scholarly journals Seeing Compensation in Photoelectric Area Scanning

1977 ◽  
Vol 33 ◽  
pp. 33-33
Author(s):  
O. G. Franz
Keyword(s):  
Relative Position ◽  
Accurate Determination ◽  
Angular Separation ◽  
Double Star ◽  
Optical Image

AbstractA method is described which, through the use of an optical image rotator in conjunction with an area scanner, allows the accurate determination of the magnitudes and relative position of the components of a double star even if the angular separation is significantly smaller than the radius of the seeing disk.

scholarly journals Application de la Methode par Deconvolution Integree Au Cas des Occultations D'etoiles Doubles

1986 ◽  
Vol 109 ◽  
pp. 113-121 ◽  
Author(s):  
M. Froeschle ◽  
C. Meyer
Keyword(s):  
Good Accuracy ◽  
Signal To Noise Ratio ◽  
Angular Separation ◽  
Brightness Distribution ◽  
Fresnel Diffraction ◽  
Usual Method ◽  
Double Star ◽  
Single Star ◽  
Magnitude Difference

The most usual method for the determination of the angular separation ρ and the magnitude difference Δm of the two components is the direct comparison of the observed diffraction pattern with a theoretical model. However, it is possible to use a deconvolution process based, for a single star, on the equation I′(x) = F′(x) * O(x), involving both the derivative of the Fresnel diffraction function for a point-like source, and that of the observed intensity. O(x) is the brightness distribution function of the occulted source.We describe here a new method, using the integrated deconvolution process (Froeschlá, Meyer, 1983), in which we determine the variations of the apparent surface of the two sources of a double star while it is being occulted. The two sources are supposed to be of the same diameter. This method has been applied to several cases of theoretical diffraction curves with different values of ρ and Δm. Noise has been added and we have studied the effect of the signal to noise ratio on determination of the parameters ρ and Δm of the pair. A good accuracy for Δm is obtained for |Δm| ≦ 1 and noise ≦ 10%. The determination of ρ is well achieved for noise level reaching 15 %. The technique has been at last applied to the observation of the occultation of SAO 95166 made by Africano et al.(1977) leading to nearly similar results.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

Computer-Assisted High-Re Solution TEM

1990 ◽  
Vol 48 (1) ◽  
pp. 162-163
Author(s):  
F.A. Ponce ◽  
H. Hikashi
Keyword(s):  
Signal To Noise Ratio ◽  
Accurate Determination ◽  
Computer Software ◽  
Video Camera ◽  
Image Contrast ◽  
Objective Lens ◽  
Computer Assisted ◽  
Optical Parameters ◽  
Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

Assessment of Sylphons Lifetime

2008 ◽  
Vol 59 (5) ◽  
pp. 605-610
Author(s):  
Alexandru Pupazescu ◽  
Stefan Minoiu ◽  
Constantin Manea
Keyword(s):  
Elevated Temperature ◽  
Strain Distribution ◽  
Accurate Determination ◽  
Multiaxial Fatigue ◽  
Tensile Curve

The paper contains an assessment of the sylphons lifetime for multiaxial fatigue. Three criteria were used two based on s � N diagram and one based on energy. For a more accurate determination of the sylphons lifetime the stress and the strain distribution been determined using FEM, the tensile curve of the steel W 4541 at elevated temperature.

Sign in / Sign up

Export Citation Format

Share Document