Digital repository: preservation environment and policy implementation

Distributed digital repositories can be used to address critical issues of long-term digital preservation and disaster management for large data centers. A policy-driven system provides an ideal solution for managing distributed repositories that require high flexibility and high configurability. Recent studies demonstrate that the integrated Rule-Oriented Data System, a peer-to-peer server middleware, provides the requisite dynamic extensibility needed to manage time-varying policies, automate validation of assessment criteria, manage ingestion processes, manage access policies, and manage preservation policies. The policy management can be implemented underneath existing digital library infrastructure such as Fedora.     

Open Embedded Control

Embedded control devices today usually allow parameter changes, and possibly activation of different pre-implemented algorithms. Full reprogramming using the complete source code is not allowed for safety, efficiency, and proprietary reasons. For these reasons, embedded regulators are quite rigid and closed concerning the control structure. In several applications, like industrial robots, there is a need to tailor the low level control to meet specific application demands. In order to meet the efficiency and safety demands, a way of building more generic and open regulators has been developed. The key idea is to use pieces of compiled executable code as functional operators, which in the simplest case may appear as ordinary control parameters. In an object oriented framework, this means that new methods can be added to controller objects after implementation of the basic control, even at run-time. The implementation was carried out in industrially well accepted languages such as C and C++. The dynamic binding at run-time differs from ordinary dynamic linking in that only a subset of the symbols can be used. This subset is defined by the fixed part of the system. The safety demands can therefore still be fulfilled. Encouraged by results from fully implemented test cases, we believe that extensive use of this concept will admit more open, still efficient, embedded systems.     

Management of hyperparathyroidism in an endemic goiter area

In an endemic goiter area patients with hyperparathyroidism (HPTH) frequently also have thyroid abnormalities. In a retrospective study of 95 patients with HPTH we assessed the diagnostic accuracy of imaging techniques (ultrasonography or radionuclide scanning) for preoperative localization of parathyroid adenomas. Altogether 86% of our patients had goiter, requiring thyroid resections in 37%. For 19 patients the parathyroid exploration was the second or third cervical operation, most of them due to goiter. We found that the overall rate of transient and permanent recurrent nerve paralysis is considerably increased in patients with previous neck surgery (26% vs. 7%). The combination of ultrasonography and radionuclide scanning can lead surgeons to the site of parathyroid lesions responsible for HPTH in 85% of cases, although frequent nodular goiters can produce pitfalls for correct imaging in iodine-deficient countries. In endemic goiter areas preoperative localization studies can be recommended in patients with primary HPTH--for evaluation of thyroid pathology possibly leading to resection or its accuracy in localizing parathyroid adenomas. These studies also seem justified in patients with previously unsuccessful neck explorations for HPTH.     

Design of an Electronically Beam Scanning Reflectarray Using Aperture-Coupled Elements

The design of a C-band electronically beam scanning reflectarray is presented. The reconfigurable reflectarray element consists of a microstrip patch, printed on a flexible membrane substrate, aperture-coupled to a transmission line loaded with two varactor diodes. The designed element allows continuous tuning of the reflected signal's phase over a 360deg range with a maximum loss of 2.4 dB at 5.4 GHz. The measured results on a 30-element reflectarray breadboard show that by varying the bias voltages on each element the main beam can be steered to large angles, up to 40deg from broadside in the H-plane. A loss analysis of the proposed reflectarray is also presented     

Discrimination of vegetation types in alpine sites with ALOS PALSAR-, RADARSAT-2-, and lidar-derived information

Natural vegetation monitoring in the alpine mountain range is a priority in the European Union in view of climate change effects. Many potential monitoring tools, based on advanced remote sensing sensors, are still not fully integrated in operational activities, such as those exploiting very high-resolution synthetic aperture radar (SAR) or light detection and ranging (lidar) data. Their testing is important for possible incorporation in routine monitoring and to increase the quantity and quality of environmental information. In this study the potential of ALOS PALSAR and RADARSAT-2 SAR scenes' synergic use for discrimination of different vegetation types was tested in an alpine heterogeneous and fragmented landscape. The integration of a lidar-based canopy height model (CHM) with SAR data was also tested. A SPOT image was used as a benchmark to evaluate the results obtained with different input data. Discrimination of vegetation types was performed with maximum likelihood classification and neural networks. Six tested data combinations obtained more than 85% overall accuracy, and the most complex input which integrates the two SARs with lidar CHM outperformed the result based on SPOT. Neural network algorithms provided the best results. This study highlights the advantages of integrating SAR sensors with lidar CHM for vegetation monitoring in a changing environment.     

Predictive hydrogeochemical modelling of bauxite residue sand in field conditions

The suitability of residue sand (the coarse fraction remaining from Bayer's process of bauxite refining) for constructing the surface cover of closed bauxite residue storage areas was investigated. Specifically, its properties as a medium for plant growth are of interest to ensure residue sand can support a sustainable ecosystem following site closure. The geochemical evolution of the residue sand under field conditions, its plant nutrient status and soil moisture retention were studied by integrated modelling of geochemical and hydrological processes. For the parameterization of mineral reactions, amounts and reaction kinetics of the mineral phases natron, calcite, tricalcium aluminate, sodalite, muscovite and analcime were derived from measured acid neutralization curves. The effective exchange capacity for ion adsorption was measured using three independent exchange methods. The geochemical model, which accounts for mineral reactions, cation exchange and activity corrected solution speciation, was formulated in the geochemical modelling framework PHREEQC, and partially validated in a saturated-flow column experiment. For the integration of variably saturated flow with multi-component solute transport in heterogeneous 2D domains, a coupling of PHREEQC with the multi-purpose finite-element solver COMSOL was established. The integrated hydrogeochemical model was applied to predict water availability and quality in a vertical flow lysimeter and a cover design for a storage facility using measured time series of rainfall and evaporation from southwest Western Australia. In both scenarios the sand was fertigated and gypsum-amended. Results show poor long-term retention of fertilizer ions and buffering of the pH around 10 for more than 5 y of leaching. It was concluded that fertigation, gypsum amendment and rainfall leaching alone were insufficient to render the geochemical conditions of residue sand suitable for optimal plant growth within the given timeframe. The surface cover simulation demonstrates that the soil moisture status in the residue sand can be ameliorated by an appropriate design of the cover layer with respect to thickness, slope and distance between lateral drains.     

Oxygen-induced Restructuring of a Pd/Fe3O4 Model Catalyst

We have studied the influence of oxygen on the structure and morphology of a Pd/Fe₃O₄ model catalyst using molecular beam (MB) methods, IR reflection absorption spectroscopy (IRAS) and scanning tunneling microcopy (STM). The model catalyst was prepared under ultrahigh vacuum (UHV) conditions by physical vapor deposition (PVD) and growth of Pd nanoparticles on an ordered Fe₃O₄ thin film on Pt(111). It is found that surface oxides are formed on the Pd nanoparticles even under mild oxidation conditions (temperatures of 500 K and effective oxygen partial pressures of around 10⁻⁶ mbar). These surface oxides are initially generated at the Pd/Fe₃O₄ interface and, subsequently, are formed at the Pd/gas interface. The process of formation and reduction of surface and interface oxides on the Pd particles is fully reversible in that all oxides formed can be fully reduced. As a result, the oxide phase acts like a storage medium for oxygen during oxidation reactions, as probed via CO oxidation. The process of surface and interface oxidation is directly connected with the onset of a non-reversible sintering process of the Pd particles. It is suggested that this sintering process occurs via a mobile Pd oxide species, which is stabilized by interaction with the Fe₃O₄ support. The restructuring is monitored via STM and IRAS using CO as a probe molecule. In addition to a decrease in particle density and Pd surface area, a reshaping of the particles occurs, which is characterized by the formation of well-ordered crystallites and with a relatively large fraction of (100) facets. After a few oxidation/reduction cycles at 500 K, the sintering process becomes very slow and the system shows a stable behavior under conditions of CO oxidation.     

Study of a CPW inductively coupled slot antenna

Coplanar waveguide (CPW) fed slot antennas are attractive due to fabrication simplicity and ease of integration with active devices. A new concept for exciting slots with a CPW line based on inductive coupling is presented. It is described how this coupling structure can be designed to tune the impedance of the antenna over a wide range. Single elements and arrays designed for 5- and 25-GHz operation are described. Simulated and measured characteristics are presented. This new coupling topology is particularly suitable for series-fed array configurations and broad-band design