8,018 research outputs found
Incentivizing Reliable Demand Response with Customers' Uncertainties and Capacity Planning
One of the major issues with the integration of renewable energy sources into
the power grid is the increased uncertainty and variability that they bring. If
this uncertainty is not sufficiently addressed, it will limit the further
penetration of renewables into the grid and even result in blackouts. Compared
to energy storage, Demand Response (DR) has advantages to provide reserves to
the load serving entities (LSEs) in a cost-effective and environmentally
friendly way. DR programs work by changing customers' loads when the power grid
experiences a contingency such as a mismatch between supply and demand.
Uncertainties from both the customer-side and LSE-side make designing
algorithms for DR a major challenge.
This paper makes the following main contributions: (i) We propose DR control
policies based on the optimal structures of the offline solution. (ii) A
distributed algorithm is developed for implementing the control policies
without efficiency loss. (iii) We further offer an enhanced policy design by
allowing flexibilities into the commitment level. (iv) We perform real world
trace based numerical simulations which demonstrate that the proposed
algorithms can achieve near optimal social cost. Details can be found in our
extended version.Comment: arXiv admin note: substantial text overlap with arXiv:1704.0453
Harnessing Flexible and Reliable Demand Response Under Customer Uncertainties
Demand response (DR) is a cost-effective and environmentally friendly
approach for mitigating the uncertainties in renewable energy integration by
taking advantage of the flexibility of customers' demands. However, existing DR
programs suffer from either low participation due to strict commitment
requirements or not being reliable in voluntary programs. In addition, the
capacity planning for energy storage/reserves is traditionally done separately
from the demand response program design, which incurs inefficiencies. Moreover,
customers often face high uncertainties in their costs in providing demand
response, which is not well studied in literature.
This paper first models the problem of joint capacity planning and demand
response program design by a stochastic optimization problem, which
incorporates the uncertainties from renewable energy generation, customer power
demands, as well as the customers' costs in providing DR. We propose online DR
control policies based on the optimal structures of the offline solution. A
distributed algorithm is then developed for implementing the control policies
without efficiency loss. We further offer enhanced policy design by allowing
flexibilities into the commitment level. We perform real world trace based
numerical simulations. Results demonstrate that the proposed algorithms can
achieve near optimal social costs, and significant social cost savings compared
to baseline methods
Investigating ultrasound–light interaction in scattering media
Significance: Ultrasound-assisted optical imaging techniques, such as ultrasound-modulated optical tomography, allow for imaging deep inside scattering media. In these modalities, a fraction of the photons passing through the ultrasound beam is modulated. The efficiency by which the photons are converted is typically referred to as the ultrasound modulation’s “tagging efficiency.” Interestingly, this efficiency has been defined in varied and discrepant fashion throughout the scientific literature.
Aim: The aim of this study is the ultrasound tagging efficiency in a manner consistent with its definition and experimentally verify the contributive (or noncontributive) relationship between the mechanisms involved in the ultrasound optical modulation process.
Approach: We adopt a general description of the tagging efficiency as the fraction of photons traversing an ultrasound beam that is frequency shifted (inclusion of all frequency-shifted components). We then systematically studied the impact of ultrasound pressure and frequency on the tagging efficiency through a balanced detection measurement system that measured the power of each order of the ultrasound tagged light, as well as the power of the unmodulated light component.
Results: Through our experiments, we showed that the tagging efficiency can reach 70% in a scattering phantom with a scattering anisotropy of 0.9 and a scattering coefficient of 4 mm⁻¹ for a 1-MHz ultrasound with a relatively low (and biomedically acceptable) peak pressure of 0.47 MPa. Furthermore, we experimentally confirmed that the two ultrasound-induced light modulation mechanisms, particle displacement and refractive index change, act in opposition to each other.
Conclusion: Tagging efficiency was quantified via simulation and experiments. These findings reveal avenues of investigation that may help improve ultrasound-assisted optical imaging techniques
Physical Primitive Decomposition
Objects are made of parts, each with distinct geometry, physics,
functionality, and affordances. Developing such a distributed, physical,
interpretable representation of objects will facilitate intelligent agents to
better explore and interact with the world. In this paper, we study physical
primitive decomposition---understanding an object through its components, each
with physical and geometric attributes. As annotated data for object parts and
physics are rare, we propose a novel formulation that learns physical
primitives by explaining both an object's appearance and its behaviors in
physical events. Our model performs well on block towers and tools in both
synthetic and real scenarios; we also demonstrate that visual and physical
observations often provide complementary signals. We further present ablation
and behavioral studies to better understand our model and contrast it with
human performance.Comment: ECCV 2018. Project page: http://ppd.csail.mit.edu
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