systems of viscous material bodies. In this paper we revisit the superradiance-tidal friction analogy within the context of ultracompact relativistic bodies. We advocate that as long as these bodies have non-zero viscosity they should undergo tidal friction that can be construed as a kind of superradiant scattering from the point of view of the dynamics of an orbiting test-body. In addition we consider the presence of anisotropic matter, which is required for at least some ultracompact bodies, if they are to sustain a radius very close to the gravitational radius. We find that the tidal friction/superradiance output is enhanced with increasing anisotropy and that strongly anisotrop...

  10. An optimal tuning strategy for tidal turbines.

    Science.gov (United States)

    Vennell, Ross

    2016-11-01

    Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This 'impatient-tuning strategy' results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing 'patient-tuning strategy' which maximizes the power output averaged over the tidal cycle. This paper presents a 'smart patient tuning strategy', which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine's average power output.

  11. Tidal currents assessment in the Tagus estuary

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca, A. (CEHIDRO, Instituto Superior Tecnico, Av. Rovisco Pais, Lisboa, (PT)); Trigo Teixeira, A. (Department of Civil Engineering and Architecture, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, Lisboa (PT))

    2007-07-01

    The authors present in this paper the results of an initial assessment of the potential of tidal currents to generate energy in the Tagus estuary. The work is divided into three phases. The first phase comprises the setting up and calibration of a detailed finite element model for the estuary starting in the ocean boundary. The model was calibrated and verified using water levels and current velocities for several measuring stations within the estuary. The measuring campaign took place in 1987 and was performed by Instituto Hidrografico of the Portuguese Navy. The records are of good quality and cover a period of spring and neap tides. The model give clear indication about the flow pattern within the estuary showing the places were high current velocities are likely to occur. Calculation of the tidal power on selected locations was made. The second phase consisted on the study of the requirements of tidal turbines in terms of site conditions: mainly the minimum water depth and current velocity required for installation. In addition a review was made to understand the development of tidal turbine technology. Three types of turbines were selected as having potential for the site, which usually are associated with moderate current velocity. The third and final phase was the study of the estuary 'map-use' through the construction of a GIS system that allows the identification of locations of potential conflict.

  12. Unravelling tidal dissipation in gaseous giant planets

    CERN Document Server

    Guenel, Mathieu; Remus, Françoise

    2014-01-01

    Tidal dissipation in planetary interiors is one of the key physical mechanisms that drive the evolution of star-planet and planet-moon systems. New constraints are now obtained both in the Solar and exoplanetary systems. Tidal dissipation in planets is intrinsically related to their internal structure. In particular, fluid and solid layers behave differently under tidal forcing. Therefore, their respective dissipation reservoirs have to be compared. In this letter, we compute separately the contributions of the potential dense rocky/icy core and the convective fluid envelope of gaseous giant planets, as a function of core size and mass. We then compare the associated dissipation reservoirs, by evaluating the frequency-average of the imaginary part of the Love numbers $k^2_2$ in each region. In the case of Jupiter and Saturn-like planets, we show that the viscoelastic dissipation in the core could dominate the turbulent friction acting on tidal inertial waves in the envelope. However, the fluid dissipation wou...

  13. A New Perspective on Job Lock.

    Science.gov (United States)

    Huysse-Gaytandjieva, Anna; Groot, Wim; Pavlova, Milena

    2013-07-01

    This paper analyses the situation when employees fail to adapt to overall job dissatisfaction. By combining the existing knowledge in economics on job lock and in psychology on employees' feeling of being 'stuck' at work, the paper explains why some employees fail to adapt when dissatisfied with their job. Thus, the paper aims to expand our understanding of why some employees are job locked or are 'stuck' at their work even though dissatisfied. Using the British household panel survey, the possibility of falling in a job-lock state is analyzed to outline a set of factors that explain why employees differ in the way they adjust to job dissatisfaction. We divide these factors into socio-demographic features, personality attributes, type of occupation, employment conditions, type of sector, and work-related contextual features. Based on results of probit regression analysis, we provide evidence that all these group of factors can jointly predict the state of job dissatisfaction, the absence of job turnover and job lock (being 'stuck' at job). Moreover, our results suggest that the adaptation to job dissatisfaction could be better understood if personality attributes (such as self-esteem) are included in the analysis. Thus, this study expands our understanding of how and why employees might feel 'stuck' at work and fall in a state of job lock.

  14. 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.

  15. Universal spin-momentum locked optical forces

    Science.gov (United States)

    Kalhor, Farid; Thundat, Thomas; Jacob, Zubin

    2016-02-01

    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 HE11 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.

  16. Thermal Diffusivity and Strength of Tidal Flat Sediments During a Tidal Simulation

    Science.gov (United States)

    2009-01-01

    energetically dynamic regions on earth. Tidal Hats are repositories of terrigenous and biogenous sediments that are shaped by tides, waves and storms and...and energetically dynamic regions on earth. Tidal flats are repositories of terrigenous and biogenous sediments that are shaped by tides, waves and...strength. Finally, sediment bearing capacity and shear strength increased with packing density with the highest shear strength occurring at depth within the

  17. Tidally Induced Bars of Galaxies in Clusters

    Science.gov (United States)

    Łokas, Ewa L.; Ebrová, Ivana; del Pino, Andrés; Sybilska, Agnieszka; Athanassoula, E.; Semczuk, Marcin; Gajda, Grzegorz; Fouquet, Sylvain

    2016-08-01

    Using N-body simulations, we study the formation and evolution of tidally induced bars in disky galaxies in clusters. Our progenitor is a massive, late-type galaxy similar to the Milky Way, composed of an exponential disk and a Navarro-Frenk-White dark matter halo. We place the galaxy on four different orbits in a Virgo-like cluster and evolve it for 10 Gyr. As a reference case, we also evolve the same model in isolation. Tidally induced bars form on all orbits soon after the first pericenter passage and survive until the end of the evolution. They appear earlier, are stronger and longer, and have lower pattern speeds for tighter orbits. Only for the tightest orbit are the properties of the bar controlled by the orientation of the tidal torque from the cluster at pericenter. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All of the bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when the tidal forces are stronger. Using all simulation outputs of galaxies at different evolutionary stages, we construct a toy model of the galaxy population in the cluster and measure the average bar strength and bar fraction as a function of clustercentric radius. Both are found to be mildly decreasing functions of radius. We conclude that tidal forces can trigger bar formation in cluster cores, but not in the outskirts, and thus can cause larger concentrations of barred galaxies toward the cluster center.

  18. Flow paths of water and sediment in a tidal marsh: relations with marsh developmental stage and tidal inundation height

    NARCIS (Netherlands)

    Temmerman, S.; Bouma, T.J.; Govers, G.; Lauwaet, D.

    2005-01-01

    This study provides new insights in the relative role of tidal creeks and the marsh edge in supplying water and sediments to and from tidal marshes for a wide range of tidal inundation cycles with different high water levels and for marsh zones of different developmental stage. Net import or export

  19. All Digital Phase-Locked Loop

    Directory of Open Access Journals (Sweden)

    Marijan Jurgo

    2013-05-01

    Full Text Available The paper reviews working principles of phase-locked loop and drawbacks of classical PLL structure in nanometric technologies. It is proposed to replace the classical structure by all-digital phase-locked loop structure. Authors described the main blocks of all-digital phase-locked loop (time to digital converter and digitally controlled oscillator and overviewed the quantization noise arising in these blocks as well as its minimization strategies. The calculated inverter delay in 65 nm CMOS technology was from 8.64 to 27.71 ps and time to digital converter quantization noise was from −104.33 to −82.17 dBc/Hz, with tres = 8.64–27.71 ps, TSVG = 143–333 ps, FREF = 20–60 MHz.Article in Lithuanian

  20. Using river locks to teach hydrodynamic concepts

    Science.gov (United States)

    Carvalho-Santos, Vagson L.; Mendes, Thales C.; Silva, Enisvaldo C.; Rios, Márcio L.; Silva, Anderson A. P.

    2013-11-01

    In this work, the use of a river lock as a non-formal setting for teaching hydrodynamical concepts is proposed. In particular, we describe the operation of a river lock situated at the Sobradinho dam, on the São Francisco River (Brazil). A model to represent and to analyse the dynamics of river lock operation is presented and we derive the dynamical equations for the rising of the water column as an example to understand the Euler equation. Furthermore, with this activity, we enable the integration of content initially introduced in the classroom with practical applications, thereby allowing the association of physical themes to content relevant in disciplines such as history and geography. In addition, experiences of this kind enable teachers to talk about the environmental and social impacts caused by the construction of a dam and, consequently, a crossover of concepts has been made possible, leading to more meaningful learning for the students.

  1. John Locke and the right to resistance

    Directory of Open Access Journals (Sweden)

    Jovanov Ilija D.

    2015-01-01

    Full Text Available John Locke was a great thinker and many works have been devoted to clear up his theories. One of the most significant, stated in his principal work, Two Treatises of Government, is the theory of the right to resistance. It was a bit revolutionary then, and to a large extent it is today. Domination of legal positivism is negation of that, by Locke, natural right. However, the fact is that in recent times the resistance to the established power occurs in a number of countries and in different forms, so that the idea of the right to resistance becomes live question again. In this regard it is interesting to consider Locke's viewpoint on this important issue and to determine whether his theory on the resistance is applicable in modern societies.

  2. Using river locks to teach hydrodynamic concepts

    CERN Document Server

    Carvalho-Santos, Vagson L; Silva, Enisvaldo C; Rios, Márcio L; Silva, Anderson A P

    2013-01-01

    In this work, the use of a river lock as a non-formal setting for teaching Q2 hydrodynamical concepts is proposed. In particular, we describe the operation of a river lock situated at the Sobradinho dam, on the S\\~ao Francisco River (Brazil). A model to represent and to analyse the dynamics of river lock operation is presented and we derive the dynamical equations for the rising of the water column as an example to understand the Euler equation. Furthermore, with this activity, we enable the integration of content initially introduced in the classroom with practical applications, thereby allowing the association of physical themes to content relevant in disciplines such as history and geography. In addition, experiences of this kind enable teachers to talk about the environmental and social impacts caused by the construction of a dam and, consequently, a crossover of concepts has been made possible, leading to more meaningful learning for the students.

  3. Locking plate osteosynthesis of clavicle fractures

    DEFF Research Database (Denmark)

    Fridberg, Marie; Ban, Ilija; Issa, Zaid

    2013-01-01

    PURPOSE: Locking plate osteosynthesis has become the preferred method for operative treatment of clavicle fractures. The method offers stable fixation, and would theoretically be associated with a low rate of fracture-related complications and reoperations. However, this remains to be explored...... in a large cohort, and our purpose was to assess the overall rates of complications and reoperations following locking plate osteosynthesis of mid-shaft clavicle fractures. METHODS: We identified all locking plate osteosynthesis of mid-shaft clavicle fractures operated upon in our department from January...... 2008 to November 2010 (n = 114). Nine patients did not attend the follow-up at our institution. The study group of 105 fractures (104 patients, 86 males) had a median age of 36 years (14-75 years). Follow-up ranged from 0.5 to 3.5 years. No patients were allowed to load the upper extremity for six...

  4. Traumatic knee extension deficit (the locked knee)

    DEFF Research Database (Denmark)

    Helmark, I C; Neergaard, K; Krogsgaard, M R

    2007-01-01

    In the present study we investigated the validity of magnetic resonance imaging (MRI) and arthroscopy in knees with acute, traumatic extension deficit (the "locked knee"), and evaluated whether arthroscopy of knees with no mechanical pathology could be avoided by MRI evaluation. The study consisted...... of 50 patients who had an acute, traumatic extension deficit of the knee. All patients were submitted to MRI prior to arthroscopy. Following MRI and surgery, standardized forms were filled out, attempting to objectify the findings. The orthopaedic surgeon was not aware of the MRI result prior to surgery......, the following results were calculated for the overall appearance of a lesion able to cause locking: Positive predictive value = 0.85, negative predictive value = 0.77, sensitivity = 0.95, specificity = 0.53. Two knees were erroneously evaluated with no mechanical locking at MRI (one bucket-handle lesion and one...

  5. A multi-band fast-locking delay-locked loop with jitter-bounded feature.

    Science.gov (United States)

    Kuo, Chien-Hung; Lai, Hung-Jing; Lin, Meng-Feng

    2011-01-01

    In this paper, a fast-locking delay-locked loop (DLL) with jitter-bounded feature is presented. In the proposed fast-locking mechanism, a frequency estimator and a programmable voltage circuit are developed to rapidly switch the control node of voltage-controlled delay line to a voltage level near the final required value. After that, the DLL output will be quickly locked by the following charge pumping on the loop filter. In the jitter-bounded approach, two phase-frequency detectors and a tunable delay are employed to hold the output clock jitter between two reference inputs after the DLL is locked. Furthermore, to enhance the flexibility of the presented DLL, a frequency multiplier with fewer active devices is also developed to provide high-frequency clock output for wideband applications. The presented DLL is implemented in a 0.18-μm 1P6M CMOS technology. The active area without contact pads is 0.34 × 0.41 mm(2). A minimum lock time of six clock cycles is measured from no reference input to locked state. The output frequency ranges of the DLL and the frequency multiplier can be measured from 200 to 400 MHz and from 1 to 2 GHz, respectively. The power dissipation of the presented DLL is 31.5 mW at a 1.8 V supply voltage.

  6. Tidal modulation of two-layer hydraulic exchange flows

    Directory of Open Access Journals (Sweden)

    L. M. Frankcombe

    2006-11-01

    Full Text Available Time-dependent, two layer hydraulic exchange flow is studied using an idealised shallow water model. It is found that barotropic time-dependent perturbations, representing tidal forcing, increase the baroclinic exchange flux above the steady hydraulic limit, with flux increasing monotonically with tidal amplitude (measured either by height or flux amplitude over a tidal period. Exchange flux also depends on the non-dimensional tidal period, γ, which was introduced by Helfrich (1995. Resonance complicates the relationship between exchange flux and height amplitude, but, when tidal strength is characterised by flux amplitude, exchange flux is a monotonic function of γ.

  7. Locke y la adulación

    Directory of Open Access Journals (Sweden)

    Tomás Chuaqui H.

    2004-01-01

    Full Text Available En este artículo se verifica la relevancia de un vicio político específico, la adulación, en las ideas de John Locke. Se muestra que para Locke la adulación proviene de agentes ilustrados que incitan a los aspirantes al poder recurriendo al orgullo que típicamente los caracteriza. Este vicio político, por ende, hace peligrar a los regímenes de poderes limitados y desconcentrados, ya que induce, a través del cultivo del orgullo, un deseo desmedido por el poder y el dominio sobre otros. Así, se precisa la importancia de la capacidad ciudadana para contener las pasiones y los vicios, propia además de la filosofía moral y de la educación de Locke, con vistas a la construcción y el mantenimiento de un régimen limitado, basado en el consentimiento, y protector de la vida libre.This article verifies the relevance of a specific political vice, namely, flattery, in John Locke's political thought. It is shown that for Locke flattery originates in learned agents whom incite aspirants to political power, appealing to the pride that typically characterizes them. This political vice, therefore, endangers the survival of political regimes of limited and decentralized powers since it incites, by catering to pride, an unchecked desire for power and domination over others. In this way, the importance of citizens' capacity to contain passions and vices, which pertains besides to Locke's moral and educational philosophies, is clarified in view of the construction and maintenance of a limited regime, based on the consent of the governed, and protective of freedom.

  8. Dynamical Tide in Action: Tidally Excited Oscillations in Kepler Heartbeat Stars

    Science.gov (United States)

    Guo, Zhao; Gies, Douglas R.; Shporer, Avi; Fuller, Jim; Isaacson, Howard T.; Kepler Eclipsing Binary Working Group

    2017-01-01

    We perform a global variability study of heartbeat stars, a class of eccentric binaries whose light curves resemble a cardiogram. The equilibrium tide is modeled by the light curve synthesis code ELC, taking advantage of the information of many possible stellar pairings from a MESA isochrone.We examine the power spectra of light curve residuals closely, searching for signatures of rotation and oscillations. Special attention is given to systems that show tidally excited oscillations/pulsations. Pulsation phases (w.r.t periastron passage) are extracted to identify the azimuthal number m, the degree of detuning (i.e., the difference between the driving frequency and the intrinsic eigenfrequency of stars), and the possibility of resonance-locking. To study non-linear mode coupling, we also search for tidally excited non-orbital-harmonic frequencies.For four particular double-lined systems with Keck HIRES spectra, we derive the orbital and fundamental parameters which can lead to further detailed asteroseismic modeling.

  9. 60-GHz CMOS phase-locked loops

    CERN Document Server

    Cheema, Hammad M; van Roermund, Arthur HM

    2010-01-01

    The promising high data rate wireless applications at millimeter wave frequencies in general and 60 GHz in particular have gained much attention in recent years. However, challenges related to circuit, layout and measurements during mm-wave CMOS IC design have to be overcome before they can become viable for mass market. ""60-GHz CMOS Phase-Locked Loops"" focusing on phase-locked loops for 60 GHz wireless transceivers elaborates these challenges and proposes solutions for them. The system level design to circuit level implementation of the complete PLL, along with separate implementations of i

  10. Frequency acquisition techniques for phase locked loop

    CERN Document Server

    Talbot, Daniel

    2012-01-01

    Many good phaselocked loops (PLL) books exist. However, how to acquire the input frequency from an unlocked state is rarely covered. This book explores the methods for achieving this locked state for a variety of conditions. Using a minimum of mathematics, it introduces engineers to performance limitations of phase/frequency detector based PLL, the quadricorrelator method for both continuous and sampled mode, sawtooth ramp-and-sample phase detector, self-sweeping self-extinguishing topology, and sweep methods using quadrature mixer based lock detection. Digital implementations versus analog are also considered.

  11. Implementation of Digital Lock-in Amplifier

    Science.gov (United States)

    Bhattacharyya, Sabyasachi; Nasir Ahmed, Ragib; Bijoy Purkayastha, Basab; Bhattacharyya, Kaustubh

    2016-10-01

    The recovery of signal under the presence of noise is utmost essential for proper communication. The signals corrupted due to noise can be recovered using various techniques. However the weak signals are more prone to noise and hence they can be easily degraded due to noise. In such cases, a digital lock-in amplifier becomes an essential device for recovery of such weak signals. Keeping the cost, speed and other considerations, we will present the implementation of digital lock-in amplifier and how it recovers the weak signal under extreme noisy conditions.

  12. Progress as Compositional Lock-Freedom

    DEFF Research Database (Denmark)

    Carbone, Marco; Dardha, Ornela; Montesi, Fabrizio

    2014-01-01

    such definition to capture a more intuitive notion of context adequacy for checking progress. Interestingly, our new catalysers lead to a novel characterisation of progress in terms of the standard notion of lock-freedom. Guided by this discovery, we also develop a conservative extension of catalysers that does...... not depend on types, generalising the notion of progress to untyped session-based processes. We combine our results with existing techniques for lock-freedom, obtaining a new methodology for proving progress. Our methodology captures new processes wrt previous progress analysis based on session types....

  13. Optimal database locks for efficient integrity checking

    DEFF Research Database (Denmark)

    Martinenghi, Davide

    2004-01-01

    In concurrent database systems, correctness of update transactions refers to the equivalent effects of the execution schedule and some serial schedule over the same set of transactions. Integrity constraints add further semantic requirements to the correctness of the database states reached upon...... the execution of update transactions. Several methods for efficient integrity checking and enforcing exist. We show in this paper how to apply one such method to automatically extend update transactions with locks and simplified consistency tests on the locked entities. All schedules produced in this way...

  14. Drag and Torque on Locked Screw Propeller

    Directory of Open Access Journals (Sweden)

    Tomasz Tabaczek

    2014-09-01

    Full Text Available Few data on drag and torque on locked propeller towed in water are available in literature. Those data refer to propellers of specific geometry (number of blades, blade area, pitch and skew of blades. The estimation of drag and torque of an arbitrary propeller considered in analysis of ship resistance or propulsion is laborious. The authors collected and reviewed test data available in the literature. Based on collected data there were developed the empirical formulae for estimation of hydrodynamic drag and torque acting on locked screw propeller. Supplementary CFD computations were carried out in order to prove the applicability of the formulae to modern moderately skewed screw propellers.

  15. Locke y la adulación

    OpenAIRE

    Tomás Chuaqui H.

    2004-01-01

    En este artículo se verifica la relevancia de un vicio político específico, la adulación, en las ideas de John Locke. Se muestra que para Locke la adulación proviene de agentes ilustrados que incitan a los aspirantes al poder recurriendo al orgullo que típicamente los caracteriza. Este vicio político, por ende, hace peligrar a los regímenes de poderes limitados y desconcentrados, ya que induce, a través del cultivo del orgullo, un deseo desmedido por el poder y el dominio sobre otros. Así, se...

  16. Locke and the education of the adolescent

    Directory of Open Access Journals (Sweden)

    Francisco T. Baciero Ruiz

    2008-12-01

    Full Text Available John Locke has been considered one of the leading figures in the His- tory of Philosophy, specially for his two famous treatises An Essay concerning Human understanding and Two Treatises on Government. None the less his work in Pedagogy, Some thougths concerning Education, is no less important, and provides the leading strings of that what ought to be the education of the gentleman, whose unavoidable foundation must be a solid education in virtue grounded in the moral principles of Christianity. Key words: Locke, Moral education, Spanish authors of the XVIth century. 

  17. Shear Stress, Turbulence Production and Dissipation in Small Tidal Channels Intersecting a Tidal Flat

    Science.gov (United States)

    Pieterse, A.; Puleo, J. A.; McKenna, T. E.

    2014-12-01

    A 16-day field experiment was conducted in March and April 2013 in a tidal wetland in Kent County, Delaware. The study area was a tidal flat fed by a second-order channel that flows into the Brockonbridge Gut, a small tributary of Delaware Bay. The goal of the field study was to investigate spatio-temporal variability in the hydrodynamics of the tidal flat and the small channels that intersect it, over the period of one spring-neap tidal cycle. The experiment combined remotely-sensed imagery with high-frequency in-situ measurements. A tower with imagers (RGB, NIR, TIR) was deployed to quantify the spatial variations of inundation of the channels, flat and marsh. In-situ sensors that measure flow velocity, sediment concentration and water depth were deployed at six locations on the tidal flat and in the channels. At three locations, a Nortek Vectrino II - profiling velocimeter was deployed that measures a 30 mm velocity profile at 1 mm vertical increments at 100 Hz. These velocity profiles are used to compute turbulent kinetic energy, turbulence dissipation and stress profiles close to the bed. Results show that peak velocities in the channels occur at the beginning and end of ebbing tide, when the water level is below the tidal flat level. At these instances, peaks in turbulence and bed stress also occur. The flow velocity and turbulence peaks are smaller when the water level does not fall below the tidal flat level. On the tidal flat, the flow velocities and turbulence are generally small compared to the intersecting tidal channel. Maximum flow velocities in the channels are around 0.4 m/s, while on the flat maximum velocities are under 0.1 m/s. A comparison is made between turbulence production and dissipation in both the channel and on the tidal flat to determine if advection and diffusion are important in this environment. In addition, the hydrodynamics at several locations in the channel are compared to investigate changes throughout the study area.

  18. Vector solitons with locked and precessing states of polarization

    OpenAIRE

    Sergeyev, Sergey; Mou, Chengbo; Rozhin, Alex; Turitsyn, Sergei

    2012-01-01

    We demonstrate experimentally new families of vector solitons with locked and precessing states of polarization for fundamental and multipulse soliton operations in a carbon nanotube mode-locked fiber laser with anomalous dispersion laser cavity.

  19. 14 CFR 27.679 - Control system locks.

    Science.gov (United States)

    2010-01-01

    ... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Control Systems § 27.679 Control system locks. If there is a device to lock the control system with the rotorcraft on the ground or water,...

  20. "Thoughts Concerning Education": John Locke On Teaching Speech

    Science.gov (United States)

    Baird, John E.

    1971-01-01

    Locke's suggestions for more effective speech instruction have gone largely unnoticed. Consequently, it is the purpose of this article to consider John Locke's criticisms, theory and specific methods of speech education. (Author)

  1. "Thoughts Concerning Education": John Locke On Teaching Speech

    Science.gov (United States)

    Baird, John E.

    1971-01-01

    Locke's suggestions for more effective speech instruction have gone largely unnoticed. Consequently, it is the purpose of this article to consider John Locke's criticisms, theory and specific methods of speech education. (Author)

  2. Phase locking of lasers with intracavity polarization elements.

    Science.gov (United States)

    Ronen, E; Fridman, M; Nixon, M; Friesem, A A; Davidson, N

    2008-10-15

    New configurations for phase locking several laser beams with intracavity polarization elements are presented. With this configuration we demonstrated efficient phase lock of up to 24 ND:YAG laser beams with only two polarization beam displacers.

  3. Robust tilt and lock mechanism for hopping actuator

    Energy Technology Data Exchange (ETDEWEB)

    Salton, Jonathan R.; Buerger, Stephen; Dullea, Kevin J.; Marron, Lisa C.; Salisbury, Curt Michael; Spletzer, Barry Louis

    2017-02-07

    A tilt and lock apparatus that includes a tilt servomechanism, a spiral torsion spring, a lock wheel, and a lock hook is described herein. The spiral torsion spring is mechanically coupled to the tilt servomechanism and the lock wheel (which includes an opening). When a shaft is positioned through the opening, rotation of the lock wheel is in unison with rotation of the shaft. An external surface of the lock wheel includes one or more grooves. The lock hook includes a head that engages and disengages the grooves. The lock wheel is stationary when the head engages one of the grooves and is rotatable when the head disengages the grooves. The head and the grooves are geometrically aligned when engaged to prevent creation of a force that acts to disengage the head responsive to an applied force acting on the shaft.

  4. Interaction between the tidal and seasonal variability of the Gulf of Maine and Scotian Shelf region

    Science.gov (United States)

    Katavouta, Anna; Thompson, Keith; Lu, Youyu; Loder, John

    2017-04-01

    In the Gulf of Maine and Scotian Shelf (off the northeastern coast of North America) tides are large and can alter the local hydrographic properties, circulation, and sea surface height through processes such as tidal rectification, mixing, and horizontal advection. Furthermore, the stratification of the water column can influence tidal elevation and currents over the shelves (e.g., baroclinic tides). To investigate this interaction, a newly developed high resolution (1/36 degree) regional circulation model is used (GoMSS model). First, numerical experiments with and without density stratification are used to demonstrate the influence of stratification on the tides. GoMSS model is then used to interpret the physical mechanisms responsible for the largest seasonal variations in the M2 surface current which occur over, and to the north of, Georges Bank. An alternating pattern of highs and lows in the summer maximum M2 surface speed in the Gulf of Maine is identified, for the first time, in both the model output and observations by a high frequency coastal radar system. This pattern consists of extended striations in tidal speed aligned with the northern flank of Georges Bank that separates the Gulf of Maine from the North Atlantic. The striations are explained in terms of a linear superposition of the barotropic tide flowing across the northern flank of Georges Bank and the reflected, phase-locked baroclinic tide. The striations have amplitudes of about 0.1 m/s and longitudinal length scales of order 100 km, and are thus of practical significance.

  5. Can one passively phase lock 25 fiber lasers?

    CERN Document Server

    Fridman, Moti; Davidson, Nir; Friesem, Asher A

    2010-01-01

    Yes, it is possible to phase lock 25 fiber lasers but only for a short time. Our experiments on passively phase locking two-dimensional arrays of coupled fiber lasers reveal that the average phase locking level of 25 lasers is low ($20%-30%$) but can exceed 90% on rare instantaneous events. The average phase locking level was found to decrease for larger number of lasers in the array and increase with the connectivity of the array.

  6. Tidal and Magnetic Interactions between a Hot Jupiter and its Host Star in the Magnetospheric Cavity of a Protoplanetary Disk

    CERN Document Server

    Chang, Shih-Hsin; Bodenheimer, Peter

    2009-01-01

    We present a simplified model to study the orbital evolution of a young hot Jupiter inside the magnetospheric cavity of a proto-planetary disk. The model takes into account the disk locking of stellar spin as well as the tidal and magnetic interactions between the star and the planet. We focus on the orbital evolution starting from the orbit in the 2:1 resonance with the inner edge of the disk, followed by the inward and then outward orbital migration driven by the tidal and magnetic torques as well as the Roche-lobe overflow of the tidally inflated planet. The goal in this paper is to study how the orbital evolution inside the magnetospheric cavity depends on the cavity size, planet mass, and orbital eccentricity. In the present work, we only target the mass range from 0.7 to 2 Jupiter masses. In the case of the large cavity corresponding to the rotational period ~ 7 days, the planet of mass >1 Jupiter mass with moderate initial eccentricities (>~ 0.3) can move to the region < 0.03 AU from its central sta...

  7. 14 CFR 23.679 - Control system locks.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Control system locks. 23.679 Section 23.679... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Design and Construction Control Systems § 23.679 Control system locks. If there is a device to lock the control system on the ground...

  8. Locke on Education and the Rights of Parents

    Science.gov (United States)

    Tuckness, Alex

    2010-01-01

    John Locke is often taken to be a staunch defender of parents' rights in the realm of education. In fact, Locke's pedagogical reasons for preferring home education to school education do not necessarily apply to similar choices in modern contexts. Locke's political argument for defining education as a duty of parents rather than the state does not…

  9. Locke on Education and the Rights of Parents

    Science.gov (United States)

    Tuckness, Alex

    2010-01-01

    John Locke is often taken to be a staunch defender of parents' rights in the realm of education. In fact, Locke's pedagogical reasons for preferring home education to school education do not necessarily apply to similar choices in modern contexts. Locke's political argument for defining education as a duty of parents rather than the state does not…

  10. 49 CFR 236.302 - Track circuits and route locking.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Track circuits and route locking. 236.302 Section 236.302 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... Standards § 236.302 Track circuits and route locking. Track circuits and route locking shall be provided...

  11. 30 CFR 56.12068 - Locking transformer enclosures.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Locking transformer enclosures. 56.12068 Section 56.12068 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... § 56.12068 Locking transformer enclosures. Transformer enclosures shall be kept locked...

  12. Magnetic field evolution in tidal disruption events

    CERN Document Server

    Bonnerot, Clément; Lodato, Giuseppe; Rossi, Elena M

    2016-01-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to be transmitted to the debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of $\\sim 10$. However, this valu...

  13. Tidal heating in close binary stellar systems

    Energy Technology Data Exchange (ETDEWEB)

    Rieutord, M.; Bonazzola, S.

    1987-07-15

    Tidal heating of a low-mass star in a close binary system, resulting from the conjugate effect of angular momentum loss and tidal action, is investigated via detailed study of the flow inside the secondary. It is found in the case of cataclysmic binaries that viscous dissipation is at most 10/sup -3/ x the nuclear luminosity of the star. It is shown, however, that the dissipation is very sensitive to the turbulent viscosity in the envelope of the secondary. The case of very close pairs of white dwarfs is also considered. It is shown that such pairs, which are thought to be the progenitors of Type I Supernovae may dissipate a power as large as 10/sup 38/ erg s/sup -1/, provided that they reach synchronization; such a heating will strongly modify the conditions in which the nuclear explosion starts.

  14. Power Generation for River and Tidal Generators

    Energy Technology Data Exchange (ETDEWEB)

    Muljadi, Eduard [National Renewable Energy Lab. (NREL), Golden, CO (United States); Wright, Alan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gevorgian, Vahan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Donegan, James [Ocean Renewable Power Company (ORPC), Portland, ME (United States); Marnagh, Cian [Ocean Renewable Power Company (ORPC), Portland, ME (United States); McEntee, Jarlath [Ocean Renewable Power Company (ORPC), Portland, ME (United States)

    2016-06-01

    Renewable energy sources are the second largest contributor to global electricity production, after fossil fuels. The integration of renewable energy continued to grow in 2014 against a backdrop of increasing global energy consumption and a dramatic decline in oil prices during the second half of the year. As renewable generation has become less expensive during recent decades, and it becomes more accepted by the global population, the focus on renewable generation has expanded from primarily wind and solar to include new types with promising future applications, such as hydropower generation, including river and tidal generation. Today, hydropower is considered one of the most important renewable energy sources. In river and tidal generation, the input resource flow is slower but also steadier than it is in wind or solar generation, yet the level of water turbulent flow may vary from one place to another. This report focuses on hydrokinetic power conversion.

  15. Tidal deformability of dark matter clumps

    CERN Document Server

    Mendes, Raissa F P

    2016-01-01

    We analyze the tidal deformability of a clump of dark matter particles, modelled by the collisionless Boltzmann equation. We adopt a wave-mechanical approach to the problem, in which the dynamical equations are approximated by a set of Schr\\"{o}dinger-Poisson equations, within the limit that the effective de Broglie wavelength is comparable to the spatial variation scale of the particle distribution. We argue that such a treatment allows for a smaller number of coupled differential equations and more accessible perturbative analyses, while keeping the description within the dynamical timescale relatively accurate. Moreover, it provides an approximate mapping between perturbed boson star configurations and dynamical dark matter clumps. We present an analysis of the tidal deformability of a minimally-coupled boson star to illustrate this (approximate) correspondence.

  16. Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay

    Directory of Open Access Journals (Sweden)

    Nasir Qassim

    2005-01-01

    Full Text Available The input frequency limit of the conventional zero-crossing digital phase-locked loop (ZCDPLL is due to the operating time of the digital circuitry inside the feedback loop. A solution that has been previously suggested is the introduction of a time delay in the feedback path of the loop to allow the digital circuits to complete their sample processing before the next sample is received. However, this added delay will limit the stable operation range and hence lock range of the loop. The objective of this work is to extend the lock range of ZCDPLL with time delay by using a chaos control. The tendency of the loop to diverge is measured and fed back as a form of linear stabilization. The lock range extension has been confirmed through the use of a bifurcation diagram, and Lyapunov exponent.

  17. Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay

    Directory of Open Access Journals (Sweden)

    Nasir Qassim

    2005-01-01

    Full Text Available The input frequency limit of the conventional zero-crossing digital phase-locked loop (ZCDPLL is due to the operating time of the digital circuitry inside the feedback loop. A solution that has been previously suggested is the introduction of a time delay in the feedback path of the loop to allow the digital circuits to complete their sample processing before the next sample is received. However, this added delay will limit the stable operation range and hence lock range of the loop. The objective of this work is to extend the lock range of ZCDPLL with time delay by using a chaos control. The tendency of the loop to diverge is measured and fed back as a form of linear stabilization. The lock range extension has been confirmed through the use of a bifurcation diagram, and Lyapunov exponent.

  18. Integration of mode-locked diode lasers

    Science.gov (United States)

    Coleman, A. Catrina; Hou, Lianping; Marsh, John H.

    2016-03-01

    Monolithic mode-locked semiconductor lasers are attractive sources of short optical pulses with advantages over more conventional sources in compactness, robustness, performance stability, power consumption, and cost savings. The use of quantum well intermixing (QWI) to integrate passive sections and surface etched distributed Bragg reflectors (DBR) into monolithic laser cavity will be described. The performance of the devices will be presented.

  19. Locking plate fixation for proximal humerus fractures.

    LENUS (Irish Health Repository)

    Burke, Neil G

    2012-02-01

    Locking plates are increasingly used to surgically treat proximal humerus fractures. Knowledge of the bone quality of the proximal humerus is important. Studies have shown the medial and dorsal aspects of the proximal humeral head to have the highest bone strength, and this should be exploited by fixation techniques, particularly in elderly patients with osteoporosis. The goals of surgery for proximal humeral fractures should involve minimal soft tissue dissection and achieve anatomic reduction of the head complex with sufficient stability to allow for early shoulder mobilization. This article reviews various treatment options, in particular locking plate fixation. Locking plate fixation is associated with a high complication rate, such as avascular necrosis (7.9%), screw cutout (11.6%), and revision surgery (13.7%). These complications are frequently due to the varus deformation of the humeral head. Strategic screw placement in the humeral head would minimize the possibility of loss of fracture reduction and potential hardware complications. Locking plate fixation is a good surgical option for the management of proximal humerus fractures. Complications can be avoided by using better bone stock and by careful screw placement in the humeral head.

  20. Soliton mode-locking in optical microresonators

    CERN Document Server

    Herr, T; Gorodetsky, M L; Kippenberg, T J

    2012-01-01

    The discovery of mode-locking via saturable absorbers has led to optical femto-second pulses with applications ranging from eye-surgery to the analysis of chemical reactions on ultra-short timescales. In the frequency domain a train of such optical pulses corresponds to a frequency comb (equidistant optical laser lines spaced by the pulse repetition rate), which find use in precision spectroscopy and optical frequency metrology. Not relying on mode-locking, frequency combs can also be generated in continuously driven high-Q Kerr-nonlinear optical microresonators via cascaded four-wave mixing. Over the past years these Kerr-combs have been demonstrated in a variety of microresonator geometries. Applying a pulse-shaping mode locking mechanism, could enable compact femto-second pulse generators. However, conventional saturable absorbers are challenging to apply to microresonators, as they affect the high-quality-factor. Here, we report on passive mode-locking in microresonators without saturable absorber. This m...

  1. School Choice Litigation after "Zelman" and "Locke"

    Science.gov (United States)

    Liekweg, John A.

    2004-01-01

    In the past 2 years, the United States Supreme Court has decided two important cases that will bear directly on legislation and litigation involving school choice programs that provide financial aid to parents of children attending religious schools. Those cases are "Zelman v. Simmons-Harris" (2002) and "Locke v. Davey" (2004). The reasoning in…

  2. El derecho de propiedad en John Locke

    Directory of Open Access Journals (Sweden)

    Jorge Luis Toyama Miyagusuku

    1998-12-01

    Full Text Available El tema que abordaremos en esta monografía se contrae en determinar los principales aspectos de la teoría sobre el derecho de propiedad del inglés John Locke (Wrington, 1632-1704, en su obra«Segundo Ensayo sobre el GobiernoCivil».John

  3. Phase locked loops design, simulation, and applications

    CERN Document Server

    Best, Roland E

    2007-01-01

    The Definitive Introduction to Phase-Locked Loops, Complete with Software for Designing Wireless Circuits! The Sixth Edition of Roland Best's classic Phase-Locked Loops has been updated to equip you with today's definitive introduction to PLL design, complete with powerful PLL design and simulation software written by the author. Filled with all the latest PLL advances, this celebrated sourcebook now includes new chapters on frequency synthesis…CAD for PLLs…mixed-signal PLLs…all-digital PLLs…and software PLLs_plus a new collection of sample communications applications. An essential tool for achieving cutting-edge PLL design, the Sixth Edition of Phase-Locked Loops features: A wealth of easy-to-use methods for designing phase-locked loops Over 200 detailed illustrations New to this edition: new chapters on frequency synthesis, including fractional-N PLL frequency synthesizers using sigma-delta modulators; CAD for PLLs, mixed-signal PLLs, all-digital PLLs, and software PLLs; new PLL communications ap...

  4. Locks & keys service moves to building 55

    CERN Document Server

    2012-01-01

    Please note that as of July 12 Locks & keys service will be at building 55 second floor. The opening hours are as follows: 08:30 am to 12:30 pm - 1:30 pm to 5:30 pm. The procedures and rules relating to applications for key and cylinder have not changed. GI-IS Group

  5. 49 CFR 236.742 - Dog, locking.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Dog, locking. 236.742 Section 236.742 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.742...

  6. Lock-free parallel garbage collection

    NARCIS (Netherlands)

    Gao, H.; Groote, J.F.; Hesselink, W.H.; Pan, Y; Chen, D; Guo, M; Cao, JN; Dongarra, J

    2005-01-01

    This paper presents a lock-free parallel algorithm for garbage collection in a realistic model using synchronization primitives offered by machine architectures. Mutators and collectors can simultaneously operate on the data structure. In particular no strict alternation between usage and cleaning

  7. "Locke, penseur subversif dans les manuscrits clandestins"

    DEFF Research Database (Denmark)

    Schøsler, Jørn

    2007-01-01

    Der gives en analyse af John Lockes subversive indflydelse på den franske Oplysning via de hemmeligt cirkulerende manuskripter fra århundredets begyndelse med kredsen omkring grev Boulainvillers ("Coterie Boulainviller") til århundredets slutning med kredsen omkring baron d'Holbach og Naigeon....

  8. El derecho de propiedad en John Locke

    OpenAIRE

    1998-01-01

    El tema que abordaremos en esta monografía se contrae en determinar los principales aspectos de la teoría sobre el derecho de propiedad del inglés John Locke (Wrington, 1632-1704), en su obra«Segundo Ensayo sobre el GobiernoCivil».John

  9. "Locke, penseur subversif dans les manuscrits clandestins"

    DEFF Research Database (Denmark)

    Schøsler, Jørn

    2007-01-01

    Der gives en analyse af John Lockes subversive indflydelse på den franske Oplysning via de hemmeligt cirkulerende manuskripter fra århundredets begyndelse med kredsen omkring grev Boulainvillers ("Coterie Boulainviller") til århundredets slutning med kredsen omkring baron d'Holbach og Naigeon....

  10. Investigation of Tidal Power, Cobscook Bay, Maine.

    Science.gov (United States)

    1980-08-01

    240 megawatt project on the Rance River in France and a 400 kilowatt station on the Kislaya Guba Gulf in the Soviet Union. Recently, studies have taken...Tidal Power Project, Maine" October 1979. 44. Ploch, Lousi A. and Nelson L. LeRoy, "Social and Economic Consequen- ces of the Dickey- Lincoln School...Regional Planning Commission," Machias, Maine, 1977. 47. U.S. Department of Energy, Southeast Power Administration, Dickey- Lincoln School Project

  11. Tidal Heating in Multilayered Terrestrial Exoplanets

    Science.gov (United States)

    Henning, Wade G.; Hurford, Terry

    2014-01-01

    The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R(sub E) is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

  12. DIRECTLY IMAGING TIDALLY POWERED MIGRATING JUPITERS

    Energy Technology Data Exchange (ETDEWEB)

    Dong Subo; Katz, Boaz; Socrates, Aristotle [Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2013-01-10

    Upcoming direct-imaging experiments may detect a new class of long-period, highly luminous, tidally powered extrasolar gas giants. Even though they are hosted by {approx} Gyr-'old' main-sequence stars, they can be as 'hot' as young Jupiters at {approx}100 Myr, the prime targets of direct-imaging surveys. They are on years-long orbits and presently migrating to 'feed' the 'hot Jupiters'. They are expected from 'high-e' migration mechanisms, in which Jupiters are excited to highly eccentric orbits and then shrink semimajor axis by a factor of {approx}10-100 due to tidal dissipation at close periastron passages. The dissipated orbital energy is converted to heat, and if it is deposited deep enough into the atmosphere, the planet likely radiates steadily at luminosity L {approx} 100-1000 L{sub Jup}(2 Multiplication-Sign 10{sup -7}-2 Multiplication-Sign 10{sup -6} L{sub Sun }) during a typical {approx} Gyr migration timescale. Their large orbital separations and expected high planet-to-star flux ratios in IR make them potentially accessible to high-contrast imaging instruments on 10 m class telescopes. {approx}10 such planets are expected to exist around FGK dwarfs within {approx}50 pc. Long-period radial velocity planets are viable candidates, and the highly eccentric planet HD 20782b at maximum angular separation {approx}0.''08 is a promising candidate. Directly imaging these tidally powered Jupiters would enable a direct test of high-e migration mechanisms. Once detected, the luminosity would provide a direct measurement of the migration rate, and together with mass (and possibly radius) estimate, they would serve as a laboratory to study planetary spectral formation and tidal physics.

  13. Interactions Between Wetlands and Tidal Inlets

    Science.gov (United States)

    2008-08-01

    Madre, TX), (3) fjord-type (e.g., Penobscot Bay , ME), and (4) tectonically created estuaries (e.g., San Francisco Bay , CA) (Pritchard 1967). This CHETN...small marsh island in San Francisco Bay , CA. Wolaver et al. (1988) measured suspended sediment flux of 827 g/m2/year into a marsh in North Inlet, SC...permanent or ephemeral inlets. Conversely, the development or construction of wetlands within an estuary reduces bay area and the tidal prism, which will

  14. Adventures of a tidally induced bar

    CERN Document Server

    Lokas, E L; Debattista, V P; Valluri, M; del Pino, A; Semczuk, M; Gajda, G; Kowalczyk, K

    2014-01-01

    Using N-body simulations, we study the properties of a bar induced in a dwarf galaxy as a result of tidal interaction with the Milky Way. The dwarf is initially composed of a disk embedded in a dark matter halo and we follow its evolution on a typical orbit for 10 Gyr. It undergoes an evolution typical of tidally stirred dwarf galaxies: it loses mass, the stellar component transforms from a disk to a spheroid and the rotation of the stars is partially replaced by random motions. A tidally induced bar forms at the first pericentre passage and survives until the end of the evolution. Fourier decomposition of the distribution of stars reveals that only even modes are significant and preserve a hierarchy so that the bar mode is always the strongest. They show a characteristic profile with a maximum, similar to simulated bars forming in isolated galaxies and observed bars in real galaxies. We adopt the maximum of the bar mode as a measure of the bar strength and we estimate the bar length by comparing the density ...

  15. Signatures of LCDM substructure in tidal debris

    CERN Document Server

    Siegal-Gaskins, Jennifer M

    2007-01-01

    In the past decade, surveys of the stellar component of the Galaxy such as SDSS and 2MASS have revealed a number of stellar streams. Current and future observations are rapidly increasing the precision and quantity of data available, raising the possibility of using tidal streams to constrain the distribution of dark matter in the halo. Simulations of hierarchical structure formation in LCDM cosmologies predict that the dark matter halo of a galaxy like the Milky Way contains a smooth component as well as hundreds of subhalos with masses of ~10^8 solar masses and greater, and it has been suggested that the existence of coherent tidal streams is incompatible with the expected abundance of substructure. We investigate the properties of tidal streams arising from the disruption of satellites in a variety of dark matter halo models. In general, we find that the halo shape and the specific orbital path more strongly determine the degree of disruption of the satellite than does the presence or absence of substructu...

  16. The tidal filament of NGC 4660

    CERN Document Server

    Kemp, S N; Marquez-Lugo, R A; Zepeda-Garcia, D; Franco-Hernandez, R; Nigoche-Netro, A; Ramos-Larios, G; Navarro, S G; Corral, L J

    2016-01-01

    NGC 4660, in the Virgo cluster, is a well-studied elliptical galaxy which has a strong disk component (D/T about 0.2-0.3). The central regions including the disk component have stellar populations with ages about 12-13 Gyr from SAURON studies. However we report the discovery of a long narrow tidal filament associated with the galaxy in deep co-added Schmidt plate images and deep CCD frames, implying that the galaxy has undergone a tidal interaction and merger within the last few Gyr. The relative narrowness of the filament implies a wet merger with at least one spiral galaxy involved, but the current state of the system has little evidence for this. However a 2-component photometric fit using GALFIT shows much bluer B-V colours for the disk component than for the elliptical component, which may represent a residual trace of enhanced star formation in the disk caused by the interaction 1-2 Gyr ago. There are brighter concentrations within the filament which resemble Tidal Dwarf Galaxies, although they are at l...

  17. Multiband lightcurves of tidal disruption events

    CERN Document Server

    Lodato, Giuseppe

    2010-01-01

    Unambiguous detection of the tidal disruption of a star would allow an assessment of the presence and masses of supermassive black holes in quiescent galaxies. It would also provide invaluable information on bulge scale stellar processes (such as two-body relaxation) via the rate at which stars are injected into the tidal sphere of influence of the black holes. This rate, in turn, is essential to predict gravitational radiation emission by compact object inspirals. The signature of a tidal disruption event is thought to be a fallback rate for the stellar debris onto the black hole that decreases as $t^{-5/3}$. This mass flux is often assumed to yield a luminous signal that decreases in time at the same rate. In this paper, we calculate the monochromatic lightcurves arising from such an accretion event. Differently from previous studies, we adopt a more realistic description of the fallback rate and of the super-Eddigton accretion physics. We also provide simultaneous lightcurves in optical, UV and X-rays. We ...

  18. Tidal effects on the shoreface: Towards a conceptual framework

    Science.gov (United States)

    Dashtgard, Shahin E.; MacEachern, James A.; Frey, Shannon E.; Gingras, Murray K.

    2012-11-01

    Tidal processes can have a significant impact on the sedimentological and ichnological character of wave-dominated shoreface deposits. As the influence of tides increases, the resulting shoreface successions begin to depart markedly from those postulated by the conventional, wave-dominated shoreface model, which was built upon essentially non-tidal shoreline settings. In shoreface settings subject to stronger tidal flux, tides can be manifest either directly or indirectly. Direct tidal effects refer to those characteristics imparted by tidal energy (e.g., tidal currents) per se, and are best expressed in offshore and lower shoreface positions. Key evidence of direct tidal control includes uniform sediment calibres from the upper shoreface to the offshore, and little or no mud preserved in the lower shoreface. Additionally, sands in the lower shoreface and offshore tend to be intensely bioturbated. Where primary stratification is preserved, it largely comprises current-generated structures. Such shoreface deposits are referred to herein as "tide-influenced shorefaces", and are expected in settings with low storm-wave input coupled with strong tidal currents (e.g., straits). Indirect tidal influences are manifest by the lateral translation of wave zones across the shoreface profile owing to changes in water depth during the tidal cycle. This is best developed in macrotidal to megatidal settings. Indirect tidal influences are more pronounced in the upper and lower shoreface, and are recorded through the interbedding of sedimentary structures produced by shoaling waves, breakers and surf, swash-backwash, and surface runoff. The boundaries between shoreface subenvironments are correspondingly poorly defined. The foreshore in settings of elevated tidal range is also generally much thicker (typically 4 to 5 m). Bioturbation tends to be patchy in distribution across the shoreface, and dominated by vertical structures. Such systems are defined as "tidally modulated

  19. Titan the earth-like moon

    CERN Document Server

    Coustenis, Athena

    1999-01-01

    This is the first book to deal with Titan, one of the most mysterious bodies in the solar system. The largest satellite of the giant planet Saturn, Titan is itself larger than the planet Mercury, and is unique in being the only known moon with a thick atmosphere. In addition, its atmosphere bears a startling resemblance to the Earth's, but is much colder.The American and European space agencies, NASA and ESA, have recently combined efforts to send a huge robot spacecraft to orbit Saturn and land on Titan. This book provides the background to this, the greatest deep space venture of our time, a

  20. Chemical composition of Earth-like planets

    CERN Document Server

    Ronco, M P; Marboeuf, U; Alibert, Y; de Elía, G C; Guilera, O M

    2015-01-01

    Models of planet formation are mainly focused on the accretion and dynamical processes of the planets, neglecting their chemical composition. In this work, we calculate the condensation sequence of the different chemical elements for a low-mass protoplanetary disk around a solar-type star. We incorporate this sequence of chemical elements (refractory and volatile elements) in our semi-analytical model of planet formation which calculates the formation of a planetary system during its gaseous phase. The results of the semi-analytical model (final distributions of embryos and planetesimals) are used as initial conditions to develope N-body simulations that compute the post-oligarchic formation of terrestrial-type planets. The results of our simulations show that the chemical composition of the planets that remain in the habitable zone has similar characteristics to the chemical composition of the Earth. However, exist differences that can be associated to the dynamical environment in which they were formed.

  1. Giant Impacts on Earth-like Worlds

    CERN Document Server

    Quintana, Elisa V; Borucki, William; Rowe, Jason F; Chambers, John E

    2015-01-01

    The late stages of terrestrial planet formation are dominated by giant impacts that collectively influence the growth, dynamical stability, composition and habitability of any planets that form. Hitherto, numerical models designed to explore these late stage collisions have been limited in two major ways. First, nearly all N-body models have assumed that two-body collisions lead to perfect accretion. Second, many of these studies lack the large number of realizations needed to account for the chaotic nature of these N-body systems. In this article we perform hundreds of simulations of late stage terrestrial planet formation using an N-body algorithm that includes fragmentation and hit-and-run collisions. We performed 140 simulations of planet accretion around a Sun-like star with Jupiter and Saturn analogs with and without this new collision model. We find that when fragmentation is included, the final planets formed are similar to those formed in the perfect-accretion model in terms of mass and number, howev...

  2. The effects of tidal range on saltmarsh morphology

    Science.gov (United States)

    Goodwin, Guillaume; Mudd, Simon

    2017-04-01

    Saltmarshes are highly productive coastal ecosystems that act simultaneously as flood barriers, carbon storage, pollutant filters and nurseries. As halophytic plants trap suspended sediment and decay in the settled strata, innervated platforms emerge from the neighbouring tidal flats, forming sub-vertical scarps on their eroding borders and sub-horizontal pioneer zones in areas of seasonal expansion. These evolutions are subject to two contrasting influences: stochastically generated waves erode scarps and scour tidal flats, whereas tidally-generated currents transport sediment to and from the marsh through the channel network. Hence, the relative power of waves and tidal currents strongly influences saltmarsh evolution, and regional variations in tidal range yield marshes of differing morphologies. We analyse several sheltered saltmarshes to determine how their morphology reflects variations in tidal forcing. Using tidal, topographic and spectral data, we implement an algorithm based on the open-source software LSDTopoTools to automatically identify features such as marsh platforms, tidal flats, erosion scarps, pioneer zones and tidal channels on local Digital Elevation Models. Normalised geometric properties are then computed and compared throughout the spectrum of tidal range, highlighting a notable effect on channel networks, platform geometry and wave exposure. We observe that micro-tidal marshes typically display jagged outlines and multiple islands along with wide, shallow channels. As tidal range increases, we note the progressive disappearance of marsh islands and linearization of scarps, both indicative of higher hydrodynamic stress, along with a structuration of channel networks and the increase of levee volume, suggesting higher sediment input on the platform. Future research will lead to observing and modelling the evolution of saltmarshes under various tidal forcing in order to assess their resilience to environmental change.

  3. A racetrack mode-locked silicon evanescent laser.

    Science.gov (United States)

    Fang, Alexander W; Koch, Brian R; Gan, Kian-Giap; Park, Hyundai; Jones, Richard; Cohen, Oded; Paniccia, Mario J; Blumenthal, Daniel J; Bowers, John E

    2008-01-21

    By utilizing a racetrack resonator topography, an on-chip mode locked silicon evanescent laser (ML-SEL) is realized that is independent of facet polishing. This enables integration with other devices on silicon and precise control of the ML-SEL's repetition rate through lithographic definition of the cavity length. Both passive and hybrid mode-locking have been achieved with transform limited, 7 ps pulses emitted at a repetition rate of 30 GHz. Jitter and locking range are measured under hybrid mode locking with a minimum absolute jitter and maximum locking range of 364 fs, and 50 MHz, respectively.

  4. Locked modes and magnetic field errors in MST

    Energy Technology Data Exchange (ETDEWEB)

    Almagri, A.F.; Assadi, S.; Prager, S.C.; Sarff, J.S.; Kerst, D.W.

    1992-06-01

    In the MST reversed field pinch magnetic oscillations become stationary (locked) in the lab frame as a result of a process involving interactions between the modes, sawteeth, and field errors. Several helical modes become phase locked to each other to form a rotating localized disturbance, the disturbance locks to an impulsive field error generated at a sawtooth crash, the error fields grow monotonically after locking (perhaps due to an unstable interaction between the modes and field error), and over the tens of milliseconds of growth confinement degrades and the discharge eventually terminates. Field error control has been partially successful in eliminating locking.

  5. International tidal gravity reference values at Wuhan station

    Institute of Scientific and Technical Information of China (English)

    许厚泽; 孙和平; 徐建桥; 陶国祥

    2000-01-01

    The international tidal gravity reference values at Wuhan station are determined accurately based on the comprehensive analysis of the tidal gravity observations obtained from 8 instruments. By comparing these with those in the tidal models given by Dehant (1997) while considering simultaneously (i) the global satellite altimeters tidal data, and (ii) the Schwiderski global tidal data and the local ones along the coast of China, it is found that the average discrepancy of the amplitude factors and of the phase differences for four main waves are given as 5.2% and 3.6% and as 0.16?and 0.08?respectively. They are improved evidently compared to those determined in early stage, indicating the important procedures in improving the Wuhan international tidal gravity reference values when including the long-series observations obtained with a superconducting gravimeter, and when considering the influence of the ocean loading and of the nearly daily free wobble of the Earth’s core.

  6. Tidal bending of glaciers: a linear viscoelastic approach

    DEFF Research Database (Denmark)

    Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph;

    2003-01-01

    In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young's) modulus E of ice derived from tidal deflection records of floating...... glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values....... This suggests that ice creep may have a significant influence on tidal bending of glaciers. Moreover, detailed tidal-deflection and tilt data from Nioghalvfjerdsfjorden glacier, northeast Greenland, cannot be explained by elastic-beam theory. We present a theory of tidal bending of glaciers based on linear...

  7. A gravito-electromagnetic analogy based on tidal tensors

    CERN Document Server

    Costa, L F; Herdeiro, Carlos A. R.

    2006-01-01

    We propose a new approach to a physical analogy between General Relativity and Electromagnetism, based on comparing tidal tensors of both theories. Using this approach we write a covariant form for the gravitational analogues of the Maxwell equations, from which the regime of validity of the analogy becomes manifest. Two explicit realisations of the analogy are given. The first one matches linearised gravitational tidal tensors to exact electromagnetic tidal tensors in Minkwoski spacetime. The second one matches exact magnetic gravitational tidal tensors for ultra-stationary metrics to exact magnetic tidal tensors of electromagnetism in curved spaces. We then establish a new proof for a class of tensor identities that define invariants of the type $\\vec{E}^2-\\vec{B}^2$ and $\\vec{E}\\cdot\\vec{B}$, and we exhibit the invariants built from tidal tensors in both gravity and electromagnetism. We contrast our approach with the two gravito-electromagnetic analogies commonly found in the literature, which are reviewed...

  8. The puzzling chemical composition of GJ 436B'S atmosphere: Influence of tidal heating on the chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Agúndez, Marcelino; Selsis, Franck [Univ. Bordeaux, LAB, UMR 5804, F-33270 Floirac (France); Venot, Olivia [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Iro, Nicolas, E-mail: Marcelino.Agundez@obs.u-bordeaux1.fr [Theoretical Meteorology group, Klimacampus, University of Hamburg, Grindelberg 5, D-20144 Hamburg (Germany)

    2014-02-01

    The dissipation of the tidal energy deposited on eccentric planets may induce a heating of the planet that affects its atmospheric thermal structure. Here we study the influence of tidal heating on the atmospheric composition of the eccentric (e = 0.16) 'hot Neptune' GJ 436b, for which inconclusive chemical abundances are retrieved from multiwavelength photometric observations carried out during primary transit and secondary eclipse. We build up a one-dimensional model of GJ 436b's atmosphere in the vertical direction and compute the pressure-temperature and molecular abundances profiles for various plausible internal temperatures of the planet (up to 560 K) and metallicities (from solar to 100 times solar), using a radiative-convective model and a chemical model which includes thermochemical kinetics, vertical mixing, and photochemistry. We find that the CO/CH{sub 4} abundance ratio increases with metallicity and tidal heating, and ranges from 1/20 to 1000 within the ranges of metallicity and internal temperature explored. Water vapor locks most of the oxygen and reaches a very high abundance, whatever the metallicity and internal temperature of the planet. The CO{sub 2}/H{sub 2}O abundance ratio increases dramatically with metallicity, and takes values between 10{sup –5}-10{sup –4} with solar elemental abundances and ∼0.1 for a metallicity 100 times solar. None of the atmospheric models based on solid physical and chemical grounds provide a fully satisfactory agreement with available observational data, although the comparison of calculated spectra and observations seems to point to models with a high metallicity and efficient tidal heating, in which high CO/CH{sub 4} abundance ratios and warm temperatures in the dayside atmosphere are favored.

  9. EXPERIMENTAL INVESTIGATIONS ON LONGITUDINAL DISPERSION CHARACTERISTICS OF TIDAL RIVERS

    Institute of Scientific and Technical Information of China (English)

    Fan Jing-yu; Wang Dao-zeng; Zhong Bao-chang

    2003-01-01

    The longitudinal dispersion characteristics of tidal rivers are experimentally investigated in a water channel. The longitudinal dispersion features and influential factors on pollutant in various stages of a tidal period in natural rivers are studied, the value ranges and variation trends of the longitudinal dispersion coefficient are obtained by means of concentration measurement. The results can provide important parameters for establishing the water quality mathematical models in tidal rivers.

  10. Organic geochemistry in Pennsylvanian tidally influenced sediments from SW Indiana

    Energy Technology Data Exchange (ETDEWEB)

    Mastalerz, M.; Kvale, E.P.; Stankiewicz, B.A.; Portle, K. [Indiana University, Bloomington, IN (United States). Indiana Geological Survey

    1999-05-01

    Tidal rhythmites are vertically stacked small-scale sedimentary structures that record daily variations in tidal current energy and are known to overlie some low-sulfur coals in the Illinois Basin. Tidal rhythmites from the Pennsylvanian Brazil Formation in Indiana were analyzed sedimentologically, petrographically, and geochemically in order to understand the character and distribution of organic matter preserved in an environment of daily interactions between marine and fresh waters.

  11. Mode-locking via dissipative Faraday instability

    Science.gov (United States)

    Tarasov, Nikita; Perego, Auro M.; Churkin, Dmitry V.; Staliunas, Kestutis; Turitsyn, Sergei K.

    2016-08-01

    Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system--spectrally dependent losses--achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser. We demonstrate features of this instability that distinguish it from both the Benjamin-Feir and the purely dispersive Faraday instability. Our results open the possibilities for new designs of mode-locked lasers and can be extended to other fields of physics and engineering.

  12. Locking GTPases covalently in their functional states

    Science.gov (United States)

    Wiegandt, David; Vieweg, Sophie; Hofmann, Frank; Koch, Daniel; Li, Fu; Wu, Yao-Wen; Itzen, Aymelt; Müller, Matthias P.; Goody, Roger S.

    2015-07-01

    GTPases act as key regulators of many cellular processes by switching between active (GTP-bound) and inactive (GDP-bound) states. In many cases, understanding their mode of action has been aided by artificially stabilizing one of these states either by designing mutant proteins or by complexation with non-hydrolysable GTP analogues. Because of inherent disadvantages in these approaches, we have developed acryl-bearing GTP and GDP derivatives that can be covalently linked with strategically placed cysteines within the GTPase of interest. Binding studies with GTPase-interacting proteins and X-ray crystallography analysis demonstrate that the molecular properties of the covalent GTPase-acryl-nucleotide adducts are a faithful reflection of those of the corresponding native states and are advantageously permanently locked in a defined nucleotide (that is active or inactive) state. In a first application, in vivo experiments using covalently locked Rab5 variants provide new insights into the mechanism of correct intracellular localization of Rab proteins.

  13. Lock-Free Parallel Access Collections

    Directory of Open Access Journals (Sweden)

    Bruce P. Lester

    2014-06-01

    Full Text Available All new computers have multicore processors. To exploit this hardware parallelism for improved performance, the predominant approach today is multithreading using shared variables and locks. This approach has potential data races that can create a nondeterministic program. This paper presents a promising new approach to parallel programming that is both lock-free and deterministic. The standard forall primitive for parallel execution of for-loop iterations is extended into a more highly structured primitive called a Parallel Operation (POP. Each parallel process created by a POP may read shared variables (or shared collections freely. Shared collections modified by a POP must be selected from a special set of predefined Parallel Access Collections (PAC. Each PAC has several Write Modes that govern parallel updates in a deterministic way. This paper presents an overview of a Prototype Library that implements this POP-PAC approach for the C++ language, including performance results for two benchmark parallel programs.

  14. Mode-locking via dissipative Faraday instability.

    Science.gov (United States)

    Tarasov, Nikita; Perego, Auro M; Churkin, Dmitry V; Staliunas, Kestutis; Turitsyn, Sergei K

    2016-08-09

    Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system-spectrally dependent losses-achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser. We demonstrate features of this instability that distinguish it from both the Benjamin-Feir and the purely dispersive Faraday instability. Our results open the possibilities for new designs of mode-locked lasers and can be extended to other fields of physics and engineering.

  15. Designing Of Pulse Phase-Locked Loops

    Directory of Open Access Journals (Sweden)

    A. A. Deryushev

    2006-01-01

    Full Text Available The paper considers pulse phase-locked loops (PPLL in which switching of structure and pa­rameters is used for improvement of dynamic and spectral characteristics Classification of existing switching algorithms is given in the paper. The paper proposes designing methodology that takes into account discrete and non-linear characteristics of the considered devices, and also requirements to synchronism, stability, speed, spectral characteristics, peculiarities of various switching algorithms. Practical approbation of the methodology has been carried out.

  16. Locked - in syndrome: a case report

    OpenAIRE

    Luján-Ramos Vanesa; Monterrosa-Salazar Erika; Polo-Verbel Luis

    2011-01-01

    The Locked-In Syndrome is an infrequent disease in our community. It is a destructiveprocess usually due to obstruction of the basilar artery. There is interruption of thedescending corticobulbar and corticospinal tracts, leaving uninvolved the fibers thatcontrol the blinking and the vertical ocular movements (allowing patient to communicate)and the ascending reticular matter. Case report: a 63 years old woman, with ahistory of hypertension and stroke, who suddenly develop dysartria, hemipare...

  17. Rehabilitation of Navigation Lock Walls: Case Histories

    Science.gov (United States)

    1987-12-01

    the low bidder, Pre mier Waterproofing Company, Denver, Colorado. 258. There was no device or test which co uld be used to measure the degree of...concrete to be in sound condition except for surface deterioration. Total resurfacing of the lock chamber would be for cosmetic reasons only and was not...replacement of deteriorated concrete may only be cosmetic and in many cases the appearance may not be satisfac- tory either. Damage from freezing and

  18. VHDL Model of Electronic-Lock System

    Directory of Open Access Journals (Sweden)

    J. Noga

    2000-04-01

    Full Text Available The paper describes the design of an electronic-lock system which wascompleted as part of the Basic VHDL course in the Department of Controland Measurement Faculty of Electrical Engineering and Informatics,Technical University of Ostrava, Czech Republic in co-operation withthe Department if Electronic Engineering, University of Hull, GreatBritain in the frame of TEMPUS project no. S_JEP/09468-95.

  19. Locked Superior Dislocation of the Acromioclavicular Joint

    Directory of Open Access Journals (Sweden)

    Salma Eltoum Elamin

    2013-01-01

    Full Text Available Acromioclavicular (AC joint injuries account for approximately 3–5% of shoulder girdle injuries (Rockwood et al., 1998. Depending on severity of injury and direction of displacement these are classified using Rockwood classification system for AC joint dislocation. We present an unusual case presenting with locked superior dislocation of the AC joint highlighting the presentation and subsequent successful surgical management of such case. To our knowledge this has not been reported previously in literature.

  20. Dither Cavity Length Controller with Iodine Locking

    Directory of Open Access Journals (Sweden)

    Lawson Marty

    2016-01-01

    Full Text Available A cavity length controller for a seeded Q-switched frequency doubled Nd:YAG laser is constructed. The cavity length controller uses a piezo-mirror dither voltage to find the optimum length for the seeded cavity. The piezo-mirror dither also dithers the optical frequency of the output pulse. [1]. This dither in optical frequency is then used to lock to an Iodine absorption line.

  1. Tidal and non-tidal sea level variations at two adjacent ports on the southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Srinivas, K.; DineshKumar, P.K.

    for the higher amplitudes of shallow water components. Meteorological residuals The regular and predictable tidal movements of the sea are continuously modified by the effects of the weather. Exchange of energy between the ocean and atmosphere occurs over a... to stormy weather. Even though tidal variations can be removed in the analysis, there could be energy in the tidal frequencies because of small timing errors in the gauge and weak interaction between the tides and the surges. The meteorological...

  2. Tidal motions and tidally induced fluxes through La Línea submarine canyon, western Alboran Sea

    Science.gov (United States)

    Lafuente, Jesús GarcíA.; Sarhan, Tarek; Vargas, Manuel; Vargas, Juan M.; Plaza, Francisco

    1999-02-01

    Detailed observations from two mooring lines deployed in La Línea submarine canyon, western Alboran Sea, are presented. This is a narrow canyon in the sense that its width is always less than the internal radius of deformation. Tidal currents within the canyon are polarized in the along-canyon direction according to its narrow nature. They have considerable amplitude (values of around 0.5 m/s are often observed) and are forced by the internal pressure gradients associated with the baroclinic tide that is generated in the surroundings. Subsequent amplification of onshore baroclinic currents within the canyon accounts for the large amplitude observed. Cross-shelf exchange through the canyon due to tidal motions is different from zero despite the close to zero mean of tidal currents. The explanation is based on the asymmetry of water properties flowing up-canyon and down-canyon (some sort of tidal rectification). Regarding the energy flux, the canyon seems to be an adequate conduit to carry energy to the shore. Estimations made from our observations indicate that energy input onto the shelf per unit length parallel to the shore at the canyon head is enough to maintain mixing on the shelf at intermediate depths.

  3. Tidal synchronization of close-in satellites and exoplanets. II. Spin dynamics and extension to Mercury and exoplanets host stars

    CERN Document Server

    Ferraz-Mello, Sylvio

    2015-01-01

    This paper deals with the application of the creep tide theory (Ferraz-Mello, CeMDA 116, 109, 2013) to the rotation of close-in satellites, Mercury, close-in exoplanets and their host stars. The solutions show two extreme cases: close-in giant gaseous planets, with fast relaxation (low viscosity) and satellites and Earth-like planets, with slow relaxation (high viscosity). The rotation of close-in gaseous planets follows the classical Darwinian pattern: it is tidally driven towards a stationary solution which is synchronized, but, if the orbit is elliptical, with a frequency larger than the orbital mean-motion. The rotation of rocky bodies, however, may be driven to several attractors whose frequencies are 1/2,1,3/2,2,5/2 ... times the mean-motion. The number of attractors increases with the viscosity of the body and with the orbital eccentricity. The classical example is Mercury, whose rotational period is 2/3 of the orbital period (3/2 attractor). The planet behaves as a molten body with a relaxation that a...

  4. Comprehensive Characterization a Tidal Energy Site (Invited)

    Science.gov (United States)

    Polagye, B. L.; Thomson, J. M.; Bassett, C. S.; Epler, J.; Northwest National Marine Renewable Energy Center

    2010-12-01

    Northern Admiralty Inlet, Puget Sound, Washington is the proposed location of a pilot tidal energy project. Site-specific characterization of the physical and biological environment is required for device engineering and environmental analysis. However, the deep water and strong currents which make the site attractive for tidal energy development also pose unique challenges to collecting comprehensive information. This talk focuses on efforts to optimally site hydrokinetic turbines and estimate their acoustic impact, based on 18 months of field data collected to date. Additional characterization efforts being undertaken by the University of Washington branch of the Northwest National Marine Renewable Energy Center and its partners include marine mammal presence and behavior, water quality, seabed geology, and biofouling potential. Because kinetic power density varies with the cube of horizontal current velocity, an accurate map of spatial current variations is required to optimally site hydrokinetic turbines. Acoustic Doppler profilers deployed on the seabed show operationally meaningful variations in flow characteristics (e.g., power density, directionality, vertical shear) and tidal harmonic constituents over length scales of less than 100m. This is, in part, attributed to the proximity of this site to a headland. Because of these variations, interpolation between stationary measurement locations introduces potentially high uncertainty. The use of shipboard acoustic Doppler profilers is shown to be an effective tool for mapping peak currents and, combined with information from seabed profilers, may be able to resolve power density variations in the project area. Because noise levels from operating turbines are expected to exceed regulatory thresholds for incidental harassment of marine mammals known to be present in the project area, an estimate of the acoustic footprint is required to permit the pilot project. This requires site-specific descriptions of pre

  5. Spitzer Observations of Tidal Dwarf Galaxies

    CERN Document Server

    Higdon, Sarah J U

    2007-01-01

    We present Spitzer observations of Tidal Dwarf Galaxies (TDGs) in three interacting systems: NGC 5291, Arp105 and Stephan's Quintet. The spectra show bright emission from polyaromatic hydrocarbons (PAHs), nebular lines and warm molecular hydrogen, characteristic of recent episodes of star formation. The PAH emission that falls in the IRAC 8.0 micron band leads to the TDGs having an extremely red IRAC color, with [4.5] - [8.0] > 3. The emission from PAHs is characterized by a model with mainly neutral 100-C PAH atoms.

  6. Modelling Galaxy Merger Timescales and Tidal Destruction

    CERN Document Server

    Simha, Vimal

    2016-01-01

    We present a model for the dynamical evolution of subhaloes based on an approach combining numerical and analytical methods. Our method is based on tracking subhaloes in an N-body simulation up to the last point that it can be resolved, and applying an analytic prescription for its merger timescale that takes dynamical friction and tidal disruption into account. When applied to cosmological N-body simulations with mass resolutions that differ by two orders of magnitude, the technique produces halo occupation distributions that agree to within 3%.

  7. Cycloidal tidal power generation - phase 2

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    This report describes the second phase of a study aimed at addressing the technical and economic viability of cycloidal tidal power generation with the objective of examining design optimisation, the building and testing a scale model, and the use of an enhanced model to estimated the overall system economic performance. Details are given of the analytical and physical modelling studies, the use of Computational Fluid Dynamics (CDF) analysis to understand the fluid flow through the cycloidal unit, the optimisation of the turbine blades, and performance predictions.

  8. Atmospheric dynamics of tidally synchronized extrasolar planets.

    Science.gov (United States)

    Cho, James Y-K

    2008-12-13

    Tidally synchronized planets present a new opportunity for enriching our understanding of atmospheric dynamics on planets. Subject to an unusual forcing arrangement (steady irradiation on the same side of the planet throughout its orbit), the dynamics on these planets may be unlike that on any of the Solar System planets. Characterizing the flow pattern and temperature distribution on the extrasolar planets is necessary for reliable interpretation of data currently being collected, as well as for guiding future observations. In this paper, several fundamental concepts from atmospheric dynamics, likely to be central for characterization, are discussed. Theoretical issues that need to be addressed in the near future are also highlighted.

  9. [Tibiotalocalcaneal arthrodesis using a humeral locking plate].

    Science.gov (United States)

    Cabrera Méndez, M P; Gamba, C; Hernández, E; Molano, J; Andrade, J C

    2016-01-01

    To describe the results of tibiotalocalcáneal arthrodesis (TTC) using a humeral locking plate. A retrospective, observational study was conducted between January 2007 and December 2013 in the Hospital Militar Central de Bogotá. The study included patients with symptomatic osteoarthritis diagnosed clinically and radiologically, and who underwent TTC arthrodesis using a humeral locking plate with a minimum follow up of 6 months. The total number patients was 35, of whom 7 (20%) were women and 28 (80%) men, with a mean age 36.3 years (19.77). 74% with post-traumatic arthritis, most of them secondary to gunshot wounds and fragmentation weapons, and neuropathic in 20%. An autogenous graft was used in 13 cases, and 14 cases using both, with a mean consolidation time of 4.37 months. Complications include, delayed union in 3 cases, and surgical site infection in 4. The postoperative functionality (AOFAS) mean was 66.7/100 points, with a score of 2.35 on a visual analogue pain scale. TTC arthrodesis using a humeral locking plate is a suitable option for fixing this type of arthrodesis, with a low rate of complications, and postoperative results that revealed satisfactory improvement in pain and consolidation. Copyright © 2015 SECOT. Published by Elsevier Espana. All rights reserved.

  10. Locking plates in proximal humerus fractures.

    Science.gov (United States)

    Strohm, P C; Helwig, P; Konrad, G; Südkamp, N P

    2007-12-01

    It is well known that proximal humerus fractures are among the three most frequent fracture types. Epidemiological invetsigations show that in people elder than 60 years the fracture of the proximal humerus is more frequent than fractures of the hip region (17). Over the last decades several techniques have been applied for treatment of proximal humerus fractures. Widely accepted is the initiation of a conservative treatment regimen for undisplaced fractures, however, the standard treatment for displaced fractures, especially three and four part fractures, is still the center of scientific debate. Many different implants have been tested and investigated, thus demonstrating lack of sufficient results. Over the last years the development of angle stable, locking implants started and clinical studies demonstrated encouraging results. In our clinic the locking proximal humerus plate and the PHILOS plate advanced to the implant of choice for treatment of displaced proximal humerus fractures. There are still cases of implant failure and humerus head necrosis, but most of these complications were caused by the fracture type and not an implant specific problem. However the overall results with these new implants are encouraging. Key words: locking plates, proximal humerus fracture, humerus, humerus fracture, PHILOS, PHP.

  11. Laser Metrology Heterodyne Phase-Locked Loop

    Science.gov (United States)

    Loya, Frank; Halverson, Peter

    2009-01-01

    A method reduces sensitivity to noise in a signal from a laser heterodyne interferometer. The phase-locked loop (PLL) removes glitches that occur in a zero-crossing detector s output [that can happen if the signal-to-noise ratio (SNR) of the heterodyne signal is low] by the use of an internal oscillator that produces a square-wave signal at a frequency that is inherently close to the heterodyne frequency. It also contains phase-locking circuits that lock the phase of the oscillator to the output of the zero-crossing detector. Because the PLL output is an oscillator signal, it is glitch-free. This enables the ability to make accurate phase measurements in spite of low SNR, creates an immunity to phase error caused by shifts in the heterodyne frequency (i.e. if the target moves causing Doppler shift), and maintains a valid phase even when the signal drops out for brief periods of time, such as when the laser is blocked by a stray object.

  12. Self-locking degree-4 vertex origami structures

    Science.gov (United States)

    Fang, Hongbin; Li, Suyi; Wang, K. W.

    2016-11-01

    A generic degree-4 vertex (4-vertex) origami possesses one continuous degree-of-freedom for rigid folding, and this folding process can be stopped when two of its facets bind together. Such facet-binding will induce self-locking so that the overall structure stays at a pre-specified configuration without additional locking elements or actuators. Self-locking offers many promising properties, such as programmable deformation ranges and piecewise stiffness jumps, that could significantly advance many adaptive structural systems. However, despite its excellent potential, the origami self-locking features have not been well studied, understood, and used. To advance the state of the art, this research conducts a comprehensive investigation on the principles of achieving and harnessing self-locking in 4-vertex origami structures. Especially, for the first time, this study expands the 4-vertex structure construction from single-component to dual-component designs and investigates their self-locking behaviours. By exploiting various tessellation designs, this research discovers that the dual-component designs offer the origami structures with extraordinary attributes that the single-component structures do not have, which include the existence of flat-folded locking planes, programmable locking points and deformability. Finally, proof-of-concept experiments investigate how self-locking can effectively induce piecewise stiffness jumps. The results of this research provide new scientific knowledge and a systematic framework for the design, analysis and utilization of self-locking origami structures for many potential engineering applications.

  13. Photosynthetic and physiological responses of native and exotic tidal woody seedlings to simulated tidal immersion

    Science.gov (United States)

    Wu, Tonggui; Gu, Shenhua; Zhou, Hefeng; Wang, G. Geoff; Cheng, Xiangrong; Yu, Mukui

    2013-12-01

    Hibiscus hamabo, a native tidal woody species, and Myrica cerifera, an exotic tidal woody species, have been widely planted on coastal beaches in subtropical China. However, whether there are differences in physiological response and tolerance to immersion between the two tidal species is still unknown. Our objectives were to evaluate differences in the photosynthetic and physiological responses to tidal immersion for the two species in the context of sea level rise. With increasing immersion, net photosynthesis, stomatal conductance, intercellular CO2 concentration, and light saturation point declined progressively for both species, whereas dark respiration and light compensation point showed the reverse trend. Lower variation was observed in H. hamabo than in M. cerifera for each index in the same treatment. Photosynthetic ability and utilization of light, especially under high light intensity, decreased for both species. Leaf soluble sugar and protein contents, and glycolate oxidase activity first increased and then decreased with increasing of immersion degree, with the higher values observed in the W4 (4 h duration, 15 cm depth) and W6 (6 h duration, 25 cm depth) treatments for H. hamabo, and W2 (2 h duration, 5 cm depth) and W4 treatments for M. cerifera. These findings indicate that H. hamabo has a better ability to keep the reduction of photosynthesis at a minimum through soluble substance regulated osmotic potential and avoiding excess light damage to the photosynthetic system through increased photorespiration, heat dissipation, chlorophyll fluorescence. Our results suggest that H. hamabo is more tolerant to tidal immersion than M. cerifera, and therefore it is better adapted to the anticipated sea level rise in future.

  14. Catalog of worldwide tidal bore occurrences and characteristics

    Science.gov (United States)

    Bartsch-Winkler, S.; Lynch, David K.

    1988-01-01

    Documentation of tidal bore phenomena occurring throughout the world aids in defining the typical geographical setting of tidal bores and enables prediction of their occurrence in remote areas. Tidal bores are naturally occurring, tidally generated, solitary, moving water waves up to 6 meters in height that form upstream in estuaries with semidiurnal or nearly semidiurnal tide ranges exceeding 4 meters. Estuarine settings that have tidal bores typically include meandering fluvial systems with shallow gradients. Bores are well defined, having amplitudes greater than wind- or turbulence-caused waves, and may be undular or breaking. Formation of a bore is dependent on depth and velocity of the incoming tide and river outflow. Bores may occur in series (in several channels) or in succession (marking each tidal pulse). Tidal bores propagate up tidal estuaries a greater distance than the width of the estuary and most occur within 100 kilometers upstream of the estuary mouth. Because they are dynamic, bores cause difficulties in some shipping ports and are targets for eradication. Tidal bores are known to occur, or to have occurred in the recent past, in at least 67 localities in 16 countries at all latitudes, including every continent except Antarctica. Parts of Argentina, Canada, Central America, China, Mozambique, Madagascar, Northern Europe, North and South Korea, the United Kingdom, and the U.S.S.R. probably have additional undiscovered or unreported tidal bores. In Turnagain Arm estuary in Alaska, bores cause an abrupt increase in salinity, suspended sediment, surface character, and bottom pressure, a decrease in illumination of the water column, and a change in water temperature. Tidal bores occurring in Turnagain Arm, Alaska, have the

  15. Dissipation in rocky planets for strong tidal forcing

    Science.gov (United States)

    Clausen, N.; Tilgner, A.

    2015-12-01

    Aims: We plan to reproduce a previously published calculation for the tidal dissipation in Io and extend the employed model to investigate the heat transport mechanism in Io and the thickness of Io's asthenosphere. Additionally, we apply this model to an exoplanet and obtain insights into the dependencies of the modified tidal quality factor (Q') on the size of the planet and its orbital eccentricity. Methods: Tidal dissipation depends on the heat transport mechanism. For strong tidal forcing an equilibrium between heat transport by convection and heat production by tidal dissipation can be obtained that determines the tidal dissipation. By this means, we checked whether convection is the dominant heat transport mechanism in Io. The tidal dissipation also depends on the interior model of Io. We considered various asthenosphere thicknesses and determined which of these gives results compatible with observations. We determined the modified tidal quality factors (Q') for Corot 7 b for various orbital parameters, but in a way that tidal forcing is strong. We used convection and melt migration as possible heat transport mechanism. We repeated this for a hypothetical planet with the size and density of Io on the orbit of Corot 7 b. Results: We find that a heat transport dominated by convection in Io is possible, but the grain sizes need to be smaller than 2.2 mm. For larger grain sizes melt migration is the dominant heat transport mechanism. Moreover, Io's asthenosphere needs to be thicker than 100 km. The computation of the modified tidal quality factors (Q') for Corot 7 b and a planet with the size and density of Io on the orbit of Corot 7 b show that Q' is scattered over several orders of magnitude, but a value of 100 for Q' is an acceptable estimate for a rocky planet under strong tidal forcing.

  16. The origin of neap-spring tidal cycles

    Science.gov (United States)

    Kvale, E.P.

    2006-01-01

    The origin of oceanic tides is a basic concept taught in most introductory college-level sedimentology/geology, oceanography, and astronomy courses. Tides are typically explained in the context of the equilibrium tidal theory model. Yet this model does not take into account real tides in many parts of the world. Not only does the equilibrium tidal model fail to explicate amphidromic circulation, it also does not explain diurnal tides in low latitude positions. It likewise fails to explain the existence of tide-dominated areas where neap-spring cycles are synchronized with the 27.32-day orbital cycle of the Moon (tropical month), rather than with the more familiar 29.52-day cycle of lunar phases (synodic month). Both types of neap-spring cycles can be recognized in the rock record. A complete explanation of the origin of tides should include a discussion of dynamic tidal theory. In the dynamic tidal model, tides resulting from the motions of the Moon in its orbit around the Earth and the Earth in its orbit around the Sun are modeled as products of the combined effects of a series of phantom satellites. The movement of each of these satellites, relative to the Earth's equator, creates its own tidal wave that moves around an amphidromic point. Each of these waves is referred to as a tidal constituent. The geometries of the ocean basins determine which of these constituents are amplified. Thus, the tide-raising potential for any locality on Earth can be conceptualized as the result of a series of tidal constituents specific to that region. A better understanding of tidal cycles opens up remarkable opportunities for research on tidal deposits with implications for, among other things, a more complete understanding of the tidal dynamics responsible for sediment transport and deposition, changes in Earth-Moon distance through time, and the possible influences tidal cycles may exert on organisms. ?? 2006 Elsevier B.V. All rights reserved.

  17. Classification of tidal inlets along the Central east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Reddy, N.A.; Vikas, M.; Rao, S.; JayaKumar S.

    ) as long as the alongshore sediment bypasses the tidal inlet. Classification of coastal systems in a broader view is necessary for the management of tidal inlets. There are several methods to classify tidal inlets based on different perspectives namely geo...

  18. Tidal Debris as a Dark Matter Probe

    CERN Document Server

    Johnston, Kathryn V

    2016-01-01

    Tidal debris streams from galaxy satellites can provide insight into the dark matter distribution in halos. This is because we have more information about stars in a debris structure than about a purely random population of stars: we know that in the past they were all bound to the same dwarf galaxy; and we know that they form a dynamically cold population moving on similar orbits. They also probe a different region of the matter distribution in a galaxy than many other methods of mass determination, as their orbits take them far beyond the typical extent of those for the bulk of stars. Although conclusive results from this information have yet to be obtained, significant progress has been made in developing the methodologies for determining both the global mass distribution of the Milky Way's dark matter halo and the amount of dark matter substructure within it. Methods for measuring the halo shape are divided into "predictive methods," which predict the tidal debris properties from the progenitor satellite'...

  19. Tidal instability in exoplanetary systems evolution

    Directory of Open Access Journals (Sweden)

    Le Gal P.

    2011-02-01

    Full Text Available A new element is proposed to play a role in the evolution of extrasolar planetary systems: the tidal (or elliptical instability. It comes from a parametric resonance and takes place in any rotating fluid whose streamlines are (even slightly elliptically deformed. Based on theoretical, experimental and numerical works, we estimate the growth rate of the instability for hot-jupiter systems, when the rotation period of the star is known. We present the physical process, its application to stars, and preliminary results obtained on a few dozen systems, summarized in the form of a stability diagram. Most of the systems are trapped in the so-called "forbidden zone", where the instability cannot grow. In some systems, the tidal instability is able to grow, at short timescales compared to the system evolution. Implications are discussed in the framework of misaligned transiting systems, as the rotational axis of the star would be unstable in systems where this elliptical instability grows.

  20. Tidal Dwarf Galaxies and Missing Baryons

    Directory of Open Access Journals (Sweden)

    Frederic Bournaud

    2010-01-01

    Full Text Available Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

  1. Tidal Disruption Events Prefer Unusual Host Galaxies

    CERN Document Server

    French, K Decker; Zabludoff, Ann

    2016-01-01

    Tidal Disruption Events (TDEs) are transient events observed when a star passes close enough to a supermassive black hole to be tidally destroyed. Many TDE candidates have been discovered in host galaxies whose spectra have weak or no line emission yet strong Balmer line absorption, indicating a period of intense star formation that has recently ended. As such, TDE host galaxies fall into the rare class of quiescent Balmer-strong galaxies. Here, we quantify the fraction of galaxies in the Sloan Digital Sky Survey (SDSS) with spectral properties like those of TDE hosts, determining the extent to which TDEs are over-represented in such galaxies. Galaxies whose spectra have Balmer absorption H$\\delta_{\\rm A}$ $-$ $\\sigma$(H$\\delta_{\\rm A}$) $>$ 4 \\AA\\ (where $\\sigma$(H$\\delta_{\\rm A}$) is the error in the Lick H$\\delta_{\\rm A}$ index) and H$\\alpha$ emission EW $$ 1.31 \\AA\\ and H$\\alpha$ EW $80\\times$ enhancement in such hosts and providing an observational link between the $\\gamma$/X-ray-bright and optical/UV-br...

  2. Tidal Friction: Darwin's Theory Re-Visited

    Science.gov (United States)

    Ferraz-Mello, Sylvio

    2009-05-01

    Our knowledge of tidal friction is even today directly founded on Darwin's theory. Many progresses from studies done in the past century deserve mention. To quote just a few, we may mention Love's theory on the elastic response of one body submitted to an external potential and the understanding of the role played by tides in generating heat in synchronous planetary satellites. We may also mention the many applications that leaded to the understanding of the evolution of systems with close-in satellites, the Earth-Moon system in the first place, and those concerning systems formed by close binary stars. However, notwithstanding the existence of some high-order formal theories, the essential of our knowledge is yet nowadays the one established by Darwin and crucial questions on the action of viscosity, for instance, remains unanswered. We still are strongly tied to Darwin's assumption that the tidal waves lag proportionally to frequency or, in some favorable cases (e.g. the Earth), that the lags are constants. We intend to critically review our current understanding of Darwin's theory and some of its limitations.

  3. Directly Imaging Tidally Powered Migrating Jupiters

    CERN Document Server

    Dong, Subo; Socrates, Aristotle

    2012-01-01

    We show that ongoing direct imaging experiments may detect a new class of long-period, highly luminous, tidally powered extrasolar gas giants. Even though they are hosted by Gyr-"old" main-sequence stars, they can be as "hot" as young Jupiters at ~100 Myr, the prime targets of direct imaging surveys. These planets, with years-long orbits, are presently migrating to "feed" the "hot Jupiters" in steady state. Their existence is expected from a class of "high-e" migration mechanisms, in which gas giants are excited to highly eccentric orbits and then shrink their semi-major axis by factor of ~ 10-100 due to tidal dissipation at successive close periastron passages. The dissipated orbital energy is converted to heat, and if it is deposited deep enough into the planet atmosphere, the planet likely radiates steadily at luminosity ~2-3 orders of magnitude larger than that of our Jupiter during a typical Gyr migration time scale. Their large orbital separations and expected high planet-to-star flux ratios in IR make ...

  4. Constraints on Tidal Heating in Enceladus

    Science.gov (United States)

    Stevenson, D. J.

    2008-12-01

    Two constraints for Enceladus seem difficult to dispute: First, that it is emitting more heat than allowed by equilibrium tidal heating models (defined as those in which the tidal heat production and orbital eccentricity are constant with time, cf. Meyer and Wisdom, 2007). Second, the maximum possible instantaneous tidal heat generation is over two orders of magnitude larger than what is observed. (This can be shown independent of any particular rheological model.) There is nothing mysterious about the simultaneous correctness of these two statements since one pertains to the orbital evolution aspect of the problem and the other pertains to the actual mechanism of dissipation. In reality, the maximum heat dissipation would never be approached since it would quench the eccentricity in a short timescale (ten to a hundred thousand years). However, this high upper bound assures us that there is no fundamental difficulty with the tidal heating mechanism, only with its constancy over long periods of time. This suggests that one should seek a model in which the eccentricity fluctuates, possibly mediated by the bounds imposed at the high end by the stress limits for ice fracture and at the low end by the stress at which motion on faults (lubricated or dry) ceases to be possible. I will describe models of this kind that are capable, at least in principle, of producing the desired heat flow in instantaneous equilibrium (i.e., without the need to store heat in the interior). This is a stress-mediated model rather than a thermally mediated model (like that advocated for Io, which has a similar disequilibrium problem). Such a model must (in analogy with successful models for Io and Europa) simultaneously provide the right environment for the desired straining of the outer part of the ice shell and a deeper environment that is sufficiently deformable so that a large tidal Love number (of order a hundred times the elastic value) can be achieved. It is argued that solid water ice

  5. Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay

    OpenAIRE

    Nasir Qassim

    2005-01-01

    The input frequency limit of the conventional zero-crossing digital phase-locked loop (ZCDPLL) is due to the operating time of the digital circuitry inside the feedback loop. A solution that has been previously suggested is the introduction of a time delay in the feedback path of the loop to allow the digital circuits to complete their sample processing before the next sample is received. However, this added delay will limit the stable operation range and hence lock range of the loop. The ob...

  6. Changing tidal hydrodynamics during different stages of eco-geomorphological development of a tidal marsh: A numerical modeling study

    Science.gov (United States)

    Stark, J.; Meire, P.; Temmerman, S.

    2017-03-01

    The eco-geomorphological development of tidal marshes, from initially low-elevated bare tidal flats up to a high-elevated marsh and its typical network of channels and creeks, induces long-term changes in tidal hydrodynamics in a marsh, which will have feedback effects on the marsh development. We use a two-dimensional hydrodynamic model of the Saeftinghe marsh (Netherlands) to study tidal hydrodynamics, and tidal asymmetry in particular, for model scenarios with different input bathymetries and vegetation coverages that represent different stages of eco-geomorphological marsh development, from a low elevation stage with low vegetation coverage to a high and fully vegetated marsh platform. Tidal asymmetry is quantified along a 4 km marsh channel by (1) the difference in peak flood and peak ebb velocities, (2) the ratio between duration of the rising tide and the falling tide and (3) the time-integrated dimensionless bed shear stress during flood and ebb. Although spatial variations in tidal asymmetry are large and the different indicators for tidal asymmetry do not always respond similarly to eco-geomorphological changes, some general trends can be obtained. Flood-dominance prevails during the initial bare stage of a low-lying tidal flat. Vegetation establishment and platform expansion lead to marsh-scale flow concentration to the bare channels, causing an increase in tidal prism in the channels along with a less flood-dominant asymmetry of the horizontal tide. The decrease in flood-dominance continues as the platform grows vertically and the sediment-demand of the platform decreases. However, when the platform elevation gets sufficiently high in the tidal frame and part of the spring-neap cycle is confined to the channels, the discharge in the channels decreases and tidal asymmetry becomes more flood-dominant again, indicating an infilling of the marsh channels. Furthermore, model results suggest that hydro-morphodynamic feedbacks based on tidal prism to channel

  7. Are Wave and Tidal Energy Plants New Green Technologies?

    Science.gov (United States)

    Douziech, Mélanie; Hellweg, Stefanie; Verones, Francesca

    2016-07-19

    Wave and tidal energy plants are upcoming, potentially green technologies. This study aims at quantifying their various potential environmental impacts. Three tidal stream devices, one tidal range plant and one wave energy harnessing device are analyzed over their entire life cycles, using the ReCiPe 2008 methodology at midpoint level. The impacts of the tidal range plant were on average 1.6 times higher than the ones of hydro-power plants (without considering natural land transformation). A similar ratio was found when comparing the results of the three tidal stream devices to offshore wind power plants (without considering water depletion). The wave energy harnessing device had on average 3.5 times higher impacts than offshore wind power. On the contrary, the considered plants have on average 8 (wave energy) to 20 (tidal stream), or even 115 times (tidal range) lower impact than electricity generated from coal power. Further, testing the sensitivity of the results highlighted the advantage of long lifetimes and small material requirements. Overall, this study supports the potential of wave and tidal energy plants as alternative green technologies. However, potential unknown effects, such as the impact of turbulence or noise on marine ecosystems, should be further explored in future research.

  8. Ice-volcanism due to tidal stress on Europa

    Institute of Scientific and Technical Information of China (English)

    LI Li; CHEN Chuxin

    2003-01-01

    Tectonism would be driven by tidal heat on Europa, and there may be ice-volcano on the surface of active Europa. We assume that ice-volcano would spurt out due to tidal stress, and calculate the velocity and height of the spurt inscale. We also find out the approximate distribution of the active volcanoes on Europa.

  9. Optical discovery of probable stellar tidal discruption flares

    NARCIS (Netherlands)

    van Velzen, S.; Farrar, G.R.; Gezari, S.; Morrell, N.; Zaritsky, D.; Ostman, L.; Smith, M.; Gelfand, J.; Drake, A.J.

    2012-01-01

    Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. The TDE flares have optical blackbody temperatures

  10. 33 CFR 117.181 - Oakland Inner Harbor Tidal Canal.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Oakland Inner Harbor Tidal Canal. 117.181 Section 117.181 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements California § 117.181 Oakland Inner Harbor Tidal Canal. The draws of the...

  11. Flow and sediment transport in an Indonesian tidal network

    NARCIS (Netherlands)

    Buschman, F.A.

    2011-01-01

    The Berau river, situated in east Kalimantan (Indonesia), drains a relatively small catchment area and splits into several interconnected tidal channels. This tidal network connects to the sea. The sea is host to extremely diverse coral reef communities. Also the land side of the region is relativel

  12. Morphodynamics of tidal inlets in a tropical monsoon area

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Verhagen, H.J.; Wang, Z.B.

    2007-01-01

    Morphodynamics of a tidal inlet system on a micro-tidal coast in a tropical monsoon influenced region is modelled and discussed. Influences of river flow and wave climate on the inlet morphology are investigated with the aid of process-based state-of-the-art numerical models. Seasonal and episodic b

  13. Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Wang, Z.B.; Verhagen, H.J.; Thuy, V.T.T.

    2008-01-01

    Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system are investigated using numerical models. The ocean forcing including tidal and wave actions and sediment transport is simulated using Delft3D model. Fluvial processes in Delft3D are taken into account as results from SOBEK RU

  14. Wave and tidal generation devices reliability and availability

    CERN Document Server

    Tavner, Peter John

    2017-01-01

    To some extent the wave and tidal generation industry is following in the wake of the wind industry, learning from the growing experience of offshore wind farm deployment. This book combines wind industry lessons with wave and tidal field knowledge to explore the main reliability and availability issues facing this growing industry.

  15. Carbon dioxide uptake by a temperate tidal sea

    NARCIS (Netherlands)

    Klaassen, Wim

    2007-01-01

    Carbon dioxide (CO2) exchange between the atmosphere and the Wadden Sea, a shallow coastal region along the northern Netherlands, has been measured from April 2006 onwards on a tidal flat and over open water. Tidal flat measurements were done using a flux chamber, and ship borne measurements using a

  16. Soil and water management strategies for tidal lowlands in Indonesia

    NARCIS (Netherlands)

    Suryadi, F.X.

    1996-01-01

    Lowland is defined as an area which is relatively low in relation to surface or groundwater levels. Tidal lowlands are lowland areas which are influenced by the vertical tides and their characteristics are in accordance with thier hydro-topographical conditions. Tidal lowlands become more and more i

  17. Optical discovery of probable stellar tidal discruption flares

    NARCIS (Netherlands)

    van Velzen, S.; Farrar, G.R.; Gezari, S.; Morrell, N.; Zaritsky, D.; Ostman, L.; Smith, M.; Gelfand, J.; Drake, A.J.

    2012-01-01

    Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. The TDE flares have optical blackbody temperatures

  18. Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Wang, Z.B.; Verhagen, H.J.; Thuy, V.T.T.

    2008-01-01

    Hydrodynamics and morphodynamics of a seasonally forced tidal inlet system are investigated using numerical models. The ocean forcing including tidal and wave actions and sediment transport is simulated using Delft3D model. Fluvial processes in Delft3D are taken into account as results from SOBEK

  19. Land use in Korean tidal wetlands: impacts and management strategies.

    Science.gov (United States)

    Hong, Sun-Kee; Koh, Chul-Hwan; Harris, Richard R; Kim, Jae-Eun; Lee, Jeom-Sook; Ihm, Byung-Sun

    2010-05-01

    The coastal landscapes in southwestern Korea include a diverse array of tidal wetlands and salt marshes. These coastal zones link the ecological functions of marine tidal wetlands and freshwater ecosystems with terrestrial ecosystems. They are rich in biological diversity and play important roles in sustaining ecological health and processing environmental pollutants. Korean tidal wetlands are particularly important as nurseries for economically important fishes and habitats for migratory birds. Diking, draining, tourism, and conversion to agricultural and urban uses have adversely affected Korean tidal wetlands. Recent large development projects have contributed to further losses. Environmental impact assessments conducted for projects affecting tidal wetlands and their surrounding landscapes should be customized for application to these special settings. Adequate environmental impact assessments will include classification of hydrogeomorphic units and consideration of their responses to biological and environmental stressors. As is true worldwide, Korean laws and regulations are changing to be more favorable to the conservation and protection of tidal wetlands. More public education needs to be done at the local level to build support for tidal wetland conservation. Some key public education points include the role of tidal wetlands in maintaining healthy fish populations and reducing impacts of nonpoint source pollution. There is also a need to develop procedures for integrating economic and environmental objectives within the overall context of sustainable management and land uses.

  20. Land Use in Korean Tidal Wetlands: Impacts and Management Strategies

    Science.gov (United States)

    Hong, Sun-Kee; Koh, Chul-Hwan; Harris, Richard R.; Kim, Jae-Eun; Lee, Jeom-Sook; Ihm, Byung-Sun

    2010-05-01

    The coastal landscapes in southwestern Korea include a diverse array of tidal wetlands and salt marshes. These coastal zones link the ecological functions of marine tidal wetlands and freshwater ecosystems with terrestrial ecosystems. They are rich in biological diversity and play important roles in sustaining ecological health and processing environmental pollutants. Korean tidal wetlands are particularly important as nurseries for economically important fishes and habitats for migratory birds. Diking, draining, tourism, and conversion to agricultural and urban uses have adversely affected Korean tidal wetlands. Recent large development projects have contributed to further losses. Environmental impact assessments conducted for projects affecting tidal wetlands and their surrounding landscapes should be customized for application to these special settings. Adequate environmental impact assessments will include classification of hydrogeomorphic units and consideration of their responses to biological and environmental stressors. As is true worldwide, Korean laws and regulations are changing to be more favorable to the conservation and protection of tidal wetlands. More public education needs to be done at the local level to build support for tidal wetland conservation. Some key public education points include the role of tidal wetlands in maintaining healthy fish populations and reducing impacts of nonpoint source pollution. There is also a need to develop procedures for integrating economic and environmental objectives within the overall context of sustainable management and land uses.

  1. Residual circulation and tidal stress in the Gulf of California

    Science.gov (United States)

    Salas-De-León, David Alberto; Carbajal-PéRez, Noel; Monreal-Gómez, Maria Adela; Barrientos-MacGregor, Gerardo

    2003-10-01

    Results of a three-dimensional nonlinear barotropic shelf model are used to study the effect of the M2 tidal stress on the residual current in the Gulf of California. The tidal stress summarizes the nonlinear interactions and forces the residual circulation. It is calculated following the method developed by [1975]. The vertical structure of the tidal stress reveals clearly the zones where the interaction between tidal currents and the basin geometry is strong. The highest values of tidal stress were found over the Salsipuedes sill and in the Ballenas Channel in the central archipelago and in the Colorado River Delta. Relatively high values of tidal stress were also found in deeper layers in the southern part. The high tidal stress values coincide well with the anomalous cold-water patches observed in the archipelago area, attributed to tidal mixing. The calculated residual currents show a maximum of about 15 cm s-1 in the upper layers in the archipelago area. At subsurface layers an anticyclonic circulation is observed. Divergence patterns in the upper layers suggest that M2 tide residuals contribute, to significant upward movements of water, on the west side of Tiburón island. This barotropic process may contribute to the generation of the observed cold patches.

  2. Tolerances for Phase Locking of Semiconductor Laser Arrays.

    Science.gov (United States)

    1988-04-18

    laser fabrication . This means that the starting material is critically important to tne success of locked laser arrays. F. TOLERANCE REQUIREMENTS ON...typically r , 0.1. Because Eq. (7) represents a small frequency deviation, and implies A - 0.5 4, this report will look into the tolerances on laser ... fabrication and operation to ensure that the free-running laser frequencies remain within this locking range. D. COMPARISON OF LOCKING CONDITION WITH

  3. Locking of metacarpophalangeal joints in a patient with acromegaly

    Energy Technology Data Exchange (ETDEWEB)

    Tani, Y.; Tanaka, N.; Isoya, Eiji [Dept. of Orthopaedic Surgery, Soseikai General Hospital, Kyoto (Japan)

    1999-11-01

    A 39-year-old man with acromegaly exhibited locking of metacarpophalangeal (MCP) joints of both index fingers. Large osteophytes were found at the metacarpal heads by radiography and computerized tomography (CT). Magnetic resonance (MR) images revealed hypertrophy of volar plates. We suggest that these characteristic acromegalic features caused locking of MCP joints. Surgery was required on one of the joints to release the locking. (orig.)

  4. The strength of polyaxial locking interfaces of distal radius plates.

    Science.gov (United States)

    Hoffmeier, Konrad L; Hofmann, Gunther O; Mückley, Thomas

    2009-10-01

    Currently available polyaxial locking plates represent the consequent enhancement of fixed-angle, first-generation locking plates. In contrast to fixed-angle locking plates which are sufficiently investigated, the strength of the new polyaxial locking options has not yet been evaluated biomechanically. This study investigates the mechanical strength of single polyaxial interfaces of different volar radius plates. Single screw-plate interfaces of the implants Palmar 2.7 (Königsee Implantate und Instrumente zur Osteosynthese GmbH, Allendorf, Germany), VariAx (Stryker Leibinger GmbH & Co. KG, Freiburg, Germany) und Viper (Integra LifeSciences Corporation, Plainsboro, NJ, USA) were tested by cantilever bending. The strength of 0 degrees, 10 degrees and 20 degrees screw locking angle was obtained during static and dynamic loading. The Palmar 2.7 interfaces showed greater ultimate strength and fatigue strength than the interfaces of the other implants. The strength of the VariAx interfaces was about 60% of Palmar 2.7 in both, static and dynamic loading. No dynamic testing was applied to the Viper plate because of its low ultimate strength. By static loading, an increase in screw locking angle caused a reduction of strength for the Palmar 2.7 and Viper locking interfaces. No influence was observed for the VariAx locking interfaces. During dynamic loading; angulation had no influence on the locking strength of Palmar 2.7. However, reduction of locking strength with increasing screw angulation was observed for VariAx. The strength of the polyaxial locking interfaces differs remarkably between the examined implants. Depending on the implant an increase of the screw locking angle causes a reduction of ultimate or fatigue strength, but not in all cases a significant impact was observed.

  5. A stand-alone tidal prediction application for mobile devices

    Science.gov (United States)

    Tsai, Cheng-Han; Fan, Ren-Ye; Yang, Yi-Chung

    2017-04-01

    It is essential for people conducting fishing, leisure, or research activities at the coasts to have timely and handy tidal information. Although tidal information can be found easily on the internet or using mobile device applications, this information is all applicable for only certain specific locations, not anywhere on the coast, and they need an internet connection. We have developed an application for Android devices, which allows the user to obtain hourly tidal height anywhere on the coast for the next 24 hours without having to have any internet connection. All the necessary information needed for the tidal height calculation is stored in the application. To develop this application, we first simulate tides in the Taiwan Sea using the hydrodynamic model (MIKE21 HD) developed by the DHI. The simulation domain covers the whole coast of Taiwan and the surrounding seas with a grid size of 1 km by 1 km. This grid size allows us to calculate tides with high spatial resolution. The boundary conditions for the simulation domain were obtained from the Tidal Model Driver of the Oregon State University, using its tidal constants of eight constituents: M2, S2, N2, K2, K1, O1, P1, and Q1. The simulation calculates tides for 183 days so that the tidal constants for the above eight constituents of each water grid can be extracted by harmonic analysis. Using the calculated tidal constants, we can predict the tides in each grid of our simulation domain, which is useful when one needs the tidal information for any location in the Taiwan Sea. However, for the mobile application, we only store the eight tidal constants for the water grids on the coast. Once the user activates the application, it reads the longitude and latitude from the GPS sensor in the mobile device and finds the nearest coastal grid which has our tidal constants. Then, the application calculates tidal height variation based on the harmonic analysis. The application also allows the user to input location and

  6. Admiralty Inlet Pilot Tidal Project Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Collar, Craig [Public Utility District No. 1 of Snohomish County, Everett, WA (United States)

    2015-09-14

    This document represents the final report for the Admiralty Inlet Pilot Tidal Project, located in Puget Sound, Washington, United States. The Project purpose was to license, permit, and install a grid-connected deep-water tidal turbine array (two turbines) to be used as a platform to gather operational and environmental data on tidal energy generation. The data could then be used to better inform the viability of commercial tidal energy generation from technical, economic, social, and environmental standpoints. This data would serve as a critical step towards the responsible advancement of commercial scale tidal energy in the United States and around the world. In late 2014, Project activities were discontinued due to escalating costs, and the DOE award was terminated in early 2015. Permitting, licensing, and engineering design activities were completed under this award. Final design, deployment, operation, and monitoring were not completed. This report discusses the results and accomplishments achieved under the subject award.

  7. Confusion around the tidal force and the centrifugal force

    CERN Document Server

    Matsuda, Takuya; Boffin, Henri M J

    2015-01-01

    We discuss the tidal force, whose notion is sometimes misunderstood in the public domain literature. We discuss the tidal force exerted by a secondary point mass on an extended primary body such as the Earth. The tidal force arises because the gravitational force exerted on the extended body by the secondary mass is not uniform across the primary. In the derivation of the tidal force, the non-uniformity of the gravity is essential, and inertial forces such as the centrifugal force are not needed. Nevertheless, it is often asserted that the tidal force can be explained by the centrifugal force. If we literally take into account the centrifugal force, it would mislead us. We therefore also discuss the proper treatment of the centrifugal force.

  8. The effect of beach slope on tidal influenced saltwater intrusion

    Science.gov (United States)

    Zhao, Z.; Shen, C.; Jin, G.; Xin, P.; Hua, G.; Tao, X.; Zhao, J.

    2015-12-01

    Beach slope changes the tidal induced saltwater-freshwater circulations in coastal aquifers. However, the effect of beach slope on tidal influenced saltwater-freshwater mixing process is far from understood. Based on sand flume experiments and numerical simulations, we investigated the intrusion process of saltwater into freshwater under tidal forcing and variable beach slopes. The sand flume experiment results show that milder slope induces larger upper saline plume (USP) and seaward salt wedge interface (SWI) under tidal forcing. While, the steady state SWI keeps stagnant with different beach slopes. Consistent with the previous research, our numerical simulations also show a lager flux exchange across the milder beach induced by the tidal fluctuations. The groundwater table fluctuates more intensify with deeper beach slope. The next step of our study will pay attention to the effect of beach slope on the instability of USP which induces the salt-fingering flow.

  9. A new high resolution tidal model in the arctic ocean

    DEFF Research Database (Denmark)

    Cancet, M.; Andersen, Ole Baltazar; Lyard, F.

    The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence......-growing maritime and industrial activities in this region. NOVELTIS and DTU Space have developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of the CryoSat Plus for Ocean (CP4O) ESA project. In particular, this atlas benefits from the assimilation of the most complete satellite...... for assimilation and validation. This paper presents the performances of this new regional tidal model in the Arctic Ocean, compared to the existing global tidal models....

  10. The interaction of tidal advection, diffusion and mussel filtration in a tidal channel

    Science.gov (United States)

    Simpson, John H.; Berx, Barbara; Gascoigne, Joanna; Saurel, Camille

    2007-12-01

    Time series measurements of flow and pigment concentrations (Chl) in the Menai Strait have revealed that the strong residual flow in a tidal channel (˜ 500 m 3 s - 1 ) transports phytoplankton from the open sea into the channel where much of it is consumed by suspension feeders, mainly in commercial beds of Mytilus edulis. The progressive depletion of phytoplankton along the channel results in a strong horizontal gradient of plankton and hence Chl. Tidal displacement of this gradient causes large (± 50% of mean) oscillations of Chl in the vicinity of the mussel beds. Vertical mixing by the strong tidal flows is sufficiently vigorous for most of the tidal cycle to ensure that downward diffusion can resupply the near-bed layer although there are indications of some transient depletion around slack water. This paradigm of the interaction of advection, diffusion and filtration determining the distribution of plankton and its supply to mussels has been encapsulated in a series of simple models forced only by boundary values. In the first, a 1-D model of tidal flow in the channel reproduces the principal features of the observed currents including the unusually large spatial change in phase of the currents and the variation of the residual transport with tidal range. The flow field from this physical model is used to drive a second model based on the advection diffusion equation for Chl with a source at the Irish Sea boundary and a sink over the mussel bed. This model illustrates the formation of a strong Chl gradient along the channel and simulates the amplitude and phase of the M 2 oscillations of Chl and the development of the M 4 variation apparent in the observations. This second model has been extended to 2-D over the mussel beds to allow investigation of the effects of water column mixing. The model indicates that only for a short period (˜ 30 min), close to slack water, is mixing sufficiently reduced to permit the development of a depletion boundary layer and

  11. Perbandingan Konsepsi Epistemologi Empirisisme Ibnu Taymiyyah dan John Locke

    National Research Council Canada - National Science Library

    Rido Kurnianto

    2014-01-01

    This paper examined the epistemological empiricism conception of Ibn Taimiyyah and John Locke based on the comparative analysis to obtain the complete description of epistemological empiricism thought...

  12. Coherent polarization locking with near-perfect combining efficiency.

    Science.gov (United States)

    Phua, P B; Lim, Yuan Liang

    2006-07-15

    We demonstrate the coherent locking of two orthogonal polarized lasers by using polarization selective loss. The two orthogonal polarizations are locked coherently to produce a resultant polarization state that sees minimal cavity loss. In contrast to the Michelson locking schemes, our scheme has the advantage of easy tunability, which helps to routinely achieve near-perfect (>99%) combining efficiency even when the power of the two arms is highly imbalanced and is varied from a power ratio of unity to >5. We also demonstrate an interesting phenomenon in which a miniscule injection of an antiphase field component from one arm into another can significantly inhibit the locking mechanism.

  13. Tidal and subtidal hydrodynamics and energetics in a constricted estuary

    Science.gov (United States)

    Zarzuelo, Carmen; López-Ruiz, Alejandro; Díez-Minguito, Manuel; Ortega-Sánchez, Miguel

    2017-02-01

    The dynamics of coastal plain estuaries are mainly associated with variable tidal forcing and local winds in combination with bathymetric complexity and coastline irregularity. Specific features, such as constricted areas, can potentially affect and energize the hydrodynamics of these types of systems. Particularly, tidal range and tidal currents can be significantly amplified where the incoming tidal wave becomes constricted. In this work, the impact of a narrow constriction on a mesotidal estuary was analysed at tidal and subtidal time scales. Tidal hydrodynamics, energy fluxes and energy dissipation were determined for the entire Cádiz Bay (southwestern Spain) using the Delft3D numerical model. Field observations were used to analyse tidal propagation and energy dissipation along the bay constriction and to calibrate and test the numerical model. The results indicate that the presence of the constriction transformed and distorted the tide and increased the tidal range and flow velocities along the channel, with implications on energy dissipation. The tidal currents were oriented along-channel at the central part of the constriction, although abrupt bathymetric changes at the channel inner boundary provoked a sudden rotation of the flow. Although the energy fluxes were higher for spring tides and were strongly influenced by winds, the energy dissipation was controlled by bed shear stresses and vertical dispersion. The significance of this energy dissipation was that it destabilized the water column, which resulted in a weakly stratified system with implications on water quality. At a subtidal scale, the residual water volume exchange was the result of the combined effects of the neap/spring tides, wind and waves, whereas tides were dominant at the tidal scale.

  14. A process study of the interaction of tidal currents, tidal mixing and density gradients in a region of freshwater influence

    Science.gov (United States)

    Xing, Jiuxing; Chen, Shengli

    2017-08-01

    A three dimensional unstructured grid model of the west coast of Britain is used to study the process of the interaction of tidal currents, tidal mixing and density gradient in the Liverpool Bay region. Calculations with M2 tidal forcing and omitting freshwater discharge show that tidal currents in the region are strong (of order 1 ms- 1), with tidal current ellipses essentially rectilinear in the surface and bottom. In the absence of tidal forcing, the freshwater is confined to a thin surface layer. With the inclusion of tidal mixing the surface layer thickens, and in the shallow water area mixed layer occupies the whole water depth. This has a significant effect of reducing its lateral spread. A detailed study of time series of velocity, salinity and turbulence reveals that at flood tide, more saline water is advected into the coastal region and rapid vertical mixing occurs, whereas at ebb tide, fresher water is advected over more saline water. The induced strong pycnocline uncouples surface and bottom layers leading to more circular tidal ellipses which rotate in opposite directions in the vertical, as found in observations. The three dimensional nature of the model reveals that this process involves both horizontal and vertical density gradients, and shows significant horizontal variability in the Liverpool Bay region.

  15. Three-dimensional semi-idealized model for tidal motion in tidal estuaries: an application to the Ems estuary

    NARCIS (Netherlands)

    Kumar, Mohit; Schuttelaars, H.M.; Roos, P.C.; Möller, M.

    2016-01-01

    In this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the firs

  16. Interior Structure and Tidal Response of Mercury

    Science.gov (United States)

    Steinke, Teresa; Sohl, Frank; Hussmann, Hauke; Knapmeyer, Martin; Wagner, Frank Walter

    2013-04-01

    Recent determinations of Mercury's mean density, polar moment of inertia factor, and the inertia of its solid outer shell provide strong constraints on the radius of its liquid core. We present an ensemble of spherically symmetric interior structure models that all satisfy the observational constraints. The models consist of a pure iron solid inner core, a liquid Fe-FeS outer core, a peridotite mantle and a crust predominantly composed of plagioclase. The sulfur content in the outer core, the iron and magnesium content of the mantle, and the crustal thickness vary throughout the ensemble. Comparison of observed and predicted moments of inertia yields admissible ranges for the outer core radius and the mantle density. From this model ensemble we derive geophysical observables that would allow further constraining the interior structure of Mercury in future experiments. The moment of inertia constraints allow for both forsterite and fayalite rich mantle compositions. Variations of mantle density trade off with crustal thickness and core composition. This non-uniqueness could be resolved using seismic travel time observations: since the P wave velocity of a fayalite mantle is significantly lower than that of the plagioclase-rich crust, a shadow zone arises as a clear discriminant between the two end-member compositions. The planet's response to solar tidal forcing strongly depends on its interior structure and rheological properties and can be parameterized in terms of the surface body tide Love numbers k2 and h2, respectively. We employ the frequency-dependent Maxwell rheology to calculate the body tide Love numbers for the main tidal period (87.97 days) using the density, rigidity and viscosity profiles of our structural models. We obtain values between 0.38 and 0.65 for k2 and between 0.70 and 1.12 for h2, respectively, thereby indicating the substantial tidal response of Mercury's interior. Furthermore we find that, via viscosity and rigidity, both k2 and h2 are

  17. Ultraviolet Spectroscopy of Tidal Disruption Flares

    Science.gov (United States)

    Cenko, Stephen B.

    2017-08-01

    When a star passes within the sphere of disruption of a massive black hole, tidal forces will overcome self-gravity and unbind the star. While approximately half of the stellar debris is ejected at high velocities, the remaining material stays bound to the black hole and accretes, resulting in a luminous, long-lived transient known as a tidal disruption flare (TDF). In addition to serving as unique laboratories for accretion physics,TDFs offer the hope of measuring black hole masses in galaxies much too distant for resolved kinematic studies.In order to realize this potential, we must better understand the detailed processes by which the bound debris circularizes and forms an accretion disk. Spectroscopy is critical to this effort, as emission and absorption line diagnostics provide insight into the location and physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). UV spectra are particularly critical, as most strong atomic features fall in this bandpass, and high-redshift TDF discoveries from LSST will sample rest-frame UV wavelengths.Here I present recent attempts to obtain UV spectra of tidal disruption flares. I describe the UV spectrum of ASASSN-14li, in which we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (2000-8000 km s-1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by 250-400 km s-1. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will

  18. Lock Wall Expedient Repair Demonstration Monitoring, John T. Myers Locks and Dam, Ohio River

    Science.gov (United States)

    2011-10-01

    reinforced polymer composites for making repairs to hydraulic navigation structures. At the time of publication of this report, COL Kevin J. Wilson...thermoplastic guide wall and deck floating pontoon at the Port Allen navigation lock in Louisiana, (e) tongue and groove vertical plank walls, (f

  19. Low-power wide-locking-range injection-locked frequency divider for OFDM UWB systems

    Energy Technology Data Exchange (ETDEWEB)

    Yin Jiangwei; Li Ning; Zheng Renliang; Li Wei; Ren Junyan, E-mail: lining@fudan.edu.c [State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203 (China)

    2009-05-01

    This paper describes a divide-by-two injection-locked frequency divider (ILFD) for frequency synthesizers as used in multiband orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) systems. By means of dual-injection technique and other conventional tuning techniques, such as DCCA and varactor tuning, the divider demonstrates a wide locking range while consuming much less power. The chip was fabricated in the Jazz 0.18 mum RF CMOS process. The measurement results show that the divider achieves a locking range of 4.85 GHz (6.23 to 11.08 GHz) at an input power of 8 dBm. The core circuit without the test buffer consumes only 3.7 mA from a 1.8 V power supply and has a die area of 0.38 x 0.28 mm{sup 2}. The wide locking range combined with low power consumption makes the ILFD suitable for its application in UWB systems.

  20. Advanced frequency synthesis by phase lock

    CERN Document Server

    Egan, William F

    2011-01-01

    "An addendum to the popular Frequency Synthesis by Phase Lock, 2nd ed, this book describes sigma-delta, a frequency synthesis technique that has gained prominence in recent years. In addition, Simulink will be employed extensively to guide the reader. Fractional-n, the still-used forerunner to sigma-delta, is also discussed. Sequences of simulated results allow the reader to gain a deeper understanding while detailed appendices provide information from various stages of development. Simulation models discussed in the chapters that are available online."--Provided by publisher.