MoDALAS: addressing assurance for learning-enabled autonomous systems in the face of uncertainty

Software and Systems Modeling - Increasingly, safety-critical systems include artificial intelligence and machine learning components (i.e., learning-enabled components (LECs)). However, when...     

Collapse of clamped and simply supported composite sandwich beams in three-point bending

Composite sandwich beams, comprising glass–vinylester face sheets and a PVC foam core, have been manufactured and tested quasi-statically. Clamped and simply supported beams were tested in three-point bending in order to investigate the initial collapse modes, the mechanisms that govern the post-yield deformation and parameters that set the ultimate strength of these beams. Initial collapse is by three competing mechanisms: face microbuckling, core shear and indentation. Simple formulae for the initial collapse loads of clamped and simply supported beams along with analytical expressions for the finite deflection behaviour of clamped beams are presented. The simply supported beams display a softening post-yield response, while the clamped beams exhibit hardening behaviour due to membrane stretching of the face sheets. Good agreement is found between the measured, analytical and finite element predictions of the load versus deflection response of the simply supported and clamped beams. Collapse mechanism maps with contours of initial collapse load and energy absorption are plotted. These maps are used to determine the minimum mass designs of sandwich beams comprising woven glass face sheets and a PVC foam core.     

Managing Federations and Cooperative Management: A Report on ManFed.Com 2011

The first IFIP/IEEE international workshop on Managing Federations and Cooperative Management (ManFed.CoM) took place in conjunction with the IFIP/IEEE International Symposium on Integrated Network Management (IM 2011) conference in Trinity College Dublin, Ireland on May 23rd 2011. The multi-mode, loosely coupled, user-centric nature of modern communications and services, coupled with the diversity of operator business models, ensure that modern end-to-end service provision frequently crosses heterogeneous management and administrative domains. Thus, management approaches that can be applied across organizational boundaries are increasingly important in a wide range of application areas. There are a number of significant, common, complex issues which must be addressed in all technologies and applications that involve federated organizations, yet research has heretofore been mostly confined to particular technical or application areas. The first installment of ManFed.Com addressed this gap by bringing together researchers from a broad array of application and technical areas who shared an interest in cross-domain management. The workshop drew out common themes, problems and issues encountered, and the solutions being designed to deal with the problems of managing information systems that span autonomous domains. More than 30 researchers participated in a lively and interactive day of paper presentation, panels and software demonstrations. The success of the inaugural event was such that the organizing committee is now committed to running further installations—we are in the process of preparing a submission to run a the 2nd ManFed.CoM in conjunction with the IEEE/IFIP Network Operations and Management Symposium (NOMS) 2012 conference. We believe that these workshops will help to provide the basis for a common understanding and common approaches to inter-domain management and governance that synthesizes the insights and best-of-breed solutions being developed in the diverse areas in which these problems are encountered. The technical program of ManFed.CoM 2011 was organized as a single track and was composed of two panels of invited experts, two full paper sessions, one short paper session and a demonstration session in which practical software tools were presented. Of the 16 papers submitted, 6 were selected for presentation as full papers, with a further 3 being presented in condensed form as short papers. All the papers submitted underwent a rigorous review process, receiving between 2 and 5 reviews each, with the accepted full papers receiving a minimum score of 7.5 out of 10 from reviewers. The papers presented constituted a good cross-section of current cross-domain management research work—they covered modeling, semantic interoperability, trust management and security, policy based management, business process orchestration, collaboration and delegation and look at management on a number of different layers—from low level network management, all the way up to high level business-driven management.     

Cyclic deformation behaviour of TiAl6V4 and TiAl6Nb7 in different quasi‐physiological media

In the present investigation the cyclic deformation behaviour of TiAl6V4 and TiAl6Nb7 was characterized in constant‐amplitude and load increase tests in laboratory air and quasi‐physiological media by cycle dependent mechanical hysteresis, temperature and/or corrosion potential measurements. Microstructural changes were evaluated by scanning electron microscopy for defined fatigue states and after specimen failure. In constant‐amplitude tests, the alloys show pronounced cyclic softening and/or hardening. In load increase tests with strain and temperature measurements, estimation values for the endurance limit were determined which were lower than the fatigue limits determined in conventional Woehler tests to a maximum cycle number of 2 × 10⁶. For loading in quasi‐physiological media, the corrosion potential reliably indicates microstructural damage on the specimen surface.     

Characterization of mechanically induced surface damage on the implant alloy TiAl6Nb7 in quasi‐physiological media

To characterize mechanically induced surface damage scratch and rotating bending tests were performed on the implant alloy TiAl6Nb7 with different surface conditions (polished, thermally oxidized, anodically oxidized) in Hank's solution and in newborn calf serum at 37°C. The surface processes taking place during repassivation or due to the fatigue loading were identified by measuring the free corrosion current and potential. Light and scanning electron microscopic investigations were used to correlate surface changes with the results of the electrochemical measurements.     

Creep Response of Sandwich Beams with a Metallic Foam Core

The creep response of metallic foam sandwich beams in 3‐point bend is investigated numerically for the case of a metallic foam core and two steel faces. The face sheets are treated as elastic, while the foam core is modeled by a viscoplastic extension of the Deshpande‐Fleck yield surface. This power‐law creeping constitutive law has been implemented within the commercial finite element code ABAQUS. It is found that the beams creep by a variety of competing mechanisms, depending upon the choice of material properties and the geometric parameters. A failure map is constructed and effect of rate dependence on the load‐deflection curves is quantified, and compared against the available experimental data.     

Design guidelines for granular particles in a conical centrifugal filter

Essential design criteria for successful drying of granular particles in a conical continuous centrifugal filter are developed in a dimensionless fashion. Four criteria are considered: minimum flow thickness (to ensure sliding bulk flow rather than particulate flow), desaturation position, output dryness and basket failure. The criteria are based on idealised physical models of the machine operation and are written explicitly as functions of the basket size l_out, spin velocity Ω and input flow rate of powder Q_p. The separation of sucrose crystals from liquid molasses is taken as a case study and the successful regime of potential operating points (l_out, Ω) is plotted for a wide range of selected values of flow rate Q_p. Analytical expressions are given for minimum and maximum values of the three independent parameters (l_out, Ω, Q_p) as a function of the slurry and basket properties. The viable operating regime for a conical centrifugal filter is thereby obtained as a function of the slurry and basket properties.     

Development of an enzyme-linked immunosorbent assay for human metallothionein-1 in plasma and urine

The development of a sensitive enzyme-linked immunosorbent assay (ELISA) for human metallothionein-1 is reported. Metallothionein was purified from postmortem human liver and used to raise high-titer antibodies in rabbits. The assay was specific for human metallothionein-1 (MT-1), and there was no significant cross-reaction with human metallothionein-2. The detection limit (sensitivity) of the assay was 5 ng/ml, and the added MT-1 could be fully recovered from plasma and urine. The normal reference range for MT-1 was 32 +/- 16 ng/ml in plasma and 10 +/- 6 ng MT-1 per micromole of creatinine in random samples of urine. No significant differences were found between the values for males and females. The concentration of MT-1 was greatly increased between 24 and 48 hours after surgery, indicating that the protein behaves like an acute phase reactant in human subjects.