A Modification Of The EM Algorithm To Estimate An Andersen-Gill Gamma Frailty Model For Multivariate Failure Time Data

A modification of the Andersen-Gill gamma shared frailty model is presented. The variance of the frailty is directly modeled by means of a generalized linear model, the EM algorithm is modified in order to simultaneously estimate a semiparametric model for the failure times and a model for the variance of the frailty. A simulation study is conducted to evaluate the performance of the proposed algorithm (EMB algorithm) and compared with other methods, a marginal model, and a conditional model. Multivariate data from a nosocomial infection study is used to illustrate the methods. The EMB fit turned out to be better than the fit obtained from a marginal model or from a conditional model. The EMB provided the best fit (being the least over-dispersed and having the highest AIC and the highest pseudo-R square) and estimated the parameters most efficiently. The proposed method is able to capture and to take into account unobservable random effects in semiparametric models

Strategic management analysis of P in the Metropolitan Area of Barcelona (Spain)

The aim of this study is to evaluate the current situation of phosphorus, an element classified and considered as critical element by the European Union, at global, European and Spanish level. Its importance, although used in many industrial application it is associated to its ole as a nutrient in fertilizers production and use. It is estimated that the phosphate resources, in the form of phosphatic rock, are limited so it is considered a non-renewable source of phosphorus and its reserves are concentrated in a few deposits in a few number of countries. This has caused the entry of phosphorus into the designated critical elements in the EU and the necessity to apply the circular economy model for its use. In this way it is intended to close the cycle of phosphorus from secondary sources. The analysis carried out of the P cycles worldwide allow to conclude that recovery of phosphorus from a) the urban water cycle, specially from the sludge generated in the waste water treatment plants (WWTP), b) compost produced from the faeces (swine solids) from animal farms or, c) ashes originated from sludge incineration are the main secondary resources to be considered nowadays. However, it has been identified the need to promote tertiary sources by improving the efficiency of phosphorus processing and use in all sectors (mining and beneficiation, agriculture), also including restricting laws limiting the use of phosphorus for essential needs and changes feeding systems. In this project, a balance flow of phosphorus in Spain using the Substance Flow Analysis (SFA) methodology, allowed to the identification of the available secondary sources and compare with other ready-made for EU27 and reference countries as Japan. Additionally to the SFA for Spain a proposal to promote and improve phosphorus cycling was centred in the Barcelona Metropolitan Area (BMA). WWTP from the BMA were as main secondary resource to promote the recovery of phosphorus from the WWTPs streams. This assessment required a detailed study of the Phosphorous balance in the BMA by using raw data provided by the WWTP management system of the BMA during the years 2011-2015. From the different streams evaluated sludge streams were considered key actors and specially the management routes and fates of sludge in these years. In 2011 most of the sludge was destined to cement industry, in a material co-substitution of coque, a fact that was declining until 2015 which were sent directly to composting plants due to the crisis in the construction sector with the reduction of cement production. This suggests the use of the sludge for the cement industry again, but the truth is that the objectives of EU on the circular economy approach for critical elements will cause that sewage sludge would not be use by the cement industry and then different sewage sludge options promoting the recovery of phosphorus will be needed. From these premises, four scenarios, postulating P-cycling options in the BMA by proposing the integration of different sludge management processes (anaerobic digestion, monoincineration, composting and recovery technology phosphorous, called Ecophos) were raised and evaluated in this project. Combining each other, a detailed analysis for energy balances, mass balances, phosphorus recovery, environmental and economic impact has been performed

An Android real-time kernel and system interface for open nano-satellite constellations

L'objectiu d'aquest treball és dissenyar i implementar part de l'arquitectura de software per a una plataforma de desenvolupament de nano-satèl·lits oberta basada en Android. Per un costat, afegir temps real al kernel. Per un altre costat, implementar un repartidor de missatges modular i flexible.The aim of this thesis is to design and implement part of the software architecture for an open nano-satellite development platform based on an Android smartphone. On one side, extend the kernel with real-time capabilities. On the other side, implement a flexible and modular message distributor

Improving the scheduler of the OmpSs-2 runtime

In a task-based model such as OmpSs-2, task creation and scheduling are critical to achieve good performance. For this reason, these areas have been redesigned in the Nanos6 runtime to make them scalable and efficient for current and future large multi-core systems

Revisiting the Feasibility of Public Key Cryptography in Light of IIoT Communications

Digital certificates are regarded as the most secure and scalable way of implementing authentication services in the Internet today. They are used by most popular security protocols, including Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS). The lifecycle management of digital certificates relies on centralized Certification Authority (CA)-based Public Key Infrastructures (PKIs). However, the implementation of PKIs and certificate lifecycle management procedures in Industrial Internet of Things (IIoT) environments presents some challenges, mainly due to the high resource consumption that they imply and the lack of trust in the centralized CAs. This paper identifies and describes the main challenges to implement certificate-based public key cryptography in IIoT environments and it surveys the alternative approaches proposed so far in the literature to address these challenges. Most proposals rely on the introduction of a Trusted Third Party to aid the IIoT devices in tasks that exceed their capacity. The proposed alternatives are complementary and their application depends on the specific challenge to solve, the application scenario, and the capacities of the involved IIoT devices. This paper revisits all these alternatives in light of industrial communication models, identifying their strengths and weaknesses, and providing an in-depth comparative analysis.This work was financially supported by the European commission through ECSEL-JU 2018 program under the COMP4DRONES project (grant agreement N∘ 826610), with national financing from France, Spain, Italy, Netherlands, Austria, Czech, Belgium and Latvia. It was also partially supported by the Ayudas Cervera para Centros Tecnológicos grant of the Spanish Centre for the Development of Industrial Technology (CDTI) under the project EGIDA (CER-20191012), and in part by the Department of Economic Development and Competitiveness of the Basque Government through the project TRUSTIND—Creating Trust in the Industrial Digital Transformation (KK-2020/00054)

A ranging method with IEEE 802.11 data frames for indoor localization

IEEE 802.11 networks constitute a suitable infrastructure for accurate indoor positioning. However, existing approaches based on fingerprinting present drawbacks that make them not suitable for most of applications. This paper presents an innovative TOA-based ranging technique over IEEE 802.11 networks intended to be the essential step of an indoors location system. This approach is based on round trip time measurements using standard IEEE 802.11 link layer frames and a statistical post-processing to mitigate the noise of the measurements. A prototype has been implemented in order to assess the validity and evaluate the performance of the proposed technique. First results show ranging accuracies of less than one meter of error in LOS situations

Integration of M-learning and LMS: a sustainability approach

Mobile phones are widely used in both rich and poor countries, unlike what happens with other ICTs. The expansion of mobile telephony in poor countries presents an opportunity to fight against digital divide. In the latter countries, mobile phones are used to get information and services about agriculture, health, and education among other areas. Specifically in the area of education there are many who think that mobile phones are a useful tool to help achieve universal primary education, one of the Millennium Development Goals proposed by the United Nations. There are many educational experiences with mobile phones for development. But most of these experiences have serious limitations that affect their long-term sustainability. In this line, the current paper provides a set of guidelines to define more sustainable and long-term viable mobile-learning projects and presents its applications to a m-learning project: the Moodbile project.Peer ReviewedPostprint (published version

How to Survive Identity Management in the Industry 4.0 Era

Industry 4.0 heavily builds on massive deployment of Industrial Internet of Things (IIoT) devices to monitor every aspect of the manufacturing processes. Since the data gathered by these devices impact the output of critical processes, identity management and communications security are critical aspects, which commonly rely on the deployment of X.509 certificates. Nevertheless, the provisioning and management of individual certificates for a high number of IIoT devices involves important challenges. In this paper, we present a solution to improve the management of digital certificates in IIoT environments, which relies on partially delegating the certificate enrolment process to an edge server. However, in order to preserve end-to-end security, private keys are never delegated. Additionally, for the protection of the communications between the edge server and the IIoT devices, an approach based on Identity Based Cryptography is deployed. The proposed solution considers also the issuance of very short-lived certificates, which reduces the risk of using expired or compromised certificates, and avoids the necessity of implementing performance expensive protocols such as Online Certificate Status Protocol (OCSP). The proposed solution has been successfully tested as an efficient identity management solution for IIoT environments in a real industrial environment.This work was supported in part by the Spanish Ministry of Science and Innovation through the National Towards zeRo toUch nEtwork and services for beyond 5G (TRUE-5G) Project under Grant PID2019-108713RB-C53, in part by the European Commission through the Electronic Components and Systems for European Leadership-Joint Undertaking (ECSEL-JU) 2018 Program under the framework of key enabling technologies for safe and autonomous drones' applications (COMP4DRONES) Project under Grant 826610, with the national financing from France, Spain, Italy, The Netherlands, Austria, Czech, Belgium, and Latvia, in part by the Ayudas Cervera para Centros Tecnologicos Grant of the Spanish Centre for the Development of Industrial Technology (CDTI) through the Project EGIDA under Grant CER-20191012, and in part by the Basque Country Government through the Creating Trust in the Industrial Digital Transformation (TRUSTIND) ELKARTEK Program Project under Grant KK-2020/00054

A Review of pedestrian indoor positioning systems for mass market applications

In the last decade, the interest in Indoor Location Based Services (ILBS) has increased stimulating the development of Indoor Positioning Systems (IPS). In particular, ILBS look for positioning systems that can be applied anywhere in the world for millions of users, that is, there is a need for developing IPS for mass market applications. Those systems must provide accurate position estimations with minimum infrastructure cost and easy scalability to different environments. This survey overviews the current state of the art of IPSs and classifies them in terms of the infrastructure and methodology employed. Finally, each group is reviewed analysing its advantages and disadvantages and its applicability to mass market applications

Performance of a time-of-arrival technique for positioning WLAN terminals

Nowadays, several systems are available for outdoor location (i.e GPS, cellular networks based…). However, there is no proper location system for indoor scenarios. The technique presented in this paper proposes the use of the existing wireless LAN infrastructure with minor changes to provide an accurate estimation of the location of mobile devices in indoor environments. This technique is based on round-trip time (RTT) measurements, which are used to estimate TOA and distances between the device to be located and WLAN access points. To avoid the cumbersome modification of the physical layer, each RTT is estimated between the transmission of an IEEE 802.11 link layer data frame and the reception of the associated acknowledgement (ACK). By applying trilateration algorithms, an accurate estimation of the mobile position is calculated.Peer ReviewedPostprint (published version