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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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At least 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Universal adsorption at the vapor-liquid interface near the consolute point

The ellipticity of the vapor-liquid interface above mixtures of methylcyclohexane (C7H14) and perfluoromethylcyclohexane (C7F14) has been measured near the consolute point T(c) = 318.6 K. The data are consistent with a model of the interface that combines a short-ranged density-vs height profile in the vapor phase with a much longer-ranged composition-versus-height profile in the liquid. The value of the free parameter produced by fitting the model to the data is consistent with results from two other simple mixtures and a mixture of a polymer and solvent. This experiment combines precision ellipsometry of the vapor-liquid interface with in situ measurements of refractive indices of the liquid phases, and it precisely locates the consolute point.

Schmidt, James W.↗
NASA NTRS1989

Fiber-matrix interface failures

Interface fractures of aluminum-graphite composites under transverse loading are expected to occur within the graphite fibers, but very near the interface. Residual stresses in aluminum, reinforced with the new high modulus pitch-based fibers, are much lower than would be expected based on simple elasticity calculations. The excess stress may be relaxed by shearing internal to the fibers or at the interface rather than by plastic flow of the matrix. The internal shearing also occurs during repeated thermal cycling of these composites; the fibers are repeatedly intruded, then extruded, during repeated temperature excursions.

Rabenberg, Lew↗
NASA NTRS1990

On the buoyancy-driven motion of a drop towards a rigid surface or a deformable interface

The deformation of a viscous drop, driven by buoyancy toward a solid surface or a deformable interface, is analyzed in the asymptotic limit of small Bond number, for which the deformation becomes important only when the drop is close to the solid surface or interface. Lubrication theory is used to describe the flow in the thin gap between the drop and the solid surface or interface, and boundary-integral theory is used in the fluid phases on either side of the gap. The evolution of the drop shape is traced from a relatively undeformed state until a dimple is formed and a long-time quasi-steady-state pattern is established. A wide range of drop to suspending phase viscosity ratios is examined. It is shown that a dimple is always formed, independently of the viscosity ratio, and that the long-time thinning rates take simple forms as inverse fractional powers of time.

Yiantsios, Stergios G.↗
NASA NTRS1989

Electronic structures of HgTe and CdTe surfaces and HgTe/CdTe interfaces

A Green's-function method has been used to study the surface and interface electronic structures of the II-VI compounds HgTe and CdTe. Localized surface and resonance states near the cation-terminated (100) surface of CdTe and the anion-terminated surface of HgTe have been found for the ideal surfaces. The energies and strengths of these surface states are altered by surface perturbations. The bulk states near the surface are drastically modified by the creation of the surface, but the band gaps remain unchanged. Numerical evaluation of the local densities of states at the Gamma and J points shows that, at the (100) interface of HgTe/CdTe, the previously observed surface states are no longer present. However, in the interface region, bulk states of one material penetrate some distance into the other material.

Schick, J. T.↗
NASA NTRS1986

The development of an intelligent user interface for NASA's scientific databases

The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has as one of its components, the development of an Intelligent User Interface (IUI). The intent of the IUI effort is to develop a friendly and intelligent user interface service that is based on expert systems and natural language processing technologies. This paper presents the design concepts, development approach and evaluation of performance of a prototype Intelligent User Interface Subsystem (IUIS) supporting an operational database.

Campbell, William J.↗
NASA NTRS1990

Automated Fluid Interface System (AFIS)

Automated remote fluid servicing will be necessary for future space missions, as future satellites will be designed for on-orbit consumable replenishment. In order to develop an on-orbit remote servicing capability, a standard interface between a tanker and the receiving satellite is needed. The objective of the Automated Fluid Interface System (AFIS) program is to design, fabricate, and functionally demonstrate compliance with all design requirements for an automated fluid interface system. A description and documentation of the Fairchild AFIS design is provided.

Source record↗
NASA NTRS1987

A study of System Interface Sets (SIS) for the host, target and integration environments of the Space Station Program (SSP)

System interface sets (SIS) for large, complex, non-stop, distributed systems are examined. The SIS of the Space Station Program (SSP) was selected as the focus of this study because an appropriate virtual interface specification of the SIS is believed to have the most potential to free the project from four life cycle tyrannies which are rooted in a dependance on either a proprietary or particular instance of: operating systems, data management systems, communications systems, and instruction set architectures. The static perspective of the common Ada programming support environment interface set (CAIS) and the portable common execution environment (PCEE) activities are discussed. Also, the dynamic perspective of the PCEE is addressed.

Mckay, Charles↗
NASA NTRS1990

Effect of convection on the microstructure of a lamellar eutectic growing with a stepped interface

A two dimensional model developed to study the influence of convective flow on the concentration field ahead of a growing lamellar eutectic is described when one phase projects out into the melt creating a stepped interface. The two dimensional convective flow field, which is periodic in the horizontal direction, was computed numerically using the software FLUENT. The velocity field generated due to the flow of melt over the steps was then incorporated into a finite difference scheme employed to solve the concentration field. The average interfacial composition was calculated and converted to lamellar spacing using the Jackson and Hunt minimum supercooling criterion. It was found that a stepped interface is more sensitive to convection than a planar interface.

Seth, Jayshree↗
NASA NTRS1991

A finite element model of conduction, convection, and phase change near a solid/melt interface

Detailed understanding of heat transfer and fluid flow is required for many aerospace thermal systems. These systems often include phase change and operate over a range of accelerations or effective gravitational fields. An approach to analyzing such systems is presented which requires the simultaneous solution of the conservation laws of energy, momentum, and mass, as well as an equation of state. The variable property form of the governing equations are developed in two-dimensional Cartesian coordinates for a Newtonian fluid. A numerical procedure for solving the governing equations is presented and implemented in a computer program. The Galerkin form of the finite element method is used to solve the spatial variation of the field variables, along with the implicit Crank-Nicolson time marching algorithm. Quadratic Langrangian elements are used for the internal energy and the two components of velocity. Linear Lagrangian elements are used for the pressure. The location of the solid/liquid interface as well as the temperatures are determined form the calculated internal energy and pressure. This approach is quite general in that it can describe heat transfer without phase change, phase change with a sharp interface, and phase change without an interface. Analytical results from this model are compared to those of other researchers studying transient conduction, convection, and phase change and are found to be in good agreement. The numerical procedure presented requires significant computer resources, but this is not unusual when compared to similar studies by other researchers. Several methods are suggested to reduce the computational times.

Viterna, Larry A.↗
NASA NTRS1991

User interface issues in supporting human-computer integrated scheduling

Explored here is the user interface problems encountered with the Operations Missions Planner (OMP) project at the Jet Propulsion Laboratory (JPL). OMP uses a unique iterative approach to planning that places additional requirements on the user interface, particularly to support system development and maintenance. These requirements are necessary to support the concepts of heuristically controlled search, in-progress assessment, and iterative refinement of the schedule. The techniques used to address the OMP interface needs are given.

Cooper, Lynne P.↗
NASA NTRS1991

The use of analytical models in human-computer interface design

Some of the many analytical models in human-computer interface design that are currently being developed are described. The usefulness of analytical models for human-computer interface design is evaluated. Can the use of analytical models be recommended to interface designers? The answer, based on the empirical research summarized here, is: not at this time. There are too many unanswered questions concerning the validity of models and their ability to meet the practical needs of design organizations.

Gugerty, Leo↗
NASA NTRS1991

Transportable Applications Environment (TAE) Plus: A NASA user interface development and management system

The transportable Applications Environment Plus (TAE Plus), developed at the NASA Goddard Space FLight Center, is a portable, What you see is what you get (WYSIWYG) user interface development and management system. Its primary objective is to provide an integrated software environment that allows interactive prototyping and development of graphical user interfaces, as well as management of the user interface within the operational domain. TAE Plus is being applied to many types of applications, and what TAE Plus provides, how the implementation has utilizes state-of-the-art technologies within graphic workstations, and how it has been used both within and without NASA are discussed.

Szczur, Martha R.↗
NASA NTRS1991

Network interface unit design options performance analysis

An analysis is presented of three design options for the Space Station Freedom (SSF) onboard Data Management System (DMS) Network Interface Unit (NIU). The NIU provides the interface from the Fiber Distributed Data Interface (FDDI) local area network (LAN) to the DMS processing elements. The FDDI LAN provides the primary means for command and control and low and medium rate telemetry data transfers on board the SSF. The results of this analysis provide the basis for the implementation of the NIU.

Miller, Frank W.↗
NASA NTRS1990

The Small Explorer Data System - A data system based on standard interfaces

The Small Explorer Data System was developed by NASA Goddard Space Flight Center using a 'standard interfaces' approach. Standard interfaces make it adaptable to a wide variety of missions. The paper describes the Small Explorer Data System with particular emphasis on the standard interfaces incorporated in both the hardware and software.

Smith, Brian S.↗
NASA NTRS1990

Hydrogen and sliding at alpha/beta interfaces of titanium alloys

Emerging evidence that the sliding between alpha and beta interfaces reported in both Ti-Mn alloys and the Ti-4.5Al-5Mo-1.5Cr ('Corona 5') alloy at room temperature is associated with hydrogen suggests that this may be a general problem contributing to Ti alloys' room-temperature creep. The present evaluation of experimental data indicates that while the hydrogen is concentrated at the Ti-Mn alloys' beta phase, no hydride formation at the alpha/beta interfaces has been reported for either the Ti-Mn alloys or Corona 5. If a hydrogen flux is needed, sliding at the alpha-beta interfaces should be a function of total hydrogen content in the alloy.

Margolin, Harold↗
NASA NTRS1990

Crystal-melt interface shape of Czochralski-grown large diameter germanium crystals

Crystal-melt interface shapes of 100 to 200 mm diameter 111-line Ge grown by the Czochralski technique have been examined using the method of fast withdrawal from the melt. Initially, the interface shape is convex, then transforms gradually into a sigmoidal shape, becomes nearly planar at about one third of the final crystal length, and finally assumes a concave profile with progressively increasing curvature. The nearly planar interface has a double-facet structure, with an annular facet at the edge of the crystal in addition to the central (111) facet. Formation of the annular facet is accompanied by a giant oscillation of the pull rate when the maximum average pull rate is exceeded. Such oscillation is detrimental to crystal quality, since it introduces a region of high dislocation density. An average pull rate maximum of 2 cm/h has been found to allow for a smooth growth of 200 mm diameter crystals. The origin of the pull rate perturbation is discussed in terms of an instantaneous change in the equilibrium shape of the meniscus.

Roth, M.↗
NASA NTRS1990

BIRD: A general interface for sparse distributed memory simulators

Kanerva's sparse distributed memory (SDM) has now been implemented for at least six different computers, including SUN3 workstations, the Apple Macintosh, and the Connection Machine. A common interface for input of commands would both aid testing of programs on a broad range of computer architectures and assist users in transferring results from research environments to applications. A common interface also allows secondary programs to generate command sequences for a sparse distributed memory, which may then be executed on the appropriate hardware. The BIRD program is an attempt to create such an interface. Simplifying access to different simulators should assist developers in finding appropriate uses for SDM.

Rogers, David↗
NASA NTRS1990

A generalized strategy for building resident database interfaces

A strategy for building resident interfaces to host heterogeneous distributed data base management systems is developed. The strategy is used to construct several interfaces. A set of guidelines is developed for users to construct their own interfaces.

Moroh, Marsha↗