On the performance of two-hop message spreading in DTNs

In this paper, a Delay Tolerant Network environment is considered where the source is in full control of the two-hop spreading mechanism by setting key parameters such as the number of copies allowed to be spread in the network and the delay bound of the messages. The introduced analysis allows for a differentiation between the source of the message and the intermediate nodes (in terms of e.g. transmission power, speed or cooperation degree). Analytical expressions for the cumulative distribution function (cdf) of the delivery delay and the induced overhead are extracted, taking into account the fact that the source node may continue spreading copies after the message delivery. In addition, a fairly accurate approximate expression for the cdf of the delivery delay is also derived and validated through simulations.     

An Adversarial Neuro-Tensorial Approach for Learning Disentangled Representations

International Journal of Computer Vision - Several factors contribute to the appearance of an object in a visual scene, including pose, illumination, and deformation, among others. Each factor...     

Multimedia education program for an active solar hot water system

An interactive multimedia education program has been developed to study the transient behaviour of an active solar heating system for domestic hot water production. The users can explore various cases, study what happens under different operating scenarios and examine the effects of altering conditions. In addition, simulation processes are used when a more quantitative understanding of the related subjects is needed, as they offer higher perceptual fidelity ( i.e. , more accurate representation of the situation being modelled). The simulation accounts for a large number of parameters and can be used to investigate their effects on the thermal efficiency of the solar collector and the system. It can also be used for an extensive set of exercises in the tertiary education sector. The operating principles and performance aspects of the different components have been considered providing a basis for understanding the components interaction and total system performance. The program is a user friendly, fast, easy-to-use and a powerful educational tool.     

Mitigating Demographic Bias in Facial Datasets with Style-Based Multi-attribute Transfer

Deep learning has catalysed progress in tasks such as face recognition and analysis, leading to a quick integration of technological solutions in multiple layers of our society. While such systems have proven to be accurate by standard evaluation metrics and benchmarks, a surge of work has recently exposed the demographic bias that such algorithms exhibit–highlighting that accuracy does not entail fairness. Clearly, deploying biased systems under real-world settings can have grave consequences for affected populations. Indeed, learning methods are prone to inheriting, or even amplifying the bias present in a training set, manifested by uneven representation across demographic groups. In facial datasets, this particularly relates to attributes such as skin tone, gender, and age. In this work, we address the problem of mitigating bias in facial datasets by data augmentation. We propose a multi-attribute framework that can successfully transfer complex, multi-scale facial patterns even if these belong to underrepresented groups in the training set. This is achieved by relaxing the rigid dependence on a single attribute label, and further introducing a tensor-based mixing structure that captures multiplicative interactions between attributes in a multilinear fashion. We evaluate our method with an extensive set of qualitative and quantitative experiments on several datasets, with rigorous comparisons to state-of-the-art methods. We find that the proposed framework can successfully mitigate dataset bias, as evinced by extensive evaluations on established diversity metrics, while significantly improving fairness metrics such as equality of opportunity.

     

Disentangling Geometry and Appearance with Regularised Geometry-Aware Generative Adversarial Networks

International Journal of Computer Vision - Deep generative models have significantly advanced image generation, enabling generation of visually pleasing images with realistic texture. Apart from...     

Experimental comparison of a solar-assisted heat pump vs. a conventional thermosyphon solar system

A solar-assisted heat pump system (SAHPS) for hot-water production has been developed and compared for its experimental performance, under similar ambient conditions with a conventional thermosyphon solar system (CTSS) with a single direct tank. Both systems were monitored from 1993 to 1997 during summer and winter time periods. The performance of CTSS was seriously affected by weather conditions, whereas SAHPS could always operate with no significant variation and with a COP above 3·0. A comparison between the two systems proved the performance of the SAHPS to be better than that of CTSS under all climatic conditions. © 1998 John Wiley & Sons, Ltd.     

Simulation and experimental performance of a solar-heated anaerobic digester

A mathematical model for simulating an innovative design of a solar-heated anaerobic digester has been developed. A swine manure digester having a useful volume of 45 m³ is constructed below ground level and its fix cover is made of flat-plate solar collectors, which are an integral part of the roof structure. The solar collectors are coupled to a heat exchanger immersed in the digester manure. The upper part of the digester, under the tilted cover, forms an airtight enclosure that is used to collect and store the daily produced biogas. The performance of the system is investigated experimentally and the results indicate that the use of solar collectors as a cover reduces the digester thermal losses and positively affects the heat balance of the digester. The system is instrumented and an automatic data logging system is used to provide data for the validation of the system. The proposed model can accurately predict the thermal behaviour of the solar-heated digester compared to the measured data.     

Optimal call admission control on a single link with a GPS scheduler

The problem of call admission control (CAC) is considered for leaky bucket constrained sessions with deterministic service guarantees (zero loss and finite delay bound) served by a generalized processor sharing scheduler at a single node in the presence of best effort traffic. Based on an optimization process, a CAC algorithm capable of determining the (unique) optimal solution is derived. The derived algorithm is also applicable, under a slight modification, in a system where the best effort traffic is absent and is capable of guaranteeing that if it does not find a solution to the CAC problem, then a solution does not exist. The numerical results indicate that the CAC algorithm can achieve a significant improvement on bandwidth utilization as compared to a (deterministic) effective bandwidth-based CAC scheme.