An Inverse Time Marching Method for the Definition of Cascade Geometry

1982 ◽  
Vol 104 (3) ◽  
pp. 650-656 ◽  
Author(s):  
G. Meauze´
Keyword(s):  
Velocity Distribution ◽  
Cross Section ◽  
Iterative Process ◽  
Suction Side ◽  
Wide Field ◽  
Closure Condition ◽  
Evolution Law ◽  
Time Marching ◽  
Definition Of ◽  
Marching Method

The article describes a so-called “inverse mode” calculation method, providing the geometry of a cascade corresponding to a given velocity distribution, and gives some examples of application. The velocity distribution may be assigned over the whole of the suction and pressure sides or over only a part of them, the remaining parts being already known. The closure condition of the profile is ensured by an iterative process on the solidity of the cascade. A second version allows the definition of the geometry of a profile with a given thickness evolution law and as assigned velocity distribution on the suction side. The method makes use of a pseudo-unsteady calculation, enabling one to treat the case of flows with shock waves in a two-dimensional stream with possible variations of cross section. This flexibility of use confers to the method a wide field of application, covering all possible configurations of flow in turbine and compressor cascades.

A new computerized method for finding effective velocity from reversed reflection traveltime data

Geophysics ◽  
1979 ◽  
Vol 44 (6) ◽  
pp. 1064-1076 ◽  
Author(s):  
K. L. Kaila ◽  
V. G. Krishna
Keyword(s):  
Velocity Distribution ◽  
Cross Section ◽  
Iterative Process ◽  
Tolerance Limit ◽  
Least Square ◽  
Reflection Point ◽  
Computerized Method ◽  
Effective Velocity ◽  
Wide Range ◽  
The Common

A new computerized method is developed using a pair of direct and reversed reflection traveltime curves from two reciprocal shotpoints for finding effective velocity [Formula: see text] appropriate to the depth of the common‐reflection‐point (CRP) for a dipping reflector. For the two sets of traveltime data, least‐square fits are made to [Formula: see text] versus [Formula: see text], where T is the traveltime for recording distance X, θ is the dip of the reflector, and d is the perpendicular distance from the shotpoint to the reflector. The observed convergence of d for any assumed reflector dip θ makes it possible to scan through a wide range of θ values by an iterative process until the velocities computed by the direct and reversed traveltime data agree within the required tolerance limit, which then yields the appropriate effective velocity, and the corresponding θ is the true dip of the reflector. This method simultaneously yields an optimum migrated depth cross‐section. It is also possible to study, by this method, velocity distribution in both vertical and lateral directions in the subsurface area under investigation.

Calculation of the Quasi Three-Dimensional Flow in a Turbomachine Blade Row

1977 ◽  
Vol 99 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Jean-Pierre Veuillot
Keyword(s):  
Finite Difference ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Through Flow ◽  
Blade Row ◽  
Time Marching ◽  
Space Discretization ◽  
Finite Volume Approach ◽  
Marching Method ◽  
Finite Difference Techniques

The equations of the through flow are obtained by an asymptotic theory valid when the blade pitch is small. An iterative method determines the meridian stream function, the circulation, and the density. The various equations are discretized in an orthogonal mesh and solved by classical finite difference techniques. The calculation of the steady transonic blade-to-blade flow is achieved by a time marching method using the MacCormack scheme. The space discretization is obtained either by a finite difference approach or by a finite volume approach. Numerical applications are presented.

scholarly journals Structure of the Balmer jump

2018 ◽  
Vol 613 ◽  
pp. A55
Author(s):  
F. Calvo ◽  
L. Belluzzi ◽  
O. Steiner
Keyword(s):  
Hydrogen Atom ◽  
Absorption Coefficient ◽  
Total Cross Section ◽  
Analytical Model ◽  
Cross Section ◽  
Quantum Structure ◽  
Balmer Series ◽  
Polarization Phenomena ◽  
Definition Of ◽  
Rapid Drop

Context.The spectrum of the hydrogen atom was explained by Bohr more than one century ago. We revisit here some of the aspects of the underlying quantum structure, with a modern formalism, focusing on the limit of the Balmer series.Aims.We investigate the behaviour of the absorption coefficient of the isolated hydrogen atom in the neighbourhood of the Balmer limit.Methods.We analytically computed the total cross-section arising from bound-bound and bound-free transitions in the isolated hydrogen atom at the Balmer limit, and established a simplified semi-analytical model for the surroundings of that limit. We worked within the framework of the formalism of Landi Degl’Innocenti & Landolfi (2004, Astrophys. Space Sci. Lib., 307), which permits an almost straight-forward generalization of our results to other atoms and molecules, and which is perfectly suitable for including polarization phenomena in the problem.Results.We analytically show that there is no discontinuity at the Balmer limit, even though the concept of a “Balmer jump” is still meaningful. Furthermore, we give a possible definition of the location of the Balmer jump, and we check that this location is dependent on the broadening mechanisms. At the Balmer limit, we compute the cross-section in a fully analytical way.Conclusions.The Balmer jump is produced by a rapid drop of the total Balmer cross-section, yet this variation is smooth and continuous when both bound-bound and bound-free processes are taken into account, and its shape and location is dependent on the broadening mechanisms.

scholarly journals Recommendations for Reporting Ion Mobility Mass Spectrometry Measurements

2018 ◽  
Author(s):  
Valerie Gabelica ◽  
Alexandre A. Shvartsburg ◽  
Carlos Afonso ◽  
Perdita E. Barran ◽  
Justin L. P. Benesch ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Cross Section ◽  
Ion Mobility ◽  
Collision Cross Section ◽  
Ion Mobility Mass Spectrometry ◽  
Gas Temperature ◽  
Mobility Data ◽  
Community Effort ◽  
Primary Standards ◽  
Definition Of

Here we present a guide on ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties on mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N, (ii) ion mobility does not measure surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model, (iii) methods relying on calibration are empirical (and thus may provide method-dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort towards establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. <br><br><br>

The Metaphor of Hunting and the Method of Division in the Sophist

2018 ◽  
pp. 55-60
Author(s):  
George Bruseker
Keyword(s):  
Iterative Process ◽  
Pedagogical Tool ◽  
Non Linear ◽  
Definition Of

This paper examines the metaphor of hunting as used in Plato’s dialogue, the Sophist. In it, we explore the idea that the example of the ‘angler’ given at the start of the dialogue is no throw-away example, but opens up the metaphor of hunting as an important element of understanding how to use the method of division introduced for coming to definitional knowledge. I argue that the use of the metaphor of hunting is a pedagogical tool that transforms the attentive student’s understanding of the method of division from a dry science of definition, to a manner of approaching the search for truth. Applied reflexively to the search for the definition of the sophist, it helps reveal that the search for knowledge is a non-linear, iterative process which requires passing-through, and abides no shortcuts. It leaves open the suggestion that the true image of knowledge and the philosopher may finally be found in a version of acquisitive rather than productive or seperative arts (as they are classified within the dialogue).

The Book, Inside and Out

2019 ◽  
pp. 239-250
Author(s):  
Warren Motte
Keyword(s):  
Iterative Process ◽  
The Status ◽  
Definition Of ◽  
Edmond Jabes

Warren Motte’s treatment of the work of Edmond Jabès argues that Jabès’s work is animated by a meditation on the idea of the book. Motte contends that despite that sustained reflection, the status of the book in Jabès’s writing remains ambiguous. Indeed, his analysis shows that Jabès always defers a coherent, functional definition of the book. Motte underscores how that process of deferral—paired with the constant iterative process of crafting new interrelated books—has resulted in a powerful œuvre that gives the reader the sense of an ideal book, but one that never quite exists materially.

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