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Publications

2023

How E-Commerce Companies Can Reduce Returns

Authors
Amorim, P; Calvo, E; Wagner, L;

Publication
MIT SLOAN MANAGEMENT REVIEW

Abstract

2023

Synthesizing Human Activity for Data Generation

Authors
Romero, A; Carvalho, P; Corte-Real, L; Pereira, A;

Publication
JOURNAL OF IMAGING

Abstract
The problem of gathering sufficiently representative data, such as those about human actions, shapes, and facial expressions, is costly and time-consuming and also requires training robust models. This has led to the creation of techniques such as transfer learning or data augmentation. However, these are often insufficient. To address this, we propose a semi-automated mechanism that allows the generation and editing of visual scenes with synthetic humans performing various actions, with features such as background modification and manual adjustments of the 3D avatars to allow users to create data with greater variability. We also propose an evaluation methodology for assessing the results obtained using our method, which is two-fold: (i) the usage of an action classifier on the output data resulting from the mechanism and (ii) the generation of masks of the avatars and the actors to compare them through segmentation. The avatars were robust to occlusion, and their actions were recognizable and accurate to their respective input actors. The results also showed that even though the action classifier concentrates on the pose and movement of the synthetic humans, it strongly depends on contextual information to precisely recognize the actions. Generating the avatars for complex activities also proved problematic for action recognition and the clean and precise formation of the masks.

2023

SIMoT: A Low-fidelity Orchestrator Simulator for Task Allocation in IoT Devices

Authors
Fragoso, T; Silva, D; Dias, JP; Restivo, A; Ferreira, HS;

Publication
2023 53RD ANNUAL IEEE/IFIP INTERNATIONAL CONFERENCE ON DEPENDABLE SYSTEMS AND NETWORKS WORKSHOPS, DSN-W

Abstract
Performing experiments with Internet-of-Things edge devices is not always a trivial task, as large physical testbeds or complex simulators are often needed, leading to low reproducibility and several difficulties in crafting complex scenarios and tweaking parameters. Most available simulators try to simulate as close to reality as possible. While we agree that this kind of high-fidelity simulation might be necessary for some scenarios, we argue that a low-fidelity easy-to-change simulator may be a good solution when rapid prototyping orchestration strategies and algorithms. In this work, we introduce SIMoT, a low-fidelity orchestrator simulator created to achieve shorter feedback loops when testing different orchestration strategies for task allocation in edge devices. We then transferred the simulator-validated algorithms to both physical and virtual testbeds, where it was possible to assert that the simulator results correlate strongly with the observations on those testbeds.

2023

Simulation Analysis of an Interleaved Silicon Carbide (SiC) Full-Bridge Converter

Authors
Rasul, A; Baptista, J;

Publication
Proceedings - 2023 IEEE International Conference on Environment and Electrical Engineering and 2023 IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2023

Abstract
Silicon carbide (SiC) switching devices have an enormous influence on power electronic systems, entitled to extraordinary outcomes attained in low switching and conduction losses. The research work exploration is to develop and analyze the interleaved SiC full-bridge converter. It is subjected to analyze the performance of silicon carbide (SiC) module-based converter design which can offer a power of 42kW. Power conversion is done between DC/AC by using a standard 1200V single-phase SiC module from Semikron [1]. The SiC-MOSFETs are controlled by an adequate galvanically isolated gate driver circuit. Several gate drivers' functionalities are added in the converter design for optimized performance and safe operation. The features include split turn-on/turn-off outputs, desaturation and active miller-clamp. The DC-link capacitors are designed to cancel the input ripple current and stabilizing the source voltage. The interleaving (180° phase-shift between the legs) helps to reduce ripple currents both, in the input capacitor as well as at the output. At the output coupled inductors are providing suppression of transverse currents between the interleaved legs. The coupled inductors help to reduce the size of the filter in the case of DC-DC or DC-AC grid-tie inverters. © 2023 IEEE.

2023

Estimating Instantaneous Vehicle Emissions

Authors
Andrade, T; Gama, J;

Publication
38TH ANNUAL ACM SYMPOSIUM ON APPLIED COMPUTING, SAC 2023

Abstract
Road transportation emissions have increased in the last few decades and have been the primary source of pollutants in urban areas with ever-growing populations. In this context, it is important to have effective measures to monitor road emissions in regions. Creating an emissions inventory over a region that can map road emissions based on vehicle trips can be helpful. In this work, we show that it is possible to use raw GPS data to estimate vehicle-related levels of pollution in a region. By transforming the data using feature engineering and calculating the vehicle-specific power (VSP) as well as various specific pollutants by using a microscopic emissions model, we show the areas with higher emissions levels made by a fleet of taxis in Porto, Portugal.

2023

Discriminative segmental cues to vowel height and consonantal place and voicing in whispered speech

Authors
Jesus, LMT; Castilho, S; Ferreira, A; Costa, MC;

Publication
JOURNAL OF PHONETICS

Abstract
Purpose: The acoustic signal attributes of whispered speech potentially carry sufficiently distinct information to define vowel spaces and to disambiguate consonant place and voicing, but what these attributes are and the underlying production mechanisms are not fully known. The purpose of this study was to define segmental cues to place and voicing of vowels and sibilant fricatives and to develop an articulatory interpretation of acoustic data.Method: Seventeen speakers produced sustained sibilants and oral vowels, disyllabic words, sentences and read a phonetically balanced text. All the tasks were repeated in voiced and whispered speech, and the sound source and filter analysed using the following parameters: Fundamental frequency, spectral peak frequencies and levels, spectral slopes, sound pressure level and durations. Logistic linear mixed-effects models were developed to understand what acoustic signal attributes carry sufficiently distinct information to disambiguate /i, a/ and /s, ?/.Results: Vowels were produced with significantly different spectral slope, sound pressure level, first and second formant frequencies in voiced and whispered speech. The low frequencies spectral slope of voiced sibilants was significantly different between whispered and voiced speech. The odds of choosing /a/ instead of /i/ were esti-mated to be lower for whispered speech when compared to voiced speech. Fricatives' broad peak frequency was statistically significant when discriminating between /s/ and /?/.Conclusions: First formant frequency and relative duration of vowels are consistently used as height cues, and spectral slope and broad peak frequency are attributes associated with consonantal place of articulation. The rel-ative duration of same-place voiceless fricatives was higher than voiced fricatives both in voiced and whispered speech. The evidence presented in this paper can be used to restore voiced speech signals, and to inform reha-bilitation strategies that can safely explore the production mechanisms of whispering.CO 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

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