Predicting Future Instance Segmentation by Forecasting Convolutional Features

Anticipating future events is an important prerequisite towards intelligent behavior. Video forecasting has been studied as a proxy task towards this goal. Recent work has shown that to predict semantic segmentation of future frames, forecasting at the semantic level is more effective than forecasting RGB frames and then segmenting these. In this paper we consider the more challenging problem of future instance segmentation, which additionally segments out individual objects. To deal with a varying number of output labels per image, we develop a predictive model in the space of fixed-sized convolutional features of the Mask R-CNN instance segmentation model. We apply the "detection head'" of Mask R-CNN on the predicted features to produce the instance segmentation of future frames. Experiments show that this approach significantly improves over strong baselines based on optical flow and repurposed instance segmentation architectures

Separation by thermal diffusion in a rotary column

A rotary thermal diffusion column with the inner cylinder rotating and the outer cylinder static was used to separate n-heptane-benzene mixtures at different speeds of rotation. The results show that the column efficiency depends on the speed of rotation. For the optimum speed the increase in efficiency relative to the static column was of the order of 8%. The role of the geometric irregularities in the annulus width on performance of the rotary column is also discussed.Calouste Gulbenkian Foundatio

A model for the interpretation of biofouling

The formation of biofilms on heat exchange surfaces was studied using water with Pseudomonas fluorescens as a contaminant and also a mixture of these bacteria and kaolin particles. In every case increasing the fluid velocity resulted in a decrease in the final amount of deposit and in the deposition rate . The effect of the fluid velocity was interpreted using a mathematical model and it was found that cell adhesion and reproduction were the fundamental processes controlling the deposition rate . The presence of inorganic particles in the deposit enhanced the biofilm growth rate . This result was explained by the differences in the structure of the fouling layers

Liquid thermal diffusion in a batch rotary column

Experimental observations of separation by thermal diffusion in rotary columns have been published, but no adequate theory to explain the column performance has been given. By consideration of the hydrodynamics within the annular space an approximate theory has been developed which shows that for a geometrically perfect column the relevant parameters affecting separation can be simply related to the corresponding static column. The relaxation-time and separation are virtually independent of the speed of rotation and separation values are more favourable for the rotary column. The application of the theory to non-perfect practical columns requires the consideration of the "equivalent annulus width" concept similar to the static case. Experimental tests conducted at different speeds of rotation in two geometrically different columns whose inner cylinder rotates and the outer is static, showed that the rotation at moderate speeds increased the equilibrium separation by about 7%, reducing, simultaneously the relaxation time by an average of 3%. These results are in good agreement with the theoretical predictions

Fractal Conductance Fluctuations of Classical Origin

In mesoscopic systems conductance fluctuations are a sensitive probe of electron dynamics and chaotic phenomena. We show that the conductance of a purely classical chaotic system with either fully chaotic or mixed phase space generically exhibits fractal conductance fluctuations unrelated to quantum interference. This might explain the unexpected dependence of the fractal dimension of the conductance curves on the (quantum) phase breaking length observed in experiments on semiconductor quantum dots.Comment: 5 pages, 4 figures, to appear in PR

Application of Neural Networks to the study of stellar model solutions

Artificial neural networks (ANN) have different applications in Astronomy, including data reduction and data mining. In this work we propose the use ANNs in the identification of stellar model solutions. We illustrate this method, by applying an ANN to the 0.8M$_\odot$ star CG Cyg B. Our ANN was trained using 60,000 different 0.8M$_\odot$ stellar models. With this approach we identify the models which reproduce CG Cyg B's position in the HR diagram. We observe a correlation between the model's initial metal and helium abundance which, in most cases, does not agree with a helium to metal enrichment ratio $\Delta$Y/$\Delta$Z=2. Moreover, we identify a correlation between the model's initial helium/metal abundance and both its age and mixing-length parameter. Additionally, every model found has a mixing-length parameter below 1.3. This means that CG Cyg B's mixing-length parameter is clearly smaller than the solar one. From this study we conclude that ANNs are well suited to deal with the degeneracy of model solutions of solar type stars.Comment: Accepted for publication in New Astronom

Influence of the SSBI mitigation on the in-band crosstalk tolerance of virtual carrier-assisted DD multi-band OFDM metro networks

In this work, the tolerance to in-band crosstalk of virtual carrier (VC)-assisted direct detection (DD) multi-band orthogonal frequency division multiplexing (MB-OFDM) metro networks, with and without signal-to-signal beat interference (SSBI) mitigation, is compared numerically for 4-ary, 16-ary and 64-ary quadrature amplitude modulation (QAM) formats in the OFDM subcarriers. Our results show that the tolerance to in-band crosstalk is improved for lower modulation format orders. The tolerance to in-band crosstalk of DD OFDM receivers considering 4-QAM modulation format at the DD OFDM subcarriers is above 14 dB higher than the one obtained for the 64-QAM modulation format, regardless the receiver configuration. We have also shown that, the tolerance to in-band crosstalk for a given modulation format order depends on the difference between the virtual carrier-to-band power ratio (VBPR) of the selected and interfering signals, as interferers with same VBPR as the selected signal leads to equal tolerance to in-band crosstalk, independently from the DD OFDM receiver configuration and the subcarrier modulation format order considered.info:eu-repo/semantics/acceptedVersio

Tolerance to in-band crosstalk of virtual carrier-assisted direct detection multi-band OFDM system

The tolerance to in-band crosstalk of virtual carrier (VC)-assisted direct detection (DD) multi-band orthogonal frequency division multiplexing (MB-OFDM) system is assessed numerically through Monte-Carlo simulation and considering a single interferer. The influence of the virtual carrier-to-band power ratio (VBPR) and the virtual carrier-to-band gap (VBG) of the interferer on the in-band tolerance is also studied. We show that, for interferers with the same VBG as the selected signal, the increase of the VBPR of the interferer leads to lower optical signal-to-noise ratio (OSNR) penalties. The increase of the VBG of the interferer with central frequency different from the selected signal also leads to lower OSNR penalties. When the central frequencies of the interferer and selected bands are the same, the variation VBG of the interferer can lead to 11 dB less tolerance to in-band crosstalk of the VC-assisted DD OFDM system.info:eu-repo/semantics/acceptedVersio

Impact of inter-core crosstalk on the performance of multi-core fibers-based SDM systems with coherent detection

Inter-core crosstalk (ICXT) can limit the multi-core fiber (MCF) systems performance and transmission reach. Over the last years, the impact of the ICXT on the performance of MCF optical communication systems with coherent detection has been investigated in several works. However, the influence of the MCF parameters and transmitted signal characteristics on the ICXT mechanism and the degradation induced by it on the performance of coherent detection MCF systems are still to be completely assessed. In this work, the impact of the ICXT on the performance of coherent detection MCF-based transmission systems is assessed through numerical simulation considering fiber linear propagation. The metrics used to assess the MCF system performance are the bit error rate (BER) and the optical signal-to-noise ratio (OSNR) penalty due to the ICXT. Our results show that the BER and the OSNR penalty due to the detected ICXT, in MCF-based systems with coherent detection, are influenced by the s kew, time misalignment between the transmitted signals and the roll-off factor of the transmitted signals. In the range of skew and roll-off factors analyzed, the maximum reduction of maximum ICXT level for a 1 dB OSNR penalty by appropriate choice of skew and roll-off factor does not exceed 1.7 dB.info:eu-repo/semantics/acceptedVersio

Inter-core crosstalk dependence on design parameters in coherent detection weakly-coupled multicore fiber systems

We assess, through numerical simulation, the dependence of the variance of the inter-core crosstalk (ICXT) and the maximum allowable ICXT level on the design parameters of coherent detection MCF systems. The analysed design parameters are the order of the quadrature amplitude modulation (QAM) signals, roll-off factor, time misalignment between the signal in different cores and skew between cores. The results show that, when the roll-off factor is 0, the maximum allowable ICXT level is independent of the skew and decreases for higher QAM orders. For a roll-off factor of 1, the maximum allowable ICXT level depends on the skew and time misalignment of core signals. In this case, the maximum allowable ICXT level increases by 3.6 dB relative to the case of roll-off factor of 0 with null skew, and by 2 dB, when the skew is much higher than the symbol period.info:eu-repo/semantics/acceptedVersio