A simple way for producing holographic filters suitable for image improvement

1978 ◽  
Vol 36 (1) ◽  
pp. 226-227
Author(s):  
K.-H. Herrmann ◽  
E. Reuber ◽  
P. Schiske
Keyword(s):  
Transfer Functions ◽  
Diffraction Order ◽  
Lateral Position ◽  
Simple Method ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wiener Filters ◽  
Image Improvement ◽  
Optical Reconstruction ◽  
Set Up

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.

High-resolution electron holography

1991 ◽  
Vol 49 ◽  
pp. 494-495
Author(s):  
Hannes Lichte
Keyword(s):  
Transfer Functions ◽  
Rotational Symmetry ◽  
Object Wave ◽  
Electron Holography ◽  
Fourier Space ◽  
Large Area ◽  
Pupil Function ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wave Aberration

The performance of an electron microscope usually is described in Fourier space by means of the wave transfer function WTF(R) = B(R) exp(iχ(R)) with the pupil function B(R) and the wave aberration χ(R). R means the spatial frequency, rotational symmetry is assumed.The exp(iχ(R)) term describes the coherent transfer of the object wave a(r)exp(iφ(r)) into the image wave A(r)exp(iФ(r)). For weak specimen (a≈1 and φ<<27π) this transfer can be sketched by means of fig. 1 which shows that a mixing occurs between the amplitudes and phases according to the respective transfer functions cosχ and sinχ. Usually, it is desirable to direct by an appropriate wave aberration x the phase of the object wave - containing the most interesting information about the object structure - into the image intensity A2. This is achieved best at Scherzer focus, however, only a comparably narrow band of spatial frequencies is evenly transferred. Lower spatial frequencies (“Large area phase contrast“) are not found in the image.

A Simple Method for the Predistortion of Filter Transfer Functions

1963 ◽  
Vol 10 (3) ◽  
pp. 447-450 ◽  
Author(s):  
J. MacDonald ◽  
G. Temes
Keyword(s):  
Transfer Functions ◽  
Simple Method

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a ringlike wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions, namely, one with and one without this ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

A Simple Approach to the Theory of Secondary Flows

1954 ◽  
Vol 5 (4) ◽  
pp. 218-234 ◽  
Author(s):  
J. H. Preston
Keyword(s):  
Simple Approach ◽  
Secondary Flows ◽  
Large Deflections ◽  
Simple Method ◽  
Vortex Sheets ◽  
Trailing Edges ◽  
Secondary Motion ◽  
Set Up ◽  
Uniform Stream

SummaryA simple method is developed for computing the trailing vorticity which arises when a non-uniform stream is turned.It is shown that, for a sudden and constant deflection of a non-uniform stream, no net trailing vorticity is set up in the exit flow and hence there is no secondary motion.In the case of an impulse cascade of finite dimensions with constant turning, it is found that the trailing vorticity has three distinct components—the passage vorticity and two components which appear as vortex sheets springing from the trailing edges of the aerofoils. It is shown that for small angles of deflection there is no net circulation associated with the trailing vorticity downstream, of the cascade, and it is inferred that this should still be so for large deflections.

scholarly journals A New and Simple Method to Capture Small Arboreal Mammals: The Suspended Pitfall

2019 ◽  
Vol 20 (1) ◽  
pp. 1-14
Author(s):  
Helder José ◽  
Iasmin Macedo ◽  
Mateus Cruz Loss
Keyword(s):  
The Other ◽  
Southeastern Brazil ◽  
Native Forest ◽  
Simple Method ◽  
Live Trap ◽  
Set Up ◽  
Cacao Plantation ◽  
Didelphis Aurita ◽  
Tree Branch ◽  
Doce River

The suspended pitfall demonstrates a new and simple mechanism to capture small arboreal and scansorial mammals. It is an arboreal version of the pitfalls traditionally used to capture terrestrial amphibians and reptiles. Buckets with bait inside are raised by a rope until they reach a tree branch at the desired height. Tests were performed in the Atlantic Forest at three different sites at the mouth of Doce River in Linhares, southeastern Brazil. In one of them suspended pitfalls were set up in the understory of a shaded cacao plantation (cabruca agroforest) in the branches of cacao trees between 2 and 3 m in height, and in the other they were placed in a native forest between 5 to 15 m in height. At the third site, suspended pitfalls were tested together with the other live traps used hitherto in the understory of other cabruca agroforest. The marsupials Didelphis aurita, Caluromys philander, Marmosa (Micoureus) paraguayana, Gracilinanus microtarsus, Marmosa murina and the rodent Rhipidomys mastacalis were captured by suspended pitfall. This live trap was capable of catching all sizes of small arboreal mammals, including juvenile individuals. This method proved to be functional for the capture of some small arboreal mammals and may be a complementary alternative for sampling in high forest strata.

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a Ring-like wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions — namely, one with and one without this Ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back-flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

In Situ Visualization of Layer Transitions during Convective Self-Assembly in a Sessile Drop

2007 ◽  
Vol 31 ◽  
pp. 117-119
Author(s):  
Li Gao ◽  
Qing Feng Yan ◽  
C.C. Wong ◽  
Yet Ming Chiang
Keyword(s):  
Self Assembly ◽  
Sessile Drop ◽  
Three Dimensional ◽  
Colloidal Crystals ◽  
Layer Transition ◽  
Simple Method ◽  
Colloidal Spheres ◽  
In Situ Visualization ◽  
Set Up

Convective self-assembly of colloidal spheres provides a simple method for fabricating two and three dimensional colloidal crystals. In this work, we investigated the layer transitions phenomena during colloidal self-assembly in a sessile drop by using an in-situ videoscopic set-up. The effects of surface charge, colloidal concentration, and surfactant additions were examined. The results show that the chemical environment plays an important role in colloidal self-assembly. In the case of ordered growth, different layer transition phenomena were observed when the colloidal concentration is different.

scholarly journals Bond graph based frequency domain sensitivity analysis of multidisciplinary systems

2002 ◽  
Vol 216 (1) ◽  
pp. 85-99 ◽  
Author(s):  
W Borutzky ◽  
J Granda
Keyword(s):  
Frequency Domain ◽  
Transfer Functions ◽  
Linear Time ◽  
Graph Model ◽  
Bond Graph ◽  
Sensitivity Matrix ◽  
Symbolic Form ◽  
Multidisciplinary Systems ◽  
Set Up ◽  
The Time Domain

Multidisciplinary systems are described most suitably by bond graphs. In order to determine unnormalized frequency domain sensitivities in symbolic form, this paper proposes to construct in a systematic manner a bond graph from another bond graph, which is called the associated incremental bond graph in this paper. Contrary to other approaches reported in the literature the variables at the bonds of the incremental bond graph are not sensitivities but variations (incremental changes) in the power variables from their nominal values due to parameter changes. Thus their product is power. For linear elements their corresponding model in the incremental bond graph also has a linear characteristic. By deriving the system equations in symbolic state space form from the incremental bond graph in the same way as they are derived from the initial bond graph, the sensitivity matrix of the system can be set up in symbolic form. Its entries are transfer functions depending on the nominal parameter values and on the nominal states and the inputs of the original model. The sensitivities can be determined automatically by the bond graph preprocessor CAMP-G and the widely used program MATLAB together with the Symbolic Toolbox for symbolic mathematical calculation. No particular program is needed for the approach proposed. The initial bond graph model may be non-linear and may contain controlled sources and multiport elements. In that case the sensitivity model is linear time variant and must be solved in the time domain. The rationale and the generality of the proposed approach are presented. For illustration purposes a mechatronic example system, a load positioned by a constant-excitation d.c. motor, is presented and sensitivities are determined in symbolic form by means of CAMP-G/MATLAB.

Sign in / Sign up

Export Citation Format

Share Document