Entrainment behaviour of high-density Geldart A powders with different shapes

Atomised and milled Ferrosilicon with average particle diameters of 38 and 50 µm respectively were fluidised with air at ambient conditions. The entrainment rate of the more spherical atomised particles was on average six times that of the irregularly shaped milled particles over the range of superficial velocities investigated. In an attempt to decouple the effect of particle size from shape, the bed was divided into theoretically isolated bins based on the distributions of particle sizes. This indicated that the atomised particles had a higher entrainment rate for particles smaller than approximately 25 µm whereas the opposite was true for particles greater than this size. None of the entrainment correlations investigated was able to predict the switch in entrainment behaviour as a function of particle sphericity and diameter. Furthermore, the traditional critical particle diameter associated with cohesive Geldart A particles was not observed for either of the two particle shapes. It is therefore concluded that neither the hydrodynamic nor Van der Waals forces acting on the particles can adequately explain the entrainment rate behaviour of differently shaped high-density Geldart A particles.     

Low surface energy polymeric films from partially fluorinated photocurable solventless liquid oligoesters

Summary We have recently shown that low surface energy polymeric films can be readily obtained from partially fluorinated hydroxyl-end-capped solventless liquid oligoesters by thermal curing [1]. Photocurable liquid oligoesters can be prepared by further substituting the remaining hydroxyl end groups with acrylic double bonds. A conventional photoinitiator containing 2-hydroxy-2-methylpropiophenone was used to cure the liquid oligoesters. As the fluorine content increases from 0 to about 1.57 wt %, the surface energy decreases by about 14 mN/m. The fluorine level in the outer few nanometers is significantly greater than that in the bulk, as revealed by XPS studies. The driving force for the surface segregation of fluorinated species comes from the large difference in surface energy between the oligoesters and their fluorinated counterparts. Received: 14 August 2001/Revised version: 10 October 2001/Accepted: 10 October 2001     

Integrating public transportation in personalised electronic tourist guides

Personalised electronic tourist guides (PETs) are mobile hand-held devices able to create tourist routes matching tourists' preferences. Transportation information has been identified as one of the most appreciated functionalities of a PET. We model the tourist planning problem, integrating public transportation, as the time-dependent team orienteering problem with time windows (TD-TOPTW) in order to allow PETs to create personalised tourist routes in real-time. We develop and compare two different approaches to solve the TD-TOPTW. Experimental results for the city of San Sebastian show that both approaches are able to obtain routes in real-time.     

Wavelength-Selective Organic Photodetectors

Spectroscopic sensing combined with optical imaging is crucial with respect to today's ever-growing demand for instant analytical techniques to be incorporated in various handheld and wearable devices. Further miniaturization and integration of such types of sensors is critical and wavelength-selective organic photodetectors (OPDs) may provide the required technology. In this progress report, some early OPD applications and their potential are presented. Crucial device parameters such as the specific detectivity, external quantum efficiency, and dark current density of visible and near-infrared wavelength-selective photodetectors are compared and assayed to theoretical and semi-empirical limits. The different organic detector approaches include the use of inherently narrow-band absorbers as well as internally filtered and microcavity devices. Each of these strategies comes with its own specific material and device design criteria, around which material development and selection should be centered to move beyond the current state of the art. As OPD technology matures, device stability becomes important and is hence also briefly discussed. Via this perspective, it is aimed to provide the reader with critical insights into the device physics and chemistry of wavelength-selective OPDs, hereby providing leverage for new ideas to bring this technology to the market.     

Multiscale characterization of pathological bone tissue

Bone is a complex natural material with a complex hierarchical multiscale organization, crucial to perform its functions. Ultrastructural analysis of bone is crucial for our understanding of cell to cell communication, the healthy or pathological composition of bone tissue, and its three-dimensional (3D) organization. A variety of techniques has been used to analyze bone tissue. This article describes a combined approach of optical, scanning electron, and transmission electron microscopy for the ultrastructural analysis of bone from the nanoscale to the macroscale, as illustrated by two pathological bone tissues. By following a top-down approach to investigate the multiscale organization of pathological bones, quantitative estimates were made in terms of calcium content, nearest neighbor distances of osteocytes, canaliculi diameter, ordering, and D-spacing of the collagen fibrils, and the orientation of intrafibrillar minerals which enable us to observe the fine structural details. We identify and discuss a series of two-dimensional (2D) and 3D imaging techniques that can be used to characterize bone tissue. By doing so we demonstrate that, while 2D imaging techniques provide comparable information from pathological bone tissues, significantly different structural details are observed upon analyzing the pathological bone tissues in 3D. Finally, particular attention is paid to sample preparation for and quantitative processing of data from electron microscopic analysis.     

Least privilege analysis in software architectures

Due to the lack of both precise definitions and effective software engineering methodologies, security design principles are often neglected by software architects, resulting in potentially high-risk threats to systems. This work lays the formal foundations for understanding the security design principle of least privilege in software architectures and provides a technique to identify violations against this principle. The technique can also be leveraged to analyze violations against the security design principle of separation of duties. The proposed approach is supported by tools and has been validated in four case studies, two of which are presented in detail in this paper.     

A 1–2 GHz high linearity transformer-feedback power-to-current LNA

This paper demonstrates that a double-loop transformer-feedback power-to-current low noise amplifier, to be implemented in a 0.2 μm GaAs p-HEMT IC process, is able to obtain a noise figure less than 0.8 dB, an input return loss less than −12 dB, a flat voltage-to-current signal transfer of 180 mS, and an input-referred third-order intercept point (IIP3) of 1.8 dBm over a wideband frequency range from 1 to 2 GHz at a power consumption of 210 mW.