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Publicações

2021

Simultaneous estimation of segmented telescope phasing errors and non-common path aberrations from adaptive-optics-corrected images

Autores
Lamb, MP; Correia, C; Sivanandam, S; Swanson, R; Zavyalova, P;

Publicação
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Abstract
We investigate the focal plane wavefront sensing technique, known as Phase Diversity, at the scientific focal plane of a segmented mirror telescope with an adaptive optics (AO) system. We specifically consider an optical system imaging a point source in the context of (i) an artificial source within the telescope structure and (ii) from AO-corrected images of a bright star. From our simulations, we reliably disentangle segmented telescope phasing errors from non-common path aberrations (NCPA) for both a theoretical source and on-sky, AO-corrected images where we have simulated the Keck/NIRC2 system. This quantification from on-sky images is appealing, as it is sensitive to the cumulative wavefront perturbations of the entire optical train; disentanglement of phasing errors and NCPA is therefore critical, where any potential correction to the primary mirror from an estimate must contain minimal NCPA contributions. Our estimates require a 1-min sequence of short-exposure, AO-corrected images; by exploiting a slight modification to the AO-loop, we find that 75 defocused images produce reliable estimates. We demonstrate a correction from our estimates to the primary and deformable mirror results in a wavefront error reduction of up to 67 percent and 65 percent for phasing errors and NCPA, respectively. If the segment phasing errors on the Keck primary are of the order of similar to 130 nm RMS, we show we can improve the H-band Strehl ratio by up to 10 percent by using our algorithm. We conclude our technique works well to estimate NCPA alone from on-sky images, suggesting it is a promising method for any AO-system.

2021

Towards Privacy-preserving Explanations in Medical Image Analysis

Autores
Montenegro, H; Silva, W; Cardoso, JS;

Publicação
CoRR

Abstract

2021

Autonomous wheelchair for patient's transportation on healthcare institutions

Autores
Baltazar, AR; Petry, MR; Silva, MF; Moreira, AP;

Publicação
SN APPLIED SCIENCES

Abstract
The transport of patients from the inpatient service to the operating room is a recurrent task in a hospital routine. This task is repetitive, non-ergonomic, time consuming, and requires the labor of patient transporters. In this paper is presented a system, named Connected Driverless Wheelchair, that can receive transportation requests directly from the hospital information management system, pick up patients at their beds, navigate autonomously through different floors, avoid obstacles, communicate with elevators, and drop patients off at the designated operating room. As a result, a prototype capable of transporting patients autonomously in hospital environments was obtained. Although it was impossible to test the final developed system at the hospital as planned, due to the COVID-19 pandemic, the extensive tests conducted at the robotics laboratory facilities, and our previous experience in integrating mobile robots in hospitals, allowed to conclude that it is perfectly prepared for this integration to be carried out.The achieved results are relevant since this is a system that may be applied to support these types of tasks in the future, making the transport of patients more efficient (both from a cost and time perspective), without unpredictable delays and, in some cases, safer.

2021

An Energy Sharing Mechanism Achieving the Same Flexibility as Centralized Dispatch

Autores
Chen, Y; Wei, W; Wang, H; Zhou, Q; Catalao, JPS;

Publicação
IEEE TRANSACTIONS ON SMART GRID

Abstract
Deploying distributed renewable energy at the demand side is an important measure to implement a sustainable society. However, the massive small solar and wind generation units are beyond the control of a central operator. To encourage users to participate in energy management and reduce the dependence on dispatchable resources, a peer-to-peer energy sharing scheme is proposed which releases the flexibility at the demand side. Every user makes decision individually considering only local constraints; the microgrid operator announces the sharing prices subjective to the coupling constraints without knowing users' local constraints. This can help protect privacy. We prove that the proposed mechanism can achieve the same disutility and flexibility as centralized dispatch, and develop an effective modified best-response based algorithm for reaching the market equilibrium. The concept of "absorbable region" is presented to measure the operating flexibility under the proposed energy sharing mechanism. A linear programming based polyhedral projection algorithm is developed to compute that region. Case studies validate the theoretical results and show that the proposed method is scalable.

2021

Transmission Expansion Planning Considering Power Losses, Expansion of Substations and Uncertainty in Fuel Price Using Discrete Artificial Bee Colony Algorithm

Autores
Mahdavi, M; Kimiyaghalam, A; Alhelou, HH; Javadi, MS; Ashouri, A; Catalao, JPS;

Publicação
IEEE ACCESS

Abstract
Transmission expansion planning (TEP) is an important part of power system expansion planning. In TEP, optimal number of new transmission lines and their installation time and place are determined in an economic way. Uncertainties in load demand, place of power plants, and fuel price as well as voltage level of substations influence TEP solutions effectively. Therefore, in this paper, a scenario based-model is proposed for evaluating the fuel price impact on TEP considering the expansion of substations from the voltage level point of view. The fuel price is an important factor in power system expansion planning that includes severe uncertainties. This factor indirectly affects the lines loading and subsequent network configuration through the change of optimal generation of power plants. The efficiency of the proposed model is tested on the real transmission network of Azerbaijan regional electric company using a discrete artificial bee colony (DABC) and quadratic programming (QP) based method. Moreover, discrete particle swarm optimization (DPSO) and decimal codification genetic algorithm (DCGA) methods are used to verify the results of the DABC algorithm. The results evaluation reveals that considering uncertainty in fuel price for solving TEP problem affects the network configuration and the total expansion cost of the network. In this way, the total cost is optimized more and therefore the TEP problem is solved more precisely. Also, by comparing the convergence curve of the DABC with that of DPSO and DCGA algorithms, it can be seen that the efficiency of the DABC is more than DPSO and DCGA for solving the desired TEP problem.

2021

Open source platform for big data exploration and analysis

Autores
Almeida, F; Kovalevski, P; Sakalauskas, D;

Publicação
Int. J. Bus. Inf. Syst.

Abstract
Despite the enormous potential of big data, it is a relatively new issue for many companies, particularly for those of smaller size that looks at this as a challenge, is unattainable and only possible for companies with high financial capacity. However, open source software presents itself as an excellent alternative for these companies, which will allow them to exploit the high volume of data they have at their disposal. In this sense, this study presents a proposal for an architecture based exclusively on open source software that includes the entire value chain of big data, from data collection to data analysis. This architecture was tested considering three emerging scenarios in which big data become very relevant and challenging, namely for mobile analytics, network analytics, and mobile analytics.

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