Browsing by Author "Fernandes, Pedro"
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- Holographic representation: Hologram plane vs. object planePublication . Bernardo, Marco V.; Fernandes, Pedro; Arrifano, Ângelo Miguel; Antonini, Marc; Fonseca, Elsa; Fiadeiro, Paulo; Pinheiro, Antonio M. G.; Pereira, ManuelaDigital holography allows the recording, storage and subsequent reconstruction of both amplitude and phase of the light field scattered by an object. This is accomplished by recording interference patterns that preserve the properties of the original object field essential for 3D visualization, the so-called holograms. Digital holography refers to the acquisition of holograms with a digital sensor, typically a CCD or a CMOS camera, and to the reconstruction of the 3D object field using numerical methods. In the current work, the different representations of digital holographic information in the hologram and in the object planes are studied. The coding performance of the different complex field representations, notably Amplitude-Phase and Real-Imaginary, in both the hologram plane and the object plane, is assessed using both computer generated and experimental holograms. The HEVC intra main coding profile is used for the compression of the different representations in both planes, either for experimental holograms or computer generated holograms. The HEVC intra compression in the object plane outperforms encoding in the hologram plane. Furthermore, encoding computer generated holograms in the object plane has a larger benefit than the same encoding over the experimental holograms. This difference was expected, since experimental holograms are affected by a larger negative influence of speckle noise, resulting in a loss of compression efficiency. This work emphasizes the possibility of holographic coding on the object plane, instead of the common encoding in the hologram plane approach. Moreover, this possibility allows direct visualization of the Object Plane Amplitude in a regular 2D display without any transformation methods. The complementary phase information can easily be used to render 3D features such as depth map, multi-view or even holographic interference patterns for further 3D visualization depending on the display technology.
- Peltier Cell Integration in Packaging Design for Minimizing Energy Consumption and Temperature Variation during Refrigerated TransportPublication . Fernandes, Pedro; Gaspar, Pedro Dinis; Silva, Pedro D.This study proposes an innovative approach to reduce temperature fluctuations in refrigerated transport during loading and unloading, aiming to minimize food waste and optimize energy consumption in the food supply chain. The solution involves integrating Peltier cells into secondary and tertiary packaging to improve system efficiency and minimize temperature variations. Four distinct tests were conducted: a reference test, continuous Peltier system operation, and two intermittent cooling tests for the hot side of the cells. The results highlight the effectiveness of this approach, particularly in the fourth test where the average final food temperature decreased from 3.2 °C (reference test) to 2.8 °C. Integrating Peltier cells into packaging shows potential benefits in minimizing food waste, reducing energy consumption, and associated emissions during refrigerated transport. This research contributes to the sustainable design and manufacturing of packaging systems, specifically in the context of refrigerated transport. By maintaining a consistent temperature environment during the critical loading and unloading phases, incorporating Peltier cells enhances the overall performance and efficiency of refrigerated transport system. These results point out the significance of exploring innovative solutions for sustainable food preservation and the decrease of waste all along the food supply chain.
- Quality comparison of the HEVC and VP9 encoders performancePublication . Fernandes, Pedro; Bernardo, Marco; Pinheiro, Antonio M. G.; Fiadeiro, Paulo; Pereira, ManuelaThis paper reports a comparison between two recent video codecs, namely the HEVC and the VP9, using High Definition Video Sequences encoded with different bit rates. A subjective test for the evaluation of the provided Quality of Experience is reported. The video sequences were shown to a panel of subjects on a High Definition LED display and the subjective tests were performed using a Single Stimulus Methodology. The results shown that the HEVC encoder provides a better visual quality on low bit rates than the VP9. Similar performance was obtained for visually lossless conditions, although the HEVC requires lower bit rates to reach that level. Moreover, the correlation of the subjective evaluation and three tested objective metrics (PSNR, SSIM, and FSIM) revealed a good representation of the subjective results, particularly the SSIM and the FSIM metrics.