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Building thermal load prediction through shallow machine learning and deep learning
Building thermal load prediction informs the optimization of cooling plant and thermal energy storage. Physics-based prediction models of building thermal load are constrained by the model and input complexity. In this study, we developed 12 data-driven models (7 shallow learning, 2 deep learning, and 3 heuristic methods) to predict building thermal load and compared shallow machine learning and deep learning. The 12 prediction models were compared with the measured cooling demand. It was found XGBoost (Extreme Gradient Boost) and LSTM (Long Short Term Memory) provided the most accurate load prediction in the shallow and deep learning category, and both outperformed the best baseline model, which uses the previous day's data for prediction. Then, we discussed how the prediction horizon and input uncertainty would influence the load prediction accuracy. Major conclusions are twofold: first, LSTM performs well in short-term prediction (1 h ahead) but not in long term prediction (24 h ahead), because the sequential information becomes less relevant and accordingly not so useful when the prediction horizon is long. Second, the presence of weather forecast uncertainty deteriorates XGBoost's accuracy and favors LSTM, because the sequential information makes the model more robust to input uncertainty. Training the model with the uncertain rather than accurate weather data could enhance the model's robustness. Our findings have two implications for practice. First, LSTM is recommended for short-term load prediction given that weather forecast uncertainty is unavoidable. Second, XGBoost is recommended for long term prediction, and the model should be trained with the presence of input uncertainty
Dynamics of the topological structures in inhomogeneous media
We present a general review of the dynamics of topological solitons in 1 and
2 dimensions and then discuss some recent work on the scattering of various
solitonic objects (such as kinks and breathers etc) on potential obstructions.Comment: based on the talk given by W.J. Zakrzewski at QTS5. To appear in the
Proceedings in a special issue of Journal of Physics
Dynamics of the topological structures in inhomogeneous media
We present a general review of the dynamics of topological solitons in 1 and
2 dimensions and then discuss some recent work on the scattering of various
solitonic objects (such as kinks and breathers etc) on potential obstructions.Comment: based on the talk given by W.J. Zakrzewski at QTS5. To appear in the
Proceedings in a special issue of Journal of Physics
Dynamics of the topological structures in inhomogeneous media
We present a general review of the dynamics of topological solitons in 1 and
2 dimensions and then discuss some recent work on the scattering of various
solitonic objects (such as kinks and breathers etc) on potential obstructions.Comment: based on the talk given by W.J. Zakrzewski at QTS5. To appear in the
Proceedings in a special issue of Journal of Physics
Skyrmions and domain walls in (2+1) dimensions
We study classical solutions of the vector O(3) sigma model in (2+1)
dimensions, spontaneously broken to O(2)xZ2. The model possesses Skyrmion-type
solutions as well as stable domain walls which connect different vacua. We show
that different types of waves can propagate on the wall, including waves
carrying a topological charge. The domain wall can also absorb Skyrmions and,
under appropriate initial conditions, it is possible to emit a Skyrmion from
the wall.Comment: plain tex : 15 pages, 21 Postscript figures, uses epsf.te
Solitons in a Baby-Skyrme model with invariance under area preserving diffeomorphisms
We study the properties of soliton solutions in an analog of the Skyrme model
in 2+1 dimensions whose Lagrangian contains the Skyrme term and the mass term,
but no usual kinetic term. The model admits a symmetry under area preserving
diffeomorphisms. We solve the dynamical equations of motion analytically for
the case of spinning isolated baryon type solitons. We take fully into account
the induced deformation of the spinning Skyrmions and the consequent
modification of its moment of inertia to give an analytical example of related
numerical behaviour found by Piette et al.. We solve the equations of motion
also for the case of an infinite, open string, and a closed annular string. In
each case, the solitons are of finite extent, so called "compactons", being
exactly the vacuum outside a compact region. We end with indications on the
scattering of baby-Skyrmions, as well as some considerations as the properties
of solitons on a curved space.Comment: 30 pages, 5 figures, revtex, major modifications, conclusions
modifie
Low Energy States in the SU(N) Skyrme Models
We show that any solution of the SU(2) Skyrme model can be used to give a
topologically trivial solution of the SU(4) one. In addition, we extend the
method introduced by Houghton et al. and use harmonic maps from S2 to CP(N-1)
to construct low energy configurations of the SU(N) Skyrme models. We show that
one of such maps gives an exact, topologically trivial, solution of the SU(3)
model. We study various properties of these maps and show that, in general,
their energies are only marginally higher than the energies of the
corresponding SU(2) embeddings. Moreover, we show that the baryon (and energy)
densities of the SU(3) configurations with baryon number B=2-4 are more
symmetrical than their SU(2) analogues. We also present the baryon densities
for the B=5 and B=6 configurations and discuss their symmetries.Comment: latex : 25 pages, 9 Postscript figures, uses eps
A Bayesian Variable Selection Approach to Major League Baseball Hitting Metrics
Numerous statistics have been proposed for the measure of offensive ability
in major league baseball. While some of these measures may offer moderate
predictive power in certain situations, it is unclear which simple offensive
metrics are the most reliable or consistent. We address this issue with a
Bayesian hierarchical model for variable selection to capture which offensive
metrics are most predictive within players across time. Our sophisticated
methodology allows for full estimation of the posterior distributions for our
parameters and automatically adjusts for multiple testing, providing a distinct
advantage over alternative approaches. We implement our model on a set of 50
different offensive metrics and discuss our results in the context of
comparison to other variable selection techniques. We find that 33/50 metrics
demonstrate signal. However, these metrics are highly correlated with one
another and related to traditional notions of performance (e.g., plate
discipline, power, and ability to make contact)
Estimating Fielding Ability in Baseball Players Over Time
Quantitative evaluation of fielding ability in baseball has been an ongoing challenge for statisticians. Detailed recording of ball-in-play data in recent years has spurred the development of sophisticated fielding models. Foremost among these approaches, Jensen et al. (2009) used a hierarchical Bayesian model to estimate spatial fielding curves for individual players. These previous efforts have not addressed evolution in a player’s fielding ability over time. We expand the work of Jensen et al. (2009) to model the fielding ability of individual players over multiple seasons. Several different models are implemented and compared via posterior predictive validation on hold-out data. Among our choices, we find that a model which imposes shrinkage towards an age-specific average gives the best performance. Our temporal models allow us to delineate the performance of a fielder on a season-to-season basis versus their entire career
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