PF-OLA: A High-Performance Framework for Parallel On-Line Aggregation

Online aggregation provides estimates to the final result of a computation during the actual processing. The user can stop the computation as soon as the estimate is accurate enough, typically early in the execution. This allows for the interactive data exploration of the largest datasets. In this paper we introduce the first framework for parallel online aggregation in which the estimation virtually does not incur any overhead on top of the actual execution. We define a generic interface to express any estimation model that abstracts completely the execution details. We design a novel estimator specifically targeted at parallel online aggregation. When executed by the framework over a massive $8\text{TB}$ TPC-H instance, the estimator provides accurate confidence bounds early in the execution even when the cardinality of the final result is seven orders of magnitude smaller than the dataset size and without incurring overhead.Comment: 36 page

Impacts of anthropogenic and environmental factors on the occurrence of shallow landslides in an alpine catchment (Urseren Valley, Switzerland)

Changes in climate and land use pose a risk to stability of alpine soils, but the direction and magnitude of the impact is still discussed controversially with respect to the various alpine regions. In this study, we explicitly consider the influence of dynamic human-induced changes on the occurrence of landslides in addition to natural factors. Our hypothesis was that if changes in land use and climate have a significant influence on the occurrence of landslides we would see a trend in the incidence of landslides over time. We chose the Urseren Valley in the Central Swiss Alps as investigation site because the valley is dramatically affected by landslides and the land use history is well documented. Maps of several environmental factors were used to analyse the spatial landslide pattern. In order to explain the causation of the temporal variation, time-series (45 years) of precipitation characteristics, cattle stocking and pasture maps were compared to a series of seven landslide investigation maps between 1959 and 2004. We found that the area affected by landslides increased by 92% from 1959 to 2004. Even though catchment characteristics like geology and slope largely explain the spatial variation in landslide susceptibility (68%), this cannot explain the temporal trend in landslide activity. The increase in stocking numbers and the increased intensity of torrential rain events had most likely an influence on landslide incidence. In addition, our data and interviews with farmers pointed to the importance of management practice

Electrotactile vision substitution for 3D trajectory following

Navigation for blind persons represents a challenge for researchers in vision substitution. In this field, one of the used techniques to navigate is guidance. In this study, we develop a new approach for 3D trajectory following in which the requested task is to track a light path using computer input devices (keyboard and mouse) or a rigid body handled in front of a stereoscopic camera. The light path is visualized either on direct vision or by way of a electro-stimulation device, the Tongue Display Unit, a 12x12 matrix of electrodes. We improve our method by a series of experiments in which the effect of the modality of perception and that of the input device. Preliminary results indicated a close correlation between the stimulated and recorded trajectories

Development of a control system for teleoperated robots using UML nd Ada 95

In this paper, a control system in the domain of teleoperated service robots is presented. A reference architecture - ACROSET - has been analyzed and designed following a concurrent object modeling and architectural design methodology (COMET) that uses UML as describing language. The architecture of the whole system has been implemented in a ship’s hull blasting robot - GOYA –using Ada 95 and GLADE. Our previous experience in developing teleoperated service robots using Ada is also presente

Standardization and quality control in data collection and assessment of threatened plant species

Informative data collection is important in the identification and conservation of rare plant species. Data sets generated by many small-scale studies may be integrated into large, distributed databases, and statistical tools are being developed to extract meaningful information from such databases. A diversity of field methodologies may be employed across smaller studies, however, resulting in a lack of standardization and quality control, which makes integration more difficult. Here, we present a case study of the population-level monitoring of two threatened plant species with contrasting life history traits that require different field sampling methodologies: the limestone glade bladderpod, Physaria filiformis, and the western prairie fringed orchid, Plantanthera praeclara. Although different data collection methodologies are necessary for these species based on population sizes and plant morphology, the resulting data allow for similar inferences. Different sample designs may frequently be necessary for rare plant sampling, yet still provide comparable data. Various sources of uncertainty may be associated with data collection (e.g., random sampling error, methodological imprecision, observer error), and should always be quantified if possible and included in data sets, and described in metadata. Ancillary data (e.g., abundance of other plants, physical environment, weather/climate) may be valuable and the most relevant variables may be determined by natural history or empirical studies. Once data are collected, standard operating procedures should be established to prevent errors in data entry. Best practices for data archiving should be followed, and data should be made available for other scientists to use. Efforts to standardize data collection and control data quality, particularly in small-scale field studies, are imperative to future cross-study comparisons, meta-analyses, and systematic reviews

World Wide Web Application Layout Tool

The World Wide Web makes it possible for programs to be run on computers without needing to be installed or classically downloaded, but the interfaces remain bound by text-centric page layout languages. This project attempts to bring fully-featured GUI (Graphical User Interface) technology to the hands of Web developers by interpreting the output of Glade, a GUI design program, as HTML which can be published on the Web