scholarly journals EFFECTS OF STANDARD AND MODIFIED GRAVITY ON INTERPLANETARY RANGES

2011 ◽  
Vol 20 (02) ◽  
pp. 181-232 ◽  
Author(s):  
L. IORIO
Keyword(s):  
Initial Conditions ◽  
A Priori ◽  
Earth Planet ◽  
General Relativistic ◽  
Heliocentric Orbits ◽  
Newtonian Constant ◽  
The Impact ◽  
Very High ◽  
Better Than

We numerically investigate the impact on the two-body range of several Newtonian and non-Newtonian dynamical effects for some Earth-planet (Mercury, Venus, Mars, Jupiter, Saturn) pairs, in view of the expected cm-level accuracy in some future planned or proposed interplanetary ranging operations. The general relativistic gravitomagnetic Lense–Thirring effect should be modeled and solved for in future accurate ranging tests of Newtonian and post-Newtonian gravity, because it falls within their measurability domain. It could a priori "imprint" the determination of some of the target parameters of the tests considered. Moreover, the ring of the minor asteroids, Ceres, Pallas, Vesta (and also many other asteroids if Mars is considered) and the trans-Neptunian objects (TNOs) act as sources of nonnegligible systematic uncertainty on the larger gravitoelectric post-Newtonian signals from which it is intended to determine the parameters γ and β of the parametrized post-Newtonian (PPN) formalism with very high precision (several orders of magnitude better than the current 10-4–10-5levels). Also, other putative, nonconventional gravitational effects, like a violation of the strong equivalence principle (SEP), a secular variation of the Newtonian constant of gravitation G, and the Pioneer anomaly, are considered. The presence of a hypothetical, distant planetary-sized body X could be detectable with future high-accuracy planetary ranging. Our analysis can, in principle, be extended to future interplanetary ranging scenarios in which one or more spacecrafts in heliocentric orbits are involved. The impact of fitting the initial conditions, and of the noise in the observations, on the actual detectability of the dynamical signatures investigated, which may be partly absorbed in the estimation process, should be quantitatively addressed in further studies.

scholarly journals Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)

2018 ◽  
Vol 618 ◽  
pp. A116 ◽  
Author(s):  
J. Prieto-Arranz ◽  
E. Palle ◽  
D. Gandolfi ◽  
O. Barragán ◽  
E. W. Guenther ◽  
...  
Keyword(s):  
Planetary System ◽  
Initial Conditions ◽  
Dynamical Evolution ◽  
Space Mission ◽  
Mass Determination ◽  
Velocity Measurements ◽  
Orbital Periods ◽  
The Masses ◽  
Better Than

Context. Multiplanet systems are excellent laboratories to test planet formation models as all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (~30 pc) detected by NASA’s Kepler or K2 space mission. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with high-precision radial-velocity measurements gathered with the FIES, HARPS, and HARPS-N spectrographs we revised the system parameters and derive the masses of the three planets. Results. We find that GJ 9827 b has a mass of Mb = 3.69−0.46+0.48 M⊕ and a radius of Rb = 1.58−0.13+0.14 R⊕, yielding a mean density of ρb = 5.11−1.27+1.74 g cm−3. GJ 9827 c has a mass of Mc = 1.45−0.57+0.58 M⊕, radius of Rc = 1.24−0.11+0.11 R⊕, and a mean density of ρc = 4.13−1.77+2.31 g cm−3. For GJ 9827 d, we derive Md = 1.45−0.57+0.58 M⊕, Rd = 1.24−0.11+0.11 R⊕, and ρd = 1.51−0.53+0.71 g cm−3. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and sub-Neptunes. The planetary bulk compositions are compatible with a scenario where all three planets formed with similar core and atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its primordial atmosphere, owing to the much lower stellarirradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmosphericescape can be studied in detail for all planets, helping us to understand how compact systems form and evolve.

scholarly journals Sulfur dioxide layer height retrieval from Sentinel-5 Precursor/TROPOMI using FP_ILM

2019 ◽  
Vol 12 (10) ◽  
pp. 5503-5517 ◽  
Author(s):  
Pascal Hedelt ◽  
Dmitry S. Efremenko ◽  
Diego G. Loyola ◽  
Robert Spurr ◽  
Lieven Clarisse
Keyword(s):  
Sulfur Dioxide ◽  
Accurate Determination ◽  
Volcanic Eruptions ◽  
Critical Parameters ◽  
Layer Height ◽  
Learning Machine ◽  
The Impact ◽  
First Time ◽  
Better Than

Abstract. The accurate determination of the location, height, and loading of sulfur dioxide (SO2) plumes emitted by volcanic eruptions is essential for aviation safety. The SO2 layer height is also one of the most critical parameters with respect to determining the impact on the climate. Retrievals of SO2 plume height have been carried out using satellite UV backscatter measurements, but, until now, such algorithms are very time-consuming. We have developed an extremely fast yet accurate SO2 layer height retrieval using the Full-Physics Inverse Learning Machine (FP_ILM) algorithm. This is the first time the algorithm has been applied to measurements from the TROPOMI instrument onboard the Sentinel-5 Precursor platform. In this paper, we demonstrate the ability of the FP_ILM algorithm to retrieve SO2 plume layer heights in near-real-time applications with an accuracy of better than 2 km for SO2 total columns larger than 20 DU. We present SO2 layer height results for the volcanic eruptions of Sinabung in February 2018, Sierra Negra in June 2018, and Raikoke in June 2019, observed by TROPOMI.

The Road to Chaos by Time-Asymmetric Hebbian Learning in Recurrent Neural Networks

2007 ◽  
Vol 19 (1) ◽  
pp. 80-110 ◽  
Author(s):  
Colin Molter ◽  
Utku Salihoglu ◽  
Hugues Bersini
Keyword(s):  
Supervised Learning ◽  
Hebbian Learning ◽  
Learning Algorithm ◽  
Initial Conditions ◽  
A Priori ◽  
Computational Cost ◽  
Chaotic Regime ◽  
Dynamical Regime ◽  
New Form ◽  
The Impact

This letter aims at studying the impact of iterative Hebbian learning algorithms on the recurrent neural network's underlying dynamics. First, an iterative supervised learning algorithm is discussed. An essential improvement of this algorithm consists of indexing the attractor information items by means of external stimuli rather than by using only initial conditions, as Hopfield originally proposed. Modifying the stimuli mainly results in a change of the entire internal dynamics, leading to an enlargement of the set of attractors and potential memory bags. The impact of the learning on the network's dynamics is the following: the more information to be stored as limit cycle attractors of the neural network, the more chaos prevails as the background dynamical regime of the network. In fact, the background chaos spreads widely and adopts a very unstructured shape similar to white noise. Next, we introduce a new form of supervised learning that is more plausible from a biological point of view: the network has to learn to react to an external stimulus by cycling through a sequence that is no longer specified a priori. Based on its spontaneous dynamics, the network decides “on its own” the dynamical patterns to be associated with the stimuli. Compared with classical supervised learning, huge enhancements in storing capacity and computational cost have been observed. Moreover, this new form of supervised learning, by being more “respectful” of the network intrinsic dynamics, maintains much more structure in the obtained chaos. It is still possible to observe the traces of the learned attractors in the chaotic regime. This complex but still very informative regime is referred to as “frustrated chaos.”

Refined Modeling of Projectile Impact Onto Submerged Structure

2008 ◽  
Author(s):  
Justin Onisoru ◽  
Ovidiu Coman ◽  
Paul Wilson ◽  
George Thomas
Keyword(s):  
Strain Rate ◽  
Structural Integrity ◽  
Initial Conditions ◽  
Safety Issue ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Material Behavior ◽  
Spent Fuel ◽  
The Impact

Structural integrity of spent fuel racks is a critical safety issue in nuclear power stations. The standard approach of evaluating the effects of an impact projectile on a submerged structure, which constitute the start point of the current study, involves three main steps: determination of the conditions just prior to the impact (that are considered as initial conditions for the analysis), setting the mechanism of transferring energy from the projectile to the target structure, and determining how that energy is absorbed by the impacted structure. Usually, the dynamics of the projectile are ideally considered, the influence of the fluid presence is restricted to the determination of the impact velocity and strain rate dependency is limited to choosing a true stress vs. strain curve corresponding to some constant strain rate. Starting from the standard engineering approach, the authors have refined the model considering more realistic dynamics of the projectile, extending the influence of the fluid to the entire analysis and using a more accurate strain rate dependant material behavior. Explicit Finite Element analyses are used in order to incorporate the desired effects.

scholarly journals DOES CASSINI ALLOW ONE TO MEASURE RELATIVISTIC ORBITAL EFFECTS IN THE SATURNIAN SYSTEM OF SATELLITES?

2007 ◽  
Vol 16 (01) ◽  
pp. 11-17 ◽  
Author(s):  
LORENZO IORIO
Keyword(s):  
Data Sets ◽  
Zonal Harmonics ◽  
Low Degree ◽  
Saturnian System ◽  
Order Of Magnitude ◽  
General Relativistic ◽  
The Mean ◽  
Natural Satellites ◽  
The Impact

In this paper we address the following question: do the recent advances in the orbit determination of the major natural satellites of Saturn obtained with the analysis of the first data sets from the Cassini spacecraft allow to detect the general relativistic gravitoelectric orbital precessions of the mean longitudes of such moons? The answer is still negative. The present-day down-track accuracy is adequate for Mimas, Enceladus, Thetys, Dione, Rhea and Titan and inadequate for Hyperion, Iapetus and Phoebe. Instead, the size of the systematic errors induced by the mismodeling in the key parameters of the Saturnian gravitational field like the even zonal harmonics Jℓ are larger than the relativistic down-track shifts by about one order of magnitude, mainly for the inner satellites like Mimas, Enceladus, Thetys, Dione, Rhea, Titan and Hyperion. Instead, Iapetus and Phoebe are not notably affected by such kind of perturbations. Moreover, the bias due to the uncertainty in Saturn's GM is larger than the relativistic down-track effects for all such moons up to two orders of magnitude (Phoebe). Thus, it would be impossible to separately analyze the mean longitudes of each satellite. Proposed linear combinations of the satellites' mean longitudes would allow to cancel out the impact of the mismodeling in the low-degree even zonal harmonics and GM, but the combined down-track errors would be larger than the combined relativistic signatures by a factor 103.

scholarly journals Recent Helioseismological Results from Space: Solar p-mode Oscillations from IPHIR on the PHOBOS Mission

1990 ◽  
Vol 121 ◽  
pp. 279-288
Author(s):  
C. Fröhlich ◽  
T. Toutain ◽  
R.M. Bonnet ◽  
A.V. Bruns ◽  
J.P. Delaboudinière ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Accurate Determination ◽  
Spectral Irradiance ◽  
High Signal ◽  
Line Shapes ◽  
Solar Spectral Irradiance ◽  
Evaluation Of Data ◽  
Very High ◽  
Better Than

AbstractIPHIR (Interplanetary Helioseismology by IRradiance measurements) is a solar irradiance experiment on the USSR planetary mission PHOBOS to Mars and its satellite Phobos. The experiment was built by an international consortium including PMOD/WRC, LPSP, SSD/ESA, KrAO and CRIP. The sensor is a three channel sunphotometer (SPM) which measures the solar spectral irradiance at 335, 500 and 865 nm with a precision of better than 1 part-per-million (ppm). It is the first experiment dedicated to the investigation of solar oscillations from space. The results presented here are from a first evaluation of data gathered during 160 days of the cruise phase of PHOBOS II, launched on July, 12th 1988. The long uninterrupted observation produces a spectrum of the solar p-mode oscillations in the 5-minute range with a very high signal-to-noise ratio, which allows an accurate determination of frequencies and line shapes of these modes.

scholarly journals Irrigation Scheduling of Maize Grown on a Vertisol Soil Under Changing Climate of Sofia’s Field

2021 ◽  
Vol 24 (s1) ◽  
pp. 1-7
Author(s):  
Maria Ivanova ◽  
Zornitsa Popova
Keyword(s):  
Climate Adaptation ◽  
Irrigation Scheduling ◽  
Irrigation Season ◽  
Present Climate ◽  
Climate Conditions ◽  
The Past ◽  
The Impact ◽  
Very High ◽  
Irrigation Requirements

Abstract The purpose of this study is to evaluate the impact of climate uncertainties on maize irrigation requirements, grown on a Vertisol soil, Sofia’s field, Bulgaria. Through the validated WinIsareg model, four irrigation scheduling alternatives are simulated for the years of “very high“, “high“ and “average“ irrigation demands of past (1952–1984) and present (1970–2004) climate. Adaptation of irrigation scheduling to the present climate conditions during the “very dry“ years (P I ≤12%) consists of an extension of the irrigation season by 15–20 days and a need of additional irrigation relative to alternative 1 and two irrigation events at alternatives 2 and 3. During the past climate alternatives 2 and 3 led to savings of 30 mm of water, while up to the current climate conditions the three irrigations alternatives should provide 360 mm of irrigation water. To obtain maximum yields in “dry“ (P I = 12–30%) years, irrigation season should end by 05/09, as in the present climate, irrigation season has shifted about a week earlier for the three alternatives. In the “average“ (P I = 30–60%) years the adaptation consist in accurately determination of the last allowed date for irrigation.

Response of Viscoelastic Plate to Impact

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
D. Ingman ◽  
J. Suzdalnitsky
Keyword(s):  
Initial Conditions ◽  
Viscoelastic Plate ◽  
Servo Control ◽  
Order Function ◽  
Damping Decrement ◽  
Vibration Process ◽  
Alternative Approaches ◽  
The Impact ◽  
Fractional Differentiation Operator

Organization of product tests in the microelectronic and optical-electronic industries by the impact method is considered. Two mathematical models: a circular plate under dynamic loading with predetermined initial conditions, and contact interaction of a falling mass and a barrier, are examined. The deflection function, curvature, and acceleration are determined. As the series for these characteristics may prove divergent, the problem is to secure sufficiently reliable results. The method of impact mechanics permits determination of the duration and force of the impact, estimation of the total energy of each mode in the expansion of the deflection function and preclusion of divergent series when determining the plate acceleration and curvature during the vibration process. In parallel, viscoelasticity is simulated with the aid of a fractional-differentiation operator, certain features of which are discussed. Representation of this operator with time-dependent order by ones with constant orders is considered. Three alternative approaches for determination of the eigenfrequency and damping decrement of a vibration process are examined. In particular, a method for calculating these characteristics under conditions of time-dependence and servo control of the order function is proposed.

scholarly journals A Statistical Methodology for Determination of Safety Systems Actuation Setpoints Based on Extreme Value Statistics

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
D. R. Novog ◽  
P. Sermer
Keyword(s):  
Nuclear Reactor ◽  
Initial Conditions ◽  
General Concept ◽  
Extreme Value Statistics ◽  
Plant Responses ◽  
True Value ◽  
Time Changes ◽  
Safety Systems ◽  
The Impact

This paper provides a novel and robust methodology for determination of nuclear reactor trip setpoints which accounts for uncertainties in input parameters and models, as well as accounting for the variations in operating states that periodically occur. Further it demonstrates that in performing best estimate and uncertainty calculations, it is critical to consider the impact of all fuel channels and instrumentation in the integration of these uncertainties in setpoint determination. This methodology is based on the concept of a true trip setpoint, which is the reactor setpoint that would be required in an ideal situation where all key inputs and plant responses were known, such that during the accident sequence a reactor shutdown will occur which just prevents the acceptance criteria from being exceeded. Since this true value cannot be established, the uncertainties in plant simulations and plant measurements as well as operational variations which lead to time changes in the true value of initial conditions must be considered. This paper presents the general concept used to determine the actuation setpoints considering the uncertainties and changes in initial conditions, and allowing for safety systems instrumentation redundancy. The results demonstrate unique statistical behavior with respect to both fuel and instrumentation uncertainties which has not previously been investigated.

scholarly journals Frequently cocited publications: Features and kinetics

2020 ◽  
Vol 1 (3) ◽  
pp. 1223-1241
Author(s):  
Sitaram Devarakonda ◽  
James R. Bradley ◽  
Dmitriy Korobskiy ◽  
Tandy Warnow ◽  
George Chacko
Keyword(s):  
Power Law ◽  
A Priori ◽  
Extended Period ◽  
A Priori Estimate ◽  
Citation Network ◽  
Priori Estimate ◽  
Lognormal Distributions ◽  
The Impact ◽  
Very High ◽  
Over Time

Cocitation measurements can reveal the extent to which a concept representing a novel combination of existing ideas evolves towards a specialty. The strength of cocitation is represented by its frequency, which accumulates over time. Of interest is whether underlying features associated with the strength of cocitation can be identified. We use the proximal citation network for a given pair of articles ( x, y) to compute θ, an a priori estimate of the probability of cocitation between x and y, prior to their first cocitation. Thus, low values for θ reflect pairs of articles for which cocitation is presumed less likely. We observe that cocitation frequencies are a composite of power-law and lognormal distributions, and that very high cocitation frequencies are more likely to be composed of pairs with low values of θ, reflecting the impact of a novel combination of ideas. Furthermore, we note that the occurrence of a direct citation between two members of a cocited pair increases with cocitation frequency. Finally, we identify cases of frequently cocited publications that accumulate cocitations after an extended period of dormancy.

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