L.S. Pontryagin's first direct method. Development of ideas

2018 ◽  
Author(s):  
Arkadii Alekseevich Chikrii
Keyword(s):  
Method Development ◽  
Direct Method

scholarly journals Influence of frequency resolution in case of frequency response function measurement in structural dynamics

2021 ◽  
Author(s):  
Zoltán Gazdagh ◽  
Balázs Vehovszky
Keyword(s):  
Frequency Response ◽  
Data Storage ◽  
Response Function ◽  
Frequency Response Function ◽  
Method Development ◽  
Direct Method ◽  
Frequency Resolution ◽  
Practical Tool ◽  
Theoretical Considerations

Frequency resolution is an essential parameter in acoustical testing, even if we are using numerical or experimental method, for example when determining frequency response function (FRF) of a dynamic mechanical system, or executing modal analysis based on the FRFs. Finer resolution leads to more accurate results, at the expense of longer calculation/measurement process and larger data size. This parameter is generally set based on rules of thumb, prior practice or with big margin for safety. This results in waste time and data storage if the required frequency resolution is overestimated, or even significant errors in the results, if it is underestimated. Present paper offers a direct, method for the conscious determination of optimal frequency resolution. It is based fully on theoretical considerations, and investigates amplitude and phase distortion at resonances as target parameters. Beside defining the steps of the process, it is tested on a real structure, and the results are presented as well, proving the applicability and the appropriateness of the method. With this method, development engineers get a practical tool for adjusting the parameters of dynamic measurements and simulations.

Characterization of frozen hydrated biological specimens by low-loss EELS

1992 ◽  
Vol 50 (2) ◽  
pp. 1572-1573
Author(s):  
Songquan Sun ◽  
Richard D. Leapman
Keyword(s):  
Water Content ◽  
Direct Method ◽  
Internal Standard ◽  
Dry Weight ◽  
Dark Field ◽  
Protein Solutions ◽  
Subcellular Compartment ◽  
Differential Shrinkage ◽  
Electron Energy Loss

Analyses of ultrathin cryosections are generally performed after freeze-drying because the presence of water renders the specimens highly susceptible to radiation damage. The water content of a subcellular compartment is an important quantity that must be known, for example, to convert the dry weight concentrations of ions to the physiologically more relevant molar concentrations. Water content can be determined indirectly from dark-field mass measurements provided that there is no differential shrinkage between compartments and that there exists a suitable internal standard. The potential advantage of a more direct method for measuring water has led us to explore the use of electron energy loss spectroscopy (EELS) for characterizing biological specimens in their frozen hydrated state.We have obtained preliminary EELS measurements from pure amorphous ice and from cryosectioned frozen protein solutions. The specimens were cryotransfered into a VG-HB501 field-emission STEM equipped with a 666 Gatan parallel-detection spectrometer and analyzed at approximately −160 C.

A Simple Real-Space Channelling Theory for Electron Diffraction and HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 64-65
Author(s):  
D. Van Dyck
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Direct Method ◽  
Real Space ◽  
Zone Axis ◽  
Phase Object ◽  
High Resolution Images ◽  
The Many ◽  
Analytical Expressions ◽  
Electron Wavefunction

The computation of the many beam dynamical electron diffraction amplitudes or high resolution images can only be done numerically by using rather sophisticated computer programs so that the physical insight in the diffraction progress is often lost. Furthermore, it is not likely that in this way the inverse problem can be solved exactly, i.e. to reconstruct the structure of the object from the knowledge of the wavefunction at its exit face, as is needed for a direct method [1]. For this purpose, analytical expressions for the electron wavefunction in real or reciprocal space are much more useful. However, the analytical expressions available at present are relatively poor approximations of the dynamical scattering which are only valid either for thin objects ((weak) phase object approximation, thick phase object approximation, kinematical theory) or when the number of beams is very limited (2 or 3). Both requirements are usually invalid for HREM of crystals. There is a need for an analytical expression of the dynamical electron wavefunction which applies for many beam diffraction in thicker crystals. It is well known that, when a crystal is viewed along a zone axis, i.e. parallel to the atom columns, the high resolution images often show a one-to-one correspondence with the configuration of columns provided the distance between the columns is large enough and the resolution of the instrument is sufficient. This is for instance the case in ordered alloys with a column structure [2,3]. From this, it can be suggested that, for a crystal viewed along a zone axis with sufficient separation between the columns, the wave function at the exit face does mainly depend on the projected structure, i.e. on the type of atom columns. Hence, the classical picture of electrons traversing the crystal as plane-like waves in the directions of the Bragg beams which historically stems from the X-ray diffraction picture, is in fact misleading.

Method development and optimization for isoflavone quantification in dry soy extract containing products

Planta Medica ◽  
2010 ◽  
Vol 76 (12) ◽  
Author(s):  
D Csupor ◽  
J Bognár ◽  
J Karsai ◽  
J Hohmann
Keyword(s):  
Method Development

HPTLC and TLC method development preliminary studies for damask rose

2017 ◽  
Author(s):  
T Agar Osman ◽  
A Gokbulut ◽  
O Demirezer Lutfiye
Keyword(s):  
Method Development ◽  
Damask Rose

Quantitative method development for measurement of Maesa lanceolata saponins by LC-MS

Planta Medica ◽  
2006 ◽  
Vol 72 (11) ◽  
Author(s):  
L Pieters ◽  
M Theunis ◽  
S Apers ◽  
A Vlietinck
Keyword(s):  
Quantitative Method ◽  
Method Development
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