On the effect of boundaries in two-phase porous flow

In this paper we study a model of an interface between two fluids in a porous medium. For this model we prove several local and global well-posedness results and study some of its qualitative properties. We also provide numerics

Del postulado práctico a la visión escatológica (Un itinerario de Kant a los románticos)

Ponencias de los tres talleres del Congreso "El fondo de la historia: Idealismo, Romanticismo y sus Repercusiones" celebrado del 22 al 24 de noviembre de 2010 en la Universidad Carlos III de Madri

Explorando la dinámica del Sn durante la síntesis de celdas de alta eficiencia basadas en Cu2ZnSnSe4

Treballs Finals de Grau d'Enginyeria de Materials, Facultat de Química, Universitat de Barcelona, Any: 2020, Tutors: Alejandro Pérez Rodriguez, Edgardo SaucedoThe need for new renewable sources of energy has been a reality for several years. Both because our current source of energy, fossil fuels, is limited, and because of the high pollution and problems associated with their use. As a solution to this problem, the development of renewable energies is our best asset. Within the wide range of possibilities, this work focuses on the energy that directly uses the enormous potential of our sun, photovoltaic energy. One of the most promising materials for emerging applications in the field of photovoltaics are the so-called kesterites, formed by the elements: Cu, Zn, Sn and Se; all of which are abundant and of low or null toxicity. The development of high efficiency cells based on kesterite faces several challenges related to the complex nature of this family of materials. Among them, the control of Sn that tends to form liquid and volatile species during the synthesis process having a strong exchange with the annealing atmosphere. In this work, the dynamics of Sn during the synthesis of the photovoltaic absorber, Cu2ZnSnSe4 (CZTSe), is investigated through a sequential process (Sputtering + Annealing). We compare the classical methodology where Sn is already incorporated in the solid precursor with a new and innovative solution in which Sn is partially incorporated in the vapour phase. The impact on the mechanism of CZTSe formation is investigated, as well as the properties of the layers and the characteristics of the finished device

Cryptocurrencies: a theorical and financial analysis.

Treball Final de Grau en Finances i Comptabilitat. Codi: FC1049. Curs acadèmic: 2018/2019Cryptocurrencies represent an alternative and modern pay mode, through new technologies. Although cryptocurrencies were used before the Great Recession of 2008, this fact achieved the development and international boom of cryptocurrencies, especially Bitcoin. The objective of this paper is to analyze cryptocurrencies, on one hand from a theoretical view (explaining history, functioning, legislation and economic effects), and on the other hand from a practical view, showing the price index between the main cryptocurrencies and other currencies, with the objective of showing the effect of cryptocurrencies, trying to find out if they suppose an investment and an alternative payment, or cryptocurrencies, or they are just unstable and at risk of become an economic "bubble". Finally, in the conclusion of this paper the potential that cryptocurrencies could have in the future will be explained

Improvements in Hardware Transactional Memory for GPU Architectures

In the multi-core CPU world, transactional memory (TM)has emerged as an alternative to lock-based programming for thread synchronization. Recent research proposes the use of TM in GPU architectures, where a high number of computing threads, organized in SIMT fashion, requires an effective synchronization method. In contrast to CPUs, GPUs offer two memory spaces: global memory and local memory. The local memory space serves as a shared scratch-pad for a subset of the computing threads, and it is used by programmers to speed-up their applications thanks to its low latency. Prior work from the authors proposed a lightweight hardware TM (HTM) support based in the local memory, modifying the SIMT execution model and adding a conflict detection mechanism. An efficient implementation of these features is key in order to provide an effective synchronization mechanism at the local memory level. After a quick description of the main features of our HTM design for GPU local memory, in this work we gather together a number of proposals designed with the aim of improving those mechanisms with high impact on performance. Firstly, the SIMT execution model is modified to increase the parallelism of the application when transactions must be serialized in order to make forward progress. Secondly, the conflict detection mechanism is optimized depending on application characteristics, such us the read/write sets, the probability of conflict between transactions and the existence of read-only transactions. As these features can be present in hardware simultaneously, it is a task of the compiler and runtime to determine which ones are more important for a given application. This work includes a discussion on the analysis to be done in order to choose the best configuration solution.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Towards a Software Transactional Memory for heterogeneous CPU-GPU processors

The heterogeneous Accelerated Processing Units (APUs) integrate a multi-core CPU and a GPU within the same chip. Modern APUs provide the programmer with platform atomics, used to communicate the CPU cores with the GPU using simple atomic datatypes. However, ensuring consistency for complex data types is a task delegated to programmers, who have to implement a mutual exclusion mechanism. Transactional Memory (TM) is an optimistic approach to implement mutual exclusion. With TM, shared data can be accessed by multiple computing threads speculatively, but changes are only visible if a transaction ends with no conflict with others in its memory accesses. TM has been studied and implemented in software and hardware for both CPU and GPU platforms, but an integrated solution has not been provided for APU processors. In this paper we present APUTM, a software TM designed to work on heterogeneous APU processors. The design of APUTM focuses on minimizing the access to shared metadata in order to reduce the communication overhead via expensive platform atomics. The main objective of APUTM is to help us understand the tradeoffs of implementing a sofware TM on an heterogeneous CPU-GPU platform and to identify the key aspects to be considered in each device. In our experiments, we compare the adaptability of APUTM to execute in one of the devices (CPU or GPU) or in both of them simultaneously. These experiments show that APUTM is able to outperform sequential execution of the applications.This work has been supported by projects TIN2013-42253-P and TIN2016-80920-R, from the Spanish Government, P11-TIC8144 and P12- TIC1470, from Junta de Andalucía, and Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech