PC-SD-VIO: A constant intensity semi-direct monocular visual-inertial odometry with online photometric calibration

2021 ◽  
pp. 103877
Author(s):  
Quanpan Liu ◽  
Zhengjie Wang ◽  
Huan Wang
Keyword(s):  
Constant Intensity ◽  
Photometric Calibration

Are HOLZ lines kinematic in off-zone-axis orientation?

1993 ◽  
Vol 51 ◽  
pp. 692-693
Author(s):  
J. M. Zuo ◽  
A. L. Weickenmeier ◽  
R. Holmestad ◽  
J. C. H. Spence
Keyword(s):  
Structure Determination ◽  
Standard Procedure ◽  
High Order ◽  
Zone Axis ◽  
Great Promise ◽  
Line Position ◽  
Measured Intensity ◽  
Constant Intensity ◽  
Axis Orientation ◽  
Diffraction Condition

The application of high order reflections in a weak diffraction condition off the zone axis center, including those in high order laue zones (HOLZ), holds great promise for structure determination using convergent beam electron diffraction (CBED). It is believed that in this case the intensities of high order reflections are kinematic or two-beam like. Hence, the measured intensity can be related to the structure factor amplitude. Then the standard procedure of structure determination in crystallography may be used for solving unknown structures. The dynamic effect on HOLZ line position and intensity in a strongly diffracting zone axis is well known. In a weak diffraction condition, the HOLZ line position may be approximated by the kinematic position, however, it is not clear whether this is also true for HOLZ intensities. The HOLZ lines, as they appear in CBED patterns, do show strong intensity variations along the line especially near the crossing of two lines, rather than constant intensity along the Bragg condition as predicted by kinematic or two beam theory.

scholarly journals Appearance of a Solitary Wave Particle Concentration in Nanofluids under a Light Field

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1291
Author(s):  
Abram I. Livashvili ◽  
Victor V. Krishtop ◽  
Polina V. Vinogradova ◽  
Yuriy M. Karpets ◽  
Vyacheslav G. Efremenko ◽  
...  
Keyword(s):  
Solitary Wave ◽  
Wave Velocity ◽  
Light Field ◽  
Particle Concentration ◽  
Colloidal Suspension ◽  
Type Equation ◽  
Concentration Wave ◽  
Nanoparticle Concentration ◽  
Constant Intensity ◽  
Concentration Convection

In this study, the nonlinear dynamics of nanoparticle concentration in a colloidal suspension (nanofluid) were theoretically studied under the action of a light field with constant intensity by considering concentration convection. The heat and nanoparticle transfer processes that occur in this case are associated with the phenomenon of thermal diffusion, which is considered to be positive in our work. Two exact analytical solutions of a nonlinear Burgers-Huxley-type equation were derived and investigated, one of which was presented in the form of a solitary concentration wave. These solutions were derived considering the dependence of the coefficients of thermal conductivity, viscosity, and absorption of radiation on the nanoparticle concentration in the nanofluid. Furthermore, an expression was obtained for the solitary wave velocity, which depends on the absorption coefficient and intensity of the light wave. Numerical estimates of the concentration wave velocity for a specific nanofluid—water/silver—are given. The results of this study can be useful in the creation of next-generation solar collectors.

A constant intensity technique to improve the performances of devices based on direct absorption spectroscopy

2015 ◽  
Vol 23 (1) ◽  
Author(s):  
A. Montori ◽  
M. De Pas ◽  
M. Giuntini ◽  
M. Siciliani De Cumis ◽  
S. Viciani ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Direct Absorption ◽  
Background Signal ◽  
Constant Intensity ◽  
Gas Concentration ◽  
Direct Absorption Spectroscopy ◽  
Frequency Scan ◽  
Time Observation ◽  
Detection Processing ◽  
Real Time Observation

Abstract We describe an all−in−fibre apparatus for Constant Intensity Direct Absorption Spectroscopy (CIDAS) for gas concentration measurements which keeps the power of a diode laser constant along the frequency sweep. The reduction of the large variation of the laser power, connected to the frequency scan, enhances the ability of detecting small variations in a background signal, resulting in an increase of the sensitivity with respect to standard direct absorption techniques. Moreover, CIDAS allows for a real−time observation of the absorption signals without any kind of post−detection processing. The apparatus has been tested with carbon dioxide (CO

Convergence to equilibrium in a traffic model with restricted passing

1979 ◽  
Vol 16 (4) ◽  
pp. 881-889 ◽  
Author(s):  
Hans Dieter Unkelbach
Keyword(s):  
Poisson Process ◽  
Limit Theorems ◽  
Point Processes ◽  
Road Traffic ◽  
Poisson Processes ◽  
Traffic Model ◽  
Cluster Point ◽  
Convergence To Equilibrium ◽  
Constant Intensity

A road traffic model with restricted passing, formulated by Newell (1966), is described by conditional cluster point processes and analytically handled by generating functionals of point processes.The traffic distributions in either space or time are in equilibrium, if the fast cars form a Poisson process with constant intensity combined with Poisson-distributed queues behind the slow cars (Brill (1971)). It is shown that this state of equilibrium is stable, which means that this state will be reached asymptotically for general initial traffic distributions. Furthermore the queues behind the slow cars dissolve asymptotically like independent Poisson processes with diminishing rate, also independent of the process of non-queuing cars. To get these results limit theorems for conditional cluster point processes are formulated.

Calibration and Validation of Infrared Sounders with Moon and Mercury

2021 ◽  
Author(s):  
Martin Burgdorf ◽  
Stefan A. Buehler ◽  
Viju John ◽  
Thomas Müller ◽  
Marc Prange
Keyword(s):  
Large Time ◽  
Angular Resolution ◽  
The Moon ◽  
Photometric Calibration ◽  
The Earth ◽  
Spread Function ◽  
Spectral Channels ◽  
Better Than ◽  
Full Disk

<p>Serendipitous observations of airless bodies of the inner solar system provide a unique means to the calibration of instruments on meteorological research satellites, because the physical properties of their surfaces change very little, even on large time scales. We investigated how certain instrumental effects can be characterised with observations of the Moon and Mercury. For this we identified and analysed intrusions of the Moon in the deep space views of HIRS/2, /3, and /4 (High-resolution Infrared Sounder) on various satellites in polar orbits and as well some images obtained with SEVIRI (Spinning Enhanced Visible Infra-Red Imager) on MSG-3 and -4 (Meteosat Second Generation), which had Mercury standing close to the Earth in the rectangular field of view.</p><p>A full-disk, infrared Moon model was developed that describes how the lunar flux density depends on phase angle and wavelength. It is particularly helpful for inter-calibration, checks of the photometric consistency of the sounding channels, and the calculation of an upper limit on the non-linearity of the shortwave channels of HIRS. In addition, we used the Moon to determine the co-registration of the different spectral channels.</p><p>Studies of the channel alignment are also presented for SEVIRI, an infrared sounder with an angular resolution about a hundred times better than HIRS. As we wanted to check the image quality of this instrument with a quasi-point source as well, we replaced here the Moon with Mercury. We found the typical smearing of the point spread function in the scan direction and occasionally a nearby ghost image, which is three to four times fainter than the main image of the planet. Both effects cause additional uncertainties of the photometric calibration.  </p>

scholarly journals Objective and subjective measures of exercise intensity during thermo-neutral and hot yoga

2018 ◽  
Vol 43 (4) ◽  
pp. 397-402 ◽  
Author(s):  
Corinne N. Boyd ◽  
Stephanie M. Lannan ◽  
Micah N. Zuhl ◽  
Ricardo Mora-Rodriguez ◽  
Rachael K. Nelson
Keyword(s):  
Oxygen Consumption ◽  
Light Intensity ◽  
Exercise Intensity ◽  
Perceived Exertion ◽  
Maximal Oxygen Consumption ◽  
Rating Of Perceived Exertion ◽  
Moderate Intensity ◽  
Subjective Measures ◽  
Moderate Intensity Exercise ◽  
Constant Intensity

While hot yoga has gained enormous popularity in recent years, owing in part to increased environmental challenge associated with exercise in the heat, it is not clear whether hot yoga is more vigorous than thermo-neutral yoga. Therefore, the aim of this study was to determine objective and subjective measures of exercise intensity during constant intensity yoga in a hot and thermo-neutral environment. Using a randomized, crossover design, 14 participants completed 2 identical ∼20-min yoga sessions in a hot (35.3 ± 0.8 °C; humidity: 20.5% ± 1.4%) and thermo-neutral (22.1 ± 0.2 °C; humidity: 27.8% ± 1.6%) environment. Oxygen consumption and heart rate (HR) were recorded as objective measures (percentage of maximal oxygen consumption and percentage of maximal HR (%HRmax)) and rating of perceived exertion (RPE) was recorded as a subjective measure of exercise intensity. There was no difference in exercise intensity based on percentage of maximal oxygen consumption during hot versus thermo-neutral yoga (30.9% ± 2.3% vs. 30.5% ± 1.8%, p = 0.68). However, exercise intensity was significantly higher during hot versus thermo-neutral yoga based on %HRmax (67.0% ± 2.3% vs. 60.8% ± 1.9%, p = 0.01) and RPE (12 ± 1 vs. 11 ± 1, p = 0.04). According to established exercise intensities, hot yoga was classified as light-intensity exercise based on percentage of maximal oxygen consumption but moderate-intensity exercise based on %HRmax and RPE while thermo-neutral yoga was classified as light-intensity exercise based on percentage of maximal oxygen uptake, %HRmax, and RPE. Despite the added hemodynamic stress and perception that yoga is more strenuous in a hot environment, we observed similar oxygen consumption during hot versus thermo-neutral yoga, classifying both exercise modalities as light-intensity exercise.

scholarly journals Analysis of full disc Ca II K spectroheliograms

2018 ◽  
Vol 609 ◽  
pp. A92 ◽  
Author(s):  
Theodosios Chatzistergos ◽  
Ilaria Ermolli ◽  
Sami K. Solanki ◽  
Natalie A. Krivova
Keyword(s):  
Synthetic Data ◽  
Calibration Method ◽  
Poor Quality ◽  
Average Error ◽  
Photometric Calibration ◽  
Solar Observations ◽  
Relative Errors ◽  
Long Term Variations ◽  
The Ideal

Context. Historical Ca II K spectroheliograms (SHG) are unique in representing long-term variations of the solar chromospheric magnetic field. They usually suffer from numerous problems and lack photometric calibration. Thus accurate processing of these data is required to get meaningful results from their analysis. Aims. In this paper we aim at developing an automatic processing and photometric calibration method that provides precise and consistent results when applied to historical SHG. Methods. The proposed method is based on the assumption that the centre-to-limb variation of the intensity in quiet Sun regions does not vary with time. We tested the accuracy of the proposed method on various sets of synthetic images that mimic problems encountered in historical observations. We also tested our approach on a large sample of images randomly extracted from seven different SHG archives. Results. The tests carried out on the synthetic data show that the maximum relative errors of the method are generally <6.5%, while the average error is <1%, even if rather poor quality observations are considered. In the absence of strong artefacts the method returns images that differ from the ideal ones by <2% in any pixel. The method gives consistent values for both plage and network areas. We also show that our method returns consistent results for images from different SHG archives. Conclusions. Our tests show that the proposed method is more accurate than other methods presented in the literature. Our method can also be applied to process images from photographic archives of solar observations at other wavelengths than Ca II K.

scholarly journals BVRI photometric calibration of the Nedeljkovic telescope

2021 ◽  
pp. 3-3
Author(s):  
A. Vudragovic ◽  
M. Jurkovic
Keyword(s):  
Ccd Camera ◽  
Color Correction ◽  
Photometric Calibration ◽  
Astronomical Station

We have done photometric calibration of the 60 cm Nedeljkovic telescope equipped with the FLI PL 230 CCD camera, mounted at the Astronomical Station Vidojevica (Serbia), using standard stars from the Landolt catalog. We have imaged 31 fields of standard stars using Johnson's BVRI filters during three nights in August 2019. We have measured both extinction and color correction. Relating our calibrated magnitudes to the magnitudes of standard stars from the Landolt catalog, we have achieved accuracy of 2%-5% for the BVRI magnitudes.

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