130,099 research outputs found
Microstructure Controlled Shear Band Pattern Formation and Enhanced Plasticity of Bulk Metallic Glasses Containing in situ Formed Ductile Phase Dendrite Dispersions
Results are presented for a ductile metal reinforced bulk metallic glass matrix composite based on glass forming compositions in the Zr-Ti-Cu-Ni-Be system. Primary dendrite growth and solute partitioning in the molten state yields a microstructure consisting of a ductile crystalline Ti-Zr-Nb β phase, with bcc structure, in a Zr-Ti-Nb-Cu-Ni-Be bulk metallic glass matrix. Under unconstrained mechanical loading organized shear band patterns develop throughout the sample. This results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass
Large supercooled liquid region and phase separation in the Zr–Ti–Ni–Cu–Be bulk metallic glasses
Results of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr-Ti-Cu-Ni-Be alloy system. The calorimetric data for five alloys, prepared along the tie line between phase separating and nonphase separating compositions, show that the transition from phase separating to nonphase separating behavior is smooth. The bulk glasses near the center of the tie line exhibit large supercooled liquid regions: Delta T approximate to 135 K, the largest known for a bulk metallic glass
Dynamic measurement of total temperature, pressure and velocity in the Langley 0.3-meter transonic cryogenic tunnel
There is theoretical and experimental evidence which indicates that a sudden or step change in the rate at which the liquid nitrogen is injected into the circuit of a cryogenic wind tunnel can cause a temperature front in the flow for several tunnel circuit times. A temperature front, which occurs at intervals equal to the circuit time, is a sudden increase or decrease in the temperature of the flow followed by a nearly constant temperature. Since these fronts can have an effect on the control of the tunnel as well as the time required to establish steady flow conditions in the test section of cryogenic wind tunnel, tests were conducted in the settling chamber in the Langley 0.3-meter Transonic Cryogenic Tunnel (0.3-m TCT) in which high response instrumentation was used to measure the possible existence of these temperature fronts. Three different techniques were used to suddenly change the rate of liquid nitrogen being injected into the tunnel and the results from these three types of tests showed that temperature fronts do not appear to be present in the 0.3-m TCT. Also included are the velocity and pressure fluctuations measured in the settling chamber downstream of the screens and the associated power spectra
Peak wind speed anemometers /maxometer/ Final report, 26 Mar. 1969 - 25 May 1970
Fabrication and testing of peak wind speed recording devic
A Framework to Manage the Complex Organisation of Collaborating: Its Application to Autonomous Systems
In this paper we present an analysis of the complexities of large group
collaboration and its application to develop detailed requirements for
collaboration schema for Autonomous Systems (AS). These requirements flow from
our development of a framework for collaboration that provides a basis for
designing, supporting and managing complex collaborative systems that can be
applied and tested in various real world settings. We present the concepts of
"collaborative flow" and "working as one" as descriptive expressions of what
good collaborative teamwork can be in such scenarios. The paper considers the
application of the framework within different scenarios and discuses the
utility of the framework in modelling and supporting collaboration in complex
organisational structures
Medical operations and life sciences activities on space station
Space station health maintenance facilities, habitability, personnel, and research in the medical sciences and in biology are discussed. It is assumed that the space station structure will consist of several modules, each being consistent with Orbiter payload bay limits in size, weight, and center of gravity
In situ transmission electron microscopy studies of shear bands in a bulk metallic glass based composite
In situ straining transmission electron microscopy (TEM) experiments were performed to study the propagation of the shear bands in the Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 bulk metallic glass based composite. Contrast in TEM images produced by shear bands in metallic glass and quantitative parameters of the shear bands were analyzed. It was determined that, at a large amount of shear in the glass, the localization of deformation occurs in the crystalline phase, where formation of dislocations within the narrow bands are observed
Coulomb-Modified Fano Resonance in a One-Lead Quantum Dot
We investigate a tunable Fano interferometer consisting of a quantum dot
coupled via tunneling to a one-dimensional channel. In addition to Fano
resonance, the channel shows strong Coulomb response to the dot, with a single
electron modulating channel conductance by factors of up to 100. Where these
effects coexist, lineshapes with up to four extrema are found. A model of
Coulomb-modified Fano resonance is developed and gives excellent agreement with
experiment.Comment: related papers available at http://marcuslab.harvard.ed
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