Engineering Papers⌕ Search

SEARCH · Engineering Papers

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

An emulator for minimizing finite element analysis implementation resources

A finite element analysis emulator providing a basis for efficiently establishing an optimum computer implementation strategy when many calculations are involved is described. The SCOPE emulator determines computer resources required as a function of the structural model, structural load-deflection equation characteristics, the storage allocation plan, and computer hardware capabilities. Thereby, it provides data for trading analysis implementation options to arrive at a best strategy. The models contained in SCOPE lead to micro-operation computer counts of each finite element operation as well as overall computer resource cost estimates. Application of SCOPE to the Memphis-Arkansas bridge analysis provides measures of the accuracy of resource assessments. Data indicate that predictions are within 17.3 percent for calculation times and within 3.2 percent for peripheral storage resources for the ELAS code.

Melosh, R. J.↗
NASA NTRS1983

Gas-Temperature Measurement With Minimal Perturbation

Method for measuring temperature of hot turbulent gases uses three heatflux calorimeters. One calorimeter measures radiative heat flux, while other two measure total heat flux (convective and radiative), at two different temperatures. Adapted for commercial uses in such operations as monitoring temperatures of flue gases, piped liquid or gaseous products, internal-combustion or jet engine exhausts.

Fu, T. S.↗
NASA NTRS1984

Minimizing Weight of Structural Designs

Approximation Concepts Code for Efficient Structural Synthesis (ACCESS3) combines methods to offer structural system designer powerful, efficient tool for synthesis of minimum-weight designs. Approximation concepts convert general structural synthesis problem into sequence of explicit problems of separable algebraic form; dual method exploits separable form to construct sequence of explicit dual functions.

Schmit, L. A., Jr.↗
NASA NTRS1983

The minimization of pylon-mounted store effects on air combat capability

Some effects of pylon-mounted missiles on aft-tail delta wing supersonic fighter concepts have been investigated. Whereas minimum drag penalties do occur with the addition of missiles, the effects at higher lifts, corresponding to maneuvering flight, are less severe and often favorable. Lower speeds and altitudes enhance the maneuvering capability and one-on-one air combat would probably tend to degenerate to subsonic speeds even though the combatants may be flying supersonic fighters. Higher speed (supersonic) flight might best be reserved for interceptors with long-range missiles where the weapon carriage effects at low angles of attack are of prime importance.

Spearman, M. L.↗
NASA NTRS1982

Computer program to minimize prediction error in models from experiments with 16 hypercube points and 0 to 6 center points

A previous report described a backward deletion procedure of model selection that was optimized for minimum prediction error and which used a multiparameter combination of the F - distribution and an order statistics distribution of Cochran's. A computer program is described that applies the previously optimized procedure to real data. The use of the program is illustrated by examples.

Holms, A. G.↗
NASA NTRS1982

Geographic Information Systems for Assessing Existing and Potential Bio-energy Resources: Their Use in Determining Land Use and Management Options which Minimize Ecological and Landscape Impacts in Rural Areas

A management construct is described which forms part of an overall landscape ecological planning model which has as a principal objective the extension of the traditional descriptive land use mapping capabilities of geographic information systems into land management realms. It is noted that geographic information systems appear to be moving to more comprehensive methods of data handling and storage, such as relational and hierarchical data management systems, and a clear need has simultaneously arisen therefore for planning assessment techniques and methodologies which can actually use such complex levels of data in a systematic, yet flexible and scenario dependent way. The descriptive of mapping method proposed broaches such issues and utilizes a current New England bioenergy scenario, stimulated by the use of hardwoods for household heating purposes established in the post oil crisis era and the increased awareness of the possible landscape and ecological ramifications of the continued increasing use of the resource.

Jackman, A. E.↗
NASA NTRS1983

Noise characterization and minimization of a precision gyroscopic rate sensor

A program has been conducted to evaluate the noise signature of Space Telescope gyros. The Space Telescope gyros provide a three-axis attitude reference using six single-degree-of-freedom gyroscopes operated with pulse rebalance electronics; the rate sensor attitude quantization is 0.00025 arcsec. The results of the noise evaluation program, including error source characterization and identification of candidate design modifications, are summarized together with the results of prototype hardware testing. It is shown that the proposed design modifications can significantly improve the rate sensor noise performance.

Dougherty, H.↗
NASA NTRS1984

Application of fuel/time minimization techniques to route planning and trajectory optimization

Rising fuel costs combined with other economic pressures have resulted in industry requirements for more efficient air traffic control and airborne operations. NASA has responded with an on-going research program to investigate the requirements and benefits of using new airborne guidance and pilot procedures that are compatible with advanced air traffic control systems and that will result in more fuel efficient flight. The results of flight testing an airborne computer algorithm designed to provide either open-loop or closed-loop guidance for fuel efficient descents while satisfying time constraints imposed by the air traffic control system is summarized. Some of the potential cost and fuel savings that are obtained with sophisticated vertical path optimization capabilities are described.

Knox, C. E.↗
NASA NTRS1984

Feedback laws for fuel minimization for transport aircraft

The Theoretical Mechanics Branch has as one of its long-range goals to work toward solving real-time trajectory optimization problems on board an aircraft. This is a generic problem that has application to all aspects of aviation from general aviation through commercial to military. Overall interest is in the generic problem, but specific problems to achieve concrete results are examined. The problem is to develop control laws that generate approximately optimal trajectories with respect to some criteria such as minimum time, minimum fuel, or some combination of the two. These laws must be simple enough to be implemented on a computer that is flown on board an aircraft, which implies a major simplification from the two point boundary value problem generated by a standard trajectory optimization problem. In addition, the control laws allow for changes in end conditions during the flight, and changes in weather along a planned flight path. Therefore, a feedback control law that generates commands based on the current state rather than a precomputed open-loop control law is desired. This requirement, along with the need for order reduction, argues for the application of singular perturbation techniques.

Price, D. B.↗
NASA NTRS1981

Computer program documentation for a subcritical wing design code using higher order far-field drag minimization

A subsonic, linearized aerodynamic theory, wing design program for one or two planforms was developed which uses a vortex lattice near field model and a higher order panel method in the far field. The theoretical development of the wake model and its implementation in the vortex lattice design code are summarized and sample results are given. Detailed program usage instructions, sample input and output data, and a program listing are presented in the Appendixes. The far field wake model assumes a wake vortex sheet whose strength varies piecewise linearly in the spanwise direction. From this model analytical expressions for lift coefficient, induced drag coefficient, pitching moment coefficient, and bending moment coefficient were developed. From these relationships a direct optimization scheme is used to determine the optimum wake vorticity distribution for minimum induced drag, subject to constraints on lift, and pitching or bending moment. Integration spanwise yields the bound circulation, which is interpolated in the near field vortex lattice to obtain the design camber surface(s).

Kuhlman, J. M.↗
NASA NTRS1982

Pharmacologic counter measures minimizing post-space flight orthostatic intolerance

The effect of bed rest on drug disposition and physiological function was investigated as part of a project to determine the cardiovascular effects of space flight. One group of subjects was given doses of lidocane, penicillin-G, and ICG during a control period and following seven days of bed rest. Cardiac function was evaluated by echo-cardiography. Renal function was evaluated in a second group before and after several days of bed rest. Inulin, para-aminohippurate, and dextran clearances were studied. In the first group, the post-bed rest parameters were not statistically different from the pre-bed rest valves. In the second study, renal function did not change significantly after seven days of bed rest. Plans for future research are reviewed.

Harrison, D. C.↗
NASA NTRS1983

Minimal upper mantle temperature variations consistent with observed heat flow and plate velocities

Heat-flow and plate-velocity measurements are used to model upper-mantle temperature variations; the results are intended to form the basis for a gravity-field-variation model and are also applicable to the interpretation of petrological and seismological data. A 5-deg grid is used, a depth of 280 km is chosen as the fully convecting level, and it is assumed that 85 percent of the global heat production (4.0 x 10 to the 13th W) comes from below this level. The velocity field is calculated by integrating the momentum equations down to 280 km (assuming laterally homogeneous viscosity and density) and then used to determine the temperature fields. The results are presented in graphs, tables, and maps. The largest lateral temperature differences are about 1500 C and occur in the top 20 km, where the largest (about 200 C/Myr) nonlinear terms of the energy equation are also found. Below 50 km, heat transfer becomes more convective than conductive, and the most significant temperature variation appears in the form of negative 'tongues' as cold as -825 C at about 100 km. Temperature variations of at least + or - 180 C are calculated at the fully convecting level.

Kaula, W. M.↗
NASA NTRS1984

An emulator for minimizing computer resources for finite element analysis

A computer code, SCOPE, has been developed for predicting the computer resources required for a given analysis code, computer hardware, and structural problem. The cost of running the code is a small fraction (about 3 percent) of the cost of performing the actual analysis. However, its accuracy in predicting the CPU and I/O resources depends intrinsically on the accuracy of calibration data that must be developed once for the computer hardware and the finite element analysis code of interest. Testing of the SCOPE code on the AMDAHL 470 V/8 computer and the ELAS finite element analysis program indicated small I/O errors (3.2 percent), larger CPU errors (17.8 percent), and negligible total errors (1.5 percent).

Melosh, R.↗
NASA NTRS1983

Vertical ascending electrophoresis of cells with a minimal stabilizing medium

Vertical fractionation of a mixture of fixed horse and human red blood cells layered over a stabilizing support medium was done to give a valid comparison with proposed space experiments. In particular, the effects of sample thickness and concentration on zone migration rate were investigated. Electrophoretic mobilities of horse and human cells calculated from zone migration rates were compatible with those obtained by microelectrophoresis. Complete cell separation was observed when low power and effective cooling were employed.

Omenyi, S. N.↗
NASA NTRS1984

The role of airfoil geometry in minimizing the effect of insect contamination of laminar flow sections

A method has been developed to predict the contamination of an airfoil by insects and the resultant performance penalty. Insect aerodynamics have been modeled and the impingement of insects on an airfoil are solved by calculating their trajectories. Upon impact, insect rupture and the resulting height of the debris is determined based on experimental data. A boundary layer analysis is performed to determine which insects cause boundary layer transition and the resultant drag penalty. A contaminated airfoil figure of merit is presented to be used to compare airfoil susceptibility. Results show that the insect contamination effects depend on accretion conditions, airfoil angle of attack and Reynolds number. The importance of the stagnation region to designing airfoils for minimum drag penalties is discussed.

Maresh, J. L.↗
NASA NTRS1985

A two-step scheme for the advection equation with minimized dissipation and dispersion errors

A two-step advection scheme of the Lax-Wendroff type is derived which has accuracy and phase characteristics similar to that of a third-order scheme. The scheme is exactly third-order accurate in time and space for uniform flow. The new scheme is compared with other currently used methods, and is shown to simulate well the advection of localized disturbances with steep gradients. The scheme is derived for constant flow and generalized to two-dimensional nonuniform flow.

Takacs, L. L.↗