An appraisal for use in reliability analysis of the test and data collection procedures in the manufacture of an inertial guidance system

Behavior of first gimbal stabilization loop for reliability analysis of inertial guidance syste

An analytical investigation of acquisition techniques and system integration studies for a radar aircraft guidance research facility, phase 2

A review of user requirements and updated instrumentation plans are presented for the aircraft tracking and guidance facility at NASA Wallops Station. User demand has increased as a result of new flight research programs; however, basic requirements remain the same as originally reported. Instrumentation plans remain essentially the same but with plans for up- and down-link telemetry more firm. With slippages in the laser acquisition schedule, added importance is placed on the FPS-16 radar as the primary tracking device until the laser is available. Limited simulation studies of a particular Kalman-type filter are also presented. These studies simulated the use of the filter in a helicopter guidance loop in a real-time mode. Disadvantages and limitations of this mode of operation are pointed out. Laser eyesafety calculations show that laser tracking of aircraft is readily feasible from the eyesafety viewpoint

Leptodactylus rugosus

Number of Pages: 5Integrative BiologyGeological Science

Method of purifying metallurgical grade silicon employing reduced pressure atmospheric control

A method in which a quartz tube is charged with chunks of metallurgical grade silicon and/or a mixture of such chunks and high purity quartz sand, and impurities from a class including aluminum, boron, as well as certain transition metals including nickel, iron, and manganese is described. The tube is then evacuated and heated to a temperature within a range of 800 C to 1400 C. A stream of gas comprising a reactant, such as silicon tetrafluoride, is continuously delivered at low pressures through the charge for causing a metathetical reaction of impurities of the silicon and the reactant to occur for forming a volatile halide and leaving a residue of silicon of an improved purity. The reactant which included carbon monoxide gas and impurities such as iron and nickel react to form volatile carbonyls

Techniques for railway restructuring

This report was sponsored by the Union of African Railways, as part of a Sub-Saharan Africa Transport Project task aimed at defining what is involved in restructuring railways so that they behave more like market driven enterprises. The question addressed in this document is not whether the railway should be restructured, but how. The report recommends four types of action to be employed in the process of institutional reform : 1) a strategic plan which defines the environment in which the railway will function and focuses on the crucial policy issues that will guide or influence the railway's planning and actions, 2) a contract plan which defines the roles and responsibilities of the railway and its owner. This plan flows from the strategic plan and should not be developed in isolation from related policy and funding objectives of the government and railway. 3) A management plan that clarifies the objectives of the senior railway executives and their roles and responsibilities in relation to the executive director, and 4) an enabling actions plan, which lists most of the initiatives that must be taken in conjunction with implementation of the first three plans. The focus should be to ensure that the roles and responsibilities defined will actually be realized in law or enforceable agreement.Railways Transport,Banks&Banking Reform,Public Sector Economics&Finance,Environmental Economics&Policies,Roads&Highways

Reversal Modes of Simulated Iron Nanopillars in an Obliquely Oriented Field

Stochastic micromagnetic simulations are employed to study switching in three-dimensional magnetic nanopillars exposed to highly misaligned fields. The switching appears to proceed through two different decay modes, characterized by very different average lifetimes and different average values of the transverse magnetization components.Comment: 3 pages, 4 figure

A Narrowband Imaging Survey for High Redshift Galaxies in the Near Infrared

A narrowband imaging survey of 276 square minutes of arc was carried out at near infrared wavelengths to search for emission line objects at high redshifts. Most of the fields contained a known quasar or radio galaxy at a redshift that placed one of the strong, restframe optical emission lines (H-alpha, [O III], H-beta, or [O II]) in the bandpass of the narrowband filter. The area weighted line flux limit over the entire survey was 3.4x10e-16 erg/cm2/s (3-sigma), while the most sensitive limits reached 1.4x10e-16 erg/cm2/s. Integrating the volume covered by all four optical emission lines in each image yields a total comoving volume surveyed of 1.4x10e5 cubic megaparsecs. Considering only H-alpha emission in the K band (2.05 < z < 2.65), where the survey is most sensitive, the survey covered a comoving volume of 3.0x10e4 cubic megaparsecs to a volume-weighted average star formation rate of 112 M-solar/yr (for Ho = 50 km/s/Mpc, Omega = 1). This is the most extensive near-infrared survey which is deep enough to have a reasonable chance at detecting strong line emission from an actively star-forming population of galaxies, when d against simple models of galaxy formation. One emission line candidate was identified in this survey, and subsequently confirmed spectroscopically.Comment: To appear in the Astronomical Journal, November 1996. 23 pages, including 2 tables and 7 figure

The effect of hydrogen on the deformation behavior of a single crystal nickel-base superalloy

The effect of hydrogen on the tensile deformation behavior of PWA 1480 is presented. Tensile tests were interrupted at different plastic strain levels to observe the development of the dislocation structure. Transmission electron microscopy (TEM) foils were cut perpendicular to the tensile axis to allow the deformation of both phases to be simultaneously observed as well as parallel to zone axes (III) to show the superdislocations on their slip planes. Similar to other nickel-base superalloys, hydrogen was detrimental to the room temperature tensile properties of PWA 1480. There was little effect on strength, however the material was severely embrittled. Even without hydrogen, the elongation-to-failure was only approximately 3 percent. The tensile fracture surface was made up primarily of ductile voids with regions of cleavage fracture. These cleavage facets are the eutectic (gamma') in the microstructure. It was shown by quantitative fractography that hydrogen embrittles the eutectic (gamma') and causes the crack path to seek out and fracture through the eutectic (gamma'). There was two to three times the amount of cleavage on the fracture surface of the hydrogen-charged samples than on the surface of the uncharged samples. The effect of hydrogen can also be seen in the dislocation structure. There is a marked tendency for dislocation trapping in the gamma matrix with and without hydrogen at all plastic strain levels. Without hydrogen there is a high dislocation density in the gamma matrix leading to strain exhaustion in this region and failure through the matrix. The dislocation structure at failure with hydrogen is slightly different. The TEM foils cut parallel to zone axes (III) showed dislocations wrapping around gamma precipitates. Zone axes (001) foils show that there is a lower dislocation density in the gamma matrix which can be linked to the effects of hydrogen on the fracture behavior. The primary activity in the gamma precipitates is in the form of superlattice intrinsic stacking faults (SISFs). These faults have also been reported in other ordered alloys and superalloys