444 research outputs found
Spatiotemporal Calibration of Atmospheric Nitrogen Dioxide Concentration Estimates From an Air Quality Model for Connecticut
A spatiotemporal calibration and resolution refinement model was fitted to
calibrate nitrogen dioxide (NO) concentration estimates from the Community
Multiscale Air Quality (CMAQ) model, using two sources of observed data on
NO that differed in their spatial and temporal resolutions. To refine the
spatial resolution of the CMAQ model estimates, we leveraged information using
additional local covariates including total traffic volume within 2 km,
population density, elevation, and land use characteristics. Predictions from
this model greatly improved the bias in the CMAQ estimates, as observed by the
much lower mean squared error (MSE) at the NO monitor sites. The final
model was used to predict the daily concentration of ambient NO over the
entire state of Connecticut on a grid with pixels of size 300 x 300 m. A
comparison of the prediction map with a similar map for the CMAQ estimates
showed marked improvement in the spatial resolution. The effect of local
covariates was evident in the finer spatial resolution map, where the
contribution of traffic on major highways to ambient NO concentration
stands out. An animation was also provided to show the change in the
concentration of ambient NO over space and time for 1994 and 1995.Comment: 23 pages, 8 figures, supplementary materia
Bulk Properties of the Oxygen Reduction Catalyst SrCo_(0.9)Nb_(0.1)O_(3-δ)
The perovskite SrCo_(0.9)Nb_(0.1)O_(3−δ) (SCN) has excellent electrochemical activity toward oxygen reduction, and it is also valuable as a possible model material for other state-of-the-art perovskite catalysts based on strontium and cobalt, such as Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ) (BSCF). Here we report thermogravimetric, conductivity, and diffraction measurements from SCN. We find that the thermodynamic stability limits of SCN are slightly more favorable than those reported for BSCF, although both materials exhibit a slow oxidative partial decomposition under likely operating conditions. In SCN, this decomposition is thermodynamically preferred when the average formal oxidation state of cobalt is greater than ∼3.0+, but due to sluggish kinetics, metastable SCN with higher cobalt valence can be observed. The oxygen stoichiometry 3−δ varies from 2.45 to 2.70 under the conditions studied, 500–1000 °C and 10^(–4)–1 bar O_2, which encompass both stable and metastable behavior. The electronic conductivity is p-type and thermally activated, with a value at 600 °C in air of 250 S cm^(–1), comparable to that of La_(0.8)Sr_(0.2)MnO_(3−δ). The polaron migration enthalpy decreases linearly from 0.30 to 0.05 eV as 3−δ increases from 2.52 to 2.64. Thermal and chemical expansivities are also reported
Automatic Piano Fingering Estimation Using Recurrent Neural Networks
Deciding piano fingerings is an essential skill for all piano players regardless of their expertise. Traditionally, pianists and piano educators first need to analyze musical scores, then they manually label the fingerings on the scores; however, this process is time-consuming and inefficient. This paper proposes a novel automatic piano fingerings estimating method by utilizing Bidirectional Long Short-term Memory (BI-LSTM) networks — a special type of Recurrent Neural Networks (RNNs). This is one of the first studies to explore the possibilities of applying deep learning to estimate piano fingerings. Together with the new method, a novel input representation is designed to capture the relations between surrounding notes. Furthermore, in addition to directly comparing the estimations with the ground-truth, this paper proposes a novel evaluation metric to assess the playability of the estimated fingerings. The results illustrate the effectiveness of the proposed method that generates playable and accurate estimated fingerings
The research on a novel levitation stage using ultrasonic and aerodynamic driving method
Acoustic/ultrasonic levitation is now widely used in industrial production processes employed in semiconductor, bioengineering nano-scale electronics and other industries where precise positioning is required. This paper describes the development of a new mixed levitation stage combining the ultrasonic and aerodynamic concepts. It is shown that the combination of these two levitation methods improves the levitation stability by reducing the system vibration caused by air vortices and hammer vibration. The proposed structure of the mixed levitation stage is described. The effect of ultrasonic levitation height and the aerodynamic levitation height is analyzed to determine their influence on the supporting ability of the mixed levitation stage. Both the experiments and modeling for the mixed levitation stage are conducted. The supporting ability of the mixed levitation stage is examined by varying the supporting masses and supporting states. A 3D computation model of the mixed levitation stage is constructed and is analyzed using the computational fluid dynamics (CFD) software. The computational and experimental results show that the levitation height of the mixed levitation is close to the sum of the ultrasonic levitation and the aerodynamic levitation heights; this result confirms that the mixed levitation promotes the supporting ability of the working stage
Robust Stochastic Bandit Algorithms under Probabilistic Unbounded Adversarial Attack
The multi-armed bandit formalism has been extensively studied under various
attack models, in which an adversary can modify the reward revealed to the
player. Previous studies focused on scenarios where the attack value either is
bounded at each round or has a vanishing probability of occurrence. These
models do not capture powerful adversaries that can catastrophically perturb
the revealed reward. This paper investigates the attack model where an
adversary attacks with a certain probability at each round, and its attack
value can be arbitrary and unbounded if it attacks. Furthermore, the attack
value does not necessarily follow a statistical distribution. We propose a
novel sample median-based and exploration-aided UCB algorithm (called
med-E-UCB) and a median-based -greedy algorithm (called
med--greedy). Both of these algorithms are provably robust to the
aforementioned attack model. More specifically we show that both algorithms
achieve pseudo-regret (i.e., the optimal regret without
attacks). We also provide a high probability guarantee of
regret with respect to random rewards and random occurrence of attacks. These
bounds are achieved under arbitrary and unbounded reward perturbation as long
as the attack probability does not exceed a certain constant threshold. We
provide multiple synthetic simulations of the proposed algorithms to verify
these claims and showcase the inability of existing techniques to achieve
sublinear regret. We also provide experimental results of the algorithm
operating in a cognitive radio setting using multiple software-defined radios.Comment: Published at AAAI'2
Divisions of labor in the thiamin biosynthetic pathway among organs of maize
The B vitamin thiamin is essential for central metabolism in all cellular organisms including plants. While plants synthesize thiamin de novo, organs vary widely in their capacities for thiamin synthesis. We use a transcriptomics approach to appraise the distribution of de novo synthesis and thiamin salvage pathways among organs of maize. We identify at least six developmental contexts in which metabolically active, non-photosynthetic organs exhibit low expression of one or both branches of the de novo thiamin biosynthetic pathway indicating a dependence on inter-cellular transport of thiamin and/or thiamin precursors. Neither the thiazole (THI4) nor pyrimidine (THIC) branches of the pathway are expressed in developing pollen implying a dependence on import of thiamin from surrounding floral and inflorescence organs. Consistent with that hypothesis, organs of the male inflorescence and flowers are shown to have high relative expression of the thiamin biosynthetic pathway and comparatively high thiamin contents. By contrast, divergent patterns of THIC and THI4 expression occur in the shoot apical meristem, embyro sac, embryo, endosperm, and root-tips suggesting that these sink organs acquire significant amounts of thiamin via salvage pathways. In the root and shoot meristems, expression of THIC in the absence of THI4 indicates a capacity for thiamin synthesis via salvage of thiazole, whereas the opposite pattern obtains in embryo and endosperm implying that seed storage organs are poised for pyrimidine salvage. Finally, stable isotope labeling experiments set an upper limit on the rate of de novo thiamin biosynthesis in maize leaf explants. Overall, the observed patterns of thiamin biosynthetic gene expression mirror the strategies for thiamin acquisition that have evolved in bacteria
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