The anatomy of tubercles: A corrosion study in a fresh water estuary

The structure and mineralogy of corrosion products formed on carbon steel coupons exposed in Duluth Superior Harbor (DSH, USA), were investigated and compared with corrosion products on similar substrata from other locations. Corrosion products in DSH form within a few months each year and are removed by ice scour and reform. The corrosion products formed in DSH are tubercles with an outer surface, an inner shell of magnetite, and a core of iron(III) oxyhydroxides, goethite, and lepidocrocite, in association with stalks produced by bacteria. In general, the tubercles formed in DSH are similar in morphology and mineralogy to corrosion products described for carbon steel and cast iron exposed to treated waters in decades‐old drinking water and cooling water systems. DSH tubercles are unique in several structural details. DSH tubercles increase areal coverage of the substratum by consolidation of tubercles. Furthermore, the core material extends into the pit and is an exact replica of the pit profile.     

Reliability Features of Large Load Commutated Inverter Drives and Some Cautions in Their Application

The special features built into load commutated inverter (LCI) drives to satisfy the demand of the paper industry for extreme reliability in critical utility type drives are examined. Examples of special circuit arrangements, redundancy, derating, and diagnostics will be discussed. Special attention will be given to the features which help make these large ac inverter drives nearly "uninterruptible." In addition to reliability, two areas of concern in applying LCI drives- harmonics and shaft torque pulsations?briefly addressed. The harmonic and torque pulsations are not considered to be problems, per se, but characteristics of the drives which must be recognized and dealt with. While LCI's do deliver the economic and functional benefits claimed by the suppliers, users are cautioned not to overlook these characteristics (harmonics and torque pulsations) in their enthusiasm to apply these new ac drive systems.     

A novel smart hybrid-Trefftz finite element for smart laminated composite plates

A novel smart hybrid-Trefftz finite element ( HTFE ) has been developed for the analysis of smart laminated composite plates. The substrates of the smart plates are symmetric and antisymmetric cross-ply plates. The derivation of this HTFE is devoid of the complicated task of finding the particular solutions of simultaneous governing partial differential equations. The Trefftz functions are constructed from the finite number of free-field exact solutions of the homogeneous simultaneous governing partial differential equations of the element domain in a straightforward manner without transforming them into a single governing equation. The HTFE is validated with the exact solutions of the smart composite plates. It is observed that this HTFE is an efficient finite element and can be utilized for the analysis of active control of smart composite structures.     

Knowledge generation in the wake of the Fukushima Daiichi nuclear power plant disaster

Scientometrics - A disaster is a crisis situation that causes significant harm to humans, the environment, the economy, and impacts upon society’s ability to cope both during the event and...     

Achieving privacy in trust negotiations with an ontology-based approach

The increasing use of Internet in a variety of distributed multiparty interactions and transactions with strong real-time requirements has pushed the search for solutions to the problem of attribute-based digital interactions. A promising solution today is represented by automated trust negotiation systems. Trust negotiation systems allow subjects in different security domains to securely exchange protected resources and services. These trust negotiation systems, however, by their nature, may represent a threat to privacy in that credentials, exchanged during negotiations, often contain sensitive personal information that may need to be selectively released. In this paper, we address the problem of preserving privacy in trust negotiations. We introduce the notion of privacy preserving disclosure, that is, a set that does not include attributes or credentials, or combinations of these, that may compromise privacy. To obtain privacy preserving disclosure sets, we propose two techniques based on the notions of substitution and generalization. We argue that formulating the trust negotiation requirements in terms of disclosure policies is often restrictive. To solve this problem, we show how trust negotiation requirements can be expressed as property-based policies that list the properties needed to obtain a given resource. To better address this issue, we introduce the notion of reference ontology, and formalize the notion of trust requirement. Additionally, we develop an approach to derive disclosure policies from trust requirements and formally state some semantics relationships (i.e., equivalence, stronger than) that may hold between policies. These relationships can be used by a credential requestor to reason about which disclosure policies he/she should use in a trust negotiation.     

A multi-angle spectrometer for automatic measurement of plant canopy reflectance spectra

The paper describes the design and operation of a multi-angle spectrometer (MAS) for automatic measurement of near-field spectral reflectances of plant canopies at hourly intervals. A novel feature of the instrument is a rotating periscope connected to a spectrometer via a fiber optic cable. Canopy reflectances are calculated for multiple view azimuths, at a single zenith angle from measurements of spectrometer dark current, incoming solar irradiance and reflected radiances. Spectral measurements are made between 300 and 1150 nm wavelength at a band-to-band spacing of 3 nm, and a bandwidth (full-width, half maximum) of 10 nm. Preliminary data analysis showed that the canopy reflectance model of Kuusk [Kuusk, A. (1995). A fast, invertible canopy reflectance model. Remote Sensing of Environment 51, 342-350] reproduced the observed large differences in visible and near-infrared (NIR) reflectances, but the model was unable to predict quantitatively the observed variations in the measured reflectance spectra with azimuth, particularly in the NIR. Discrepancies between model and measurements are likely due to the inhomogeneous nature of the forest canopy in contrast to the assumption of a uniformly absorbing turbid medium in the model. Measurements using the MAS can be used to investigate directional dependences of reflectance indices and for testing BRDF models used to separate geometrical and plant physiological contributions to the reflectance signals. The MAS provides continuous sampling of reflectance indices which can be compared with canopy properties such as chlorophyll content and photosynthetic capacity.     

Tracking leukocytes in vivo with shape and size constrained active contours

Inflammatory disease is initiated by leukocytes (white blood cells) rolling along the inner surface lining of small blood vessels called postcapillary venules. Studying the number and velocity of rolling leukocytes is essential to understanding and successfully treating inflammatory diseases. Potential inhibitors of leukocyte recruitment can be screened by leukocyte rolling assays and successful inhibitors validated by intravital microscopy. In this paper, we present an active contour or snake-based technique to automatically track the movement of the leukocytes. The novelty of the proposed method lies in the energy functional that constrains the shape and size of the active contour. This paper introduces a significant enhancement over existing gradient-based snakes in the form of a modified gradient vector flow. Using the gradient vector flow, we can track leukocytes rolling at high speeds that are not amenable to tracking with the existing edge-based techniques. We also propose a new energy-based implicit sampling method of the points on the active contour that replaces the computationally expensive explicit method. To enhance the performance of this shape and size constrained snake model, we have coupled it with Kalman filter so that during coasting (when the leukocytes are completely occluded or obscured), the tracker may infer the location of the center of the leukocyte. Finally, we have compared the performance of the proposed snake tracker with that of the correlation and centroid-based trackers. The proposed snake tracker results in superior performance measures, such as reduced error in locating the leukocyte under tracking and improvements in the percentage of frames successfully tracked. For screening and drug validation, the tracker shows promise as an automated data collection tool.     

Processing sodium tellurite melts in low gravity drop shaft: part I Melt evaporation and formation of solid particles from vapor

Glasses of Na₂O·8TeO₂ and Na₂O·4TeO₂ compositions adhered to a small platinum heating coil (2 to 3 mm ID, 5 to 6 mm long) were melted and evaporated in low gravity using the drop shaft at the Japan Microgravity Center (JAMIC). The gravity level attained during the 10 s free fall was in the order of 10^–3 g. The species evaporated from the melt in low gravity generally formed a spherical smoke cloud surrounding the melt, whose size depended on the melt temperature and also on the time the melt evaporated in low gravity. The shape of the cloud was found to depend on several other factors, namely, the uniformity of heating, amount of melt, and the presence of gas bubbles in the melt. The evaporating species formed nearly perfect spheres of pure TeO₂ whose diameter ranged from 0.05 to 20 m. The size of TeO₂ microspheres increased with increasing melt temperature and time in low gravity, and was 5 to 10 times larger than that of similar particles prepared at 1-g.     

Two-step K(+)-Na+ and Ag(+)-Na+ ion-exchanged glass waveguides for C-band applications

A two-step K(+)-Na+ and Ag(+)-Na+ ion-exchange technique is introduced to fabricate single-mode channel waveguides in BK7 glass for the telecom-wavelength region. The dependencies of insertion loss, polarization-dependent loss (PDL), end bending loss of curved waveguides on channel width, diffusion time, and annealing time are investigated. Results show that postannealing is a required process for improving waveguide properties and an optimal annealing time exists. Although relatively narrow mask openings are used in most one-step ion-exchange processes, a wider channel width, to as wide as 10 microm, is preferred for this two-step method. The minimum coupling loss to/from single-mode fiber and the propagation loss is found to be 0.4 dB and 0.3 dB/cm, respectively. For 5-cm-long waveguides the PDL is less than 0.1 dB. For the S-bend structure the cosine curve exhibit apparently a lower bending loss than the double-arc curve.