An Ethnographic-Case Study of Beliefs, Context Factors, and Practices of Teachers Integrating Technology

This ethnographic-case study explored the beliefs, context factors, and practices of three middle school exemplary teachers that led to a technology-enriched curriculum. Findings suggest that these middle school teachers believe technology is a tool that adds value to lessons and to students learning and motivation. Due to a personal interest in technology, these teachers are self-taught and apply for grants to acquire new hardware and software. They receive support for release time to continue with ongoing professional development, which has helped to change their teaching strategies from teacher-centered to student-centered. They are not afraid to take risk using trial and error, flexible planning, project-based lessons, varying roles, varying grouping, and providing multiple activities in their classroom practices

Intact and Degraded Component Criticality Calculations of N Reactors Spent Nuclear Fuel

The objective of this calculation is to perform intact and degraded mode criticality evaluations of the Department of Energy's (DOE) N Reactor Spent Nuclear Fuel codisposed in a 2-Defense High-Level Waste (2-DHLW)/2-Multi-Canister Overpack (MCO) Waste Package (WP) and emplaced in a monitored geologic repository (MGR) (see Attachment I). The scope of this calculation is limited to the determination of the effective neutron multiplication factor (k{sub eff}) for both intact and degraded mode internal configurations of the codisposal waste package. This calculation will support the analysis that will be performed to demonstrate the technical viability for disposing of U-metal (N Reactor) spent nuclear fuel in the potential MGR

TRIGA FUEL PHASE I AND II CRITICALITY CALCULATION

The purpose of this calculation is to characterize the criticality aspect of the codisposal of TRIGA (Training, Research, Isotopes, General Atomic) reactor spent nuclear fuel (SNF) with Savannah River Site (SRS) high-level waste (HLW). The TRIGA SNF is loaded into a Department of Energy (DOE) standardized SNF canister which is centrally positioned inside a five-canister defense SRS HLW waste package (WP). The objective of the calculation is to investigate the criticality issues for the WP containing the five SRS HLW and DOE SNF canisters in various stages of degradation. This calculation will support the analysis that will be performed to demonstrate the viability of the codisposal concept for the Monitored Geologic Repository (MGR)

Direct measurement of the phase coherence length in a GaAs/GaAlAs square network

The low temperature magnetoconductance of a large array of quantum coherentloops exhibits Altshuler-Aronov-Spivak oscillations which periodicitycorresponds to 1/2 flux quantum per loop.We show that the measurement of the harmonics content in a square networkprovides an accurate way to determine the electron phase coherence length$L\_{\phi}$ in units of the lattice length without any adjustableparameters.We use this method to determine $L\_{\phi}$ in a network realised from a 2Delectron gas (2DEG) in a GaAS/GaAlAs heterojunction. The temperaturedependence follows a power law $T^{-1/3}$ from 1.3 K to 25 mK with nosaturation, as expected for 1D diffusive electronic motion andelectron-electron scattering as the main decoherence mechanism.Comment: Additional experimental data in version

Proximity DC squids in the long junction limit

We report the design and measurement of Superconducting/normal/superconducting (SNS) proximity DC squids in the long junction limit, i.e. superconducting loops interrupted by two normal metal wires roughly a micrometer long. Thanks to the clean interface between the metals, at low temperature a large supercurrent flows through the device. The dc squid-like geometry leads to an almost complete periodic modulation of the critical current through the device by a magnetic flux, with a flux periodicity of a flux quantum h/2e through the SNS loop. In addition, we examine the entire field dependence, notably the low and high field dependence of the maximum switching current. In contrast with the well-known Fraunhoffer-type oscillations typical of short wide junctions, we find a monotonous gaussian extinction of the critical current at high field. As shown in [15], this monotonous dependence is typical of long and narrow diffusive junctions. We also find in some cases a puzzling reentrance at low field. In contrast, the temperature dependence of the critical current is well described by the proximity effect theory, as found by Dubos {\it et al.} [16] on SNS wires in the long junction limit. The switching current distributions and hysteretic IV curves also suggest interesting dynamics of long SNS junctions with an important role played by the diffusion time across the junction.Comment: 12 pages, 16 figure

Enrico Fermi Fast Reactor Spent Nuclear Fuel Criticality Calculations: Degraded Mode

The objective of this calculation is to characterize the nuclear criticality safety concerns associated with the codisposal of the Department of Energy's (DOE) Enrico Fermi (EF) Spent Nuclear Fuel (SNF) in a 5-Defense High-Level Waste (5-DHLW) Waste Package (WP) and placed in a Monitored Geologic Repository (MGR). The scope of this calculation is limited to the determination of the effective neutron multiplication factor (k{sub eff}) for the degraded mode internal configurations of the codisposal WP. The results of this calculation and those of Ref. 8 will be used to evaluate criticality issues and support the analysis that will be performed to demonstrate the viability of the codisposal concept for the Monitored Geologic Repository

Magnetic field asymmetry of mesocopic dc rectification in Aharonov Bohm rings

Fundamental Casimir-Onsager symmetry rules for linear response do not apply to non linear transport. This motivates the investigation of nonlinear dc conductance of mesoscopic GaAs/GaAlAs rings in a 2 wire configuration. The second order current response to a potential bias is of particular interest. It is related to the sensitivity of conductance fluctuations to this bias and contains information on electron interactions not included in the linear response. In contrast with the linear response which is a symmetric function of magnetic field we find that this second order response exhibits a field dependence which contains an antisymmetric part. We analyse the flux periodic and aperiodic components of this asymmetry and find that they only depend on the conductance of the rings which is varied by more than an order of magnitude. These results are in good agreement with recent theoretical predictions relating this asymmetric response to the electron interactions.Comment: 5 pages, 4 figure