scholarly journals Description of alpha-clustering of 8Be nucleus states in high-precision theoretical approach

2020 ◽  
Vol 44 (12) ◽  
pp. 124105
Author(s):  
D. M. Rodkin ◽  
Yu. M. Tchuvil’sky
1997 ◽  
Vol 11 (19) ◽  
pp. 2303-2310 ◽  
Author(s):  
Sergio Curilef ◽  
Andrés R. R. Papa

A theoretical approach within a quantum-group formalism has recently been proposed and successfully compared to Greywall's high precision measurements of the liquid 4 He specific heat. We calculate here the specific heat for 4 He using Tsallis' non-extensive thermostatistics. A comparative analysis reveals that there is a temperature range where our theoretical results yield the best fitting to experimental data.


2021 ◽  
Vol 6 ◽  
pp. 26
Author(s):  
Alois Resch ◽  
Thomas Aigenbauer

Linear concentrating Fresnel collectors are available in various scales for providing solar thermal heat in the temperature range beyond 100 °C. For raising the flexibility in applying such collector systems on mounting sites with restricted space availability, the presented research project investigated the possibilities for adapting an existing Fresnel collector with a mirror surface of 22 m2 towards more compactness by using only one half of the mirror field. Therefore, the receiver was relocated and the focus alignment of the mirrors had to be adapted. The theoretical approach by geometrical calculation of the single mirror angles using MATLAB™ was successful, although the required effort for developing such an optical model was high. Furthermore, the resulting angle information obtained by the calculation is difficult to realise on the mirror field, because a high-precision goniometer would be necessary in order to adjust the mirror stripes accordingly. On the other hand, an experimental approach was analysed for realising on-site focus alignment of the single mirror field. The focussed beam of a conventional laser pointer was directed to each of the mirror stripes, while adjusting the corresponding mirror angle until the reflected beam impinged on the center of the receiver. In the end, the experimental procedure turned out to be favourable, because it is simple and reliable, and it requires much less effort. In this way, the adaption of the Fresnel mirror field was successful, as the concentration and the tracking is working as expected.


Author(s):  
Marcos F. Maestre

Recently we have developed a form of polarization microscopy that forms images using optical properties that have previously been limited to macroscopic samples. This has given us a new window into the distribution of structure on a microscopic scale. We have coined the name differential polarization microscopy to identify the images obtained that are due to certain polarization dependent effects. Differential polarization microscopy has its origins in various spectroscopic techniques that have been used to study longer range structures in solution as well as solids. The differential scattering of circularly polarized light has been shown to be dependent on the long range chiral order, both theoretically and experimentally. The same theoretical approach was used to show that images due to differential scattering of circularly polarized light will give images dependent on chiral structures. With large helices (greater than the wavelength of light) the pitch and radius of the helix could be measured directly from these images.


Author(s):  
J. C. Russ ◽  
T. Taguchi ◽  
P. M. Peters ◽  
E. Chatfield ◽  
J. C. Russ ◽  
...  

Conventional SAD patterns as obtained in the TEM present difficulties for identification of materials such as asbestiform minerals, although diffraction data is considered to be an important method for making this purpose. The preferred orientation of the fibers and the spotty patterns that are obtained do not readily lend themselves to measurement of the integrated intensity values for each d-spacing, and even the d-spacings may be hard to determine precisely because the true center location for the broken rings requires estimation. We have implemented an automatic method for diffraction pattern measurement to overcome these problems. It automatically locates the center of patterns with high precision, measures the radius of each ring of spots in the pattern, and integrates the density of spots in that ring. The resulting spectrum of intensity vs. radius is then used just as a conventional X-ray diffractometer scan would be, to locate peaks and produce a list of d,I values suitable for search/match comparison to known or expected phases.


Author(s):  
K. Z. Botros ◽  
S. S. Sheinin

The main features of weak beam images of dislocations were first described by Cockayne et al. using calculations of intensity profiles based on the kinematical and two beam dynamical theories. The feature of weak beam images which is of particular interest in this investigation is that intensity profiles exhibit a sharp peak located at a position very close to the position of the dislocation in the crystal. This property of weak beam images of dislocations has an important application in the determination of stacking fault energy of crystals. This can easily be done since the separation of the partial dislocations bounding a stacking fault ribbon can be measured with high precision, assuming of course that the weak beam relationship between the positions of the image and the dislocation is valid. In order to carry out measurements such as these in practice the specimen must be tilted to "good" weak beam diffraction conditions, which implies utilizing high values of the deviation parameter Sg.


Author(s):  
Klaus-Ruediger Peters

Differential hysteresis processing is a new image processing technology that provides a tool for the display of image data information at any level of differential contrast resolution. This includes the maximum contrast resolution of the acquisition system which may be 1,000-times higher than that of the visual system (16 bit versus 6 bit). All microscopes acquire high precision contrasts at a level of <0.01-25% of the acquisition range in 16-bit - 8-bit data, but these contrasts are mostly invisible or only partially visible even in conventionally enhanced images. The processing principle of the differential hysteresis tool is based on hysteresis properties of intensity variations within an image.Differential hysteresis image processing moves a cursor of selected intensity range (hysteresis range) along lines through the image data reading each successive pixel intensity. The midpoint of the cursor provides the output data. If the intensity value of the following pixel falls outside of the actual cursor endpoint values, then the cursor follows the data either with its top or with its bottom, but if the pixels' intensity value falls within the cursor range, then the cursor maintains its intensity value.


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