Failure Filtrations for Fenced Sensor Networks

In this paper we consider the question of sensor network coverage for a 2-dimensional domain. We seek to compute the probability that a set of sensors fails to cover given only non-metric, local (who is talking to whom) information and a probability distribution of failure of each node. This builds on the work of de Silva and Ghrist who analyzed this problem in the deterministic situation. We first show that a it is part of a slightly larger class of problems which is #P-complete, and thus fast algorithms likely do not exist unless P$=$NP. We then give a deterministic algorithm which is feasible in the case of a small set of sensors, and give a dynamic algorithm for an arbitrary set of sensors failing over time which utilizes a new criterion for coverage based on the one proposed by de Silva and Ghrist. These algorithms build on the theory of topological persistence

TOPOLOGICAL STRUCTURE OF SPATIALLY-DISTRIBUTED NETWORK CODED INFORMATION

In this paper we generalize work using topological methods for testing wireless/sensor network coverage to the problem of covering a geographically-distributed wireless network with linear network coded data. We define the coverage complex, a new type of simplicial complex built on the nodes of the network which captures properties of the data coverage, and use tools from algebraic topology, persistent homology, and matroid theory to study it. The coverage complex shares properties with the Rips complex, however it also suffers from a more diverse variety of potential failures. We extend the standard coverage criteria to account for some of these situations using persistent homology, multi-sheeted localized covers of the space, and Mayer-Vietoris sequences. We also investigate the combinatorial properties of the coverage complex, determining the correspondence between it and the lattice of linear subspaces of a vector space. Finally we present algorithms for computing coverage complexes, present a software package designed to compute and experiment with coverage complexes, and provide a summary of ongoing and future work

Topological data analysis of zebrafish patterns

Self-organized pattern behavior is ubiquitous throughout nature, from fish schooling to collective cell dynamics during organism development. Qualitatively these patterns display impressive consistency, yet variability inevitably exists within pattern-forming systems on both microscopic and macroscopic scales. Quantifying variability and measuring pattern features can inform the underlying agent interactions and allow for predictive analyses. Nevertheless, current methods for analyzing patterns that arise from collective behavior only capture macroscopic features, or rely on either manual inspection or smoothing algorithms that lose the underlying agent-based nature of the data. Here we introduce methods based on topological data analysis and interpretable machine learning for quantifying both agent-level features and global pattern attributes on a large scale. Because the zebrafish is a model organism for skin pattern formation, we focus specifically on analyzing its skin patterns as a means of illustrating our approach. Using a recent agent-based model, we simulate thousands of wild-type and mutant zebrafish patterns and apply our methodology to better understand pattern variability in zebrafish. Our methodology is able to quantify the differential impact of stochasticity in cell interactions on wild-type and mutant patterns, and we use our methods to predict stripe and spot statistics as a function of varying cellular communication. Our work provides a new approach to automatically quantifying biological patterns and analyzing agent-based dynamics so that we can now answer critical questions in pattern formation at a much larger scale

Comparative diagnosis of irrigation performance and productivity along the Senegal Valley in Mauritania.Opportunities for improvement

In the last fifty years, concerted efforts have been spent on improving irrigation technology and management, both in academic and professional circles. Despite all this, irrigation has failed to keep up with projected results. Understanding of causes and processes behind this poor performance is needed, especially in regions like the Sahel, where irrigation could play a fundamental role for food security and livelihoods. This research deepens into the causes of low productivity and abandonment of rice-based irrigated agriculture in the Senegal River valley in Mauritania. Performance assessment and benchmarking are means by which it is possible to analyse and compare water management practices within and across irrigation schemes while identifying measures to improve irrigation delivery service and resources use. Four were the specific objectives of this study. First, to evaluate the performance and variability in productivity and input use of a number of small- and large-scale irrigation schemes. Second, to study patterns of spatial variability of land productivity and water use in large irrigation schemes. Third, to establish benchmarks for productivity and performance that shall serve as reference for the improvement of irrigation schemes. Fourth, to draft concrete and fundamental propositions on what irrigation models are most appropriate for the conditions in Mauritania and how to steer future policy actions consequently. Rapid appraisal process (RAP) and benchmarking techniques allowed systematic compilation of technical, organisational, institutional, and financial information. Data collected during repetitious field visits, semi-structured interviews, and direct measurements constituted the basis for the calculation of external and internal irrigation performance indicators used in the comparative analysis of the irrigation schemes. The indicators used were: irrigation intensity, water delivery capacity, relative irrigation supply, land productivity, water productivity, energy productivity, equity, reliability, flexibility, adequacy, and efficiency. Rice production was measured in a representative sample of plots in each studied irrigation scheme. Water use was quantified based on flow rate measurements and records of pumping time. Benchmarking was based on hierarchical cluster (HCA) and data envelopment (DEA) analyses that allowed, respectively, grouping and ranking of irrigation schemes according to a set of indicators previously obtained from the performance assessment. Benchmarking of small and large schemes showed that land productivity and technical efficiency were highly variable in irrigation schemes along the Senegal valley in Mauritania; however, both DEA and HCA showed that there were some productive and efficient schemes. DEA also identified the particular efficient schemes that should be taken as reference for improvement of each inefficient scheme. Performance assessment indicated that the state of the infrastructure and irrigation management are key factors in determining the variability of productivity and efficiency. Drainage turned out to have a greater influence than irrigation in determining intra-scheme spatial variability of yield and irrigation intensity in large schemes. Comparison of small- and large-scale irrigation schemes showed that, on a pure technical basis, large schemes did not perform worse than small schemes. However, small schemes showed greater variability, which may indicate a larger margin for improvement and also existence of successful schemes. The analysis of strengths and weaknesses of alternative irrigation models in Mauritania and their future perspectives for food security indicated that both large- and small-scale rice schemes are caught in a process known as “rehabilitation followed by deterioration trap” which must be reversed through the development of management capacity and physical upgrading of the irrigation infrastructure. Complete transfer of large schemes can only be pursued after extensive training, physical upgrading, and improved yields. The contribution of horticulture-based irrigation models to food security, poverty alleviation, and gender-equitable wealth creation lies in the development of a supportive environment of institutions and services for the autonomous replication of these systems. More research on the potential of private irrigation and agribusinesses, and related threats, is needed. Finally, sound policy planning and implementation requires updated national statistics that today are not available.En los últimos cincuenta años, tanto en el ámbito científico como en el profesional se han producido muchos esfuerzos para mejorar la tecnología y la gestión del riego. Sin embargo, al menos en los países en desarrollo, los resultados están todavía muy por debajo de las expectativas, a pesar de que el regadío constituye un suporte importante de la seguridad alimentaria y el sustentamiento de las poblaciones locales. En este contexto se coloca esta investigación, que pretende profundizar en las causas de la baja productividad y del abandono del regadío orientado a la producción de arroz en el valle del Río Senegal en Mauritania. La evaluación del funcionamiento de perímetros de riego y la identificación de los que pueden servir de referencia son medios para el análisis y la mejora de la calidad del servicio de riego y la eficiencia del uso de los recursos. Cuatro son los objetivos concretos de esta tesis. Primero, evaluar el funcionamiento de un conjunto de perímetros de riego grandes y pequeños, así como analizar las causas de la variabilidad de su productividad y la eficiencia. Segundo, estudiar los patrones de variabilidad espacial de la productividad y el uso del agua de los grandes perímetros de riego. Tercero, establecer fronteras (“benchmarks”) de productividad y eficiencia que sirvan de referencia para la mejora de los perímetros de riego. Cuarto, proponer recomendaciones fundamentales y concretas sobre qué modelos de riego se adaptan a las condiciones de la región y, sobre ello, plantear políticas y actuaciones futuras. Las metodologías "rapid appraisal process" (RAP) y "benchmarking" han permitido obtener y analizar sistemáticamente información sobre aspectos socio-económicos, institucionales, de infraestructura y de gestión del riego. La información recompilada en visitas periódicas, entrevistas semi-estructuradas y medidas directas ha servido para calcular los siguientes indicadores del funcionamiento interno y externo de los perímetros: intensidad del riego, capacidad de suministro de agua, suministro relativo de riego, productividad de la tierra, productividad del agua, productividad de la energía, equidad, flexibilidad, adecuación y eficiencia. El rendimiento del arroz se midió en una muestra de parcelas en cada perímetro. El volumen de agua utilizada se determinó a partir de medidas del caudal de bombeo y del registro del tiempo de bombeo en cada perímetro. El "benchmarking" se basó en análisis de conglomerados (AC) y análisis envolvente de datos ("data envelopment analysis", DEA), que permitieron agrupar y ordenar los perímetros según un conjunto de indicadores previamente obtenidos con la metodología RAP. Los resultados de la evaluación mostraron gran variabilidad entre los perímetros de riego con respeto a la productividad y la eficiencia del uso de los recursos. Sin embargo, tanto AC como DEA indicaron que hay perímetros que destacan por su productividad y eficiencia. DEA sirvió además para identificar los perímetros más eficientes que pueden servir de referencia para cada uno de los perímetros menos eficientes. El diagnóstico comparativo mostró que la gran variabilidad encontrada es debida en mucha parte a la infraestructura y a la gestión del riego y del drenaje. En los grandes perímetros, el drenaje es un factor clave en la determinación de la variabilidad espacial de la productividad y la intensidad de riego. Contra lo comúnmente expresado, las grandes zonas regables no funcionaron peor que los pequeños perímetros. Grandes y pequeños perímetros colectivos de arroz están atrapados en un círculo vicioso de degradación-rehabilitación que hay que romper con mejoras tecnológicas, institucionales y de las infraestructuras. La transferencia de los grandes perímetros a las comunidades de regantes solo será posible una vez que se haya invertido en formación y capacitación y después de mejoras infraestructurales. Otros modelos de riego como los basados en la producción hortícola son importantes para alcanzar la seguridad alimentaria. Sin embargo, para que sean replicables autónomamente, tienen que ser acompañados del desarrollo de infraestructuras, mercados y servicios apropiados. Los perímetros privados y las grandes inversiones con capital extranjero requieren un estudio más profundo de su potencial y riesgos asociados. Por último, las políticas de riego y su actuación práctica requieren estadísticas robustas y actualizadas que por el momento faltan en Mauritania

Dynamical and topological tools for (modern) music analysis

Is it possible to represent the horizontal motions of the melodic strands of a contrapuntal composition, or the main ideas of a jazz standard as mathematical entities? In this work, we suggest a collection of novel models for the representation of music that are endowed with two main features. First, they originate from a topological and geometrical inspiration; second, their low dimensionality allows to build simple and informative visualisations. Here, we tackle the problem of music representation following three non-orthogonal directions. We suggest a formalisation of the concept of voice leading (the assignment of an instrument to each voice in a sequence of chords) suggesting a horizontal viewpoint on music, constituted by the simultaneous motions of superposed melodies. This formalisation naturally leads to the interpretation of counterpoint as a multivariate time series of partial permutation matrices, whose observations are characterised by a degree of complexity. After providing both a static and a dynamic representation of counterpoint, voice leadings are reinterpreted as a special class of partial singular braids (paths in the Euclidean space), and their main features are visualised as geometric configurations of collections of 3-dimensional strands. Thereafter, we neglect this time-related information, in order to reduce the problem to the study of vertical musical entities. The model we propose is derived from a topological interpretation of the Tonnetz (a graph commonly used in computational musicology) and the deformation of its vertices induced by a harmonic and a consonance-oriented function, respectively. The 3-dimensional shapes derived from these deformations are classified using the formalism of persistent homology. This powerful topological technique allows to compute a fingerprint of a shape, that reflects its persistent geometrical and topological properties. Furthermore, it is possible to compute a distance between these fingerprints and hence study their hierarchical organisation. This particular feature allows us to tackle the problem of automatic classification of music in an innovative way. Thus, this novel representation of music is evaluated on a collection of heterogenous musical datasets. Finally, a combination of the two aforementioned approaches is proposed. A model at the crossroad between the signal and symbolic analysis of music uses multiple sequences alignment to provide an encompassing, novel viewpoint on the musical inspiration transfer among compositions belonging to different artists, genres and time. To conclude, we shall represent music as a time series of topological fingerprints, whose metric nature allows to compare pairs of time-varying shapes in both topological and in musical terms. In particular the dissimilarity scores computed by aligning such sequences shall be applied both to the analysis and classification of music

Nevada test site annual site environmental report for calendar year 1995

Monitoring and surveillance on and around the Nevada Test Site (NTS) by US Department of Energy (DOE) contractors and NTS user organizations during 1995 indicated that operations on the NTS were conducted in compliance with applicable federal and DOE regulations and guidelines. All discharges of radioactive liquids remained onsite in containment ponds, and there was no indication of potential migration of radioactivity to the offsite area through groundwater. Surveillance around the NTS indicated that airborne radioactivity from diffusion, evaporation of effluents, or resuspension was not detectable offsite, and no measurable net exposure to members of the offsite population was detected through the offsite dosimetry program. There were no nonradiological releases to the offsite area. Hazardous wastes were shipped offsite to approved disposal facilities. Compliance with the various regulations stemming from the National Environmental Policy Act (NEPA) is being achieved and, where mandated, permits for air and water effluents and waste management have been obtained from the appropriate agencies. Cooperation with other agencies has resulted in seven different consent orders and agreements. Support facilities at off-NTS locations complied with the requirements of air quality permits and state or local wastewater discharge and hazardous waste permits

Seven Years of Membranes: Feature Paper 2017

For the last seven years, Membranes has provided an outstanding platform for the publication of articles at the forefront of research in the areas of membrane fabrication, characterization and application. This Special Issue, entitled “Seven Years of Membranes: Feature Paper 2017,” celebrates this achievement. The articles included in this Special Issue, written by prominent researchers in the field, provide an authoritative and up-to-date account of the advances in membrane science and technology. They describe new methods for the fabrication of organic, inorganic and mixed matrix membranes and their utilization in improving the efficiency of membrane-based separation processes, such as membrane distillation, nanofiltration, ultrafiltration, reverse osmosis, and gas permeation. A number of articles are focused on water treatment, which, because of its significance to sustainable development, is one of the main areas of membrane research and application. These articles report novel techniques for the clean-up of contaminated waters, and the desalination of industrial effluents, brackish water and seawater