Human display monitoring and failure detection: Control theoretic models and experiments

Two newly developed control theoretic models for human display monitoring and decision making are presented that use the information structure of the well-known optimal control model of human response. Experimental paradigms with six dominant task variables (i.e. number of displayed processes, bandwidths, event probabilities, field of view, process couplings, and failure couplings), deduced from vehicle and process control situations, are the basis for extensive validation studies including eye-movement recordings. The broad coverage of the paradigms and the high degree of data/model correspondence provide the predictive potential for the analysis, design, and evaluation of man-machine systems. The relation of these models to existing prediction schemes is outlined.     

Electrical conduction phenomena in thin tetracene films

Thin film aluminium oxide capacitors using anodic Al₂O₃ as the dielectric are described. The dependence of oxide thickness and dielectric loss on anodization voltage was studied. Variation of capacitance with temperature and frequency was also investigated. The capacitors were used in conjunction with tantalum resistors to fabricate an astable multivibrator circuit and the waveforms were recorded. The combination of aluminium oxide capacitors and tantalum resistors has some advantages over all-tantalum RC networks.     

Toughening of nanoporous glasses using porogen residuals

Nanoporous glasses are inherently brittle materials that become increasingly fragile with increasing porosity. We show that remarkable increases in fracture energy can be obtained from remnants of the porogen molecules used to create the nanoscale pores. The interfacial fracture energy of approximately 2.6 J m(-2) for dense methylsilsesquioxane glass films is shown to increase by over one order of magnitude to >30 J m(-2) for glasses containing 50 vol.% porosity. The increased fracture resistance is related to a powerful molecular-bridging mechanism that was modelled using bridging mechanics. The study demonstrates that significant increases in interfacial fracture energy may be obtained using strategies involving controlled decomposition of the porogen molecule during processing of nanoporous glasses. The implications are important for a range of emerging optical, electronic and biological technologies that use nanoporous thin films, but are limited by the degradation of mechanical properties with increasing porosity.     

Transfer of volatile substances from water to the atmosphere

Mass transfer coefficients and the degree of saturation of the exit gas are important parameters in transferring volatile organic substances from water to the atmosphere. Aeration systems in batch and continuous flow reactors are discussed based on theoretical analysis and experimental data. Three different ranges of the degree of saturation of the exit gas are introduced and their significance for model experiments and technical operations is evaluated. The effect of the aeration system and of surface active agents on the mass transfer coefficient of tetrachloroethylene is studied. Mass transfer coefficients for six nonpolar volatile organic compounds are presented. The stripping efficiencies of different types of gas-liquid contact devices used in water and waste water treatment are assessed.     

A new accurate and precise 3-D segmentation method for skeletal structures in volumetric CT data

We developed a highly automated three-dimensionally based method for the segmentation of bone in volumetric computed tomography (CT) datasets. The multistep approach starts with three-dimensional (3-D) region-growing using local adaptive thresholds followed by procedures to correct for remaining boundary discontinuities and a subsequent anatomically oriented boundary adjustment using local values of cortical bone density. We describe the details of our approach and show applications in the proximal femur, the knee, and the skull. The accuracy of the determination of geometrical parameters was analyzed using CT scans of the semi-anthropomorphic European spine phantom. Depending on the settings of the segmentation parameters cortical thickness could be determined with an accuracy corresponding to the side length of 1 to 2.5 voxels. The impact of noise on the segmentation was investigated by artificially adding noise to the CT data. An increase in noise by factors of two and five changed cortical thickness corresponding to the side length of one voxel. Intraoperator and interoperator precision was analyzed by repeated analysis of nine pelvic CT scans. Precision errors were smaller than 1% for trabecular and total volumes and smaller than 2% for cortical thickness. Intraoperator and interoperator precision errors were not significantly different. Our segmentation approach shows: 1) high accuracy and precision and is 2) robust to noise, 3) insensitive to user-defined thresholds, 4) highly automated and fast, and 5) easy to initialize.