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

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

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

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

An Extended Star Formation History for the Galactic Center from Hubble Space Telescope/NICMOS Observations

We present Hubble Space Telescope (HST) Near-Infrared Camera and Multiobject Spectrometer (NICMOS) observations as evidence that continuous star formation has created much of the central stellar cusp of the Galaxy. The data are the deepest ever obtained for a Galactic Center (GC) population, being $>$50% complete for \mnk$<19.3$, or initial stellar masses $\gtrsim$2 \Msun. We use Geneva and Padova stellar evolution models to produce synthetic luminosity functions for burst and continuous star formation scenarios, finding that the observations are fit best by continuous star formation at a rate that is consistent with the recent star formation activity that produced the three massive young clusters in the central 50 \pc. Further, it is not possible to fit the observations with ancient burst models, such as would be appropriate for an old population like that in Baade's Window or NGC6528

Solution of Orthopositronium lifetime Puzzle

The intrinsic decay rate of orthopositronium formed in ${\rm SiO_2}$ powder is measured using the direct $2\gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined. The decay rate of orthopositronium is found to be $7.0396\pm0.0012 (stat.)\pm0.0011 (sys.)\mu s^{-1}$, which is consistent with our previous measurements with about twice the accuracy. Results agree well with the $O(\alpha^2)$ QED prediction, and also with a result reported very recently using nanoporous film