14,580 research outputs found
The battle of the boards
a) Interactive whiteboards can seem very impressive for language teaching - but traditional boards are better.
b) Twelve classroom activities which a traditional board does better than an interactive whiteboard
CF6 Jet Engine Performance Improvement: High Pressure Turbine Active Clearance Control
An active clearance control system was developed which reduces fuel consumption and performance degradation. This system utilizes compressor discharge air during takeoff and fan discharge air during cruise to impinge on the shroud structure to improve the thermal response. The system was evaluated in component and engine tests. The test results demonstrated a performance improvement of 0.7 percent in cruise SFC
Coincident switch closing reduces error in motor-driven timer
To cut the lag-lead in motor-driven timing devices, the timing circuit has been extended to include a second switch. This is actuated in time with the first but driven directly at a speed x times faster than the first
Vibrational population distributions in nonequilibrium nozzle expansion flows
Experimental measurements and theoretical calculations of the vibrational population distribution in nonequilibrium nozzle expansion flows of gas mixtures are reported. These studies were directed toward determining whether vibrational energy exchange pumping could lead to laser action on the vibrational bands of a diatomic molecule. Three different types of experiments were conducted. These showed (1) that vibrational energy was preferentially transferred from N2 to CO in supersonic nozzle flows containing these gases; (2) that under some conditions this vibrational energy exchange pumping mechanism created population inversions in the vibrational levels of CO; and (3) that at large expansion ratios the magnitude of these population inversions was sufficient to sustain lasing in the nozzle. A theoretical model was developed to calculate vibrational state population distributions in gas dynamic expansions of a mixture of diatomic gases. Although only isothermal calculations have been completed, these data indicate that population inversions are predicted for conditions similar to those obtained in the nozzle expansion flows
Scalable Population Synthesis with Deep Generative Modeling
Population synthesis is concerned with the generation of synthetic yet
realistic representations of populations. It is a fundamental problem in the
modeling of transport where the synthetic populations of micro-agents represent
a key input to most agent-based models. In this paper, a new methodological
framework for how to 'grow' pools of micro-agents is presented. The model
framework adopts a deep generative modeling approach from machine learning
based on a Variational Autoencoder (VAE). Compared to the previous population
synthesis approaches, including Iterative Proportional Fitting (IPF), Gibbs
sampling and traditional generative models such as Bayesian Networks or Hidden
Markov Models, the proposed method allows fitting the full joint distribution
for high dimensions. The proposed methodology is compared with a conventional
Gibbs sampler and a Bayesian Network by using a large-scale Danish trip diary.
It is shown that, while these two methods outperform the VAE in the
low-dimensional case, they both suffer from scalability issues when the number
of modeled attributes increases. It is also shown that the Gibbs sampler
essentially replicates the agents from the original sample when the required
conditional distributions are estimated as frequency tables. In contrast, the
VAE allows addressing the problem of sampling zeros by generating agents that
are virtually different from those in the original data but have similar
statistical properties. The presented approach can support agent-based modeling
at all levels by enabling richer synthetic populations with smaller zones and
more detailed individual characteristics.Comment: 27 pages, 15 figures, 4 table
Better age estimations using UV-optical colours: breaking the age-metallicity degeneracy
We demonstrate that the combination of GALEX UV photometry in the FUV (~1530
angstroms) and NUV (~2310 angstroms) passbands with optical photometry in the
standard U,B,V,R,I filters can efficiently break the age-metallicity
degeneracy. We estimate well-constrained ages, metallicities and their
associated errors for 42 GCs in M31, and show that the full set of
FUV,NUV,U,B,V,R,I photometry produces age estimates that are ~90 percent more
constrained and metallicity estimates that are ~60 percent more constrained
than those produced by using optical filters alone. The quality of the age
constraints is comparable or marginally better than those achieved using a
large number of spectrscopic indices.Comment: Published in MNRAS (2007), 381, L74 (doi:
10.1111/j.1745-3933.2007.00370.x
Chinese Nationalism And Cross-strait Relations In The Post-war Era
Taiwan has played a prominent role in Chinese politics since the founding of the
People's Republic of China (PRC) in 1949. For decades, the Chinese Communist
Party (CCP) called for the "liberation" of the island, with the tone of the rhetoric
changing but not the goal of unification. While cross-strait relations may have
warmed under the Ma Ying-jeou administration and Sino-American relations
beyond the Taiwan issue have greatly improved in the past decade, the role which
Taiwan plays in Chinese nationalism may still lead to an undesired conflict. This
article highlights the role of Taiwan within the Chinese nationalism and
specifically how the island's democratisation challenges this narrative. While
economic relations between both sides increase, these underlying tensions do not
preclude future military confrontation
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