Lukas Rosenthaler

GEOSSAV: a simulation tool for subsurface applications ☆

Geostatistical Environment fOr Subsurface Simulation And Visualization (GEOSSAV) is a tool for the integration of hard and soft data into stochastic simulation and visualization of distributions of geological structures and hydrogeological properties in the subsurface. GEOSSAV, as an interface to selected geostatistical modules (bicalib, gamv, vargplt, and sisim) from the Geostatistical Software LIBrary, GSLIB (GSLIB: Geostatistical Software Library and Users Guide, 2nd Edition, Oxford University Press, Oxford, 1998, 369pp), can be used for data analysis, variogram computation of regularly or irregularly spaced data, and sequential indicator simulation of subsurface heterogeneities. Sequential indicator simulation, based on various kriging techniques (simple, ordinary, and Bayesian), is suitable for the simulation of continuous variables such as hydraulic conductivity of an aquifer or chemical concentrations at a contaminated site, and categorical variables which indicate the presence or absence of a particular lithofacies. The software integration platform and development environment of GEOSSAV is Tool command language (Tcl) with its graphical user interface, Toolkit (Tk), and a number of Tcl/Tk extensions. The standard Open Graphics Library application programming interface is used for rendering three-dimensional (3D) data distributions and for slicing perpendicular to the main coordinate axis. Export options for finite-difference groundwater models allow either files that characterize single model layers (which are saved in ASCII matrix format) or files that characterize the complete 3D flow model setup for MODFLOW-based groundwater simulation systems (which are saved in block-centered flow package files (Users documentation for MODFLOW-96, an update to the US Geological Survey modular finite-difference ground-water flow model, Geological Survey Open-File Report 96-485, Reston, VA, 1996, 56pp)). GEOSSAV can be used whenever stochastic solutions are preferred to solve site-specific heterogeneity problems, e.g., in the field of hydrology, groundwater, groundwater and/or soil contamination, site remediation, air pollution, and ecology. An example from the Rhine/Wiese aquifer near Basel demonstrates the application of GEOSSAV on geostatistical data analysis and subsurface visualization. GEOSSAV has been successfully tested on Microsoft Windows NT 4.0/2000/XP and on SuSE Linux 7.3. The current version is available at http://www.unibas.ch/ earth/pract.

The DISTARNET approach to reliable autonomic long-term digital preservation

The rapidly growing production of digital data, together with their increasing importance and essential demands for their longevity, urgently require systems that provide reliable long-term preservation of digital objects. Most importantly, these systems have to ensure guaranteed availability over a long period of time, as well as integrity and authenticity of the preserved data and their metadata. This means that all kinds of technical problems need to be reliably handled and that the evolution of data formats is supported. At the same time, systems need to scale with the volume of data to be archived. In this paper, we present DISTARNET, a fully distributed system that reliably executes pre-defined workflows for long-term preservation. Moreover, DISTARNET is designed as an open system that allows the curators of digital objects to specify new processes to cope with additional challenges.

A distributed archival network for process-oriented autonomic long-term digital preservation

The reliable and consistent long-term preservation of digital content and metadata is becoming increasingly important -- even though the storage media used are potentially subject to failures, or the data formats may become obsolete over time. A common approach is to replicate data across several sites to increase their availability. Nevertheless, network, software, or hardware failures as well as the evolution of data formats have to be coped with in a timely and, ideally, an autonomous way, without intervention of an administrator. In this paper we present DISTARNET, a distributed, autonomous long-term digital preservation system. Essentially, DISTARNET exploits dedicated processes to ensure the integrity and consistency of data with a given replication degree. At the data level, DISTARNET supports complex data objects, the management of collections, annotations, and arbitrary links between digital objects. At process level, dynamic replication management, consistency checking, and automated recovery of the archived digital objects is provided utilizing autonomic behavior governed by preservation policies without any centralized component. We present the concepts and implementation of the distributed DISTARNET preservation approach. Most importantly, we provide details of the qualitative and quantitative evaluation of the DISTARNET system. The former addresses the effectiveness of the internal preservation processes while the latter evaluates DISTARNETs performance regarding the overall archiving storage capacity and scalability.

Electronic imaging: a tool for the reconstruction of faded color photographs and color movies

A method to restore faded color materials by digital image processing is presented. The algorithms used for the reconstruction are based on photographic experiments, i.e., on accelerated fading tests of various photographic materials. The densities of the original and the faded materials were measured. Based on this data, a mathematical model for fading can be described by a linear equation. The faded image is digitized using a scanner of high spatial and photometric resolution. For good spectral resolution, channel separations are done with narrow- band interference filters. The original colors are reconstructed by applying the inverse of the facing equation. The corrected image is exposed with a high-resolution film recorder on color film. The method shows good results for color slides, prints, and 16 mm movies.

PEVIAR: Digital originals

Even decades after the advent of computer technology, preserving information in digital archives remains a challenging task. Technological progress on all levels calls for migration as an essential component of any digital archive. Migration, however, is not only expensive, but also makes it difficult to ensure the authenticity of digital documents. The University of Basels Imaging and Media Lab has developed PEVIAR (Permanent Visual Archive), an archiving solution addressing one of the fundamental challenges of digital archiving, migration, and introducing the notion of digital originals. Essentially, digital documents are inseparably bound to a migration-free medium, thereby overcoming the transient nature of todays state-of-the-art storage systems.

DASCH: Data and Service Center for the Humanities

Research data in the humanities needs to be sustainable, and access to digital resources must be possible over a long period. Only if these prerequisites are fulfilled can research data be used as a source for other projects. In addition, reliability is a fundamental requirement so that digital sources can be cited, reused, and quoted. To address this problem, we present our solution: the Data and Service Center for the Humanities located in Switzerland. The centralized infrastructure is based on flexible and extendable software that is in turn reliant on modern technologies. Such an approach allows for the straightforward migration of existing research project databases with limited life spans in the humanities. We will demonstrate the basic concepts behind this proposed solution and our first experiences in the application thereof.

A Benchmark for RDF-based Metadata Management in Distributed Long-Term Digital Preservation

In a large variety of applications, the long-term, guaranteed availability of data is becoming increasingly important. Thus, long-term digital preservation systems have to be inherently distributed to allow content to be replicated. This affects both the preservation of the actual digital objects and their associated metadata. For the latter, RDF has become the prevalent data model. Ensuring data integrity and consistency requires periodic checks to timely detect inconsistencies, for instance due to (partial) hardware failures, and trigger repair actions. Hence, the access characteristics to metadata in longterm digital preservation significantly differs from metadata management in other types of applications. In addition, the increasing size of digital archives challenges the consistency checks of the associated metadata. In this paper, we introduce a novel benchmark for triple store-based metadata management that jointly takes into account the specific access patterns of long-term preservation systems: i.) complex periodic consistency checks, ii.) concurrent read and write requests to the archive, and iii.) the actions to be taken on data to re-establish consistency if a violation has been detected. Furthermore, we present the results of this benchmark applied to our distributed long-term digital preservation system DISTARNET.

Digital slide reproduction using densitometry

Many contemporary art collections contain important art installations where artists have used 35 mm slides as the primary medium. The number of ours these works are on show makes it necessary to regularly change the slides due to light fading. With funding from the Henry Moore Foundation. The conservation department at Tate initiated a project to examine ways in which digital technology could be used to aid the conservation of these works. The aim of the project was to place the original slides in cold storage and explored the possibility of using digital technology to make duplicate sets for display in the gallery. The reproductions needed to be of very high quality both in terms of resolution and color management. This paper discusses the use of densitometry to calibrate both device dependent and device independent systems for digitally reproducing 35 mm slides using a scanner and a film recorder and the effect of metamery when using slide films which employ different dyes.

New scanning approach for motion picture digitizing

For digital restoration of motion picture films the correct scanning (actually measuring physical properties i.e. optical densities) is vital. Therefore thus, the delicate handling of aged films and the prohibitive high prices of commercially available scanners forced the development of a simple yet good quality film scanning device. The scanning principle and the increasing aspects specific to digital restoration will be discussed.