Best-choice problems involving uncertainty of selection and recall of observations

1981 ◽  
Vol 18 (2) ◽  
pp. 415-425 ◽  
Author(s):  
Joseph D. Petruccelli
Keyword(s):  
Optimal Selection ◽  
Selection Procedures ◽  
Special Cases ◽  
Optimal Procedures ◽  
A Current

This paper explores best choice problems which allow both recall of applicants and uncertainty of a current applicant accepting an offer of employment. Properties of optimal selection procedures are derived for the general case. Optimal procedures and the associated probabilities of obtaining the best applicant are found in two special cases. The results unify and extend those of Yang (1974) and Smith (1975).

Best-choice problems involving uncertainty of selection and recall of observations

1981 ◽  
Vol 18 (02) ◽  
pp. 415-425 ◽  
Author(s):  
Joseph D. Petruccelli
Keyword(s):  
Optimal Selection ◽  
Selection Procedures ◽  
Special Cases ◽  
Optimal Procedures ◽  
A Current

This paper explores best choice problems which allow both recall of applicants and uncertainty of a current applicant accepting an offer of employment. Properties of optimal selection procedures are derived for the general case. Optimal procedures and the associated probabilities of obtaining the best applicant are found in two special cases. The results unify and extend those of Yang (1974) and Smith (1975).

Full-information best-choice problems with recall of observations and uncertainty of selection depending on the observation

1982 ◽  
Vol 14 (2) ◽  
pp. 340-358 ◽  
Author(s):  
Joseph D. Petruccelli
Keyword(s):  
Distribution Function ◽  
Continuous Distribution ◽  
Random Variables ◽  
Continuous Distribution Function ◽  
Optimal Selection ◽  
Full Information ◽  
Selection Procedures ◽  
General Properties ◽  
Special Cases ◽  
Optimal Procedures

n i.i.d. random variables with known continuous distribution function F are observed sequentially with the object of choosing the largest. After any observation, say the kth, the observer may solicit any of the first k observations. If the (k – t)th is solicited, the probability of a successful solicitation may depend on t, the number of observations since the (k – t)th, and on the quantile of the (k – t)th observation. General properties of optimal selection procedures are obtained and the optimal procedures and their probabilities of success are derived in some special cases.

Full-information best-choice problems with recall of observations and uncertainty of selection depending on the observation

1982 ◽  
Vol 14 (02) ◽  
pp. 340-358 ◽  
Author(s):  
Joseph D. Petruccelli
Keyword(s):  
Distribution Function ◽  
Continuous Distribution ◽  
Random Variables ◽  
Continuous Distribution Function ◽  
Optimal Selection ◽  
Full Information ◽  
Selection Procedures ◽  
General Properties ◽  
Special Cases ◽  
Optimal Procedures

n i.i.d. random variables with known continuous distribution function F are observed sequentially with the object of choosing the largest. After any observation, say the kth, the observer may solicit any of the first k observations. If the (k – t)th is solicited, the probability of a successful solicitation may depend on t, the number of observations since the (k – t)th, and on the quantile of the (k – t)th observation. General properties of optimal selection procedures are obtained and the optimal procedures and their probabilities of success are derived in some special cases.

On Drift Instabilities in a Collisionless Electron-Proton Plasma from the point of view of Energy Absorption of Resonant Particles

1963 ◽  
Vol 18 (4) ◽  
pp. 446-453 ◽  
Author(s):  
Asbjørn Kildal
Keyword(s):  
Energy Absorption ◽  
Constant Electric Field ◽  
Wave Length ◽  
Collisionless Plasma ◽  
Phase Region ◽  
Point Of View ◽  
Electrostatic Waves ◽  
Transverse Current ◽  
Special Cases ◽  
A Current

The present paper is essentially devoted to the study of instabilities of electrostatic waves in a current-carrying collisionless plasma. As the underlying physical cause of the instabilities is the same as that of the LANDAU damping in an electron plasma, a detailed analysis of the latter is first given. It is shown that the damping may be considered as being due to the fact that there are more electrons in the phase-region where energy is absorbed by the particles from the field than in the phase-region where energy is given up to the field.We then proceed to the evaluation of the energy absorption A of the resonant particles, first in the absence of an external magnet field, B0 , next when the wave is propagated under an arbitrary angle with respect to B0 . When A > 0, the wave is damped, and vice-versa. Without appeal to a dispersion equation, stability criteria can thus be found, dependent on the wave frequency and wave-vector. Next some special cases are investigated and compared with the results of other authors where such results exist.As a consequence of the fact that some ions and electrons, the resonant particles, experience a constant electric field, these particles also experience a constant drift transverse to both E and B0. This drift gives rise to a transverse current which is closely related to the damping or growing of the wave. An expression for this current, averaged over one wave-length is found.

The Recruitment, Selection, and Training of Blind Vending Stand Operators

1970 ◽  
Vol 64 (10) ◽  
pp. 325-329
Author(s):  
Ronald G. Rice ◽  
John E. Muthard ◽  
Neil S. Dumas
Keyword(s):  
Present Report ◽  
State Agencies ◽  
National Scale ◽  
Selection Procedures ◽  
Rate Of Success ◽  
And Training ◽  
A Current

□ At the present time, there does not seem to be sufficient need to justify the expense of validating a selection battery on a national scale. The results of the questionnaire indicated a current rate of success in rehabilitating VSO's which could not be improved appreciably by a selection battery. The present report provides a current look at the evaluation, selection, training, and follow-up success experienced by state agencies. The feasibility of continuing study of the VSO and the review of possible selection procedures have also been reviewed.

Ageostrophic instability of ocean currents

1982 ◽  
Vol 117 ◽  
pp. 343-377 ◽  
Author(s):  
R. W. Griffiths ◽  
Peter D. Killworth ◽  
Melvin E. Stern
Keyword(s):  
Potential Vorticity ◽  
Lower Layer ◽  
Rotation Period ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Inertial Effects ◽  
Mean Flow ◽  
Special Cases ◽  
Free Streamlines ◽  
A Current

We investigate the stability of gravity currents, in a rotating system, that are infinitely long and uniform in the direction of flow and for which the current depth vanishes on both sides of the flow. Thus, owing to the role of the Earth's rotation in restraining horizontal motions, the currents are bounded on both sides by free streamlines, or sharp density fronts. A model is used in which only one layer of fluid is dynamically important, with a second layer being infinitely deep and passive. The analysis includes the influence of vanishing layer depth and large inertial effects near the edges of the current, and shows that such currents are always unstable to linearized perturbations (except possibly in very special cases), even when there is no extremum (or gradient) in the potential vorticity profile. Hence the established Rayleigh condition for instability in quasi-geostrophic models, where inertial effects are assumed to be vanishingly small relative to Coriolis effects, does not apply. The instability does not depend upon the vorticity profile but instead relies upon a coupling of the two free streamlines. The waves permit the release of both kinetic and potential energy from the mean flow. They can have rapid growth rates, the e-folding time for waves on a current with zero potential vorticity, for example, being close to one-half of a rotation period. Though they are not discussed here, there are other unstable solutions to this same model when the potential vorticity varies monotonically across the stream, verifying that flows involving a sharp density front are much more likely to be unstable than flows with a small ratio of inertial to Coriolis forces.Experiments with a current of buoyant fluid at the free surface of a lower layer are described, and the observations are compared with the computed mode of maximum growth rate for a flow with a uniform potential vorticity. The current is observed to be always unstable, but, contrary to the predicted behaviour of the one-layer coupled mode, the dominant length scale of growing disturbances is independent of current width. On the other hand, the structure of the observed disturbances does vary: when the current is sufficiently narrow compared with the Rossby deformation radius (and the lower layer is deep) disturbances have the structure predicted by our one-layer model. The flow then breaks up into a chain of anticyclonic eddies. When the current is wide, unstable waves appear to grow independently on each edge of the current and, at large amplitude, form both anticyclonic and cyclonic eddies in the two-layer fluid. This behaviour is attributed to another unstable mode.

scholarly journals Refined cut selection for benders decomposition: applied to network capacity expansion problems

2021 ◽  
Author(s):  
René Brandenberg ◽  
Paul Stursberg
Keyword(s):  
Benders Decomposition ◽  
Capacity Expansion ◽  
Network Capacity ◽  
Selection Procedures ◽  
Computational Evaluation ◽  
Special Cases ◽  
Math Program ◽  
Cut Generation ◽  
New Perspective ◽  
The One

AbstractIn this paper, we present a new perspective on cut generation in the context of Benders decomposition. The approach, which is based on the relation between the alternative polyhedron and the reverse polar set, helps us to improve established cut selection procedures for Benders cuts, like the one suggested by Fischetti et al. (Math Program Ser B 124(1–2):175–182, 2010). Our modified version of that criterion produces cuts which are always supporting and, unless in rare special cases, facet-defining. We discuss our approach in relation to the state of the art in cut generation for Benders decomposition. In particular, we refer to Pareto-optimality and facet-defining cuts and observe that each of these criteria can be matched to a particular subset of parametrizations for our cut generation framework. As a consequence, our framework covers the method to generate facet-defining cuts proposed by Conforti and Wolsey (Math Program Ser A 178:1–20, 2018) as a special case. We conclude the paper with a computational evaluation of the proposed cut selection method. For this, we use different instances of a capacity expansion problem for the european power system.

scholarly journals Hydromagnetic Stability of a Current Layer

1955 ◽  
Vol 8 (3) ◽  
pp. 319 ◽  
Author(s):  
RE Loughhead
Keyword(s):  
Magnetic Field ◽  
Normal Modes ◽  
Marginal Stability ◽  
Current Layer ◽  
Special Cases ◽  
Uniform Current ◽  
A Current

The hydromagnetic stability of a uniform current flowing along a magnetic field and confined within a pair of parallel planes is discussed by the method of normal modes. The condition for marginal stability is derived and discussed with reference to two special cases.

scholarly journals On the Inverse EEG Problem for a 1D Current Distribution

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
George Dassios ◽  
George Fragoyiannis ◽  
Konstantia Satrazemi
Keyword(s):  
Current Distribution ◽  
Three Dimensional ◽  
Spherical Model ◽  
One Dimensional ◽  
Special Cases ◽  
Nonlinear Algebraic System ◽  
Arbitrary Location ◽  
Spherical Conductor ◽  
The Brain ◽  
A Current

Albanese and Monk (2006) have shown that, it is impossible to recover the support of a three-dimensional current distribution within a conducting medium from the knowledge of the electric potential outside the conductor. On the other hand, it is possible to obtain the support of a current which lives in a subspace of dimension lower than three. In the present work, we actually demonstrate this possibility by assuming a one-dimensional current distribution supported on a small line segment having arbitrary location and orientation within a uniform spherical conductor. The immediate representation of this problem refers to the inverse problem of electroencephalography (EEG) with a linear current distribution and the spherical model of the brain-head system. It is shown that the support is identified through the solution of a nonlinear algebraic system which is investigated thoroughly. Numerical tests show that this system has exactly one real solution. Exact solutions are analytically obtained for a couple of special cases.

MHD stagnation-point flows at a current sheet including viscous and resistive effects: general two-dimensional solutions

1990 ◽  
Vol 44 (3) ◽  
pp. 525-546 ◽  
Author(s):  
T. D. Phan ◽  
B. U. Ö. Sonnerup
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Current Sheet ◽  
Stagnation Point ◽  
Angle Of Incidence ◽  
Two Dimensional ◽  
Viscous Effects ◽  
Special Cases ◽  
The Magnetic Field ◽  
A Current

Exact solutions are presented of two-dimensional steady-state incompressible stagnation point flows at a current sheet separating two colliding plasmas. They describe the process of resistive field annihilation (zero reconnection) where the magnetic field in each plasma is strictly parallel to the current sheet, but may have different magnitudes and direction on its two sides. The flow in the (x, y) plane toward the current sheet, located at x = 0, may have an arbitrary angle of incidence and an arbitrary amount of divergence from or convergence towards the stagnation point. We find the most general form of the solution for the plasma velocity and for the magnetic field. For the z compenents of the flow and field, solutions in the form of truncating power series in y are found. The cases obtained in this study contain the solutions obtained by Parker, Sonnerup & Priest, Gratton et al. and Besser, Biernat & Rijnbeek as special cases. The role of viscosity in determining the flow and field configurations is examined. When the two colliding plasmas have the same viscosity and density, it is shown that viscous effects usually are important only in strongly divergent or convergent viscous flows with viscous Reynolds number of the order of unity or smaller. For astrophysical applications the viscous Reynolds number is usually high and the effects of viscosity on the interaction of plasmas of similar properties are small. The formulation of the stagnation-point flow problem involving plasmas of different properties is also presented. Sample cases of such flows are shown. Finally, a possible application of the results from this study to the earth's magnetopause is discussed briefly.

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