A. Pérez-Navarro

RSS and Sensor Fusion Algorithms for Indoor Location Systems on Smartphones

Location-based applications require knowing the user position constantly in order to find out and provide information about user’s context. They use GPS signals to locate users, but unfortunately GPS location systems do not work in indoor environments. Therefore, there is a need of new methods that calculate the location of users in indoor environments using smartphone sensors. There are studies that propose indoor positioning systems but, as far as we know, they neither run on Android devices, nor can work in real environments. The goal of this chapter is to address that problem by presenting two methods that estimate the user position through a smartphone. The first method is based on euclidean distance and use Received Signal Strength (RSS) from WLAN Acces Points present in buildings. The second method uses sensor fusion to combine raw data of accelerometer and magnetometer inertial sensors. An Android prototype that implements both methods has been created and used to test both methods. The conclusions of the test are that RSS technique works efficiently in smartphones and achieves to estimate the position of users well enough to be used in real applications. On the contrary, the test results show that sensor fusion technique can be discarded due to bias errors and low frequency readings from accelerometers sensor.

How Can Semantic Be Introduced in GIS Mobile Applications: Expectations, Theory and Reality

With the advent of GPS and the spread of smart phones (iPhone, Android, etc.) have proliferated applications dealing with geographic information. Many of these applications are beginning to provide semantic information through: 1) the classification of tourist attractions in categories (thesauri tourism categories Open Street Map, etc.), and 2) the representation of metadata (Linked Geo Data, Crossing, etc.). However, mobile devices do not still uses all this potential. This paper presents a comprehensive study on the main formalisms to include Semantic and Geographic Data within a mobile device, and how to get them work efficiently just in the mobile, without internet connection. The article presents several options to implement these technologies and, for every option shows the limitations of such implementation. Therefore provides a glimpse into the various options available to implement semantic geographic applications on mobile devices. To mark the goal, the study shows a case study where ontologies have been used to provide semantics to a travel assistant that runs on mobile devices. The goal is an application able to offer personalized touristic routes different for every single user, that take into account, for example, the user interests and time available, and all the processes must be run within the mobile device. The main contribution of the paper is to manage and combine semantic data and geographic information within a mobile device, and doing it without internet connection, and for an end-user application.

Mott transition in the two-dimensional Hubbard model

Abstract We are interested in the description of the Mott–Hubbard transition from a perturbation theory arising from a two-dimensional Hubbard model. The self-energy within the random phase approximation presents some inconsistencies; one of them is that its imaginary part presents more than one zero, which is a violation of the Luttinger theorem. We use a Bogolyubov transformation and within a spin density wave mean field, we recalculate the self-energy in the new ground state, and it is able to describe the Mott–Hubbard transition, satisfying the Luttinger condition.

Spin fluctuation effects in the normal state of Hubbard systems

Abstract We obtain and discuss the self-energy and the renormalized electronic structure of the normal state in strongly correlated electron systems within the pseudogap regime. The considered effective potentials are found from spin fluctuations within a Hubbard single band model. We find that the self-energy tends to violate the Luttinger theorem as the bandwidths are narrowed and also as the Hubbard U increases. This is an indication that a new fundamental state should be used to describe the system under these conditions. We have used an antiferromagnetic fundamental state and found that in this case the new self-energy does satisfy the Luttinger theorem.

Implementation of High Complex Routing Algorithms in Mobile Devices: The Itiner@ Case

The emergence of smart phones increasingly powerful opens a new range of possibilities in terms of uses and applications. However, given its limited memory and CPU, some potential applications are very difficult or even impossible to implement. This is the case, for example, in a route calculation application. In the context of Itiner@ project, which is a personalized route assistant completely autonomous that should work even without Internet connection, all processes must be fully implemented locally on the mobile device. Since it is a project focused on leisure, it is important to get a satisfactory user experience, so besides being able to execute the route calculation and personalization algorithm, the system must be efficient. In this sense, recursive algorithms consume too many resources or are too slow to be used in a mobile device. Then, it has been necessary to develop new algorithms depending on the limitations of these devices. This paper presents the process followed and difficulties encountered in implementing an algorithm to calculate routes that run entirely on a mobile device efficiently.

Mott Transition in the Two-Dimensional Hubbard Model

We are interested in the description of the Mott-Hubbard transition from a perturbation theory arising from a two-dimensional Hubbard model. We calculate the self-energy within the random phase approximation and a double-Lorentzian as a non-interacting density of states. The paramagnetic ground state is unstable for realistic values of U, since the self-energy presents some inconsistencies ; one of them is that its imaginary part presents more than one zero, which is a violation of the Luttinger theorem. We use a Bogolyubov transformation and within a spin density wave mean field, the antiferromagnetic correlations of wave vector Q = (π/a,π/a) are included. We recalculate the self-energy in the new ground state and then it is able to describe the Mott-Hubbard transition, and the Luttinger theorem is satisfied.

Quasiparticle structure of Sr2RuO4

Abstract The non-copper layered perovskite, Sr 2 RuO 4 , is expected to be a very useful reference material for interpreting experiments on the high T c cuprate superconductors. A band structure calculation for Sr 2 RuO 4 is performed. Starting from the electronic structure determined in the local density formalism, the Dysons equation with self-energies arising from the Hubbard hamiltonian is solved by diagonalizing the Greens function in k -space. The density of states is obtained by considering the renormalization factor and the life-times of the quasiparticle states in each pole of the interacting system. This leads to modification of the density of states calculated in the local density formalism, and the results fit experimental data not only in the position of peaks, but also in their intensity and in the number of states at Fermi level.

Itiner@: Ontology for Personalizing Tourist Routes in Mobile Devices

Several applications that support users when doing tourism have appeared during the last years. These applications, though popular, have not become a reliable and dependable tourist assistant because they offer little personalization, which eventually may overwhelm users with too much information. An effective mobile application should store tourist information in a way that facilitates the identification of relevant points of interest to the user and the relevant information about them. The relevance of information depends also on the context. This paper presents an ontology that can store information about points of interest (POI), preferences and habits of users and time information. The presented ontology is aligned with the ontology Linked Geo Data to facilitate the importation of data to and from it. The ontology has been integrated into a mobile application called Itiner@ to create custom routes for each user based on his/her preferences, personal situation, means of transport, area to visit, date and duration of the visit. The main contribution of this work is to identify the relevant information to mobile touristic applications and to show how to use an ontology to improve the functionalities of geographic information system through the use of semantic information.

Present@: A virtual environment for dissertation defense

At the end of their technical studies, students have to present a final project in order to finish their degree. With this project, students prove that they have got all of the competences they should have acquired. Some competencies, such as the ability to communicate orally or the ability to argue may be evaluated during a face-to-face dissertation defense, but how to translate this evaluation scenario to a virtual environment is a challenge. This paper faces the problem of presenting dissertations in a virtual environment, to evaluate the aforementioned competences. The solution proposed, called Present@, is focused in teaching and technical dimensions, and is complemented with some materials and tutorials that help students to acquire those competences. Therefore, the paper shows Present@ as a solution to the problems that virtual universities have to face when dealing with the evaluation of final degree projects and particularly in their defense. Present@ has been tested over 131 students during six semesters and the results show that it actually helps students to acquire the desired competences in virtual environments. In addition, the analysis about the use of the tool has denoted that videos are an efficient mechanism to evaluate the ability to communicate of students and to work on transversal competencies. Some students also commented that the use of videos make the dissertation defense more natural and closer to face-to-face environments.

LDA+Σ (ω) Method for the Electronic Structure of Strongly Correlated Antiferromagnetic Materials: Application to La2CuO4

In this paper we present a method for obtaining the quasiband structure and the renormalized density of quasistates of strongly correlated systems with antiferromagnetic ordering. We calculate the electronic structure of La 2 CuO 4 in order to test this method. The first step required is to calculate the electronic structure from the local density approximation (LDA) in order to obtain the initial non-interacting ground state. The LDA density of states in strongly correlated systems usually presents serious discrepancies with experimental results. As is well known, these discrepancies, fundamentally concerning photoemission, are due to the fact that the dynamic correlation effects are not taken into account within the LDA. In order to include these effects, we obtain a self-energy potential which allows the initial LDA electronic structure to connect with that of the antiferromagnetic ground state arising from a Bogolyubov-like transformation. Within this new ground state, we determine an antiferromagnetic self-energy by means of a spin density wave procedure, and the interacting Green function yields a density of states which is in reasonable agreement with the experimental photoemission result.