2,768 research outputs found
Low phase-shift amplifier
Single-stage MOSFET amplifier is described which is identical to standard neutralized amplifier except that neutralization provided by broadband transformer is applied to AGC gate instead of signal gate. Neutralization of drain-to-control gate capacity minimizes the phase change induced by variation in AGC
High-Temperature, Low-Cycle Fatigue Behavior of Tantalum
High temperature, low cycle fatigue tests of tantalum in inert argon atmospher
Frequency and timing system for the consolidated DSN and STDN tracking network
The consolidation on the existing Deep Space Network (DSN) and colocated Goddard Spaceflight Tracking and Data Network (STDN) stations into a multiple antenna array is discussed. Each site includes a signal processing center (SPC) centered in an array of four or five antennas each located within approximately 300 to 800 meters of the SPC. A central frequency and timing system (FTS) located in the SPC contains reference frequency, timing and time code generation, and distribution equipment for both the SPC and each antenna with its associated front end antenna control building. The reference frequency distribution and clock equipment are driven by a hydrogen maser as the prime frequency standard with cesium beam frequency standard as the secondary
Fluctuations and scaling in creep deformation
The spatial fluctuations of deformation are studied in creep in the Andrade's
power-law and the logarithmic phases, using paper samples. Measurements by the
Digital Image Correlation technique show that the relative strength of the
strain rate fluctuations increases with time, in both creep regimes. In the
Andrade creep phase characterized by a power law decay of the strain rate
, with , the fluctuations obey
, with . The local
deformation follows a data collapse appropriate for an absorbing
state/depinning transition. Similar behavior is found in a crystal plasticity
model, with a jamming or yielding phase transition
Learning the language of school history: the role of linguistics in mapping the writing demands of the secondary school curriculum
This paper reports on a research study which used the tools of functional linguistics to illuminate the writing requirements of the history curriculum in the context of Australian secondary schools. It shows how the resulting linguistic description was integrated into a sequence of teaching and learning activities through collaboration between linguist specialists and content/pedagogic specialists. These activities were designed to facilitate students’ writing skills whilst simultaneously developing their historical knowledge. An independent evaluation of the approach pointed to positive changes in teachers’ attitudes and behaviours regarding the role of language in learning history. Equally, students’ writing improved, particularly in terms of its organisation and structure
Study to determine experimentally the feasibility of new methods for improving thermal conductance of mechanical joints in a vacuum Summary research report, 8 Apr. - 30 Sep. 1966
Surface-plateauing techniques, and flexible surface membranes for improved thermal conductance of mechanical joints in vacuu
Spatial fluctuations in transient creep deformation
We study the spatial fluctuations of transient creep deformation of materials
as a function of time, both by Digital Image Correlation (DIC) measurements of
paper samples and by numerical simulations of a crystal plasticity or discrete
dislocation dynamics model. This model has a jamming or yielding phase
transition, around which power-law or Andrade creep is found. During primary
creep, the relative strength of the strain rate fluctuations increases with
time in both cases - the spatially averaged creep rate obeys the Andrade law
, while the time dependence of the spatial
fluctuations of the local creep rates is given by . A similar scaling for the fluctuations is found in the logarithmic
creep regime that is typically observed for lower applied stresses. We review
briefly some classical theories of Andrade creep from the point of view of such
spatial fluctuations. We consider these phenomenological, time-dependent creep
laws in terms of a description based on a non-equilibrium phase transition
separating evolving and frozen states of the system when the externally applied
load is varied. Such an interpretation is discussed further by the data
collapse of the local deformations in the spirit of absorbing state/depinning
phase transitions, as well as deformation-deformation correlations and the
width of the cumulative strain distributions. The results are also compared
with the order parameter fluctuations observed close to the depinning
transition of the 2 Linear Interface Model or the quenched Edwards-Wilkinson
equation.Comment: 27 pages, 18 figure
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