Propellant-powered actuator for gas generators

Hydrazine operated monopropellant generators are used for spacecraft rocket engines and propellant pressurization systems. Measured work output of monopropellant actuators compares favorably with output of squib-type actuators

Ferromagnetic-fluid logic devices

Logic element switches flows of low pressure process control fluid in fluidics assemblies. Device operates both electrically and fluidically and is controlled by passing permanent magnet or electromagnet over elements, thus providing proximity switching functions

Nitrogen tetroxide flow decay study for the Orbital Workshop Propulsion System Final report

Flow decay of nitrogen tetroxide in Orbital Workshop Propulsion Syste

HOPDM Modular Solver for LP Problems User's Guide to version 2.12

The paper provides a description of HOPDM, a library of routines for solving large scale linear programming problems and its implementation at IIASA. HOPDM stands for Higher Order Primal Dual Method. The algorithm implemented in HOPDM is a new variant of a primal-dual logarithmic barrier method that uses multiple correctors of centrality. The newest version of the library -- HOPDM 2.12 -- is a robust and efficient LP code that compares favorably with the up to date commercial solvers. The paper contains an outline of the algorithm implemented in HOPDM and information about results of tests done with large LP problems developed at IIASA. Finally, the paper provides with details of the implementation of HOPDM and its use at IIASA, as well as with information about availability of the portable version of the HOPDM library

SAP- Modular Tool for Specification and Analysis of User Preferences in Multiple-Criteria Model Analysis

Model based Decision Support Systems (DSS) often use multiple-criteria optimization for selecting Pareto-efficient solutions. Such a selection is based on interactive specification of user preferences. This can be done by specification of aspiration and reservation levels for criteria. Diverse graphical user interface could be used for specification of these levels as well as for interpretation of results. In the approach presented in this paper the specified aspiration and reservation levels are used for generation of component achievement functions for corresponding criteria. Such functions can be interpreted as fuzzy membership functions or as functions, which reflect the degree of satisfaction with given values of criteria. The paper outlines the methodological background and modular structure of a DSS shell for multiple-criteria analysis of decision problems that can be represented as Linear Programming (LP) or Mixed Integer Programming (MIP) problems. The DSS shell has been used at IIASA for analysis of decision problems in water quality management and land use for sustainable development planning. The pilot implementation of one component of that DSS, namely the modular software tool for interactive specification of user preferences is described in more detail. The tool has been also used as in a DSS for analysis of non-linear problems in several engineering applications

Solving a Class of LP Problems with a Primal-Dual Logarithmic Barrier Method

Applying a higher order primal-dual logarithmic barrier method for solving large real-life linear programming problems is addressed in this paper. The efficiency of interior point algorithm on these problems is compared with the one of the state-of-the-art simplex code MINOS version 5.3. Based on such experience, a wide class of LP problems is identified for which logarithmic barrier approach seems advantageous over the simplex one. Additionally, some practical rules for model builders are derived that should allow them to create problems that can easily be solved with logarithmic barrier algorithms

Multicriteria Methodology for the NEEDS Project

This report begins with an overview of multicriteria analysis methods, and the basic principles of developing mathematical models for such analysis. An overview of various representation of user preferences is then presented, including methods based on pairwise comparisons of criteria and those based on scalarizing functions. This is followed by a summary of structures of criteria and alternatives. Next, basic properties of multi-criteria analysis are discussed, followed by a more detailed presentation of the similarities of and differences between the main methods based on scalarizing functions. This report concludes that existing methods do not best meet the needs of the NEEDS project, presents the reasons, and proposes a new methodology for development. Depending upon the development and testing of this new methodology, an existing method will also be chosen as a backup for comparative or alternate use

Rotational Symmetry of Classical Orbits, Arbitrary Quantization of Angular Momentum and the Role of Gauge Field in Two-Dimensional Space

We study the quantum-classical correspondence in terms of coherent wave functions of a charged particle in two-dimensional central-scalar-potentials as well as the gauge field of a magnetic flux in the sense that the probability clouds of wave functions are well localized on classical orbits. For both closed and open classical orbits, the non-integer angular-momentum quantization with the level-space of angular momentum being greater or less than $\hbar$ is determined uniquely by the same rotational symmetry of classical orbits and probability clouds of coherent wave functions, which is not necessarily $2\pi$-periodic. The gauge potential of a magnetic flux impenetrable to the particle cannot change the quantization rule but is able to shift the spectrum of canonical angular momentum by a flux-dependent value, which results in a common topological phase for all wave functions in the given model. The quantum mechanical model of anyon proposed by Wilczek (Phys. Rev. Lette. 48, 1144) becomes a special case of the arbitrary-quantization.Comment: 6 pages, 5 figure

Multicriteria Methodology for the NEEDS Project

This report begins with an overview of multicriteria analysis methods, and the basic principles of developing mathematical models for such analysis. An overview of various representation of user prefereces is then presented, including methods based on pairwise comparisons of criteria and those based on scalarizing functions. This is followed by a summary of structures of criteria and alternatives. Next, basic properties of multi-criteria analysis are discussed, followed by a more detailed presentation of the similarities of and differences between the main methods based on scalarizing function. This report concludes that existing methods do not best meet the needs of the NEEDS project, presents the reasons, and proposes a new methodology for development. Depending upon the development and testing of this new methodology, an existing method will also be chosen as a backup for comparative or alternate use