Showing papers by "University of Avignon published in 2020"

Multi-UAV-Enabled Load-Balance Mobile-Edge Computing for IoT Networks

Abstract: Unmanned aerial vehicles (UAVs) have been widely used to provide enhanced information coverage as well as relay services for ground Internet-of-Things (IoT) networks. Considering the substantially limited processing capability, the IoT devices may not be able to tackle with heavy computing tasks. In this article, a multi-UAV-aided mobile-edge computing (MEC) system is constructed, where multiple UAVs act as MEC nodes in order to provide computing offloading services for ground IoT nodes which have limited local computing capabilities. For the sake of balancing the load for UAVs, the differential evolution (DE)-based multi-UAV deployment mechanism is proposed, where we model the access problem as a generalized assignment problem (GAP), which is then solved by a near-optimal solution algorithm. Based on this, we are capable of achieving the load balance of these drones while guaranteeing the coverage constraint and satisfying the quality of service (QoS) of IoT nodes. Furthermore, a deep reinforcement learning (DRL) algorithm is conceived for the task scheduling in a certain UAV, which improves the efficiency of the task execution in each UAV. Finally, sufficient simulation results show the feasibility and superiority of our proposed load-balance-oriented UAV deployment scheme as well as the task scheduling algorithm.

A survey of quaternion neural networks

Abstract: Quaternion neural networks have recently received an increasing interest due to noticeable improvements over real-valued neural networks on real world tasks such as image, speech and signal processing. The extension of quaternion numbers to neural architectures reached state-of-the-art performances with a reduction of the number of neural parameters. This survey provides a review of past and recent research on quaternion neural networks and their applications in different domains. The paper details methods, algorithms and applications for each quaternion-valued neural networks proposed.

Interactions between cell wall polysaccharides and polyphenols: Effect of molecular internal structure.

Abstract: Cell wall polysaccharides (CPSs) and polyphenols are major constituents of the dietary fiber complex in plant-based foods. Their digestion (by gut microbiota) and bioefficacy depend not only on their structure and quantity, but also on their intermolecular interactions. The composition and structure of these compounds vary with their dietary source (i.e., fruit or vegetable of origin) and can be further modified by food processing. Various components and structures of CPSs and polyphenols have been observed to demonstrate common and characteristic behaviors during interactions. However, at a fundamental level, the mechanisms that ultimately drive these interactions are still not fully understood. This review summarizes the current state of knowledge on the internal factors that influence CPS-polyphenol interactions, describes the different ways in which these interactions can be mediated by molecular composition or structure, and introduces the main methods for the analysis of these interactions, as well as the mechanisms involved. Furthermore, a comprehensive overview is provided of recent key findings in the area of CPS-polyphenol interactions. It is becoming clear that these interactions are shaped by a multitude of factors, the most important of which are the physicochemical properties of the partners: their morphology (surface area and porosity/pore shape), chemical composition (sugar ratio, solubility, and non-sugar components), and molecular architecture (molecular weight, degree of esterification, functional groups, and conformation). An improved understanding of the molecular mechanisms that drive interactions between CPSs and polyphenols may allow us to better establish a bridge between food processing and the bioavailability of colonic fermentation products from CPSs and antioxidant polyphenols, which could ultimately lead to the development of new guidelines for the design of healthier and more nutritious foods.

Recent advances in scaling-up of non-conventional extraction techniques: Learning from successes and failures

Abstract: The impact of the extraction technologies on product yield and analytical profile is relevant. This review is aiming to discuss recent experiences of successes and failures in non-conventional extraction scaling-up, to better understand the challenges and designing of existing and new techniques. Understanding the crucial extraction factors at laboratory and pilot scale is of paramount value for the engineering work of scaling-up. Besides, a careful analysis and modelling of heat and mass transfer and energy consumption, the design of industrial extraction plants driven by economic and environmental factors, are well covered in the present review. Current trend strongly favors scaling-up of green approaches that consumes less organic solvent(s), involves minimal operational steps, provides high throughput capability and assures highest yield at lower costs. Current and future challenges in scaling-up extraction of bioactive compounds require a parallel development of suitable analytical methods to monitor the process and ensure high yield and quality.

ELGAR - a European Laboratory for Gravitation and Atom-interferometric Research

Abstract: Gravitational Waves (GWs) were observed for the first time in 2015, one century after Einstein predicted their existence. There is now growing interest to extend the detection bandwidth to low frequency. The scientific potential of multi-frequency GW astronomy is enormous as it would enable to obtain a more complete picture of cosmic events and mechanisms. This is a unique and entirely new opportunity for the future of astronomy, the success of which depends upon the decisions being made on existing and new infrastructures. The prospect of combining observations from the future space-based instrument LISA together with third generation ground based detectors will open the way towards multi-band GW astronomy, but will leave the infrasound (0.1 Hz to 10 Hz) band uncovered. GW detectors based on matter wave interferometry promise to fill such a sensitivity gap. We propose the European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), an underground infrastructure based on the latest progress in atomic physics, to study space-time and gravitation with the primary goal of detecting GWs in the infrasound band. ELGAR will directly inherit from large research facilities now being built in Europe for the study of large scale atom interferometry and will drive new pan-European synergies from top research centers developing quantum sensors. ELGAR will measure GW radiation in the infrasound band with a peak strain sensitivity of 3.3×10-22/sqrt(Hz) at 1.7 Hz. The antenna will have an impact on diverse fundamental and applied research fields beyond GW astronomy, including gravitation, general relativity, and geology.

Land-use history impacts functional diversity across multiple trophic groups.

Abstract: Land-use change is a major driver of biodiversity loss worldwide. Although biodiversity often shows a delayed response to land-use change, previous studies have typically focused on a narrow range of current landscape factors and have largely ignored the role of land-use history in shaping plant and animal communities and their functional characteristics. Here, we used a unique database of 220,000 land-use records to investigate how 20-y of land-use changes have affected functional diversity across multiple trophic groups (primary producers, mutualists, herbivores, invertebrate predators, and vertebrate predators) in 75 grassland fields with a broad range of land-use histories. The effects of land-use history on multitrophic trait diversity were as strong as other drivers known to impact biodiversity, e.g., grassland management and current landscape composition. The diversity of animal mobility and resource-acquisition traits was lower in landscapes where much of the land had been historically converted from grassland to crop. In contrast, functional biodiversity was higher in landscapes containing old permanent grasslands, most likely because they offer a stable and high-quality habitat refuge for species with low mobility and specialized feeding niches. Our study shows that grassland-to-crop conversion has long-lasting impacts on the functional biodiversity of agricultural ecosystems. Accordingly, land-use legacy effects must be considered in conservation programs aiming to protect agricultural biodiversity. In particular, the retention of permanent grassland sanctuaries within intensive landscapes may offset ecological debts.

How agroforestry systems influence soil fauna and their functions - a review

Abstract: Agroforestry systems have enhanced diversity of cultivated plants compared to monocultures, and are expected to affect associated biodiversity. Despite a growing body of literature on the importance of soil fauna, the known effects of different agroforestry types on soil fauna communities and functions have not yet been synthesized. We scanned publications on soil fauna in agroforestry systems. Our aim was to give an overview of strengths and weaknesses of the existing data, in terms of spatial coverage and representation of diverse agroforestry types and soil fauna groups and functions. Our database includes sixty-seven articles, mostly focusing on tropical regions and perennial crop agroforestry systems. Soil macrofauna are the most studied fauna group. The most common question addressed is the comparison of the effect of land use types on communities. Effects on fauna abundance and diversity are mainly positive when agroforestry is compared to cropland, and neutral or negative when compared to forests. Few publications actually measure soil fauna functions, or characterize their interactions and evolution in time and space depending on system design and management. Further work on soil fauna in agroforestry should harness ecological theory and address questions of spatial structure and scale, temporal dynamics and ecological interaction networks and how they determine ecosystem functioning.

Narrowing uncertainties in the effects of elevated CO2 on crops

Abstract: Plant responses to rising atmospheric carbon dioxide (CO2) concentrations, together with projected variations in temperature and precipitation will determine future agricultural production. Estimates of the impacts of climate change on agriculture provide essential information to design effective adaptation strategies, and develop sustainable food systems. Here, we review the current experimental evidence and crop models on the effects of elevated CO2 concentrations. Recent concerted efforts have narrowed the uncertainties in CO2-induced crop responses so that climate change impact simulations omitting CO2 can now be eliminated. To address remaining knowledge gaps and uncertainties in estimating the effects of elevated CO2 and climate change on crops, future research should expand experiments on more crop species under a wider range of growing conditions, improve the representation of responses to climate extremes in crop models, and simulate additional crop physiological processes related to nutritional quality. Understanding of the effects of elevated CO2 on crops has improved sufficiently that modelling future climatic effects on agriculture should eliminate ‘no CO2’ simulations. Further advancement in the estimation of the effects can be realized by studying a wider variety of crop species under a wider range of growing conditions, improving the representation of responses to climate extremes in crop models and simulating additional crop physiological processes related to nutritional quality.

Ultrasound and Microwave as Green Tools for Solid-Liquid Extraction

Abstract: Solid-liquid extraction is an important step to obtain bioactive compounds from a natural matrix such as microalgae, aromatic or medicinal herbs, and fruits and vegetables. For example, the microalgal cell wall disruption is an important and complex stage, and effective methods of disruption are fundamental to extract targeted molecules. Ultrasound and microwave are two extraction techniques considered as intensification techniques to reduce processing time, energy, and solvents. Indeed, compared with conventional methods, these techniques present the advantages of being efficient, fast, and industrially mature. Ultrasound and microwave have been involved in several studies to extract targeted compounds such as phenolics, carotenoids, and chlorophyll. This chapter will present ultrasound and microwave as suitable green extraction technologies for obtaining functional compounds from microalgae as an example of natural matrix.

Comparison between Pressurized Liquid Extraction and Conventional Soxhlet Extraction for Rosemary Antioxidants, Yield, Composition, and Environmental Footprint.

Abstract: Nowadays, "green analytical chemistry" challenges are to develop techniques which reduce the environmental impact not only in term of analysis but also in the sample preparation step. Within this objective, pressurized liquid extraction (PLE) was investigated to determine the initial composition of key antioxidants contained in rosemary leaves: Rosmarinic acid (RA), carnosic acid (CA), and carnosol (CO). An experimental design was applied to identify an optimized PLE set of extraction parameters: A temperature of 183 °C, a pressure of 130 bar, and an extraction duration of 3 min enabled recovering rosemary antioxidants. PLE was further compared to conventional Soxhlet extraction (CSE) in term of global processing time, energy used, solvent recovery, raw material used, accuracy, reproducibility, and robustness to extract quantitatively RA, CA, and CO from rosemary leaves. A statistical comparison of the two extraction procedure (PLE and CSE) was achieved and showed no significant difference between the two procedures in terms of RA, CA, and CO extraction. To complete the study showing that the use of PLE is an advantageous alternative to CSE, the eco-footprint of the PLE process was evaluated. Results demonstrate that it is a rapid, clean, and environmentally friendly extraction technique.

Trust Management in Industrial Internet of Things

Abstract: Automobile manufacturers around the world are increasingly deploying Industrial Internet of Things (IIoT) devices in their factories to accompany the Industrial Revolution 4.0. Security and privacy are the main limitations to the integration of Internet of Things (IoT) into industrial processes. Therefore, it is necessary to protect industrial data contained in IIoT devices and keep them confidential. As a step towards this direction, in this paper, we propose a dynamic trust management model suitable for industrial environments. We propose also to change the traditional centralized architecture of IIoT networks in automotive plants into a hybrid architecture based on a set of new industrial relationship rules. The performance evaluation in this work is done in two parts. In the first part, we compare our proposed architecture with the traditional architecture of the plant’s IIoT network. The results of this comparison show that our architecture is more suitable to simplify trust management of IIoT devices. In the second part, we demonstrated the ability, the adaptiveness and the resiliency of our proposed trust model against behavioral changes of IIoT nodes in malicious environments.

Opuntia Ficus Indica Edible Parts: A Food and Nutritional Security Perspective

Abstract: Cactus Opuntia ficus indica is widely distributed in (semi-) arid regions. Fruit and cladodes are processed into many food products. Cladodes are used as vegetables, but their main use is flour, wh...

'Community': a useful concept in heritage studies?

Abstract: This article aims to show the clearly differentiated national context in which concepts of community as used in heritage developed from the late nineteenth century to the present day. In the first part of this article, we look at the origins of the academic use of ‘community’ in Germany from the late nineteenth century to the present day arguing that its association with National Socialism has tainted the concept permanently. In the second part of this article, we move to France, where we also find a long-term scepticism when it comes to the concept of community. The strong republican tradition, which mistrusted everything that was capable of constructing identities that would divide and compartmentalise the republican ethos, rejected notions of community. Ideas associated with community were usually seen as particularist and therefore incompatible with the universalism of republicanism in France. In the final part of the article, we compare the sceptical reception of ‘community’ in the German and French cases with a far more positive left-wing tradition of community studies in Britain. The comparison of the uses of the concept of community in those three countries shows how a transnational dialogue can lead to more theoretically aware use of the concept of ‘community’.

2-methyloxolane as alternative solvent for lipid extraction and its effect on the cactus (Opuntia ficus-indica L.) seed oil fractions

Abstract: The potential of 2-methyloxolane (2-MeO) as an alternative solvent to extract cactus seed oil was compared, in qualitative and quantitative terms, with that of n-hexane, a solvent commonly used for the extraction of edible or cosmetic oils. With 2-MeO, the oil yield was higher (9.55 ± 0.12 g/100 g) than the oil extracted with n-hexane (8.86 ± 0.25 g/100 g). The chemical and physical parameters quality indices (acidity, peroxide value and extinction coefficients (K232 and K270 ) of 2-methyloxolane extracted oil were found to be much higher than that of oil extracted with n-hexane. A suitable refining scheme will have to be applied, probably leading to slight additional cost and losses. Also, the results showed that the sterol content was higher in the oil obtained with 2-MeO (111.5 ± 2.5 mg/100 g) as a solvent when compared to the oil extracted with n-hexane (102.1 ± 7.54 mg/100 g). However, fatty acid and tocopherol content were not influenced by the extraction solvent. Therefore, the bio-based solvent 2-methyloxolane can be considered as an excellent alternative to the petroleum-based solvent n-hexane for edible/cosmetic oil extraction. The utilization of 2-MeO for oil extraction can drastically reduce the health and environmental impacts associated with n-hexane.