ANALYSIS OF THE IMPACT OF CELESTIAL BODIES ON DIFFERENCES IN MEASURED HEIGHT / DANGAUS KŪNŲ ĮTAKOS IŠMATUOTAM AUKŠČIŲ SKIRTUMUI TYRIMAS / АНАЛИЗ ВЛИЯНИЯ НЕБЕСНЫХ ТЕЛ НА ИЗМЕРЕННУЮ РАЗНИЦУ ВЫСОТ

2011 ◽  
Vol 37 (3) ◽  
pp. 101-104
Author(s):  
Darius Popovas
Keyword(s):  
High Precision ◽  
Lunar Phase ◽  
Height Difference ◽  
Correction Rate ◽  
Celestial Bodies ◽  
The Impact ◽  
Deflection Of Vertical

Under the effect of celestial bodies, the deflection of vertical induces changes in the levelled height difference. Therefore, it is necessary to evaluate the produced effect on high-precision levelling data. The article analyses the dependency of lunisolar correction on the lunar phase and azimuth of the levelling line and correction rate of changes. The paper also revises formulas for calculating lunisolar correction derived from using tide generating potential. Santrauka Straipsnyje analizuojama vertikalės nuokrypio dėl dangaus kūnų įtaka išmatuotam aukščių skirtumui. Šią įtaką būtina įvertinti apdorojant precizinės niveliacijos matavimų duomenis. Įvertinta potvynio pataisos priklausomumas nuo Mėnulio fazių ir niveliacijos linijos azimuto bei pataisos kitimo greitis. Taikant potvynio potencialo išraišką, gautos patikslintos išmatuoto aukščių skirtumo vertinimo formulės. Резюме Под влиянием небесных тел отклонение вертикали вызывает изменения в разнице высот, полученной нивелированием. Необходимо оценить этот эффект в данных высокоточной нивеляции. Были проанали зированы зависимость лунно-солнечных поправок от лунных фаз, азимута линии нивеляций и скорости изменения поправки. Получены уточненные формулы для расчета лунно-солнечной поправки с использованием приливного потенциала.

scholarly journals Relativistic aspects of rotational motion of celestial bodies

2009 ◽  
Vol 5 (S261) ◽  
pp. 112-123 ◽  
Author(s):  
S. A. Klioner ◽  
E. Gerlach ◽  
M. H. Soffel
Keyword(s):  
High Precision ◽  
Rotational Motion ◽  
Earth Rotation ◽  
Theoretical Framework ◽  
Reference Systems ◽  
The Moon ◽  
Newtonian Theory ◽  
Recent Developments ◽  
Celestial Bodies ◽  
Near Future

AbstractRelativistic modelling of rotational motion of extended bodies represents one of the most complicated problems of Applied Relativity. The relativistic reference systems of IAU (2000) give a suitable theoretical framework for such a modelling. Recent developments in the post-Newtonian theory of Earth rotation in the limit of rigidly rotating multipoles are reported below. All components of the theory are summarized and the results are demonstrated. The experience with the relativistic Earth rotation theory can be directly applied to model the rotational motion of other celestial bodies. The high-precision theories of rotation of the Moon, Mars and Mercury can be expected to be of interest in the near future.

scholarly journals Expected performances of the Characterising Exoplanet Satellite (CHEOPS)

2020 ◽  
Vol 635 ◽  
pp. A22 ◽  
Author(s):  
A. Deline ◽  
D. Queloz ◽  
B. Chazelas ◽  
M. Sordet ◽  
F. Wildi ◽  
...  
Keyword(s):  
Light Curve ◽  
High Precision ◽  
Background Level ◽  
Monte Carlo Algorithm ◽  
Complete Analysis ◽  
Transiting Planets ◽  
End To End ◽  
Set Up ◽  
The Impact

Context. The characterisation of Earth-size exoplanets through transit photometry has stimulated new generations of high-precision instruments. In that respect, the Characterising Exoplanet Satellite (CHEOPS) is designed to perform photometric observations of bright stars to obtain precise radii measurements of transiting planets. The CHEOPS instrument will have the capability to follow up bright hosts provided by radial-velocity facilities. With the recent launch of the Transiting Exoplanet Survey Satellite (TESS), CHEOPS may also be able to confirm some of the long-period TESS candidates and to improve the radii precision of confirmed exoplanets. Aims. The high-precision photometry of CHEOPS relies on careful on-ground calibration of its payload. For that purpose, intensive pre-launch campaigns of measurements were carried out to calibrate the instrument and characterise its photometric performances. This work reports on the main results of these campaigns. It provides a complete analysis of data sets and estimates in-flight photometric performance by means of an end-to-end simulation. Instrumental systematics were measured by carrying out long-term calibration sequences. Using an end-to end model, we simulated transit observations to evaluate the impact of in-orbit behaviour of the satellite and to determine the achievable precision on the planetary radii measurement. Methods. After introducing key results from the payload calibration, we focussed on the data analysis of a series of long-term measurements of uniformly illuminated images. The recorded frames were corrected for instrumental effects and a mean photometric signal was computed on each image. The resulting light curve was corrected for systematics related to laboratory temperature fluctuations. Transit observations were simulated, considering the payload performance parameters. The data were corrected using calibration results and estimates of the background level and position of the stellar image. The light curve was extracted using aperture photometry and analysed with a transit model using a Markov chain Monte Carlo algorithm. Results. In our analysis, we show that the calibration test set-up induces thermally correlated features in the data that can be corrected in post-processing to improve the quality of the light curves. We find that on-ground photometric performances of the instrument measured after this correction is of the order of 15 parts per million over five hours. Using our end-to-end simulation, we determine that measurements of planet-to-star radii ratio with a precision of 2% for a Neptune-size planet transiting a K-dwarf star and 5% for an Earth-size planet orbiting a Sun-like star are possible with CHEOPS. These values correspond to transit depths obtained with signal-to-noise ratios of 25 and 10, respectively, allowing the characterisation and detection of these planets. The pre-launch CHEOPS performances are shown to be compliant with the mission requirements.

A Fusion Navigation of Double Laser Radar for Intelligent Vehicle

2011 ◽  
Vol 346 ◽  
pp. 711-718 ◽  
Author(s):  
Li Xia Meng ◽  
Fu Chun Sun ◽  
Hua Ping Liu ◽  
Tao Chu
Keyword(s):  
Field Method ◽  
Road Surface ◽  
Laser Radar ◽  
Intelligent Vehicle ◽  
Height Difference ◽  
The Road ◽  
Potential Field Method ◽  
Regular Shape ◽  
The Impact ◽  
Navigation Method

A navigation method is presented for intelligent vehicle based on fusion of double laser radar. Given laser radar model and road curb model, road curbs are detected by one laser radar tilt-mounted on the intelligent vehicle, and they restrict the vehicle to travel inside the road surface. First, obstacle information from two laser radar are unified to same reference frame and fused, then they are implemented using angle potential field method, the best navigation angle is computed under the road curb restriction. Experiments show the algorithm works well in spite of road-boundary has regular shape or not, and is free from the impact of height difference of the road curb and road surface.

The Impact of Different Axial Oil Chamber Design on Hydrostatic Spindle

2015 ◽  
Vol 789-790 ◽  
pp. 296-299
Author(s):  
Shao Hsien Chen ◽  
Shang Te Chen ◽  
Chien Cheng Hsu
Keyword(s):  
High Precision ◽  
Large Scale ◽  
Development Trend ◽  
Ball Screw ◽  
Precision Machining ◽  
Radial Clearance ◽  
Axial Stiffness ◽  
Key Technologies ◽  
Bearing Stiffness ◽  
The Impact

High-precision machining and large-scale tool are the most primary development trend of current machine tool and hydrostatic products are key technologies of high-precision machining equipments. However, these equipments mostly process miniature components, thus the adopted tools are relatively small and the spindles mainly use are mainly built-in types of HSK32 to HSK25 with revolutions speed over 25,000rpm. Some processing equipments are even equipped with hydrostatic or gas-static spindles. The study extends the axial oil chamber to radial ones to expand the action area of axial oil pressure and form a closed oil seal edge by combining the radial clearance. Consequently, the axial bearing stiffness can be enhanced to enlarge the application scope of hydrostatic spindle. The design mode can enhance axial stiffness of spindle modules or strengthen the stiffness of hydrostatic spindle in a ball screw.

Seasonal variation of Mercury's exosphere deduced from MESSENGER data and simulation study

2020 ◽  
Author(s):  
Yudai Suzuki ◽  
Kazuo Yoshioka ◽  
Go Murakami ◽  
Ichiro Yoshikawa
Keyword(s):  
Seasonal Variation ◽  
Solar Radiation ◽  
Radiation Pressure ◽  
Seasonal Variability ◽  
Solar Radiation Pressure ◽  
Space Environment ◽  
Generation Process ◽  
Surface Transport ◽  
Celestial Bodies ◽  
The Impact

<p>Celestial bodies with surface-bound exosphere are valuable because we can directly see the interaction between the bodies and space environment to which they are exposed. This interaction is especially expected to be clearly observed around Mercury. This research aims to clarify the generation process of neutral sodium exosphere, through the comparison between the data from MASCS onboard MESSENGER spacecraft and 3-D model calculation considering generation, transportation and dissipation processes.</p><p>First, seasonal variability of the amount of sodium exosphere is analyzed for each local time (LT) using MASCS data. Previous research has shown that the amount of sodium above LT12 reaches a maximum at aphelion, and it is found that this maximum is seen only above LT12. In addition, two hypotheses proposed by the research: the increase in the surface sodium density of the dayside due to fast rotation of terminator, and the expansion of exosphere owing to weaker radiation pressure, were turned out to be inconsistent with seasonal variability above LT06 and the results of test particle calculations.</p><p>Following these results, in order to understand the key process of the seasonal variation of the amount of sodium especially around LT12, 3-D sodium exosphere model including release from the surface, transport due to gravity and solar radiation pressure, and dissipation due to ionization caused by solar radiation is constructed. The results from numerical calculation is consistent with the observations by MASCS in terms of the vertical profile and the seasonal variability above LT06 and LT18, but the maximum at aphelion above LT12 could not be reproduced. Then, when the existence of the impact of comet dust stream is assumed as a local and short-term sodium source, the model with impact of 10<sup>8</sup>kg comets per Mercury year could reproduce observations.</p><p>Using the model constructed in this study, the sodium distribution which would be observed by MSASI onboard MIO spacecraft is predicted. The comparison between the calculation and observation by MSASI will provide us new insights into the interaction between the celestial bodies and space environment.</p><p>In this presentation, we will summarize the results of comparison between observations by MASCS and 3-D Monte Carlo simulation about the seasonal variability of Mercury’s sodium exosphere.</p>

Design of DDS-Like Clock Generator Using Bidirectional Integration

2013 ◽  
Vol 284-287 ◽  
pp. 2627-2631
Author(s):  
Hsin Chuan Chen
Keyword(s):  
High Precision ◽  
Communication Systems ◽  
Frequency Synthesizer ◽  
Frequency Error ◽  
Clock Generator ◽  
Hardware Complexity ◽  
Time Intervals ◽  
Low Jitter ◽  
Phase Interpolation ◽  
The Impact

In many applications such as digital communication systems, a reconfigurable clock is required to switch the desired frequency at necessary time. However, using the conventional direct digital frequency synthesizer (DDS) as a pulse or clock generator may cause jitter problems, therefore phase-interpolation approaches are used to generate a pulse or clock with correct time intervals. Focusing on design methodology, a high-precision DDS-like clock generator without phase accumulator and phase interpolation is proposed in this paper, which only uses the bidirectional integration on a single capacitor to directly achieve the clock output with correct time intervals. It also can avoid the impact on frequency error caused by the capacitance error. Therefore, the proposed DDS-like clock generator using bidirectional integration can provides a low-jitter and high-precision clock output, and it also has less hardware complexity.

Screw Conveyor Design and Processing in Rubber Production

2011 ◽  
Vol 221 ◽  
pp. 394-398
Author(s):  
Ping Fu ◽  
Shan Hu Li ◽  
Chuan Sheng Wang
Keyword(s):  
High Precision ◽  
Processing Method ◽  
Screw Conveyor ◽  
Design Parameters ◽  
Rubber Production ◽  
Actual Production ◽  
Helical Blade ◽  
The Impact

Powder was fed to improving or increasing rubber performance in rubber production. Due to the variety of powder, different feeding quantity and material liquidity and high precision needed, often choose screw conveyor to convey and weigh all kinds of powder. This paper mainly introduce the structure of the screw conveyor for rubber production, analyses the impact of the main parameters of screw conveyor on its performance and conveying capacity. A method of chosen and confirmed the mainly design parameters of screw conveyor was illustrated, and introduced the helical blade and screw shaft of the screw conveyor processing method combining with actual production.

Magnetorheological (MR) Jet Finishing Technology

2004 ◽  
Author(s):  
William I. Kordonski ◽  
Aric B. Shorey ◽  
Marc Tricard
Keyword(s):  
High Precision ◽  
Material Removal ◽  
High Speed ◽  
Axial Magnetic Field ◽  
Fundamental Property ◽  
Cfd Modeling ◽  
Surface Shear Stress ◽  
Round Jet ◽  
Mr Polishing Fluid ◽  
The Impact

Conformal (or freeform) and steep concave optics are important classes of optics that are difficult to finish using conventional techniques due to mechanical interferences and steep local slopes. One suitable way to polish these classes of optics is by using a jet of abrasive/fluid mixture. In doing so, the energy required for polishing may be supplied by the radial spread of a liquid jet, which impinges a surface to be polished. Such fluid flow may generate sufficient surface shear stress to provide material removal in the regime of chemical mechanical polishing. Once translated into a polishing technique, this unique tool may resolve a challenging problem of finishing steep concave surfaces and cavities. A fundamental property of a fluid jet is that it begins to lose its coherence as the jet exits a nozzle. This is due to a combination of abruptly imposed longitudinal and lateral pressure gradients, surface tension forces, and aerodynamic disturbance. This results in instability of the flow over the impact zone and consequently polishing spot instability. To be utilized in deterministic high precision finishing of remote objects, a stable, relatively high-speed, low viscosity fluid jet, which remains collimated and coherent before it impinges the surface to be polished, is required. A method of jet stabilization has been proposed, developed and demonstrated whereby the round jet of magnetorheological fluid is magnetized by an axial magnetic field when it flows out of the nozzle. It has been experimentally shown that a magnetically stabilized round jet of MR polishing fluid generates a reproducible material removal function (polishing spot) at a distance of several tens of centimeters from the nozzle. In doing so, the interferometrically derived distribution of material removal for an axisymmetric MR Jet, which impinges normal to a plane glass surface, coincides well with the radial distribution of rate of work calculated using computational fluid dynamics (CFD) modeling. Polishing results support the assertion that the MR Jet finishing process may produce high precision surfaces on glasses and single crystals. The technology is most attractive for the finishing of complex shapes like freeform optics, steep concaves and cavities.

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