1,080 research outputs found
Waterfowl and their role in lake ecosystems. [Translation from: Wiadomosci Ekologiczne 19, 355-371, 1973.]
We know very little about the role of birds in different ecosystems, despite numerous interesting works of researchers and amateur ornithologist scattered throughout the world. Less attention is paid to freshwater ecosystems because of the difficulties encountered in the experimental methods as well as a lack of interest on behalf of hydrobiologists, for the activities of birds in these ecosystems. This article summarises types and morphoecological forms of waterfowl and their place in the lake ecosystem
Postan - A Package for Postoptimal Analysis (An Extension of Minos)
This paper presents a new software package which has been developed in collaboration with IIASA The new package, POSTAN, is designed for postoptimal analysis of linear programming problems, and is embedded in the well-known linear and nonlinear programming code MINOS. POSTAN is composed of a number of FORTRAN subroutines which may be called by adding some new keywords to the original list of MINOS specifications. The main function of POSTAN is to determine the ranges in which certain parameters may be changed without affecting the optimal solution and/or the optimal basis.
In this paper the authors outline the general form of the linear programming problems studied, describe the six new subroutines in some detail, and illustrate this description with a printout obtained in the solution of a sample problem. The mathematical theory behind the software package is given in an Appendix
Postan 3 - Extended Postoptimal Analysis Package for Minos
This paper is one of the series of 11 Working Papers presenting the software for interactive decision support and software tools for developing decision support systems. These products constitute the outcome of the contracted study agreement between the System and Decision Sciences Program at IIASA and several Polish scientific institutions. The theoretical part of these results is presented in the IIASA Working Paper WP-88-071 entitled "Theory, Software and Testing Examples in Decision Support Systems" which contains the theoretical and methodological backgrounds of the software systems developed within the project.
This paper presents the POSTAN 3 package. This package constitutes the tool for postoptimal analysis for linear and linear-fractional programming problems. POSTAN consists of a number of FORTRAN routines which are incorporated into MINOS, the well known linear and nonlinear programming code developed at the Stanford University. The postoptimal analysis is performed after MINOS has found an optimal solution and is initiated by extending the original MINOS specification file. The main function of POSTAN is ranging with respect to parameters specified by the user and computing the sensitivity coefficients
First generation of optical fiber phase reference distribution system for TESLA
This report describes the design of a phase stable Fiber Optic (FO) link for the TESLA technology based projects. The concept of this long optical link, with a feedback system suppressing long term drifts of the RF signal phase is described. Stability requirements are given and most important design issues affecting the system performance are discussed. The technical design issues of system components like laser transmitter and optical phase shifter are described in detail. Last sections depict the software developed for system control and experimental results obtained after system was assembled
Magnetoresistance of a semiconducting magnetic wire with domain wall
We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.Comment: 5 pages, 2 figure
The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor
We investigated the nature of the magnetic phase transition in the
Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the
range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization
measurements performed in the magnetic field up to 90 kOe and temperature range
2-200 K showed that the magnetic ordering at temperatures below T = 50 K
exhibits features characteristic for both spin-glass and ferromagnetic phases.
The modified Sherrington - Southern model was applied to explain the observed
transition temperatures. The calculations showed that the spin-glass state is
preferred in the range of the experimental carrier concentrations and Mn
content. The value of the Mn hole exchange integral was estimated to be J/pd/ =
0.45+/-0.05 eV. The experimental magnetization vs temperature curves were
reproduced satisfactory using the non-interacting spin-wave theory with the
exchange constant J/pd/ values consistent with those calculated using modified
Sherrington - Southern model. The magnetization vs magnetic field curves showed
nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of
strong magnetic frustration in the system. The experimental results were
reproduced theoretically with good accuracy using the molecular field
approximation-based model of a disordered ferromagnet with long-range RKKY
interaction.Comment: 9 pages, 6 figure
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