A Unification of Ensemble Square Root Kalman Filters

In recent years, several ensemble-based Kalman filter algorithms have been developed that have been classified as ensemble square-root Kalman filters. Parallel to this development, the SEIK (Singular ``Evolutive'' Interpolated Kalman) filter has been introduced and applied in several studies. Some publications note that the SEIK filter is an ensemble Kalman filter or even an ensemble square-root Kalman filter. This study examines the relation of the SEIK filter to ensemble square-root filters in detail. It shows that the SEIK filter is indeed an ensemble-square root Kalman filter. Furthermore, a variant of the SEIK filter, the Error Subspace Transform Kalman Filter (ESTKF), is presented that results in identical ensemble transformations to those of the Ensemble Transform Kalman Filter (ETKF) while having a slightly lower computational cost. Numerical experiments are conducted to compare the performance of three filters (SEIK, ETKF, and ESTKF) using deterministic and random ensemble transformations. The results show better performance for the ETKF and ESTKF methods over the SEIK filter as long as this filter is not applied with a symmetric square root. The findings unify the separate developments that have been performed for the SEIK filter and the other ensemble square-root Kalman filters

Chiral transition in a magnetic field and at finite baryon density

We consider the quark-meson model with two quark flavors in a constant external magnetic field $B$ at finite temperature $T$ and finite baryon chemical potential $\mu_B$. We calculate the full renormalized effective potential to one-loop order in perturbation theory. We study the system in the large-$N_c$ limit, where we treat the bosonic modes at tree level. It is shown that the system exhibits dynamical chiral symmetry breaking, i. e. that an arbitrarily weak magnetic field breaks chiral symmetry dynamically, in agreement with earlier calculations using the NJL model. We study the influence on the phase transition of the fermionic vacuum fluctuations. For strong magnetic fields, $|qB|\sim5m_{\pi}^2$ and in the chiral limit, the transition is first order in the entire $\mu_B-T$ plane if vacuum fluctuations are not included and second order if they are included. At the physical point, the transition is a crossover for $\mu_B=0$ with and without vacuum fluctuations.Comment: 11 pages. 5figs. V2: fixed a few typos and added refs. Submitted to PRD. V3: Added refs and substantial revision of tex

Operational tsunami modelling with TsunAWI – recent developments and applications

In this article, the tsunami model TsunAWI (Alfred Wegener Institute) and its application for hindcasts, inundation studies, and the operation of the tsunami scenario repository for the Indonesian tsunami early warning system are presented. TsunAWI was developed in the framework of the German-Indonesian Tsunami Early Warning System (GITEWS) and simulates all stages of a tsunami from the origin and the propagation in the ocean to the arrival at the coast and the inundation on land. It solves the non-linear shallow water equations on an unstructured finite element grid that allows to change the resolution seamlessly between a coarse grid in the deep ocean and a fine representation of coastal structures. During the GITEWS project and the following maintenance phase, TsunAWI and a framework of pre- and postprocessing routines was developed step by step to provide fast computation of enhanced model physics and to deliver high quality results

Contributos da internet na resolução de problemas

A Matemática é essencial para o desenvolvimento da sociedade, pode ter um forte carácter formativo e contribuir para a actualização e formação ao longo da vida. A utilização das Tecnologias de Informação e Comunicação no dia-a-dia e no contexto escolar, nas suas variadas formas e potencialidades, poderá ser um forte contributo para a diminuição do insucesso escolar e, de um modo particular, para a aprendizagem da Matemática. A importância da Internet no estudo da Matemática, nomeadamente na resolução de problemas, pode constituir uma estratégia para o aprofundamento da Matemática e um incentivo à sua aprendizagem e utilização. A apresentação de situações que conduzam à resolução de problemas tem sido e continua a ser uma das recomendações mais importantes em Educação Matemática. Existe no entanto alguma inércia no sistema de ensino de tal forma que muitos professores resistem a mudarem de práticas, persistindo nos exercícios e tarefas que em geral exigem pouco raciocínio. Nesta apresentação pretende-se reflectir sobre uma experiência que está a ser desenvolvida no âmbito do doutoramento em Estudos da Criança, na Universidade do Minho – Braga, cujo tema é a resolução de problemas matemáticos, tendo como meio de apoio uma plataforma Web. Neste sentido será apresentado um breve resumo do projecto, seguido de fundamentação teórica, enfatizando aspectos relacionados com a metodologia e com os resultados esperados com a investigação a realizar. Neste projecto, para além da preocupação em apreciar o efeito que o apoio disponibilizado aos alunos a partir da plataforma Moodle tem nos resultados de aprendizagem, avaliados através de instrumentos de recolha de dados construídos e validados para o efeito, numa perspectiva de recolha e análise de dados próxima de uma abordagem de investigação quantitativa, será ainda dada particular ênfase à interacção desenvolvida entre os alunos durante o processo colaborativo de ensino e aprendizagem. A análise da interacção será orientada, com uma abordagem próxima da investigação qualitativa, apreciando as publicações dos alunos nos fóruns de discussão online, no sentido de averiguar a forma de interacção predominante, tendo como ponto de partida a categorização das interacções numa das formas: monólogos, interacção convergente e interacção divergente. Nesta fase inicial do desenvolvimento do projecto, não existem ainda muitos dados recolhidos, no entanto iremos apresentar os resultados da pilotagem do teste, aplicado a duas turmas, uma do 5.º ano e outra do 6.º ano de escolaridade, do 2.º Ciclo do Ensino Básico, num dos agrupamentos verticais de escolas do distrito de Bragança. Analisadas as formas de interacção referidas e os resultados dos testes coloca-se o desafio de averiguar de que modo, cada uma delas pode contribuir para a construção do conhecimento matemático, nomeadamente no domínio da resolução de problemas

Complying with Data Handling Requirements in Cloud Storage Systems

In past years, cloud storage systems saw an enormous rise in usage. However, despite their popularity and importance as underlying infrastructure for more complex cloud services, today's cloud storage systems do not account for compliance with regulatory, organizational, or contractual data handling requirements by design. Since legislation increasingly responds to rising data protection and privacy concerns, complying with data handling requirements becomes a crucial property for cloud storage systems. We present PRADA, a practical approach to account for compliance with data handling requirements in key-value based cloud storage systems. To achieve this goal, PRADA introduces a transparent data handling layer, which empowers clients to request specific data handling requirements and enables operators of cloud storage systems to comply with them. We implement PRADA on top of the distributed database Cassandra and show in our evaluation that complying with data handling requirements in cloud storage systems is practical in real-world cloud deployments as used for microblogging, data sharing in the Internet of Things, and distributed email storage.Comment: 14 pages, 11 figures; revised manuscript, accepted for publication in IEEE Transactions on Cloud Computin

Формування конкурентних переваг підприємства в умовах зовнішньоекономічної діяльності

Abstract Background Whole genome sequencing has become fast, accurate, and cheap, paving the way towards the large-scale collection and processing of human genome data. Unfortunately, this dawning genome era does not only promise tremendous advances in biomedical research but also causes unprecedented privacy risks for the many. Handling storage and processing of large genome datasets through cloud services greatly aggravates these concerns. Current research efforts thus investigate the use of strong cryptographic methods and protocols to implement privacy-preserving genomic computations. Methods We propose Fhe-Bloom and Phe-Bloom, two efficient approaches for genetic disease testing using homomorphically encrypted Bloom filters. Both approaches allow the data owner to securely outsource storage and computation to an untrusted cloud. Fhe-Bloom is fully secure in the semi-honest model while Phe-Bloom slightly relaxes security guarantees in a trade-off for highly improved performance. Results We implement and evaluate both approaches on a large dataset of up to 50 patient genomes each with up to 1000000 variations (single nucleotide polymorphisms). For both implementations, overheads scale linearly in the number of patients and variations, while Phe-Bloom is faster by at least three orders of magnitude. For example, testing disease susceptibility of 50 patients with 100000 variations requires only a total of 308.31 s (σ=8.73 s) with our first approach and a mere 0.07 s (σ=0.00 s) with the second. We additionally discuss security guarantees of both approaches and their limitations as well as possible extensions towards more complex query types, e.g., fuzzy or range queries. Conclusions Both approaches handle practical problem sizes efficiently and are easily parallelized to scale with the elastic resources available in the cloud. The fully homomorphic scheme, Fhe-Bloom, realizes a comprehensive outsourcing to the cloud, while the partially homomorphic scheme, Phe-Bloom, trades a slight relaxation of security guarantees against performance improvements by at least three orders of magnitude

BLOOM: BLoom filter based oblivious outsourced matchings

Whole genome sequencing has become fast, accurate, and cheap, paving the way towards the large-scale collection and processing of human genome data. Unfortunately, this dawning genome era does not only promise tremendous advances in biomedical research but also causes unprecedented privacy risks for the many. Handling storage and processing of large genome datasets through cloud services greatly aggravates these concerns. Current research efforts thus investigate the use of strong cryptographic methods and protocols to implement privacy-preserving genomic computations