scholarly journals Third-Body Perturbation in the Case of Elliptic Orbits for the Disturbing Body

2008 ◽  
Vol 2008 ◽  
pp. 1-14 ◽  
Author(s):  
R. C. Domingos ◽  
R. Vilhena de Moraes ◽  
A. F. Bertachini De Almeida Prado
Keyword(s):  
Numerical Study ◽  
Orbital Elements ◽  
Third Body ◽  
Smooth Curves ◽  
The Earth ◽  
Elliptic Orbits ◽  
Time Period ◽  
Long Time ◽  
The Mean ◽  
The Stability

This work presents a semi-analytical and numerical study of the perturbation caused in a spacecraft by a third-body using a double averaged analytical model with the disturbing function expanded in Legendre polynomials up to the second order. The important reason for this procedure is to eliminate terms due to the short periodic motion of the spacecraft and to show smooth curves for the evolution of the mean orbital elements for a long-time period. The aim of this study is to calculate the effect of lunar perturbations on the orbits of spacecrafts that are traveling around the Earth. An analysis of the stability of near-circular orbits is made, and a study to know under which conditions this orbit remains near circular completes this analysis. A study of the equatorial orbits is also performed.

scholarly journals On the Causes of Palaeoclimatic Variations and of the Ice Ages in Particular

1953 ◽  
Vol 2 (13) ◽  
pp. 213-218
Author(s):  
E. J. Öpik
Keyword(s):  
Nuclear Reactions ◽  
Gas Diffusion ◽  
Seasonal Temperature ◽  
The Sun ◽  
Orbital Elements ◽  
Ice Ages ◽  
Solar Mass ◽  
The Earth ◽  
Change In The Mean ◽  
The Mean

AbstractA method of quantitative climatological analysis is developed by applying the principle of geometric similarity to the convective heat transport, which is assumed to vary with the 1.5 power of temperature difference. The method makes possible the calculation of the change in the mean annual, or seasonal temperature, produced by a variation in insolation, cloudiness, snow cover, etc.It is shown that the variations in the orbital elements of the earth cannot account for the phenomena of the ice ages; the chronology of the Quaternary, based on these variations, has no real foundation.Palaeoclimatic variations are most probably due to variations of solar luminosity. These can be traced to periodical re-adjustments in the interior of the sun, produced by an interplay between nuclear reactions and gas diffusion, repeating themselves after some 250 million years. Complications from the outer envelope of the sun lead to additional fluctuations of a shorter period, of the order of 100,000 years to be identified with the periodical advance and retreat of the glaciers during the Quaternary.Calculations of the variations of luminosity in a star of solar mass substantiate this hypothesis.

scholarly journals Numerical study of fractional nonlinear Schrödinger equations

2014 ◽  
Vol 470 (2172) ◽  
pp. 20140364 ◽  
Author(s):  
Christian Klein ◽  
Christof Sparber ◽  
Peter Markowich
Keyword(s):  
Fractional Laplacian ◽  
Blow Up ◽  
Numerical Study ◽  
One Dimensional ◽  
Time Dynamics ◽  
Nonlinear Schrödinger ◽  
Stability And Instability ◽  
Long Time ◽  
The Stability ◽  
Fractional Nonlinear Schrödinger Equation

Using a Fourier spectral method, we provide a detailed numerical investigation of dispersive Schrödinger-type equations involving a fractional Laplacian in an one-dimensional case. By an appropriate choice of the dispersive exponent, both mass and energy sub- and supercritical regimes can be identified. This allows us to study the possibility of finite time blow-up versus global existence, the nature of the blow-up, the stability and instability of nonlinear ground states and the long-time dynamics of solutions. The latter is also studied in a semiclassical setting. Moreover, we numerically construct ground state solutions of the fractional nonlinear Schrödinger equation.

Low selenocentric orbits stability analysis

2020 ◽  
Author(s):  
Chongrui Du ◽  
O.L. Starinova
Keyword(s):  
Rate Of Change ◽  
The Sun ◽  
Space Systems ◽  
The Moon ◽  
Orbital Structure ◽  
Motion Modeling ◽  
The Earth ◽  
Long Time ◽  
The Stability

The tasks of studying the Moon require long-term functioning space systems. Most of the low selenocentric orbits are known to be unstable, which requires a propellant to maintain the orbital structure. For these orbits, the main disturbing factors are the off-center gravitational field of the Moon and the gravity of the Earth and the Sun. This paper analyzes the stability of low selenocentric orbits according to passive motion modeling and takes into account these main disturbing factors. We put forward a criterion for determining the stability of the orbit and used it to analyze the circular orbit of the Moon at an altitude of 100 kilometers. According to different initial data and different dates, we obtained ranges of the Moon’s orbits with good stability. At the same time, we analyzed the rate of change in the longitude of the ascending node, and found a stable low lunar orbit which can operate for a long time.

Thermal effects on the figure of the Moon

1967 ◽  
Vol 296 (1446) ◽  
pp. 266-269 ◽  
Keyword(s):  
Thermal Effects ◽  
Hydrostatic Equilibrium ◽  
Moment Of Inertia ◽  
The Moon ◽  
Moments Of Inertia ◽  
The Earth ◽  
Principal Moments Of Inertia ◽  
Long Time ◽  
The Stability ◽  
Lunar Rotation

Before discussing its cause, one must be clear in exactly what respect the lunar figure deviates from the equilibrium one. This is necessary because there has been confusion over the question for a long time. It was known early that the Moon’s ellipsoid of inertia is triaxial and that the differences of the principal moments of inertia determined from observations are several times larger than the theoretical values corresponding to hydrostatic equilibrium. The stability of lunar rotation requires that the axis of least moment of inertia point approximately towards the Earth and the laws of Cassini show that it is really so.

scholarly journals Time scale of ovarian maturation in Greenland halibut (Reinhardtius hippoglossoides, Walbaum)

2003 ◽  
Vol 60 (4) ◽  
pp. 767-773 ◽  
Author(s):  
S Junquera ◽  
E Román ◽  
J Morgan ◽  
M Sainza ◽  
G Ramilo
Keyword(s):  
Ovarian Development ◽  
Data Series ◽  
Development Phase ◽  
Greenland Halibut ◽  
Annual Basis ◽  
Time Period ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
Long Time ◽  
The Mean ◽  
One Year

Abstract Evidence for a prolonged ovarian development phase in Greenland halibut is presented. The reproductive cycle in this species was originally described based on the assumption that this phase should last about one year. The results of the present study, which involves data series covering a long time period and different geographic areas, show instead that there is more than one year between the mean age of the females that are at the onset of ovarian development and the mean age of the females that are actually spawning. There are two possible interpretations for this observation. One is that the ovarian development phase (vitellogenesis) could last more than one year and thus as a consequence, individual spawning would not necessarily occur on an annual basis. The other would be the existence of a high proportion of non-spawning females every year for other reasons not related with the natural rhythm of oocyte development.

scholarly journals Long time frames to detect the impact of changing COVID-19 measures, Canada, March to July 2020

2021 ◽  
Vol 26 (40) ◽  
Author(s):  
Jessica E Stockdale ◽  
Renny Doig ◽  
Joosung Min ◽  
Nicola Mulberry ◽  
Liangliang Wang ◽  
...  
Keyword(s):  
Population Level ◽  
Time Frame ◽  
Control Measures ◽  
Type Model ◽  
Time Period ◽  
Long Time ◽  
The Mean ◽  
Reported Data ◽  
Time Frames ◽  
The Impact

Background Many countries have implemented population-wide interventions to control COVID-19, with varying extent and success. Many jurisdictions have moved to relax measures, while others have intensified efforts to reduce transmission. Aim We aimed to determine the time frame between a population-level change in COVID-19 measures and its impact on the number of cases. Methods We examined how long it takes for there to be a substantial difference between the number of cases that occur following a change in COVID-19 physical distancing measures and those that would have occurred at baseline. We then examined how long it takes to observe this difference, given delays and noise in reported cases. We used a susceptible-exposed-infectious-removed (SEIR)-type model and publicly available data from British Columbia, Canada, collected between March and July 2020. Results It takes 10 days or more before we expect a substantial difference in the number of cases following a change in COVID-19 control measures, but 20–26 days to detect the impact of the change in reported data. The time frames are longer for smaller changes in control measures and are impacted by testing and reporting processes, with delays reaching ≥ 30 days. Conclusion The time until a change in control measures has an observed impact is longer than the mean incubation period of COVID-19 and the commonly used 14-day time period. Policymakers and practitioners should consider this when assessing the impact of policy changes. Rapid, consistent and real-time COVID-19 surveillance is important to minimise these time frames.

scholarly journals On the Causes of Palaeoclimatic Variations and of the Ice Ages in Particular

1953 ◽  
Vol 2 (13) ◽  
pp. 213-218 ◽  
Author(s):  
E. J. Öpik
Keyword(s):  
Nuclear Reactions ◽  
Gas Diffusion ◽  
Seasonal Temperature ◽  
The Sun ◽  
Orbital Elements ◽  
Ice Ages ◽  
Solar Mass ◽  
The Earth ◽  
Change In The Mean ◽  
The Mean

Abstract A method of quantitative climatological analysis is developed by applying the principle of geometric similarity to the convective heat transport, which is assumed to vary with the 1.5 power of temperature difference. The method makes possible the calculation of the change in the mean annual, or seasonal temperature, produced by a variation in insolation, cloudiness, snow cover, etc. It is shown that the variations in the orbital elements of the earth cannot account for the phenomena of the ice ages; the chronology of the Quaternary, based on these variations, has no real foundation. Palaeoclimatic variations are most probably due to variations of solar luminosity. These can be traced to periodical re-adjustments in the interior of the sun, produced by an interplay between nuclear reactions and gas diffusion, repeating themselves after some 250 million years. Complications from the outer envelope of the sun lead to additional fluctuations of a shorter period, of the order of 100,000 years to be identified with the periodical advance and retreat of the glaciers during the Quaternary. Calculations of the variations of luminosity in a star of solar mass substantiate this hypothesis.

Stability bounds on turbulent Poiseuille flow

1988 ◽  
Vol 187 ◽  
pp. 435-449 ◽  
Author(s):  
G. R. Ierley ◽  
W. V. R. Malkus
Keyword(s):  
Reynolds Number ◽  
Reynolds Stress ◽  
Poiseuille Flow ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Linear Instability ◽  
Mean Flow ◽  
Starting Point ◽  
The Mean ◽  
The Stability

For steady-state turbulent flows with unique mean properties, we determine a sense in which the mean velocity is linearly supercritical. The shear-turbulence literature on this point is ambiguous. As an example, we reassess the stability of mean profiles in turbulent Poiseuille flow. The Reynolds & Tiederman (1967) numerical study is used as a starting point. They had constructed a class of one-dimensional flows which included, within experimental error, the observed profile. Their numerical solutions of the resulting Orr-Sommerfeld problems led them to conclude that the Reynolds number for neutral infinitesimal disturbances was twenty-five times the Reynolds number characterizing the observed mean flow. They found also that the first nonlinear corrections were stabilizing. In the realized flow, this latter conclusion appears incompatible with the former. Hence, we have sought a more complete set of velocity profiles which could exhibit linear instability, retaining the requirement that the observed velocity profile is included in the set. We have added two dynamically generated modifications of the mean. The first addition is a fluctuation in the curvature of the mean flow generated by a Reynolds stress whose form is determined by the neutrally stable Orr-Sommerfeld solution. We find that this can reduce the stability of the observed flow by as much as a factor of two. The second addition is the zero-average downstream wave associated with the above Reynolds stress. The three-dimensional linear instability of this modification can even render the observed flow unstable. Those wave amplitudes that just barely will ensure instability of the observed flow are determined. The relation of these particular amplitudes to the limiting conditions admitted by an absolute stability criterion for disturbances on the mean flow is found. These quantitative results from stability theory lie in the observationally determined Reynolds-Tiederman similarity scheme, and hence are insensitive to changes in Reynolds number.

scholarly journals Aphakia korrekciója irisklip műlencse retropupillaris beültetésével

2017 ◽  
Vol 158 (1) ◽  
pp. 20-24
Author(s):  
Antal Szabó ◽  
András Papp ◽  
Ágnes Borbándy ◽  
Zsuzsanna D. Géhl ◽  
Zoltán Zsolt Nagy ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Intraocular Lens ◽  
Secondary Procedure ◽  
Medical Optics ◽  
Corrected Visual Acuity ◽  
Time Period ◽  
The Mean ◽  
The Stability ◽  
Best Corrected Visual Acuity

Abstract: Introduction and aim: The correction of aphakia might be a challenge for the surgeon. The aim of this study is to describe the authors’ experience with the implantation of the retropupillary iris clip intraocular lens. Method: Patients between January 2014 and December 2015 were included in the retrospective study. Retropupillary implantation of iris clip intraocular lens VRSA 54 (AMO Advanced Medical Optics, USA) was performed in all cases. The minimum follow up period was three months. The stability of the intraocular lens and the intraoperative and postoperative complications and the visual acuity were evaluated. Results: During this time period 11 cases (1 female, 10 males) were included in the study. The mean age at the time of the implantation was 57.7 years (between 25–74 years). In 4 cases the iris clip lens was implanted during the first intervention, in 7 cases during the secondary procedure. In all cases the lens was fixated onto the iris posteriorly. The best corrected visual acuity before the iris clip implantation was 0.43 (0.1–1.0) and postoperatively at the time of the follow up 0.49 (0.04–1.0). Conclusions: With the use of the retropupillary implanted iris clip intraocular lens all of the patients could have been rehabilitated without major complications. Orv. Hetil., 2017, 158(1), 20–24.

scholarly journals MEMBANGUN MODEL PENYEBARAN PENYAKIT AKIBAT ASAP KEBAKARAN HUTAN

2018 ◽  
Vol 15 (1) ◽  
pp. 36-47
Author(s):  
B Kurniawan ◽  
R Ratianingsih ◽  
Hajar Hajar
Keyword(s):  
Critical Points ◽  
Forest Fires ◽  
Disease Spread ◽  
Asymptotically Stable ◽  
Short Time Period ◽  
Time Period ◽  
Long Time ◽  
The Stability ◽  
Short Time ◽  
Threshold Point

Forest fires impact a very serious problem because it could cause health problem, especially respiratory disease such as (ISPA), Asthma and Bronchitis. The study of the health disorders is conducted by consider mathematicaly the spread of disease due to forest fires smoke. The model is constructed by devide the human population into six subpopulations, that is vulnerable S(t), exposed E(t), Asthma infected A(t), Bronchitis infected B(t) and recovered R(t).The governed model is analyted at every critical points using Routh-Hurwitz method. The results gives two critical points that describe a free disease conditions ( ) and an endemic conditions ( ). A stabil ( ) is occured if  and  where the threshold point of the stability is expressed as  and   . Endemic conditions  will be asymptotically stable when  and  with  . The condition of free disease of forest fires is occured in a long time period, while the endemic conditions is occurred in a short time period. It could be interpreted that the disease spread due to the forest fires smoke is not easy to overcome.

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