Reliable floating point computation of minimal bases
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Gejji, R. R.↗
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Results for “Minimization”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A minimal-chip-count TDM bussing concept for RAMP
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Dunn, W. R.↗
On minimizing the number of calculations in design-by-analysis codes
A method is presented for aerodynamic design for a specified pressure distribution, using analysis codes only. The method requires a very conservative number of analysis runs, and therefore is appropriate when the analysis code is a large code in terms of storage and/or running time. Three model problems illustrate some capabilities and limitations of the method.
Barger, Raymond L.↗
Profile modification to minimize spur gear dynamic loading
An analytical computer simulation program for dynamic modeling of low-contact-ratio spur gear systems is presented. The procedure computes the static transmission error of the gears operating under load and uses a fast Fourier transform to generate the frequency spectrum of the static transmission error at various tooth profile modifications. The dynamic loading response of an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. Correlations were found between various profile modifications and the resulting dynamic loads. An effective error, obtained from frequency domain analysis of the static transmission error of the gears, gave a very good indication of the optimum profile modification to reduce gear dynamic loading. Design curves generated by dynamic simulation at various profile modifications are given for gear systems operated at various loads. Optimum profile modifications can be determined from these design curves for improved gear design.
Lin, Hsiang Hsi↗
Ground-based experiments on the minimization of convection during the growth of crystals from solution
Crystals were grown from solution in the earth's gravitational field with the substantial absence of convection by (1) downward unidirectional growth in an isothermally cooled solution and (2) upward unidirectional growth in a positive vertical thermal gradient. Growth rates were 1.3 to 1.8 times the predictions for convectionless growth, and an order of magnitude less than for growth with vigorous convection. Crystals grown in the isothermal configuration were of comparable or superior quality to those grown with substantial convection. The imposition of a 0.5 to 0.8 C/mm gradient greatly stabilized the growth interface so that flat (001) surfaces could be grown on KDP. Crystals grown in a thermal gradient, however, were filled with far more fluid inclusions than crystals grown isothermally.
Nerad, B. A.↗
Pilot evaluation of population-minimal ground tracks in the airport community
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Deloach, Richard↗
Thermal stress minimized, two component, turbine shroud seal
In a turbine machine, a two-component shroud seal which maximizes insulation and sealing around the rotating turbine blades, and is made by independently fabricating each of the two components then joining them together, is disclosed. The two components may be joined together at room temperature. The resulting shroud seal provides greater engine efficiency and thrust.
Handschuh, Robert F.↗
Minimal parameter solution of the orthogonal matrix differential equation
As demonstrated in this work, all orthogonal matrices solve a first order differential equation. The straightforward solution of this equation requires n sup 2 integrations to obtain the element of the nth order matrix. There are, however, only n(n-1)/2 independent parameters which determine an orthogonal matrix. The questions of choosing them, finding their differential equation and expressing the orthogonal matrix in terms of these parameters are considered. Several possibilities which are based on attitude determination in three dimensions are examined. It is shown that not all 3-D methods have useful extensions to higher dimensions. It is also shown why the rate of change of the matrix elements, which are the elements of the angular rate vector in 3-D, are the elements of a tensor of the second rank (dyadic) in spaces other than three dimensional. It is proven that the 3-D Gibbs vector (or Cayley Parameters) are extendable to other dimensions. An algorithm is developed employing the resulting parameters, which are termed Extended Rodrigues Parameters, and numerical results are presented of the application of the algorithm to a fourth order matrix.
Bar-Itzhack, Itzhack Y.↗
Material tradeoffs to minimize flooding reactivity
In the GE 100 KWe SP-100 design, the array of fuel pins in the core was surrounded by a thin neutron barrier made of a mixture of Nb-1 percent Zr and 20 percent B4C. The purpose of this barrier was to prevent the return to the reactor of thermalized neutrons in the event of a reactor flooding accident. Neutronically, the barrier produced a reduction in k sub eff of 15 percent. However, a mixture of Nb-1 percent Zr and B4C is a development item and may not be possible to produce. Several alternatives to this design were investigated. These include the use of W-26 percent Re for the fuel barrier and the introduction of fuel pin ducts made of Ta-8 percent W-2 percent Hf, Hf-10 percent Nb or pure Re. The use of W-26 percent Re for the fuel barrier material in place of W, and the use of T111, Hf-10 percent Nb, or Re duct material in place of Nb-1 percent Zr or Nb-1 percent Zr-20 percent B4C were found to substantially decrease k sub eff in the flooding situation. The best choice neutronically for duct material is Hf-10 percent Nb, because of its small impact on the k sub eff of the normal core.
Protsik, R.↗
Optimal rejection of persistent disturbances, robust stability, and mixed sensitivity minimization
The problem of optimal disturbance rejection of bounded persistent disturbances is solved in the general nonsquare case. The minimum value of the objective function can be obtained by solving a semiinfinite linear programming problem, and an iterative procedure for obtaining approximate solutions is introduced. Application of the l1-optimal problem to robustness is discussed. A mixed sensitivity problem is formulated and shown to guarantee good disturbance rejection in the presence of plant perturbations.
Dahleh, Munther A.↗
Minimization of squared angular error to reduce bias
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Rennie, Michael W.↗
Adaptive wall technology for minimization of wall interferences in transonic wind tunnels
Modern experimental techniques to improve free air simulations in transonic wind tunnels by use of adaptive wall technology are reviewed. Considered are the significant advantages of adaptive wall testing techniques with respect to wall interferences, Reynolds number, tunnel drive power, and flow quality. The application of these testing techniques relies on making the test section boundaries adjustable and using a rapid wall adjustment procedure. A historical overview shows how the disjointed development of these testing techniques, since 1938, is closely linked to available computer support. An overview of Adaptive Wall Test Section (AWTS) designs shows a preference for use of relatively simple designs with solid adaptive walls in 2- and 3-D testing. Operational aspects of AWTS's are discussed with regard to production type operation where adaptive wall adjustments need to be quick. Both 2- and 3-D data are presented to illustrate the quality of AWTS data over the transonic speed range. Adaptive wall technology is available for general use in 2-D testing, even in cryogenic wind tunnels. In 3-D testing, more refinement of the adaptive wall testing techniques is required before more widespread use can be planned.
Wolf, Stephen W. D.↗
Minimal parameter solution of the orthogonal matrix differential equation
As demonstrated in this work, all orthogonal matrices solve a first order differential equation. The straightforward solution of this equation requires n sup 2 integrations to obtain the element of the nth order matrix. There are, however, only n(n-1)/2 independent parameters which determine an orthogonal matrix. The questions of choosing them, finding their differential equation and expressing the orthogonal matrix in terms of these parameters are considered. Several possibilities which are based on attitude determination in three dimensions are examined. It is shown that not all 3-D methods have useful extensions to higher dimensions. It is also shown why the rate of change of the matrix elements, which are the elements of the angular rate vector in 3-D, are the elements of a tensor of the second rank (dyadic) in spaces other than three dimensional. It is proven that the 3-D Gibbs vector (or Cayley Parameters) are extendable to other dimensions. An algorithm is developed employing the resulting parameters, which are termed Extended Rodrigues Parameters, and numerical results are presented of the application of the algorithm to a fourth order matrix.
Baritzhack, Itzhack Y.↗
Capabilities of wind tunnels with two-adaptive walls to minimize boundary interference in 3-D model testing
An initial wind tunnel test was made to validate a new wall adaptation method for 3-D models in test sections with two adaptive walls. First part of the adaptation strategy is an on-line assessment of wall interference at the model position. The wall induced blockage was very small at all test conditions. Lift interference occurred at higher angles of attack with the walls set aerodynamically straight. The adaptation of the top and bottom tunnel walls is aimed at achieving a correctable flow condition. The blockage was virtually zero throughout the wing planform after the wall adjustment. The lift curve measured with the walls adapted agreed very well with interference free data for Mach 0.7, regardless of the vertical position of the wing in the test section. The 2-D wall adaptation can significantly improve the correctability of 3-D model data. Nevertheless, residual spanwise variations of wall interference are inevitable.
Rebstock, Rainer↗
Minimizing the total harmonic distortion for a 3 kW, 20 kHz ac to dc converter using SPICE
This paper describes the SPICE model of a transformer-rectified-filter (TRF) circuit and the Micro-CAP (Microcomputer Circuit Analysis Program) model and their application. The models were used to develop an actual circuit with reduced input current THD. The SPICE analysis consistently predicted the THD improvements in actual circuits as various designs were attempted. In an effort to predict and verify load regulation, the incorporation of saturable inductor models significantly improved the fidelity of the TRF circuit output voltage.
Lollar, Louis F.↗
Minimization of spacecraft disturbances in space-robotic systems
Virtual manipulators for an arbitrary point of a real open chain space manipulator are presented. These virtual manipulators can be used to generate a disturbance map which can be used to select paths that reduce spacecraft disturbances. The present technique is applied to a simple two-link manipulator mounted on a free-floating spacecraft.
Vafa, Zia↗
Function minimization with partially correct data via simulated annealing
The simulated annealing technique has been applied successfully to the problem of estimating the coefficients of a function in cases where only a portion of the data being fitted to the function is truly representative of the function, the rest being erroneous. Two examples are given, one in photometric function fitting and the other in pattern recognition. A schematic of the algorithm is provided.
Lorre, Jean J.↗
Profile modification to minimize spur gear dynamic loading
An analytical computer simulation program for dynamic modeling of low-contact-ratio spur gear systems is presented. The procedure computes the static transmission error of the gears operating under load and uses a fast Fourier transform to generate the frequency spectrum of the static transmission error at various tooth profile modifications. The dynamic loading response of an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. Correlations were found between various profile modifications and the resulting dynamic loads. An effective error, obtained from frequency domain analysis of the static transmission error of the gears, gave a very good indication of the optimum profile modification to reduce gear dynamic loading. Design curves generated by dynamic simulation at various profile modifications are given for gear systems operated at various loads. Optimum profile modifications can be determined from these design curves for improved gear design.
Lin, H. H.↗