Beamforming and Multiuser Detection in CDMA Systems with External Interferences

Multiuser detection has been investigated to mitigate the near-far effect in CDMA systems. Antenna arrays have been shown to provide spatial diversity and cancel undesired signals. In this paper we consider the synergy of both multiuser detection and antenna arrays for the base station of a CDMA system. The receiver we proposed consists of the known multiuser decorrelator, which cancels multiple-access interferences followed by a beamformer for each user, which cancels the external interferences. This receiver adds an extra branch to the decorrelator. This additional branch, corresponding to a fictitious user with an unused code and zero power, allows to estimate the external interference signal subspace and compute a suitable beamforming weight-vector that cancels the external interferences. The receiver is also extended to the asynchronous case and all of this without any training signal or any a priori spatial information.Peer ReviewedPostprint (published version

Blind multi-user combining at the base station for asynchronous CDMA systems

This paper studies the potential benefits of antenna arrays in cellular CDMA communications and proposes a powerful scheme to undertake the array processing at the base station in CDMA mobile systems. The proposed technique exploits the temporal structure of CDMA signals. The necessary information is extracted directly from the received signals, thus no training signal orPeer ReviewedPostprint (published version

Blind multiuser adaptive combining for asynchronous cdma systems

This paper presents a novel technique to globally estimate and track the direction of arrival (DOA) of different users in an asynchronous CDMA system. The estimates are obtained exploiting the temporal structure of CDMA signals. No training signal nor a priori spatial information is required. The necessary information is extracted directly from the received signals. The proper combining of the overall information present at the receiver after the despreading, jointly with an Eigenvalue Decomposition (EVD), let as estimate the generalized steering vector for each user. Furthermore, a direct iteration method is introduced in our scheme in order to make the array robust to channel variations and to reduce the computational load of the EVD required for each user.Peer ReviewedPostprint (published version

Risk aversion and debt maturity structure

We study the relationship of risk aversion and debt maturity structure. In a model in which adverse selection in financial markets creates a role for the use of short-term debt, we allow the possibility of borrowers being risk-averse. This creates a trade-off between reduced expected financing costs and higher risk and allows for the study of the effect of risk aversion on optimal maturity structure. We prove that, as risk aversion increases, so does the percentage of debt that is long-term.risk aversion, debt maturity structure, adverse selection.

Los sistemas de acreditación : aproximación conceptual y teórica

Cuando se habla de sistemas de acreditación en la literatura pedagógica y en los textos legales siempre se hace como un medio llamado a cumplir varias funciones sociales y educativas al mismo tiempo: para responder a los acelerados cambios sociales, para elevar el nivel de formación de la población, para reducir la exclusión social, para mejorar la transparencia del mercado de trabajo, etc. En este artículo se analiza la perspectiva teórica y conceptual de los sistemas de acreditación, exponiendo algunas ideas para el debate sobre las razones pedagógicas que podrían justificar y legitimar estas nuevas estrategias educativas, y proponiendo finalmente lo que podrían ser algunas bases conceptuales de los sistemas de acreditación, así como una clasificación de los mismos.Quan parlem de sistemes d'acreditació en la literatura pedagògica i en els textos legals sempre es fa a fi de complir diferents funcions socials i educatives alhora: per respondre als accelerats canvis socials, per augmentar el nivell formatiu de la població, per reduir l'exclusió social, per millorar la transparència del mercat de treball, etc. En aquest article s'analitza la perspectiva teòrica i conceptual dels sistemes d'acreditació, exposant algunes idees per al debat sobre les raons pedagògiques que podrien justificar i legitimar aquestes noves estratègies educatives, i proposant finalment el que podrien ser les bases conceptuals dels sistemes d'acreditació, així com una classificació d'aquests.When we talk about accreditation systems both in pedagogic literature and in legal texts we always do it as a means of fulfilling several educational and social functions at the same time: to answer the fast-growing social changes, to promote the level of competence in the population, to reduce social exclusion, to improve transparency in the labour market, etc. This article tries to analyse the conceptual and theoretical perspective of accreditation systems, presenting some ideas for the debate on the pedagogical reasons that could justify and legitimise these new strategies and finally propose what might be considered some of the conceptual bases of accreditation systems as well as their classification

System for the management of the technical maintenance of a company

This project consists on the creation and development of a model to manage technical maintenance within a company. The first part of the model is based on a control system made through worksheets using the EXCEL program. This part allows the analysis and decision making for the continuous improvement of maintenance and to reach pre-established objectives. The second part consists on a simulation system made through the ARIS program (software used in the business modelling). This part allows to test and simulate the proposed improvements for technical maintenance and observe their consequences. Prior to the creation and development of the model, certain indicators have been defined as control variables of the system, specifically the KPIs. Thereby, a search and a selection of the most useful indicators have been carried out in order to evaluate maintenance in the model. The KPIs quantify the different sections of the maintenance and allow to work with numerical values. In this way, maintenance comparisons can be made through the values of the indicators. Finally, an exemplary case has been displayed to portray the operation of the model. In this section, the initial state is analysed and solutions are proposed. Then, each one of them is simulated to observe the effects in the maintenance plan. At the end, a comparison is made between them and they are organized accordingly to their improvement in the technical maintenance plan

Tatjana Gajić. Paradoxes of Stasis: Literature, Politics, and Thought in Francoist Spain. Lincoln: U of Nebraska P, 2019.

Review of Tatjana Gajić. Paradoxes of Stasis: Literature, Politics, and Thought in Francoist Spain. Lincoln: U of Nebraska P, 2019. 219 pp

New business model for auction houses based on blockchain

Over the last few years, and perhaps due to the global pandemic, activity around blockchain technology, cryptocurrencies, and crypto-assets has become socially popular and mainstream. This technology presents a new digital infrastructure and offers a new governance model in the ecosystem that can bring improvements to current systems and represent a turning point. In the frenetic and constantly evolving world we live in, the implementation of these new technologies is a challenge for companies, and their early adoption can be a turning point for their growth and future development. The project's starting point is born at this precise moment when different companies and industries are racing to join the new technology and try to adapt and take advantage of it. In particular, there has been a revolution in the art sector thanks to the invention of NFTs and their use linked to the creation and trade of digital art. Despite the existence of significant and recognized marketplaces where these assets are traded, large auction houses have maintained a relevant role in managing some of the most famous NFTs auctions. Their role has meant nothing more than incorporating these new assets into their catalogs and, in some cases, creating digital spaces where they can exhibit them. This thesis presents a new business model for auction houses based on blockchain to enable them to go a step further and take full advantage of the possibilities and improvements that this technology offers. The new business model developed incorporates several applications of the technology in the current system to improve it and satisfy the new needs and requirements of the market. In order to carry out the design of the new model, the document first proposes a compilation chapter of the two main topics to be dealt with. On the one hand, historical documentation of auctions and auction houses up to their current model has been carried out to understand their evolution. On the other hand, a detailed explanation of blockchain technology and its set of applications has been developed to understand its characteristics and the possibilities it offers. Finally, in order to give the most accurate picture of the current situation, a state-of-the-art is developed in a timeline format with the most significant related events that have taken place over the last year. Once the foundations on which the new business model is built have been understood and internalized, the project enters the second chapter, where the current situation on the topic is analyzed in detail through three different analyses. First, the state-of-the-art is examined in-depth, and the characteristics and conclusions that define the present situation are drawn. For this purpose, the different news items are examined objectively in order to distinguish the reasons behind the events, understanding how and why they have taken place. Secondly, a set of interviews have been conducted with different actors involved in the main topic of the thesis in order to have a first-hand opinion and hear different perspectives. To conclude the analysis and deepen in the field of blockchain technology and particularly in the possibilities of smart contracts, a programming course in blockchain has been carried out in parallel to the project's development. The document section shows a summary of the follow-up of the course and explains all the new concepts acquired during the course. Finally, the last chapter of the thesis shows a description of the new business model for auction houses based on blockchain as a result of the analysis of the project. The first section develops the new system and its characteristics, the design of the blockchain infrastructure and its operation, and presents the modifications made to the new business model. The chapter continues with the justification for creating the model and explains how it arises from taking advantage of the opportunities offered by the new technology and the possible results and benefits that auction houses can obtain. In addition, other sections are added that qualitatively define the roadmap to be followed for its implementation, the economic analysis, and the environmental impact of the new model. To conclude, a feasibility analysis is carried out to show the current weaknesses to be taken into account before adopting the new modelNegli ultimi anni e a causa della pandemia globale, l'attività intorno alla tecnologia blockchain, alle criptovalute e ai crypto asset è diventata socialmente popolare e un argomento mainstream. Questa tecnologia presenta una nuova infrastruttura digitale e offre un nuovo modello di governance nell'ecosistema che può portare miglioramenti ai sistemi attuali. Nel mondo frenetico e in continua evoluzione in cui viviamo, l'implementazione di queste nuove tecnologie è una sfida per le aziende, e la loro adozione precoce può essere un punto di svolta per la loro crescita e sviluppo futuro. Il punto di partenza del progetto nasce in questo preciso momento in cui diverse aziende e industrie stanno correndo per unirsi alla nuova tecnologia e cercare di adattarsi e trarne vantaggio. In particolare, c'è stata una rivoluzione nel settore dell'arte grazie all'invenzione degli NFT e al loro utilizzo legato alla creazione e al commercio di arte digitale. Nonostante l'esistenza di importanti e riconosciuti marketplace di questi beni, le grandi case d'asta hanno mantenuto un ruolo rilevante nella gestione di alcune delle più famose aste di NFTs. Il loro ruolo non ha significato altro che incorporare questi nuovi beni nei loro cataloghi e, in alcuni casi, creare spazi digitali dove poterli esporre. Questa tesi presenta un nuovo modello di business per le case d'asta basato sulla blockchain per permettere loro di fare un passo avanti e sfruttare al massimo le possibilità e i miglioramenti che questa tecnologia offre. Il nuovo modello di business sviluppato incorpora diverse applicazioni della tecnologia nel sistema attuale per migliorarlo e soddisfare le nuove esigenze e richieste del mercato. Per realizzare la progettazione del nuovo modello, il documento propone innanzitutto un capitolo di compilazione dei due temi principali da trattare. Da un lato, è stata realizzata una documentazione storica delle aste e delle case d'asta fino al loro modello attuale per comprendere la loro evoluzione. Dall'altro, è stata sviluppata una spiegazione dettagliata della tecnologia blockchain e del suo insieme di applicazioni per capire le sue caratteristiche e le possibilità che offrono. Infine, al fine di dare il quadro più accurato della situazione attuale, è stato sviluppato uno stato dell'arte in formato timeline con gli eventi correlati più significativi che hanno avuto luogo nell'ultimo anno. Una volta che le basi su cui è costruito il nuovo modello di business sono state comprese e interiorizzate, il progetto entra nel secondo capitolo, dove la situazione attuale sull’argomento viene analizzata in dettaglio attraverso di tre diverse analisi. In primo luogo, si esamina in profondità lo stato dell'arte e si tracciano le caratteristiche e le conclusioni che definiscono la situazione attuale. A questo scopo, le diverse notizie vengono esaminate in modo oggettivo per distinguere le ragioni dietro gli eventi, capendo come e perché sono avvenuti. In secondo luogo, sono state condotte una serie di interviste con diversi partecipanti riguardo l'argomento principale della tesi, al fine di avere un'opinione di prima mano e sentire diverse prospettive. Per concludere l'analisi e approfondire nel campo della tecnologia e in particolare nelle possibilità degli smart contracts, è stato realizzato un corso di programmazione in blockchain in parallelo allo sviluppo del progetto. La sezione del documento mostra un riassunto del seguito del corso e spiega tutti i nuovi concetti acquisiti durante il corso. Infine, l'ultimo capitolo della tesi mostra una descrizione del nuovo modello di business per le case d'asta basato su blockchain come risultato dell'analisi del progetto. La prima sezione sviluppa il nuovo sistema e le sue caratteristiche, la progettazione dell'infrastruttura blockchain e il suo funzionamento, e presenta le modifiche apportate al nuovo modello di business. Il capitolo continua con la giustificazione della creazione del modello e spiega come nasce dallo sfruttamento delle opportunità offerte dalla nuova tecnologia e i possibili risultati e benefici che le case d'asta possono ottenere. Inoltre, vengono aggiunte altre sezioni che definiscono qualitativamente la tabella di marcia da seguire per la sua implementazione, l'analisi economica e l'impatto ambientale del nuovo modello. Per concludere, viene effettuata un'analisi di fattibilità per mostrare le attuali debolezze da prendere in considerazione prima di adottare il nuovo modell

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