THE FLOW OF WATER THROUGH SMOOTH OPEN CHANNELS OF NARROW RECTANGULAR AND T-SHAPED CROSS SECTIONS.

1967 ◽  
Vol 36 (2) ◽  
pp. 325-349
Author(s):  
J ALLEN ◽  
M I ULLAH ◽  
Keyword(s):  
Cross Sections ◽  
Open Channels

scholarly journals On the Statistical Theory of Nuclear Reactions

1978 ◽  
Vol 31 (2) ◽  
pp. 151 ◽  
Author(s):  
WK Bertram
Keyword(s):  
Statistical Theory ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Reaction Cross ◽  
Open Channels ◽  
S Matrix ◽  
Reaction Cross Sections

The statistical theory of energy-averaged reaction cross sections is examined using the pole expansion of the S-matrix. Exact expressions for the average cross sections in terms of the parameters of the S-matrix are derived for the case when there are two open channels. It is shown that when the number of channels exceeds two, the average cross sections can be evaluated provided the poles of the S-matrix are evenly spaced.

III. Hydraulic problems on the cross-sections of pipes and channels

1888 ◽  
Vol 44 (266-272) ◽  
pp. 101-109
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Open Channels ◽  
The Cross

In that division of hydromechanics which is devoted to the investigation of the flow of liquids through pipes and open channels, the resistance due to the friction of the contained liquid against the sides of the pipes or channels has led to expressions for the velocity as a function of the dimensions and shape of the cross-section commonly designated as the hydraulic mean depth. This quantity is defined as the quotient of the area of the cross-section of the liquid by that part of its perimeter in contact with the pipe or channel. In a full pipe this perimeter is identical with that of the pipe’s cross-section, and in practice this is generally a circle.

scholarly journals Entropy Wake Law for Streamwise Velocity Profiles in Smooth Rectangular Open Channels

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 654
Author(s):  
Domenica Mirauda ◽  
Maria Grazia Russo
Keyword(s):  
Free Surface ◽  
Cross Sections ◽  
Water Discharge ◽  
Longitudinal Velocity ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Streamwise Velocity ◽  
Open Channels ◽  
Entropy Model ◽  
Modified Entropy

In narrow open channels, the three-dimensional nature of the flow and the transport momentum from the sidewalls to the central region cause the maximum longitudinal velocity to occur below the water surface. The entropy model is unable to accurately describe the velocities near the free surface when the dip phenomenon exists. The present paper proposes a new dip-modified entropy law for steady open channel flows, which consists of three additional terms: the first one similar to Coles’ function; the second one linearly proportional to the logarithmic distance from the free surface; and the third one depending on the cubic correction near the maximum velocity. The validity of the new model was tested on a set of laboratory measurements carried out in a straight rectangular flume with smooth boundaries and for different values of water discharge, bottom slope, and aspect ratio. A detailed error analysis showed good agreement with the data measured through the present research and a more accurate prediction of the velocity-dip-position compared with the one evaluated through the original entropy model. In addition, the modified entropy wake law matched very well with other literature data collected in rectangular cross-sections with different flow conditions.

scholarly journals Ein einfaches Modell zum Vergleich der Theorien von Hauser-Feshbach und P. A. Moldauer

1968 ◽  
Vol 23 (7) ◽  
pp. 955-961
Author(s):  
F. Schmidt
Keyword(s):  
Elastic Scattering ◽  
Cross Section ◽  
Compound Nucleus ◽  
Cross Sections ◽  
Channel Model ◽  
Open Channels ◽  
Nucleus Formation ◽  
Compound Nucleus Formation ◽  
The Cross

We discuss and compare the theories of HAUSER and FESHBACH and P. A. MOLDAUER by a simple two channel model. It is found that after a good fit of parameters only the cross sections of compound-elastic scattering differ substantially. Most differences appear if there are a few open channels. The consequences for the cross section of compound nucleus formation and also for calculations by the evaporation mdel are considered. By our model an evident foundation is given for the statement that MOLDAUER'S theorie would be valid for 〈Γλc〉/D ≦ 1.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

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